,,use ,,of ,,those ,,connected ,,with ,,mines4999999 includes the original illustrations and in which the chemical equations are easier to read4 ,see #ahgea-;h4htm or #ahgea-;h4zip3 7https3_/_/www4gutenberg4org_/dirs_/#a_/ h_/g_/e_/ahgea_/ahgea-;h_/#ahgea-;h4htm7 or 7https3_/_/www4gutenberg4org_/dirs_/#a_/ h_/g_/e_/ahgea_/ahgea-;h4zip7 ,transcriber's ,note3 ,text3 ,words surrounded by a tilde such as this means the word is in bold face4 ,words surrounded by underscores like this means the word is in italics in the text4 ,letters in brackets with an sign before it means that the letters have a macron over them1 e4g4 ,h,ac signifies that the ,ac has a macron over it4 ,numbers and equations3 ,parentheses have been added to clarify fractions4 ,underscores before bracketed numbers in equations denote a subscript4 ,superscripts are designated with a caret and brackets1 e4g4 #aa4ac is #aa4a to the third power4 ,the symbol 4'4 designates the symbol usually used for therefore 7three periods in a triangle shape74 ,a down arrow is represented by a vertical line over a capital ,v4 ,like this3 ,v ,minor typographical errors have been corrected4 ,footnotes have been moved to the end of the chapter1 and all advertisements have been moved to the end of the book4 ,a ,,text-,,book ,,of ,,assaying3 ,,for ,,the ,,use ,,of ,,those ,,connected ,,with ,,mines4 by ,c4 ,,and ,j4 ,j4 ,,beringer4 ,revised by ,j4 ,j4 ,,beringer1 ,assoc4 of the ,royal ,school of ,mines2 ,fellow of the ,chemical ,society and of the ,inst4 of ,chemistry2 ,principal of the ,camborne ,mining ,school2 and ,late ,public ,analyst for the ,county of ,cornwall4 ,with numerous ,diagrams and ,tables4 ,ninth ,edition4 ,london3 ,charles ,griffin and ,company1 ,limited1 ,exeter ,street1 ,strand4 #aijd4 ,all rights reserved4 ,,publisher',s ,,note ,,to ,,the ,,ninth ,,edition ,the continued popularity of the present work1 the last edition of which was published only a little over a year ago1 continues to be a source of gratification to the publishers1 who have much pleasure in issuing the present edition4 ,january #aijd4 ,,preface ,,to ,,the ,,sixth ,,edition ,the principal changes in this edition are additions to the articles on ,gold1 ,cyanides1 and ,nickel1 and a much enlarged ,index4 ,the additional matter covers more than forty pages4 ,j4 ,j4 ,,beringer4 ,,camborne1 ,january #aijj4 ,,preface4 ,the ,text-book now offered to the public has been prepared to meet the existing want of a practical handy book for the ,assayer4 ,to mining men the word assaying conveys a sufficiently clear meaning1 but it is difficult to define4 ,some writers limit it to the determination of silver and gold1 and others imagine that it has only to do with furnace-work4 ,these limitations are not recognised in practice4 ,in fact1 assaying is becoming wider in its scope1 and the distinction between assayers and analysts will in time be difficult to detect4 ,we have endeavoured rather to give what will be of use to the assayer than to cover the ground within the limits of a faulty definition4 ,at first our intention was to supply a description of those substances only which have a commercial value1 but on consideration we have added short accounts of the rarer elements1 since they are frequently met with1 and occasionally affect the accuracy of an assay4 ,under the more important methods we have given the results of a series of experiments showing the effect of varying conditions on the accuracy of the process4 ,such experiments are often made by assayers1 but seldom recorded4 ,statements like those generally made--that this or that substance interferes--are insufficient4 ,it is necessary to know under what conditions and to what extent4 ,students learning any particular process cannot do better than repeat such a series of experiments4 ,by this means they will1 at the same time1 acquire the skill necessary for performing an assay and a confidence in their results based upon work under different conditions4 ,the electrolytic method of copper assaying given under ,copper is a modification of ,luckow's2 it was introduced by us into the offices of the ,rio ,tinto ,copper ,company1 and has been in use for many years with success4 ,this modification is now employed in copper-works in ,spain1 ,germany1 and ,england1 and is used in place of the dry assay for the commercial valuation of copper ores4 ,we have adhered to the gram and the c4c4 as the units of weight and volume4 ,those who prefer working with grains and grain-measures can use the figures given1 multiplied by ten4 ,for example3--,when #a gram is mentioned1 #aj grains should be used1 and #aj grain-measures take the place of #a c4c4 ,it is not advisable to mix the two systems1 as by using gram weights and grain-measures4 ,we have intentionally to a large extent omitted to mention the names of those who have originated or modified the various processes4 ,the practice of naming a process after its discoverer has developed of late years1 and is becoming objectionable4 ,it is a graceful thing to name a gas-burner after ,bunsen1 or a condenser after ,liebig2 but when the practice has developed so far that one is directed to ,finkenerise a residue1 or to use the ,reichert-,meissl-,wollny process1 it is time to stop4 ,we are indebted to the standard works of ,allen1 ,crookes1 ,fresenius1 ,lunge1 ,michell1 ,percy1 and ,sutton1 and wish to express our sense of special indebtedness to ,mr4 ,richard ,smith1 of the ,royal ,school of ,mines4 ,one or two of the illustrations are taken from ,mr4 ,sexton's excellent little book on ,qualitative ,analysis4 ,our obligation to some others is mentioned in the text4 ,finally1 we have to thank for assistance in the experimental work ,messrs4 ,bailey1 ,beswick1 ,clarke1 ,grant1 ,higgins1 and ,smith4 ,,the ,,authors4 ,,camborne1 ,nov4 #ahhi4 ,,contents4 ,,part ,i4 ,,chapter ,i4 ,,introductory4 ,page ,object of assaying #a ,sampling #a ,drying3 determination of moisture #e ,calculation and statement of results #g ,laboratory books and report forms #i ,quantity to be taken for an assay #aa ,exercises #ad ,,chapter ,,ii4 ,,methods ,,of ,,assaying4--,,dry ,,gravimetric ,,methods4 ,methods of assaying #ae ,gravimetric methods #ae ,mechanical separations #af ,dry assays #af 7a7 ,fluxes #af 7b7 ,reducing agents #ba 7c7 ,oxidising agents #bb 7c7 ,apparatus #bd ,,chapter ,,iii4 ,,wet ,,gravimetric ,,methods4 ,wet gravimetric methods #bg 7a7 ,solution #bi 7b7 ,precipitation #cj 7c7 ,filtration #ca 7c7 ,drying and igniting #cb ,,chapter ,,iv4 ,,volumetric ,,assays4 ,titrometric assays #ce 7a7 ,standard solutions #cf 7b7 ,standardising #cg 7c7 ,methods of working #db 7c7 ,indirect titration #dc ,colorimetric assays #dd ,gasometric assays #dd ,,chapter ,v4 ,,weighing ,,and ,,measuring4 ,weighing #dg ,measuring liquids #di 7a7 ,graduated flasks #di 7b7 ,pipettes #ej 7c7 ,burettes #ea ,measuring gases #eb ,,chapter ,,vi4 ,,reagents4 ,acids1 c4 #ed ,bases1 salts1 c4 #ei ,,chapter ,,vii4 ,formul1 equations1 c4 #fh ,,chapter ,,viii4 ,,specific ,,gravity4 ,introductory #ge ,determination of specific gravity-- 7a7 ,hydrometers #gf 7b7 ,specific gravity bottles #gh ,calculations depending on specific gravity #hd ,,part ,,ii4 ,,chapter ,,ix4 ,,silver1 ,,gold1 ,,platinum1 ,,cyanides1 ,,mercury4 ,,silver--,detection #hg ,dry assay #hg 7#a7 ,scorification #hh 7#b7 ,pot assays1 average ores #ij ores with metallic oxides #ia ores with metallic sulphides #ia ,explanatory notes on the fusion #ic ,the effect of charcoal1 flour1 c4 #id ,the effect of nitre #ie ,the effect of mineral sulphides #ie 7#c7 ,cupellation #ih ,the loss of silver #aja ,condition affecting the loss #ajb ,methods of correction #ajc ,lead required for cupellation #aje 7#d7 ,calculation of the results in ounces to the ton of #bbdj lbs4 ,table #ajg ,ores with metallic particles #ajh 7#e7 ,explanatory notes #aaj 7#f7 ,examples of dry silver assays #aac ,wet assays #aaf ,gravimetric method #aag ,gay-,lussac's method #aai ,volhard's method #aba ,a modified ,gay-,lussac #abc ,volhard's method applied to arsenic #abd ,,gold--,detection #abf ,amalgamation assay #abf ,dry assay #abg 7#a7 ,size of charges #abg 7#b7 ,sampling #abg 7#c7 ,assay tons #aca 7#d7 ,small buttons1 weighing #aca measuring #acc 7#e7 ,concentration in lead #acf ,quartz ores #acf ,ores with oxide of iron #ach ,ores with metallic sulphides #aci 7#f7 ,cyanide charges1 residues1 c4 #adj 7#g7 ,cupellation #adb ,cupels #adb ,cupellation temperature #adc ,cupellation loss #ade 7#h7 ,inquartation #adf 7#i7 ,flatting #adi 7#aj7 ,parting1 in flasks #aea in test tubes #aeb in glazed crucibles #aec ,loss1 c4 #aed 7#aa7 ,check assays1 surcharge #aed 7#ab7 ,bullion assays in special apparatus #aef ,silver1 c41 in gold bullion #aeg 7#ac7 ,sampling of base bullion1 c4 #aeg ,,cyanides--,commercial cyanides #afj ,double cyanides #afa ,prussic acid #afb ,gold-dissolving power of cyanide liquor #afb ,assay for cyanide strength #afc1 #afe ,assay of commercial cyanide #afg ,alkalinity of cyanides #afg ,acidity of ores #afh ,metals in cyanide liquors #afi ,cyanicides #afi ,,platinum #agj ,,iridium #aga ,,mercury #aga ,dry assay #agb ,wet method #agc ,,chapter ,x4 ,,copper1 ,,lead1 ,,thallium1 ,,bismuth1 ,,antimony4 ,,copper--,introductory #age ,dry assay #agf ,valuation of copper ores #aha ,wet methods #ahc 7#a7 ,electrolytic assay #ahd ,volumetric methods #aid 7#a7 ,cyanide method #aid 7#b7 ,iodide method #aii 7#c7 ,colorimetric method #bjc ,examination of commercial copper #bje ,,lead #baa ,dry assay #baa ,wet assay #bac 7#a7 ,gravimetric method #bac 7#b7 ,volumetric method #bad 7#c7 ,colorimetric method #bah ,,thallium #bai ,,bismuth #bbj ,dry assay #bba ,wet method #bba 7#a7 ,gravimetric determination #bbb 7#b7 ,colorimetric assay #bbc ,,antimony #bbe ,dry assay #bbe ,wet method #bbg 7#a7 ,gravimetric assay #bbh 7#b7 ,volumetric method #bbi ,,chapter ,,xi4 ,,iron1 ,,nickel1 ,,cobalt1 ,,zinc1 ,,cadmium4 ,,iron #bca ,gravimetric determination #bcc ,permanganate and bichromate methods #bcd ,stannous chloride method #bdd ,colorimetric determination #bdg ,,nickel #bea ,dry assay #bea ,electrolytic assay #bed ,titration by cyanide #bee ,,cobalt #bei ,,zinc #bfa ,gravimetric method #bfb ,volumetric method #bfc ,gasometric method #bff ,,cadmium #bfi ,,chapter ,,xii4 ,,tin1 ,,tungsten1 ,,titanium4 ,,tin #bga ,vanning #bgc ,dry assay #bgf ,detection1 c4 #bgi ,gravimetric determination #bha ,volumetric determination #bhb ,examples #bhd ,,titanium #bib ,,tungsten #bie ,,niobic ,,and ,,tantalic ,,oxides #big ,,chapter ,,xiii4 ,,manganese1 ,,chromium1 ,,etc4 ,,manganese #bih ,gravimetric determination #cjj ,volumetric determination #cjj ,ferrous sulphate assay #cja ,iodine assay #cjb ,colorimetric determination #cjf ,,chromium #cjg ,,vanadium #caj ,,molybdenum #caa ,,uranium #cab ,,chapter ,,xiv4 ,,earths1 ,,alkaline ,,earths1 ,,alkalies4 ,,alumina #cad ,,thoria #cag ,,zirconia #cag ,,cerium #cah ,,lanthanum ,,and ,,didymium #cai ,,yttria #cai ,,beryllia #cai ,,lime #cbj ,,strontia #cbd ,,baryta #cbf ,,magnesia #cbh ,,the ,,alkalies #ccj ,,sodium #ccd ,,potassium #ccf ,,lithium #cch ,c,,sium #cci ,,rubidium #cdj ,,ammonium #cdj ,,part ,,iii4 ,,chapter ,,xv4 ,,oxygen ,,and ,,oxides--,,the ,,halogens4 ,,oxygen #cdd ,,oxides #cde ,,water #cej ,,the ,,halogens #ceh ,,chlorine #cei ,,bromine #cfa ,,iodine #cfb ,,fluorine #cfc ,,chapter ,,xvi4 ,,sulphur ,,and ,,sulphates4 ,,sulphur #cfg ,gravimetric determination #cfi ,volumetric determination #cgj ,,sulphates #cgg ,,selenium #cgi ,,tellurium #cgi ,,chapter ,,xvii4 ,,arsenic1 ,,phosphorus1 ,,nitrogen4 ,,arsenic #cha ,gravimetric determination #chc ,volumetric method1 iodine #chd uranic acetate #chi ,,phosphorus #cid ,gravimetric determination #cif ,volumetric determination #cig ,,nitrogen ,,and ,,nitrates #djj ,,chapter ,,xviii4 ,,silicon1 ,,carbon1 ,,boron4 ,,silicon ,,and ,,silicates #dje ,,carbon ,,and ,,carbonates #dad ,,coals #dah ,,shales #dbj ,,carbonates #dbd ,,boron ,,and ,,borates #dbi ,,appendix ,a4 ,table of atomic weights and other constants #dcc ,table for converting degrees of the centigrade thermometer into degrees of ,fahrenheit's scale #dce ,tables showing strengths of aqueous solutions of nitric and hydrochloric acids1 of ammonia and of sulphuric acid #dcf ,,appendix ,b4 ,estimation of small quantities of gold #ddj ,practical notes on the iodide process of copper assaying #dda ,method of separating cobalt and nickel #ddb ,,appendix ,c4 ,a lecture on the theory of sampling #ddd ,,index #dej ,a ,,text-,,book ,,of ,,assaying4 ,,chapter ,i4 ,,introductory4 ,assaying has for its object the determination of the quantities of those constituents of a material which add to or detract from its value in the arts and manufactures4 ,the methods of assaying are mainly those of analytical chemistry1 and are limited by various practical considerations to the determination of the constituents of a small parcel1 which is frequently only a few grains1 and rarely more than a few ounces1 in weight4 ,from these determinations calculations are made1 which have reference to a mass of material of1 perhaps1 hundreds of tons4 ,but in all cases1 whether the mass under consideration be large or small1 whether the material be obtained by mining1 grown1 or manufactured1 the assayer is supposed to receive a small quantity1 called the sample1 which is1 or ought to be1 the exact counterpart of the mass of material that is being dealt with4 ,the taking and making of this sample is termed sampling2 and the men whose special work it is to select such samples are the samplers4 ,but although sampling is thus distinct from assaying1 the assayer should be familiar with the principles of sampling1 and rigorous in the application of these principles in the selecting1 from the sample sent him1 that smaller portion upon which he performs his operations4 ,sampling4--,in the case of gases1 there is absolutely no trouble in mixing4 ,the only difficulty is in drawing off a fair sample where1 as in flues1 the body of the gas is in motion1 and varies a little in composition from time to time4 ,in this case1 care must be taken to draw off uniformly a sufficient volume of the gas during a prolonged period2 any portion of this larger volume may then be taken for the analytical operation4 ,in the case of liquids1 which mix more or less easily--and this class includes metals1 c41 in the state of fusion--more or less severe agitation1 followed by the immediate withdrawal of a portion1 will yield a fairly representative sample4 ,in the case of solids1 the whole mass must be crushed1 and1 if not already of fairly uniform quality1 mixed1 before sampling can take place4 ,most of the material which a sampler is called upon to deal with1 is1 however1 in a more or less divided state and fairly uniform4 ,in practice it is assumed that #e per cent4 of the whole 7 #a_/bjth71 if taken in portions of equal weight and at frequent and regular intervals1 will represent the mass from which it was taken4 ,taking a heap of ore1 ,a1 and selecting one out of every twenty spade-1 bag-1 barrow-1 or wagon-fuls1 according to the quantity of stuff in the heap1 there is obtained a second heap1 ,b1 containing one-twentieth of the stuff of the heap ,a4 ,if we crush the stuff in ,b until this heap contains approximately the same number of stones as ,a did--which means1 crushing every stone in ,b into about twenty pieces--,b will become the counterpart of ,a4 ,selecting in the same manner #e per cent4 of ,b1 there is got a third heap1 ,c4 ,this alternate reduction and pulverising must be carried on until a sample of suitable size is obtained4 ,this may be expressed very clearly thus3-- ,a #ajjj tons of rocks and lumpy ore4 ,b #ej rough stones1 #a_/bjth of ,a4 ,c #b4e small stones1 #a_/bjth of ,b4 ,d #j4abe coarse powder1 #a_/bjth of ,c4 ,illustration3 ,,fig4 #a4 ,,cone ,,partly ,,reduced ,,cone ,,plan ,,of ,,frustrum ,,divided4 ,,elevation ,,of ,,frustrum ,,divided4 ,if the material to be sampled is already a dry powder1 #e per cent4 of it should be heaped in a cone2 each lot being added on the apex of the cone already formed1 so that it may distribute itself by falling evenly in all directions4 ,when the cone is completed1 convert it into a low frustrum of a cone by drawing stuff uniformly and in a direct line from the centre to the circumference4 ,draw two diameters at right angles to each other1 and reserving any two alternate quarters1 reject the others4 ,mix2 and form another cone1 and proceed until a sample is got of the bulk required4 ,this is the usual plan1 and all samples should be treated in this way when the stuff is fine enough to fall evenly down the sides of a cone4 ,samples as they reach the assay office are seldom in a fit state for the work of the assayer2 they are generally too coarse1 and ought always to be more than he wants for any particular determination4 ,the portion he requires should never be taken at hap-hazard2 the sample must be reduced systematically to the quantity required4 #a4 ,if the sample is a liquid3 it is sufficient to shake the bottle1 and take out a measured or weighed quantity for the assay4 #b4 ,if a liquid with a solid in suspension3 measure the whole of it4 ,filter4 ,make up the filtrate with the wash-water or water to the original bulk4 ,assay it4 ,dry and weigh the residue1 and make a separate assay of it4 #c4 ,if of a creamy consistency1 free from heavy particles3 mix well2 spread out evenly on a glazed tile4 ,take up equal portions at equal distances4 ,mix and assay4 #d4 ,if a mud of coarse and fine particles1 or of particles of unequal density3 weigh and transfer to a porcelain dish1 or weigh in the dish4 ,dry at #ajj ,c41 weigh4 ,treat the residue as a solid capable of being powdered4 #e4 ,if a solid capable of being powdered1 or already powdered3 heap up into a cone2 flatten with a spatula2 divide along two diameters at right angles1 and carefully reject the whole of two alternate quarters1 brushing away any fine powder4 ,mix the other quarters1 and repeat 7if necessary74 ,for small quantities a fine state of division is essential4 #f4 ,if a solid with metallic particles3 powder and pass through a sieve2 the metallic particles will not pass through4 ,weigh both portions and assay separately4 ,sifting should be followed by a very thorough mixing4 #g4 ,if a metal or alloy in bar or ingot3 clean the upper surface of the bar1 and bore through the bar4 ,use the borings4 ,if the ingot or bar is small1 cut it through and file the section4 ,filings must be freed from fragments of the file by means of a magnet2 and from oil1 if any be present1 by washing with a suitable solvent4#a ,where practicable1 metals and alloys are best sampled by melting and granulating4 ,the student must carefully avoid any chance of mixing dirt or particles of other samples with the particular sample which he is preparing4 ,one ore should be done at a time1 and when finished1 it should be labelled and wrapped up1 or bottled1 before starting on a fresh sample4 ,when an ore requires to be very finely ground in an agate mortar1 it is often advisable to mix with a little pure alcohol and rub until free from grit2 dry at #ajj ,c4 and mix well before weighing4 ,when an assay is required of a quantity of ore made up of parcels of different weight and quality1 each parcel should be separately sampled and parts of each sample1 bearing to each other the same proportion by weight as the original parcels1 should be taken and mixed4 ,for example1 a lot of ore is made up of one parcel of ,a1 #egj tons1 one of ,b1 #ahj tons1 and another of ,c1 #ej tons2 a sample representing the whole may be got by mixing #eg parts of a sample of ,a with #ah parts of a sample of ,b1 and #e parts of a sample of ,c4 ,illustration3 ,,fig4 #b4 ,a bruising plate1 like that in fig4 #b1 is convenient for general office work4 ,the slab is of cast iron1 about an inch thick4 ,it is firmly supported on a solid block of wood1 and pivoted for convenience in emptying4 ,the bruising-hammer is steel-faced1 about #d inches square1 and #a-a_/b inch thick4 ,the block is firmly fixed to a small table or tressel1 so that the slab is about #b feet #f inches from the ground4 ,the slab is cleaned1 and the sample collected with the help of a stiff-haired brush4 ,drying3 ,determination of ,moisture4--,in practice1 the moisture is generally determined by the samplers1 and the proportion is specified in grains per pound on the label attached to the sample when it reaches the assay office4 ,the method adopted is usually to dry #a lb4 #gjjj grs4 of the ore in a frying-pan heated over a gas flame1 or in an ordinary oven1 until a cold bright piece of metal or glass is no longer damped when held over it4 ,the loss of weight in grains moisture4 ,properly1 however1 this work should be done by the assayer1 if only for the following reason4 ,it is assumed that the dry ore of the sampler and of the assayer are the same thing2 according to the nature of the ore1 this may or may not be the case4 ,the assayer1 however1 uses the sample which he has dried for his moisture-determination1 as the dry ore on which he makes his other assays1 and no variation in moisture would influence the other and more important determinations4 ,some ores are sent to the smelter with from #e to #ae per cent4 of adherent water4 ,in these cases it is best to spread out the sample1 and taking equal portions fairly at regular intervals1 weigh into a ,berlin dish #bj grams4 ,this should then be dried over a sand-bath1 or if the ore is likely to be injured by excess of heat1 over a water-bath until the weight is constant4 ,the loss of weight multiplied by #e gives the percentage of water present4 ,example3-- ,weight of dish wolfram #cb4fg grms4 dish #ab4fg ----- wolfram #bj4jj dish wolfram #cb4fg dried #cj4ae ----- water #b4eb #b4eb #e #ab4f #ab4f4 ,there are other ores which are not apparently wet1 but in the state called air-dried4 ,it is easier to take fair samples of these1 and1 consequently1 it is not necessary to use so large a quantity as #bj grams4 ,but with a smaller quantity1 extra precautions must be taken4 ,all dry solids at ordinary temperatures absorb moisture from the air4 ,the amount varies with the nature of the material and with the quantity of surface exposed4 ,light bulky powders absorb more than heavy ones1 because of the greater condensing surface4 ,it is on this account that it is well to weigh substances1 which have been dried1 between close-fitting watch-glasses4 ,the method of determining moisture is to weigh out into the glasses #e grams of ore1 and dry in the water-oven until there is no further loss of weight4 ,on taking the glasses out of the oven1 they should be at once closed1 the clip put on1 and after cooling in a desiccator weighed4 ,if after a second trial the loss is the same1 or only increased by a milligram1 the determination is finished4 ,example3-- ,weight of glasses pyrites #ca4jdgj grms4 glasses #bf4jdgj ------- pyrites #e4jjjj glasses pyrites1 dried #a hour #cj4hife dried #a-a_/b #cj4hieg #ca4jdgj dried #cj4hieg ------- moisture #j4aeac #j4aeac #bj #c4jbf #c4jb4 ,illustration3 ,,fig4 #c4 ,sometimes it may be advisable to dry #aj grams1 in which case multiplying the loss by #aj will give the percentage4 ,the dried ore should be transferred to a weighing-tube 7fig4 #c71 and reserved for the subsequent determinations4 ,the weighing-tube with the ore must be marked1 and kept in a desiccator4 ,most ores and inorganic substances can be dried1 and their moisture determined by the loss in this way4 ,when1 however1 the substance contains another somewhat volatile ingredient1 it is exposed over sulphuric acid in a desiccator for two days 7if in vacuo1 all the better71 and the loss determined4 ,moisture in dynamite should be determined in this way4 ,when water is simply mechanically mixed with a substance it presents but little difficulty4 ,the combined water is a different matter4 ,slaked lime1 even when perfectly dry1 contains much water2 and if the water of soda crystals were separated and frozen1 it would occupy a volume equal to that of the original crystals4 ,perfectly dry substances may contain much water1 and this combined water is retained by different materials with very unequal vigour4 ,sodium sulphate and sodium phosphate crystals lose water even when exposed under ordinary conditions to dry air4 ,soda crystals when heated melt1 and at a moderate temperature give off their water with ebullition4 ,the temperature at which all the water is given up varies with each particular salt2 the actual determination of the water in each case will require somewhat different treatment4 ,such determinations1 however1 are seldom required2 and from a practical point of view this combined water causes no trouble4 ,in assaying ores1 we term moisture all water which is lost by exposure in a water-oven at #ajj ,c41 and the dry ore is the ore which has been dried at this temperature4 ,no advantage1 but rather endless confusion1 would be caused by varying the temperature with the object of estimating the whole of the water which a hydrated salt may contain4 ,the results of the assay of the other components should be calculated on the dry ore4 ,one advantage of this is obvious3--,the dry ore has a constant composition1 and the results of all assays of it will be the same1 no matter when made2 the moisture1 however1 may vary from day to day1 and would be influenced by a passing shower of rain4 ,it is well to limit this variability to the moisture by considering it apart1 and thus avoid having the percentage1 say1 of copper rising and falling under the influence of the weather4 ,in the case of certain salts1 however1 such as soda crystals and hydrated sulphate of copper 7when these constitute the bulk of the substance to be assayed71 it is as well to perform the assay on the moist1 or at any rate air-dried1 substance4#b ,it would be equally convenient to calculate on the substance dried at #ajj ,c42 but in this case it would be well1 in order to avoid a somewhat shallow criticism1 to replace the term moisture by the longer but equivalent phrase water lost at #ajj ,c4 ,calculation and ,statement of ,results4--,by far the most generally convenient method of stating the results of an assay is that of the percentage or parts in a hundred1 and to avoid a needlessly troublesome calculation it is well to take such a quantity of ore for each assay as by a simple multiplication will yield the percentage4 ,in these calculations decimals are freely employed1 and students should make themselves familiar with the methods of using them4 ,other methods of statement are in use1 and have advantages in certain special cases4 ,with bullion the parts in a thousand are given1 and in those cases in which the percentage is very small1 as in water analysis1 it is convenient to report on parts in #ajj1jjj1 or even on parts per #a1jjj1jjj4 ,these are easily got from the corresponding percentages by shifting the decimal point one1 three1 or four places to the right4 ,thus #ib4e per cent4 is #ibe per thousand2 and #j4jjcf per cent4 is #c4f per #ajj1jjj1 or #cf per million4 ,with ores of tin1 silver1 and gold1 the result is stated as so many cwts41 lbs41 or ozs41 in the ton4 ,with dressed tin ores as they are sent to the smelter1 the produce is given in cwts4 and quarters to the ton4 ,the corresponding percentage may be obtained by multiplying by five2 or1 inversely1 if the percentage is given1 the produce may be got by dividing by five4 ,a produce of #ac-a_/b equals a percentage of #ac4ee #fg4e2 and a percentage of #gj4j equals a produce of #gj_/e #ad4 ,with tin ores as raised 7in which the percentage is small7 the reduction must be carried to pounds per ton4 ,one per cent4 equals #bb4d lbs4 to the ton2 consequently1 if we multiply the percentage by #bb4d1 the produce will be given4 ,thus1 if an ore contains #f4g per cent4 of oxide of tin1 the produce is #f4gbb4d #aej lbs4 7or #a cwt41 #a quarter1 and #aj lbs47 to the ton4 ,with gold and silver ores1 the proportion of precious metal is small1 and it is necessary to carry the reduction to ozs4 and dwts4 to the ton2 and since gold and silver are sold by troy weight1 whilst the ton is avoirdupois1 it is of importance to remember that the ounces in the two systems are not the same4 ,a ton contains #ae1fhj1jjj grains1 which equal #fec1ccc4c dwts4 or #cb1fff4f ozs4 7troy74 ,the following rules are useful3-- ,to get ozs4 7troy7 per ton1 multiply parts per #ajj1jjj by #j4cbg2 ,to get dwts4 per ton1 multiply parts per #ajj1jjj by #f4ec2 ,to get grains per ton1 multiply parts per #ajj1jjj by #aef4h4 ,where liquids are being assayed1 cubic centimetres are held to be equivalent to grams1 and the usual method of statement is1 so many parts by weight in so many by measure4 ,where the statement is made as grams per litre or grains per gallon1 there can be no doubt as to what is meant2 and even if it be expressed in parts per #ajj1jjj1 parts by weight in a measured volume must be understood unless the contrary is expressly stated4 ,in some cases1 where the density of the solution differs greatly from that of water1 the percentage by weight may be given2 and in others1 mixtures of two or more liquids1 the percentages may be given by volume or by weight2 as so many c4c4 in #ajj c4c41 or as so many grams in #ajj grams1 or even as so many grams in #ajj c4c4 ,in such cases it must be distinctly shown which method of statement is adopted4 ,one grain per gallon means #a grain in #gj1jjj grain-measures1 or one part in #gj1jjj4 ,dividing by #g and multiplying by #aj will convert grains per gallon into parts per #ajj1jjj4 ,inversely1 dividing by #aj and multiplying by #g1 will convert parts per #ajj1jjj into grains per gallon4 ,grams per litre are parts per #ajjj2 multiplying by #ajj will give parts per #ajj1jjj1 and multiplying by #gj will give grains per gallon4 ,among foreign systems of weights1 the ,french is by far the best4 ,kilograms 7#b4bje lbs47 per quintal 7#bbj4e lbs47 are parts per cent42 and grams 7#ae4dc grs47 per quintal are parts per #ajj1jjj4 ,from the rule already given1 grams per quintal may be converted into ounces to the ton by multiplying by #j4cbg4 ,the ,german loths per centner 7#a_/b oz4 7avoirdupois7 to #ajj lbs47 equal parts per #cbjj2 they are converted into parts per cent4 by dividing by #cb1 or into ounces 7troy7 per ton by multiplying by #aj4bjh4 ,in the ,united ,states1 as a sort of compromise between the avoirdupois and metric systems1 a ton is taken as #bjjj lbs4 ,there1 too1 the custom is adopted of reporting the gold and silver contents of an ore as so many dollars and cents to the ton4 ,in the case of gold1 an ounce is considered to be worth #bj4fgah dollars4 ,with silver1 the nominal value is #a4bibi dollars per ounce1 but frequently in assay reports it is taken as one dollar4 ,the practice is objectionable4 ,the prices of metals vary with the fluctuations of the market1 and if the assayer fixed the price1 the date of his report would be all important2 if1 on the other hand1 he takes a fixed price which does not at all times agree with the market one1 it leaves a path open for the deception of those unacquainted with the custom4 ,american dollars on the ton of #bjjj lbs4 may be converted into ounces in the ton of #bbdj lbs4 by dividing by #a4aedd in the case of silver1 and by #ah4deg in the case of gold4 ,laboratory ,books and ,report ,forms4--,the record which the assayer makes of his work must be clear and neat1 so that reference1 even after an interval of years1 should be certain and easy4 ,one method should be adopted and adhered to4 ,where there are a large number of samples1 three books are required4 ,sample ,book4--,this contains particulars of the samples 7marks1 c471 which are entered by the office-clerk as they arrive4 ,he at the same time puts on each sample the distinguishing number4 ,,example ,,of ,,page ,,of ,,sample ,,book4 ---------------------------------------- ---------------------- ,date4 ,number4 ,sample4 ,remarks4 ---------------------------------------- ---------------------- ,feb4 #a #dhb ,tough ,copper ,for ,arsenic4 #b ,x ,piece of ,metal ,for ,ni and ,cu4 #dhc ,tough ,copper4 #gc ,silver ,precipitate1 ,with ,letter4 #d casks1 #bd cwt4 #a qr4 #did ,purple ,ore1 #bjj tons4 #a ,j4,t4 ,lead ,ore1 #a ,j4,t4 ,from ,corsica4 #b ,j4,t4 #b ,j4,t4 ---------------------------------------- ---------------------- ,laboratory ,book4 ,this is the ,assayer's note-book1 in which he enters clearly the particulars of his work--the results obtained1 as well as how these results were arrived at4 ,the calculations should be done on scrap-paper1 and should not be entered1 although1 of course1 detail enough must be shown to enable the results to be recalculated4 ,,example ,,of ,,page ,,of ,,laboratory ,,book4 ,purple ,ore #e grams #ai_/aj_/hi #j4jjdb grm4 #j4jjba ------ ,colorimetric #j4jjfc #bj #j4ac ,copper #dhb ,tough ,copper #aj grams ,feb4 #a_/hi #aj4e c4c4 ,uranium4 #j4eb ,arsenic #bjhb ,tough ,copper #aj grams #ab4g c4c4 ,uranium4 #j4fc ,arsenic #dia #aj grams ,tough ,copper #ac4g c4c4 ,uranium ,feb4 #a_/hi #j4fh ,arsenic ,standard of ,uranium acetate4 #j4aej gram ,as#b,o#c #bc4c c4c4 ,uranium4 4'4 #ajj cc4 ,uranium #j4e gram ,as4 #ajjga #e grams ,tin ,ore ,cruc4 and ,sn,o#b #i4fjfe grms4 ,feb4 #c_/hi ,cruc4 and ,ash #i4dbce ------ ,sn,o#b #j4ahcj #b4hh ,tin ,the ,assay ,book4--,this is the ,official book1 and is a combination of the ,sample and ,laboratory books4 ,it corresponds with the report-forms4 ,without being loaded with detail1 it should contain sufficient to characterise each sample4 ,key to following example page of ,assay book3 ,,dr ,,date ,,reported4 ,not ,det4 ,not detected ,,example ,,of ,,page ,,of ,,assay ,,book4 ---------------------------------------- --------------------------------- ,,description ,,of ,,sample4 ,water ,assay on ---------------------------------------- - ,lost at the ,dry ,date4 ,material4 ,weight4 ,no4 #ajj ,c4,material4 ,,dr ---------------------------------------- ---------------------------- #ahhi toncwtqrslbs ,feb4 #a,tough cake copper #dhb ,arsenic1 #j4eb #g ,tough cake copper #bjhb ,arsenic1 #j4fc #g ,tough cake copper #dia ,arsenic1 #j4fh #g ,feb4 #b,nickel disc for ,c4,r4 ,x ,copper1 #gc4ge #g ,nickel1 #bd4cd ,iron1 #b4ah ----- #ajj4bg ------ ,silver precipitate1 #bd #a #j #gc ,not #d casks det4 ,silver1 #d4hea #aj ,gold1 #j4jbae ,lead1 #ai4cg ,zinc1 #b4jj ,silver1 #aehd4g ozs4 per ton ,gold1 #g4j ozs4 per ton ,purple ore #bjj #did ,not ,copper1 #j4ac #aa det4 ,sulphur #j4ae ---------------------------------------- ---------------------------- ,when the number of samples is small1 the ,sample ,book may be omitted1 and the entries made in the ,assay ,book as the samples arrive4 ,report-forms4 ,these should entail as little writing as possible in making out the report4 ,for general purposes the form given on p4 #ab is useful4 ,the quantity of substance to be taken for any particular assay depends largely upon the method of assay adopted4 ,there are1 however1 some general considerations which should be remembered1 and some devices for simplifying the calculations which should be discussed4 ,the smaller the percentage of the substance to be determined1 the larger should be the amount of the ore taken4 ,the following table will give a general idea as to this3-- ,percentage of the substance ,amount of ore1 c4 to to be determined4 be weighed4 #ajj-aj #a gram4 #aj-e #b grams4 #e-a #e #a-j4a #aj #j4a-j4ja #bj ,illustration3 ,,assay ,,note ,the rougher the method of assay adopted1 the larger should be the quantity of ore taken4 ,if the degree of accuracy attainable with the methods and instruments at the assayer's service is known1 it is easy to calculate what quantity should be taken for any particular case4 ,if the results are good within #j4jja gram1 then1 taking #a gram of ore we can report within #j4a per cent41 or if they are good within #j4jjjb gram1 taking #bj grams of ore1 we can report within #a part per #ajj1jjj1 or very closely within #f-a_/b dwt4 to the ton4 ,if it is wished to be yet more particular in reporting1 larger quantities must be taken4 ,the difficulty of manipulating very small or very large precipitates1 c41 must be borne in mind4 ,so1 too1 must the fact that the greater the weight of the final product of an assay1 the less1 as a rule1 is the percentage error4 ,the distinction between absolute and percentage error1 often overlooked1 is important4 ,if #j4e gram of silver be cupelled with #bj grams of lead1 there may be obtained a button of #j4die gram2 the absolute loss is #j4jje gram1 and this equals #a per cent4 of the silver present4 ,similarly1 cupelling #j4a gram1 the resulting button may be #j4jih2 the absolute loss is only #j4jjb gram1 but this equals #b per cent4 of the silver present4 ,in the same way the student should see that the two results1 #ia4e per cent4 and #ib4j per cent41 are really more concordant than the results #i4a per cent4 and #i4b per cent4 ,a device often adopted in practice where a large number of assays of one kind are made1 and the report is given as so many ounces or pounds to the ton1 is that known as the assay ton4 ,the assay ton may be any arbitrary and convenient weight1 but its subdivisions must bear to it the same relations as pounds and ounces bear to the actual ton4 ,on the other hand1 in a laboratory where many kinds of work are performed1 different sets of weights of this kind would only tend to confusion1 even if they were not unnecessary4 ,with a set of gram weights and its subdivisions anything may be done4 ,if it is desired to report as pounds to the ton1 then1 since there are #bbdj lbs4 to the ton1 a weight of #b4bdj grams may be taken as the assay ton1 and each #j4jja gram yielded will equal #a lb41 or #bb4d grams may represent the ton1 and each #j4ja gram a pound4 ,similarly1 since there are #cb1fff4f ozs4 troy to the ton2 if we take #cb4fffg grams as the assay ton1 each #j4jja gram will equal #a oz4 to the ton4 ,in some cases it may be convenient to have1 in addition to the usual gram weights1 one or other of the assay tons mentioned above1 but generally it is better to work on a purely decimal system1 and convert when required into ounces per ton1 c41 either by actual calculation or by reference to a set of tables4 ,,practical ,,exercises4 ,the student should practise such calculations as the following3-- #a4 ,calculate the percentages in the following cases3-- 7a7 ,ore taken1 #b grams2 copper found1 #j4baee4 7b7 #a4e gram2 iron found1 #j4hcdj4 7c7 #cj grams2 lead found1 #bc4b4 #b4 ,calculate the parts per thousand in the following3-- 7a7 ,bullion taken1 #a4a gram2 silver found1 #a4jag4 7b7 #a4ad gram2 silver found1 #a4jbf4 7c7 #j4f gram2 gold found1 #j4eejj4 #c4 ,calculate parts per #ajj1jjj in the following3-- 7a7 ,ore taken1 #bj grams2 silver found1 #j4jjge4 7b7 #ej grams2 gold found1 #j4jjbf4 7c7 ,water taken1 #ejj c4c42 solids found1 #j4abje4 #d4 ,calculate cwts4 to the ton in the following3-- 7a7 ,ore taken1 #e grams2 tin found1 #b4haf4 7b7 #e grams2 tin found1 #c4abh4 7c7 ,an ore with #fh4b per cent4 of tin4 #e4 ,calculate lbs4 to the ton in the following3-- 7a7 ,an ore with #c4bh per cent4 oxide of tin4 7b7 ,ore taken1 #bj grams2 oxide of tin found1 #a4fg4 #f4 ,calculate ozs4 7troy7 to the ton in the following3-- 7a7 ,ore taken1 #ej grams2 gold found1 #j4jjce4 7b7 #bj grams2 silver found1 #j4jbhg4 7c7 #be grains2 silver found1 #j4jafd4 #g4 ,calculate in grains per gallon3-- 7a7 #j4ea gram per litre4 7b7 #bd4f parts per #ajj1jjj4 7c7 ,solution taken1 #ajj c4c42 copper found1 #j4jjde gram4 7c7 #ej c4c42 iron found1 #j4afe gram4 #h4 ,convert into ozs4 7troy7 per ton3-- 7a7 #g loths per centner4 7b7 #cj grams per quintal4 7c7 #ae parts per #ajj1jjj4 ,,footnotes3 #a ,ether or carbon bisulphide4 #b ,such substances are best dried by pressing between folds of dry filter-paper4 ,,chapter ,,ii4 ,,methods ,,of ,,assaying4--,,dry ,,gravimetric ,,methods4 ,the methods of assaying are best classed under two heads1 ,gravimetric and ,volumetric1 in the former of which the final results are weighed1 whilst in the latter they are measured4 ,a commoner and older division is expressed in the terms much used in practice--wet assays and dry assays4 ,wet assays include all those in which solvents1 c4 7liquid at the ordinary temperature71 are mainly used2 and dry assays1 those in which solid re-agents are almost exclusively employed4 ,dry assays form a branch of gravimetric work1 and we shall include under this head all those assays requiring the help of a wind furnace4 ,wet assays1 as generally understood1 would include not only those which we class as wet gravimetric assays1 but also all the volumetric processes4 ,gravimetric ,methods aim at the separation of the substance from the other matters present in the ore1 so that it may be weighed2 and1 therefore1 they must yield the whole of the substance in a pure state4 ,it is not necessary that a metal should be weighed as metal2 it may be weighed in the form of a compound of definite and well known composition4 ,for example1 one part by weight of silver chloride contains 7and1 if pure1 always contains7 #j4gebg part of silver2 and a quantity of this metal can be as exactly determined by weighing it as chloride as by weighing it in the metallic state4 ,but in either case the metal or its chloride must be pure4 ,exact purity and complete separation are not easily obtained2 and methods are used which are defective in one or both of these respects4 ,it is well to note that an impure product increases the result1 whilst a loss of the substance decreases it2 so that if both defects exist in a process they tend to neutralise each other4 ,of dry methods generally1 it may be said that they neither give the whole of the substance nor give it pure2 so that they are only calculated to show the amount of metal that can be extracted on a manufacturing scale1 and not the actual quantity of it present4 ,their determinations are generally rough and always low4 ,the gold and silver determinations1 however1 will compare very favourably with any of the other processes for the estimation of these metals in their ores4 ,the calculation of the results of a gravimetric assay has already been referred to4 ,if the result is to be stated as percentage1 it may always be done by the following rule3--,multiply the weight of the substance got by the percentage of metal it contains1 and divide by the weight of ore taken4 ,gravimetric methods are divided into three groups3 7#a7 mechanical separations2 7#b7 dry methods2 and 7#c7 wet methods4 ,mechanical ,separations4--,under this head are classed the method of assaying tin ores1 known as vanning1 and the amalgamation assay for gold4 ,a set of sieves to determine the relative proportion of powders of different degrees of fineness is sometimes useful4 ,a set with #aj1 #bj1 #dj and #hj meshes to the inch is convenient4 ,dry ,assays4--,an important distinction between wet and dry methods of assaying is1 that in the former the substance is got into the liquid state by solution1 whilst in the latter fusion is taken advantage of4 ,the difference between solution and fusion is easily illustrated3 a lump of sugar heated over a candle-flame melts or fuses2 suspended in water it dissolves4 ,many substances which are insoluble or infusible of themselves1 become soluble or fusible when mixed with certain others2 thus1 in this way1 solution is got with the aid of reagents1 and fusion with the help of fluxes4 ,for example1 lead is insoluble in water1 but if nitric acid be added1 the metal rapidly disappears4 ,it is convenient1 but somewhat inaccurate1 to say that the acid dissolves the lead4 ,if the lead be acted on by nitric acid alone1 without water1 it is converted into a white powder1 which does not dissolve until water is added2 in this case it is obvious that the water is the solvent4 ,the function of the acid is to convert the lead into a soluble compound4 ,fluxes may act as true solvents4 ,fused carbonate of soda dissolves baric carbonate1 and perhaps in many slags true solution occurs2 but in the great majority of cases a flux is a solid reagent added for the purpose of forming a fusible compound with the earthy or stony minerals of the ore4 ,few of the minerals which occur in the gangue of an ore are fusible2 and still fewer are sufficiently fusible for the purposes of the assayer1 consequently the subject is one of importance1 and it ought to be treated on chemical principles4 ,an idea of the composition of some of the more frequently occurring rocks may be gathered from the following table1 which represents rough averages3-- ---------------------------------------- ------------------------- ,oxide,lime and ,silica4,alumina4 of ,magnesia4,alkalies4 iron ---------------------------------------- ------------------------- ,sandstone1 grit1 quartzite1 c4 #hj-ajj -- -- -- -- ,granite1 gneiss1 quartz-porphyry1 fire-clay1 c4 #gj-ge #ac-bj #b #b #e-h ,less in fire-clay4 ,mica-schist #fe #ah #e #c #c ,trachyte1 syenite #fj #ag #g #d-g #f-i ,clay-slate #fj #ah #aj #h #c ,diorite #ed #ag #ab #i #c-d ,horneblende-rock #ej #ah #ae #ab #c-d ,brick-clay #ej #cd #h #f -- ,china-clay #dg #ci -- -- -- ,basalt1 dolerite1 c4 #ej #ae #ae #af #c ,serpentine #dd -- -- #dd -- ,chalk1 limestone1 dolomite1 c4 -- -- -- #de-ee -- ---------------------------------------- ------------------------- ,silica itself1 and the silicates of alumina1 of lime1 and of magnesia1 are practically infusible2 the silicates of soda1 of potash1 and of iron are easily fusible if the base 7soda1 potash1 or oxide of iron7 be present in sufficient quantity1 and if1 in the case of the iron1 it is present mainly as lower oxide 7ferrous silicate74 ,the addition of lime1 oxide of iron1 or alkali to silicate of alumina results in the formation of a double silicate of alumina and lime1 or of alumina and iron1 c41 all of which are easily fusible4 ,similarly1 if to a silicate of lime we add oxide of iron1 or soda1 or even alumina1 a fusible double silicate will be formed4 ,thus lime1 soda1 oxide of iron1 and clay1 are fluxes when properly used2 but since lime1 clay 7and oxide of iron if there be any tendency to form peroxide71 are of themselves infusible1 any excess of these fluxes would tend to stiffen and render pasty the resulting slag4 ,so1 too1 soda1 which is a very strong base1 may act prejudicially if it be in sufficient excess to set free notable quantities of lime and magnesia1 which but for that excess would exist in combination as complex fusible silicates4 ,there are many minerals which with but little soda form a glass1 but with more yield a lumpy scoriacious mass4 ,there are many minerals1 too1 which are already basic 7for example1 calcite71 and which1 when present1 demand either a less basic or an acid flux according to the proportions in which they exist4 ,for purposes of this kind borax1 or glass1 or clay with more or less soda may be used1 and of these borax is by far the most generally useful4 ,an objection to too basic a slag 7and a very important one7 is the speed with which it corrodes ordinary crucibles4 ,these crucibles1 consisting of quartz and clay1 are rapidly attacked by lime1 soda and bases generally4 ,illustration3 ,,fig4 #d4 ,in considering what is and what is not a good slag1 certain chemical properties are of importance4 ,if a mixture of many substances be fused and allowed to solidify in a crucible1 there will be found some or all of the following4 ,at the bottom of the crucible 7fig4 #d7 a button of metal1 resting on this a speise2 then a regulus1 next a slag made up of silicates and borates and metallic oxides1 and lastly1 on the top another layer of slag1 mainly made up of fusible chlorides and sulphates4 ,in assaying operations the object is generally to concentrate the metal sought for in a button of metal1 speise or regulus1 and to leave the earthy and other impurities as far as possible in the slag2 whether there be one or two layers of slag is a matter of indifference2#c but the chemical action of the lower layer upon the speise1 or regulus1 or metal1 is of great importance4 ,a regulus is a compound of one or more of the metals with sulphur2 it is usually brittle1 often crystalline1 and of a dull somewhat greasy lustre4 ,it is essential that the slag1 when solid1 shall be so much more brittle than the regulus1 that it shall be easy to crumble1 and remove it without breaking the latter2 and it must not be basic4 ,the effect of fusing a regulus with a basic slag is well seen when sulphide of lead is fused with carbonate of soda2 the result is a button of metal 7more or less pure71 and a slag containing sulphides of lead and sodium2 and again1 if sulphide of lead be fused with an excess of oxide of lead1 a button of lead will be got1 and a slag which is simply oxide of lead 7with whatever it may have taken up from the crucible71 or if a sufficient excess has not been used1 oxide of lead mixed with some sulphide4 ,when 7as is most frequently the case7 the desire is to prevent the formation of regulus1 these reactions may be taken advantage of1 but otherwise the use of a flux having any such tendency must be avoided4 ,a good slag 7from which a regulus may be easily separated7 may be obtained by fusing1 say1 #bj grams of ore with borax #ae grams1 powdered glass #ae grams1 fluor spar1 #bj grams1 and lime #bj grams2 by quenching the slag in water as soon as it has solidified1 it is rendered very brittle4 ,sulphide of iron formed during an assay will remain diffused through the slag1 instead of fusing into a button of regulus1 if the slag contain sulphide of sodium4 ,the same is true of other sulphides if not present in too great a quantity1 and if the temperature is not too high4 ,speises are compounds of a metal or metals with arsenic4 ,they are chiefly of interest in the metallurgy of nickel1 cobalt1 and tin4 ,they are formed by heating the metal or ore in covered crucibles with arsenic and1 if necessary1 a reducing agent4 ,the product is fused with more arsenic under a slag1 consisting mainly of borax4 ,they are very fusible1 brittle compounds4 ,on exposure to the air at a red heat the arsenic and the metal simultaneously oxidize4 ,when iron1 cobalt1 nickel1 and copper are present in the same speise1 they are eliminated in the order mentioned4 ,slags from which metals are to be separated should not be too acid2 at least1 in those cases in which the metal is to be reduced from a compound1 as well as separated from earthy impurities4 ,where the object is simply to get a button of metal from a substance in which it is already in the metallic state1 but mixed with dross 7made up of metallic oxides1 such as those of zinc or iron71 from which it is desired to separate it1 an acid flux like borax is best2 or1 if the metal is easily fusible1 and there would be danger of loss of metal by oxidation or volatilising1 it may be melted under a layer of resin or fat4 ,common salt is sometimes used with a similar object1 and is often useful4 ,under certain conditions1 however1 it has a tendency to cause the formation of volatile chlorides with a consequent loss of metal4 ,in the great majority of cases1 the fusion of the metal is accompanied by reduction from the state of oxide2 in these the slag should be basic4 ,it is not easy to reduce the whole of a reducible oxide 7say oxide of copper or of iron7 from a slag in which it exists as a borate or silicate2 there should be at least enough soda present to liberate it4 ,when the object is to separate one metal1 say copper1 without reducing an unnecessary amount of another 7iron7 at the same time1 a slag with a good deal of borax is a distinct advantage4 ,the slag then will probably not be free from copper1 so that it will be necessary to powder and mix the slag with some soda and a reducing agent1 and to again fuse the slag in order to separate this residual metal4 ,in all those cases in which the slag retains an oxide of a heavy metal1 this cleaning of the slag is advisable1 and in the case of rich ores necessary4 ,slags containing sulphides are especially apt to retain the more easily reducible metals4 ,the following are the ordinary and most useful fluxes3-- ,soda4--,the powdered bicarbonate1 sold by druggists as carbonate of soda1 is generally used4 ,it gives off its water and excess of carbonic acid readily and without fusion4 ,where the melting down is performed rapidly1 the escaping gas is apt to cause trouble by frothing1 and so causing waste of the material4 ,ordinary carbonate of soda1 when hydrated 7soda crystals71 melts easily1 and gives off its water with ebullition4 ,it is unfit for use in assaying1 but when dried it can be used instead of the bicarbonate4 ,one part of the dried carbonate is equivalent to rather more than one and a half parts of the bicarbonate4 ,from two to four parts of the flux are amply sufficient to yield a fluid slag with one part of earthy matter4 ,this statement is also true of the fluxes which follow4 ,borax is a hydrated biborate of soda1 containing nearly half its weight of water4 ,when heated it swells up1 loses its water1 and fuses into a glass4 ,the swelling up may become a source of loss in the assay by pushing some of the contents out of the crucible4 ,to avoid this1 fused or dried borax may be used1 in which case a little more than half the amount of borax indicated will suffice4 ,borax will flux almost anything1 but it is especially valuable in fluxing lime1 c41 and metallic oxides2 as also in those cases in which it is desired to keep certain of the latter in the slag and out of the button of metal4 ,oxide of ,lead1 in the form of red lead or litharge1 is a valuable flux2 it easily dissolves those metallic oxides which are either infusible or difficultly fusible of themselves1 such as oxides of iron or copper4 ,the resulting slag is strongly basic and very corrosive2 no crucible will long withstand the attack of a fused mixture of oxides of lead and copper4 ,with silicates1 also1 it forms very fusible double silicates2 but in the absence of silicates and borates it has no action upon lime or magnesia4 ,whether the lead be added as litharge or as red lead1 it will exist in the slag as monoxide 7litharge72 the excess of oxygen of the red lead is thus available for oxidising purposes4 ,if this oxidising power is prejudicial1 it may be neutralised by mixing the red lead with #a per cent4 of charcoal4 ,glass3 broken beakers and flasks1 cleaned1 dried1 and powdered will do4 ,it should be free from lead4 ,fluor3 fluor-spar as free as possible from other minerals1 powdered4 ,it helps to flux phosphate of lime1 c41 and infusible silicates4 ,lime3 should be fresh and powdered4 ,it must not be slaked4 ,powdered white marble 7carbonate of lime7 will do2 but nearly double the quantity must be taken4 ,one part of lime produces the same effect as #a4h parts of the carbonate of lime4 ,tartar and black flux1 are reducing agents as well as fluxes4 ,the black flux1 which may be obtained by heating tartar1 is a mixture of carbonate of potash and charcoal4 ,,reducing ,,agents4--,the distinction between reducing agents and fluxes 7too often ignored7 is an important one4 ,fluxes yield slags2 reducing agents give buttons of regulus or of metal4 ,the action of a reducing agent is the separation of the oxygen or sulphur from the metal with which it is combined4 ,for example1 the mineral anglesite 7lead sulphate7 is a compound of lead1 sulphur1 and oxygen2 by carefully heating it with charcoal the oxygen is taken away by the charcoal1 and a regulus of lead sulphide remains4 ,if the regulus be then fused with metallic iron the sulphur is removed by the iron1 and metallic lead is left4 ,the charcoal and the iron are reducing agents4 ,but in defining a reducing agent as one which removes oxygen1 or sulphur1 from a metallic compound so as to set the metal free1 it must be remembered that sulphur itself will reduce metallic lead from fused litharge1 and that oxygen will similarly set free the metal in fused lead sulphide4 ,there is no impropriety in describing sulphur as a reducing agent2 but it is absurd to call oxygen one4 ,some confusion will be avoided if these substances and those which are opposite to them in property be classed as oxidising and de-oxidising1 sulphurising1 and de-sulphurising agents4 ,most oxidising agents also act as de-sulphurisers4 ,the de-oxidising agents most in use are the following3-- ,charcoal4--,powdered wood charcoal2 it contains more or less hygroscopic moisture and about #c or #d per cent4 of ash4 ,the rest may be considered carbon4 ,carbon heated with metallic oxides takes the oxygen2 at low temperatures it forms carbon dioxide1 and at higher ones1 carbon monoxide4 ,other conditions besides that of temperature have an influence in producing these results2 and as the quantity of charcoal required to complete a definite reaction varies with these1 it should be calculated from the results of immediate experience rather than from theoretical considerations4 ,flour4--,ordinary wheat flour is convenient in use4 ,on being heated it gives off inflammable gases which have a certain reducing effect1 and a residue of finely divided carbon is left4 ,it is likely to vary in the quantity of moisture it contains4 ,two parts of flour should be used where one part of charcoal would be otherwise required4 ,tartar4--,this is crude hydric potassic tartrate2 the purified salt1 cream of tartar1 may be used4 ,on being heated it gives off inflammable gases1 and leaves a residue formed of potassic carbonate mixed with finely divided carbon4 ,five parts of tartar should be used in the place of one of charcoal4 ,anthracite or ,culm is a kind of coal containing #ij per cent4 or more of carbon4 ,it gives off no inflammable gas4 ,it is denser1 and takes longer in burning1 than charcoal4 ,its reducing effect is little inferior to that of charcoal4 ,almost any organic substance can be used as a reducing agent1 but it is well not to select one which melts1 swells up1 or gives off much water and gas when heated in the furnace4 ,potassic ,cyanide is an easily fusible and somewhat volatile salt1 which1 when fused1 readily removes oxygen and sulphur from metallic compounds1 and forms potassic cyanate or sulphocyanate as the case may be4 ,commercial samples vary much in purity2 some contain less than #ej per cent4 of the salt4 ,for assaying1 only the better qualities should be used4 ,iron is a de-sulphurising rather than a de-oxidising agent4 ,iron is used in the form of rods1 #a_/b-;inch in diameter1 or of nails1 or of hoop iron4 ,in the last case it should be thin enough to be bent without difficulty4 ,wrought iron crucibles are very useful in the processes required for making galena assays4 ,the chief oxidising agents 7which are also de-sulphurisers7 are the following3-- ,nitre1 or ,potassic ,nitrate4--,this salt fuses very easily to a watery liquid4 ,it oxidises most combustible substances with deflagration1 and thereby converts sulphides into sulphates1 arsenides into arsenates1 and most metals into oxides4 ,in the presence of strong bases1 such as soda1 the whole of the sulphur is fully oxidised2 but in many cases some arsenic is apt to escape1 and to give rise to a peculiar garlic-like odour4 ,the sulphates of soda and potash are thus formed1 and float as a watery liquid on the surface of the slag4 ,red lead is an oxide of lead4 ,about one-quarter of its oxygen is very loosely held1 and1 hence1 is available for oxidising purposes1 without any separation of metallic lead4 ,the rest of the oxygen is also available2 but for each part of oxygen given off1 about #ac parts of metallic lead are deposited4 ,in silver assays this power of readily giving up oxygen is made use of4 ,the residual oxide 7litharge7 acts as a flux4 ,hot air is the oxidising agent in roasting operations4 ,the sulphur and arsenic of such minerals as mispickel and pyrites are oxidised by the hot air and pass off as sulphur dioxide and white arsenic4 ,the metals generally remain in the form of oxide1 mixed with more or less sulphate and arsenate4 ,the residue may remain as a powdery substance 7a calx71 in which case the process of roasting is termed calcination2 or it may be a pasty mass or liquid4 ,in the calcination of somewhat fusible minerals1 the roasting should be done at a low temperature to avoid clotting2 arsenic and sulphur being with difficulty burnt off from the clotted mineral4 ,a low temperature1 however1 favours the formation of sulphates2 and these 7if not removed7 would reappear in a subsequent reduction as sulphides4 ,these sulphates may be decomposed by a higher temperature towards the end of the operation2 their removal is rendered more certain by rubbing up the calx with some culm and re-roasting1 or by strongly heating the calx after the addition of solid ammonic carbonate4 ,in roasting operations1 as large a surface of the substance as possible should be exposed to the air4 ,if done in a crucible1 the crucible should be of the ,cornish type1 short and open1 not long and narrow4 ,for calcinations1 roasting dishes are useful3 these are broad and shallow1 not unlike saucers1 but unglazed4 ,in those cases in which the products of the roasting are liquid at the temperature used1 a scorifier 7fig4 #ch7 is suitable if it is desired to keep the liquid2 but if the liquid is best drained off as quickly as it is formed1 a cupel 7fig4 #e7 should be used4 ,illustration3 ,,fig4 #e4 ,a scorifier is essentially a roasting dish sufficiently thick to resist1 for a time1 the corrosive action of the fused metallic oxides it is to contain4 ,the essential property of a cupel is1 that it is sufficiently porous to allow the fused oxide to drain into it as fast as it is formed4 ,it should be large enough to absorb the whole of the liquid2 and of course must be made of a material upon which the liquid has no corrosive action4 ,cupels do not bear transport well2 hence the assayer generally has to make them1 or to supervise their making4 ,a quantity of bone ash is carefully mixed with water so that no lumps are formed1 and the mixture is then worked up by rubbing between the hands4 ,the bone ash is sufficiently wet when its cohesion is such that it can be pressed into a lump1 and yet be easily crumbled into powder4 ,cupel moulds should be purchased4 ,they are generally made of turned iron or brass4 ,they consist of three parts 7#a7 a hollow cylinder2 7#b7 a disc of metal2 and 7#c7 a piston for compressing the bone ash and shaping the top of the cupel4 ,the disc forms a false bottom for the cylinder4 ,this is put in its place1 and the cylinder filled 7or nearly so7 with the moistened bone ash4 ,the bone ash is then pressed into shape with the piston1 and the cupel finished with the help of three or four smart blows from a mallet4 ,before removing the piston1 turn it half-way round upon its axis so as to loosen and smooth the face of the cupel4 ,the cupel is got out by pressing up the disc of metal forming the false bottom2 the removal is more easily effected if the mould is somewhat conical1 instead of cylindrical1 in form4 ,the cupels are put in a warm place to dry for two or three days4 ,a conveniently sized cupel is #a-a_/d inches in diameter and about #c_/d inch high4 ,the cavity of the cupel is about #a_/d inch deep1 and something of the shape shown in fig4 #e4 ,illustration3 ,,fig4 #f4 ,illustration3 ,,fig4 #g4 ,illustration3 ,,fig4 #h4 ,there are two kinds of furnaces required1 the wind and muffle furnaces4 ,these are built of brick1 fire-brick1 of course1 being used for the lining4 ,they are connected with a chimney that will provide a good draught4 ,figure #f shows a section of the wind furnace1 fig4 #g a section of the muffle furnace1 and fig4 #h a general view of a group comprising a muffle and two wind furnaces suitable for general work4 ,when in operation1 the furnaces are covered with iron-bound tiles4 ,the opening under the door of the muffle is closed with a loosely fitting brick4 ,the floor of the muffle is protected with a layer of bone-ash1 which absorbs any oxide of lead that may be accidentally spilt4 ,the fire bars should be easily removable4 ,few tools are wanted2 the most important are some cast-iron moulds1 tongs 7fig4 #i71 stirrers for calcining 7fig4 #aj71 and light tongs of a special form for handling scorifiers and cupels 7see ,,silver74 ,illustration3 ,,fig4 #i4 ,illustration3 ,,fig4 #aj4 ,the coke used should be of good quality2 the formation of a fused ash 7clinker71 in any quantity1 causes ceaseless trouble1 and requires frequent removal4 ,the coke should be broken into lumps of a uniform size 7about #b in4 across7 before being brought into the office4 ,the furnace should be well packed by stirring1 raising the coke and not ramming it1 and it should be uniformly heated1 not hot below and cold above4 ,in lighting a furnace1 a start is made with wood and charcoal1 this readily ignites and sets fire to the coke1 which of itself does not kindle easily4 ,in commencing work1 add 7if necessary7 fresh coke1 and mix well2 make hollows1 and into these put old crucibles2 pack around with coke1 so that the surface shall be concave1 sloping upwards from the mouths of the crucibles to the sides of the furnace2 close the furnace1 and1 when uniformly heated1 substitute for the empty crucibles those which contain the assays4 ,it is rarely advisable to have a very hot fire at first1 because with a gradual heat the gases and steam quietly escape through the unfused mass1 while with too strong a heat these might make some of the matter in the crucible overflow4 ,moreover1 if the heat should be too strong at first1 the flux might melt and run to the bottom of the crucible1 leaving the quartz1 c41 as a pasty mass above2 with a gentler heat combination is completed1 and the subsequent fiercer heat simply melts the fusible compound into homogeneous slag4 ,the fused material may be left in the crucible and separated from it by breaking when cold4 ,it is generally more convenient to pour it into cast-iron moulds4 ,these moulds should be dry and smooth4 ,they act best when warmed and oiled or black-leaded4 ,air entering through the fire-bars of a furnace and coming in contact with hot coke combines with it1 forming a very hot mixture of carbonic acid and nitrogen2 this ascending1 comes in contact with more coke1 and the carbonic acid is reduced to carbonic oxide2 at the top of the furnace1 or in the flue1 the carbonic oxide meeting fresh air1 combines with the oxygen therein and re-forms carbonic acid4 ,in the first and third of these reactions1 much heat is evolved2 in the second1 the furnace is cooled a little4 ,it must always be remembered1 that the carbonic oxide of the furnace gases is a reducing agent4 ,when these gases are likely to exert a prejudicial effect1 and a strongly oxidising atmosphere is required1 the work is best done in a muffle4 ,,footnotes3 #c ,there is an exception to this1 as when the slag is liable to be acted on when exposed to the air and to the gases of the furnace4 ,in this case a layer of fused common salt floating on the slag1 so as to protect it from the air and furnace gases1 is a distinct advantage4 ,,chapter ,,iii4 ,,wet ,,gravimetric ,,methods4 ,in dry assays the metal is almost always separated and weighed as metal2 in wet gravimetric assays the metal is more usually weighed in the form of a definite compound of known composition4 ,the general methods of working resemble those of ordinary chemical analysis1 and their successful working is greatly helped by a knowledge of1 at any rate1 those compounds of the metal which enable it to be separated1 and of those which are the most convenient forms in which it can be weighed4 ,but the work of the assayer differs from that of the analyst1 inasmuch as the bulk of his estimations are made upon material of practically the same kind1 varying only in richness2 consequently in assaying1 it is possible 7and necessary7 to work on such a definite plan as will involve the least amount of labour in weighing and calculating4 ,the assayer connected with mining has generally two classes of material to deal with3 those comparatively rich and those comparatively poor4 ,for example1 silver in bullion and in ores2 copper precipitates or regulus1 and copper ores and slags2 and black tin and tin ores4 ,he is only occasionally called on to assay the intermediate products4 ,it is indispensable that he should have an approximate knowledge of the substance to be determined4 ,with new ores this information is best got by a qualitative testing4 ,knowing that only certain bodies are present1 it is evident that the number of separations can be reduced1 and that simple methods can be devised for arriving at the results sought for4 ,the best method is that which involves the least number of separations4 ,the reactions must be sharp and complete1 and yet not be liable to error under varying conditions4 ,to bring the richer and poorer materials under the same conditions for the assay1 a small weight1 say #a gram of the richer1 and a larger weight 7#e or #aj grams7 of the poorer1 substance is weighed up4 ,a method is then adopted which will concentrate the whole of the metal 7either during or after solution7 in a product which need not necessarily be pure4 ,the work on this product is comparatively easy4 ,in separating small quantities of a substance from a large bulk of impurities1 the group separations must not as a rule be too much relied on4 ,very large precipitates carry down small quantities of bodies not belonging to the group1 more especially when there is a tendency to form weak double compounds4 ,the re-dissolving and re-precipitating of bulky precipitates should be avoided4 ,when a large number of assays of the same kind have to be carried out1 a plan something like the following is adopted3--,the samples1 after having been dried1 are placed in order on a table at the left hand of the assayer4 ,he takes the first1 marks it with a number1 samples and weighs up the quantity required1 and transfers it to a flask1 which is similarly marked4 ,as the weighings are finished1 the samples are placed in the same order on his right hand4 ,the assistant takes the flasks in batches of four or five at a time to the fume cupboard1 where he adds a measured quantity of acid4 ,when solution has been effected1 dilution with a measured volume is generally necessary4 ,the assayer sees to this and 7whilst the funnels and filters are being prepared7 makes any separation that is necessary4 ,the filters are arranged in order on a rack 7fig4 #aa71 and need not be marked unless the precipitates or residues have subsequently to be dried4 ,the filters are washed with hot water1 and if the filtrates are wanted flasks are placed beneath1 if not1 the solution is drained off down the sink4 ,precipitation or reduction 7or whatever it may be7 is now made2 the assistant filters the prepared samples1 one at a time1 whilst the assayer is engaged with the others4 ,the same style of work is continued until the assays are completed4 ,if one should be spoiled1 it is better to allow it to stand over for assaying along with the next batch4 ,if one filters slowly or is in any way less forward than the rest1 it may lessen the accuracy of the other assays1 owing to oxidation1 c41 it should1 therefore1 be put on one side4 ,the assays are dealt with in batches of ten or twenty1 so that a large quantity of work can be quickly finished4 ,illustration3 ,,fig4 #aa4 ,when the assays are finished1 it is the duty of the assistant to clean the apparatus 7with reagents1 if necessary71 and to put the vessels in the place set apart for them4 ,flasks are best kept inverted on a rack1 so that they may be dry and clean by the next morning4 ,berlin crucibles must be cleaned and ignited4 ,the amount of apparatus employed should be as little as is feasible4 ,the assay should be carried out as much as possible in the same flask4 ,the bench must be clean1 and altogether free from apparatus not in actual use4 ,crucibles and dishes in which weighings are made should be marked with numbers or letters2 and their weights recorded1 together with the date of weighing1 in a small ledger1 which is kept in the drawer of the balance4 ,by this means a record of the wear of each piece of apparatus is obtained1 and1 what is more important1 much weighing is saved1 and increased confidence is gained4 ,the weight of each piece of apparatus need not be taken daily4 ,it will be seen from the record in the book and a knowledge of the use it has been put to how often a checking of the weight is necessary4 ,the entries are made in black lead as follows3-- ,dish1 ,a4 ,feb4 #c #i4dbaj grams4 #e #i4dbbe #f #i4dbcj #g #i4dbjj ,platinum vessels and apparatus lose1 and porcelain ones slightly gain1 weight with continued use4 ,the special details of the work is given under each assay2 certain general instructions will be given here4 ,solution4--,it is not always necessary to get the whole of the mineral in solution1 provided the body sought for is either completely dissolved or altogether left in the residue4 ,it is often only by a qualitative examination of the solution 7or residue1 as the case may be7 that the assayer can satisfy himself that it is free from the substance sought4 ,but previous experience with the same kind of ore will show to what extent this testing is necessary4 ,solution is generally best effected in flasks2 but where the resulting liquid has afterwards to be evaporated to dryness and ignited1 evaporating dishes 7fig4 #ab7 are used4 ,with them clock glasses are used as covers during solution to avoid loss through effervescence4 ,evaporating dishes are also best when an insoluble residue has to be collected1 since it is difficult to wash out most residues from a flask4 ,bumping occurs less frequently in dishes than in flasks4 ,illustration3 ,,fig4 #ab4 ,after the addition of the acid1 and mixing by agitation1 the vessel containing the substance is heated4 ,this is best done on the hot plate 7fig4 #ac74 ,this consists of a slab of cast iron about half or three-quarters of an inch thick1 supported on loose fire bricks1 and heated by two or three ring burners 7figs4 #ad and #ae74 ,the burners are connected to the gas supply by means of lead tubing1 to which they are soldered4 ,flasks and dishes after being put on the plate are not further handled until solution is complete or the evaporation is carried to dryness4 ,the hot plate is contained in a cupboard so as to be out of the reach of cold draughts4 ,illustration3 ,,fig4 #ac4 ,illustration3 ,,fig4 #ad4 ,illustration3 ,,fig4 #ae4 ,the action of the acids and other solvents is described in the chapter on ,reagents4 ,precipitation4--,in precipitating add sufficient of the reagent to complete the reaction4 ,the student must be on his guard against adding a very large excess1 which is the commoner error4 ,in some reactions the finishing point is obvious enough2 either no more precipitate is formed1 or a precipitate is completely dissolved1 or some well-marked colour or odour is developed or removed4 ,in those cases in which there is no such indication1 theoretical considerations should keep the use of reagents within reasonable limits4 ,the solutions of the reagents 7see ,,reagents7 are generally of five or ten per cent4 strength4 ,a small excess over that demanded by theory should be sufficient4 ,illustration3 ,,fig4 #af4 ,illustration3 ,,fig4 #ag4 ,illustration3 ,,fig4 #ah4 ,illustration3 ,,fig4 #ai4 ,filtration4--,solutions are best filtered hot whenever the assay allows of this being so done4 ,the precipitate should be allowed to settle1 and the clear liquid decanted on the filter with the aid of a glass rod if necessary4 ,the filter-paper must not be too large1 but at the same time it must not be overloaded with the precipitate4 ,there should be ample room for washing4 ,for general use three sizes of filter-paper are sufficient4 ,common quick filtering-paper 7,english7 is best for most work in assaying4 ,the specially prepared paper 7,swedish or ,rhenish7 is used for collecting those precipitates which have to be weighed4 ,the papers are folded as shown in fig4 #af1 and should not project above the funnel4 ,the filter-paper works better if damped with hot water4 ,in special cases filtering is hastened by means of an air-pump4 ,the apparatus used consists of a water-jet 7fig4 #ag71 which is connected with the tap1 as also with a bottle fitted as shown in fig4 #ah4 ,the pump draws the air out from the bottle1 and atmospheric pressure forces the liquid through the filter-paper4 ,the bottom of the funnel is provided with a platinum cone1 which supports the filter-paper1 and prevents its breaking4 ,the pump is only used in exceptional cases2 nearly all the filtrations required by the assayer can be made without it4 ,the usual methods of supporting the funnel during filtration are shown in fig4 #ai4 ,where the filtrate is not wanted1 pickle bottles make convenient supports4 ,after the precipitate has been thrown on the filter1 it is washed4 ,in washing1 several washings with a small quantity of water are more effective than a few with a larger quantity of that fluid4 ,the upper edge of the filter-paper is specially liable to escape complete washing4 ,excessive washing must be avoided2 the point at which the washing is complete is found by collecting a little of the filtrate and testing it4 ,the precipitate is removed from the filter-paper for further treatment by opening out the paper and by washing the precipitate with a jet of water from a wash-bottle into a beaker1 or back through the funnel into the flask4 ,in some cases1 when the precipitate has to be dissolved in anything in which it is readily soluble1 solution is effected in the filter itself allowing the liquid to run through as it is formed4 ,drying and ,igniting4--,precipitates1 as a rule1 require drying before being ignited4 ,with small precipitates the filter-paper may be opened out1 and placed on a warm asbestos slab till dry2 or the funnel and the filter with the precipitate is placed in a warm place1 and supported by any convenient means4 ,the heat must never be sufficient to char the paper4 ,some precipitates must be dried at a temperature not higher than #ajj ,c4 ,these are placed in the water-oven 7fig4 #bj71 and1 when apparently dry1 they are taken from the funnel1 placed between glasses1 and then left in the oven till they cease to lose weight4 ,such precipitates are collected on tared filters4 ,those precipitates which will stand a higher temperature are dried in the hot-air oven at a temperature of from #abj to #aej4 ,the drying is continued until they appear to be free from moisture1 and until the precipitate ceases to adhere to the filter4 ,in drying sulphides the heat must not be raised to the melting point of sulphur1 since1 if there is any free sulphur present1 it fuses and filters through4 ,illustration3 ,,fig4 #bj4 ,the precipitate1 having been dried1 is transferred to a watch-glass4 ,the filter-paper is opened out over a sheet of note-paper1 and1 with a camel-hair brush1 the precipitate is gently brought into the glass4 ,most precipitates come away easily1 and the transfer can be made without apparent loss4 ,the watch-glass is covered by the funnel1 and the filter-paper 7folded into a quadrant7 held by the tweezers and set fire to with the flame of a ,bunsen burner4 ,it is allowed to burn over the crucible1 into which the black bulky ash is allowed to drop1 and two or three drops of nitric acid are then added4 ,the crucible is placed on a pipe-stem triangle 7fig4 #ba71 supported on a tripod4 ,it is at first heated gently with a ,bunsen burner1 and afterwards more strongly1 until the residue is free from carbon4 ,it is cooled1 and treated with any acid necessary to convert the small amount of precipitate into the state in which it is to be weighed2 heated again1 and cooled4 ,the main precipitate is transferred to the crucible1 and the heating repeated very gently at first1 but more strongly towards the end of the operation4 ,it is next placed in the muffle1 and1 after two or three minutes at a red heat1 it is removed and allowed to cool in the desiccator before weighing4 ,this is for bodies that will bear a red heat2 for those compounds that require a lower temperature the heating in the muffle is omitted4 ,the muffle used for this purpose must not be used at the same time for cupelling2 a gas muffle 7fig4 #bb71 such as one of ,fletcher's1 is best4 ,a desiccator 7fig4 #bc7 is an air-tight vessel which prevents access of moisture1 c41 to the substance4 ,usually the air in it is kept dry by means of a basin containing sulphuric acid4 ,illustration3 ,,fig4 #ba4 ,illustration3 ,,fig4 #bb4 ,illustration3 ,,fig4 #bc4 ,the crucible is removed from the muffle with the tongs and carried to the desiccator4 ,it is best1 in an office1 to have a large desiccator permanently fixed alongside the balance1 into which all substances may be put before being weighed4 ,the substance is removed from the bench or muffle in the small hand apparatus generally sold1 and carried to the balance room to be transferred to the large desiccator1 where it is allowed to become thoroughly cold before being weighed4 ,twenty minutes is generally the time allowed after ignition before it is advisable to weigh4 ,bodies allowed to cool in the air after they have been ignited will absorb moisture1 and hot bodies placed in the balance-pan will disturb the equilibrium and show false results4 ,compounds that absorb moisture must be weighed quickly2 they should1 therefore1 be weighed in covered vessels4 ,such compounds are detected by their continually-increasing weight4 ,they should be ignited and weighed again in a well-covered dish4 ,substances that have been washed with alcohol1 ether1 or any readily volatile liquid are dried in the water oven4 ,they quickly dry if there is no water present1 and are generally fit for weighing in less than one hour4 ,sometimes drying for a few minutes only will be sufficient4 ,the weight of the crucible and precipitate having been obtained1 the weight of the crucible and ash is deducted2 for example-- ,crucible and precipitate #aj4ahc grams4 ,crucible and ash #i4ebg ------ #j4fef ,the weight of the ash is best added to that of the crucible4 ,the amount of ash in filter-papers must not be neglected1 although papers are now made almost free from ash1 and the amount to be deducted is found by taking eight or ten papers and burning them until they become white1 and then weighing the ash4 ,the amount varies from #j4jjd to #j4jjje gram for different papers4 ,having determined the ash1 place in the balance-drawer three of the filter-papers pinned together1 with the weights marked on them in the way shown in fig4 #bd1 so as to be readily seen when there is occasion to refer to them4 ,illustration3 ,,fig4 #bd4 ,it must be remembered that the determination of small quantities of substances generally involves the use of reagents which are often contaminated1 as an impurity1 with the body sought for4 ,thus1 in assaying silver1 the oxide of lead or metallic lead used is rarely free from silver2 and in the case of arsenic1 the acids1 zinc or ferric chloride are sure to contain arsenic4 ,the same observation applies to the precipitation of lead by zinc1 c4 ,the errors caused by these impurities are more marked in the determination of material having small quantities of metal than in that of ores which contain larger quantities4 ,errors of this kind are counteracted or neutralised by blank or blind determinations4 ,these consist in carrying out by the side of and during the assay a duplicate experiment with the reagents only1 which are thereby subjected to the same processes of solution1 evaporation1 filtration1 c4 ,the final result thus obtained is deducted from that given by the assay1 the difference gives the corrected result4 ,in some cases1 where it is desired or necessary to have a tangible residue or precipitate1 some pure inert material is added4 ,,chapter ,,iv4 ,,volumetric ,,assays4 ,these have been already described as those in which the results are got by measuring1 either--7#a7 the volume of a reagent required to complete some reaction1 or 7#b7 the volume of the resulting product4 ,for example1 if a permanganate of potash solution be added to a solution containing a weighed amount of iron1 dissolved in sulphuric acid1 the strong colour of the permanganate of potash will be removed until a certain quantity of it has been added4 ,repeating the experiment1 it will be found that the same amount of iron decolorises the same volume of the permanganate solution within certain narrow limits of variation1 known as error of experiment4 ,this error is due to variation in the method of working and to slight differences in the weighings and measurings2 it is present in all experimental methods1 although the limits of variation are wider in some than in others4 ,apart from this error of experiment1 however1 it is certain that a given volume of the permanganate of potash solution corresponds to a definite weight of iron1 so that if either is known the other may be calculated4 ,similarly1 if a known weight of zinc 7or of carbonate of lime7 be dissolved in hydrochloric acid1 a gas will be given off which can be measured1 and so long as the conditions of the experiment do not vary1 the same weight of zinc 7or of carbonate of lime7 gives off the same volume of gas4 ,the weight of the one can be determined from the volume of the other4 ,or1 again1 the quantity of some substances may be measured by the colour of their solutions1 on the principle that1 other things being equal1 the colour of a solution depends upon the quantity of colouring matter present4 ,so that if two solutions of the same substance are equally coloured they are of equal strength4 ,in this way an unknown may be compared with a known strength1 and a fairly accurate determination may be made4 ,these three illustrations serve as types of the three chief classes of volumetric assays--titrometric1 gasometric1 and colorimetric4 ,titrometric ,assays4--,within the limits of the error of experiment1 a definite volume of a solution or gas represents a certain weight of metal or other substance1 hence the exact weight may be determined by experiment4 ,the error of experiment may be reduced to insignificant dimensions by repeating the experiment1 and taking the mean of three or four determinations4 ,this will at the same time show the amount of variation4 ,thus1 if #j4e gram of iron were dissolved and found to require #ej4c cubic centimetres of the solution of permanganate of potash1 and if on repeating1 #ej4d1 #ej4b1 and #ej4c c4c4 were required1 the experimenter would be justified in saying that #ej4c c4c4 of the permanganate solution represent #j4e gram of iron1 and that his results were good within #j4b c4c4 of the permanganate solution4 ,so that if in an unknown solution of iron1 #ej4e c4c4 of the permanganate solution were used up1 he could state with confidence that it contained a little more than #j4e gram of iron4 ,with a larger experience the confidence would increase1 and with practice the experimental error will diminish4 ,but supposing that the unknown solution required1 say1 #ajj4e instead of #ej4e c4c41 he would not be justified in saying that1 since #ej4c c4c4 are equivalent to #j4e gram1 #ajj4f c4c4 are equivalent to twice that amount2 and that1 consequently1 the unknown solution contained a little less than #a gram of iron2 or1 at least1 he could not say it except he 7or some one else7 had determined it by experiment4 ,but if on dissolving #a gram of iron1 he found it to require #ajj4f c4c4 of the solution1 and in another experiment with #j4h gram of iron that #hj4e c4c4 of the solution were required1 he would be justified in stating that the volume of solution required is proportional to the quantity of metal present4 ,there are a large number of volumetric assays of which this is true1 but that it is true in any particular case can only be proved by experiment4 ,even where true it is well not to rest too much weight upon it1 and in all cases the quantity of metal taken1 to determine the strength of the solution used1 should not differ widely from that present in the assay4 ,there are certain terms which should be explained here4 ,when the solution of a reagent is applied under such conditions that the volume added can be correctly determined1 the operation is called titrating1 the solution of the reagent used the standard solution1 and the process of determining the strength of the standard solution is standardising4 ,the standard is the quantity of metal equivalent to #ajj c4c4 of the standard solution4 ,standard ,solutions4--,in making these the salt is accurately weighed and transferred to a litre flask1 or to the graduated cylinder1 and dissolved4 ,the method of dissolving it varies in special cases1 and instructions for these will be found under the respective assays4 ,generally it is dissolved in a small quantity of liquid1 and then diluted to the mark4 ,for those substances that require the aid of heat1 the solution is made in a pint flask1 cooled1 and transferred2 after which the flask is well washed out4 ,after dilution1 the liquids in the measuring vessel must be thoroughly mixed by shaking4 ,this is more easily and better done in the cylinder than in the litre flask4 ,the solution is next transferred to a dry ,winchester bottle and labelled4 ,the label may be rendered permanent by waxing it4 ,standard solutions should not be kept in a place exposed to direct sunlight4 ,oxidising and reducing solutions1 such as those of permanganate of potash1 ferrous sulphate1 iodine1 hyposulphite of soda1 c41 gradually weaken in strength2 the solutions of other salts are more stable2 while those of potassium bichromate and baric chloride are almost permanent4 ,solutions of potassium permanganate may be kept for a month or so without much change4 ,the solutions of hyposulphite of soda and of iodine should be examined weekly4 ,ferrous sulphate solutions1 if acidulated with sulphuric acid1 may be depended on for two or three weeks without fresh standardising4 ,before filling the burette1 the ,winchester bottle should be well shaken and a portion of about #ej or #ajj c4c4 poured into a dry beaker or test-glass4 ,besides the standard solutions1 which are required for titrating an assay1 permanent solutions of the metal or acid of equivalent strength are very useful4 ,when the finishing point of a titration has been overstepped 7i4e41 the assay has been overdone71 a measured volume1 say #e or #aj c4c41 of a solution containing the same metal may be added4 ,the titration can then be continued1 but more cautiously1 and the value in c4c4 for the quantity added be deducted from the final reading4 ,standardising4--,suppose the object is to standardise a solution of permanganate similar to that referred to above4 ,a convenient quantity of iron 7say #j4e gram7 would be weighed out1 dissolved in dilute sulphuric acid1 and the solution titrated4 ,suppose #di4f c4c4 of the permanganate solution are required1 then #di4f 3 #j4e 33 #ajj 3 x x #a4jjh gram4 ,this result1 #a4jjh gram1 is the standard4 ,when a gas is measured1 the standard may be calculated in the same way4 ,for example3 with #j4bbd gram of zinc1 #ge4h c4c4 of gas were obtained4 ,then the quantity of zinc equivalent to #ajj c4c4 of the gas is got by the proportion4 #ge4h 3 #j4bbd 33 #ajj 3 x x #j4biee gram4 ,using the term standard in this sense1 the following rules hold good3-- ,to find the weight of metal in a given substance3--,multiply the standard by the number of c4c4 used and divide by #ajj4 ,for example3 a piece of zinc was dissolved and the gas evolved measured #gc4i c4c4 ,then by the rule1 #j4bieegc4i_/ajj should give the weight of the piece of zinc4 ,this gives #j4bahd gram4 ,to find the percentage of metal in a given substance3--,multiply the standard by the number of c4c4 used and divide by the weight of substance taken4 ,for example3 if #b grams of a mineral were taken1 and if on titrating with the permanganate solution 7standard #a4jjh7 #fj4d c4c4 were required1 then 7#a4jjhfj4d7_/b #cj4dd4 ,this is the percentage4 ,if the standard is exactly #a gram1 and #a gram of ore is always taken1 these calculations become very simple4 ,the c4c4 used give at once the percentage1 or divided by #ajj give the weight of metal4 ,if it is desired to have a solution with a standard exactly #a4j gram1 it is best first to make one rather stronger than this1 and then to standardise carefully4 ,divide #ajjj by the standard thus obtained and the result will be the number of c4c4 which must be taken and be diluted with water to #a litre4 ,for example3 suppose the standard is #a4jjh1 then #ajjj_/a4jjh gives #iib1 and if #iib c4c4 be taken and diluted with water to #ajjj c4c4 a solution of the desired strength will be obtained4 ,the standard of this should be confirmed4 ,a simpler calculation for the same purpose is to multiply the standard by #ajjj2 this will give the number of c4c4 to which #a litre of the solution should be diluted4 ,in the above example a litre should be diluted to #ajjh c4c4 ,it has been assumed in these rules that the titration has yielded proportional results2 but these are not always obtained4 ,there can be no doubt that in any actual re-action the proportion between any two re-agents is a fixed one1 and that if we double one of these then exactly twice as much of the other will enter into the re-action2 but in the working it may very well be that no re-action at all will take place until after a certain excess of one or of both of the re-agents is present4 ,in titrating lead with a chromate of potash solution1 for example1 it is possible that at the end of the titration a small quantity of the lead may remain unacted on2 and it is certain that a small excess of the chromate is present in the solution4 ,so1 too1 in precipitating a solution of silver with a standard solution of common salt1 a point is reached at which a small quantity of each remains in solution2 a further addition either of silver or of salt will cause a precipitate1 and a similar phenomenon has been observed in precipitating a hydrochloric acid solution of a sulphate with baric chloride4 ,the excess of one or other of the re-agents may be large or small2 or1 in some cases1 they may neutralise each other4 ,considerations like these emphasise the necessity for uniformity in the mode of working4 ,whether a process yields proportional results1 or not1 will be seen from a series of standardisings4 ,having obtained these1 the results should be arranged as in the table1 placing the quantities of metal used in the order of weight in the first column1 the volumes measured in the second1 and the standards calculated in the third4 ,if the results are proportional1 these standards will vary more or less1 according to the delicacy of the process1 but there will be no apparent order in the variation4 ,the average of the standards should then be taken4 -------------------------------------- ,weight4 ,volume found4 ,standard -------------------------------------- #j4bafj gram #gb4i c4c4 #j4bifc #j4bahe #gc4i #j4bieg #j4bcfe #gi4i #j4biei #j4bddj #hb4c #j4bifd #j4beee #he4i #j4bigd -------------------------------------- ,any inclination that may be felt for obtaining an appearance of greater accuracy by ignoring the last result must be resisted4 ,for1 although it would make no practical difference whether the mean standard is taken as #j4bifa or #j4bifc1 it is well not to ignore the possibility that an error of #j4d c4c4 may arise4 ,a result should only be ignored when the cause of its variation is known4 ,in this series the results are proportional1 but the range of weights 7#j4baf-j4beee gram7 is small4 ,all processes yield fairly proportional results if the quantities vary within narrow limits4 ,as to results which are not proportional1 it is best to take some imaginary examples1 and then to apply the lesson to an actual one4 ,a series of titrations of a copper solution by means of a solution of potassic cyanide gave the following results3-- ---------------------------------------- - ,copper taken4 ,cyanide used4 ,standard4 ---------------------------------------- - #j4a gram #aa4i c4c4 #j4hdjc #j4b #bc4g #j4hdch #j4c #ce4f #j4hdbf #j4d #dg4f #j4hdjc ---------------------------------------- - ,these are proportional1 but by using a larger quantity of acid and ammonia in the work preliminary to titration1 we might have had to use #a c4c4 of cyanide solution more in each case before the finishing point was reached4 ,the results would then have been3 ---------------------------------------- - ,copper taken4 ,cyanide used4 ,standard4 ---------------------------------------- - #j4a gram #ab4i c4c4 #j4ggeb #j4b #bd4g #j4hjig #j4c #cf4f #j4haia #j4d #dh4f #j4hbcj ---------------------------------------- - ,it will be noted that the value of the standard increases with the weight of metal used2 and calculations from the mean standard will be incorrect4 ,by subtracting the lowest standardising from the highest1 a third result is got free from any error common to the other two2 thus3-- #j4d gram #dh4f c4c4 cyanide4 #j4a #ab4i --- ---- #j4c #ce4g ,and the standard calculated from this corrected result is #j4hdjd4 ,further1 if #j4c gram requires #ce4g c4c41 then #j4a gram should require #aa4i c4c41 or #a4j c4c4 less than that actually found4 ,we may therefore use the following rules for working processes which do not yield proportional results4 ,make a series of two or three titrations1 using very different quantities of metal in each4 ,subtract the lowest of these from the highest1 and calculate the standard with the remainder4 ,calculate the volume required by this standard in any case1 and find the excess or deficit1 as the case may be4 ,if an excess1 subtract it from the result of each titration2 if a deficit1 add it2 and use the standard in the usual way4 ,the following table shows an actual example3-- ---------------------------------------- ,chalk taken4 ,gas obtained4 ,standard4 ---------------------------------------- #j4jhgc gram #ag4h c4c4 #j4dijd #j4acje #bg4c #j4dghj #j4afij #ce4h #j4dgba #j4aije #dj4d #j4dgae #j4bdfj #eb4e #j4dfhf #j4cjjj #fd4j #j4dfhg ---------------------------------------- ,it will be seen that the standard decreases as the quantity of chalk increases2 this points to a deficiency in the quantity of gas evolved4 ,then #j4cjjj #fd4j c4c4 #j4jhgc #ag4h ------ ---- #j4babg #df4b and #j4babgajj_/df4b #j4dfjd4 ,then1 multiplying the weight of chalk taken by #ajj1 and dividing by #j4dfjd1 we get the calculated results of the following table3-- ---------------------------------------- ---------------- ,chalk taken4 ,gas found4 ,gas calculated4 ,difference4 ---------------------------------------- ---------------- #j4jhgc gram #ag4h c4c4 #ah4i c4c4 -#a4a c4c4 #j4acje #bg4c #bh4c -#a4j #j4afij #ce4h #cf4g -#j4i #j4aije #dj4d #da4d -#a4j #j4bdfj #eb4e #ec4d -#j4i #j4cjjj #fd4j #fe4a -#a4a ---------------------------------------- ---------------- ,by adding #a c4c4 to the quantity of gas obtained1 and taking #j4dfjd as the standard1 the calculated results will agree with those found with a variation of #j4a c4c4 ,when a large number of assays of the same kind are being made1 this method of calculation is convenient2 when1 however1 only one or two determinations are in question1 it is easier to make a couple of standardisings1 taking quantities as nearly as possible the same as those present in the assays4 ,sometimes it is necessary to draw up a table which will show1 without calculation1 the weight of substance equivalent to a given volume of gas or of solution4 ,the substance used for standardising should be1 whenever possible1 a pure sample of the substance to be determined--that is1 for copper assays pure copper should be used1 for iron assays pure iron1 and so on2 but when this cannot be got an impure substance may be used1 provided it contains a known percentage of the metal1 and that the impurities present are not such as will interfere with the accuracy of the assay4 ,including compounds with these1 the standard may be calculated by multiplying the standard got in the usual way1 by the percentage of metal in the compound or impure substance1 and dividing by #ajj4 ,if1 for example1 the standard #a4jjh gram was obtained by using a sample of iron containing #ii4g per cent4 of metal1 the corrected standard would be #a4jjhii4g_/ajj #a4jje4 ,in volumetric analysis the change brought about must be one in which the end of the reaction is rendered prominent either by a change of colour or by the presence or absence of a precipitate4 ,if the end of the reaction or finishing-point is not of itself visible1 then it must be rendered visible by the use of a third reagent called an indicator4 ,for example1 the action of sulphuric acid upon soda results in nothing which makes the action conspicuous2 if1 however1 litmus or phenolphthalein be added the change from blue to red in the first case1 or from red to colourless in the second1 renders the finishing-point evident4 ,some indicators cannot be added to the assay solution without spoiling the result2 in which case portions of the assay solution must be withdrawn from time to time and tested4 ,this withdrawal of portions of the assay solution1 if rashly done1 must result in loss2 if1 however1 the solution is not concentrated1 and if the portions are only withdrawn towards the end of the titration1 the loss is very trifling1 and will not show-up on the result4 ,the usual plan adopted is to have a solution of the indicator placed in drops at fairly equal intervals distributed over a clean and dry white porcelain-plate3 a drop or two of the solution to be tested is then brought in contact with one of these and the effect noted4 ,another plan is to have thin blotting-paper1 moistened with a solution of the indicator and dried2 a drop of the solution to be tested placed on this shows the characteristic change4 ,when the assay solution contains a suspended solid which interferes with the test1 a prepared paper covered with an ordinary filter-paper answers very well2 a drop of the solution to be tested is placed on the filter-paper1 and1 sinking through1 shows its effect on the paper below4 ,except when otherwise stated1 all titrations should be made at the ordinary temperature2 cooling1 if necessary1 by holding the flask under the tap4 ,when a titration is directed to be made in a boiling solution1 it must be remembered that the standard solution is cold1 and that every addition lowers the temperature of the assay4 ,on running the solution from the burette into the assay1 do not let it run down the side of the flask4 ,if a portion of the assay has to be withdrawn for testing1 shake the flask to ensure mixing1 and then take out a drop with the test-rod2 the neglect of these precautions may give a finishing-point too early4 ,this is generally indicated by a sudden finish1 in which case on shaking the flask and again testing no reaction is got4 ,do not remove the drop on the point of the burette with the test-rod2 let it remain where it is or drop it into the solution by carefully opening the clip4 ,generally the methods of working are as follows3-- 7#a7 ,when the finishing-point depends on a change of colour in the solution4--,increase the bulk of the assay up to from #ajj to #aej c4c4 with water4 ,boil or cool1 as the case may be4 ,run in the standard solution from a burette speedily1 until the re-agent appears to have a slower action1 and shake or stir all the time4 ,then run #a c4c4 or so at a time1 still stirring1 and finally add drops until the colour change is got4 7#b7 ,when an outside-indicator is used4--,pour the standard solution from a burette into the assay until #e or #f c4c4 from the finishing-point2 then run in #a c4c4 at a time 7stirring and testing on the plate between each7 until the indicator shows the change wanted1 and deduct #j4e c4c4 for excess4 ,when greater accuracy is sought for a duplicate assay is made4 ,in this case the standard solution is run in close up to the end1 and the operation is finished off with a few drops at a time4 7#c7 ,where the finishing-point depends upon the absence of a precipitate and no outside-indicator is used4--,as in the last case1 run in the standard solution up to within a few c4c4 of the end1 then run in #a c4c4 at a time until a precipitate is no longer formed1 but here #a4e c4c4 must be deducted for excess1 since it is evident that the whole of the last c4c4 must have been1 and a portion of the previous one may have been1 in excess4 ,indirect ,titration4--,the action of permanganate of potash upon a ferrous solution is one of oxidation1 hence it is evident that if any other oxidising agent is present it will count as permanganate4 ,in such a case the titration can be used 7indirectly7 to estimate the quantity of such oxidising agent1 by determining how much less of the permanganate is used4 ,for example1 suppose that #a gram of iron dissolved in sulphuric acid requires #ajj c4c4 of standard permanganate to fully oxidise it1 but that the same amount of iron only requires #ce4f c4c4 of the same standard permanganate if it has been previously heated with #j4e gram of black oxide of manganese4 ,here it is evident that #j4e gram of black oxide does the work of #fd4d c4c4#d of the permanganate solution1 and that these quantities are equivalent2 moreover1 if #fd4d c4c4 correspond with #j4e gram1 then #ajj c4c4 correspond with #j4ggfd which is the standard4 ,on theoretical grounds1 and by a method of calculation which will be explained further on 7under the heading ,calculations from ,formul71 it can be found that if the standard for iron is #a gram1 that for the black oxide will be #j4ggfd gram4 ,the principles of these indirect titrations become clearer when expressed in a condensed form4 ,thus1 in the example selected1 and using the formul ,fe ,iron1 ,k,mn,o#d permanganate of potash1 and ,mn,o#b oxide of manganese1 we have3-- 7#a7 #a gram ,fe #ajj c4c4 ,k,mn,o#d 7#b7 #a gram ,fe #ce4f c4c4 ,k,mn,o#d #j4e gram ,mn,o#b 4'4 #ajj c4c4 ,k,mn,o#d #ce4f c4c4 ,k,mn,o#d #j4e gram ,mn,o#b 7#ajj-ce4f7 c4c4 ,k,mn,o#d #j4e gram ,mn,o#b #fd4d c4c4 ,k,mn,o#d #j4e gram ,mn,o#b ,the iron does not enter into the calculation if the same quantity is present in the two experiments4 ,an indirect titration thus requires three determinations1 but if more than one assay is to be carried on1 two of these need not be repeated4 ,the standard is calculated in the usual way4 ,colorimetric ,assays4--,these are assays in which the colour imparted to a solution by some compound of the metal to be determined is taken advantage of2 the depth of colour depending on the quantity of metal present4 ,they are generally used for the determination of such small quantities as are too minute to be weighed4 ,the method of working is as follows3--,a measured portion of the assay solution 7generally #b_/c1 #a_/b1 #a_/c1 or #a_/d of the whole71 coloured by the substance to be estimated1 is placed in a white glass cylinder standing on a sheet of white paper or glazed porcelain4 ,into an exactly similar cylinder is placed the same amount of re-agents1 c41 as the portion of the assay solution contains1 and then water is added until the solutions are of nearly equal bulk4 ,next1 a standard solution of the metal being estimated is run in from a burette1 the mixture being stirred after each addition until the colour approaches that of the assay4 ,the bulk of the two solutions is equalised by adding water4 ,then more standard solution is added until the tints are very nearly alike4 ,next1 the amount added is read off from the burette1 still more is poured in until the colour is slightly darker than that of the assay1 and the burette read off again4 ,the mean of the readings is taken1 and gives the quantity of metal added4 ,it equals the quantity of metal in the portion of the assay4 ,if this portion was one-half of the whole1 multiply by two2 if one-third1 multiply by three1 and so on4 ,when the quantity of metal in very dilute solutions is to be determined1 it is sometimes necessary to concentrate the solutions by boiling them down before applying the re-agent which produces the coloured compound4 ,such concentration does not affect the calculations4 ,gasometric ,assays4--,gasometric methods are not much used by assayers1 and1 therefore1 those students who wish to study them more fully than the limits of this work will permit1 are recommended to consult ,winkler and ,lunge's text-book on the subject4 ,the methods are without doubt capable of a more extended application4 ,in measuring liquids1 ordinary variations of temperature have but little effect1 and variations of atmospheric pressure have none at all1 whereas with gases it is different4 ,thus1 #ajj c4c4 of an ordinary aqueous solution would1 if heated from #aj ,c4 to #bj ,c41 expand to about #ajj4ae c4c4 #ajj c4c4 of a gas similarly warmed would expand to about #ajc4e c4c41 and a fall of one inch in the barometer would have a very similar effect4 ,and in measuring gases we have not only to take into account variations in volume due to changes in temperature and atmospheric pressure1 but also that which is observed when a gas is measured wet and dry4 ,water gives off vapour at all temperatures1 but the amount of vapour is larger as the temperature increases4 ,by ignoring these considerations1 errors of #c or #d per cent4 are easily made2 but1 fortunately1 the corrections are simple1 and it is easy to construct a piece of apparatus by means of which they may be reduced to a simple calculation by the rule of three4 ,the volume of a gas is1 in practice1 usually reduced to that which it would be at a temperature of #j ,c41 when the column of mercury in the barometer is #gfj mm4 high4 ,but1 although convenient1 this practice is not always necessary4 ,the only thing required is some way of checking the variations in volume1 and of calculating what the corrected volume would be under certain fixed conditions4 ,suppose that at the time a series of standardisings is being made1 #ajj c4c4 of air were confined in a graduated tube over moist mercury4 ,these #ajj c4c4 would vary in volume from day to day1 but it would always be true of them that they would measure #ajj c4c4 under the same conditions as those under which the standardisings were made4 ,if1 then1 in making an actual assay1 #ce4d c4c4 of gas were obtained1 and the air in the tube measured #aje c4c41 we should be justified in saying1 that if the conditions had been those of the standardising1 the #aje c4c4 would have measured #ajj c4c41 and the #ce4d c4c4 would have been #cc4g2 for #aje3 #ajj33 #ce4d3 #cc4g4 ,the rule for using such a piece of apparatus for correcting volumes is3--,multiply the c4c4 of gas obtained by #ajj1 and divide by the number of c4c4 of air in the apparatus4 ,if it is desired to calculate the volumes under standard conditions 7that is1 the gas dry1 at #j ,c4 and #gfj mm4 barometric pressure7 the calculations are easily performed1 but the temperature and pressure must be known4 ,correction for ,moisture4--,the vapour tension of water has been accurately determined for various temperatures1 and it may be looked upon as counteracting the barometric pressure4 ,for example1 at #ae ,c4 the vapour tension equals #ab4g millimetres of mercury2 if the barometer stood at #gej mm41 the correction for moisture would be made by subtracting #ab4g from #gej1 and taking #gcg4c mm4 to be the true barometric pressure4 ,the vapour tensions for temperatures from #j ,c4 to #bj ,c4 are as follows3-- ---------------------------------------- ----------- ,temp4 ,tension4 ,temp4 ,tension4 ,temp4 ,tension4 ---------------------------------------- ----------- #j #d4f mm4 #g #g4e mm4 #ad #aa4i mm4 #a #d4i mm4 #h #h4j mm4 #ae #ab4g mm4 #b #e4c mm4 #i #h4f mm4 #af #ac4e mm4 #c #e4g mm4 #aj #i4b mm4 #ag #ad4d mm4 #d #f4a mm4 #aa #i4h mm4 #ah #ae4c mm4 #e #f4e mm4 #ab #aj4e mm4 #ai #af4c mm4 #f #g4j mm4 #ac #aa4b mm4 #bj #ag4d mm4 ---------------------------------------- ------------ ,the correction for pressure is3--,multiply the volume by the actual pressure and divide by #gfj4 ,the correction for temperature3--,multiply the volume by #bgc and divide by the temperature 7in degrees ,centigrade7 added to #bgc4 ,for all three corrections the following rules hold good4 ,to reduce to #j ,c4 and #gfj mm4 dry4 ,volume #j4ceib 7,pressure-tension7 ,corrected volume -------------------------------------- ,temperature #bgc ,to find the volume1 which a given volume under standard conditions would assume1 if those conditions are altered4 ,volume #b4ghd 7,temperature #bgc7 ,resulting volume ------------------------------------ ,pressure - tension ,as an example1 we will suppose that it is desired to enclose in the apparatus referred to on p4 #de1 a volume of air1 which1 when dry 7at #j ,c4 and #gfj mm471 shall measure #ajj c4c41 whilst the actual temperature is #ae ,c41 and the pressure #gej mm4 ,the second formula is the one to be used1 and we get #ajh4g c4c4 #ajj c4c4#b4ghdbhh ,required volume ---------------------- #gej-ab4g #hjagi4b ------- #gcg4c #ajh4g c4c4 ,,footnotes3 #d #ajj-ce4f #fd4d4 ,,chapter ,v4 ,,weighing ,,and ,,measuring4 ,weighing4--,the system of weights and measures which we have adopted is the ,french or metric system2 in this the gram 7#ae4dc grains7 is the unit of weight2 the only other weight frequently referred to is the milligram1 which is #j4jja1 or #a_/ajjj gram4 ,the unit of volume is the cubic centimetre1 which is approximately the volume of #a gram of water1 and which thus bears to the gram the same relation as grain-measures bear to grains4 ,it is usual to write and even pronounce cubic centimetre shortly as c4c41 and the only other denomination of volume we shall have occasion to use is the litre1 which measures #ajjj c4c41 and is roughly #a-c_/d pints4 ,the weights used are kept in boxes in a definite order1 so that the weights on the balance can be counted as well by noting those which are absent from the box as by counting those present on the scale-pan4 ,the weights run #ej1 #bj1 #aj1 #aj1 #e1 #b1 #a1 #a and #a grams1 and are formed of brass4 ,the fractions of the gram are generally made of platinum or of aluminium1 and are arranged in the following order3--#j4e1 #j4b1 #j4a1 #j4a1 and #j4je1 #j4jb1 #j4ja1 #j4ja4 ,these may be marked in this way1 or they may be marked #ejj1 #bjj1 #ajj1 #ajj1 #ej1 #bj1 #aj1 #aj2 the #ejj meaning #ejj milligrams4 ,some makers send out weights in the series #ej1 #bj1 #bj1 #aj1 c4 ,weights of less than #j4ja gram are generally present in a box1 but it is much more convenient to work with a rider4 ,this is a piece of wire which in the pan weighs #j4ja gram2 it is made in such a form that it will ride on the beam1 and its effective weight decreases as it approaches the centre4 ,if the arm of the beam is divided into tenths1 then each tenth counting from the centre outward equals #j4jja gram or #a milligram1 and if these tenths be further subdivided the fractions of a milligram are obtained2 and these give figures in the fourth place of decimals4 ,a fairly good balance should be sensitive to #j4jjja gram4 ,the weights must never be touched with the fingers1 and the forceps for moving them is used for no other purpose4 ,when not in actual use the box is kept closed4 ,the weights must not be allowed to remain on the pan of the balance4 ,the balance-case must not be open without some reason4 ,it must be fixed level1 and1 once fixed1 must not be needlessly moved4 ,the bench on which it stands should be used for no other purpose1 and no one should be allowed to lean upon it4 ,illustration3 ,,fig4 #be4 ,when using a balance sit directly in front of it4 ,ordinarily the substance to be weighed is best put on the pan to the user's left2 the weights and the rider are then easily manipulated4 ,powders1 c41 should not be weighed directly on the balance2 a counterpoised watch-glass or metal scoop 7fig4 #be7 should be used4 ,in some cases it is advisable to use a weighing-bottle4 ,this is a light1 well-stoppered bottle 7fig4 #c7 containing the powdered ore4 ,it is first filled and weighed2 then some of the substance is carefully poured from it into a beaker or other vessel1 and it is weighed again2 the difference in the two weighings gives the weight of substance taken4 ,a substance must always be cold when weighed1 and large glass vessels should be allowed to stand in the balance-box a little while before being weighed4 ,always have the balance at rest when putting on or taking off anything from the pans4 ,put the weights on systematically4 ,in using the rider 7except you have a reason to the contrary71 put it on at the #e2 if this is too much1 then try it at the #c2 if then the weights are too little1 try at the #d1 if still not enough1 the correct weight must be between the #d and #e2 try half-way between4 ,it is best to work with the balance vibrating2 equilibrium is established when the vibration to the left is the mean of the preceding and succeeding vibrations to the right4 ,for example1 if it vibrates #f divisions to the right on one swing1 and #e divisions on the next1 the intermediate vibration to the left should have been #e-a_/b4 ,note whether the substance increases in weight whilst on the balance4 ,if it does it may be because it was put on warm1 and is cooling1 or it may be because it is taking up moisture from the air4 ,substances which take up moisture rapidly should be weighed in clipped watch-glasses or in light-weighing bottles or tubes4 ,students1 in recording the weights1 should first read off those missing from the box1 writing down each order of figures as determined2 first tens1 then units1 and so on4 ,remember that the first four platinum weights give the figures of the first place of decimals1 the second four give the second place1 and that the third and fourth places are given by the rider4 ,having taken down the figures1 confirm them by reading off the weights as you put them back into the box4 ,do not rest a weight on the palm of your hand for convenience in reading the mark upon it4 ,remember one weight lost from a box spoils the set4 ,do not take it for granted that the balance is in equilibrium before you start weighing3 try it4 ,illustration3 ,,fig4 #bf4 ,measuring ,liquids4--,for coarse work1 such as measuring acids for dissolving ores1 graduated glasses similar to those used by druggists may be used4 ,it is well to have two sizes--a smaller graduated into divisions of #e c4c4 7fig4 #bf71 and a larger with divisions equal to #aj c4c4 ,no measurement of importance should be made in a vessel of this kind1 as a slight variation in level causes a serious error4 ,graduated flasks must be used when anything has to be made up to a definite bulk1 or when a fixed volume has to be collected4 ,if1 for example1 a certain weight of substance has to be dissolved and diluted to a litre1 or if the first #ej c4c4 of a distillate has to be collected1 a flask should be used4 ,each flask is graduated for one particular quantity2 the most useful sizes are #ajjj c4c41 #ejj c4c41 #bjj c4c41 #ajj c4c41 and #ej c4c4 ,the mark should be in the narrowest part of the neck1 and should be tangential to the curved surface of the liquid when the flask contains the exact volume specified4 ,the level of a curved surface of liquid is at first somewhat difficult to read3 the beginner is in doubt whether the surface should be taken at ,a1 ,b1 or ,c 7fig4 #bg74 ,it is best to take the lowest reading ,c4 ,in some lights it is difficult to find this2 in such cases a piece of white paper or card held behind and a little below1 so as to throw light up and against the curved surface1 will render it clear4 ,in reading1 one should look neither up at nor down upon the surface1 but the eye should be on the same level with it4 ,it must be kept in mind that flasks contain the quantity specified1 but deliver less than this by the amount remaining in them and damping the sides4 ,if it is desired to transfer the contents say of a #ajj c4c4 flask to a beaker1 it will be necessary to complete the transfer by rinsing out the flask and adding the washings2 otherwise there will be a sensible loss4 ,graduated cylinders 7fig4 #bh7 are convenient for preparing standard solutions4 ,illustration3 ,,fig4 #bg4 ,illustration3 ,,fig4 #bh4 ,illustration3 ,,fig4 #bi4 ,pipettes and burettes are graduated to deliver the quantities specified4 ,the principle of the pipette1 and the advantages and disadvantages of its various forms1 may be understood by considering the first form shown in fig4 #bi4 ,it is essentially a bulbed tube drawn out to a jet at its lower end1 and having on each side of the bulb a mark so placed that when the surface of the liquid falls from the upper to the lower mark the instrument shall deliver exactly #ajj c4c4 ,the bore of the jet should be of such a size as will allow the level of the liquid to fall at the rate of about one foot in two minutes4 ,if it runs more quickly than this1 an appreciable error arises from the varying amount of liquid remaining1 and damping the sides of the bulb4 ,the flow of liquid from a pipette must not be hastened by blowing into it4 ,the lower tube or nose of the pipette should be long enough to reach into the bottle or flask containing the liquid about to be measured4 ,the pipette is filled by sucking at the open end with the mouth2 this method of filling renders the use of the instrument dangerous for such liquids as strong acids1 ammonia1 and such poisonous solutions as that of potassic cyanide4 ,one attempt with a fairly strong solution of ammonia will teach the beginner a very useful lesson4 ,as soon as the liquid rises above the upper mark in the pipette1 the mouth is withdrawn1 and the pipette quickly closed by pressing the upper aperture with the index finger of the right hand2 it is well to have the finger slightly moist1 but not damp4 ,the neck of the pipette should be long enough to allow its being firmly grasped by the fingers and thumb of the right hand without inconvenience4 ,the pipette is first held in a vertical position long enough to allow any moisture outside the tube to run down1 and then the liquid is allowed to run out to the level of the upper mark2 this is easily effected by lessening the pressure4 ,if the finger is wet1 the flow will be jerky1 and good work impossible4 ,the pipette is next held over the vessel into which the #ajj c4c4 are to be put1 and the liquid allowed to run out4 ,when the bulb is nearly empty1 the flow should be checked by replacing the finger1 and the liquid allowed to escape slowly until the lower mark is reached4 ,the pipette is then withdrawn2 it is in the withdrawing that the disadvantage of this particular form#e makes itself felt4 ,it must be withdrawn very steadily1 as the slightest shock causes the remaining column of liquid to vibrate1 whereby air is drawn in and the liquid is forced out4 ,this disadvantage is got rid of by making the mouth of the jet the lower limit1 or1 in other words1 allowing the instrument to empty itself4 ,there are two forms of such pipettes2 in the one generally recommended in ,gay-,lussac's silver assay 7the last shown in fig4 #bi7 the nose is replaced by a jet4 ,this is most conveniently filled by stopping the jet with the finger1 and allowing the liquid to flow in a fine stream into the neck until the pipette is filled1 and then working as just described4 ,the other form is the one in general use2 in fact1 a long nose to a pipette is so convenient that it may almost be said to be necessary4 ,but the accuracy is slightly diminished2 a long narrow tube makes a poor measuring instrument because of the amount of liquid it finally retains4 ,a defect possessed by both forms is the retention of a drop of varying size in the nozzle4 ,whatever method is adopted for removing this drop must be always adhered to4 ,the most convenient form is the one last described1 and the most useful sizes are #ajj c4c41 #ej c4c41 #bj c4c41 #aj c4c41 and #e c4c4 ,ten c4c4 pipettes graduated into tenths of a cubic centimetre are very useful3 those are best in which the graduation stops short of the bottom4 ,all measurements should be made at the ordinary temperature2 and1 before being used1 the pipette should be rinsed out with a cubic centimetre or so of the solution to be measured4 ,after using1 it should be washed out with water4 ,burettes differ mainly from pipettes in having the flow of liquid controlled from below instead of from above4 ,the best form is that known as ,mohr's1 one kind of which is provided with a glass stopcock1 while the other has a piece of india-rubber tube compressed by a clip4 ,the latter cannot be used for solutions of permanganate of potash or of iodine1 or of any substance which acts on india-rubber2 but in other respects there is little to choose between the two kinds4 ,a burette delivering #ajj c4c41 and graduated into fifths 7i4e41 each division #j4b c4c471 is a very convenient size4 ,for some kinds of work1 #ej c4c4 divided into tenths 7i4e41 each division #j4a c4c47 may be selected4 ,burettes may be fixed in any convenient stand2 they must be vertical and should be so placed that the assayer can read any part of the graduated scale without straining4 ,when not in use1 they should be kept full of water4 ,when using a burette1 the water must be run out2 the burette is next rinsed with some of the solution to be used1 and drained2 and then it is filled with the solution4 ,next squeeze the india-rubber tube so as to disentangle air-bubbles and1 by smartly opening the clip1 allow the tube and jet to be filled2 see that no bubbles of air are left4 ,then run out cautiously until the level of the liquid in the burette stands at zero4 ,in reading the level with very dark-coloured liquids it is convenient to read from the level ,a 7fig4 #bg71 and1 provided it is done in each reading1 there is no objection to this4 ,the accuracy of the reading of a burette is sensibly increased by the use of an ,erdmann float4 ,this is an elongated bulb1 weighted with mercury1 and fitting 7somewhat loosely7 the tube of the burette4 ,it floats in the solution1 and is marked with a horizontal line2 this line is taken as the level of the liquid4 ,if the burette is filled from the top1 the float rises with aggravating slowness1 and this is its chief disadvantage4 ,the float must come to rest before any reading is made4 ,illustration3 ,,fig4 #cj4 ,a convenient plan for filling a burette from below is shown in fig4 #cj4 ,the diagram explains itself4 ,the bottle containing the standard solution is connected with the burette by a syphon arrangement through the glass tube and ,t-piece4 ,the flow of liquid into the burette is controlled by the clip4 ,when this clip is opened1 the burette fills2 and when it is closed1 the burette is ready for use in the ordinary way4 ,measuring ,gases4--,lange's nitrometer 7fig4 #fi7 is a very convenient instrument for many gasometric methods4 ,it requires the use of a fair quantity of mercury4 ,in fig4 #ca1 there is a representation of a piece of apparatus easily fitted up from the ordinary material of a laboratory4 ,it is one which will serve some useful purposes4 ,it consists of a wide-mouthed bottle fitted 7by preference7 with a rubber cork4 ,the cork is perforated1 and in the perforation is placed a glass tube which communicates with the burette4 ,the burette is connected by a rubber tube and a ,y-piece1 either with another burette or with a piece of ordinary combustion-tube of about the same size4 ,the wide-mouthed bottle contains either a short test-tube or an ordinary phial with its neck cut off4 ,in working the apparatus the weighed substance is put in the bottle and the re-agent which is to act on it1 in the test-tube2 the cork is then inserted4 ,the liquid in the two burettes is next brought to the same level1 either by pouring it in at ,a or running it out at ,b4 ,the level of the liquid in the apparatus for correcting variation in volume is then read and noted4 ,next1 after seeing that the level of the liquid in the burette has not changed1 turn the bottle over on its side so that the re-agent in the test-tube shall be upset into the bottle4 ,then1 as the volume of the gas increases1 lower the liquid in the burette by running it out at ,b1 and at the same time keep the level in ,a half an inch or so lower than that in the burette4 ,when the action has finished bring the liquid in the two vessels to the same level and read off the burette4 ,this part of the work must always be done in the same manner4 ,illustration3 ,,fig4 #ca4 ,the volume corrector for gas analysis is a graduated glass tube of #abj c4c4 capacity inverted over a narrow glass cylinder of mercury4 ,it contains #j4b or #j4c c4c4 of water and a volume of air1 which1 if dry and under standard conditions1 would measure #ajj c4c4 ,the actual volume varies from day to day1 and is read off at any time by bringing the mercury inside and outside to the same level4 ,this is done by raising or lowering the tube1 as may be required4 ,any volume of gas obtained in an assay can be corrected to standard temperature and pressure by multiplying by #ajj and dividing by the number of c4c4 in the corrector at the time the assay is made4 ,,footnotes3 #e ,it is best to use this form with a glass stopcock1 or with an india-rubber tube and clip1 after the manner of a ,mohr's burette4 ,,chapter ,,vi4 ,,re-,,agents4--,,acids1 ,,etc4 ,acetic ,acid1 ,h,ac or ,c#b;,h#d,o#b4 7sp4 gr4 #a4jdd1 containing #cc per cent4 real acid74--,an organic acid1 forming a class of salts1 acetates1 which are for the most part soluble in water1 and which1 on ignition1 leave the oxide or carbonate of the metal4 ,it is almost always used in those cases where mineral acids are objectionable4 ,to convert1 for example1 a solution of a substance in hydrochloric acid into a solution of the same in acetic acid1 alkali should be added in excess and then acetic acid4 ,many compounds are insoluble in acetic acid1 which are soluble in mineral acids1 such as ferric phosphate1 ferric arsenate1 zinc sulphide1 calcium oxalate1 c41 so that the use of acetic acid is valuable in some separations4 ,the commercial acid is strong enough for most purposes1 and is used without dilution4 ,aqua ,regia is a mixture of #a part by measure of nitric acid and #c parts of hydrochloric acid4 ,the acids react forming what is practically a solution of chlorine4#f ,the mixture is best made when wanted1 and is chiefly used for the solution of gold and platinum and for opening up sulphides4 ,when solutions in aqua regia are evaporated1 chlorides are left4 ,bromine1 ,br4 7sp4 gr4 #c4j74 ,practically pure bromine4--,it is a heavy reddish-brown liquid and very volatile4 ,it boils at #fj ,c41 and1 consequently1 must be kept in a cool place4 ,it gives off brown irritating vapours1 which render its use very objectionable4 ,generally it answers the same purpose as aqua regia1 and is employed where the addition of nitric acid to a solution has to be specially avoided4 ,it is also used for dissolving metals only from ores which contain metallic oxides not desired in the solution4 ,bromine ,water is simply bromine shaken up with water till no more is dissolved4 ,carbonic ,acid1 ,,co#b4--;,a heavy gas1 somewhat soluble in water2 it is mainly used for providing an atmosphere in which substances may be dissolved1 titrated1 c41 without fear of oxidation4 ,it is also used in titrating arsenic assays with iodine when a feeble acid is required to prevent the absorption of iodine by the alkaline carbonate4 ,it is prepared when wanted in solution1 by adding a gram or so of bicarbonate of soda and then as much acid as will decompose the bicarbonate mentioned4 ,when a quantity of the gas is wanted1 it is prepared1 in an apparatus like that used for sulphuretted hydrogen1 by acting on fragments of marble or limestone with dilute hydrochloric acid4 ,citric ,acid 7,h#c;,ci or ,c#f;,h#h,o#g4;,h#b,o7 is an organic acid which occurs in colourless crystals1 soluble in less than their weight of water4 ,the solution must be freshly prepared1 as it gets mouldy when kept4 ,it forms a comparatively unimportant class of salts 7citrates74 ,it is used in the determination of phosphoric acid1 chiefly for the purpose of preventing the precipitation of phosphates of iron and alumina by ammonia1 and in a few similar cases4 ,the commercial crystals are used2 they should be free from sulphuric acid and leave no ash on ignition4 ,hydrochloric ,acid1 ,h,cl in water1 7sp4 gr4 #a4af4 ,it contains #cb per cent4 of hydrogen chloride74--,it is sometimes called muriatic acid1 and when impure1 spirit of salt4 ,the acid solution should be colourless and free from arsenic1 iron1 and sulphuric acid4 ,it forms an important family of salts1 the chlorides4 ,it is the best acid for dissolving metallic oxides and carbonates1 and is always used by the assayer when oxidising agents are to be avoided4 ,the acid is used without dilution when no directions are expressly given to dilute it4 ,it has no action on the following metals3 gold1 platinum1 arsenic1 and mercury2 it very slightly attacks antimony1 bismuth1 lead1 silver1 and copper4 ,tin is more soluble in it1 but with difficulty2 whilst iron1 zinc1 nickel1 cobalt1 cadmium1 and aluminium easily dissolve with evolution of hydrogen and the formation of the lower chloride if the metal forms more than one class of salts4 ,all the metallic oxides1 except a few of the native and rarer oxides1 are dissolved by it with the formation of chlorides of the metal and water4 ,dilute ,hydrochloric ,acid is made by diluting the strong acid with an equal volume of water4 ,this is used for dissolving precipitates obtained in the general course of analysis and the more easily soluble metals4 ,hydrofluoric ,acid1 ,,hf4--,a solution in water may be purchased in gutta-percha or lead bottles4 ,it is of variable strength and doubtful purity4 ,it must always be examined quantitatively for the residue left on evaporation4 ,it is used occasionally for the examination of silicates4 ,it attacks silica1 forming fluoride of silicon1 which is a gas4 ,when the introduction of another base will not interfere with the assay1 the substance may be mixed in the platinum dish with fluoride of ammonium1 or of potassium1 or of calcium1 and hydrochloric acid1 instead of treating it with the commercial acid4 ,it is only required in special work4 ,the fumes and acid are dangerous1 and1 of course1 glass or porcelain vessels cannot be used with it4 ,iodine1 ,i4--,this can be obtained in commerce quite pure1 and is often used for standardising4 ,it is very slightly soluble in water1 but readily dissolves in potassium iodide solution4 ,it closely resembles chlorine and bromine in its properties1 and can be used for dissolving metals without1 at the same time1 attacking any oxide which may be present4 ,it is chiefly used as an oxidizing agent in volumetric work1 being sharp in its reactions and easily detected in minute quantities4 ,it cannot be used in alkaline solutions1 since it reacts with the hydrates1 and even with the carbonates1 to form iodides and iodates4 ,iodine is soluble in alcohol4 ,nitric ,acid1 ,,hno#c4 7,sp4 gr4 #a4db2 boiling point #aba ,c42 contains #gj per cent4 by weight of hydrogen nitrate74--,it is convenient to remember that one c4c4 of this contains #a gram of real acid4 ,it combines the properties of an acid and of an oxidising agent4 ,one c4c4 contains #j4gf gram of oxygen1 most of which is very loosely held1 and easily given up to metals and other oxidisable substances4 ,consequently it will dissolve many metals1 c41 upon which hydrochloric acid has no action4 ,all sulphides 7that of mercury excepted7 are attacked by it1 and for the most part rendered soluble4 ,it has no action on gold or platinum1 and very little on aluminium4 ,the strong acid at the ordinary temperature does not act on iron or tin2 and in most cases it acts better when diluted4 ,some nitrates being insoluble in nitric acid1 form a protecting coat to the metal which hinders further action4 ,where the strong acid does act the action is very violent1 so that generally it is better to use the dilute acid4 ,when iron has been immersed in strong nitric acid it not only remains unacted on1 but assumes a passive state2 so that if1 after being wiped1 it is then placed in the dilute acid1 it will not dissolve4 ,tin and antimony are converted into insoluble oxides1 while the other metals 7with the exception of those already mentioned7 dissolve as nitrates4 ,during the solution of the metal red fumes are given off1 which mainly consist of nitrogen peroxide4 ,the solution is often coloured brown or green because of dissolved oxides of nitrogen1 which must be got rid of by boiling4 ,generally some ammonium nitrate is formed1 especially in the cases of zinc1 iron1 and tin1 when these are acted on by cold dilute acid4 ,sulphur1 phosphorus1 and arsenic are converted into sulphuric1 phosphoric1 and arsenic acids respectively1 when boiled with the strong acid4 ,dilute ,nitric ,acid4--,dilute #a volume of the strong acid with #b of water4 ,oxalic ,acid1 ,h#b,o or 7,h#b;,c#b,o#d4b;,h#b,o47--,this is an organic acid in colourless crystals4 ,it forms a family of salts--the oxalates4 ,it is used in standardising2 being a crystallised and permanent acid1 it can be readily weighed4 ,it is also used in separations1 many of the oxalates being insoluble4 ,for general use make a #aj per cent4 solution4 ,use the commercially pure acid4 ,on ignition the acid should leave no residue4 ,illustration3 ,,fig4 #cb4 ,sulphuretted ,hydrogen4 ,hydrosulphuric acid1 ,,sh#b4--;,a gas largely used in assaying1 since by its action it allows of the metals being conveniently classed into groups4 ,it is soluble in water1 this liquid dissolving at the ordinary temperature about three times its volume of the gas4 ,the solution is only useful for testing4 ,in separations1 a current of the gas must always be used4 ,it is best prepared in an apparatus like that shown in fig4 #cb1 by acting on ferrous sulphide with dilute hydrochloric acid4 ,when iron has to be subsequently determined in the assay solution1 the gas should be washed by bubbling it through water in the smaller bottle2 but for most purposes washing can be dispensed with4 ,the gas is very objectionable1 and operations with it must be carried out in a cupboard with a good draught4 ,when the precipitation has been completed1 the apparatus should always be washed out4 ,the effect of this acid on solutions of the metals is to form sulphides4 ,all the metallic sulphides are insoluble in water2 but some are soluble in alkaline1 and some in acid1 solutions4 ,if sulphuretted hydrogen is passed through an acid solution containing the metals till no further precipitation takes place1 a precipitate will be formed containing sulphides insoluble in the acid4 ,on filtering1 adding ammonia 7to render the filtrate alkaline71 and again passing the gas1 a further precipitate will be obtained1 consisting of sulphides insoluble in an alkaline solution1 but not precipitable in an acid one2 the filtrate may also contain sulphides not precipitable in an acid solution1 which are soluble in an alkaline one2 these will be thrown down on neutralising4 ,again1 the metals precipitated in the acid solution form sulphides which may be divided into groups1 the one consisting of those which are soluble1 and the other of those which are not soluble1 in alkalies4 ,this classification is shown in the following summary3-- #a4 ,precipitable in an acid solution4 7a7 ,soluble in ,alkalies4--,sulphides of ,as1 ,sb1 ,sn1 ,au1 ,pt1 ,ir1 ,mo1 ,te1 and ,se4 7b7 ,insoluble in ,alkalies4--,sulphides of ,ag1 ,pb1 ,hg1 ,bi1 ,cu1 ,cd1 ,pd1 ,rh1 ,os1 and ,ru4 #b4 ,not precipitated in an acid solution1 but thrown down in an alkaline one4 ,sulphides of ,mn1 ,zn1 ,fe1 ,ni1 ,co1 ,in1 ,tl1 and ,ga4 ,these can again be divided into those which are dissolved by dilute acids and those which are not4 #c4 ,not precipitated in an acid or alkaline solution1 but thrown down on neutralising the latter4 ,sulphides of ,v and ,w4 ,sulphuretted hydrogen is a strong reducing agent4 ,ferric salts are thereby quickly reduced to ferrous2 in hot solutions nitric acid is decomposed4 ,these changes are marked by a precipitation of sulphur1 and the student must be careful to pass the gas sufficiently long1 and not be too hasty in concluding that no sulphide will form because it does not at once make its appearance4 ,the best indication that it has been passed long enough is the smell of the gas in the solution after shaking4 ,sulphurous ,acid1 ,h#b,,so#c4--,the reagent used may be regarded as a saturated solution of sulphur dioxide in water4 ,it may be purchased1 and keeps for a long time4 ,it may be made by heating copper with sulphuric acid and passing the gas formed into water4 ,the heat should be withdrawn when the gas is coming off freely4 ,it is used as a reducing agent1 and should not be diluted4 ,sulphuric ,acid1 ,h#b,,so#d4 7,sp4 gr4 #a4hd1 containing #if per cent4 of real acid1 ,h#b,,so#d47--,this acid forms insoluble sulphates with salts of lead1 strontium1 and barium4 ,it has a high boiling point1 #bij ,c41 and1 when evaporated with salts of the more volatile acids1 converts them into sulphates4 ,when nitrates or chlorides are objectionable in a solution1 evaporation with sulphuric acid removes them4 ,in working with this acid caution is necessary1 since1 on mixing with water1 great heat is evolved2 and1 if either the acid or water has been previously heated1 a serious accident may result4 ,in diluting the acid it should be poured into cold water4 ,glass vessels containing boiling sulphuric acid should be handled as little as possible1 and should not be cooled under the tap4 ,the action of diluted sulphuric acid on metals closely resembles that of dilute hydrochloric acid4 ,magnesium1 aluminium1 iron1 zinc1 nickel1 cobalt1 manganese1 and cadmium dissolve1 with evolution of hydrogen1 in the cold acid1 or when warmed4 ,the action of hot and strong sulphuric acid is altogether different2 it acts as an oxidising agent1 and is itself reduced to sulphur dioxide or even to sulphur4 ,the following metals are attacked in this way3--copper1 bismuth1 mercury1 silver1 antimony1 tin1 and lead4 ,gold1 platinum1 and arsenic are not affected4 ,this property is made use of in parting silver from gold and platinum4 ,metallic sulphides are similarly attacked2 but this method of opening up minerals has the disadvantage of giving rise to the formation of anhydrous sulphates of iron1 c41 which are not readily dissolved when afterwards diluted4 ,the use of sulphuric acid in assaying is 7for these reasons7 to be avoided4 ,its chief use is as a drying agent1 since it has a strong affinity for water4 ,air under a bell jar may be kept dry by means of a basin of sulphuric acid1 and gases bubbled through it are freed from water-vapour4 ,dilute ,sulphuric ,acid4--,this is made by diluting #a volume of the strong acid with #d of water4 ,tartaric ,acid1 ,h#b,t or ,c#d;,h#f,o#f4--;,a crystallised organic acid1 soluble in less than its own weight of water1 or in less than three parts of alcohol4 ,it is used for the same purposes as citric acid is4 ,the solution is made when required4 ,,bases1 ,,salts1 c4 ,alcohol1 ,c#b;,h#f,o4 7,commercial alcohol of sp4 gr4 #j4hch2 it contains #hd per cent4 by weight of alcohol47--,it should burn with a non-luminous flame and leave no residue4 ,it is used for washing precipitates where water is inapplicable1 and for facilitating drying4 ,ammonia1 ,,nh#c4 7,commercial ammonia1 a solution having a sp4 gr4 of #j4hh to #j4hi1 and containing about #cc per cent4 of ammonia47--,it is used as an alkali 7more commonly than soda or potash71 since an excess of it is easily removed by boiling4 ,the salts of ammonium formed by it may be removed by igniting1 or by evaporating in a porcelain dish with an excess of nitric acid4 ,it differs in a marked way from soda or potash in its solvent action on the oxides or hydrates of the metals4 ,salts of the following metals are soluble in an ammoniacal solution in the presence of ammonic chloride3--copper1 cadmium1 silver1 nickel1 cobalt1 manganese1 zinc1 magnesium1 sodium1 potassium1 and the alkaline earths4 ,dilute ,ammonia is made by diluting #a vol4 of commercial ammonia with #b of water4 ,the dilute ammonia is always used2 but in assays for copper a stronger solution 7#a of strong ammonia to #a of water7 is required4 ,ammonic ,carbonate 7,am#b;,,co#c7 is prepared by dissolving one part of the commercial sesquicarbonate of ammonia in four parts of water1 and adding one part of strong ammonia4 ,ammonic ,bicarbonate 7,h,am,c,o#c7 is prepared by saturating a solution of the sesquicarbonate of ammonia with carbon dioxide4 ,ammonic ,chloride1 ,am,cl4--,use the commercial salt in a #bj per cent4 solution in water4 ,the salt should leave no residue on ignition4 ,ammonic ,molybdate4--,the solution is prepared as follows3--,dissolve #ajj grams of the powdered commercial salt in #bjj c4c4 of dilute ammonia1 and pour the solution in a slow stream into #gej c4c4 of dilute nitric acid2 make up to #a litre1 and allow the mixture to settle before using4 ,it is used for the purpose of separating phosphoric oxide from bases and from other acids1 and also as a test for phosphates and arsenates4 ,in using this solution the substance must be dissolved in nitric acid1 and a considerable excess of the reagent added 7#ej c4c4 is sufficient to precipitate #j4a gram ,p#b,o#e72 when the phosphate is in excess no precipitate will be got4 ,the precipitate is phospho-molybdate of ammonia4 ,ammonic ,nitrate 7,am,n,o#c7 is used in the separation of phosphoric oxide by the molybdate method1 and occasionally for destroying organic matter4 ,it is soluble in less than its own weight of water4 ,the solution is made when wanted4 ,ammonic ,oxalate 7,am#b;,c#b,o#d4b;,h#b,o7 is used chiefly for the separation of lime4 ,the solution is made by dissolving #ae grams of the salt in #ajj c4c4 of water4 ,ammonic ,sulphide may be purchased in the state of a strong solution4 ,it is yellow1 and contains the disulphide1 ,s#b;,am#b4 ,it serves the same purpose as is obtained by passing a current of sulphuretted hydrogen through an ammoniacal solution2 but has the disadvantage of loading the solution with sulphur1 which is precipitated when the solution is subsequently acidified4 ,it is useful for dissolving the lower sulphide of tin 7,sn,s74 ,baric ,carbonate 7,ba,c,o#c7 is sometimes used for precipitating the weaker bases4 ,it should be prepared when wanted by precipitating a solution of baric chloride with ammonic carbonate and washing4 ,the moist precipitate is used without drying4 ,baric ,chloride1 ,ba,cl#b4b;,h#b,o4--,a crystallised salt1 soluble in #b-a_/b parts of water4 ,it is used for the detection and separation of sulphates4 ,make a #aj per cent4 solution4 ,black ,flux4--,a mixture of finely divided carbon with carbonate of potash or with carbonates of potash and soda4 ,it is prepared by heating tartar or rochelle salt until no more combustible gas is given off4 ,one gram will reduce about #b grams of lead from litharge4 ,borax1 ,na#b;,b#d,o#g4aj;,h#b,o4--,it is chiefly used as a flux in dry assaying1 as already described4 ,it is also used in testing before the blowpipe2 many metallic oxides impart a characteristic colour to a bead of borax in which they have been fused4 ,calcium ,chloride4--,the crystallised salt is ,ca,cl#b4f;,h#b,o2 dried at #bjj ,c4 it becomes ,ca,cl#b4b;,h#b,o1 and when fused it becomes dehydrated4 ,the fused salt1 broken into small lumps1 is used for drying gases4 ,it combines with water1 giving off much heat2 and dissolves in a little more than its own weight of water4 ,strong solutions may be used in baths in which temperatures above the boiling-point of water are required4 ,one part of the salt and #b of water give a solution boiling at #aab1 and a solution of #b parts of the salt in #a of water boils at #aeh4 ,the salt is very little used as a reagent4 ,calcium ,fluoride or ,fluor ,spar1 ,ca,f#b4--,the mineral is used as a flux in dry assaying2 it renders slags which are thick from the presence of phosphates1 c41 very fluid4 ,mixed with hydrochloric acid it may sometimes be used instead of hydrofluoric acid4 ,calcium ,carbonate1 ,ca,c,o#c4--;,it is precipitated in a pure state by ammonic carbonate from a solution of calcium chloride4 ,it is used for standardising4 ,in the impure state1 as marble or limestone1 it is used in the preparation of carbonic acid4 ,calcium ,hydrate or ,lime ,water4--,this is used in testing for carbon dioxide and in estimating the amount of that gas present in air4 ,it may be made by slaking quicklime and digesting the slaked lime with water4 ,one hundred c4c4 of water at #ae ,c4 dissolves #j4acfh grams of the hydrate 7,ca,h#b,o#b71 and hot water dissolves still less4 ,milk of lime is slaked lime suspended in water4 ,cobalt ,nitrate 7,co7,,no#c7b4f;,h#b,o7 is used in a #aj per cent4 solution for the detection of oxides of zinc1 aluminium1 c42 on ignition with which it forms characteristically coloured compounds4 ,copper1 ,cu4--,pure copper1 as obtained by electrolysis1 can be purchased4 ,this only should be used4 ,copper ,oxide1 ,cu,o4--,it occurs as a black1 heavy1 and gritty power1 and is used for the oxidation of carbon and hydrogen in organic substances4 ,it should be ignited and cooled out of contact with air just before using1 since it is hygroscopic4 ,oxide of copper which has been used may be again utilised after calcination4 ,copper ,sulphate 7,cu,s,o#d4e;,h#b,o7 contains #be4d per cent4 of copper4 ,it is used in the outer cell of a ,daniell-battery4 ,the commercial salt is used for this purpose4 ,the re-crystallised and pure salt is used for preparing the anhydrous sulphate1 which is used for detecting moisture in gases4 ,for this purpose it is dried at #bjj ,c4 till no trace of green or blue colour remains4 ,it must be prepared when wanted4 ,it may be conveniently used in the form of pumice-stone1 saturated with a solution of the salt and dried4 ,traces of moisture develop a green colour4 ,ferric ,chloride1 ,fe#b;,cl#f4 7,when crystallised1 ,fe#b;,cl#f4f;,h#b,o47--,the solution is prepared as described under iron4 ,the commercial salt contains arsenic1 and1 since the chief use of ferric chloride is for the determination of this substance1 it must be purified 7see under ,,arsenic74 ,ferric ,sulphate 7,fe#b7,,so#d7c7 is a yellowish white deliquescent salt4 ,it is used as an indicator in volumetric silver assaying1 and for the separation of iodine from bromine4 ,it may be purchased as iron alum1 ,am#b;,fe#b7,,so#d7d4bd;,h#b,o4 ,but it is best prepared by adding strong sulphuric acid to ferric hydrate in equivalent proportions4 ,use it as a solution containing #b or #c per cent4 of iron4 ,ferrous ,sulphate1 ,fe,s,o#d4g;,h#b,o4--,the granulated form is best1 and can be purchased pure4 ,it is used for standardising4 ,it keeps better in crystals than in solution4 ,it is readily soluble in water1 but the solution is best made with the help of a little free acid4 ,as a re-agent use a #aj per cent4 solution4 ,the crystals should be clear bluish-green2 if their colour is dark green1 brown1 or blue1 they should be rejected4 ,ferrous ,sulphide 7,fe,s7 is used for the preparation of sulphuretted hydrogen4 ,it may be purchased and broken in small lumps1 nut-size1 for use4 ,fusion ,mixture 7,k#b;,,co#c4,na#b;,,co#c7 is a mixture of potassic and sodic carbonates in the proportions of #ac of the former to #aj of the latter1 by weight4 ,it is hygroscopic4 ,a mixture of the bicarbonates is better1 being purer and less apt to get damp4 ,gallic ,acid 7,c#g;,h#f,o#e4;,h#b,o7 is an organic acid1 occurring as a pale fawn-coloured crystalline powder1 soluble in #ajj parts of cold water1 or in #c parts of boiling water4 ,it is used for the determination of antimony4 ,a #aj per cent4 solution in warm water is made when required4 ,hydrogen 7,h7 is a gas4 ,it is obtained by acting on zinc with dilute hydrochloric or sulphuric acid4 ,it is used as a reducing agent1 and for providing an atmosphere free from oxygen4 ,it reduces metallic oxides at a high temperature4 ,it must be freed from water2 and special precautions should be taken to prevent an admixture with air4 ,it is generally required in a current which can be continued for an hour or more without interruption4 ,the preparation can be conveniently carried out in the apparatus shown 7fig4 #cc74 ,a quart bottle is half filled with sheet zinc1 and connected with bulbs filled with sulphuric acid1 and with a calcium chloride tube4 ,the last is connected with the apparatus through which the gas has to be passed4 ,dilute hydrochloric acid mixed with a few cubic centimetres 7#bj c4c4 to #a pint7 of stannous chloride sol4 to fix any dissolved oxygen1 is placed in the funnel1 and let into the bottle by opening the stopcock when required4 ,care must be taken to let the hydrogen escape for some time before starting the reduction4 ,illustration3 ,,fig4 #cc4 ,gold1 ,au4--,gold1 obtained by cupelling and parting1 is for most purposes sufficiently pure4 ,it is best kept in the shape of foil4 ,when the purer metal is required1 gold should be dissolved in aqua regia1 the solution evaporated to a paste1 diluted1 allowed to stand1 and filtered4 ,the filtered solution is acidified with hydrochloric acid1 warmed1 and precipitated with sodium sulphite4 ,the precipitate is collected1 washed1 and fused on charcoal4 ,iron1 ,fe4--,the soft wire 7thin7 is used for standardising4 ,rods are used in dry assays as a desulphurising agent4 ,steel must not be used1 since it is not pure1 and contains a variable amount of iron4 ,lead1 ,pb4--,granulated lead or lead-foil is used in the dry assay for silver and gold1 and in the preparation of lead salts4 ,it can be obtained very pure1 but always contains more or less silver1 #a or #b milligrams in #ajj grams4 ,the amount of silver it contains must be determined and recorded4 ,lead ,acetate 7,pb,ac#b4c;,h#b,o1 or ,pb7,c#b;,h#c,o#b7b4c;,h#b,o7 is used as a test1 specially for the detection and estimation of sulphuretted hydrogen4 ,prepare a #aj per cent4 solution for use4 ,lead ,nitrate 7,pb7,,no#c7b7 can be purchased pure4 ,it is used for standardising4 ,lead ,dioxide 7,pb,o#b7 occurs as a dark-brown powder4 ,it is used as an oxidizing agent and for absorbing sulphurous oxide4 ,it can be prepared by digesting red lead with warm dilute nitric acid2 washing and drying the residue4 ,litharge1 ,pb,o4--,it can be purchased as a yellow heavy powder4 ,it is used in dry assaying as a flux1 as a desulphurising agent1 and also as a source of lead4 ,it always contains some silver1 the amount of which must be determined4 ,litmus4--,this is an organic colouring matter which is turned red by acids and blue by alkalies4 ,for ordinary purposes it is best used as litmus paper1 which may be purchased in small books4 ,a solution is prepared by digesting #ae or #bj grams of the commercial litmus in #ajj c4c4 of water on the water bath4 ,after being allowed to settle1 it is filtered and made just faintly red with acetic acid4 ,then there is added a drop or two of a solution of soda and #aj c4c4 of alcohol4 ,it should be kept in a loosely-covered bottle4 ,magnesia1 ,mg,o4--,it may be purchased as calcined magnesia4 ,it is used for making magnesia mixture1 and should be kept in a corked wide-mouthed bottle4 ,magnesia ,mixture4--,dissolve #bb grams of magnesia in about a quarter of a litre of dilute hydrochloric acid1 avoiding excess4 ,add #e grams of magnesia1 boil1 and filter4 ,add #cjj grams of ammonic chloride1 and #bej c4c4 of strong ammonia2 and dilute with water to #b litres4 ,it should be kept in a stoppered winchester4 ,magnesium ,sulphate1 ,mg,s,o#d4g;,h#b,o4--,it can be purchased very pure1 and is occasionally used as a standard salt4 ,manganese ,dioxide1 ,mn,o#b4--;,it is used in the preparation of chlorine4 ,the commercial article is not pure1 but is sufficiently so for this purpose4 ,marble1 ,ca,c,o#c4--;,fragments of the white crystalline variety only should be used4 ,it is used as a source of lime and of carbon dioxide4 ,mercury1 ,hg4--,this can be purchased pure4 ,it should have a bright surface1 flow without a tail1 and leave no residue on ignition4 ,it is used as a standard2 for amalgamation2 and as a confining liquid in gas analysis4 ,mercuric ,chloride 7,hg,cl#b7 may be purchased pure4 ,make a #e per cent4 solution in water4 ,it is used for destroying an excess of stannous chloride2 for removing sulphuretted hydrogen from solution2 and as a test for stannous salts4 ,microcosmic ,salt1 ,h,am,na,p,o#d4h;,h#b,o4--,when fused ,na,p,o#c is formed4 ,it is used in testing for metallic oxides and silica before the blowpipe4 ,the crystals are sometimes used as a standard for phosphoric acid4 ,nessler's ,solution4--,mode of preparation3 ,dissolve #ce grams of potassium iodide in #ajj c4c4 of water2 dissolve #ag grams of mercuric chloride in #cjj c4c4 of water1 and pour this solution into that of the iodide till a permanent precipitate is produced2 make up to #a litre with a #bj per cent4 solution of potash2 add mercuric chloride till a precipitate is again formed2 allow to settle and decant4 ,it is used for detecting ammonia4 ,nitre4--,this is potassium nitrate4 ,platinum ,chloride1 #b;,h,cl4,pt,cl#d4 7,in the crystallised form it has #f;,h#b,o74--,it may be made as follows3--,take #e grams of clean platinum scrap and dissolve in a flask at a gentle heat in #ej c4c4 of hydrochloric acid with the occasional addition of some nitric acid2 evaporate to a paste2 and then dissolve in #ajj c4c4 of water4 ,it is used for separating and determining potassium4 ,phenolphthalein is an organic compound used as an indicator2 more especially in determining the weaker acids1 it cannot be used in the presence of ammonia4 ,dissolve half a gram in #ajj c4c4 of dilute alcohol4 ,potassium ,bicarbonate1 ,,khco#c4--;,it may be purchased pure2 on ignition it leaves the carbonate1 ,k#b;,,co#c1 which may be used as a standard4 ,potassium ,cyanide1 ,,kcn4--,it is used in the dry assay as a reducing agent4 ,the commercial salt is very impure4 ,purchase that sold as potassic cyanide 7gold7 which contains about #ie per cent4 of ,,kcn4 ,it is used for copper assaying and occasionally in separation4 ,make a #aj per cent4 solution when wanted4 ,potassium ,bichromate1 ,k#b;,cr#b,o#g4 ,it may be purchased nearly pure4 ,it is used as an oxidising agent1 for determining iron2 and as a test solution4 ,for this last purpose a #aj per cent4 solution is prepared4 ,potassium ,chlorate 7,k,cl,o#c7 can be purchased pure4 ,it is used with hydrochloric acid as a substitute for aqua regia4 ,potassium ,ferrocyanide 7,k#d;,fe7,,cn7#f4c;,h#b,o71 or yellow prussiate of potash1 is used as a test2 as an indicator2 and for the determination of zinc4 ,make a #e per cent4 solution4 ,potassium ,ferricyanide 7,k#f;,fe#b7;,,cn7#ab71 or red prussiate of potash1 is used for testing2 and as an indicator4 ,make a #e per cent4 solution when wanted1 as it decomposes on keeping4 ,potassium ,hydrate1 ,,kho4 ,purchase that purified with alcohol4 ,it is an alkali1 and is used for absorbing carbonic acid1 c4 ,potassium ,iodide1 ,,ki4 ,it may be purchased nearly pure4 ,it is used as a test and for dissolving iodine4 ,it should be used in a #aj per cent4 solution freshly made4 ,the solution decomposes on exposure to light1 with separation of iodine4 ,potassium ,nitrate 7,,kno#c7 can be purchased pure4 ,it is used in the dry way as an oxidizing agent4 ,it is very fusible4 ,it decomposes at a low temperature into potassium nitrite 7,,kno#b7 and free oxygen2 and at a higher temperature leaves potash 7,k#b,o74 ,it oxidizes sulphur and carbon with explosive violence4 ,this action may be moderated by mixing the nitre with carbonate of soda1 common salt1 or some other inert body4 ,potassium ,nitrite1 ,,kno#b4--,the commercial article is not pure1 but is sufficiently so for the purpose required4 ,a saturated solution is used in the separation of cobalt2 the solution is made when wanted4 ,potassium ,permanganate1 ,k,mn,o#d4--,this salt can be purchased sufficiently pure4 ,it is much used as an oxidizing agent4 ,potassium ,bisulphate 7,,khso#d7 is used as a dry reagent for opening up minerals4 ,it fuses2 and at a much higher temperature is converted into potassium sulphate with loss of sulphuric acid4 ,potassium ,sulphocyanate 7,,kcns7 is used for the detection and determination of traces of ferric iron2 as also in the separation of silver and copper from some of the other metals4 ,make a #aj per cent4 solution4 ,it should show no colour on the addition of hydrochloric acid4 ,red ,lead 7,pb#c,o#d7 is used in the dry assay as a flux instead of litharge1 from which it differs in containing a little more oxygen4 ,when acted on by nitric acid a brown residue of lead dioxide is left1 nitrate of lead going into solution4 ,like litharge it always carries silver2 about #b milligrams in #ajj grams4 ,silver1 ,ag4--,pure silver in foil is required as a standard4 ,it may be prepared as follows3--,dissolve scrap silver in dilute nitric acid and decant off from any residue2 dilute the solution with hot water and add hydrochloric acid until there is no further precipitate1 stir2 allow the precipitate to settle2 decant and wash2 dry the precipitate1 mix it with twice its bulk of carbonate of soda and fuse the mixture in a crucible until tranquil2 clean the button and roll or hammer it into foil4 ,sodium ,acetate1 ,na,c#b;,h#c,o#b4c;,h#b,o4--,the crystals may be purchased sufficiently pure4 ,make a #bj per cent4 solution in water4 ,it is used for replacing mineral acids by acetic acid4#g ,sodium ,acetate and ,acetic ,acid4--,a solution is used in the determination of phosphates and arsenates2 #ajj grams of the salt is dissolved in #ejj c4c4 of acetic acid1 and diluted with water to one litre4 ,sodium ,bicarbonate 7,na,h,c,o#c7;is used as a flux in dry methods4 ,on ignition it leaves the carbonate 7,na#b;,,co#c71 which is used as a standard reagent4 ,make a #bj per cent4 solution of the carbonate for use4 ,it should be free from chlorides or sulphates1 or if impure the amount of impurities must be determined4 ,sodium ,hydrate1 ,na,h,o4 ,it may be purchased in sticks1 which should be kept in a well-corked bottle4 ,it is sometimes called caustic soda4 ,it is a strong alkali4 ,it is used for neutralizing acid solutions and for separations where ammonia is unsuitable4 ,make a #e per cent4 solution for use4 ,sodium ,hyposulphite1 ,na#b,s#b,o#h4e;,h#b,o4--,it may be purchased pure4 ,it is generally known as hypo4 ,it is used as a standard4 ,sodium ,sulphite 7,na#b,,so#c4g;,h#b,o7 is used as a reducing agent4 ,sodium ,phosphate1 ,na#b;,,hpo#d4ab;,h#b,o4 ,the crystals may be purchased pure1 but they effloresce in dry air with loss of water4 ,it is used as a standard and for precipitating magnesia1 c4 ,make a #aj per cent4 solution4 ,stannous ,chloride1 ,sn,cl#b4b;,h#b,o4--,the crystals are best purchased4 ,if kept dry and free from air they are fairly permanent4 ,a solution is made by dissolving #bj grams in #aj c4c4 of hydrochloric acid and diluting to #a litre4 ,the solution is not permanent4 ,it is a strong reducing agent1 and is chiefly used in solution for this purpose4 ,tin1 ,sn4--,grain tin should be purchased4 ,it is not pure1 but contains #ii4e per cent4 of the metal4 ,the chief impurity is copper4 ,it can be used as a standard4 ,when acted on with hot hydrochloric acid it slowly dissolves 7more rapidly in contact with platinum7 and forms stannous chloride4 ,uranium ,acetate1 ,,uo#b7;,c#b;,h#c,o#b7b4;,h#b,o4--,it is best purchased in crystals4 ,the solution is used for the determination of phosphates and arsenates4 ,a solution of #c per cent4 strength is occasionally used as an indicator4 ,uranium ,nitrate1 ,,uo#b7,,no#c7b4f;,h#b,o4--,this salt is very soluble in water and is sometimes used instead of the acetate1 which is somewhat difficult to dissolve4 ,water1 ,h#b,o4--,spring or well water is sufficiently pure for most purposes1 #ajj c4c4 will leave a residue of from #aj to #cj milligrams1 so that where a salt has to be dissolved out1 evaporated1 and weighed it should be replaced by distilled water4 ,rain water1 melted snow1 c41 always leave less residue than spring water2 but in other respects they are often dirtier4 ,distilled water is best prepared in the office1 a glass or tin condenser being used4 ,zinc1 ,zn4--,it is sold in a granulated form or in sticks4 ,it generally contains over #a per cent4 of lead1 with a little iron and arsenic4 ,it is used for separating metals from their solutions1 and generally as a reducing agent4 ,for the preparation of hydrogen1 and in most other cases1 scrap sheet zinc may be used4 ,zinc ,oxide1 ,zn,o4--,the commercial oxide sometimes contains carbonate4 ,zinc ,sulphate1 ,zn,s,o#d4g;,h#b,o4--,it is occasionally used as a standard1 and can be purchased nearly pure4 ,,footnotes3 #f #c;,h,cl ,,hno#c ,cl#b ,n,o,cl #b;,h#b,o4 #g ,na,c#b;,h#c,o#b ,h,cl ,h#d;,c#b,o#b ,na,cl4 ,,chapter ,,vii4 ,,formul1 ,,equations1 ,,etc4 ,formul and equations are a kind of short hand for expressing briefly and in the language of the atomic theory the facts of chemical composition and reaction4 ,the convenience of this method of expressing the facts justifies a short description of it here4 ,on comparing the percentage composition of a series of compounds the proportions in which the elements combine appears to be regulated by no simple law4 ,for example3 ,realgar4 ,orpiment4 ,mispickel4 ,pyrites4 ,arsenic #ga4d #fj4i #df4j -- ,sulphur #bh4f #ci4a #ai4f #ec4c ,iron -- -- #cd4d #df4g ------ ------ ------ ------ #ajj4j #ajj4j #ajj4j #ajj4j ,but if in these examples the composition is calculated1 not on #ajj parts1 but on #ajg1 #bdf1 #afc1 and #abj parts respectively1 evidence of a simple law becomes apparent4 ,realgar4 ,orpiment4 ,mispickel4 ,pyrites4 ,arsenic #ge4j #aej4j #ge4j -- ,sulphur #cb4j #if4j #cb4j #fd4j ,iron -- -- #ef4j #ef4j ------ ------ ------ ------ #ajg4j #bdf4j #afc4j #abj4j ,it will be seen that the proportion of arsenic is #ge or twice #ge1 that of iron is #ef1 and that of sulphur #cb or some simple multiple of #cb4 ,the series of examples might be extended indefinitely1 and it would still be found that the combining proportions held good4 ,the number #ge is spoken of as the combining weight1 or1 more frequently1 as the atomic weight of arsenic4 ,similarly #ef is the atomic weight of iron1 and #cb the atomic weight of sulphur4 ,the importance of this law of chemical combination is altogether independent of the atomic theory2 but this theory furnishes the simplest explanation of the facts4 ,according to it a chemical compound is made up of exactly similar groups of particles4 ,the particles of each elementary substance are all alike1 but differ from those of other elements in weight4 ,ultimate particles are called atoms1 and the groups of atoms are called molecules4 ,the atomic weight of any particular element is the weight of its atom compared with the weight of an atom of hydrogen4 ,the atom of sulphur1 for instance1 is #cb times as heavy as the atom of hydrogen1 and the atomic weight of sulphur is #cb4 ,the molecular weight is the sum of the atomic weights of the group4 ,the molecule of pyrites contains two atoms of sulphur and one of iron3 on referring to the table of atomic weights it will be seen that the atomic weights are--sulphur #cb1 and iron #ef4 ,the molecular weight1 therefore1 is #cbcbef--that is1 #abj4 ,the meaning of this is1 #abj parts by weight of iron pyrites contain #fd parts of sulphur and #ef parts of iron2 and this is true whether the parts by weight be grains or tons4 ,the symbol or formula of an atom is generally the initial letter or letters of the ,latin or ,english name of the substance4 ,the atom of hydrogen is written ,h1 that of oxygen ,o1 of sulphur ,s1 of iron 7ferrum7 ,fe1 and so on4 ,a list of these symbols is given in the table of atomic weights4 ,the formula of a molecule is obtained by placing together the symbols of the contained atoms4 ,thus1 ,fe represents an atom of iron1 ,s an atom of sulphur1 while ,fe,s represents the molecule of sulphide of iron as containing one atom of each element4 ,when more than one atom of an element is present this is shown by writing a figure under and after the symbol2 thus1 ,fe,s#b represents a molecule with one atom of iron and two atoms of sulphur1 ,fe#b,s#c similarly shows one with two atoms of iron and three of sulphur4 ,when a group of atoms is enclosed in brackets1 a figure after and under the bracket multiplies all within it2 for example1 ,pb7,,no#c7b is another way of writing ,pb,n#b,o#f4 ,sometimes it is convenient to represent the atoms of a molecule as divided into two or more groups2 this may be done by writing the formul of the groups1 and separating each simple formula by a full stop4 ,slaked lime1 for instance1 has the formula ,ca,h#b,o#b2 or1 as already explained1 we may write it ,ca7,,ho7#b2 or1 if for purposes of explanation we wished to look on it as lime 7,ca,o7 and water 7,h#b,o71 we could write it ,ca,o4,h#b,o4 ,a plus sign 77 has a different meaning2 ,ca,o ,h#b,o indicates quantities of two substances1 water and lime1 which are separate from each other4 ,the sign of equality 77 is generally used to separate a statement of the reagents used from another statement of the products of the reaction2 it may be translated into the word yields or becomes4 ,the two statements form an equation4 ,ignoring the quantitative relation1 the meaning of the equation ,ca,o ,h#b,o ,ca,o4,h#b,o is3 lime and water yield slaked lime4 ,by referring to a table of atomic weights we can elicit the quantitative relations thus3-- ,ca,o ,h#b,o ,ca,h#b,o#b ,v ,v ,v ,ca #dj ,h#b #b #ab ,ca #dj ,o #af ,o #af ,h#b #b #ab -- -- ,o#b #cb #afb #ef #ah -- #gd ,or1 putting it in words1 #ef parts of lime combine with #ah parts of water to form #gd parts of slaked lime4 ,this equation enables one to answer such a question as this3--,how much lime must be used to produce #a cwt4 of slaked lime8 for1 if #gd lbs4 of slaked lime require #ef lbs4 of lime1 #aab lbs4 will require 7#efaab7_/gd1 or about #hd-c_/d lbs4 ,as another example having a closer bearing on assaying take the following question3--,in order to assay #e grams of 'black tin' 7,sn,o#b7 by the cyanide process1 how much potassic cyanide 7,,kcn7 will be required8 ,the reaction is ,sn,o#b #b,,kcn ,sn #b,,kcno ,v ,v ,sn #aah ,k #ci ,o#b #cb ,c #ab --- ,n #ad #aej -- #feb #acj ,what is sought for here is the relation between the quantities of ,sn,o#b and ,,kcn4 ,note that a figure before a formula multiplies all that follows up to the next stop or plus or equality sign4 ,the question is now resolved to this3 if #aej grams of oxide of tin require #acj grams of cyanide1 how much will #e grams require8 #aej 3 #acj 33 #e 3 x x #d4cc grams4 ,a problem of frequent occurrence is to find the percentage composition of a substance when its formula has been given4 ,for example3 ,what percentage of iron is contained in a mineral having the formula #b;,fe#b,o#c4c;,h#b,o8 ,bringing this formula together we have ,fe#d;,h#f,o#i4 ,find the molecular weight4 ,fe#d #bbd #efd ,h#f #f #af ,o#i #add #afi --- #cgd ,then we get3 #cgd parts of the mineral contain #bbd of iron4 ,how much will #ajj contain8 #cgd 3 #bbd 33 #ajj 3 x x #ei4hi4 ,and the answer to the question is #ei4hi per cent4 ,again1 suppose the question is of this kind3--,how much crystallised copper sulphate 7,cu,s,o#d4e;,h#b,o7 will be required to make #b litres of a solution1 #a c4c4 of which shall contain #j4jjaj gram of copper8 ,a litre is #ajjj c4c41 so1 therefore1 #b litres of the solution must contain #j4jja gram #bjjj1 or #b grams4 ,how much crystallised copper sulphate will contain this amount of metal8 ,cu #fc4c ,s #cb4j ,o#d #fd4j #afd #e;,h#b,o #ij4j #ahe ----- #bdi4c ,if #fc4c grams of copper are contained in #bdi4c grams of sulphate1 in how much is #b grams contained4 #fc4c 3 #bdi4c 33 #b grams 3 x x #g4hgfi grams4 ,the answer is1 #g4hgfi grams must be taken4 ,as a sample of another class of problem similar in nature to the last 7but a little more complicated7 take the following3--,what weight of permanganate of potash must be taken to make #b litres of a solution1 #ajj c4c4 of which shall be equivalent to #a gram of iron8 ,in the first place the #b litres must be equivalent to #bj grams of iron1 for there are #bj #ajj c4c4 in two litres4 ,in the titration of iron by permanganate solution there are two reactions4 ,first in dissolving the iron ,fe ,h#b,,so#d ,fe,s,o#d ,h#b ,v #ef and second1 in the actual titration1 #aj;,fe,s,o#d #b,k,mn,o#d #i;,h#b,,so#d #b,mn,s,o#d #e;,fe#b7,,so#d7c #b,,khso#d #h;,h#b,o ,v ,k #ci ,mn #ee ,o#d #fd --- #aeh #b #caf ,as before1 attention is confined to the two substances under consideration--viz41 ,fe and ,k,mn,o#d4 ,in the second equation1 we find #caf parts of the permanganate are required for #aj molecules of ,fe,s,o#d2 and in the first equation #ef parts of iron are equivalent to one molecule of ,fe,s,o#d1 therefore #efj of iron are equivalent to #caf of permanganate2 and the question is1 ,how much of the permanganate will be equivalent to #bj grams of iron8 #efj 3 #caf 33 #bj grams 3 x4 x #aa4bhf grams4 ,the answer is #aa4bhf grams4 ,very similar to this last problem is the question suggested under the head ,indirect ,titration 7p4 #dc74 ,if #ajj c4c4 of the standard permanganate solution are equivalent to #a gram of iron1 how much peroxide of manganese will they be equivalent to8 ,the equation for dissolving the iron is already given2 the second equation is #b;,fe,s,o#d ,mn,o#b #b;,h#b,,so#d ,fe#b7,,so#d7b ,mn,s,o#d #b;,h#b,o ,v ,mn #ee ,o#b #cb -- #hg ,it will be seen that #hg grams of peroxide of manganese are equivalent to #aab grams of iron4 ,how much then is equivalent to #a gram of iron8 #aab 3 #hg 33 #a gram 3 x x #j4ggfg gram4 ,it is sometimes convenient to calculate the formula of a substance from its analysis4 ,the method of calculating is shown by the following example4 ,required the formula of a mineral which gave the following figures on analysis3-- ,cupric oxide 7,cu,o7 #aj4eh ,ferrous oxide 7,fe,o7 #ae4fi ,zinc oxide 7,zn,o7 #j4ce ,sulphuric oxide 7,,so#b7 #bh4hb ,water 7,h#b,o7 #dd4ga ------ #ajj4ae ,first find the molecular weights of ,cu,o1 ,fe,o1 c41 and divide the corresponding percentages by these figures4 ,thus1 ,cu,o #fc4caf #gi4c and #aj4eh divided by #gi4c gives #j4accd4 ,similarly ,fe,o #efaf #gb and #ae4fi divided by #gb gives #j4bagi4 ,treated in the same way the oxide of zinc1 sulphuric oxide and water give as results #j4jjdc1 #j4cfjb and #b4dhd4 ,classify the results as follows3-- ,bases4 ,acids4 ,water4 ,cu,o #j4accd ,,so#c #j4cfjb ,h#b,o #b4dhd ,fe,o #j4bagi ,zn,o #j4jjdc ---------- ------------- ------------ ,,ro #j4ceef ,,ro#c #j4cfjb ,r#b,o #b4dhd ,the figures #j4ceef1 #j4cfjb and #b4dhd should be then divided by the lowest of them--i4e41 #j4ceef2 or where1 as in this case1 two of the figures are very near each other the mean of these may be taken--i4e41 #j4cegi4 ,whichever is taken the figures got will be approximately #a1 #a and #g4 ,the formula is then ,,ro4,,so#c4g;,h#b,o in which ,r is nearly #b_/eths copper1 #c_/eths iron and a little zinc4 ,this formula requires the following percentage composition1 which for the sake of comparison is placed side by side with the actual results4 ,calculated4 ,found4 ,cupric oxide #aa4bi #aj4eh ,ferrous oxide #ae4cg #ae4fi ,zinc oxide nil #j4ce ,sulphuric oxide #bh4dg #bh4hb ,water #dd4hd #dd4ga ----- ------ #ii4ig #ajj4ae ,trimming the results of an analysis to make them fit in more closely with the calculations from the formula would be foolish as well as dishonest4 ,there can be no doubt that the actual analytical results represent the composition of the specimen much more closely than the formula does2 although perhaps other specimens of the same mineral would yield results which would group themselves better around the calculated results than around those of the first specimen analysed4 ,it must be remembered that substances are rarely found pure either in nature or in the arts2 so that in most cases the formula only gives an approximation to the truth4 ,in the case of hydrated salts there is generally a difficulty in getting the salt with exactly the right proportion of water4 ,,practical ,,exercises4 ,the following calculations may be made3-- #a4 ,calculate standards in the following cases-- 7a7 ,silver taken1 #a4jjc gram4 ,standard salt used1 #ajj4ae c4c4 7b7 ,iron taken1 #j4g gram4 ,bichromate used1 #fi4f c4c4 #b4 ,calculate percentages3-- 7a7 ,ore taken1 #a gram4 ,solution used1 #fe4b c4c4 ,standard1 #j4ihg gram4 7b7 ,ore taken1 #a gram4 ,barium sulphate got1 #a4dcb gram4 ,barium sulphate contains #ac4gc per cent4 of sulphur1 and the percentage of sulphur in the ore is wanted4 7c7 ,barium sulphate is ,ba,s,o#d4 ,calculate the percentage of sulphur it contains1 for use in the preceding question4 #c4 ,a method of estimating the quantity of peroxide in a manganese ore is based on the following reactions3-- 7#a7 ,mn,o#b #d;,h,cl ,mn,cl#b ,cl#b #b;,h#b,o4 7#b7 ,cl ,,ki ,k,cl ,i4 ,to how much ,mn,o#b is #a gram of ,iodine 7,i7 equivalent8 #d4 ,a mineral has the following composition3-- ,carbonic acid 7,,co#b7 #ai4ji ,copper oxide 7,cu,o7 #ga4df ,water 7,h#b,o7 #i4jb ,what is its formula8 #e4 ,how much copper is contained in #a4e gram of crystallized copper sulphate 7,cu,s,o#d4e;,h#b,o78 ,how much of these crystals must be taken to give #j4d gram of copper8 #f4 ,how much ferrous sulphate crystals 7,fe,s,o#d4g;,h#b,o7 must be taken to yield #b litres of a solution1 #ajj c4c4 of which shall contain #j4ef gram of iron8 #g4 ,galena is ,pb,s1 and hmatite ,fe#b,o#c4 ,what percentages of metal do these minerals contain8 ,,chapter ,,viii4 ,,specific ,,gravity4 ,the relation of the weight of a substance to its volume should be kept in mind in all cases where both weight and volume are dealt with4 ,students are apt to imagine that on mixing equal volumes of1 say1 sulphuric acid and water1 an acid of half the strength must be obtained4 ,if the statement of strength is in parts by weight this will lead to considerable error4 ,for example1 #ajj c4c4 of sulphuric acid containing #ih per cent4 by weight of real acid1 will1 if diluted with #ajj c4c4 of water1 yield a solution containing not #di per cent4 by weight1 but about #fc4e per cent4 of the acid4 ,the reason is this3 the #ajj c4c4 of sulphuric acid weighs #ahd grams1 and contains #ahj4cb grams of real acid1 while the #ajj c4c4 of water weighs only #ajj grams2 the mixed water and acid weighs #bhd grams1 and contains #ahj4cb of real acid1 which is equivalent to nearly #fc4e per cent4 by weight4 ,if1 however1 the method of statement be volumetric1 it would be correct to say that doubling the volume halves the strength3 if #ajj c4c4 of brine contains #aj grams of salt1 and is diluted with water to #bjj c4c41 it would be of one-half the former strength1 that is1 #ajj c4c4 of the solution would contain #e grams of salt4 ,this confusion is avoided by always stating the strengths as so many grams or c4c4 in #ajj c4c4 of the liquid4 ,but obviously it would be advantageous to be able to determine quickly the weight of any particular substance corresponding to #a c4c4 or some other given volume4 ,moreover1 in descriptions of processes the strengths of acids and solutions are frequently defined neither by their gravimetric nor volumetric composition1 but by a statement either of specific gravity or of the degrees registered by ,twaddell's or ,beaum's hydrometer4 ,thus1 in the description of the process of gold parting1 one writer gives3 ,the acid should be of #a4b specific gravity2 and another says3 ,the acid must not be stronger than #cb ,beaum4 ,these considerations justify an account of the subject in such a work as this4 ,and on other grounds the determination of a specific gravity is one of the operations with which an assayer should be familiar4 ,the meaning of specific gravity is present in the mind of every one who uses the sentence lead is heavier than water4 ,this is meaningless except some such phrase as bulk for bulk be added4 ,make the sentence quantitative by saying3 bulk for bulk lead is #aa4cf times heavier than water1 and one has the exact meaning of3 the specific gravity of lead is #aa4cf4 ,a table of the specific gravities of liquids and solids shows how many times heavier the substances are than water4 ,it is better1 however1 to look upon the specific gravity 7written shortly1 sp4 g47 as the weight of a substance divided by its volume4 ,in the metric system1 #a c4c4 of water at #d ,c4 weighs with sufficient exactness #a gram2 consequently1 the sp4 g41 which states how many times heavier than water the substance is1 also expresses the weight in grams of one c4c4 of it4 ,so that if a #ajj c4c4 flask of nitric acid weighs1 after the weight of the flask has been deducted1 #abj grams1 #a c4c4 of the acid weighs #a4b gram1 and the sp4 g4 is #a4b4 ,the specific gravity1 then1 may be determined by dividing the weight of a substance in grams by its volume in c4c42 but it is more convenient in practice to determine it by dividing the weight of the substance by the weight of an equal volume of water4 ,and since the volumes of all substances1 water included1 vary with the temperature1 the temperature at which the sp4 g4 is determined should be recorded4 ,even then there is room for ambiguity to the extent that such a statement as the following1 the specific gravity of the substance at #ej ,c4 is #j4ijaj1 may mean when compared with water at #ej ,c4 or #d ,c41 or even #ae4e ,c4 ,for practical purposes it should mean the first of these1 for in the actual experiments the water and the substance are compared at the same temperature1 and it is well to give the statement of results without any superfluous calculation4 ,in the metric system the standard temperature is #d ,c41 for it is at this point that #a c4c4 of water weighs exactly #a gram4 ,in ,england1 the standard temperature is #fj ,f4 7#ae4e ,c471 which is supposed to be an average temperature of the balance-room4 ,the convenience of the ,english standard1 however1 is merely apparent2 it demands warming sometimes and sometimes cooling4 ,for most purposes it is more convenient to select a temperature sufficiently high to avoid the necessity of cooling at any time4 ,warming to the required temperature gives very little trouble4 ,determination of ,specific ,gravity4--,there is a quick and easy method of determining the density or sp4 g4 of a liquid1 based upon the fact that a floating body is buoyed up more by a heavy liquid than by a light one4 ,the method is more remarkable for speed than accuracy1 but still is sufficiently exact4 ,the piece of apparatus used for the purpose is endowed with a variety of names--sp4 g4 spindle1 hydrometer1 areometer1 salimeter1 alcoholimeter1 lactometer1 and so on1 according to the special liquid upon which it is intended to be used4 ,it consists of a float with a sinker at one end and a graduated tube or rod at the other4 ,it is made of metal or glass4 ,generally two are required1 one for liquids ranging in sp4 g4 from #a4jjj to #b4jjj1 and another1 which will indicate a sp4 g4 between #j4gjj and #a4jjj4 ,the range depends on the size of the instrument4 ,for special work1 in which variations within narrow limits are to be determined1 more delicate instruments with a narrower range are made4 ,illustration3 ,,fig4 #cd4 ,in using a hydrometer1 the liquid to be tested is placed in a cylinder 7fig4 #cd7 tall enough to allow the instrument to float1 and not too narrow4 ,the temperature is taken1 and the hydrometer is immersed in the fluid4 ,the mark on the hydrometer stem1 level with the surface of the liquid1 is read off4 ,with transparent liquids it is best to read the mark under and over the water surface and take the mean4 ,the graduation of hydrometers is not made to any uniform system4 ,those marked in degrees ,baum or ,twaddell1 or according to specific gravity1 are most commonly used4 ,the degrees on ,baum's hydrometer agree among themselves in being at equal distances along the stem2 but they are proportional neither to the specific gravity1 nor to the percentage of salt in the solution4 ,they may be converted into an ordinary statement of specific gravity by the following formul3-- ,sp4 g4 #add4c_/7add4c-;degrees ,baum47 or putting the rule in words1 subtract the degrees ,baum from #add4c1 and divide #add4c with the number thus obtained4 ,for example3 #cb ,baum equals a sp4 g4 of #a4bhe4 #add4c_/7add4c-cb7 #add4c_/7aab4c7 #a4bhe ,this rule is for liquids heavier than water2 for the lighter liquids the rule is as follows3-- ,sp4 g4 #adf_/7acf degrees ,baum47 or in words divide #adf by the number of degrees ,baum added to #acf4 ,for example3 ammonia of #cj ,beaum has a sp4 g4 of #j4hhj 7nearly74 #adf_/7acfcj7 #adf_/aff #j4hgie ,a simple series of calculations enables one to convert a ,beaum hydrometer into one showing the actual sp4 g4 ,graduation1 according to sp4 g4 is the most convenient for general purposes4 ,in these instruments the distances between the divisions become less as the densities increase4 ,twaddell's hydrometer is graduated in this way3 ,each degree ,twaddell is #j4jje in excess of unity4 ,to convert into sp4 g4 multiply the degrees ,twaddell by #j4jje1 and add #a4 ,for example3 #be ,twaddell equals a sp4 g4 of #a4abe4 #be4jje #j4abe2 #a4jjj #a4abe4 ,there is a practice which ignores the decimal point and speaks of a sp4 g4 of #aabe instead of #a4abe4 ,in some cases it is convenient1 and inasmuch as no substance has a real sp4 g4 of much over #bj1 it can lead to no confusion4 ,the figures expressed in this way represent the weight of a litre in grams4 ,some hydrometers are graduated so as to show at a glance the percentage composition of the liquid they are intended to be used with4 ,gay-,lussac designed one to show the alcoholic strength of mixtures of alcohol and water2 the construction of others upon the same principle is easy and perhaps useful4 ,but when the principle is applied to complex liquids and mixed solutions1 it is misleading4 ,the various methods of graduation ought all to give place to one showing a simple statement of the sp4 g4 ,the method of determining sp4 g4 with the hydrometer is obviously inapplicable to the case of solids1 and in the case of liquids it should not be used where exact figures are required4 ,there are several other methods which may be used1 but on the whole those with the specific gravity bottle are most convenient4 ,illustration3 ,,fig4 #ce4 ,the specific gravity bottle 7fig4 #ce7 is a light flask of about #be c4c4 capacity1 provided with a well-fitting perforated stopper4 ,it is essentially a graduated flask1 which measures a constant volume1 but it does not much matter what the volume is4 ,in taking the sp4 g4 of a liquid 7or1 what is the same thing1 a fused solid7 there is wanted the weights 7#a7 of the flaskful of water and 7#b7 of the flaskful of the liquid4 ,dividing the second by the first gives the required sp4 g4 ,the actual weighings required are-- 7#a7 of the dry and empty flask1 7#b7 of the flask filled with water1 and 7#c7 of the flask filled with the liquid4 ,the weighing of the flask once made need not be often repeated4 ,it is well to do so now and then for safety's sake2 but one weighing will serve for a large number of determinations4 ,the same remarks apply to the weighing of the bottle filled with water4 ,the bottle is dried by rinsing out first with alcohol and afterwards with ether2 ether is very volatile1 and a short exposure in a warm place will soon drive off the little remaining about the sides4 ,the ether vapour should be sucked out through a glass tube4 ,see that the bore of the stopper is dry as well as the bottle4 ,let the dry bottle stand in the box of the balance for a minute or two before weighing4 ,the weight is1 strictly speaking1 not that of the empty bottle1 but of the bottle filled with air4 ,the empty bottle would weigh from #bj to #cj milligrams less4 ,correcting for this would1 in most cases1 only make a difference in the fourth place of decimals1#h so that it is better to ignore the error4 ,the weight of the flask filled with water is got by filling it with distilled water1 and inserting the stopper4 ,the excess of water will overflow at the margin and through the bore4 ,the bottle is wiped with a soft1 dry cloth1 taking care not to squeeze or warm the bottle4 ,the bottle will remain filled to the top of the stopper4 ,it is allowed to stand in the balance box for a minute or two1 and then weighed4 ,distilled water1 as stated1 should be used2 the use of ordinary water may increase the weight by #e or #f milligrams4 ,many waters1 if they have not previously been boiled1 give off bubbles of air which render the weighing worthless4 ,the temperature of the water is of greater importance2 lowering the temperature #b will increase the weight by #aj or #ab milligrams4 ,a beaker of water may be warmed or cooled to the required temperature2 then the bottle is filled from it1 and quickly weighed4 ,if the balance-room is cooler than the water1 the latter will draw back into the bottle1 and a few small bubbles of air will enter2 but even in extreme cases this will only increase the weight by a very small fraction of a milligram4 ,there is more trouble caused when the room is warmer1 for the liquid then expands and protrudes as a drop resting on the top of the stopper4 ,there will in this case be loss by evaporation1 which in the case of the more volatile liquids1 such as alcohol1 is serious4 ,to prevent this loss1 as well as any that may arise by overflow1 the stopper should be dilated above into a small cup1 ,a 7fig4 #cf71 which may itself be stoppered4 ,in a bottle of this kind the neck of the stopper is graduated1 and the bottle is considered full when the liquid stands at the level of the mark in the neck4 ,on inserting the stopper1 the liquid rises into the cup1 and is reduced to the level of the mark by absorption with pieces of filter-paper4 ,illustration3 ,,fig4 #cf4 ,for most purposes1 however1 there is no need for cooling and allowing room for subsequent expansion4 ,the assayer1 as a rule1 can select his own standard temperature1 and may choose one which will always necessitate warming4 ,it will be handier in this case to have a bottle with a thermometer stopper4 ,of the two types shown in fig4 #cg1 that with the external thermometer tube 7,a7 is more generally useful4 ,illustration3 ,,fig4 #cg4 ,the bottle is filled at a lower temperature1 and is then gently warmed so as to slowly raise the temperature to the required degree4 ,the superfluous liquid is then at once wiped off1 and the bottle cooled and weighed4 ,the weight of the flask filled with the liquid whose sp4 g4 has to be determined is ascertained in a similar way4 ,of course the temperature must be the same4 ,if the liquid does not mix with water1 the bottle should be dried before filling1 but otherwise the flask need only be rinsed out two or three times with the liquid4 ,having obtained the three weighings1 deduct the weight of the bottle from each of the others to get the weights of the water and liquid respectively4 ,divide the latter by the former1 the result shows the sp4 g4 ,as an example1 take the following1 in which a rather large sp4 g4 bottle was used3-- #a4 ,weight of bottle #ci4bii gram #b4 ,weight of bottle and water #ha4hhd #c4 ,weight of bottle and paraffin #gc4adf ,by subtracting #a from #b and #c the result is as follows3-- #ha4hhd grams #gc4adf grams #ci4bii #ci4bii ------ ------ #db4ehe of water4 #cc4hdg of paraffin4 ,divide the weight of the paraffin by that of the water-- #db4ehe7cc4hdgj7j4gidh #bi4hjie ------- 4444444 ,the sp4 g4 of the paraffin is #j4gidh4 ,the sp4 g4 of a fusible solid may be obtained in the same way at a temperature some degrees above its fusing point4 ,the sp4 g4 of a solid in powder or gravel sufficiently fine to pass through the neck of the bottle is easily determined4 ,if the bottle filled with water weighs #ej grams1 and there is placed on the pan alongside of it #bj grams of a sand1 the weight of the two together will of course be #gj grams4 ,but if the sand is put in the bottle1 it evidently displaces its own bulk of water2 and if1 on again weighing1 the weight is found to be #fb instead of #gj grams1 it is because the #bj grams of sand has displaced #h grams of water4 ,bulk for bulk1 the sand is #b-a_/b times as heavy4 ,in practice1 the weight of the bottle filled with water will probably be already known2 if not1 it must be determined4 ,a certain quantity1 say #bj grams1 of the powdered substance is then transferred carefully to the bottle4 ,the bottle need not be dry inside1 but its neck and outside must be4 ,in making this transference a careful worker will make no loss1 and the mode of working saves a little time4 ,but it is better to weigh the dry flask2 put into it #aj to #bj grams of the powder1 and weigh again4 ,the increase in weight gives accurately the weight of powder in the bottle4 ,about two-thirds fill the bottle with distilled water1 and mix with the powder by gentle shaking4 ,air bubbles will disentangle themselves1 and rise to the surface of the water4 ,wash back anything adhering to the stopper with a jet of water1 and fill the bottle almost to overflowing4 ,allow it to stand for a minute or so2 replace the stopper2 warm to the required temperature2 take off the superfluous moisture2 wipe and weigh4 ,as an example1 take the following3-- #a4 ,weight of bottle #ab4fha grams #b4 bottle filled with water #cg4gjh #c4 bottle with wolfram #dj4hba #d4 bottle with wolfram and water #fa4aii ,subtract 7#a7 from 7#c7 to get the weight of wolfram taken3 #dj4hba grams #ab4fha ------ #bh4adj add the weight of the wolfram to the weight of the bottle filled with water3 #bh4adj grams #cg4gjh ------ #fe4hdh subtract 7#d7 from this to get the weight of water displaced3 #fe4hdh grams #fa4aii ------ #d4fdi ,divide the weight of the wolfram by the weight of the water displaced to get sp4 g43 #d4fdi7bh4adj7f4jec #bg4hid ------ 444444 ,if the solid is soluble in water1 or has a tendency to float1 some liquid other than water is used4 ,paraffin oil or oil of turpentine will do4 ,the process is as follows3--,the weight of the dry and empty bottle having been determined1 add a sufficiency of the substance and weigh again to find how much has been added4 ,fill up with paraffin oil and weigh again4 ,clean out the substance by rinsing with paraffin2 fill up and weigh4 ,calculate the sp4 g4 as if water had been used1 and multiply by the sp4 g4 of the paraffin4 ,for example3 #a4 ,weight of bottle #ci4bii grams #b4 bottle and nitre #eg4hcj #c4 bottle and paraffin #gc4adf #d4 bottle and paraffin and nitre #hd4ffe #e4 bottle and water #ha4hhd ,first from 7#a717c71 and 7#e71 calculate the sp4 g4 of the paraffin as already shown4 ,it will be #j4gidh4 ,deduct 7#a7 from 7#b7 to get the weight of the nitre3 #eg4hcj grams #ci4bii ------ #ah4eca add this to 7#c73 #ah4eca grams #gc4adf ------ #ia4fgg and deduct 7#d7 to find the weight of the equal bulk of paraffin4 #ia4fgg grams #hd4ffe ------ #g4jab divide the weight of the nitre by the weight of the paraffin3 #g4jab7ah4eca7b4fdbg ------ 444444 ,the sp4 g41 taking paraffin as the standard instead of water1 is #b4fdbg4 ,multiply this by the sp4 g4 of paraffin1 #j4gidh1 and the result is #b4ajjd as the sp4 g4 of nitre compared with water4 ,similarly1 a sp4 g4 compared with water at say #ej ,c4 can be converted into one compared with water at standard temperature1 by multiplying by the sp4 g4 of water at #ej ,c4 ,the following table gives the sp4 g4 of water at various temperatures3-- ---------------------------------------- ------------ ,degrees ,degrees ,degrees ,centigrade4,sp4 ,g4,centigrade4,sp4 ,g4,centigrade4,sp4 ,g4 ---------------------------------------- ------------ #d #a4jjjj #bj #j4iihb #dj #j4iibc #aj #j4iiig #be #j4iiga #ej #j4ihha #ae #j4iiia #cj #j4iieg #ajj #j4iehf ---------------------------------------- ------------ ,if1 for example1 a substance at #ej ,c4 has a sp4 g4 of #j4ijaj as compared with water at #ej ,c41 it will have 7compared with water at #d ,c47 a sp4 g4 of #j4ijajj4ihha2 or #j4hijc4 ,the figures #j4hijc represent the sp4 g4 of the substance at #ej ,c4 compared with water at #d ,c4 ,except in comparing the sp4 gravities of the same substance at different temperatures1 a calculation of this kind serves no useful purpose4 ,in taking the specific gravity of a solid not in powder1 a lump of it is freed from loose particles and its exact weight determined4 ,by means of a horse hair with a slip knot it is suspended to the balance1 and beneath it is placed1 out of contact with the balance pan1 a beaker of distilled water4 ,the horse hair must be long enough to keep the mineral well beneath the surface of the water so as to allow the balance to vibrate4 ,air bubbles are removed by touching with a camel-hair pencil4 ,whilst the mineral is suspended in water the weight is again taken4 ,it will weigh less than before1 and the difference between the two weighings gives the weight of water 7and consequently the volume7 displaced by the mineral4 ,the weight in air divided by the difference is the specific gravity4 ,thus ,weight in air #c4bagj grams ,weight in water #b4gjej ------ ,difference #j4eabj gram #c4bagj_/j4eabj equals #f4bh1 the sp4 g4 ,the sp4 g4 of a substance depends mainly on its composition1 but is affected by certain conditions4 ,the effect of temperature has been already considered4 ,air holes and empty spaces lessen the specific gravity of otherwise solid bodies2 and metals1 which after fusion become imperfect solids1 have their density increased by hammering or rolling4 ,but metals when free from pores have their density diminished when rolled1 without annealing4 ,the effects of these conditions are slight when compared with those due to the presence of impurities4 ,for simple substances1 or mixtures of only two substances1 a determination of sp4 g4 is a sufficient check on the composition for many practical purposes2 and with more complex mixtures1 such as slags and some of the products of dressing operations in which the material does not differ much in its nature from time to time1 such a determination will yield information of considerable value1 and afford a check upon the proper working of a process4 ,when the mixing of two substances is accompanied by a change in volume1 the sp4 g4 of the mixture can only be learnt by experiment4 ,but when the substances have no such action on each other the resulting sp4 g4 can be calculated4 ,some of these calculations have a practical interest as well as an educational value4 ,students should practise them so as to become familiar with the relations between weight and volume4 ,when substances are mixed by volume1 the sp4 g4 of the mixture is the mean of those of its constituents1 and may be calculated in the usual way for obtaining averages4 #a c4c4 of a substance having a sp4 g4 of #a4d mixed with #a c4c4 of another having a sp4 g4 of #a4j will yield #b c4c4 of a substance having a sp4 g4 of #a4b4 ,if1 however1 we write gram instead of c4c4 in the above statement1 the resulting sp4 g4 will be #a4af4 ,the simplest plan is to remember that the sp4 g4 is the weight divided by the volume 7sp4 g4 w_/v7 and the sp4 g4 of a mixture is the sum of the weights divided by the sum of the volumes 7sp4 g4 7w w' w1 c47_/7v v' v1 c4774 ,in the above example the sum of the volumes is #b c4c42 the weights 7got by multiplying each volume by its corresponding sp4 g47 are #a4d gram and #a gram4 ,the sum of the weights divided by the sum of the volumes is #b4d_/b or #a4b4 ,the sp4 g4 of a mixture of #aj c4c4 of a substance having a sp4 g4 of #a4b1 with #ae c4c4 of another having a sp4 g4 of #a4e may be thus found3-- sp4 g4 7#abbb4e7_/7ajae7 #a4ch multiply each volume by its sp4 g4 to get its weight3 #aja4b #ab #aea4e #bb4e add these together 7#abbb4e #cd4e7 and divide by the sum of the volumes 7#ajae #be73 #be7cd4e7a4ch #be -- #ie1 c4 ,the sp4 g4 will be #a4ch1 provided the mixture is not accompanied by any change of volume4 ,the same formula will serve when the proportion of the ingredients is given by weight4 ,a mixture of #d parts by weight of galena 7sp4 g4 #g4e7 with #e parts of blende 7sp4 g4 #d7 will have a sp4 g4 of #e4jf3 sp4 g4 7#de7_/7j4eca4be7 #i_/a4gh #e4jf ,it is necessary in this case to calculate the volumes of the galena and of the blende1 which is done by dividing the weights by the sp4 gravities3 thus1 #d divided by #g4e gives #j4ec and #e divided by #d gives #a4be4 ,the converse problem is a little more difficult4 ,given the sp4 g4 of a mixture and of each of the two ingredients1 the percentage by weight of the heavier ingredient may be ascertained by the following rule1 which is best expressed as a formula4 ,there are three sp4 gravities given2 if the highest be written ,h1 the lowest ,l and that of the mixture ,m1 then3 ,percentage of heavier mineral 7#ajj;,h7,m-,l77_/7,m7,h-,l77 ,suppose a sample of tailings has a sp4 g4 of #c4j1 and is made up of quartz 7sp4 g4 #b4f7 and pyrites 7sp4 g4 #e4a73 then the percentage of pyrites is #bg3 7#ajje4a7c-b4f77_/7c7e4a-b4f77 7#eajj4d7_/7cb4e7 #bjd_/g4e #bg4b ,the same problem could be solved with the help of a little algebra by the rule already given1 as thus3 the sp4 g4 of a mixture equals the sum of the weights of the constituents divided by the sum of the volumes4 ,then #ajj grams of the tailings with x per cent4 of pyrites contain #ajj-x per cent4 of quartz4 ,the sum of the weights is #ajj4 ,the volume of the pyrites is x_/#e4a and of the quartz 7#ajj-x7_/#b4f4 ,then we have by the rule #c #ajj_/77x_/#e4a77ajj-x7_/#b4f7 #c #acbf_/7eaj-b4ex7 #bjd #g4ex and x #bg4b ,if the percentage 7,p7 and sp4 g4 7,h7 of one constituent and the sp4 g4 7,m7 of the mixture are known1 the sp4 g4 of the other constituent may be calculated by the following formula1 in which x is the required sp4 g43 x 77#ajj-,p7,m,h7_/77#ajj;,h7-7,p,m77 ,for example1 tailings 7sp4 g4 #c4j7 containing #bg4b per cent4 of pyrites 7sp4 g4 #e4a7 will contain 7#ajj-bg4b71 #gb4h per cent4 of earthy matter having a mean sp4 g4 of x3 x 77#ajj-bg4b7ce4a7_/77ajje4a7-7bg4bc77 #aaac4hd_/dbh4d #b4f ,the differences in sp4 g4 corresponding to differences in strength have been carefully determined and tabulated in the case of the stronger acids and of many other liquids4 ,such tables are given at the end of this book4 ,to ,calculate the ,weight of a ,measured ,volume of ,mineral or ,rock4--,multiply the cubic feet by #fb4d and then multiply by the sp4 g4 of the stuff1 the answer gives the weight in pounds4 ,for example1 #ajj cubic feet of quartz weighs #ajjfb4db4f #af1bbd lbs4 ,the weight of any mass of mineral of known extent and sp4 g4 is ascertained in this way4 ,the following table gives the specific gravities of some of the commoner minerals4 ,barytes #d4e ,blende #d4j ,calcite #b4f ,cassiterite #f4i ,chalybite #c4h ,copper pyrites #d4b ,fluor #c4a ,galena #g4e ,hmatite #e4j ,mispickel #f4b ,pyrites #e4j ,quartz #b4f ,,footnotes3 #h ,the difference of #bj or #cj milligrams is disregarded here because it detracts equally from the actual weight of the water and liquid to be determined4 ,if the liquid is a heavy one the difference shows itself in the third or second place of decimals4 ,the correction may be made by deducting from the weight of the flask #j4jjab grams for each gram of water it holds4 ,,part ,,ii4--,,the ,,metals4 ,,chapter ,,ix4 ,,silver1 ,,gold1 ,,cyanides1 ,,platinum1 ,,mercury4 ,,silver4 ,silver is widely diffused1 and has been found in most mining districts4 ,it occurs native in sufficient quantity to constitute one of the chief ores of the metal4 ,it also occurs combined with sulphur 7as in argentite71 with sulphur and antimony 7as in stephanite or brittle silver ore1 and in pyrargyrite or ruby silver71 and with copper1 sulphur1 antimony1 and arsenic1 as in polybasite4 ,chloride of silver occurs native as horn silver or kerargyrite4 ,silver is found in the ores of other metals1 such as fahlerz1 which sometimes contains from two to ten per cent4 of the metal1 and galena1 which is an important source of it2 in fact1 galena is never found entirely free from silver4 ,it is present also in greater or less quantity in the ores of copper and zinc4 ,silver dissolves readily in nitric acid1 forming silver nitrate4 ,it only forms one family of salts1 and of these the chloride and nitrate are of chief importance to the assayer4 ,the formation of the chloride of silver on the addition of hydrochloric acid or a soluble chloride to the nitric acid solution1 serves for the recognition and separation of silver4 ,the precipitated chloride is white 7becoming violet on exposure to light71 insoluble in nitric acid1 soluble in ammonia1 hyposulphite of soda1 or concentrated solutions of chlorides4 ,the best confirmatory test is made by wrapping the precipitate in a little sheet lead1 and cupelling1 when the silver will be left in the metallic state1 and is easily recognized4 ,dry ,assay4--,this assay is made up of two parts3 7#a7 the concentration of the silver in a button of lead2 and 7#b7 the cupellation of the resulting alloy4 ,the concentration of the button of lead may be effected either by scorification or by fusion in a crucible4 ,the scorification assay is performed in a scorifier1 which is a shallow open-mouthed dish about #b-a_/b inches across1 with a very thick bottom to enable it to withstand the corrosive action of the slag4 ,a charge of more than #c or #e grams of the ore cannot be worked in one1 and with such small charges the unavoidable variations have a serious effect on the figures reported4 ,a difference of one milligram on the weight of the button of silver got represents a difference of #f or #aj ounces per ton4 ,with rich ores such variation is unavoidable under any conditions1 and the only safe plan is to take the mean of several assays4 ,but with poorer ores the accuracy of the assay1 as well as convenience in working1 is much increased by working in a crucible with larger charges4 ,in scorification the proportion of lead required for scorifying #a gram of ore is in average cases from #aj to #ae grams1 sinking in the case of galena to #b grams1 and rising with earthy and refractory substances to from #cj to #dj grams4 ,but by fusing in a crucible with well-selected fluxes1 a proportion of #d of flux to #a of ore is generally sufficient2 and not only is the proportion of added matter less1 but it is also easier to manipulate large quantities in crucibles1 so that1 although in some cases the crucible assay is more troublesome and less satisfactory1 yet with poor and earthy ores it is the best method of dealing with them2 while when properly worked it yields results as accurate as scorification does4 ,as a general rule1 if more than #e grams of ore must be taken1 the crucible assay should be adopted4 ,illustration3 ,,fig4 #ch4 ,scorification ,assay4--,the charge of ore is usually #c grams1 sometimes #e2 the lead varies from #cj to #gj grams1 and the quantity of soda1 borax1 or powdered glass added varies from #j4c to #c or #d grams4 ,it is generally recommended to have the lead granulated1#i and to mix the ore with about half of it in the scorifier2 then to put on the rest of the lead2 and finally to sprinkle the borax or glass on the top4 ,it answers just as well1 however1 to use the lead in the shape of foil1 and wrap the ore up in it2 and if the ore contains much sulphur1 the borax may with advantage be added 7wrapped in a little tissue paper7 some five or ten minutes after the operation has started4 ,illustration3 ,,fig4 #ci4 ,the process of scorification is as follows3--,a scorifier 7fig4 #ch7 of convenient size having been selected 7one #b-a_/b inches across is most generally useful71 it is dried at a gentle heat for about ten minutes4 ,the charge is then put into it1 and it is introduced1 with the help of a scorifier tongs 7fig4 #ci71 into a muffle heated considerably above redness4 ,the muffle is then closed1 and when the metal has melted down1 it is opened1 but the temperature is kept up4 ,a ring of slag will1 after a time1 form around the metal1 and when this appearance 7known as the eye7 presents itself1 the temperature may be lowered4 ,when the eye has disappeared--that is1 when the layer of slag has quite closed in--a pinch of powdered culm wrapped in tissue paper is added4 ,as soon as the slag has again become tranquil1 the scorifier is taken out1 and its contents are poured into a mould 7fig4 #dj71 the slag is detached1 and saved4 ,if the button of metal weighs more than #cj grams1 its size is reduced by another scorification in the same scorifier1 which should have been replaced in the muffle immediately after the contents had been poured out4 ,if the ore is not a very rich one1 the button of lead will carry practically all the silver2 but with rich ores it is more satisfactory to save the slag1 and subsequently to melt it down with the cupel on which the lead has been treated1 so as to recover the silver lost in the slag1 together with that absorbed in the cupel1 at one operation4 ,or1 if the cupellation loss is neglected or calculated in some other manner1 the slag or slags from the scorifier may be powdered and mixed with #bj grams of oxide of lead1 #e grams of borax1 and #a gram of charcoal4 ,this should be melted down in a small crucible1 and the resulting button of lead cupelled4 ,illustration3 ,,fig4 #dj4 ,if the scorification has been unsatisfactory1 the quantity of silver obtained from the slag will be by no means inconsiderable4 ,the usual explanation is that with sulphury ores compounds of metallic oxides and sulphides 7oxysulphides7 are formed1 which remain in the slag1 retaining considerable quantities of the precious metal4 ,it is said that under certain conditions such a slag may contain as much as #aj per cent4 of silver4 ,an excess of lead and a high temperature prevents the formation of these oxysulphides4 ,but if much silver is present in the ore1 the slag cannot be safely thrown away1 even if sulphur is absent1 and the process has been satisfactorily performed4 ,if the crust which appears on the surface of the lead does not clear1 add a small lump of borax and #bj grams more lead2 then close the muffle1 and keep the temperature as high as possible4 ,if the slag forms properly1 but shows unfused or only half-fused lumps1 even when the scorification has proceeded for some time1 add more borax1 and stir with an iron rod4 ,the slag adhering to the rod must be detached by hammering1 and replaced in the scorifier4 ,if the ore consists largely of quartz1 soda should be added instead of borax2 or1 if it contains much copper1 powdered quartz may be used4 ,if the scorifier at the end of an operation is more than usually corroded1 the borax should be replaced in subsequent assays on similar ores by powdered glass or quartz4 ,if a fairly fluid slag is formed which does not clear from the metal and show the eye1 more lead and a higher temperature is wanted4 ,as a general rule1 it may be stated that when a scorification is unsatisfactory1 what is wanted is more heat1 more lead1 or more borax4 ,it is a safe plan when work has to be done on a strange ore1 to make three or four assays with varying quantities of lead4 ,the proportion of lead is right when a further addition does not yield a higher result4 ,the proper proportion having been found1 a note of it should be made for future use4 ,,pot ,,assays4 ,the object of the fusion in a crucible1 like that of scorification1 is to concentrate the silver in a button of lead which is to be subsequently cupelled2 and to retain the earthy and waste matters in the slag4 ,it is necessary to consider the quality of the slag and the weight and quality of the lead4 ,the slag when fused should be liquid and homogeneous1 and not too corrosive on the crucible4 ,the button of lead should be soft1 malleable1 and free from a coating of regulus4#aj ,in weight it should not differ much from the ore taken4 ,with #bj grams of ore1 for example1 a button of lead weighing from #ah to #be grams will be satisfactory3 less than this would leave an undue proportion of silver in the slag2 and more would be unnecessarily large for cupelling1 and would increase the loss in that operation4 ,with average ores1 take #bj grams of the powdered ore and mix with #cj grams of soda1 #dj grams of red-lead or litharge1 #e grams of borax1 and from #b to #b4e grams of flour1 and place in an ,e crucible 7,battersea round74 ,put these in the furnace at a red heat1 cover the crucible1 and gradually raise the temperature until the whole charge has melted down and is in a state of tranquil fusion4 ,pour into a mould1 and replace the crucible in the furnace4 ,as soon as the lead is solid1 detach the slag and put it back into the crucible2 and when it is again fluid1 charge on to it with a copper scoop a mixture of #bj grams of oxide of lead1 and #a gram of charcoal3 when fusion has again become tranquil1 pour and detach the button of lead4 ,the lead buttons should be hammered into discs with rounded edges1 and be freed from slag2 if too big for a cupel they may be scorified together in a small scorifier1 but it is better to cupel them separately4 ,ores containing ,metallic ,oxides4--,peroxides of iron1 manganese1 and copper interfere by counteracting the effect of the charcoal or flour1 and thus reducing the size of the lead button4 ,peroxide of iron will reduce the weight of lead by a little more than its own weight2 and peroxide of manganese has about twice this effect4 ,when these oxides are present an additional quantity of flour must be used1 and precautions must be taken to prevent reoxidation of the slag by the furnace gases4 ,this may best be prevented by using a layer of common salt as a cover to the charge4 ,when the ores contain a good deal of quartz or stony matter1 the fluxes just given 7for average ores7 will do2 but the proportion of soda should be diminished1 and that of the borax1 oxide of lead1 and flour increased as the quantity of metallic oxides become greater4 ,if the ore contains practically no quartz1 the soda may be altogether omitted1 and some glass or powdered quartz added4 ,the following charge may be taken as an example3 weigh up #bj grams of the powdered ore1 #ae grams each of soda and borax1 #fj grams of oxide of lead1 and #e grams of flour4 ,mix and place them in an ,e crucible1 and cover with a layer of from a quarter to half an inch of common salt4 ,place in the furnace as before4 ,the salt will give off a considerable amount of fume1 which will1 to a certain extent1 conceal the state of the charge3 when the crucible has been in the furnace for about #be minutes remove it and pour out the contents immediately4 ,with ores that produce a thick slag the addition of #e grams of fluor spar will be an advantage4 ,it may happen that with an unknown ore the first assay will be more or less unsatisfactory3 but from it the necessity for adding more or less flour will be learnt1 and a second assay1 with the necessary modification of the charge1 should give a good result4 ,ores containing much ,sulphides4--,ores of this class may be easily recognized1 either by the appearance of the minerals they contain or by the odour of sulphurous oxide 7,,so#b7 which they evolve when roasted on a spatula4 ,the sulphides most commonly present1 in addition to the sulphurized minerals of silver1 are pyrites1 galena1 blende1 and mispickel4 ,when they are present in only a moderate amount1 their effect is simply to increase the weight of the button of lead2 and this is easily counteracted by reducing the amount of flour1 or by omitting it4 ,when in larger amounts1 they not only yield large buttons1 but also render the metal sulphury1 sometimes even giving a button of regulus instead of lead4 ,this last evil may be remedied 7#a7 by putting in a rod of iron as soon as the charge has fused1 or 7#b7 it may be counteracted by a proper addition of nitre1 or 7#c7 when the sulphides present are only those of iron or copper the sulphur may be removed by calcining1 and the ore converted into one of the class containing metallic oxides4 ,the calcination is effected as follows3--,weigh up #bj grams of the powdered ore and place it in a wide-mouthed crucible sufficiently large to perform the subsequent melting down in4 ,the roasting must be done at a gentle heat at first1 so as to avoid clotting3 the mouth of the crucible should project considerably above the coke1 and should slope forward towards the worker4 ,the charge must be occasionally stirred with the stirrer 7fig4 #aj7 so as to expose fresh surfaces to the action of the air1 and to prevent adhesion to the sides of the crucible4 ,the stirrer should not be removed till the calcination is finished4 ,the temperature should be raised at the end to a good red heat2 and 7to ensure the decomposition of any sulphate that may be formed7 the roasted ore should be rubbed up in a mortar with a pinch of anthracite1 and again calcined4 ,it is then mixed with fluxes as described1 and fused in the same crucible4 ,the calcination of an ore is a work occupying a good deal of time1 and1 in most cases1 it is better to take advantage of the desulphurizing power of red lead or nitre4 ,red lead by itself will do1 but a large quantity of it will be required2 #a part of a metallic sulphide needs from #bj to #ej parts of red lead to yield a button free from sulphur2 whereas at most from #b to #b-a_/b parts of nitre are sufficient4 ,there is sometimes an advantage in having a considerable excess of oxide of lead in the slag1 but where there is no such reason1 #b parts of red lead to #a of ore is enough4 ,a charge which will do for most sulphides is the following3 #bj grams of ore1 #dj to #ajj grams of red lead1 #bj grams of soda1 #e of borax1 and sufficient nitre 7or perhaps flour7 to give a button of about #be grams of lead4 ,how much this must be 7if not already known7 may be approximately determined by fusing #c grams of the ore and #c grams of soda in a small crucible 7,c7 with #ej grams of litharge 7not red lead7 under a cover of salt1 and weighing the resulting button of lead4 ,subtract #c from the weight of lead obtained1 and the difference multiplied by #a4c will give the quantity in grams of nitre required4 ,if the button of lead weighs less than #c grams flour must be added4 ,if this is not satisfactory repeat the assay1 adding an extra gram of nitre for each #d grams of lead in excess of that required1 or #a gram of flour for a #ab-;gram deficiency4 ,in the method in which iron is used as a de-sulphurising agent1 only as much oxide of lead should be added as will give a button of lead of the required size4 ,rather a large button of lead should be got1 and the slag should be strongly alkaline2 if the ore does not already carry a large amount of sulphur some should be added4 ,the fusion should be performed at a low temperature 7similar to that for a galena assay71 and should be continued for some time after it has become tranquil4 ,take #bj grams of the ore1 #dj grams of soda1 #dj grams of oxide of lead1 and #e or #aj grams of borax2 place this mixture in a crucible 7with a rod of iron1 as in the galena assay71 cover1 and fuse for about half an hour4 ,take out the rod1 washing it in the slag1 and1 in a minute or two1 pour4 ,clean and cupel the button of lead4 ,general ,remarks on the ,fusion4--,other things being equal1 the smaller the quantity of the slag the better1 provided there is sufficient to cover the metal4 ,the presence of peroxides of the heavy metals is prejudicial1 since they tend to increase the quantity of silver retained in the slag4 ,it may be given as a general rule that when iron1 copper1 manganese1 c41 are present1 there is a more than ordinary need for cleaning the slags1 and care must be taken to keep these metals in the state of lower oxide4 ,in selecting the fluxes1 it should be remembered that soda is the best for quartz1 and borax for lime and metallic oxides4 ,and that with ores almost free from gangue some quartz or glass should be added to protect the crucible4 ,two parts of soda are enough to flux #a part of quartz2 whilst of borax1 or oxide of lead1 #d parts are barely sufficient4 ,oxide of lead has the advantage of being heavy and so does not occupy much space in the crucible2 on the other hand1 if the melting down be performed too quickly1 or if oxide of lead only is used1 this high specific gravity is a disadvantage1 for the lighter earthy matter floats as a pasty mass on the more fluid oxide of lead1 and thus escapes its action4 ,when metallic sulphides are present in the ore1 an excess of oxide of lead helps to keep the sulphur out of the button of metal4 ,in addition to the oxide of lead required as a flux1 some will be required to provide the lead in which the silver is to be collected4 ,oxide of lead1 mixed with charcoal or flour1 yields1 when heated1 a multitude of minute buttons of metal uniformly distributed through the mass of the charge2 as the charge melts down these run together and fall to the bottom2 this shower of lead collects the silver more easily than a single button at the bottom of the crucible could do4 ,only that portion of the oxide of lead which remains in the slag can be considered as a flux2 very often the first indication of an excessive reduction of lead is the pastiness of the slag rendered thick by the withdrawal of the oxide of lead which would have kept it fluid4 ,if1 in an assay1 it is found that #e parts of flux are not sufficient for #a part of ore1 the remedy lies in using a different flux rather than in taking a larger quantity4 ,on the ,reducing ,effect of ,charcoal1 ,flour1 and ,tartar4--,the weight to be got from a given charge will depend 7provided sufficient oxide of lead is present7 upon the proportion of the reducing agents in it4 ,we have thought it well to illustrate this part of the subject by a series of experiments which the learner will do well to practise for himself before proceeding to the assay of actual ores4 ,take #hj grams of litharge and #bj grams of a mixture of borax and soda4 ,fuse three lots 7#a7 with #a4e gram of charcoal1 7#b7 with #c grams of flour1 and 7#c7 with #g4e grams of tartar4 ,weigh the buttons of lead obtained1 and divide each by the weight of reducing agent used4 ,the results will differ somewhat with the dryness and quality of the flour1 etc41 used2 in one series of experiments they were as follows3-- ,gram4 ,grams4 ,gram4 ,grams4 #a4e charcoal gave #cd4j lead 4'4 #a charcoal #bb4f lead4 #c4j flour #cc4e 4'4 #a flour #aa4b #g4e tartar #ch4j 4'4 #a tartar #e4j ,the use of flour as a reducing agent has many advantages1 and it is well to remember that #a gram of flour reduces about #aa grams of lead2 and that charcoal has twice1 and tartar one-half1 this reducing effect4 ,on the ,reducing ,effect of ,charcoal1 c41 on ,red ,lead4--,it is often easier to obtain red lead of good quality than it is litharge1 and by a large number of assayers red lead is the form of oxide of lead always used4 ,red lead1 however1 contains an excess of oxygen which will use up some of the reducing agent before lead separates out4 ,on making a series of experiments 7similar to the last1 but using #hj grams of red lead instead of the litharge7 the results were1 with the same quantities of the reducing agents3-- ,with charcoal1 #ah grams of lead4 flour1 #ah tartar1 #bb ,comparing these with the results with litharge1 in the previous table it will be seen that the same quantity of reducing agent has in each case brought down #af grams less of lead1 so that a larger amount of the reducing agent must be added to get a button of the same weight as that obtained with litharge4 ,to get a button of a desired weight1 say #bb grams1 we must add reducing agent sufficient to throw down #bb #af or #ch grams of lead1 which would require #c4d grams of flour4 ,if this amount of flour is fused with #hj grams of red lead1 a button of lead weighing #bb grams will be formed1 the other #af grams being kept up by the oxygen of the red lead4 ,if the quantity of red lead differs from #hj grams1 this rule must be modified4 ,with #dj grams of red lead1 for example1 we should add an excess of reducing agent sufficient to throw down #h grams of lead instead of #af4 ,similarly1 with #afj grams of red lead1 we should add enough to throw down #cb grams4 ,the following rule will enable one to calculate the weight of flour required to produce a button of lead of any desired weight from any given quantity of red lead4 ,each #e grams of red lead present diminishes the weight of the lead by #a gram4 ,if then we divide the weight of red lead in a charge by #e1 and add this to the weight of lead required1 the sum divided by #aa will give the weight of flour which must be added4 ,using #hj grams of red lead and wanting a button of #bj grams1 we should add #c4c grams of flour4 #hj_/e #af2 #afbj #cf2 #cf_/aa #c4c nearly4 ,the following are some results obtained which will illustrate the rule3-- ,red ,lead used4 ,flour used4 ,lead got4 #dj grams #c grams #be4j grams #ajj #c #ac4e #hj #d #cj4j #hj #e #dj4j ,on the ,reducing ,effect of ,metallic ,sulphides1 and the ,counteracting ,effect of ,nitre4--,the sulphides found in ores will reduce a button of lead from oxide of lead just as flour does2 and1 as charcoal1 flour and tartar differ in their reducing power1 so equal weights of the different mineral sulphides throw down different weights of lead4 ,one gram of iron pyrites yields about #aa grams of lead4 ,one gram of copper pyrites1 blende1 fahlerz1 or mispickel1 yields #g or #h grams of lead1 whilst #a gram of antimonite will give #f1 and #a gram of galena only a little over #c grams4 ,it is evident that if an ore carries much of these sulphides1 the quantity of lead reduced will be very much larger than that required for an assay4 ,to counteract this effect nitre is added2 #a gram is added for each #d grams of lead in excess of that required4 ,for example3 with a #bj-;gram charge of an ore containing #ej per cent4 of pyrites1 if no nitre were added1 #aaj grams of lead would be got2 or1 if there was not sufficient oxide of lead to yield this quantity of metal1 the button would be sulphury4 ,to reduce the weight of the button by #hj grammes1 we should add #bj grams of nitre1 if litharge were used2 or if red lead were used1 we should add #af grams of nitre1 since the oxidizing effect of #bj grams of red lead is equivalent to that of #a of nitre1 and since #hj grams of red lead are generally used in a charge4 ,two assays of an ore of this kind with these quantities of nitre gave #bf4j grams of lead with litharge1 and #bb4e grams with red lead4 ,it is best to use in these assays #hj grams of red lead1 #bj of soda1 and #e of borax1 with #bj grams of the ore4 ,if the lead got by the preliminary fusion in a small crucible with litharge 7described under ores containing much sulphides7 is known1 the following table will indicate the quantity of nitre1 or flour1 to be added with this charge3-- ---------------------------------------- ---------------------------- ,lead got in ,preliminary ,fusion ,flour to be added ,nitre to be added with #c grams of ,ore4 to the ,assay4 to the ,assay4 ---------------------------------------- ---------------------------- #j4j gram #c4c grams none #c4j grams #a4c gram -- #f4j none #d4j grams #i4j -- #i4j #ab4j -- #ad4j #ae4j -- #ai4j #ah4j -- #bd4j #ba4j -- #bi4j ---------------------------------------- ---------------------------- ,if litharge is used in the assay instead of red lead #d grams more nitre1 or #a4e gram less flour must be used4 ,when more than a few grams of nitre are added to a charge the proportion of soda and borax should be increased1 because one of the products of the reaction of nitre upon sulphides in the presence of soda is sulphate of soda1 and because the soda thus used up no longer serves as a flux2 more borax should be added1 as it is the best flux for the metallic oxides which are formed in the process4 ,if in an assay too large a button of lead is got1 even after this calculation has been made1 and the assay is repeated1 add #a gram more nitre for each #d grams of lead in excess4 ,sometimes the assay appears tranquil before the nitre has produced its full effect2 in such cases it is well to seize the crucible with the tongs and mix its fused contents by rotating them2 if this causes an effervescence1 the crucible should be replaced in the fire and the fusion continued4 ,the following experiments will illustrate the extent to which the above rules may be relied on4 ,in all of them the standard flux was used1 viz43--#hj grams of red lead1 #bj of soda1 and #e of borax4 ,pyrites #e #e #e #e #b4e #e #aj #ae #bj ,quartz -- #bj -- #bj #ag4e #ae #aj #e ,nitre -- -- #e #e -- #d #af #bh4e #da ,lead got #db4e #cf4j #af4j #ai4j #aa4e #bb4e #bb4e #bf4e #bg4e ,copper ,pyrites #h #h #h #h ,quartz -- #ab -- #ab ,nitre -- -- #d #d ,lead got #dg4e #cd4j #cc4j #bf4j ,antimonite #h #h #h #h ,quartz -- #ab -- #ab ,nitre -- -- #d #d ,lead got #bi4j #bf4j #ac4j #ac4j ,galena #aj #aj #aj #aj #ae #bj ,quartz4 -- #ae -- #ae #e -- ,nitre -- -- #c #c #c4e #g ,lead got #ag4j #ai4j #h4j #h4j #ah4e #ah4e ,a similar set of experiments1 with #hj grams of litharge instead of #hj grams of red lead1 gave3-- ,pyrites #d #d #d #d #g #aj ,quartz -- #ae -- #ae #ac #aj ,nitre -- -- #e #e #ab4e #bj ,lead got #df4e #dj4e #be4e #bd4e #bg4j #bf4e ,copper ,pyrites #e #e #e #e ,quartz -- #ae -- #ae ,nitre -- -- #e #e ,lead got #dd4e #cb4e #bc4j #be4j ,blende #e #e #e #e #aj ,quartz -- #ae -- #ae #aj ,nitre -- -- #e #e #ae ,lead got #da4e #ch4e #ba4e #bb4e #ba4f ,antimonite #e #e #e #e #aj ,quartz -- #ae -- #ae #aj ,nitre -- -- #e #e #aj ,lead got #ca4j #cb4e #aa4e #ab4e #ah4g ,galena #aj #aj #aj #aj #ae #bj ,quartz -- #ae -- #ae #e -- ,nitre -- -- #e #e #g4e #aa ,lead got #cc4e #cc4e #ac4j #ad4j #ai4e #bb4g ,the variation in some of these experiments1 in which we might have expected similar results1 is due to the fact that the sulphur1 and in some cases the metals1 are capable of two degrees of oxidation4 ,for example3 theoretically #a gram of iron pyrites 7,fe,s#b7 would yield #h4f grams of lead if the sulphur were oxidised to sulphurous oxide 7,,so#b71 and the iron to ferrous oxide 7,fe,o72 whilst if the sulphur were oxidised to sulphate 7,,so#c71 and the iron to ferric oxide1 #ab4i grams of lead will be thrown down4 ,similarly the yield with copper pyrites would be #g4e or #aa4f2 with blende1 #f4d or #h4e2 with antimonite1 #e4e or #h2 and with galena1 #b4f or #c4d4 ,as regards the metals1 the lower oxide will always be formed if the assay is carried out properly 7fused under a cover1 and with a sufficiency of reducing agent74 ,but the proportion of sulphur oxidised completely will vary with the conditions of the assay4 ,with a slag containing much soda the tendency will be to form sulphate1 and1 in consequence1 a big reduction of lead2 whilst with an acid slag containing much quartz the tendency will be for the sulphur to go off as sulphurous oxide 7,,so#b74 ,in a fusion with litharge alone all the sulphur will be liberated as the lower oxide1 whilst with much soda it will be wholly converted into sulphate4 ,for example3 #c grams of an ore containing a good deal of pyrites and a little galena1 gave1 when fused with litharge1 #af4e grams of lead4 ,a similar charge1 containing in addition #bj4j grams of soda1 gave #bb4e grams of lead4 ,it will be noted from the experiments that #a gram of nitre kept up on the average #d grams of lead2 the range being from #c4b with acid slags to #e4c with very basic ones4 ,these facts serve to explain some apparently irregular results got in practice4 ,,cupellation4 ,the process is as follows3--,the cupels1 which should have been made some time before and stored in a dry place1 are first cleaned by gentle rubbing with the finger and blowing off the loose dust2 and then placed in a hot muffle and heated to redness for from #e to #aj minutes before the alloy to be cupelled is placed on them4 ,the reasons for this are sufficiently obvious3 the sudden evolution of much steam will blow a cupel to pieces2 and1 if the whole of the water has not been removed before the cupel is filled with molten lead1 the escaping steam will bubble through1 and scatter about particles of the metal4 ,if some particles of unburnt carbon remain in the bone ash1 a similar result will be produced by the escape of bubbles of carbonic acid as soon as the fused litharge comes in contact with them4 ,the cupels having been prepared are arranged in a definite order in the muffle1 and the assay buttons are arranged in a corresponding order on some suitable tray 7cupel tray1 fig4 #da72 the heat of the muffle being at bright redness4 ,then with the help of the tongs 7fig4 #db7 the assay buttons should be placed each in its proper cupel2 a note having been previously made of the position it is to occupy1 and the door of the muffle closed4 ,illustration3 ,,fig4 #da4 ,this part of the work should be done promptly1 so as not to unduly cool the muffle3 the start requires a fairly high temperature1 and is a critical part of the process4 ,a black crust forms at once on the surface of the lead2 but this ought soon to fuse and flow in greasy drops from off the face of the metal1 so as to leave the latter fluid with a well-defined outline1 and much brighter than the cupel4 ,if this clearing does not take place1 the buttons are said to be frozen2 in which case the temperature must be raised1 some pieces of charcoal put in the muffle1 and the door closed4 ,if they still do not clear1 the heat must have been much too low1 and it is best to reject them and repeat the assays4 ,illustration3 ,,fig4 #db4 ,when the buttons have cleared it is well to check the draught of the furnace1 and to partly open the door of the muffle1 so as to work at as low a temperature as is compatible with the continuation of the process4#aa ,too low a temperature is indicated by the freezing of the buttons and the consequent spoiling of the assays4 ,experience soon enables one to judge when the heat is getting too low4 ,a commoner error is to have the heat too high3 it should be remembered that that which was high enough to clear the buttons at starting is more than sufficient to keep the process going4 ,at the finish a higher temperature is again required3 therefore the door of the muffle should be closed and the furnace urged4 ,the finish is easily recognised4 ,the drops of litharge which in the earlier stages flow steadily from the surface of the alloy1 thin off later to a luminous film4 ,at the end this film appears in commotion1 then presents a brilliant play of colours1 and1 with a sudden extinction1 the operation is finished4 ,the metal again glows for an instant whilst becoming solid4 ,if the button is a small one the cupel is withdrawn at once and placed on that square of the cupel tray which corresponds to the position it occupied in the muffle4 ,if1 however1 it is fairly large precautions must be taken to prevent spirting4 ,molten silver dissolves oxygen from the air and gives it off on solidifying2 the escape of the gas on sudden cooling is violent and1 by throwing off particles of the metal1 may cause loss4 ,this is called vegetation or spirting4 ,the silver is apparently solid when spirting takes place2 the crust breaks suddenly and some of the metal is forced out4 ,the evil is best guarded against by slow cooling and avoiding draughts4 ,with large buttons of silver precautions should never be omitted4 ,one plan is to allow the cupels to cool in the muffle itself1 the mouth being closed with hot charcoal4 ,another is to cover the cupel with another cupel previously heated to redness2 in this case the silver cools between two hot cupels1 and1 of course1 cools slowly4 ,a third plan is to withdraw the cupel to the door of the muffle1 holding it until it begins to get solid and then immediately to put it back into the hotter part of the muffle4 ,silver remains after cupellation in flattened elliptical buttons1 adhering but only slightly to the cupel4 ,its upper surface should show faint markings as if it were crystalline4 ,the presence of platinum renders it still more crystalline1 but removes the characteristic lustre and renders the metal dull and grey4 ,copper1 if not completely removed1 has a very marked effect on the appearance of the button3 the metal is spread out1 damping1 as it were1 and firmly adhering to the cupel1 which latter in the neighbourhood of the metal is almost black with oxide of copper4 ,sometimes the silver button is globular1 or even more sharply rounded on its under than on its upper surface2 it is said that this is due to the presence of lead4 ,gold may be present even to the extent of #ej per cent4 without showing any yellow colour4 ,the appearance of the cupel affords some useful information4 ,the presence of cracks evidently due to shrinkage indicates a badly made cupel4 ,if1 however1 they are accompanied by a peculiar unfolding of the cupel1 the margin losing its distinctness1 it is because of the presence of antimony4 ,when lead is the only easily oxidisable metal present1 the stained portion of cupel is yellow when cold4 ,a greenish tint may be due to small quantities of copper or1 perhaps1 nickel1 cobalt1 or platinum4 ,larger quantities of copper give a greenish grey or almost black colour4 ,a dark green and corroded cupel may be due to iron4 ,rings of pale-coloured scoria may be due to tin1 zinc1 antimony1 or arsenic4 ,when the cupel shows signs of the presence of these metals in objectionable quantity1 it is well to repeat the assay and scorify so as to remove them before cupellation4 ,the button should be detached from the cold cupel by seizing with a pair of pliers3 the under surface should be distorted by squeezing or hammering the button so as to loosen the adhering bone ash4 ,the cleaning is easily completed by rubbing with a clean hard brush4 ,after cleaning the buttons are best put on a tray of marked watch-glasses1 and then taken to the balance and weighed4 ,the weight of silver got needs a small correction2 7#a7 by deducting for the amount of silver introduced by the lead or oxide of lead used in the assay2#ab and 7#b7 by adding for the cupellation loss4 ,loss in ,cupellation4--,during the whole process of cupelling a silver lead alloy a more or less abundant fume may be observed rising from the cupel4 ,this furnishes an evident loss of lead and a possible loss of silver2 for although silver at the temperature of cupellation gives off no appreciable vapour1 it is known that such fume formed on a large scale contains silver4 ,it is1 however1 difficult to believe that the small amount of lead vapourised carries with it a weighable amount of silver4 ,that it does not do so in the ordinary way of working is shown by the fact that a button of silver equal in weight to the silver lost in cupelling may be got by smelting the cupel and cupelling the resulting button of lead4 ,the loss of silver by volatilisation is altogether inconsiderable1 unless the temperature at which the operation is performed is much too high4 ,another possible source of loss is the infiltration of small particles of alloy into the cupel4 ,the cupel is necessarily porous1 and particles of metal may perhaps drain into it1 more especially if the bone ash is not in fine powder2 but if this is the main source of loss it is hard to see why1 in cupelling equal weights of silver and gold1 the loss is not equal in each case4 ,it is not easy to believe that the mere filtration of the fused alloy will effect such a change in the proportion of the metals as that which actually occurs4 ,for example3 a cupel on which an alloy consisting of #j4hj gram of silver1 #j4dg gram of gold1 and #be grams of lead had been cupelled1 was found to contain #g-a_/b milligrams of silver1 and rather less than half a milligram of gold4 ,assuming1 for the sake of argument1 that the gold present had filtered into the cupel in the form of small drops of alloy1 it would have been accompanied by less than a milligram of silver1 and the presence of the extra #f or #g milligrams of silver must have been due to a different cause4 ,there can1 thus1 be little doubt that the cause of the greater part of the cupellation loss is a chemical one and cannot be counteracted by a mechanical contrivance4#ac ,in cupellation1 then1 there is a loss1 apart from imperfect working1 inherent in the process itself2 and as the amount of this loss varies under different conditions1 it is necessary to study it somewhat in detail4 ,the following experiments are taken without selection from the work of one student4 ,three experiments were made for each determination1 and the mean result is given4 ,by range is meant the difference between the highest and lowest result and the percentage loss is calculated on the silver present4 ,the silver added in the lead used has been deducted4 ,effect of ,varying ,lead4--,in each experiment #j4d gram of silver was taken and cupelled with the lead4 ,the silver loss and range are expressed in milligrams4 ---------------------------------------- ------------ ,lead ,used4 ,silver ,lost4 ,range4 ,percentage ,loss4 ---------------------------------------- ------------ ,grams4 #aj #f4e #a4j #a4fb #bj #g4j #a4j #a4ge #dj #ab4j #a4e #c4jj #fj #ab4g #j4e #c4ag ---------------------------------------- ------------ ,the loss increases with the lead used4 ,effect of ,varying ,temperature4--#j4d gram of silver was cupelled with #bj grams of lead4 ,temperature4 ,silver ,lost4 ,range4 ,percentage ,loss4 ,bright red #g4j #a4j #a4ge ,clear yellow #ag4c #a4g #d4cb ,the difference in temperature in these experiments was much greater than would occur even with careless work4 ,effect of ,varying ,silver4--#bj grams of lead were used in each cupellation4 ---------------------------------------- --------------- ,silver ,taken4 ,silver ,lost4 ,range4 ,percentage ,loss4 ---------------------------------------- ------------------ ,milligrams4 #ab4e #j4g #j4b #e4f #be4j #a4d #j4a #e4f #ej4j #a4f #j4d #c4b #ajj4j #b4i #j4c #b4i #bjj4j #e4f #j4e #b4h #djj4j #g4j #a4j #a4g #hjj4j #i4g #a4j #a4b ---------------------------------------- --------------- ,it will be seen that1 although the quantity of silver lost increases with the silver present1 the percentage loss is greater on the smaller buttons4 ,the following results are often quoted3--,cupelling #a grain of silver with #aj grains of lead1 the loss was #a4bb per cent42 #aj grains of silver with #ajj grains of lead1 loss #a4ac per cent42 #be grains of silver cupelled with #bej grains of lead1 lost #a4jg per cent4 ,the proportion of silver to lead was the same in the three experiments1 and the largest button gave the best result4 ,evidently1 if the quantities of lead had been the same in the three experiments 7say1 #bej grains in each case71 the loss on the smaller quantities of silver would appear worse in the comparison4 ,in judging these results1 it must be borne in mind that it is difficult to regulate the temperature1 c41 in consecutive experiments so as to get exactly similar results1 so that the range in consecutive cupellations is greater than that in a batch cupelled side by side4 ,effect of ,copper and ,antimony4--#j4a gram of silver was cupelled with #bj grams of lead1 and to one batch #j4e gram of antimony1 and to another #j4e gram of copper was added4 ,loss in ,silver ,lost4 ,range4 ,percentage4 ,without addition #b4i #j4c #b4i ,with antimony #c4b #j4b #c4b ,with copper #d4i #a4g #d4i ,perhaps the antimony has so small an effect because it is eliminated in the earlier part of the process1 while the silver is still alloyed with1 and protected by1 a large proportion of lead2 whilst the copper on the other hand makes its fiercest attack towards the close1 when the silver is least capable of resisting it4 ,the ill effects of copper are most strongly felt when the quantity of lead present is not sufficient to remove it3 the coppery button of silver got under these conditions is very considerably less than the weight of silver originally taken4 ,although the above is a fair statement of the loss attending average work1 it will not do in very important and exact work to place too much reliance on the figures given1 or1 indeed1 on any other set of figures1 with the object of correcting the result of an assay4 ,each man must rely on his own work4 ,it is easy to determine what allowance must be made for the loss in cupellation by cupelling side by side with the assay piece an alloy of similar and known composition4 ,for1 if the two pieces are very nearly alike1 we may justly conclude that the loss on each will be the same2 and if1 further1 we take the average of three or four such determinations we shall get results accurate within #j4a per cent4 ,the method of getting such results may be best explained by one or two illustrations4 ,this method of working is termed assaying by checks4 ,suppose we have an alloy of silver and lead in unknown proportions and that by cupelling two lots of #aj grams each there is got from ,i4 #j4abbf gram of silver1 and from ,,ii4 #j4abbi gram4 ,we should know from general experience that the actual quantity of silver present was from #b to #d milligrams more than this4 ,to determine more exactly what the loss is1 the following plan is recommended3--,the two silver buttons are wrapped up each in #aj grams of lead1 and cupelled side by side with two other lots of #aj grams of the original alloy4 ,if now the two buttons ,i4 and ,,ii4 weigh #j4abjb and #j4abjc1 they will have suffered in this second cupellation an average loss of #b4e milligrams4 ,suppose the two fresh lots of alloy gave #j4abcc and #j4abce of silver1 the average loss on these would also be #b4e milligrams4 ,add this loss to each result1 and take the mean2 which is in this case #j4abei4 ,if copper is present in the alloy as well as silver1 it is necessary to add about the same quantity of copper to the checks as is supposed1 or known1 to be present in the assays4 ,if the substance to be assayed is an alloy of silver and copper1 first cupel #j4e gram of it1 with1 say1 #aj grams of lead1 and weigh the resulting button of silver1 in order to get an approximate knowledge of its composition4 ,suppose the button weighs #j4cice gram4 ,we know that this is below the truth3 for the sake of round numbers take it as #j4d1 and assume that the rest of the alloy 7#j4a gram7 was copper4 ,two check pieces are then weighed out1 each containing #j4d gram silver and #j4a gram of copper wrapped in #e grams of lead4 ,of course the silver must be pure4 ,and there is also weighed out two 7or better1 four7 assay pieces each containing half a gram of the alloy wrapped in #e grams of lead4 ,the whole lot are then cupelled as nearly as possible under the same conditions4 ,with four assay pieces1 the cupels should be placed close together in two rows of three across the muffle2 the two check pieces are put in the middle cupels4 ,suppose the buttons of silver got weighed as follows3-- ,check pieces ,i4 #j4cidj ,,ii4 #j4cide ,assay pieces ,i4 #j4cije ,,ii4 #j4ciab ,,iii4 #j4ciaj ,,iv4 #j4ciji ,the average loss on the two check pieces is #e4g milligrams1 and the average result of the four assay pieces is #j4ciji4 ,add the average loss to the average result1 and there is got the corrected result1 #j4ciff4 ,and if #j4e gram of alloy contain #j4ciff of silver1 #ajjj will contain #gic4b of silver1 and this is the degree of fineness4 ,a correction for the loss in cupellation is always made in this way when rich alloys are being assayed2 and in the case of rich ores it may be done after the manner of the first of the above illustrations4 ,there is another method of working which relies more on experiment4 ,this is to smelt the cupel as described further on 7p4 #aad71 and to again cupel the resulting button of lead4 ,the button of silver got in this second cupellation is added to that first obtained4 ,it will sometimes1 but not often1 happen that the two buttons together will slightly exceed in weight the silver which was actually present4 ,this is because of the retention in the buttons of a small quantity of lead4 ,it has been stated that the proportion of lead thus retained may be as much as #a of the silver present2 this1 however1 can only be under exceptional conditions4 ,a determination of the actual silver in the buttons got in the series of cupellations quoted on pages #ajb1 #ajc1 gave an average percentage of #ii4he1 so that even with the larger buttons the effect of the retained lead would be only to increase the weight by about #a milligram4 ,in the method of working with checks1 the retained lead has no disturbing influence4 ,the proportion of lead required for the cupellation of any particular alloy requires consideration4 ,with too much lead the time occupied in the process is increased1 and so is the loss of silver2 on the other hand1 too little lead is of greater disadvantage than too much4 ,from #h to #af parts of lead are required for each part of silver alloy1 or1 if gold is present1 about twice as much as this must be used4 ,for the cupellation of #a gram of a silver copper alloy containing different percentages of copper1 the following quantities of lead should be used3-- ,percentage of ,copper in ,alloy4 ,lead ,required4 #e #f grams #aj #h #bj #aj #cj #ab #dj #ad #ej-ajj #af-ah ,the alloy1 in not too large pieces1 is wrapped in the required weight of lead foil and charged into the cupel at once2 or the lead may be put in first1 and1 when the cupellation has fairly started1 the alloy may be added wrapped in tissue paper2 or a portion of the lead may be first started and the alloy wrapped in the remaining lead and subsequently added4 ,the cupellation of large quantities of alloy or of alloys which contain tin1 antimony1 iron1 or any substance which produces a scoria1 or corrodes the cupel1 must be preceded by a scorification4 ,the advantages of this are that the slag is poorer in precious metal than that found on a cupel and is more easily collected and cleaned2 that larger quantities of metal can be treated1 and that1 even if the substance is in part infusible1 or produces at the start a clinkery mass or scoria1 the oxide of lead gradually accumulates1 fluxes the solid matters1 and produces a good final result2 but if the oxide of lead by itself is not sufficient for the purpose1 borax or some other flux can be easily added4 ,if the button of silver got is very small its weight may be estimated from its size2 but it must be remembered that the weight varies as the cube of the diameter4 ,if one button has twice the diameter of another it is eight times as heavy and so on4 ,scales specially constructed for measuring silver and gold buttons may be purchased2 but it is much better to make the measurement with the help of a microscope provided with an eyepiece micrometer4 ,if the length of the long diameter of a silver button be taken the following table will give the corresponding weight in milligrams3-- ---------------------------------------- ---- ,diameter4 ,weight4 ,diameter4 ,weight4 ---------------------------------------- -------- #j4jd inch #c4f #j4jae inch #j4ai #j4jce #b4d #j4jad #j4ae #j4jc #a4e #j4jac #j4ab #j4jbe #j4i #j4jab #j4jig #j4jb #j4de #j4jaa #j4jge #j4jai #j4d #j4jaj #j4jef #j4jah #j4cc #j4jjh #j4jbh #j4jag #j4bg #j4jjf #j4jab #j4jaf #j4bc #j4jjd #j4jjd ---------------------------------------- ---- ,the weight of a corresponding button of gold is got by multiplying by #b4be4 ,these figures are based on those given by ,plattner1 and apply only to buttons of such shape as those left after cupellation4 ,a sphere of silver #j4ja inch in diameter would weigh #j4ji milligram1 and a similar sphere of gold weighs #j4afg milligram4 ,it is safer1 however1 to compare with a micrometer the diameter of the button whose weight has to be determined with that of a standard button of nearly equal size whose weight is known4 ,the weights of the two buttons are proportional to the cubes of their diameters4 ,this plan of working is described more fully in ,appendix ,b41 page #ddj4 ,calculation of the ,results4--,after deducting for the silver added1 and correcting for the cupellation loss1 the calculation is made in the usual way2 reporting as so many parts per thousand in the case of rich alloys and as so many ounces and pennyweights1 or better as ounces and decimals of an ounce1 in the case of poor alloys and ores4 ,in this last case1 however1 it is less fatiguing to refer to a set of tables which give1 either directly or by means of simple addition1 the produce corresponding to any weight obtained from certain given weights of the substance4 ,the following table gives the produce in ounces and decimals of an ounce per ton of #bbdj pounds3-- ---------------------------------------- ------------------------------ ,weight of ,ore taken4 ,weight of ---------------------------------------- -------------- ,metal got4 #c grams4 #e grams4 #bj grams4 #ej grams4 #ajj grams4 ---------------------------------------- -------------------------- #j4jjja #a4ji #j4fe #j4af #j4jf #j4jc #j4jjjb #b4ah #a4ca #j4cc #j4ac #j4jf #j4jjjc #c4bg #a4if #j4di #j4bj #j4aj #j4jjjd #d4cf #b4fa #j4fe #j4bf #j4ac #j4jjje #e4dd #c4bg #j4hb #j4cc #j4af #j4jjjf #f4ec #c4ib #j4ih #j4ci #j4ai #j4jjjg #g4fb #d4eg #a4ad #j4df #j4bc #j4jjjh #h4ga #e4bc #a4ca #j4eb #j4bf #j4jjji #i4hj #e4hh #a4dg #j4ei #j4bi #j4jja #aj4hi #f4ec #a4fc #j4fe #j4cc #j4jjb #ba4gh #ac4jg #c4bg #a4ca #j4fe #j4jjc #cb4fg #ai4fj #d4ij #a4if #j4ih #j4jjd #dc4ef #bf4ac #f4ec #b4fa #a4ca #j4jje #ed4dd #cb4fg #h4ag #c4bg #a4fc #j4jjf #fe4cc #ci4bj #i4hj #c4ib #a4if #j4jjg #gf4bb #de4gc #aa4dc #d4eg #b4bi #j4jjh #hg4aa #eb4bg #ac4jg #e4bc #b4fa #j4jji #ih4jj #eh4hj #ad4gj #e4hh #b4id #j4ja #ajh4hi #fe4cc #af4cc #f4ec #c4bg #j4jb #bag4gh #acj4fg #cb4fg #ac4jg #f4ec #j4jc #cbf4fg #aif4jj #di4jj #ai4fj #i4hj #j4jd #dce4ef #bfa4cc #fe4cc #bf4ac #ac4jg #j4je #edd4dd #cbf4fg #ha4fg #cb4fg #af4cc #j4jf #fec4cc #cib4jj #ih4jj #ci4bj #ai4fj #j4jg #gfb4bb #deg4cc #aad4cc #de4gc #bb4hg #j4jh #hga4aa #ebb4fg #acj4fg #eb4bg #bf4ac #j4ji #ihj4jj #ehh4jj #adg4jj #eh4hj #bi4dj #j4a #ajhh4hi #fec4cc #afc4cc #fe4cc #cb4fg #j4b #bagg4gh #acjf4fg #cbf4fg #acj4fg #fe4cc #j4c #cbff4fg #aifj4jj #dij4jj #aif4jj #ih4jj #j4d #dcee4ef #bfac4cc #fec4cc #bfa4cc #acj4fg #j4e #eddd4dd #cbff4fg #haf4fg #cbf4fg #afc4cc #j4f #fecc4cc #cibj4jj #ihj4jj #cib4jj #aif4jj #j4g #gfbb4bb #degc4cc #aadc4cc #deg4cc #bbh4fg #j4h #hgaa4aa #ebbf4fg #acjf4fg #ebb4fg #bfa4cc #j4i #ihjj4jj #ehhj4jj #adgj4jj #ehh4jj #bid4jj #a4j #ajhhh4hi #fecc4cc #afcc4cc #fec4cc #cbf4fg ---------------------------------------- -------------------------- ,when1 as in this table1 the fraction of an ounce is expressed by two places of decimals1 it may be reduced to pennyweights 7dwts47 by dividing by #e4 ,for example1 #j4dj of an ounce is #h dwts4 ,the fraction of a dwt4 similarly expressed may be converted into grains with sufficient exactness by dividing by #d4 ,thus1 #a4fc ozs4 equal #a oz4 #ab4fj dwts41 or #a oz4 #ab dwts4 #ae grains4 ,in ,england it is usual to report in ounces and decimals of an ounce4 ,the way to use the table is best shown by an example4 ,suppose a button of silver weighing #j4jdce gram was obtained from #bj grams of ore4 ,look down the #bj-;gram column of the table1 and select the values corresponding to each figure of the weight1 thus3-- #j4jd #fe4cc ozs4 to the ton #j4jjc #d4ij #j4jjje #j4hb ------ ----- #j4jdce #ga4je ,add these together4 ,the produce is #ga4je ozs41 or #ga ozs4 #a dwt4 to the ton4 ,or1 suppose an ore is known to contain #a4bd per cent4 of silver4 ,look down the #ajj-;gram column1 select the values1 and add them together as before4 #a4j #cbf4fg ozs4 per ton #j4b #fe4cc #j4jd #ac4jg ---- ------ #a4bd #dje4jg ,this gives #dje ozs4 #a dwt4 #aj grains to the ton4 ,the calculation becomes more complicated when1 as is frequently the case1 the ore contains metallic particles4 ,these show themselves by refusing to pass through the sieve when the ore is powdered4 ,when they are present1 a large portion1 or if feasible the whole1 of the sample is powdered and sifted4 ,the weights of the sifted portion and of the metallics1 or prills1 are taken2 the sum of these weights gives that of the whole of the sample taken4 ,it is very important that nothing be lost during the operation of powdering4 ,each portion has to be assayed separately4 ,it is usual to assay a portion of the sifted sample1 say1 #bj or #ej grams1 and to add to the produce of this its share of the metallics4 ,this way of calculating1 which is more convenient than correct1 is illustrated by the following example3-- ,weight of whole sample #djj grams ,made up of sifted portions #cii ,metallics #a --- #djj ,twenty grams of the sifted portion1 when assayed1 gave #j4ajej gram of silver4 ,the whole of the metallics scorified and cupelled gave #j4hdb gram of silver4 ,since the #bj grams assayed was #a-bjth of the whole1 #a-bjth part of the #j4hdb gram of silver 7from the metallics7 must be added to its produce4 ,we thus get #j4adga gram 7#j4ajej #j4jdba74 ,referring to the #bj gram column1 we get-- #j4a #afc4cc #j4jd #fe4cc #j4jjg #aa4dc #j4jjja #j4af ------ ------ #j4adga #bdj4be ounces per ton4 ,a more legitimate method of calculation is as follows3--,calculate separately the produce of each fraction as if they were from different ores4 ,multiply each produce 7best stated in per cents47 by the weight of the corresponding fraction4 ,add together the products1 and divide by the weight of the whole sample4 ,taking the same example for illustration1 we have3-- ,metallics4--,weight #a gram4 #a gram of it yielded #j4hdb grams of silver4 4'4 ,produce #hd4b per cent4 ,produce multiplied by the weight is still #hd4b4 ,sifted ,portion4--,weight #cii grams4 #bj grams of it yielded #j4aje gram of silver4 4'4 ,produce #j4ebe per cent4 ,produce multiplied by weight 7#j4ebe #cii7 is #bji4dge4 ,add together2 and divide by #djj1 the weight of the whole sample-- #hd4b #bji4dge ------- #djj7 #bic4fge 7#j4gcdb #j4gcdb is the total produce of the ore in per cents4 ,referring to the #ajj-;gram column in the table we find #bci4hd ounces to the ton as the produce4 #j4g #bbh4fg #j4jc #i4hj #j4jjd #a4ca #j4jjjb #j4jf ------ #bci4hd ,comparing this with the result calculated by the first method--viz41 #bdj4bf1 we see that that was #j4ch oz41 or between #g and #h dwts4 too high4 ,with ores containing metallics it is of great importance to powder the whole of the selected sample without loss during the process2 and of even greater importance to well mix the sifted portion1 of which the last portions to come through the sieve are apt to be more than ordinarily rich through the grinding down of some portions of the metallic prills4 ,remarks on ,cupellation4--,cupellation is at once the neatest and the most important of the dry methods of assaying4 ,its purpose is to remove easily oxidisable metals1 such as lead and copper1 from silver and gold1 which are oxidisable with difficulty4 ,metals of the first class are often spoken of as base1 and gold and silver as noble metals4 ,when lead is exposed to the action of air at a temperature a little above redness1 it combines with the oxygen of the air to form litharge1 an oxide of lead1 which at the temperature of its formation is a liquid4 ,consequently1 if the lead rests on a porous support1 which allows the fused litharge to drain away as fast as it is formed1 a fresh surface of the lead will be continually exposed to the action of the air1 and the operation goes on until the whole of the lead has been removed4 ,silver or gold exposed to similar treatment does not oxidise1 but retains its metallic condition2 so that an alloy of lead and silver similarly treated would yield its lead as oxide1 which would sink into the support1 while the silver would remain as a button of metal4 ,the porous support1 which is called a cupel7fig4 #e71 should absorb the slag 7oxide of lead1 etc47 just as a sponge absorbs water1 but must be sufficiently fine-grained to be impervious to the molten metal4 ,at first sight it appears difficult to filter1 as it were1 a fluid slag from a fluid metal2 but an ordinary filter-paper damped with oil will allow oils to run through and yet retain the water2 but damped with water it will allow water to run through and retain oils4 ,similarly1 fused slags damp and filter through a cupel1 but the molten metal not damping it withdraws itself into a button1 which is retained4 ,although1 of course1 if the cupel is very coarse-grained the metal may sink into the hollows4 ,copper1 antimony1 tin1 and most other metals1 form powdery oxides1 which are not of themselves easily fusible1 and it is necessary when these are present to add some solvent or flux to render the oxide sufficiently fluid4 ,fortunately1 oxide of lead is sufficient for the purpose2 hence1 mixed oxides of copper and lead1 provided the lead is present in proper proportion1 form a fluid slag4 ,in separating copper from silver or gold1 advantage is taken of this fact2 for1 although we cannot cupel an alloy of copper and silver1 it is easy to cupel an alloy of copper1 silver and lead4 ,if1 however1 the lead is not present in sufficient quantity1 the whole of the copper will not be removed1 and the button of silver1 still retaining copper1 will be found embedded in a coating of black oxide of copper4 ,copper oxidises less easily than lead does2 and1 consequently1 the alloy which is being cupelled becomes relatively richer in copper as the operation proceeds4 ,it is on this account that the ill-effects of the copper make themselves felt at the close of the operation1 and that the oxide of copper is found accumulated around the button of silver4 ,tin and antimony1 on the other hand1 are more easily oxidised2 and the tendency of their oxides to thicken the slag makes itself felt at the commencement3 if the button of alloy once frees itself from the ring or crust of unfused oxide first formed1 the cupellation proceeds quietly1 and leaves a clean button of silver in the centre4 ,but in either case the cupellation is imperfect1 and should be repeated with a larger proportion of lead4 ,an unfused and1 consequently1 unabsorbed slag tends to retain small buttons of alloy or metal1 and thus cause serious loss4 ,there is a principle underlying many of the phenomena of dry silver assaying which the student should endeavour to understand2 and which serves to emphasise and explain some facts which without an explanation may present difficulties4 ,if a button of melted lead be covered with a layer of slag rich in oxide of lead1 and a second metal be added1 this other metal distributes itself between the metal and slag in proportions which depend mainly upon the ease with which it is oxidised1 and to a large extent upon the relative quantities of material present4 ,easily oxidisable metals such as zinc1 iron1 antimony and tin1 will go mainly into the slag1 and1 if the proportion of the slag is large1 very little will go into the metal4 ,on the other hand1 with metals oxidisable with difficulty1 such as silver1 gold1 and platinum1 the reverse holds true2 nearly the whole of the metals will go into the lead1 and very little into the slag4 ,if1 however1 the slag be very rich1 say in antimony1 the lead will contain antimony2 and1 on the other hand1 if the lead be very rich in silver1 the slag will contain silver in appreciable quantity4 ,copper1 which is near lead in the facility with which it is oxidised1 will serve for the purpose of a detailed example4 ,the results of actual analyses of metal and slag formed in contact with each other are shown in the following table3-- ---------------------------------------- ------------- ,percentage ,composition ,percentage ,composition of the ,metal4 of the ,slag4 ---------------------------------------- ----------- ,lead4 ,copper4 ,lead4 ,copper4 #f4h #ic4b #ga4d #ba4d #bj4j #hj4j #gh4j #ag4j #bh4j #gb4j #hj4j #ab4e #cb4j #fh4j #hf4j #f4g #he4j #ae4j #ij4j #c4f ---------------------------------------- ----------- ,it will be seen from this table that the slag is always much richer in lead and poorer in copper than the metal with which it is in contact4 ,the ratio of lead to copper in these five samples is3-- ,in the ,metal4 ,in the ,slag4 #a 3 #ad #a 3 #j4c #a 3 #d #a 3 #j4b #a 3 #b4e #a 3 #j4af #a 3 #b #a 3 #j4jh #a 3 #j4af #a 3 #j4jd ,assuming these figures to be correct1 the following statement is approximately true4 ,on oxidising an alloy of #aj grams of copper and #aj grams of lead1 and pouring off the slag when #c grams of lead have gone into it1 there will be a loss of 7owing to the slag carrying it off7 about #j4b gram of copper4 ,on repeating the operation1 the next #c grams of lead will carry with them about #j4e gram of copper2 and on again repeating1 #c grams of lead will remove #j4h gram of copper4 ,finally1 the last gram of lead will carry with it #j4c gram of copper1 and there will be left a button of copper weighing #h4c grams4 ,the slag will have carried off altogether #a4g gram of copper1 which is #ag per cent4 of the metal originally present4 ,with the more perfect exposure to the air1 and quicker removal of the slag1 which results from heating on a cupel1 the loss would be heavier4 ,karsten got by actual experiment on cupelling copper and lead in equal proportions1 a loss of #ba4be per cent4 ,going back to the example3 if the slag were collected and fused with a suitable reducing agent so as to convert1 say1 half of it into metal1 that half would contain nearly the whole of the copper 7such a reduction is called cleaning the slag74 ,on reoxidising this metal1 another button of copper is formed which1 added to the first1 would reduce the loss from #ag per cent4 to1 say1 #g or #h per cent4 ,and it is conceivable that by a series of similar operations1 almost the whole of the #aj grams of copper originally taken might be recovered4 ,in practice the problem is 7as far as the copper is concerned7 not how to save1 but how most easily to remove it2 and since the removal of this metal is quicker from an alloy containing not too much lead1 it is evident that two or three operations with small quantities of lead will be more effectual than a single treatment with a larger quantity4 ,with those metals 7tin1 antimony1 c47 which pass quickly into the slag1 the contrary is true2 hence with these it is necessary to have enough lead present1 so that the slag formed at the outset shall contain enough oxide of lead to make it fluid4 ,as silver is so much less easily oxidised than copper1 we should reasonably expect that the proportion of silver carried off in the oxide of lead would be considerably less than that of the copper indicated in the above example4 ,indeed1 there are one or two facts which tend to encourage the hope that the operation may be conducted without any loss4 ,if a piece of pure silver foil is exposed on a cupel to air at the usual temperature of cupellation1 it undergoes very little change2 it does not even fuse2 it loses nothing in weight1 and does not oxidise4 ,in fact1 even if oxide of silver were formed under these conditions1 it could not continue to exist1 for it is decomposed into silver and oxygen at a temperature considerably below redness4 ,on the other hand1 oxide of silver is not reduced to metal by heat alone1 when mixed with an excess of oxide of lead2 while metallic silver is converted into oxide when heated with the higher oxides of lead1 copper1 and some other metals4 ,that silver1 and even gold 7which is more difficult to oxidise than silver71 may be carried off in the slag in this way1 is in agreement with general experience4 ,if #aj grams of silver are cupelled with #aj grams of lead1 there will be a loss of about #ej milligrams of silver1 which is in round numbers #a-cjth of the corresponding copper loss2 with #aj grams of gold and #aj grams of lead1 the loss will be #d or #e milligrams1 which is about #a-abth of the corresponding silver loss4 ,determination of ,silver in ,assay ,lead4--,scorify #ej grams of the lead with #j4e gram of powdered quartz or glass at not too high a temperature4 ,when the eye has closed in1 pour2 reject the slag1 and cupel the button of lead4 ,remove the cupel from the muffle immediately the operation is finished4 ,weigh1 and make a prominent note of the result in the assay book1 as so many milligrams of silver contained in #ajj grams of lead4 ,determination of ,silver in ,red ,lead or ,litharge4--,fuse #ajj grams of the oxide with from #aj to #bj grams of borax2 and in the case of litharge with #b grams or with red lead #d grams of flour4 ,cupel the lead1 and weigh the button of silver4 ,note the result as in the last case4 ,determination of ,silver in ,argentiferous ,lead4--,be careful in taking the sample1 since with rich silver lead alloys the error from bad sampling may amount to several parts per cent4 ,cupel two lots of #bj grams each1 and weigh the buttons of silver4 ,add to these the estimated cupel loss1 and calculate the result4 ,or wrap each button of silver in #bj grams of assay lead1 and re-cupel side by side with two fresh lots of #bj grams each of the alloy4 ,calculate the loss incurred1 and add on to the weight of the two fresh buttons got4 ,determination of ,silver in ,bullion4--,the remarks made under the last heading as to the importance of correct sampling apply with equal force here4 ,make a preliminary assay by cupelling #j4a gram of the alloy with #a gram of assay lead2 calculate the percentage composition4 ,refer to the table on page #aje to find what weight of lead is required for cupelling #a gram of alloy4 ,weigh out four lots of #a gram each1 and wrap them in the required quantity of lead4 ,make two check pieces by weighing up two lots of fine silver equal to that which you believe to be present in the assay pieces2 add copper to make up the weight to #a gram1 and wrap in the same quantity of lead as was used for the assays4 ,illustration3 ,,fig4 #dc4 ,prepare six cupels and charge them in the annexed order 7fig4 #dc71 and cupel4 ,guard against spirting4 ,clean and weigh the buttons of silver4 ,add the mean loss on the two check pieces to the mean weight of the four assay pieces2 this multiplied by #ajjj will give the degree of fineness4 ,determination of ,silver in ,copper4--,the silver is best separated in the wet way before cupelling1 but if the proportion is not too small1 it can be found by cupellation4 ,weigh up #c grams of the metal1 wrap in #cj grams of sheet lead1 and cupel2 when the cupellation has proceeded for fifteen minutes1 add #bj grams more lead1 and continue till finished4 ,weigh the button of silver4 ,the cupellation loss will be five or six per cent4 of the silver present4 ,determine it by powdering the saturated portion of the cupel and fusing in a large ,cornish crucible with #cj grams each of soda and borax1 #aj grams of fluor spar1 and #a-a_/b gram of charcoal4 ,cupel the resulting button of lead1 and add #aj grams more of lead towards the close of the operation4 ,deduct the weight of silver contained in the lead used from the weight of the two buttons1 and calculate to ounces to the ton4 ,in an experiment in which #j4aige gram of silver was present1 the weight of the button from the first cupellation was #j4ahfg1 and that of the button from the second1 after correcting for the lead added1 was #j4jaaj gram4 ,determination of ,silver in ,galena4 ,by ,pot ,assay4--,mix #bj grams of the powdered ore with #cj grams of red lead1 #bj grams of soda1 and #e grams of borax1 as also with from #g to #aj grams of nitre4 ,fuse and pour4 ,clean the slag if the ore is rich4 ,cupel the buttons of lead4 ,make the usual corrections and calculate in ounces to the ton4 ,by ,scorification4--,take #aj grams of the ore1 #cj grams of lead1 and #j4e gram of borax4 ,scorify1 clean the slag by adding anthracite after the eye has closed in3 cupel the button of lead4 ,weigh the button of silver1 make the necessary corrections1 and calculate to ounces to the ton4 ,the determination may also be made by cupelling the button of lead got in the dry lead assay4 ,a sample of galena determined by the three methods gave the following results3-- ,by pot assay #g4ah ozs4 per ton4 scorification #g4jb lead assay #f4gb ,determination of ,silver in an ,ore4 ,by ,pot ,assay4--,take #bj grams of the powdered ore and mix with #cj grams of soda1 #dj grams of red lead1 and #e grams of borax1 as also with from #b to #c grams of flour4 ,fuse3 pour4 ,clean the slag by fusing with #bj grams of red lead and two grams of flour4 ,cupel the buttons of lead2 weigh2 make the necessary corrections1 and calculate to ounces to the ton4 ,by ,scorification4--,take #e grams of the powdered ore1 #ej grams of lead1 and #j4e gram of soda or borax4 ,scorify4 ,clean the slag by fusing in a crucible as in the pot assay4 ,cupel1 c4 ,examples4--,by ,pot ,assay4--,ore taken #bj grams4 ,silver got #j4bhic gram ,silver from slag #j4jjfj ,silver lost in cupellation #j4jajj ------ #j4cjec ,deduct silver in red lead #j4jjag ------ ,silver in ore #j4cjcf #die4i ozs4 per ton4 ,by ,scorification4--,ore taken1 #c grams4 ,silver got4 #j4jdbe gram ,silver from slag #j4jjbb ,silver lost in cupellation #j4jjbj ------ #j4jdfg ,deduct silver in lead #j4jjae ------ ,silver in ore #j4jdeb #dib4b ozs4 per ton4 ,determination of ,silver in ,silver ,precipitate4--,this substance contains1 in addition to metallic silver and gold1 sulphates of lead and lime2 oxides of zinc1 copper1 and iron2 and more or less organic matter4 ,the sample as received is generally free from water at #ajj ,c42 and1 since it rapidly absorbs water1 care should be taken in weighing it4 ,since it contains combined water it is not suited for scorifying2 therefore the determination of silver and gold 7fine metal7 is made by pot assay4 ,weigh up #e grams of the precipitate1 mix with #ajj grams of litharge and #a gram of charcoal4 ,melt in a crucible at a moderate heat and pour4 ,detach the slag1 replace in the crucible1 and1 when fused1 add a mixture of #bj grams of litharge and #a gram of charcoal4 ,when the fusion is again tranquil1 pour2 and cupel the two buttons of lead4 ,in a sample worked in this manner the mean of four determinations gave #j4fhai gram of fine metal2 deducting #a milligram for the silver contained in the oxide of lead1 and adding #h milligrams for the cupellation loss1 there is got #j4fhhi gram or #ac4ggh per cent4 of silver 7and gold7 in the sample4 ,determination of ,silver in ,burnt ,ores4 ,by ,pot ,assay4--,roasted cupriferous pyrites containing small quantities of gold and silver comes under this heading4 ,the following mixture will give a fluid slag which is heavy and tough when cold3-- ,ore4 ,borax4 ,sand4 ,litharge4 ,charcoal4 #ajj #ej #ej #ajj #g ,mix2 place in a large crucible2 cover with salt2 and melt down under cover4 ,when fused drop in an iron rod for a few minutes1 and about a couple of minutes after its withdrawal1 pour the charge quickly into a large conical mould4 ,the button of lead should weigh about #ej grams4 ,cupel and weigh the silver4 ,the litharge may be replaced by red lead1 in which case another gram of charcoal powder must be added4 ,in our experience the results obtained by this method are about #bj per cent4 less than the actual content of the ore4 ,the results of two assays1 after deducting for the silver in the litharge used1 were #c4i and #d4a milligrams2 and a third assay1 in which #e4d milligrams of silver had been added1 gave #i4b1 which1 after deducting the added silver1 leaves #c4h milligrams4 ,the average of the three results is #c4i milligrams from the #ajj grams of ore4 ,two lots of #ajj grams of the same ore treated in the wet way gave #e4b and #e4j milligrams of silver4 ,burnt ores from ,spanish pyrites carry about #j4jje per cent4 of silver4 ,,wet ,,methods4 ,silver is got into solution from its ores by attacking with nitric acid1 but it is best1 after dissolving1 to cautiously add dilute hydrochloric acid1 and to carefully avoid excess4 ,if the quantity of silver is very small the solution is allowed to stand twenty-four hours1 but1 otherwise1 it is warmed and filtered as soon as it clears4 ,dry the residue and concentrate the silver in a button of lead by pot method or scorification1 according to the amount of stony matter present4 ,cupel the lead1 and the resulting button will be free from all metals1 except perhaps gold4 ,it may be weighed2 or dissolved in nitric acid1 and the silver determined gravimetrically in the diluted and filtered solution4 ,it is better to weigh the metal and afterwards to determine the gold in it1 estimating the silver by difference4 ,silver alloys are dissolved in dilute nitric acid 7free from chlorides71 diluted1 and filtered4 ,the solution is then ready for gravimetric determination4 ,sulphuretted hydrogen precipitates silver 7like copper71 completely1 even from fairly acid solutions4 ,,gravimetric ,,determination4 ,add dilute hydrochloric acid in small excess to the hot dilute solution1 which must contain free nitric acid4 ,heat and stir until the solution clears4 ,decant through a small filter1 and wash with hot water1 acidulated at first with a little nitric acid if bismuth is suspected to be present4 ,dry quickly1 transfer as much as possible of the precipitate to a watch-glass2 burn and ignite the filter paper1 treating the ash first with two drops of nitric acid and then with one of hydrochloric1 and again dry4 ,add the rest of the silver chloride and heat slowly over a ,bunsen burner until it begins to fuse4 ,cool and weigh4 ,the precipitate is silver chloride 7,ag,cl7 and contains #ge4bg per cent4 of silver4 ,the moist precipitate is heavy and curdy2 it is decomposed by direct sunlight1 becoming violet under its influence4 ,when heated it is yellowish2 and1 since it is volatile at a high temperature1 it must not1 in drying1 be heated above its fusing point4 ,the fused chloride can be removed from the crucible 7to which it adheres strongly7 by digesting with dilute acid and zinc4 ,for the determination of silver in nearly pure bullion the following process is used3--,weigh up #a4ejed gram of the alloy4 ,with this amount of alloy each #b milligrams of silver chloride formed is equivalent to #a degree of fineness1 so that the weight of the silver chloride obtained 7stated in milligrams and divided by #b7 will give the degree of fineness4 ,transfer to a bottle 7known as bottles for the ,indian mint assay7 and dissolve in #aj c4c4 of dilute nitric acid1 then make up with water to #bjj c4c4 and add #c c4c4 of dilute hydrochloric acid4 ,allow to stand a few minutes and then shake4 ,fill the bottle completely with water1 allow to settle1 and syphon off the clear liquid2 pour on more water1 shake gently to break up the lumps1 and again fill the bottle with water4 ,invert over the mouth of the bottle a porous ,wedgwood crucible1 somewhat similar to those used in gold parting4 ,take firm hold of the crucible and bottle1 and invert promptly so that the silver chloride may be collected in the crucible4 ,allow to stand a little while for the precipitate to settle1 and then carefully remove the crucible under water4#ad ,drain off most of the water and break up the silver chloride with the help of a well-rounded glass rod4 ,this greatly facilitates the subsequent drying4 ,dry first on the water bath and then on the iron plate4 ,remove the dried silver chloride1 by inverting the crucible1 and weigh it4 ,as an example1 #c determinations of silver in a coin carried out in this way gave3-- 7#a7 #a4hejj gram ,ag,cl #ibe4j fineness4 7#b7 #a4hdih #ibd4i 7#c7 #a4hejb #ibe4a ,determination of ,silver in ,burnt ,ores4--,take #ajj grams of the ore and place in a large beaker of #b-a_/b litres capacity1 and cover with #cge c4c4 of hydrochloric acid4 ,boil for half an hour until the oxides are dissolved and the residue looks like sand and pyrites2 then add #bj c4c4 of nitric acid1 and boil till free from nitrous fumes4 ,dilute to #b litres with water1 and pass a current of sulphuretted hydrogen till the iron is reduced1 the copper and silver precipitated1 and the liquor smells of the gas4 ,this takes about one hour and a half4 ,filter off the precipitate 7rejecting the solution7 and wash with warm water4 ,dry and transfer to an evaporating dish1 adding the ashes of the filter paper4 ,heat gently with a ,bunsen burner until the sulphur burns1 and then calcine until no more sulphurous oxide comes off4 ,when cold add #cj c4c4 of nitric acid1 boil and dilute to #ajj c4c4 ,add #a c4c4 of very dilute hydrochloric acid 7#a to #ajj71ae stir well1 and allow to stand overnight4 ,decant on to a ,swedish filter paper1 dry and calcine4 ,mix the ashes with #ajj grams of litharge and #a gram of charcoal1 and fuse in a small crucible4 ,detach the button of lead and cupel4 ,weigh and make the usual corrections4 ,as an example1 #ajj grams of ore treated in this way gave #e4h milligrams of silver2 deducting #j4h for the silver added in the oxide of lead leaves #e milligrams obtained from the ore4 ,another experiment on #ajj grams of the same ore to which #e milligrams of silver had been added gave #aa4j milligrams4 ,deduct #e4h for the silver added2 this leaves #e4b milligrams as the silver obtained from the ore4 ,these give1 as a mean result1 #j4jjea per cent41 or #a4ff ounce per ton4 ,determination of ,silver in ,commercial ,copper4--,for the method of doing this1 with an example and experiment1 see under the heading of ,examination of ,commercial ,copper4 ,,volumetric ,,methods4 ,there are two of these1 one adapted for the determination of silver in alloys of approximately known composition1 and the other of more general application4 ,the first of these1 generally known as ,gay-,lussac's method is1 as regards its working1 perfect in principle2 but it requires a practically constant quantity of silver1 that is1 one which varies by a few milligrams only in each determination4 ,it is a confirmatory method rather than a determinative one4 ,the other is known as ,volhard's1 and resembles in principle and method an ordinary volumetric process4 ,gay-,lussac's method is based on the precipitation of silver from a nitric acid solution by a solution of sodium chloride4 ,the point at which the whole of the silver is precipitated being recognised by the standard solution ceasing to give a precipitate4 ,the process depends for its success upon1 7#a7 the ease which silver chloride separates out from the solution leaving it clear after shaking1 and1 7#b71 the cloudiness produced by the reaction of very small quantities of silver nitrate and sodium chloride4 ,in working1 a quantity of the sodium chloride solution equal to #a gram of silver is added at once to the assay2 and1 when the solution has been rendered clear by shaking1 the residual silver 7which should not exceed a few milligrams7 is estimated with the help of a weaker solution of sodium chloride4 ,the success in working evidently depends upon the accuracy with which the first addition of the salt solution is made4 ,on this account the standard solution is run in from a special pipette capable of delivering a practically invariable volume of solution4 ,it is not so important that this shall deliver exactly #ajj c4c4 as that in two consecutive deliveries the volume shall not differ by more than #j4je c4c4 ,the dilute salt solution is one-tenth of the strength of that first run in1 and #a c4c4 of it is equivalent to #a milligram of silver4 ,ordinarily it is run in #a c4c4 at a time 7and an ordinary burette may be used for this purpose71 shaking between each addition until it ceases to give a precipitate4 ,if many such additions have to be made the operation not only becomes tedious1 but the solution also ceases to clear after shaking1 so that it becomes impossible to determine the finishing point4 ,if the assay contains less than one gram of silver the first addition of the dilute salt solution of course produces no precipitate4 ,five milligrams of silver in solution 7#e c4c47 is then added1 and the assay proceeded with in the usual way2 #e milligrams of silver being deducted from the amount found4 ,there is required for the assay a standard solution of sodium chloride1 which is prepared by dissolving #e4dafb grams of the salt 7made by neutralizing carbonate of soda with hydrochloric acid7 in water and diluting to one litre4 #ajj c4c4 of this is equivalent to #a gram of silver4 ,the weaker solution of salt is made by diluting #ajj c4c4 of the stronger one to one litre4 ,one c4c4 of this will equal #a milligram of silver1 or #j4a c4c4 of the stronger solution4 ,a standard solution of silver equivalent to the dilute salt solution is made by dissolving #a gram of fine silver in #aj c4c4 of dilute nitric acid1 and diluting with water to one litre4 ,illustration3 ,,fig4 #dd4 ,the solution of salt is standardised as follows3--,weigh up #a4jjc gram of fine silver and dissolve in #be c4c4 of dilute nitric acid in a bottle provided with a well-fitting flat-headed stopper4 ,heat on the water bath to assist solution1 resting the bottle in an inclined position4 ,when dissolved blow out the nitrous fumes with the help of a glass tube bent at right angles4 ,run in from a stoppered pipette 7as shown in fig4 #dd7 #ajj c4c4 of the standard salt solution1 and shake vigorously until the solution clears4 ,fill an ordinary burette with the weaker standard salt solution1 and run #a c4c4 into the assay bottle1 letting it run down the side so that it forms a layer resting on the assay solution4 ,if any silver remains in solution a cloudy layer will be formed at the junction where the two liquids meet4 ,this is best observed against a black background ,if a cloudiness is seen1 shake1 to clear the liquid1 and run in another c4c4 of salt1 and continue this until a cloudiness is no longer visible4 ,deduct #a4e c4c4 from the amount of the weaker sodium chloride solution run in4 ,divide the corrected reading by #aj1 and add to the #ajj c4c4 ,this will give the volume of strong salt solution equivalent to the silver taken4 ,if the first addition of the weaker salt solution causes no cloudiness add #e c4c4 of the silver solution from an ordinary pipette1 shake1 and then run in the weaker salt solution1 working as before4 ,these #e milligrams of silver added must be allowed for before calculating4 ,as an example3--#a4jajj gram of fine silver was taken for standardising a solution and #d c4c4 of the weaker salt solution were run in4 ,deducting #a4e and dividing by #aj gives #j4be c4c4 to be added to the #ajj c4c4 #ajj4be 3 #a4jajj 33 #ajj 3 x x #a4jjge which is the standard of the salt solution4 ,the method of working an assay may be gathered from the following example3--,in the determination of silver in some buttons left after cupellation1 it was assumed that these would contain #ii4e per cent4 of silver4 ,for the assay it was necessary to take a quantity that should contain a little more than #a4jjge grams of silver2 then #ii4e 3 #ajj 33 #a4jjge 3 x x #a4jabe ,to ensure a slight excess1 there was taken #a4jaej gram of the buttons1 which was treated in exactly the same way as for the standardising4 ,the quantity of the weaker salt solution required was #g c4c42 deducting #a4e c4c41 and dividing by #aj1 gives #ajj4ee c4c4 of strong salt solution1 which is equivalent to #a4jacj gram of silver4 ,this being obtained from #a4jae gram of alloy1 is equal to #ii4h per cent41 or #iih4j fine4 ,the ,effect of ,temperature4--,the standardising and the assay must be done at the same time1 since a difference of #e ,c4 makes a difference of #j4a c4c4 in measuring the #ajj c4c4 of strong solution of salt4 ,it is always best to prepare a standard with each batch of assays4 ,,sulphocyanate ,,method4--,volhard's process is based upon the precipitation of silver in nitric acid solutions with potassium sulphocyanate1 the finishing point being the development of a reddish-brown colour1 produced by the action of the excess of sulphocyanate upon ferric sulphate4 ,the white sulphocyanate settles readily1 leaving the liquor clear2 and a persistent brown coloration in the liquid indicates the finish4 ,the assay must be carried out in the cold2 and water free from chlorides#af must be used4 ,the standard sulphocyanate of potassium solution is made by dissolving #d-a_/b or #e grams of the salt 7,k,cy,s7 in water1 and diluting to #a litre4 #ajj c4c4 are about equivalent to #j4e gram of silver4 ,the standard silver nitrate solution is made by dissolving #e grams of fine silver in #ej c4c4 of dilute nitric acid1 boiling off nitrous fumes1 and diluting to #a litre4 ,the indicator is a saturated solution of iron alum1 or a solution of ferric sulphate of equivalent strength made by titrating acid ferrous sulphate with potassium permanganate4 ,use #b c4c4 for each assay4 ,the sulphocyanate solution is standardised by placing #ej c4c4 of the silver nitrate solution in a flask with #bj c4c4 of dilute nitric acid1 diluting to #ajj c4c4 with water1 and running in the sulphocyanate until the greater part of the silver is precipitated2 then adding #b c4c4 of the ferric indicator1 and continuing the titration until a reddish-brown colour is developed1 and remains permanent after shaking continuously4 ,the assay is similarly performed1 the silver being used in the state of a nitric acid solution4 ,the effect of variations in the conditions of the assay may be seen from the following experiments1 in which #bj c4c4 of standard silver nitrate were used3-- ,effect of ,varying ,temperature3-- ,temperature #aj ,c4 #cj ,c4 #gj ,c4 #ajj ,c4 ,sulphocyanate reqd4 #ai4f c4c4 #ai4c c4c4 #ai4j c4c4 #ah4f c4c4 ,effect of ,varying ,nitric ,acid3--,varying nitric acid has no effect1 except that with a fairly acid solution the finishing point is somewhat sharper4 ,nitric acid added #e c4c4 #aj c4c4 #bj c4c4 #ej c4c4 ,sulphocyanate reqd4 #ai4f c4c4 #ai4e c4c4 #ai4f c4c4 #ai4f c4c4 ,effect of ,varying ,bulk3-- ,bulk #ej c4c4 #ajj c4c4 #bjj c4c4 #cjj c4c4 ,sulphocyanate reqd4 #ai4e c4c4 #ai4f c4c4 #ai4f c4c4 #ai4g c4c4 ,effect of ,varying ,ammonic ,nitrate3-- ,ammonic nitrate #j gram #a gram #e grams #aj grams ,sulphocyanate reqd4 #ai4f c4c4 #ai4f c4c4 #ai4g c4c4 #ai4i c4c4 ,effect of ,varying ,silver3-- ,silver added #a c4c4 #aj c4c4 #bj c4c4 #ej c4c4 #ajj c4c4 ,sulphocyanate reqd4 #a4j c4c4 #i4gj c4c4 #ai4f c4c4 #di4d c4c4 #ii4j c4c4 ,this method is valuable for determining silver in salts1 alloys1 and solutions1 where no more than an ordinary degree of accuracy is demanded4 ,it is easy1 and applicable under most of the usual conditions4 ,its greatest disadvantage is the brown coloration produced by the sulphocyanate when the assay is nearly1 but not quite1 finished2 and the slowness with which this is removed on shaking up with the precipitate4 ,this is worse with large quantities of precipitate1 and if about #a gram of silver is present1 it gives an indefiniteness to the finish which lowers the precision of the process to about #a in #ejj2 this is useless for the assays of bullion4 ,one writer states that this inconvenience is due to portions of liquid being entangled in the precipitate1 but it appears much more likely to be due to the action of the precipitate itself4 ,in attempting to apply the process to the assay of bullion by working it on the principle of a ,gay-,lussac assay1 it was found that a very considerable excess of silver was required to complete the reaction4 ,in these experiments #ajj c4c4 of sulphocyanate 7very accurately measured7 was run into the solution containing the weighed portion of bullion 7fine silver7 and1 after shaking the solution1 was filtered4 ,in the filtrate the remaining silver1 if there should be any1 was determined by the ordinary titration1 but with sulphocyanate of one-tenth the strength4 ,this final titration was quite satisfactory4 ,the amount of silver precipitated by the first #ajj c4c41 however1 varied with the quantity of silver present as in the following series4#ag ,silver present4 ,silver precipitated4 #a4acdb gram4 #a4acbb gram4 #a4acge #a4acce #a4adje #a4acea #a4adhd #a4acgi ,these1 of course1 preclude a method of the kind aimed at1 and at the same time emphasise the importance of uniformity of work in the ordinary process4 ,in the determination of chlorides in sea-water1 ,dittmar used a combined method3 precipitating the bulk of the silver as chloride1 and after filtering1 determining the small excess of silver by sulphocyanate4 ,this modification answers admirably when applied to the assay of bullion4 ,in the ordinary ,gay-,lussac method1 the precipitation of the bulk of the silver by the #ajj c4c4 of salt solution leaves nothing to be desired1 either as to ease in working or accuracy of result2 the silver precipitate settles quickly1 and leaves a clear liquor admirably fitted for the determination of the few milligrams of silver remaining in solution4 ,but the method of determining this residual silver by adding successive small quantities of salt so long as they continue to give a precipitate is unsatisfactory1 and1 judged on its own merits apart from the rest of the process1 could hardly escape condemnation4 ,it is clumsy in practice1 for the continued adding of small portions of salt solution is laborious and becomes impossible with more than a few milligrams of silver in solution4 ,the proposed modification is simple2 having precipitated the silver with the #ajj c4c4 of salt solution1 as described under ,gay-,lussac's method 7page #abj71 shake till the liquor clears1 and filter into a flask1 washing with a little distilled water4 ,add #b c4c4 of ferric indicator to the filtrate and titrate with a standard sulphocyanate solution made by diluting the ordinary standard solution to such an extent that #ajj c4c4 after diluting shall be equivalent to #j4a gram of silver4#ah ,calculate the weight of silver found by sulphocyanate and add it to the weight which #ajj c4c4 of the salt solution will precipitate4 ,an advantage of this modification is that an excess of #ae milligrams may be determined as easily and exactly as #e4 ,in standardising the salt solution1 then1 weigh up1 say #a4jaej gram of pure silver1 dissolve and titrate4 ,suppose #ac4e c4c4 of sulphocyanate required2 then these are equivalent to 4#jace gram of silver1 7#ajj c4c4 4#a72 the silver precipitated by the salt is #a4jaej-4jace--;i4e41 #a4jjae gram1 which is the standard4 ,application of the ,method to ,assays for ,arsenic4--,if silver nitrate be added to a neutral solution of an arsenate of one of the alkali metals1 silver arsenate 7,ag#c;,as,o#d71 is thrown down as a dark-red precipitate4 ,if1 after adding excess of silver nitrate to insure a complete precipitation1 the arsenate of silver be filtered off1 the weight of the arsenic could be estimated from the weight of silver arsenate formed4 ,but this may be done much more conveniently by dissolving the precipitate in nitric acid1 and titrating with sulphocyanate2 the silver found will be to the arsenic present as #cbd 7#ajhc7 is to #ge4 ,the mineral is best treated by the method given in the third paragraph on page #chb2 but the solution1 after being acidified with nitric acid1 should be made exactly neutral with ammonia4 ,a small excess of silver nitrate should then be added1 and since acid is liberated in the reaction1 the liquor must again be neutralised4#ai ,the precipitate must then be filtered off1 and washed with distilled water4 ,then dissolve it in the paper by slowly running over it #bj c4c4 of dilute nitric acid4 ,wash the filter with distilled water1 collecting with the filtrate in a small flask4 ,add #b c4c4 of ferric indicator and titrate4 ,if the sulphocyanate solution be made up with #aa or #ab grams of the potassium salt to the litre1 and be then standardised and diluted1 so that for #ajj c4c4 it shall equal #a4jh gram of silver1 7see p4 #ch71 then it will also equal 4#be gram of arsenic 7,as74 ,except for ores rich in arsenic1 it will be better to work with a solution one half this strength4 ,the standard as calculated from an experiment with pure silver should be checked by another using pure resublimed white arsenic1 ,as#b,o#c1 which contains #ge4ge of the metal4 ,the quantity of white arsenic taken1 4#a or 4#b gram1 should contain about as much arsenic as will be present in the assays4 ,it is converted into sodium arsenate by evaporating to a small bulk with nitric acid and neutralising with soda4 ,the precipitation and titration of the silver arsenate should be exactly as in the assays4 ,the difficulty of the method is in the neutralising2 which has to be very carefully done since silver arsenate is soluble in even faintly acid solutions2 one drop of nitric acid in #ajj c4c4 of water is enough to produce an absolutely worthless result2 and an excess of acid much less than this is still very prejudicial4 ,the addition of a little sodium acetate to the solution after the final neutralising has a good effect4 ,arsenic in ,mispickel4--,weigh up 4#bej gram of the finely-powdered ore1 and place in a ,berlin crucible about #a-a_/d or #a-a_/b inch in diameter4 ,treat with #aj or #ab drops1 one drop at a time1 of strong nitric acid1 warm very gently1 but avoid much heating4 ,put on a thin layer of nitre1 and rather more than half fill the crucible with a mixture of equal parts of soda and nitre4 ,heat quickly in the blow-pipe flame1 and when the mass is fused and effervescing1 withdraw and allow to cool4 ,boil out with water1 filter and wash4 ,insert a piece of litmus paper and cautiously neutralise with nitric acid1 using ammonia to neutralise any accidental excess of the acid4 ,add a gram or so of ammonium nitrate and silver nitrate in excess1 neutralise again with ammonia and add two or three grams of sodium acetate4 ,filter off the precipitate1 wash and titrate4 ,in the fusion care should be taken to avoid much effervescence 7an excess of the soda mitigates this7 and the operation should be stopped as soon as the whole has entered into fusion4 ,,colorimetric ,,determination4 ,there is1 properly speaking1 no colorimetric method1 but the following1 which is sometimes used1 is based on similar principles4 ,it is useful for the determination of small quantities of silver in substances which yield clear solutions with nitric acid4 ,dissolve a weighed quantity of the substance in nitric acid1 and dilute to a definite bulk4 ,divide into two equal parts4 ,to one1 add a drop or two of dilute hydrochloric acid1 stir and filter4 ,to the other1 add a similar amount of dilute acid1 and then to the filtered portion run in from a burette standard silver nitrate 7#a c4c4 #j4e milligram silver7 until the solutions are equally turbid4 ,calculate in the usual way4 ,,gold4 ,gold occurs in nature chiefly as metal4 ,it always contains more or less silver1 and1 in alluvial sands1 c41 may be associated with platinum and iridium4 ,gold is insoluble in hydrochloric or nitric acid1 but is dissolved by aqua regia or by solutions of iodine1 bromine1 or chlorine4 ,it is taken up by mercury1 forming an amalgam1 from which the mercury may be driven off by heat4 ,when gold occurs in particles of any size1 it is readily detected by its appearance1 but when finely disseminated through a large quantity of rock1 it is separated and detected by the amalgamation assay--described below--or by a process of washing somewhat similar to vanning1 or by the following test3--,powder and1 if necessary1 roast #ej to #ajj grams of the ore1 put on it three or four crystals of iodine and enough alcohol to cover it2 allow to stand for half an hour2 a piece of filter paper moistened with the liquid and burnt leaves an ash with a distinctly purple tint if any gold is present4 ,it is better1 however1 to filter off the solution1 evaporate1 and ignite4 ,then1 either take up with mercury1 and ignite the amalgam so as to get a speck of the metallic gold2 or treat with a few drops of aqua regia1 and test the solution with stannous chloride3 a purple coloration indicates gold4 ,,amalgamation ,,assay4--,this does not attempt to give the total produce of gold1 but rather the quantity which can be extracted on a large scale2 therefore it should imitate as closely as possible the process adopted in the mine or district for extracting the metal4 ,take #b lbs of the ore in powder and roast2 make into a stiff paste with hot water and rub up for an hour or so with a little mercury4 ,wash off the sand carefully1 and collect the amalgam4 ,drive off the mercury by heat1 and weigh the residual gold4 ,it is best to cupel it with lead before weighing4 ,in an experiment on a lot of ore which contained #j4ahi gram of gold1 #j4agi gram was obtained by the above process1 equal to about #id-a_/b per cent4 recovered4 ,with ores generally1 the yield may be from #hj to #ij per cent4 of the actual gold present4 ,,dry ,,assay4 ,the dry assay of gold ores resembles in its main particulars the dry assay for silver by the crucible method2 and for much that is of importance in its discussion the student is referred to what is written under ,silver on pp4 #ij-aac4 ,size of ,assay ,charges4--,gold ores rarely contain more than a few ounces1 often only a few pennyweights of gold to the ton2 consequently1 the button of gold obtainable from such quantities of ore as may be conveniently worked by assaying methods is often so small as to require more than ordinary care in its manipulation4 ,one milligram of gold forms a button of about the size of one of the full-stops on this page1 and compared with a million similar particles of quartz 7about four ounces71 represents a produce of a quarter of an ounce to the ton3 a proportion such as the assayer is frequently called on to determine4 ,it is evident1 therefore1 that a charge of half an ounce or less of the ore1 such as is usual with silver ores1 would demand of the worker both skill and care in the handling of the minute quantity of gold to be obtained from it4 ,fortunately the work is simple and precise1 so that in practised hands and with only a #e-;gram charge the assay of a #e-;dwt4 ore is practicable2 with so small a charge1 however1 the result is barely perceptible on a sensitive balance3 the button of gold should be measured under a microscope4 ,it follows1 therefore1 that larger charges of say #ej1 #ajj1 or even #bjj grams1 have an advantage in that they lessen the strain on the worker's attention1 and1 except in the case of the poorest mineral1 bring the button of gold within the scope of the balance4 ,on the other hand1 the inconvenience of the larger charges lies in the amount of fluxes and consequent size of the crucibles required to flux them4 ,sampling4--,a further consideration in favour of the larger charges is the matter of sampling4 ,in preparing his ore1 the student should ask himself what reasonable expectation he has that the portion he puts in the furnace will be of average richness4 ,the larger charges are likely to be nearer than the smaller ones to the average of the parcel of ore from which they are taken4 ,in explanation of this1 let us suppose a large heap of #e-;dwt4 ore1 in sand of the coarseness of full-stops1 and containing all its gold in particles of #a milligram1 as uniformly distributed as care and labour in the mixing can accomplish4 ,such a heap could not possibly occur in practice1 but it will serve for purposes of illustration4 ,now1 one ton of the sand1 however taken1 would contain appreciably the same quantity of gold as any other ton4 ,for a ton would contain about #hjjj particles of gold2 and even if two separate tons differed by as much as #ajj particles 7which they are just likely to do71 this would mean only a difference of #a or #b grains to the ton4 ,on the other hand1 two portions of #ad lbs41 which should contain on the average #ej particles of gold1 are likely enough to differ by #aj particles1 and this1 calculated on a ton1 means a difference of #a dwt4 ,it is easy to see that something like this should be true2 for on calculating the #ad-lb4 lot up to a ton1 the deviation from the average1 whatever it may be1 is multiplied by #afj2 whereas1 if the ton were made up by adding #ad-lb4 lot to #ad-lb4 lot1 up to the full tale1 then a large proportion of the errors 7some being in excess and some in defect7 would neutralise each other4 ,an average which is practically true when dealing with thousands1 and perhaps sufficiently exact with hundreds1 would be merely misleading when applied to tens and units4 ,reasonable safety in sampling1 then1 is dependent largely on the number of particles of gold in the charge taken1 and the risk of an abnormal result is less1 the larger the charge taken4 ,by doubling the charge1 however1 we merely double the number of particles4 ,powdering finely is much more effective2 for1 since the weight of a particle varies as the cube of the diameter1 halving the diameter of the particles increases their number eight-fold4 ,if1 now1 we modify our illustration by assuming the particles to have only one-sixth the diameter of a full-stop 7which would represent a powder of a fineness not unusual in ores prepared for assaying71 we should multiply the number of particles by #bjj 7#f #f #f #baf74 ,we should then reasonably expect a #ad-lb4 parcel of the powder to give as safe a sample as a ton of the sand would give2 and portions of a size fit for crucible work1 say #ej or #ajj grams1 would be as safe as #aj or #bj-lb4 samples of the coarser stuff4 ,for example1 #fj grams of such powder would contain1 for a #e-;dwt4 ore1 about #ajj particles2 and in the majority of cases the error due to sampling would be less than #aj or #ab grains to the ton1 and would only occasionally exceed a pennyweight4 ,with richer ores the actual deviation stated as so much to the ton of ore might be greater1 but it would represent a smaller proportion1 stated in percentage of the gold actually present1 and would ultimately fall within the limits of unavoidable error4 ,it will be seen that the size of the quartz particles has no direct bearing on the argument2 and1 in fact1 the coarseness of the quartz only interferes by preventing the uniform mixing of the sand and by binding together several particles of gold2 in this last case1 particles so united must1 of course1 count as one larger particle4 ,now1 there are some natural ores in which the gold particles are all very small2 with these fine powdering and mixing yields a product from which a sample may be safely taken4 ,then1 again1 in tailings1 before or after treatment with cyanide1 we have a similar material1 inasmuch as the coarser gold has been removed by previous amalgamation4 ,with these1 it is not unusual to take the portion for assay without any further powdering1 since they are poor in gold1 and have already been stamped and passed through a sieve of say thirty holes to the inch 7linear74 ,but there are other ores1 in lump showing no visible gold1 which contain the gold in all possible degrees of fineness1 from say prills of a milligram or so down to a most impalpable powder4 ,the treatment of these cannot be so simple and straightforward4 ,suppose a parcel of #ajjj grams 7say #b lbs47 of such ore in fine powder1 containing on an average #a particle of #a milligram 7the presence or absence of which makes a difference of 4#f dwt4 on the ton71 #aj others of about 4#e milligram 7each representing 4#c dwt471 and #ajj others1 which are too coarse to pass through an #hj sieve1 and having an average weight of 4#a milligram 7each 4#jf dwt471 and that the rest of the gold1 equivalent altogether to #b ounces to the ton1 is so finely divided that a charge of #ej grams may be taken without any considerable risk of its interfering with the sampling4 ,then in a #ej-;gram charge there would be one chance in twenty of getting the milligram particle1 in which case the result would be #ab4ce dwts4 too high2 on the other hand1 if it were not present the result would on this account be 4#fe dwt4 too low4 ,of the ten 4#e-milligram particles1 it is as likely as not that one will be present1 and its presence or absence would cause an error of #c4c dwts41 more or less4 ,of the #ajj particles of 4#a milligram1 there would probably be from #c to #g1 instead of #e1 the proper number2 this would mean a variation of #b4f dwts4 from the true proportion4 ,so that the probable result would range about #e dwts4 more or less than the #b-a_/b ozs41 which is the true produce1 and there are possibilities of astounding results4 ,it is true that the majority of the results would be well within these limits1 and now and again the heart of the student would be gladdened by a beautiful concordance in duplicate assays2 nevertheless1 there can be no reasonable expectation of a good assay1 and to work in this way1 on a #ej-;gram charge1 would be to court failure4 ,the coarse gold must ruin the assay4 ,the difficulty may be met by concentrating the whole of the coarse gold in a small fraction of the ore1 by sifting and making a separate assay of this fraction4 ,a portion of the ore1 of about #ajjj grams1 is ground to a very fine powder and passed through an #hj sieve1 re-grinding when necessary1 until only #bj or #cj grams is left of the coarser powder4 ,this is mixed with fluxes and carried through as a separate assay4 ,the sifted portion is thoroughly mixed1 and a portion of it1 say #cj or #ej grams1 taken for assay4 ,the weights of the two portions must be known1 and care must be taken that nothing is lost in the powdering4 ,the method of calculating the mean result from the two assays is shown on page #aji4 ,in this way of working there is no advantage in continuing the grinding until the coarser fraction is reduced to a gram or so--rather the contrary2 and rubbing on until all the gold is sent through the sieve is to be distinctly avoided4 ,the student must bear in mind that what he is aiming at is the exclusion of all coarse gold from the portion of ore of which he is going to take only a fraction4 ,the question of the smaller sampling of gold ores has been dwelt on at considerable length1 as befits its importance1 in order that the student may be impressed with a sense of its true meaning4 ,sampling is not a mystery1 nor does the art lie in any subtle manner of division4 ,it is1 of course1 absolutely necessary that the stuff to be sampled shall be well mixed1 and the fractions taken1 so that each part of the little heap shall contribute its share to the sample4 ,moreover1 it must be remembered that tossing about is a poor sort of mixing1 and that everything tending to separate the large from the small1 the light from the heavy1 or the soft from the hard 7as happens in sifting71 must be avoided1 or1 if unavoidable1 must be remedied by subsequent mixing4 ,with a well-taken sample1 we may rely on a great majority of our results falling within normal limits of error2 but nothing can be more certain than that1 in a moderately large experience we shall get1 now and again1 deviations much more considerable4 ,these erratic assays can only be met by the method of working duplicates1 which call attention to the fault by discordant results4 ,such faulty assays should be repeated in duplicate1 so that we may rest the decision on three out of four determinations4 ,the likelihood of two very faulty assays being concordant is remote2 but with very important work1 as in selling parcels of ore1 even this risk should be avoided1 as concordance in these cases is demanded in the reports of two or more assayers4 ,the following actual reports on a disputed assay will illustrate this3 7a7 #e ozs4 #a dwt42 7b7 #e ozs4 #aj dwts4 #ab grains2 7c7 #e ozs4 #aa dwts42 7c7 #e ozs4 #aa dwts4 #ab grs4 ,the mean result of several assays1 unless there be some fault in the method1 will be very fairly exact2 and individual assays1 with an uncertainty of #a in #bj1 may1 by repetition1 have this reduced to #a in #ajj or less4 ,assay ,tons1 etc4--,having decided on taking a larger or smaller portion1 the exact quantity to be used will be either some round number of grams1 such as #ej or #ajj1 easily calculable into percentage2 or it will be that known as the ,assay ,ton 7see page #ac7 or some simple multiple or fraction of it1 which is easily calculable into ounces4 ,the reports1 too1 are at least as often made as ounces in the short ton of #bjjj lbs41 as on the more orthodox ton of #bbdj lbs4 ,now the short ton is equal to #bi1aff4f troy ounces2 and the corresponding assay ton is got from it by replacing ounces by milligrams4 ,the advantage of its use is that if one assay ton of ore has been taken1 the number of milligrams of gold obtained is also the number of ounces of gold in a ton of the ore1 and there is absolutely no calculation4 ,even if half an assay ton has been taken the only calculation needed is multiplying the milligrams by two4 ,on the other hand with a charge of two assay tons the milligrams need halving4 ,where weights of this kind 7i4e41 assay tons7 are not at hand they may be easily extemporised out of buttons of tin or some suitable metal1 and it is better to do this than to array out the grams and its fractions at each weighing4 ,the sets of assay tons1 however1 are easily purchased4 ,as stated on page #ac1 the assay ton for #bbdj lbs4 is #cb4fffg grams2 and for the short ton1 #bi4affg grams4 ,if1 however1 the round number of grams be used and the result brought by calculation to the produce on #ajj grams1 the conversion to ounces to the ton may be quickly effected by the help of the table on page #ajg4 ,as this table only deals with the ton of #bbdj lbs41 it is supplemented here by a shortened one dealing only with the produce of #ajj grams and stating the result in ounces troy to the short ton of #bjjj lbs4 ,estimation of ,small ,quantities of ,gold4--,by the ,balance4 ,in estimating minute quantities of gold there are one or two points1 of importance to an assayer only in this assay1 where they will often allow one to avoid the working of inconveniently large charges4 ,one of these is known as weighing by the method of vibrations4 ,,table ,,for ,,calculating ,,ounces ,,to ,,the ,,short ,,ton ,,from ,,the ,,yield ,,of ,,gold ,,from #ajj ,,grams ,,of ,,ore4 ---------------------------------------- ------------------- ,milligram4,ounces to,milligrams4,ounces to,milligrams4,ounces to the ,ton4 the ,ton4 the ,ton4 ---------------------------------------- ------------------- #j4ja #j4jjc #j4d #j4aag #g4j #b4jdb #j4jb #j4jjf #j4e #j4ade #h4j #b4ccc #j4jc #j4jji #j4f #j4age #i4j #b4fbe #j4jd #j4jab #j4g #j4bjd #aj4j #b4iaf #j4je #j4jad #j4h #j4bcc #bj4j #e4hcc #j4jf #j4jag #j4i #j4bfb #cj4j #h4gej #j4jg #j4jbj #a4j #j4bib #dj4j #aa4fff #j4jh #j4jbc #b4j #j4ehc #ej4j #ad4ehc #j4ji #j4jbf #c4j #j4hge #fj4j #ag4ejj #j4aj #j4jbi #d4j #a4afg #gj4j #bj4daf #j4bj #j4jeh #e4j #a4deh #hj4j #bc4ccc #j4cj #j4jhg #f4j #a4gej #ij4j #bf4bej ---------------------------------------- ------------------- ,suppose a balance at rest in perfect equilibrium1 with the pointer exactly over the middle point of the scale4 ,let the scale be a series of points at equal distances along a horizontal line2 then1 if a small weight be placed on one pan1 the pointer will deviate from its vertical position and come to rest opposite some definite part of the scale1 which will depend upon the magnitude of the weight added4 ,the law determining this position is a very simple one2 the deviation as measured along the points of the scale varies directly as the weight added4 ,for example1 with an ordinarily sensitive balance1 such as is used for general purposes1 one milligram will move the pointer along1 say1 three divisions of the scale2 then two milligrams will move it six divisions2 half a milligram1 one and a half divisions2 and so on4 ,of course1 with a more sensitive balance the deviations will be greater4 ,now the point at which the needle comes to rest is also the middle point about which it vibrates when swinging4 ,for example1 if the needle swings from the third to the seventh division on the right then 7#gc7_/b it will come to rest on the fifth4 ,in working by this method the following conventions are useful3 ,always place the button to be weighed on the left pan of the balance1 the weights on the right2 count the divisions of the scale from the centre to right and left1 marking the former and the latter -2 thus -#e is the fifth division to the left4 ,then the position of rest is half the algebraic sum of two readings4 ,for example1 let the readings be #g to the right and #c to the left1 then 7#g-c7_/b #b4 ,the mean division is the second division to the right4 ,if the student will place himself in front of a balance and repeat the following observations and replace the figures here given by his own1 he will have no difficulty in grasping the method4 ,first determine the bias of the balance2 suppose the unloaded balance swings #a4be and -#a2 the bias then is 7#a4be-a7_/b 4#abe or one-eighth of a division to the right4 ,now having put on the button to be weighed let the readings be #g4e and #i4be1 and 7#g4ei4be7_/b #h4cge4 ,then the effect of the button has been to move the pointer from 4#abe to #h4cge1 or #h4be divisions to the right2 we should1 therefore1 add the weight equivalent of #h4be divisions to the weights1 whatever they may be on the right hand pan of the balance2 if the divisions were to the left 7- divisions7 we should subtract4 ,the value of #a division is easily determined4 ,suppose the button in the example were a #a milligram weight1 then we should have found that #a milligram #h4be divisions 4'4 #a division 4#aba milligram4 ,this method of working adds very considerably to the power of a balance in distinguishing small quantities4 ,illustration3 ,,fig4 #dd;a4 ,by the ,microscope4--,the use of the microscope also is a real advantage in estimating the weights of minute buttons of gold where there is no undue risk in sampling1 and where an error of say #a in #bj on the quantity of gold is tolerable4 ,for ores with copper1 lead1 zinc1 c41 as well as for tailings rather poor in gold1 this leaves a wide field of usefulness4 ,the method is described on page #ddj1 but the description needs supplementing for those who are not accustomed to the use of a microscope4 ,the eye-piece of a microscope 7fig4 #dd;a1 ,a7 unscrews at a1 showing a diaphragm at b1 which will serve as a support for an eye-piece micrometer4 ,this last1 ,b1 is a scale engraved on glass1 and may be purchased of any optical instrument maker1 though it may be necessary to send the eye-piece to have it properly fitted4 ,when resting on the diaphragm it is in focus for the upper lens1 so that on looking through the microscope1 the scale is clearly seen in whatever position the instrument may be as regards the object being looked at4 ,suppose this to be a small button of gold on a shallow1 flat watch-glass1 on the stage of the microscope4 ,bring the button under the objective 7i4e41 the nose of the microscope71 which should be about a quarter of an inch above the watch-glass2 then looking through the instrument1 raise the tube until the button of gold1 or at least some dust on the glass1 comes into focus4 ,if the button is not in the field1 rest the thumbs and index fingers1 using both hands1 on the edge of the watch-glass1 pressing lightly but steadily1 and give the glass a slow1 short1 sweeping motion2 the button will perhaps appear as an ill-defined blackness1 because not quite in focus4 ,bring this into the centre of the field4 ,raise or lower the microscope until the button appears with sharp outlines4 ,if the scale does not cover the button1 rotate the eye-piece2 this will bring the scale into a new position4 ,since the divisions over the button are less distinct than the others1 it is best to read the latter4 ,thus1 in fig4 #dd;b1 there are #cf divisions on one side of the button1 and #ce on the other1 making altogether #ga4 ,the whole scale is #hj1 therefore the diameter of the button is #i divisions4 ,the value of each division obviously varies with the magnifying power employed4 ,with most microscopes there is a telescopic arrangement whereby the tube may be lengthened2 if this be done and the button again brought in focus1 it will be seen that1 as measured on the scale1 the button is much larger than before4 ,it is evident1 therefore1 the micrometer must always be used in the same way4 ,the method given in the appendix 7page #ddj71 for finding the value of the scale when gold buttons are to be measured is easy and satisfactory4 ,when the button of gold is so small that there is considerable risk of losing it in transferring to a watch-glass1 it may be measured on the cupel1 but for this purpose it must be well illuminated2 this is best done by concentrating light on it with a lens1 or with what comes to the same thing1 a clean flask filled with water4 ,illustration3 ,,fig4 #dd;b4 ,most assayers1 however1 using a micrometer in this way1 would like to know its absolute value4 ,to do this1 a stage micrometer must be purchased4 ,this is like an ordinary microscope slide 7fig4 #dd;a1 ,c71 and when looked at through a microscope it shows 7fig4 #dd;c7 lines ruled on the glass at distances of tenths and hundredths of a millimetre1 ten of each1 so that the full scale is #a4a mm4 ,in the case illustrated1 #fj divisions of the scale in the eye-piece are just equal to the #a4a mm41 therefore #a division equals 4#jahc mm4 ,a cube of this diameter would contain 74#jahc4jahc4jahc7 4#jjjjjfabhe cubic mm4 ,the corresponding sphere is got by multiplying by 4#ebcf2 this gives 4#jjjjjcbji cb4 mm4 ,the weight of #a cb4 mm4 of water is #a milligram2 and1 since gold is #ai4b times as heavy as water 7sp4 g4 #ai4b71 the contents in cb4 mm4 must be multiplied by #ai4b4 ,this gives 4#jjjjfaf milligram as the weight of a sphere of gold measuring #a division4 ,illustration3 ,,fig4 #dd;c4 ,if every result had to be calculated in this way the method would be very laborious2 but1 having the figures for the first division1 those of the others may be calculated by multiplying by the cube of the corresponding number4 ,thus1 for the third division 7#ccc #bg71 the content of the cube 74#jjjjjfabhebg7 is 4#jjjafee cb4 mm42 the content of the sphere 74#jjjjjcbjibg7 is 4#jjjjhff cb4 mm42 and the corresponding sphere of gold 74#jjjjfafbg7 is 4#jjaff milligram4 ,with the help of a table of cubes the whole calculation for #be or #cj divisions may be made in half an hour1 and the results preserved in the form of a table will simplify all future work4 ,assay ,operations4--,the actual work of the assay resolves itself into three operations3--7#a7 ,the fusion of the ore and concentration of the fine metal 7i4e41 gold and silver7 in a button of lead2 7#b7 ,the cupellation of the lead1 whereby a button of fine metal is obtained2 and 7#c7 the parting of the gold which separates it from the accompanying silver4 ,the following description takes the order as here given1 but the student1 in learning the method1 should first practise cupellation if he has not already done so2 next he should practise the separation of gold from silver1 taking known weights of fine gold 7p4 #fc71 varying from 4#e or 4#c gram down to quite minute quantities1 and not resting satisfied until a sensitive balance can barely distinguish between the weights of gold taken and found4 ,it may be noted here that if he has not a flatting mill at his disposal1 then for large buttons it is better to make an alloy with eight or nine parts of silver to one of gold1 and attack it with acid without previous flattening1 rather than accept the risk and labour of beating out a less easily attacked alloy to the necessary thinness with a hammer4 ,it is only after a sense of security in gold parting has been acquired1 that the attack of an ore can be profitably accomplished1 and even then simple and easy ores should be first taken1 passing on to others more difficult1 either because of a more complex mineral composition or a difficulty in sampling4 ,concentration of the fine ,metal in ,lead4--,the best flux for quartz1 which makes up the earthy matter of most gold ores1 is soda1 and this is best added as carbonate or bicarbonate4 ,by theory1#bj #ej grams of quartz will require #hh4e grams of the carbonate1 or #adj grams of the bicarbonate1 to form sodium silicate1 which is a glassy1 easily-fusible substance1 making a good slag4 ,if the bicarbonate is used1 and heat is applied gradually1 steam and carbonic acid are given off at a comparatively low temperature1 and the carbonate is left2 at a higher temperature 7about #hjj ,c41 or a cherry-red heat7 the carbonate fuses attacking the quartz1 and giving off more carbonic acid2 as the heat increases1 and the attack on the quartz 7which of itself is infusible7 becomes complete1 the whole mass settles down to a liquid sodium silicate1 which is sufficiently fluid to allow the gold and lead to settle to the bottom4 ,the fluid slag does to a certain extent dissolve some of the crucible1 but not seriously4 ,in a perfect working of this experiment1 the first evolution of gases 7steam and carbonic acid7 should be gentle1 so as to run no risk of its blowing the fine powder out of the crucible2 and the heat at which the second evolution of carbonic acid is produced should be maintained until the reaction is completed1 so that there may be little or no formation of gas in the fused mass to cause an effervescence which may force some of the charge over the edges of the crucible4 ,of course1 in practice the ideal fusion is not attained1 but there is no difficulty in approaching it closely enough to prevent the charge at any time rising above the level it reached at first in the crucible1 and this should be accomplished4 ,it is usual with quartzose ores to rely mainly on the action of carbonate of soda1 but not entirely4 ,litharge is also used2 it forms1 on fusion with quartz1 a silicate of lead1 which is a yellow glass1 easily fusible1 and more fluid in the furnace than silicate of soda is4 ,by theory1 #ej grams of quartz would require #ahf grams of litharge4#ba ,the reaction takes place without evolution of gas1 and in its working the only point is to so regulate the heat that the litharge shall not fuse and drain under the unattacked quartz1 leaving it as a pasty mass on the surface4 ,now1 if in making up a charge for #ej grams of ore1 we took #ajj grams of bicarbonate of soda 7equivalent to about #fc grams of the carbonate71 this being five-sevenths of #adj grams 7which by itself would be sufficient71 leaves two-sevenths of the quartz to be fluxed by other reagents3 two-sevenths of #ahf grams 7say #eb grams7 of litharge would serve for this purpose4 ,but if we used #aj grams of borax1 which has a fluxing action about equal to that of the litharge1 then #dj grams of the latter1 or 7making an allowance for the quartz being not quite pure7 say #ce grams1 will suffice4 ,the fluxes1 then1 for the #ej grams of ore would be3 bicarbonate of soda #ajj grams1 litharge #ce grams1 and borax #aj grams2 we could decrease any of these1 and proportionately increase either or both of the others1 and still rely on getting a fusible slag1 which is the whole of the function of a flux1 considered simply as a flux4 ,it should be remembered1 however1 that the slag is a bi-silicate or acid slag1 and that its acid character is increased by increasing the proportion of borax4 ,but in addition to the fluxes there is required about #cj or #dj grams of lead to collect the silver and gold4 ,this is best added as litharge 7say #dj grams7 and flour 7#d grams71 or charcoal powder 7#b grams74 ,see pages #ic and #id4 ,the full charge1 then1 would be3 ,ore #ej grams4 ,bicarbonate of soda #ajj ,litharge #ge ,borax #aj ,flour #d ,these should be mixed1 placed in a suitable crucible 7a ,g ,battersea1 round1 will do71 and heated1 at first at a red heat1 but finally much hotter1 so as to get a fluid and clean slag4 ,when the charge has been in tranquil fusion for some little time1 take it out and pour it into an iron mould4 ,when cold1 detach the button of lead4 ,the slag should be glassy1 all through alike1 and easily separable from the metal4 ,with ordinary ores1 this slag may be considered as free from gold4 ,in an experiment in which #ij milligrams of gold were added1 the full amount was obtained from the lead produced by the first fusion4 ,but in certain cases1 more especially where large amounts of metallic oxides are present1 the slag is not so clean1 and with these the slag should be powdered1 mixed with #dj grams of litharge and #d of flour1 and melted again2 it is an advantage to add a small prill of say #b or #c milligrams of silver to the charge1 as it insures a visible product in the cupellation4 ,indeed1 this last precaution is a good one to be taken wherever there is reason to expect very small buttons4 ,it has the further advantage1 that1 if the quantity of silver necessary for inquartation is known1 the right quantity may be added here1 so as to save a subsequent operation4 ,ores containing ,oxides of ,iron4--,of the metallic oxides likely to be present in a slag1 oxide of iron is the most important4 ,gold is occasionally found in a matrix of this substance1 and in the assay of concentrates largely made up of pyrites1 this oxide will be formed in the preliminary calcination4 ,now1 the lower oxide of iron 7ferrous oxide1 ,fe,o7 is easy to deal with2 fused borax will dissolve about its own weight of it1 and a silicate of soda 7such as makes up the bulk of a slag in a gold assay7 will take up at least half as much4 ,but the higher oxide 7ferric oxide1 ,fe#b,o#c7 is more refractory2 even #f parts of borax yields a poor product1 and slags with any considerable percentage of it are not satisfactory4 ,a student attempting to recover gold from some hmatite 7in which there was about half an ounce of the metal71 found in the slag nearly a gram of gold1 although in the first fusion the slag appeared perfectly fluid4 ,there is1 however1 no difficulty in getting good slags1 even with large quantities of iron4 ,for example1 with #ej grams of ferric oxide1 #aj of quartz1 #cj of borax1 #cj of soda1#bb #ej of litharge1 and #g of flour1 the result was quite satisfactory4 ,so1 too1 was #be of quartz1 #ej of soda1 #ej of litharge1 and #g of flour4 ,it is well1 however1 in such cases to have an ample proportion of flux and to aim at a larger button of lead than usual by increasing the proportion of flour or charcoal 7see also page #ia74 ,a charge used on the ,randt for roasted concentrates 7which we may roughly speak of as quartz and ferric oxide71 is one assay ton 7about #cj grams7 each of ore1 soda1 and borax1 and one and a half assay ton of litharge and #b grams of charcoal4 ,whilst1 for the same material1 from which most of the gold has been extracted by chloridising1 #b4e tons each of ore1 borax1 and soda1 #d of litharge1 and #d grams of charcoal are needed4 ,this quantity requires a large crucible 7,i ,battersea1 round74 ,in this the proportion of silicate of soda and borax counted together is to the oxide of iron as #d to #a1 on the supposition that the quartz and oxide of iron of the ore are in about equal quantities2 but1 in the larger charge especially1 much oxide of lead would also remain as a flux4 ,ores containing ,sulphides4--,in assaying ores containing a large proportion of pyrites or mispickel1 or both1 the best plan is to take a portion and calcine so as to convert it into a product of the kind just considered4 ,the weighed portion of ore should be placed in a clean crucible and be heated to incipient redness3 with pyrites the first effect is to drive off about half the sulphur as vapour which burns as flame over the ore4 ,at this stage care should be taken that there is no great increase of temperature1 otherwise there may be more or less fusion1 which would spoil the operation4 ,when the sulphur flame ceases the solid sulphide of iron burns with visible incandescence and the charge should now be stirred with a flattened iron rod so as to expose fresh portions to the air4 ,the top of the furnace must be open1 so that air may have free access to the crucible4 ,when stirring is no longer followed by visible burning the heat may be raised to full redness4 ,the crucible is then lifted out 7the stirrer still resting in it7 and if the charge gives off no odour of burning sulphur it is shaken out into an iron mortar and mixed with the fluxes1 taking care to clean the stirrer in the mixture4 ,the charge is then replaced in the crucible in which the roasting was done and fused in the furnace4 ,the resulting button of lead is cupelled for fine metal4 ,ores rich in sulphides requiring this treatment are frequently concentrates4 ,for their assay take #a assay ton 7#cj grams71 calcine and mix with an equal weight of soda and of borax 7#cj grams each71 and half as much again of litharge 7#a4e tons or #de grams71 and with #b grams of charcoal or #e grams of flour4 ,where the sulphides are present in smaller proportion 7#aj per cent4 or less71 they may be taken as serving the purpose of flour or charcoal 7see page #ie72 the sulphur and iron are oxidised at the expense of the litharge with a consequent separation of lead as metal4 ,if the proportion of sulphides is not sufficient to give a large enough button of lead1 some charcoal or flour should be added4 ,on the other hand1 if they are in small excess and give a button of lead somewhat sulphury1 i4e41 hard and brittle1 it may be remedied by the judicious addition of nitre2 this last reagent1 however1 should not be used in large quantity4 ,a plan much used to prevent sulphury buttons is to insert an iron rod or a nail in the charge in the crucible2 the iron takes the sulphur forming sulphide of iron which in moderate quantity does not form a separate layer of matte but dissolves in the slag4 ,a slag formed of #ej grams of quartz1 #ajj soda1 and some borax1 may take up in this way some #aj or #ab grams of sulphide of iron4 ,if1 however1 an ore gives a layer of matte or speise1 it is best to repeat the assay by the method of calcining before fusion4 ,cyanide ,charges1 etc4--,in assaying the tailings which are to be treated in a cyaniding plant the following charge is used3 ,tailings #c assay tons or #ajj grams4 ,litharge #d4e #aej ,soda #d4e #aej ,borax 4#ge #be ,the sand is assayed without any further crushing and the assay is made in duplicate4 ,the residues after treatment with cyanide1 differing from the tailings merely in being poorer in gold because of the extraction by the solution of cyanide1 are run down with the same fluxes in the same relative proportions4 ,but four charges of #b4e assay tons 7say #ge grams7 are worked1 and two of the resulting buttons are scorified together and then cupelled1 etc41 so as to give duplicate assays on charges of #e assay tons4 ,this is one of the cases in which it is desirable to add a small portion of silver before cupelling4 ,in assaying the cyanide liquors for gold1 #b assay tons of the liquor are measured out 7#eh4c c4c4 for the ton of #bjjj lbs41 #fe4c c4c4 for the other7 and are evaporated to dryness in a lead dish weighing about #ce grams4 ,such a dish is easily extemporised out of a piece of lead foil1 if the ordinary vessel is not at hand2 but care must be taken that the lead is free from gold4 ,the dish with the dried residue is then scorified and the resulting button of lead is cupelled4 ,illustration3 ,,fig4 #dd;c4 ,in some cases the fusion of the ore may be replaced by a treatment with solution of cyanide of potassium and the gold recovered from the solution in the way just described4 ,for this purpose the ore should be in not too fine powder1 otherwise there will be great difficulty in filtering2 a sand which will pass a #cj sieve and having no large proportion of very fine stuff will do4 ,not less than #bjj grams should be taken2 and as an extraction apparatus a bell jar capable of holding half as much again may be used4 ,such a jar may be extemporised by cutting off the bottom of a bottle by leading a crack around it with a red hot poker2 or a lamp chimney will serve the purpose4 ,the smaller mouth of the jar is closed by a perforated cork provided with a clipped tube after the manner of a burette 7see fig4 #dd;c74 ,in the jar1 just over the cork1 put a plug of loose asbestos or glass wool1 or a piece of sponge to act as a filter2 a layer of broken glass1 coarse at the bottom and fine at the top1 will serve the same purpose4 ,on this1 place the charge of ore to be extracted4 ,prepare a solution of cyanide of potassium in water1 with #e or #aj grams of the salt to the litre4 ,it may be that the whole point of the assay depends on the solution being of a definite strength2 as1 for example1 where the relative efficiency of solutions of different strengths is being determined1 when it will be best to estimate the quantity of cyanide of potassium in the dilute solution by the method given at the end of this article 7page #afj74 ,pour the cyanide solution on to the ore1 letting the first portions to come through run into the beaker1 but as soon as the ore is thoroughly wetted close the clip and allow to stand for several hours4 ,then1 opening the clip1 run through more cyanide solution and then water1 so as to wash the gold-carrying liquor thoroughly into the beaker4 ,it is no matter if the liquor is a little bit turbid2 transfer it to a lead dish1 evaporate1 scorify1 and cupel in the usual fashion4 ,the assay of gold-zinc slimes1 which is the precipitate formed by zinc acting on cyanide solutions of gold1 may be made by wrapping #b or #c grams in #dj grams of sheet lead and scorifying1 cupelling1 c4 ,the amount of impurity in the stuff varies greatly2 it is usually calcined and mixed thoroughly with soda #dj per cent41 borax #cj per cent41 and sand #aj per cent41 and melted in graphite pots4 ,the buttons of bullion obtained are afterwards remelted with borax and run into bars1 the fineness of which varies from #fjj to #hcj thousandths4 ,the bars are sampled by chipping off diagonally opposite corners3 or better1 by drilling1 the drillings being freed from pieces of steel with the help of a magnet4 ,cupellation4#bc--,the cupellation of lead for gold differs very little from that of lead carrying silver4 ,when the gold is accompanied by a larger proportion of silver1 and both have to be determined1 the cupellation must be conducted exactly as in a silver assay1 the usual precautions being taken to moderate the temperature so as to lessen the cupellation loss and to promote a slow and undisturbed solidification in order to avoid spirting4 ,if1 however1 the gold predominates the finish should be effected at a higher heat1 as the melting-point of gold is #ajj higher than that of silver4 ,the bad effect of a higher temperature in increasing the cupellation loss need hardly be considered in the case of such small buttons of gold as are obtained in assaying gold ores1 as any loss there may be is hardly appreciable by the balance4 ,with larger quantities of gold1 however 7as in assaying gold bullion71 this loss becomes important2 and it is therefore necessary to very carefully regulate the temperature of the muffle so as to minimise the loss4 ,the cupels are made of well-burnt bone-ash1 of the fineness of coarse wheat flour1 moistened with one-twelfth its weight of water and compressed into shape in suitable moulds4 ,the moulds sold for this purpose are often of unsuitable shape4 ,since lead has a specific gravity of over #aa1 a cup to hold from #ae to #be grams of molten lead need not have a capacity of more than about #b c4c4 ,a hollow about #a inch across and #a_/d inch deep is sufficient2 and the body of the cupel to absorb this weight of lead should itself weigh from #bj to #be grams4 ,the button of lead in a gold assay may be twice as heavy as this4 ,for these larger buttons a hollow #a-a_/c inch across and #a_/c inch deep will be sufficient4 ,if these larger cupels are not at hand the larger buttons will have to be reduced in size by a scorification before cupelling4 ,in some cases this preliminary scorification is advantageous or even necessary3 this may be because the lead is hard and impure1 or it may be that a very small button of gold is expected4 ,in the latter case it is best to scorify the lead down to something less than #a gram1 and to perform the cupellation on a specially prepared small fine cupel4 ,these small cupels are best made by grinding the unsaturated portion of a used cupel to a fine powder1 and compressing the dry powder into a small ,berlin crucible or scorifier2 the face should be made quite smooth by pressure from a pestle4 ,on such cupels a small speck of gold 7less than 4#ja milligram7 will be left in a good shape and easily visible2 but the cupel must be withdrawn from the muffle as soon as the cupellation is finished to make sure of always getting the button in good condition4 ,in places1 such as ,mints1 where large numbers of bullion assays are regularly made a special form of cupel is used so that not less than six dozen assays may all be cupelled at the same time in a muffle of ordinary size4 ,these cupels are square blocks1 a little less than #b inches across1 and a little more than three quarters of an inch deep4 ,each block carries four hollows of about 4#g inch across and 4#c inch deep4 ,a muffle1 on a floor space of #f inches by #ab1 would take #c of these blocks abreast and #f deep1 and thus provide the means for #gb assays4#bd ,cupels made with wet bone-ash should be slowly dried2 and if in the muffle they can be slowly brought to an orange-red heat it is all the better4 ,under no circumstances must the lead be placed on the cupel before the latter has been so thoroughly heated that it can no longer give off steam or gas of any kind4 ,for this gas bubbling through the molten metal spatters it1 thus spoiling one assay and throwing doubt on all the rest4 ,again1 the risk of freezing at the start is much greater with a cupel which has not been properly heated4 ,the best plan is to do all the cupellations in batches4 ,after the muffle has cooled down for the withdrawal of the last batch1 and the old cupels have been taken out1 the new cupels for the next batch should be put in their place4 ,the furnace should then be stoked and made ready for the next cupellations2 by the time the furnace is ready the cupels will be ready also4 ,there should be no unnecessary handling of the cupels once they have been placed in the muffle4 ,the cupellation temperature for gold is an orange-red heat or perhaps a little hotter4 ,beginners1 who are apt to overheat their furnace1 should avoid a heat which can properly be called yellow4 ,dr4 ,t4,k4 ,rose#be has determined the temperature of a muffle during the cupellation of gold-silver alloys at the ,royal ,mint4 ,in one muffle the temperature ranged from #ajfe to #ajie ,c42 the lower temperature was of course in the front of the muffle4 ,in another it ranged from #ajbb to #ajfb1 and here the muffle appeared to the eye decidedly cooler than usual4 ,the alloy left after cupelling was made up of #a part of gold to #b-a_/b parts of silver1 and was fused at #ieb2 hence the usual temperature of cupellation was1 say1 #abj or #acj above the melting-point of the residual metal4 ,to obtain some real knowledge as to the meaning of these figures1 the student should prepare pointed pieces of the following metals3 silver1 which melts at #ide2 gold1 which melts at #ajce2 and an alloy1 half silver1 half gold1 which melts at #iij4 ,these should be placed on clean cupels in a muffle almost entirely closed2 the temperature should be very slowly raised1 and the appearance of the muffle when each metal begins to melt should be carefully noted4 ,the cupelling temperature in ,dr4 ,rose's experiment was as much above the melting-point of gold as this is above that of the silver-gold alloy4 ,the finish of the cupellation of gold or gold-silver alloys is practically the same as with pure silver2 there is the same thinning out of the litharge into a luminous film which becomes iridescent before the brightening4 ,but the danger of spirting decreases as the proportion of gold becomes greater1 and disappears when the gold is much over #cj per cent4 ,nevertheless it is well to let such buttons become solid undisturbed and protected from draughts in the body of the muffle4 ,this means closing the muffle and allowing the furnace to cool down somewhat before withdrawing the cupels4 ,buttons solidified in this way are more malleable than when they are withdrawn promptly on the finish of the cupellation4 ,this is important with large buttons1 as in a bullion assay4 ,on the other hand1 very small buttons1 especially such as have to be measured rather than weighed1 should be withdrawn as soon as the luminous film has disappeared4 ,for when this is done the button can be loosened from the cupel by merely touching it with the point of a pin1 and is then safely and easily transferred to a watch glass by touching it with the head of a pin which has been moistened4 ,it adheres to this1 and if the pin is not too wet comes off at once on touching the glass1 or in any case will do so on gentle warming4 ,molten gold1 with little or no silver1 has a peculiar colour which is easy to recognise2 it is more globular than a button of silver of the same size would be1 and it shows less adhesion to the cupel4 ,just after becoming solid it glows beautifully1 and this is so marked that it is a valuable help in finding the position of a button when it is more than ordinarily minute4 ,if the button left from cupellation is yellow it is at least half gold1 and a rough guess as to the proportion of gold may be made from its yellowness2 the rest of the metal is generally silver4 ,the presence of platinum or one of the platinum group of metals makes the surface of the button dull and crystalline4 ,the native alloy of osmium and iridium does not alloy with gold1 however1 but falls to the bottom of the molten metal4 ,it shows itself in the subsequent parting as a black spot or streak on the under surface4 ,the buttons are removed from the cupel with a pair of pliers and then brushed to remove adherent litharge and bone-ash4 ,some assayers advise cleaning by dipping in warm dilute hydrochloric acid followed by washing in water and drying4 ,the button is next weighed4 ,when the quantity of silver obtained is not required to be known the weighing may sometimes be omitted4 ,the next operation in either case is parting either with or without a previous inquartation4 ,the loss of gold in cupellation is by no means always inconsiderable4 ,in three cupellations of #a gram of gold with #bj grams of lead made purposely at a very high temperature the cupel absorbed #f4jd1 #f4bj1 and #f4de milligrams of gold4 ,hence at a high temperature there may easily be a loss of more than half a per cent4 of the gold4 ,in ten cupellations with the same quantities of gold and lead1 but at an ordinary temperature1 the gold recovered from the cupels varied from #a4cg to #a4ib milligrams1 and gave an average of #a4ei milligrams4 ,in round numbers the cupellation loss of pure gold is 4#ae per cent4 ,but if the gold be alloyed with silver the loss is diminished1 as is shown by the following experiments4 ,gold1 4#c gram1 was cupelled with #aj grams of lead and varying amounts of silver1 and the cupels were assayed for gold with the following results3 ,silver in the alloy 4#c gram 4#f gram 4#i gram ,gold in the cupel 4#dg milligram 4#cb milligram 4#ag milligram ,these1 calculated on the 4#c gram of gold1 give the loss as 4#aeg1 4#ajg and 4#jeg per cent4 respectively4 ,the effect of copper1 on the other hand1 is to increase the cupellation loss1 which1 silver being absent1 may from this cause rise to 4#c per cent41 even when the temperature is not excessive4 ,in the ordinary assay of gold-copper alloys a constant weight of the alloy is always taken2 hence as the weight of copper in a cupel charge increases1 the weight of gold decreases4 ,the silver1 on the other hand1 is always very nearly two and a half times as much as the gold1 whatever its quantity may be4 ,but the cupellation loss is smaller with less gold and greater with more copper1 and it so happens in these assays that these two opposites nearly neutralise one another4 ,mr4 ,w4,f4 ,lowe#bf found the gold recoverable from the cupels on which #bj grains of gold bullion had been treated varied only between 4#jad and 4#jae grain 7i4e4 from 4#jg to 4#jge per cent4 of the bullion treated71 although the quality of the bullion varied from #i to #bb carat4#bg ,but in the poorest bullion there was only #g4e grains of pure gold1 while in the richest there were #ah4c grains2 yet each lost on the cupel the same weight of gold1 viz41 4#jad grain4 ,when reckoned in percentages of the actual gold present the losses are 4#ahg per cent4 and 4#jgf per cent4 respectively4 ,the heavier percentage loss is mainly due to the increased quantity of copper4 ,as with silver so with gold the predominant cause of the cupellation loss is the solution of the metal in the molten litharge which passes into the cupel4 ,three lots of #a gram of gold cupelled each with #bj grams of lead repeatedly1 so as to make #ac cupellations in all1 lost in actual weight #ce4gb milligrams4 ,the gold recovered from the cupels amounted altogether to #cd4ef milligrams4 ,this shows that1 compared with the absorption by the cupel1 the other causes of loss are inconsiderable4 ,the loss of gold by volatilisation is1 however1 a real one4 ,the dust from the flues of assay furnaces has been tested on several occasions and found to contain gold1 though in small quantity4 ,thus ,mr4 ,lowe found 4#jgc per cent4 of silver and 4#jjjcc per cent4 of gold in such a material4 ,the lead volatilised from a gold bullion assay would need to be ten times as rich as this to account for a loss of gold equal to the hundredth part of a milligram4 ,dr4 ,rose1 in the paper already quoted1 believes that on a 4#e gram charge of standard bullion the loss from volatilisation is not less than 4#jbe nor more than 4#je milligram of gold4 ,by way of conclusion it may be said that the cupellation loss of gold is about 4#jg per cent41 and that it is largely met or even over corrected by a compensating error due to silver retained in the gold after parting4 ,inquartation4--,the method of separating the gold from the silver in gold-silver alloys by boiling with nitric acid does not act equally well in all cases4 ,an alloy half silver half gold1 rolled to thin sheet and boiled for half an hour with nitric acid1 may still retain more than two-thirds of its silver4 ,an alloy of #a part gold and #a4g parts of silver gives up practically the whole of its silver under similar treatment4 ,the gold is left in a coherent1 though easily broken1 sheet retaining the shape of the original alloy4 ,the gold thus left is quite spongy and porous1 so that the acid can penetrate into its innermost portions4 ,but if the silver is in large excess in the alloy1 the removal of the silver is less complete1 and the residual gold1 instead of holding together in a form easy to manipulate1 falls to a powder which requires care and time in its treatment4 ,the older assayers1 therefore1 added silver to their gold in such proportion that the alloy for parting should be one quarter gold to three quarters silver4 ,this operation they called inquartation4 ,the modern practice is to aim at getting an alloy with #b-a_/b parts of silver and #a part of gold4 ,in gold bullion assays this proportion should be obtained with fair exactness4 ,and in the parting of such gold buttons as are obtained in assaying ores it is well to aim at this proportion1 though absolute precision is not a matter of importance4 ,if the button left on cupelling the lead from an assay of an ore appears white1 it is best to assume that it already contains at least a sufficiency of silver1 in the absence of any knowledge to the contrary4 ,this will be true in almost all cases4 ,but if1 on parting1 it does not lose at least two-thirds of its weight1 this indicates that the assumption was not justified2 and also what quantity of silver must be added to the button before again attempting to part4 ,generally the fault will be in the other direction2 the silver will be in excess and the gold will break up and demand very careful treatment4 ,if1 however1 such a button is yellow1 then1 from its weight and depth of colour1 a rough estimate can be made of how much gold is contained in it4 ,silver must be added to make the total weight #c-a_/b times as much as that of the gold supposed to be present4 ,thus1 if the button weighs #aj milligrams and is supposed to contain #h milligrams of gold1 then #h multiplied by #c-a_/b is #bh2 the button must1 in such case1 be made up to #bh milligrams by adding #ah milligrams of silver4 ,in judging of the quality of the gold button1 no ordinary error will very seriously affect the result4 ,if1 in the example just given1 the quantity of gold present was really #g or even #i milligrams of gold1 the resulting alloy would still have been suitable for such partings4 ,in fact1 in routine assays1 where the quantity as well as the quality of the gold is known within fair limits1 it is often the custom to add the silver for inquartation to the lead during the first cupellation4 ,but in the assay of rich gold alloys such approximate work will not do4 ,if the composition is not already known with a fair degree of accuracy preliminary assays must be made4 ,weigh up two lots of #ajj milligrams of the alloy and wrap each in #c grams of lead4 ,to one add #cjj milligrams of silver4 ,cupel both4 ,the button containing the added silver must be flattened and boiled with #ae c4c4 of nitric acid2 and the resulting gold must be washed1 dried1 ignited and weighed4 ,this1 in milligrams1 gives directly the percentage of gold4 ,the weight of the other button gives the percentage of gold and silver2 the difference between the two gives the percentage of silver4 ,the rest will1 perhaps1 be copper4 ,the composition of the alloy being known1 or having been determined as just described1 the calculation of how much silver must be added is fairly simple4 ,the following is an example4 ,suppose the bullion contains #ib per cent4 of gold1 #a per cent4 of silver and #g per cent4 of copper1 and that 4#e gram of it is to be taken for an assay4 ,the 4#e gram1 then1 will contain ,gold 4#dfj gram ,silver 4#jje ,copper 4#jce ,but the total silver required is 4#df gram #b4e4 ,this equals #a4ae4 ,allowing for the 4#jje gram of silver already present1 #a4ade gram of silver must be added4 ,the silver is incorporated with the gold1 and at the same time the copper is eliminated1 by cupelling with sheet lead4 ,how much sheet lead must be used will depend partly on how much bullion is taken1 partly on how much copper it contains4 ,four grams of lead will do for a 4#e gram charge2 and for a 4#c gram charge1 #c grams may be used4 ,but with #bj per cent4 of copper these amounts should be doubled2 with #dj per cent4 of copper they should be trebled2 and with over #fj per cent4 of copper four times as much lead should be used4 ,for small buttons of gold as little lead as may be relied on to start cupelling may be taken2 the lead may conveniently be in the form of little cups made by folding lead foil on a piece of glass rod4 ,with a large number of bullion assays systematically worked and checked a simple plan would be to always use the quantity of lead required by the alloy containing most copper which turns up for assay4 ,this weight1 cut out of lead foil1 would be kept in stock folded into little bags ready to receive the bullion and silver4 ,the silver used for inquartation must1 of course1 be free from gold and is best prepared by the assayer who is to use it 7see p4 #ff74 ,it should not be in long strips or angular pieces likely to perforate the lead in which it is folded4 ,when wrapped in the lead it should be in the middle and should make as compact a parcel as possible4 ,each little parcel1 as completed1 should be placed on a tray in its properly numbered compartment4 ,its position here should correspond to that it will occupy in the muffle and eventually in the cupel tray4 ,the cupellation must be made with all the requisite precautions4 ,a good smooth malleable button is needed for the next operation1 which is known as flatting4 ,illustration3 ,,fig4 #de4 ,flatting4--,small buttons1 such as are got in assaying most gold ores1 are placed on a polished steel anvil and flattened by one or two blows with a hammer4 ,the flattened discs are heated to dull redness on a clean cupel and are then ready for parting4 ,somewhat larger buttons may be similarly treated1 but they should be annealed 7i4e4 heated to redness and allowed to cool7 during the flattening4 ,the silver-gold alloy left from the cupellation is soft and bends like lead2 but after hammering or rolling it becomes harder1 gets a spring in it like a piece of mainspring and cracks or splits somewhat easily4 ,there should be no cracks or stripping or even roughness on the flattened metal1 since such defects may cause the loss of small particles either during the flattening or in the subsequent treatment with acid4 ,the softness of the metal is restored by heating4 ,in bullion assays the flatting of the buttons requires care and practice for its skilful working4 ,the strips of alloy for parting should be of uniform thickness and condition so that the action of the acid shall be equal in all cases4 ,the button is taken from the cupel1 cleaned and placed on the anvil3 it is then struck a heavy blow which widens it to about #c_/d inch in diameter2 this blow is followed by two others1 one a little in front1 the other behind1 which lengthen the disc and give a very blunt roof-like slope to its upper face4 ,it should then be annealed4 ,this may be done by putting it in a just red-hot scorifier heated in a muffle3 it very soon attains the right heat and may then be transferred to a cold scorifier2 the hot scorifier should be put back into the muffle4 ,the softened disc is then taken to the rolls 7,fig4 #de74 ,the rolls are loosened until the disc can be pressed between them4 ,looking through the interval between them the rolls should appear exactly parallel2 if they are not1 one adjusting screw should be loosened and the other tightened until parallelism is obtained4 ,the rolls are now turned and the disc should be drawn through without any great effort4 ,beginners are apt to err by trying to do too much with one turn of the handle4 ,it is easy to stop whilst the rolls are only just gripping the metal and then to bring the disc back by reversing the action4 ,if the disc was originally level and the rolls are parallel1 the metal will appear as a strip which has been merely lengthened4 ,if the rolls are tighter on one side the strip will be bowed2 the tighter side will correspond with the outer curve of the crescent4 ,a mistake of this kind may be amended by passing the strip through the rolls the other way1 so as to reverse the irregularity and so straighten the strip4 ,the screw on the looser side should then be tightened until parallelism is obtained2 after which more care should be taken to tighten the two screws equally4 ,the rolling should be stopped when the strip is #c or #d inches long and of the thickness of an ordinary visiting card4 ,the strip should be annealed during the rolling and again at the finish4 ,parting4--,the thin sheet of metal is dropped into hot dilute nitric acid and boiled for five or six minutes after the brisk action of the acid on the metal has ceased4 ,at this stage nearly all the silver has gone into solution as nitrate of silver and the acid is charged with this salt4 ,this acid is poured off and the residual metal is again boiled for from #bj to #cj minutes with a second lot of stronger acid4 ,this leaves the gold almost pure1 though it may still retain from 4#je to 4#a per cent4 of silver4 ,treatment with the first acid only would probably leave three or four times as much4 ,the nitric acid used should be free from hydrochloric1 sulphuric1 iodic and telluric acids4 ,in testing it for the first of these add nitrate of silver and dilute with distilled water2 there should be no turbidity4 ,in testing for the others evaporate three lots in dishes over a water-bath4 ,test one for sulphates by adding water and barium chloride4 ,test another for iodates by taking up with a little water1 adding a few drops of starch paste and then dilute sulphurous acid solution a little at a time2 there should be no blue colour4 ,test the third for tellurium by heating with #a c4c4 of strong sulphuric acid until dense fumes come off2 allow to cool considerably2 a piece of tin foil added to the warm acid develops a fine purple colour if only a trace of tellurium is present4 ,the presence of lower oxides of nitrogen1 which impart a brown colour to the acid1 is objectionable2 they1 however1 are removed by boiling the diluted acid before using it for parting4 ,it is usual to keep a stock of the acid suitably diluted to the two strengths required for the parting4 ,these are known as the parting acids4 ,the first parting acid is the weaker and is used in the first attack on the metal4 ,the specific gravity generally recommended for it is about #a4b4 ,it may be prepared either by diluting the strong acid with about its own volume of distilled water1 or by suitably diluting the second parting acid which has been already used in an assay2 the small proportion of silver this contains is not harmful for this purpose4 ,the second parting acid has a specific gravity of about #a4c1 and may be made by diluting the strong acid with half its volume of distilled water4 ,parting in ,flasks4--,flasks are most convenient for the larger partings1 as in bullion assays2 and should always be used for this purpose unless some of the special parting apparatus1 like that used in ,mints1 is available4 ,many assayers use flasks1 though of a smaller size1 for the ordinary partings in assaying gold ores4 ,the flasks are either bulbs with long necks 7,fig4 #df7 which ought to be heated on rose burners of special construction2 or they are small flat-bottomed conical flasks which may be conveniently heated on a hot-plate and are1 in this respect1 much easier to deal with in general work4 ,the following instructions apply to the parting of an alloy containing a few decigrams of gold together with the proper proportion of silver4 ,illustration3 ,,fig4 #df4 ,the strip from the rolls1 after being softened by annealing1 is folded on itself on a glass rod into a roll or cornet4 ,it should be so plastic that it will retain the shape thus given it and not spring open on removing the pressure of the fingers4 ,about #ej c4c4 of the first parting acid are placed in a #f-ounce conical flask and heated to boiling2 the flask is then withdrawn1 and tilted a little to one side1 whilst the cornet is cautiously dropped into it2 there will be a sudden issue of hot vapours and a prompt withdrawal of the hand is advisable4 ,the flask is replaced on the hot plate and the acid is kept boiling for #aj or #ae minutes4 ,the flask is then withdrawn and the acid diluted with about an equal volume of distilled water4 ,if the flask has a thick glass band around its neck1 a little way down1#bh care must be taken to use hot water1 for any sudden chill will certainly crack the flask where it is thus thickened4 ,the liquor is carefully decanted into a clean beaker and is then thrown into a jar marked waste silver4 ,about #dj c4c4 of the second parting acid1 heated to boiling1 is then poured into the flask1 which is then replaced on the hot plate4 ,the boiling is continued for #ae or #bj minutes or even longer4 ,at this stage bumping has to be specially guarded against2 after a little experience it is easy to see when this is imminent and the flask should be withdrawn to a cooler part of the plate2 it is better to prolong the heating at a temperature below boiling than to run the risk of disaster4 ,some of the older writers1 however1 are rather insistent on vigorous boiling with large bubbles4 ,the addition of a small ball of well-burnt clay of about the size of a pea has been recommended1 as it lessens the tendency to irregular and dangerous boiling4 ,at the end of the treatment with the second acid the flask is withdrawn from the plate and the acid is diluted with an equal volume of distilled water4 ,the liquor is carefully decanted into a beaker1 and then poured into a jar or ,winchester marked acid waste2 it serves for making the first parting acid4 ,the flask is then washed twice with hot distilled water2 the washings must be carefully decanted from the gold4 ,the flask is then filled with water4 ,a parting cup 7size ,b7 is then placed over its mouth1 like a thimble on the tip of a finger4 ,this cup is of unglazed porous earthenware of such texture that it absorbs the last few drops of water left on drying2 and with a surface to which the gold does not adhere even on ignition4 ,the gold should fall out cleanly and completely on merely inverting the cup over the pan of the balance4 ,the flask and cup are then inverted so that the flask stands mouth down in the cup2 a little of the water from the flask flows into the cup1 but only a little4 ,the gold falls steadily through the water into the cup4 ,when time has been allowed for even the finest of the gold to have settled into the cup1 the flask is removed4 ,this is easiest done under water4 ,the cup1 with the flask still resting in it1 is dipped under water in a basin2 as soon as the neck of the flask is immersed the crucible can safely be drawn away from under it and then lifted out of the water4 ,the flask should not be taken away first1 for the rush of water from it may easily sweep the gold out of the cup4 ,the water in the cup is then drained off and the cup is dried at not too high a temperature2 for if the last drop or two of water should boil there is danger of spattering the gold out of the crucible4 ,when it is dry1 the cup is heated on a pipe-clay triangle over a ,bunsen burner1 or on a slab of asbestos in a muffle1 to a dull-red heat4 ,this brings the gold to colour2 that is1 the loose tender dark coloured gold becomes bright yellow and coherent2 and is in a state fit to be transferred to the balance and weighed4 ,all unnecessary transferences must be avoided4 ,as soon as the cup is cool it may be inverted over the pan of the balance1 when the gold will fall out cleanly or1 at the worst1 a gentle tap with the finger will be sufficient to detach it4 ,parting in test-tubes1 or in the smaller conical flasks1 is used in the assay of gold ores of ordinary richness4 ,the work is exactly like that just described in all its main features4 ,generally speaking much less acid will be used2 for example1 in test-tubes and for small buttons1 #c or #d c4c4 of each acid is quite enough4 ,again1 the action need not be so prolonged2 #aj or #ae minutes in each acid is sufficient4 ,so1 too1 the heating may be less2 it is very convenient to support the test-tubes in a water-bath1 or merely to rest them in a beaker of boiling water2 and there is no serious objection to doing this4 ,a smaller parting cup should be used2 the ,a size is suitable4 ,the button1 on the other hand1 should be beaten thinner than is needed for the larger partings4 ,if the silver should be in excess and the gold becomes much broken up1 ample time should be given for subsidence from the test-tube or flask into the parting cup4 ,parting in glazed crucibles or dishes4--,this method of working has the advantage that there is no transference of the gold until it is placed on the pan of the balance4 ,on the other hand1 in the boiling more care is required in adjusting the temperature4 ,the following instructions apply to the treatment of very small buttons1 to which the method is more particularly applicable2 but very little modification is needed for the treatment of larger buttons4 ,the smallest sized ,berlin crucibles answer admirably4 ,they should be cleaned by treatment with hot and strong sulphuric acid1 followed by washing in distilled water2 the comfort and ease of working mainly depends on the thoroughness of this cleaning4 ,the crucible1 one-third full with the first parting acid1 is heated on the hot plate until the acid is almost boiling4 ,the flattened and annealed button is dropped into it and the heating continued with1 at most1 gentle boiling for a few minutes4 ,the crucible is then filled with distilled water1 which cools it enough for easy handling2 and when the gold has settled the liquor is poured off along a glass rod into a clean beaker4 ,any greasiness of the crucible makes itself felt here and is very objectionable4 ,the crucible is then one-third filled with the second parting acid and the heating resumed1 care being taken not to raise the temperature too high2 this should be continued much longer than before1 say for five or ten minutes or even longer according to the size of the button4 ,distilled water is again added and1 when it is drained off1 the washing with distilled water is twice repeated4 ,it will not be possible to drain off the last drop of water2 but if the gold is coherent1 the crucible can be so inclined that this drop drains away from the gold1 in which case the drying can be done rapidly2 the boiling of the water will do no harm4 ,but when the gold is much broken up1 it will collect in the middle of this drop and the drying must be done gently2 best by putting the crucible in a warm place4 ,when dry1 the crucible is heated till the gold changes colour1 but the heat must be kept well below redness4 ,when cold1 the gold is transferred directly to the pan of the balance4 ,with minute specks of gold which will require measuring1 it is best to put a small piece of lead foil 7say 4#a gram7 in the crucible over the gold1 and then heat the crucible to above redness over a blowpipe4 ,whilst the lead is oxidising it is easily swept round in a bath of molten litharge by merely tilting the crucible4 ,in this way any separated specks of gold can be taken up with certainty4 ,when the worker is satisfied that the lead has had ample opportunity for taking up the gold1 the lead must be kept in one place and the heat slowly lowered4 ,by this means the button becomes supported in comparatively pure litharge and when solid can be picked out quite easily with a pair of pliers and in a very clean condition4 ,the lead button is then cupelled on a very fine cupel1 as already described4 ,the method of working last described destroys the crucible4 ,if the gold is not quite so small this may be avoided4 ,a small piece of lead foil should be hammered out until it is perfectly flexible4 ,it is then shaped into a tray and the gold is transferred to it4 ,the lead is then folded over1 with the help of two pins2 and cupelled4 ,if the crucible shows a black stain on heating it is because some silver remains through bad washing4 ,it shows poor work and the assay should be repeated4 ,the silver retained in the gold after parting is1 in bullion assays1 an important matter2 it is roughly equal to the loss of gold due to absorption by the cupel4 ,mr4 ,lowe working on 4#e oz4 of gold1 obtained by parting in assaying bullion1 found it to contain 4#abc per cent4 of silver4 ,dr4 ,rose in some special assay pieces found by a less direct method of assaying1 from 4#jf to 4#ji per cent4 of silver4 ,the proportion of silver retained varies in a marked way with the proportion of gold to silver in the alloy before parting4 ,it is generally stated that the retained silver is least when this proportion is #a to #b-a_/b1 and more or less silver than this leads to a less pure gold after parting4 ,platinum in an alloy being parted is dissolved along with the silver either altogether or in part4 ,it imparts a straw yellow colour to the parting acid4 ,palladium gives an orange colour to the acid4 ,the loss of gold by solution in the acid during parting is small1 but easily demonstrable4 ,on a #ejj-milligram charge of bullion it may amount to from 4#je to 4#ae milligram2 i4e4 from 4#ja to 4#jc per cent4 ,it is due to gold actually dissolved and not merely held in suspension4 ,assaying with checks4 ,surcharge4--,it will be seen from what has been stated that the errors in gold parting are of two kinds3 viz4 7#a7 a loss of gold on the cupel and to a less extent by solution in the acid1 and 7#b7 an apparent gain of gold due to the retention of silver in the parted material4 ,both errors are small1 and as they are of an opposite character they tend to neutralise each other4 ,hence they are altogether without effect on the accuracy of the assays of ores when the total gold is reckoned in milligrams4 ,and even with the larger amounts present in bullion assays their influence is so small that an uncorrected result is still fairly accurate2 the resultant error would not be more than one part in two or three thousand4 ,it is customary to report the purity of bullion1 or its fineness as it is called1 in parts per thousand of bullion4 ,the sum of the errors of an assay1 which is called the surcharge1 is reported in the same way4 ,thus a surcharge of 4#c means that the gold as weighed was 4#c part per #ajjj more than the gold actually present4 ,but a surcharge - 4#c means that on the whole there was a loss of 4#c part per #ajjj in the assay4 ,speaking roughly the retained silver will vary with the weight of gold present2 if one alloy contains twice as much gold as another the retained silver will be about twice as much also4 ,on the other hand1 as already explained1 the cupellation loss on the poorer alloy is as much as1 or even more than1 with the richer one1 because of the copper1 c4 present4 ,with rich gold alloys the silver more than compensates for the loss and the surcharge is positive2 but with poorer alloys the loss is greater and the surcharge is negative4 ,in ,mints and places where bullion assays must be made with the highest attainable accuracy1 the surcharge is determined by experiment1 and the proper correction is made in the reports on the bullion4 ,this is done by making assays of gold of the highest degree of purity alongside of those of the bullion whose quality has to be determined4 ,these checks are so made that they do not differ from the actual assays in any material point4 ,thus1 being of the same quality and weight and undergoing exactly the same treatment1 they may reasonably be expected to have the same surcharge as the assays they imitate4 ,suppose the bullion being assayed varies only a little1 up or down1 from #ijj gold and #ajj copper in the thousand1 and that 4#e gram of it is used in each assay4 ,a quantity of gold differing only a little from 4#dej gram would be very exactly weighed and placed with 4#jej gram of copper in the same weight of lead as is being used in the other assays4 ,it would be cupelled1 parted1 c41 as nearly as possible under the same conditions as the actual assays4 ,suppose the pure gold weighed 4#dejaf gram and the parted gold weighed 4#dejbe gram1 the gain in weight1 4#jjjji gram1 would be deducted from the actual assays4 ,a surcharge correction is never applied except to bullion of the same quality as that represented by the check assay it was calculated from4 ,it is evident that unless the gold is of the highest degree of purity these check assays will introduce an error almost equal to that which it is designed to remedy4 ,moreover1 to work the checks to the greatest advantage1 a very systematic and uniform method of working must be adopted4 ,parting in special apparatus4--,one plan for obtaining greater uniformity is to stamp each cornet with a number for purposes of identification1 and to treat several1 including one or more check assays in the same acid contained in a beaker2 all the assays under these conditions evidently receive precisely the same acid treatment4 ,such a plan can of course only be adopted where there is no risk of the gold breaking up during the parting4 ,an improvement on this is to have a porcelain basin#bi about #h-a_/b inches in diameter and with a capacity of about #a-a_/b litres4 ,it is provided with a porcelain cover with #cj numbered holes through which tubes dip into the acid4 ,the cover is removable4 ,the tubes are like test-tubes and are supported by the cover2 their bottoms are perforated with holes or slits4 ,the acid is placed in the basin and boiled over a flat burner2 it enters the tubes through the slits4 ,the cornets are placed each in its proper tube4 ,when the boiling is finished1 the cover with the tubes is lifted and at the same time the acid drains back into the basin4 ,a dip into a basin of distilled water washes at one operation all #cj assays4 ,the cover is then put on a basin containing the stronger parting acid which is already boiling4 ,this boiling is continued for half an hour4 ,the cover with the #cj cornets is then lifted out from the acid and dipped two or three times in distilled water to wash off the last traces of acid4 ,to transfer the cornets from the tubes to the porous cups the whole of the tube must be dipped under the water2 otherwise the operation is exactly as when working with test-tubes4 ,a still simpler method of working is to use small platinum cups#cj provided with fine slits which admit the acid but retain the gold4 ,a number of these1 say #fj1 are supported on a platinum tray4 ,the parting acids are boiled in platinum dishes under a hood2 and the #fj cornets 7each in its proper cup7 are placed in the acid all at once3 the tray carrying the cups is provided with a handle suitable for this purpose4 ,after a proper boiling the tray is lifted out of the weaker acid into the stronger one1 where it undergoes the second boiling4 ,it is next dipped several times in distilled water and lastly1 after a gentle drying1 it is raised to an annealing temperature which must not be too high for fear of the gold sticking to the platinum4 ,after cooling1 the cornets are transferred from the platinum cups directly to the pan of the balance4 ,here all #fj cornets have exactly the same treatment and the checks may be compared with great exactness with the other assays accompanying them4 ,there is1 too1 a great saving of labour4#ca ,silver1 c41 in gold bullion4--,the base metals are generally determined by cupelling 4#e gram of the alloy with #e grams of lead4 ,the loss in cupellation having been allowed for by any of the usual methods 7see p4 #ajd7 the gold and silver contents are given4 ,by deducting the gold the proportion of silver is obtained4 ,the silver is generally determined by difference in this way4 ,if it is desired to dissolve out the copper1 silver1 c41 and to determine them in the wet way1 the gold must first be alloyed with a sufficiency of some other metal to render it amenable to the attack by acid4 ,cadmium is the metal generally recommended1 and the alloy is made by melting together a weighed portion of the gold with five or six times its weight of cadmium in a ,berlin crucible and under a thin layer of potassium cyanide4 ,lead with gold or silver4--,large quantities of lead carrying gold and silver are sold to refiners in bars weighing about #ajj lbs4 each4 ,the assay of these alloys presents no special difficulties1 but the sampling of them is a question which may be profitably discussed4#cb ,a molten metal may be conceived to have all the physical states observed in ordinary liquids1 although these cannot be actually seen owing to its opaqueness4 ,there is no doubt that pure lead at a temperature only a little above its melting-point can contain a large proportion of gold in such a manner that it may in a figurative way be spoken of as a clear solution4 ,any small portion withdrawn from the molten metal would afford a perfect sample4 ,the same would be true of any pure alloy of lead and silver in which the silver does not exceed the proportion of #b-a_/b per cent4#cc ,on the other hand1 if the molten metal contains much more than 4#e per cent4 of zinc1 more than 4#a per cent4 of copper1 or a larger quantity of silver1 it may be likened to a turbid liquor4 ,the resemblance holds good so far that if the molten lead be further heated1 whereby its solvent power on the added metal is increased1 the turbidity will disappear1 or at least be considerably diminished4 ,a portion taken at random from such a molten metal may1 or may not1 give a good sample4 ,the suspended insoluble matter will tend to concentrate itself in the upper or lower parts of the liquid according to whether it is heavier or lighter than it2 and this separation may occur with extreme slowness or with fair rapidity4 ,however1 it is generally agreed that in the case of such alloys as occur in practice1 samples taken in this way are quite satisfactory and are the best obtainable4 ,the precautions insisted on are that the lead shall be made as hot as practicable2 that it shall be stirred up at the time of taking the sample2 and that the portion withdrawn shall be taken out with a ladle at least as hot as the molten metal4 ,the further precaution that if any dross be on the surface of the metal it shall be skimmed off and separately sampled and assayed is almost too obvious to require mention4 ,an alternative and1 perhaps1 better way of taking the sample is to withdraw portions at equal intervals from the stream of metal whilst the pot is being emptied2 equal weights taken from these portions and mixed 7by melting or in some other way7 give a fair sample of the whole4 ,in addition1 separate assays of each portion will show to what extent the metal lacks uniformity in composition ,for example1 samples taken at the beginning1 middle1 and end of a run gave the following results in ozs4 of silver per ton3 #dge1 #dgb1 #dff1 showing an average result of #dga ozs4 ,fifteen fractions taken at regular intervals during the same pouring ranged from #dge ozs4 to #dfd ozs43 the average result was #dfi4h ozs4 ,the same lead cast into bars and sampled by sawing gave an average of #dgj ozs4#cd ,in another case#ce samples drawn at the beginning1 middle1 and end of a run gave #acde ozs41 #acce ozs4 and #acca ozs4 ,the mean result in such cases is always a reasonably safe one1 but evidently where the metal varies a good deal it is safer to take more than three dips4 ,imagine such lead run into moulds and allowed to become solid as bars2 the difference between bar and bar would not be greater than that between corresponding dip samples4 ,but in each bar the distribution of the silver and gold is very seriously affected during solidification4 ,chips taken from the same bar of auriferous lead may show in one place #bc ozs4 of gold to the ton1 in another #ci ozs42 similarly with silver they may vary as much as from #ijj ozs4 to #aejj ozs4 to the ton4 ,this rearrangement of the constituents of a bar takes place whilst the lead is partly solid1 partly liquid4 ,the most useful conception of such half-solidified metal is that of a felted spongy mass of skeleton crystals of comparatively pure lead saturated with a still fluid enriched alloy4 ,if the solidification of an ingot of impure tin be watched it will be evident that the frosted appearance of the surface is due to the withdrawal of the fluid portion from a mat of crystals of purer tin which have been for some time solid and a contraction of the mass4 ,the shrinking of the last part to become solid is further shown by the collapse of the surface of the ingot where weakest2 that is1 a furrow is formed on the flat surface4 ,in other cases of fused metal there is expansion instead of contraction in this final stage of the solidification1 and the enriched alloy then causes the upper face of the ingot to bulge outwards4 ,there are other causes effecting the redistribution of the metals through the ingot4 ,there can be no general rule of wide application showing which part of a bar is richest and which poorest in the precious metals4 ,this will depend on the quantities of gold or silver1 on the quantities and kinds of other metals present and on the manner of casting4 ,the student is advised to consult ,mr4 ,claudet's paper which has been already referred to4 ,the best method of sampling such bars is to melt them all down and to take a dip sample of the molten metal in one or other of the methods already described4 ,according to ,mr4 ,claudet this should be done in all cases where the gold exceeds one or two ounces or where the silver exceeds #bjj ozs4 to the ton4 ,if during the melting down some dross has formed this must be skimmed off1 weighed and separately sampled and assayed4 ,the clean lead also must be weighed1 sampled and assayed4 ,the mean result must be calculated4 ,thus #ad tons #e cwts4 of clean lead assaying #cb ozs4 to the ton will contain #def ozs4 of silver2 #ae cwt4 dross assaying #bj ozs4 to the ton will contain #ae ozs4 of silver4 ,the #ae tons of lead and dross will contain #dga ozs4 of silver or #ca4d ozs4 per ton4 ,of the methods of sampling which avoid melting the bars1 that known as sawing is the only one which is thoroughly satisfactory4 ,in it the bars are brought to a circular saw having fine teeth and are sawn across either completely or halfway through2 in this way a quantity of lead sawdust is obtained 7say #a lb4 or so from a bar7 which represents exactly the average of the bar along the particular cross section taken and approximately that of the whole bar4 ,a bar of lead1 which by dip assay gave #ccd ozs4 to the ton1 gave on three transverse sections #ccc ozs41 #cce ozs4 and #cca ozs4 ,the variation may be greater than this1 but with a large number of bars1 where each bar is cut across in as far as possible a different place1 these variations tend to neutralise each other and a good sample is obtained4 ,two or three cwt4 of sawdust may be obtained in this way2 this is thoroughly mixed and reduced by quartering in the usual way or by a mechanical sampler4 ,a sample of #b or #c lbs4 is sent to the assayer4 ,this being contaminated with the oil used in lubricating the saw is freed from it by washing with carbon bisulphide1 ether or benzene and dried4 ,then1 after mixing1 #ajj to #bjj grams of it are carefully weighed and placed in a hot crucible1 the heat of which should be sufficient to melt all the lead4 ,the molten lead should not be overheated and should show no loss due to the melting4 ,the removal of the oil may have decreased the weight by perhaps one half per cent4 ,if the lead gives dross on heating it may be melted under #aj or #bj grams of potassium cyanide1 which prevents the formation of dross4 ,samples are sometimes taken with a drill1 gouge or chisel1 though no method of this kind is quite satisfactory4 ,one plan adopted is to use a punch which1 when driven into the bar1 gives a core or rod of metal about half as long as the bar is thick and about one-eighth of an inch across4 ,with five bars side by side it is customary to drive in the punch at one end on the first bar1 and at the opposite end on the last one1 and on the others in intermediate positions in such a manner that all the holes will be along a diagonal of the rectangle enclosing the bars4 ,the bars are then turned over and similar portions punched out through the bottoms of the bars and along the other diagonal4 ,or one set of five may be sampled along the top and the next set along the bottom of the bars4 ,silver and gold present in bars of copper are subject to the same irregularity of distribution as in lead4 ,the sampling of such bars is guided by the same principles4#cf ,,cyanides4 ,the cyanides ought perhaps to be considered along with chlorides1 bromides and iodides in ,chapter ,,xv4 ,but they are treated here because they owe their importance to their use in the extraction of gold and because their determination has become a part of the ordinary work of an assayer of gold ores4 ,formerly1 the cyanide most easily obtained in commerce was potassium cyanide2 and it was generally sold in cakes which might contain as little as #dj per cent4 or as much as #ie per cent4 of the pure salt4 ,it became customary to express the quality of a sample of commercial cyanide by saying it contained so much per cent4 of potassium cyanide4 ,the commercial product now made by improved methods of manufacture is actually sodium cyanide1 but is called potassium cyanide 7probably with the words double salt on the label72 it contains cyanide equivalent to something over #ajj per cent4 of potassium cyanide in addition to a large proportion of sodium carbonate and other impurities4 ,what is wanted in most cases is merely a soluble cyanide1 and it is a matter of indifference whether the base be sodium or potassium4 ,but since #di parts of sodium cyanide 7,na,c,n #di7 are equivalent to #fe parts of potassium cyanide 7,,kcn #fe7 it is evident that a pure sample of sodium cyanide would contain cyanide equivalent to little less than #acc per cent4 of potassium cyanide4 ,therefore a sample of cyanide reported on in this way may be rich in cyanide1 and yet have much impurity4 ,the commonest impurity in commercial cyanide is carbonate of sodium or potassium4 ,this may be tested for by dissolving1 say1 #b grams in a little water and adding barium chloride4 ,there may be formed a white precipitate of barium carbonate1 which if filtered off1 washed and treated with acid1 will dissolve with effervescence4 ,cyanate may be tested for in the solution from which the barium carbonate has been filtered by adding a little soda and boiling2 if cyanates are present they decompose1 giving off ammonia 7which may be tested for in the steam7 and yielding a further precipitate of barium carbonate4#cg ,if the soda alone gave a further precipitate of barium carbonate1 this may1 perhaps1 be due to the presence of bicarbonates4 ,alkaline sulphides may be present in small quantity in commercial cyanide4 ,their presence is shown at once when the sample is being tested for its strength in cyanide1 inasmuch as the first few drops of silver nitrate solution produce at once a darkening of the liquor4 ,a special test for sulphide may be made by adding a drop or two of solution of acetate of lead to four or five c4c4 of soda solution and adding this to a clear solution of the suspected cyanide4 ,this will cause a black precipitate or colour1 if any sulphide is present4 ,the cyanides of the heavier metals combine with the alkaline cyanides to form double cyanides4 ,some of these1 ferrocyanide and ferricyanide of potassium for example1 have such characteristic properties that the fact that they are cyanides may be overlooked4 ,others1 such as potassium zinc cyanide 7,k#b,zn,cy#d71 have much less distinctiveness3 they behave more or less as a mixture of two cyanides and are1 moreover1 so easily decomposed that it may be doubted if they can exist in dilute alkaline solutions4 ,in reporting the cyanide strength of a cyanide liquor as equivalent to so much per cent4 of potassium cyanide1 there is a question as to whether the cyanide present in the form of any of these double cyanides should be taken into account4 ,it must be remembered that the object of the assay is not to learn how much of the cyanide exists in the solution as actual potassium cyanide2 reporting the strength in terms of this salt is a mere matter of convenience2 what is really desired is to know how much of the cyanide present in the liquor is free or available for the purposes of dissolving gold4 ,every one is agreed as to the exclusion of such cyanides as the following3 potassium ferrocyanide 7,k#d;,fe,cy#f71 potassium ferricyanide 7,k#c;,fe,cy#f71 potassium silver cyanide 7,k,ag,cy#b71 and potassium aurocyanide 7,k,au,cy#b72 and the double cyanides with copper or nickel4 ,but with cyanide liquors containing zinc the position is less satisfactory4 ,one method of assay gives a lower proportion of cyanide when this metal is present2 and the loss of available cyanide thus reported depends1 though in a fitful and uncertain way1 upon the quantity of zinc present4 ,the other method of assay reports as full a strength in cyanide as if no zinc were present4 ,unfortunately1 using both methods and accepting the difference in the results as a measure of the quantity of zinc present1 or at any rate of the zinc present as cyanide1 is not satisfactory4 ,it appears best to use the method which ignores the zinc2 and to determine the amount of zinc by a special assay of the liquor for this metal4 ,the cyanide present as hydrogen cyanide or prussic acid 7,h,cy7 is practically useless as a gold solvent4 ,hence any report on the strength of a cyanide liquor which assigned to this the same value as its equivalent of alkaline cyanide would be misleading4 ,on the other hand1 it is available cyanide inasmuch as a proper addition of sodium hydrate#ch would restore its value4 ,the question of the presence or absence of free prussic acid is involved in the larger one as to whether the cyanide solution has the right degree of alkalinity4 ,the assay for cyanide should include the hydrogen cyanide with the rest4 ,a rough test of the power of a cyanide liquor for dissolving gold may be made by floating a gold leaf on its surface and noting the time required for its solution4 ,this test might1 perhaps1 be improved by taking1 say1 #bj c4c4 of the liquor and adding three or four gold leaves so that the gold shall always be in considerable excess4 ,the liquor should not be diluted as this will affect the result4 ,it should be allowed to stand for a definite time1 say at least two or three hours1 or better1 that corresponding to the time the liquor is left in contact with the ore in actual practice4 ,the liquor should then be filtered off and1 with the washings1 be evaporated in a lead dish as in the assay of cyanide liquors for gold 7p4 #ada74 ,the gold obtained on cupelling1 less any gold and silver originally present in the liquor1 would be the measure of the gold dissolving power4 ,,the ,,assay ,,for ,,cyanide ,,by ,,titration ,,with ,,silver ,,nitrate4 ,the determination of the quantity of a cyanide is made by finding how much silver nitrate is required to convert the whole of the cyanide into potassium silver cyanide#ci or one of the allied compounds4 ,it will be seen from the equation that #agj parts by weight of silver nitrate are required for #acj parts by weight of potassium cyanide4 ,as already explained it is customary to report the cyanide-strength in terms of potassium cyanide1 even when only the sodium salt is present4 ,one gram of potassium cyanide will require #a4cjgf gram of silver nitrate4 ,the standard solution of silver nitrate is made by dissolving #ac4jgf grams of silver nitrate in distilled water and diluting to #a litre2 #ajj c4c4 of such a solution are equivalent to #a gram of potassium cyanide4#dj ,the titration is performed in the usual way1 running the standard solution of silver nitrate into a solution containing a known weight or volume of the material containing the cyanide4 ,the finishing point is determined in one of two ways1 both of which are largely used4 ,in the first place1 as long as there remains any free cyanide in the solution the silver nitrate will combine with it forming the double cyanide and yielding a clear solution2 but as soon as all the free cyanide is used up the silver nitrate will react with the double cyanide#da forming silver cyanide1 which separates as a white precipitate and renders the solution turbid4 ,but1 in the second place1 if potassium iodide is present in the solution the excess of silver nitrate will react with it1#db rather than with the double cyanide2 and silver iodide will separate as a yellowish turbidity which is easily recognised4 ,in working with pure solutions1 the two finishing points give the same results2 and this is true even when there is much difference in the degree of dilution4 ,the finishing point with the iodide1 however1 has an advantage in precision4 ,moreover1 it is but little affected by variations in alkalinity1 which render the other finishing point quite useless4 ,the great difference between the two is shown when zinc is present in the solution4 ,in this case1 when working without the iodide1 the first appearance of a turbidity is less distinct2 the turbidity increases on standing and as a finishing point is unsatisfactory4 ,it can be determined with precision only by very systematic working and after some experience4 ,the turbidity is due to the separation of an insoluble zinc compound4 ,a most important point 7to which reference has already been made7 is that less silver nitrate is required to give this turbidity and1 consequently1 a lower strength in cyanide is reported4 ,on the other hand1 as much silver nitrate is required to give the yellow turbidity due to silver iodide as would be required if no zinc were present4 ,unfortunately the difference in the two titrations does not depend merely on the quantity of zinc present2 as it is also influenced by the extent of dilution1 the degree of alkalinity of the solution1 and the quantity of cyanide present4 ,in an experiment with 4#jee gram of zinc sulphate and 4#a gram of potassium cyanide the difference in the two finishing points was only 4#a c4c42 whereas with 4#d gram of potassium cyanide1 the other conditions being the same1 the difference was #a4e c4c4 of standard silver nitrate4 ,on the assumption that all the zinc was present as potassium zinc cyanide 7,k#b,zn,cy#d7 the difference should have been #e c4c4 in each case4 ,again1 repeating the experiment with 4#d gram of potassium cyanide1 but with 4#aa gram of crystallised zinc sulphate1 the difference was #f4e c4c43 that is1 merely doubling the quantity of zinc increased the difference by more than four times4 ,hence it would appear better to use the method with the iodide and make a separate assay for the zinc4 ,but since the student may be called on to use the other method1 he is advised to practice it also4 ,the assay without iodide4--,the standard solution of silver nitrate is placed in a small burette divided into tenths of a c4c4 ,ten c4c4 of the cyanide solution to be assayed is transferred to a small flask and diluted with water to about #gj c4c4 ,the silver solution is then run in from the burette 7with constant shaking of the flask71 a little at a time but somewhat rapidly1 until a permanent turbidity appears4 ,since #a c4c4 of the silver nitrate solution corresponds to 4#ja gram of potassium cyanide1 it also corresponds to 4#a per cent4 of this salt counted on the #aj c4c4 of cyanide solution taken4 ,the titration should be performed in a fairly good uniform light4 ,the learner should practice on a fairly pure solution of potassium cyanide at first1 and this may conveniently have a strength of about #a per cent4 ,for practice with solutions containing zinc make a solution containing #a4a gram of crystallised zinc sulphate in #ajj c4c4 and slowly add measured quantities of from #a to #e c4c4 of this to the #aj c4c4 of cyanide liquor before diluting for the titration4 ,if a cyanide solution blackens on the addition of the silver nitrate it contains sulphide4 ,in this case1 shake up a considerable bulk of the liquor with a few grams of lead carbonate1 allow to settle and make the assay on #aj c4c4 of the clear liquor4 ,if the cyanide liquor be suspected to contain free prussic acid1 take #aj c4c4 for the assay as usual2 but1 before titrating1 add 4#a or 4#b gram of sodium carbonate4 ,on no condition must caustic soda or ammonia be added4 ,the difference between the results1 with and without the addition of carbonate of soda1 is supposed to measure the quantity of free prussic acid4 ,if this has to be reported it is best done as prussic acid equivalent to 444 per cent4 of potassium cyanide4 ,suppose1 for example1 the difference in the two titrations equals #a c4c4 of standard silver nitrate2 the prussic acid found would be equivalent to 4#a per cent4 of potassium cyanide4 ,the assay with iodide4--,the standard solution of silver nitrate is placed in a burette divided into tenths of a c4c4 ,take #aj c4c4 of the cyanide liquor1 which should previously have been treated with white lead for the removal of sulphides if these happened to be present4 ,transfer to a small flask1 add #c or #d drops of a solution of potassium iodide and #b or #c c4c4 of a solution of sodium hydrate2 dilute to #fj or #gj c4c4 with water4 ,if much zinc is present the soda may be increased to #bj or #cj c4c4 with advantage4 ,the standard solution should be run in somewhat rapidly1 but a little at a time1 so that the precipitate at first formed shall be small and have only a momentary existence4 ,the titration is continued until there is a permanent yellowish turbidity4 ,the most satisfactory and exact finish is got by ignoring any faint suspicion of a turbidity and accepting the unmistakable turbidity which the next drop of silver nitrate is sure to produce4 ,this finishing point gives results which are exactly proportional to the quantity of cyanide present2 and it can be recognised with more than ordinary precision even in solutions which are not otherwise perfectly clear4 ,each c4c4 of the standard silver nitrate solution corresponds to 4#ja gram of potassium cyanide2 and if #aj c4c4 of the liquor are taken for assay this corresponds to 4#a per cent4 or #b lbs4 to the short ton or #b4bd lbs4 to the long ton4 ,as already explained the result should be reported as cyanide equivalent to so much per cent4 of potassium cyanide4 ,the following experimental results were obtained with a solution of potassium cyanide made up to contain about #a4b per cent4 of the salt4 ,effect of varying cyanide4--,the bulk before titration was in each case #fj c4c42 #b c4c4 of soda and #c drops of potassium iodide were used in each case4 ,cyanide added #dj c4c4 #cj c4c4 #bj c4c4 #aj c4c4 #e c4c4 #a c4c4 ,silver required #dg4j c4c4 #ce4be c4c4 #bc4e c4c4 #aa4g c4c4 #e4h c4c4 #a4ae c4c4 ,accepting the result for #dj c4c4 as correct1 the others are in very satisfactory agreement4 ,effect of varying dilution4--,the conditions were those of the #dj c4c4 experiment in the last series2 but varying amounts of water were used in diluting4 ,water added none #ajj c4c4 #bjj c4c4 #djj c4c4 ,silver required #dg4j c4c4 #dg4j c4c4 #dg4j c4c4 #dg4je c4c4 ,very considerable dilution therefore has no effect4 ,effect of varying soda4--,the conditions were those of the #dj c4c4 experiment in the first series1 except that varying amounts of soda solution were used4 ,soda added none #aj c4c4 #cj c4c4 ,silver required #df4ie c4c4 #dg4j c4c4 #dg4j c4c4 ,this alkali therefore has no prejudicial effect4 ,effect of ammonia4--,soda causes turbidity in some cyanide liquors2 with these it should be replaced by #b or #c c4c4 of dilute ammonia with a gram or so of ammonium chloride4 ,the following experiments with dilute ammonia show that larger quantities of this reagent must be avoided4 ,ammonia added none #aj c4c4 #cj c4c4 #fj c4c4 ,silver required #df4ie c4c4 #dg4ae c4c4 #dg4g c4c4 #di4e c4c4 ,effect of sodium bicarbonate4--,in this experiment #a gram of bicarbonate of soda was used instead of the soda or ammonia of the other experiments4 ,the silver nitrate required was only #df4de c4c4 instead of the #dg4j c4c4 which is the normal result4 ,this is probably due to the liberation of prussic acid and shows the importance of having the solution alkaline4 ,effect of zinc4--,in each experiment #dj c4c4 of the cyanide solution and 4#e gram of zinc sulphate crystals were used and the bulk was made up to #ajj c4c4 before titrating4 ,soda added #a c4c4 #e c4c4 #aj c4c4 #be c4c4 ,silver required #dg4a c4c4 #dg4j c4c4 #df4i c4c4 #df4i c4c4 ,the work was easier with the more alkaline solutions4 ,the titration in the presence of zinc is comparatively easy1 but1 in learning it1 it is well to have a burette with cyanide so that if a titration be overdone it can be brought back by the addition of #a or #b c4c4 more cyanide and the finish repeated2 a quarter of an hour's work in this way will ensure confidence in the method4 ,effect of other substances4--,it was found that an alkaline cyanate1 sulphocyanate1 ferrocyanide1 nitrite1 borate1 silicate or carbonate has no effect4 ,the ferricyanide had a small influence and1 as might be expected1 hyposulphite is fatal to the assay4 ,the addition of salts of lead and cadmium was without effect4 ,on the other hand1 nickel produces its full effect2 and the quantity of nickel added can be calculated with accuracy from the extent of its interference with the titration4 ,assay of commercial cyanide of potassium4--,break off #bj or #cj grams of the cyanide in clean fresh pieces1 weigh accurately to the nearest centigram4 ,dissolve in water containing a little sodium hydroxide2 transfer to a #b-litre flask3 dilute to #b litres2 add a few grams of white lead2 shake up and allow to settle4 ,run #ej c4c4 of the clear liquor from a burette into an #h oz4 flask2 add #b or #c c4c4 of soda solution and #c drops of potassium iodide4 ,titrate with the standard solution of silver nitrate4 ,the percentage may be calculated by multiplying the number of c4c4 used by #dj 7#ej c4c4 is one fortieth of the #b litres7 and dividing by the weight of commercial cyanide originally taken4 ,alkalinity of commercial potassium cyanide and of cyanide solutions4--,hydrocyanic acid like carbonic acid has no action on methyl-orange2#dc hence the alkaline cyanides may be titrated with normal acid as easily as the carbonates or hydrates4 #ajj c4c4 of normal acid will neutralise #f4e grams of pure potassium cyanide4#dd ,a solution of commercial cyanide prepared as for the assay last described1 but best without the addition of white lead1 may be used for the test4 ,take #ej c4c4 of it2 tint faintly yellow with methyl-orange and titrate with normal acid till the liquor acquires a permanent reddish tint4 ,in the case of the purer samples of cyanide the quantity of acid used will correspond exactly with that required to neutralise the actual quantity of cyanide present as determined by the assay with nitrate of silver4 ,the less pure samples will show an excess of alkalinity because of the presence of sodium carbonate or of potassium carbonate4 ,in comparing the alkalinity and cyanide strength of a solution the simplest plan is to take #fe c4c4 of the solution and titrate with normal acid2 for in this case each c4c4 of normal acid corresponds to 4#a per cent4 of potassium cyanide4 ,in systematic assays of this kind1 the alkalinity would no doubt be generally in excess of that required by the cyanide present3 there would be no inconvenience in recording such excess in terms of potassium cyanide4 ,determination of the acidity of an ore4--,most ores have the power of destroying more or less of the alkalinity of a cyanide solution and in a proportionate degree of damaging its efficiency4 ,an assay is needed to determine how much lime or soda must be added for each ton of ore in order to counteract this4 ,whether this acidity should be reported in terms of the lime or of the soda required to neutralise it will depend on which of these reagents is to be used in the actual practice4 ,again1 if the ore is washed with water before treating with cyanide on the large scale1 then the assay should be made of the acidity of the ore after a similar washing4 ,the standard solutions of acid and alkali used for this determination may be one-fifth normal4 #bjj c4c4 of the normal solution should be diluted to #a litre in each case1 #a c4c4 of the resulting solutions would be equivalent to #h milligrams of soda 7,na,h,o7 or #e4f milligrams of lime1 ,ca,o4 ,it must be remembered this refers to the pure bases in each case4 ,suppose it is desired to report as so many lbs4 of lime to the short ton 7#bjjj lbs47 of ore4 ,since #a c4c4 of the standard solution is equivalent to #e4f milligrams of lime1 if we take #bjjj times this weight of ore 7i4e4 #aa1bjj milligrams or #aa4b grams7 for the assay1 each c4c4 of standard solution will be equivalent to #a lb4 of lime to the short ton4#de ,total acidity4--,weigh out #aa4b grams of the ore1 place them in a four-inch evaporating dish and measure on to it from a burette #aj or #bj c4c4 of the standard solution of soda4 ,stir the soda solution into the ore and allow to stand for #ae or #bj minutes with occasional stirring4 ,stir up with #cj or #dj c4c4 of water1 float a piece of litmus paper on the liquid and titrate with the standard solution of acid4 ,if the ore is strictly neutral the quantity of acid required to redden the litmus will be the same as the quantity of soda originally used4 ,if the ore is acid1 less acid will be used4 ,for example1 if #aj c4c4 of soda were used and only #g c4c4 of acid were required1 the ore will have done the work of the remaining #c c4c4 of acid4 ,and the ton of ore will require #c lbs4 of lime to neutralise its acidity4 ,acidity after washing4--,take #aa4b grams of the ore2 wash thoroughly with water and immediately treat the residue1 without drying1 exactly as just described4 ,examination of cyanide solutions for metals1 c4--,take a measured quantity of the solution1 say #bj c4c4#df and evaporate in a small dish with1 say1 half a c4c4 of strong sulphuric acid4 ,evaporate at first1 on a water-bath in a well ventilated place1 but finish off with a naked ,bunsen flame1 using a high temperature at the end in order to completely decompose the more refractory double cyanides4 ,allow to cool2 moisten with strong hydrochloric acid2 warm with a little water and test for the metals in the solution by the ordinary methods4 ,since the quantities of the metals likely to be present may be given in milligrams the work must be carefully performed4 ,it may be worth while to determine the proportions of lime and magnesia as well as those of the metals proper4 ,or the #bj c4c4 of cyanide liquor may be evaporated with #e c4c4 of strong nitric acid to dryness and gently ignited and the residue taken up with #b or #c c4c4 of strong hydrochloric acid4 ,copper1 iron1 and zinc can be rapidly determined in such a solution1 as follows4 ,dilute with water to #aj or #ae c4c41 add an excess of ammonia1 and filter4 ,the precipitate will contain the iron as ferric hydrate2 dissolve it in a little hot dilute sulphuric acid3 reduce with sulphuretted hydrogen2 boil off the excess of gas1 cool and titrate with standard potassium permanganate 7p4 #bcf74 ,determine the copper in the filtrate colorimetrically 7p4 #bjc72 but avoid further dilution4 ,then add dilute hydrochloric acid1 so as to have an excess of #d or #e c4c4 after neutralising the ammonia2 add some clean strips of lead foil1 and boil until the solution has for some time become colourless4 ,titrate with standard potassium ferrocyanide 7p4 #bfc7 without further dilution1 and bearing in mind that at most only one or two c4c4 will be required4 ,examination of an ore for cyanicides4--,place #ajj grams of the ore with #bjj c4c4 of a cyanide solution of known strength 7say 4#a or 4#b per cent47 in a bottle and agitate for a definite time1 such as one or two days4 ,filter off some of the liquor and assay for cyanide1 using say #bj c4c4 ,calculate how much cyanide has been destroyed in the operation4 ,evaporate #bj c4c4 with sulphuric or nitric acid and examine for metal4 ,test another portion for sulphides1 c4 ,the student who has mastered the methods of assaying can greatly improve himself by working out such problems as the above4 ,,platinum4 ,platinum occurs in nature in alluvial deposits associated with gold and some rare metals1 generally in fine metallic grains1 and1 occasionally1 in nuggets4 ,it is a grey metal with a high specific gravity1 #ba4e when pure and about #ah4j in native specimens4 ,it is fusible only at the highest temperature1 and is not acted on by acids4 ,it is dissolved by warm aqua regia1 forming a solution of platinic chloride1 ,h#b,pt,cl#f4 ,this substance on evaporation remains as a brownish red deliquescent mass2 on drying at #cjj ,c4 it is converted into platinous chloride1 ,pt,cl#b1 and becomes insoluble1 and at a higher temperature it is converted into platinum4 ,all platinum compounds yield the metal in this way4 ,platinic chloride combines with other chlorides to form double salts1 of which the ammonic and potassic platino-chlorides are the most important4 ,platinum alone is not soluble in nitric acid2 but when alloyed with other metals which dissolve in this acid it too is dissolved2 so that in gold parting1 for example1 if platinum was present1 some1 or perhaps the whole of it would go into solution with the silver4 ,such alloys1 however1 when treated with hot sulphuric acid leave the platinum in the residue with the gold4 ,platinum is detected when in the metallic state by its physical characters and insolubility in acids4 ,in alloys it may be found by dissolving them in nitric acid or in aqua regia1 evaporating with hydrochloric acid1 and treating the filtrate with ammonic chloride and alcohol4 ,a heavy yellow precipitate marks its presence4 ,the assay of bullion1 or of an alloy containing platinum1 may be made as follows3 ,take #j4b gram of the alloy and an equal weight of fine silver1 cupel with sheet lead1 and weigh4 ,the loss in weight1 after deducting that of the silver added1 gives the weight of the base metals1 copper1 lead1 c4 ,flatten the button and part by boiling with strong sulphuric acid for several minutes4 ,when cold1 wash1 anneal1 and weigh4 ,the weight is that of the platinum and gold4 ,the silver may be got by difference4 ,re-cupel the metal thus got with #ab or #ae times its weight of silver1 flatten and part the gold with nitric acid in the usual way 7see under ,gold71 and the platinum will dissolve4 ,the gold may contain an alloy of osmium and iridium2 if so1 it should be weighed and treated with aqua regia4 ,the osmiridium will remain as an insoluble residue1 which can be separated and weighed4 ,its weight deducted from that previously ascertained will give the weight of the gold4 ,when the platinum only is required1 the alloy must be dissolved by prolonged treatment with aqua regia1 the solution evaporated to dryness1 and the residue extracted with water4 ,the solution thus obtained is treated with ammonic chloride in large excess and with some alcohol4 ,a sparingly soluble#dg yellow ammonic platinum chloride is thrown down1 mixed1 perhaps1 with the corresponding salts of other metals of the platinum group4 ,gold will be in solution4 ,the solution is allowed to stand for some time1 and then the precipitate is filtered off1 washed with alcohol1 dried1 and transferred 7wrapped in the filter paper7 to a weighed crucible4 ,it is ignited1 gently at first1 as there is danger of volatilising some of the platinum chloride1 and afterwards intensely4 ,with large quantities of platinum the ignition should be performed in an atmosphere of hydrogen4 ,cool and weigh as metallic platinum4 ,,iridium ,occurs in nature alloyed with osmium as osmiridium or iridosmine1 which is rather abundant in the auriferous beach sands of ,northern ,california 7,dana74 ,it occurs in bright metallic scales1 which do not alloy with lead1 and are insoluble in aqua regia4 ,iridium also occurs in most platinum ores1 and forms as much as two per cent4 of some commercial platinum4 ,in chemical properties it resembles platinum1 but the ammonic irido-chloride has a dark red colour1 and on ignition leaves metallic iridium1 which does not dissolve in aqua regia diluted with four or five times its volume of water and heated to a temperature of #dj or #ej ,c4 ,the other metals of the platinum group are ,palladium1 ,rhodium1 ,osmium1 and ,ruthenium4 ,they differ from gold1 platinum1 and iridium by the insolubility of their sulphides in a solution of sodium sulphide4 ,palladium is distinguished by the insolubility of its iodide2 and ,osmium by the volatility of its oxide on boiling with nitric acid4 ,,mercury4 ,mercury occurs native and1 occasionally1 alloyed with gold or silver in natural amalgams2 but its chief ore is the sulphide1 cinnabar4 ,it is comparatively rare1 being mined for only in a few districts4 ,it is chiefly used in the extraction of gold and silver from their ores 7amalgamation72 for silvering mirrors1 c4 ,mercury forms two series of salts1 mercurous and mercuric1 but for the purposes of the assayer the most important property is the ease with which it can be reduced to the metallic state from either of these4 ,mercury itself is soluble in nitric acid1 forming1 when the acid is hot and strong1 mercuric nitrate4 ,cinnabar is soluble only in aqua regia4 ,mercurous salts are generally insoluble1 and may be converted into mercuric salts by prolonged boiling with oxidising agents 7nitric acid or aqua regia74 ,the salts of mercury are volatile1 and1 if heated with a reducing agent or some body capable of fixing the acid1 metallic mercury is given off1 which may be condensed and collected4 ,mercury is separated from its solutions by zinc or copper1 or it may be thrown down by stannous chloride1 which1 when in excess1 gives a grey powder of metallic mercury1 or1 if dilute1 a white crystalline precipitate of mercurous chloride4 ,nitric acid solutions of mercury yield the metal on electrolysis2 and1 if the pole on which the metal comes down be made of gold or copper1 or is coated with these1 the separated mercury will adhere thereto4 ,it may then be washed and weighed4 ,the best tests for mercury next to obtaining globules of the metal are3 7#a7 a black precipitate with sulphuretted hydrogen from acid solutions1 which is insoluble in nitric acid2 and 7#b7 a white precipitate with stannous chloride4 ,,dry ,,method4 ,illustration3 ,,fig4 #dg4 ,weigh up #e grams1 if the ore is rich1 or #aj grams1 if a poorer mineral4 ,take a piece of combustion tube from #ah inches to #b feet long1 closed at one end1 and place in it some powdered magnesite1 so as to fill it to a depth of #b or #c inches1 and on that a layer of an equal quantity of powdered lime 7not slaked74 ,mix the weighed sample of ore in a mortar with #aj grams of finely powdered lime and transfer to the tube2 rinse out the mortar with a little more lime1 and add the rinsings4 ,cover with a layer of six or seven inches more lime and a loosely fitting plug of asbestos4 ,draw out the tube before the blowpipe to the shape shown in fig4 #dg1 avoiding the formation of a ridge or hollow at the bend which might collect the mercury4 ,tap gently1 holding the tube nearly horizontal1 so as to allow sufficient space above the mixture for the passage of the gases and vapours which are formed4 ,place the tube in a tube furnace1 and1 when in position1 place a small beaker of water so that it shall just close the opening of the tube4 ,the point of the tube should not more than touch the surface of the water4 ,bring the tube gradually to a red heat1 commencing by heating the lime just behind the asbestos plug1 and travelling slowly backwards4 ,when the portion of the tube containing the ore has been heated to redness for some time the heat is carried back to the end of the tube4 ,the magnesite readily gives up carbonic acid1 which fills the tube and sweeps the mercury vapour before it4 ,some of the mercury will have dropped into the beaker1 and some will remain as drops adhering to the upper part of the neck4 ,whilst the tube is still hot cut off the neck of the tube just in front of the asbestos plug 7a drop of water from the wash bottle will do this71 and wash the mercury from the neck into the beaker4 ,the mercury easily collects into a globule1 which must be transferred1 after decanting off the bulk of the water1 to a weighed ,berlin crucible4 ,the water is removed from the crucible1 first by the help of filter paper1 and then by exposing in a desiccator over sulphuric acid1 where it should be left until its weight remains constant4 ,it should not be warmed4 ,example3--#e grams of an ore treated in this way gave #d4bfe grams of mercury1 equivalent to #he4c per cent4 ,pure cinnabar contains #hf4b per cent4 ,,wet ,,methods4 ,solution4--,since solutions of chloride of mercury cannot be boiled without risk of loss1#dh nitric acid solutions should be used wherever possible4 ,no mercury-containing minerals are insoluble in acids2 but cinnabar requires aqua regia for solution4 ,in dissolving this mineral nitric acid should be used1 with just as much hydrochloric acid as will suffice to take it up4 ,to separate the mercury1 pass sulphuretted hydrogen in considerable excess through the somewhat dilute solution4 ,the precipitate should be black1 although it comes down at first very light coloured4 ,it is filtered1 washed1 and transferred back to the beaker1 and then digested with warm ammonic sulphide4 ,the residue1 filtered1 washed1 and boiled with dilute nitric acid1 will1 in the absence of much lead1 be pure mercuric sulphide4 ,if much lead is present1 a portion may be precipitated as sulphate1 but can be removed by washing with ammonic acetate4 ,to get the mercury into solution1 cover with nitric acid and a few drops of hydrochloric1 and warm till solution is effected4 ,dilute with water to #ej or #ajj c4c4 ,,gravimetric ,,determination4 ,this may be made by electrolysis4 ,the same apparatus as is used for the electrolytic copper assay may be employed1 but instead of a cylinder of platinum one cut out of sheet copper should be taken1 or the platinum one may be coated with an evenly deposited layer of copper4 ,fix the spiral and weighed copper cylinder in position1 couple up the battery1 and when this has been done put the nitric acid solution of the mercury in its place4#di ,the student had better refer to the description of the ,electrolytic ,copper ,assay4 ,the mercury comes down readily1 and the precipitation is complete in a few hours3 it is better to leave it overnight to make sure of complete reduction4 ,disconnect the apparatus1 and wash the cylinder1 first with cold water1 then with alcohol4 ,dry by placing in the water oven for two or three minutes4 ,cool and weigh3 the increase in weight gives the amount of metallic mercury4 ,it must be remembered that copper will precipitate mercury without the aid of the battery2 but in this case copper will go into solution with a consequent loss in the weight of the cylinder3 this must be avoided by connecting the battery before immersing the electrodes in the assay solution4 ,the electrolysed solution should be treated with an excess of ammonia1 when a blue coloration will indicate copper1 in which case the electrolysis is unsatisfactory4 ,with a little care this need not happen4 ,gold cylinders may preferably be used instead of copper2 but on platinum the deposit of mercury is grey and non-adherent1 so that it cannot be washed and weighed4 ,,volumetric ,,methods4 ,several methods have been devised3 for the details of these the student is referred to ,sutton's ,handbook of ,volumetric ,analysis4 ,,questions4 #a4 ,the specific gravity of mercury is #ac4eif4 ,what volume would #h grams occupy8 #b4 ,if #c4afi grams of cinnabar gave #b4gah grams of mercury1 what would be the percentage of the metal in the ore8 #c4 ,pour solution of mercuric chloride on mercury and explain what happens4 #d4 ,on dissolving #j4c gram of mercury in hot nitric acid1 and passing sulphuretted hydrogen in excess through the diluted solution1 what weight of precipitate will be got8 ,,footnotes3 #i ,lead may be granulated by heating it to a little above the melting point1 pouring it into a closed wooden box1 and rapidly agitating it as it solidifies4 #aj ,a rod of iron placed in the crucible with the assays will decompose any regulus that may be formed4 #aa ,with buttons poor in silver the lowering of the temperature at this stage is not a matter of importance4 #ab #ajj grams of the lead1 or of its oxide1 will contain from #a4e to #b4e milligrams4 #ac ,still the precautions of having cupels well made from bone ash in fine powder1 and of working the cupellation at as low a temperature as possible are very proper ones1 provided they are not carried to an absurd excess4 #ad ,be careful to remove the crucible before taking the bottle out of the basin of water2 if this is not done the chloride may be washed out of it4 #ae #a c4c4 of this dilute acid will precipitate #h or #i milligrams of silver4 #af ,chlorides interfere not merely by removing silver as insoluble silver chloride1 but also by making it difficult to get a good finishing point1 owing to the silver chloride removing the colour from the reddened solution4 #ag ,these results were obtained when using ammonium sulphocyanate1 and cannot be explained by the presence of such impurities as chlorides1 c4 #ah ,multiply the standard by #ajjj1 and dilute #ajj c4c4 of the standard solution to the resulting number of c4c4 ,thus1 with a solution of a standard 4#die1 dilute #ajj c4c4 to #die c4c41 using1 of course1 distilled water4 #ai ,h,na#b;,as,o#d #c;,ag,n,o#c ,ag#c;,as,o#d ,,hno#c #b,na,n,o#c4 #bj ,si,o#b ,na#b;,,co#c ,,co#b ,na#b,si,o#c ,si,o#b #b,na,h,c,o#c #b;,,co#b ,na#b,si,o#c ,h#b,o4 #ba ,pb,o ,si,o#b ,pb,si,o#c #bb ,here and elsewhere in this article when a flux is spoken of as soda the bicarbonate is meant4 #bc ,see the description of the process commencing on p4 #ih and the explanatory remarks on p4 #aaj4 #bd ,percy1 ,metallurgy of ,silver and ,gold1 p4 #beh4 #be ,limits of ,accuracy attained in ,gold-bullion ,assay1 ,trans4 ,chem4 ,soc41 #ahic4 #bf ,assaying and ,hall-marking at the ,chester ,assay ,office4 ,w4,f4 ,lowe4 ,journ4 ,soc4 ,chem4 ,industry1 ,sept4 #ahhi4 #bg ,fine or pure gold is #bd carat4 ,nine carat gold therefore contains #i parts of gold in #bd of the alloy2 eighteen carat gold contains #ah parts of gold in #bd2 and so on4 #bh ,the mouth of the flask must not have a rim around it4 #bi ,see ,assaying and ,hall-marking at the ,chester ,assay ,office1 by ,w4,f4 ,lowe4 ,journ4 ,soc4 ,chem4 ,industry1 ,sept4 #ahhi4 #cj ,percy1 ,metallurgy of ,silver and ,gold1 p4 #bfc4 #ca ,see also ,the ,assaying of ,gold ,bullion1 by ,c4 ,whitehead and ,t4 ,ulke4 ,eng4 and ,mining ,journal1 ,new ,york1 ,feb4 #ab1 #ahih4 #cb ,consult ,percy's ,metallurgy of ,silver and ,gold1 p4 #agb2 ,a4,c4 ,claudet1 ,trans4 ,inst4 ,mining and ,metallurgy1 vol4 vi4 p4 #bi2 ,g4,m4 ,roberts ,trans4 ,amer4 ,inst4 ,mining ,engineers1 ,buffalo ,meeting1 #ahih2 ,j4 and ,h4,s4 ,pattinson1 ,journ4 ,soc4 ,chem4 ,industry1 vol4 xi4 p4 #cba4 #cc ,heycock and ,neville1 ,journ4 ,chem4 ,soc41 #ahib1 p4 #ijg4 #cd ,g4,m4 ,roberts4 #ce ,a4,c4 ,claudet4 #cf ,the ,sampling of ,argentiferous and ,auriferous ,copper1 by ,a4,r4 ,ledoux4 ,journ4 ,canadian ,mining ,institute1 #ahii4 #cg ,na,c,n,o ,ba,cl#b ,na,h,o ,h#b,o ,,nh#c ,ba,c,o#c #b ,na,cl4 #ch ,h,cy ,na,h,o ,na,cy ,h#b,o4 #ci #b,,kcn ,ag,n,o#c ,k,ag7,,cn7#b ,,kno#c4 #dj ,if it be desired to make a solution so that #ajj c4c4 shall be equivalent to #a gram of sodium cyanide1 then #ah4jhe grams of silver nitrate should be taken for each litre4 #da ,ag,n,o#c ,k,ag,cy#b #b ,ag,cy ,,kno#c4 #db ,ag,n,o#c ,,ki ,ag,i ,,kno#c4 #dc ,see pp4 #cbb1 #cbc1 and #cbd for a description of the methods for measuring the quantity of acid or alkali4 #dd ,,kcn ,h,cl ,k,cl ,,hcn #de ,taking #af4j grams of ore1 each c4c4 #a lb4 of soda to the short ton4 ,the corresponding figures for the long ton are #ab4edd grams for lime and #ag4ib grams for soda4 #df ,in which case each 4#ja gram of metal found equals #a lb to the short ton of solution4 #dg #ajj c4c4 of water dissolves #j4ff gram of the salt2 it is almost insoluble in alcohol or in solutions of ammonic chloride4 #dh ,according to ,personne mercuric chloride is not volatilised from boiling solutions when alkaline chlorides are present4 #di ,the solution should contain about #j4be gram of mercury1 and a large excess of nitric acid must be avoided4 ,,chapter ,x4 ,,copper--,,lead--,,thallium--,,bismuth- -,,antimony4 ,,copper4 ,copper occurs native in large quantities1 especially in the ,lake ,superior district2 in this state it is generally pure4 ,more frequently it is found in combination4 ,the ores of copper may be classed as oxides and sulphides4 ,the most abundant oxidised ores are the carbonates1 malachite and chessylite2 the silicates1 as also the red and black oxides1 occur less abundantly4 ,all these yield their copper in solution on boiling with hydrochloric acid4 ,the sulphides are more abundant4 ,copper pyrites 7or yellow ore71 erubescite 7or purple ore71 and chalcocite 7or grey ore7 are the most important4 ,iron pyrites generally carries copper and is frequently associated with the above-mentioned minerals4 ,these are all attacked by nitric acid4 ,they nearly all contain a small quantity of organic matter1 and frequently considerable quantities of lead1 zinc1 silver1 gold1 arsenic1 bismuth1 c4 ,the copper ores are often concentrated on the mine before being sent into the market1 either by smelting1 when the product is a regulus or matte1 or by a wet method of extraction1 yielding cement copper or precipitate4 ,a regulus is a sulphide of copper and iron1 carrying from #cj to #dj per cent4 of copper4 ,a precipitate1 which is generally in the form of powder1 consists mainly of metallic copper4 ,either regulus or precipitate may be readily dissolved in nitric acid4 ,copper forms two classes of salts1 cuprous and cupric4 ,the former are pale coloured and of little importance to the assayer4 ,they are easily and completely converted into cupric by oxidising agents4 ,cupric compounds are generally green or blue1 and are soluble in ammonia1 forming deep blue solutions4 ,,dry ,,assay4 ,that1 for copper1 next after those for gold and silver1 holds a more important position than any other dry assay4 ,the sale of copper ores has been regulated almost solely in the past by assays made on the ,cornish method4 ,it is not pretended that this method gives the actual content of copper1 but it gives the purchaser an idea of the quantity and quality of the metal that can be got by smelting4 ,the process is itself one of smelting on a small scale4 ,as might be expected1 however1 the assay produce and the smelting produce are not the same1 there being a smaller loss of copper in the smelting4 ,the method has worked very well1 but when applied to the purchase of low class ores 7from which the whole of the copper is extracted by wet methods7 it is unsatisfactory4 ,the following table1 which embodies the results of several years' experience with copper assays1 shows the loss of copper on ores of varying produce4 ,the figures in the fourth column show how rapidly the proportion of copper lost increases as the percentage of copper in the ore falls below #cj per cent4 ,for material with more than #cj per cent4 the proportion lost is in inverse proportion to the copper present4 ,,loss ,,of ,,copper4 ---------------------------------------- ------------------ ,copper present4 ,dry ,assay4 ,margin4 ,loss on #ajj ,parts of ,copper4 ---------------------------------------- ------------------ ,per cent4 ,per cent4 ,per cent4 #ajj #ih #b4j #b4j #ie #ib-a_/b #b4e #b4f #ij #hg-c_/h #b4f #b4i #he #hb-c_/h #b4f #c4j #hj #gg-c_/h #b4f #c4b #ge #gb-c_/h #b4f #c4e #gj #fg-a_/b #b4e #c4f #fe #fb-a_/b #b4e #c4h #fj #eg-e_/h #b4d #d4j #ee #eb-c_/d #b4c #d4b #ej #dg-c_/d #b4b #d4d #de #dc #b4j #d4e #dj #ch-a_/h #a4h #d4f #ce #cc-a_/d #a4g #d4h #cj #bh-a_/b #a4ej #e4j #be #bc-a_/b #a4ej #f4j #bj #ah-a_/b #a4ef #g4h #ah #af-a_/b #a4ec #h4e #af #ad-a_/b #a4dh #i4c #ad #ab-e_/h #a4dj #aj4j #ab #aj-e_/h #a4cg #aa4d #aj #h-c_/d #a4bh #ab4h #h #f-g_/h #a4ad #ad4c #f #e #a4je #ag4e #e #d #a4jj #bj4j #d #c #a4jj #be4j #c4ge #b-c_/d #j4ig #bf4j #c4ej #b-i_/af #j4id #bg4j #c4be #b-e_/af #j4ia #bh4j #c4jj #b-a_/h #j4hg #bi4j #b4ge #a-ae_/af #j4hb #cj4j #b4ej #a-c_/d #j4gg #ca4j #b4be #a-a_/b #j4gb #cb4j #b4jj #a-e_/af #j4ff #cc4j ---------------------------------------- ------------------ ,the wet assay being known1 the dry assay can be calculated with the help of the above table by deducting the amount in the column headed margin opposite the corresponding percentage4 ,for example1 if the wet assay gives a produce of #ag4ab per cent41 there should be deducted #a4e2 the dry assay would then be #ae4fb1 or1 since the fractions are always expressed in eighths1 #ae-e_/h4 ,with impure ores1 containing from #be to #ej per cent4 of copper1 the differences may be perhaps #a_/d greater4 ,wet methods are gradually replacing the dry assay1 and it is probable that in the future they will supersede it2 for stock-taking1 and the various determinations required in smelting works and on mines1 they are generally adopted1 because they give the actual copper contents1 and since it is obvious that a knowledge of this is more valuable to the miner and smelter4 ,moreover1 the working of the dry method has been monopolised by a small ring of assayers1 with the double result of exciting outside jealousy and1 worse still1 of retarding the development and improvement of the process4 ,the principal stages of the dry assay are3 7#a7 the concentration of the copper in a regulus2 7#b7 the separation of the sulphur by calcining2 7#c7 the reduction of the copper by fusion2 and 7#d7 the refining of the metal obtained4 ,the whole of these operations are not necessary with all copper material4 ,ores are worked through all the stages2 with mattes1 the preliminary fusion for regulus is omitted2 precipitates are simply fused for coarse copper1 and refined2 and blister or bar coppers are refined1 or1 if very pure1 subjected merely to washing4 ,the quantity of ore generally taken is #djj grains1 and is known as a full trial2 but for rich material1 containing more than #ej per cent4 of copper1 a half trial1 or #bjj grains1 is used4 ,fusion for ,regulus4--,the ore 7either with or without a previous imperfect roasting to get rid of any excess of sulphur7 is mixed with borax1 glass1 lime1 and fluor spar2 and1 in some cases1 with nitre1 or iron pyrites1 according to the quality of the ore4 ,the mixture is placed in a large ,cornish crucible1 and heated as uniformly as possible in the wind furnace1 gradually raising the temperature so as to melt down the charge in from #ae to #bj minutes4 ,the crucible is removed and its contents poured into an iron mould4 ,when the slag is solid1 it is taken up with tweezers and quenched in water4 ,the regulus is easily detached from the slag4 ,it should be convex above and easily broken1 have a reddish brown colour1 and contain from #dj to #fj per cent4 of copper4 ,a regulus with more than this is too fine1 and with less too coarse4 ,a regulus which is too fine is round1 compact1 hard1 and of a dark bluish grey on the freshly broken surface4 ,a coarse regulus is flat and coarse grained1 and more nearly resembles sulphide of iron in fracture and colour4 ,if an assay yields a regulus too coarse1 a fresh determination is made with more nitre added1 or the roasting is carried further4 ,with low class ores a somewhat coarse regulus is an advantage4 ,if1 on the other hand1 the regulus is too fine1 less nitre or less roasting is the remedy4 ,with grey copper ores and the oxidised ores1 iron pyrites is added4 ,calcining the ,regulus4--,it is powdered in an iron mortar and transferred to a small ,cornish crucible1 or 7if the roasting is to be done in the muffle7 to a roasting dish or scorifier4 ,the calcining is carried out at a dull red heat1 which is gradually increased4 ,the charge requires constant stirring at first to prevent clotting1 but towards the end it becomes sandy and requires less attention4 ,if the temperature during calcination has been too low sulphates are formed1 which are again reduced to sulphides in the subsequent fusion4 ,to prevent this the roasted regulus is recalcined at a higher temperature1 after being rubbed up with a little anthracite4 ,the roasted substance must not smell of burning sulphur when hot4 ,it is practically a mixture of the oxides of copper and iron4 ,fusion for ,coarse ,copper4--,the calcined regulus is mixed with a flux consisting of borax and carbonate of soda1 with more or less tartar according to its weight4 ,some assayers use both tartar and nitre1 the former of course being in excess4 ,the charge is returned to the crucible in which it was calcined1 and is melted down at a high temperature1 and1 as soon as tranquil1 poured4 ,when solid it is quenched and the button of metal separated4 ,the slag is black and glassy4 ,the small quantity of copper which it retains is recovered by a subsequent cleaning1 together with the slags from the next operation4 ,the button of coarse copper obtained must be free from a coating of regulus4 ,it will vary somewhat in appearance according to the nature and quantity of the impurities4 ,refining the ,coarse ,copper4--,the same crucible is put back in the furnace1 deep down and under the crevice between the two bricks4 ,when it has attained the temperature of the furnace the coarse copper is dropped into it and the furnace closed4 ,the copper will melt almost at once with a dull surface1 which after a time clears1 showing an eye4 ,some refining flux is then shot in from the scoop 7fig4 #dh71 and1 when the assay is again fluid1 it is poured4 ,when cold the button of metal is separated4 ,illustration3 ,,fig4 #dh4 ,the button of fine copper is flat or pitted on its upper surface1 and is coated with a thin orange film2 it must have the appearance of good copper4 ,if it is covered with a red or purple film1 it is overdone or burnt4 ,if1 on the other hand1 it has a rough1 dull appearance1 it is not sufficiently refined4 ,assays that have been burnt are rejected4 ,those not sufficiently fine are treated as coarse copper1 and again put through the refining operation4 ,cleaning the ,slags4--,these are roughly powdered and re-fused with tartar1 etc41 as in the fusion for coarse copper4 ,the button of metal got is separated 7if big enough refined7 and weighed4 ,the details of the process are slightly varied by different assayers3 the following will be good practice for the student4 ,determination of ,copper in ,copper ,pyrites4--,powder1 dry1 and weigh up #bj grams of the ore4 ,mix with #bj grams each of powdered lime and fluor1 #ae grams each of powdered glass and borax1 and #e or #aj grams of nitre4 ,transfer to a large ,cornish crucible and fuse under a loose cover at a high temperature for from #ae to #bj minutes4 ,when fluid and tranquil pour into a mould4 ,when the slag has solidified1 but whilst still hot1 quench by dipping two or three times in cold water4 ,avoid leaving it in the water so long that it does not dry after removal4 ,when cold separate the button1 or perhaps buttons1 of regulus by crumbling the slag between the fingers4 ,see that the slag is free from regulus4 ,it should be light coloured when cold and very fluid when hot4 ,reject the slag4 ,powder the regulus in a mortar and transfer to a small crucible4 ,calcine1 with occasional stirring1 until no odour of sulphurous oxide can be detected4 ,shake back into the mortar1 rub up with about #a gram of powdered anthracite1 and re-calcine for #aj minutes longer4 ,mix the calcined regulus with #aj grams of tartar1 #bj grams of soda1 and #c grams of borax2 and replace in the crucible used for calcining4 ,fuse at a bright red heat for #aj or #ae minutes4 ,pour1 when tranquil4 ,as soon as solid1 quench in water1 separate the button of copper1 and save the slag4 ,to refine the copper a very hot fire is wanted1 and the fuel should not be too low down in the furnace4 ,place the crucible well down in the fire and in the middle of the furnace4 ,the same crucible is used1 or1 if a new one is taken1 it must be glazed with a little borax4 ,when the crucible is at a good red heat1 above the fusing point of copper1 drop the button of copper into it1 and close the furnace4 ,watch through the crevice1 and1 as soon as the button has melted and appears clear showing an eye1 shoot in #aj grams of refining flux1 close the furnace1 and1 in a few minutes1 pour2 then separate the button of copper4 ,add the slag to that from the coarse copper fusion1 and powder4 ,mix with #e grams of tartar1 #j4e gram of powdered charcoal1 and #b grams of soda4 ,fuse in the same crucible1 and1 when tranquil1 pour2 quench1 and pick out the prills of metal4 ,if the copper thus got from the slags is coarse looking and large in amount1 it must be refined2 but1 if small in quantity1 it may be taken as four-fifths copper4 ,the combined results multiplied by five give the percentage of copper4 ,the refining flux is made by mixing #c parts 7by measure7 of powdered nitre1 #b-ab of tartar1 and #a of salt4 ,put in a large crucible1 and stir with a red-hot iron until action has ceased4 ,this operation should be carried out in a well-ventilated spot4 ,for pure ores in which the copper is present1 either as metal or oxide1 and free from sulphur1 arsenic1 c41 the concentration of the copper in a regulus may be omitted1 and the metal obtained in a pure state by a single fusion4#ej ,it is necessary to get a fluid neutral slag with the addition of as small an amount of flux as possible4 ,the fusion should be made at a high temperature1 so as not to occupy more than from #bj to #be minutes4 ,thirty grams of ore is taken for a charge1 mixed with #bj grams of cream of tartar1 and #aj grams each of dried borax and soda4 ,if the gangue of the ore is basic1 carrying much oxide of iron or lime1 silica is added1 in quantity not exceeding #aj grams4 ,if1 on the other hand1 the gangue is mainly quartz1 oxide of iron up to #g grams must be added4 ,example4--,twenty grams of copper pyrites1 known to contain #bg4f per cent4 of copper1 gave by the method first described #e4bb grams of copper1 equalling #bf-a_/h per cent4 ,another sample of #bj grams of the same ore1 calcined1 fused with #dj grams of nitre1 and washed to ensure the removal of arsenic and sulphur1 and treated according to the second method1 gave a button weighing #e4bg grams1 equalling #bf-c_/h per cent4 ,the ore contained a considerable quantity of lead4 ,lead renders the assay more difficult1 since after calcination it remains as lead sulphate1 and in the fusion for coarse copper reappears as a regulus on the button4 ,the ,estimation of ,moisture4--,the ,cornish dry assayer very seldom makes a moisture determination4 ,he dries the samples by placing the papers containing them on the iron plate of the furnace4 ,it is well known that by buying the copper contents of pyrites by ,cornish assay1 burning off the sulphur1 and converting the copper into precipitate1 a large excess is obtained4 ,,notes ,,on ,,the ,,valuation ,,of ,,copper ,,ores4 ,closely bound up with the practice of dry copper assaying is that of valuing a parcel of copper ore4 ,the methods by which the valuation is made have been described by ,mr4 ,westmoreland1#ea and are briefly as follows3--,the produce of the parcel is settled by two assayers1 one acting for the buyer1 the other for the seller2 with the help1 in case of non-agreement1 of a third1 or referee1 whose decision is final4 ,the dry assayers who do this are in most cases helped1 and sometimes1 perhaps1 controlled1 by wet assays made for one or both of the parties in the transaction4 ,in the case of ticketing1 the parcels are purchased by the smelters by tender1 and the value of any particular parcel is calculated from the average price paid1 as follows3--,the standard1 or absolute value of each ton of fine copper in the ore1 is the price the smelters have paid for it1 plus the returning charges or cost of smelting the quantity of ore in which it is contained4 ,the value of any particular parcel of ore is that of the quantity of fine copper it contains1 calculated on this standard1 minus the returning charges4 ,the ton consists of #ba cwts41 and it is assumed that the settled produce is the actual yield of the ore4 ,if at a ticketing in ,cornwall #ihe tons of ore containing #fc4c tons of fine copper 7by dry assay7 brought #beia #abs41 the standard would be #hc #aes4 ,this is calculated as follows3--,the returning charge is fixed at #ees4 per ton of ore4 ,this on #ihe tons will amount to #bgjh #aes4 ,add this to the actual price paid1 and there is got #ecjj as the value of the fine copper present4 ,the weight of copper in these #ihe tons being #fc4c tons1 the standard is #ecjj_/fc4c1 or #hc #aes4 7nearly74 ,the value of a parcel of #aej tons of a #f per cent4 ore on the same standard would be arrived at as follows3--,the #aej tons at #f per cent4 would contain #i tons 7#aejf_/ajj7 of fine copper4 ,this1 at #hc #aes4 per ton1 would give #gec #aes4 ,from this must be deducted the returning charges on #aej tons of ore at #ees4 per ton1 or #dab #ajs4 ,this leaves #cda #es4 as the value of the parcel4 ,at ,swansea the returning charge is less than in ,cornwall1 and varies with the quality of the ore4 ,this appears equitable1 since in smelting there are some costs which are dependent simply on the number of tons treated1 and others which increase with the richness4 ,the returning charge then is made up of two parts1 one fixed at so much 7#abs4 #b;d47 per ton of ore treated1 and the other so much 7#cs4 #i;d47 per unit of metal in the ore4 ,in this way the returning charge on a ton of ore of #h-c_/d produce would be 7#abs4 #b;d477#h-c_/d7cs4 #i;d4771 or #b #es4 ,if1 for example1 ,chili bars1 containing #if per cent4 of copper1 bring #ej per ton1 the standard is #ga #is4 #d;d4 ,it is got at in this way4 ,the returning charge on a #if per cent4 ore is 7#abs4 #b;d477#if7cs4 #i;d4771 or #ah #abs4 #b;d4 ,this added to #ej gives #fh #abs4 #b;d41 and this multiplied by #ajj and divided by #if 7#ajj tons of the bars will contain #if tons of fine copper7 will give #ga #is4 #d;d4 ,the price of #ajj tons of pyrites1 containing #b-a_/d per cent4 of copper by dry assay1 would be got on this standard as follows3--,the parcel of ore would contain #b-a_/d tons of copper4 ,this multiplied by the standard gives #afj #afs4 #j;d4 ,from this must be deducted the returning charge1 which for #a ton of ore of this produce would be 7#abs4 #b;d47 7#b-a_/d7cs4 #i;d477 or #a #js4 #g;d41 and on the #ajj tons is #ajb #ahs4 #d;d4 ,this would leave #eg #ags4 #aj;d4 as the price of the parcel1 or #aas4 #g;d4 per ton4 ,this would be on the standard returning charge of #des4 7for #h-c_/d per cent4 ore72 if a smaller returning charge was agreed on1 say #chs41 the difference in this case1 #gs41 would be added to the price per ton4 ,,wet ,,methods4 ,the solubility of the ores of copper in acid has already been described1 but certain furnace products1 such as slags1 are best opened up by fusion with fusion mixture and a little nitre4 ,the method of dissolving varies with the nature of the ore4 ,with #e grams of pyrites1 a single evaporation with #bj c4c4 of nitric acid will give a residue completely soluble in #cj c4c4 of hydrochloric acid4 ,if the ore carries oxide of iron or similar bodies1 these are first dissolved up by boiling with #bj c4c4 of hydrochloric acid1 and the residue attacked by an addition of #e c4c4 of nitric4 ,when silicates decomposable by acid are present1 the solution is evaporated to dryness to render the silica insoluble2 the residue extracted with #cj c4c4 of hydrochloric acid1 and diluted with water to #aej c4c4 ,it is advisable to have the copper in solution as chloride4 ,to separate the copper1 heat the solution nearly to boiling 7best in a pint flask71 and pass a rapid current of sulphuretted hydrogen for four or five minutes until the precipitate settles readily and the liquid smells of the gas4 ,when iron is present it will be reduced to the ferrous state before the copper sulphide begins to separate4 ,the copper appears as a brown coloration or black precipitate according to the quantity present4 ,filter through a coarse filter1 wash with hot water containing sulphuretted hydrogen1 if necessary4 ,wash the precipitate back into the flask1 boil with #aj c4c4 of nitric acid1 add soda till alkaline1 and pass sulphuretted hydrogen again4 ,warm and filter1 wash and redissolve in nitric acid1 neutralise with ammonia1 add ammonic carbonate1 boil and filter4 ,the copper freed from impurities will be in the solution4 ,acidulate and reprecipitate with sulphuretted hydrogen4 ,when the nature of the impurities will allow it1 this process may be shortened to first filtering off the gangue1 then precipitating with sulphuretted hydrogen and washing the precipitate on the filter first with water and then with ammonium sulphide4 ,having separated the copper as sulphide1 its weight is determined as follows4 ,dry and transfer to a weighed porcelain crucible1 mix with a little pure sulphur1 and ignite at a red heat for #e or #aj minutes in a current of hydrogen4 ,allow to cool while the hydrogen is still passing4 ,weigh4 ,the subsulphide of copper thus obtained contains #gi4he per cent4 of copper2 it is a greyish-black crystalline mass1 which loses no weight on ignition if air is excluded4 ,copper may be separated from its solutions by means of sodium hyposulphite4 ,the solution is freed from hydrochloric and nitric acids by evaporation with sulphuric acid2 diluted to about a quarter of a litre2 heated nearly to boiling2 and treated with a hot solution of sodium hyposulphite 7added a little at a time7 until the precipitate settles and leaves the solution free from colour4 ,the solution contains suspended sulphur4 ,the precipitate is easily washed1 and under the proper conditions the separation is complete1 but the separation with sulphuretted hydrogen is more satisfactory1 since the conditions as to acidity1 c41 need not be so exact4 ,zinc or iron is sometimes used for separating copper from its solutions1 but they are not to be recommended4 ,,electrolytic ,,assay4 ,the separation of copper by means of a current of electricity is largely made use of1 and forms the basis of the most satisfactory method for the determination of this metal4 ,if the wire closing an electric circuit be broken1 and the two ends immersed in a beaker of acidulated water or solution of any salt1 the electricity will pass through the liquid1 bringing about some remarkable changes4 ,hydrogen and the metals will be liberated around that part of the wire connected with the zinc end of the battery1 and oxygen1 chlorine1 and the acid radicals will be set free around the other4 ,different metals are deposited in this way with varying degrees of ease1 and whether or not any particular metal will be deposited depends--7#a7 on the conditions of the solution as regards acid and other substances present1 and 7#b7 on the intensity of the current of electricity used4 ,for analytical purposes the metal should be deposited not only free from the other metals present1 but also as a firm coherent film1 which may afterwards be manipulated without fear of loss4 ,this is1 in the case of copper and many other metals1 effected by a simple control of the conditions4 ,it is necessary that the electrodes1 or wires which bring the electricity into the solution1 should be made of a material to which the deposited metal will adhere1 and which will not be attacked by substances originally present or set free in the solution4 ,they are generally made of platinum4 ,there are various arrangements of apparatus used for this purpose1 but the following plan and method of working is simple and effective1 and has been in daily use with very satisfactory results for the last five or six years4 ,the battery used is made up of two ,daniell cells1 coupled up for intensity as shown in fig4 #di--that is1 with the copper of one connected with the zinc of the other4 ,for eight or ten assays daily the quart size should be used1 but for four or five two pint cells will be sufficient4 ,illustration3 ,,fig4 #di4 ,the outer pot of each cell is made of sheet copper1 and must be clean and free from solder on the inside4 ,it is provided near the top with a perforated copper shelf in the shape of a ring1 into which the inner or porous cell loosely fits4 ,it is charged with a saturated solution of copper sulphate1 and crystals of this salt must be added1 and always kept in excess4 ,when the battery is at work copper is being deposited on the inner surface of this pot4 ,the inner or porous pot contains the zinc rod1 and is charged with a dilute acid1 made by diluting one volume of sulphuric acid up to ten with water4 ,the object of the porous pot is to prevent the mixing of the acid and copper sulphate solutions1 without interrupting the flow of electricity4 ,the copper sulphate solution will last for months1 but the acid must be emptied out and recharged daily4 ,the zinc rods must be well amalgamated by rubbing with mercury under dilute acid until they show a uniformly bright surface4 ,they should not produce a brisk effervescence when placed in the acid in the porous pot before coupling up4 ,the battery when working is apt to become dirty from the creeping of the copper and zinc sulphate solution4 ,it must be kept away from the working bench1 and is best kept in a box on the floor4 ,illustration3 ,,fig4 #ej4 ,the connection of the battery with1 and the fixing of1 the electrodes may be made by any suitable arrangement1 but the following is a very convenient plan4 ,the wire from the zinc is connected by means of a binding screw with a piece of stout copper wire1 which1 at a distance sufficiently great to allow of easy coupling with the battery1 is led along the back of a piece of hard wood4 ,this is fixed horizontally about one foot above the working bench4 ,the general arrangement is shown in fig4 #ej1 in which1 however1 for the sake of economy of space1 the battery is placed on the working bench instead of on the floor4 ,the piece of wood is one inch square and three or four feet long4 ,it is perforated from front to back at distances of six inches by a number of small holes1 in which are inserted screws like that shown in fig4 #ea4 ,these are known as terminals1 and may be obtained of any electrician4 ,the head of each screw is soldered to the wire mentioned above as running along the back and as being connected with the zinc end of the battery4 ,these terminals serve to fix the electrodes on which the copper is to be deposited4 ,the wire from the copper end of the battery is similarly connected by a connecting screw 7fig4 #eb7 with another wire 7,h in fig4 #ec71 which runs along the top of the rod and has soldered to it1 at distances of six inches1 cylindrical spirals of copper wire4 ,these should project from the rod at points about half-way between the terminals already described4 ,they may be made by wrapping copper wire around a black-lead pencil for a length of about three inches4 ,illustration3 ,,fig4 #ea4 ,illustration3 ,,fig4 #eb4 ,illustration3 ,,fig4 #ec4 ,the rod is perforated from top to bottom with a series of small holes1 one in advance of each terminal but as near it as possible4 ,into these short pieces of glass tube are inserted to ensure insulation4 ,these receive the other electrodes1 which are connected with the wire leading to the copper end of the battery1 through the spirals1 with the help of a binding screw4 ,the figure will make this clear4 7,fig4 #ec47 ,illustration3 ,,fig4 #ed ,the electrodes consist of a platinum spiral and cylinder4 ,the spiral should have the shape shown in ,a1 fig4 #ed4 ,when in work it is passed through one of the holes fitted with glass tubes and connected with the copper end of the battery4 ,the thickness of the wire of which it is made is unimportant1 provided it is stout enough to keep its form and does not easily bend4 ,the spiral will weigh about #h grams4 ,the cylinder 7,c1 fig4 #ed7 will weigh about #ab grams4 ,it should have the shape shown in the figure4 ,in working it is clamped to one of the terminals1 and on it the copper is deposited4 ,a cylinder will serve for the deposition of from #a to #a4e gram of copper4 ,it is made by rivetting a square piece of foil on to a stiff piece of wire1 and then bending into shape over a glass tube or piece of rounded wood4 ,each cylinder carries a distinctive number1 and is marked by impressing ,roman numerals on the foil with the blade of a knife4 ,the weight of each is carefully taken and recorded4 ,they lose slightly in weight when in use1 but the loss is uniform1 and averages half a milligram per month when in daily use4 ,the cylinders are cleaned from deposited copper by dissolving off with nitric acid and washing with water2 and from grease by igniting4 ,the beakers1 to contain the solution of copper to be electrolysed1 are ordinary tall beakers of about #bjj c4c4 capacity1 and are marked off at #ajj c4c4 and #aej c4c4 ,they are supported on movable stands1 consisting of wooden blocks about six inches high and three inches across4 ,the bar of wood which carries the connecting wires and electrodes is permanently fixed over the working bench1 at such a height that1 with the beakers resting on these blocks1 the electrodes shall be in position for working4 ,to fix the electrodes to the rod1 remove the stand and beaker and pass the long limb of the spiral up through one of the glass tubes4 ,connect it with the free end of the copper spiral by means of a connecting screw 7fig4 #eb71 and then draw out and bend the copper spiral so that the platinum one may hang freely4 ,screw the wire of the cylinder to the terminal1 and1 if necessary1 bend it so that the cylinder itself may be brought to encircle the rod of the spiral in the manner shown in fig4 #ec4 ,the general method of working is as follows3--,the quantity of ore to be taken for an assay varies with the richness of the ore1 as is shown in the following table3-- ,percentage of ,copper ,quantity of ,ore in the ,ore4 to be taken4 #a to #e #e grams #e to #aj #c #aj to #cj #b #cj to #ej #a4e #ej to #ajj #a ,the weighed quantity of ore is dissolved by evaporating with nitric acid and taking up with hydrochloric1 as already described4 ,any coloured residue which may be left is generally organic matter3 it is filtered off1 calcined1 and any copper it contains is estimated colorimetrically4 ,nearly always1 however1 the residue is white and sandy4 ,the copper is separated from the solution as sulphide by means of a rapid current of sulphuretted hydrogen4 ,the liquid is decanted off through a filter1 the precipitate washed once with hot water and then rinsed back into the flask 7the filter paper being opened out7 with a jet of water from a wash bottle4 ,fifteen c4c4 of nitric acid are added to the contents of the flask1 which are then briskly boiled until the bulk is reduced to less than #aj c4c4 ,the boiling down is carried out in a cupboard free from cold draughts1 so as to prevent the condensation of acid and steam in the neck of the flask4 ,twenty c4c4 of water are next added1 and the solution is warmed1 and filtered into one of the beakers for electrolysis4 ,the filtrate and washings are diluted with water to the #ajj c4c4 mark1 and the solution is then ready for the battery4 ,it must not contain more than #aj per cent4 by volume of nitric acid4 ,the number and weight of the platinum cylinder having been recorded1 both electrodes are fixed in position and the wooden block removed from under them4 ,the beaker containing the copper solution is then brought up into its place with one hand1 and the block replaced with the other so as to support it4 ,all the assays having been got into position1 the connecting wires are joined to the battery4 ,if everything is right bubbles of oxygen at once stream off from the spiral1 and the cylinder becomes tarnished by a deposit of copper4 ,if the oxygen comes off but no copper is deposited1 it is because the assay solution contains too much nitric acid4 ,if no action whatever takes place1 it is because the current is not passing4 ,in this case examine the connections to see that they are clean and secure1 and the connecting wires to see that they are not touching each other4 ,the action is allowed to go on for sixteen or seventeen hours1 so that it is best to let the current act overnight4 ,in the morning the solutions will appear colourless1 and a slow stream of oxygen will still be coming off from the spiral4 ,a wash-bottle with cold distilled water and two beakers1 one with distilled water and the other with alcohol1 are got ready4 ,the block is then removed1 the spiral loosened and lowered with the beaker4 ,the cylinder is next detached and washed with a stream of water from the wash-bottle1 the washings being added to the original solution4 ,the current from the battery is not stopped until all the cylinders are washed4 ,after being dipped in the beaker of water and once or twice in that with the alcohol1 it is dried in the water-oven for about three minutes1 and then weighed4 ,the increase in weight is due to deposited copper4 ,this should be salmon-red in colour1 satin-like or crystalline in appearance1 and in an even coherent deposit1 not removed by rubbing4 ,it is permanent in air when dry1 but sulphuretted hydrogen quickly tarnishes it1 producing coloured films4 ,with ores containing even very small proportions of bismuth1 the deposited copper has a dark grey colour1 and when much of this metal is present the copper is coated with a grey shaggy deposit4 ,it still remains to determine any copper left undeposited in the solution4 ,this does not generally exceed four or five milligrams1 and is estimated colorimetrically4 ,thirty c4c4 of dilute ammonia 7one of strong ammonia mixed with one of water7 are added to the electrolysed solution1 which is then diluted up to the #aej c4c4 mark with water4 ,it is mixed1 using the spiral as stirrer1 and1 after standing a few minutes to allow the precipitate to settle1 #ajj c4c4 of it are filtered off through a dry filter for the colorimetric determination4 ,since only two-thirds of the solution are taken for this1 the quantity of copper found must be increased by one-half to get the quantity actually present4 ,illustration3 ,,fig4 #ee4 ,the colorimetric determination may be made in the manner described under that head1 but where a number of assays are being carried out it is more convenient to have a series of standard phials containing known amounts of copper in ammoniacal solution4 ,by comparing the measured volume of the assay solution with these1 the amount of copper present is determined at a glance4 ,these standard bottles1 however1 can only be economically used where a large number of assays are being made daily4 ,a convenient plan is to get a quantity of white glass four-ounce phials1 like that in fig4 #ee1 and to label them so that they shall contain #ajj c4c4 when filled up to the bottom of the labels4 ,the labels should be rendered permanent by coating with wax1 and be marked with numbers indicating the milligrams of copper present4 ,the bottles are stopped with new clean corks1 and contain1 in addition to the specified quantity of copper1 #f c4c4 of nitric acid and #aj c4c4 of strong ammonia1 with sufficient water to make up the bulk to #ajj c4c4 ,the copper is best added by running in the requisite amount of a standard solution of copper1 each c4c4 of which contains #j4jja gram of the metal4 ,the standard bottles should be refilled once every three or four months1 since their colorimetric value becomes slowly less on keeping4 ,the following determinations of a set which had been in use for three months will illustrate this4 ,the figures indicate milligrams of copper in #ajj c4c43 the first row gives the nominal and the second row the actual colorimetric value of the standards4 ,the difference between the two shows the deterioration4 #a #b #c #d #f #h #aj #ab #ad #a #b #c #c4g #e4e #g4e #i #aa #ac ,the amount of copper in the assay is got by increasing that found colorimetrically by one-half and adding to that found on the platinum cylinder4 ,the percentage is calculated in the usual way4 ,the following examples will illustrate this1 as well as the method of recording the work in the laboratory book3-- ---------------------------------------- ----- ,cylinder ,i4 ,cu #i4edaj ,cylinder ,i4 #i4eagj ------ #j4jbdj ,by colour #ajj c4c4 #j4jjae #j4jjjg #j4jjbb ------ ------ #j4jjbb #j4jbfb ,,ix4 ,sample4 ,took #e grams4 ,copper #j4eb ---------------------------------------- ----- ,cylinder ,,vi4 ,cu #aj4egje ,cylinder ,,vi4 #aj4jdcg ------- #j4ebfh ,by colour1 #ajj c4c4 #j4jjgj #j4jjce #j4jaje ------ ------ #j4jaje #j4ecgc ,matte1 ,no4 #ajgj4 ,took #a4e gram4 ,copper #ce4hb ---------------------------------------- ----- ,cylinder ,,xiii4 ,cu #ab4jceb ,cylinder ,,xiii4 #aa4jdje ------- #j4iidg ,by colour #ajj c4c4 #j4jjje #j4jjjb #j4jjjg ------ ------ #j4jjjg #j4iied ,x4 ,sample1 ,cake copper4 ,took #a4jjec gram4 ,copper #ii4jj ---------------------------------------- ----- ,in the electrolytic assay of metals1 alloys1 precipitates1 and other bodies rich in copper1 the preliminary separation of the copper by sulphuretted hydrogen is unnecessary4 ,it is sufficient to dissolve the weighed sample in #aj c4c4 of nitric acid1 boil off nitrous fumes1 dilute to #ajj c4c4 with water1 and then electrolyse4 ,general ,considerations4--,in the preliminary work with the copper sulphide there is a small loss owing to its imperfect removal in washing the filter paper1 and another small loss in dissolving in nitric acid owing to the retention of particles in the fused globules of sulphur4 ,to determine its amount the filter-papers and sulphur were collected from forty assays1 and the copper in them determined4 ,the average amount of copper in each assay was #j4age gram2 that left on the filter paper was #j4jjjfg gram2 and that retained by the sulphur #j4jjjjc gram2 thus showing an average loss from both sources of #j4jjjgj gram4 ,the determinations from another lot of forty-two similar assays gave on an average ,copper left on filter paper #j4jjjgj gram ,copper retained by sulphur4 #j4jjjjd ,the loss from these sources is trifling1 and need only be considered when great accuracy is required4 ,the deposition of the copper under the conditions given is satisfactory1 but1 as already stated1 if the solution contain more than #aj per cent4 of nitric acid it is not thrown down at all2 or if a stronger current is used1 say that from three ,bunsen cells1 it will be precipitated in an arborescent brittle form1 ill adapted for weighing4 ,it may be noted here that increasing the size of the cells does not necessarily increase the intensity of the current4 ,in two determinations on pure electrotype copper the following results were obtained3-- ,copper ,taken4 ,copper ,found4 #j4hihh gram #j4hihe gram #j4hcje #j4hcjc ,the presence of salts of ammonia1 c41 somewhat retards the deposition1 but has no other ill effect4 ,the organic matter generally present in copper ores interferes more especially in the colorimetric determination of the residual copper4 ,it can be detected on dissolving the ore as a light black residue insoluble in nitric acid4 ,it is filtered off at once1 or1 if only present in small amount1 it is carried on in the ordinary process of the assay and separated in the last filtration before electrolysis4 ,the following experiments were made to test the effect of the presence of salts of foreign metals in the solution during the precipitation of copper by electrolysis3-- ---------------------------------------- ----------------------------- ,copper ,taken4 ,other ,metal ,added4 ,copper ,found4 ---------------------------------------- ----------------------------- #j4ajjj gram #j4ajjj gram of silver #j4ahjj #j4ajej #j4ajjj #j4bjjj #j4ajcj #j4ajjj mercury #j4bjaj #j4ajcg #j4ajjj #j4bjae #j4ajbj #j4ajjj lead #j4ajbj #j4ajcj #j4ajjj #j4ajbh #j4ajaj #j4ajjj arsenic #j4ajaj #j4ajjg #j4ajjj #j4ajbb #j4ajcj #j4ajjj antimony #j4ajej #j4ajcd #j4ajjj #j4ajeg #j4jiij #j4abjj tin #j4jiij #j4ajad #j4ajjj #j4ajae #j4ajjj #j4ajjj bismuth #j4affb #j4ajdj #j4ajjj cadmium #j4ajeb #j4ajji #j4acjj zinc #j4ajag #j4ajad #j4ajjj nickel #j4ajjg #j4ajgi #j4abjj iron #j4ajhi #j4ajed #j4ajjj chromium 7,cr#b,o#c7 #j4ajce #j4ajcd #j4ajjj 7,k#b;,cr,o#d7 #j4ajaj #j4ajge #j4ajjj aluminium #j4ajgh #j4ajaj #j4ajjj manganese #j4jihj ---------------------------------------- ----------------------------- ,it will be seen from these that mercury1 silver1 and bismuth are the only metals which are precipitable#eb along with the copper under the conditions of the assay4 ,mercury1 which if present would interfere1 is separated because of the insolubility of its sulphide in nitric acid4 ,bismuth is precipitated only after the main portion of the copper is thrown down4 ,it renders the copper obviously unsuitable for weighing4 ,it darkens1 or forms a greyish coating on1 the copper2 and this darkening is a delicate test for bismuth4 ,in assaying ores containing about three and a half per cent4 of copper1 and known to contain bismuth in quantities scarcely detectable in ordinary analysis1 the metal deposited was distinctly greyish in colour1 and would not be mistaken for pure copper4 ,ten grams of this impure copper were collected and analysed1 with the following results3-- ,copper #ii4df per cent4 ,bismuth #jj4cj ,iron #jj4ad ,arsenic #jj4aj ------ #ajj4jj ,the quantity of copper got in each assay was #j4age gram1 and consequently the bismuth averaged #j4jjjec gram4 ,to separate the bismuth in such a case the deposit is dissolved off by warming it in the original solution4 ,the bismuth is precipitated by the addition of ammonic carbonate1 and the solution1 after filtering and acidifying with nitric acid1 is re-electrolysed4 ,determination of ,copper in ,commercial ,copper4--,take from #a to #a4e gram1 weigh carefully1 and transfer to a beaker2 add #bj c4c4 of water and #aj c4c4 of nitric acid2 cover with a clock glass1 and allow to dissolve with moderate action2 boil off nitrous fumes1 dilute to #ajj c4c41 and electrolyse4 ,the cylinder must be carefully weighed1 and the electrolysis allowed to proceed for #bd hours4 ,the weight found will be that of the copper and silver4 ,the silver in it must be determined#ec and deducted4 ,determination of ,copper in ,brass1 ,german ,silver1 or ,bronze4--,treat in the same manner as commercial copper4 ,if nickel is present1 the few milligrams of copper remaining in the electrolysed solution should be separated with sulphuretted hydrogen1 the precipitated sulphide dissolved in nitric acid1 and determined colorimetrically4 ,,volumetric ,,processes4 ,there are two of these in use1 one based on the decolorising effect of potassic cyanide upon an ammoniacal copper solution1 and the other upon the measurement of the quantity of iodine liberated from potassic iodide by the copper salt4 ,the cyanide process is the more generally used1 and when carefully worked1 on certain understood and orthodox conditions1 yields good results2 but probably there is no method of assaying where a slight deviation from these conditions so surely leads to error4 ,an operator has no difficulty in getting concordant results with duplicate assays2 yet different assayers1 working1 without bias1 on the same material1 get results uniformly higher or lower2 a difference evidently due to variations in the mode of working4 ,where a large number of results are wanted quickly it is a very convenient method4 ,the iodide process is very satisfactory when worked under the proper conditions4 ,,cyanide ,,method4 ,the process is based upon the facts--7#a7 that when ammonia is added in excess to a solution containing cupric salts1 ammoniacal copper compounds are formed which give to the solution a deep blue colour2 and 7#b7 that when potassic cyanide is added in sufficient quantity to such a solution the colour is removed1 double cyanides of copper and potassium or ammonium being formed4#ed ,in the explanation generally given the formation of cuprous cyanide is supposed#ee2 but in practice it is found that one part of copper requires rather more than four parts of cyanide1 which agrees with the former1 rather than the latter1 explanation4 ,reliance on the accuracy of the process cannot rest upon the supposition that the cyanide required for decoloration is proportional to the copper present1 for varying quantities of ammonia salts1 ammonia and water1 and differences of temperature have an important effect4 ,the results are concordant and exact only when the cyanide is standardised under the same conditions as it is used4 ,it is best to have the assay solution and that used for standardising as nearly as possible alike1 and to titrate the two solutions side by side4 ,this demands an approximate knowledge of the quantity of copper contained in the ore and a separation of the bulk of the impurities4 ,for the titration there is required a standard solution of potassium cyanide made by dissolving #db grams of the salt1 known to dealers as ,potassium ,cyanide 7,gold71 in water and diluting to one litre3 #ajj c4c4 of this will be about equivalent to one gram of copper4 ,for poor ores the solution may conveniently be made half this strength4 ,the solution of the ore and the separation of the copper as sulphide are effected in the same ways as have been already described for electrolysis4 ,similarly1 too1 the sulphide is attacked with #ae c4c4 of nitric acid and the assay boiled down to #aj c4c4 ,add #bj c4c4 of water and warm1 filter into a pint flask1 wash well with water1 and dilute to about #aej c4c42 add #cj c4c4 of dilute ammonia1 and cool4 ,prepare a standard by dissolving a quantity of electrotype copper 7judged to be about the same as that contained in the assay7 in #bj c4c4 of water and #aj c4c4 of nitric acid1 boil off the nitrous fumes1 and dilute to #aej c4c43 add #cj c4c4 of dilute ammonia and cool4 ,fill a burette with the standard cyanide solution4 ,the burette with syphon arrangement1 figured on page #eb1 is used4 ,a number of titrations can be carried on at the same time provided the quantity of copper present in each is about the same4 ,this is regulated in weighing up the ore4 ,the flasks must of course be marked1 and should be arranged in series on a bench in front of a good light and at such a height that the liquid can be looked through without stooping4 ,supposing about #ej c4c4 of cyanide will be required1 #cj c4c4 should be run into each1 and each addition be recorded as soon as made2 then run #ae c4c4 into each4 ,the solutions will now probably show marked differences of tint3 add #a c4c4 of cyanide to the lighter ones and more to the darker1 so as to bring the colours to about the same depth of tint4 ,they should all be of nearly equal tint just before finishing4 ,at the end add half a c4c4 at a time until the colours are completely discharged4 ,a piece of damp filter paper held between the light and the flask assists in judging the colour when nearly finished4 ,overdone assays show a straw yellow colour which deepens on standing4 ,the following will illustrate the notes recorded of five such assays and one standard3-- 7#a7 #cj c4c4 #ae c4c4 #e c4c4 #b c4c4 #a c4c4 #a_/b c4c4 -- c4c4 #ec-a_/b c4c4 7#b7 #cj #ae #a #a #a #a_/b -- #dh-a_/b 7#c7 #cj #ae #c #a #a #a_/b -- #ej-a_/b 7#d7 #cj #ae #e #b #a #a_/b #a_/b #ed 7#e7 #cj #ae #b #a #a #a_/b -- #di-a_/b 7#f7 #cj #ae #b #a #a #a_/b #a_/b #ej standard ,three grams of ore were taken1 and the standard contained #j4dhj gram of copper4 ,in this series the difference of half a c4c4 means about #j4ae per cent4 on the ore2 with a little practice it is easy to estimate whether the whole or half of the last addition should be counted4 ,to get satisfactory results1 the manner of finishing once adopted must be adhered to4 ,the following experiments show the effect of variation in the conditions of the assay3--,use a solution of copper nitrate1 made by dissolving #aj grams of copper in #ej c4c4 of water and #ce c4c4 of nitric acid1 and diluting to a litre4 #ajj c4c4 #a gram of copper4 ,effect of ,varying ,temperature4--,in these experiments #bj c4c4 of copper nitrate were used1 with #aj c4c4 of nitric acid1 #cj c4c4 of dilute ammonia1 and water to #bjj c4c4 ,the results were-- ,temperature #ae #cj #gj #ajj ,cyanide required #ba4e c4c4 #bj4h c4c4 #ai4g c4c4 #ah4h c4c4 ,the temperature is that of the solution before titrating4 ,these show the importance of always cooling before titrating1 and of titrating the assay and standard at the same temperature4 ,effect of ,varying ,bulk4--,the quantities of copper1 acid1 and ammonia were the same as in the last-mentioned experiments4 ,the results were3-- ,bulk #ajj4j c4c4 #bjj4j c4c4 #cjj4j c4c4 #djj4j c4c4 ,cyanide required #bc4c #ba4g #ba4d #ba4d ,these show that large variations in bulk must be avoided4 ,effect of ,varying ,ammonia4--,the quantities of copper and acid were the same as in the series of experiments last noticed4 ,the bulk was #bjj c4c4 ,the results were3-- ,dilute ammonia #bj4j c4c4 #cj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,cyanide required #bj4i #ba4g #bb4c #bd4f ,effect of ,varying ,acid4--,the quantities of copper and water were the same as in the last-noticed set of experiments3 #cj c4c4 of dilute ammonia were used4 ,nitric acid #e4j c4c4 #aj4j c4c4 #ae4j c4c4 ,cyanide required #ba4f #ba4g #ba4e ,on adding nitric acid to the solution it combines with a portion of the ammonia to form ammonic nitrate2 it will be seen from the last series of experiments that the lessening of the amount of free ammonia will decrease the quantity of cyanide required2 but1 on the other hand1 the ammonic nitrate which is at the same time formed will increase the amount required2 under the conditions of the assay these two effects neutralise each other1 and such differences in the quantity of acid as are likely to occur are unimportant4 ,effect of ,varying ,ammonic ,salts4--,the quantities of copper1 water1 and ammonia were the same as in the last mentioned set of experiments1 but no nitric acid was used4 ,ammonic nitrate added #a gram #e grams #aj grams #bj grams ,cyanide required #ba4b c4c4 #bb4a c4c4 #bc4a c4c4 #bd4a c4c4 ,these show that combined ammonia seriously affects the titration1 and that the principle sometimes recommended of neutralising the acid with ammonia1 and then adding a constant quantity of ammonia1 is not a good one1 because there is then an interference both by the ammonia and by the variable quantity of ammonic salts4 ,the same quantity of combined ammonia has the same effect1 whether it is present as sulphate1 nitrate1 chloride1 or acetate1 as the following experiments show4 ,four lots of #bj c4c4 of copper nitrate were taken1 and #bj c4c4 of dilute ammonia added to each4 ,these were carefully neutralised with the respective acids1 rendered alkaline with #cj c4c4 more of ammonia1 cooled1 diluted to bulk1 and titrated4 ,the results were3-- ,with sulphuric acid #bb4e c4c4 of cyanide nitric acid #bb4f hydrochloric acid #bb4f acetic acid #bb4e ,effect of ,foreign ,salts4--,sulphates1 nitrates and chlorides of sodium or potassium have no action1 whilst the hydrates1 carbonates1 bicarbonates1 sulphites1 and nitrites have an important effect4 ,the interference of ammonic salts has already been shown4 ,salts of silver1 zinc1 and nickel react with cyanide just as copper does1 and consequently interfere4 ,ferrous salts are sure to be absent1 and ferric salts yield ferric hydrate with the ammonia1 which is not acted on by the cyanide1 but1 owing to its bulkiness1 it settles slowly2 this lengthens the time required for titration1 and so modifies the manner of working4 ,an assay should not be worked with ferric hydrate present1 unless the standard contains about the same amount of it4 ,on mines it is often inconvenient to separate the copper by means of sulphuretted hydrogen2 hence it is customary to titrate without previous separation4 ,in this case1 instead of standardising the cyanide with electrotype copper1 a standard ore should be used4 ,this should be an ore 7of the same kind as those being assayed7 in which the copper has been carefully determined4 ,effect of ,varying ,copper4--,in these experiments #aj c4c4 of nitric acid1 #cj c4c4 of ammonia1 and water to #bjj c4c4 were used4 ,copper nitrate present #a4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,cyanide required #j4g #aa4b #ba4g #ed4e #ajh4a ,these results show that under the conditions laid down the various causes of disturbance nearly neutralise one another1 and the results within a fair range are practically proportional4 ,determination of ,copper in ,copper ,pyrites4--,weigh up #b grams of the dried and powdered ore1 and place in an evaporating dish about four inches in diameter4 ,cover with #bj c4c4 of nitric acid and put on a hot plate4 ,evaporate to dryness without further handling4 ,allow to cool and take up with #cj c4c4 of hydrochloric acid1 boil1 dilute1 and transfer to a pint flask1 filtering if necessary4 ,make up the bulk with the washings to about #aej c4c4 ,precipitate with sulphuretted hydrogen1 filter1 and wash back the precipitate into the flask4 ,add #ae c4c4 of nitric acid1 and boil down rapidly to #aj c4c4 ,dilute1 add #cj c4c4 of dilute ammonia1 make up to #aej c4c41 and cool4 ,for the standard1 weigh up #j4e gram of copper1 more or less1 according to the quantity judged to be present in the assay4 ,dissolve in #bj c4c4 of dilute nitric acid1 boil off nitrous fumes1 add #cj c4c4 of dilute ammonia1 make up to the same bulk as that of the assay1 and cool4 ,titrate the two solutions side by side and as nearly as possible in the same manner4 ,since the assay solution is often turbid from the presence of small quantities of lead and of iron from incomplete washing1 and since this slight precipitate is very slow in settling1 the standard can hardly be compared strictly with the assay4 ,this can be counteracted by precipitating in both solutions a mixture of ferric and aluminic hydrates1 which settles readily and leaves the supernatant liquor clear4 ,to effect this1 boil the nitric acid solutions with #cj c4c4 of a solution containing #ae grams each of alum and ferrous sulphate to the litre4 ,in an actual determination #b grams of the ore were taken and compared with #j4e gram of copper4 ,the assay required #eg4g c4c4 of cyanide and the standard #eb4e c4c4 #eb4e 3 #j4e 33 #eg4g 3 #j4edie ,this on #b grams of ore #bg4dg per cent42 the same sample by electrolysis gave #bg4fj per cent4 of copper4 ,determination without ,previous ,separation4--,dissolve up #b grams as before1 but1 instead of passing sulphuretted hydrogen1 add #cj c4c4 of dilute ammonia1 shake well1 and cool4 ,prepare a standard by dissolving #j4e gram of copper in #a c4c4 of nitric acid1 add #j4f gram of iron in the form of ferric chloride and #bj c4c4 of hydrochloric acid1 dilute to about #aej c4c41 add #cj c4c4 of dilute ammonia1 and cool4 ,titrate the two solutions side by side4 ,in a determination on the sample last used1 #eh c4c4 were required for the assay and #ec c4c4 for the standard1 which indicates #bg4c per cent4 of copper4 ,this method of working is somewhat rough4 ,,iodide ,,method4 ,this is based upon the fact that when potassic iodide in excess is added to a strong solution of a cupric salt in a faintly acid solution1 cuprous iodide is formed and an equivalent of iodine liberated4#ef ,the iodine is measured by titrating with a solution of sodium hyposulphite1#eg using starch paste as indicator4 ,the iodine is soluble in the excess of potassium iodide1 forming a deep brown solution2 the hyposulphite is added until this brown colour is almost removed4 ,starch paste is then added1 and strikes with the remaining iodine a dirty blue colour4 ,the addition of the hypo is continued until the blue colour is discharged4 ,the end reaction is sharp2 a drop is sufficient to complete it4 ,as regards the titration1 the process leaves little to be desired2 the quantity of hypo required is strictly proportional to the copper present1 and ordinary variations in the conditions of working are without effect4 ,the presence of salts of bismuth masks the end reaction because of the strong colour imparted to the solution by the iodide of bismuth4 ,under certain conditions there is a return of the blue colour in the assay solution after the finishing point has apparently been reached1 which is a heavy tax on the patience and confidence of the operator4 ,this is specially apt to occur when sodium acetate is present1 although it may also be due to excessive dilution4 ,the standard hypo solution is made by dissolving #ci4ah grams of the crystallised salt 7,na#b,s#b,o#c4e;,h#b,o7 in water and diluting to one litre4 ,one hundred c4c4 will equal one gram of copper4 ,the starch solution is made by mixing #a gram of starch into a thin paste with cold water1 pouring it into #bjj c4c4 of boiling water1 and continuing the boiling for a minute or so4 ,the solution must be cold before use1 and about #b c4c4 is used for each assay4 ,it should not be added until the bulk of the iodine has been reduced4 ,to standardise the hypo1 weigh up #j4c or #j4d gram of pure copper1 dissolve in #e c4c4 of dilute nitric acid1 boil off nitrous fumes1 and dilute with an equal bulk of cold water4 ,add soda solution until a permanent precipitate is obtained1 and then #a c4c4 of acetic acid4 ,this should yield a clear solution4 ,fill an ordinary burette with the hypo4 ,add #c grams of potassium iodide crystals to the copper solution1 and1 when these are dissolved1 dilute to #ajj c4c4 with water4 ,run in the hypo solution rather quickly until the brown colour is nearly discharged--i4e41 to within #c or #d c4c4 of the finish4 ,add #b c4c4 of the starch solution1 and continue the addition of the hypo a few drops at a time until the tint suddenly changes to a cream colour4 ,the blue colour must not return on standing three or four minutes4 ,calculate the standard in the usual way4 ,in assaying ores1 the copper is dissolved and separated with sulphuretted hydrogen as in the other processes1 but the sulphide should be washed more completely to ensure the absence of iron salts4 ,the following experiments show the effect of variation in the conditions of the assay4 ,use a solution of copper sulphate containing #ci4ch grams of copper sulphate crystals 7,cu,s,o#d4e;,h#b,o7 in the litre4 #ajj c4c4 equal #a4jj gram of copper4 ,effect of ,varying ,temperature4--,the assay after the addition of the potassic iodide must be kept cold1 else iodine may be volatilised4 ,effect of ,varying ,potassium ,iodide4--,in various descriptions of the process the amount of iodide required is variously stated at from a few crystals to as much as #aj grams4 ,the proportion required by theory for #a gram of copper is a little over #e grams3 an excess1 however1 is required to keep the liberated iodine in solution4 ,on economic grounds this excess should not be extravagant2 if the student uses #aj parts of the iodide for each part of copper in the assay he will have sufficient4 ,in the experiments there were used #bj c4c4 of the copper sulphate1 with varying amounts of potassic iodide1 and the following results were got3-- ,potassic iodide added #a4e gram #c grams #e grams ,hypo required #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 ,in these the iodide was added direct to the solution containing the copper1 which was afterwards diluted to #ajj c4c4 and titrated4 ,in another series the iodide was added after the dilution to #ajj c4c41 and the results were3-- ,potassic iodide added #a4e gram #c grams #e grams #aj grams ,hypo required #bj4j c4c4 #bj4a c4c4 #bj4j c4c4 #bj4j c4c4 ,effect of ,varying ,bulk4--,in these experiments1 #bj c4c4 of copper sulphate were taken1 #c grams of potassic iodide added1 and also water to the required bulk4 ,bulk #bj4j c4c4 #ajj4j c4c4 #bjj4j c4c4 #ejj4j c4c4 ,hypo required #bj4j #bj4j #bj4j #ai4i ,in the last of these experiments the colour was discharged at #ah c4c41 but gradually returned until #ai4i c4c4 had been run in4 ,it will be seen that considerable variation in bulk does not interfere4 ,effect of ,acetic ,acid4--,these experiments were like the last series mentioned1 but the bulk was #ajj c4c41 and varying amounts of acetic acid were added4 ,acetic acid added #j c4c4 #a4j c4c4 #e4j c4c4 #aj4j c4c4 #bj4j c4c4 ,hypo required #bj4j #bj4a #bj4a #bj4j #bj4b ,acetic acid1 then1 does not interfere to any serious extent4 ,effect of ,varying ,sodium ,acetate4--,these experiments were like those last mentioned1 but without acetic acid1 and with varying amounts of sodium acetate4 ,sodium acetate added #j gram #a gram #b grams #e grams #aj grams ,hypo required #bj4j c4c4 #bj4j c4c4 #bj4b c4c4 #ai4c c4c4 #ah4b c4c4 ,in the #e grams experiment1 when the finishing point had been apparently reached the colour slowly returned2 but as the results generally on titrating were not satisfactory a repetition of the experiment was made with the addition of #e c4c4 of acetic acid1 which gave an equally bad result4 ,effect of ,foreign ,salts4--,the conditions of these experiments were the same as before4 ,the salts were added and dissolved before the addition of the potassium iodide4 ,using #e grams 7or in the case of the acids1 #e c4c471 the results were as follows3-- dilute ,acetic ,salt added -- ,h#b,,so#d acid ,na,ac ,na,cl ,hypo required #bj4j c4c4 #bj4j c4c4 #bj4a c4c4 #ai4c c4c4 #bj4a c4c4 ,salt added ,,kno#c ,na#b,,so#d ,am,cl ,am#b,,so#d ,hypo required #bj4b c4c4 #ah4g c4c4 #bj4j c4c4 #ai4i c4c4 ,the low result with the sulphate of soda was evidently due to the formation of a sparingly soluble double salt1 which removed copper from the solution2 on adding a little acetic acid the full amount of hypo was required4 ,the effect of the presence of certain metals is important4 ,the method of determining it was to add the substance to the solution containing the copper1 and partly precipitate with soda solution2 then treating with #a c4c4 of acetic acid1 adding the iodide1 and proceeding as before4 ,substance ,added4 ,hypo ,required1 - #bj4 c4c #j4jej gram arsenic as ,as#b,o#e #bj4j #j4jej antimony as ,sb,cl#e #ai4h #j4jej lead as ,pb7,,no#c7b #bj4a ,a similar experiment with #j4jej gram of bismuth nitrate could not be determined1 the end-reaction being masked4 ,bismuth iodide is soluble in potassic iodide1 forming a brown solution1 the colour of which is very similar to that produced by iodine2 and although it does not strike a blue colour with starch1 hypo has an action on it4 ,a similar experiment with #j4jej gram of iron as ferric chloride required #bb4c c4c4 of hypo1 and the colour returned on standing4 ,this shows that ferric acetate liberates iodine under the conditions of the assay4 ,trying to counteract this1 by adding to a similar solution #j4e gram of phosphate of soda dissolved in a little water1 #ai4g c4c4 of hypo were required instead of #bj4j1 but the assay showed signs of returning colour4 ,in standardising1 the same result was obtained1 whether the copper was present as nitrate or sulphate before neutralising4 ,effect of ,varying ,copper4--,with the same conditions as before1 but with varying amounts of copper and a proportionally increasing quantity of iodide1 the results were3-- ,copper present #a4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,hypo required #a4j #aj4j #bj4j #ej4j #ajj4j showing the results to be exactly proportional4#eh ,determination of ,copper in ,copper ,pyrites4--,take #b grams of the dried and powdered ore and treat in a porcelain dish with #bj c4c4 of nitric acid1 and evaporate to dryness4 ,take up with #cj c4c4 of hydrochloric acid1 dilute1 and transfer to a pint flask2 make up with water to #bjj c4c41 warm1 and pass sulphuretted hydrogen to excess4 ,filter1 and wash the precipitate with water acidified with sulphuric acid4 ,wash the precipitate back into the flask1 and dissolve with #ae c4c4 of nitric acid4 ,evaporate almost to dryness2 add #bj c4c4 of water1 and boil till free from nitrous fumes2 filter off the sulphur and gangue2 neutralise with soda1 avoiding excess2 add #a or #b c4c4 of acetic acid1 and shake till clear4 ,add #e grams of potassium iodide1 dilute to #ajj c4c41 and titrate4 ,the following is an example3-- #j4e gram of copper required #ej4e c4c4 hypo4 ,the assay required #ee4f which is equal to #bg4e per cent4 of copper4 ,,colorimetric ,,process4 ,this is based on the blue coloration of ammoniacal copper solutions4 ,the quantity of copper in #ajj c4c4 of the assay solution should not be more than #ae milligrams1 or less than half a milligram4 ,it is not so delicate as most other colorimetric methods1 but nevertheless is a very useful one4 ,the manner of working is the same as that described under iron4 ,standard ,copper ,solution4--,weigh up #j4e gram of electrotype copper1 dissolve in #aj c4c4 of nitric acid1 boil off nitrous fumes1 and dilute to #a litre4 #a c4c4 #j4e milligram4 ,in nearly all cases it will be necessary to separate the copper with sulphuretted hydrogen from a solution of about #e grams of the material to be assayed4 ,the filter paper containing the sulphide 7and1 probably1 much sulphur7 is dried and burnt4 ,the ashes are dissolved in #e c4c4 of dilute nitric acid1 #aj c4c4 of dilute ammonia added1 and the solution filtered through a coarse filter into a ,nessler tube1 washing the paper with a little dilute ammonia4 ,the estimation of the colour and calculation of the result are made in the way described on page #dd4 ,the effect of varying conditions on the assay may be seen from the following experiments4 ,effect of ,varying ,temperature4--,the effect of increased temperature is to slightly decrease the colour1 but this can only be observed when a fair quantity of copper is present4 #a4j c4c4 at #ae showed the colour of #a4j c4c4 at #gj #b4e #b4g #e4j #e4j #aj4j #i4j ,effect of ,varying ,ammonia4--,the solution must1 of course1 contain free ammonia2 about #e c4c4 of dilute ammonia in #ej c4c4 bulk is the quantity to be used in the experiments4 ,a larger quantity affects the results1 giving lower readings and altering the tint4 ,with small quantities of ammonia the colour approaches a violet2 with larger1 a sky-blue4 #b4e c4c4 with #be c4c4 of strong ammonia read #b4b c4c4 #e4j #d4j #aj4j #h4j ,effect of ,ammonic ,salts4--,the following table shows the results after addition of ammonic salts3-- ---------------------------------------- --------------------------- ,c4c4 ,present4 ,with #aj grams ,with #aj grams ,with #aj grams ,ammonic ,nitrate4 ,ammonic ,chloride4 ,ammonic ,sulphate4 ---------------------------------------- --------------------------- #b4e #b4e #b4e #b4j #e4j #e4j #e4c #d4c #aj4j #aj4j #aj4j #h4e ---------------------------------------- --------------------------- ,these show that sulphates should be avoided1 and either nitrate or chloride solutions be used in the standard as well as in the assay4 ,determination of ,copper in a ,manganese ,ore4--,treat #c grams of the ore with #bj c4c4 of hydrochloric acid1 and evaporate to dryness4 ,take up with #aj c4c4 of hydrochloric acid2 dilute to about #bjj c4c41 and pass sulphuretted hydrogen until the solution smells of the gas2 filter1 burn1 take up with #e c4c4 of dilute nitric acid1 add #aj c4c4 of dilute ammonia1 and filter into the ,nessler tube1 and make up with the washings to #ej c4c4 ,into the standard tube put #e c4c4 of dilute nitric acid and #aj c4c4 of dilute ammonia4 ,make up to nearly #ej c4c4 with water1 and run in the standard copper until the colours are equal4 ,in a determination #d c4c4 7 #b4j milligrams of copper7 were required2 this in #c grams of ore #j4jg per cent4 ,determination of ,copper in ,black ,tin4--,weigh up #c grams of the dried ore1 boil with #aj c4c4 of hydrochloric acid1 and afterwards add #a c4c4 of nitric2 boil off nitrous fumes1 evaporate to about #e c4c41 dilute to #ej c4c41 add #bj c4c4 of dilute ammonia2 stir1 and filter4 ,if much iron is present1 dissolve the precipitate of ferric hydrate in acid1 and reprecipitate with ammonia4 ,mix the two filtrates1 and dilute to #ajj c4c4 ,take #ej c4c4 for the test4 ,a sample of #c grams of an ore treated in this way required #e4b c4c4 of standard copper to produce equality of tint4 ,this gives #j4ce per cent4 ,determination of ,copper in ,tin4--,weigh up #a gram of the sample1 transfer to an evaporating dish1 and cover with #cj c4c4 of aqua regia4 ,warm until the metal has dissolved1 then evaporate almost to dryness4 ,take up with a few c4c4 of hydrochloric acid and again evaporate4 ,dissolve the residue in #aj c4c4 of dilute hydrochloric acid and transfer to a #ajj c4c4 flask4 ,add #aj c4c4 of dilute ammonia and make up with water to the containing mark4 ,filter off #ej c4c4 of the solution into a ,nessler glass and determine the copper in it colorimetrically4 ,,examination ,,of ,,commercial ,,copper4 ,very pure copper can be obtained in commerce1 owing to the demand for metal of high conductivity for electrical purposes1 which practically means for metal free from impurities4 ,much of the metal sold contains as much as one per cent4 of foreign substances1 of which arsenic is the most important4 ,the other elements to be looked for are bismuth1 lead1 antimony1 silver1 gold1 iron1 nickel1 cobalt1 sulphur1 and oxygen4 ,in blister copper 7which is the unrefined metal71 aluminium1 silicon1 and phosphorus may be met with4 ,oxygen4--,all commercial copper carries oxygen2 most of it is present as cuprous oxide1 which is dissolved by molten copper4 ,the estimation of oxygen is often made by difference4 ,the copper and the other impurities being determined1 the rest is assumed to be oxygen4 ,probably this is nearly correct1 but the whole of the oxygen should not be ascribed to cuprous oxide2 for any arsenic the metal contained would be present as cuprous arsenite1 since arsenide of copper and cuprous oxide could not exist together at the temperature of fusion without interacting4 ,in the report of the analysis1 it is best to state the proportion of oxygen thus3-- ,oxygen ---- per cent4 by difference4 ,there is a method of determination by fusing #e or #aj grams in a brasqued crucible1 and counting the loss as oxygen2 and another method for the determination of cuprous oxide based on the reaction of this substance with nitrate of silver4#ei ,about #b grams of silver nitrate1 dissolved in #ajj c4c4 of water1 is allowed to act upon #a gram of the copper in the cold4 ,the precipitate is filtered off1 washed thoroughly with water1 and the basic salt dissolved and determined colorimetrically4 ,one part of copper found represents #a4fh part of cuprous oxide1 or #j4ai part of oxygen4 ,copper generally carries from #j4a to #j4b per cent4 of oxygen4 ,silver is found in most samples1 but occurs in variable proportions2 when it amounts to #cj ounces per ton it has a commercial value4 ,to determine its amount1 dissolve #aj grams of the copper in #ce c4c4 of nitric acid and #ej c4c4 of water1 boil off nitrous fumes1 and dilute to about #ajj c4c4 ,one or two c4c4 of dilute hydrochloric acid 7one to #ajj of water7 are added1 stirred in1 and the precipitate allowed to settle for twenty-four hours4 ,filter through a double ,swedish paper1 dry1 burn1 and cupel the ashes with one gram of sheet lead4 ,ten grams of a sample of copper gave in this way #d4g milligrams of silver4 ,ten grams of the same copper1 to which #bd milligrams of silver had been added gave #bh4b milligrams4 ,gold4--,to determine it1 dissolve #aj1 #bj1 or #ej grams of the sample in #ce1 #gj1 or #age c4c4 of nitric acid and an equal volume of water1 boil till free from nitrous fumes1 and dilute to double its volume4 ,allow to stand for some time1 decant on to a filter1 dry1 burn1 and cupel the ashes with #a gram of sheet lead4 ,if silver is present1 owing to traces of chlorides in the re-agents used1 parting will be necessary4 7,see ,gold47 ,working in this way on #bj grams of copper1 to which #a4h milligram of gold had been added1 a button weighing #b4j milligrams was obtained4 ,antimony is not a frequent impurity of copper3 it can be detected in quantities over #j4a per cent4 by a white residue of ,sb#b,o#d1 insoluble in nitric acid4 ,with material containing only small quantities of antimony the white oxide does not show itself for some time1 but on long-continued boiling it separates as a fine powder4 ,it is best 7when looking for it7 to evaporate the nitric acid solution to the crystallising point1 to add a little fresh nitric acid and water1 and then to filter off the precipitate4 ,after weighing it should be examined for arsenic and bismuth4 ,lead4--,refined coppers are often free from lead1 anything more than traces being seldom found2 in coarse coppers it is sometimes present in considerable quantities4 ,its presence may be detected in the estimation of the copper electrolytically1 the platinum spiral becoming coated with a brown or black deposit of lead dioxide4 ,the depth of colour varies with the lead present1 and obviously could be made the basis of an approximate estimation4 ,the colour shows itself within an hour or so1 but is best observed when all the copper has been deposited4 ,electrolysing a solution of one gram of pure copper1 to which #j4e milligram of lead had been added1 the deposit was dark brown2 in a similar solution with #a milligram of lead it was much darker1 and with #b milligrams it was black4 ,under the conditions of the assay the dioxide cannot be weighed1 as it partly dissolves on breaking the current4 ,when lead has been found1 its quantity may be estimated by evaporating to dryness the nitric acid solution to which an excess of sulphuric acid has been added1 taking up with water1 and filtering off and weighing the lead sulphate4 ,the separation of traces of lead as chromate is a fairly good one4 ,dissolve #e grams of the copper in #ag c4c4 of nitric acid and an equal volume of water2 boil off nitrous fumes1 neutralise with soda1 and afterwards acidulate with acetic acid2 and dilute to a litre4 ,add #bj grams of sodium acetate1 warm1 and precipitate the lead with a dilute solution of potassium chromate4 ,copper chromate 7yellow7 may be at the same time thrown down1 but it is readily soluble on diluting4 ,filter off the precipitate2 wash it into a beaker and pass sulphuretted hydrogen2 oxidise the sulphide and weigh as lead sulphate4 ,treated in this way #e grams of copper yielded sulphate of lead equal to #b4j milligrams of lead4 ,five grams of the same sample to which #aj milligrams of lead were added gave #aa4d milligrams4 ,nickel and ,cobalt4--,nickel is always present in larger or smaller quantities in commercial copper1 and1 perhaps1 has an influence on the properties of the metal4 ,it is determined as follows3--,dissolve #aj grams of the copper in #ce c4c4 of nitric acid and an equal bulk of water1 boil off nitrous fumes and neutralise with soda1 add #b grams of carbonate of soda dissolved in water1 boil1 and filter4 ,acidify the filtrate with #b or #c c4c4 of dilute nitric acid and dilute to #a or #a-a_/b litres4 ,pass sulphuretted hydrogen through the cold solution till the copper is all down and the liquid smells of the gas4 ,filter and evaporate the filtrate to a small bulk1 and determine the nickel by electrolysing the solution rendered ammoniacal1 or by precipitating as sulphide and weighing as sulphate4 7,see under ,nickel47 ,the precipitate1 after weighing1 should be tested for cobalt4 ,if present it is separated with potassium nitrite as described under ,cobalt4 ,ten grams of copper gave #f4j milligrams of nickel2 and another lot of #aj grams of the same copper1 to which #aj4j milligrams of nickel had been added1 gave #ag4b milligrams4 ,sulphur4--,the amount of sulphur in refined copper is very small1 seldom exceeding #j4jje per cent4 ,in coarse copper1 as might be expected1 it is found in larger quantities4 ,in determining it1 it is first converted into sulphuric acid1 and then precipitated and weighed as barium sulphate4 ,the precipitation cannot be effected from a nitric acid solution4 ,ten grams of copper are dissolved in nitric acid1 as for the other determinations1 and then boiled with excess of hydrochloric acid till the nitric acid is completely removed4 ,there is then added a few drops of a dilute solution of baric chloride1 and the solution is allowed to stand for some hours4 ,the baric sulphate is filtered off and weighed4 ,the necessity for precipitating from a hydrochloric acid solution is seen from the following determinations4 ,in each experiment #aj grams of copper was used1 and a known weight of sulphur1 in the form of copper sulphate1 added4 ---------------------------------------- ---------------------- ,sulphur added4 ,sulphur found in ,sulphur found in ,hydrochloric ,acid ,solution4,nitric ,acid ,solution4 ---------------------------------------- ---------------------- #e milligrams #h milligrams #j4jc milligrams #aj #aa #j4jc #ae #ag #ab4jj ---------------------------------------- ---------------------- ,bismuth4--,nearly all samples of copper contain bismuth1 but only in small quantities4 ,it is best determined colorimetrically as described under ,bismuth4 ,the method of concentrating and preparing the solution for colorimetric assay is as follows4 ,dissolve #aj grams of copper in nitric acid1 as in the other determinations2 neutralise with soda2 add #a or #a4e grams of bicarbonate of soda and boil for ten minutes2 filter1 dissolve the precipitate in hot dilute sulphuric acid2 add sulphurous acid and potassium iodide in excess1 and boil till free from iodine4 ,filter and dilute to #ejj c4c4 ,take #ej c4c4 of the yellow solution for the determination4 ,a few c4c4 of a dilute solution of sulphurous acid 7#a in #ajj7 will prevent the liberation of iodine4 ,the following experiments test the method of separation4 ,ten grams of copper were treated as above and precipitated with #a4e gram of soda2 the precipitate contained #j4f milligram of bismuth 7 #j4jjf per cent474 ,the filtrate treated with another #a4e gram of soda gave a precipitate which was free from bismuth4 ,to the filtrate from this was added #a4j milligram of bismuth1 and another fraction was precipitated with #a4e gram of soda4 ,in this precipitate was found #a4j milligram of bismuth4 ,to the filtrate another milligram of bismuth was added and the separation with soda repeated4 ,the bismuth was separated from this precipitate with ammonic carbonate before determination1 and #j4i milligram was found4 ,arsenic4--,the proportion of arsenic in copper varies from #j4ja to #j4ge per cent4 whilst in coarse copper it may amount to #b or even #c per cent4 ,to determine it1 dissolve #e1 #aj1 or #bj grams of the copper 7according to the amount of arsenic present7 in #ah c4c41 #ce c4c41 or #gj c4c4 of nitric acid1 and an equal volume of water4 ,boil off the nitrous fumes1 dilute to #ajj c4c4 and neutralise with soda2 add #a4e or #b grams of carbonate of soda dissolved in a little water1 and boil4 ,filter 7washing is unnecessary7 and dissolve back into the flask with a little dilute hydrochloric acid2 add #cj c4c4 of dilute ammonia and #be c4c4 of magnesia mixture1 and allow to stand overnight4 ,the whole of the arsenic is precipitated as ammonic-magnesic arsenate in one hour1 but it is advisable to leave it longer4 ,the precipitate may be dried and weighed1 or1 better1 titrated with uranium acetate4 7,see ,arsenic47 ,to test this method of separation #aj grams of pure copper were taken and #j4bjj gram of arsenic dissolved with it4 ,the arsenic was determined by titration with uranium acetate1 and #j4bjj gram was found4 ,two other similar experiments with #j4jhj and #j4jaj gram of arsenic added1 gave #j4jgi and #j4jab gram respectively4 ,antimony or bismuth may be present without interfering with the titration4 ,with #j4ajj gram of antimony and #j4ajj gram of arsenic1 #j4ajj gram of arsenic was found2 and in another case1 with #j4ajj gram of bismuth and #j4jfj gram of arsenic1 #j4jfj gram was found4 ,in these experiments the antimony and bismuth were present in the assay solution when titrated4 ,for a gravimetric determination they would require to be removed before precipitating with magnesia mixture4 ,phosphorus1 if present1 counts as arsenic in the proportion of #a to #b4d2 but1 except in the case of coarse coppers1 it is always absent4 ,iron1 if present1 interferes by forming a white flocculent precipitate of ferric arsenate after the addition of the sodium acetate and preliminary to the titration4 ,each milligram of iron abstracts1 in this way1 #a4c milligrams of arsenic4 ,iron4--,refined coppers carry traces of iron1 varying from #j4jja to #j4ja per cent4 ,it is best determined during the arsenic estimation4 ,the precipitate of the ammonic-magnesic arsenate will contain the whole of the iron as ferric hydrate4 ,on dissolving in hydrochloric acid1 neutralising with ammonia1 adding #e c4c4 of sodic acetate1 diluting1 and boiling1 it reappears as a white precipitate of ferric arsenate4 ,it is filtered off 7the arsenic being estimated in the filtrate71 dissolved in warm hydrochloric acid1 and determined colorimetrically as described under ,iron4 ,a series of experiments testing the separation is there given4 ,phosphorus4--,refined coppers do not carry phosphorus1 although it may be present in coarse copper up to #a per cent4 or more4 ,in such samples the following method is adopted for the estimation of both phosphorus and arsenic4 ,dissolve #aj grams of copper and #j4a1 #j4b1 or #j4c gram of iron wire 7according to the amount of arsenic and phosphorus present7 in #ce c4c4 of nitric acid and an equal volume of water4 ,add soda till the free acid is nearly neutralised4 ,next add a strong solution of sodium acetate1 until the solution ceases to darken on further addition1 then dilute with water to half a litre4 ,the solution is best contained in a large beaker2 it is next heated to the boiling point1 and at once removed and allowed to settle4 ,if the precipitate is light coloured it is evidence that sufficient iron has not been added1 or1 if it is green1 from basic copper salts1 it shows that the solution was not sufficiently acid4 ,in either case start afresh4 ,filter off the precipitate and wash with hot water containing a little sodium acetate1 dissolve it off the filter with hot dilute hydrochloric acid1 add ammonia in excess1 and pass sulphuretted hydrogen for five minutes4 ,warm at about #gj ,c4 for a quarter of an hour4 ,filter4 ,the clear yellow filtrate contains the arsenic and phosphorus4 ,add dilute sulphuric acid in excess2 filter off the yellow precipitate of sulphide of arsenic1 dissolve it in nitric acid1 and titrate with uranium acetate1 as described under ,arsenic4 ,the filtrate from the sulphide of arsenic is rendered alkaline with ammonia and magnesia mixture added4 ,the solution is stirred1 and allowed to stand overnight4 ,the precipitate of ammonic-magnesic phosphate is filtered off1 dissolved1 and titrated with uranium acetate1 using the same standard solution as is used in the arsenic assay3 #j4e gram of arsenic equals #j4bjg gram of phosphorus4 ,copper4--,the method of determining this has been described under ,electrolytic ,assay4 ,in the method of concentration by fractional precipitation with sodic carbonate 7which is adopted in most of these determinations7 the precipitate will contain all the bismuth1 iron1 and alumina2 the arsenic and phosphorus as cupric arsenate and phosphate2 and the greater part of the lead1 antimony1 and silver4 ,the nickel and cobalt1 and the sulphur as sulphuric acid1 will remain in solution with the greater part of the copper4 ,,practical ,,exercises4 #a4 ,according to a wet assay #b grams of a certain ore contained #j4cfej gram of copper4 ,what would you expect the dry assay produce to be8 #b4 ,a standard solution is made by dissolving #be grams of potassic cyanide and diluting to a litre4 ,assuming the salt to be #ih per cent4 real cyanide1 what would #ajj c4c4 of the solution be equivalent to in grams of copper8 #c4 ,how would you make a solution of hypo of such strength that #ajj c4c4 shall equal #j4fcc gram of copper8 #d4 ,what weight of ore1 containing #ag4j per cent4 of copper1 would you take in order to get about #j4e gram of copper in solution for electrolysis8 #e4 ,the solution of copper in nitric acid is effected by the following reaction3-- #c;,cu #h;,,hno#c #c;,cu7,,no#c7b #d;,h#b,o #b,,no4 ,what volume of nitric acid will be required to dissolve #a gram of copper8 ,,lead4 ,the chief ore of lead is galena1 a sulphide of lead1 common in most mining districts1 and frequently associated with blende and copper-pyrites4 ,it always carries more or less silver2 so that in the assay of the ore a silver determination is always necessary4 ,carbonate 7cerussite71 sulphate 7anglesite71 and phosphate 7pyromorphite7 of lead also occur as ores1 but in much smaller quantities4 ,lead ores are easily concentrated 7owing to their high specific gravity1 c47 by mechanical operations1 so that the mineral matter sent to the smelter is comparatively pure4 ,lead is readily soluble in dilute nitric acid4 ,the addition of sulphuric acid to this solution throws down heavy1 white1 and insoluble lead sulphate4 ,galena is soluble in hot hydrochloric acid1 sulphuretted hydrogen being evolved2 but the action is retarded by the separation of the sparingly soluble lead chloride4 ,if a rod of zinc is placed in this solution1 metallic lead is precipitated on it as a spongy mass1 the lead chloride being decomposed as fast as it is formed4 ,the opening up of the ore is thus easily effected1 the sulphur going off as sulphuretted hydrogen1 and the lead remaining in a form easily soluble in dilute nitric acid4 ,galena itself is readily attacked by nitric acid1 part of the lead going into solution1 and the rest remaining as insoluble lead sulphate4 ,the sulphate is due to the oxidation of the sulphur by nitric acid2 its amount will vary with the quantity and concentration of the acid used4 ,sulphate of lead is soluble in solutions of ammonium or sodium acetate2 or it may be converted into carbonate by boiling with carbonate of soda4 ,the carbonate1 after washing off the sulphate of soda1 dissolves easily in nitric acid4 ,the precipitation of lead from acid solutions with sulphuric acid1 and the solubility of the precipitate in ammonium acetate1 distinguishes it from all other metals4 ,the addition of potassium chromate to the acetate solution reprecipitates the lead as a yellow chromate4 ,,dry ,,assay4 ,the dry assay of lead is largely used1 but it is only applicable to rich or concentrated ores1 and even with these only gives approximate results4 ,both lead and lead sulphide are sensibly volatile at a moderately-high temperature2 hence it is necessary to obtain a slag which is easily fusible4 ,as a reducing agent iron is almost always used1 and this is added either in the form of an iron rod1 or the crucible itself is made of this metal4 ,the flux used is carbonate of soda4 ,when a clay crucible is used1 the method of working is as follows3--,weigh up #be grams of the dry and powdered ore1 mix with an equal weight of soda and #b grams of tartar2 place in a crucible 7,e4 ,battersea round71 and then insert a piece of iron rod about half an inch in diameter1 and of such a length that it will just allow the crucible to be covered4 ,the rod should be pushed down so as to touch the bottom of the crucible1 and the mixture should be covered with a sprinkling of borax4 ,place in a furnace heated to1 but not above1 redness1 and cover the crucible4 ,in about twenty minutes the charge will be fused3 the fusion is complete when bubbles of gas are no longer being evolved2 and then1 but not till then1 the iron is withdrawn1 any adhering buttons of lead being washed off by dipping the rod a few times in the slag4 ,cover the crucible1 leave it for a minute or two1 and then pour4 ,detach the slag1 when cold1 by hammering4 ,the weight of the button multiplied by #d gives the percentage4 ,the commoner errors of students in working the process are too high a temperature and too quick a withdrawal4 ,a sample of ore treated in this manner gave on duplicate assay #ag4e and #ag4f grams of lead1 equalling #gj4j and #gj4d per cent4 respectively4 ,by wet assay the sample gave #gc4c per cent4 ,using an iron crucible1 the results will be #a per cent4 or so higher4 ,the crucible must be made of wrought iron2 and1 if it has been previously used1 should be cleaned by heating to dull redness and scraping the scale off with a stirrer4 ,take #cj grams of the ore1 mix with #cj grams of soda and #c grams of tartar2 put the mixture in the crucible1 and cover with a sprinkling of borax2 heat for about twenty minutes at not too high a temperature1 and then scrape down the slag adhering to the side with a stirrer4 ,leave in the furnace till action has ceased4 ,before pouring1 tap the pot gently1 and then tilt it so as to make the slag wash over the part of the crucible along which the charge is to be poured4 ,pour2 and1 when cold1 clean and weigh the button of metal4 ,a crucible may be used from ten to twenty times4 ,these assays are for ores containing the lead chiefly as sulphide4 ,for oxidised ores1 charcoal or tartar is employed as the reducing agent4 ,the student may practise on red lead as follows3--,take #cj grams of red lead2 mix with #aj grams each of borax and soda and about #a4e gram of powdered charcoal2 place in a small clay crucible with a cover 7,c4 ,battersea round71 fuse at a gentle heat1 and pour when action ceases4 ,this assay will only take a few minutes4 ,where lead is present as phosphate 7as in the case of pyromorphite71 or mixed with phosphates 7as sometimes happens71 carbonate of soda is a suitable flux2 but the phosphate of soda which is formed makes a thick tenacious slag1 which is very apt to be carried out of the pot by the escaping gas4 ,a wide-mouthed clay pot is taken and a little fluor spar added4 ,for the assay of pyromorphite the following charge may be used3--,ore1 #bj grams2 soda1 #be grams2 tartar1 #g grams2 and fluor spar1 #e grams2 and #b grams of borax as a cover4 ,this will melt down in about ten minutes1 and should be poured as soon as tranquil4 ,,wet ,,assay4 ,in the case of galena the best method of getting the lead into solution is to treat with hydrochloric acid and zinc4 ,put #a gram of the ore in an evaporating dish #d inches across1 and cover with #aj c4c4 of dilute hydrochloric acid4 ,heat till the evolution of sulphuretted hydrogen becomes sluggish1 and then drop in a piece of zinc rod4 ,if the solution effervesces too strongly1 dilute it4 ,continue the heating until the sulphide is seen to be all dissolved2 when the lead is all precipitated1 pour off the liquid and wash twice with cold water4 ,peel off the precipitated lead with the help of a glass rod1 and then clean the zinc4 ,cover the lead with #bj c4c4 of water and #e c4c4 of dilute nitric acid1 and heat gently till dissolved2 all the lead will be in solution1 and1 when filtered off from the gangue1 will be ready for a gravimetric determination4 ,for volumetric work this filtering is unnecessary4 ,the chief objection to this method is that commercial zinc carries considerable quantities of lead4 ,although this can be determined and allowed for1 the correction required is in most cases too large to be satisfactory4 ,the following method is applicable in all cases1 but is more troublesome3--,treat #a gram of the ore with #aj c4c4 of dilute nitric acid in an evaporating dish covered with a clock-glass1 and evaporate till nearly dry4 ,take up with #ej c4c4 of water1 and add #aj c4c4 of dilute sulphuric acid4 ,filter4 ,the residue contains the lead as sulphate1 together with the insoluble matter of the ore and globules of sulphur4 ,warm with a solution of ammonium acetate1 and filter4 ,the lead will be in the filtrate1 and is recovered in a state fit for direct gravimetric estimation by the addition of dilute sulphuric acid4 ,if the volumetric method is to be used1 the lead sulphate should be dissolved out with a solution of sodium acetate instead of with the ammonium salt solution4 ,,gravimetric ,,determination4 ,the lead is separated and precipitated as sulphate1 as already described4 ,the solution must be allowed to stand1 and the clear liquid be decanted through a filter4 ,transfer the precipitate1 and wash with very dilute sulphuric acid 7#a or #b c4c4 in #ajj c4c4 of water74 ,the acid must be completely removed with one or two washes with cold water1 and then with alcohol4 ,the volume of liquid required for washing is small1 as the precipitate is dense and easily cleaned2 but the washing must be carefully done1 since if any acid remains it will1 on drying1 char the paper1 and render the subsequent work troublesome4 ,dry1 transfer to a watch-glass1 and burn the filter paper1 collecting its ash in a weighed porcelain crucible4 ,the filter paper must be freed as much as possible from the lead sulphate before burning1 and the ash treated with a drop or two of nitric and sulphuric acids4 ,transfer the lead sulphate to the crucible2 ignite gently1 keeping the temperature below redness2 cool1 and weigh4 ,the precipitate will contain #gc4f per cent4 of lead oxide or #fh4c per cent4 of lead4 ,determination of ,lead in ,commercial ,zinc4--,take #aj grams of zinc1 and treat 7without heating7 with #fj c4c4 of dilute hydrochloric acid4 ,when the zinc is nearly all dissolved1 decant off the clear liquid1 and dissolve the residue in #b c4c4 of dilute nitric acid4 ,evaporate till most of the acid is removed2 dilute to #bj or #cj c4c4 with water1 and add #aj c4c4 of dilute sulphuric acid4 ,filter off1 and weigh the lead sulphate4 ,ten grams treated in this way gave--#j4afaj gram of lead sulphate1 equivalent to #a4aj per cent4 of lead4 ,,volumetric ,,method4 ,this is based upon the reaction between chromate of potash and soluble lead salts in neutral solutions1 whereby an insoluble yellow chromate of lead is produced4#fj ,an excess of the chromate is required to complete the reaction1 so that the point at which an indicator shows the presence of undecomposed chromate cannot be satisfactorily taken as the finish4 ,therefore an excess of the standard chromate must be run in1 and such excess determined4 ,chromate of lead is not precipitated from strong nitric acid solutions1 and only incompletely from dilute ones4 ,acids generally are detrimental to the precipitation1 and must be neutralised before titrating4 ,if the lead is present as sulphate in sodic acetate solution1 it is well to render it distinctly alkaline with ammonia4 ,lead chromate precipitated in the cold is a lemon-yellow1 light precipitate1 very difficult to filter3 on heating to #dj ,c4 the colour becomes orange2 at #fj ,c4 it assumes a deeper hue1 and becomes flocculent2 and at a boiling temperature it still further darkens and settles readily4 ,these changes in colour are not due to any chemical change1 as will be seen by testing the filtrate for chromium or lead3 this is an advantage to the assay1 since it is only at the higher temperature that the precipitate can be easily filtered4 ,the lead is not completely precipitated1 but the amount remaining in solution is only #b or #c milligrams1 which is just sufficient to give a dark coloration with sulphuretted hydrogen4 ,the standard chromate of potash solution is made by dissolving #g4ac grams of bichromate of potash and #b4j grams of caustic soda in water1 and diluting to #a litre2 or #i4dj grams of the neutral chromate 7,k#b;,cr,o#d7 may be dissolved and diluted to #a litre3 #ajj c4c4 will be equivalent to #a4jjj gram of lead4 ,standard ,lead ,solution4--#af grams of nitrate of lead 7,pb7,,no#c7b7 are dissolved in water and diluted to #a litre2 #ajj c4c4 will contain #a4jjj gram of lead4 ,acetate of ,soda ,solution4--#bej grams of the crystallised salt 7,na,ac4#c;,h#b,o7 are dissolved1 and diluted to #a litre4 ,use #dj c4c4 for each assay4 ,in the titration the assay solution should measure #aej to #bjj c4c41 and should be boiling or nearly so4 ,it is best contained in a pint flask1 and the standard chromate solution used with an ordinary burette4 ,run in the chromate solution in a steady stream until the whole of the lead has been precipitated4 ,the amount required for this may be calculated3 for example1 #a gram of an #hj per cent4 ore would require #hj c4c4 ,a little of the assay may be filtered off1 and if it does not show a yellow colour in the filtrate run in #b c4c4 more of the standard solution and continue this addition till a colour is shown4 ,after this run in another c4c4 to ensure an excess1 dilute to #bej c4c41 and heat to boiling2 allow to settle for three or four minutes1 filter off #ej c4c4 into a ,nessler glass1 and determine the excess of chromate colorimetrically4 ,the excess found in the #ej c4c4 must1 of course1 be multiplied by five1 and then be deducted from the quantity of chromate originally run into the assay solution4 ,the quantity to be deducted should not exceed #c c4c4 ,where a number of determinations are made the colorimetric estimation is facilitated by using a series of standard phials similar to those described under the ,electrolytic ,copper ,assay4 ,the determination is rendered sharper and less liable to error by the addition of a few drops of acetic acid to convert the chromate into bichromate4 ,the same chromate solution must be used in this determination as was used in the precipitation4 ,in standardising the chromate solution1 the standard lead nitrate solution is used4 ,a quantity containing about as much lead as the assay is supposed to contain is measured off1 rendered alkaline with dilute ammonia1 and then neutralised with acetic acid1 using a small piece of litmus paper dropped into the solution as indicator4 ,then dilute1 boil1 and titrate4 ,when the lead in the assay has been separated as sulphate and dissolved in sodic acetate1 less chromate is apparently required1 and in this case it will be necessary to precipitate the lead in the standard with an equivalent of sodic sulphate and redissolve in sodic acetate just as in the assay4 ,in these solutions 7although there is considerable chromate in excess7 a further addition of #e or #f c4c4 of the chromate solution will cause a further precipitate4 ,the following experiments show the effect of variation in the conditions of the assay3-- ,effect of ,varying ,temperature4--,twenty c4c4 of lead nitrate solution and #aj grams of sodium acetate were used2 diluted to #bjj c4c41 heated to the desired temperature1 and titrated4 ,the results were3-- ,temperature #ae #cj #ej #ajj ,chromate required #ai4h c4c4 #ai4e c4c4 #ai4c c4c4 #ai4b c4c4 ,the first two of these filtered badly1 the precipitate coming through the filter2 the last was very satisfactory in the working4 ,effect of ,varying ,bulk4--,using #bj c4c4 of lead nitrate1 and #aj grams of sodium acetate as before1 diluting to the required bulk1 heating to boiling1 and titrating1 the results were3-- ,bulk #ajj4j c4c4 #bjj4j c4c4 #ejj4j c4c4 #ajjj4j c4c4 ,chromate required #ai4f #ai4c #ai4d #ai4d ,effect of ,varying ,acetic ,acid4--,since the experiments are carried out in the presence of sodic acetate1 acetic acid is the only acid whose effect need be considered4 ,working as before1 but with #bjj c4c4 bulk and varying amounts of the acid1 the results were3-- ,acid present -- #aj4j c4c4 #bj4j c4c4 #dj4j c4c4 ,chromate required #ai4g c4c4 #ai4a #ah4e #ag4c ,these experiments show that only slight quantities of acid are admissible4 ,effect of ,varying ,sodium ,acetate4--,with the same conditions as before1 but with varying weights of sodium acetate1 the results were3-- ,sodium acetate present -- #e grams #aj grams #be grams #ej grams ,chromate required #ai4g c4c4 #ai4f c4c4 #ai4f c4c4 #ah4h c4c4 #ag4h c4c4 ,these experiments show that excessive quantities of sodium acetate must be avoided4 ,ammonium acetate interferes to a greater extent1 and if both acetic acid and this salt are present1 each exerts its disturbing influence4 ,with #aj grams of ammonium acetate1 #ai4d c4c4 of the chromate solution were required instead of #ai4g c4c4 in the absence of this salt2 with #aj grams of the acetate and #aj c4c4 of acetic acid1 only #ah4f c4c4 were required4 ,effect of ,foreign ,salts4--,as already stated1 sulphates interfere4 ,twenty c4c4 of the lead nitrate solution were taken1 precipitated with sulphate of soda1 and the precipitate dissolved in #aj grams of sodium acetate and titrated as before4 ,duplicate experiments required #ah4f c4c4 and #ah4g c4c4 of the chromate solution4 ,a similar experiment with #dj c4c4 of lead nitrate required #cg4d c4c4 of chromate4 ,if the sulphate had not been present1 the results would have been #ai4g c4c4 and #ci4d c4c4 respectively4 ,effect of ,varying ,lead4--,in these experiments the conditions were as before1 but with varying amounts of lead4 ,lead nitrate solution present #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,chromate solution required4 #i4d #ai4g #dh4h #ih4b ,determination of ,lead in ,galena4--,weigh up #a gram of the powdered and dried ore1 and boil in an evaporating dish with #aj c4c4 of dilute hydrochloric acid4 ,when the action becomes sluggish1 dilute with an equal bulk of water1 and add a weighed piece of zinc rod about #a inch long and quarter-inch across4 ,keep up a moderate action by warming till the ore is seen to be completely attacked and the lead precipitated4 ,decant off the solution1 wash once1 strip off the lead1 wash and weigh the remaining zinc4 ,dissolve the lead in #e c4c4 of dilute nitric acid1 and #e c4c4 of water with the aid of heat4 ,dilute and transfer to a pint flask2 add a slight excess of dilute ammonia1 and render faintly acid with acetic acid4 ,dilute to #aej c4c41 heat to boiling1 and run in the standard chromate in slight excess1 noting the amount required1 and make up to #bej c4c4 with water4 ,boil the solution1 allow to settle for a minute or so1 filter off #ej c4c41 and determine the excess of chromate colorimetrically4 ,as an example1 #a gram of an impure galena was precipitated with #ge c4c4 of standard chromate 7#ajj c4c4 #a4jbj gram lead74 ,the excess found in #ej c4c4 was #j4c c4c41 which1 multiplied by #e1 gives #a4e c4c4 as the excess in the whole solution4 ,the remaining #gc4e c4c4 of chromate required by the assay1 are equivalent to #j4gdig gram of lead4 ,the zinc used up weighed #a4e grams1 and contained #j4jafe gram of lead4 ,thus we get-- ,lead in the assay #j4gdig gram ,lead from the zinc #j4jafe ------ 4'4 ,lead in the galena #j4gccb ,equivalent to #gc4c per cent4 ,another sample1 in which the galena was accompanied with a large quantity of pyrites1 gave the following results3--,three grams were treated with #cj c4c4 of dilute hydrochloric acid and a rod of zinc4 ,the zinc and lead were carefully transferred to another vessel1 the zinc cleaned1 and the lead 7dissolved in #e c4c4 of dilute nitric acid and #bj c4c4 of water7 treated as before4 #ad4e c4c4 of the chromate were required #j4adgi gram lead ,lead in #b grams of zinc #j4jbbj ------ 4'4 ,lead in #c grams of the ore #j4abei ,equivalent to #d4bj per cent4 ,the same ore gave by separation of the lead with sulphuretted hydrogen1 and conversion into sulphate1 #d4af per cent4 ,with fairly pure ores1 free from sulphate1 the assay may be made more quickly as follows3 ,dissolve #a gram of the finely powdered ore by boiling gently with #dj c4c4 of dilute hydrochloric acid for #ae minutes2 cool2 add a few drops of permanganate2 neutralise with ammonia1 add acetic acid and a little sodium acetate4 ,titrate with standard chromate4 ,,colorimetric ,,process4 ,this is based upon the brown coloration produced in very dilute solutions of lead by the action of a solution of sulphuretted hydrogen4 ,the quantity of lead in the #ej c4c4 of the assay solution must not much exceed #j4e milligram1 nor be less than #j4ja4 ,the sulphuretted hydrogen is used in the form of a solution1 and is not bubbled through the assay4 ,the principle of working is the same as previously described4 ,standard ,lead ,solution4--,each c4c4 of this should contain #j4a milligram of lead4 ,it is made by diluting #aj c4c4 of the solution of lead nitrate1 described under the volumetric process1 to #a litre4 ,sulphuretted hydrogen water is made by passing a current of the washed gas into water till the latter is saturated4 ,five c4c4 of the sulphuretted hydrogen water are put into a ,nessler tube1 the measured portion of the assay solution added1 and the whole diluted with water to the #ej c4c4 mark4 ,into the standard ,nessler tube the same amount of the sulphuretted hydrogen water is put1 and diluted to nearly #ej c4c4 ,the standard lead solution is then run in till the tints are equal4 ,the assay solution must not contain much free acid1 and if the conditions will allow it1 may with advantage be rendered alkaline with ammonia4 ,the chief cause of disturbance is the precipitation of lead sulphide forming a black turbid solution instead of a brown clear one4 ,this may be caused by using hot solutions or an excess of acid4 ,other metals precipitable by sulphuretted hydrogen must be absent as well as strong oxidising agents4 ,effect of ,varying ,temperature4--,the effect of increased temperature is to change the colour from brown to black1 and to render the estimation difficult4 #a c4c4 at #ae ,c4 showed the colour of #j4e c4c4 at #fj ,c4 #b #a4e at #fj ,c4 #c #e4j at #ej ,c4 ,effect of ,varying ,time4--,the colour becomes lighter on standing3 #b c4c4 on standing #aj1 #bj1 and #dj minutes became equal in colour to #a4g c4c4 ,effect of ,acids and ,ammonia4--,two c4c4 of the solution with #b c4c4 of dilute hydrochloric acid became cloudy and equivalent to about #b4e c4c42 and a similar result was got with #b c4c4 of dilute sulphuric acid4 ,with #b c4c4 of dilute ammonia the solution became somewhat darker1 or equal to #b4c c4c42 but gave a very clear solution easy to compare4 ,determination of ,lead in ,commercial ,zinc4--,dissolve #j4a gram of the metal in #a c4c4 of dilute nitric acid evaporates till a solid separates out1 dilute to #ajj c4c4 with water1 and take #bj c4c4 for assay4 ,a sample treated in this way required #b4d c4c42 this multiplied by #e gives #ab4j c4c41 equivalent to #a4b milligram of lead1 or #a4b per cent4 ,by gravimetric assay the sample gave #a4aj per cent4 ,,practical ,,exercises4 #a4 ,thirty grams of galena gave on dry assay #ba grams of lead2 and this1 on cupellation1 gave #ae milligrams of silver4 ,calculate the results in per cents4 of lead and in ounces of silver to the ton of ore4 #b4 ,how many ounces of silver to the ton would be contained in the lead got from this ore if the loss in smelting is equal to that of the assay8 #c4 ,having given you a sample of white lead freed from oil by washing with ether1 how would you proceed to determine the percentage of lead in it8 ,,thallium4 ,thallium is a rare metal1 found in small quantities in some varieties of iron and copper pyrites1 and in some lithia micas4 ,it resembles lead in appearance4 ,its compounds resemble the salts of the alkalies in some respects2 and1 in others1 those of the heavy metals4 ,it is detected by the green colour which its salts impart to the flame4 ,this1 when examined with the spectroscope1 shows only one bright green line4 ,it is separated and estimated by dissolving in aqua regia2 converting into sulphate by evaporation with sulphuric acid2 separating the second group of metals with sulphuretted hydrogen in the acid solution1 boiling off the excess of the gas2 nearly neutralising with carbonate of soda2 and precipitating the thallium with an excess of potassic iodide4 ,on allowing the liquid to stand for some time a bright yellow precipitate of thallous iodide separates out4 ,this is collected on a weighed filter2 washed with cold water1 finishing off with alcohol2 dried at #ajj ,c41 and weighed4 ,the precipitate is thallous iodide ,tl,i1 and contains #fa4f per cent4 of thallium4 ,,bismuth4 ,bismuth is nearly always found in nature in the metallic state2 but occasionally it is met with as sulphide in bismuthine and as carbonate in bismutite4 ,it is also found in some comparatively rare minerals1 such as tetradymite1 combined with tellurium1 and associated with gold4 ,in minute quantities it is widely distributed3 it is a common constituent of most copper ores2 hence it finds its way into refined copper1 which is seldom free from it4 ,it is occasionally met with in silver in sufficient quantity to interfere with the working qualities of that metal4 ,bismuth compounds are used in medicine and in the manufacture of alloys4 ,bismuth possesses many useful properties4 ,it has considerable commercial value1 and sells at a high price4 ,the metal is brittle1 breaks with a highly crystalline fracture1 and has a characteristic reddish-yellow colour4 ,it is almost insoluble in hydrochloric1 but readily dissolves in nitric1 acid2 and gives1 if the acid is in excess1 a clear solution4 ,bismuth salts have a strong tendency to separate out as insoluble basic compounds2 this is more especially true of the chloride which1 on diluting with a large volume of water1 becomes milky2 the whole of the bismuth separating out4 ,the nitrate1 carbonate1 and hydrate yield the oxide 7,bi#b,o#c7 on ignition4 ,this oxide closely resembles litharge4 ,it combines with silica1 forming fluid slags2 and at a red heat is liquid enough to be absorbed by a cupel2 in fact1 bismuth may take the place of lead in cupellation4 ,the metal itself is easily fusible1 and may be separated from its ores by liquation4 ,the assay of bismuth by wet methods presents little difficulty1 and is fairly accurate4 ,the price of the metal is such that only methods which yield good results should be adopted2 and1 since bismuth is volatile at the temperature of the furnace1 and is found mixed with ores not easy to flux1 as also with metals which are not easily separated by the dry method1 the dry assay can only be considered as having a qualitative value4 ,,dry ,,assay4 ,by ,liquation4--,this is adapted to ores containing the bismuth as metal4 ,take #bj grams of the powdered ore and place in a crucible with a perforated bottom1 put this crucible into another of about the same size and lute the joint4 ,lute on a cover1 place in the furnace and heat to redness4 ,the bismuth melts readily and drains into the lower crucible from which1 when cold1 it is taken and weighed4 ,by ,fusion4--,for fairly pure ores the process is as follows3--,take #bj grams of the ore and mix with #bj grams of fusion mixture1 #aj grams of salt and #e or #aj grams of potassium cyanide2 place in a crucible1 cover1 and fuse at a moderate temperature for about fifteen minutes2 pour2 when cold detach the metal and weigh4 ,for coppery ores in which the metals are present as sulphides use the fluxes just given with #b grams of charcoal 7instead of the cyanide7 and a little sulphur4 ,for coppery ores in which the metals are present as oxides1 mix #bj grams of the ore with #aj grams of fusion mixture1 #d grams of salt1 #d grams of sulphur and #b grams of charcoal2 and fuse4 ,a considerable percentage of bismuth is lost in these assays2 it is stated as being nearly #h per cent4 of the metal present4 ,,wet ,,methods4 ,detection4--,bismuth is detected by dissolving the substance in nitric or hydrochloric acid and precipitating the diluted solution with sulphuretted hydrogen4 ,the precipitated sulphides1 after digesting with soda and washing1 are dissolved in nitric acid and the solution boiled with ammonium carbonate4 ,the precipitate is washed and then warmed with dilute sulphuric acid4 ,the solution will contain the bismuth4 ,add a solution of potassium iodide in excess1 and boil2 a yellow or dark brown solution proves that bismuth is present4 ,another good test for small quantities of bismuth is to add tartaric acid to the solution to be tested1 and then to make it alkaline with potash4 ,add a few c4c4 of ,schneider's liquid1#fa and heat4 ,a brownish-black colour is produced by as little as one part of bismuth in #bjj1jjj of solution4 ,the test is not applicable in the presence of mercury1 copper1 or manganese4 ,compounds of bismuth fused with cyanide of potassium in a ,berlin crucible readily give a globule of bismuth which is recognised by its appearance and fracture4 ,solution and ,separation4--,the solution of bismuth compounds presents no difficulty4 ,they are soluble in nitric acid or aqua regia1 and1 provided the solution is sufficiently acid1 they remain dissolved4 ,in separating it from other metals the solution is made up to about #ajj c4c4 and treated with a current of sulphuretted hydrogen4 ,the bismuth comes down in a tolerably strong acid solution4 ,the sulphide is decanted on to a filter and washed4 ,it is next digested with ammonic sulphide2 or1 better 7especially when other metals are present71 dissolved in nitric acid1 and treated with an excess of ammonia and a current of sulphuretted hydrogen4 ,the precipitate is filtered off and evaporated to dryness with nitric acid4 ,it is taken up with a few drops of sulphuric acid and a little water2 and warmed and filtered1 if necessary4 ,the filtrate is nearly neutralised with ammonia2 ammonium carbonate added in slight excess2 and the liquid heated to boiling and filtered4 ,the bismuth will be contained in the precipitate with perhaps traces of lead1 antimony1 tin1 or sometimes iron from incomplete separation or washing4 ,when only traces of a precipitate are got it must be tested4 ,the bismuth precipitate is readily soluble in dilute nitric acid4 ,,gravimetric ,,determination4 ,the bismuth having been separated and dissolved in nitric acid#fb is precipitated 7after dilution7 by the addition of carbonate of ammonium in slight excess1 and boiling4 ,the precipitate is filtered off1 washed with hot water1 dried1 ignited1 and weighed4 ,the ignition should be performed carefully at not above a low red heat4 ,the oxide which is formed has1 at this temperature1 a dark yellow or brown colour1 and becomes yellow on cooling4 ,it is bismuthic oxide 7,bi#b,o#c7 and contains #hi4fe per cent4 of bismuth4 ,fusion with potassium cyanide at a temperature just sufficient to melt the salt reduces it to the metal which falls to the bottom and runs into a globule4 ,the button of metal may be weighed1 but it often sticks tenaciously to the bottom of the crucible4 ,the precipitation with ammonic carbonate must not be made in a sulphate or chloride solution2 since basic compounds would then be thrown down1 and the result on weighing would either be too low 7because of the volatilisation of the chloride71 or too high 7because of the retention of sulphuric acid74 ,bismuth compounds in a nitric acid solution are readily decomposed by the electric current1 but the deposited bismuth is not coherent4 ,it comes down in shaggy tufts which are difficult to wash and easy to oxidise4 ,,volumetric ,,assay4 ,there are two methods which have been proposed2 one based on the precipitation as chromate and the estimation of the chromic acid2 and the other on the precipitation as oxalate and subsequent titration with permanganate of potash4 ,these offer little advantage over the easy gravimetric determination4 ,,colorimetric ,,method4 ,bismuth iodide dissolves in excess of potassium iodide1 forming a yellow-coloured solution1 indistinguishable in colour from that given by iodine4 ,the colour1 however1 is not removed by boiling or by sulphurous acid4 ,since none of the commoner metals give such a colour1 and free iodine is easily separated by boiling1 this method is specially suited for small determinations of bismuth4 ,it requires a solution of bismuth1 made by dissolving #j4a gram of bismuth in a drop or so of nitric acid1 evaporating with a little sulphuric acid and diluting with water to #a litre4 #a c4c4 will contain #j4a milligram of bismuth4 ,and a solution of sulphurous acid1 made by diluting #aj c4c4 of the commercial acid to #a litre with water4 ,the determination is made in the usual way3 #ej c4c4 of the prepared solution1 which should not carry more than #j4ge milligram nor less than #j4ja milligram of bismuth1 are placed in a ,nessler tube and the colour compared with that observed in a similar tube containing water and potassium iodide on adding the standard solution of bismuth4 ,the assay solution is prepared by separating the bismuth with sulphuretted hydrogen1 boiling the precipitate with nitric acid1 and evaporating with sulphuric acid4 ,take up with water1 add #aj or #bj c4c4 of solution of potassium iodide1 boil off any iodine liberated1 dilute1 filter1 and make up to #ajj c4c4 ,according to the depth of colour take #aj1 #bj1 or #ej c4c4 and transfer to the ,nessler tube4 ,add a few c4c4 of the solution of sulphurous acid4 ,into the other ,nessler tube put as much potassium iodide solution as is contained in the assay tube1 with sulphurous acid and water to within a few c4c4 of the bulk4 ,then add the standard bismuth solution till the tints are equal4 ,the student must be careful not to confuse the colour of the bismuth iodide with that of free iodine4 ,if the yellow colour is removed by boiling and returns on standing it is due altogether to iodine2 if it is lessened by the addition of a few drops of the dilute sulphurous acid1 it is in part due to it4 ,hence the necessity of having a little free sulphurous acid in each tube4 ,a strong solution must not be used1 since it liberates iodine from potassium iodide4 ,the following experiments illustrate the effect of variation in the conditions of the assay3-- ,effect of ,varying ,temperature4--,at a higher temperature the colour is somewhat lessened4 #a4j c4c4 at #ae ,c4 showed the colour of #j4h c4c4 at #gj ,c4 #b4e #b4j #e4j #e4j ,effect of ,free ,acid4-- #b4e c4c4 with #e c4c4 of nitric acid equalled #b4e c4c4 #e4j sulphuric acid #e4j ,hydrochloric acid almost completely removes the colour1 which1 however1 is restored by the addition of a few crystals of potassium iodide4 ,effect of ,alkalies4--,ammonia1 soda1 or potash destroys the colour1 but it is restored on acidifying with nitric or sulphuric acid4 ,effect of ,ammonic ,salts4--,the following table shows the results after addition of ammonic salts3-- ---------------------------------------- ----------------------- ,c4c4 present4,with #aj grams ,with #aj grams ,with #aj grams ,ammonic ,nitrate4,ammonic ,sulphate4,ammonic ,chloride4 ---------------------------------------- ----------------------- #a4j c4c4 #j4i c4c4 #a4a c4c4 -- #b4e #b4e #b4g -- #e4j #e4j #e4e -- ---------------------------------------- ----------------------- ,ammonic chloride1 like hydrochloric acid1 removes the colour1 which may be restored on the addition of more potassium iodide4 ,nitrates and sulphates do not thus interfere4 ,effect of ,foreign ,salts4--,sodic hyposulphite almost completely removes the colour4 ,copper salts liberate iodine2 but when this has been removed by boiling and the cuprous iodide has been filtered off there is no further interference4 ,dilute solutions of lead salts give no colour4 ,,practical ,,exercises4 #a4 ,a fusible alloy is made up of #h parts of bismuth1 #e of lead1 and #c of tin4 ,what weight of oxide of bismuth1 ,bi#b,o#c1 would you get on the analysis of #a gram of it8 #b4 ,what weight of bismuth can be got from #b grams of the subnitrate ,bi,o,n,o#c4;,h#b,o8 #c4 ,how would you detect and separate arsenic1 lead1 and copper in a sample of bismuth8 ,,antimony4 ,antimony occurs in the native state1 but is rare2 its common ore is antimonite1 the sulphide 7,sb#b,s#c74 ,jamesonite and other sulphides of lead and antimony are frequently met with4 ,sulphide of antimony is also a constituent of fahlerz and of many silver ores4 ,antimonite occurs generally in fibrous masses1 has a lead-like metallic lustre1 is easily cut with a knife1 and melts in the flame of a candle4 ,antimony itself has a very crystalline fracture1 is brittle1 and has a bluish-white colour4 ,it is used in the preparation of alloys with lead and tin for the manufacture of type-metal4 ,it is readily fusible1 and imparts hardness and the property of taking a sharp cast to its alloys4 ,it is practically insoluble in hydrochloric acid4 ,on boiling with strong nitric acid it is converted into antimonic oxide 7,sb#b,o#e71 which is a powder almost insoluble in this acid or in water1 but which may be got into solution with difficulty by the prolonged action of hydrochloric and tartaric acids4 ,antimonic oxide is converted on ignition into the tetroxide 7,sb#b,o#d7 with loss of oxygen4 ,antimony forms two series of salts1 antimonious and antimonic2 and advantage is taken of this in its determination volumetrically4 ,either sulphide of antimony yields antimonious chloride on boiling with hydrochloric acid1 sulphuretted hydrogen being given off2 and1 in the case of antimonic sulphide1 sulphur is deposited4 ,antimonious is converted into antimonic chloride by treatment with permanganate of potash in an acid solution4 ,antimonic chloride and potassium iodide react1 forming antimonious chloride and free iodine4 ,this latter may be got rid of by boiling4 ,sulphide of antimony is separated from the ore by liquation2 this regulus is met with in commerce as crude antimony4 ,,dry ,,assay4 ,an approximate determination of the amount of sulphide of antimony in an ore may be made by fusing and liquating in a luted double crucible in the manner described under bismuth4 ,this is unsatisfactory4 ,the determination of metallic antimony in an ore is made either by fusion with potassium cyanide or by fusion with iron1 as in the galena assay4 ,both methods yield poor results2 and1 where iron is used1 it must be added in quantity only sufficient for desulphurising2 this amounts to about #dj per cent4 in pure ores4 ,if the iron is in excess it alloys with the reduced antimony4 ,if1 on the other hand1 it is insufficient1 the metal will contain sulphur2 or sulphide of antimony will be lost in the slag4 ,the following note1 for which we are indebted to ,mr4 ,bedford ,mc,neill1 ,a4,r4,s4,m41 gives a description of the method adopted in the commercial valuation of a parcel of antimony ore3-- ,the antimony smelter1 when he wishes to determine the value of any parcel of ore--usually the sulphide--that may be offered for sale1 practically has recourse to the smelting operation4 ,that is1 a quantity of #b or #c cwts4 taken by his sampler having been obtained1 he treats it under the immediate supervision of the foreman smelter as if it formed part of the ore in process of daily reduction at his works4 ,he thus determines by actual trial the output which it may fairly be anticipated will be yielded by the bulk1 and upon the result of this trial or assay1 and the knowledge gained of the actual behaviour of the ore under treatment1 he bases his tender1 knowing that1 should he secure the parcel1 he may confidently expect a similar return4 ,briefly1 the process consists of the three ordinary operations of-- 7a7 ,singling or removing most of the antimony from the ore2 7b7 ,doubling2 7c7 ,refining or starring4 ,but in the assay sufficient information is generally given by the first two of these4 ,a new pot having been taken and made hot in the furnace1 #dj or #de lbs4 of the ore is weighed in 7the mineral from the necessities of sampling not exceeding walnut size72 #a to #c lbs4 of salt cake is now added to render the separation of the resulting sulphide of iron more easy1 as also to assist in the fusion of the gangue2 #bj to #be lbs4 of tin-plate scrap1 beaten more or less into ball shape1 is weighed1 placed on the top of the ore and salt cake1 and the whole brought to a state of fusion4 ,the foreman from time to time takes notice of the behaviour of the ore under the working conditions4 ,ores that manifest a tendency to boil or froth require the admixture of other more sluggish mineral in order to render their reduction economically practicable4 ,after #a-a_/d to #a-a_/b hours 7the time depending mainly on the temperature71 the contents of the crucible are usually in a state of tranquil fusion4 ,the pot is now lifted from the fire1 and its contents transferred to a conical iron mould1 the empty pot being immediately put back into the fire1 and the latter mended with sufficient coke for another run4 ,the conical mould 7when dealing with a strange ore1 and the possibility of insufficient iron being present to satisfy the sulphur contents7 is wiped inside with clay previous to pouring in the molten charge4 ,otherwise the mould itself will be attacked1 and the contents after solidifying will require to be chiselled out piecemeal4 ,a further #dj lbs4 of the ore is now charged into the crucible with iron as above2 but before this second charge is ready to be drawn an inspection of the first may suggest the addition of either #c or #e lbs4 more iron1 or #e or #aj lbs4 more ore4 ,it is a good fault rather to aim at an excess of iron as tending to clean the ore from antimony1 any of the latter that 7from an insufficiency of iron7 may be left in the slag from the first process being irretrievably lost2 whereas1 if the iron be in excess1 that which is combined with the crude antimony resulting from the first process is easily got rid of by adding #c to #e lbs4 or so of ore in the second process4 ,this latter1 as practised for the determination of the value of a parcel of ore1 consists in selecting two of the best quality singles1 resulting from perhaps four or five trials as above1 and running them down with a few pounds of salt cake1 or a mixture of salt cake with ,american potash1 and 7as is generally necessary7 a small addition of ore4 ,upon the final result 7confirmed perhaps on another pair of singles1 and1 judging from the total weight or output of the metal as calculated from the ore used in singling1 plus any added in the doubling1 the crystalline fracture and face of the metal1 its colour1 etc47 the price to be offered for the parcel of ore is fixed4 ,,wet ,,methods4 ,detection4--,the antimony1 if any1 being got into solution by treating the ore with hydrochloric acid or aqua regia may be detected by evaporating with hydrochloric acid1 diluting1 and filtering into the cover of a platinum crucible or 7better7 a platinum dish4 ,a small lump of zinc is then added1 and1 if antimony is present1 the dish will in a minute or so be stained black with a deposit of metallic antimony4 ,this stain is removed by nitric1 but not by hydrochloric1 acid4 ,the reaction is delicate and characteristic2 arsenic under like conditions is evolved as arseniuretted hydrogen1 and tin is deposited as metal on the zinc4 ,solution4--,ores1 c41 containing antimony are best opened up by boiling with hydrochloric acid or aqua regia2 treatment with nitric acid should be avoided wherever possible1 since it forms antimonic acid1 which is subsequently dissolved only with difficulty4 ,salts of antimony in solution have a tendency to form insoluble basic salts2 so that care must be exercised in diluting4 ,compounds such as antimonite which are soluble in hydrochloric should be dissolved at once in that acid4 ,separation4--,to the solution add potash in excess and a little free sulphur1 and pass a current of sulphuretted hydrogen for some minutes2 allow to digest for an hour or so on a hot plate2 filter2 and wash the residue4 ,acidulate the filtrate with hydrochloric acid3 the precipitate will contain the antimony 7as ,sb#b,s#e71 and possibly arsenic or tin4 ,the precipitate is transferred to a beaker and boiled with hydrochloric acid2 the solution is filtered off and diluted4 ,add a few crystals of tartaric acid1 and pass a current of sulphuretted hydrogen for some time4 ,the first flocculent precipitate will become denser1 and render the filtering more easy4 ,transfer the precipitate 7after washing free from chlorides7 to a ,berlin dish1 and treat cautiously with fuming nitric acid4 ,the action of this acid on the sulphide is very violent4 ,evaporate and ignite1 transfer to a silver dish1 and fuse with four or five times its weight of caustic soda1 cool and extract with a little water1 then add an equal volume of alcohol1 and allow to stand overnight4 ,filter1 wash with dilute alcohol4 7,the filtrate will contain the tin47 ,the residue contains the antimony as antimonate of soda1 and is dissolved off the filter with hot dilute hydrochloric1 with the help of a little tartaric1 acid4 ,the filtrate is now ready for the gravimetric determination4 ,,gravimetric ,,assay4 ,pass a current of sulphuretted hydrogen through the solution containing the antimony to which a little tartaric acid has been previously added4 ,pass the gas till the precipitate becomes dense1 and the antimony is all down4 ,the solution must not be too strongly acid4 ,filter off the precipitate1 wash with hot water1 dry in the water oven1 transfer to a weighed porcelain dish1 and cautiously treat with fuming nitric acid4 ,continue the action on the water bath till the sulphur and antimony are completely oxidised4 ,evaporate2 ignite1 gently at first1 then strongly over the blast2 cool1 and weigh4 ,the residue is a white infusible powder1 and consists of antimony tetroxide1 ,sb#b,o#d1 containing #gh4id per cent4 of the metal4 ,determination of ,antimony as ,bigallate4--,what appears to be a very good method has been worked out by ,m4,a4 ,guyard1 and is described in ,crookes' ,select ,methods1 p4 #cih4 ,the antimony must be in solution as antimonious chloride1 and must not be accompanied by an excess of hydrochloric acid4 ,to ensure these conditions1 the solution is treated with potassium iodide until no more iodine is evolved1 and is then evaporated to remove the excess of hydrochloric acid4 ,to the concentrated1 and nearly neutral1 solution a freshly-prepared solution of gallic acid is added in slight excess4 ,a bulky white precipitate is formed that settles rapidly4 ,the solution is diluted with hot water and washed by decantation4 ,then the precipitate is collected on a weighed double filter1 washed once or twice with hot water1 and dried at #ajj ,c4 ,the dried substance is antimony bigallate1 and contains #dj4he per cent4 of antimony4 ,it should be completely soluble in ammonium sulphide4 ,the solution in which the antimony is precipitated need not be quite free from other metals4 ,,volumetric ,,method4 ,this is based on the reduction of antimonic chloride 7,sb,cl#e7 to antimonious 7,sb,cl#c7 by the action of potassium iodide in strong hydrochloric acid solution4#fc ,iodine is at the same time liberated1 and the amount of antimony reduced is got at by titrating with sodium hyposulphite1 which measures the iodine set free4 ,the standard solution of sodium hyposulphite is made by dissolving #da4cb grams of the salt 7,na#b,s#b,o#c4e;,h#b,o7 in water1 and diluting to #a litre4 ,one hundred c4c4 will be equivalent to about #a gram of antimony4 ,it is standardised with the help of a solution of antimony made as follows3--,weigh up #e grams of powdered antimony1 transfer to a flask1 and cover with #ej c4c4 of hydrochloric acid2 boil1 and add nitric acid 7#e or #aj drops at a time7 until the metal is dissolved4 ,allow the action of the nitric acid to cease before adding more4 ,boil down to a small bulk1 add #bej c4c4 of hydrochloric acid1 and dilute to nearly #a litre4 ,warm until any precipitate which has formed is redissolved2 allow to cool slowly1 and run in from a pipette a weak solution of permanganate until a faint brown colour is produced4 ,dilute to exactly #a litre2 #ajj c4c4 contain #j4e gram of antimony as antimonic chloride4 ,in standardising1 take #ej c4c4 of the antimony solution1 and transfer to a flask2 add #b grams of potassium iodide crystals1 and when dissolved1 after standing a few minutes1 run in the solution of hypo from an ordinary burette until the greater part of the iodine has been reduced4 ,add a few drops of starch solution1 and continue the addition of the hypo until the muddy-green colour changes to a clear brownish-yellow4 ,the solution must be shaken after each addition of the hypo4 ,in determining antimony in ore1 weigh up #j4e to #a gram1 and dissolve in hydrochloric acid with1 if necessary1 the help of chlorate of potash4 ,the antimony is separated as sulphide1 redissolved in hydrochloric acid1 and oxidised with a crystal of chlorate of potash4 ,chlorine is boiled off1 and the solution diluted with an equal bulk of water4 ,to the clear cold solution potassium iodide is added1 and after a few minutes the liberated iodine is titrated with hypo1 as already described4 ,the method only yields satisfactory results when the standard and assay are carried out alike4 ,,footnotes3 #ej ,modern ,american ,methods of ,copper ,smelting 7,dr4 ,peters74 #ea ,journal of the ,society of ,chemical ,industry1 vol4 v4 ,no4 #b4 #eb ,lead when present is precipitated on the spiral in the form of a dark powder of dioxide 7,pb,o#b74 ,manganese is also thrown down on the spiral as dioxide 7,mn,o#b71 the solution at the same time becomes violet from the formation of permanganic acid4 #ec ,see the method given under ,examination of ,commercial ,copper4 #ed ,cu,s,o#d #d,k,cy #b,k,cy4,cu,cy#b ,k#b,,so#d4 #ee #b;,cu,s,o#d #c,k,cy ,am#b,o ,cu#b;,cy#b ,am#b,,so7#d7 ,k#b,,so#d ,k,cy,o4 #ef #b;,cu,s,o#d #d,,ki ,cn#b;,i#b #b;,i #b,k#b,,so#d4 #eg #b,na#b,s#b,o#c #b;,i #b,na,i ,na#b,s#d,o#f4 #eh ,for further information1 see ,appendix ,b41 and a paper by ,j4,w4 ,westmoreland1 ,journal of the ,society of ,chemical ,industry1 vol4 v4 p4 #dh4 #ei #c;,cu#b,o #f;,ag,n,o#c #c;,h#b,o #b;,cu#b;,h#c,o#c,,no#c #b;,cu7,,no#c7b #f;,ag4 7,insoluble basic salt47 #fj ,k#b;,cr,o#d ,pb7,,no#c7b ,pb,cr,o#d #b,,kno#c #fa ,made by dissolving #ab grams of tartaric acid and #d grams of stannous chloride in water1 and adding potash solution till it is alkaline4 ,the solution should remain clear on heating to #fj or #gj ,c4 #fb ,it must be remembered that arsenate of bismuth is completely insoluble in this acid4 #fc ,sb,cl#e #b,,ki ,i#b ,sb,cl#c #b,k,cl4 ,,chapter ,,xi4 ,,iron--,,nickel--,,cobalt--,,zinc--,,ca dmium4 ,,iron4 ,iron rusts or oxidises very readily1 and1 consequently1 is rarely found in the metallic state in nature2 such native iron as is found being generally of meteoric origin or imbedded in basalt and other igneous rocks4 ,it chiefly occurs as oxide1 as in magnetite1 hmatite1 and in the brown iron ores and ochres4 ,chalybite1 which is carbonate of iron1 is an ore of great importance4 ,iron is found combined with sulphur in pyrrhotine and pyrites1 and together with arsenic in mispickel4 ,it is a common constituent of most rocks1 imparting to them a green1 black1 or brown colour2 and is present1 either as an essential part or as an impurity1 in most substances4 ,the chemistry of iron is somewhat complicated by the existence of two oxides1 each of which gives rise to a well-marked series of compounds4 ,those derived from the lower oxide1 known as ferrous salts1 are generally pale and greenish4 ,ferric salts are derived from the higher oxide1 and are generally red1 brown1 or yellow4 ,the existence of these two well-marked families of salts renders the assay of iron comparatively easy1 for the quantity of iron present in a solution can be readily measured by the amount of oxidising or reducing agent required to convert it from the one state into the other--that is1 from ferrous to ferric1 or from ferric to ferrous1 as the case may be4 ,in the red and brown iron ores and ochres ferric iron is present2 in chalybite the iron is in the ferrous state2 and in magnetite it is present in both forms4 ,traces of iron in the ferrous state may be found 7even in the presence of much ferric iron7 by either of the following tests3-- #a4 ,ferricyanide of potassium gives a blue precipitate or green coloration2 with ferric salts a brown colour only is produced4 #b4 ,a solution of permanganate of potassium is decolorised by a ferrous salt1 but not by a ferric one4 ,traces of ferric iron can be detected 7even in the presence of much ferrous iron7 by the following tests3-- 7#a7 ,by the brown or yellow colour of the solution1 especially when hot4 7#b7 ,by giving a pink or red coloration with sulphocyanide of potassium4 ,substances containing oxide of iron yield the whole of the iron as metal when fused at a high temperature with charcoal and suitable fluxes4 ,the metal1 however1 will contain varying proportions of carbon and other impurities1 and its weight can only afford a rough knowledge of the proportion of the metal in the ore4 ,there are two or three methods of dry assay for iron1 but they are not only inexact1 but more troublesome than the wet methods1 and need not be further considered4 ,chalybite and the hydrated oxides dissolve very readily in hydrochloric acid2 hmatite and magnetite dissolve with rather more difficulty4 ,iron itself1 when soft1 is easily soluble in dilute hydrochloric1 or sulphuric1 acid4 ,pyrites1 mispickel1 c41 are insoluble in hydrochloric acid1 but they are readily attacked by nitric acid4 ,certain minerals1 such as chrome iron ore1 titaniferous iron ore1 and some silicates containing iron1 remain in the residue insoluble in acids4 ,some of these yield their iron when attacked with strong sulphuric acid1 or when fused with the acid sulphate of potash4 ,generally1 however1 it is better in such stubborn cases to fuse with carbonate of soda1 and then attack the melt with hydrochloric acid4 ,when nitric acid1 or the fusion method1 has been used1 the metal will be in solution in the ferric state1 no matter in what condition it existed in the ore4 ,but with dilute hydrochloric or sulphuric acid it will retain its former degree of oxidation4 ,hydrochloric acid1 for example1 with chalybite 7ferrous carbonate7 will give a solution of ferrous chloride2 with hmatite 7ferric oxide7 it will yield ferric chloride2 and with magnetite 7ferrous and ferric oxides7 a mixture of ferrous and ferric chlorides4 ,metallic iron yields solutions of ferrous salts4 ,it is convenient to speak of the iron in a ferrous salt as ferrous iron1 and when in the ferric state as ferric iron4 ,frequently it is required to determine how much of the iron exists in an ore in each condition4 ,in such cases it is necessary to keep off the air whilst dissolving2 the operation should1 therefore1 be performed in an atmosphere of carbonic acid4 ,separation4--,the separation of the iron from the other substances is as follows3--,silica is removed by evaporating the acid solution1 and taking up with acid1 as described under ,silica2 the whole of the iron will be in solution4 ,the metals of ,groups ,i4 and ,,ii4 are removed by passing sulphuretted hydrogen1 and at the same time the iron will be reduced to the ferrous state4 ,the solution should be filtered into a #af oz4 flask1 boiled to get rid of the gas1 and treated 7whilst boiling7 with a few drops of nitric acid1 in order to convert the whole of the iron into the ferric state4 ,when this condition is arrived at1 an additional drop of nitric acid causes no dark coloration4 ,the boiling must be continued to remove nitrous fumes4 ,next add caustic soda solution until the colour of the solution changes from yellow to red4 ,the solution must be free from a precipitate2 if the soda be incautiously added a permanent precipitate will be formed1 in which case it must be redissolved with hydrochloric acid1 and soda again1 but more cautiously1 added4 ,after cooling1 a solution of sodium acetate is added until the colour of the solution is no longer darkened4 ,the solution1 diluted to two-thirds of the flaskful with water1 is heated to boiling4 ,long-continued boiling must be avoided4 ,the precipitate is filtered quickly through a large filter1 and washed with hot water containing a little acetate of soda4 ,the precipitate will contain all the iron and may also contain alumina1 chromium1 titanium1 as well as phosphoric1 and1 perhaps1 arsenic acids4#fd ,dissolve the precipitate off the filter with dilute sulphuric acid1 avoiding excess1 add tartaric acid and then ammonia in excess4 ,pass sulphuretted hydrogen1 warm1 and allow the precipitate to settle4 ,filter and wash with water containing a little ammonic sulphide4 ,,gravimetric ,,method4 ,dissolve the precipitate in dilute hydrochloric acid2 peroxidise with a few drops of nitric acid and boil1 dilute to about #bjj c4c41 add ammonia 7with constant stirring7 till the liquid smells of it1 and heat to boiling4 ,wash as much as possible by decantation with hot water4 ,transfer to the filter1 and wash till the filtrate gives no indication of soluble salts coming through4 ,the filtrate must be colourless and clear4 ,the wet precipitate is very bulky1 of a dark-brown colour and readily soluble in dilute acids1 but insoluble in ammonia and dilute alkalies4 ,when thrown down from a solution containing other metals it is very apt to carry portions of these with it1 even when they are by themselves very soluble in ammoniacal solutions4 ,it must be dried and ignited1 the filter paper being burnt separately and its ash added4 ,when further ignition ceases to cause a loss of weight1 the residue is ferric oxide 7,fe#b,o#c71 which contains #gj per cent4 of iron4 ,the weight of iron therefore can be calculated by multiplying the weight of oxide obtained by #j4g4 ,the presence of ammonic chloride causes loss of iron during the ignition1 and organic matter causes an apparent loss by reducing the iron to a lower state of oxidation4 ,when the iron in the solution much exceeds #j4b gram the volumetric determination is generally adopted1 as the bulkiness of the precipitate of ferric hydrate makes the gravimetric method very inconvenient4 ,,volumetric ,,methods4 ,as already explained these are based on the measurement of the volume of a reagent required to bring the whole of the iron from the ferrous to the ferric state 7oxidation71 or from the ferric to the ferrous 7reduction74 ,ferrous compounds are converted into ferric by the action of an oxidising agent in the presence of an acid4 ,either permanganate or bichromate of potash is generally used for this purpose4#fe ,ferric compounds are reduced to ferrous by the action of3-- 7#a7 ,stannous chloride2 7#b7 ,sulphuretted hydrogen2 7#c7 ,sodium sulphite2 or 7#d7 ,zinc4#ff ,the processes1 then1 may be divided into two kinds1 one based on oxidation and the other on reduction4 ,in each case the titration must be preceded by an exact preparation of the solution to be assayed in order that the iron may be in the right state of oxidation4 ,,permanganate ,,and ,,bichromate ,,methods4 ,these consist of three operations3-- 7#a7 ,solution of the ore2 7#b7 ,reduction of the iron to the ferrous state2 and 7#c7 ,titration4 ,solution4--,the only point to be noticed concerning the first operation 7in addition to those already mentioned7 is that nitric acid must be absent4 ,if nitric acid has been used1 evaporate to dryness1 of course without previous dilution2 add hydrochloric or sulphuric acid1 and boil for five or ten minutes4 ,dilute with water to about #ajj c4c41 and warm until solution is complete4 ,the reduction is performed by either of the following methods3-- #a4 ,with ,stannous ,chloride4--,fill a burette with a solution of stannous chloride1#fg and cautiously run the liquid into the hot assay solution 7in which the iron is present as chloride7 until the colour is discharged4 ,a large excess of the stannous chloride must be avoided4 ,then add #e c4c4 of a #b-a_/b per cent4 solution of mercuric chloride1 this will cause a white precipitate 7or a grey one if too large an excess of the stannous chloride has been added74 ,boil till the solution clears1 cool1 dilute1 and titrate4 #b4 ,with ,sulphuretted ,hydrogen4--,cool the solution and pass through it a current of washed sulphuretted hydrogen till the liquid smells strongly of the gas after withdrawal and shaking4 ,a white precipitate of sulphur will be formed1 this will not interfere with the subsequent titration provided it is precipitated in the cold4 ,if1 however1 the precipitate is coloured 7showing the presence of the second group metals71 or if the precipitation has been carried out in a hot solution1 it should be filtered off4 ,boil the solution until the sulphuretted hydrogen is driven off2 this may be tested by holding a strip of filter paper dipped in lead acetate solution in the steam issuing from the flask4 ,the presence of sulphuretted hydrogen should be looked for rather than its absence4 ,it is well to continue the boiling for a few minutes after the gas has been driven off4 ,cool and titrate4 #c4 ,with ,sodium ,sulphite4--,add ammonia 7a few drops at a time7 until the precipitate first formed redissolves with difficulty4 ,if a permanent precipitate is formed1 redissolve with a few drops of acid4 ,to the warm solution add from #b to #c grams of sodium sulphite crystals4 ,the solution will become strongly coloured1 but the colour will fade away on standing for a few minutes in a warm place4 ,when the colour is quite removed1 add #bj c4c4 of dilute sulphuric acid1 and boil until the steam is quite free from the odour of sulphurous acid4 ,cool and titrate4 #d4 ,with ,zinc4--,add about #aj grams of granulated zinc2 if the hydrogen comes off violently add water2 if1 on the other hand1 the action is very slow1 add sufficient dilute sulphuric acid to keep up a brisk effervescence4 ,the reduction is hastened by warming1 and is complete when the solution is quite colourless and a drop of the liquid tested with sulphocyanate of potassium gives no reaction for ferric iron4 ,filter through glass wool or quick filtering paper4 ,the zinc should be still giving off gas rapidly1 indicating a freely acid solution2 if not1 acid must be added4 ,wash with water rendered acid4 ,cool and titrate4 ,with regard to the relative advantages of the different methods they may be roughly summed up as follows3--,the stannous chloride method has the advantage of immediately reducing the ferric iron whether in hot or cold solution and under varied conditions in regard to acidity1 but has the disadvantage of similarly reducing salts of copper and antimony1 which1 in a subsequent titration1 count as iron4 ,moreover1 there is no convenient method of eliminating any large excess of the reagent that may have been used2 and1 consequently1 it either leaves too much to the judgment of the operator1 or entails as much care as a titration4 ,students generally get good results by this method4 ,the sulphuretted hydrogen method also has the advantage of quick reduction under varying conditions1 and the further one of adding nothing objectionable to the solution2 in fact it removes certain impurities4 ,the disadvantages are the necessity for boiling off the excess of the gas1 and of filtering off the precipitated sulphur1 although this last is not necessary if precipitated cold4 ,the tendency with students is to get high results4 ,the sodium sulphite method has the advantages of being clean and neat1 and of requiring no nitration4 ,on the other hand it requires practice in obtaining the best conditions for complete reduction2 and1 as with sulphuretted hydrogen1 there is the necessity for boiling off the gas1 while there is no simple and delicate test for the residual sulphurous acid4 ,in addition1 if an excess of sodium sulphite has been used and enough acid not subsequently added1 the excess will count as iron4 ,students generally get low results by this method4 ,the advantages of the zinc method are1 that it is easily worked and that the excess of zinc is readily removed by simply filtering4 ,the disadvantages are the slowness#fh with which the last portions of ferric iron are reduced1 the danger of loss by effervescence1 the precipitation of basic salts1 and1 perhaps1 of iron1 and the loading of the solution with salts of zinc1 which in the titration with bichromate have a prejudicial effect4 ,the tendency in the hands of students is to get variable results1 sometimes low and sometimes high4 ,generally speaking1 the sulphuretted hydrogen and sodium sulphite methods are to be preferred4 ,carefully worked each method will yield good results4 ,the titration may be done with a standard solution of 7#a7 permanganate of potash1 or 7#b7 bichromate of potash4 #a4 ,with ,permanganate of ,potash4--,prepare a standard solution by dissolving #b4hb grams of the salt and diluting to one litre4 ,the strength of this should be #ajj c4c4 #j4e gram of iron1 but it varies slightly1 and should be determined 7and afterwards checked every two or three weeks7 by weighing up #j4b gram of iron wire1 dissolving in #aj c4c4 of dilute sulphuric acid1 diluting to about #ajj c4c41 and titrating4 ,the standard solution must be put in a burette with a glass stopcock1 as it attacks india-rubber4 ,the assay should be contained in a pint flask1 and be cooled before titrating4 ,the standard solution must be run in until a pinkish tinge permeates the whole solution2 this must be taken as the finishing point4 ,when certain interfering bodies are present this colour quickly fades1 but the fading must be ignored4 ,with pure solutions the colour is fairly permanent1 and a single drop of the potassium permanganate solution is sufficient to determine the finishing point4 #b4 ,with ,bichromate of ,potash4--,prepare a standard solution by dissolving #d4ci grams of the powdered and dried salt in water1 and diluting to #a litre4 ,this solution is permanent1 its strength is determined by dissolving #j4b gram of iron wire in #aj c4c4 of dilute sulphuric acid1 diluting to about a quarter of a litre1 and titrating4 ,also prepare a test solution by dissolving #j4a gram of ferricyanide of potassium in #ajj c4c4 of water4 ,this solution does not keep well and must be freshly prepared4 ,an ordinary burette is used4 ,the assay is best contained in a glazed earthenware dish1 and may be titrated hot or cold4 ,to determine the finishing point1 place a series of drops of the ferricyanide solution on a dry white glazed plate4 ,the drops should be of about the same size and be placed in lines at fairly equal distances4 ,the bichromate is run in1 in a steady stream1 the assay solution being continuously stirred until the reaction is sensibly slackened4 ,then bring a drop of the assay with the stirrer in contact with one of the test drops on the plate4 ,the standard can be safely run in #a c4c4 at a time1 so long as the test drop shows signs of a precipitate4 ,when only a coloration is produced run in cautiously a few drops at a time so long as two drops of the assay gives with the test a colour which is even faintly greener than two drops of the assay solution placed alongside4 ,the finishing point is decided and practically permanent1 although it demands a little practice to recognise it4 ,the titration with permanganate of potassium has the advantage of a more distinct finishing point and easier mode of working2 its application1 however1 is somewhat limited by the disturbing effects of hydrochloric acid4 ,the bichromate method has the advantage of a standard solution which does not alter in strength1 and the further one of being but little affected by altering conditions of assay4 ,hydrochloric acid has practically no effect on it4 ,both methods give accurate results and are good examples of volumetric methods4 ,the following results illustrate the extent to which the methods may be relied on2 and the influence which the various conditions of experiment have on the assay4 ,solutions of ferrous sulphate and of ferrous chloride were made containing #j4e gram of iron in each #ajj c4c41 thus corresponding to the standard solutions of permanganate and bichromate of potassium4 ,these last were prepared in the way already described4 ,the solution of ferrous sulphate was made by dissolving #e4ja grams of iron wire in #ajj c4c4 of dilute sulphuric acid and diluting to #a litre4 ,a similar solution may be made by dissolving #bd4hb grams of pure ferrous sulphate crystals in water1 adding #ajj c4c4 of dilute sulphuric acid1 and diluting to #a litre4 ,rate of ,oxidation by ,exposure to ,air4--,this is an important consideration1 and if the rate were at all rapid would have a serious influence on the manner of working1 since exclusion of air in the various operations would be troublesome4 #bj c4c4 of the solution of ferrous sulphate were taken in each experiment1 acidified with #aj c4c4 of dilute sulphuric acid1 and diluted to #ajj c4c4 ,the solution was exposed1 cold1 in an open beaker for varying lengths of time1 and titrated with permanganate of potassium4 ,time exposed #a hour #a day #b days #c days c4c4 required #ai4b #ai4a #ai4j #ai4j ,these results show that the atmospheric oxidation in cold solutions is unimportant4 ,with boiling solutions the results are somewhat different2 a solution which at the outset required #bj c4c4 of permanganate of potassium1 after boiling for an hour in an open beaker 7without any precautions to prevent oxidation71 water being added from time to time to replace that lost by evaporation1 required #ai4b c4c4 ,if the solution be evaporated to dryness the oxidising power of concentrated sulphuric acid comes into play1 so that very little ferrous iron will be left4 ,a solution evaporated in this way required only #b4b c4c4 of permanganate of potassium4 ,effect of ,varying ,temperature4--,in these experiments the bulk was in each case #ajj c4c41 and #aj c4c4 of dilute sulphuric acid were present4 ,the permanganate required by #a c4c4 of ferrous sulphate was1 at #ae #a4j c4c41 and at #gj #a4a c4c4 #aj #i4g #i4h #ajj #ig4g #if4h ,the lower result with the #ajj c4c4 may be due to oxidation from exposure4 ,effect of ,varying ,bulk4--,the following experiments show that considerable variations in bulk have no practical effect4 ,in each case #bj c4c4 of ferrous sulphate solution and #aj c4c4 of dilute acid were used4 ,bulk of assay #cj c4c4 #ajj c4c4 #ejj c4c4 #ajjj c4c4 ,permanganate required #bj4j #bj4j #bj4b #bj4e ,effect of ,free ,sulphuric ,acid4--,free acid is necessary for these assays2 if there is an insufficiency1 the assay solution1 instead of immediately decolorising the permanganate1 assumes a brown colour4 ,the addition of #aj c4c4 of dilute sulphuric acid suffices to meet requirements and keep the assay clear throughout4 ,the following experiments show that a considerable excess of acid may be used without in the least affecting the results4 ,in each case #bj c4c4 of ferrous sulphate were used4 ,dilute sulphuric acid #a4j c4c4 #e4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,permanganate required #ai4c #ai4c #ai4c #ai4c #ai4c #ai4c ,effect of ,foreign ,salts4--,when the assay has been reduced with zinc varying quantities of salts of this metal pass into solution1 the amount depending on the quantity of acid and iron present4 ,salts of sodium or ammonium may similarly be introduced4 ,it is essential to know by experiment that these salts do not exert any effect on the titration4 ,the following series of experiments show that as much as #ej grams of zinc sulphate may be present without interfering4 ,zinc sulphate present #j gram #a gram #aj grams #ej grams ,permanganate required #ai4c c4c4 #ai4c c4c4 #ai4c c4c4 #ai4c c4c4 ,magnesium1 sodium1 and ammonium salts1 are equally without effect4 ,ammonic sulphate present #j gram #a gram #aj grams ,permanganate required #ai4c c4c4 #ai4b c4c4 #ai4c c4c4 ,sodic sulphate present #j gram #a gram #aj grams ,permanganate required #ai4c c4c4 #ai4c c4c4 #ai4c c4c4 ,magnesic sulphate present #j gram #a gram #aj grams ,permanganate required #ai4c c4c4 #ai4c c4c4 #ai4c c4c4 ,effect of ,varying ,amounts of ,iron4--,it is important to know within what limits the quantity of iron in an assay may safely vary from that used in standardising4 ,in the following experiments the conditions as to bulk1 acidity1 and mode of working were the same as before3-- ,ferrous sulphate solution taken #a c4c4 #aj c4c4 #bj c4c4 #ej c4c4 #ajj c4c4 ,permanganate required #a4j #i4g #ai4f #dh4i #ig4g ,the ferrous sulphate solution is here a little weaker than that of the permanganate of potassium1 but the results show that the permanganate required is proportional to the iron present4 ,titrations in ,hydrochloric ,solutions4--,these are less satisfactory than those in sulphuric solutions1 since an excess of hydrochloric acid decomposes permanganate of potassium1 evolving chlorine1 and since the finishing point is indicated1 not by the persistence of the pink colour of the permanganate1 but by a brown coloration probably due to perchloride of manganese4 ,nevertheless1 if the solution contains only from #e to #aj per cent4 of free hydrochloric acid 7sp4 g4 #a4af7 the results are the same as those obtained in a sulphuric acid solution4 ,equal weights 7#j4a gram7 of the same iron wire required exactly the same quantity of the permanganate of potassium solution 7#bj c4c47 whether the iron was dissolved in dilute sulphuric or dilute hydrochloric acid4 ,the following series of experiments are on the same plan as those given above with sulphuric acid solutions4 ,a solution of ferrous chloride was made by dissolving #e4ja grams of iron wire in #ej c4c4 of dilute hydrochloric acid and diluting to #a litre4 ,the dilute hydrochloric acid was made by mixing equal volumes of the acid 7sp4 g4 #a4af7 and water4 ,rate of ,atmospheric ,oxidation4--#bj c4c4 of the ferrous chloride solution were acidified with #aj c4c4 of the dilute hydrochloric acid and diluted to #ajj c4c4 ,this solution was exposed cold in open beakers4 ,time exposed -- #a hour #a day #b days #c days ,permanganate required #ai4f c4c4 #ai4f c4c4 #ai4e c4c4 #ai4d c4c4 #ai4e c4c4 ,similar solutions boiled required1 before boiling1 #bj c4c42 after boiling for one hour1 replacing the water as it evaporated1 #ai4c c4c42 and after evaporation to a paste and redissolving1 #ag4j c4c4 ,effect of ,varying ,temperature4--,solutions similar to the last were titrated and gave the following results3-- ,temperature #ae #cj #ej #gj ,permanganate required #ai4h c4c4 #ai4f c4c4 #ai4e c4c4 #ai4d c4c4 ,effect of ,varying ,bulk4--,as before1 #bj c4c4 of the iron solution1 and #aj c4c4 of the dilute acid were diluted to the required volumes and titrated4 ,bulk #cj c4c4 #ajj c4c4 #ejj c4c4 #ajjj c4c4 ,permanganate required #bj4d #bj4c #bj4h #ba4e ,the variation due to difference in bulk here1 although only equal to an excess of #j4g milligram of iron for each #ajj c4c4 of dilution1 are about three times as great as those observed in a sulphuric acid solution4 ,effect of ,free ,hydrochloric ,acid4--,in these experiments #bj c4c4 of the ferrous chloride solution were used with varying quantities of acid1 the bulk of the assay in each case being #ajj c4c4 ,dilute acid present #e c4c4 #aj c4c4 #ej c4c4 #ajj c4c4 ,permanganate required #bj4b #bj4b #bj4e #ba4j ,the last had a very indistinct finishing point1 the brown coloration being very evanescent4 ,the effect of the acid is modified by the presence of alkaline and other sulphates1 but not by sulphuric acid4 ,repeating the last experiment we got-- ,without further addition #ba4j c4c4 ,with #ajj c4c4 of dilute sulphuric acid #bb4j #aj grams ammonic sulphate #bj4e #aj sodic sulphate #bj4j #aj magnesium sulphate #bj4d #aj manganese sulphate #bj4b ,the results with these salts1 in counteracting the interference of the acid1 however1 were not a complete success1 since the end-reactions were all indistinct1 with the exception1 perhaps1 of that with the manganese sulphate4 ,effect of ,varying ,amounts of ,iron4--,in these experiments the bulk of the assay was #ajj c4c41 and #aj c4c4 of acid were present4 ,ferrous chloride used #a c4c4 #aj c4c4 #bj c4c4 #ej c4c4 #ajj c4c4 ,permanganate required #a4a #aj4c #bj4c #ej4d #ajj4a ,in making himself familiar with the permanganate of potassium titration1 the student should practise by working out a series of experiments similar to the above1 varying his conditions one at a time so as to be certain of the cause of any variation in his results4 ,he may then proceed to experiment on the various methods of reduction4 ,a solution of ferric chloride is made by dissolving #e4ja grams of iron wire in #ej c4c4 of hydrochloric acid 7sp4 g4 #a4af71 and running from a burette nitric acid diluted with an equal volume of water into the boiling iron solution1 until the liquid changes from a black to a reddish-yellow4 ,about #d4e c4c4 of the nitric acid will be required1 and the finishing point is marked by a brisk effervescence4 ,the solution of iron should be contained in an evaporating dish1 and boiled briskly1 with constant stirring4 ,there should be no excess of nitric acid4 ,boil down to about half its bulk2 then cool1 and dilute to one litre with water4 ,twenty c4c4 of this solution diluted to #ajj c4c4 with water1 and acidified with #aj c4c4 of dilute hydrochloric acid1 should not decolorise any of the permanganate of potassium solution2 this shows the absence of ferrous salts4 ,and #bj c4c4 of the same solution1 boiled with #bj c4c4 of the ferrous sulphate solution1 should not decrease the quantity of permanganate required for the titration of the ferrous sulphate added4 ,in a series of experiments on the various methods of reduction1 the following results were got4 ,the modes of working were those already described4 7#a7 ,with ,stannous ,chloride4--,twenty c4c4 of the ferric chloride solution required1 after reduction with stannous chloride1 #bj c4c4 of permanganate4 ,fifty c4c4 of a solution of ferrous chloride1 which required on titration #di4h c4c4 of permanganate1 required for re-titration 7after subsequent reduction with stannous chloride7 #ej c4c4 of the permanganate solution4 7#b7 ,with ,sulphuretted ,hydrogen4--,two experiments with this gas1 using in each #bj c4c4 of the ferric chloride solution1 and #aj c4c4 of hydrochloric acid1 required 7after reduction7 #bj4b c4c4 and #bj4a c4c4 of permanganate4 ,repeating the experiments by passing the gas through a nearly boiling solution1 but in other respects working in the same way1 #ba4c c4c4 and #ba4f c4c4 of the permanganate solution were required4 ,the sulphur was not filtered off in any of these4 ,in another experiment1 in which #ej c4c4 of the ferrous sulphate solution were titrated with permanganate1 #dh c4c4 of the latter were required4 ,the titrated solution was next reduced with sulphuretted hydrogen1 brought to the same bulk as before1 and again titrated2 #dg4i c4c4 of the permanganate of potassium solution were required4 7#c7 ,with ,sodium ,sulphite4--,twenty c4c4 of the ferric chloride solution1 reduced with sodium sulphite1 required #ai4i c4c4 of permanganate4 ,in one experiment #ej c4c4 of the ferrous sulphate solution were titrated with permanganate2 #di4c c4c4 of the last-mentioned solution were required4 ,the titrated solution was reduced with sodium sulphite1 and again titrated2 it required #di4b c4c4 of the permanganate of potassium solution4 7#d7 ,with ,zinc4--,twenty c4c4 of the ferric chloride solution1 reduced with zinc and titrated1 required #bj4h c4c4 of permanganate4 ,fifty c4c4 of a solution of ferrous sulphate which required #di4g c4c4 of permanganate1 required for re-titration1 after reduction with zinc1 #di4g c4c4 ,the student should next practise the titration with bichromate1 which is more especially valuable in the estimation of hydrochloric acid solutions4 ,the following experiments are on the same plan as those already given4 ,in each experiment 7except when otherwise stated7 there were present #bj c4c4 of the ferrous chloride solution1 and #aj c4c4 of dilute hydrochloric acid1 and the bulk was #cjj c4c4 ,effect of ,varying ,temperature4--,the quantities of the bichromate of potassium solution required were as follows3-- ,temperature #ae #cj #gj #ajj ,bichromate required #bj4b c4c4 #bj4c c4c4 #bj4c c4c4 #bj4d c4c4 ,effect of ,varying ,bulk4-- ,bulk #ej c4c4 #ajj c4c4 #bjj c4c4 #ejj c4c4 #ajjj c4c4 ,bichromate required #bj4d #bj4d #bj4d #bj4e #bj4h ,effect of ,varying ,acid4--,in these1 variable quantities of dilute hydrochloric acid were used4 ,acid present #aj c4c4 #ej c4c4 #ajj c4c4 ,bichromate required #bj4c #bj4c #bj4b ,effect of ,foreign ,salts4--,the effect of the addition of #aj grams of crystallized zinc sulphate was to decrease the quantity of bichromate required from #bj4c c4c4 to #bj4a c4c41 but the colour produced with the test-drop was very slight at #ah4e c4c41 and with incautious work the finishing point might have been taken anywhere between these extremes4 ,zinc should not be used as a reducing agent preliminary to a bichromate titration4 ,ten grams of ammonic sulphate had the effect of rendering the finishing point faint for about #j4e c4c4 before the titration was finished1 but there was no doubt about the finishing point when allowed to stand for a minute4 ,the student should note that a titration is not completed if a colour is developed on standing for five or ten minutes4 ,ten grams of sodic sulphate had no effect2 #bj4c c4c4 were required4 ,effect of ,varying ,iron4--,the results are proportional1 as will be seen from the following details3-- ,ferrous chloride present #a4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,bichromate required #a4j #aj4b #bj4c #ea4j #ajb4c ,the student may now apply these titrations to actual assays of minerals4 ,the following examples will illustrate the mode of working and of calculating the results3-- ,determination of ,iron in ,chalybite4--,weigh up #a gram of the dry powdered ore1 and dissolve in #aj c4c4 of dilute sulphuric acid and an equal volume of water with the aid of heat4 ,avoid evaporating to dryness4 ,dilute and titrate4 ,the result will give the percentage of iron existing in the ore in the ferrous state4 ,some ferric iron may be present4 ,if it is wished to determine this also1 add 7in dissolving another portion7 #aj c4c4 of dilute hydrochloric acid to the sulphuric acid already ordered1 and reduce the resulting solution before titrating4 ,by dissolving and titrating 7without previous reduction7 one has a measure of the ferrous iron present2 by dissolving1 reducing1 and then titrating1 one can measure the total iron2 and as the iron exists in only two conditions1 the total iron1 less the ferrous iron1 is the measure of the ferric iron4 ,determination of ,iron in ,brown or ,red ,ores or ,magnetite4--,weigh up #j4e gram of the ore 7powdered and dried at #ajj ,c471 and dissolve in from #aj to #bj c4c4 of strong hydrochloric acid1 boiling until all is dissolved1 or until no coloured particles are left4 ,dilute1 reduce1 and titrate4 ,determination of ,iron in ,pyrites4--,weigh up #a gram of the dry powdered ore1 and place in a beaker4 ,cover with #aj c4c4 of strong sulphuric acid1 mix well by shaking1 and place on the hot plate without further handling for an hour or so until the action has ceased4 ,allow to cool1 and dilute to #ajj c4c4 ,warm until solution is complete4 ,reduce and titrate4 ,determination of ,iron in ,substances ,insoluble in ,acids4--,weigh up #a gram of the ore1 mix with #e or #f grams of carbonate of soda and #j4e gram of nitre by rubbing in a small mortar1 and transfer to a platinum crucible4 ,clean out the mortar by rubbing up another gram or so of soda1 and add this to the contents of the crucible as a cover4 ,fuse till tranquil4 ,cool4 ,extract with water4 ,if the ore carries much silica1 evaporate to dryness with hydrochloric acid to separate it4 ,re-dissolve in hydrochloric acid1 and separate the iron by precipitating with ammonia and filtering4 ,if only a small quantity of silica is present1 the aqueous extract of the melt must be filtered1 and the insoluble residue washed and dissolved in dilute hydrochloric acid4 ,reduce and titrate4 ,a convenient method of at once separating iron from a solution and reducing it1 is to add ammonia1 pass sulphuretted hydrogen through it1 filter1 and dissolve the precipitate in dilute sulphuric acid4 ,the solution1 when boiled free from sulphuretted hydrogen1 is ready for titrating4 ,,stannous ,,chloride ,,process4 ,the colour imparted to hot hydrochloric acid solutions by a trace of a ferric compound is so strong1 and the reducing action of stannous chloride is so rapid1 that a method of titration is based upon the quantity of a standard solution of stannous chloride required to completely decolorise a solution containing ferric iron4 ,this method is more especially adapted for the assay of liquors containing much ferric iron and of those oxidised ores which are completely soluble in hydrochloric acid4 ,it must be remembered1 however1 that it only measures the ferric iron present1 and when 7as is generally the case7 the total iron is wanted1 it is well to calcine the weighed portion of ore previous to solution in order to get the whole of the iron into the higher state of oxidation1 since many ores which are generally supposed to contain only ferric iron carry a considerable percentage of ferrous4 ,the stannous chloride solution is made by dissolving #bj grams of the commercial salt 7,sn,cl#b4b;,h#b,o7 in #ajj c4c4 of water with the help of #bj c4c4 of dilute hydrochloric acid1 and diluting to a litre4 ,the solution may be slightly opalescent1 but should show no signs of a precipitate4 ,the strength of this is about equivalent to #a gram of iron for each #ajj c4c4 of the solution1 but it is apt to lessen on standing1 taking up oxygen from the air1 forming stannic chloride4 ,a larger proportion of hydrochloric acid than is ordered above would remove the opalescence1 but at the same time increase this tendency to atmospheric oxidation1 as the following experiments show4 ,the stannous chloride solution 7#bj c4c47 was mixed with varying amounts of strong hydrochloric acid 7sp4 g4 #a4af71 diluted to #ajj c4c41 and exposed in open beakers for varying lengths of time2 and the residual stannous chloride measured by titration with permanganate4 ,the quantities required were as follows3-- ,time ,exposed4 #ej per cent4 ,acid4 #aj per cent4 ,acid4 #a per cent4 ,acid4 #a hour #cc4b c4c4 #cd4d c4c4 #cd4e c4c4 #a day #e4j #bd4j #bg4f #b days #c4j #ad4e #ba4c ,these indicate very clearly the increased susceptibility to oxidation in strongly acid solutions4 ,a standard solution of ferric chloride is prepared in the same manner as that described under the experiments on the methods of reduction2 but it should be of twice the strength1 so that #ajj c4c4 may contain #a gram of iron4 ,this solution is used for standardising the stannous chloride when required2 and must be carefully prepared2 and tested for the presence of nitric acid4 ,the titration is more limited in its application than either of the oxidising processes because of the restrictions as to bulk1 quality and quantity of free acid present1 and other conditions of the solution to be assayed4 ,the following experiments show the conditions necessary for a successful titration4 ,effect of ,varying ,temperature4--,twenty c4c4 of ferric chloride solution with #bj c4c4 of strong hydrochloric acid1 diluted to #ej c4c41 gave the following results when titrated3-- ,temperature #ae #cj #gj #ajj ,stannous chloride required #bb4h c4c4 #bb4j c4c4 #bb4a c4c4 #bb4j c4c4 ,the finishing point1 however1 is more distinct the hotter the solution2 so that it is best in all cases to run the standard into the boiling solution4 ,effect of ,varying ,bulk4--,solutions containing the same quantity of iron and acid as the last1 but diluted to various bulks1 and titrated while boiling1 gave the following results3-- ,bulk #cj c4c4 #ajj c4c4 #ejj c4c4 ,stannous chloride required #ba4e #ba4g #bd4c ,effect of ,varying ,quantities of ,hydrochloric ,acid4--,in these experiments the bulk before titration was #ej c4c4 except in the last1 in which it was #gj c4c4 ,with less than #e c4c4 of strong hydrochloric acid the finishing point is indistinct and prolonged4 ,strong hydrochloric acid present #e c4c4 #aj c4c4 #bj c4c4 #cj c4c4 #ej c4c4 ,stannous chloride required #ba4a #ba4a #ba4b #ba4h #bb4b ,effect of ,free ,sulphuric ,acid4--,in these experiments #bj c4c4 of hydrochloric acid were present1 and the bulk was #ej c4c4 ,strong sulphuric acid present -- c4c4 #c c4c4 #e c4c4 #aj c4c4 ,stannous chloride required #ba4f #bb4c #bb4i #bc4a ,this interference of strong sulphuric acid may be completely counteracted by somewhat modifying the mode of working4 ,another experiment1 like the last of this series1 required #ba4f c4c4 ,effect of ,foreign ,salts4--,experiments in which #aj grams of various salts were added showed them to be without effect4 ,the results were as follows3-- ,salt present -- ,am,cl ,am#b,,so#d ,mg,cl#b ,stannous chloride required #ba4f c4c4 #ba4f c4c4 #ba4f c4c4 #ba4f c4c4 ,salt present ,ca,cl#b ,fe,cl#b ,al#b;,cl#f ,stannous chloride required #ba4h c4c4 #ba4f c4c4 #ba4f c4c4 ,effect of ,varying ,iron4--,titrating a solution 7with #bj c4c4 of hydrochloric acid7 measuring #ej c4c41 and kept boiling1 the quantity of stannous chloride solution required is practically proportional to the iron present4 ,ferric chloride added #a c4c4 #aj c4c4 #bj c4c4 #ej c4c4 #ajj c4c4 ,stannous chloride required #a4a #aj4e #bj4f #ea4d #ajb4f ,the student1 having practised some of the above experiments1 may proceed to the assay of an iron ore4 ,determination of ,iron in ,brown ,iron ,ore4--,weigh up #a gram of the dried and powdered ore1 calcine in the cover of a platinum crucible1 and dissolve up in an evaporating dish#fi with #bj c4c4 of strong hydrochloric acid4 ,when solution is complete1 dilute to #ej c4c4 after replacing any acid that may have been evaporated4 ,boil1 and run in the stannous chloride solution until the colour is faintly yellow2 boil again1 and continue the addition of the stannous chloride solution1 stirring continuously until the solution appears colourless4 ,note the quantity of the stannous chloride solution required4 ,suppose this to be #ei c4c4 ,take #fj c4c4 of the standard ferric chloride solution1 add #bj c4c4 of hydrochloric acid1 boil and titrate in the same way as before4 ,suppose this to require #fa c4c4 ,then as #fa is equivalent to #fj of the iron solution1 #ei is equivalent to #eh4ac4gj ,this gives the percentage4 ,it is not necessary to standardise the stannous chloride solution in this way with each sample assayed1 the ratio #fa3 #fj would serve for a whole batch of samples2 but the standardising should be repeated at least once each day4 ,,colorimetric ,,method4 ,this method is valuable for the determination of small quantities of iron present as impurities in other metals or ores4 ,it is based on the red coloration developed by the action of potassic sulphocyanate on acid solutions of ferric salts4 ,standard ,ferric ,chloride ,solution4--,take #a c4c4 of the ferric chloride solution used for standardising the stannous chloride solution1 add #b c4c4 of dilute hydrochloric acid1 and dilute to #a litre with water4 #a c4c4 #j4ja milligram4 ,solution of ,potassic ,sulphocyanate4--,dissolve #fj grams of the salt in water1 and dilute to a litre4 ,it should be colourless4 ,use #aj c4c4 for each test4 ,the quantity of the substance to be weighed for the assay should not contain more than a milligram of iron2 consequently1 if the ore contain more than #j4a per cent4 of that metal1 less than a gram of it must be taken4 ,the method is as follows3--,weigh up #a gram of the substance and dissolve in a suitable acid2 dilute2 and add permanganate of potash solution until tinted4 ,boil for some time and dilute to #ajj c4c4 ,take a couple of ,nessler tubes1 holding over #ajj c4c41 but marked at #ej c4c42 label them #a and #b2 and into each put #aj c4c4 of the potassic sulphocyanate solution and #b c4c4 of dilute hydrochloric acid4 ,the solutions should be colourless4 ,to #a add #aj c4c4 of the assay solution1 and dilute to the #ej c4c4 mark4 ,to the other add water1 but only to within #e or #aj c4c4 of this mark4 ,now run in the standard ferric chloride solution from a small burette1 #a c4c4 at a time1 stirring after each addition till the colour is nearly equal to that of the assay 7,no4 #a74 ,at this stage bring the solution to the same level by diluting1 and make a further addition of the standard ferric chloride solution till the colours correspond4 ,the amount of iron will be the same in each tube2 that in the standard may be known by reading off the volume from the burette and multiplying by #j4ja milligram4 ,if the #aj c4c4 of the assay solution gave a colour requiring more than #e or #f c4c4 of the standard ferric chloride solution1 repeat the determination1 taking a smaller proportion4 ,the effect of varying conditions on the assay will be seen from the following experiments3-- ,effect of ,varying ,temperature4--,the effect of increase of temperature is to lessen the colour2 in fact1 by boiling1 the colour can be entirely removed4 ,all assays are best carried out in the cold4 #a c4c4 at #ae would only show the colour of #j4ge c4c4 at #de #b #a4ge #e #d4j ,effect of ,time4--,the effect of increase of time is to increase the colour1 as will be seen from the following experiments3-- #b c4c4 on standing #aj minutes became equal to #b4be c4c4 #b #bj #b4ge #b #dj #c4jj ,effect of ,free ,acid4--,if no acid at all be present1 the sulphocyanate of potassium solution removes the colour it first produces1 so that a certain amount of acid is necessary to develop the colour4 ,the use of a large excess has a tendency to increase the colour produced4 #e c4c4 nitric acid 7sp4 g4 #a4d7 read #c4g c4c4 instead of #b c4c4 with the dilute acid4 #e c4c4 sulphuric acid 7sp4 g4 #a4cb7 read #b4b c4c4 instead of #b c4c4 with the dilute acid4 #e c4c4 hydrochloric acid 7sp4 g4 #a4af7 read #b4e c4c4 instead of #b c4c4 with the dilute acid4 ,effect of ,foreign ,metals4--,lead1 mercury1 cadmium1 bismuth1 arsenic1 tin1 antimony1 nickel1 cobalt1 manganese1 aluminium1 zinc1 strontium1 barium1 calcium1 magnesium1 sodium1 or potassium1 when separately present in quantities of from #ajj to #bjj times the weight of iron present1 do not interfere if they have previously been brought to their highest oxidised condition by boiling with nitric acid or by treating with permanganate4 ,arsenic and phosphoric acids interfere unless an excess of free hydrochloric or other acid is present4 ,oxalic acid 7but not tartaric acid7 in minute quantities destroys the colour4 ,nitrous acid strikes a red colour with the sulphocyanate of potassium2 consequently1 when nitric acid has been used in excess1 high results may be obtained4 ,copper and some other metals interfere1 so that in most cases it is advisable to concentrate the iron before estimating it4 ,a blank experiment should always be made with the reagents used in order to determine the iron1 if any1 introduced during the solution1 c41 of the substance assayed4 ,determination of ,iron in ,metallic ,copper4--,this may be most conveniently done during the estimation of the arsenic4 ,the small quantity of white flocculent precipitate which may be observed in the acetic acid solution before titrating1 contains the whole of the iron as ferric arsenate4 ,it should be filtered off1 dissolved in #aj c4c4 of dilute hydrochloric acid1 and diluted to #ajj c4c42 #aj c4c4 of this may be taken for the estimation4 ,for example3 #aj grams of copper were taken1 and the iron estimated2 #c4j c4c4 of standard ferric chloride solution were used1 equivalent to #j4jc milligram of iron2 this multiplied by #aj 7because only #a_/ajth of the sample was taken7 gives #j4c milligram as the iron in #aj grams of copper4 ,this equals #j4jjc per cent4 ,in a series of experiments with this method working on #aj-;gram lots of copper1 to which known quantities of iron had been added1 the following were the results3-- ,iron present #j4jae #j4jgj #j4ajj #j4die ,iron found #j4jae #j4jfa #j4jhg #j4ebb ,when no arsenic is present in the copper1 the iron can be separated by fractionally precipitating with sodic carbonate1 dissolving in ammonia1 and filtering off the ferric hydrate4 ,coppers generally carry more iron the less arsenic they contain4 ,determination of ,iron in ,metallic ,zinc4--,dissolve #a gram of zinc in #aj c4c4 of dilute hydrochloric acid1 adding a drop or two of nitric acid towards the end to effect complete solution4 ,boil1 dilute1 and tint with the permanganate of potassium solution2 boil till colourless1 and dilute to #ajj c4c4 ,take #aj c4c4 for the determination4 ,make a blank experiment by boiling #aj c4c4 of dilute hydrochloric acid with a drop or two of nitric acid2 add a similar quantity of the permanganate of potassium solution1 boiling1 c41 as before4 ,the quantity of iron in zinc varies from less than #j4jje to more than #b4j per cent4 ,when #a gram is taken and worked as above1 each c4c4 of ferric chloride solution required indicates #j4ja per cent4 of iron4 ,determination of ,iron in ,metallic ,tin4--,cover #a gram of tin with #e c4c4 of hydrochloric acid1 add #a c4c4 of nitric acid1 and evaporate to dryness4 ,take up with #b c4c4 of dilute hydrochloric acid1 add #aj c4c4 of the potassic sulphocyanate solution1 and make up to #ej c4c4 ,probably the colour developed will be brown instead of red owing to the presence of copper2 in this case1 add to the standard as much copper as the assay is known to contain 7which must have previously been determined2 see ,copper72 the titration is then carried out in the usual way4 ,or the iron may be separated from the copper in the tin by the following process3--,dissolve #e grams of metal in #cj c4c4 of hydrochloric acid and #e c4c4 of nitric acid1 and evaporate to dryness4 ,take up with #e c4c4 of dilute hydrochloric acid1 add #aj grams of potash dissolved in #cj c4c4 of water1 and warm till the tin is dissolved4 ,pass sulphuretted hydrogen1 boil1 cool1 and filter4 ,the iron and copper will be in the precipitate4 ,they are separated in the ordinary manner4 ,,practical ,,exercises4 #a4 ,calculate from the following determinations the percentages of ferrous1 ferric1 and total iron in the sample of ore used4 #a gram of ore dissolved and titrated required #bf4g c4c4 of bichromate of potassium solution4 #a gram of ore dissolved1 reduced1 and titrated required #dc4e c4c4 of bichromate of potassium solution4 ,standard #a4jad4 #b4 ,one gram of an ore contained #j4cjg gram of ferrous iron and #j4fee gram of total iron4 ,the iron existing as oxide1 what are the percentages of ferrous oxide 7,fe,o7 and ferric oxide 7,fe#b,o#c7 in the ore8 #c4 ,one gram of brown iron ore dissolved in hydrochloric acid required #ei4b c4c4 of stannous chloride 7standard #j4icj74 ,another gram dissolved in acid and titrated with permanganate required #h4b c4c4 7standard #j4diea74 ,calculate the percentages of ferrous1 ferric1 and total iron4 #d4 ,another gram of the same ore1 roasted1 dissolved and titrated with stannous chloride1 required #fc4e c4c4 ,to what extent does this result confirm the others8 #e4 ,two grams of a metal were dissolved and diluted to #ajj c4c4 ,five c4c4 were taken for a colorimetric determination1 and required #d4e c4c4 of the standard ferric chloride solution4 ,what is the percentage of iron in the metal8 ,,nickel4 ,nickel and cobalt are closely related in their chemical properties1 and may best be considered together4 ,nickel is the commoner of the two1 and is met with in commerce alloyed with copper and zinc as ,german silver2 as also in the coinage of the ,united ,states and on the ,continent4 ,it is used for plating polished iron and steel goods1 forming a coating little liable to rust and taking a good polish4 ,the ores of nickel are not very common4 ,kupfernickel and chloanthite are arsenides of nickel with1 generally1 more or less iron and cobalt4 ,noumeite and garnierite are hydrated silicates of nickel and magnesia4 ,the chief sources of nickel are these silicates1 which are found in large quantity in ,new ,caledonia2 and a pyrites found in ,norway1 containing three or four per cent4 of the metal4 ,in smaller quantities it is more widely distributed1 being frequently met with in copper ores2 consequently1 commercial copper is rarely free from it4 ,nickel is readily soluble in moderately concentrated nitric acid4 ,its salts are mostly green1 and soluble in excess of ammonia1 forming blue solutions2 in these respects it resembles copper4 ,the acid solutions1 however1 are not precipitated by sulphuretted hydrogen1 although in alkaline solutions a black sulphide is formed which is insoluble in dilute hydrochloric acid4 ,if the sulphide is formed in a solution containing much free ammonia1 the precipitation is incomplete1 some sulphide remaining in the solution and colouring it dark brown4 ,these reactions serve to distinguish and separate nickel from other metals1 except cobalt4 ,if the separated sulphide be heated in a borax bead1 the colour obtained will be a sherry brown in the outer flame1 and grey or colourless in the inner flame if nickel only is present4 ,in the presence of cobalt these colours are masked by the intense and characteristic blue yielded in both flames by that metal4 ,,dry ,,assay4 ,the dry assay of nickel 7cobalt being at the same time determined7 is based on the formation of a speise which will carry the cobalt1 nickel1 copper1 and some of the iron of the ore in combination with arsenic4 ,a speise of this kind1 fused and exposed at a red heat to air1 first loses arsenide of iron by oxidation4 ,it is only when the iron has been oxidised that the arsenide of cobalt begins to be attacked2 and when the removal of the cobalt is complete1 the nickel commences to pass into the slag1 the copper being left till last4 ,the changes are rendered evident by fusion in contact with borax4 ,the process is as follows3--,weigh up #e grams of the ore1 and calcine thoroughly on a roasting dish in the muffle4 ,rub up with some anthracite1 and re-roast4 ,mix intimately with from #c to #e grams of metallic arsenic1 and heat in a small covered clay crucible at dull redness in a muffle until no more fumes of arsenic come off 7about #ae minutes74 ,take out the crucible1 and inject a mixture of #bj grams of carbonate of soda1 #e grams of flour1 and #b grams of fused borax4 ,place in the wind furnace1 and raise the temperature gradually until the charge is in a state of tranquil fusion4 ,pour2 when cold1 detach the button of speise1 and weigh4 ,weigh out carefully a portion of about #a gram of it4 ,place a shallow clay dish in the muffle1 and heat it to bright redness2 then add about #a4e gram of borax glass wrapped in a piece of tissue paper2 when this has fused1 drop the piece of speise into it4 ,close the muffle until the speise has melted1 which should be almost at once4 ,the arsenide of iron will oxidise first1 and when this has ceased the surface of the button brightens4 ,remove it from the muffle1 and quench in water as soon as the button has solidified4 ,the borax should be coloured slightly blue4 ,weigh3 the loss is the arsenide of iron4 ,repeat the operation with the weighed button on another dish1 using rather less borax4 ,continue the scorification until a film1 green when cold1 floating on the surface of the button shows that the nickel is beginning to oxidise4 ,cool1 separate1 and weigh the button as before4 ,the loss is the arsenide of cobalt4 ,if copper is absent1 the speise is now arsenide of nickel4 ,the weight of nickel corresponding to the arsenide got is calculated by multiplying by #j4fjg2 and1 similarly1 the weight of the cobalt is ascertained by multiplying the loss in the last scorification by #j4fae4ga ,it must be remembered that the nickel and cobalt so obtained are derived from a fraction only of the speise yielded by the ore taken1 so that the results must be multiplied by the weight of the whole of the speise1 and divided by the weight of the fragment used in the determination4 ,as an example1 suppose #e grams of ore gave #c4c grams of speise1 and #a4a gram of this gave #j4h gram of nickel arsenide4 ,then-- #j4hj4fjg #j4dhef gram of nickel #j4dhefc4c_/a4a #a4def gram of nickel ,and this being obtained from #e grams of ore is equivalent to #bi4ab per cent4 ,when copper is also present1 weigh up accurately about #j4e gram of gold1 and place it on the scorifier with the button of nickel and copper arsenide1 using borax as before4 ,scorify until the button shows the bluish-green colour of a fused gold-copper alloy4 ,then cool1 and weigh the button of copper and gold4 ,the increase in weight of the gold button gives the copper as metal4 ,the weight of the copper multiplied by #a4cie is the weight of the copper arsenide 7,cu#c;,as7 present4 ,the difference will be the nickel arsenide4 ,the student should enter the weighings in his book as follows3 ,ore taken -- grams ,speise got -- ,speise taken -- grams ,arsenides of cobalt1 nickel1 and copper -- nickel and copper -- ,gold added -- ,gold and copper got -- ,showing ,cobalt -- per cent4 ,nickel -- ,copper -- ,,wet ,,methods4 ,solution and ,separation4--,two or three grams of a rich ore1 or #e to #aj grams if poor1 are taken for the assay4 ,if much arsenic is present 7as is usually the case71 the ore must be calcined before attacking with acids4 ,transfer to a flask2 and boil1 first with hydrochloric acid until the oxides are dissolved1 and then with the help of nitric acid1 until nothing metalliferous is left4 ,dilute1 nearly neutralise with soda1 and separate the iron as basic acetate1#gb as described in page #bcc4 ,through the filtrate pass sulphuretted hydrogen till saturated4 ,allow to settle 7best overnight71 filter1 and wash4 ,transfer the precipitate to a beaker1 and dissolve in nitric acid4 ,dilute with water1 pass sulphuretted hydrogen1 and filter off the precipitate1 if any4 ,boil off the gas1 add ammonia until a precipitate is formed1 and then acidify somewhat strongly with acetic acid4 ,pass sulphuretted hydrogen in a slow stream until any white precipitate of zinc sulphide1 there may be1 begins to darken4 ,filter2 to the filtrate add ammonia1 and pass sulphuretted hydrogen4 ,the precipitate will contain the nickel and cobalt as sulphides4 ,where small quantities of nickel and cobalt are present1 and an approximate determination is sufficient1 they can be concentrated as follows3--,remove the copper1 c41 by passing sulphuretted hydrogen through the acid solution and filtering2 add ammonia to the filtrate1 and again pass sulphuretted hydrogen2 then heat nearly to boiling1 and filter4 ,dissolve the precipitate off the filter with dilute hydrochloric acid2 the residue will contain nearly all the nickel and cobalt as sulphides4 ,separation of ,nickel and ,cobalt4--,dissolve the sulphides separated as above in nitric acid2 render alkaline with a solution of potash1 then acidify with acetic acid2 add a concentrated solution of nitrite of potash4 ,the liquid after this addition must have an acid reaction4 ,allow to stand for #bd hours in a warm place4 ,filter off the yellow precipitate of nitrite of potash and cobalt1 and wash with a #aj per cent4 solution of acetate of potash4 ,the cobalt is determined in the precipitate in the way described under ,cobalt4 ,the nickel is separated from the solution by boiling with sodic hydrate1 filtering1 and dissolving the precipitate in nitric acid4 ,the solution will contain the nickel4 ,,gravimetric ,,determination4 ,the solution1 which contains the nickel free from other metals1 is heated1 and a solution of sodic hydrate added in slight excess4 ,the precipitate is filtered off1 washed with boiling water1 dried1 ignited at a red heat1 and weighed when cold4 ,the ignited substance is nickel oxide 7,ni,o71 and contains #gh4fg per cent4 of nickel4 ,the oxide is a green powder1 readily and completely soluble in hydrochloric acid1 and without action on litmus paper4 ,it is very easily reduced by ignition in hydrogen to metallic nickel4 ,illustration3 ,,fig4 #ef4 ,nickel is also determined by electrolysis1 as follows3--,the nitric acid solution is rendered strongly ammoniacal1 and placed under the electrolytic apparatus used for the copper assay4 ,three cells 7fig4 #ef71 however1 must be used1 coupled up for intensity1 that is1 with the zinc of one connected with the copper of the next4 ,the electrolysis is allowed to go on overnight1 and in the morning the nickel will be deposited as a bright and coherent film4 ,a portion of the solution is drawn off with a pipette2 if it smells of ammonia1 has no blue colour1 and gives no precipitate with ammonic sulphide1 the separation is complete4 ,wash the cylinder containing the deposited metal1 first with water and then with alcohol1 as in the copper assay4 ,dry in the water oven1 and weigh4 ,the increase in weight is metallic nickel4 ,as an example3--,there was taken #a gram of a nickel alloy used for coinage4 ,it was dissolved in #aj c4c4 of nitric acid1 and diluted to #ajj c4c4 with water4 ,the copper was then precipitated by electrolysis4 ,it weighed #j4gcd gram4 ,the solution1 after electrolysis1 was treated with sulphuretted hydrogen1 and the remaining copper was thrown down as sulphide1 and estimated colorimetrically4 ,this amounted to #c-a_/b milligrams4 ,the filtrate was evaporated1 treated with ammonia1 warmed1 and filtered4 ,the ferric hydrate was dissolved in dilute acid1 and reprecipitated1 dried1 ignited1 and weighed4 ,its weight was #j4jcaj gram4 ,the two filtrates were mixed1 and reduced in bulk to about #ej c4c42 a considerable excess of ammonia was added1 and the nickel precipitated by electrolysis4 ,it weighed #j4bdcd gram4 ,these quantities are equivalent to3 ,copper #gc4ge per cent4 ,nickel #bd4cd ,iron #b4ag ------ #ajj4bf ,,volumetric ,,determination4 ,an alkaline solution of potassium cyanide1 to which a little potassium iodide has been added1 can be assayed for its strength in cyanide by titrating with a standard solution of silver nitrate4 ,nickel interferes with this assay1 doing the work of its equivalent of silver2 and the quantity of nickel present can be calculated from the amount of its interference in the titration4 ,a volumetric assay for nickel is based on this4 ,it has the disadvantage of all indirect titrations in that it requires two standard solutions4 ,on the other hand it gives good results even under unfavourable conditions1 and is applicable in the presence of much zinc4 ,small quantities of cobalt will count as so much nickel1 but larger quantities make the assay unworkable4 ,some of the other metals--lead for example--have no appreciable effect2 but practically the solution demands a preliminary treatment which would result in their removal4 ,nevertheless it is a very satisfactory method and makes the determination of nickel quick and comparatively easy in most cases4 ,the standard solution of silver nitrate is made by dissolving #ad4dh grams of recrystallised silver nitrate in distilled water and diluting to #a litre3 #ajj c4c4 of this solution are equivalent to #j4be gram of nickel4#gc ,the standard solution of potassium cyanide should be made so as to be exactly equal to the silver nitrate solution4 ,this can be done as follows3 ,weigh up #ab grams of good potassium cyanide 7#ie per cent471 dissolve in water1 add #ej c4c4 of a #aj per cent4 solution of sodium hydrate and dilute to #a litre4 ,fill one burette with this and another with the solution of silver nitrate4 ,run #ej c4c4 of the cyanide into a flask2 add a few drops of potassium iodide solution and titrate with the standard silver nitrate until there is a distinct permanent yellowish turbidity4 ,the titration is more fully described under ,cyanide1 p4 #afe4 ,the cyanide solution will be found rather stronger than the silver nitrate2 dilute it so as to get the two solutions of equal value4 ,for example1 #ea4c c4c4 of silver nitrate may have been required3 then add #a4c c4c4 of water to each #ej c4c4 of the cyanide solution remaining4 ,if the full #iej c4c4 are available1 then add to them #bd4g c4c4 of water4 ,after mixing1 take another #ej c4c4 and titrate with the silver nitrate2 the two solutions should now be exactly equal4 ,the cyanide solution1 being strongly alkaline with soda1 keeps very well2 but its strength should be checked from time to time by titrating with silver nitrate2 should there be any slight inequality in the strengths of the two solutions it is easily allowed for in the calculations4 ,the titration4--,the solution1 containing not much more than #j4a gram of nickel1 and free from the interfering metals1 must be cooled4 ,it is next neutralised and then made strongly alkaline with a solution of soda 7,na,h,o72 an excess of #bj or #cj c4c4 suffices4 ,this will produce a precipitate4 ,the cyanide solution is now run in from a burette until the solution clears1 after which an excess of about #bj c4c4 is added4 ,it is well to use some round number of c4c4 to simplify the calculation4 ,add a few drops of potassium iodide solution1 and run in the standard solution of silver nitrate from a burette4 ,this should be done a little at a time1 though somewhat rapidly1 and with constant shaking1 till a permanent yellow precipitate appears4 ,if the addition of the cyanide did not result in a perfectly clear solution1 this is because something besides nickel is present4 ,the residue may be filtered off1 though with a little practice the finishing-point may be detected with certainty in the presence of a small precipitate4 ,if the student has the slightest doubt about a finish he should run in another #e c4c4 of the cyanide and again finish with silver nitrate4 ,the second result will be the same as the first4 ,for example1 if #dj c4c4 of cyanide and #cj c4c4 of silver nitrate were required at the first titration1 then the #de c4c4 of cyanide in the second titration will require #ce c4c4 of silver nitrate4 ,the difference between the quantities of the two solutions used in each case will be #aj c4c4 ,it is this difference in the readings of the two burettes which measures the quantity of nickel present4 ,each c4c4 of the difference is equal to 4#jjbe gram of nickel4 ,but if the cyanide solution is not exactly equal in strength to the silver nitrate1 the quantity of cyanide used should be calculated to its equivalent in silver nitrate before making the subtraction4 ,the following experimental results illustrate the accuracy of the assay and the effect upon it of varying conditions4 ,a solution containing #a gram of nickel sulphate 7,ni,s,o#d4f;,h#b,o7 in #ajj c4c4 was used4 ,by a separate assay the sulphate was found to contain #bb4be per cent4 of nickel4 ,for the sake of simplicity the results of the experiments are stated in weights of nickel in grams4 ,effect of varying excess of ,cyanide ,solution4--,in each experiment there was #bj c4c4 of the nickel solution1 equal to 4#jdde gram of nickel4 ,there were also #aj c4c4 of soda solution1 #c or #d drops of potassium iodide and sufficient water to bring the bulk to #ajj c4c4 before titrating4 ,cyanide in excess #f c4c4 #d c4c4 #h c4c4 #ab c4c4 #be c4c4 ,nickel found 4#jdcd 4#jdcf 4#jddj 4#jddb 4#jddd ,although the difference between the highest and lowest of these results is only #a milligram1 their meaning is quite obvious4 ,the excess of cyanide should not be less than #bj c4c4 ,effect of varying the quantity of ,soda4--,there were two series of experiments1 one with #b c4c4 of nickel solution 7 4#jjdd gram of nickel71 the other with #bj c4c4 ,the conditions were as before1 except that the quantity of soda was varied4 ,soda added #e c4c4 #ae c4c4 #cj c4c4 ,nickel found1 #ast series 4#jjcg 4#jjdb 4#jjde #bnd series 4#jddd 4#jddd 4#jddb ,these show that the presence of much soda1 though it has only a small effect1 is beneficial rather than otherwise4 ,ammonia has a bad effect1 if present in anything like the same quantities4 ,effect of varying the ,nickel4--,in experiments with #aj1 #bj1 and #dj c4c4 of the nickel solution1 the results were3-- ,nickel present 4#jbbb 4#jdde 4#jhij ,nickel found 4#jbbj 4#jddb 4#jhhd ,effect of ,zinc4--,in these experiments #bj c4c4 of nickel solution 7 4#jdde gram of nickel71 #aj c4c4 of soda1 #f drops of potassium iodide and water to #ajj c4c4 were used4 ,the excess of cyanide was purposely kept at from #aj to #ae c4c41 which is hardly sufficient4 ,zinc added #j 4#be gram4 4#e gram4 ,nickel found 4#jddb 4#jddj 4#jdjg ,on increasing the excess of cyanide to over #bj c4c4 and doubling the quantity of soda1 the experiment with #j4e gram of zinc gave #j4dda gram of nickel4 ,hence the titration is satisfactory in the presence of zinc provided that not fewer than #bj or #cj c4c4 of soda are used1 and that the excess of cyanide is such that not fewer than #bj or #cj c4c4 of silver nitrate are required in the titration4 ,moreover1 these precautions should be taken whether zinc is present or not4 ,effect of other ,metals4--,if metals of the first and second groups are present they should be removed by passing sulphuretted hydrogen and filtering4 ,if iron is present it must be removed1 since ferrous salts use up much cyanide1 forming ferrocyanides1 and ferric salts yield ferric hydrate1 which obscures the end reaction4 ,hence the sulphuretted hydrogen must be boiled off and the iron removed as basic ferric acetate by the method described on p4 #bcc4 ,if the precipitate is bulky it should be dissolved in a little dilute acid1 neutralised and again precipitated as basic acetate4 ,the nickel will be in the two filtrates4 ,in the absence of manganese and cobalt the titration may be made without further separation4 ,manganese does not directly interfere1 but the precipitated hydrate1 which rapidly darkens through atmospheric oxidation1 obscures the end reaction4 ,it may be removed by passing sulphuretted hydrogen through the filtrate from the acetate separation3 sulphides of nickel1 cobalt and zinc will be precipitated1 whilst manganese remains in solution3 the addition of more sodium acetate may assist the precipitation4 ,the precipitate must be filtered off and dissolved in nitric acid3 the solution should be evaporated to dryness4 ,the filtrate may retain a little nickel2 if so1 add ammonia till alkaline1 then acidify with acetic acid and again filter2 any small precipitate obtained here should be added to that first obtained4 ,it is only when cobalt is present that any further separation is required4 ,cobalt hydrate takes up oxygen from the air1 and on adding potassium cyanide some may refuse to dissolve2 and the solution itself acquires a brown colour1 which becomes deeper on standing4 ,at this stage the cobalt is easily separated4 ,the solution containing the nickel and cobalt with no great excess of acid1 is made alkaline by adding #bj c4c4 of soda exactly as in preparing for a titration4 ,so1 too1 the solution of cyanide is added so as to have an excess of #bj or #cj c4c42 the solution may have a brown colour1 but if it is not quite clear it must be filtered4 ,then warm 7boiling is not needed7 and add from #ej to #ajj c4c4 of bromine water4 ,this throws down all the nickel as black peroxide in a condition easy to filter4 ,filter it off and wash with water4 ,the precipitate can be dissolved off the filter with the greatest ease by a little warm sulphurous acid4 ,the filtrate and washings1 boiled till free from sulphurous acid1 yield the nickel as sulphate in a clean condition4 ,determination of ,nickel in ,nickel ,sulphate ,crystals4--,take #j4e gram of the salt1 dissolve in #ej c4c4 of water and add #be c4c4 of solution of soda4 ,run in from a burette1 say1 #fj c4c4 cyanide4 ,add a few drops of potassium iodide and titrate back with silver nitrate4 ,suppose #ae4e c4c4 of the latter is required4 ,then #ae4e c4c4 subtracted from #fj c4c4 leaves #dd4e c4c41 and since #ajj c4c4 #j4be gram of nickel1 #dd4e c4c4 will equal #j4aaabe gram of nickel4 ,this in #j4e gram of the salt equals #bb4be per cent4 ,determination of ,nickel in ,german ,silver4--,weigh up #j4e gram of the alloy1 and dissolve in a dish with #e or #aj c4c4 of dilute nitric acid4 ,add #e c4c4 of dilute sulphuric acid and evaporate till all the nitric acid is removed4 ,cool1 take up with #ej c4c4 of water1 and when dissolved pass sulphuretted hydrogen through the solution4 ,filter off the precipitate and wash with water containing sulphuretted hydrogen and dilute sulphuric acid4 ,boil down the filtrate and washings to get rid of the excess of the gas2 add some nitric acid and continue the boiling4 ,cool1 neutralise the excess of acid with soda1 add #a gram of sodium acetate and boil4 ,filter off the precipitate which contains the iron4 ,the filtrate1 cooled and rendered alkaline with soda1 is ready for the titration4 ,,cobalt ,occurs less abundantly than nickel4 ,its chief ores are smaltite and cobaltite1 which are arsenides of cobalt1 with more or less iron1 nickel1 and copper4 ,it also occurs as arseniate in erythrine1 and as oxide in asbolan or earthy cobalt1 which is essentially a wad carrying cobalt4 ,it is mainly used in the manufacture of smalts for imparting a blue colour to glass and enamels4 ,the oxide of cobalt forms coloured compounds with many other metallic oxides4 ,with oxide of zinc it forms ,rinman's green2 with aluminia1 a blue2 with magnesia1 a pink4 ,this property is taken advantage of in the detection of substances before the blow-pipe4 ,the compounds of cobalt in most of their properties closely resemble those of nickel1 and the remarks as to solution and separation given for the latter metal apply here4 ,solutions of cobalt are pink1 whilst those of nickel are green4 ,the detection of cobalt1 even in very small quantity1 is rendered easy by the strong blue colour which it gives to the borax bead1 both in the oxidising and in the reducing flame4 ,it is concentrated from the ore in the same way as nickel1 and should be separated from that metal by means of potassic nitrite in the way described4 ,the dry assay of cobalt has been given under ,nickel4 ,,gravimetric ,,method4 ,the yellow precipitate from the potassium nitrite1 after being washed with the acetate of potash1 is washed with alcohol1 dried1 transferred to a weighed porcelain crucible1 and cautiously ignited with an excess of strong sulphuric acid4 ,the heat must not be sufficient to decompose the sulphate of cobalt1 which decomposition is indicated by a blackening of the substance at the edges4 ,the salt bears a low red heat without breaking up4 ,if blackening has occurred1 moisten with sulphuric acid1 and ignite again4 ,cool and weigh4 ,the substance is a mixture of the sulphates of cobalt and potash 7#b;,co,s,o#d #c,k#b,,so#d71 and contains #ad4ag per cent4 of cobalt4 ,cobalt is also gravimetrically determined1 like nickel1 by electrolysis1 or by precipitation with sodic hydrate4 ,in the latter case1 the ignited oxide will be somewhat uncertain in composition1 owing to its containing an excess of oxygen4 ,consequently1 it is better to reduce it by igniting at a red heat in a current of hydrogen and to weigh it as metallic cobalt4 ,,practical ,,exercises4 #a4 ,in the dry assay of an ore containing cobalt1 nickel1 and copper1 the following results were obtained4 ,calculate the percentages4 ,ore taken1 #e grams4 ,speise formed1 #j4ii gram4 ,speise taken4 #j4ii gram4 ,arsenides of cobalt1 nickel1 and copper got1 #j4ge gram4 ,arsenide of nickel and copper got1 #j4ed gram4 ,gold added1 #j4e gram4 ,gold and copper got1 #j4fa gram4 #b4 ,calculate the percentage composition of the following compounds3 ,co#b;,as1 ,ni#b;,as1 and ,cu#b;,as4 #c4 ,a sample of mispickel contains #g per cent4 cobalt4 ,what weight of the mixed sulphates of potash and cobalt will be obtained in a gravimetric determination on #a gram of the ore8 #d4 #j4caeg gram of metal was deposited by the electrolysis of a nickel and cobalt solution4 ,on dissolving in nitric acid and determining the cobalt #j4befc gram of potassium and cobalt sulphates were got4 ,find the weights of cobalt and nickel present in the deposit4 #e4 ,what should be the percentage composition of pure cobaltite1 its formula being ,co,as,s8 ,,zinc4 ,zinc occurs in nature most commonly as sulphide 7blende72 it also occurs as carbonate 7calamine7 and silicate 7smithsonite74 ,each of these is sufficiently abundant to be a source of the metal4 ,the metal is known in commerce as spelter when in ingots1 and as sheet zinc when rolled4 ,it is chiefly used in the form of alloys with copper1 which are known as brasses4 ,it is also used in the form of a thin film1 to protect iron goods from rusting--galvanised iron4 ,ores of zinc1 more especially blende1 are met with in most lead1 copper1 gold1 and silver mines1 in larger or small quantities scattered through the lodes4 ,those ores which generally come under the notice of the assayer are fairly rich in zinc2 but alloys and metallurgical products contain it in very varying proportions4 ,zinc itself is readily soluble in dilute acids2 any residue which is left after boiling with dilute hydrochloric or sulphuric acid consists simply of the impurities of the metal2 this is generally lead4 ,all zinc compounds are either soluble in1 or are decomposed by1 boiling with acids1 the zinc going into solution4 ,zinc forms only one series of salts1 and these are colourless4 ,their chief characteristic is solubility in an alkaline solution1 from which sulphuretted hydrogen produces a white precipitate of zinc sulphide4 ,zinc is detected by dissolving the substance in hydrochloric or nitric acid1 boiling1 and adding sodic hydrate in excess1 filtering1 and adding ammonic sulphide to the filtrate4 ,the precipitate contains the zinc1 which can be dissolved out by boiling with dilute sulphuric acid1 and detected by the formation of a white precipitate on the addition of potassic ferrocyanide4 ,the dry assay of zinc can only be made indirectly1 and is unsatisfactory4 ,zinc is volatile1 and at the temperature of its reduction is a gas4 ,it is impracticable to condense the vapour so as to weigh the metal1 consequently its amount is determined by loss4 ,the following method gives approximate results3 ,take #aj grams of the dried and powdered ore and roast1 first at a low temperature and afterwards at a higher one1 with the help of carbonate of ammonia to decompose the sulphates formed2 cool and weigh4 ,the metals will be present as oxides4 ,mix with #b grams of powdered charcoal and charge into a black-lead crucible heated to whiteness1 cover loosely1 and leave in the furnace for about a quarter of an hour4 ,uncover and calcine the residue1 cool and weigh4 ,the loss in weight multiplied by #h4jc gives the percentage of zinc in the ore4 ,,wet ,,methods4 ,solution and separation may be effected as follows3 ,treat #a or #c grams of the substance with #aj or #cj c4c4 of hydrochloric acid or aqua regia2 evaporate to dryness2 take up with #aj c4c4 of hydrochloric acid and dilute to #ajj c4c42 heat nearly to boiling2 saturate with sulphuretted hydrogen2 filter1 and wash with water acidulated with hydrochloric acid4 ,boil off the sulphuretted hydrogen and peroxidise with a few drops of nitric acid4 ,cool2 add caustic soda till nearly1 but not quite1 neutralised1 and separate the iron as basic acetate by the method described under ,iron4 ,to the filtrate add ammonia till alkaline1 and pass sulphuretted hydrogen4 ,allow to settle and decant on to a filter4 ,dissolve off the precipitate from the filter with hot dilute hydrochloric acid4 ,the solution will contain the zinc1 together with any manganese the ore contained1 and1 perhaps1 traces of nickel and cobalt4 ,if the zinc is to be determined volumetrically1 and manganese is present1 this latter is separated with carbonate of ammonia1 as described further on2 but if a gravimetric method is used1 and only small quantities of manganese are present1 it is better to proceed as if it were absent1 and to subsequently determine its amount1 which should be deducted4 ,,gravimetric ,,determination4 ,the solution containing the zinc is contained in an evaporating dish1 and freed from sulphuretted hydrogen by boiling1 and1 if necessary1 from an excess of acid by evaporation4 ,the evaporating dish must be a large one4 ,cautiously add sodium carbonate to the hot1 moderately dilute solution1 until the liquid is distinctly alkaline1 and boil4 ,allow the precipitate to settle1 decant on to a filter1 and wash with hot water4 ,dry1 transfer to a porcelain crucible 7cleaning the paper as much as possible71 add the ash1 ignite1 and weigh4 ,the substance weighed is oxide of zinc1 which contains #hj4bf per cent4 of the metal4 ,it is a white powder1 becoming yellow when heated4 ,it must not show an alkaline reaction when moistened4 ,if it contains manganese this metal will be present as sesquioxide 7,mn#b,o#c74 ,its amount can be determined by dissolving in dilute acid and boiling with an excess of sodic hydrate4 ,the oxide of manganese will be precipitated1 and can be ignited and weighed4 ,its weight multiplied by #a4jce must be deducted from the weight of oxide of zinc previously obtained4 ,the results yielded by the gravimetric determination are likely to be high1 since the basic carbonate of zinc frequently carries down with it more or less soda which is difficult to wash off4 ,,volumetric ,,determination ,this method is based on the facts that zinc salts in an acid solution decompose potassium ferrocyanide1 forming a white insoluble zinc compound2 and that an excess of the ferrocyanide can be detected by the brown coloration it strikes with uranium acetate4 ,the method resembles in its working the bichromate iron assay4 ,the standard solution of potassium ferrocyanide is run into a hot hydrochloric acid solution of the zinc until a drop of the latter brought in contact with a drop of the indicator 7uranium acetate7 on a white plate strikes a brown colour4 ,the quantity of zinc in the solution must be approximately known2 run in a little less of the ferrocyanide than is expected will be necessary2 test a drop or two of the assay1 and then run in1 one or two c4c4 at a time1 until the brown colour is obtained4 ,add #e c4c4 of a standard zinc solution1 equivalent in strength to the standard ferrocyanide1 re-titrate1 and finish off cautiously4 ,of course #e c4c4 must be deducted from the reading on the burette4 ,the precipitate of zinc ferrocyanide formed in the assay solution is white2 but if traces of iron are present1 it becomes bluish4 ,if the quantity of ferrocyanide required is known within a few c4c41 the finishing point is exactly determined in the first titration without any addition of the standard zinc solution4 ,unfortunately this titration serves simply to replace the gravimetric determination1 and does not1 as many volumetric processes do1 lessen the necessity for a complete separation of any other metals which are present4 ,most metals give precipitates with ferrocyanide of potassium in acid solutions4 ,if the conditions are held to1 the titration is a fairly good one1 and differences in the results of an assay will be due to error in the separation4 ,ferric hydrate precipitated in a fairly strong solution of zinc will carry with it perceptible quantities of that metal4 ,similarly1 large quantities of copper precipitated as sulphide by means of sulphuretted hydrogen will carry zinc with it1 except under certain nicely drawn conditions4 ,when much copper is present it is best separated in a nitric acid solution by electrolysis4 ,the titration of the zinc takes less time1 and1 with ordinary working1 is more trustworthy than the gravimetric method4 ,the standard ferrocyanide solution is made by dissolving #dc4b grams of potassium ferrocyanide 7,k#d;,fe,cy#f4c;,h#b,o7 in water1 and diluting to a litre4 ,one hundred c4c4 are equal to #a gram of zinc4 ,the standard zinc solution is made by dissolving #aj grams of pure zinc in #ej c4c4 of hydrochloric acid and #ajj or #bjj c4c4 of water1 and diluting to #a litre1 or by dissolving #dd4ae grams of zinc sulphate 7,zn,s,o#d4g;,h#b,o7 in water with #cj c4c4 of hydrochloric acid1 and diluting to #a litre4 ,one hundred c4c4 will contain #a gram of zinc4 ,the uranium acetate solution is made by dissolving #j4b gram of the salt in #ajj c4c4 of water4 ,to standardise the ferrocyanide measure off #ej c4c4 of the standard zinc solution into a #aj oz4 beaker1 dilute to #ajj c4c41 and heat to about #ej ,c4 7not to boiling74 ,run in #dg or #dh c4c4 of the ferrocyanide solution from an ordinary burette1 and finish off cautiously4 ,fifty divided by the quantity of ferrocyanide solution required gives the standard4 ,in assaying ores1 c41 take such quantity as shall contain from #j4a to #a gram of zinc1 separate the zinc as sulphide1 as already directed4 ,dissolve the sulphide off the filter with hot dilute hydrochloric acid1 which is best done by a stream from a wash bottle4 ,evaporate the filtrate to a paste1 add #e c4c4 of dilute hydrochloric acid1 dilute to #ajj c4c4 or #aej c4c41 heat to about #ej ,c41 and titrate4 ,manganese1 if present1 counts as so much zinc1 and must be specially separated1 since it is not removed by the method already given4 ,the following method will effect its removal4 ,to the hydrochloric acid solution of the zinc and manganese add sodium acetate in large excess and pass sulphuretted hydrogen freely4 ,allow to settle1 filter off the zinc sulphide and wash with sulphuretted hydrogen water4 ,the precipitate1 freed from manganese1 is then dissolved in hydrochloric acid and titrated4 ,the following experiments show the effect of variation in the conditions of the assay3-- ,effect of ,varying ,temperature4--,using #bj c4c4 of the standard zinc solution1 #e c4c4 of dilute hydrochloric acid1 and diluting to #ajj c4c4 ,temperature #ae ,c4 #cj ,c4 #gj ,c4 #ajj ,c4 ,ferrocyanide required #bj4f c4c4 #bj4c c4c4 #bj4c c4c4 #bj4c c4c4 ,the solution can be heated to boiling before titrating without interfering with the result2 but it is more convenient to work with the solution at about #ej ,c4 ,cold solutions must not be used4 ,effect of ,varying ,bulk4--,these were all titrated at about #ej ,c41 and were like the last1 but with varying bulk4 ,bulk #be4j c4c4 #ej4j c4c4 #ajj4j c4c4 #bjj4j c4c4 ,ferrocyanide required #bj4b #bj4d #bj4c #bj4d ,any ordinary variation in bulk has no effect4 ,effect of ,varying ,hydrochloric ,acid4-- ,with #ajj c4c4 bulk and varying dilute hydrochloric acid the results were3-- ,acid added #j4j c4c4 #a4j c4c4 #e4j c4c4 #aj4j c4c4 #bj4j c4c4 ,ferrocyanide required #bd4d #bj4b #bj4c #bj4c #bj4g ,effect of ,foreign ,salts4--,the experiments were carried out under the same conditions as the others4 ,five grams each of the following salts were added3-- ,salt added ,ammonic ,ammonic ,sodium ,sodium chloride4 sulphate4 chloride4 sulphate4 ,ferrocyanide required #bj4c c4c4 #bj4e c4c4 #bj4f c4c4 #bj4d c4c4 ,salt added ,potassium ,magnesium ,nil4 ,nitrate4 sulphate4 ,ferrocyanide required #bj4b c4c4 #bj4d c4c4 #bj4d c4c4 ,in a series of experiments in which foreign metals were present to the extent of #j4jej gram in each1 with #bj c4c4 of zinc solution and #e c4c4 of dilute hydrochloric acid1 those in which copper sulphate1 ferrous sulphate1 and ferric chloride were used1 gave 7as might be expected7 so strongly coloured precipitates that the end reaction could not be recognised4 ,the other results were3-- ,ferrocyanide required4 ,with nothing added4 #bj4c c4c4 #j4jej gram lead 7as chloride7 #bj4i #j4jej manganese 7as sulphate7 #be4e #j4jej cadmium 7as sulphate7 #bc4e #j4jej nickel 7as sulphate7 #bf4b ,effect of ,varying ,zinc4--,these were titrated under the usual conditions1 and gave the following results3-- ,zinc added #a4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,ferrocyanide required #a4a #aj4b #bj4c #ej4f #aja4j ,determination of ,zinc in a ,sample of ,brass4--,take the solution from which the copper has been separated by electrolysis and pass sulphuretted hydrogen until the remaining traces of copper and the lead are precipitated1 filter1 boil the solution free from sulphuretted hydrogen1 put in a piece of litmus paper1 and add sodic hydrate solution in slight excess2 add #aj c4c4 of dilute hydrochloric acid 7which should render the solution acid and clear72 warm1 and titrate4 ,a sample of #j4e gram of brass treated in this manner required #af4d c4c4 of ferrocyanide 7standard #ajj c4c4 #j4iiji zinc71 which equals #j4afbe gram of zinc or #cb4e per cent4 ,determination of ,zinc in ,blende4--,dissolve #a gram of the dried and powdered sample in #be c4c4 of nitric acid with the help of two or three grams of potassium chlorate dissolved in the acid4 ,evaporate to complete dryness1 taking care to avoid spirting4 ,add #g grams of powdered ammonium chloride1 #ae c4c4 of strong ammonia and #be c4c4 of boiling water2 boil for one minute and see that the residue is all softened4 ,filter through a small filter1 and wash thoroughly with small quantities of a hot one per cent4 solution of ammonium chloride4 ,add #be c4c4 of hydrochloric acid to the filtrate4 ,place in the solution some clean lead foil1 say #aj or #bj square inches4 ,boil gently until the solution has been colourless for three or four minutes4 ,filter1 wash with a little hot water2 and titrate with standard ferrocyanide4 ,determination of ,zinc in ,silver ,precipitate4--,this precipitate contains lead sulphate1 silver1 copper1 iron1 zinc1 lime1 c4 ,weigh up #e grams of the sample1 and extract with #cj c4c4 of dilute sulphuric acid with the aid of heat4 ,separate the copper with sulphuretted hydrogen1 peroxidise the iron with a drop or two of nitric acid1 and separate as acetate4 ,render the filtrate ammoniacal1 pass sulphuretted hydrogen2 warm1 and filter4 ,dissolve the precipitated zinc sulphide in dilute hydrochloric acid1 evaporate1 dilute1 and titrate4 ,silver precipitates carry about #b4e per cent4 of zinc4 ,,gasometric ,,method4 ,metallic zinc is readily soluble in dilute hydrochloric or sulphuric acid1 hydrogen being at the same time evolved4#gd ,the volume of the hydrogen evolved is obviously a measure of the amount of zinc present in the metallic state4 ,the speed with which the reaction goes on 7even in the cold7 and the insolubility of hydrogen renders this method of assay a convenient one4 ,it is especially applicable to the determination of the proportion of zinc in zinc dust4 ,the apparatus described in the chapter on gasometric method is used4 ,the method of working is as follows3 ,fill the two burettes with cold water to a little above the zero mark1 place in the bottle about #j4be gram of the substance to be determined1 and in the inner phial or test tube #e c4c4 of dilute sulphuric acid2 cork the apparatus tightly and allow to stand for a few minutes2 then bring the water to the same level in the two burettes by running out through the clip at the bottom4 ,read off the level of the liquid in the graduated burette4 ,turn the bottle over sufficiently to spill the acid over the zinc1 and then run water out of the apparatus so as to keep the liquid in the two burettes at the same level1 taking care not to run it out more quickly than the hydrogen is being generated4 ,when the volume of gas ceases to increase1 read off the level of the liquid1 deduct the reading which was started with2 the difference gives the volume of hydrogen evolved4 ,at the same time read off the volume of air in the volume corrector1 which must be fixed alongside the gas burettes4 ,make the correction4 ,for example3 ,a piece of zinc weighing #j4bhce gram was found to give #ii4i c4c4 of gas at a time when the corrector read #ajd c4c4#ge ,then the corrected volume is #ajd 3 #ajj 33 #ii4i 3 x4 x #if4j c4c4 #ajj c4c4 of hydrogen at #j ,c4 and #gfj mm4 is equivalent to #j4biab gram of zinc2 therefore the quantity of zinc found is #ajj 3 #if 33 #j4biab 3 x4 x #j4bgie gram of zinc4 ,this being contained in #j4bhce gram of metal is equivalent to #ih4e per cent4 ,as an example of a determination in which reducing the volume of liberated hydrogen to #j ,c4 and #gfj mm4 is avoided1 the following may be taken3-- #j4bcae gram of pure zinc gave #hb4a c4c4 of gas2 and the volume of air in the corrector was #ajc4f c4c4 #j4bhce gram of the assay gave #ii4i c4c4 of gas2 and the volume of air in the corrector was #ajd4j c4c42 #ajd 3 #ajc4f 33 #ii4i 3 x4 x #ii4e c4c4 ,this is the volume of gas got in the assay if measured under the same conditions as the standard1 #hb4a 3 #ii4e 33 #j4bcae 3 x4 x #j4bhjf4 ,then #j4bhce 3 #j4bhjf 33 #ajj3 x4 x #ih4i per cent4 ,as these assays can be made quickly1 it is well for the sake of greater accuracy to make them in duplicate1 and to take the mean of the readings4 ,one set of standardisings will do for any number of assays4 ,the student must carefully avoid unnecessary handling of the bottle in which the zinc is dissolved4 ,colorimetric ,method4--,zinc salts being colourless1 there is no colorimetric determination4 ,,examination ,,of ,,commercial ,,zinc4 ,take #bj grams of zinc1 and dissolve them in dilute nitric acid2 boil1 allow to settle2 filter2 wash1 dry2 ignite the precipitate1 if any1 and weigh as oxide of tin4 ,examine this for arsenic4 ,lead4--,add ammonia and carbonate of ammonia to the liquid1 and boil1 filter off the precipitate1 wash with hot water4 ,digest the precipitate with dilute sulphuric acid2 filter1 wash1 and weigh the sulphate of lead4 ,iron4--,to the filtrate from the sulphate of lead add ammonia1 and pass sulphuretted hydrogen2 digest1 and filter4 7,save the filtrate47 ,dissolve the precipitate in hydrochloric acid1 oxidise with nitric acid1 and precipitate with ammonia4 ,wash1 ignite1 and weigh as ferric oxide4 ,calculate to iron4 ,arsenic4--,to the filtrate from the sulphide of iron add hydrochloric acid in slight excess2 filter off1 and wash the precipitate4 ,rinse it back into the beaker1 dissolve in nitric acid1 filter from the sulphur1 and add ammonia1 in excess1 and magnesia mixture4 ,filter off the ammonic-magnesic arsenate1 and wash with dilute ammonia4 ,dry1 ignite with nitric acid1 and weigh as magnesic pyrarsenate4 ,calculate to arsenic1 and add to that found with the tin4 ,copper4--,to the filtrate from the ammonia and ammonic carbonate add sulphuric acid in small excess1 and pass sulphuretted hydrogen4 ,allow to settle1 filter1 and wash4 ,rinse the precipitate into a beaker1 boil with dilute sulphuric acid1 and filter4 7,save the filtrate47 ,dry1 burn the paper with the precipitate1 treat with a drop or two of nitric acid1 ignite1 and weigh as copper oxide4 ,calculate to copper4 ,cadmium4--,to the filtrate from the sulphide of copper add ammonia1 so as to nearly neutralise the excess of acid1 and pass sulphuretted hydrogen4 ,collect and weigh the precipitate as cadmium sulphide1 as described under ,cadmium4 ,,practical ,,exercises4 #a4 ,what weight of hydrogen will be evolved in dissolving #a gram of zinc in dilute sulphuric acid8 #b4 ,how many c4c4 would this quantity of hydrogen measure at #j ,c4 and #gfj m4m48 7#a litre weighs #j4jhif gram74 #c4 #j4bc gram of zinc are found to give #gg4i c4c4 of hydrogen4 ,in another experiment under the same conditions #hj4b c4c4 are got4 ,what weight of zinc was used for the second experiment8 #d4 ,a sample of blende is found to contain #ee per cent4 of zinc4 ,what percentage of zinc sulphide did the sample contain8 #e4 ,how much metallic lead would be precipitated from a solution of lead acetate by #a gram of zinc8 ,,cadmium4 ,cadmium occurs in nature as cadmium sulphide in greenockite1 ,cd,s1 which is very rare4 ,it is widely diffused in calamine1 blende1 and other zinc ores1 forming1 in some cases1 as much as #b or #c per cent4 of the ore4 ,oxide of cadmium forms the brown blaze of the zinc smelters4 ,sulphide of cadmium is used as a pigment 7cadmium yellow72 and the metal and some of its salts are useful reagents4 ,the salts of cadmium closely resemble those of zinc4 ,the hydrate1 however1 is insoluble in excess of potash1 and the sulphide is insoluble in dilute acids4 ,it forms only one series of salts4 ,cadmium is detected by giving with sulphuretted hydrogen in solutions1 not too strongly acid1 a yellow precipitate1 which is insoluble in solutions of the alkalies1 alkaline sulphides1 or cyanide of potassium4 ,solution and ,separation4--,substances containing cadmium are soluble in acids4 ,the solution is evaporated to dryness 7to render any silica that may be present insoluble7 and taken up with #aj c4c4 of dilute hydrochloric acid4 ,dilute to #ajj c4c41 and pass sulphuretted hydrogen4 ,filter1 digest the precipitate with soda1 wash1 and boil with dilute sulphuric acid4 ,filter2 the filtrate contains the cadmium and1 possibly1 a small quantity of zinc1 from which it is best separated by reprecipitating with sulphuretted hydrogen4 ,,gravimetric ,,determination4 ,the solution containing the cadmium freed from the other metals is precipitated with sulphuretted hydrogen in a moderately-acid solution4 ,the precipitate is collected on a weighed filter1 and washed1 first with an acid solution of sulphuretted hydrogen1 and afterwards with water4 ,it is dried at #ajj ,c4 and weighed4 ,if free sulphur is suspected to be present1 extract with bisulphide of carbon1 and again weigh4 ,the residue is cadmium sulphide1 which contains #gg4gh per cent4 of cadmium4 ,it is a yellow powder insoluble in solutions of the alkalies1 alkaline sulphides1 or cyanide of potassium4 ,it dissolves readily in acid4 ,it cannot be ignited in a current of hydrogen without loss4 ,,volumetric ,,method4 ,the solution containing the cadmium is concentrated by evaporation1 and mixed with an excess of oxalic acid and alcohol4 ,the precipitate is filtered1 washed with alcohol1 dissolved in hot hydrochloric acid1 and titrated with permanganate of potassium4 ,,footnotes3 #fd ,when chromium is present some of the iron may escape precipitation but it can be recovered from the solution by means of ammonic sulphide4 #fe 7#a7 #aj;,fe,s,o#d #b,k,mn,o#d #h;,h#b,,so#d #e;,fe#b7,,so#d7c #b,mn,s,o#d ,k#b,,so#d #h;,h#b,o4 7#b7 #f;,fe,cl#b ,k#b;,cr#b,o#g #ad;,h,cl #c;,fe#b;,cl#f ,cr#b;,cl#f #b,k,cl #g;,h#b,o4 #ff 7#a7 ,fe#b;,cl#f ,sn,cl#b #b;,fe,cl#b ,sn,cl#d4 7#b7 ,fe#b;,cl#f ,,sh#b #b;,fe,cl#b #b;,h,cl ,s4 7#c7 ,fe#b;,cl#f ,na#b,,so#c ,h#b,o #b;,fe,cl#b ,na#b,,so#d #b;,h,cl4 7#d7 ,fe#b;,cl#f ,zn #b;,fe,cl#b ,zn,cl#b4 #fg #bj grams of stannous chloride and #bj c4c4 of dilute hydrochloric acid are diluted to one litre4 #fh ,the maximum reducing effect of zinc is obtained by exposing as large a surface as possible of the metal in a hot concentrated solution containing but little free acid 7,thorpe74 #fi ,about #e inches in diameter4 #gj #fa3 #fj33 #ei3 #eh4ac4 ,the iron in the ore is1 then1 the same in amount as that in #eh4ac c4c4 of the ferric chloride solution2 and since #ajj c4c4 of the latter contain #a gram of iron1 #eh4ac c4c4 of the same contains #j4ehac gram of iron2 and1 further1 if #a gram of ore carries this amount of iron1 #ajj grams of ore will obviously give #eh4ac grams of iron4 #ga ,these compounds are ,ni#b;,as and ,co#b;,as4 #gb ,with large quantities of iron the ferric precipitate should be re-dissolved and re-precipitated4 ,the filtrate must be added to the original filtrate4 #gc #d,k,cy ,ni,s,o#d ,k#b,ni,cy#d ,k#b,,so#d #b,k,cy ,ag,n,o#c ,k,ag,cy#b ,,kno#c 4'4 #b;,ag,n,o#c ,ni #gd ,zn ,h#b,,so#d ,h#b ,zn,s,o#d4 #ge ,these #ajd c4c4 are equivalent to #ajj c4c4 of dry air at #j ,c4 and #gfj mm4 ,,chapter ,,xii4 ,,tin--,,tungsten--,,titanium4 ,,tin4 ,tin occurs in nature as cassiterite 7containing from #ij to #ie per cent4 of oxide of tin71 which mineral is the source from which the whole of the tin of commerce is derived4 ,tin also occurs as sulphide combined with sulphides of copper and iron in the mineral stannine or bell-metal ore4 ,it is a constituent of certain rare minerals1 such as tantalite4 ,the methods of assaying tin in actual use are remarkable when compared with those of other metals4 ,the more strictly chemical methods are rendered troublesome by the oxide being insoluble in acids1 resembling in this respect the gangue with which it is associated4 ,moreover1 it is not readily decomposed by fusion with alkalies4 ,the oxide has first to be reduced to metal before the tin can be dissolved4 ,the reduction may be performed by fusing with potassic cyanide1 by heating to moderate redness in a current of hydrogen or coal gas1 or by heating to a higher temperature with carbon4 ,the reduced metal is only slowly dissolved by hydrochloric acid1 and although it is readily soluble in aqua regia1 the solution cannot be evaporated or freed from the excess of acids1 by boiling1 without loss of tin1 because of the volatility of stannic chloride4 ,there has long been a difficulty in getting a quick wet method4 ,the process of assaying tin ores adopted in the mines of ,cornwall is a mechanical one known as vanning1 the object of which is to find the percentage of black tin1 which1 it is well to remember1 is not pure cassiterite1 much less pure oxide of tin4 ,tin ore1 as taken from the lode1 contains from #b to #e per cent4 of cassiterite1 and is mainly made up of quartz1 felspar1 chlorite1 schorl1 and other stony minerals1 together with more or less mispickel1 iron and copper pyrites1 oxide of iron1 and wolfram4 ,the cassiterite has a specific gravity 7#f4d to #g4a7 considerably higher than that of the vein-stuff 7#b4e to #c4j71 and is concentrated by a series of washings till it is free from the lighter material4 ,those minerals which have a specific gravity approaching that of the cassiterite are not completely removed4 ,the mispickel and copper and iron pyrites are converted into oxides by roasting1 and are in great part removed by a subsequent washing4 ,the concentrated product is known as black tin1 and in this condition is sold to the smelter4 ,the chief foreign matters in the black tin are silica1 oxides of iron and copper1 and wolfram1 with traces of manganese and niobic acid2 and in certain stream ores there may be as much as #f or #g per cent4 of titaniferous iron4 ,the black tin from the mines contains from #e to #ab per cent4 of water1 and is sold and assayed wet4 ,a series of typical samples of black tin ranged as follows3-- ---------------------------------------- ------------------------ ,source of ,material4 ,percentage of ,metal ,specific ,gravity4 in ,dry ,ore4 ---------------------------------------- ------------------------ ,good mine ore #gb4j #f4ci ,inferior do4 #ga4e #f4fd ,titaniferous stream ore #fg4j #f4ci ,mine ore with wolfram #fd4e #f4fg ,ore from stream works #eh4e #e4ii ---------------------------------------- ------------------------ ,it will be seen from these figures that black tin is a very variable substance2 and that the specific gravity is largely influenced by the impurities2 hence1 it is only an indication of the percentage of metal when the same kind of ore is dealt with4 ,as already pointed out1 the object of vanning is to determine the proportion of black tin in the lode stuff4 ,the relation between the actual content in oxide of tin and the produce got by vanning has been tested on several occasions with results which show a fair degree of approximation4 ,the following are some published results of assays of the same batch of ore4 ,the vanning results were obtained by a ,cornish vanner of recognised ability1 and the wet assays by two ,london firms of the highest standing3-- ,vanning results3 7,average7 #ia lbs4 of black tin4 ,wet ,assay results3 ,a #hc4g lbs4 of stannic oxide4 ,b #gi4g lbs4 ,the vanner reported his black tin as containing #gj per cent4 of tin4 ,this will bring his result1 if calculated as stannic oxide1 to #hj4i lbs4 to the ton2 which agrees with the others4 ,according to our experience the van assay agrees fairly well with the wet one1 if the black tin is assumed to contain #ib4e per cent4 of stannic oxide 7,sn,o#b74 ,vanners are1 as a rule1 skilful men1 and show remarkable dexterity in separating the black tin1 with the help of their apparatus1 which consists simply of a shovel and a kieve of water4 ,an account of the process is given below4 ,but different vanners1 all good men1 will get different results working on material new to them4 ,the black tin weighed by the vanner is supposed to correspond in quality with the black tin returned from the floors of the mine for which he is assaying1 but this differs materially in different mines with the nature of the gangue4 ,the process leaves too much to the judgment of the vanner4 ,it is more than probable that in practice the returns from the dressing-floors check the assayer1 instead of1 as should properly be the case1 the assayer checking the returns4 ,it is only when this last is done that any control is had over the system of dressing4 ,a correct assay of this ore is a matter of some importance1 because of the high price of the metal4 ,the method of assaying the black tin is a dry one1 and consists of mixing it with culm1 and submitting it in a black-lead crucible to the highest temperature of a wind furnace4 ,the sample is taken wet as it arrives at the smelting house1 and is assayed direct4 ,the product of the assay is examined1 and a deduction of a considerable percentage is very properly made for impurities1 since the assay really determines the percentage1 not merely of tin1 but of the bodies present which are reducible at a white heat4 ,the judgment as to how much is to be deducted is assisted partly by an examination of the metal got from the assay1 and partly by the experience acquired in smelting similar ores4 ,the produce1 which is that of the impure tin1 is stated in parts in twenty2 thus a produce of #ad is equivalent to #gj per cent41 or to #ad cwt4 per ton4 ,illustration3 ,,fig4 #eg4 ,,mechanical ,,separation4--,,vanning4 ,this process1 which has already been referred to1 is carried out as follows3--,after sampling the ore in the ordinary way1 a quantity 7varying with its richness7 is weighed out4 ,special weights are generally used4 ,the standard weight1 marked #bjj1 weighs about an ounce2 with poor ores this quantity is taken for an assay1 but with richer ores #ajj or even #ej is sufficient4 ,the unit of weight has no special name1 but the parts in #bjj are spoken of as the produce2 thus1 if #bjj of ore were taken and #i4e of black tin were separated1 the produce would be #i-a_/b3 obviously half the produce will give the percentage4 ,the weighed portion of the ore is placed on the vanning shovel4 ,the vanner stands in front of a tub of water 7kieve7 and allows #cj or #dj c4c4 of water to flow on to the ore4 ,he then raises the shovel a little above the surface of the water1 and1 holding it nearly horizontal1 briskly rotates the water by imparting to the shovel a slight circular motion1 passing into an elliptical one 7front to back74 ,this causes the finer mud to be suspended in the liquid1 which is then run off1 leaving the body of the ore in the centre of the shovel4 ,this is repeated until the water after standing a moment is fairly clear4 ,about half as much water as before is brought on2 then1 with a motion which is similar to the previous one1 but with a jerk added in one direction1 the heavier minerals are thrown up1 and the stony matter brought back4 ,the jerk is produced just as the wave of water is returning4 ,the descending wave of water draws with it the bulkier and lighter particles of the ore1 whilst the heavier matter lying on the bottom is scarcely affected by it4 ,the jerky motion1 however1 carries it to the front of the shovel4 ,the lighter stuff is washed off1 and the residue dried by holding the shovel over the furnace4 ,it now corresponds1 more or less1 to the stuff which on the mine is sent to the calciner4 ,it is swept from the shovel into a scoop1 and transferred to a hot crucible2 in which it is calcined until free from sulphur4 ,some vanners calcine their samples before commencing to van4 ,the calcined ore is shaken out of the crucible on to the shovel2 rubbed up with a hammer2 and washed 7as at first7 to get rid of the finer and lighter waste4 ,the separating motions are again gone through2 and the head of the best of the black tin is thrown well up on one side of the shovel in the form of a crescent1 so as to leave room on the shovel to work with the tailings4 ,the quantity of water used is kept low1 to prevent this crop tin from being washed back again4 ,the tailings are then crushed to free the tin from adherent oxide of iron2 and again washed to throw up the remaining tin ore4 ,as this tin is finely divided1 it is more difficult to bring it up1 so that a vigorous and rapid motion is required4 ,the tailings are now washed off1 and the whole of the black tin is brought into the centre of the shovel4 ,it requires two or three washings more to free it from the waste it contains4 ,very small quantities of water are used4 ,the purity of the black tin can be seen by its appearance on the shovel4 ,the cleaned ore is dried as before1 freed from particles of iron with the aid of a magnet1 and weighed4 ,the weighings are carried to #a_/hth of the unit used4 ,the following example illustrates the method of calculation adopted on the mine4 ,a parcel of #a ton #b cwt4 #c qrs4 of tin ore with a produce of #de 7equal to #bb-a_/b per cent47 contains #e cwt4 #j qrs4 #ab lbs4 of black tin4 ,this result is obtained as follows3-- ton cwt4 qrs4 #a #b #c #i ----------------- #aj #d #c equivalent to multiplying by #de4 #e ---------------- #e4a #c #c strike off the first figure to the right4 #d multiply by #d to reduce to quarters4 --------- #d #ab #c --------- #d #ae #bh multiply by #bh to reduce to pounds4 ----- #aab #ae ----- #ab4g strike off the first figure to the right4 ,similarly1 a parcel of #bj tons #aj cwt4 with a produce of #i-a_/b contains #ai cwt4 #a qr4 #be lbs4 of black tin4 ,for the following information1 as well as for much of that already given about vanning1 we are indebted to ,captain ,reynolds1 of ,cook's ,kitchen ,mine4 ,to have a complete set of tools for all vanning purposes1 it will be necessary to get the following3--,a vanning shovel #ad inches long and #ac inches wide1 weighing not over #b-c_/d pounds4 ,it is made of hammered sheet iron of the shape shown in fig4 #eg4 ,it must have a light wooden handle 7preferably of deal7 #c feet long4 ,a bruising hammer1 weighing #b-a_/b pounds1 with a handle #a foot long4 ,a pair of tongs 7furnace7 #b-a_/b feet long1 made of #a_/b-;inch round iron4 ,and a set of ordinary clay crucibles for calcining4 ,there ought to be two sets of scales and weights3 the first should be confined to weighing the powdered tin stuff1 and the second ought to be a much higher class one1 for weighing the black tin obtained4 ,the furnace for roasting the sample should be #aj inches square and #ab inches deep1 with the fire-bars at the bottom three-quarters of an inch apart4 ,the water-box for vanning in should be at least #d feet long1 #b feet #f inches wide1 and #h inches deep4 ,,dry ,,methods4 ,for the following description of the process adopted in ,cornwall we are indebted to ,mr4 ,a4,k4 ,barnett1 ,f4,g4,s41 of ,chyandour4 ,cornish ,method4--,tin ,ore ,assay4--,the ore to be smelted or assayed should be concentrated to say not less than #ej per cent4 of metallic tin2 though to obtain satisfactory results it should be brought nearer #gj per cent41 as with ore containing less than #dj to #ej per cent4 of metal there will be a considerable loss both in the assaying and in the smelting4 ,if the ore to be operated on does not contain this quantity of metal1 then the sample 7if coarse7 must be reduced to a fine state1 the gangue being removed by vanning1 and the ore saved for the fire assay4 ,the method adopted for the determination of tin in the ore is as follows3--,about #b-a_/b ounces troy 7#abjj grains1 or about #hj grams7 of the ore to be assayed is weighed out and mixed on a flat copper pan 7shaped with a long lip7 with one-fifth of its weight 7#bdj grains1 or #ae4e grams7 of powdered culm 7anthracite74 ,the mixture of ore and culm is either transferred to a black-lead crucible before the latter is put into the furnace1 or1 as some prefer1 it is carefully swept into a crucible which has been imbedded in the fire4 ,some assayers cover their pots with a flat cover placed loosely on1 while others leave the mixture in the open pot4 ,the furnace1 which has been previously fired to a strong heat1 is then covered1 and the sample is subjected to a sharp fire for a period of from twelve to twenty minutes4 ,no definite time can be stated1 as1 besides the strength of the fire1 the quality and condition of the ore1 and the impurities associated with it1 greatly affects the time required for the complete reduction of the ore4 ,as soon as the mixture in the crucible has settled down to a uniform white heat1 and any very slight ebullition which may have taken place has subsided1 the crucible is gently shaken1 removed from the fire 7the culm-ash or slag which covers the metal being carefully drawn aside with an iron scraper71 and the metal is poured quickly into an iron ingot-mould1 which is usually placed on a copper pan to save the culm-slag and the adherent metal which comes out with it4 ,the crucible is then carefully scraped1 and the scrapings1 together with the contents of the mould and pan1 are transferred to a mortar4 ,there the ingot of tin is freed from slag and then taken to the scales4 ,the rest1 after being finely powdered1 is passed through a sieve4 ,the flattened particles of tin which remain on the sieve are weighed with the ingot 7the lump1 as it is called72 whilst the siftings are vanned on a shovel1 and 7the slag being washed off7 the fine tin is collected1 dried1 and weighed with the rest3 the whole gives the produce or percentage of metal in the ore4 ,the results of the assays are expressed in cwts4 of metal in the ton of ore4 ,the percentage is rarely given and never used in ,cornwall4 ,thus--#ac-a_/b ,produce would mean that the assay yielded results at the rate of #ac-a_/b cwts4 of metal for one ton of the ore4 ,some assayers use a little powdered fluor-spar to assist the fusion of refractory slags4 ,a small quantity of borax will also occasionally be of service for ores containing silica in excess of any iron that may be present4 ,the borax renders the slag more fusible1 and assists the formation of a larger lump 7with less fine tin in the slag7 than would be obtained by the use of culm alone4 ,the quality and the percentage of pure tin in the metal will vary considerably1 according to the impurities that are associated with the ore to be assayed4 ,the crude lump is then remelted in a small iron ladle at as low a temperature as possible1 and the fused metal is poured into a shallow trench about #d inches long by #c_/d of an inch wide cut in a block of white marble4 ,the metal will be silvery-white if the temperature employed be correct2 if too hot1 the surface will show a yellow1 red1 or blue colour 7according to the heat employed72 in such case the metal should be remelted at a lower temperature4 ,if the metal on cooling remains perfectly clear and bright1 then it may be assumed that the tin is of good quality and commercially pure4 ,a crystallised or frosted appearance of the metal indicates the presence of some alloy1 say of iron1 copper1 zinc1 lead1 antimony1 c4 ,the assayer who has had much practice can readily distinguish the metal or metals that are associated with the ore by noting the appearance of the tin on cooling2 and can fairly judge the quantity of impurity present by the amount of the crystallisation or stain4 ,whilst the foregoing method of assaying cannot lay claim to scientific accuracy1 it is by no means so imperfect as some writers would have us believe1 who state that a loss of #e to #aj per cent4 arises in the operation4 ,it is certainly the most ready and expeditious mode of determining the commercial value of a parcel of tin ore1 which1 after all1 is the main object of all assaying operations4 ,the difficulty which beginners find in obtaining satisfactory results1 and any loss of metal which those not accustomed to the process may incur1 will invariably occur in the vanning of the powdered slag for the fine tin1 the rest of the operations being easy of execution1 and requiring only the ordinary care necessary for all metallurgical work4 ,there is no doubt that if low percentage ores containing silica are assayed in this manner1 low results are obtained1 as it is impossible to reduce the whole of the tin in the presence of free silica2 with this class of ores1 care should be taken to remove some of the silica by preliminary vanning1 or some flux should be added which will combine with the silica1 and so prevent its entering into combination with the tin4 ,low quality tin ores containing iron1 copper1 lead1 zinc1 antimony1 etc41 combined with arsenic1 sulphur1 or oxygen1 will give very much higher results than the actual percentage of tin in the sample4 ,the other metals 7being readily reduced in the presence of tin7 alloy with it1 and give a hard lump difficult to fuse in the iron ladle2 where the quantity of foreign metals is large1 the metal can only be melted to a stiff pasty mass2 so that 7in determining the value of a ton of tin ore1 or even reporting on the percentage of tin it contains7 not only must the weight of the assay be the basis for calculation1 but the quality and character of the metal obtained must also be considered4 ,thus two ores of tin might be assayed both yielding a similar produce1 say #ac-a_/b 7#fg-a_/b per cent471 and yet one might contain #e per cent4 less tin than the other4 ,if it be required to obtain the pure metal from tin ores containing the ores of other metals associated with them1 the latter must be removed by digesting in strong hydrochloric acid1 and washing4 ,the assay may then be conducted in the usual way1 and a fairly pure lump will be obtained4 ,if wolfram be present in any appreciable quantity in the ore1 it considerably reduces the proportion of lump1 and at the same time it increases the fine tin 7or prillion1 as it is termed7 in the assay4 ,this may be got rid of by boiling in aqua regia1 and dissolving out the tungstic acid which has been liberated by means of ammonia4 ,it will be seen that this method of assaying tin has its advantages and its drawbacks4 ,it is quickly performed2 with ores of good quality it gives results not to be excelled by any other process2 and it gives the smelter the actual alloy and quality of metal he may expect to get in the smelting of the ore1 which no other mode of assaying will do3 against which may be set the skill required to obtain accurate results with the vanning shovel2 the loss of metal in poor ores containing an excess of silica2 and the high results from ores containing a large quantity of metallic impurities4 ,cyanide ,method4--,weigh up #bj grams of the ore and dry it on a scoop over the ,bunsen flame4 ,when dry1 weigh1 and calculate the percentage of water from the loss in weight4 ,transfer the dried ore to an evaporating dish1 and cover with #cj c4c4 of hydrochloric acid2 boil for #aj or #ab minutes1 and then add #e c4c4 of nitric acid and boil again4 ,dilute with water1 and filter4 ,transfer the filter and its contents to an ,e ,battersea crucible1 and calcine it for a few minutes4 ,cool1 and weigh the residue4 ,the loss equals the oxides soluble in acid4 ,transfer the residue to the crucible and mix it with its own weight of cyanide of potassium2 add a similar amount of cyanide as a cover4 ,place in the furnace1 and when the charge has attained the temperature of the furnace 7in from #c to #f minutes71 remove it at once2 tap the pot vigorously several times1 and then pour its contents quietly into a mould4 ,dissolve the slag in water1 clean1 dry1 and weigh the button of tin4 ,,wet ,,methods4 ,detection4--,tin ore is detected by its insolubility in acids1 high specific gravity1 and characteristic appearance in water4 ,the powder is separated from the lighter gangue by washing4 ,it is fused in a ,berlin crucible with five times its weight of potassic cyanide at a moderately high temperature in a muffle1 or over the blowpipe4 ,the slag is washed off with water1 and the metallic buttons or residue treated with hydrochloric acid 7not aqua regia71 for some time4 ,one portion of the solution strikes a purple colour with chloride of gold1 another portion gives a white or grey precipitate or cloudiness with mercuric chloride4 ,these reactions are characteristic of tin as stannous chloride4 ,metallic tin treated with nitric acid becomes converted into a white insoluble powder 7metastannic acid74 ,aqua regia dissolves tin readily1 forming stannic chloride1 and in this solution the metal is detected by precipitation with sulphuretted hydrogen1 which gives a yellow precipitate4 ,tin in solution as stannic or stannous chloride is precipitated as metal by means of zinc4 ,the fact that tin forms two well-defined series of compounds is taken advantage of in assaying 7just as in the case of iron71 by determining how much of an oxidising agent is required to convert it from the stannous into the stannic state4 ,for example1 on the addition of a solution of permanganate of potash to a solution of stannous chloride the oxidation goes on rapidly1 and the finishing point is sharp and distinct2 but acid solutions of stannous chloride quickly take up oxygen from that dissolved in the water used and from the air4 ,unfortunately1 there is no obvious sign that such oxidation has taken place1 except that 7fatal to the assay7 a smaller volume of the permanganate is required4 ,great care is required with such solutions1 both before and during titration4 ,the addition of an excess of ferric chloride to the stannous solution1 as soon as the whole of the tin has been dissolved1 will lessen this liability to oxidation4 ,separation4--,if the tin is present in an alloy1 the substance is boiled in an evaporating dish with dilute nitric acid until the whole of the material is attacked4 ,evaporate nearly to dryness1 dilute1 boil for a few minutes1 and filter off the white insoluble residue4 ,under certain circumstances this residue will be nearly free from other metals1 in which case it is ignited and weighed4 ,if not known to be pure it must be ignited1 reduced in a current of hydrogen1 and treated as subsequently described4 ,when the tin is present as insoluble oxide in an ore1 the substance is finely powdered1 and from #a to #e grams of it 7according to its richness7 boiled with #cj c4c4 of hydrochloric acid in an evaporating dish till the oxide of iron is seen to be dissolved4 ,then add #a c4c4 of nitric acid 7or more if much pyrites1 c41 is present7 and continue the boiling till these are decomposed2 dilute and filter off1 washing first with dilute acid and afterwards with a little dilute ammonia1 dry1 ignite1 and place in a combustion tube 7together with the filter-ash7 and heat to redness for about thirty minutes in a current of dried hydrogen4 ,illustration3 ,,fig4 #eh4 ,the oxide of tin is placed in a porcelain boat 7fig4 #eh71 which is then introduced into a piece of combustion tube4 ,the latter1 wrapped in a piece of wire gauze1 is supported on a couple of iron rings1 and heated by one or two ,bunsen burners in a furnace fitted up with loose fire-brick tiles1 as shown in fig4 #ei4 ,illustration3 ,,fig4 #ei4 ,when the reduction is complete the tube is allowed to cool2 the boat is removed and the tin dissolved4 ,add a rod of zinc to the freely-acid hot solution1 and in a few minutes decant through a filter and wash with water1 after having removed the zinc4 ,wash the precipitated metal back into the beaker1 and dissolve in #aj c4c4 of dilute nitric acid1 evaporate off the excess of acid2 dilute1 boil1 and filter4 ,wash1 dry1 ignite strongly in a porcelain crucible1 and weigh4 ,in the absence of antimony the above separation works very well1 but if this metal is present in quantity the metals precipitated on the zinc must be covered with hydrochloric acid and treated with a few drops of nitric4 ,it is then warmed with iron wire until no more of the latter dissolves4 ,the antimony is precipitated as metal1 and the tin remains in solution as stannous chloride4 ,the antimony is filtered off1 and may be washed with alcohol1 and weighed1 whilst the tin in the filtrate is precipitated with zinc1 and treated as already described4 ,,gravimetric ,,method4 ,if the tin is not already in the metallic state it is reduced to this condition by the method given 7precipitation by zinc74 ,treat the finely-divided metal 7washed free from chlorides7 in a four-inch evaporating dish with #aj c4c4 of dilute nitric acid1 cover with a clock-glass1 and apply a gentle heat until the precipitate appears of a white colour and the metal is completely attacked4 ,evaporate nearly to dryness on a water-bath2 then add #ej c4c4 of water1 heat to boiling1 and filter4 ,wash with hot water1 dry1 transfer to a weighed porcelain crucible1 add the filter-ash1 ignite strongly1 and weigh4 ,the precipitate after ignition is stannic oxide 7,sn,o#b74 ,it is a yellowish-white powder 7darker whilst hot71 insoluble in acids1 and contains #gh4fg per cent4 of tin4 ,cold dilute nitric acid dissolves tin to a clear solution1 which becomes a white enamel-like jelly on heating2 this 7filtered off1 washed1 and dried7 forms an opal-like substance1 which is converted on ignition into stannic oxide with evolution of nitrous fumes4 ,stannic oxide when ignited with chlorides is more or less completely converted into stannic chloride1 which volatilises4 ,the presence of chlorides during the evaporation with nitric acid causes a similar loss4 ,determination of ,tin in an ,alloy4--7,bronze47--,take #b grams1 and attack with #bj c4c4 of dilute nitric acid in a covered beaker with the aid of heat4 ,boil till the bulk is reduced by one-half1 dilute with #ej c4c4 of water1 allow to settle for a few minutes1 and filter2 wash well first with water acidulated with a little nitric acid1 and afterwards with water2 dry1 ignite1 and weigh as stannic oxide4 ,determination of ,tin in ,tin ,ore4--,treat #e grams of the dried and finely-powdered ore with #cj c4c4 of hydrochloric acid in a four-inch evaporating dish4 ,after the soluble oxides have been dissolved add #a or #b c4c4 of nitric acid1 boil off nitrous fumes1 dilute1 and filter4 ,dry the filter1 transfer the cleaned ore to a piece of combustion tube ten or twelve inches long and narrowed at one end4 ,pass a current of hydrogen through the tube and heat to redness for #cj minutes2 cool whilst the gas is still passing4 ,dissolve in #bj c4c4 of dilute hydrochloric acid and keep the solution tinted with permanganate of potassium4 ,when the colour of the permanganate becomes permanent dilute to a bulk of #ej c4c4 with water1 filter1 and wash4 ,heat2 add a rod of zinc weighing about #c grams2 allow to stand for a few minutes2 decant through a filter2 and wash1 removing the remaining zinc and returning the tin to the beaker4 ,treat with #e c4c4 of dilute nitric acid1 boil for some time1 take up with water1 filter1 wash1 dry1 ignite1 and weigh as stannic oxide4 ,,volumetric ,,method4 ,titration with ,solution of ,permanganate of ,potassium4--,this titration may be made either directly on the solution of stannous chloride 7prepared by dissolving the precipitated metal in hydrochloric acid71 or indirectly1 on a solution of ferrous chloride 7produced by the reducing action of the precipitated metal on ferric chloride74 ,the standard solution of permanganate of potassium is made by dissolving #e4cef grams of the salt in water and diluting to one litre4 #ajj c4c4 are equivalent to #a4jj gram of tin4 ,the precipitated tin is transferred to a flask2 and dissolved in #aj c4c4 hydrochloric acid1 with the aid of heat and in an atmosphere of carbonic acid4 ,the acid and metal are placed in the flask2 which is then filled with the gas1 and stopped with a cork provided with a rubber valve4 ,when solution is complete the flask is again filled with carbonic acid4 ,fifty c4c4 of water freed from air and saturated with carbonic acid are then added4 ,this water is made by adding a gram of bicarbonate of soda and #b c4c4 of hydrochloric acid to #ajj c4c4 of water3 the effervescence sweeps out the dissolved oxygen4 ,the permanganate of potassium solution is then run in from a stop-cock burette in the usual way until a faint pink tinge is obtained4 ,the following experiments show the effect of variations in the conditions of the assay4 ,a solution of stannous chloride equivalent in strength to the permanganate was made by dissolving #ai4jf grams of the crystallised salt 7,sn,cl#b4b;,h#b,o47 in #ej c4c4 of water and #aj c4c4 of hydrochloric acid and diluting to #a litre with water freed from dissolved oxygen4 #ajj c4c4 contain #a gram of tin4 ,in the first experiments tap water was used and no precautions were taken for excluding air4 ,except when otherwise stated1 #bj c4c4 of the stannous chloride were used in each experiment with #aj c4c4 of hydrochloric acid1 and were diluted to #ajj c4c4 with water before titration4 ,effect of ,varying ,hydrochloric ,acid4 ,acid added #a4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 ,permanganate required #ah4h #ah4i #ah4h #ah4h ,the only effect of the increase in quantity of acid was to give the brown of perchloride of manganese instead of the pink of permanganic acid to mark the finishing point4 ,effect of ,varying ,temperature4 ,temperature #ae ,c4 #ej ,c4 #gj ,c4 #ajj ,c4 ,permanganate required #ah4h c4c4 #ah4g c4c4 #ah4f c4c4 #ah4d c4c4 ,rate of ,atmospheric ,oxidation4--,solutions ready for titration were exposed to air at the ordinary temperature for varying lengths of time and then titrated4 ,time exposed #j min4 #e min4 #aj min4 #bj min4 #fj min4 ,permanganate required #ah4h c4c4 #ah4h c4c4 #ah4h c4c4 #ah4h c4c4 #ah4f c4c4 ,it is best to titrate at once1 although the loss by oxidation is only small after one hour's exposure4 ,effect of ,varying ,tin4 ,stannous chloride added #a4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,permanganate required #j4g #h4h #ah4j #dg4d #ie4d ,effect of ,varying ,bulk4 ,bulk #ej4j c4c4 #ajj4j c4c4 #bjj4j c4c4 #ejj4j c4c4 ,permanganate required4 #i4j #ah4c #ag4d #ae4a ,the two last series show an interference1 which is due to the oxygen dissolved in the water1 as may be seen from the following similar experiments1 which were1 however1 performed with water freed from oxygen and in which the titrations were effected in an atmosphere of carbonic acid4 ,effect of ,varying ,tin4--,a new solution of stannous chloride was used4 ,stannous chloride added #a4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,permanganate required #a4j #aj4j #ai4h #di4f #ii4c ,effect of ,varying ,bulk4 ,bulk #cj4j c4c4 #ej4j c4c4 #ajj4j c4c4 #bjj4j c4c4 #ejj4j c4c4 ,permanganate required #ai4h #ai4h #ai4h #ai4h #ai4h ,it will be seen that in working under these conditions the results are proportional and the method satisfactory4 ,examination of ,tin ,phosphide4--7,phosphor ,tin47--,this substance is used in the manufacture of phosphor bronze and similar alloys4 ,it is a crystalline1 imperfectly-malleable1 metallic substance4 ,it is soluble in hydrochloric acid with effervescence2 phosphoretted hydrogen1 which inflames on the addition of a drop or two of nitric acid1 being evolved4 ,it is attacked by nitric acid1 yielding a white powder of stannic phosphate2 this is not easily decomposed by ammonium sulphide or readily soluble in hydrochloric acid4 ,phosphor-tin is made up only of tin and phosphorus4 ,for the estimation weigh up #a gram4 ,place in a weighed ,berlin dish2 and cover with #aj c4c4 of nitric acid and #c or #d c4c4 of water4 ,let the reaction proceed 7under a clock-glass7 on the water-bath till complete4 ,remove the glass2 evaporate to dryness1 and ignite1 at first gently over a ,bunsen burner1 and afterwards in the muffle at a red heat4 ,cool in the desiccator1 and weigh as quickly as possible when cold4 ,the substance contains the tin as stannic oxide1 ,sn,o#b1 and the phosphorus as phosphoric oxide1 ,p#b,o#e4 ,the increase in weight on the gram of substance taken gives the weight of the oxygen taken up by the phosphorus and tin1 and since #a gram of tin takes up only #j4bga gram of oxygen1 and #a gram of phosphorus takes up #a4bi gram1 the proportion of tin to phosphorus can be calculated from the increase in weight4 ,for example1 #a gram of a sample gave #a4cdaj gram of mixed oxides1 which is #j4jgj gram in excess of that which would be got with pure tin4 ,if the substance was all phosphorus the excess would be #a4jaij gram2 consequently the proportion of phosphorus in the substance is #j4jgj _/ #a4jai1 or #f4hg per cent4 ,the tin is calculated by difference1 #ic4ac per cent4 ,another method of separating and determining the phosphorus is as follows3--,take #a gram of the substance and add to it #ae c4c4 of hot aqua regia4 ,boil till dissolved1 dilute1 and precipitate the tin with sulphuretted hydrogen4 ,to the filtrate add ammonia and magnesia mixture4 ,filter2 wash the precipitate with dilute ammonia2 dry1 ignite1 and weigh as magnesic pyrophosphate4 ,calculate the phosphorus1 and take the tin by difference4 ,a sample of phosphor tin gave-- ,tin #ic4a per cent4 7by difference7 ,phosphorus #f4i ----- #ajj4j ,tin ,arsenide4--,this is met with in tin-smelting2 it closely resembles the phosphide1 but the crystals have a duller grey appearance4 ,it contains simply tin and arsenic4 ,the determination is made by treating #a gram of the substance with nitric acid and weighing the mixed oxides of tin and arsenic in the same manner as in the case of the phosphide4 ,one gram of arsenic will give #a4ecc gram of arsenic oxide1 ,as#b,o#e2 consequently the excess of weight of the mixed oxides over #a4bga gram must be divided by #j4bfb2 the result multiplied by #ajj gives the percentage of arsenic4 ,in consequence of the higher atomic weight of arsenic the results by this method are not so close as with the phosphide4 ,each milligram of excess weight 7over #a4bga7 represents #j4ch per cent4 of arsenic1 ,as4 ,both in this and in the corresponding phosphide determination care must be taken to avoid absorption of moisture1 by allowing the oxides to cool in a desiccator and weighing quickly4 ,the percentage of arsenic is better determined as follows3--,weigh up #a gram of the substance1 dissolve in aqua regia1 dilute1 and pass sulphuretted hydrogen4 ,render alkaline with ammonia1 and add ammonium sulphide till the precipitate is dissolved4 ,add magnesia mixture4 ,filter off the precipitate1 wash with dilute ammonia1 ignite with a few drops of nitric acid1 and weigh as magnesic pyrarsenate4 ,calculate the arsenic and take the tin by difference4 ,a sample treated in this way gave-- ,tin #if4h per cent4 by difference ,arsenic #c4b ----- #ajj4j ,examination of ,black ,tin4--,dry the ore1 and reduce it to a fine powder4 ,weigh up #b grams1 and boil with #bj c4c4 of hydrochloric acid and #b c4c4 of nitric for ten or fifteen minutes4 ,filter1 and reserve the filtrate4 ,tungstic ,acid4--,digest the residue with about #ej c4c4 of water and a few c4c4 of dilute ammonia for a few minutes1 and filter2 collect the filtrate in a weighed porcelain dish1 evaporate to dryness1 ignite1 and weigh as tungstic acid1 ,,wo#c4 ,stannic ,oxide4--,dry1 ignite1 and weigh the insoluble residue4 ,transfer to a porcelain boat1 and reduce in a current of hydrogen at a red heat for half an hour4 ,allow to cool whilst the hydrogen is still passing4 ,transfer the boat to a beaker1 and dissolve up the tin in #aj c4c4 of hydrochloric acid and a c4c4 or so of nitric4 ,wash out the combustion tube with some acid and add the washing to the contents of the beaker4 ,warm gently1 dilute with water1 and filter4 ,collect1 dry1 ignite1 and weigh the insoluble residue4 ,through the filtrate pass a rapid current of sulphuretted hydrogen1 allow to settle1 and filter4 ,wash the precipitate with hot water1 dry1 calcine gently2 ignite with ammonium carbonate1 and weigh as stannic oxide1 ,sn,o#b4 ,the insoluble residue will in most cases retain some tin4 ,fuse it with fusion mixture1 take up with hydrochloric acid1 filter1 pass sulphuretted hydrogen through the filtrate1 collect and wash the sulphide of tin4 ,ignite and weigh as stannic oxide1 and add it to that previously obtained4 ,copper4--,pass sulphuretted hydrogen through the acid filtrate obtained in the first cleaning of the ore1 collect the precipitate1 and wash first with soda solution and then with hot water4 ,dry1 ignite1 and weigh as cupric oxide1 ,cu,o4 ,mix the filtrate with that from the main portion of the sulphide of tin4 ,ferric ,oxide4--,boil off the sulphuretted hydrogen from the mixed filtrates and peroxidise with nitric acid4 ,add ammonia in slight excess1 boil1 filter1 dry1 ignite1 and weigh the precipitate as ferric oxide4 ,this will be practically pure1 but the iron in it must be determined by dissolving and titrating4 ,the filtrate from the iron may contain zinc1 lime1 and magnesia1 but rarely in quantities sufficient to be determined4 ,silica1 c4---,the silica may be calculated from the weight of the residue insoluble in acid1 after the reduction of the tin in hydrogen1 by deducting from it the weight of the oxide of tin subsequently found4 ,or it may be determined as follows3--,the insoluble portion is fused with fusion mixture1 and taken up with hydrochloric acid1 as already described4 ,on filtering1 the filter will retain a portion of the silica4 ,the rest is recovered1 after the removal of the stannous sulphide1 by evaporating to dryness1 taking up with hydrochloric acid1 and filtering through the same filter4 ,it is washed1 dried1 ignited1 and weighed as silica4 ,the filtrate from the silica is boiled with a little nitric acid and precipitated with ammonia4 ,the precipitate is collected1 washed1 ignited1 and weighed as ferric oxide and alumina 7but it frequently contains oxide of titanium74 ,when the last is present it is determined by fusing with bisulphate of potash and extracting with cold water4 ,the solution is nearly neutralised with ammonia1 charged with sulphurous acid1 and boiled4 ,the precipitate is collected1 washed1 dried1 ignited1 and weighed as oxide of titanium1 ,ti,o#b4 ,the difference between this weight and that of the combined oxides gives the ferric oxide and alumina4 ,the filtrate from the mixed oxides is examined for lime and magnesia4 ,sulphur4--,rub up #e grams of the ore with #e grams of nitre1 transfer to a porcelain dish1 and fuse over a ,bunsen burner for fifteen minutes4 ,when cold1 extract with water1 and determine the sulphur volumetrically with standard barium chloride4 ,the sulphur may be present as sulphide or sulphate4 ,arsenic4--,take #e grams1 and evaporate with nitric acid2 dilute1 add ammonia1 pass sulphuretted hydrogen1 and filter4 ,to the filtrate add magnesia mixture4 ,collect the precipitate1 ignite with nitric acid1 and weigh as magnesic pyrarsenate4 ,the following may be taken as an example of the composition of an impure black tin3-- ,tungstic acid #a4h ,stannic oxide #gi4j ,silica #b4f ,titanic oxide #j4h ,copper oxide #j4i ,ferric oxide #ac4d ,sulphur #j4d ,arsenic #j4c ---- #ii4b ,examination of ,hardhead4--,in the smelting of tin ores a quantity of speise1 known as hardhead1 is produced4 ,it is essentially an arsenide of iron1 carrying a considerable quantity of tin4 ,much of this last is present in the form of small buttons of metal distributed through the mass4 ,the buttons can be seen on careful inspection1 and become evident on powdering4 ,in assaying the substance1 a variation in the usual method of sampling is required1 because of the quantity of metal present which cannot be powdered4 ,after powdering as finely as possible1 the coarse particles are sifted off and weighed4 ,the weight of the powder is also taken4 ,the method of working is best illustrated by an example4 ,a sample of hardhead weighed #aee4a grams1 and gave #ba4j grams of coarse particles1 equivalent to #ac4e per cent4 of the whole4 ,the fine portion weighed #acd grams1 which is equivalent to #hf4e per cent4 ,thirteen and a half grams of the coarse material were dissolved in aqua regia1 and diluted with water to #a litre4 ,ten c4c4 of this contain #j4ace gram of the metallic portion1 which is the amount contained in #a gram of the original hardhead4 ,if1 in a determination1 #a gram of the substance is wanted1 weigh up #j4hfe gram of the powdered portion1 and add to it #aj c4c4 of the solution4 ,it will be seen that these together make up #a gram of the original sample4 ,the solution of the metallic portion must be saved until the analysis is finished4 ,tin and ,copper4--,weigh up the portion of the powdered stuff equivalent to #a gram of the sample4 ,transfer to a flask1 and cover with #aj c4c4 of the solution of the metallic portion and #aj c4c4 of aqua regia4 ,boil gently till oxidation is complete and the nitric acid for the greater part driven off4 ,dilute to #ajj c4c4 with water1 and pass sulphuretted hydrogen for some time4 ,filter1 wash with hot water1 and rinse through the funnel back into the flask4 ,digest with yellow sodium sulphide until only a light1 flocculent1 black precipitate is left4 ,filter this off1 wash with hot water1 dry1 calcine1 treat with a little nitric acid1 ignite1 and weigh as copper oxide1 ,cu,o4 ,the weight multiplied by #j4gihc gives the weight of copper4 ,the filtrate containing the tin is rendered acid with hydrochloric acid1 and filtered4 ,the precipitate is rinsed into a half-pint beaker1 covered with #bj c4c4 of hydrochloric acid1 and boiled down to about #bj c4c4 ,the solution is filtered off from the sulphur and sulphide of arsenic1 which1 after washing with hot water1 is transferred to a flask labelled arsenic4 ,a strip of sheet zinc 7#b in4 by #a in47 is placed in the solution4 ,the evolution of hydrogen should be brisk4 ,in five or ten minutes decant off a few c4c4 of the liquid1 and test with sulphuretted hydrogen for tin4 ,if no yellowish precipitate is formed1 decant off the rest of the liquid1 and wash the precipitated metal with hot water two or three times by decantation4 ,the metal should be in a lump2 if there are any floating particles they must be made to sink by compression with a glass rod4 ,transfer the washed metal to an evaporating dish #c or #d in4 across1 and cover with a few c4c4 of hot water4 ,add nitric acid drop by drop till the tin is completely attacked4 ,evaporate nearly to dryness1 and add a drop or two more of nitric acid and #bj c4c4 of water4 ,boil and filter4 ,wash with hot water1 dry1 ignite1 and weigh as stannic oxide1 ,sn,o#b4 ,calculate to metallic tin by multiplying by #j4ghfg4gf ,the filtrate from the first treatment with sulphuretted hydrogen will probably no longer smell of the gas4 ,warm and pass the gas for a few minutes longer4 ,filter off any precipitate of sulphide of arsenic1 and transfer it to the flask for arsenic4 ,boil the filtrate 7ignoring any signs of a further precipitation of arsenic7 with a few c4c4 of nitric acid1 and separate the iron as basic acetate4 ,wash2 reserve the filtrate for cobalt4 ,iron4--,rinse back the basic acetate1 precipitate into the flask1 add ammonia1 dilute with water to about #ajj c4c41 and pass sulphuretted hydrogen for a few minutes4 ,filter1 and wash with hot water4 ,collect the filtrate in the flask labelled arsenic4 ,boil the precipitate with dilute sulphuric acid1 filter1 and titrate the filtrate with the permanganate of potassium solution after boiling off the sulphuretted hydrogen4 ,report the result as iron4 ,the sulphuric acid will not effect complete solution1 a light black residue will remain1 chiefly sulphur2 this must be rinsed into the filtrate from the acetate separation4 ,it contains cobalt4 ,cobalt4--,the filtrate from the acetate separation will have a pink colour4 ,render it ammoniacal and pass sulphuretted hydrogen4 ,collect the precipitate on a filter1 dry1 and ignite4 ,dissolve in hydrochloric acid1 and evaporate nearly to dryness with an excess of nitric acid4 ,dilute with #aj or #bj c4c4 of water and add potash solution in slight excess4 ,add acetic acid until the solution is acid and the precipitate is quite dissolved4 ,add #bj or #cj c4c4 of a strong solution of potassium nitrite1 and determine the cobalt1 as described on pp4 #bed1 #bef4 ,boil the filtrate from the cobalt1 precipitate with hydrochloric acid1 render ammoniacal1 and test for zinc1 nickel1 and manganese4 ,the remainder of the tin will be contained in the flask labelled arsenic4 ,acidify with hydrochloric acid and filter4 ,rinse into a beaker1 and evaporate to a small bulk with #aj c4c4 of nitric acid4 ,dilute and filter4 ,dry the precipitate1 consisting of stannic arsenate 7#b,sn,o#b4;,as#b,o#e71 ignite1 and weigh4 ,calculate the tin it contains by multiplying by #j4ddec1 and add to that already found4 ,arsenic4--,this is determined in a separate portion4 ,weigh up a portion of the powder equivalent to #a gram of the hardhead1 place in a pint flask1 and boil with #aj c4c4 of nitric acid4 ,when action has ceased add #aj c4c4 of the solution of the metallic portion and then hydrochloric acid 7a few drops at a time7 till solution is complete4 ,warm gently in dissolving1 but do not boil4 ,dilute to about #ajj c4c41 render alkaline with ammonia1 and add #bj c4c4 of yellow ammonium sulphide4 ,digest at a gentle heat for about thirty minutes1 filter1 and wash4 ,add #ej c4c4 of magnesia mixture1 shake well1 allow to stand for an hour1 filter1 and wash with dilute ammonia4 ,the precipitate is dissolved and then titrated with uranium acetate1 or it is evaporated with nitric acid1 ignited1 and weighed as pyrarsenate of magnesia4 ,calculate the result to arsenic1 ,as4 ,sulphur4--,weigh up a portion of the powder equivalent to #b or #c grams of the hardhead4 ,rub up in a mortar with #e grams of nitre and fuse in a porcelain dish for ten minutes4 ,extract with water1 add #bj or #cj c4c4 7as the case may be7 of the solution of the metallics4 ,add #aj grams of sodic acetate1 and ferric chloride until the precipitate turns brown2 dilute with water to half a litre1 boil1 and titrate with standard baric chloride1 as described under ,sulphur4 ,report as sulphur4 ,a sample of hardhead examined in this way gave-- ,sulphur #c4jj ,arsenic #bg4aj ,tin #bb4b ,copper #a4fd ,iron #dc4b ,cobalt #b4f ------ #ii4gd ,examination of ,tin ,slags4--,in tin smelting works the term slag is applied to the unfused portion of the charge4 ,it is made up of unburnt anthracite and small lumps of slag proper together with some buttons of metallic tin4 ,this is rarely1 if ever1 assayed4 ,the slag proper 7or1 as it is generally called1 glass7 is a silicate of iron1 alumina1 and lime1 containing from #c to #g per cent4 of tin4 ,it is thus examined3--,the sample after bruising on an iron plate1 is reduced to a very fine powder by grinding in an agate mortar4 ,in this state it is in most cases readily decomposed by hydrochloric acid4 ,determination of ,tin4--,where the percentage of tin only is required1 take #b grams of the powdered slag and well mix with it #bj c4c4 of hydrochloric acid1 and heat to boiling4 ,add #a c4c4 of nitric acid1 allow to stand for fifteen minutes1 dilute with water1 and filter4 ,pass a rapid current of sulphuretted hydrogen for some time4 ,allow to settle1 and filter4 ,the precipitate1 after washing with hot water1 is dried1 and gently calcined until the greater part of the sulphur is burnt off4 ,it is then strongly ignited in the muffle 7or over the blowpipe7 with the addition of a small lump of ammonic carbonate4 ,the residue is weighed as stannic oxide 7,sn,o#b72 and is calculated to metallic tin by multiplying by #j4ghg4 ,the percentage on the slag is calculated in the usual way4 ,the tin is always best determined in the examination of slags by a separate assay carried out in this way4 ,the determination of the other constituents is thus made3-- ,silica4--,take #b grams of the powdered slag and cover them1 in a small evaporating dish1 with #bj c4c4 of hydrochloric acid2 mix well by stirring with a glass rod2 and evaporate to dryness4 ,if 7as is generally the case7 tungsten is present the solution will be blue4 ,take up with #bj c4c4 of hydrochloric acid4 ,add #a c4c4 of nitric acid2 and reduce by boiling to about half the bulk4 ,add about #bj c4c4 of water1 boil1 and filter4 ,wash the residue with hot dilute hydrochloric acid4 ,it consists of silica with the tungstic acid4 ,wash it back into the dish2 and digest with #e or #aj c4c4 of a cold solution of ammonic carbonate4 ,filter2 and collect the filtrate and washings in a weighed porcelain dish4 ,dry the residue1 ignite strongly1 and weigh as silica1 ,si,o#b4 ,in certain exceptional cases this may contain some unaltered cassiterite1 which is easily recognised by its appearance4 ,tungsten4--,the ammonic carbonate filtrate from the silica is evaporated to dryness1 ignited strongly over the blowpipe1 and weighed4 ,the residue is tungstic acid1 ,,wo#c4 ,the tungsten may be conveniently reported in this form1 although it is probably present as a lower oxide4 ,tin4--,the acid filtrate from the silica and tungstic acid is treated with sulphuretted hydrogen4 ,the sulphide of tin is filtered off4 ,since the percentage of tin has been already determined1 this precipitate may be neglected2 or may be treated in the same way as the previous one1 so as to check the result4 ,since some stannic chloride will have been lost in the evaporation1 a low result may be expected4 ,the tin should be reported as stannous oxide2 and is calculated by multiplying the percentage of tin by #a4acf4 ,the filtrate from the tin is boiled rapidly down to remove sulphuretted hydrogen2 and then peroxidised with #a or #b c4c4 of nitric acid4 ,it is cooled1 transferred to a graduated flask1 and diluted with water to #bjj c4c4 ,ferrous ,oxide and ,alumina4--,half the filtrate from the tin 7that is1 #ajj c4c47 is taken1 nearly neutralised with soda1 and treated with sodium acetate4 ,the basic acetate precipitate obtained on boiling is filtered off and washed4 ,reserve the filtrate4 ,the precipitate is dissolved off the filter with hot dilute hydrochloric acid2 and the solution thus formed is treated with a slight excess of ammonia1 and boiled4 ,the precipitate is filtered off1 washed with hot water1 dried1 ignited1 and weighed as mixed ferric oxide and alumina4 ,the ignited precipitate is then dissolved with sulphuric and hydrochloric acids2 and the iron determined in the solution by titration with the solution of stannous chloride4 ,the iron found is calculated to and reported as ferrous oxide1 ,fe,o 7factor #a4bhf74 ,to find the alumina1 which is best estimated by difference1 multiply the iron by #a4dbh to get the weight of ferric oxide1 and deduct this from the weight of alumina and ferric oxide found4 ,this1 of course1 gives the alumina4 ,a direct determination may be made by removing the tin from the titrated solution with sulphuretted hydrogen1 filtering1 nearly neutralising with ammonia1 and boiling with a few grams of hyposulphite of soda4 ,the precipitate1 filtered1 washed1 and ignited1 is the alumina1 which is weighed4 ,the direct determination gives a slightly low result4 ,oxides of ,zinc and ,manganese4--,these are determined in the filtrate from the basic acetate precipitate by rendering alkaline with ammonia1 and passing a current of sulphuretted hydrogen4 ,generally a small1 but decided1 precipitate of alumina comes down1 together with sulphides of any zinc or manganese which is present4 ,the precipitate is allowed to settle1 dried1 ignited1 and weighed4 ,the metals are separately determined in it2 and the residue is counted as alumina1 and added to that already found4 ,the mixed precipitate amounts to from #a to #b per cent4 of the sample4 ,lime4--,the filtrate from the last is treated with ammonic oxalate1 boiled for a few minutes1 allowed to settle1 and filtered4 ,the precipitate is washed with hot water2 dried2 ignited2 and weighed as carbonate1 after gentle ignition2 or as lime1 after strong ignition in the muffle4 ,magnesia4--,the filtrate from the lime is treated with sodic phosphate and ammonia4 ,it is well mixed by stirring1 and allowed to stand overnight4 ,the precipitate is washed with dilute ammonia1 dried1 ignited1 and weighed as pyrophosphate4 ,soda and ,potash4--,these are determined in the remaining half of the filtrate from the tin4 ,the solution is rendered ammoniacal with ammonia2 and treated1 first with sulphuretted hydrogen1 and then with ammonium oxalate4 ,the precipitate is filtered off and rejected4 ,the filtrate is evaporated in a small porcelain dish over a ,bunsen burner1 or on the sand bath2 and towards the close 7or earlier if the evaporation is not proceeding well7 nitric acid is added4 ,the evaporation is carried to dryness2 and the residue heated nearly to redness4 ,the residue1 which consists of magnesia with carbonates and chlorides of the alkalies1 is extracted with water2 and filtered4 ,the filtrate is evaporated with hydrochloric acid in a weighed platinum dish1 ignited gently1 and weighed4 ,this gives the weight of the mixed chlorides of sodium and potassium2 which are then separated and determined as described under ,potash4 ,it must be remembered when calculating the percentage that 7with the exception of the silica1 tungstic acid1 and tin7 the determinations have been made on #a gram of the sample4 ,the following analysis will illustrate the composition of such a slag3-- ,tungstic acid #a4c ,silica #ci4d ,stannous oxide #h4a ,ferrous oxide #bf4b ,alumina #ad4h ,oxide of manganese traces ,lime #g4i ,magnesia #j4e ,alkalies calculated as soda #a4g ----- #ii4i ,,titanium4 ,titanium only occurs as a mineral in its oxidised state1 or as titanic oxide 7,ti,o#b74 ,it is a substance which has little commercial value1 and is generally recognised as one of the rare bodies2 although1 in small quantities1 it is widely disseminated4 ,it occurs in granite1 basalt1 and other igneous rocks in quantities up to as much as #a per cent4 ,it is also met with in clays and iron ores1 and in river sands1 in which it is often associated with stream tin4 ,the proper minerals of titanium are rutile 7,ti,o#b71 titaniferous iron 7titanate of iron71 and sphene 7titanate and silicate of lime74 ,the oxide of titanium 7like cassiterite and quartz7 is undecomposed by hydrochloric or nitric acid2 so that it is generally found in the residue insoluble in acids4 ,the titanates1 however1 are attacked1 and a portion of the titanium dissolves2 so that it must be looked for in both the filtrate and residue4 ,oxide of titanium in its native form1 or after ignition1 may be made soluble by fusing the finely-divided substance with fusion mixture in a platinum dish4 ,the resulting titanate is dissolved out of the melt by cold hydrochloric acid4 ,the method most commonly used is fusion with bisulphate of potash4 ,this renders the oxide of titanium soluble in cold water4 ,the process is as follows3--,the substance is extracted with hydrochloric and nitric acids1 and the solution reserved for further treatment2 the residue is dried1 moistened with sulphuric acid1 and evaporated once or twice to dryness with hydrofluoric acid4 ,it is then fused with bisulphate of potash1 and the melt extracted with cold water until all soluble matter is removed4 ,the solution is filtered4 ,the residue may consist of unremoved silica1 and oxides of tantalum1 niobium1 and1 perhaps1 chromium4 ,on the prolonged boiling of the filtrate1 the oxide of titanium 7and oxide of zirconium1 if any7 is precipitated4 ,any titanium dissolved by the first extraction with acids is recovered in the following way3--,sulphuretted hydrogen is passed into the acid solution1 and any precipitate that may be formed is filtered off4 ,the filtrate is oxidised1 and the iron1 aluminium1 and titanium are separated as basic acetates 7see under ,iron74 ,the precipitate is dried and fused with bisulphate of potash4 ,the melt is extracted with cold water1 filtered if necessary1 and the solution rendered first faintly alkaline with ammonia1 then very slightly acid with sulphuric acid4 #cj or #dj c4c4 of a saturated solution of sulphurous acid is added1 and the oxide of titanium precipitated by prolonged boiling4 ,it is filtered off1 added to the precipitate previously got1 ignited with ammonic carbonate towards the end1 and then weighed4 ,detection4--,titanium is detected in an insoluble residue by fusing the residue for some time in a bead of microcosmic salt4 ,in the reducing flame it gives a violet colour1 which becomes reddish-brown if much iron is present4 ,in the oxidising flame it gives a colourless or whitish bead4 ,it is best detected in acid solutions by the deep brown or iodine colour developed on adding hydroxyl4 ,a solution of this can be prepared by pouring peroxide of barium 7,ba,o#b7 diffused in water into dilute hydrochloric acid 7a little at a time71 and keeping the acid in excess4 ,separation4--,in the usual course of an analytical separation the hydrate of titanium will be thrown down with ferric hydrate1 c41 on the addition of ammonic chloride and ammonia4 ,it is best separated from this precipitate by fusion with bisulphate of potash1 as already described1 but it must be remembered that the presence of much mineral acid prevents complete precipitation when the solution is boiled4 ,further1 if phosphates are present1 the precipitate will contain phosphoric oxide2 it may be freed from this by fusion with sodium carbonate4 ,a very good method of separating titanium from iron is to add tartaric acid and ammonia to the solution1 and then precipitate the iron 7as sulphide7 with sulphuretted hydrogen4 ,the filtrate contains the titanium1 which is recovered by evaporating and igniting4 ,it may be separated from zirconia by the action of sodium carbonate1 which precipitates both2 but when concentrated1 redissolves the zirconia4 ,the separation from large quantities of silica is best effected by evaporating with hydrofluoric acid1 which volatilises the silicon2 but sulphuric acid must be present1 otherwise some titanium also will be lost1 as may be seen from the following experiments1#gg in which oxide of titanium 7pure1 ignited7 was evaporated to dryness with a quantity of hydrofluoric acid known by experiment to be sufficient to volatilise #a gram of silica4 ,without sulphuric acid1 #j4jdff gram of titanic oxide left #j4jcdj gram1 showing a loss of about #be per cent4 ,with sulphuric acid the following results were obtained3-- ,oxide taken4 ,left after ,evaporation and ,ignition4 #j4jcdj gram #j4jcdj gram #j4jdad #j4jdac #j4jebj #j4jebj #j4jceb #j4jceb ,,gravimetric ,,determination4 ,the titanic hydrate thrown down by ammonia 7or on boiling the solution from the bisulphate7 is collected1 washed1 dried1 ignited strongly with the addition of a little ammonic carbonate1 and weighed4 ,the substance is titanic oxide 7,ti,o#b71 and is generally reported as such4 ,it contains #fj4ih per cent4 of titanium4 ,it should be white1 if pure 7,holland71 white1 yellow1 or brown 7,fresenius71 or black 7,tidy74 ,,volumetric ,,method4 ,a method has been proposed based on the reduction of titanic oxide by zinc in hydrochloric acid solutions to the sesquioxide4 ,the reduction is marked by the development of a violet or green colour1 the former with chlorides and the latter when fluorides are present4 ,the quantity of titanium reduced is measured by titrating with permanganate of potassium solution4 ,the water used must be free from dissolved oxygen4 ,,tungsten ,,and ,,tungstates4 ,tungsten occurs in nature only in the oxidised state1 or as tungstic acid 7,,wo#c71 either free1 as in wolframine1 or combined with oxides of manganese and iron1 as in wolfram1 or with lime1 as in scheelite4 ,wolfram occurs associated with tin ores1 the value of which is consequently lowered4 ,both wolfram and scheelite are of considerable importance as a source of tungstic acid for the manufacture of sodium tungstate1 which is used as a mordant and for some other purposes1 and as a source of metallic tungsten1 which is used in steel-making4 ,the tungsten minerals have a high specific gravity 7#f to #g4e74 ,on treatment with hydrochloric acid or aqua regia they are decomposed2 the yellow tungstic acid separates and remains insoluble4 ,tungsten itself is insoluble in nitric acid or aqua regia2 but is converted into tungstic acid 7,,wo#c7 by prolonged and strong ignition in air4 ,alloys containing tungsten leave tungstic acid after treatment with nitric acid or aqua regia4 ,tungstic acid may be got into solution after fusion with alkalies or alkaline carbonates4 ,this solution gives with hydrochloric acid a white precipitate of tungstic acid1 which becomes yellow on boiling1 but the separation is not complete4 ,fusion with bisulphate of potash gives a residue1 which does not dissolve in water1 but is soluble in ammonic carbonate4 ,for the assay of minerals containing tungsten these reactions are only occasionally taken advantage of for testing or purifying the separated tungstic acid4 ,detection4--,the minerals are easily recognised by their physical characters1 and the yellow tungstic acid separated by boiling with acids is the best test for its presence2 this1 after decanting and washing1 immediately dissolves in a few drops of dilute ammonia4 ,a solution of tungstate acidulated with hydrochloric acid becomes intensely blue on the addition of stannous chloride and warming4 ,fused in a bead of microcosmic salt it gives a clear blue colour 7reddish-brown if iron is also present7 in the reducing flame1 but is colourless in the oxidising flame4 ,solution and ,separation4--,the decomposition and solution of natural tungstates is difficult to effect owing to the separation of tungstic acid2 the method of treatment is as follows3--,boil the finely-powdered substance with hydrochloric acid or aqua regia till it apparently ceases to be attacked2 dilute1 filter1 and wash with dilute hydrochloric acid4 ,cover with dilute ammonia1 and filter the solution1 which contains ammonic tungstate1 into an evaporating dish4 ,treat the residue again with acid1 and again dissolve out the separated tungstic acid with ammonia1 and repeat this operation until decomposition is complete4 ,by this means there will be obtained--7#a7 a solution containing tungstate of ammonia2 7#b7 an insoluble residue with silicates1 and oxides of tin1 niobium1 tantalum1 c42 and 7#c7 an acid solution containing the soluble bases4 ,the tungstate of ammonia requires simple evaporation on the water-bath and gentle ignition in order to cause the tungstic acid to be left in an almost pure state2 possibly1 it may carry a little silica4 ,,gravimetric ,,determination4 ,the tungstic acid is dissolved1 and separated as ammonic tungstate1 and1 after evaporation1 is gently ignited1 the heat being increased towards the end4 ,the residual tungstic acid is fixed1 so that when the ammonia has been driven off it may be strongly heated without loss4 ,it is a dark yellow or brown powder whilst hot1 which becomes a light yellow on cooling4 ,if any reduction has taken place it will be more or less greenish4 ,it is weighed when cold1 and is the trioxide or tungstic acid 7,,wo#c71 which contains #gi4ca per cent4 of tungsten4 ,after its weight has been taken its purity is checked by fusing with hydric potassic sulphate1 extracting with water1 and treating the residue with ammonic carbonate4 ,any silica present will be left undissolved2 it should be separated and weighed1 and its weight deducted from that of the tungstic acid found4 ,determination of ,tungstic ,acid in ,wolfram4--,take #b grams of the finely-powdered sample and boil with #ej c4c4 of hydrochloric acid for half an hour1 adding #e c4c4 of nitric acid towards the end4 ,allow to stand overnight and boil again for #ae or #bj minutes2 dilute with an equal volume of water1 and filter4 ,wash with dilute hydrochloric acid1 dissolve in a few c4c4 of warm dilute ammonia1 and dilute to #bjj c4c4 with distilled water2 allow to settle1 and filter4 ,evaporate in a weighed dish1 ignite1 and weigh4 ,the following analysis will illustrate the composition of a sample of ,cornish wolfram as brought into the market3-- ,tungstic acid #ej4a ,cassiterite #aj4i ,ferrous oxide #bd4f ,manganous oxide #e4d ,niobic oxide1 alumina1 c4 #c4e ,silica #a4b ,copper oxide #b4g ,zinc oxide #j4bb ,arsenic #j4ea ,sulphur #j4bj ----- #ii4cc ,,niobic ,,and ,,tantalic ,,oxides4 ,these oxides are commonly met with in samples of wolfram and tinstone1 especially niobic4 ,they are probably present in the form of columbite1 a niobate of iron and manganese2 and tantalite1 a tantalate of the same metals4 ,on boiling with hydrochloric acid they are both liberated1 and remain for the greater part 7all the niobic7 in the insoluble residue with the tungstic acid4 ,on removing the latter with dilute ammonia they remain as a white insoluble precipitate1 very prone to run through the filter on washing4 ,they may be dissolved in hydrofluoric acid either at once or after fusion with bisulphate of potash1 and extraction with cold water4 ,to the solution in hydrofluoric acid gradually add a boiling solution of acid potassium fluoride 7,,hf1 ,,kf474 ,potassic fluotantalate 7soluble in #bjj parts of water7 separates out first1 and afterwards potassic fluoniobate 7soluble in #ab parts of water74 ,the separated salts 7after heating with sulphuric acid and washing out the potassium sulphate formed7 are ignited with ammonic carbonate1 and weighed as tantalic oxide 7,ta#b,o#e7 and niobic oxide 7,nb#b,o#e7 respectively4 ,they are both white powders4 ,the oxide of niobium dissolved in a bead of microcosmic salt gives a bluish colour in the reducing flame4 ,the oxide of tantalum dissolves in the bead1 but gives no colour4 ,,footnotes3 #gf ,this will give almost the whole of the tin2 a further portion will be got in subsequent work1 and must be added to this result4 #gg ,published by ,p4 ,holland1 in the ,chemical ,news1 vol4 lix4 p4 #bg4 ,,chapter ,,xiii4 ,,manganese1 ,,chromium1 c4 ,,manganese4 ,manganese occurs mainly as black oxide 7,mn,o#b7 in the mineral pyrolusite2 and1 in a less pure form1 in psilomelane and wad4 ,the value of the ore depends rather on the percentage of available oxygen than on the proportion of metal present4 ,the results of assays are generally reported as so much per cent4 of the dioxide 7,mn,o#b74 ,in smaller quantities it is very widely distributed4 ,manganese itself has a value for steel-making2 or1 rather1 for the making of spiegeleisen and ferro-manganese1 which are used in the ,bessemer and ,siemens processes4 ,for this purpose the percentage of the metal 7,mn7 is required4 ,consequently the minerals of manganese may be considered in two aspects--7#a7 as a source of oxygen2 and 7#b7 as a source of manganese4 ,these will require separate consideration4 ,the black oxide is mainly used in the preparation of chlorine1 liberation of which it brings about when treated with hot hydrochloric acid1 or with a mixture of common salt and sulphuric acid4 ,the quantity of chlorine which is obtained depends upon the proportion of dioxide present2#gh and in assaying may either be measured by its equivalent of iodine liberated1 or by the oxidising effect on an acid solution of ferrous sulphate4 ,when the ore also carries substances which have a reducing effect 7such as ferrous compounds71 such assays will give1 not the total dioxide 7,mn,o#b71 but less1 by the amount required to oxidise these impurities2 and this is exactly what is required in valuing such an ore for commercial purposes4 ,manganese compounds are characterised by the readiness with which they may be converted into highly-oxidised bodies4 ,solution of manganese in hydrochloric acid1 rendered alkaline with ammonia1 yields a clear solution1#gi which rapidly takes up oxygen from the air1 forming a brown precipitate of the oxide 7,mn#b,o#c74 ,the addition of bromine or chlorine to such a solution determines the precipitation of a still higher oxide 7approximately ,mn,o#b74 ,on treating a compound containing manganese with nitric acid and dioxide of lead 7,pb,o#b71 the oxidation is carried still further1 a purple-coloured solution of permanganic acid 7,h,mn,o#d or ,h#b,o4,mn#b,o#g7 being formed4 ,on fusing minerals containing 7even traces of7 manganese with sodium carbonate in an open crucible1 a green melt is obtained which owes its colour to sodium manganate 7,na#b,mn,o#d or ,na#b,o4,mn,o#c74 ,this salt is soluble in water1 forming a green solution2 which1 when rendered acid1 rapidly changes into the permanganate with the characteristic purple colour4 ,permanganate of potash is a salt much used in assaying1 with some properties of which the student will have already become familiar4 ,compounds of manganese1 on boiling with strong hydrochloric acid1 yield manganous chloride#hj 7,mn,cl#b74 ,the properties given above serve for the detection of manganese2 the higher oxides are distinguished by causing the evolution of chlorine 7with its peculiarly suffocating smell7 when acted on with hydrochloric acid2 while the green melt1 with sodium carbonate1 can be relied on for the recognition of manganese itself4 ,there is no dry assay of manganese ores4 ,,wet ,,methods4 ,strong hydrochloric acid is the best solvent for ores of manganese2 but where the proportion of dioxide 7,mn,o#b7 is required1 the solution is effected during the assay4 ,the ore should be in a very fine state of division before treatment with acids4 ,the separation of manganese from other metals is thus effected3 ,ignite1 in order to destroy any organic matter which may be present2 dissolve in hydrochloric acid1 and evaporate to dryness1 to separate silica4 ,take up with hydrochloric acid1 dilute1 pass sulphuretted hydrogen1 and filter4 ,boil off the excess of gas1 peroxidise the iron with a drop or two of nitric acid1 and separate the iron as basic acetate 7as described under ,iron74#ha ,if the iron precipitate is bulky1 it is dissolved in a little hydrochloric acid1 reprecipitated1 and the filtrate added to the original one4 ,neutralise with soda1 and add bromine in excess2 heat gradually to boiling1 allow to settle1 and filter4 ,the precipitate is impure dioxide of manganese 7containing alkalies and1 possibly1 cobalt or nickel74 ,,gravimetric ,,determination4 ,dissolve the precipitate in hydrochloric acid1 and boil2 add a slight excess of carbonate of soda1 warm1 and filter4 ,wash with hot water1 dry1 carefully ignite in an open ,berlin crucible1 and weigh4 ,the substance is the brown oxide 7,mn#c,o#d71 and contains #gb4je per cent4 of manganese4 ,if the percentage of dioxide is required it may be calculated by multiplying the percentage of manganese by #a4ehb4 ,it must be borne in mind that the manganese should never be calculated to dioxide except when it is known to exist in the ore only in that form4 ,,volumetric ,,methods4 ,the two methods are based on the oxidising effect of manganese dioxide2 and if the metal does not already exist in this form it will require a preliminary treatment to convert it4 ,the following method due to ,mr4 ,j4 ,pattinson#hb effects this3 ,a quantity of the ore containing not more than 4#be grams of the metal 7,mn71 is dissolved in hydrochloric acid in a pint beaker1 and1 if necessary1 #c or #d c4c4 of nitric acid are added to peroxidise the iron1 and ferric chloride is added if required1 so that there may be at least as much iron as manganese4 ,calcium carbonate is added till the solution is slightly red2 and next the redness is removed by the cautious addition of acid2 #cj c4c4 of zinc chloride solution 7containing #ae grams of zinc per litre7 are added1 the liquid is brought to boil and diluted to about #cjj c4c4 with boiling water2 #fj c4c4 of a solution of bleaching powder 7#cc grams to the litre and filtered71 rendered slightly greenish by acid1 are then run in and are followed by #c grams of calcium carbonate suspended in #ae c4c4 of boiling water4 ,during effervescence the beaker is covered1 the precipitate is stirred1 and #b c4c4 of methylated spirit are mixed in4 ,the precipitate is collected on a large filter1 washed with cold water1 and then with hot1 till free from chlorine1 which is tested for with starch and potassium iodide4 ,the acid ferrous sulphate solution 7presently described7 is then measured into the beaker1 and the precipitate1 still in the paper1 added2 more acid is added 7if necessary71 and the solution is diluted and titrated4 ,in place of bleaching powder solution1 #ij c4c4 of bromine water 7containing #bb grams per litre7 may be used4 ,,ferrous ,,sulphate ,,assay4 ,this method1 which is the one commonly used1 is based on the determination of the amount of ferrous iron oxidised by a known weight of the ore4 ,it is known that #hg parts of the dioxide will oxidise #aab parts of ferrous iron2#hc therefore #a gram will oxidise #a4bhg gram of ferrous iron1 or #a gram of ferrous iron oxidised will be equivalent to #j4ggfh gram of the dioxide4 ,the finely-divided substance containing the dioxide is digested in a solution of a known quantity of iron in sulphuric acid4 ,the iron1 of course1 must be in excess1 which excess is determined when the ore is dissolved by titrating with standard permanganate or bichromate of potash solution4 ,the assay resolves itself into one for the determination of ferrous iron1 for which the standard solutions and method of working described under ,iron are used4 ,the assay is as follows3--,for rich ores1 #b grams of clean soft iron wire are treated1 in a pint flask1 with #ajj c4c4 of dilute sulphuric acid and warmed till dissolved4 ,carefully sample the ore1 and in one portion determine the moisture at #ajj ,c42 grind the rest in a ,wedgwood mortar with a little pure alcohol until free from grit4 ,this reduces the substance to a finely-divided state and assists solution4 ,evaporate off the alcohol and dry at #ajj ,c41 mix well1 and keep in a weighing-bottle4 ,weigh up #b grams and add them to the solution of iron in the flask2 carefully wash it all down into the acid liquid4 ,on rotating the flask the ore will rapidly dissolve1 but gentle heat may be used towards the end to complete the solution4 ,when the residue is clean and sandy-looking1 and free from black particles1 the flask is cooled1 and the residual ferrous iron is determined by titration with permanganate4 ,the iron thus found1 deducted from the #b grams taken1 will give the amount of iron peroxidised by the dioxide contained in the #b grams of ore4 ,this divided by #b and multiplied by #gg4fh will give the percentage of dioxide in the sample1 or multiplied by #di4da will give that of metallic manganese4 ,when the quantity of manganese or of the dioxide to be determined is small1 it is not necessary to use #b grams of iron2 #a gram1 or even less1 may be taken4 ,the iron may be used in the form of a standard solution of ferrous sulphate and portions measured off1 thus saving the labour of weighing4 ,determination of ,dioxide in a ,manganese ,ore4--,weigh up #a or #b grams of the finely-powdered ore#hd and an equal weight of pure iron wire1 dissolve the wire in #ej or #ajj c4c4 of dilute sulphuric acid1 and1 when solution is complete1 add the ore and warm till it too is dissolved4 ,cool and titrate the remaining ferrous iron with the permanganate or bichromate of potassium solution4 ,for example1 #j4gefj gram of pyrolusite and #a4jjj gram of iron were taken and treated as above2 #ac4i c4c4 of permanganate 7standard #ajj c4c4 #j4dibj gram iron7 were required2 this indicates that #j4jfhd gram of iron was left unoxidised by the ore4 ,the iron oxidised1 then1 was #j4icaf gram 7#a4jjj - #j4jfhd72 multiplying this by #j4ggfh1 we find that #j4gbcg gram is the quantity of manganese dioxide which was present4 ,this is equivalent to #ie4gg per cent42 #j4gefj 3 #j4gbcg 33 #ajj 3 #ie4gg4 ,,iodine ,,method4 ,it has been already stated that when dioxide of manganese is boiled with strong hydrochloric acid chlorine is given off1 and that the amount of chlorine so liberated is a measure of the dioxide present4 ,if the chlorine is passed into a solution of potassium iodide1 an equivalent of iodine will be set free4#he ,this is apparently a very indirect way of determining how much of the dioxide is present2 but the reactions are very sharp1 and the final determination of the iodine is an easy one4 ,illustration3 ,,fig4 #fj4 ,the finely-powdered sample of dioxide is placed in a small flask provided with an exit tube leading into a solution of potassic iodide 7fig4 #fj74 ,on adding hydrochloric acid and boiling1 the chlorine evolved is driven into the iodide solution and there absorbed2 the boiling is continued till the steam and hydrochloric acid fumes have driven the last portions of the chlorine out of the flask and into the solution4 ,in this experiment there is a strong tendency for the iodide solution to rush back into the flask4 ,this tendency is overcome by avoiding draughts and regulating the heat2 or by placing a lump of magnesite in the flask1 which acts by evolving carbonic acid and so producing a steady outward pressure4 ,when the distillation is finished the tube containing the iodine is detached and washed out into a beaker4 ,if the solution is strongly acid it should be almost neutralised by the cautious addition of dilute ammonia4 ,if crystals of iodine have separated1 potassium iodide must be added in quantity sufficient to dissolve them4 ,the condenser must be kept cool whilst the chlorine is passing into it4 ,the solution1 transferred to a beaker1 is titrated with a standard solution of sodic hyposulphite 7#ajj c4c4 #a4bg gram iodine or #j4dce gram of dioxide of manganese74 ,in titrating1 the solution should be cold1 or not warmer than #cj ,c4 ,the bulk may vary from #ajj to #bjj c4c42 but it is best always to work with the same volume4 ,the hypo is run in with constant agitation until the brown colour has been reduced to a light yellow2 #e c4c4 of starch solution are then added and the titration cautiously continued until the end is reached2 the finish is indicated by a change from blue to colourless4 ,the assay solution may be acidified with acetic1 sulphuric1 or hydrochloric acid before titrating with hypo2 but it must be only faintly so4 ,an excess of acid may be nearly neutralised with ammonia without interference1 but excess of alkali is fatal4 ,bicarbonate of soda must not be used in excess2 it is best to avoid it altogether4 ,the assay solution should be titrated at once1 as it weakens on standing2 and the hypo solution should be standardised every two or three days1 as its strength is not constant4 ,the standard solution of hyposulphite of soda is made by dissolving #be grams of the salt 7,na#b,s#b,o#c4e;,h#b,o7 in water and diluting to #a litre4 #ajj c4c4 are equivalent to #a4bg gram of iodine4 ,this solution is standardised by weighing1 in a small beaker1 about half a gram of iodine1 to which is added a crystal or two of potassium iodide and a few drops of water4 ,when dissolved1 the solution is diluted to #ajj c4c41 and titrated in the manner described4 ,the starch solution is made in the manner described under the iodide copper assay4 #e c4c4 are used for each titration4 ,in determining the effects of variations in the condition of the assay a solution of iodine was used1 which was equivalent in strength to the hypo solution4 ,it was made by dissolving #ab4g grams of iodine with #be grams of potassium iodide in a little water and diluting to #a litre4 #ajj c4c4 of this solution were found 7at the time of the experiments7 to be equivalent to #ajb4j c4c4 of the hypo4 ,effect of ,varying ,temperature4--,the bulk of the solution was #ajj c4c42 #bj c4c4 of iodine were taken1 and #e c4c4 of starch solution were added towards the end as indicator4 ,these conditions are also those of the other experiments1 except where otherwise stated4 ,iodine being volatile1 it is to be expected that with hot solutions low results will be obtained4 ,temperature #ae #bj #dj #fj #hj ,hypo required #bj4d c4c4 #bj4d c4c4 #bj4a c4c4 #ai4b c4c4 #ae4e c4c4 ,these show that the temperature should not much exceed #bj4 ,effect of ,exposure of the ,iodine ,solution4--,twenty c4c4 of the iodine were diluted to #ajj c4c41 and exposed for varying lengths of time in open beakers at the ordinary temperature1 and then titrated4 ,time exposed -- #a day #b days #c days ,hypo required #bj4d c4c4 #af4a c4c4 #ac4f c4c4 #i4d c4c4 ,effect of ,varying ,bulk4--,these experiments were carried out in the usual way1 bulk only varying4 ,bulk #ajj4j c4c4 #bjj4j c4c4 #cjj4j c4c4 #ejj4j c4c4 ,hypo required #bj4d #bj4d #bj4d #bj4d ,effect of ,varying ,acid4--,these experiments were under the usual conditions1 the bulk being #ajj c4c4 ,the results were-- ,acetic acid -- #a4e c4c4 #cj4j c4c4 ,hypo required #bj4d c4c4 #bj4g #bj4g ,hydrochloric acid -- #a4e c4c4 #ae4j c4c4 ,hypo required #bj4d c4c4 #bj4f #bj4i ,sulphuric acid -- #j4e c4c4 #bj4j c4c4 ,hypo required #bj4d c4c4 #bj4g #ae4b #hf ,nitric acid -- #j4e c4c4 #aj4j c4c4 ,hypo required #bj4d c4c4 #ba4e could not be titrated4 ,in the application of this titration to the assay of manganese ores1 hydrochloric and hydriodic acids are the only ones likely to be present4 ,effect of ,alkalies4--,on theoretical grounds the presence of these is known to be inadmissible4 ,a solution rendered faintly alkaline with ammonia required only #aa4b c4c4 of hypo2 and another1 with #j4e gram of caustic soda1 required #d4j c4c4 instead of #bj4d c4c4 as in neutral solutions4 ,effect of nearly ,neutralising ,hydrochloric ,acid ,solutions with ,ammonia4--,provided care is taken not to add excess of ammonia1 this has a good effect1 counteracting the interference of excess of acid4 ,thus #bj c4c4 of iodine 7as before7 required #bj4d c4c4 of hypo2 with #ae c4c4 of hydrochloric acid #bj4g c4c4 were required1 but with #ae c4c4 of acid1 nearly neutralised with dilute ammonia #bj4d c4c4 were used4 ,effect of the ,addition of ,starch4--,the addition of varying quantities of starch has no effect1 provided it is added when the titration is nearly finished1 as the following experiments show3-- ,starch added #a4j c4c4 #e4j c4c4 #aj4j c4c4 #ej4j c4c4 ,hypo required #bj4d #bj4d #bj4d #bj4e ,but if the starch is added before the titration1 the results are liable to error4 ,starch added #a4j c4c4 #ej4j c4c4 ,hypo required #bj4d #bd4j ,the starch should be used fresh1 and is best made on the day it is used2 after four days the finishing point is not so good4 ,effect of ,varying ,potassium ,iodide4--,an excess of iodide is always required to keep the iodine in solution2 a larger excess has little effect4 ,iodide added -- #a gram #bj grams ,hypo required #bj4d c4c4 #bj4e c4c4 #bj4f c4c4 ,the #bj c4c4 of iodine used1 itself contained #j4e gram of potassium iodide4 ,effect of ,foreign ,salts4-- ,bicarbonate of soda added -- #j4e gram #a4e gram #e4j grams ,hypo required #bj4d c4c4 #ah4b c4c4 #ag4a c4c4 #af4j c4c4 ,the solution obviously must be free from bicarbonate of soda4 ,this should be remembered1 since when titrating arsenic assays with iodine it must be present2 and students must avoid confounding the two titrations4 ,in some other experiments1 in which #aj grams each of the salts were taken1 the following results were obtained3-- ,salt added -- ,am,cl ,am,n,o#c ,am#b,,so#d ,hypo required #bj4d c4c4 #bj4e c4c4 #bj4c c4c4 #bj4b c4c4 ,salt added ,na,cl ,na,n,o#c ,na#b,,so#d ,hypo required #bj4c c4c4 #bj4d c4c4 #bj4d c4c4 ,effect of ,varying ,iodine4-- ,iodine added #a4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,hypo required #a4c #aj4b #bj4d #ea4j #ajb4j ,determination of ,dioxide in a ,manganese ,ore4--,weigh up #j4be to #j4c gram of the powdered ore2 place in a flask1 cover with #aj c4c4 of hydrochloric acid1 and close the flask with a paraffined cork1 and bulbs 7as shown in fig4 #fj71 having previously charged the bulb with #e grams of potassium iodide in strong solution4 ,heat the flask1 and boil cautiously for about fifteen minutes4 ,wash the contents of the bulbs into a large beaker1 nearly 7but not quite7 neutralise with dilute ammonia1 and titrate with the standard hypo4 ,as an example1 #j4bfge gram of pyrolusite was taken1 and required #fj4c c4c4 of standard hypo 7#ajj c4c4 equal #a4ahe gram iodine1 or #j4djdb gram ,mn,o#b71 which equals #j4bdcg gram of the dioxide or #ia4a per cent4 ,,colorimetric ,,method4 ,when compounds of manganese free from chlorides are boiled with nitric acid and dioxide of lead1#hg the manganese is converted into permanganic acid1 which is soluble and tints the solution violet4 ,the depth of colour depends on the amount of manganese present1 and this should not much exceed #aj milligrams4 ,a quantity of substance containing not more than this amount of manganese should be boiled for a few minutes with #be c4c4 of a solution containing #e c4c4 of nitric acid1 and #aj or #bj c4c4 of dilute sulphuric acid1 with #b or #c grams of lead dioxide4 ,filter through asbestos1 wash by decantation with dilute sulphuric acid1 make up with distilled water#hh to a definite bulk1 and take a measured portion for the colorimetric determination4 ,the standard solution of manganese is made by dissolving #j4adce gram of permanganate of potash 7,k,mn,o#d7 in a little water acidulated with nitric acid1 and diluting to #a litre4 ,one c4c4 will contain #j4je milligram of manganese4 ,,practical ,,exercises4 #a4 ,what percentage of manganese 7,mn7 is contained in permanganate of potash 7,k,mn,o#d78 #b4 ,ten c4c4 of a solution of permanganate of potash is found to oxidise #aj c4c4 of an acid solution of ferrous sulphate4 ,the manganese is determined in the titrated solution by precipitation as dioxide and titrating4 ,how much of the ferrous solution will be oxidised in the second titration8 #c4 ,what weight of potassium iodide would be just sufficient to absorb the chlorine evolved by #j4e gram of pure dioxide of manganese8 #d4 ,what weight of iron must be dissolved up so as to have an excess of #j4be gram after oxidation by #a gram of pure dioxide8 #e4 ,what weight of the brown oxide1 ,mn#b,o#d will be left on igniting #a gram of the pure dioxide8 ,,chromium4 ,chromium occurs in nature chiefly as chromite or chrome iron ore 7,fe,o#b;,cr#b,o#c1 with more or less ,mg,o and ,al#b,o#c71 which is the chief ore4 ,it is a constituent of some silicates1 and is frequently met with in very small quantities in iron ores4 ,it occurs as chromate in crocoisite 7,pb,cr,o#d71 and some other rare minerals4 ,the metal is used in steel-making4 ,steel containing about #j4e per cent4 of it is rendered very hard2 but its chief value is in its salts1 the chromates4 ,these are highly-coloured compounds1 generally red or yellow4 ,some of the insoluble chromates are used as pigments2 chromate of lead or chrome-yellow is the most important4 ,the soluble chromates1 those of soda and potash1 are valuable chemicals1 and are largely used in the preparation of pigments1 dyeing and tanning1 and as oxidising agents4 ,chromium forms two important classes of compounds--chromic salts1 corresponding to the oxide ,cr#b,o#c1 and chromates1 which contain the trioxide ,cr,o#c4 ,solutions of chromic salts are green1 whilst those of the chromates are yellow4 ,chromates are reduced to chromic salts by the action of most reducing agents in the presence of an acid2 and this property is used in assaying for the volumetric determination of ferrous iron1 c4 ,the chromates in solution are more stable than other similar oxidising agents1 and consequently are generally used in the laboratory as one of the standard oxidising agents for volumetric analysis4 ,they have the disadvantage of requiring an outside indicator4 ,bichromate of potash 7,k#b;,cr#b,o#g7 is the salt generally used for this purpose4 ,chromic salts are oxidised to chromate by fusion with fusion mixture and nitre1 or by treating with chlorine in an alkaline solution4 ,chromic salts closely resemble those of ferric iron1 and in the ordinary course of analysis chromic hydrate 7green7 is precipitated together with ferric hydrate1 alumina1 c41 on the addition of ammonic chloride and ammonia4 ,the ignited oxide1 ,cr#b,o#c1 however1 is not reduced on heating to redness in a current of hydrogen4 ,detection4--,chromium is detected by fusing the powdered substance with fusion mixture and nitre4 ,the melt is extracted with water and filtered4 ,the filtrate is acidified with acetic acid1 and treated with a few drops of a solution of lead acetate4 ,a yellow precipitate indicates chromium4 ,substances containing chromium impart a green colour to the borax bead in both flames4 ,small quantities of chromate in neutral solution can be found by the dark or violet-red colouration imparted thereto on boiling with a dilute decoction of logwood4 ,solution and ,separation4--,chromates and chromic salts are generally soluble in water or dilute acids4 ,chrome iron ore1 however1 and ignited chromic oxide are insoluble2 and the former presents considerable difficulty on attempting to open up by the usual methods4 ,a large number of mixtures have been tried in order to get all the chromium in a soluble form4 ,among these are the following4 ,one part of the very finely-powdered ore is fused with any of these mixtures4 7#a7 #aj parts of bisulphate of potash4 7#b7 #e parts of bisulphate of potash and #e parts of potassium fluoride4 7#c7 #e parts of hydric potassic fluoride4 7#d7 #ab parts of bisulphate of potash2 and1 afterwards1 with #f parts of carbonate of soda and #f parts of nitre4 7#e7 #h parts of borax2 afterwards1 with carbonate of soda till it ceases to effervesce2 then1 with #c parts of carbonate of soda and #c of nitre4 7#f7 #d parts of borax and #f parts of fusion mixture4 7#g7 #ab parts of caustic potash4 7#h7 #aj parts of caustic soda and #cj of magnesia4 7#i7 #e parts of caustic soda and #c of magnesia4 7#aj7 #b parts of carbonate of soda and #a of lime4 7#aa7 #f parts of soda-lime and #b of chlorate of potash4 7#ab7 ,sodium peroxide4 ,of these1 numbers #a1 #b1 and #c yield the chromium in a form soluble in dilute acids1 as chromic salt4 ,the rest in a form soluble in water1 as potassium or sodium chromate4 ,on boiling an insoluble chromium compound with chlorate of potash and nitric acid1 the chromium passes into solution as chromate4 ,this method1 however1 does not answer for chrome iron ore4 ,in the fusion methods the ore must be very finely powdered1 well mixed with the fluxes1 and subjected to a prolonged fusion in a platinum vessel at a high temperature4 ,undecomposed particles require re-fusion4 ,the aqueous extract containing the chromate is ready for volumetric work1 except in those cases where nitre has been used4 ,for gravimetric work the solution is acidified with hydrochloric acid1 then mixed with ammonia in slight excess1 boiled1 and filtered4 ,the filtrate is acidified with hydrochloric acid1 and treated with sulphuretted hydrogen1 warmed1 rendered slightly alkaline with ammonia1 and the gas again passed4 ,the chromium is precipitated as chromic hydrate mixed with sulphur from the reduction with sulphuretted hydrogen4 ,it is filtered off1 washed with hot water1 and ignited4 ,it is weighed as chromic oxide4 ,,gravimetric ,,determination4 ,the solution containing the chromium1 freed from other metals and earths and in the form of 7green7 chromic salt1 is heated to boiling4 ,if any chromate is present reduce it with sodium sulphite or sulphuretted hydrogen4 ,add ammonia in slight excess1 boil till the liquid is free from a red tint1 and allow to settle for a few minutes4 ,filter1 wash with hot water1 dry1 and ignite strongly in a loosely-covered crucible4 ,cool1 and weigh4 ,the substance is chromic oxide1 ,cr#b,o#c1 and contains #fh4fb per cent4 of chromium4 ,it is a dark-green powder insoluble in acids4 ,when1 as is generally the case1 the chromium exists altogether as chromate 7phosphates and arsenates being absent7 it is best to proceed as follows3--,render the solution acid with acetic acid1 then add sodium acetate to the solution and heat nearly to boiling2 next treat with a slight excess of acetate of lead1 and boil4 ,allow to settle1 and filter4 ,wash the precipitate with hot water1 dry in the water-oven or at a low temperature4 ,transfer the precipitate to a weighed ,berlin crucible1 burn the filter separately1 ignite below redness1 cool in the desiccator1 and weigh4 ,the substance is lead chromate1 ,pb,cr,o#d1 and contains #af4a per cent4 of chromium1 or #bc4ec per cent4 of chromic oxide 7,cr#b,o#c74 ,,volumetric ,,method4 ,this is based on the oxidation of ferrous iron by the solution containing the chromium as chromate4 ,a known weight of iron 7#j4e1 #a1 or #a4e gram1 according to the quantity of chromate7 is dissolved in #ej c4c4 of dilute sulphuric acid4 ,the solution containing the chromate is added1 and the remaining ferrous iron titrated with the permanganate or bichromate of potassium solution1 as described under ,iron4 ,the iron thus found is deducted from that taken1 and the difference gives the iron oxidised by the chromate4 ,this multiplied by #j4caja gives the chromium1 ,cr1 and when multiplied by #j4debi gives the chromic oxide1 ,cr#b,o#c4 ,,colorimetric ,,method4 ,small quantities of chromium may be determined1 after conversion into chromate1 colorimetrically4 ,the solution1 which should not contain more than a few milligrams in #ajj c4c41 is acidified with acetic acid and compared against an equal volume of water rendered acid with acetic acid and tinted with a standard bichromate of potassium solution4 ,this standard bichromate is made by dissolving #b4hbg grams of the salt in water and diluting to #a litre4 ,one c4c4 will contain #a milligram of chromium1 ,cr4 ,the manner of working this assay is the same as that adopted in the other colorimetric processes4 ,determination of ,chromium in ,steel4#hi--,weigh up #b4d grams1 dissolve in hydrochloric acid1 and evaporate to dryness4 ,fuse with sodium carbonate and nitre1 extract with water1 and make up to #cja c4c4 ,take #bej c4c4 of the clear liquor1 boil with hydrochloric acid1 add sodium phosphate1 and then ammonia in slight excess4 ,heat till clear4 ,filter off the precipitate1 dissolve it in hydrochloric acid1 and evaporate to dryness4 ,take up with a little acid1 filter1 and precipitate with a slight excess of ammonia4 ,wash1 ignite1 and weigh as chromium phosphate 7#c;,cr#b,o#c1b,p#b,o#e71 which contains #db4b per cent4 of chromium4 ,,vanadium4 ,vanadium occurs in certain rare minerals1 such as vanadinite 7#c,pb#c7,,vo#d7b4,pb,cl#b71 a vanadate of lead2 mottramite1 a vanadate of copper and lead2 and dechenite1 a vanadate of lead and zinc4 ,it is occasionally found in iron and copper ores and in the slags from them4 ,in ,spanish copper-precipitates it is found along with chromium1 and is probably derived from the iron used for precipitating4 ,the vanadates1 like the chromates1 are coloured compounds1 generally yellow or red4 ,on reduction1 blue solutions are got4 ,in their general reactions vanadates resemble phosphates4 ,vanadium is detected by the red colouration produced by passing sulphuretted hydrogen into ammoniacal solutions for some time4 ,on adding an acid to the filtered solution a brown precipitate of the sulphide is produced4 ,this gives with borax a colourless bead in the oxidising1 and a green one in the reducing1 flame4 ,it is separated by fusing the ore with potassic nitrate1 extracting with water and precipitating with baric chloride4 ,the precipitate is boiled with dilute sulphuric acid1 filtered1 neutralised with ammonia1 and saturated with ammonic chloride4 ,ammonium vanadate separates out4 ,it is filtered off1 ignited1 and weighed as vanadic oxide1 ,v#b,o#e1 containing #ef4ah per cent4 of vanadium4 ,,molybdenum4 ,molybdenum occurs in nature chiefly as molybdenite 7,mo,s#b72 it also occurs in wulfenite1 a molybdate of lead 7,pb,mo,o#d71 and in molybdic ochre 7,mo,o#c74 ,molybdate of ammonia is an important reagent in the determination of phosphates1 the manufacture of which compound is the chief purpose to which molybdenum is applied4 ,iron and copper ores frequently contain molybdenum1 sometimes in quantity2 consequently it is met with in slags and pig-iron4 ,molybdenum forms several series of salts4 ,in those corresponding to the lower oxides it is basic2 but the trioxide 7,mo,o#c7 is the acid oxide which forms a series of salts called the molybdates4 ,all molybdenum compounds are converted into the trioxide by boiling with nitric acid4 ,the trioxide is a white powder readily dissolved by ammonia4 ,it fuses at a red heat1 and volatilises freely in contact with air4 ,it is slightly soluble in water4 ,molybdates are easily reduced1 with the production of coloured solutions1 by most reducing agents4 ,sulphuretted hydrogen first produces a blue tint1 and then precipitates a brown sulphide4 ,the precipitation as sulphide is only complete on prolonged treatment2 a green colour indicates that some molybdenum still remains in solution4 ,the precipitated sulphide is soluble in ammonium sulphide4 ,detection4--,molybdenum is detected by its behaviour with sulphuretted hydrogen4 ,molybdenite can only be mistaken for graphite1 from which it is easily distinguished by yielding sulphur dioxide on roasting1 and by giving1 on charcoal1 a yellowish white incrustation1 which becomes blue on touching it for a moment with the reducing flame4 ,the borax-bead is colourless in the oxidising1 and dark-brown in the reducing1 flame4 ,,gravimetric ,,determination4 ,the solution containing the molybdate is neutralised and treated with an excess of mercurous nitrate4 ,the precipitate is allowed to settle for some time1 filtered1 and washed with a dilute solution of mercurous nitrate4 ,then it is dried1 transferred to a weighed ,berlin crucible containing ignited oxide of lead1 mixed1 ignited1 and weighed4 ,the increase in weight gives the amount of trioxide1 ,mo,o#c4 ,this contains #ff4g per cent4 of molybdenum4 ,,uranium4 ,uranium occurs chiefly as pitchblende1 which is an impure oxide 7,u#c,o#h74 ,it is also found as sulphate in uranochre1 johannite1 c42 and as phosphate in the uranites1 torbernite 7hydrated phosphate of uranium and copper71 and autunite 7hydrated phosphate of uranium and lime74 ,it also occurs in some rarer minerals4 ,the oxide is used for colouring glass2 and the nitrate and acetate are used as reagents4 ,uranium yellow1 used for enamel painting1 is sodium uranate4 ,the uranates1 in which the oxide of uranium acts as an acid1 are mostly insoluble and of secondary importance4 ,uranium forms two families of salts1 uranous and uranic2 corresponding to the oxides ,,uo#b and ,,uo#c respectively4 ,the former are generally green and the latter yellow4 ,uranous salts are converted into uranic by boiling with nitric acid or other oxidising agents4 ,uranic salts1 on the other hand1 are easily reduced by sulphuretted hydrogen1 stannous chloride or zinc4 ,this property is made use of in determining the quantity of uranium in pure solutions by titrating with permanganate of potassium solution as in the case with iron4 ,detection4--,the most characteristic reaction of the uranium compounds is their behaviour in the presence of alkaline carbonates in which they are freely soluble2 even ammonium sulphide will not precipitate uranium from these solutions4 ,on neutralising the carbonate with an acid a uranate of the alkali is precipitated4 ,ammonia or sodic hydrate 7free from carbonates7 give yellow precipitates1 which are insoluble in excess of the reagent1 but are soluble in acids4 ,ferrocyanide of potassium gives a reddish-brown precipitate4 ,uranium colours the borax-bead yellowish-green in the oxidising1 and green in the reducing1 flame4 ,solution and ,separation4--,the compounds of uranium are soluble in acids4 ,powder the substance and evaporate with an excess of nitric acid4 ,take up with hydrochloric acid1 dilute1 pass sulphuretted hydrogen1 and filter4 ,peroxidise the filtrate with a little nitric acid1 add an excess of ammonic carbonate and some ammonium sulphide1 and filter4 ,render the solution acid1 boil2 and precipitate the uranium by means of ammonia4 ,filter off1 and wash it with dilute ammonic chloride4 ,ignite1 and weigh as protosesqui-oxide1 ,u#c,o#h4 ,,gravimetric ,,determination4 ,the solution containing the uranium free from other metals is1 if required1 first peroxidised by boiling with nitric acid4 ,ammonia in slight excess is added to the nearly-boiling solution4 ,a yellow precipitate is formed1 which is filtered off hot and washed with a dilute solution of ammonium chloride4 ,the precipitate is dried and ignited2 and weighed as ,u#c,o#h1 which contains #hd4h per cent4 of uranium4 ,,volumetric ,,method4 ,this is based on the precipitation of uranium as phosphate from acetic acid solutions and the recognition of complete precipitation by testing with potassic ferrocyanide2 it is the converse of the process for the volumetric determination of phosphate4 ,the standard solution of phosphate is prepared by dissolving #bi4hce grams of hydric sodic phosphate 7,na#b;,,hpo#d4ab;,h#b,o7 in water and diluting to #a litre4 #ajj c4c4 will be equivalent to #b grams of uranium4 ,take #a gram of the sample 7or1 if poor in uranium1 #b grams7 and separate the uranium as described4 ,dissolve the precipitate in nitric acid and evaporate to a small bulk1 add #b grams of sodium acetate1 dilute with water to #ajj c4c41 and boil4 ,titrate the boiling solution with the sodium phosphate till it ceases to give a brown colouration with potassium ferrocyanide4 ,calculate the percentage in the usual way4 ,,footnotes3 #gh ,mn,o#b #d;,h,cl ,mn,cl#b ,cl#b #b;,h#b,o4 #gi ,provided a sufficiency of ammonic chloride is present4 #hj ,with some silicates1 c41 a preliminary fusion with sodium carbonate will be necessary4 #ha ,instead of sodium acetate1 ammonium succinate can be used4 #hb ,journ4 ,soc4 ,chem4 ,industry1 vol4 x4 p4 #ccc4 #hc ,mn,o#b #b;,fe,s,o#d #b;,h#b,,so#d ,fe#b7,,so#d7c ,mn,s,o#d #b;,h#b,o4 #hd ,if the ore is very rich1 a smaller quantity 7#j4ge or #a4e gram7 must be taken2 otherwise the iron will be insufficient4 #he ,mn,o#b #d;,h,cl ,mn,cl#b #b;,h#b,o ,cl#b4 ,cl#b #b,,ki #b,k,cl ,i#b4 #hf ,iodine probably lost by volatilisation4 #hg ,obtained as a brown powder by digesting red lead with nitric acid and filtering4 #hh ,the water for dilution and the dilute sulphuric acid used for washing should be previously tested1 to see they have no reducing action1 with dilute permanganate of potassium solution4 #hi ,arnold and ,hardy1 ,chemical ,news1 vol4 lvii4 p4 #aec4 ,,chapter ,,xiv4 ,,earths1 ,,alkaline ,,earths1 ,,alkalies4 ,,alumina4 ,alumina1 the oxide of aluminium 7,al#b,o#c71 is found in nature fairly pure in the mineral corundum2 transparent and coloured varieties of which form the gems sapphire and ruby4 ,a coarser compact variety contaminated with oxide of iron constitutes emery4 ,compounded with silica1 alumina forms the base of clays and many rock-forming minerals4 ,china clay 7or kaolin7 is used as a source of alumina4 ,bauxite1 hydrated alumina1 is also used for the same purpose--that is1 for the preparation of sulphate of alumina4 ,the mineral cryolite is a fluoride of aluminium and sodium4 ,corundum is characterised by a high specific gravity 7#d4j7 and extreme hardness4 ,by these it is distinguished from felspar and similar minerals1 which it somewhat resembles in general appearance4 ,aluminium is used for a variety of small purposes3 it is white1 light1 and very tenacious2 but owing to the difficulty of its reduction it is expensive4 ,aluminium forms one series of salts which closely resemble those of ferric iron4 ,it forms an interesting series of double sulphates1 known as the alums4 ,common potash alum is ,al#b7,,so#d7c1,k#b,,so#d1bd;,h#b,o4 ,detection4--,alumina is not precipitated from its acid solution by sulphuretted hydrogen1 but it is thrown down by ammonia 7with the other earths7 as a white hydrate1 soluble in soda and insoluble in ammonic carbonate4 ,filtered off and ignited1 it assumes1 after treatment with nitrate of cobalt before the blowpipe1 a blue colour which is characteristic4 ,with natural compounds containing metallic oxides this colour is masked4 ,it is more satisfactory to make a separation in the wet way and to test the ignited oxide4 ,separation and ,solution4--,if the substance is insoluble in hydrochloric acid it is finely powdered and fused with fusion mixture with the help1 in the case of corundum 7which is very refractory7 of a little caustic soda or potash4 ,the method of working is the same as that described for opening up silicates4 ,see under ,silica4 ,corundum cannot be powdered in ,wedgwood1 or even agate1 mortars2 since it rapidly wears these away and becomes contaminated with their powder4 ,it is best to use a hard steel mortar and to extract the metallic particles from the bruised sample with a magnet or dilute acid4 ,when the substance has been completely attacked and dissolved1 it is evaporated to dryness with an excess of hydrochloric acid on the water-bath to render any silica present insoluble4 ,the residue is extracted with hydrochloric acid and freed from the second group of metals by means of sulphuretted hydrogen4 ,the filtrate from this 7after removing the sulphuretted hydrogen by boiling7 is nearly neutralised1 and treated with #h or #aj grams of hyposulphite of soda#ij in solution4 ,it is then boiled till the sulphurous oxide is driven off4 ,the precipitate is filtered off1 ignited1 and weighed as alumina4 ,it is sometimes more convenient to proceed as follows3--,after boiling off the sulphuretted hydrogen peroxidise the iron with a little nitric acid1 add a solution of ammonic chloride1 and then ammonia in very slight excess2 boil1 filter1 wash1 ignite1 and weigh the oxides4 ,these generally consist of ferric oxide and alumina4 ,it is a common practice to determine the iron1 calculate it to ferric oxide1 and so to estimate the alumina indirectly4 ,this may be done either by igniting in a current of hydrogen and estimating the iron by the weight of oxygen lost2 or1 by dissolving with sulphuric and hydrochloric acids1 and determining the iron volumetrically4 ,it should be borne in mind that these oxides will also contain any phosphoric oxide that happened to be in the mineral4 ,in general analyses of samples containing alumina1 it may be contained in both the soluble and insoluble portions4 ,in these cases it is better to fuse the sample with fusion mixture before treatment with acids4 ,the alumina in the fused mass will exist in a state soluble in acids4 ,,gravimetric ,,determination4 ,solutions containing alumina free from the other metals are diluted to a convenient bulk and heated nearly to boiling4 ,add chloride of ammonium1 and then ammonia in slight excess2 boil1 allow to settle1 filter1 and wash with hot water4 ,dry the precipitate1 and ignite in a platinum or porcelain crucible at the strongest heat4 ,cool1 and weigh4 ,the substance is alumina1 ,al#b,o#c1 which contains #eb4id per cent4 of aluminium4 ,it is only in special cases1 such as the analysis of metals and alloys1 that it is reported as aluminium4 ,the percentage of alumina is generally given4 ,ignited alumina is difficultly soluble in acids2 it is not reduced by hydrogen at a red heat4 ,ignited with ammonium chloride portions are volatilised4 ,direct ,determination of ,alumina in the ,presence of ,iron4--,the iron and alumina are precipitated as hydrates by ammonia4 ,the precipitate is dissolved in hydrochloric acid and the iron reduced to the ferrous state4 ,it is then added to a hot solution of potash or soda4 ,the solution is boiled till the precipitate settles readily1 filtered1 and washed with hot water4 ,the alumina is contained in the filtrate1 which is acidified with hydrochloric acid and the alumina precipitated therefrom as hydrate with ammonia1 as just described4 ,determination of ,alumina in the ,presence of ,phosphates and ,iron4--,for details1 see a paper by ,r4,t4 ,thomson in the ,journal of the ,society of ,chemical ,industry1 v4 p4 #aeb4 ,the principles of the method are as follows3--,if the substance does not already contain sufficient phosphoric oxide to saturate the alumina1 some phosphate is added4 ,the iron is reduced to the ferrous state and phosphate of alumina precipitated in an acetic acid solution4 ,it is purified by reprecipitation1 ignited1 and weighed as phosphate 7,al#b,o#c1,p#b,o#e71 which contains #da4h per cent4 of alumina1 ,al#b,o#c4 ,,examination ,,of ,,clays4 ,moisture4--,take #e grams of the carefully-prepared sample and dry in the water-oven till the weight is constant4 ,loss on ,ignition4--,weigh up #b grams of the sample used for the moisture determination1 and ignite in a platinum-crucible to redness1 cool1 and weigh4 ,silica and ,insoluble ,silicates4--,weigh up another #b grams of the dried sample1 and place them in a platinum dish2 moisten with water1 and cover with #bj c4c4 of sulphuric acid4 ,evaporate and heat gently to drive off the greater portion of the free acid4 ,allow to cool2 and repeat the operation4 ,extract by boiling with dilute hydrochloric acid1 filter1 wash1 dry1 ignite1 and weigh4 ,the quantity of insoluble silicates is determined by dissolving out the separated silica with a strong boiling solution of sodium carbonate4 ,the residue 7washed1 dried1 and ignited7 is weighed1 and reported as sand4 ,alumina and ,ferrous ,oxide4--,to the filtrate from the silica add soda solution till nearly neutral1 and then sodium acetate4 ,boil and filter off the precipitate4 ,reserve the filtrate4 ,dissolve the precipitate in hydrochloric acid1 and dilute to exactly #bjj c4c4 ,divide into two parts of #ajj c4c4 each4 ,in one determine the iron by reducing and titrating in the way described under volumetric iron4 ,calculate the percentage as ferrous oxide1 unless there are reasons to the contrary1 also calculate its weight as ferric oxide4 ,to the other portion add ammonia in slight excess1 and boil4 ,filter1 wash with hot water1 dry1 ignite1 and weigh as mixed alumina and ferric oxide4 ,the weight of the ferric oxide has already been determined in the first portion3 deduct it1 and the difference is the weight of alumina4 ,lime4--,to the reserved filtrate1 concentrated by evaporation1 add ammonium oxalate and ammonia2 boil1 filter1 ignite strongly1 and weigh as lime4 ,magnesia is separated from the filtrate by adding sodium phosphate4 ,it is weighed as magnesium pyrophosphate4 ,potash and ,soda4--,these are determined in a fresh portion of the sample by ,lawrence ,smith's method1 as described on page #ccc4 ,,thoria4 ,this is an oxide of thorium1 ,th,o#b4 ,it is only found in a few rare minerals4 ,it is a heavy oxide1 having1 when strongly ignited1 a specific gravity of #i4b4 ,in the ordinary course of analysis it will be separated and weighed as alumina4 ,it is separated from this and other earths by the following method4 ,the solution in hydrochloric acid is nearly neutralised and then boiled with sodium hyposulphite4 ,the thoria will be in the precipitate4 ,it is dissolved1 and the solution heated with ammonium oxalate in excess4 ,the precipitate is thorium oxalate1 which is washed with hot water1 dried1 and ignited4 ,it is then weighed as thoria1 ,th,o#b4 ,thoria which has been ignited is not readily soluble in acids4 ,,zirconia4 ,the oxide of zirconium1 ,zr,o#b1 is found in the mineral zircon1 a silicate of zirconia1 ,zr,si,o#d4 ,when heated intensely it becomes very luminous1 and is used on this account for incandescent lights4 ,in the ordinary course it is thrown down by ammonia with the other earths1 from which it is thus separated3--,the hydrates precipitated in the cold1 and washed with cold water1 are dissolved in hydrochloric acid1 nearly neutralised with soda1 and precipitated by boiling with hyposulphite of soda4 ,dissolve2 and from the hydrochloric acid solution precipitate the thoria 7if any7 with ammonium oxalate4 ,to the filtrate add carbonate of ammonia1 which will precipitate any titanium present4 ,the zirconia will be in solution1 and is recovered by precipitating with potassium sulphate1 or by evaporating the solution and igniting4 ,it is separated from alumina by taking advantage of its insolubility in potassic hydrate4 ,it is estimated in zircons in the following way3--,the powdered substance is fused with bisulphate of potash1 and extracted with dilute sulphuric acid4 ,the residue is fused with caustic soda and extracted with water4 ,the portion not dissolved1 consisting of zirconate of soda1 is dissolved in hydrochloric acid4 ,the solution is diluted1 filtered if necessary1 and treated with ammonia in excess4 ,the precipitate is filtered off1 washed with hot water1 dried1 ignited1 and weighed as zirconia1 ,zr,o#b4 ,this is a white powder1 which is insoluble in acids2 even in hydrofluoric acid it is only slightly attacked4 ,,cerium4 ,cerium occurs as silicate 7together with the oxides of lanthanum1 didymium1 iron and calcium7 in the mineral cerite1 which is its chief source4 ,it also occurs as phosphate in monazite1 and as fluoride in fluocerite4 ,the oxalate is used in medicine4 ,cerium forms two classes of salts corresponding to the oxides1 cerous oxide 7,ce#b,o#c7 and ceric oxide 7,ce,o#b74 ,compounds of cerium with volatile acids yield dioxide on ignition2 and this1 on solution in hydrochloric acid1 yields cerous chloride and chlorine4 ,in the ordinary course cerium is thrown down along with alumina and the other earths by ammonia4 ,it is separated by dissolving the hydrates in hydrochloric acid1 and oxidizing with chlorine water4 ,on treating with oxalic acid1 cerium1 lanthanum1 and didymium are precipitated as oxalates1 which on ignition are converted into oxides4 ,these are soluble in acids4 ,their solution in hydrochloric acid is nearly neutralised2 acetate of soda is then added1 and an excess of sodium hypochlorite4 ,on boiling1 the cerium is precipitated as dioxide1 which is filtered off1 ignited1 and weighed4 ,cerium is detected by giving with borax a bead which is yellow in the oxidising1 and colourless in the reducing flame4 ,traces of cerium compounds boiled with dioxide of lead and nitric acid will give a yellow solution4 ,,lanthanum ,,and ,,didymium occur together with cerium in cerite1 and are separated with that metal as oxalates1 as described under ,cerium4 ,didymium salts have a rose or violet colour1 and impart 7when in sufficient quantity7 the same colour to the borax bead4 ,solutions have a characteristic absorption-spectrum4 ,the separation of lanthanum and didymium in the solution from which the cerium has been precipitated is effected by precipitating them together as oxalates1 igniting1 and dissolving in dilute nitric acid4 ,this solution is then evaporated to dryness and ignited1 for a few minutes1 just below redness4 ,a subnitrate of didymium is formed1 and remains as an insoluble residue on extracting with hot water4 ,the separated salts are treated with ammonia and ignited1 and weighed as oxides 7,la#b,o#c and ,di#b,o#c74 ,,yttria4 ,yttria is found in gadolinite and some other rare minerals4 ,it is precipitated along with the other earths by ammonia4 ,it is distinguished by the insolubility of its hydrate in potash1 by the insolubility of its oxalate in oxalic acid1 and by not being precipitated by hyposulphite of soda or potassium sulphate4 ,further1 it is precipitated by potash in the presence of tartaric acid as an insoluble tartrate4 ,this reaction distinguishes the members of the yttria group from most of the other earths4 ,the other members of the group closely resemble it1 and amongst them are erbia1 terbia1 ytterbia1 scandia1 c4 ,,beryllia4 ,the oxide of beryllium1 ,be,o 7also known as glucina71 occurs in nature mainly as silicate4 ,beryl1 the green transparent variety of which is the emerald1 is the best known of these4 ,it is a silicate of alumina and beryllia4#ia ,some other minerals in which it occurs are phenakite1 euclase1 and chrysoberyl4 ,in the ordinary course of analysis1 beryllia will be precipitated with alumina1 c41 by ammonic hydrate4 ,it is distinguished by the solubility of its hydrate in ammonic carbonate1 by not being precipitated by boiling with sodium hyposulphite1 and by not being precipitated by ammonic sulphide from an ammonic carbonate solution4 ,the analysis of silicates containing beryllia is thus effected4 ,the finely powdered substance is fused with twice its weight of potassium carbonate2 and the melt is extracted with water1 and evaporated with a slight excess of sulphuric acid to render the silica insoluble4 ,treat with water1 filter1 and evaporate the filtrate until a crust is formed4 ,potash alum crystallises out4 ,the liquor is poured off into a warm strong solution of ammonium carbonate4 ,ferric hydrate and alumina will be precipitated4 ,they are filtered off1 re-dissolved1 and again precipitated in ammonic carbonate solution2 the combined filtrates are boiled for some time1 and acidified slightly with hydrochloric acid4 ,the carbon dioxide is boiled off1 and the beryllia is then precipitated as hydrate with ammonia4 ,the hydrate is washed with hot water1 dried1 ignited1 and weighed as beryllia1 ,be,o4 ,beryllia has a specific gravity of #c4jh4 ,it is white1 infusible1 and insoluble in water4 ,after ignition1 it is insoluble in acids1 except sulphuric1 but is rendered soluble by fusion with alkalies4 ,beryllia1 in a solution of carbonate of ammonia1 is precipitated as carbonate on boiling in proportion as the carbonate of ammonia is volatilised4 ,the hydrate is dissolved by a boiling solution of ammonic chloride1 ammonia being evolved4 ,,the ,,alkaline ,,earths4 ,,lime4 ,lime is an oxide of calcium1 ,ca,o4 ,it occurs abundantly in nature1 but only in a state of combination4 ,the carbonate 7,ca,c,o#c71 found as limestone1 chalk1 and other rocks1 and as the minerals calcite and arragonite1 is the most commonly occurring compound4 ,the hydrated sulphate1 gypsum 7,ca,s,o#d4b;,h#b,o71 is common1 and is used in making plaster of ,paris4 ,anhydrite 7,ca,s,o#d7 also occurs in rock masses1 and is often associated with rock salt4 ,phosphate of lime1 in the forms of apatite1 phosphorite1 coprolite1 c41 is largely mined4 ,lime is a component of most natural silicates4 ,calcium also occurs1 combined with fluorine1 in the mineral fluor 7,ca,f#b74 ,in most of these the acid is the important part of the mineral2 it is only the carbonate which is used as a source of lime4 ,lime1 in addition to its use in mortars and cements1 is valuable as a flux in metallurgical operations1 and as a base in chemical work on a large scale4 ,a mixture of lime and magnesia is used in the manufacture of basic fire-bricks4 ,carbonate of lime on ignition1 especially when in contact with reducing substances1 loses carbonic acid1 and becomes lime4 ,this is known as quicklime2 on treatment with water it becomes hot1 expands1 and falls to a powder of slaked lime or calcium hydrate 7,ca,h#b,o#b74 ,the hydrate is slightly soluble in water 7#j4acfh gram in #ajj c4c471 forming an alkaline solution known as lime-water4 ,calcium hydrate is more generally used suspended in water as milk of lime4 ,as a flux it is used either as limestone or as quicklime4 ,silica forms with lime a compound1 calcium silicate1 which is not very fusible2 but when alumina and other oxides are present1 as in clays and in most rocky substances1 the addition of lime gives a very fusible slag4 ,detection4--,calcium is detected by the reddish colour which its salts impart to the flame4 ,it is best to moisten with hydrochloric acid 7or1 in the case of some silicates1 to treat with ammonium fluoride7 before bringing the substance into the flame4 ,when seen through a spectroscope1 it shows a large number of lines1 of which a green and an orange are most intense and characteristic4 ,calcium is detected in solution 7after removal of the metals by treatment with sulphuretted hydrogen and ammonium sulphide7 by boiling with ammonium oxalate and ammonia4 ,the lime is completely thrown down as a white precipitate4 ,lime is distinguished from the other alkaline earths by forming a sulphate insoluble in dilute alcohol1 but completely soluble in a boiling solution of ammonium sulphate4 ,lime compounds are for the most part soluble in water or in dilute hydrochloric acid4 ,calcium fluoride must be first converted into sulphate by evaporation in a platinum dish with sulphuric acid4 ,insoluble silicates are opened up by fusion with fusion mixture1 as described under ,silica4 ,separation4--,the separation of lime is effected by evaporating with hydrochloric acid1 to separate silica2 and by treating with sulphuretted hydrogen1 to remove the second group of metals4 ,if the substance contains much iron1 the solution is next oxidised by boiling with a little nitric acid2 and the iron1 alumina1 c41 are removed as basic acetates4 ,the filtrate is treated with ammonia and sulphuretted hydrogen1 and allowed to settle4 ,the filtrate from this is heated to boiling1 treated with a solution of ammonium oxalate in excess1 boiled for five or ten minutes1 allowed to settle for half an hour1 and filtered4 ,the precipitate contains all the lime as calcium oxalate4 ,,gravimetric ,,determination4 ,the precipitate of calcium oxalate is washed with hot water1 dried1 transferred to a weighed platinum crucible1 and ignited at a temperature not above incipient redness4 ,this ignition converts the oxalate into carbonate1 with evolution of carbonic oxide1 which burns at the mouth of the crucible with a blue flame4#ib ,generally a small quantity of the carbonate is at the same time converted into lime4 ,to reconvert it into carbonate1 moisten with a few drops of ammonic carbonate solution1 and dry in a water-oven4 ,heat gently over a ,bunsen burner1 cool1 and weigh4 ,the substance is calcium carbonate 7,ca,c,o#c71 and contains #ef per cent4 of lime 7,ca,o74 ,it is a white powder1 and should show no alkaline reaction with moistened litmus-paper4 ,where the precipitate is small1 it is better to ignite strongly over the blowpipe1 and weigh directly as lime4 ,with larger quantities1 and when many determinations have to be made1 it is easier to make the determination volumetrically4 ,,volumetric ,,methods4 ,these are carried out either by dissolving the oxalate at once in dilute sulphuric acid1 and titrating with permanganate of potassium solution2 or by calcining it to a mixture of lime and carbonate1 and determining its neutralising power with the standard solutions of acid and alkali4 ,titration with ,permanganate of ,potassium ,solution4--,this solution is made by dissolving #e4fdc grams of the salt in water1 and by diluting to #a litre2 #ajj c4c4 are equivalent to #j4e gram of lime4 ,the solution is standardised by titrating a quantity of oxalic acid about equivalent to the lime present in the assay2 #j4e gram of lime is equivalent to #a4abe gram of crystallised oxalic acid4 ,the standardising may be done with iron4 ,the standard found for iron multiplied by #j4e gives that for lime4 ,the process is as follows3--,the calcium oxalate 7having been precipitated and washed1 as in the gravimetric process7 is washed through the funnel into a flask with hot dilute sulphuric acid1 boiled till dissolved1 diluted to #bjj c4c4 with water1 and heated to about #hj ,c4 ,the standard solution of permanganate is then run in1 7not too quickly1 and with constant shaking7 until a permanent pink tinge is produced4 ,the c4c4 used multiplied by the standard1 and divided by the weight of the substance taken1 will give the percentage of lime4 ,estimation of ,lime by ,alkalimetry4--,the methods of determining the amount of an alkali or base by means of a standard acid solution1 or1 conversely1 of determining an acid by means of a standard alkaline solution1 are so closely related that they are best considered under one head4 ,the same standard solution is applicable for many purposes1 and1 consequently1 it is convenient to make it of such strength that one litre of it shall equal an equivalent in grams of any of the substances to be determined4 ,such solutions are termed normal4 ,for example1 a solution of hydrochloric acid 7,h,cl #cf4e7 containing #cf4e grams of real acid per litre1 would be normal and of equivalent strength to a solution containing either #ag grams of ammonia 7,,nh#c #ag7 or #dj grams of sodic hydrate 7,na,h,o #dj7 per litre4 ,it will be seen in these cases that the normal solution contains the molecular weight in grams per litre2 and1 if solutions of these strengths be made1 it will be found that they possess equal neutralising value4 ,if1 now1 a solution containing #ih grams of sulphuric acid 7,h#b,,so#d #ih7 per litre be made1 it will be found to have twice the strength of the above solution1 that is1 #ajj c4c4 of the soda would only require #ej c4c4 of the acid to neutralise it4 ,the reason for this will be seen on inspecting the equations3-- ,na,h,o ,h,cl ,na,cl ,h#b,o4 #b,na,h,o ,h#b,,so#d ,na#b,,so#d #b;,h#b,o4 ,acids like sulphuric acid are termed bibasic1 and their equivalent is only half the molecular weight4 ,thus1 a normal solution of sulphuric acid would contain #di grams 7#ih_/b7 of real acid per litre4 ,similarly1 lime and most of the bases are bibasic1 as may be seen from the following equations2 hence their equivalent will be half the molecular weight4 #b;,h,cl ,ca,o ,ca,cl#b ,h#b,o4 #b;,h,cl ,mg,o ,mg,cl#b ,h#b,o4 ,the standard normal solution of hydrochloric acid is made by diluting #ajj c4c4 of the strong acid to one litre with water4 ,this will be approximately normal4 ,in order to determine its exact strength1 weigh up #c grams of recently ignited pure sodium carbonate or of the ignited bicarbonate4 ,transfer to a flask and dissolve in #bjj c4c4 of water2 when dissolved1 cool1 tint faintly yellow with a few drops of a solution of methyl orange1 and run in the standard acid from a burette till the yellow changes to a pink4 ,read off the number of c4c4 used1 and calculate to how much sodium carbonate #ajj c4c4 of the acid are equivalent4 ,if the acid is strictly normal1 this will be #e4c grams4 ,it will probably be equivalent to more than this4 ,now calculate how much strictly normal acid would be equivalent to the standard found4 ,for example3 suppose the standard found is #e4e gram of sodium carbonate1 then-- #e4c 3 #e4e 33 #ajj 3 x 7where x is the quantity of normal acid required74 x #ajc4h c4c4 ,to get the acid of normal strength1 we should then add #c4h c4c4 of water to each #ajj c4c4 of the standard solution remaining4 ,suppose there were left #icj c4c4 of the approximate acid1 #ce4c c4c4 of water must be added and mixed4 ,it should then be checked by another titration with pure sodium carbonate4 ,the standard solution of semi-normal alkali4 ,the best alkali for general purposes is ammonia1 but1 since it is volatile 7especially in strong solutions71 it is best to make it of half the usual strength1 or semi-normal4 ,one litre of this will contain #h4e grams of ammonia 7,,nh#c71 and #ajj c4c4 of it will just neutralise #ej c4c4 of the normal acid4 ,take #ajj c4c4 of dilute ammonia and dilute with water to one litre4 ,run into a flask #ej c4c4 of the standard acid1 tint with methyl orange1 and run in from a burette the solution of ammonia till neutralised4 ,less than #ajj c4c4 will probably be used4 ,suppose #ie c4c4 were required1 there should have been #ajj1 hence there is a deficiency of five4 ,then1 for each #ie c4c4 of standard ammonia left1 add #e c4c4 of water1 and mix well4 #ajj c4c4 will now be equivalent to #ej c4c4 of the acid4 ,as an example of the application of this method1 we may take the determination of lime in limestone1 marble1 and similar substances4 ,determination of ,lime in ,limestone4--,weigh up #a gram of the dried sample1 and dissolve in #be c4c4 of normal acid1 cool1 dilute to #ajj c4c41 and titrate with the semi-normal solution of alkali 7using methyl-orange as an indicator74 ,divide the c4c4 of alkali used by #b1 subtract from #be1 and multiply by #j4jbh to find the weight of lime4 ,this method is not applicable in the presence of other carbonates or oxides1 unless the weight of these substances be afterwards determined and due correction be made4 ,,strontia4 ,strontia1 the oxide of strontium 7,sr,o71 occurs in nature as sulphate1 in the mineral celestine 7,sr,s,o#d71 and as carbonate in strontianite 7,sr,c,o#c74 ,it is found in small quantities in limestones1 chalk1 c4 ,strontia is used in sugar-refining1 and for the preparation of coloured lights4 ,detection4--,it is detected by the crimson colour which its compounds 7when moistened with hydrochloric acid7 impart to the flame4 ,the spectrum shows a large number of lines1 of which a red1 an orange1 and a blue are most characteristic4 ,it resembles lime in many of its compounds1 but is distinguished by the insolubility of its sulphate in a boiling solution of ammonium sulphate1 and by the insolubility of its nitrate in alcohol4 ,from baryta1 which it also resembles1 it is distinguished by not yielding an insoluble chromate in an acetic acid solution1 by the solubility of its chloride in alcohol1 and by the fact that its sulphate is converted into carbonate on boiling with a solution formed of #c parts of potassium carbonate and #a of potassium sulphate4 ,it is got into solution in the same manner as lime4 ,the sulphate should be fused with fusion mixture1 extracted with water1 and thoroughly washed4 ,the residue will contain the strontia as carbonate1 which is readily soluble in dilute hydrochloric or nitric acid4 ,separation4--,it is separated 7after removal of the silica and metals1 as described under ,lime7 by adding ammonia and ammonia carbonate1 and allowing to stand for some hours in a warm place4 ,in the absence of baryta or lime it is filtered off1 and weighed as strontium carbonate1 which contains #gj4ag per cent4 of strontia4 ,it is separated from baryta by dissolving in a little hydrochloric acid1 adding ammonia in excess1 and then acidifying with acetic acid1 and precipitating the baryta with potassium bichromate1 as described under ,baryta4 ,the strontia is precipitated from the filtrate by boiling for some time with a strong solution of ammonic sulphate and a little ammonia4 ,fifty parts of ammonic sulphate are required for each part of strontia or lime present4 ,the precipitate is filtered off1 and washed first with a solution of ammonic sulphate1 and then with alcohol4 ,it is dried1 ignited and weighed as strontium sulphate4 ,,gravimetric ,,determination4 ,the determination of strontia in pure solutions is best made by adding sulphuric acid in excess and alcohol in volume equal to that of the solution4 ,allow to stand overnight1 filter1 wash with dilute alcohol1 dry1 ignite at a red heat1 and weigh as sulphate 7,sr,s,o#d74 ,this contains #ef4d per cent4 of strontia 7,sr,o72 or #dg4g per cent4 of strontium4 ,,baryta4 ,baryta1 oxide of barium 7,ba,o71 commonly occurs in combination with sulphuric oxide in the mineral barytes or heavy spar 7,ba,s,o#d71 and in combination with carbon dioxide in witherite 7,ba,c,o#c74 ,these minerals are not unfrequently found in large quantity 7associated with galena and other metallic sulphides7 in lodes4 ,small isolated crystals of these are frequently found in mining districts4 ,barium is a constituent of certain mineral waters4 ,the minerals are recognised by their high specific gravity and their crystalline form4 ,compounds of barium are often used by the assayer1 more especially the chloride and hydrate4 ,the salts are1 with the exception of the sulphate1 generally soluble in water or hydrochloric acid4 ,in such solutions sulphuric acid produces a white precipitate of baric sulphate1 which is practically insoluble in all acids4 ,the dioxide 7,ba,o#b7 is used for the preparation of oxygen4 ,on strong ignition it gives up oxygen1 and is converted into baryta 7,ba,o71 which1 at a lower temperature1 takes up oxygen from the air1 re-forming the dioxide4 ,detection4--,barium is detected by the green colour its salts1 especially the chloride1 give to the flame4 ,this1 viewed through the spectroscope1 shows a complicated spectrum1 of which two lines in the green are most easily recognised and characteristic4 ,the salts of barium give no precipitate with sulphuretted hydrogen in either acid or alkaline solution1 but with sulphuric acid they at once give a precipitate1 which is insoluble in acetate of soda4 ,in solutions rendered faintly acid with acetic acid1 they give a yellow precipitate with bichromate of potash4 ,these reactions are characteristic of barium4 ,baryta is got into solution in the manner described under ,lime2 but in the case of the sulphate the substance is fused with three or four times its weight of fusion mixture4 ,the melt is extracted with water1 washed1 and the residue dissolved in dilute hydrochloric acid4 ,separation4--,the separation is thus effected3--,the solution in hydrochloric acid is evaporated to dryness1 re-dissolved in hot dilute hydrochloric acid1 and sulphuric acid is added to the solution till no further precipitate is formed4 ,the precipitate is filtered off1 and digested with a solution of ammonium acetate or of sodium hyposulphite at #ej or #fj ,c4 to dissolve out any lead sulphate4 ,the residue is filtered off1 washed1 dried1 and ignited4 ,the ignited substance is mixed with four or five times its weight of fusion mixture1 and fused in a platinum-dish over the blowpipe for a few minutes4 ,when cold1 it is extracted with cold water1 filtered1 and washed4 ,the residue is dissolved in dilute hydrochloric acid1 and 7if necessary7 filtered4 ,the solution contains the barium as baric chloride mixed1 perhaps1 with salts of strontium or lime4 ,to separate these1 ammonia is added till the solution is alkaline1 and then acetic acid in slight excess4 ,chromate of baryta is then thrown down1 by the addition of bichromate of potash1 as a yellow precipitate4 ,it is allowed to settle1 filtered and washed with a solution of acetate or of nitrate of ammonia4 ,it is dried1 ignited gently1 and weighed4 ,it is ,ba,cr,o#d1 and contains #fj4dg per cent4 of baryta4 ,,gravimetric ,,determination4 ,the gravimetric determination of baryta1 when lime and strontia are absent1 is as follows3--,the solution1 if it contains much free acid1 is nearly neutralised with ammonia1 and then diluted to #ajj or #bjj c4c4 ,it is heated to boiling1 and dilute sulphuric acid is added till no further precipitation takes place4 ,the precipitate is allowed to settle for a few minutes1 decanted through a filter1 and washed with hot water2 and1 afterwards1 dried1 transferred to a porcelain crucible1 and strongly ignited in the muffle or over the blowpipe for a few minutes4 ,it is then cooled1 and weighed as sulphate of baryta 7,ba,s,o#d74 ,it contains #fe4fg per cent4 of baryta 7,ba,o74 ,in determining the baryta in minerals which are soluble in acid1 it is precipitated direct from the hydrochloric acid solution 7nearly neutralised with ammonia7 by means of sulphuric acid4 ,the precipitated baric sulphate is digested with a solution of ammonic acetate2 and filtered1 washed1 ignited1 and weighed4 ,,volumetric ,,determination4 ,the principle and mode of working of this is the same as that given under the ,sulphur ,assay2 but using a standard solution of sulphuric acid instead of one of barium chloride4 ,the standard solution of sulphuric acid is made to contain #cb4jb grams of sulphuric acid 7,h#b,,so#d71 or an equivalent of a soluble alkaline sulphate1 per litre4 #ajj c4c4 will be equal to #e grams of baryta4 ,five grams of the substance are taken1 and the baryta they contain converted into carbonate 7if necessary74 ,the carbonate is dissolved in dilute hydrochloric acid4 ,ten grams of sodium acetate are added1 and the solution1 diluted to #ejj c4c41 is boiled1 and titrated in the manner described4 ,lead salts must be absent in the titration1 and so must strontia and lime4 ,ferrous salts should be peroxidised by means of permanganate or chlorate of potash4 ,other salts do not interfere4 ,,magnesia4 ,magnesia1 the oxide of magnesium 7,mg,o7 occurs in nature in the rare mineral periclase 7,mg,o72 and hydrated1 as brucite 7,mg,h#b,o#b74 ,as carbonate it occurs in large quantity as magnesite 7,mg,c,o#c71 which is the chief source of magnesia4 ,mixed with carbonate of lime1 it forms magnesian limestone and dolomite4 ,it is present in larger or smaller quantity in most silicates2 and the minerals1 serpentine1 talc1 steatite and meerschaum are essentially hydrated silicates of magnesia4 ,soluble magnesian salts occur in many natural waters2 more especially the sulphate and the chloride4 ,kieserite 7,mg,s,o#d4;,h#b,o7 occurs in quantity at ,stassfurt1 and is used in the manufacture of ,epsom salts4 ,detection4--,magnesia is best detected in the wet way4 ,its compounds give no colour to the flame1 and the only characteristic dry reaction is its yielding a pink mass when ignited before the blowpipe 7after treatment with a solution of cobalt nitrate74 ,in solution1 it is recognised by giving no precipitate with ammonia or ammonic carbonate in the presence of ammonic chloride1 and by giving a white crystalline precipitate on adding sodium phosphate or arsenate to the ammoniacal solution4 ,magnesia differs from the other alkaline earths by the solubility of its sulphate in water4 ,magnesia is dissolved by boiling with moderately strong acids2 the insoluble compounds are fused with fusion mixture1 and treated as described under ,silicates4 ,separation4--,it is separated by evaporating the acid solution to dryness to render silica insoluble1 and by taking up with dilute hydrochloric acid4 ,the solution is freed from the second group of metals by means of sulphuretted hydrogen1 and the iron1 alumina1 c41 are removed with ammonic chloride1 ammonia1 and ammonic sulphide4 ,the somewhat diluted filtrate is treated1 first1 with ammonia1 and then with carbonate of ammonia in slight excess4 ,it is allowed to stand for an hour in a warm place1 and then filtered4 ,the magnesia is precipitated from the filtrate by the addition of an excess of sodium phosphate and ammonia4 ,it is allowed to stand overnight1 filtered1 and washed with dilute ammonia4 ,the precipitate contains the magnesia as ammonic-magnesic phosphate4 ,in cases where it is not desirable to introduce sodium salts or phosphoric acid into the assay solution1 the following method is adopted4 ,the solution 7freed from the other alkaline earths by ammonium carbonate7 is evaporated in a small porcelain dish with nitric acid4 ,the residue 7after removing the ammonic salts by ignition7 is taken up with a little water and a few crystals of oxalic acid1 transferred to a platinum dish1 evaporated to dryness1 and ignited4 ,the residue is extracted with small quantities of boiling water and filtered off2 while the insoluble magnesia is washed4 ,the filtrate contains the alkalies4 ,the residue is ignited1 and weighed as magnesia4 ,it is ,mg,o4 ,,gravimetric ,,determination4 ,the solution containing the magnesia is mixed with chloride of ammonium and ammonia in excess4 ,if a precipitate should form1 more ammonic chloride is required4 ,add sodium phosphate solution in excess1 stir and allow to stand overnight4 ,filter and wash the precipitate with dilute ammonia4 ,dry1 transfer to a platinum or porcelain crucible1 and ignite 7finally at intense redness72 cool1 and weigh4 ,the substance is magnesic pyrophosphate 7,mg#b,p#b,o#g71 and contains #cf4jd per cent4 of magnesia4 ,,volumetric ,,method4 ,the magnesia having been precipitated as ammonic-magnesic phosphate1 which is the usual separation1 its weight can be determined volumetrically by the method of titration described under ,phosphates4 ,the same standard solution of uranium acetate is used4 ,its standard for magnesia is got by multiplying the standard for phosphoric oxide by #j4edic4 ,for example1 if one hundred c4c4 are equivalent to #j4e gram of phosphoric oxide1 they will be equivalent to 7#j4e 4#edic7 #j4bgdf gram of magnesia4 ,the method of working and the conditions of the titration are the same as for the phosphate titration4 ,the quantity of substance taken for assay must not contain more than #j4a or #j4b gram of magnesia4 ,after precipitating as ammonic-magnesic phosphate with sodium phosphate1 and well washing with ammonia1 it is dissolved in dilute hydrochloric acid1 neutralised with ammonia1 and sodic acetate and acetic acid are added in the usual quantity4 ,the solution is boiled and titrated4 ,,examination ,,of ,a ,,limestone4 ,silica and ,insoluble ,silicates4--,take one gram of the dried sample and dissolve it in #aj c4c4 of dilute hydrochloric acid2 filter2 wash1 dry1 and ignite the residue4 ,organic ,matter4--,if the residue insoluble in hydrochloric acid shows the presence of organic matter1 it must be collected on a weighed filter and dried at #ajj4 ,on weighing1 it gives the combined weights of organic and insoluble matter4 ,the latter is determined by igniting and weighing again4 ,the organic matter is calculated by difference4 ,lime4--,where but little magnesia is present1 this is determined by titration with standard acid4 ,take one gram1 and dissolve it in #be c4c4 of normal hydrochloric acid4 ,tint with methyl-orange and titrate with semi-normal ammonia4 ,divide the quantity of ammonia used by #b1 deduct this from #be1 and multiply the remainder by #b4h4 ,this gives the percentage of lime4 ,where magnesia is present1 the same method is adopted1 and the magnesia 7which is separately determined7 is afterwards deducted4 ,the percentage of magnesia found is multiplied by #a4d1 and the result is deducted from the apparent percentage of lime got by titrating4 ,magnesia4--,dissolve #b grams of the limestone in hydrochloric acid1 and separate the lime with ammonia and ammonium oxalate4 ,the filtrate is treated with sodium phosphate1 and the magnesia is weighed as pyrophosphate1 or titrated with uranium acetate4 ,iron4--,dissolve #b grams in hydrochloric acid1 reduce1 and titrate with standard permanganate of potassium solution4 ,this gives the total iron4 ,the ferrous iron is determined by dissolving another #b grams in hydrochloric acid and at once titrating with the permanganate of potassium solution4 ,manganese4--,dissolve #bj grams in hydrochloric acid1 nearly neutralise with soda1 add sodium acetate1 boil1 and filter4 ,to the filtrate add bromine2 boil1 and determine the manganese in the precipitate4 ,see page #cjj4 ,phosphoric ,oxide4--,this is determined by dissolving the ferric acetate precipitate from the manganese separation in hydrochloric acid1 adding ammonia in excess1 and passing sulphuretted hydrogen4 ,filter and add to the filtrate magnesia mixture4 ,the precipitate is collected1 washed with ammonia1 ignited1 and weighed as pyrophosphate4 ,,the ,,alkalies4 ,the oxides of sodium1 potassium1 lithium1 csium1 and rubidium and ammonia are grouped under this head4 ,of these csia and rubidia are rare1 and lithia comparatively so4 ,they are easily distinguished by their spectra4 ,they are characterised by the solubility of almost all their salts in water1 and1 consequently1 are found in the solutions from which the earths and oxides of the metals have been separated by the usual group re-agents4 ,the solution from which the other substances have been separated is evaporated to dryness1 and the product ignited to remove the ammonic salts added for the purpose of separation4 ,the residue contains the alkali metals generally1 as chlorides or sulphates4 ,before determining the quantities of the particular alkali metals present1 it is best to convert them altogether1 either into chloride or sulphate1 and to take the weight of the mixed salts4 ,it is generally more convenient to weigh them as chlorides4 ,they are converted into this form1 if none of the stronger acids are present1 by simply evaporating with an excess of hydrochloric acid4 ,nitrates are converted into chlorides by this treatment4 ,when sulphates or phosphates are present1 the substance is dissolved in a little water1 and the sulphuric or phosphoric acid precipitated with a slight excess of acetate of lead in the presence of alcohol4 ,the solution is filtered1 and the excess of lead precipitated with sulphuretted hydrogen4 ,the filtrate from this is evaporated to dryness with an excess of hydrochloric acid1 and the residue1 consisting of the mixed chlorides1 is gently ignited and weighed4 ,in many cases 7such as the analysis of slags and of some natural silicates where the percentage of alkalies is small7 the percentage of soda and potash 7which most commonly occur7 need not be separately determined4 ,it is sufficient to report the proportion of mixed alkalies2 which is thus ascertained3--,dissolve the ignited and weighed chlorides in #ajj c4c4 of distilled water1 and titrate with the standard solution of silver nitrate 7using potassic chromate as indicator7 in the manner described under ,chlorine4 ,the c4c4 of silver nitrate used gives the weight in milligrams of the chlorine present4 ,multiply this by #j4gge1 and deduct the product from the weight of the mixed chlorides4 ,this will give the combined weight of the alkalies 7,na#b,o and ,k#b,o7 present4 ,for example1 #j4jbff gram of mixed chlorides required on titrating #ad4b c4c4 of silver nitrate1 which is equivalent to #j4jadb gram of chlorine4 ,this multiplied by #j4gge gives #j4jaaj to be deducted from the weight of the mixed chlorides4 ,mixed chlorides #j4jbff gram ,deduction #j4jaaj ------ ,mixed alkalies #j4jaef ,assuming this to have been got from #a gram of a rock1 it would amount to #a4ef per cent4 of potash and soda4 ,the relative proportions of the potash and soda can be ascertained from the same determination4 ,sodium and potassium chlorides have the following composition3-- ,sodium #ci4ch ,potassium #eb4df ,chlorine #fj4fb ,chlorine #dg4ed ----- ----- #ajj4jj #ajj4jj ,the percentage of chlorine in the mixed chlorides is calculated4 ,it necessarily falls somewhere between #dg4e and #fj4f per cent41 and approaches the one or the other of these numbers as the proportion of the sodium or potassium preponderates4 ,each per cent4 of chlorine in excess of #dg4e represents #g4fc per cent4 of sodium chloride in the mixed chlorides4 ,the percentage of potash and soda in the substance can be calculated in the usual way4 ,sodium chloride multiplied by #j4ecjb gives its equivalent of soda 7,na#b,o71 and potassium chloride multiplied by #j4fcag gives its equivalent of potash 7,k#b,o74 ,the weight of sodium chloride in the mixed chlorides is also calculated thus3--,take the same example for illustration4 ,multiply the chlorine found by #b4ajc4 ,this gives-- 7#j4jadbb4ajc7 #j4jbihg4 ,from the product deduct the weight of the mixed chlorides found-- ,product #j4jbihg ,mixed chlorides #j4jbffj ------- ,difference #j4jjcbg ,the difference multiplied by #c4fbhh gives the weight of sodium chloride in the mixture4 ,in this case it equals #j4jaah gram4 ,the potassium chloride is indicated by the difference between this and the weight of the mixed chlorides4 ,it equals #j4jadh gram4 ,we have now got-- ,sodium chloride #j4jaah gram ,potassium chloride #j4jadh from #a gram of the rock taken4 ,multiplying these by their factors we have 7,soda #j4jaahj4ecjb2 ,potash #j4jadhj4fcag7-- ,soda #j4fbe per cent4 ,potash #j4ice ,concentration of the ,alkalies4--,with the exception of magnesia1 all the other bases are separated from the alkalies in the ordinary course of work without the addition of any re-agent which cannot be removed by simple evaporation and ignition4 ,consequently1 with substances soluble in acids1 successive treatment of the solution with sulphuretted hydrogen1 ammonia1 ammonic sulphide1 and ammonic carbonate1 filtering1 where necessary1 will yield a filtrate containing the whole of the alkalies with ammonic salts and1 perhaps1 magnesia4 ,the filtrate is evaporated in a small porcelain dish1 with the addition of nitric acid towards the finish4 ,it is carried to dryness and ignited4 ,the residue is taken up with a little water1 treated with a few crystals of oxalic acid1 and again evaporated and ignited4 ,the alkaline salts are extracted with water1 and filtered from the magnesia into a weighed platinum dish4 ,the solution is then evaporated with an excess of hydrochloric acid1 ignited at a low red heat1 and weighed4 ,the residue consists of the mixed alkaline chlorides4 ,for substances 7such as most silicates and similar bodies7 not completely decomposed by acids1 ,lawrence ,smith's method is generally used4 ,this is as follows3--,take from #j4e to #a gram of the finely powdered mineral1 and mix1 by rubbing in the mortar1 with an equal weight of ammonium chloride4 ,then mix with eight times as much pure calcium carbonate1 using a part of it to rinse out the mortar4 ,transfer to a platinum crucible1 and heat gently over a ,bunsen burner until the ammonic chloride is decomposed 7five or ten minutes74 ,raise the heat to redness1 and continue at this temperature for about three quarters of an hour4 ,the crucible must be kept covered4 ,cool1 and turn out the mass into a #d-;inch evaporating dish2 wash the crucible and cover with distilled water1 and add the washings to the dish2 dilute to #fj or #hj c4c41 and heat to boiling4 ,filter and wash4 ,add to the filtrate about #a4e gram of ammonium carbonate2 evaporate to about #dj c4c41 and add a little more ammonic carbonate and some ammonia4 ,filter into a weighed platinum dish1 and evaporate to dryness4 ,heat gently1 to drive off the ammonic chloride1 and ignite to a little below redness4 ,cool and weigh4 ,the residue consists of the mixed alkaline chlorides4 ,separation of the ,alkali-,metals from each other4--,sodium and lithium are separated from the other alkali-metals by taking advantage of the solubility of their chlorides in the presence of platinic chloride2 and from one another by the formation of an almost insoluble lithic phosphate on boiling with a solution of sodium phosphate in a slightly alkaline solution4 ,csium1 rubidium1 and potassium yield precipitates with platinic chloride1 which are somewhat soluble1 and must be precipitated from concentrated solutions4 ,csium and rubidium are separated from potassium by fractional precipitation with platinum chloride4 ,their platino-chlorides1 being less soluble than that of potassium1 are precipitated first4 ,one hundred parts of boiling water dissolve #e4ah of the potassium platino-chloride1 #j4fcd of the rubidium salt1 and #j4cgg of the corresponding csium compound4 ,the separation of lithium1 csium1 and rubidium is seldom called for1 owing to their rarity4 ,the details of the separation of potassium from sodium are described under ,potassium4 ,ammonia compounds are sharply marked off from the rest by their volatility1 and it is always assumed that they have been removed by ignition2 if left in the solution1 they would count as potassium compounds4 ,they will be considered under ,ammonia4 ,,sodium4 ,sodium is the commonest of the alkali metals4 ,it is found in nature chiefly combined with chlorine as common salt 7,na,cl74 ,this mineral is the source from which the various compounds of sodium in use are prepared4 ,sodium occurs abundantly as nitrate 7,na,n,o#c7 in ,chili saltpetre1 and as silicate in various minerals1 such as albite 7or soda-felspar74 ,it occurs as fluoride in cryolite 7,na#c;,al,f#f71 and as carbonate in natron1 c4 ,sulphates are also found4 ,sodium is very widely diffused1 few substances being free from it4 ,the detection of sodium is easy and certain1 owing to the strong yellow colour its salts impart to the flame2 this1 when viewed by the spectroscope1 shows a single yellow line4#ic ,the extreme delicacy of this test limits its value1 because of the wide diffusion of sodium salts4 ,it is more satisfactory to separate the chloride1 which may be recognised by its taste1 flame coloration1 fusibility1 and negative action with reagents4 ,the chloride dissolved in a few drops of water gives with potassium metantimoniate1 a white precipitate of the corresponding sodium salt4 ,sodium salts are dissolved out from most compounds on treatment with water or dilute acids4 ,insoluble silicates are decomposed and the alkali rendered soluble by ,lawrence ,smith's method1 which has just been described4 ,the separation of the sodium from the mixed chlorides is effected in the following way3--,the chlorides are dissolved in a little water and the potassium separated as platino-chloride4 ,the soluble sodium platino-chloride1 with the excess of platinum1 is boiled1 mixed with sulphuric acid1 evaporated to dryness1 and ignited4 ,on extracting with water1 filtering1 evaporating1 and igniting1 sodium sulphate is left1 and is weighed as such4 ,it is more usual1 and quite as satisfactory1 to calculate the weight of the sodium chloride by difference from that of the mixed chlorides1 by subtracting that of the potassium chloride1 which is separately determined4 ,for example1 #a gram of a rock gave--,mixed chlorides1 #j4jbff gram1 and #j4jdhf gram of potassic platino-chloride4 ,this last is equivalent to #j4jadi gram of potassium chloride4 ,mixed chlorides found #j4jbff ,deduct potassium chloride #j4jadi ------ ,leaves sodium chloride #j4jaag ,the weight of sodium chloride found1 multiplied by #j4ecjb1 gives the weight of the soda 7,na#b,o74 ,,gravimetric ,,determination4 ,the solution1 which must contain no other metal than sodium1 is evaporated in a weighed platinum crucible or dish4 ,towards the finish an excess1 not too great1 of sulphuric acid is added1 and the evaporation is continued under a loosely fitting cover4 ,the residue is ignited over the blowpipe1 a fragment of ammonic carbonate being added towards the end1 when fumes of sulphuric acid cease to be evolved4 ,this ensures the removal of the excess of acid4 ,the crucible is cooled in the desiccator1 and weighed4 ,the substance is sulphate of soda 7,na#b,,so#d71 and contains #dc4ff per cent4 of soda 7,na#b,o71 or #cb4ch per cent4 of sodium 7,na74 ,,volumetric ,,methods4 ,there are various methods used for the different compounds of sodium4 ,there is no one method of general application4 ,thus with common salt the chlorine is determined volumetrically2 and the sodium1 after deducting for the other impurities1 is estimated by difference4 ,with sodic carbonate and caustic soda1 a given weight of the sample is titrated with standard acid1 and the equivalent of soda estimated from the alkalinity of the solution4 ,with sodium sulphate1 a modification of the same method is used4 ,to a solution of #c4ee grams of the salt contained in a half-litre flask1 #bej c4c4 of a solution of baryta water is added4 ,the volume is made up to #ejj c4c4 with water4 ,the solution is mixed and filtered4 ,half of the filtrate is measured off1 treated with a current of carbonic acid1 and then boiled4 ,it is transferred to a half-litre flask1 diluted to the mark1 shaken up1 and filtered4 #bej c4c4 of the filtrate1 representing a quarter of the sample taken1 is then titrated with standard acid4 ,the standard acid is made by diluting #bej c4c4 of the normal acid to #a litre4 ,the c4c4 of acid used multiplied by #b gives the percentage4 ,a correction must be made to counteract the effect of impurities in the baryta as well as errors inherent in the process4 ,this is small1 and its amount is determined by an experiment with #c4ee grams of pure sodium sulphate4 ,,examination ,,of ,,common ,,salt4 ,moisture4--,powder and weigh up #aj grams of the sample into a platinum dish4 ,dry in a water oven for an hour1 and afterwards heat to bare redness over a ,bunsen burner4 ,cool1 and weigh4 ,the loss gives the water4 ,chlorine4--,weigh up two separate lots of #a gram each2 dissolve in #ajj c4c4 of water1 and determine the chlorine by titrating with the standard silver nitrate solution1 using chromate of potash as indicator4 ,see ,chlorine4 ,insoluble ,matter4--,dissolve #aj grams of the salt in water with the help of a little hydrochloric acid4 ,filter off the sediment1 wash1 ignite1 and weigh4 ,this residue is chiefly sand4 ,dilute the nitrate to #ejj c4c4 ,lime4--,take #bej c4c4 of the filtrate1 render ammoniacal and add ammonium oxalate2 wash1 dry1 and ignite the precipitate4 ,weigh as lime 7,ca,o74 ,magnesia4--,to the filtrate from the lime add phosphate of soda4 ,allow to stand overnight1 filter1 wash with dilute ammonia1 dry1 ignite1 and weigh as pyrophosphate4 ,sulphuric ,oxide4--,to the remaining #bej c4c4 of the filtrate from the insoluble1 add an excess of barium chloride4 ,collect1 wash1 dry1 ignite1 and weigh the barium sulphate4 ,sodium4--,it is estimated by difference4 ,the following may be taken as an example3-- ,moisture #j4ce ,insoluble matter #j4dj ,lime #j4dj ,magnesia #j4je ,sulphuric oxide #j4fj ,chlorine #ei4fj ,sodium #ch4fj ------ #ajj4jj ,,potassium4 ,potassium occurs in nature as chloride1 in the mineral sylvine 7,k,cl71 and more abundantly combined with magnesium chloride1 in earnallite 7,k,cl4,mg,cl#b4f;,h#b,o74 ,it occurs as nitrate in nitre 7,,kno#c71 and as silicate in many minerals1 such as orthoclase 7or potash-felspar7 and muscovite 7or potash-mica74 ,potassium compounds are detected by the characteristic violet colour they impart to the flame4 ,the presence of sodium salts masks this tint1 but the interference can be neutralised by viewing the flame through a piece of blue glass4 ,viewed through the spectroscope1 it shows a characteristic line in the red and another in the violet4 ,these1 however1 are not so easy to recognise or obtain as the sodium one4 ,concentrated solutions of potassium salts give a yellow crystalline precipitate with platinum chloride1 and a white crystalline one with the acid tartrate of soda4 ,for these tests the solution is best neutral4 ,these tests are only applicable in the absence of compounds other than those of potassium and sodium4 ,,gravimetric ,,determination4 ,this process serves for its separation from sodium4 ,take #a gram of the sample and dissolve it in an evaporating dish with #ej c4c4 of water4 ,acidify with hydrochloric acid in quantity sufficient 7if the metals are present as chlorides7 to make it acid1 or1 if other acids are present1 in at least such quantity as will provide the equivalent of chlorine4 ,add #c grams of platinum1 in solution as platinum chloride1 and evaporate on a water-bath to a stiff paste1 but not to dryness4 ,moisten with a few drops of platinic chloride solution without breaking up the paste by stirring4 ,cover with #bj c4c4 of strong alcohol1 and wash the crystals as much as possible by rotating the dish4 ,allow to settle for a few moments1 and decant through a filter4 ,wash in the same way two or three times until the colour of the filtrate shows that the excess of the platinum chloride used is removed4 ,wash the precipitate on to the filter with a jet of alcohol from the wash-bottle2 clean the filter-paper1 using as little alcohol as possible4 ,dry in the water-oven for an hour4 ,brush the precipitate into a weighed dish1 and weigh it4 ,it is potassium platino-chloride 7,k#b,pt,cl#f71 and contains #af4jc per cent4 of potassium1 or #cj4ef per cent4 of potassium chloride 7,k,cl71 which is equivalent to #ai4c per cent4 of potash 7,k#b,o74 ,if the filter-paper is not free from precipitate1 burn it and weigh separately4 ,the excess of weight over that of the ash will be due to platinum and potassic chloride 7,pt and #b,k,cl74 ,this multiplied by #a4dac will give the weight of the potassic platino-chloride from which it was formed4 ,it must be added to the weight of the main precipitate4 ,the mixed alkaline chlorides obtained in the usual course of analysis are treated in this manner2 the quantity of platinum added must be about three times as much as the mixed chlorides weigh4 ,,volumetric ,,methods4 ,these are the same as with soda4 ,examination of ,commercial ,carbonate of ,potash4--,the impurities to be determined are moisture1 silica1 and insoluble matter1 chlorine1 sulphuric oxide1 and oxide of iron4 ,these determinations are made in the ways described under the examination of common salt4 ,the potassium is determined by converting it into chloride and precipitating with platinum chloride1 c41 as just described4 ,available ,alkali4--,weigh up #bc4e grams of the sample1 dissolve in water1 and make up to #ejj c4c4 ,take #ej c4c41 tint with methyl orange1 and titrate with the normal solution of acid4 ,the c4c4 of acid used multiplied by #b gives the percentage of available alkali calculated as potash 7,k#b,o74 ,soda4--,this is calculated indirectly in the following way3--,deduct from the potassium found the quantity required for combination with the chlorine and sulphuric oxide present1 and calculate the remainder to potash 7,k#b,o74 ,the apparent surplus excess of available alkali is the measure of the soda present4 ,carbon ,dioxide4--,the c4c4 of acid used in the available alkali determination1 multiplied by #b4b and divided by #b4ce1 gives the percentage of carbon dioxide4 ,,lithium4 ,lithia1 the oxide of lithium 7,li#b,o71 occurs in quantities of #c or #d per cent4 in various silicates1 such as lepidolite 7or lithia-mica71 spodumene1 and petalite4 ,it also occurs as phosphate in triphyline4 ,it is a constituent of the water of certain mineral springs4 ,a spring at ,wheal ,clifford contained as much as #j4cgb gram of lithium chloride per litre4 ,in small quantities1 lithia is very widely diffused4 ,the ,detection of lithia is rendered easy by the spectroscope2 its spectrum shows a red line lying about midway between the yellow sodium line and the red one of potassium4 ,it also shows a faint yellow line4 ,the colour of the flame 7a crimson7 is characteristic4 ,the reactions of the lithium compounds lie between those of the alkalies and of the alkaline earths4 ,solutions are not precipitated by tartaric acid nor by platinic chloride4 ,the oxide is slowly soluble in water4 ,the carbonate is not freely soluble4 ,lithia is completely precipitated by sodic phosphate1 especially in hot alkaline solutions4 ,in its determination the mixed alkaline chlorides obtained in the separation of the alkalies are dissolved in water1 a solution of soda is added in slight excess1 and the lithia precipitated with sodic phosphate4 ,before filtering1 it is evaporated to dryness and extracted with hot water rendered slightly ammoniacal4 ,the residue is transferred to a filter1 dried1 ignited1 and weighed4 ,the precipitate is lithium phosphate 7#c,li#b,o1 ,p#b,o#e71 and contains #ch4h per cent4 of lithia4 ,the separation of lithia from magnesia is not given by the usual authorities4 ,wohler recommends evaporating the solution to dryness with carbonate of soda4 ,on extracting the residue with water1 the lithia dissolves out and is determined in the filtrate4 ,one hundred parts of water dissolve1 at the ordinary temperature1 #j4gfi parts of lithium carbonate 7,li#b;,,co#c72 the basic magnesia compound is almost insoluble in the absence of carbon dioxide and ammonium salts4 ,,caesium4 ,the oxide of caesium1 caesia 7,cs#b,o71 is found associated with lithia in lepidolite1 c41 and1 together with rubidium1 in many mineral waters4 ,the mineral pollux is essentially a silicate of alumina and caesia2 it contains #cd4j per cent4 of the latter oxide4 ,caesium is best detected by the spectroscope1 its spectrum being characterised by two lines in the blue and one in the red2 the latter is about midway between the lithium and sodium lines4 ,if not detected by the spectroscope1 or specially looked for1 caesia would1 in the ordinary course of work1 be separated with the potash and weighed as potassium platino-chloride4 ,caesia is separated from all the other alkalies by adding to the acid solution of the mixed chlorides a strongly acid cold solution of antimonious chloride4 ,the acid used must be hydrochloric4 ,the caesium is precipitated as a white crystalline precipitate 7,cs,cl4,sb,cl#c71 which is filtered off1 and washed1 when cold1 with strong hydrochloric acid2 since it is decomposed by water or on warming4 ,the precipitate is washed into a beaker1 and treated with sulphuretted hydrogen2 after filtering off the sulphide of antimony1 the solution leaves1 on evaporation1 the caesium as chloride4 ,,rubidium4 ,rubidium occurs widely diffused in nature1 but in very small quantities4 ,it is generally associated with caesium4 ,it is detected by the spectroscope1 which shows two violet lines and two dark red ones4 ,like caesium1 it is precipitated with platinic chloride1 and in the ordinary course of work would be weighed as potassium4 ,it is separated from potassium by fractional precipitation with platinic chloride4 ,rubidium platino-chloride is much less soluble than the potassium salt4 ,,ammonium4 ,it is usual to look upon the salts of ammonia as containing a compound radical 7,,nh#d ,am71 which resembles in many respects the metals of the alkalies4 ,ammonium occurs in nature as chloride in sal ammoniac 7,am,cl71 as sulphate in mascagnine 7,am#b,,so#d71 as phosphate in struvite 7,am,mg,p,o#d4ab;,h#b,o74 ,minerals containing ammonium are rare1 and are chiefly found either in volcanic districts or associated with guano4 ,ammonia and ammonium sulphide occur in the waters of certain ,tuscan lagoons1 which are largely worked for the boracic acid they contain4 ,the crude boracic acid from this source contains from #e to #aj per cent4 of ammonium salts4 ,it is from these that the purer forms of ammonium compounds of commerce known as from volcanic ammonia are derived4 ,but the bulk of the ammonia of commerce is prepared from the ammoniacal liquors obtained as bye-products in the working of certain forms of blast furnaces and coke ovens1 and more especially in gas-making4 ,ammonia hardly comes within the objects of assaying2 but it is largely used in the laboratory1 and the assayer is not unfrequently called on to determine it4 ,ammonium salts are mostly soluble in water4 ,in strong solutions they give a yellow precipitate of ammonium platino-chloride on the addition of chloride of platinum2 and with the acid tartrate of soda yield a white precipitate of hydric ammonic tartrate4 ,these reactions are similar to those produced with potassium compounds4 ,heated with a base1 such as lime or sodic hydrate1 ammonium salts are decomposed1 yielding ammonia gas 7,,nh#c71 which is readily soluble in water4 ,the solution of this substance is known as ammonic hydrate or ammonia4 ,they are volatilised on ignition2 either with1 or without1 decomposition according to the acid present4 ,this fact is of importance in analytical work2 since it allows of the use of alkaline solutions and reagents which leave nothing behind on heating4 ,it must be remembered1 however1 that1 although ammonic chloride is volatile1 it cannot be volatilised in the presence of substances which form volatile chlorides without loss of the latter4 ,for example3 ferric oxide and alumina are thus lost1 volatilising as chlorides2 and there are some other compounds 7notably ammonic magnesic arsenate7 which on heating to redness suffer reduction4 ,the presence of ammonic chloride in such cases must be avoided4 ,detection4--,compounds of ammonium are detected by their evolving ammonia when mixed or heated with any of the stronger bases4 ,the ammonia is recognised by its odour1 by its alkaline reaction with litmus paper1 and by yielding white fumes1 when brought in contact with fuming acid4 ,in consequence of the use of ammonium salts and ammonia as reagents1 it is necessary to make a special test for and determination of ammonium4#id ,in the ordinary course of work it will be lost on ignition4 ,the determination presents little difficulty1 and is based on the method used for its detection4 ,illustration3 ,,fig4 #fa4 ,solution and ,separation4--,although ammonium salts are soluble in water1 there is no necessity for dissolving them4 ,the compound containing the ammonia is boiled with an alkaline solution2 and the liberated ammonia condensed and collected4 ,the substance is weighed out into a flask of about #bjj c4c4 capacity4 ,the flask is closed with a rubber cork perforated to carry a #bj c4c4 pipette and a bulb exit tube4 ,the latter is connected with a receiver1 which is a small flask containing dilute hydrochloric acid 7fig4 #fa74 ,the flask containing the substance is corked1 and the greater part of the soda solution is run in from the pipette4 ,the solution is then boiled4 ,the ammonia volatilises1 and is carried over into the hydrochloric acid1 with which it combines to form ammonic chloride4 ,the distillation is carried on gently until the bulk of the liquid is driven over4 ,the ammonia in the receiver will be mixed only with the excess of hydrochloric acid4 ,this separation is used in all determinations4 ,,gravimetric ,,determination4 ,the contents of the flask are transferred to a weighed platinum dish1 and evaporated on the water-bath4 ,it is dried until the weight is constant4 ,the chloride of ammonium remains as a white mass which1 after cooling in a desiccator1 is weighed4 ,it contains #cc4gb per cent4 of ammonium 7,,nh#d71 or #ca4he per cent4 of ammonia 7,,nh#c74 ,on heating over the ,bunsen burner it is completely volatilised1 leaving no residue4 ,,volumetric ,,determination4 ,weigh up #a4g gram of the substance and place it in the flask4 ,measure off #ej c4c4 of the normal solution of acid1 place them in the receiver1 and dilute with an equal volume of water4 ,run in through the pipette 7by opening the clip7 #bj c4c4 of a strong solution of soda1 boil until the ammonia has passed over1 and then aspirate a current of air through the apparatus4 ,disconnect the receiver1 and tint its contents with methyl orange4 ,titrate the residual acid with a semi-normal solution of alkali4 ,divide the c4c4 of the alkali solution used by #b1 and deduct from the #ej c4c4 ,the difference will give the number of c4c4 of the normal acid solution neutralised by the ammonia distilled over4 ,each c4c4 of acid so neutralised1 represents #a per cent4 of ammonia in the sample4 ,if the results are to be reported as ammonium1 #a4h gram of the sample is taken instead of #a4g gram4 ,,colorimetric ,,determination4 ,this is effected by means of ,nessler's reagent1 which strikes a brown colour with traces of ammonia1 even with a few hundredths of a milligram in #ajj c4c4 of liquid4 ,with larger quantities of ammonia the reagent gives a precipitate4 ,this reagent is a strongly alkaline solution of potassic mercuric iodide2 and is thus made3-- ,nessler's solution3 ,dissolve #ag grams of mercuric chloride in #cjj c4c4 of water2 and add the solution to one of #ce grams of potassium iodide in #ajj c4c4 of water until a permanent precipitate is produced4 ,both solutions must be cold4 ,then make up to a litre by adding a #bj per cent4 solution of potash4 ,add more of the mercuric chloride 7a little at a time7 until a permanent precipitate is again formed4 ,allow to settle1 decant1 and use the clear liquor4 ,four or five c4c4 are used for each #ajj c4c4 of liquid to be tested4 ,a ,standard ,solution of ,ammonia is made by dissolving #j4cae gram of ammonic chloride in water1 and diluting to #ajj c4c4 ,ten c4c4 of this are taken and diluted to #a litre4 ,one c4c4 contains #j4ja milligram of ammonia 7,,nh#c74 ,in working1 the solution containing the ammonia is diluted to a definite volume1 and to such an extent that #ej c4c4 of it shall not contain more than #j4jb or #j4jc milligram of ammonia4 ,fifty c4c4 of it are transferred to a ,nessler glass and mixed with #b c4c4 of ,nessler's reagent4 ,the colour is noted1 and an estimate made as to the amount of ammonia it indicates4 ,a measured quantity of the standard ammonia1 judged to contain about as much ammonia as that in the assay1 is then put into another ,nessler glass4 ,it is diluted to #ej c4c4 with water1 and mixed with #b c4c4 of ,nessler4 ,after standing a minute or two1 the colours in the two glasses are compared4 ,if the tints are equal1 the assay is finished2 but if the standard is weaker or stronger than the assay1 another standard1 containing more or less ammonia1 as the case may be1 must be prepared and compared with the assay4 ,two such experiments will generally be sufficient2 but1 if not1 a third must be made4 ,the addition of more standard ammonia to the solution to which the ,nessler has already been added does not give a satisfactory result4 ,when the ammonia in #ej c4c4 has been determined1 that in the whole solution is ascertained by a suitable multiplication4 ,by #aj1 for example1 if the bulk was #ejj c4c41 or by #bj if it was a litre4 ,distilled water is used throughout4 ,it must be free from ammonia2 and is best prepared by distilling an ammonia-free spring water4 ,,footnotes3 #ij ,al#b;,cl#f #c,na#b,s#b,o#c #c;,h#b,o ,al#b7;,,ho7#f #f,na,cl #c,s #c,,so#b #ia #c;,be,o1,al#b,o#c1f,si,o#b #ib ,ca,c#b,o#d ,ca,c,o#c;,,co4 #ic ,resolved into two with a powerful spectroscope4 #id ,ammonium compounds are frequently produced when dissolving metals in nitric acid2 or when nitrates are heated in the presence of the metals4 ,,part ,,iii--,,non-,,metals4 ,,chapter ,,xv4 ,,oxygen ,,and ,,oxides4--,,the ,,halogens4 ,,oxygen4 ,oxygen occurs in nature in the free state1 forming #bc per cent4 by weight1 or #ba per cent4 by volume of the atmosphere2 but1 since it is a gas1 its presence is easily overlooked and its importance underestimated4 ,except in the examination of furnace-gases1 c41 the assayer is not often called upon to determine its quantity1 but it forms one of his most useful reagents1 and there are many cases where he cannot afford to disregard its presence4 ,it occurs not only in the air1 but also dissolved in water2 ordinary waters containing on an average #j4jjjhe per cent4 by weight1 or #j4he parts per #ajj1jjj4 ,chemically1 it is characterised by its power of combining1 especially at high temperatures1 with the other elements1 forming an important class of compounds called oxides4 ,this combination1 when rapid1 is accompanied by the evolution of light and heat2 hence oxygen is generally called the supporter of combustion4 ,this property is taken advantage of in the operation of calcining1 scorifying1 cupelling1 c4 ,the importance of a free access of air in all such work is seen when it is remembered that #a litre of air contains #j4bige gram of oxygen1 and this quantity will only oxidise #j4aaae gram of carbon1 #j4bige gram of sulphur1 or #c4hdi grams of lead4 ,oxidation takes place at the ordinary temperature with many substances4 ,examples of such action are seen in the weathering of pyrites1 rusting of iron1 and 7in the assay office7 the weakening of solutions of many reducing agents4 ,for methods of determining the percentage of oxygen in gases1 for technical purposes1 the student is referred to ,winkler ,lunge's ,technical ,gas ,analysis4 ,,oxides4 ,oxides are abundant in nature1 almost all the commonly occurring bodies being oxidised4 ,water 7,h#b,o7 contains #hh4h per cent4 of oxygen2 silica1 lime1 alumina1 magnesia1 and the other earths are oxides1 and the oxides of the heavier metals are in many cases important ores2 as1 for example1 cassiterite 7,sn,o#b71 hmatite 7,fe#b,o#c71 magnetite 7,fe#c,o#d71 and pyrolusite 7,mn,o#b74 ,in fact1 the last-named mineral owes its value to the excess of oxygen it contains1 and may be regarded as an ore of oxygen rather than of manganese4 ,most of the metals1 when heated to redness in contact with air1 lose their metallic lustre and become coated with1 or 7if the heating be prolonged7 altogether converted into1 oxide4 ,this oxide was formerly termed a calx1 and has long been known to weigh more than the metal from which it was obtained4 ,for example1 one part by weight of tin becomes1 on calcining1 #a4bga parts of oxide 7putty powder74 ,the student will do well to try the following experiments3--,take #bj grams of tin and heat them in a muffle on a scorifier1 scraping back the dross as it forms1 and continuing the operation until the whole of the metal is burnt to a white powder and ceases to increase in weight4#ie ,take care to avoid loss1 and1 when cold1 weigh the oxide formed4 ,the oxide should weigh #be4db grams1 which increase in weight is due to the oxygen absorbed from the air and combined with the metal4 ,it can be calculated from this experiment 7if there has been no loss7 that oxide of tin contains #ba4cc per cent4 of oxygen and #gh4fg per cent4 of tin4 ,oxidation is performed with greater convenience by wet methods1 using reagents1 such as nitric acid1 which contain a large proportion of oxygen loosely held4 ,such reagents are termed oxidising agents4 ,besides nitric acid1 permanganate of potash1 bichromate of potash1 and peroxide of hydrogen are largely used for this purpose4 ,one c4c4 of nitric acid contains as much oxygen as #b4ef litres of air1 and the greater part of this is available for oxidising purposes4 ,try the following experiment3--,take #b grams of tin and cover in a weighed ,berlin dish with #bj c4c4 of dilute nitric acid1 heat till decomposed1 evaporate to dryness1 ignite1 and weigh4 ,the #b grams of tin should yield #b4edb grams of oxide4 ,the increase in weight will be proportionally the same as in the previous experiment by calcination1 and is due to oxygen1 which in this case has been derived from the nitric acid4 ,the percentage of oxygen in this oxide of tin 7or in any of the oxides of the heavier metals7 may be directly determined by heating such oxides in a current of hydrogen1 and collecting and weighing the water formed4 ,it is found by experiment that #hh4hf parts by weight of oxygen1 combining with #aa4ad parts of hydrogen1 form #ajj parts of water2 so that from the weight of water formed it is easy to calculate the amount of oxygen the oxide contained4 ,illustration3 ,,fig4 #fb4 ,take #a gram of the dried and powdered oxide and place it in a warm dry combustion tube4 ,place the tube in a furnace1 and connect at one end with a hydrogen apparatus provided with a sulphuric acid bulb for drying the gas1 and at the other with a weighed sulphuric acid tube for collecting the water formed4 ,the apparatus required is shown in fig4 #fb4 ,pass hydrogen through the apparatus1 and1 when the air has been cleared out1 light the furnace4 ,continue the heat and current of hydrogen for half an hour 7or longer1 if necessary74 ,allow to cool4 ,draw a current of dry air through the weighed tube4 ,weigh4 ,the increase in weight gives the amount of water formed1 and this1 multiplied by #j4hhhf1 gives the weight of the oxygen4 ,the percentage of oxygen thus determined should be compared with that got by the oxidation of the metal4 ,it will be practically the same4 ,the following results can be taken as examples3-- ,twenty grams of tin1 calcined as described1 gave #be4cg grams of oxide4 ,two grams of tin1 oxidised with nitric acid and ignited1 gave #b4eea grams of oxide4 ,one gram of the oxide of tin1 on reduction in a current of hydrogen1 gave #j4bcfj gram of water 7equivalent to #j4bjih gram of oxygen71 and left #j4gijj gram of metal4 ,ten grams of ferrous sulphate gave1 on strong ignition1 #b4hih grams of ferric oxide 7,fe#b,o#c7if instead of #b4hgg4 ,the student should similarly determine the percentage of oxygen in oxides of copper and iron4 ,the former oxide may be prepared by dissolving #e grams of copper in #ej c4c4 of dilute nitric acid1 evaporating to dryness1 and strongly igniting the residue4 ,the oxide of iron may be made by weighing up #aj grams of powdered ferrous sulphate 7 to #b4jad grams of iron7 and heating1 at first gently1 to drive off the water1 and then at a red heat1 until completely decomposed4 ,the weight of oxide1 in each case1 should be determined2 and the percentage of oxygen calculated4 ,compare the figures arrived at with those calculated from the formula of the oxides1 ,cu,o and ,fe#b,o#c4 ,it would be found in a more extended series of experiments that the same metal will1 under certain conditions1 form two or more oxides differing among themselves in the amount of oxygen they contain4 ,these oxides are distinguished from one another by such names as higher and lower oxides1 peroxides1 protoxides1 dioxides1 c4 ,the oxides may be conveniently classified under three heads3-- 7#a7 ,those that are reduced to metal by heat alone1 such as the oxides of mercury1 silver1 platinum1 gold1 c42 7#b7 ,those which are reduced by hydrogen at a red heat1 which includes the oxides of the heavy metals2 7#c7 ,those which are not reduced by these means1 good examples of which are silica1 alumina1 the alkalies1 and the alkaline earths4 ,another important classification is into acid1 basic and neutral oxides4 ,the oxides of the non-metallic elements1 such as sulphur1 carbon1 phosphorus1 c41 are1 as a rule1 acid2 and the more oxygen they contain1 the more distinctly acid they are4 ,the oxides of the metals are nearly all basic2 and1 as a rule1 the less oxygen they contain1 the more distinctly basic they are4 ,the basic oxides1 which are soluble in acids1 give rise to the formation of salts when dissolved therein4 ,during the solution1 water is formed1 but no gas is evolved4 ,the oxide dissolved in each case neutralizes an equivalent of the acid used for solution4#ig ,the basic properties of many of these can be taken advantage of for their determination4 ,this is done in the case of soda1 potash1 lime1 c41 by finding the quantity of acid required to neutralize a given weight of the substance4 ,there are some oxides which1 under certain conditions1 are acid to one substance 7a stronger base7 and basic to another 7a stronger acid74 ,for example1 the oxides of lead and of tin1 as also alumina1 dissolve in caustic soda1 acting as acids2 whilst1 on the other hand1 they combine with sulphuric or hydrochloric acid1 playing the part of bases4 ,the oxides known as earths1 when ignited1 are many of them insoluble in acids1 although easily dissolved before ignition4 ,it is common in complete analyses of minerals to meet with cases in which the sum total of the elements found falls short of the amount of ore taken2 and here oxygen must be looked for4 ,for example1 this occurs in the case of a mixture of pyrites with oxide of iron1 or in a mixture of sulphides and sulphates4 ,the state in which the elements are present1 and the percentage 7say of sulphides and sulphates7 can in many cases be determined2 but this is not always required4 ,when the difference between the sum total and the elements found is small1 it is reported as oxygen and loss4 ,when1 however1 it is considerable1 the oxygen may be reported as such2 and its amount be either determined directly in the way already described1 or calculated from the best determination that can be made of the relative amounts of oxides1 sulphides1 sulphates1 c41 present4 ,such cases require a careful qualitative analysis to find out that the substance is present2 and then the separation of each constituent is made as strictly as possible4 ,these remarks apply especially to ores of the heavy metals4 ,the separation of the constituents is effected with suitable solvents applied in proper order4 ,the soluble sulphates1 for example1 are extracted with water2 the oxides by the dilute acids or alkalies in which they are known to be soluble4 ,the oxygen in the sulphates and oxides thus obtained is estimated by determining the sulphur and metals in the solutions1 and calculating the amount of oxygen with which they combine4 ,the metals of the earths and alkalies are almost invariably present as oxides1 and are reported as such2 except it is known that they are present in some other form1 such as fluoride or chloride4 ,thus1 silica1 alumina1 lime1 water1 c41 appear in an analysis2 even in those cases where oxygen and loss is also mentioned4 ,as an example of such a report1 take the following analysis of ,spanish pyrites3-- ,sulphur #di4jj ,iron #dc4ee ,copper #c4bj ,arsenic #j4dg ,lead #j4ic ,zinc #j4ce ,lime #j4aj ,silica1 c4 #j4fc ,water #j4gj ,oxygen and loss #a4jg ----- #ajj4jj ,the following example will illustrate the mode of calculating and reporting4 ,a mineral1 occurring as blue crystals soluble in water1 and found on testing to be a mixed sulphate of iron and copper1 gave on analysis the following results3-- ,water #dd4ea per cent4 ,sulphuric oxide #bh4hb ,copper #h4dd ,ferrous iron #aa4ha ,ferric iron #j4ch ,zinc #j4bh ----- #id4bd ,there is here a deficiency of #e4gf per cent4 due to oxygen4 ,nothing else could be found1 and it is known that in the sulphates the metals exist as oxides4 ,by multiplying the weight of the copper by #a4beb1 the weight of copper oxide 7,cu,o7 will be ascertained2 in this case it equals #aj4eg per cent4 ,the ferrous iron multiplied by #a4bhf will give the ferrous oxide 7,fe,o72 in this case #ae4ai per cent4 ,the ferric iron multiplied by #a4dbh will give the ferric oxide 7,fe#b,o#c72 in this case #j4ed per cent4 ,the zinc multiplied by #a4bdf will give the zinc oxide 7,zn,o72 in this case it equals #j4ce per cent4 ,the analysis will be reported as-- ,water #dd4ea ,sulphuric oxide #bh4hb ,copper oxide #aj4eg equal to copper #h4dd ,ferrous oxide #ae4ai ,ferric oxide #j4ed ,zinc oxide #j4ce ----- #ii4ih ,the following 7,a7 is an analysis of a sample of ,south ,american copper ore1 which will serve as a further illustration4 ,the analysis showed the presence of #f4hi per cent4 of ferrous oxide1 and some oxide of copper4 ,the analysis 7,b7 is that of an ore from the same mine after an imperfect roasting4 ,it will be seen that the carbonates have been converted into sulphates4 ,if the total sulphur simply had been determined1 and the sulphate overlooked1 the oxygen and loss would have been #e4fe per cent41 an amount which would obviously require an explanation4 ,a4 ,b4 ,water #j4be #j4ei ,organic matter #j4ed -- ,sulphur #bi4ej #ba4cc ,copper #aj4ib #i4hj ,copper #i4eg ,copper oxide #j4bh ,iron #cb4ji #ci4gc ,iron #cd4cb ,ferric oxide #g4gc ,lead #j4ce #j4ab ,zinc #j4hf #j4fi ,cobalt #j4jf #j4aa ,lime #e4be #g4fi ,magnesia #b4cc #b4ee ,sulphuric oxide #a4jj #e4cj ,carbon dioxide #h4hg -- ,insoluble silicates #e4ab #h4ch ,oxygen and loss #b4hf #b4dg ----- ,potash #j4ae #ajj4jj ,soda #a4ji ----- #ajj4jj ,,water4 ,water occurs in minerals in two forms1 free and combined4 ,the term moisture ought1 strictly1 to be limited to the first1 although1 as has already been explained1 it is more convenient in assaying to apply the term to all water which is driven off on drying at #ajj ,c4 ,the combined water is really a part of the mineral itself1 although it may be driven off at a high temperature1 which varies with the base4 ,in some cases a prolonged red heat is required2 whilst with crystallised salts it is sometimes given off at the ordinary temperatures4 ,this latter phenomenon1 known as efflorescence1 is mostly confined to artificial salts4 ,the determination of the combined water may often be made by simply igniting the substance from which the moisture has been removed4 ,the quantity of water may be determined1 either indirectly by the loss1 or directly by collecting it in a calcium chloride tube1 and weighing4 ,in some cases1 in which the loss on ignition does not give simply the proportion of combined water1 it can be seen from the analysis to what else the loss is due2 and1 after a proper deduction1 the amount of water can be estimated4 ,for example1 #a gram of crystallised iron sulphate was found to contain on analysis #j4bhgg gram of sulphuric oxide2 and on igniting another gram1 #j4bhgg gram of ferric oxide was left4 ,as the salt is known to be made up of ferrous oxide1 sulphuric oxide1 and combined water1 the combined water can be thus calculated3 #j4bhgg gram of ferric oxide is equal to #j4behi gram of ferrous oxide1#ih and consequently1 the loss on ignition has been diminished by #j4jbhh gram1 which is the weight of oxygen absorbed by the ferrous oxide during calcining4 ,the loss on ignition was #j4gabc gram1 to which must be added #j4jbhh gram2 hence #j4gdaa gram is the weight of the combined sulphuric oxide and water present4 ,deducting the weight of sulphuric oxide found1 #j4bhgg gram1 there is left for combined water #j4decd gram4 ,the composition of #a gram of the dry salt is then3-- ,water #j4decd ,sulphuric oxide #j4bhgg ,ferrous oxide #j4behi ------ #a4jjjj ,the following is another example3--,a sample of malachite lost on ignition #bh4dg per cent41 leaving a residue which was found on analysis to be made up of oxide of copper 7equal to #gj4af per cent4 on the mineral71 and silica and oxide of iron 7equal to #a4cg per cent474 ,carbon dioxide and water 7but nothing else7 was found to be present1 and the carbon dioxide amounted to #ai4fd per cent42 deducting this from the loss on ignition1 we have #h4hb as the percentage of water present4 ,the analysis was then reported as follows3-- ,cupric oxide #gj4af equal to #ef4j copper4 ,silica and ferric oxide #a4cg ,carbon dioxide #ai4fd ,water #h4hb ----- #ii4ii ,illustration3 ,,fig4 #fc4 ,direct ,determination of ,combined ,water4--,transfer about #c grams of the substance to a piece of combustion tube 7#h or #aj inches long71 attached 7as in fig4 #fc7 at one end to a ,u-tube containing sulphuric acid1 and at the other end to a calcium chloride tube4 ,the last is weighed previous to the determination4 ,the tube should be warmed to ensure complete dryness1 and must be free from a misty appearance4 ,aspirate a current of air through the apparatus1 heat the mineral by means of a ,bunsen burner1 cautiously at first1 and afterwards to redness 7if necessary74 ,the water is driven off and condenses in the calcium chloride tube1 which is afterwards cooled and weighed4 ,the increase in weight is due to the water4 ,if the substance gives off acid products on heating1 it is previously mixed with some dry oxide of lead or pure calcined magnesia4 ,,examination ,,of ,,waters4 ,the assayer is occasionally called on to test water for the purpose of ascertaining the nature and quantity of the salts contained in it1 and whether it is or is not fit for technical and drinking purposes4 ,in mineral districts the water is generally of exceptional character1 being more or less charged1 not only with earthy salts1 but also frequently with those of the metals4 ,distilled water is only used by assayers in certain exceptional cases1 so that by many it would be classed among the rarer oxides4 ,water of ordinary purity will do for most purposes1 but the nature and quantity of the impurities must be known4 ,the following determinations are of chief importance3-- ,total ,solids at #ajj ,c4--,where simply the amount is required1 take #ajj c4c4 and evaporate on the water-bath in a weighed dish2 then dry in the water-oven1 and weigh4 ,total ,solids ,ignited4--,the above residue is very gently ignited 7keeping the heat well below redness71 and again weighed4 ,a larger loss than #d or #e parts per #ajj1jjj on the water requires an explanation4 ,chlorine4--,take #ajj c4c4 of the water in a porcelain dish1 add #b c4c4 of a #e per cent4 solution of neutral potassic chromate1 and titrate with a neutral standard solution of nitrate of silver1 made by dissolving #d4ghi grams of crystallised silver nitrate in distilled water1 and diluting to #a litre4 ,the addition of the nitrate of silver is continued until the yellow of the solution assumes a reddish tint4 ,the reaction is very sharp4 ,each c4c4 of nitrate of silver used is equal to #a part by weight of chlorine in #ajj1jjj of water4 ,at inland places this rarely amounts to more than #a in #ajj1jjj2 but near the sea it may amount to #c or #e4 ,more than this requires explanation1 and generally indicates sewage pollution4 ,nitric ,pentoxide 7,n#b,o#e74--;,it is more generally reported under the heading1 nitrogen as nitrates4 ,take #bej c4c4 of the water and evaporate to #b or #c c4c42 acidulate with a few drops of dilute sulphuric acid1 and transfer to a nitrometer 7using strong sulphuric acid to wash in the last traces74 ,the sulphuric acid must be added to at least twice the bulk of the liquid4 ,shake up with mercury4 ,the mercury rapidly flours1 and nitric oxide is given off 7if any nitrate is present74 ,the volume of the nitric oxide 7corrected to normal temperature and pressure71 multiplied by #j4be1 gives the parts of nitrogen per #ajj1jjj2 or1 multiplied by #j4ife1 will give the nitric pentoxide in parts per #ajj1jjj4 ,in well and spring waters the nitrogen may amount to #j4c or #j4d parts per #ajj1jjj2 or in richly cultivated districts #j4g or #j4h parts per #ajj1jjj4 ,an excess of nitrates is a suspicious feature1 and is generally due to previous contamination4 ,ammonia4--,take #ejj c4c4 of the water and place them in a retort connected with a ,liebig's condenser4 ,add a drop or two of a solution of carbonate of soda and distil over #ajj c4c42 collect another #ej c4c4 separately4 ,determine the ammonia in the distillate colorimetrically 7with ,nessler's solution1 as described under ,ammonia7 and compare with a standard solution of ammonic chloride containing #j4jcae gram of ammonic chloride in #a litre of water4 ,one c4c4 contains #j4ja milligram of ammonia4 ,the second distillate will show little1 if any1 ammonia in ordinary cases4 ,the amounts found in both distillates are added together1 and expressed in parts per #ajj1jjj4 ,waters 7other than rain and tank waters7 which contain more than #j4jjc per #ajj1jjj are suspicious4 ,organic ,matter4--,the organic matter cannot be determined directly2 but for ordinary purposes it may be measured by the amount of permanganate of potassium which it reduces1 or by the amount of ammonia which it evolves on boiling with an alkaline permanganate of potassium solution4 ,a4 ,albuminoid ,ammonia4--,to the residue left after distilling the ammonia add #ej c4c4 of a solution made by dissolving #bjj grams of potash and #h grams of potassium permanganate in #aajj c4c4 of water1 and rapidly boiling till the volume is reduced to #a litre 7this should be kept in a well stoppered bottle1 and be occasionally tested to see that it is free from ammonia74 ,continue the distillation1 collecting #ej c4c4 at a time1 until the distillate is free from ammonia4 ,three or four fractions are generally sufficient4 ,determine the ammonia colorimetrically as before4 ,if the total albuminoid ammonia does not exceed #j4jje in #ajj1jjj1 the water may be regarded as clean as regards organic matter2 if it amounts to more than #j4jae1 it is dirty4 ,b4 ,oxygen ,consumed4--,a standard solution of permanganate of potash is made by dissolving #j4cie gram of the salt in water and diluting to #a litre4 ,each c4c4 equals #j4a milligram of available oxygen4 ,the following are also required3--#a4 ,a solution of sodium hyposulphite containing #a gram of the salt 7,na#b,s#b,o#c4e;,h#b,o7 in #a litre of water4 #b4 ,dilute sulphuric acid1 made by adding one part of the acid to three of water1 and titrating with the permanganate solution till a faint pink persists after warming for several hours4 #c4 ,starch paste4 #d4 ,potassium iodide solution4 ,take #bej c4c4 of the water in a stoppered bottle1 add #aj c4c4 of sulphuric acid and #aj c4c4 of the permanganate1 and allow to stand in a warm place for four hours4 ,then add a few drops of the solution of potassium iodide1 and titrate the liberated iodine with hypo1 using starch paste towards the end as an indicator4 ,to standardise the hyposulphite1 take #bej c4c4 of water and #aj c4c4 of sulphuric acid1 and a few drops of potassium iodide2 then run in #aj c4c4 of the permanganate solution1 and again titrate2 about #cj c4c4 of the hypo will be used4 ,the difference in the two titrations1 divided by the last and multiplied by #aj1 will give the c4c4 of permanganate solution used in oxidising the organic matter in the #bej c4c4 of water4 ,each c4c4 represents #j4jd parts of oxygen in #ajj1jjj4 ,metals4--,these may for the most part be estimated colorimetrically4 ,lead4--,take #ajj c4c4 of the water in a ,nessler tube1 and add #aj c4c4 of sulphuretted hydrogen water1 and compare the tint1 if any1 against a standard lead solution1 as described under ,colorimetric ,lead4 ,report in parts per #ajj1jjj4 ,copper4--,proceed as with the last-mentioned metal2 but1 if lead is also present1 boil down #ejj c4c4 to about #ej c4c41 then add ammonia1 filter1 and estimate the copper in the blue solution1 as described under ,colorimetric ,copper4 ,iron4--,take #ej c4c41 or a smaller quantity 7if necessary71 dilute up to the mark with distilled water1 and determine with potassium sulphocyanate1 as described under ,colorimetric ,iron4 ,zinc4--,zinc is the only other metal likely to be present2 and1 since it cannot be determined colorimetrically1 it must be separately estimated during the examination of the total solids4 ,examination of ,total ,solids4--,evaporate #ejj c4c4 to dryness with a drop or two of hydrochloric acid4 ,take up with hydrochloric acid1 filter1 ignite1 and weigh the residue as silica4 ,to the filtrate add a little ammonic chloride and ammonia1 boil and filter1 ignite1 and weigh the precipitate as oxide of iron and alumina4 ,collect the filtrate in a small flask1 add a few drops of ammonium sulphide or pass sulphuretted hydrogen1 cork the flask1 and allow to stand overnight2 filter1 wash1 and determine the zinc gravimetrically as oxide of zinc4 ,if copper or lead were present1 they should have been previously removed with sulphuretted hydrogen in the acid solution4 ,to the filtrate add ammonic oxalate and ammonia1 boil for some time1 allow to stand1 filter1 wash1 ignite1 and weigh as lime4 ,evaporate the filtrate with nitric acid1 and ignite4 ,take up with a few drops of dilute hydrochloric acid1 add baric hydrate in excess1 evaporate1 and extract with water4 ,the residue contains the magnesia2 boil with dilute sulphuric acid1 filter1 precipitate it with phosphate of soda and ammonia1 and weigh as pyrophosphate4 ,the aqueous extract contains the alkalies with the excess of barium4 ,add sulphuric acid in slight excess1 filter1 evaporate1 and ignite strongly4 ,the residue consists of the sulphates of the alkalies 7which are separately determined1 as described under ,potash74 ,sulphuric ,oxide 7,,so#c74--,take #bjj c4c4 and boil to a small bulk with a little hydrochloric acid1 filter 7if necessary71 add baric chloride solution in slight excess to the hot solution1 filter1 ignite1 and weigh as baric sulphate4 ,carbon ,dioxide 7free74--,carbon dioxide exists in waters in two forms1 free and combined4 ,the latter generally occurs as bicarbonate1 although on analysis it is more convenient to consider it as carbonate1 and to count the excess of carbon dioxide with the free4 ,the method is as follows3--,to determine the free carbon dioxide1 take #ajj c4c4 of the water1 place them in a flask with #c c4c4 of a strong solution of calcium chloride and #b c4c4 of a solution of ammonic chloride1 next add #ej c4c4 of lime-water4 ,the strength of the lime-water must be known4 ,make up to #bjj c4c4 with distilled water1 stop the flask1 and allow the precipitate to settle4 ,take out #ajj c4c4 of the clear solution with a pipette1 and titrate with the standard solution of acid4#ii ,the number of c4c4 required1 multiplied by two1 and deducted from that required for the #ej c4c4 of lime-water1 and then multiplied by #j4jjde1 will give the carbon dioxide present other than as normal carbonates4 ,carbon ,dioxide combined as normal carbonate4--#ajj c4c4 of the water are tinted with phenacetolin or lacmoid2 then heated to near boiling1 and titrated with standard acid4 ,the number of c4c4 used1 multiplied by #j4jjde1 will give the weight in grams of the combined carbon dioxide4 ,free ,acid4--,in some waters 7especially those from mining districts7 there will be no carbonates4 ,on the contrary1 there may be free mineral acid or acid salts4 ,in these cases it is necessary to determine the amount of acid 7other than carbon dioxide7 present in excess of that required to form normal salts4 ,this is done in the following way3--,make an ammoniacal copper solution by taking #ac grams of copper sulphate 7,cu,s,o#d4e;,h#b,o71 dissolving in water1 adding solution of ammonia until the precipitate first formed has nearly dissolved1 and diluting to #a litre4 ,allow to settle1 and decant off the clear liquid4 ,the strength of this solution is determined by titrating against #aj or #bj c4c4 of the standard solution of sulphuric acid 7#ajj c4c4 #a gram ,h#b,,so#d74 ,the finishing point is reached as soon as the solution becomes turbid from precipitated cupric hydrate4 ,at first1 as each drop falls into the acid solution1 the ammonia and cupric hydrate combine with the free acid to form ammonic and cupric sulphates2 but as soon as the free acid is used up1 the ammonia in the next drop not only precipitates an equivalent of cupric hydrate from the solution1 but also throws down that carried by itself4 ,this method is applicable in the presence of metallic sulphates other than ferric4 ,the standardising and titration should be made under the same conditions4 ,since sulphuric acid and sulphates are predominant in waters of this kind1 it is most convenient to report the acidity of the water as equivalent to so much sulphuric acid4 ,dissolved ,oxygen4--,for the gasometric method of analysing for dissolved oxygen1 and for the ,schtzenberger's volumetric method1 the student is referred to ,sutton's ,volumetric ,analysis4 ,the following is an easy method of estimating the free oxygen in a water3--,take #bj c4c4 of a stannous chloride solution 7about #bj grams of the salt with #aj c4c4 of hydrochloric acid to the litre72 add #aj c4c4 of hydrochloric acid1 and titrate in an atmosphere of carbon dioxide with standard permanganate of potassium solution 7made by dissolving #a4ige gram of the salt in #a litre of water3 #a c4c4 equals #j4e milligram of oxygen74 ,a similar titration is made with the addition of #ajj c4c4 of the water to be tested4 ,less permanganate will be required in the second titration1 according to the amount of oxygen in the water2 and the difference1 multiplied by #j4e1 will give the weight of the oxygen in milligrams4 ,small quantities of nitrates do not interfere4 ,in ,,reporting the results of the analysis1 it is customary to combine the acids and bases found on some such principle as the following3--,the sulphuric oxide is calculated as combined with the potash1 and reported as potassic sulphate 7,k#b,,so#d72 the balance of the sulphuric oxide is then apportioned to the soda1 and reported as sulphate of soda 7,na#b,,so#d72 if any is still left1 it is reported as calcium sulphate 7,ca,s,o#d71 and after that as magnesic sulphate 7,mg,s,o#d74 ,when the sulphuric oxide has been satisfied1 the chlorine is distributed1 taking the bases in the same order1 then the nitric pentoxide1 and lastly the carbon dioxide4 ,but any method for thus combining the bases and acids must be arbitrary and inaccurate4 ,it is extremely improbable that any simple statement can represent the manner in which the bases and acids are distributed whilst in solution2 and1 since different chemists are not agreed as to any one system1 it is better to give up the attempt1 and simply state the results of the analysis4 ,this has only one inconvenience4 ,the bases are represented as oxides2 and1 since some of them are present as chlorides1 the sum total of the analysis will be in excess of the actual amount present by the weight of the oxygen equivalent to the chlorine present as chloride4 ,the following is an example of such a statement3-- ,parts per #ajj1jjj4 ,total solids1 dried at #ajj ,c4 #bh4gc ,chlorine #a4gj ,nitrogen as nitrate #j4jc ,ammonia #j4jja ,albuminoid ammonia #j4jjd ,oxygen consumed in #d hours #j4ja ,the solids were made up as under3-- ,per #ajj1jjj of the ,water4 ,potash #j4ch ,soda #b4ja ,magnesia #a4dd ,lime #aj4ee ,ferric oxide #j4ja ,silica #j4cj ,sulphuric oxide #c4fi ,nitrogen pentoxide #j4aa ,carbon dioxide #h4ch ,chlorine #a4gj ,volatile and organic matter #j4ff ----- #bi4bc ,less oxygen equivalent to chlorine found #j4ci ----- #bh4hd ,for the preparation of distilled water1 the apparatus shown in fig4 #fd is convenient for laboratory use4 ,it consists of a copper retort heated by a ring gas-burner1 and connected with a worm-condenser4 ,illustration3 ,,fig4 #fd ,,practical ,,exercise4 ,a mineral1 on analysis1 gave the following results3--,water1 #dd4id per cent42 sulphuric oxide1 #bh4gb per cent42 ferrous iron1 #ac4ib per cent42 ferric iron1 #j4ce per cent42 copper1 #f4a per cent4 ,the mineral was soluble in water1 and showed nothing else on testing4 ,how would you report the analysis8 ,calculate the formula for the salt4 ,,the ,,halogens4 ,there is a group of closely allied elements to which the name halogen 7salt-producer7 has been given4 ,it comprises chlorine1 bromine1 iodine1 and fluorine4 ,these elements combine directly with metals1 forming as many series of salts 7chlorides1 bromides1 iodides1 and fluorides71 corresponding to the respective oxides1 but differing in their formul by having two atoms of the halogen in the place of one atom of oxygen4 ,for example1 ferrous oxide is ,fe,o and ferrous chloride is ,fe,cl#b1 and1 again1 ferric oxide is ,fe#b,o#c1 whilst ferric chloride is ,fe#b;,cl#f4 ,these salts differ from the carbonates1 nitrates1 c41 in containing no oxygen4 ,consequently1 it is incorrect to speak of such compounds as chloride of potash1 fluoride of lime1 c41 since potash and lime are oxides4 ,it is important to bear this in mind in reporting analyses in which determinations have been made1 say1 of chlorine1 magnesia1 and potash1 or of fluorine1 silica1 and alumina4 ,it is necessary in all such cases to deduct from the total an amount of oxygen equivalent to the halogen found1 except1 of course1 where the base has been determined and recorded as metal4 ,compounds containing oxides and fluorides1 c41 do not lend themselves to the method of determining the halogen by difference4 ,for example1 topaz1 which1 according to ,dana1 has the formula ,al#b,si,o#d;,f#b1 would yield in the ordinary course of analysis-- ,alumina #ee4d ,silica #cb4f ,fluorine #bj4f ----- #ajh4f ,the oxygen equivalent to #bj4f per cent4 fluorine may be found by multiplying the percentage of fluorine by #j4dba2 it is #h4g per cent41 and must be deducted4 ,the analysis would then be reported thus3-- ,alumina #ee4d ,silica #cb4f ,fluorine #bj4f ----- #ajh4f ,less oxygen equivalent to fluorine #h4g ----- #ii4i ,take as an illustration the following actual analysis by ,f4,w4 ,clarke and ,j4,s4 ,diller3-- ,alumina #eg4ch ,silica #ca4ib ,fluorine #af4ii ,potash #j4ae ,soda #a4cc ,water #j4bj ------ #ajg4ig ,deduct oxygen equivalent #g4af ------ #ajj4ha ,in calculating the factor for the oxygen equivalent1 divide the weight of one atom of oxygen 7#af7 by the weight of two atoms of the halogen2 for example1 with chlorine it would be #af_/ga or #j4bbec2 with bromine1 #af_/afj or #j4ajjj2 with iodine1 #af_/bed or #j4jfc2 and with fluorine1 #af_/ch or #j4dba4 ,,chlorine ,,and ,,chlorides4 ,chlorine occurs in nature chiefly combined with sodium1 as halite or rock salt 7,na,cl74 ,with potassium it forms sylvine 7,k,cl71 and1 together with magnesium1 carnallite 7,k,cl4,mg,cl#b4f;,h#b,o74 ,of the metalliferous minerals containing chlorine1 kerargyrite1 or horn silver 7,ag,cl71 and atacamite1 an oxychloride of copper 7,cu,cl#b4c;,cu7,,ho7#b47 are the most important4 ,apatite 7phosphate of lime7 and pyromorphite 7phosphate of lead7 contain a considerable amount of it4 ,chlorine is a gas of a greenish colour1 possessing a characteristic odour1 and moderately soluble in water4 ,it does not occur native1 and is generally prepared by the action of an oxidising agent on hydrochloric acid4 ,it combines directly with metals at the ordinary temperature 7even with platinum and gold71 forming chlorides1 which 7except in the case of silver7 are soluble4 ,it is important in metallurgy1 because of the extensive use of it in extracting gold by chloridising processes4 ,it is also used in refining gold4 ,detection4--,compounds containing the oxides of chlorine are not found in nature1 because of the readiness with which they lose oxygen4 ,by reduction they yield a chloride2 the form in which chlorine is met with in minerals4 ,in testing1 the compound supposed to contain a chloride is boiled with water1 or1 in some cases1 dilute nitric acid4 ,to the clear solution containing nitric acid a few drops of nitrate of silver solution are added4 ,if1 on shaking1 a white curdy precipitate1 soluble in ammonia1 separates out1 it is sufficiently satisfactory evidence of the presence of chlorides4 ,solution and ,separation4--,the chlorides are generally soluble in water1 and are got into solution by extracting with warm dilute nitric acid4 ,or1 if insoluble1 the substance is fused with carbonate of soda1 extracted with water1 and the filtrate acidified with nitric acid4 ,for the determination1 it is not necessary to obtain the solution of the chloride free from other acids or metals4 ,if tin1 antimony1 mercury1 or platinum is present1 it is best to separate by means of sulphuretted hydrogen4 ,the chloride is determined in the solution after removal of the excess of the gas4 ,where traces of chlorides are being looked for1 a blank experiment is made to determine the quantity introduced with the reagents4 ,one hundred c4c4 of ordinary water contains from #a to #c milligrams of chlorine4 ,on the addition of nitrate of silver to the nitric acid solution1 chloride of silver separates out4 ,this is free from other substances1 except1 perhaps1 bromide and iodide4 ,,gravimetric ,,determination4 ,freely mix the solution containing the chloride with dilute nitric acid1 filter 7if necessary71 and treat with nitrate of silver4 ,heat nearly to boiling1 and1 when the precipitate has settled1 filter1 and wash with hot distilled water4 ,dry1 and transfer to a weighed ,berlin crucible4 ,burn the filter-paper separately1 and convert any reduced silver into chloride by alternate treatment with drops of nitric and of hydrochloric acid4 ,add the main portion to this1 and heat cautiously till the edges of the mass show signs of fusing 7about #bfj74 ,cool in the desiccator and weigh4 ,the substance is chloride of silver 7,ag,cl71 and contains #bd4gc per cent4 of chlorine4 ,the precipitated chloride is filtered and washed as soon as possible after settling1 since on exposure to light it becomes purple1 and loses a small amount of chlorine4 ,,volumetric ,,method4 ,there are several volumetric methods2 but that based on the precipitation of silver chloride in neutral solution1 by means of a standard solution of silver nitrate 7using potassium chromate as indicator71 is preferred4 ,silver chromate is a red-coloured salt2 and1 when silver nitrate is added to a solution containing both chloride and chromate1 the development of the red colour marks off sharply the point at which the chloride is used up4 ,silver chromate is decomposed and consequently decolorised by solution of any chloride4 ,the solution for this method must be neutral1 since free acid prevents the formation of the red silver chromate4 ,if not already neutral1 it is neutralised by titrating cautiously with a solution of soda4 ,in a neutral solution1 other substances 7such as phosphates and arsenates7 also yield a precipitate with a solution of nitrate of silver2 and will count as chloride if they are not removed4 ,the ,standard ,solution of ,nitrate of ,silver is made by dissolving #bc4id grams of the salt 7,ag,n,o#c7 in distilled water1 and diluting to #a litre2 #ajj c4c4 are equal to #j4e gram of chlorine4 ,the indicator is made by adding silver nitrate to a strong neutral solution of yellow chromate of potash 7,k#b;,cr,o#d71 till a permanent red precipitate is formed4 ,the solution is allowed to settle1 and the clear liquid decanted into a stoppered bottle labelled chromate indicator for chlorine4 ,standardise the silver nitrate by weighing up #j4e gram of pure sodium chloride 7or potassium chloride74 ,transfer to a flask and dissolve in distilled water2 dilute to #ajj c4c4 ,fill an ordinary burette with the standard silver solution1 and 7after adjusting7 run into the flask a quantity sufficient to throw down the greater part of the chlorine4 ,add a few drops of the chromate indicator and continue the addition of the silver nitrate until the yellow colour of the solution becomes permanently tinted red1 after shaking4 ,this shows that the chlorine is all precipitated1 and that the chromate is beginning to come down4 ,the further addition of a couple of drops of the silver solution will cause a marked difference in the tint4 ,read off the quantity run in1 and calculate the standard4 ,one gram of sodium chloride contains #j4fjfb gram of chlorine2 and #a gram of potassium chloride contains #j4dged gram4 ,for the determination of small quantities of chloride 7a few milligrams71 the same method is used2 but the standard solution is diluted so that each c4c4 is equal to #a milligram of chlorine2 and the chromate indicator is added before titrating4 ,the standard solution is made by measuring off #bjj c4c4 of the solution described above1 and diluting with distilled water to #a litre4 ,,bromine ,,and ,,bromides4 ,bromine closely resembles chlorine in the nature of its compounds4 ,it does not occur free in nature1 but is occasionally found in combination with silver as bromargyrite 7,ag,br7 and1 together with chloride1 in embolite4 ,it mainly occurs as alkaline bromides in certain natural waters4 ,nearly all the bromine of commerce is derived from the mother liquors of salt-works--i4e41 the liquors from which the common salt has been crystallised out4 ,bromine combines directly with the metals1 forming a series of salts--the bromides4 ,in ordinary work they are separated with1 and 7except when specially tested for7 counted as1 chlorides4 ,they are detected by adding chlorine water to the suspected solution and shaking up with carbon bisulphide4 ,bromine colours the latter brown4 ,,iodine ,,and ,,iodides4 ,iodine does not occur in nature in the free state2 and iodides are rare1 iodargyrite or iodide of silver 7,ag,i7 being the only one which ranks as a mineral species4 ,iodates are found associated with ,chili saltpetre1 which is an important source of the element4 ,iodine and ,iodides are largely used in the laboratory1 and have already been frequently referred to4 ,it is used as an oxidising agent in a similar manner as permanganate and bichromate of potash1 especially in the determinations of copper1 arsenic1 antimony1 and manganese4 ,iodine is not readily soluble in water2 but dissolves easily in a concentrated solution of potassium iodide4 ,its solutions are strongly coloured2 a drop of a dilute solution colours a large volume of water decidedly yellow2 on the addition of starch paste1 this becomes blue4 ,the delicacy of this reaction is taken advantage of in titrations to determine when free iodine is present4 ,the blue colour may be alternately developed and removed by the addition of iodine 7or an oxidising agent7 and hyposulphite of soda 7or some other reducing agent74 ,in decolorising1 the solution changes from blue or black to colourless or pale yellow according to circumstances4 ,sometimes the solution1 instead of remaining colourless1 gradually develops a blue which recurs in spite of the further addition of the reducing agent4 ,in these cases the conditions of the assay have been departed from1 or 7and this is more often the case7 there is some substance present capable of liberating iodine4 ,iodine forms a series of salts--the iodides--resembling in many respects the chlorides4 ,these can be obtained by direct combination of the metals with iodine4 ,detection4--,free iodine is best recognised by the violet vapours evolved from the solution on heating1 and by the blue or black colour which it strikes on the addition of starch paste4 ,iodides are detected by boiling with strong solutions of ferric sulphate or chloride4 ,iodine is liberated1 distilled over1 and collected4 ,chlorine also liberates iodine from iodides2 and this reaction is frequently made use of in assaying4 ,a process based on this is described under ,manganese4 ,all substances which liberate chlorine on boiling with hydrochloric acid 7dioxides1 bichromates1 permanganates1 c47 are determined in a similar way4 ,solution and ,separation4--,most iodides are soluble in water or dilute acids4 ,the separation is effected by distilling the substance with solution of ferric sulphate1 and collecting the vapour in a dilute solution of sulphurous acid or arsenite of soda4 ,on the completion of the distillation1 the iodine will be in the distillate as iodide2 and the gravimetric determination is made on this4 ,,gravimetric ,,determination4 ,to the solution containing the iodine1 as iodide1 and which is free from chlorides 7and bromides71 add a little dilute nitric acid and nitrate of silver till no further precipitate is produced4 ,filter off1 wash with hot water1 and dry4 ,clean the filter-paper as much as possible1 and burn it4 ,collect the ash in a weighed porcelain crucible1 add the main portion1 and heat to incipient fusion2 cool1 and weigh4 ,the substance is silver iodide1 and contains #ed4jc per cent4 of iodine4 ,,volumetric ,,method4 ,this is for the titration of free iodine1 and is practically that which is described under ,manganese4 ,the substance to be determined is distilled with ferric sulphate1 and the iodine is collected in a solution of potassium iodide1 in which it readily dissolves4 ,if flaky crystals separate out in the receiver1 more potassium iodide crystals are added4 ,when the distillation is finished1 the receiver is disconnected1 and its contents washed out into a beaker and titrated with hypo4 ,the standard solution of hypo is made by dissolving #ai4eh grams of hyposulphite of soda 7,na#b,s#b,o#c4e;,h#b,o7 in water and diluting to #a litre2 #ajj c4c4 are equal to #a gram of iodine4 ,to standardise the solution1 weigh up #j4be gram of pure iodine in a small beaker4 ,add #b or #c crystals of potassium iodide2 cover with water2 and1 when dissolved1 dilute to #ej or #ajj c4c4 ,titrate1 and calculate the standard4 ,,fluorine ,,and ,,fluorides4 ,fluorine is frequently met with as calcium fluoride or fluor-spar 7,ca,f#b74 ,it occurs less abundantly as cryolite 7,na#c;,al,f#f71 a fluoride of aluminium and sodium1 which is used in glass-making4 ,certain other rarer fluorides are occasionally met with4 ,fluorine is also found in apatite1 and in some silicates1 such as topaz1 tourmaline1 micas1 c4 ,hydrofluoric acid is used for etching glass and opening up silicates4 ,it attacks silica1 forming fluoride of silicon 7,si,f#d71 which is volatile4 ,silica is by this means eliminated from other oxides1 which1 in the presence of sulphuric acid1 are fixed4 ,the commercial acid is seldom pure1 and generally weak2 and the acid itself is dangerously obnoxious4 ,the use of ammonium fluoride 7or sodium fluoride7 and a mineral acid is more convenient4 ,determinations of this kind are made in platinum dishes enclosed in lead or copper vessels in a well-ventilated place4 ,fluor-spar is useful as a flux in dry assaying2 it renders slags1 which would otherwise be pasty1 quite fluid4 ,fluorides generally are fusible1 and impart fusibility to substances with which they form weak compounds4 ,their fluxing action does not depend on the removal of silicon as fluoride4 ,detection4--,fluorides in small quantity are easily overlooked unless specially sought for4 ,in larger amounts they are recognised by the property hydrofluoric acid has of etching glass4 ,a watch-glass is warmed1 and a layer of wax is melted over the convex side4 ,when cold1 some lines are engraved on the waxed surface with any sharp-pointed instrument4 ,the substance to be tested is powdered2 and moistened1 in a platinum dish1 with sulphuric acid4 ,the watch-glass is filled with cold water and supported over the dish4 ,the dish is then carefully warmed1 but not sufficiently to melt the wax4 ,after a minute or two1 the glass is taken off1 and the wax removed4 ,if the substance contained fluorine1 the characters will be found permanently etched on the glass4 ,an equally good1 but more rapid1 test is to mix the powdered substance with some silica1 and to heat the mixture in a test tube with sulphuric acid4 ,silicon fluoride is evolved1 and1 if a moistened glass rod is held in the tube1 it becomes coated with a white deposit of silica1 formed by the decomposition of the silicon fluoride by the water4 ,this is also used as a test for silica2 but in this case the substance is mixed with a fluoride1 and the experiment must obviously be carried out in a platinum vessel4 ,separation and ,determination4--,the determination of fluorine is difficult4 ,in the case of fluorides free from silicates 7such as fluor-spar71 it is determined indirectly by decomposing a weighed portion with sulphuric acid1 evaporating1 igniting1 and weighing the residual sulphate4 ,the increase in weight multiplied by #j4fee gives the weight of fluorine4 ,in the presence of silica this method does not answer1 because of the volatilisation of silicon fluoride4 ,in these cases ,whler adopted the following plan1 which resembles that for the indirect determination of carbon dioxide4 ,mix the weighed substance in a small flask with powdered silica and sulphuric acid4 ,the mouth of the flask is closed with a cork carrying a tube which is filled1 the first half with calcium chloride and the second half with pumice coated with dried copper sulphate4 ,the apparatus is weighed quickly1 and then warmed till decomposition is complete4 ,a current of dry air is aspirated for a minute or two2 and the apparatus again weighed4 ,the loss in weight gives that of the silicon fluoride 7,si,f#d71 which1 multiplied by #j4gcjg1 gives the weight of fluorine4 ,fresenius uses the same reaction2 but collects and weighs the silicon fluoride4 ,the finely powdered and dried substance is mixed with ten or fifteen times its weight of ignited and powdered silica4 ,the mixture is introduced into a small dry flask connected on one side with a series of drying-tubes1 and on the other with an empty tube 7to condense any sulphuric acid74 ,to this last is joined a drying-tube containing chloride of calcium and anhydrous copper sulphate4 ,this is directly connected with a series of three weighed tubes in which the fluoride of silicon is collected4 ,the last of these is joined to another drying-tube4 ,the first weighed tube contains pumice and cotton wool1 moistened with water2 the second tube contains soda-lime as well as 7in the upper half of the second limb7 fused calcium chloride between plugs of wool2 the third tube is filled half with soda-lime and half with fused calcium chloride4 ,the distilling-flask containing the substance mixed with silica is charged with #dj or #ej c4c4 of sulphuric acid1 and placed on the hot plate4 ,alongside it is placed a similar dry flask containing a thermometer1 and the temperature in this is kept at #aej or #afj ,c4 ,a current of air is sent through the tubes during the operation1 which takes from one to three hours for from #j4a to #a gram of the substance4 ,a correction is made by deducting #j4jja gram for every hour the dried air has been passed through4 ,the increase in weight of the three tubes gives the weight of the silicon fluoride4 ,penfield uses a similar arrangement1 but passes his silicon fluoride into an alcoholic solution of potassium chloride4 ,silica and potassium silico-fluoride are precipitated1 and hydrochloric acid is set free4#ajj ,the acid thus liberated is titrated1 with a standard solution of alkali1 in the alcoholic solution1 and from the amount of free acid found the fluorine is calculated4 ,the weight of hydrochloric acid 7,h,cl7 found1 multiplied by #a4efb1 gives the weight of the fluorine4 ,with this method of working1 fewer ,u-tubes are required4 ,the exit tube from the flask is bent so as to form a small ,v1 which is kept cool in water2 this is directly connected with the ,u-tube containing the alcoholic solution of potassium chloride4 ,the flask with the assay is heated for about two hours1 and a current of dry air is aspirated throughout the determination4 ,fluoride of silicon is a gas not easily condensed to a liquid3 but is immediately decomposed by water or moist air4 ,,footnotes3 #ie ,this will require two or three hours to thoroughly complete4 ,it is best to powder the oxide first produced1 and recalcine4 #if ,no magnetic oxide was formed4 #ig ,for example3-- ,ca,o #b;,h,cl ,ca,cl#b ,h#b,o4 ,pb,o ,h#b,,so#d ,pb,s,o#d ,h#b,o4 ,mg,o #b;,,hno#c ,mg7,,no#c7b ,h#b,o4 ,al#b,o#c #f;,h,cl ,al#b;,cl#f #c;,h#b,o4 ,fe#b,o#c #c;,h#b,,so#d ,fe#b7,,so#d7c #c;,h#b,o4 #ih ,fe#b,o#c3 #b;,fe,o33 #j4bhgg3 #j4behi4 #ii #ajj c4c4 contain #a gram of sulphuric acid4 #ajj #c,si,f#d #d,k,cl #b;,h#b,o #b,k#b,si,f#f ,si,o#b #d;,h,cl4 ,,chapter ,,xvi4 ,,sulphur ,,and ,,sulphates4 ,sulphur occurs native in volcanic districts1 and is mined in ,sicily1 ,italy1 and ,california in considerable quantities4 ,combined with metals 7sulphides71 it is common in all mineral districts4 ,iron pyrites 7,fe,s#b7 is the most abundant source of this element4 ,sulphates1 such as gypsum1 are fairly common1 but have no value so far as the sulphur in them is concerned4 ,in coal it exists as an impurity1 occurring partly as a constituent of organic compounds4 ,sulphur1 whether free or combined with metals1 forms1 on burning1 sulphurous oxide 7,,so#b71 which by the action of oxidising agents and water is converted into sulphuric acid4 ,it forms two oxides1 sulphurous 7,,so#b7 and sulphuric 7,,so#c71 which combine with bases to form sulphites and sulphates4 ,sulphites are of little importance to the assayer1 and are converted into sulphates by the action of nitric acid and other oxidising agents4 ,the native sulphides1 when acted on with hydrochloric acid1 give off sulphuretted hydrogen2 with nitric acid or aqua regia1 sulphates are formed1 and more or less sulphur separated4 ,sulphur is detected in sulphides by the irritating odour of sulphurous oxide given off on roasting1 by the evolution of sulphuretted hydrogen when treated with hydrochloric acid1 or by a white precipitate of barium sulphate formed when barium chloride is added to the aqua regia solution4 ,dry ,assay4--,there is no method of general application4 ,free or native sulphur may be volatilised1 condensed1 and weighed1 but pyrites only gives up a portion of its sulphur when heated in a closed vessel1 while most sulphides1 and all sulphates1 give up none at all4 ,in the determination of sulphur in brimstone1 #aj grams of the substance are taken1 placed in a small porcelain dish1 heated over a ,bunsen burner in a well-ventilated place1 and ignited4 ,when the sulphur has been completely burnt off1 the residue 7which consists chiefly of sand7 is collected and weighed4 ,in a separate portion the moisture and arsenic are determined2 the amounts of these are deducted from the loss in the first experiment4 ,the difference1 multiplied by #aj1 gives the percentage of sulphur4 ,,wet ,,methods4 ,solution4--,all sulphates1 excepting those of lead1 barium1 strontium1 and lime1 are soluble in water or dilute acid4 ,all sulphides1 except cinnabar1 are converted into sulphates by the action of nitric acid at a gentle heat2 or1 better1 by the action of a mixture of three volumes of nitric acid and one volume of hydrochloric acid4 ,this last attacks cinnabar as well4 ,with most substances it is difficult to convert the whole of the sulphur into sulphuric acid4 ,the sulphur separates out at first as a dark spongy mass1 which 7on continued treatment7 changes to light-coloured flakes4 ,when the solution becomes concentrated and the temperature rises sufficiently1 the sulphur fuses into one or more honey-coloured globules which1 owing to the small surface they oppose to the acid1 are very slowly oxidised4 ,it is not desirable to assist the formation of these globules2 therefore1 the temperature is kept as low as possible1 and strong nitric acid is used4 ,when such globules form1 it is best to allow the solution to cool1 when the globules will solidify4 ,they can then be filtered off and picked out from the insoluble residue1 dried1 weighed1 ignited1 and again weighed1 the loss being counted as sulphur4 ,with iron pyrites this difficulty seldom occurs4 ,metallic sulphides when fused with an excess of nitre are completely oxidised4 ,if the ore is rich in sulphur1 some inert body 7such as sodium chloride1 or1 better1 sodium carbonate7 is added to dilute the action4 ,with pure sulphur1 the action is so energetic as to cause an explosion1 so that care should be taken4 ,with burnt ores 7incompletely calcined pyrites71 there is sufficient oxide of iron present to prevent too rapid action4 ,these fusions with nitre are best conducted in a platinum dish covered with a piece of platinum foil4 ,the ore is ground with the nitre to ensure complete mixing4 ,the heat need not be excessive1 so that a single ,bunsen burner placed beneath the dish will suffice2 if the bottom of the dish is seen to be red-hot1 it is sufficient4 ,on cooling and extracting with water1 the sulphur will pass into solution as potassium sulphate1 which is then filtered off from the insoluble oxides of iron1 copper1 c4 ,the filtrate1 after having been treated with a large excess of hydrochloric acid1 evaporated to dryness1 and re-dissolved in water1 is ready for the determination4 ,lead sulphate may be dissolved by boiling with ammonium acetate4 ,the insoluble sulphates of barium1 strontium1 and lime1 are decomposed by fusing with #d or #e times their weight of fusion mixture4 ,the alkaline sulphates are then dissolved out with water1 and filtered off from the insoluble residue4 ,the filtrate is rendered acid with hydrochloric acid4 ,separation4--,the determination of the sulphuric acid in these solutions by precipitation with barium chloride also serves as a separation2 but in hot acid solutions containing copper1 and more especially iron salts1 the baric sulphate has a strong tendency to carry down amounts of those bodies1 varying1 no doubt1 with the conditions of the precipitation4 ,boiling hydrochloric acid fails to completely extract them4 ,moreover1 the use of hot concentrated hydrochloric acid causes a loss by dissolving barium sulphate4 ,nitric acid and nitrates must be decomposed by prolonged boiling and evaporation with hydrochloric acid4 ,the iron may be removed by adding a slight excess of ammonia to the faintly acid solution1 filtering off1 and washing the precipitated ferric hydrate with hot water4 ,by slightly acidulating the filtrate with hydrochloric acid1 it will be rendered ready for the determination4 ,,gravimetric ,,method4 ,this assay is one of those which strikingly shows the necessity of getting the assay solution under proper conditions1 in order to obtain satisfactory results4 ,the method has been repeatedly investigated1 and the conclusion arrived at1 that it can be correct only by accident4 ,yet there are many chemists who get good results1 and place considerable faith in its accuracy4 ,this can only be due to differences in the manner of working4 ,it is generally understood that nitric acid or nitrates must be absent2 and our experience fully confirms this4 ,precipitations in nitrate solutions are worthless1 as the following experiments show4 ,in each experiment the bulk of the solution was #aej c4c4 ,the solutions contained #aj grams of nitre1 were freely acid with hydrochloric acid1 and were precipitated 7while boiling7 with slight excess of baric chloride4 ,sulphuric acid taken #j4jbj gram #j4jej gram #j4ajj gram found #j4jai #j4jdg #j4jih taken #j4ejj #a4jjd #a4jjj found #j4ebf #a4abf #a4abf ,all the precipitates were boiled with hydrochloric acid1 and thoroughly washed before weighing4 ,the results of some other experiments on this subject are given under sulphur in the examination of commercial copper1 page #bjg4 ,the solution having been obtained free from nitrates and chlorates 7and containing but little free hydrochloric acid71 is largely diluted1 heated to boiling1 and precipitated with a moderate excess of a solution of chloride of barium 7#h parts of the crystallized barium chloride are sufficient for #a of sulphur74 ,it is allowed to settle for half-an-hour1 and then decanted through a filter4 ,the precipitate is shaken up with boiling water1 rendered slightly acid1 filtered1 washed1 dried1 ignited1 and weighed4 ,the ignited precipitate1 when pure1 is white1 and is not decomposed at a red heat2 it is barium sulphate 7,ba,s,o#d71 and contains #ac4gc per cent4 of sulphur1 or #cd4cc per cent4 of sulphuric oxide 7,,so#c74 ,determination of ,sulphur in ,pyrites4--,weigh up half a gram of the dried and powdered sample1 and treat with #aj c4c4 of a mixture of #c volumes of nitric acid and #a volume of hydrochloric acid1 occasionally heating4 ,evaporate to dryness1 treat with #e c4c4 of hydrochloric acid1 and again evaporate2 take up with #a c4c4 of hydrochloric acid and #ajj c4c4 of hot water1 filter through a small filter1 and wash4 ,the residue may contain sulphates of lead1 barium1 or lime2 it must be separately examined1 if the total sulphur is wanted4 ,the filtrate is heated1 and rendered slightly alkaline with ammonia4 ,filter off the precipitated ferric hydrate through a quick filter1 and wash with hot water4 ,if necessary1 evaporate the bulk to about #bjj c4c41 render faintly acid with hydrochloric acid1 and add #bj c4c4 of solution of barium chloride2 allow to stand for half-an-hour1 and decant through a filter4 ,wash with hot water1 dry1 ignite1 and weigh4 ,pure pyrites contains #ec4cc per cent4 of sulphur4 ,,volumetric ,,method4 ,this is based upon the easy conversion of all sulphur compounds into sulphates by fusion with nitre or by oxidation with nitric acid2 and on the determination of the sulphate formed by titration in an acetic acid solution with baric chloride4#aja ,the finishing point is determined by filtering off portions of the assay solution1 and testing with sulphuric acid4 ,a slight excess of baric chloride will cause a precipitate4 ,the process may be divided into--7#a7 the preparation of the solution1 and 7#b7 the titration4 ,preparation of the ,solution4--,weigh up from #a to #e grams of the dried and powdered substance1 and mix intimately with #d grams of powdered nitre2 clean out the mortar with another gram of nitre1 and add this as a cover4 ,heat in a platinum crucible for fifteen minutes at a low temperature2 cool1 and extract with water in an evaporating-dish about #i inches across1 and holding #gjj or #hjj c4c4 ,add #aj grams of sodium acetate and #aj c4c4 of acetic acid1 and dilute to half a litre4 ,boil4 ,the solution is ready for titrating4 ,substances which lose sulphur on heating 7such as pyrites7 are thus treated3--,weigh up #a gram1 and evaporate nearly to dryness with #aj c4c4 each of nitric and hydrochloric acids4 ,take up with #aj c4c4 of hydrochloric acid1 and again boil down to a small bulk2 dilute and transfer to a #i-;inch evaporating-dish2 add #aj grams of sodium acetate and #e c4c4 of acetic acid1 dilute to half a litre1 and boil4 ,the solution is ready for titrating4 ,sulphates may be dissolved up in the dish itself with the help of a c4c4 or so of hydrochloric acid2 sodium acetate and acetic acid are then added2 and1 after dilution and boiling1 the solutions are at once titrated4 ,the solution before titration must contain no free mineral acid1 but #e or #aj c4c4 of acetic acid should be present4 ,it must contain #aj grams of sodium acetate1 or sufficient to convert any free mineral acid into its corresponding sodic salt2 or1 if chlorides1 nitrates or sulphates of the metals are present1 sufficient to decompose them4 ,if a precipitation occurs1 as is the case with ferric salts1 c41 the solution is titrated with the precipitate in it4 ,the ,titration4--,the standard solution of barium chloride is made by dissolving #gf4be grams of the crystallized salt 7,ba,cl#b4b;,h#b,o7 in distilled water1 and diluting to #a litre4 #ajj c4c4 will equal #a gram of sulphur4 ,as indicator1 use dilute sulphuric acid4 ,the strength of the solution may be checked by the titration of #e grams of ferrous sulphate 7oxidized with permanganate of potassium or a few drops of nitric acid71 which should require #eg4e c4c4 of the barium chloride solution2 or any pure sulphate of known composition can be used2 anhydrous salts should be preferred4 ,illustration3 ,,fig4 #fe4 ,fill an ordinary #ajj c4c4 burette with the solution of barium chloride4 ,the evaporating dish containing the assay solution is placed on a round burner 7as shown in fig4 #fe71 and the solution is kept steadily boiling4 ,an ordinary ,bunsen-burner flame will cause bumping1 and should not be used4 ,run in the standard solution in quantity known to be insufficient2 then withdraw a portion of about #b c4c41 with a pipette1 and filter through a fine filter-paper into a test tube4 ,run in another #j4e c4c4 of the standard solution1 and withdraw and filter into a test tube another portion of #b c4c42 and continue this operation until half-a-dozen or more portions have been drawn off4 ,the test tubes should be arranged in order in a stand resting on a piece of paper1 so that each test tube representing #j4e c4c4 of the standard baric chloride may have its value recorded beneath it 7fig4 #ff74 ,add to each test tube #c drops of dilute sulphuric acid2 that which shows the first appearance of a precipitate marks the point at which the titration is complete4 ,suppose1 for example1 that the test tube marked #dh4e c4c4 shows no precipitate1 while that at #di4j c4c4 shows one1 it is evident that the finishing point lies between these readings4 ,with a little practice1 one can judge from the appearance of the precipitate in the #di c4c4 tube1 whether #a_/d c4c4 should be deducted or not4 ,illustration3 ,,fig4 #ff4 ,it is better to add dilute sulphuric acid1 and to watch for the appearance of a precipitate in the test tube1 than to add baric chloride and to look for its non-appearance2 besides1 baric chloride is much less likely to be present in a test tube as impurity than sulphates are4 ,in this way the chance of error from what are termed accidental causes is diminished4 ,the following experiments show the effect of variation in the conditions of titration3-- ,make a standard solution of sulphuric acid by diluting #dc4fe grams of sulphuric acid 7sp4 g4 #a4fafe7 to #a litre3 #ajj c4c4 will contain #a gram of sulphur4 ,an equivalent solution may be made by dissolving #ajj4fb grams of sodium sulphate crystals 7,na#b,,so#d4aj;,h#b,o71 or #hf4hh grams of ferrous sulphate 7,fe,s,o#d4g;,h#b,o71 in water 7oxidising the latter71 and diluting to #a litre4 ,the order in which these experiments are given is that in which they were made in an investigation into the conditions under which the titration could most accurately be effected4 ,effect of ,hydrochloric and ,nitric ,acids4--,the titrations were performed in the manner already described1 but sodic acetate and acetic acid were absent4 ,twenty c4c4 of the standard solution of sulphuric acid were used4 ,hydrochloric acid present #j4j c4c4 #a4j c4c4 #b4j c4c4 #e4j c4c4 ,baric chloride required #bj4j #bj4j #ai4g #ab4e ,nitric acid present #j4j c4c4 #a4j c4c4 #b4j c4c4 #e4j c4c4 ,baric chloride required #bj4j #ai4e #ah4j #aj4j ,these show clearly the interference of free mineral acids1 although very dilute hydrochloric acid 7#a c4c4 in #ejj of water7 has no effect4 ,effect of ,acetic and ,citric ,acids4--,a similar series of experiments with these acids gave the following results3-- ,acetic acid present #j4j c4c4 #e4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,baric chloride required #bj4j #bj4j #bj4j #bj4j ,citric acid present #j gram #a gram #e grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 ,these acids do not interfere4 ,effect of ,sodic ,acetate and ,acetic ,acid4--,in each of these experiments #e c4c4 of acetic acid was present4 ,sodium acetate added #j gram #a gram #aj grams #ej grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 ,as sodic acetate and acetic acid did not interfere1 it became desirable to make some experiments on the finishing point4 ,the first object sought for was the smallest amount of the standard baric chloride in #ejj c4c4 of water1 required to give an indication when tested in the manner already described4 ,baric ,chloride ,conditions of ,assay ,solution4 required4 ,water only #j4je c4c4 ,with #aj grams of sodium acetate and #e c4c4 of acetic acid #j4je ,the same with #e grams of nitre #j4aj ,like the last1 but with #e grams of salt instead of nitre #j4aj ,these show that as small an amount of baric chloride solution as is equal to only #j4jjjjjb gram of sulphur in the #b c4c4 of solution tested yields a decided precipitate on the addition of #c drops of sulphuric acid4 ,to determine whether the same finishing point is obtained on testing the filtered portions in the test tubes with baric chloride as is obtained on testing with sulphuric acid1 a titration was made with #bj c4c4 of standard solution of sulphuric acid1 together with the usual quantities of sodic acetate and acetic acid2 and two lots of #b c4c4 each were filtered into two sets of test tubes after each addition of the standard baric chloride4 ,to one series #c drops of baric chloride solution were added1 and to the other #c drops of sulphuric acid4 ,the results were-- ,with ,dilute ,with ,baric ,baric ,chloride added4 ,sulphuric ,acid4 ,chloride ,solution4 #ai4e c4c4 ,clear ,cloudy #ai4ge ,clear ,cloudy #bj4j ,finished ,finished #bj4be ,cloudy ,clear #bj4e ,cloudy ,clear ,the two methods of testing give the same result4 ,but this balance is disturbed in the presence of much nitre1 the indications with baric chloride being disturbed by an opalescence for some c4c4 beyond the finishing point4 ,in solutions containing free hydrochloric or nitric acid1 a precipitate is obtained with either baric chloride or sulphuric acid4 ,effect of ,varying ,sulphur4--,in these and the subsequent experiments the titrations were performed in the presence of #aj grams of sodic acetate and #aj c4c4 of acetic acid in the manner already described4 ,standard sulphuric acid used #e4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,baric chloride required #e4j #aj4j #bj4j #ej4j #ajj4j ,effect of ,varying ,temperature4--,with #e c4c4 of standard sulphuric acid titrated at #ae ,c41 #e c4c4 of baric chloride were required2 but with larger quantities the results were altogether unsatisfactory when titrated cold4 ,effect of ,varying ,bulk4-- ,bulk #ajj4j c4c4 #bjj4j c4c4 #ejj4j c4c4 #ajjj4j c4c4 ,baric chloride required #bj4j #bj4j #bj4j #bj4e ,considerable variation in bulk has no effect1 but #ejj c4c4 is the most convenient volume to work with4 ,it is well to occasionally replace the water boiled off during titration4 ,effect of ,foreign ,salts4--,in all these experiments #bj c4c4 of sulphuric acid were used1 and the titration was performed in the ordinary way4 ,sodic chloride added #j gram #e grams #aj grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #ai4g c4c4 ,ammonic chloride added #j gram #e grams #aj grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #ai4e c4c4 ,calcic chloride added #j gram #a gram #b grams #e grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #ai4b c4c4 #ai4j c4c4 ,zinc chloride added #j gram #a gram #c grams #e grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 ,ferrous chloride added #j gram #a gram #c grams #e grams ,baric chloride required #bj4j c4c4 #ai4g c4c4 #ai4e c4c4 #ai4j c4c4 ,ferric chloride added #j gram #a gram #c grams #e grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 ,copper chloride added #j gram #a gram #c grams #e grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 ,potassic ,nitrate added #j gram #a gram #e grams #aj grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 #ai4j c4c4 ,potassic ,nitrite added #j gram #a gram #e grams ,baric chloride required #bj4j c4c4 #bj4j c4c4 #bj4j c4c4 ,sodic phosphate added #j gram #a gram ,baric chloride required #bj4j c4c4 #bb4e c4c4 ,sodic arsenate added #j gram #a gram ,baric chloride required #bj4j c4c4 #bj4e c4c4 ,in the absence of ferric salts1 phosphates and arsenates count as sulphur4 ,in two series of experiments for determining the effect of varying amounts of sulphur in the form of ferrous sulphate1 we obtained the following results3--,in the first series the assay solution was prepared in the manner we have described for ,pyrites2 and in the second series1 by fusion with nitre4 ,sulphur added #j4jej gram #j4ajj gram #j4bjj gram ,baric chloride required 7#a7 #e4j c4c4 #aj4j c4c4 #bj4j c4c4 7#b7 #d4g #aj4j #bj4j ,sulphur added #j4ejj gram #a4jjj gram ,baric chloride required 7#a7 #ej4j c4c4 #ajj4j c4c4 7#b7 #ej4j #ajj4j ,more than #e grams of nitre must not be used in an assay2 and1 since the requisite amount of nitre considerably exceeds that sufficient to oxidise the sulphur1 not more than #j4e gram of unoxidised sulphur should be present in the portion of the sample weighed up for determination4 ,when the amount of sulphur present is not known within reasonable limits1 the test portions may be tried with a drop of baric chloride solution instead of sulphuric acid1 so that the diminishing quantity of precipitate may give warning of an approach to the finishing point4 ,determination of ,sulphur in ,blende4--,weigh up #a gram of dried and powdered blende1 and mix and fuse with #e grams of nitre in the manner described4 ,place the dish and its contents in the titrating-dish1 extract with water1 add #aj grams of sodium acetate and #aj c4c4 of acetic acid1 remove and wash the platinum-dish1 and dilute to #ejj c4c42 boil and titrate4 ,in the example1 duplicate determinations required 7a7 #cb4j c4c41 7b7 #cb4be c4c41 giving an average of #cb4a per cent4 of sulphur4 ,determination of ,sulphur in ,chalcopyrite 7,yellow ,copper ,ore74--,take #a gram of the finely-powdered sample1 and #e grams of nitre4 ,sprinkle a little of the nitre in a small ,wedgwood mortar1 place the ore on it1 and cover with #b or #c grams more of the nitre4 ,rub up together1 and transfer to a small porcelain dish2 clean out the mortar with the rest of the nitre1 and add to the contents of the dish4 ,cover with a piece of platinum foil1 and heat gently with a ,bunsen burner till the nitre melts and the stuff shows signs of deflagrating2 remove the heat1 and allow the action to go on by itself for a minute or so1 then heat over the ,bunsen burner for #aj minutes4 ,cool2 transfer the whole to the titrating-dish2 boil with #ejj c4c4 of water2 remove the small dish and foil2 add sodic acetate and acetic acid1 and titrate4 ,for example1 #a gram required #cd4e c4c4 of barium chloride 7standard #a4jje gram ,s71 which is equivalent to #cd4g per cent4 sulphur4 ,the theoretical percentage is #cd4h4 ,determination of ,sulphur in ,chalcocite 7,grey ,copper ,ore74--,proceed as in the last experiment but1 since the action with nitre is more moderate1 no special precautions need be taken on heating4 ,a platinum dish may be used4 ,an example which was heated for #cj minutes required #bj4e c4c4 of the barium chloride solution4 ,this is equivalent to #bj4f per cent4 of sulphur4 ,the theoretical yield is #bj4b per cent4 ,determination of ,sulphur in ,pyrites4--,take #a gram of the finely-powdered sample1 cover with #aj c4c4 of nitric acid1 and1 when action has ceased1 evaporate to a small bulk4 ,add #c or #d c4c4 of hydrochloric acid1 and again evaporate to a paste4 ,take up with #a or #b c4c4 of dilute hydrochloric acid1 dilute with water1 transfer to a titrating-dish1 add #aj grams of sodic acetate and #e c4c4 of acetic acid1 and dilute with water to #ejj c4c4 ,boil and titrate4 ,an example with #a gram of a pure crystallized pyrites required #eb4g c4c4 of the barium chloride solution1 which is equivalent to #ec4j per cent4 of sulphur4 ,theory requires #ec4c per cent4 of sulphur4 ,determination of ,sulphur in ,mispickel4--,take #a gram of the powdered ore and evaporate with #aj c4c4 of nitric acid1 and take up with #c or #d c4c4 of hydrochloric acid4 ,if any globules of sulphur remain1 again evaporate with nitric acid4 ,dilute1 and transfer to the titrating-dish4 ,add #aj grams of sodic acetate1 dilute with water1 boil1 and titrate4 ,the mispickel carries 7according to theory7 exactly sufficient iron to precipitate the arsenic as ferric arsenate in an acetic acid solution1 so no more iron need be added4 ,the ferric arsenate will separate out as a yellowish-white flocculent precipitate4 ,an example required1 in duplicate experiment1 #ah4e c4c4 and #ah4g c4c4 of barium chloride1 equivalent to #ah4g per cent4 of sulphur4 ,the formula1 ,fe,s#b4;,fe,as#b1 requires #ai4f percent41 but the sulphur generally varies considerably from this amount4 ,determination of ,sulphur in ,burnt ,ores4--,take #e grams of the dried and powdered ore1 and rub up with #d grams of nitre2 transfer to the platinum-dish2 clean out the mortar with another gram of nitre1 and add this as a cover4 ,heat1 and extract with water as before2 add the sodium acetate and acetic acid2 and titrate4 ,burnt ores carry from #b4e to #e per cent4 of sulphur4 ,a series of four determinations gave3-- ,baric ,chloride ,required4 ,percentage of ,sulphur4 ,gravimetric ,results4 #ab4f c4c4 #b4eb #b4de #bi4i #e4ih #e4hd #ah4a #c4fb #c4ec #bb4j #d4dj #d4dc ,for ores carrying less than #a per cent4 of sulphur1 take #aj grams for the assay4 ,determination of ,sulphuric ,oxide 7,,so#c7 in ,sulphates4--,when the sulphur exists in the sample received by the assayer in an oxidised state as sulphate1 it is usual to report it in terms of sulphuric oxide 7,,so#c74 ,in this case1 the metal must also be reported as oxide4 ,for example1 an analysis of copper sulphate would be thus reported3-- ,oxide of copper 7,cu,o7 #ca4h ,sulphuric oxide 7,,so#c7 #cb4a ,water #cf4a ----- #ajj4j ,the percentage of sulphur multiplied by #b4e gives the percentage of sulphuric oxide4 ,thus a sample of copper sulphate containing #ab4he per cent4 of sulphur will contain #ab4he #b4e or #cb4ab per cent4 of sulphuric oxide4 ,in minerals and metallurgical products1 it is common to find the sulphur in both conditions--i4e41 as sulphate and sulphide4 ,generally in these the percentage of sulphur only is wanted2 but this will depend entirely on commercial requirements1 and not on the fancy of the assayer4 ,soluble sulphates are determined separately by extracting with small quantities of cold water1 so as to avoid the separation of basic sulphates1 or1 if the sulphides present are not at the same time attacked1 by dilute hydrochloric acid4 ,lead sulphate may be extracted by boiling with ammonic acetate2 whilst barium1 strontium1 and1 perhaps1 calcium sulphate1 will be mainly found in the residue insoluble in acids4 ,weigh up from #b to #e grams of the material according to the amount of sulphur judged to be present1 and dissolve them in the titrating-dish with #a c4c4 of hydrochloric acid and #ej c4c4 of water4 ,add #aj grams of sodic acetate1 and #aj c4c4 of acetic acid2 dilute1 boil1 and titrate4 ,in the case of ferric salts1 half the quantity of acetic acid will be better1 as then the ferric iron will be precipitated1 and a colourless solution will be left1 in which the end reaction is more readily distinguished4 ,determined in this way1 #e gram samples of the following salts gave the results indicated below3-- ,barium ,chloride ,salt4 ,required4 ,sulphuric ,oxide4 ,copper sulphate #fd4be c4c4 #cb4ab ,magnesium sulphate #fe4be #cb4fb ,zinc sulphate #ef4be #bh4ab ,ferrous sulphate #eh4be #bi4ab ,sodium sulphate #ea4be #be4fj ,determination of ,sulphuric ,oxide in ,barytes 7,heavy spar74--,fuse #b grams of the powdered mineral with #e grams of fusion mixture for five minutes2 and1 when cold1 extract with water4 ,filter1 acidulate the filtrate with an excess of #aj c4c4 of acetic acid1 dilute1 boil1 and titrate4 ,for example1 a transparent crystallised sample required #bg4j c4c4 of barium chloride1 which is equivalent to #ac4f per cent4 of sulphur1 or #cd4j per cent4 of sulphuric oxide4 ,theory requires #cd4c per cent4 of the latter4 ,since both carbonate of soda and potash are liable to contain sulphates1 a blank determination should be made on #e grams of the fusion mixture1 and the amount found be deducted from that got in the assay4 ,,practical ,,exercises4 #a4 ,the price of sulphur in an ore being #d-a_/b;d4 per unit in the northern markets1 what would be the price of a ton of ore containing #di per cent4 of sulphur8 ,what would be the effect on the price of an error of #j4be per cent4 in the assay8 #b4 ,pyrites carries #ej per cent4 of sulphur1 and on calcining yields #gj per cent4 of its weight of burnt ore4 ,supposing the burnt ore carries #c4e per cent4 of sulphur1 what proportion of the sulphur will have been removed in the calcining8 #c4 ,how would blende compare with pyrites as a source of sulphur for sulphuric acid making8 #d4 ,how would you determine the percentage of sulphuric oxide in a sample of gypsum8 ,what is sulphuric oxide1 and what relation does it bear to sulphur8 #e4 ,a mineral contains #bj4g per cent4 of water1 #cb4d per cent4 of lime1 and #ah4f per cent4 of sulphur4 ,what is its probable composition8 ,what experiment would you try to determine the accuracy of your conclusion8 ,,selenium occurs in nature combined with copper1 mercury1 and lead1 in certain rare minerals4 ,in small quantities it is found in many ores4 ,it is detected in solution by the red precipitate produced on boiling the acid solution with sodium sulphite4 ,this reaction is used for its determination4 ,solution4--,the solution is effected by boiling with nitric acid or aqua regia1 or by fusing with nitre4 ,to separate the selenium1 the solution is evaporated with an excess of hydrochloric acid and a little sodium or potassium chloride4 ,this destroys any nitric acid that may be present1 and reduces selenic acid 7,h#b,se,o#d7 to selenious 7,h#b,se,o#c74 ,the solution is diluted with water1 and treated with a solution of sulphite of soda4 ,it is warmed1 and at last boiled4 ,the selenium separates as a red precipitate1 which 7on boiling7 becomes denser and black4 ,it is collected on a weighed filter1 washed with hot water1 dried at #ajj ,c41 and weighed as pure selenium4 ,selenium can be precipitated with sulphuretted hydrogen as a sulphide1 which is readily soluble in ammonium sulphide4 ,this sulphide may be oxidised with hydrochloric acid and chlorate of potash2 and the selenium separated in the manner described4 ,,tellurium4 ,tellurium occurs in nature1 native1 and in combination with gold1 silver1 bismuth and lead4 ,it is sometimes met with in assaying gold ores4 ,it may be detected by the purple colour it imparts to strong sulphuric acid when dissolved in the cold1 and by the black precipitate of metallic tellurium which its solutions yield on treatment with a reducing agent4 ,telluric acid is reduced to tellurous 7with evolution of chlorine7 on boiling with hydrochloric acid4 ,solution is effected by boiling with aqua regia1 or by fusing with nitre and sodium carbonate4 ,separation4--,tellurium closely resembles selenium in its reactions4 ,it is separated and determined in the same way4 ,like it1 it forms a sulphide soluble in ammonium sulphide4 ,it is distinguished from selenium by the insolubility1 in a solution of cyanide of potassium1 of the metal precipitated by sodium sulphite2 whereas selenium dissolves1 forming a soluble potassic seleno-cyanide4#ajb ,for the determination1 solution is effected by fusing with nitre and sodium carbonate1 dissolving out the tellurate of potash with water1 and boiling with hydrochloric acid4 ,tellurous compounds are formed1 with evolution of chlorine2 and the solution1 on treating with a reducing agent 7such as sulphurous acid or stannous chloride71 yields metallic tellurium2 which is washed1 dried at #ajj ,c41 and weighed4 ,,footnotes3 #aja ,ba,cl#b ,na#b,,so#d ,ba,s,o#d #b,na,cl4 #ajb ,se ,k,cy ,k,cy,se4 ,,chapter ,,xvii4 ,,arsenic1 ,,phosphorus1 ,,nitrogen4 ,,arsenic4 ,the chief source of the arsenic of commerce is arsenical pyrites1 or mispickel1 which contains about #de per cent4 of arsenic 7,as74 ,arsenic also occurs as a constituent of several comparatively rare minerals2 and1 as an impurity1 it is very widely distributed4 ,white arsenic is an oxide of arsenic1 and is obtained by roasting arsenical ores1 and refining the material 7crude arsenic71 which condenses in the flues4 ,arsenic itself is volatile1 and many of its compounds have the same property4 ,it forms two well-defined series of salts1 corresponding to the oxides3 arsenious oxide 7,as#b,o#c71 and arsenic oxide 7,as#b,o#e74 ,these combine with bases to form arsenites and arsenates respectively4 ,boiling with nitric acid converts the lower into the higher oxide2 and powerful reducing-agents1 such as cuprous chloride1 have the opposite effect4 ,arsenic may be detected by dissolving the substance in hydrochloric acid1 or in aqua regia 7avoiding an excess of nitric acid71 and adding a little of this solution to the contents of a small flask in which hydrogen is being made by the action of zinc and hydrochloric acid4 ,the ignited jet of hydrogen assumes a blue colour if arsenic is present1 and a cold porcelain dish held in the flame 7fig4 #fg7 becomes coated with a dark deposit of metallic arsenic4 ,antimony produces a similar effect1 but is distinguished by the insolubility of its deposit in a cold solution of bleaching-powder4 ,illustration ,,fig4 #fg4 ,arsenites are distinguished by the volatility of the chloride2 by decolorising a solution of permanganate of potassium1 and by immediately giving a yellow precipitate with sulphuretted hydrogen4 ,arsenates are distinguished 7after converting into soda salts by boiling with carbonate of soda and neutralising7 by giving with nitrate of silver a red precipitate1 and with magnesia mixture a white crystalline one4 ,dry ,assay4--,there is no dry assay which is trustworthy4 ,the following method is sometimes used to find the proportion of arsenious oxide in crude arsenic3--,weigh up #e grams of the dried sample1 and place them in a clean dry test-tube about #f inches long4 ,tie a small filter-paper over the mouth of the tube1 so as to prevent air-currents4 ,heat the tube cautiously so as to sublime off the white arsenic into the upper part of the tube4 ,cut off the bottom of the test-tube by wetting whilst hot4 ,scrape out the arsenic and weigh it4 ,the weight gives an approximate idea of the quantity1 and the colour of the quality1 of the white arsenic obtainable from the sample4 ,some workers 7sellers7 weigh the residue1 and determine the white arsenic by difference4 ,in determining the percentage of moisture in these samples1 the substance is dried on a water-bath or in a water-oven4 ,,wet ,,methods4 ,solution4--,where1 as in crude arsenic1 the substance is arsenious oxide 7,as#b,o#c7 mixed with impurities1 the arsenic is best got into solution by warming with caustic soda1 and neutralising the excess with hydrochloric acid2 it will be present as sodium arsenite4 ,metals and alloys are acted on by means of nitric acid2 or the arsenic may be at the same time dissolved and separated by distilling with a strongly-acid solution of ferric chloride1 in the way described under ,volumetric ,methods4 ,with minerals1 mattes1 c41 solution is thus effected3--,the finely-powdered substance is mixed 7in a large platinum or porcelain crucible7 with from six to ten times its weight of a mixture of equal parts of carbonate of soda and nitre4 ,the mass is then heated gradually to fusion1 and kept for a few minutes in that state4 ,when cold1 it is extracted with warm water1 and filtered from the insoluble residue4 ,the solution1 acidified with nitric acid and boiled1 contains the arsenic as sodium arsenate4 ,with mispickel1 and those substances which easily give off arsenic on heating1 the substance is first treated with nitric acid1 evaporated to dryness1 and then the residue is treated in the way just described4 ,when the arsenic is present as arsenite or arsenide1 distillation with an acid solution of ferric chloride will give the whole of the arsenic in the distillate free from any metal except1 perhaps1 tin as stannic chloride4 ,with arsenates1 dissolve the substance in acid and then add an excess of soda4 ,pass sulphuretted hydrogen into the solution2 warm1 and filter4 ,acidulate the filtrate1 and pass sulphuretted hydrogen4 ,decant off the liquid through a filter1 and digest the precipitate with ammonic carbonate2 filter1 and re-precipitate with hydrochloric acid and sulphuretted hydrogen4 ,allow to stand in a warm place1 and filter off the yellow sulphide of arsenic4 ,wash it into a beaker1 clean the filter-paper 7if necessary7 with a drop or two of dilute ammonia2 evaporate with #aj c4c4 of dilute nitric acid to a small bulk2 dilute2 and filter off the globules of sulphur4 ,the filtrate contains the arsenic as arsenic acid4 ,,gravimetric ,,method4 ,having got the arsenic into solution as arsenic acid1 and in a volume not much exceeding #ej c4c41 add about #bj c4c4 of dilute ammonia and #bj c4c4 of magnesia mixture4 ,stir with a glass rod1 and allow to settle overnight4 ,filter1 and wash with dilute ammonia1 avoiding the use of large quantities of wash water4 ,dry1 transfer the precipitate to a ,berlin crucible1 and clean the filter-paper thoroughly4 ,burn this paper carefully and completely2 and add the ash to the contents of the crucible1 together with #d or #e drops of nitric acid4 ,evaporate with a ,bunsen burner1 and slowly ignite1 finishing off with the blow-pipe or muffle4 ,cool1 and weigh4 ,the ignited precipitate is pyrarsenate of magnesia 7,mg#b;,as#b,o#g71 and contains #dh4d per cent4 of arsenic 7,as74 ,instead of igniting the precipitate with nitric acid1 it may be collected on a weighed filter-paper1 dried at #ajj ,c41 and weighed as ammonic-magnesic arsenate 7#b;,am,mg,as,o#d4;,h#b,o71 which contains #ci4e per cent4 of arsenic4 ,the results in this case are likely to be a little higher4 ,the drying is very tedious1 and is likely to leave behind more water than is allowed for in the formula4 ,in a series of determinations in which the arsenic was weighed in both forms1 the results were3-- ,ammonic-magnesic ,arsenic ,magnesium ,pyrarsenate ,arsenic ,arsenate in grams4 in grams4 in grams4 in grams4 #j4jjhj #j4jjcb #j4jjfe #j4jjca #j4jdjj #j4jaeh #j4jccj #j4jafj #j4jgii #j4jcaf #j4jfcc #j4jcjf #j4afjj #j4jfcb #j4abhg #j4jfbc #j4djjj #j4aehj #j4cbje #j4aeea #j4giij #j4caef #j4fdce #j4caad ,,volumetric ,,methods4 ,there are two methods3 one for determining the arsenic in the lower1 and the other in the higher state of oxidation4 ,in the first-mentioned method this is done by titrating with a standard solution of iodine2 and in the latter with a solution of uranium acetate4 ,where the arsenic already exists as arsenious oxide1 or where it is most conveniently separated by distillation as arsenious chloride1 the iodine method should be used2 but when the arsenic is separated as ammonic-magnesic arsenate or as sulphide1 the uranium acetate titration should be adopted4 ,,iodine ,,process4 ,this is based on the fact that sodium arsenite in a solution containing an excess of bicarbonate of soda is indirectly oxidised by iodine to sodium arsenate1#ajc and that an excess of iodine may be recognised by the blue colour it strikes with starch4 ,the process is divided into two parts--7#a7 the preparation of the solution1 and 7#b7 the titration4 ,preparation of the ,solution4--,for substances like crude arsenic1 in which the arsenic is present as arsenious oxide1 the method is as follows3--,take a portion which shall contain from #j4be to #j4e gram of the oxide1 place in a beaker1 and cover with #aj c4c4 of sodic hydrate solution2 warm till dissolved1 put a small piece of litmus paper in the solution1 and render acid with dilute hydrochloric acid4 ,add #b grams of bicarbonate of soda in solution1 filter 7if necessary71 and dilute to #ajj c4c4 ,the solution is now ready for titrating4 ,illustration3 ,,fig4 #fh4 ,where the arsenic has to be separated as arsenious chloride1 the process is as follows3#ajd--,weigh up #a gram of the finely-powdered ore 7metals should be hammered out into a thin foil or be used as filings71 and place in a #af-ounce flask provided with a well-fitting cork1 and connected with a ,u-tube1 as shown in the drawing 7fig4 #fh74 ,the ,u-tube should contain #b or #c c4c4 of water1 and is cooled by being placed in a jar or large beaker of cold water4 ,the water used for cooling should be renewed for each assay4 ,pour on the assay in the flask #ej c4c4 of a ferric chloride mixture1 made by dissolving #fjj grams of calcium chloride and #cjj grams of ferric chloride in #fjj c4c4 of hydrochloric acid1 and making up to #a litre with water4 ,firmly cork up the apparatus1 and boil over a small ,bunsen-burner flame for fifteen or twenty minutes1 but avoid evaporating to dryness4 ,disconnect the flask1 and pour away its contents at once to prevent breakage of the flask by their solidification4 ,the arsenic will be condensed in the ,u-tube1 together with the greater part of the hydrochloric acid2 transfer the distillate to a beaker washing out the tube two or three times with water2 add a small piece of litmus paper2 neutralise with ammonia2 render faintly acid with dilute hydrochloric acid2 add #b grams of bicarbonate of soda in solution2 and dilute to #bej c4c4 ,the solution is now ready for titrating4 ,the arsenic comes over in the early part of the distillation1 as will be seen from the following experiment1 made on #a gram of copper precipitate2 in which experiment the distillate was collected in separate portions at equal intervals1 and the arsenic in each portion determined3-- ,time ,iodine ,equivalent to ,arsenic ,distilling4 ,required4 in the ,distillate4 #e minutes #ab4j c4c4 #j4jdej gram #e #j4ag #j4jjje #e #j4j #e #j4j ,to dryness #j4j ,the volume of each distillate was about #e c4c4 ,in this operation the metals are converted into chlorides by the action of ferric chloride1 which gives up a part of its chlorine1 and becomes reduced to the ferrous salt4 ,the calcium chloride does not enter into the chemical reaction1 but raises the temperature at which the solution boils1 and is essential for the completion of the distillation4#aje ,two experiments with material containing #c4dh per cent4 of arsenic gave--7#a7 with ferric chloride alone1 #b4gd per cent42 and 7#b7 with the addition of calcium chloride1 #c4dh per cent4 ,it is always necessary to make a blank determination with #a gram of electrotype copper1 to find out the amount of arsenic in the ferric chloride mixture4#ajf ,unfortunately1 a correction is always required4 ,this amounts to about #j4ae per cent4 of arsenic on each assay1 even when the mixture has been purified2 and this constitutes the weakness of the method1 since1 in some cases1 the correction is as much as1 or even greater than1 the percentage to be determined4 ,the acid distillate containing the arsenious chloride may be left for an hour or so without much fear of oxidation2 but it is safer to neutralise and then to add the bicarbonate of soda1 as the following experiments show4 ,several portions of a solution1 each having a bulk of #ajj c4c41 were exposed for varying lengths of time1 and the arsenic in each determined4 ,acid ,solutions4 ,neutralised ,solutions4 ,time ,exposed4 ,iodine ,arsenic ,found4 ,iodine ,arsenic ,found4 ,required4 ,required -- #ah4b c4c4 #j4jacf gram #ah4a c4c4 #j4jacf gram #a hour #ah4b #j4jacf #ah4b #j4jacf #b hours #ag4g #j4jacc #ah4j #j4jace #d #ag4e #j4jaca #ah4d #j4jach #e #ag4j #j4jabg #ah4c #j4jacg ,the ,titration4--,make a standard solution of iodine by weighing up in a beaker #af4icc grams of iodine and #cj grams of potassium iodide in crystals2 add a few c4c4 of water1 and1 when dissolved1 dilute to #a litre3 #ajj c4c4 will equal #j4ejj gram of arsenic4 ,a solution of starch similar to that used in the iodide-copper assay will be required4 ,use #b c4c4 for each assay4 ,variations in the quantity of starch used do not interfere2 but the solution must be freshly prepared1 as after seven or eight days it becomes useless4 ,to standardise the iodine solution1 weigh up #j4c gram of white arsenic2 dissolve in caustic soda2 neutralise2 after acidulating1 add #b grams of bicarbonate of soda and #b c4c4 of the starch solution1 and dilute to #bjj c4c4 with cold water4 ,fill a burette having a glass stop-cock with the iodine solution1 and run it into the solution of arsenic1 rapidly at first1 and then more cautiously1 till a final drop produces a blue colour throughout the solution4 ,calculate the standard in the usual way4 ,white arsenic contains #ge4gf per cent4 of arsenic4 ,the following experiments show the effect of variation in the conditions of the titration3-- ,make a solution of arsenic by dissolving #f4fj grams of white arsenic in #ajj c4c4 of sodic hydrate solution2 render slightly acid with hydrochloric acid2 add #aj grains of bicarbonate of soda1 and dilute to #a litre3 #ajj c4c4 will contain #j4ej gram of arsenic4 ,effect of ,varying ,temperature4--,the reaction goes on very quickly in the cold1 and1 since there is no occasion for heating1 all titrations should therefore be carried out cold4 ,effect of ,varying ,bulk4--,in these experiments1 #bj c4c4 of arsenic solution were taken1 #b grams of bicarbonate of soda and #b c4c4 of starch solution added1 and water supplied to the required bulk4 ,the results were3-- ,bulk #ej4j c4c4 #ajj4j c4c4 #bej4j c4c4 #ejj4j c4c4 ,iodine required #bj4j #bj4j #bj4j #bj4j ,considerable variation in bulk does not interfere4 ,effect of ,varying ,bicarbonate of ,soda4--,this salt must be present in each titration in considerable excess1 to prevent the interference of free acid4 ,the bicarbonate must be dissolved without heating1 as neutral carbonates should be avoided4 ,bicarbonate added #a gram #b grams #e grams #aj grams ,iodine required #bj4a c4c4 #bj4j c4c4 #bj4a c4c4 #bj4j c4c4 ,these results show that large variation in the quantity of bicarbonate has no effect4 ,effect of ,free ,acid4--,in these experiments1 the arsenic taken1 the starch1 and the bulk were as before1 but no bicarbonate was added4 ,in one case the solution was rendered acid with #e c4c4 of acetic acid1 and in the other with #e c4c4 of hydrochloric acid2 in both cases the interference was strongly marked1 and no satisfactory finishing point could be obtained4 ,this was much more marked with the hydrochloric acid4 ,effect of ,foreign ,salts4--,the process for getting the arsenic into solution will exclude all metals except tin1 but the solution will be charged with sodium or ammonium salts in the process of neutralising1 so that it is only necessary to see if these cause any interference4 ,the alkaline hydrates1 including ammonia1 are plainly inadmissible1 since no free iodine can exist in their presence4 ,monocarbonates similarly interfere1 but to a much less extent2 hence the necessity for rendering the assay distinctly acid before adding the bicarbonate of soda4 ,with #bj c4c4 of arsenic solution2 and with bulk1 soda1 and starch as before1 the results obtained were3-- ,iodine required4 ,with #bj grams of ammonic chloride #bj4j c4c4 #bj grams of sodium chloride #bj4j #bj grams of sodium acetate #bj4j #j4jej gram of tin1 as stannic chloride #ai4f ,without any addition #bj4j ,the interference of the stannic salt is probably mechanical1 the precipitate carrying down some arsenious acid4 ,effect of ,varying ,arsenic4--,with bulk1 starch1 and soda as before1 but with varying arsenic1 the results were3-- ,arsenic added #a4j c4c4 #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,iodine required #a4a #i4i #bj4j #ej4j #ajj4j ,determination of ,arsenic in ,metallic ,copper4--,put #a gram of the copper filings1 freed from particles of the file with a magnet1 into a #af-oz4-flask2 and distil with the ferric chloride mixture1 as above described4 ,neutralise the distillate2 acidify2 add bicarbonate of soda and starch2 dilute2 and titrate with the standard solution of iodine4#ajg ,make a blank determination with #a gram of electrotype copper1 proceeding exactly as with the assay2 and deduct the amount of arsenic found in this experiment from that previously obtained4 ,working in this way on a copper containing #j4ch per cent4 of arsenic and #j4hj per cent4 of antimony1 #j4ch per cent4 of arsenic was found4 ,determination of ,white ,arsenic in ,crude ,arsenic4--,weigh out #a gram of the dried and powdered substance 7or #j4e gram if rich71 and digest with #aj c4c4 of a #aj per cent4 solution of soda2 dilute to about #ej c4c41 and filter4 ,render faintly acid with hydrochloric acid1 and filter 7if necessary72 add #b or #c grams of bicarbonate of soda in solution1 then #e c4c4 of starch1 and titrate the cold solution with the standard solution of iodine4 ,the following is an example3-- #a gram of crude arsenic required #ec4g c4c4 ,iodine2 #ajj c4c4 ,iodine #j4fjjj gram white arsenic2 #ajj 3 #ec4g 33 #j4f 3 #j4cbbb1 or #cb4b per cent4 ,with the test-tube method of dry assaying1 this same sample gave results varying from #cc to #ce per cent4 of white arsenic1 which 7judging from its appearance7 was impure4 ,,uranic ,,acetate ,,process4 ,this may be looked upon as an alternative to the gravimetric method4 ,it is applicable in all cases where the arsenic exists in solution as arsenic acid or as arsenate of soda4 ,the process may be considered in two parts3 7#a7 the preparation of the solution1 and 7#b7 the titration4 ,preparation of the ,solution4--,if the arsenic has been separated as sulphide1 it is sufficient to attack it with #aj or #ae c4c4 of nitric acid1 and to heat gently till dissolved1 avoiding too high a temperature at first4 ,afterwards continue the heat till the separated sulphur runs into globules1 and the bulk of the acid has been reduced to #c or #d c4c4 ,dilute with #bj or #cj c4c4 of water2 put in a piece of litmus paper2 and add dilute ammonia until just alkaline4 ,then add #e c4c4 of the sodium acetate and acetic acid solution 7which should make the solution distinctly acid72 dilute to #aej c4c41 and heat to boiling4 ,the solution is ready for titrating4 ,when the arsenic exists in a nitric acid solution mixed with much copper1 it is separated in the way described under ,examination of ,commercial ,copper 7,arsenic and ,phosphorus71 pages #bjh1 #bji4 ,if the arsenic has been separated as ammonium-magnesium arsenate1 and phosphates are known to be absent2 dissolve the precipitate 7after filtering1 but without washing7 in dilute hydrochloric acid4 ,add dilute ammonia till a slight precipitate is formed1 and then #e c4c4 of the sodium acetate and acetic acid solution2 dilute to #aej c4c41 and heat to boiling4 ,titrate4 ,if phosphates are present 7which will always be the case if they were present in the original substance1 and no separation with sulphuretted hydrogen has been made71 the phosphorus will count in the subsequent titration as arsenic 7one part of phosphorus counting as #b4d parts of arsenic74 ,it will be necessary to dissolve the mixed arsenate and phosphate of magnesia in hydrochloric acid4 ,add about four or five times as much iron 7as ferric chloride7 as the combined phosphorus and arsenic present will unite with1 and separate by the basic acetate process as described under ,,phosphorus in the ,examination of ,commercial ,copper1 page #bji4 ,obviously1 when phosphates are present1 it is easier to separate the arsenic as sulphide than to precipitate it with the magnesia mixture4 ,the ,titration4--,the standard solution of uranium acetate is made by dissolving #cd4a grams of the salt 7with the help of #be c4c4 of acetic acid7 in water2 and diluting to #a litre4 ,the water and acid are added a little at a time1 and warmed till solution is effected2 then cooled1 and diluted to the required volume3 #ajj c4c4 will equal #j4ej gram of arsenic4 ,the sodic acetate and acetic acid solution is made by dissolving #ajj grams of sodic acetate in #ejj c4c4 of acetic acid1 and diluting with water to #a litre4 ,five c4c4 are used for each assay4 ,the solution of potassic ferrocyanide used as indicator is made by dissolving #aj grams of the salt in #ajj c4c4 of water4 ,to standardise the solution of uranium acetate1 weigh up a quantity of white arsenic 7,as#b,o#c7 which shall be about equivalent to the arsenic contained in the assay 7#j4a or #j4b gram72 transfer to a flask1 and dissolve in #aj c4c4 of nitric acid with the aid of heat4 ,evaporate to a small bulk 7taking care to avoid the presence of hydrochloric acid72 dilute with water2 add a small piece of litmus paper2 render faintly alkaline with ammonia2 then add #e c4c4 of the sodic acetate mixture2 dilute to #aej c4c42 and heat to boiling4 ,fill an ordinary burette with the uranium acetate solution1 and run into the assay a quantity known to be insufficient4 ,again heat for a minute or two4 ,arrange a series of drops of the solution of ferrocyanide of potassium on a porcelain slab1 and1 with the help of a glass rod1 bring a drop of the assay solution in contact with one of these4 ,if no colour is produced1 run in the uranium acetate1 #a c4c4 at a time1 testing after each addition1 till a brown colour is developed4 ,it is best to overdo the assay1 and to count back4 ,it is not necessary to filter off a portion of the assay before testing with the ferrocyanide1 since the precipitate 7uranic arsenate7 has no effect4 ,the following experiments show the effect of variation in the conditions of titration4 ,make a solution of arsenic acid by dissolving #d4ie grams of arsenious acid 7,as#b,o#c7 in a covered beaker with #ce c4c4 of nitric acid2 evaporate down to #g or #h c4c42 and dilute with water to #a litre3 #ajj c4c4 will contain #j4cge gram of arsenic4 ,use #bj c4c4 for each experiment4 ,effect of ,varying ,temperature4--,it is generally recommended to titrate the boiling solution1 since it is possible that the precipitation is only complete on boiling4 ,low results are obtained in a cold solution1 the apparent excess of uranium acetate striking a colour at once2 on boiling1 however1 it ceases to do so2 consequently1 the solution should always be boiled directly before testing4 ,in four experiments made in the way described1 but with #bj c4c4 of a solution of arsenic acid stronger than that given 7#ajj c4c4 #j4e gram ,as71 the results at varying temperatures were3-- ,temperature #ae ,c4 #cj ,c4 #gj ,c4 #ajj ,c4 ,uranium required #ah4j c4c4 #ah4e c4c4 #ah4e c4c4 #ah4g c4c4 ,effect of ,varying ,bulk4--,these experiments were like those last mentioned1 but were titrated boiling1 and the volume was varied3-- ,bulk #ej4j c4c4 #ajj4j c4c4 #bjj4j c4c4 #cjj4j c4c4 ,uranium required #ad4j #ad4j #ad4e #ae4j ,considerable variations in bulk are to be avoided4 ,effect of ,varying ,sodium ,acetate4--,these experiments were carried out like those last noticed1 but the bulk was #aej c4c41 and varying amounts of sodic acetate were added in excess of the quantity used in the experiments previously described3-- ,sodic acetate added #j gram #a gram #aj grams #bj grams ,uranium required #ad4e c4c4 #ad4e c4c4 #af4j c4c4 #ah4j c4c4 ,it is evidently important that the quantity of this salt present in each titration be measured out1 so as to avoid variation4 ,effect of ,varying the ,sodium ,acetate and ,acetic ,acid ,solution4--,acetic ,acid also affects the results1 but in the opposite direction1 by preventing the precipitation of uranium arsenate4 ,with varying volumes of the solution now under notice1 the results were3-- ,solution added #j4j c4c4 #e4j c4c4 #aj4j c4c4 #ae4j c4c4 ,uranium required #ad4e #ad4e #ad4e #ad4j ,solution added #bj4j #cj4j #dj4j #ej4j ,uranium required #ac4b #aj4j #f4j #b4j ,these show that the quantity ordered 7#e c4c47 must be adhered to4 ,effect of ,foreign ,salts4--,in these experiments1 #aj grams of the salt 7the effect of which it was desired to determine7 were added to a solution in other respects resembling those previously used3-- ,salt added ,ammonic ,ammonic ,ammonic ,magnesium sulphate nitrate chloride sulphate ,uranium required #ae4e c4c4 #ae4e c4c4 #ae4c c4c4 #ae4c c4c4 ,without any addition1 #ae4j c4c4 were required2 and in another experiment1 in which #cj grams of ammonic salts were present1 #ae4f c4c4 of uranium solution were required4 ,such variations in the amount of ammonic salts as occur in ordinary working are unimportant4 ,phosphates1 of course1 interfere4 ,in fact1 the uranium acetate solution can be standardised by titrating with a known weight of phosphate1 and calculating its equivalent of arsenic4 ,thus1 in an experiment with #j4f gram of hydric sodic phosphate 7,na#b;,,hpo#d4ab;,h#b,o71 equivalent to #j4jeaie gram of phosphorus1 or #j4abef gram of arsenic1 #bc4be c4c4 of a solution of uranium acetate were required4 ,the same solution standardised with white arsenic gave a standard of which #ajj c4c4 #j4eccc gram arsenic4 ,on this standard the #j4f gram of sodic phosphate should have required #bc4e c4c4 ,experiments in which #j4a gram of bismuth and #j4a gram of antimony were present with #j4a gram of arsenic1 showed no interference on the titration4 ,ferric or aluminic salts would remove their equivalent of arsenic1 and1 consequently1 must be removed before titrating4 ,effect of ,varying ,arsenic4--,varying amounts of metallic arsenic were weighed up and dissolved in nitric acid1 c41 and titrated3-- ,arsenic taken #j4jaj gram #j4jej gram #j4ajj gram #j4bjj gram ,arsenic found #j4jaj #j4jej #j4ajj #j4aig ,these experiments show that the method yields good results within these limits4 ,determination of ,arsenic in ,mispickel4--,weigh up #a gram of the dried and powdered ore1 and evaporate to near dryness with #bj c4c4 of dilute nitric acid4 ,make up to #ajj c4c4 with water1 and pass sulphuretted hydrogen to reduce the ferric iron to the ferrous state1 then add #bj c4c4 of dilute ammonia1 and again pass sulphuretted hydrogen4 ,warm1 filter1 and evaporate the filtrate to drive off the excess of ammonia2 then add #aj c4c4 of nitric acid1 and boil down till the sulphide of arsenic at first precipitated is dissolved2 neutralise2 add #e c4c4 of sodium acetate and acetic acid solution2 transfer to a pint flask1 boil1 and titrate4 ,for example1 an impure sample of ore required1 in duplicate assay of half a gram each1 when treated in the above-mentioned way1 #ci4f and #ci4e c4c4 of the uranium acetate solution 7#ajj c4c4 #j4ecg gram of arsenic71 equivalent to #j4baad gram of arsenic1 or #db4c per cent4 ,an alternative method is as follows4 ,powder the ore very finely and weigh up 4#e gram4 ,place in a #b-c_/d inch berlin dish and add strong nitric acid1 one drop at a time until the action ceases2 with care there need be no very violent reaction4 ,dry over a water bath4 ,cover with #b grams of nitre and over this spread #e grams of a mixture of equal parts of nitre and carbonate of soda4 ,fuse in a muffle or over a large gentle blow-pipe flame for #d or #e minutes4 ,this will spoil the dish4 ,allow to cool and boil out in a larger dish with #ajj c4c4 of water4 ,filter and wash into an #h oz4 flask4 ,acidify the liquor with nitric and boil down to about #ajj c4c4 ,the acid should not be in too large excess1 but an excess is needed to destroy nitrites4 ,neutralise with soda or ammonia4 ,add #e c4c4 of the mixture of sodium acetate and acetic acid4 ,titrate with uranium acetate4 ,determination of ,arsenic 7,as7 in ,crude ,arsenic4--,the method given under the iodine titration simply determines that portion of the arsenic which is present in the substance as arsenious oxide or white arsenic4 ,the following method will give the total arsenic in the sample4 ,it would be incorrect to report this as so much per cent4 of arsenious oxide1 although it may be reported as so much per cent4 of arsenic equivalent to so much per cent4 of white arsenic1 thus3-- ,arsenic #cj4j per cent4 ,equivalent to white arsenic #ci4f ,the equivalent of white arsenic is calculated by multiplying the percentage of arsenic by #a4cb4 ,the method of determining the percentage of arsenic is as follows3---,boil #a gram of the sample with #aj c4c4 of nitric acid4 ,when the bulk of the solution has been reduced to one-half1 and red fumes are no longer evolved1 dilute with a little water1 and filter into a flask4 ,neutralise the filtrate1 add #e c4c4 of sodic acetate solution1 boil and filter4 ,the precipitate 7ferric arsenate7 is transferred to a small beaker1 treated with #e c4c4 of dilute ammonia1 and sulphuretted hydrogen passed through it4 ,the iron sulphide is filtered off1 and the filtrate evaporated with an excess of nitric acid4 ,when the solution is clear1 it is neutralised1 and #a or #b c4c4 of sodic acetate solution having been added1 is then mixed with the first filtrate4 ,the solution is boiled and titrated4 ,a sample treated in this way required #di4b c4c4 of the uranium acetate solution 7#ajj c4c4 #j4ecg gram of arsenic71 equivalent to #bf4d per cent4 ,determination of ,arsenic in ,brimstone4--,take #aj grams of the substance1 and powder in a mortar2 rub up with #aj c4c4 of dilute ammonia and a little water2 rinse into a pint flask2 pass a current of sulphuretted hydrogen2 and warm on a hot plate for a few minutes4 ,filter1 acidulate the filtrate with sulphuric acid2 filter off the precipitate2 attack it with #aj c4c4 of nitric acid2 and proceed as in the other determinations4 ,,practical ,,exercises4 #a4 ,mispickel contains #de4j per cent4 of arsenic1 to how much white arsenic will this be equivalent8 #b4 ,how would you make a standard solution of iodine so that #ajj c4c4 shall be equivalent to #a gram of white arsenic8 #c4 ,what weight of arsenic is contained in #a gram of pyrarsenate of magnesia1 and what weight of ammonic-magnesic arsenate would it be equivalent to8 #d4 ,the residue1 after heating #aj grams of crude arsenic1 weighed #j4fb gram4 ,what information does this give as to the composition of the substance8 ,if another #aj grams of the substance1 heated on a water-bath1 lost #j4dc gram1 what conclusions would you draw1 and how would you report your results8 #e4 ,if a sample of copper contained #j4e per cent4 of arsenic1 and #a gram of it were taken for an assay1 how much standard uranium acetate solution would be required in the titration8 ,,phosphorus ,,and ,,phosphates4 ,phosphorus rarely occurs among minerals except in its highest oxidized state1 phosphoric oxide 7,p#b,o#e71 in which it occurs abundantly as rock phosphate1 a variety of apatite which is mainly phosphate of lime4 ,phosphates of most of the metallic oxides are found4 ,phosphoric oxide in small quantities is widely diffused1 and is a constituent of most rocks4 ,its presence in varying amounts in iron ores is a matter of importance1 since it affects the quality of the iron obtainable from them4 ,phosphorus occurs in alloys in the unoxidized state4 ,it is directly combined with the metal1 forming a phosphide4 ,in this manner it occurs in meteoric iron4 ,the alloy phosphor-bronze is made up of copper1 tin1 zinc1 and phosphorus4 ,phosphates are mined in large quantities for the use of manure manufacturers1 and for making phosphorus4 ,phosphorus and arsenic closely resemble each other in their chemical properties1 more especially those which the assayer makes use of for their determination4 ,phosphorus forms several series of salts2 but the phosphates are the only ones which need be considered4 ,pyrophosphate of magnesia1 which is the form in which phosphoric oxide is generally weighed1 differs from the ordinary phosphate in the proportion of base to acid4 ,metaphosphates differ in the same way4 ,if these are present1 it must be remembered they act differently with some reagents from the ordinary phosphates1 which are called orthophosphates4 ,they are1 however1 all convertible into orthophosphates by some means which will remove their base1 such as fusion with alkaline carbonates1 boiling with strong acids1 c4#ajh ,phosphides are converted into phosphates by the action of nitric acid or other oxidizing agents4 ,dilute acids1 when they act on the substance1 evolve phosphuretted hydrogen 7,,ph#c74 ,the student should be on his guard against losing phosphorus in this manner4 ,there is no dry assay for phosphorus4 ,all assays for it are made either gravimetrically or volumetrically4 ,the separation of phosphoric oxide is made as follows3--,the ore or metal is dissolved in acid and evaporated1 to render the silica insoluble4 ,it is taken up with hydrochloric acid1 diluted with water1 and treated with sulphuretted hydrogen4 ,the filtrate is boiled1 to get rid of the excess of gas1 and treated with nitric acid1 to peroxidize the iron present4 ,if the iron is not present in more than sufficient quantity to form ferric phosphate with all the phosphorus present1 some ferric chloride is added4 ,the iron is then separated as basic acetate4 ,the precipitate will contain the phosphorus1 together with any arsenic acid not reduced by the sulphuretted hydrogen4 ,the precipitate should have a decided brown colour4 ,the precipitate is washed1 transferred to a flask1 and treated first with ammonia1 and then with a current of sulphuretted hydrogen4 ,the filtrate from this 7acidulated with hydrochloric acid1 and1 if necessary1 filtered7 contains the phosphorus as phosphoric acid4 ,this method is not applicable in the presence of alumina1 chromium1 titanium1 or tin1 if the solution is effected with nitric acid4 ,the precipitate obtained by the action of nitric acid on tin retains any phosphoric or arsenic oxide that may be present4 ,a method of separation more generally applicable and more convenient to work is based on the precipitation of a yellow phospho-molybdate of ammonia1#aji by the action of an excess of ammonic molybdate upon a solution of a phosphate in nitric acid4 ,dissolve the substance by treatment with acid1 and evaporate to dryness4 ,take up with #aj c4c4 of nitric acid1 and add #bj grams of ammonic nitrate1 together with a little water4 ,next put in the solution of ammonium molybdate solution in the proportion of about #ej c4c4 for each #j4a gram of phosphoric oxide judged to be present4 ,warm to about #hj ,c41 and allow to stand for an hour4 ,filter1 and wash with a #aj per cent4 solution of ammonic nitrate4 ,it is not necessary that the whole of the precipitate be placed on the filter2 but the beaker must be completely cleaned4 ,dissolve the precipitate off the filter with dilute ammonia1 and run the solution into the original beaker4 ,run in from a burette1 slowly and with stirring1 magnesia mixture1 using about #ae c4c4 for each #j4a gram of phosphoric oxide4 ,allow to stand for one hour4 ,the white crystalline precipitate contains the phosphorus as ammonium-magnesium phosphate4 ,phosphate of lead is decomposed by sulphuric acid2 the lead is converted into the insoluble lead sulphate1 and the phosphoric acid is dissolved4 ,phosphate of copper and phosphate of iron may be treated with sulphuretted hydrogen2 the former in an acid1 and the latter in an alkaline1 solution4 ,phosphate of alumina is generally weighed without separation of the alumina1 since this requires a fusion4 ,in all cases the aim is to get the phosphoric oxide either free1 or combined with some metal whose phosphate is soluble in ammonia4 ,joulie's method of separation is as follows3--,one to ten grams of the sample are treated with hydrochloric acid1 and evaporated to dryness with the addition 7if any pyrites is present7 of a little nitric acid4 ,the residue is taken up with hydrochloric acid1 cooled1 transferred to a graduated flask1 and diluted to the mark4 ,it is then shaken up1 filtered through a dry filter1 and a measured portion 7containing about #j4je gram of phosphoric acid7 transferred to a small beaker4 ,ten c4c4 of a citric-acid solution of magnesia#aaj is added1 and then an excess of ammonia4 ,if an immediate precipitate is formed1 a fresh portion must be measured out and treated with #bj c4c4 of the citrate of magnesia solution and with ammonia as before4 ,the beaker is put aside for from two to twelve hours4 ,the precipitate is then filtered off and washed with weak ammonia2 it contains the phosphorus as ammonium-magnesium phosphate4 ,,gravimetric ,,determination4 ,if the phosphate is not already in the form of ammonic-magnesic phosphate1 it is converted into this by the addition to its solution of an excess of ammonia and magnesia mixture4 ,in order to get the precipitate pure1 the magnesia mixture is run in gradually 7by drops7 from a burette1 with constant stirring4 ,a white crystalline precipitate at once falls1 if much phosphorus is present2 but1 if there is only a small quantity1 it may be an hour or two before it shows itself4 ,the solution is best allowed to rest for twelve or fifteen hours 7overnight7 before filtering4 ,the presence of tartaric acid should be avoided2 and the appearance of the precipitate should be crystalline4 ,the solution is decanted through a filter1 and the precipitate washed with dilute ammonia1 using as little as may be necessary4 ,the precipitate is dried1 transferred to a weighed ,berlin or platinum crucible2 the filter-paper is carefully burnt1 and its ash added to the precipitate1 which is then ignited1 at first gently over a ,bunsen burner1 and then more strongly over the blowpipe or in the muffle4 ,the residue is a white mass of magnesium pyrophosphate containing #bg4ib per cent4 of phosphorus1 or #fc4if per cent4 of phosphoric oxide4 ,,volumetric ,,method4 ,instead of separating and weighing this compound1 the phosphoric oxide in it can be determined by titration4 ,in many cases the ore may be dissolved and immediately titrated without previous separation4 ,it is better1 however1 to carry the separation so far as to get phosphoric acid1 an alkaline phosphate1 or the magnesia precipitate4 ,it may then be prepared for titration in the following way3--,the precipitate in the last case 7without much washing7 is dissolved in a little hydrochloric acid1 and the solution in any case rendered fairly acid4 ,dilute ammonia is added till it is just alkaline1 and then #e c4c4 of the sodic acetate and acetic acid mixture 7as described under the ,arsenic ,assay74 ,this should yield a clear distinctly-acid solution4 ,it is diluted to #ajj or #aej c4c41 heated to boiling1 and titrated with the uranium acetate solution1 using that of potassic ferrocyanide as indicator4 ,the standard solution required is made by dissolving #ce grams of uranium acetate in water with the aid of #be c4c4 of acetic acid1 and diluting to #a litre4 ,an equivalent solution of phosphoric oxide is made by dissolving #be4ba grams of crystallised hydric disodic phosphate 7,h,na#b,,po#d4ab;,h#b,o7 in water1 and making up to #a litre4 #ajj c4c4 will contain #j4e gram of phosphoric oxide 7,p#b,o#e71 or #j4bahc gram of phosphorus4 ,in making this solution1 transparent crystals only must be used4 ,the uranium acetate solution is only approximately equivalent to this1 so that its exact standard must be determined4 ,sodic ,acetate and ,acetic ,acid ,solution4--,it is the same as that described under ,arsenic4#aaa ,use #e c4c4 for each assay4 ,the following experiments show the effect of variation in the conditions of the titration3-- ,effect of ,varying ,temperature4--,the solution should be titrated while boiling4 ,this is especially necessary for the last few c4c4 in order to get a decided and fixed finishing point4 ,temperature #ae ,c4 #cj ,c4 #gj ,c4 #ajj ,c4 ,uranium required #ah4j c4c4 #ai4b c4c4 #ai4j c4c4 #ah4i c4c4 ,effect of ,varying ,bulk4-- ,bulk #ej4j c4c4 #ajj4j c4c4 #bjj4j c4c4 #cjj4j c4c4 ,uranium required #ah4h #ah4i #ai4j #ai4c ,variation in bulk affects the results2 therefore1 a constant bulk should be adhered to4 ,effect of ,varying ,sodium ,acetate and ,acetic ,acid ,solution4-- ,sodium acetate and acetic acid solution #j4j c4c4 #a4j c4c4 #e4j c4c4 #aj4j c4c4 #bj4j c4c4 ,uranium required #ah4i #ah4i #ai4j #ah4h #ag4e ,as in the titration with arsenates1 an excess is dangerous to the assay2 a definite quantity 7#e c4c47 should1 therefore1 be used4 ,effect of ,foreign ,salts4--,besides the sodium acetate1 c41 added1 the only salts likely to be present are those of ammonia and magnesia4 ,in three experiments1 in one of which no foreign salts were introduced1 while in the other two #e grams of ammonic chloride and of magnesium sulphate respectively were added1 there were required3-- ,with ammonic chloride #ah4h c4c4 ,uranium solution ,with magnesium sulphate #ai4j ,without foreign salts #ah4i ,effect of ,varying ,phosphate4-- ,phosphate solution added #aj4j c4c4 #bj4j c4c4 #ej4j c4c4 #ajj4j c4c4 ,uranium required #i4h #ah4i #dg4f #id4e ,the quantity of phosphoric oxide in the assay solution for the conditions of titration should not be much less than #j4je gram4 ,for smaller quantities the uranium solution should be diluted to half its strength1 and the assay solution concentrated by reducing its bulk to #ej c4c4 and using #b4e c4c4 of the sodium acetate and acetic acid solution4 ,determination of ,phosphoric ,oxide in ,apatite4--,weigh up #j4e gram of the dried and powdered sample1 and dissolve it in #e c4c4 of hydrochloric acid4 ,evaporate to a paste1 add #e c4c4 of the sodic acetate and acetic acid solution1 dilute to #ajj c4c4 with water1 boil1 and titrate with uranium acetate solution4 ,in an example1 #j4e gram of apatite required #cg4d c4c4 of uranium acetate solution 7standard equal to #j4ebia gram of phosphoric oxide74 ,the sample therefore contained #j4aigi gram of ,p#b,o#e1 equal to #ci4eh per cent4 ,determination of ,phosphoric ,oxide in an ,iron ,ore4--,take #aj grams1 boil with #ej c4c4 of hydrochloric acid1 and evaporate to a paste2 take up with #aj c4c4 of dilute hydrochloric acid1 and dilute with water to #djj c4c4 ,pass sulphuretted hydrogen for nearly a quarter of an hour2 warm1 and filter4 ,boil off the excess of gas2 cool1 add ammonia till nearly neutral1 and then a few drops of ferric chloride solution1 and #d or #e grams of sodium acetate1 with a drop or two of acetic acid4 ,boil and filter4 ,dissolve the precipitate in hot dilute hydrochloric acid1 and add citro-magnesia mixture and ammonia2 allow to stand overnight2 filter1 ignite1 and weigh4 ,in an example1 #aj grams of ore gave #bh4e milligrams of magnesic pyrophosphate1 which is equivalent to #j4ah per cent4 of phosphoric oxide4 ,determination of ,phosphorus in ,iron4--,take from #b to #aj grams 7according to the amount of phosphorus present71 and dissolve in aqua regia1 keeping the nitric acid in excess2 evaporate to dryness and take up with hydrochloric acid1 boil1 dilute1 and filter4 ,add #aj c4c4 of nitric acid1 nearly neutralise with ammonia1 render acid with #c or #d c4c4 of nitric acid1 and add #aj or #bj c4c4 of ammonic molybdate solution4 ,heat for some time1 allow to settle1 filter1 and wash the precipitate with a solution of ammonic nitrate4 ,dissolve the precipitate in dilute ammonia1 nearly neutralise with dilute hydrochloric acid1 and add first magnesia mixture1 and then ammonia2 allow to stand overnight2 filter1 wash with dilute ammonia1 dry1 ignite1 and weigh as magnesic pyrophosphate4 ,calculate to phosphorus4 ,,practical ,,exercises4 #a4 ,ten grams of an iron yielded #ab milligrams of pyrophosphate of magnesia4 ,what percentage of phosphorus did the metal contain8 #b4 ,ten grams of an iron ore gave #ab milligrams of pyrophosphate4 ,what percentage of phosphoric oxide did it contain8 #c4 ,what weight of apatite #c;,ca#c7,,po#d7b4;,ca,cl,f would require #ej c4c4 of standard uranium solution 7#ajj c4c4 equal to #j4e gram of ,p#b,o#e78 #d4 ,you have reason to believe that a precipitate which has been weighed as magnetic pyrophosphate contains some arsenate4 ,how would you determine the amount of phosphate really present8 #e4 ,twenty c4c4 of a solution of sodic phosphate containing #j4ajj gram of ,p#b,o#e was found to require a solution containing #j4gjj gram of hydrated uranium acetate in a titration4 ,the precipitate contains #hj4ji per cent4 uranium oxide and #ai4ia per cent4 of phosphoric oxide4 ,what percentage of uranium oxide was contained in the uranic acetate8 ,,nitrogen ,,and ,,nitrates4 ,nitrogen occurs in nature in the free state1 and forms about four-fifths of the atmosphere4 ,in combination1 as nitrate1 it is found in nitre 7,,kno#c71 and ,chili saltpetre 7,na,n,o#c71 minerals which have a commercial importance4 ,the latter occurs in beds1 and is extensively worked for use as a manure and in the preparation of nitric acid4 ,nitrogen is mainly characterised by negative properties1 although many of its compounds are very energetic bodies4 ,it is a gas1 present everywhere1 but so inactive that the assayer can always afford to ignore its presence1 and1 except in testing furnace gases1 c41 he is never called on to determine its quantity4 ,the nitrates are an important class of salts1 and may be looked on as compounds of the bases with nitric pentoxide 7,n#b,o#e74 ,they are1 with the exception of a few basic compounds1 soluble in water1 and are remarkable for the ease with which they give up their oxygen4 ,the alkaline nitrates fuse readily1 and lose oxygen with effervescence forming nitrites2 while at a higher temperature they yield more oxygen and lose their nitrogen1 either as a lower oxide or as nitrogen4 ,the nitrates of the metals1 on heating1 leave the oxide of the metal4 ,it is as yielders of oxygen that nitrates are so largely used in the manufacture of explosives4 ,gunpowder contains from #fe to #ge per cent4 of potassium nitrate 7nitre74 ,nitrates are best detected and determined by their yielding nitric oxide when treated with sulphuric acid and a suitable reducing agent1 such as ferrous sulphate1 mercury1 or copper4 ,nitric oxide is a colourless gas very slightly soluble in water4 ,it combines at once with oxygen1 on mixing with the air1 to form brown nitrous fumes1 and dissolves in a solution of ferrous sulphate1 producing a characteristic blackish-brown colour4 ,it is this colour which affords the best and most easily-applied test for nitrates4 ,the substance suspected to contain nitrates is dissolved in about #a c4c4 of water1 and treated with an equal volume of strong sulphuric acid4 ,after cooling1 a solution of ferrous sulphate is poured on its surface1 so as to form a layer resting on it4 ,on standing1 a brown or black ring is developed where the liquids join1 if any nitrate or nitrite is present4 ,nitrites are distinguished from nitrates by effervescing and yielding brown fumes when treated with a little dilute sulphuric acid4 ,the separation of nitrates is in many cases difficult4 ,generally1 on treating the substance with water1 the nitrate will be in the solution1 and is filtered off from any insoluble matter4 ,in the exceptional cases it is got into solution by treating with a boiling solution of sodium carbonate2 the nitrate will contain it as an alkaline nitrate4 ,since1 however1 in their determination1 nitrates are never separated and weighed as such1 the difficulty of separating them has little importance4 ,usually1 the determination can be made on the original aqueous solution1 and it is never necessary to do more than remove any special substance which has a bad effect2 and this is easily done by the usual reagents4 ,,gravimetric ,,determination4 ,it follows from what has been said that there is no direct gravimetric determination4 ,the percentage of nitrogen pentoxide 7,n#b,o#e7 in a comparatively pure nitrate is sometimes determined indirectly in the following way3--,place in a platinum-crucible #d or #e grams of powdered and cleaned quartz4 ,ignite1 cool in a desiccator1 and weigh with the cover4 ,mix #a gram of the dried and powdered salt with the quartz in the crucible by stirring with a stout platinum-wire4 ,cover the crucible1 and heat in a ,bunsen-burner flame at scarcely visible redness for half-an-hour4 ,cool and weigh4 ,the loss in weight gives the amount of nitrogen pentoxide4 ,sulphates and chlorides in moderate quantity do not interfere4 ,the following is an example of the process3-- ,crucible and sand #bf4fdhe grams ,nitre taken #a4jjjj ------- #bg4fdhe ,weight after ignition #bg4aafj ------- ,loss on ignition #j4ecbe ,this is equal to #ec4be per cent4 of nitrogen pentoxide4 ,,volumetric ,,determination4 ,this is based on the oxidising action of nitric acid1 or of nitrates in acid solutions on ferrous salts4 ,the pentoxide 7,n#b,o#e7 of the nitrate is reduced to nitric oxide 7,,no71 so that #ccf parts of iron peroxidised represent #ajh parts of nitric pentoxide as oxidising agent4#aab ,the quantity of iron peroxidised is determined by taking a known quantity of ferrous salt1 oxidizing with a weighed sample of nitrate1 and then determining the residual ferrous iron by titration with bichromate or permanganate of potassium solution4 ,the difference between the ferrous iron taken and that found1 gives the amount oxidized by the nitrate4 ,the speed with which nitric oxide takes up oxygen from the air1 and thus becomes capable of oxidising more iron1 renders some precautions necessary2 ferrous chloride should1 therefore1 be used1 since it is easier to expel nitric oxide 7by boiling7 from solutions of a chloride than it is from those of a sulphate4 ,the process is as follows3--,dissolve #b grams of thin soft iron wire in #ej c4c4 of hydrochloric acid in a flask provided with an arrangement for maintaining an atmosphere of carbon dioxide4 ,when the iron has dissolved1 allow the solution to cool1 and add #j4e gram of the nitrate4 ,heat gently for a few minutes1 and then boil until the nitric oxide is expelled4 ,an atmosphere of carbon dioxide must be kept up4 ,dilute with water1 and titrate the residual iron with standard solution of bichromate of potassium4 ,the standard bichromate is made by dissolving #ag4e grams of the salt 7,k#b;,cr#b,o#g7 in water1 and diluting to #a litre3 #ajj c4c4 equal #b grams of iron4 ,deduct the weight of iron found from the #b grams originally taken1 and multiply by #j4cbad4 ,this gives the weight of the pentoxide in the sample4 ,in an example1 #j4e gram of nitre was taken1 and #ei4d c4c4 of the bichromate solution were required4 ,the #ei4d c4c4 thus used are equivalent to #a4aih gram of iron4 ,this leaves #j4hbb gram as the quantity oxidised by the nitre1 which1 multiplied by #j4cbad1 gives #j4bfdb gram for the nitrogen pentoxide1 or #eb4h per cent4 ,,gasometric ,,method4 ,this is based upon the measurement of the nitric oxide evolved on shaking up a weighed quantity of the nitrate with sulphuric acid over mercury in a nitrometer4 ,each c4c4 of nitric oxide obtained1 when reduced to normal temperature and pressure1 is equivalent to3-- #j4fbg milligram of nitrogen4 #a4cdc of nitric oxide4 #b4dah of nitric pentoxide4 #b4hbj of nitric acid4 #c4hje of sodium nitrate4 #d4ebc of potassium nitrate4 ,in working on substances not rich in nitrates1 an ordinary nitrometer 7fig4 #fi7 is used2 but in the assay of sodium nitrate1 nitroglycerine1 c41 an instrument provided with a bulb having a capacity of #ajj c4c4 is employed4 ,illustration3 ,,fig4 #fi4 ,the plan of working is as follows3--,the measuring tube is filled with mercury until it reaches up into the tap1 and the levelling-tube is placed so that it contains an inch or two of mercury4 ,if the nitrate is in solution1 #b or #c c4c4 of the liquid 7dilute liquids are brought to this bulk by evaporation7 are measured into the cup4 ,the levelling-tube is lowered a little1 and the tap cautiously opened until all but the last drop of the liquid has run in4 ,the cup is then rinsed with #b or #c c4c4 of sulphuric acid1 which is run in in the same way1 and the operation is repeated with another lot of acid4 ,the measuring-tube is now taken from the clamp1 and shaken for two or three minutes1 until no more gas is given off4 ,it is replaced1 and the mercury-level in the two tubes adjusted4 ,then it is allowed to stand until the froth has subsided1 and the gas has cooled to the temperature of the room4 ,the volume of the gas is then read off4 ,in adjusting the level1 account must be taken of the sulphuric acid in the measuring-tube2 this is allowed for by having the mercury higher in the other tube by1 say1 #a mm4 for each #f4e mm4 of sulphuric acid1 or it is counterpoised by an equal height of sulphuric acid in the levelling-tube1 in which case the two mercury-levels are made to correspond4 ,on opening the tap after reading off the volume1 there should be no change in the level of the mercury4 ,if it should rise or fall a little1 a slight increase or decrease 7say #j4a c4c47 is made to the volume previously read off4 ,in working with nitrate of soda1 c41 in the bulb nitrometer1 it is necessary to take a quantity of the substance which will yield more than #ajj and less than #aej c4c4 of the gas4 ,,footnotes3 #ajc ,na#c;,as,o#c ,h#b,o #b;,i ,na#c;,as,o#d #b;,,hi4 ,the acid is at once neutralised4 #ajd ,mr4 ,thomas ,gibb is the originator of this ingenious process4 #aje ,by taking hold of the water present1 it may prevent the dissociation of arsenious chloride4 #ajf ,it is difficult to get ferric chloride free from arsenic2 but the following treatment will remove #hj or #ij per cent4 of the arsenic contained in the commercial material3--,dissolve #b or #c lbs4 of ferric chloride with the smallest amount of water that will effect solution with the addition of #ajj c4c4 of hydrochloric acid2 add a solution of sulphurous acid in quantity sufficient to reduce #b or #c per cent4 of the iron to the ferrous state2 allow to stand a week2 and then boil1 to remove the hydrochloric acid added4 ,nitric acid1 which is prejudicial1 is also removed by this treatment4 #ajg ,when the amount of arsenic to be estimated is small 7as in refined coppers71 it is better to use a weaker solution of iodine4 ,this is made by diluting #bjj c4c4 of the standard solution with water to #a litre4 ,each c4c4 will equal #j4a per cent41 if #a gram of the metal has been taken for the assay4 #ajh ,the constitution of these phosphates may be thus illustrated-- ,magnesic meta-phosphate ,mg,o4,p#b,o#e4 ,magnesic pyro-phosphate #b,mg,o4,p#b,o#e4 ,magnesic ortho-phosphate #c,mg,o4,p#b,o#e4 #aji ,the composition of which is-- ,mo,o#b #ij4gd1 ,p#b,o#e #c4ad1 7,,nh#d7b,o #c4eg1 ,h#b,o #b4ee #ajj4jj4 #aaj ,this is made by adding #bg grams of magnesium carbonate 7a little at a time7 to a solution of #bgj grams of citric acid in #cej c4c4 of warm water2 and1 when dissolved1 adding #djj c4c4 of dilute ammonia1 and making up the bulk to #a litre2 #bj c4c4 of the solution is sufficient for #j4a gram of ,p#b,o#e1 although more will be required if much iron or alumina is present4 #aaa ,for the details of the titration1 the student is referred to the same place4 #aab ,n#b,o#e #f;,fe,o #c;,fe#b,o#c #b,,no4 ,,chapter ,,xviii4 ,,silicon1 ,,carbon1 ,,boron4 ,,silicon ,,and ,,silicates4 ,in assaying1 more especially products direct from the mine1 there is always found1 when the rock is siliceous1 a quantity of white sandy-looking substance1 insoluble in acids1 which is sometimes accompanied by a light gelatinous material very difficult to filter4 ,this is variously described as insoluble1 sand1 insoluble silicates1 gangue1 or rocky matter4 ,it may be pure quartz2 but oftener it is mixed with silicates from the rock containing the mineral4 ,some silicates1 but not many1 are completely decomposed by boiling with hydrochloric acid or aqua regia2 and others are partly so1 they yield a gelatinous precipitate of silica which greatly interferes with the filtering4 ,it is a common practice with assayers to carry the first attack of the sample with acids to dryness1 and to take up with a fresh portion of acid4 ,by this means the separated silica becomes granular and insoluble1 and capable of being filtered off and washed with comparative ease4 ,this residue may be ignited and weighed2 and be reported as so much per cent4 of silica and silicates insoluble in acids4 ,unless specially wanted1 a determination of its constituents need not be made4 ,when required1 the analysis is best made on the ignited residue1 and separately reported as analysis of the insoluble portion4 ,silicon only occurs in nature in the oxidised state2 but the oxide generally known as silica 7,si,o#b7 is common1 being represented by the abundant minerals--quartz1 flint1 c4 ,silica1 combined with alumina1 lime1 oxide of iron1 magnesia and the alkalies1 forms a large number of rock-forming minerals4 ,most rock masses1 other than limestones1 contain over #ej per cent4 of silica4 ,the following are analyses of some of the commoner silicates2 but it must be noted that these minerals often show great variation in composition4 ,this is more especially true of chlorite1 schorl1 hornblende and augite4 ,table has been split into two because of its width--,transcriber ---------------------------------------- --------------------------------- ,ferric ,ferrous ,silica ,alumina ,oxide1 ,oxide1 ,fluorine1 ,si,o#b4;,al#b,o#c4;,fe#b,o#c4 ,fe,o4 ,water c4 ---------------------------------------- --------------------------------- ,potash-felspar #fe4b #ah4b #j4b -- ,soda-felspar #fg4j #ai4b -- #j4c ,lime-felspar #dc4c #ce4d -- #a4c ,potash-mica #de4g #cc4g #c4a -- ,f 7#j4h7 ,h#b,o 7#d4i7 ,magnesia-mica #ci4a #ae4d #g4a -- ,f 7#j4g7 ,hornblende #dj4f #ad4c #e4h #g4b ,augite #ej4j #c4g #b4d #f4f ,mn,o 7#j4a7 ,almandine 7,garnet7 #ci4g #ai4g -- #ci4g ,mn,o 7#a4h7 ,chlorite 7,peach7 #cb4a #ah4e -- -- ,h#b,o 7#ab4a7 ,schorl #cg4j #cc4a #i4c #f4b ,b#b,o#c 7#g4g7 ,f 7#a4e7 ,china-clay #df4g #ci4f -- -- ,h#b,o 7#ac4d7 ,talc #fa4g -- -- #a4g ,h#b,o 7#c4h7 ,serpentine #db4i -- -- #c4h ,h#b,o 7#ab4f7 ,olivine #ci4c -- -- #ad4h ---------------------------------------- --------------------------------- ---------------------------------------- ------------------------------ ,lime1,magnesia,potash ,soda1 ,fluorine1 ,ca,o4 ,mg,o4 ,k#b,o4,na#b,o4 ,water1 c4 ---------------------------------------- ------------------------------ ,potash-felspar -- -- #ad4g #a4e ,soda-felspar #a4b #a4h #b4b #g4b ,lime-felspar #ag4d #j4ce #j4e #j4i ,potash-mica -- #a4a #g4e #b4h ,f 7#j4h7 ,h#b,o 7#d4i7 ,magnesia-mica -- #bc4f #g4e #b4f ,f 7#j4g7 ,hornblende #ab4e #ad4j #a4e #a4f ,augite #bb4h #ac4e -- -- ,mn,o 7#j4a7 ,almandine 7,garnet7 -- -- -- -- ,mn,o 7#a4h7 ,chlorite 7,peach7 -- #cf4g -- -- ,h#b,o 7#ab4a7 ,schorl #j4e #b4f #j4g #a4d ,b#b,o#c 7#g4g7 ,f 7#a4e7 ,china-clay -- -- -- -- ,h#b,o 7#ac4d7 ,talc -- #ca4g -- -- ,h#b,o 7#c4h7 ,serpentine -- #dj4e -- -- ,h#b,o 7#ab4f7 ,olivine -- #de4h -- -- ---------------------------------------- ------------------------------ ,silicon1 from a chemical point of view1 is an interesting body4 ,it combines with iron to form a silicide2 and is present in this condition in cast iron4 ,only in the case of the analysis of this and similar substances is the assayer called on to report the percentage of silicon4 ,silicon is readily converted into silica by the action of oxidizing agents4 ,silica forms only one series of salts--the silicates--which have in many cases a complex constitution2 thus there are a large number of double silicates1 which vary among themselves1 not only in the relation of base to acid 7which is the essential difference71 but also in the ratio of the bases between themselves 7which varies with almost every specimen74 ,silica is detected by heating the substance with a fluoride and sulphuric acid in a platinum-crucible4 ,on holding a rod1 moistened with a drop of water1 over the escaping fumes1 the white crust of silica formed on the drop of water shows its presence4 ,the insolubility of a fragment of the mineral in a bead of microcosmic salt1 is also a very good test2 the fragment1 on prolonged heating1 does not lose its angular form4 ,there is no dry assay for this substance1 nor volumetric method2 when the determination is required1 it is carried out gravimetrically and1 generally1 by the following plan4 ,if the sample contains oxides1 sulphides1 c41 in any quantity1 these are first dissolved out by treatment with acid1 evaporated to dryness1 taken up with hydrochloric acid1 and filtered4 ,the dried residue is treated in the same way as the silicates4 ,some silicates are completely decomposed by such treatment2 but it saves time 7unless one is sure that no undecomposable silicate is present7 to treat these in the same way as the others4 ,on the other hand1 there are some silicates which are only attacked with difficulty even by fusion with alkaline carbonates2 consequently1 it is always well to have the substance reduced to the finest state of division by careful powdering1 as this greatly assists the subsequent action4 ,with very hard silicates1 the grinding away of the mortar in this operation will be perceptible2 the foreign matter thus introduced must not be ignored4 ,previously igniting the substance sometimes assists the powdering2 but it is best to use a steel mortar4 ,the particles of steel can be removed by a magnet1 or1 where the nature of the substance will allow it1 by boiling with a little dilute hydrochloric acid4 ,the dried and powdered material is intimately mixed with four times its weight of fusion mixture in a platinum-crucible or dish4 ,it is then moderately heated over a ,bunsen burner1 and afterwards more strongly fused over a blast1 or enclosed in a clay crucible in the wind-furnace4 ,the action is continued until the fused mass is perfectly tranquil4 ,with very refractory substances1 the action must be long continued at a high temperature4 ,when sufficiently cold1 the crucible is examined to see that no particles of foreign matter are adhering to its outer surface4 ,it is then transferred to a five- or six-inch evaporating-dish1 where its contents are acted upon with warm water for some time4 ,the melt will slowly dissolve1 but the solution should be hastened by keeping the liquid moderately acid with hydrochloric acid4 ,when the melt has dissolved1 clean and remove the platinum-dish1 and evaporate the solution to a paste4 ,continue the evaporation to dryness on a water-bath 7not on the hot plate71 and whilst drying stir with a glass rod1 feeling at the bottom of the dish for any unfused particles1 which1 if present1 can be detected by their grittiness4 ,if there is much grit1 it will be necessary to repeat the assay2 but with a small quantity it will only be necessary to refuse the grit and silica after ignition4 ,during solution of the melt and evaporation 7which may be carried on together71 a clear solution will not be obtained1 a flocculent silica will separate out1 and towards the end of the evaporation the mass will get gelatinous4 ,the drying of the jelly must be finished on the water-bath2 first1 because at this temperature the silica is rendered insoluble in hydrochloric acid1 whilst the solubility of the alumina1 iron1 c41 is unaffected1 which would not be the case at a much higher temperature2 and second1 because the gelatinous residue requires very cautious drying to prevent loss from spirting4 ,when dry1 the substance is moistened1 and heated with strong hydrochloric acid1 and the sides of the dish are washed down with water4 ,the silica is washed by decantation two or three times with hydrochloric acid and hot water1 before being thrown on to the filter4 ,the filtrate is again evaporated to dryness1 taken up with a little hydrochloric acid and water and again filtered4 ,the residue on the filter is silica4 ,the two lots of silica are washed free from chlorides with hot water1 dried on an air-bath1 transferred to a platinum-crucible1 ignited gently at first1 at last strongly over the blast or in a muffle1 cooled in a desiccator1 and weighed4 ,the white powdery precipitate is silica 7,si,o#b71 and its weight1 multiplied by #ajj1 and divided by the weight of ore taken1 gives the percentage of silica in the sample4 ,where the percentage of silicon is wanted1 which is very rarely the case1 it is got by multiplying this result by #j4dffg4 ,it is always necessary to examine the purity of the body weighed as silica4 ,this is done by re-fusing the material weighed1 and re-determining the silica in it2 or1 better1 by mixing a weighed portion in a platinum-dish with a little strong sulphuric acid1 covering with hydrofluoric acid1 and evaporating4 ,in the latter case1 the silica will be converted into fluoride1 which will be driven off1 and the impurities will be left behind as sulphates of barium1 phosphate and oxide of tin1 titanium1 c4 ,this must be weighed and deducted from the weight of the silica4 ,in a complete examination of a silicate it should be treated with the precipitate containing alumina1 ferric oxide1 c4 ,,examination ,,of ,,silicates4 ,the student interested in the analysis of rocks and rock-forming minerals is advised to consult a valuable paper by ,dr4 ,w4,f4 ,hillebrand in the ,bulletin of the ,united ,states ,geological ,survey1 ,no4 #adh1 to which ,i am very largely indebted in the revision of the following pages4 ,moisture4--,five grams of the powdered sample is dried between watch-glasses in the water-oven for two hours1 or till its weight is constant2 and the loss is reported as water lost at #ajj ,c4 ,the rest of the determinations are made on this dried mineral4 ,combined ,water1 c4--,weigh up #a gram of the substance1 and ignite over the blowpipe for some time in a platinum-crucible1 cool in a desiccator1 and weigh4 ,record the loss as loss on ignition1 not as combined water4 ,silica4--,the ignition should have been performed in an oxidising atmosphere in a muffle or over a slanting blowpipe flame2 this will ensure the oxidation of any pyrites or other sulphide present1 which if unoxidised would injure the crucible in the next operation4 ,the ignited residue is mixed with #f or #g grams of anhydrous sodium carbonate4 ,this reagent should be the purest obtainable1 but its purity should be checked1 or rather its impurities should be determined by running a check or blank assay with #aj grams of it through the stages of the analysis2 the impurities will be chiefly silica1 alumina and lime1 and altogether they ought not to exceed #a milligram4 ,the crucible with the mixture is heated at first gently over a ,bunsen and afterwards more strongly in an oxidising atmosphere in a muffle or over the blowpipe4 ,the fused mass is allowed to cool in the crucible1 and is then dissolved out in a basin with water and a small excess of hydrochloric acid4 ,after the removal and cleaning of the crucible1 the liquor is evaporated almost to dryness4 ,dr4 ,hillebrand advises stopping short of complete dryness4 ,the residue is taken up with a little hydrochloric acid and water and filtered and washed4 ,the liquor1 including the washings1 is again evaporated and taken up with water and a little acid4 ,usually about #a per cent4 of silica will be thus recovered4 ,it is to be filtered off and washed and added to the main silica4 ,the filtrate is reserved4 ,the silica1 thoroughly washed1 is dried and ignited at a high temperature for twenty or thirty minutes4 ,it is then weighed in a platinum crucible4 ,after weighing it is treated with hydrofluoric acid and a little sulphuric1 carefully evaporated and ignited strongly4 ,the residue1 which in extreme cases may amount to #b or #c per cent4 of the rock1 is weighed and deducted from the weight of the impure silica4 ,it is retained in the crucible4 ,alumina1 c4--,the filtrate from silica is treated by the basic acetate method4 ,that is1 it is first treated by a cautious addition of a solution of soda1 almost to the point of producing a precipitate1 in order to neutralise the excess of acid2 #b or #c grams of sodium acetate are added1 and the whole boiled for a minute or so4 ,the precipitate is filtered off and washed only slightly4 ,save the filtrate4 ,the precipitate is dissolved in hydrochloric1 or1 perhaps better1 in nitric acid2 and is reprecipitated by adding an excess of ammonia and boiling4 ,the precipitate is filtered and washed with water containing #b per cent4 of ammonium nitrate4 ,both filtrates are evaporated separately to a small bulk1 a drop or two of ammonia being added to the second towards the finish4 ,they are next filtered into a #f or #h-ounce flask through a small filter1 the second filtrate coming after1 and serving in a manner as wash water for the first#aac4 ,the two washed alumina precipitates are dried and placed in the platinum crucible containing the residue from silica after treatment with hydrofluoric acid4 ,they are then ignited in an oxidising atmosphere at a high temperature for about #aj minutes4 ,the weight1 including that of the residue from the silica1 is noted as that of alumina1 c4 ,the weighed oxides are next fused with bisulphate of potash for some hours4 ,the bisulphate should have been first fused1 apart1 until the effervescence from the escape of steam has stopped4 ,the melt is dissolved out with cold water and dilute sulphuric acid1 and any insoluble residue is filtered off1 washed1 ignited and weighed4 ,the filtrate is reserved for determinations of iron and titanium4 ,the residue1 after weighing1 may be treated with hydrofluoric and sulphuric acids for any silica1#aad which would be determined by loss4 ,it may be tested for barium sulphate by treatment with hot strong sulphuric acid2 in which this salt dissolves1 but is again insoluble 7and so comes out as a white precipitate7 on diluting with cold water2 the acid also must be cold before adding the water4 ,the filtrate containing the iron is reduced with sulphuretted hydrogen1 boiled till free from that gas1 filtered and titrated with a standard solution of permanganate of potassium4 ,the iron found is calculated to ferric oxide by dividing by 4#g4 ,the iron solution after titration serves for the determination of titanium oxide 7,ti,o#b74 ,this is done colorimetrically1 by adding peroxide of hydrogen free from hydrofluoric acid1 and comparing the brown colour produced with that produced by the addition of a standard solution of titanium to an equal volume of water containing sulphuric acid4#aae ,the alumina is determined by difference4 ,from the weight of the combined precipitate which has been recorded as ,alumina1 c41 deduct 7#a7 the residue1 insoluble1 after fusion with bisulphate2 7#b7 the ferric oxide2 7#c7 the titanium oxide2 and 7#d7 the phosphoric oxide 7,p#b,o#e71 the amount of which is subsequently determined in a separate portion4 ,this gives the alumina4 ,manganous oxide1 c4--,the filtrate from the alumina1 c4 contained in a #f or #h-ounce flask1 which it nearly fills1 is made slightly alkaline with ammonia and treated with a small excess of ammonium sulphide2 the flask is then corked and placed on one side for some time 7a day or so7 so that the manganese sulphide may separate4 ,the precipitate is filtered off and washed with water containing ammonium chloride and a few drops of ammonium sulphide4 ,the filtrate is reserved for lime1 c4 ,the precipitate is digested with sulphuretted hydrogen water1 to which one-fifth of its volume of strong hydrochloric acid has been added2 this dissolves the sulphides of zinc and manganese2 any black residue should be tested for copper and perhaps nickel4 ,the solution is evaporated to dryness1 taken up with a little water and treated with a small excess of solution of carbonate of soda4 ,it is boiled and again evaporated1 washed out with hot water and filtered on to a small filter1 dried1 ignited1 and weighed as ,mn#c,o#d4 ,it is calculated to ,mn,o4 ,it may contain1 and should be tested for oxide of zinc1 which1 if present1 must be deducted4 ,if the dish becomes stained during evaporation1 take up with a few drops of hydrochloric and sulphurous acids1 evaporate1 and then treat with carbonate of soda4 ,lime1 c4--,the filtrate from the manganese sulphide is boiled1 and without cooling1 treated with ammonium oxalate in solution1 which also should be heated to boiling4 ,the liquid is filtered off and reserved for magnesia4 ,the precipitate is dissolved in very little hydrochloric acid and reprecipitated by adding ammonium oxalate and ammonia to the boiling solution4 ,the filtrate and washings from this are reserved for magnesia4 ,the precipitate is either dissolved in dilute sulphuric and titrated with permanganate of potash as described under ,lime 7p4 #cbb72 or it is ignited and weighed as oxide4 ,in this last case it may be examined for barium and strontium1 the former of which will rarely be present4 ,magnesia4--,the filtrate from the first lime precipitate is treated with sodium phosphate and ammonia1 and allowed to stand overnight4 ,it is then filtered4 ,the precipitate is dissolved in hydrochloric acid2 the solution is filtered into the beaker containing the solution from the second lime precipitate4 ,ammonia and sodium phosphate are again added1 and the precipitate1 after standing1 is filtered off1 washed with water containing ammonia2 it is then dried1 ignited and weighed as magnesium pyrophosphate4 ,this is calculated into magnesia4 ,potash and ,soda4--,weigh out 4#e gram of the dried ore1 and mix with an equal quantity of ammonic chloride2 and to the mixture add gradually #d grams of calcium carbonate 7precipitated74 ,introduce into a platinum-crucible and cover loosely4 ,heat1 at first1 gently2 and then at a red heat for from forty to sixty minutes4 ,transfer to a porcelain dish1 and digest with #fj or #hj c4c4 of water2 warm and filter3 to the filtrate add ammonic carbonate and ammonia1 and filter2 evaporate the filtrate to dryness1 adding a few drops more of ammonic carbonate towards the end2 when dry1 heat gently1 and then raise the temperature to a little below redness4 ,dissolve in a small quantity of water1 add a drop of ammonic carbonate1 and filter through a small filter into a weighed platinum dish4 ,evaporate1 ignite gently1 and weigh4 ,the residue contains the soda and potash of the mineral as chlorides4 ,to determine the proportion of potassium1 dissolve this residue in a little water1 add platinum chloride in excess1 evaporate to a paste1 extract with alcohol1 decant through a small weighed filter1 wash with alcohol1 and dry at #ajj ,c4 ,weigh4 ,the substance is potassium platinic chloride 7#b,k,cl4,pt,cl#d74 ,its weight1 multiplied by #j4aida1 will give the weight of potash 7,k#b,o74 ,to find the proportion of soda1 multiply the weight of the potassium platinic chloride by #j4cjf2 this gives the weight of potassium chloride4 ,deduct this from the weight of the mixed chlorides first got2 the difference will be the sodium chloride1 which weight1 multiplied by #j4ec1 will give the weight of soda 7,na#b,o74 ,ferrous ,oxide4--,when a qualitative test shows both ferric and ferrous oxide to be present1 the proportion of the ferrous oxide must be separately determined4 ,the finely ground mineral mixed with dilute sulphuric acid is treated on a water bath with hydrofluoric acid4 ,solution is best effected in an atmosphere of carbonic acid4 ,in about an hour the decomposition is complete1 and the solution is diluted with cold water1 and titrated with the solution of bichromate or of permanganate of potassium4 ,the iron found is multiplied by #a4bhf1 and reported as ferrous oxide4 ,to find the proportion of ferric oxide1 the ferrous iron found is multiplied by #a4dbh1 and this is deducted from the weight of ferric oxide obtained by precipitation with ammonia4 ,the ammonia precipitate contains the whole of the iron as ferric oxide2 hence the necessity for calculating the ferrous oxide as ferric1 and deducting it4 ,phosphoric ,oxide 7,p#b,o#e74--,weigh up #e grams of the finely-divided and dry sample1 and digest with #aj or #bj c4c4 of nitric acid2 evaporate to dryness on the water-bath2 take up with a little dilute nitric acid2 dilute with water2 and filter4 ,add a few grams of ammonic nitrate and #aj c4c4 of ammonium molybdate solution1 heat nearly to boiling1 and allow to settle2 filter off1 and wash the yellow precipitate4 ,dissolve with dilute ammonia1 add magnesia mixture1 and allow to stand overnight4 ,filter1 wash with dilute ammonia1 dry1 ignite1 and weigh as pyrophosphate of magnesia4 ,the weight1 multiplied by #j4fcif1 gives the weight of phosphoric oxide4 ,soluble ,silica4--,some silicates are acted on by hydrochloric acid1 and leave on evaporation a residue2 which1 when the soluble salts have been washed out1 consists generally of the separated silica with perhaps quartz and unattacked silicates4 ,it should be ignited1 weighed and boiled with a solution containing less than #aj per cent4 of caustic soda3 this dissolves the separated silica4 ,the liquor is diluted1 rendered faintly acid1 and filtered4 ,the residue is washed1 ignited and weighed4 ,the loss gives the soluble silica4 ,estimation of ,silica in ,slags 7,ferrous silicates74--,take #a gram of the powdered slag1 treat with aqua regia1 evaporate to dryness1 extract with hydrochloric acid1 filter1 dry1 ignite1 and fuse the ignited residue with fusion mixture1 then separate and weigh the silica in the usual way4 ,slags are for the most part decomposed by boiling with aqua regia1 but it will be found more convenient and accurate to first extract with acids and then to treat the residue as an insoluble silicate4 ,estimation of ,silica and ,insoluble ,silicates in an ,ore4--,take #b grams of the powdered mineral1 evaporate with nitric acid 7if sulphides are present71 treat the dried residue 7or the original substance if sulphides are absent7 with #aj or #bj c4c4 of hydrochloric acid2 again evaporate to dryness1 take up with dilute hydrochloric acid1 filter1 wash1 ignite1 and weigh4 ,estimation of ,silicon in ,iron4--,place #b grams of the metal 7borings or filings7 in a four-inch evaporating dish1 and dissolve 7with aid of heat7 in #be c4c4 of dilute nitric acid4 ,evaporate to complete dryness1 take up with #bj c4c4 of hydrochloric acid1 and allow to digest for one hour4 ,boil down to a small bulk1 dilute with a #e per cent4 solution of hydrochloric acid1 boil1 and filter4 ,wash with acid and water1 dry1 ignite in a platinum crucible1 and weigh the ,si,o#b4 ,this1 multiplied by #j4dfgc1 gives the weight of the silicon4 ,the percentage is calculated in the usual way4 ,,practical ,,exercises4 #a4 ,a certain rock is a mixture of #gj per cent4 of quartz1 #be per cent4 of potash-felspar1 and #e per cent4 of potash-mica4 ,what per cent4 of silica will it contain8 #b4 ,two grams of a mixture of silica and cassiterite left1 after reduction in hydrogen1 #a4gh grams4 ,assuming all the oxide of tin to have been reduced1 what will be the percentage of silica8 #c4 ,the formula of a compound is #b;,fe,o4,si,o#b4 ,what percentage of silica will it contain8 #d4 ,two grams of a sample of cast-iron gave #j4jbe gram of silica4 ,find the percentage of silicon in the metal4 #e4 ,what weights of quartz and marble 7,ca,c,o#c7 would you take to make #cj grams of a slag having the formula ,ca,o4,si,o#b8 ,,carbon ,,and ,,carbonates4 ,carbon compounds enter so largely into the structure of organised bodies that their chemistry is generally considered apart from that of the other elements under the head of ,organic ,chemistry4 ,carbon occurs1 however1 among minerals not only in the oxidised state 7as carbonates71 but also in the elementary form 7as in diamond and graphite71 and combined with hydrogen1 oxygen1 c4 7as in petroleums1 bitumens1 lignites1 shales1 and coals74 ,in small quantities organic matter is widely diffused in minerals and rocks4 ,in shales and clays it may amount to as much as #aj or #bj per cent4 7mainly as bituminous and coaly matters74 ,the assayer has only to take account of the organic matter when it is of commercial importance1 so that in assays it is generally included under loss on ignition4 ,in coals1 shales1 lignites1 c41 the carbon compounds are1 on heating1 split up into oils and similar compounds4 ,the products of distillation may be classified as water1 gas1 tars1 coke1 and ash4 ,the assay of these bodies generally resolves itself into a distillation1 and1 in the case of the shales1 an examination of the distillates for the useful oils1 paraffin1 creosote1 c41 contained in them4 ,elementary carbon is found in nature in three different forms1 but these all re-act chemically in the same way4 ,they combine with oxygen to form the dioxide4#aaf ,the weight of oxygen required to burn a given weight of any form of carbon is the same1 and the resulting product from all three has the same characteristic properties4 ,carbon dioxide is the common oxide of carbon4 ,a lower oxide exists1 but on burning it is converted into the dioxide4 ,wherever the oxidation of carbon takes place1 if there is sufficient oxygen1 carbon dioxide 7carbonic acid7 is formed2 this re-action is the one used for the determination of carbon in bodies generally4 ,the dioxide has acid properties1 and combines with lime and other bases forming a series of salts called carbonates4 ,the carbon-compounds 7other than carbonates1 which will be subsequently considered7 occurring in minerals are generally characterised by their sparing solubility in acids4 ,the diamond is distinguished from other crystals by its hardness1 lustre1 and specific gravity4 ,it may be subjected to a red heat without being apparently affected1 but at a higher temperature it slowly burns away4 ,graphite1 also1 burns slowly1 but at a lower temperature4 ,the other bodies 7coals1 shales1 c47 differ considerably among themselves in the temperature at which they commence to burn4 ,some1 such as anthracite1 burn with little or no flame1 but most give off gases1 which burn with a luminous flame4 ,they deflagrate when sprinkled on fused nitre1 forming carbonate of potash4 ,in making this test the student must remember that sulphur and1 in fact1 all oxidisable bodies similarly deflagrate1 but it is only in the case of carbon compounds that carbonate of potash is formed4 ,carbon unites with iron and some of the metals to form carbides2 combined carbon of this kind is detected by the odour of the carburetted hydrogen evolved when the metal is treated with hydrochloric acid2 for example1 on dissolving steel in acid4 ,the natural carbon compounds1 although1 speaking generally1 insoluble in hydrochloric or nitric acids1 are more or less attacked by aqua regia4 ,the assayer seldom requires these compounds to be in solution4 ,the presence of organic matter#aag interferes with most of the reactions which are used for the determination of the metals4 ,consequently1 in such cases1 it should be removed by calcination unless it is known that its presence will not interfere4 ,when calcination is not admissible it may be destroyed by heating with strong sulphuric acid and bichromate or permanganate of potash or by fusion with nitre4 ,carbon may be separated from other substances by conversion into carbon dioxide by burning4 ,in most cases substances soluble in acids are first removed1 and the insoluble residue dried1 weighed1 and then calcined or burned in a current of air4 ,the quantity of organic matter may be determined indirectly by the loss the substance undergoes1 but it is better to determine the organic carbon by confining the calcination in a tube1 and collecting and weighing the carbon dioxide formed4 ,each gram of carbon dioxide is equivalent to #j4bgbg gram of carbon4 ,illustration3 ,,fig4 #gj4 ,illustration3 ,,fig4 #ga4 ,instead of a current of oxygen or air1 oxide of copper may be more conveniently used4 ,the operation is as follows3--,take a clean and dry piece of combustion tube drawn out and closed at one end1 as shown in the figure 7fig4 #gj71 and about eighteen inches long4 ,fit it with a perforated cork connected with a ,u-tube 7containing freshly-fused calcium chloride in coarse grains7 and a set of potash bulbs 7fig4 #ga7 7containing a strong solution of potash71 the exit of which last is provided with a small tube containing calcium chloride or a stick of potash4 ,both the ,u-tube and bulbs should have a loop of fine wire1 by which they may be suspended on the hook of the balance for convenience in weighing4 ,they must both be weighed before the combustion is commenced2 to prevent absorption of moisture during weighing1 c41 the ends are plugged with pieces of tube and glass rod4 ,fill the combustion tube to a depth of about eight inches with some copper oxide1 which has been recently ignited and cooled in a close vessel4 ,put in the weighed portion for assay and a little fresh copper oxide1 and mix in the tube by means of an iron wire shaped at the end after the manner of a corkscrew4 ,put in some more oxide of copper1 and clean the stirrer in it4 ,close loosely with a plug of recently ignited asbestos1 place in the furnace1 and connect the ,u-tube and bulbs in the way shown in the sketch 7fig4 #gb74 ,illustration3 ,,fig4 #gb4 ,see that the joints are tight1 and then commence the combustion by lighting the burners nearest the ,u-tube2 make the first three or four inches red hot1 and gradually extend the heat backwards the length of the tube1 but avoid too rapid a disengagement of gas4 ,when gas ceases to come off1 open the pointed end of the tube and draw a current of dried air through the apparatus4 ,the carbon dioxide is absorbed in the potash bulbs1 and their increase in weight multiplied #j4bgbg gives the amount of carbon in the substance taken4 ,the increase in weight in the calcium chloride tube will be due to the water formed by the oxidation of the combined hydrogen4 ,if this last is required the increase in weight multiplied by #j4aaa gives its amount4 ,,coals4 ,the determination of the actual carbon in coals and shales is seldom called for2 if required1 it would be performed in the way just described4#aah ,the ordinary assay of a sample of coal involves the following determinations--moisture1 volatile matter1 fixed carbon1 ash1 and sulphur4 ,these are thus carried out3-- ,determination of ,moisture4--,take #c grams of the powdered sample and dry in a water-bath for an hour or so4 ,the loss is reported as moisture4 ,coals carry from #a to #b per cent4 ,if the drying is carried too far1 coals gain a little in weight owing to oxidation1 so that it is not advisable to extend it over more than one or two hours4 ,determination of ,volatile ,matter4--,this determination is an approximate one1 and it is only when working under the same conditions with regard to time1 amount of coal taken1 and degree of heat used1 that concordant results can be arrived at4 ,it is a matter of importance whether the coal has been previously dried before heating or not1 since a difference of #b per cent4 may be got by working on the dried or undried sample4 ,take #b grams of the powdered1 but undried1 sample of coal1 place in a weighed platinum crucible1 and support this over a good ,bunsen burner by means of a thin platinum-wire triangle4 ,the heat is continued until no further quantity of gas comes off and burns at the mouth4 ,this takes only a few minutes4 ,the cover is tightly fitted on1 and when cold the crucible is weighed4 ,the loss in weight1 after deducting the moisture1 gives the volatile matter1 and the residue consists of fixed carbon and ash4 ,determination of ,ash4--,the coke produced in the last operation is turned out into a porcelain dish and ignited over a ,bunsen burner till the residue is free from particles of carbon4 ,calcination is hastened by stirring with a platinum wire4 ,the operation may be done in a muffle1 but this gives results a few tenths of a per cent4 too low4 ,the dish is cooled in a dessicator1 and weighed4 ,the increase in weight gives the amount of ash1 and the difference between this and the weight of the coke gives the fixed carbon4 ,the assay is reported as follows3-- ,moisture at #ajj ,c4 ---- per cent4 ,volatile matter ---- ,fixed carbon ---- ,ash ---- contains sulphur ---- per cent4 ,determination of ,sulphur4--,the sulphur exists in the coal partly in organic combination1 partly as metallic sulphide 7iron pyrites1 marcasite1 c471 and1 perhaps1 as sulphate4 ,so that the sulphur determination must be separately reported1 since a portion will go off with the volatile matter1 and the remainder would be retained and weighed with the coke4 ,the sulphur is thus determined3--,take #a gram of the coal and mix with #a4e gram of a mixture of #b parts of calcined magnesia and #a part of carbonate of soda1 and heat in a platinum crucible for one hour or until oxidation is complete4 ,turn out the mass and extract it with water and bromine1 filter1 acidulate with hydrochloric acid1 boil off the bromine1 and precipitate with baric chloride 7estimating gravimetrically as given under ,sulphur74 ,another method is as follows3--,take #a gram of the coal and drop it gradually from a sheet of note paper on to #e grams of fused nitre contained in a platinum dish4 ,extract with water1 acidify with acetic acid1 and estimate volumetrically as described under ,sulphur4 ,illustration3 ,,fig4 #gc4 ,calorific ,effect of ,coals4--,the heat-giving value of a coal is best expressed in the number of pounds of water1 previously heated to the boiling point1 which it will convert into steam4 ,this is generally termed its evaporative-power4 ,it may be determined by means of the calorimeter 7fig4 #gc74 ,this consists of a glass cylinder marked to hold #bi4jaj grains of water4 ,the instrument consists of a perforated copper stand1 provided with a socket and three springs4 ,the socket holds a copper cylinder which is charged with #cj grains of the dried coal mixed with #cjj grains of a mixture of #c parts of potassium chlorate and #a part of nitre4 ,the charge is well packed in the cylinder and provided with a small fuse of cotton saturated with nitre4 ,fill the glass cylinder to its mark with water and take the temperature with a thermometer marked in degrees ,fahrenheit4 ,ignite the fuse and immediately cover with the outer copper cylinder 7extinguisher-fashion71 which will be held in its place by the springs4 ,the stop-cock should be closed before this is done4 ,place the apparatus quickly in the cylinder of water4 ,when the action is over open the stop-cock and agitate the water by raising and lowering the instrument a few times4 ,again take the temperature4 ,the rise in temperature1 plus #aj per cent4 for the heat used in warming the apparatus and lost by radiation1 gives the evaporative-power4 ,the following is an example3-- ,temperature before experiment #fg4j ,f4 ,temperature after #gi4j -------- ,rise #ab4j #a_/ajth #a4b -------- ,gives #ac4b ,one pound of the coal will evaporate #ac4b pounds of water4 ,,shales1 ,,etc4 ,the assay of these is carried out in the same way as that of coals1 but the volatile matters are separately examined1 and1 in consequence1 a larger quantity of material must be used4 ,for the moisture1 volatile matter1 fixed carbon and ash1 the determinations are the same1 but a special distillation must be made to obtain a sufficient quantity of the volatile products for subsequent examination4 ,take #ejj or #ajjj grams of the well-sampled and powdered shale1 and introduce into a cast-iron retort as shown in fig4 #gd4 ,lute the joint with fire-clay1 place the cover on1 and bolt it down4 ,the bolts should have a covering of fire-clay to protect them from the action of the fire4 ,place the retort in a wind furnace1 supporting it on a brick1 and pack well around with coke4 ,build up the furnace around and over the retort with loose fire-bricks1 and heat gradually4 ,illustration3 ,,fig4 #gd4 ,as soon as water begins to drip1 the tube of the retort is cooled by wrapping a wet cloth around it1 and keeping wet with water4 ,the water is kept from running into the receiver by a ring of damp fire-clay4 ,a quantity of gas first comes over and will be lost1 afterwards water and oily matters4 ,the retort must be red hot at the close of the distillation1 and when nothing more distils off1 which occurs in about two or three hours1 the wet cloth is removed1 and the tube heated with a ,bunsen burner to drive forward the matter condensed in it into the receiver1 and thus to clean the tube4 ,it can be seen when the tube is clean by looking up through it into the red-hot retort4 ,the receiver is then removed1 and the retort1 taken from the furnace1 is allowed to cool4 ,when cold it is opened1 and the fixed carbon and ash weighed1 as a check on the smaller assay4 ,the distillate of water and oil is warmed1 and will separate into two layers1 the upper one of which is oil1 and the lower water4 ,these are measured1 and if the specific gravity of the oil is taken1 its weight may be calculated4 ,if the two liquids do not separate well1 the water may be filtered off1 after cooling1 through a damped filter4 ,the separation is1 however1 best effected in a separator 7fig4 #ge74 ,the liquids are poured into this1 allowed to settle1 and the lower layer drained off4 ,the volume of the water is measured and its weight calculated in per cents4 on the amount of shale taken4 ,illustration3 ,,fig4 #ge4 ,examination of the ,oil4--,a sufficient quantity of the oil must be got1 so that if one distillation does not yield enough1 the requisite quantity must be obtained by making two or more distillations4 ,the oils are mixed1 and the mixture1 after having had its volume and specific gravity ascertained1 is placed in a copper retort1 and re-distilled with the aid of a current of steam4 ,the residue in the retort is coke4 ,the distillate is separated from the water by means of the separator1 and shaken for ten minutes with one-twentieth of its bulk of sulphuric acid 7sp4 g4 #a4gj74 ,the temperature should not be allowed to rise above #dj4 ,allow to stand1 and run off the acid tar4 ,the oil is now shaken up with from #aj c4c4 to #bj c4c4 of sodic hydrate solution 7sp4 g4 #a4c71 allowed to stand1 warmed for half-an-hour1 and the soda-tar run off4 ,on mixing this soda-tar with dilute acid1 the crude shale oil creosote separates1 and is measured off4 ,the purified oil is next re-distilled in fractions1 which come over in the following order3--,naphtha1 light oil1 heavy oil1 and still bottoms4 ,for the first product1 which is only got from certain shales1 the receiver is changed when the distillate has a specific gravity of #j4gh4 ,for the second product the process is continued till a drop of the distillate1 caught as it falls from the neck of the retort on a cold spatula1 shows signs of solidifying4 ,this is crude light oil4 ,the receiver is changed1 and the heavy oil comes over2 towards the end a thick brown or yellow viscid product is got4 ,the receiver is again changed1 and the distillation carried to dryness4 ,the crude light oil is washed cold with #b per cent4 of sulphuric acid 7concentrated71 and afterwards with excess of soda4 ,thus purified it is again distilled to dryness1 three fractions being collected as before4 ,naphtha1 which is added to the main portion1 and measured2 light oil1 which is also measured2 and heavy oil1 which is added to that got in the first distillation4 ,this last is poured into a flat-bottom capsule1 and allowed to cool slowly4 ,the temperature may with advantage be carried below freezing-point4 ,the cooled cake is pressed between folds of linen1 and the paraffin scale detached and weighed4 ,the results may be reported thus3-- ,naphtha1 sp4 g4 ---- ,light oil1 sp4 g4 ---- ,heavy oil1 sp4 g4 ---- ,paraffin scale ---- ,coke1 c4 ---- ,the results are calculated in per cents4 on the oil taken4 ,some workers take their fractions at each rise of #ej ,c4 ,the composition of average shale1 as given by ,mills1 is as follows3--,specific gravity1 #a4hgg2 moisture1 #b4ed4 ,gas ,volatile matter1 water1 ammonia #bc4ec ,oil ,fixed carbon #ab4fi ,ash #fc4gd #ii4if ,the ash is made up of silica1 #ee4f2 ferric oxide1 #ab4b2 alumina1 #bb4ad2 lime1 #a4e2 sulphur1 #j4i2 soluble salts 7containing #j4ib per cent4 sulphuric oxide71 #h4c4 ,total sulphur in shale #a4h per cent4 in ash #a4c ,for further information on these assays1 and for the assay of petroleums1 bitumens1 c41 the student is referred to ,allen's ,commercial ,organic ,analysis1 ,vol4 ,,ii4 ,determination of ,organic ,carbon in a ,limestone4--,take #a or #b grams and dissolve with a very slight excess of dilute hydrochloric acid1 evaporate to dryness1 and determine the carbon in the residue by combustion with copper oxide4 ,estimation of ,carbon in a ,sample of ,graphite 7,black-lead74--,weigh up #a or #b grams in a dish and calcine in the muffle till the carbon is burnt off4 ,weigh the residue1 and calculate the carbon by difference4 ,illustration3 ,,fig4 #gf4 ,illustration3 ,,fig4 #gg4 ,illustration3 ,,fig4 #gh4 ,determination of ,carbon in ,iron4--,the carbon exists in two states--free 7graphite7 and combined4 ,the following process estimates the total carbon3--,the carbon existing as graphite may be separately estimated in another portion by the same process1 but using hydrochloric acid to dissolve the iron instead of the copper solution3--,weigh up #b grams of the iron 7or a larger quantity if very poor in carbon71 and attack it with #cj grams of ammonic-cupric chloride#aai dissolved in #ajj c4c4 of water4 ,let the reaction proceed for a quarter-of-an-hour1 and then warm until the copper is dissolved4 ,allow to settle1 and filter through a filtering-tube4 ,this is a piece of combustion tube drawn out and narrowed at one end1 as shown in fig4 #gf4 ,the narrow part is blocked with a pea of baked clay1 and on this is placed half-an-inch of silica sand 7previously calcined to remove organic matter71 then a small plug of asbestos1 and then a quarter-of-an-inch of sand4 ,the tube is connected with a pump working at a gentle pressure1 and the solution is filtered through the tube with the aid of a small funnel 7fig4 #gg74 ,the residue is washed1 first with dilute hydrochloric acid1 and then with distilled water4 ,the tube is dried by aspirating air through it1 and gently warming with a ,bunsen burner4 ,the tube is then placed in a small combustion-furnace1 and connected with calcium chloride and potash bulbs1 as shown in fig4 #gh4 ,the potash bulb to the right of the figure must be weighed4 ,a slow stream of air is drawn through the apparatus1 and the heat gradually raised2 in from thirty minutes to one hour the combustion will be complete4 ,the potash bulbs are then disconnected and weighed1 and the increase multiplied by #j4bgbg gives the weight of carbon4 ,,carbonates4 ,carbon dioxide1 which is formed by the complete oxidation of carbon1 is a gas with a sweetish odour and taste1 having a strong affinity for alkalies1 and forming a series of compounds termed carbonates4 ,the gas itself occurs in nature1 and is sometimes met with in quantity in mining4 ,the carbonates occur largely in nature1 forming mountain masses of limestone1 c4 ,carbonates of many of the metals1 such as carbonate of lead 7cerussite71 carbonate of iron 7chalybite71 carbonates of copper 7malachite and chessylite71 and carbonate of magnesia 7magnesite71 are common4 ,all the carbonates 7those of the alkalies and alkaline earths excepted7 are completely decomposed on ignition into the oxide of the metal and carbon dioxide2 but the temperature required for this decomposition varies with the nature of the base4 ,all carbonates are soluble with effervescence in dilute acids2 some1 such as chalybite and magnesite1 require the aid of heat4 ,the alkaline carbonates are soluble in water2 the rest1 with the exception of the bicarbonates1 are insoluble therein4 ,carbonates are recognised by their effervescence with acids--a stream of bubbles of gas are given off which collect in the tube1 and possess the property of extinguishing a lighted match4 ,the most characteristic test for the gas is a white precipitate1 which is produced by passing it into lime or baryta-water1 or into a solution of subacetate of lead4 ,the expulsion of carbon dioxide by the stronger acids serves for the separation of this body from the other acids and bases4 ,dry ,assay4--,there is no dry assay in use4 ,any method which may be adopted will necessarily be applicable only to special compounds4 ,,wet ,,methods4 ,there are several methods in use which leave little to be desired either in speed or accuracy4 ,we will give 7#a7 a gravimetric method in which the estimation may be made directly by weighing the carbonic acid1 or1 indirectly1 by estimating the carbon dioxide from the loss2 7#b7 a volumetric one1 by which an indirect determination is made of the gas2 and 7#c7 a gasometric method1 in which the volume of carbon dioxide given off is measured1 and its weight deducted4 ,illustration3 ,,fig4 #gi4 ,illustration3 ,,fig4 #hj4 ,direct ,gravimetric ,method4--,fit up the apparatus shown in the diagram 7fig4 #gi74 ,the various tubes are supported by a fixed rod with nails and wire loops1 and connected by short lengths of rubber-tubing4 ,the first tube contains soda-lime4 ,the small flask is fitted with a rubber-stopper perforated with two holes1 through one of which passes the tube of a pipette holding #be or #cj c4c4 ,this pipette is to contain the acid4 ,the substance to be determined is weighed out into the flask4 ,the second tube contains strong sulphuric acid2 the third1 pumice stone1 saturated with copper sulphate solution1 and dried until nearly white 7at #bjj ,c472 the fourth contains recently fused calcium chloride2 and the fifth1 which is the weighed tube in which the carbonic acid is absorbed1 contains calcium chloride and soda-lime1#abj as shown in fig4 #hj4 ,the sixth also contains calcium chloride and soda-lime2 its object is to prevent the access of moisture and carbonic acid to the weighed tube from this direction2 it is connected with an aspirator4 ,having weighed the ,u-tube and got the apparatus in order1 weigh up #a1 #b1 or #e grams of the substance and place in the flask4 ,fill the pipette with dilute acid1 close the clamp1 and cork the flask4 ,then see that the apparatus is tight4 ,open the clamp and allow from #aj to #bj c4c4 of the acid to run on to the assay4 ,carbonic acid will be evolved and will be driven through the tubes4 ,the gas should bubble through the sulphuric acid in a moderate and regular stream4 ,when the effervescence slackens the clamp is opened and the greater part of the remaining acid run in4 ,when the effervescence has ceased the clamp is opened to its full extent and a current of air drawn through with an aspirator4 ,a gentle heat is applied to the flask2 but it should not be prolonged or carried to boiling4 ,after the removal of the heat a gentle current of air is drawn through the apparatus for #cj or #dj minutes4 ,the weighed ,u-tube1 which in the early part of the operation will have become warm if much carbonic acid was present1 will by this time be cold4 ,it is disconnected1 plugged1 and weighed4 ,the increase in weight is due to the carbon dioxide of the sample4 ,example4--,ore taken #a gram4 ,weight of tube1 before #db4febe grams after #dc4jidj ------- ,increase equals ,,co#b #j4ddae ,illustration3 ,,fig4 #ha4 ,indirect ,gravimetric1 or ,determination by ,loss4--,take a ,geissler's carbonic-acid apparatus 7fig4 #ha7 and place in the double bulb some strong sulphuric acid4 ,put into the other bulb1 the stopcock being closed1 #c or #d c4c4 of nitric acid diluted with water4 ,leave the apparatus in the balance-box for a few minutes and weigh4 ,introduce into the flask 7through ,a7 about #a gram of the powdered substance and again weigh to find the exact amount added4 ,allow the acid to run gradually on to the carbonate1 and when solution is complete1 heat and aspirate4 ,cool and again weigh2 the loss in weight is the carbonic acid4 ,for ,example3-- ,weight of apparatus and acids #he4did grams marble #hf4hgi ------ ,equal to marble taken #a4che ,weight of apparatus and marble #hf4hgi grams minus carbonic acid #hf4bfib ------- ,equal to carbonic acid #j4fjih #a4che 3 #ajj 33 #j4fjih 3 x x #dd4jc per cent4 ,the substance contains #dd4jc per cent4 of carbonic acid2 a duplicate experiment gave #dc4gc per cent4 ,this method is quicker1 but less exact1 than the direct gravimetric determination4 ,,volumetric ,,method4 ,this1 which is of somewhat limited application1 is based upon the determination of the quantity of acid required to decompose the carbonate4 ,it consists in adding to a weighed quantity of the mineral a known amount of standard solution of acid which is in excess of that required to effect the decomposition4 ,the quantity of residual acid is then determined by titrating with standard solution of alkali4 ,this method has been described under ,lime4 ,,gasometric ,,method4 ,this method is the quickest of all1 and the least troublesome after the apparatus has been once prepared4 ,it yields fairly accurate results when worked in the manner described below2 but if greater precautions are taken the results are exact4 ,it depends on the measurement of the volume of gas given off on treating the weighed sample with acid4 ,the apparatus described1 page #eb1 is used4 ,weigh out a portion of the mineral which shall contain not more than #j4ae gram of carbonic acid 7or #j4d gram of carbonate of lime7 and put it in the bottle4 ,put in the inner tube #aj c4c4 of dilute hydrochloric acid 7#a--a71 cork tightly1 and read off the level of the liquid in the burette after adjusting the pressure4 ,turn the acid over on to the mineral4 ,run out the water so as to keep the level in the two burettes the same4 ,when effervescence has ceased1 rotate the contents of the bottle2 finally1 adjust the level in the burettes and read off the volume4 ,the increase in volume is due to the evolved carbon dioxide4 ,at the same time read off the volume corrector4 ,some of the carbon dioxide remains dissolved in the acid in the generating bottle1 and the quantity thus dissolved will depend on the amount of carbonate as well as on the amount of acid present4 ,consequently1 a measured quantity of acid should be used in each assay and a comparative experiment made with a known weight of pure carbonate of lime which will yield about the same volume of gas4 ,the number of c4c4 of gas got in the assay multiplied by #d4g will give the number of milligrams of pure carbonate of lime that must be taken for the standard4 ,with ordinary work the error rarely exceeds half a c4c4 ,the following example will illustrate the calculations3-- ,one gram of a mineral was taken1 and yielded #di4j c4c4 of gas4 ,the volume corrector reading was #ajj4d c4c4 #j4bdje gram of pure carbonate of lime was then taken1 and treated in the same way2 #ej4e c4c4 of gas were got4 ,the volume corrector still read #ajj4d c4c4 #j4bdje gram of carbonate of lime is equivalent to #j4ajeh gram of carbon dioxide2 then1 #ej4e 3 #di4j 33 #j4ajeh 3 x x #aj4bf per cent4 ,estimation of ,carbonic ,acid in the ,air of ,mines4--,according to a series of analyses by ,angus ,smith1 the proportion of carbonic acid in the air of underground workings varied from #j4jd to #b4g per cent4 by volume4 ,in places where men are working the proportion ought not to reach #j4be per cent4 ,a simple method of determining whether a sample of air reaches this limit 7#j4be per cent47 is described by ,dr4 ,c4 ,le ,neve ,foster in the ,proceedings of the ,mining ,association and ,institute of ,cornwall for #ahhh4 ,the apparatus used is an ordinary corked #h-ounce medicine bottle4 ,this is filled with the air to be examined by sucking out its contents with a piece of rubber-tube4 ,half-an-ounce of dilute lime-water#aba 7tinted with phenolphthalein7 is poured in4 ,if1 on corking the bottle and shaking1 the colour is not discharged1 the air contains less than #j4be per cent4 of carbon dioxide4 ,if the colour fades slowly1 and does not finally vanish till after a great deal of shaking1 it may be assumed that the percentage of carbon dioxide does not greatly exceed one quarter2 whereas1 if the disappearance is rapid after a very few shakes1 the contrary1 of course1 is the case4 ,the dilute lime-water is measured out and carried in ordinary half-ounce phials4 ,this method does not pretend to great accuracy1 but as a method of distinguishing between good and bad air it is very convenient1 and will be found useful4 ,for determining the actual proportion in the air the following plan is adopted3--,take a bottle which will hold about #ej ounces1 and measure its capacity2 fill the bottle with the air to be examined1 pour in #ajj c4c4 of lime-water1 and shake up for some time2 add phenolphthalein1 and titrate the remaining calcium hydrate with standard solution of oxalic acid4 ,the solution of oxalic acid is made by dissolving #b4be grams of re-crystallised oxalic acid 7,h#b;,c#b,o#d4b;,h#b,o7 in water and diluting to #a litre4 ,one c4c4 #j4jja gram of lime 7,ca,o71 or #j4jjjgheg gram of carbon dioxide4 ,take #ajj c4c4 of the same lime-water1 to which add the same amount of phenolphthalein as before4 ,titrate4 ,the difference between the two readings gives the amount of acid equivalent to the lime-water neutralised by the carbon dioxide4 ,the number of c4c4 thus used up1 when multiplied by #j4cihi1 gives the number of c4c4 of carbon dioxide 7at #j ,c4 and #gfj mm47 in the volume of air taken4 ,this volume1 which is that of the bottle less #ajj c4c41 must in accurate work be reduced to the normal temperature and pressure4#abb ,the percentage by volume can then be calculated4 ,,practical ,,exercises4 #a4 ,in a gasometric determination #ga4c c4c4 of gas were obtained from #j4bjee gram of mineral4 ,the volume corrector reading was #ajb4b c4c4 #j4cdde gram of pure carbonate of lime gave #gd4a c4c4 ,the volume corrector reading was #ajj4f4 ,what is the percentage of carbon dioxide in the substance8 #b4 ,what volume of dry gas at #j ,c4 and #gfj m4m4 pressure should be obtained from #j4cdde gram of carbonate of lime8 #a c4c4 of ,,co#b under these conditions weighs #a4ig milligrams4 #c4 ,a sample of coal is reported on as follows3-- ,specific gravity #a4cae ,moisture #a4jja ,volatile matter #ce4dhd ,fixed carbon #ej4agb ,ash #ab4jbh ------- #ajj4jjj ,what is there about this requiring explanation8 #d4 ,calculate the percentage of carbonic acid in a mineral from the following data3-- ,weight of apparatus and acids #hg4jhhh grams plus mineral #hh4hheh after loss of carbonic acid #hh4ajjj #e4 ,a sample of pig iron contains #a4dc per cent4 of combined and #b4jb per cent4 of free carbon4 ,taking #b grams of it for each determination1 what weight of ,,co#b will be got on burning the residue from solution in ammonium cupric chloride1 and what from the residue after solution in hydrochloric acid8 ,,boron ,,and ,,borates4 ,boron occurs in nature as boric acid or sassoline 7,h#c;,,bo#c72 borax or tincal 7,na#b;,b#d,o#g4aj;,h#b,o72 ulexite or boronatrocalcite 7#b;,ca,b#d,o#g4,na#b;,b#d,o#g72 borocalcite 7,ca,b#d,o#g4d;,h#b,o72 boracite1 #b,mg#c;,b#h,o#ae4,mg,cl#b1 and some other minerals4 ,boric acid is also a constituent of certain silicates1 such as tourmaline1 axinite1 and datholite4 ,the natural borates are used in the preparation of borax1 which is largely employed as a preservative agent1 for fluxing1 and for other purposes4 ,there is only one series of boron compounds which have any importance4 ,these are the borates in which the trioxide 7,b#b,o#c7 acts the part of a weak acid4 ,the addition of any acid liberates boric acid1 which separates out in cold solutions as a crystalline precipitate4 ,boric acid is soluble in alcohol and in hot water4 ,on evaporating these solutions it is volatilised1 although the anhydrous oxide is fixed at a red heat4 ,the borates are mostly fusible compounds1 and are soluble in acids and in solutions of ammonic salts4 ,detection4--,boron in small quantities will escape detection unless specially looked for1 but there is no difficulty in detecting its presence4 ,heated in the ,bunsen-burner flame with ,turner's test1 it gives an evanescent yellowish-green colour1 due to fluoride of boron 7,,bf#c74 ,turner's test is a mixture of #e parts of bisulphate of potash and #a part of fluor spar4 ,boric acid itself imparts a characteristic green colour to the flame1 which gives a spectrum made up of four well-marked and equidistant lines1 three in the green and one in the blue4 ,solutions of boric acid give with turmeric paper1 which has been dipped into it and dried1 a characteristic red tint4 ,this is a very delicate test1 but in trying it a blank experiment should be carried out alongside with a solution made up of the same re-agents which have been used in liberating the boric acid in the sample4 ,solution and ,separation4--,the solution presents no difficulty1 but the separation is troublesome4 ,the best method is that of ,gooch2 who1 if necessary1 first fuses with carbonate of soda1 and after the removal of chlorides and fluorides 7by nitrate of silver or a lime salt71 evaporates the aqueous extract with nitric or acetic acid to dryness in a retort and1 subsequently1 with repeated doses of #aj c4c4 each of methyl alcohol4 ,the distillate contains the boron as boric acid4 ,half a gram of the trioxide 7,b#b,o#c7 is completely carried over by two evaporations1 each with #aj c4c4 of the alcohol2 but if water or foreign salts are present1 more than this is required4 ,in ordinary cases six such evaporations are sufficient for #j4b gram of the oxide4#abc ,,gravimetric ,,determination4 ,before the introduction of ,gooch's process it was usual to determine the boron trioxide by difference4 ,if the alcoholic distillate containing the boric acid is digested with about #a gram 7a known weight7 of lime for ten or fifteen minutes1 the alcohol can be evaporated off without danger of loss4 ,either calcium nitrate or acetate 7which will be formed at the same time7 yields lime upon subsequent ignition4 ,consequently1 the increase in weight1 after ignition1 upon that of the lime taken gives the amount of boron trioxide present4 ,the trioxide contains #ca4d per cent4 of boron 7,b74 ,since magnesia does not form a soluble hydrate it cannot satisfactorily be used instead of lime4 ,illustration3 ,,fig4 #hb4 ,the apparatus required is shown in fig4 #hb4 ,it consists of a small retort or evaporating vessel made out of a pipette of #bjj c4c4 capacity4 ,this is heated by means of a paraffin-bath at #acj or #adj ,c4 ,it is connected with an upright condenser1 at the lower end of which is a small flask which serves as a receiver4 ,the quantity of the borate taken should contain not more than #j4b gram of the trioxide4 ,insoluble compounds are dissolved in nitric acid at once1 or1 if necessary1 first fused with sodium carbonate4 ,with soluble and alkaline borates sufficient nitric acid is added to render it faintly acid4 ,the solution is then introduced into the retort4 ,the lime1 to retain the boric acid in the distillate1 is ignited in the crucible in which the evaporation of the distillate is to be made subsequently4 ,it is then cooled in the desiccator for ten minutes1 and weighed4 ,the lime is transferred to the receiving flask and slaked with a little water4 ,the retort is lowered into the bath so that only the rear dips below the surface4 ,the evaporation is carried to dryness1 the retort being lowered further into the bath as the evaporation proceeds4 ,ten c4c4 of methyl alcohol are introduced upon the residue1 and the evaporation again started4 ,six such portions of alcohol are thus distilled and #b c4c4 of water are introduced and evaporated between the second and third1 as also between the fourth and fifth distillations4 ,if acetic acid is used instead of nitric in the first instance this addition of water is unnecessary4 ,the distillate is evaporated in the crucible ignited over the blowpipe1 cooled in the desiccator for ten minutes and weighed4 ,the increase in weight gives the boron trioxide4 ,the results tend to be from #a to #b milligrams too high4 ,,volumetric ,,method4 ,this method is applicable to the indirect determination of boric acid in borax and similar compounds4 ,it is based on the measurement of the quantity of normal solution of acid required to replace the boric acid1 and1 consequently1 is rather a measure of the soda present4 ,the process is an alkalimetric one1 and is carried out as follows3--,weigh up #c grams of the sample and dissolve in water4 ,tint with methyl orange1 and run in from an ordinary burette normal solution of sulphuric acid until a pink tint is got4 #ajj c4c4 of the normal solution of acid are equal to #g4j grams of boron trioxide 7,b#b,o#c71 or #aj4a grams of anhydrous borax 7,na#b;,b#d,o#g74 ,examination of ,borax4--,in addition to the determination just given1 the following determinations are also required3-- ,water4--,take about #b grams and heat to tranquil fusion in a platinum crucible4 ,count the loss in weight as water4 ,sulphuric ,oxide4--,take #b grams1 dissolve in water1 acidify with hydrochloric acid1 filter1 and precipitate with barium chloride4 ,wash the precipitate1 ignite1 and weigh as barium sulphate 7see ,sulphur74 ,chlorine4--,take #b grams1 dissolve in water1 acidify with nitric acid1 filter1 and add silver nitrate4 ,collect1 wash1 and weigh the precipitate as silver chloride4 ,alumina4--,take #e or #aj grams1 dissolve in water1 boil1 add ammonia in slight excess1 and filter off the precipitate when it has settled4 ,wash with hot water1 ignite1 and weigh as alumina 7,al#b,o#c74 ,,footnotes3 #aac ,if the dishes show a manganese stain1 wash them out with a few drops of hydrochloric and sulphurous acids4 ,pass the acid liquor through the same small filter but collect the liquor apart4 ,make ammoniacal and again pass through the filter1 this time collecting the liquid with the main filtrate4 #aad ,this rarely amounts to more than #a milligram4 #aae ,to make this1 dissolve #a gram of titanium oxide by fusing for some time with an excess of bisulphate of potash and dissolve out with cold water and sulphuric acid4 ,dilute to #a litre1 having previously added not less than #ej c4c4 of strong sulphuric acid3 #a c4c4 will contain 4#ja gram of ,ti,o#b4 ,for the assay take #aj c4c4 of this1 add #b c4c4 of peroxide of hydrogen and dilute to #ajj c4c4 ,run this from a burette into the flask until the colour equals that of the assay4 ,each c4c4 equals #a milligram of ,ti,o#b4 ,fluorides must be absent4 #aaf ,c ,o#b ,,co#b #aag ,for example1 soluble organic acids formed by partial oxidation with nitric acid4 #aah ,for coals1 and other bodies containing sulphur1 chromate of lead should be used instead of oxide of copper2 and the temperature should be limited to dull redness4 #aai ,this may be prepared by dissolving #ecd grams of ammonium chloride and #hed grams of crystallized cupric chloride 7,cu,cl#b4b;,h#b,o7 in hot water and crystallizing4 #abj ,soda-lime is made by dissolving #ajj grams of soda in water1 and carefully slaking #bjj grams of lime with it4 ,evaporate to dryness in an iron dish and ignite at a low red heat in a crucible4 ,use the small lumps4 #aba ,made by diluting #a part by measure of saturated lime-water up to #aj with recently boiled distilled water4 #abb ,see under ,gasometric ,assays4 #abc ,see ,a ,method for the ,separation and ,estimation of ,boric ,acid1 by ,f4,a4 ,gooch1 ,chemical ,news1 ,january #g1 #ahhg4 ,,appendix ,a4 ,,table ,,of ,,atomic ,,weights ,,and ,,other ,,constants4 ---------------------------------------- ---------- ,symbols4 ,names4 ,atomic ,specific ,melting ,weights4 ,gravity4 ,points4 ---------------------------------------- ---------- ,c4 ,ag ,silver #ajg4i #aj4e #ajjj ,al ,aluminium #bg4j #b4g #gjj ,as ,arsenic #ge4j #e4i ,au ,gold #aig4c #ai4b #abjj ,b ,boron #aa4j #b4g ,ba ,barium #acg4j #d4j ,be ,beryllium #i4j #b4a ,bi ,bismuth #bjh4i #i4h #bgj ,br ,bromine #hj4j #c4b -#be ,c ,carbon #ab4j ,ca ,calcium #dj4j #a4f ,cd ,cadmium #aab4j #h4f #cae ,ce ,cerium #adj4b #f4g ,cl ,chlorine #ce4e ,co ,cobalt #ei4j #h4e ,cr ,chromium #eb4a #g4c ,cs ,caesium #acb4i #a4i #be ,cu ,copper #fc4d #h4i #ajij ,di ,didymium #adb4c #f4e ,er ,erbium #aff4c ,f ,fluorine #ai4j ,fe ,iron #ef4j #g4h ,ga ,gallium #fi4j #e4i #cj ,ge ,germanium #gb4c ,h ,hydrogen #a4j ,hg ,mercury #bjj4j #ac4f -#dj ,i ,iodine #abf4h #d4i #ajf ,in ,indium #aac4g #g4d #age ,ir ,iridium #aic4a #bb4d ,k ,potassium #ci4a #j4hf #fb4e ,la ,lanthanum #ach4b #f4a ,li ,lithium #g4j #j4ei #ahj ,mg ,magnesium #bd4c #a4g ,mn ,manganese #ee4j #h4j ,mo ,molybdenum #if4j #h4f ,n ,nitrogen #ad4j ,na ,sodium #bc4j #j4ig #ie4f ,nb ,niobium #id4j #d4a ,ni ,nickel #eh4g #h4i ,o ,oxygen #af4j ,os ,osmium #aia4g #bb4d ,p ,phosphorus #ca4j #a4h #dd ,pb ,lead #bjf4i #aa4d #ccd ,pd ,palladium #ajf4f #aa4d #acej ,pt ,platinum #aie4j #ba4e #bjjj ,rb ,rubidium #he4e #a4e #ch4e ,rh ,rhodium #ajc4e #ab4a ,ru ,ruthenium #aja4f #aa4d ,s ,sulphur #cb4j #b4j #aae ,sb ,antimony #abj4j #f4g #dbe ,se ,selenium #gi4j #d4h #ajj ,si ,silicon #bh4d #b4j ,sn ,tin #aai4j #g4c #bce ,sr ,strontium #hg4f #b4e ,ta ,tantalum #ahb4f ,te ,tellurium #abe4j #f4b #dhj ,th ,thorium #bcb4f #g4h ,ti ,titanium #dh4j #e4c ,tl ,thallium #bjd4b #aa4i #bid ,u ,uranium #bci4f #ah4d ,v ,vanadium #ea4d #e4e ,w ,tungsten #ahd4j #ai4a ,y ,yttrium #hi4a ,yb ,ytterbium #agc4j ,zn ,zinc #fe4c #f4i #dbc ,zr ,zirconium #ij4f #d4a ,the atomic weights in this table are in accord with the numbers given by ,f4,w4 ,clarke 7,dec4 #f1 #ahij71 chief chemist of the ,united ,states ,geological ,survey4 ,illustration3 ,table for ,converting ,degrees of the ,centigrade ,thermometer into ,degrees of ,fahrenheit's ,scale4 ,nitric ,acid4 ,table showing the percentage1 by ,weight1 of ,real ,acid 7,,hno#c7 in ,aqueous ,solutions of ,nitric ,acid of different ,specific ,gravities4 ,temperature1 #ae ,c4 ---------------------------------------- -- #a4ecj #ajj4j #a4dje #ff4j #a4bje #cc4j #a4ebg #ii4j #a4djj #fe4j #a4aih #cb4j #a4ebd #ih4j #a4cie #fd4j #a4aib #ca4j #a4ebj #ig4j #a4cij #fc4j #a4ahe #cj4j #a4eaf #if4j #a4chf #fb4j #a4agi #bi4j #a4eac #ie4j #a4chj #fa4j #a4agb #bh4j #a4eji #id4j #a4cgd #fj4j #a4aff #bg4j #a4ejf #ic4j #a4cfh #ei4j #a4aei #bf4j #a4ejc #ib4j #a4cfc #eh4j #a4aeb #be4j #a4dii #ia4j #a4ceh #eg4j #a4ade #bd4j #a4die #ij4j #a4cec #ef4j #a4ach #bc4j #a4dib #hi4j #a4cdf #ee4j #a4acb #bb4j #a4dhh #hh4j #a4cda #ed4j #a4abf #ba4j #a4dhe #hg4j #a4cce #ec4j #a4abj #bj4j #a4dhb #hf4j #a4cbi #eb4j #a4aad #ai4j #a4dgh #he4j #a4cbc #ea4j #a4ajh #ah4j #a4dgd #hd4j #a4cag #ej4j #a4ajb #ag4j #a4dgj #hc4j #a4caa #di4j #a4jif #af4j #a4dfg #hb4j #a4cjd #dh4j #a4jhi #ae4j #a4dfc #ha4j #a4bih #dg4j #a4jhc #ad4j #a4dfj #hj4j #a4bia #df4j #a4jgg #ac4j #a4def #gi4j #a4bhd #de4j #a4jga #ab4j #a4deb #gh4j #a4bgg #dd4j #a4jfe #aa4j #a4ddi #gg4j #a4bgj #dc4j #a4jfj #aj4j #a4dde #gf4j #a4bfd #db4j #a4jec #i4j #a4ddb #ge4j #a4beg #da4j #a4jdg #h4j #a4dch #gd4j #a4bea #dj4j #a4jda #g4j #a4dce #gc4j #a4bdd #ci4j #a4jcd #f4j #a4dca #gb4j #a4bch #ch4j #a4jbh #e4j #a4dbg #ga4j #a4bcb #cg4j #a4jbb #d4j #a4dbc #gj4j #a4bbe #cf4j #a4jaf #c4j #a4dah #fi4j #a4bah #ce4j #a4jaj #b4j #a4dad #fh4j #a4bab #cd4j #a4jjd #a4j #a4daj #fg4j ---------------------------------------- --- ,,hydrochloric ,,acid4 ,table showing the percentage1 by ,weight1 of ,real ,acid 7,h,cl7 in ,aqueous ,solutions of ,hydrochloric ,acid of different ,specific ,gravities4 ,temperature1 #ae ,c4 ---------------------------------------- ------------------ #a4bjjj #dj4gh #a4adaj #bh4ed #a4jgih #af4ca #a4aihb #dj4cg #a4achi #bh4ac #a4jggh #ae4ij #a4aifd #ci4if #a4acfi #bg4gb #a4jgeh #ae4di #a4aidf #ci4ee #a4acdi #bg4cb #a4jgch #ae4jh #a4aibh #ci4ad #a4acbh #bf4ia #a4jgah #ad4fh #a4aiaj #ch4gd #a4acjh #bf4ej #a4jfig #ad4bg #a4ahic #ch4cc #a4abhg #bf4aj #a4jfgg #ac4hf #a4ahge #cg4ib #a4abfg #be4fi #a4jfeg #ac4de #a4aheg #cg4ea #a4abdg #be4bh #a4jfcg #ac4je #a4ahdf #cg4aa #a4abbf #bd4hg #a4jfag #ab4fd #a4ahbb #cf4gj #a4abjf #bd4df #a4jeig #ab4bc #a4ahjb #cf4bi #a4aahe #bd4jf #a4jegg #aa4hb #a4aghb #ce4hh #a4aafd #bc4fe #a4jeeg #aa4da #a4agfb #ce4dg #a4aadc #bc4bd #a4jecg #aa4ja #a4agda #ce4jg #a4aabc #bb4hc #a4jeag #aj4fj #a4agba #cd4ff #a4aajb #bb4dc #a4jdig #aj4ai #a4agja #cd4be #a4ajhb #bb4jb #a4jdgg #i4gh #a4afha #cc4hd #a4ajfa #ba4fa #a4jdeg #i4ch #a4affa #cc4dc #a4ajda #ba4bj #a4jdcg #h4ig #a4afda #cc4jc #a4ajbj #bj4gi #a4jdag #h4ef #a4afbj #cb4fb #a4ajjj #bj4ci #a4jcig #h4ae #a4aeii #cb4ba #a4jihj #ai4ih #a4jcgg #g4ge #a4aegh #ca4hj #a4jifj #ai4eg #a4jceg #g4cd #a4aeeg #ca4dj #a4jici #ai4af #a4jccg #f4ic #a4aecf #cj4ii #a4jiai #ah4gf #a4jcah #f4eb #a4aeae #cj4eh #a4jhii #ah4ce #a4jbih #f4aa #a4adid #cj4ag #a4jhgi #ag4id #a4jbgi #e4ea #a4adgc #bi4gf #a4jhei #ag4ec #a4jbei #e4cj #a4adeb #bi4cf #a4jhch #ag4ab #a4jbci #d4hi #a4adca #bh4ie #a4jhah #af4gb #a4jbjj #d4ja ---------------------------------------- ------------------ ,,ammonia4 ,table showing the percentage1 by ,weight1 of ,real ,ammonia 7,,nh#c7 in ,aqueous ,solutions of ,ammonia of different ,specific ,gravities4 ,temperature1 #ad ,c4 ---------------------------------------- -------------- #j4hhdd #cf4j #j4iade #bc4f #j4iecd #aa4f #j4hheb #ce4f #j4iaef #bc4b #j4iedi #aa4b #j4hhfj #ce4b #j4iafh #bb4h #j4iefc #aj4h #j4hhfh #cd4h #j4iahj #bb4d #j4iegh #aj4d #j4hhgg #cd4d #j4iaia #bb4j #j4ieic #aj4j #j4hhhe #cd4j #j4ibjc #ba4f #j4ifjh #i4f #j4hhid #cc4f #j4ibae #ba4b #j4ifbc #i4b #j4hijc #cc4b #j4ibbg #bj4h #j4ifci #h4h #j4hiaa #cb4h #j4ibci #bj4d #j4ifed #h4d #j4hibj #cb4d #j4ibea #bj4j #j4ifgj #h4j #j4hibi #cb4j #j4ibfd #ai4f #j4ifhe #g4f #j4hich #ca4f #j4ibgg #ai4b #j4igja #g4b #j4hidh #ca4b #j4ibhi #ah4h #j4igag #f4h #j4hieg #cj4h #j4icjb #ah4d #j4igcc #f4d #j4hifg #cj4d #j4icad #ah4j #j4igdi #f4j #j4higf #cj4j #j4icbg #ag4f #j4igfe #e4f #j4hihf #bi4f #j4icdj #ag4b #j4igha #e4b #j4hiif #bi4b #j4icec #af4h #j4igij #d4h #j4ijjf #bh4h #j4icff #af4d #j4ihjg #d4f #j4ijaf #bh4d #j4ichj #af4j #j4ihbc #d4b #j4ijbf #bh4j #j4icic #ae4f #j4ihci #c4h #j4ijcf #bg4f #j4idjg #ae4b #j4ihee #c4d #j4ijdg #bg4b #j4idbj #ad4h #j4ihgc #c4j #j4ijeg #bf4h #j4idcd #ad4d #j4ihij #b4f #j4ijfh #bf4d #j4iddi #ad4j #j4iijg #b4b #j4ijgh #bf4j #j4idfc #ac4f #j4iibd #a4h #j4ijhi #be4f #j4idgg #ac4b #j4iida #a4d #j4iajj #be4b #j4idia #ab4h #j4iiei #a4j #j4iaaa #bd4h #j4ieje #ab4d #j4iige #j4f #j4iabb #bd4d #j4iebj #ab4j #j4iiia #j4b #j4iacc #bd4j ---------------------------------------- -------------- ,,sulphuric ,,acid4 ,table showing the percentage1 by ,weight1 of ,real ,acid 7,h#b,,so#d7 in ,aqueous ,solutions of ,sulphuric ,acid of varying ,specific ,gravity4 ,temperature1 #ae ,c4 ---------------------------------------- -------- #a4hch #ajj4j #a4efh #ff4j #a4bdg #cc4j #a4hdj #ii4j #a4eeg #fe4j #a4bci #cb4j #a4hda #ih4j #a4ede #fd4j #a4bca #ca4j #a4hda #ig4j #a4ecd #fc4j #a4bbc #cj4j #a4hdj #if4j #a4ebc #fb4j #a4bae #bi4j #a4hch #ie4j #a4eab #fa4j #a4bjf #bh4j #a4hcf #id4j #a4eja #fj4j #a4aih #bg4j #a4hcd #ic4j #a4dij #ei4j #a4aij #bf4j #a4hca #ib4j #a4dhj #eh4j #a4ahb #be4j #a4hbg #ia4j #a4dfi #eg4j #a4agd #bd4j #a4hbb #ij4j #a4deh #ef4j #a4afg #bc4j #a4haf #hi4j #a4ddh #ee4j #a4aei #bb4j #a4hji #hh4j #a4dch #ed4j #a4aea #ba4j #a4hjb #hg4j #a4dbh #ec4j #a4add #bj4j #a4gid #hf4j #a4dah #eb4j #a4acf #ai4j #a4ghf #he4j #a4djh #ea4j #a4abi #ah4j #a4ggg #hd4j #a4cih #ej4j #a4aba #ag4j #a4gfg #hc4j #a4chh #di4j #a4aac #af4j #a4gef #hb4j #a4cgi #dh4j #a4ajf #ae4j #a4gde #ha4j #a4cgj #dg4j #a4jih #ad4j #a4gcd #hj4j #a4cfa #df4j #a4jia #ac4j #a4gbb #gi4j #a4cea #de4j #a4jhc #ab4j #a4gaj #gh4j #a4cdb #dd4j #a4jge #aa4j #a4fih #gg4j #a4ccc #dc4j #a4jfh #aj4j #a4fhf #gf4j #a4cbd #db4j #a4jfa #i4j #a4fge #ge4j #a4cae #da4j #a4jec #h4j #a4ffc #gd4j #a4cjf #dj4j #a4jdf #g4j #a4fea #gc4j #a4big #ci4j #a4jci #f4j #a4fci #gb4j #a4bhi #ch4j #a4jcb #e4j #a4fbg #ga4j #a4bha #cg4j #a4jbe #d4j #a4fae #gj4j #a4bgb #cf4j #a4jai #c4j #a4fjd #fi4j #a4bfd #ce4j #a4jac #b4j #a4eib #fh4j #a4bef #cd4j #a4jjf #a4j #a4ehj #fg4j ---------------------------------------- -------- ,,appendix ,b4 ,,estimation ,,of ,,small ,,quantities ,,of ,,gold4#abd ,in the case of small buttons of gold the weight can be determined more easily and accurately by measuring with the help of a microscope than by the actual use of a balance4 ,moreover1 the method of measurement is applicable to the determination of quantities of gold too minute to affect even the most delicate balance4 ,for quantities of gold of from 4#e to 4#jje milligram a microscope with #a_/b inch objective and ,b eyepiece is suitable4 ,the measurements are made with the help of a scale engraved 7or1 better1 photographed7 on a circular piece of glass which rests on the diaphragm of the eyepiece4 ,this scale and the object upon the stage can be easily brought into focus at the same time4 ,the button of gold obtained by cupelling is loosened from the cupel by gently touching with the moistened point of a knife2 it generally adheres to the knife1 and is then transferred to a glass slide4 ,the slide is placed on the stage of the microscope1 illuminated from below2 and the button is brought into focus1 and so placed that it apparently coincides with the scale4 ,the diameters in two or three directions 7avoiding the flattened surface7 are then read off3 the different directions being got by rotating the eyepiece4 ,the mean diameter is taken4 ,the weight of the button is arrived at by comparing with the mean diameter of a standard prill of gold of known weight4 ,the weights are in the proportion of the cubes of the diameters4 ,for example1 suppose a prill has been obtained which measures #ab4e divisions of the scale1 and that a standard prill weighing #j4a milligram measures #aa4a divisions4 ,the weight will be calculated as follows3 #aa4ac 3 #ab4ec 33 #j4a 3 x #j4aab4eab4eab4e x -------------------- #j4adc milligram4 #aa4aaa4aaa4a ,the calculations are simplified by the use of a table of cubes4 ,the standard prills used in the comparison should not differ much in size from the prills to be determined4 ,they are prepared by alloying known weights of gold and lead1 so as to get an alloy of known composition1 say one per cent4 gold4 ,portions of the alloy containing the weight of gold required 7say #j4a milligram7 are then weighed off and cupelled on small smooth cupels1 made with the finest bone-ash4 ,care must be taken to remove the cupels as soon as cupellation has finished4 ,several standard prills of the same size should be made at the same time1 and their mean diameter calculated4 ,the lead for making the gold-lead alloy is prepared from litharge purified by reducing from it about #aj per cent4 of its lead by fusion with a suitable proportion of flour2 the purified litharge is powdered1 mixed with sufficient flour and reduced to metal4 ,in determining the gold contained in small buttons of silver-gold alloy obtained in assaying 7and in which the silver is almost sure to be in excess of that required for parting71 transfer the button from the cupel to a small clean porcelain crucible2 pour on it a drop or two of nitric acid 7diluted with half its bulk of water71 and heat gently and cautiously until action has ceased4 ,if the residual gold is broken up1 move the crucible so as to bring the particles together1 so that they may cohere4 ,wash three or four times with distilled water1 about half filling the crucible each time and decanting off against the finger4 ,dry the crucible in a warm place2 and when dry1 but whilst still black1 take the gold up on a small piece of pure lead4 ,half a grain of lead is sufficient1 and it is best to hold it on the point of a blunt penknife1 and press it on the gold in the crucible4 ,the latter generally adheres4 ,transfer to a small smooth cupel and place in the muffle4 ,when the cupellation has finished1 the button of gold is measured as already described4 ,,practical ,,notes ,,on ,,the ,,iodide ,,process ,,of ,,copper ,,assaying4 ,for the following remarks and experiments we are indebted to ,mr4 ,j4,w4 ,westmoreland1 who has had considerable experience with the process4 ,having dissolved the ore he converts the metals into sulphates by evaporating with sulphuric acid4 ,the copper is then separated as subsulphide by means of hyposulphite of soda1 and the precipitate is washed1 dried1 and calcined4 ,the resulting oxide of copper is then dissolved in nitric acid2 and to the concentrated solution1 a saturated solution of carbonate of soda is added in sufficient quantity to throw down a considerable proportion of the copper4 ,acetic acid is added to dissolve the precipitate1 and when this is effected more of the acid is poured on so as to render the solution strongly acid4 ,to this potassium iodide crystals are added in the proportion of ten parts of iodide to each one part of copper supposed to be present4 ,the solution is then titrated with hypo as usual4 ,for the examination of technical products experiments made in sulphuric acid solutions have no value1 since arsenic acid1 which is generally present to a greater or less extent1 affects the end reaction4 ,in such solutions bismuth may also interfere4 ,the solution best suited for the assay is one containing acetate of soda and free acetic acid4 ,the presence of acetate of soda counteracts the interference of arsenic and of bismuth4 ,the return of the blue colour after titration is due to the excessive dilution of the assay1 or to an insufficiency of potassium iodide1 or to the presence of nitrous fumes4 ,the interference of an excess of sodium acetate is avoided by adding more iodide crystals to the extent of doubling the usual amount4 ,the interference of lead can be avoided by the addition of sulphuric acid or of phosphate of soda to the acid solution containing the copper1 and before neutralising with carbonate of soda4 ,the end reaction is1 however1 with care distinguishable without this addition4 ,the following experiments1 each containing 4#jfdh gram of lead1 were made by him in illustration3 ---------------------------------------- ------------------------------ ,copper taken4 ,reagent added4 ,copper found4 ,end reaction4 ---------------------------------------- ------------------------------ 4#bjib gram -- 4#bjgg gram fairly satisfactory 4#baja -- 4#bjib 4#bafg sulphuric acid 4#baeb 4#baag 4#bajh 4#baji phosphate of soda 4#bjib good1 colourless 4#bbje 4#bagd rather yellow ---------------------------------------- ------------------------------ ,effect of ,sodium ,acetate4--,each solution contained 4#ccdc gram of copper4 a4b4c4 d4 e4 f4 g4 grams4 grams4 grams4 grams4 grams4 ,acetate added -- #af4b #af4b #af4b #af4b ,iodide added #c4e #c4e #g4j #c4e #g4j ,copper found 4#ccdc 4#ccbd 4#ccea 4#cbfi 4#ccef ,in these experiments1 except with the excessive quantities of acetate of soda and the insufficiency of potassium iodide in the cases of c and f1 there was no difficulty with the after-blueing4 ,,method ,,of ,,separating ,,cobalt ,,and ,,nickel4 ,the following method of separating and estimating cobalt and nickel has been described by ,mr4 ,james ,hope1#abe with whom it has been in daily use for several years with completely satisfactory results4 ,the quantity of ore taken should contain about 4#e gram of the mixed metals4 ,it is dissolved in hydrochloric acid or aqua regia1 and the solution evaporated to dryness4 ,the residue is taken up with dilute hydrochloric acid and hot water4 ,the solution is filtered off from the silica1 freed from second group metals by treatment with sulphuretted hydrogen and filtered1 and after oxidation with nitric acid is separated from iron and alumina by the basic acetate method 7page #bcc74 ,the precipitate is redissolved in a little hydrochloric acid1 and again precipitated by sodium acetate4 ,the two filtrates are mixed and treated with a little acetic acid1 and the cobalt and nickel are then precipitated as sulphides by a current of sulphuretted hydrogen4 ,the precipitate is filtered off1 washed1 dried1 and calcined1 and the resulting oxides are weighed to get an idea as to the quantity of the two metals present4 ,the calcined precipitate is dissolved in a small covered beaker in aqua regia with the help of a few drops of bromine to remove any separated sulphur1 and the solution evaporated to dryness with a few drops of sulphuric acid4 ,the residue is dissolved in hot water1 diluted to about #ej c4c41 and heated to boiling4 ,about #b grams 7four times the quantity of mixed metals present7 of ammonium phosphate 7,am,h#b,,po#d7 are weighed off1 dissolved in the smallest possible quantity of water1 and boiled for a minute or two with a few c4c4 of dilute sulphuric acid4 ,this is added to the boiling-hot solution of cobalt and nickel1 which is then treated cautiously with dilute ammonia until the precipitate partially dissolves4 ,the addition of the ammonia is continued drop by drop with constant stirring1 until the cobalt comes down as a pink precipitate of ammonium cobalt phosphate 7,am,co,p,o#d74 ,the beaker is placed on the top of a water bath with occasional stirring for five or ten minutes4 ,the blue liquid containing the nickel is decanted through a small filter and the precipitate is dissolved with a few drops of dilute sulphuric acid4 ,the resulting solution is treated with a small excess of ammonium phosphate and the cobalt again precipitated by the cautious addition of ammonia exactly as before4 ,the precipitate containing the whole of the cobalt is filtered off and washed with small quantities of hot water4 ,the filtrate is added to the previous one containing the greater part of the nickel4 ,the ammonium cobalt phosphate is dried1 transferred to a platinum crucible1 and ignited over a ,bunsen flame for fifteen or twenty minutes4 ,a purple coloured cobalt pyrophosphate 7,co#b,p#b,o#g7 is thus formed1 and is weighed4 ,it contains #dj4c per cent4 of cobalt4 ,the mixed filtrates containing the nickel are placed in a tall beaker1 and dilated if necessary to about #bjj c4c4 ,ten c4c4 of strong ammonia are added1 and the solution1 heated to #gj ,c41 is ready for electrolysis4 ,a battery of two #a-a_/b pint ,bunsen cells is used4 ,this is found capable of depositing from 4#ae to 4#bj gram of nickel per hour1 and from two to three hours is generally sufficient for the electrolysis4 ,the electrode with the deposited nickel is washed with distilled water1 afterwards with alcohol as described under copper1 and is then dried and weighed4 ,the following results obtained with this method by ,mr4 ,hope illustrate the accuracy of the method4 ,they were obtained by working on solutions containing known weights of the two metals3 ---------------------------------------- ---------- ,taken4 ,found4 ---------------------------------------- -------- ,cobalt4 ,nickel4 ,cobalt4 ,nickel4 ---------------------------------------- -------- 4#abcf gram 4#aaee gram 4#abdb gram 4#aaee gram 4#abcf 4#jegg 4#abcb 4#jege 4#bdgb 4#jegg 4#bddi 4#jehe 4#cgjh 4#jegg 4#cgja 4#jehj 4#jfah 4#cdfe 4#jfai 4#cded 4#jfah 4#bcaj 4#jfbe 4#bbie 4#jfah 4#aaee 4#jfba 4#aaee ---------------------------------------- -------- ,,footnotes3 #abd ,for fuller information see a paper on ,the ,estimation of ,minute ,quantities of ,gold1 by ,dr4 ,george ,tate2 read before the ,liverpool ,polytechnic ,society1 ,nov4 #ahhi4 #abe ,journal of the ,society of ,chemical ,industry1 ,no #d1 vol4 ix4 ,april #cj1 #ahij4 ,,appendix ,c4 ,a ,,lecture ,,on ,,the ,,theory ,,of ,,sampling4 ,the problem of the sampler is essentially the same as that of the student of statistics4 ,one aims at getting a small parcel of ore1 the other a number of data1 but each hopes to obtain what shall represent a true average applicable to a much larger mass of material4 ,ignoring the mechanical part of the problems1 the sampling errors of the one and the deviations from the average of the other are the same thing4 ,it may be doubted whether many not specially trained in the study of statistics could answer such a question as the following3--,seven hundred thousand men being employed1 there are1 in a given year1 one thousand deaths from accident4 ,assuming the conditions to remain unaltered1 within what limits could one foretell the number of deaths by accident in any other year8 ,on the other hand1 there is a widespread belief in the efficacy of what is called the law of averages4 ,even the ordinary newspaper reader is accustomed to look on the national death-rate or birth-rate as a thing capable of being stated with accuracy to one or two places of decimals1 and he knows that the annual number of suicides is practically constant4 ,if a man played whist often and kept a record of the number of trumps n each hand1 he would find fortune treated him quite fairly2 in a year's play the average number would deviate very little from the theoretical average1 i4e41 one-quarter of thirteen4 ,and a knowledge of this truth is useful1 and that not merely in keeping ejaculations in due restraint4 ,but every good player knows more than this3 he has a sense of what variations in the number of trumps may reasonably be expected4 ,for example1 he will be prepared to risk something on neither of his opponents having more than five trumps1 and will accept it as a practical certainty that no one has more than eight4 ,much of what is known as good judgment is based on a proper estimate of deviations from the average4 ,the question has an important bearing on sampling1 as may be seen from the fact that shuffling and dealing at cards are but modifications of the well-known mixing and quartering of the sampler4 ,because of this bearing on sampling and for other reasons1 ,i became many years ago much interested in the question1 and gave to its solution perhaps more labour than it was worth4 ,in books on ,medical ,statistics the answer to the question is stated in a mathematical formula1 called ,poisson's formula1 which1 in a modified form1 ,i shall give further on4 ,but this did not satisfy me1 because ,i wanted to learn what a reasonably safe limit of error actually meant1 and this could be best learnt by experiment2 so with the help of some friends ,i went in for a thorough course of penny-tossing4 ,tossing a penny twenty times1 an average result would be ten heads and ten tails4 ,to find the deviations from this1 we tossed two hundred twenties1 i4e41 four thousand times4 ,of the two hundred1 thirty-three gave the exact average1 viz43--#aj heads2 sixty-four gave an error of one1 viz43--#i or #aa heads2 forty-nine1 an error of two2 twenty-six1 an error of three2 twenty1 an error of four2 eight gave an error of five1 and this limit was not exceeded4 ,from these we may say that six is a reasonably safe limit of error4 ,ninety-seven cases1 say one-half1 gave an error not exceeding one2 and the mean error is #a4h4 ,in other words1 in twenty tosses you will not get more than #af nor less than #d heads2 you are as likely as not to get #i1 #aj1 or #aa heads2 and lastly1 if you lost in twenty throws all heads or tails over #aj your average loss would be #a4h penny1 or say roughly #b;d4 on the twenty throws4 ,it was necessary to compare these with another series containing a larger average1 say that of #ajj heads in #bjj throws4 ,i confess the labour of tossing pennies two hundred at a time was little to our taste4 ,so from a bag of pennies borrowed from the bank1 we weighed out samples containing two hundred1 and for an evening we were busy counting heads and tails in these4 ,the heads in sixty samples ranged from #hj to #aad4 ,one hundred heads occurred seven times4 ,the extent and frequency of the errors is shown in the table4 --------------------------------------- ,error4,no4 of ,error4,no4 of ,error4,no4 of ,times4 ,times4 ,times4 --------------------------------------- #a #h #f #c #aa #a #b #e #g #c #ad #c #c #f #h #c #ae #a #d #c #i #g #ah #b #e #f #aj #a #bj #a ---------------------------------------- ---- ,we may call the limit of error #ba4 ,twenty-nine results out of sixty1 say one-half1 had an error not exceeding #d2 and the mean error is #e4f4 ,in comparing these with the series #aj in #bj we must1 working by rule1 divide not by #aj but by #c4af1 the square root of #aj2 for if we multiply an average by any number#abf the error is also multiplied but only by the square root of the number4 ,the error varies as the square root of the number4 ,now #ba_/c4af #f4f limit of error for #aj in #bj4 #e4f_/c4af #a4h mean error #d_/c4af #a4b probable error ,it will be seen that these calculated results agree fairly well with those actually obtained4 ,the rule by which these calculations are made is important and will bear further illustration4 ,to calculate the number of heads in #cbjj throws1 we have to find the limit of error on a true average of #afjj in #cbjj4 ,this being #af times the average of #ajj in #bjj1 the corresponding errors must be multiplied by #d4 ,this gives #bad #hd limit of error4 #e4fd #bb4d mean error4 #dd #af probable error4 ,the results ,i have actually obtained with these large numbers are hardly enough to base much on1 but have a value by way of confirmation4 ,expecting #afjj heads1 the actual numbers were #aefj1 #aeif1 #afdc1 #aeeg1 #aeia1 #afje1 #afae1 #aede4 ,it will be seen that exactly half are within the probable error2 but this1 considering the small number of results1 must be more or less of an accident2 it is more to the point they are all well within the limits of error4 ,i have a large number of other results which with a single exception are all in accord with those given2 and this exception only just overstepped the limits4 ,it was like a case of nine trumps1 which though in a sense possible1 is very unlikely to happen in any one's experience4 ,but even now we are not quite in a position to answer the question with which we started4 ,if you refer to it you will see that we are face to face with this problem3 the limit of variation on the #ajjj who died would be say #gj1abg ignoring decimals4 ,but if we calculate on the number who did not die1 viz4--#fii1jjj1abh we shall get a variation #bf times as great as this4 ,but it is evident the variation must be the same in each case4 ,i submitted this kind of problem also to the test of experiment1 the results of which gave me great faith in ,poisson's formula4 ,imagine two hundred pennies in a bag all heads up4 ,any shaking will spoil this arrangement and give a certain proportion of tails4 ,and1 further1 the probable effect of shaking and turning will be to reduce the preponderance of heads or tails whichever may be in excess4 ,this of course is the reason why we are so unlikely to get more than #abj of them in either position4 ,but if the two hundred pennies are increased to #bj1jjj by adding pennies which have tails on both sides1 then the shaking or mixing would be less effective4 ,we should still expect as an average result to get the #ajj heads but in #bj1jjj instead of #bjj4 ,the variation will be #bh or #bi on the #ajj instead of #bj4 ,and this is a better limit in such cases4 ,taking #bh as the limit of error on #ajj instances and proportionally increasing the others so that the mean error becomes #g4h and the probable error #e4f1 we may now calculate the answer without gross mistake4 ,the probable variation on the #ajjj deaths by accident will be #ah1 the mean variation will be #bd4f1 and the limits of variation #hh4e4 ,one such table showing in five years a mean number of deaths of about #aabj per annum gives an annual deviation of about #ej up or down of this4 ,it will be seen at once that an improvement of #cj or #dj in any one year would be without meaning1 but that an improvement of from #ajj to #bjj would indicate some change for the better in the circumstances of the industry4 ,before applying these principles to the elucidation of some of the problems of sampling it will be well to give ,poisson's formula 7in a modified form7 and to illustrate its working4 ,let x equal the number of cases of one sort1 y the cases of the other sort1 and z the total4 ,in the example1 z will be the #gjj1jjj engaged in the industry2 x will be the #ajjj killed by accidents1 and y will be the #fii1jjj who did not so die4 ,the limit of deviation or error calculated by ,poisson's formula will be the square root of #hxy_/z4 ,replacing x1 y and z by the figures of the example we get the square root of 7#hajjjfiijjj7_/gjj1jjj1 which works out to the square root of #gihh4eg1 or #hi4c4 ,which means that we may reasonably expect the number of deaths not to vary from #ajjj by more than #hi1 i4e41 they will be between #ajij and #iaj4 ,it will be seen that this number is in very satisfactory agreement with #hh4e given by the rougher calculation based on my own experiments4 ,to come to the question of sampling4 ,consider a powder of uniform fineness and fine enough to pass through an #hj sieve4 ,for purposes of calculation this may be assumed to be made up of particles of about one-eighth of a millimetre across 7say roughly #a_/bjj of an inch72 cubed1 this gives the content as about #a_/ejj 7strictly #a_/eab7 of a cubic m4m4 ,now one cubic m4m4 of water weighs #a milligram2 therefore #ejj such particles if they have the specific gravity of water weigh #a milligram1 and otherwise weigh #a milligram multiplied by the sp4 gr43 #ejj particles of ruby silver 7,pyrargyrite7#abi will weigh #e4h milligrams and will contain nearly #c4e milligrams of silver4 ,now suppose a portion of #c4bffg grams 7#a_/aj ,assay ,ton7 of silver ore to contain #ejj such particles of ruby silver and no other material carrying silver3 such an ore would contain #ce ozs4 of silver to the ton4 ,but the limits of variation on #ejj particles would be #bhacj multiplied by the square root of #e1 or #fb particles4 ,thus the limit of sampling error would amount to just one-eighth of the silver present1 or say to rather more than #d ozs4 to the ton2 the mean sampling error would be rather more than a quarter of this1 or say about #a4c ozs4 to the ton4 ,on the other hand1 if one took for the assay a charge six times greater 7say about #bj grams71 the number of particles would be #cjjj and the limits of variation would be #bh multiplied by the square root of #cj1 or #aec particles1 which is very closely #a_/bj of the silver present1 or say #a4ge ozs4 to the ton1 whilst the mean error would amount to about 4#e ozs4 to the ton4 ,to work these examples by ,poisson's formula let us assume the gangue to have a mean sp4 gr4 of #c4 ,then #ejj particles would weigh #c milligrams2 and #c4bfjiaca grams would contain #edc1ejj particles4 ,there would be then #ejj of ruby silver and #edc1ejj of gangue1 together #edd1jjj1 and the formula gives the square root of 7#hejjedcejj7_/eddjjj1 which works out to #fc particles as against #fb by the other method4 ,a practical conclusion from this is of course that either the ore must be powdered more finely or a larger portion than #c grams must be taken for the assay4 ,moreover1 it is evident that on such an ore no small sample must be taken containing less than several million particles4 ,consider now a copper ore of the same uniform fineness containing particles of copper pyrites 7sp4 gr4 #d7 of which #ajjj particles will weigh #h milligrams1 mixed with gangue of which #ajjj particles weigh #f milligrams4 ,if one gram of such ore contain 4#e gram of copper pyrites 7 4#agbe gram copper7 and 4#e gram of gangue1 these will contain #fb1ejj and say #hc1ejj particles respectively4 ,altogether #adf1jjj particles4 ,with ,poisson's formula this gives the limit of sampling error as the square root of 7#hfbejjhcejj7_/adfjjj or #eba particles4 ,but a variation of #eba on #fb1ejj is a variation of 4#hc per cent4 ,the percentage of copper in the ore is #ag4be per cent41 and 4#hc per cent4 of this is 4#ad per cent4 ,the limits of sampling error1 therefore1 are #ag4aa per cent4 and #ag4ci per cent4 ,again1 it must be remembered that the mean sampling error would be a little over one-quarter of this1 or say from #ag4b per cent4 to #ag4c per cent4 ,the practical conclusion is that a powder of this degree of fineness is not fine enough4 ,in the last place let us consider a similar iron ore containing #ij per cent4 of hmatite 7sp4 gr4 #e7 and #aj per cent4 of gangue 7sp4 gr4 #c71 #a gram of such ore will contain #ij1jjj particles of hmatite weighing 4#i gram and containing 4#fc gram of iron with say #af1ejj particles of gangue weighing 4#a gram4 ,altogether #ajf1ejj particles4 ,poisson's formula then gives the limits of variation as the square root of 7#hijjjjafejj7_/ajfejj or #ccd particles4 ,but #ccd on #ij1jjj is #j4bc on #fc4j1 which is the percentage of iron present4 ,the limits of sampling error then are #fb4gg per cent4 and #fc4bc per cent4 and the mean variation is from #fb4id per cent4 to #fc4jf per cent4 ,these examples are worthy of careful consideration1 and it must be remembered that the calculations are made on the assumption that the ore is made up of uniform particles of mineral of such fineness as would pass easily through an #hj sieve1 but which does not pretend to represent with great exactness the fineness of the powdered ore customary in practice4 ,they show that having passed through such a sieve is no proof of sufficient powdering1 not that all ores powdered and so sifted are unfit for assaying4 ,this last would be an absurd and illogical conclusion4 ,if an ore be powdered to a fairly fine sand and then be passed through a series of sieves1 say a #dj1 #fj1 and #hj1 in such a state that little or none remains on the first1 but the others retain a large proportion2 then of that which comes through the #hj sieve1 perhaps two-thirds by weight may be even coarser than the powder ,i have used in the example4 ,of the rest most may be of about half this diameter2 the weight of the really fine powder may be quite inconsiderable4 ,on the other hand1 if the grinding be continued until1 on sifting1 little or nothing that is powderable remains on the sieves2 then in the sifted product the proportions will be very different4 ,this last1 of course1 is the only right way of powdering4 ,also it is evident that so much depends on the manner of powdering that nothing precise can be stated as to the average coarseness of the powder4 ,suppose1 however1 by good powdering a product is obtained which may be represented by a uniform powder with particles #a_/bjth of a millimetre in diameter 7say roughly #a_/ejj inch74 ,compared with the previous powder1 the diameter has been divided by #b4e2 their number1 therefore1 in any given weight has been increased by the cube of #b4e1 which is #ae4f4 ,but the value of a sample varies as the square root of the number of particles4 ,hence the reduction in size and consequent increase in number has made the sample nearly four times better than before2 and it will be seen that this brings the sampling error within tolerable limits4 ,there are one or two words of warning which should be given4 ,in the first place1 using a #ij sieve instead of an #hj must not be too much relied on2 the powder ,i took in the example would pass through it4 ,it is a question of good powdering rather than of fine sifting4 ,in the second place1 a set of1 say half-a-dozen1 assays concordant within #a oz4 where the theory gives #d ozs4 as the limit of error does not upset the theory3 the theory itself states this as likely4 ,it is the error you may get in one or two assays out of a hundred1 not the error you are likely to get in any one assay1 which is considered under the heading limit of error4 ,accepting the result just arrived at that a portion of #a gram may be safely taken for an assay if the particles are #a-bjth of a millimetre in diameter1 the further question remains as to what weight of the original sample must be reduced to this degree of fineness4 ,this may be answered on the principle that the same degree of excellence should be aimed at in each of a series of samplings4 ,this principle is illustrated in the table on page #b4 ,a fine sand1 such as would pass a #dj sieve but be retained on a #fj sieve1 would be fairly represented by particles one-quarter of a millimetre in diameter4 ,this being five times coarser1 to contain the same number of particles must be #abe times 7the cube of #e7 as heavy2 therefore #abe grams of it can be taken with the same degree of safety as #a gram of the finer powder4 ,of such a sand about this weight should be taken and reduced to the finer powder4 ,if the ore were in coarse sand1 say in particles #a millimetre in diameter1 this would be four times as coarse as that last considered1 and we should have to take #fd times as much of it3 #fd times #abe grams is #h kilos1 or say roughly from #ae to #bj lbs4 ,this should be crushed to the finer size and mixed2 then from #ajj to #aej grams should be taken and ground to the finest powder4 ,there is1 however1 a reason why1 on the coarser stuff1 a smaller proportion may safely be used4 ,this becomes more evident if we consider a still coarser sample4 ,a heap of ore in stones about #b inches across would be #ej times coarser than the sand1 and an equivalent sample would need to be #abe1jjj times heavier2 this would amount to about #ajjj tons4 ,experienced samplers would say that under such conditions so large a sample was hardly necessary4 ,this is because ,i have assumed in the calculations that the grains of copper pyrites1 for example1 were all copper pyrites and the particles of gangue were free from copper4 ,this would be true or nearly so for the very fine powder1 but far from true in the case of the ore heap4 ,in the heap probably few of the stones would be pure ore and still fewer would be free from copper4 ,the stones would differ among themselves in their copper contents only within certain comparatively narrow limits4 ,and it is evident that1 if replacing one stone by another1 instead of resulting in the gain or loss of all the copper one or other contained1 merely affected the result to one-tenth of this amount1 then a sample of #a-ajjth of the weight 7say #aj tons7 would be equally safe4 ,it should be remembered1 however1 that while the man who samples on a large scale can safely and properly reduce the size of his samples on this account1 yet the principle is one which counts less and less as the stuff becomes more finely divided1 and ought to be ignored in the working down of the smaller samples which come to the assayer4 ,,footnotes3 #abf ,the #aj in #bj multiplied by #aj #ajj in #bjj4 #abg ,multiply the errors for #ajj by the square root of #aj4 #abh ,multiply the errors for #ajj by the square root of #fiij4 #abi ,sp4 ,gr4 #e4h4 ,silver #fj per cent4 #acj ,taking #bh as the limit of variation on #ajj4 #aca ,the weight of the ore less the weight of ruby silver in it4 ,,index4 ,acid measures1 #di ,acidimetry1 #cbc ,acidity of ores1 #afh ,acids1 #ed strength of1 #ed1 #ge1 #dcf ,air of mines1 carbonic acid in1 #dbh ,alkalies1 #ccj determination of1 #cca ,lawrence ,smith's method for1 #ccc1 #dab separation of1 #ccb ,alkalimetry1 #cbc ,alkaline earths1 #cbj ,alumina1 #cad determination of1 #cae in mineral phosphates1 #caf separation of1 #cad1 #caf ,amalgamation1 #abf ,ammonia1 detection of1 #cda determination of1 #cdb in natural waters1 #cec ,antimony1 #bbe detection of1 #bbg dry assay for1 #bbf gravimetric assay1 #bbh separation of1 #bbh volumetric assay1 #bbi ,arsenic1 #cha detection of1 #cha dry assay for1 #chb gravimetric assay1 #chc in brimstone1 #cic in crude arsenic1 #chh1 #cic in mispickel1 #abe1 #cib iodine1 assay for1 #chf separation by distilling1 #chd uranium acetate1 assay for1 #chi ,volhard's method applied to1 #abd ,assay book1 #aa note1 #ab results1 #g tons1 #ac1 #aca ,assaying1 #a methods1 #ae ,assays1 check1 #aed preliminary1 #adg ,atomic weights1 #fi table of1 #dcc ,barium1 #cbf ,baryta1 #cbf ,barytes1 sulphur in1 #cgh ,base bullion1 sampling of1 #aeg ,basic acetate separation1 #bcc ,baum's hydrometer1 #gg ,beryllia1 #cai ,bismuth1 #bbj colorimetric assay1 #bbc detection of1 #bba gravimetric determination of1 #bbb in commercial copper1 #bjh separation of1 #bbb ,black tin1 #bga an analysis of1 #bhg assay of1 #bgf copper in1 #bjd examination of1 #bhe separation by vanning1 #bgb ,blank assays1 #cd ,blende1 sulphur in1 #cge zinc in1 #bff ,book1 assay1 #aa laboratory1 #aj sample1 #i ,boracic acid4 ,see ,boron ,borax1 examination of1 #dca ,boron1 #dbi direct determination of1 #dca ,brass1 copper in1 #aid zinc in1 #bfe ,bromine and bromides1 #cfa ,bronze1 copper in1 #aid tin in1 #bha ,burettes1 #ea ,burnt ore1 silver in1 #aaf1 #aah sulphur in1 #cgg ,cadmium1 #bfi gravimetric determination1 #bfi separation of1 #bfi ,caesium1 #cci ,calcination1 #bb1 #ib1 #aci1 #cde ,calcium1 #cbj detection of1 #cba gravimetric determination1 #cba separation of1 #cba titration with normal acid1 #cbb titration with permanganate1 #cbb ,calculation of results1 #g ,calculations from formul1 #gj ,calorific effect of coal1 #dai ,calorimeter1 #dai ,calx1 #cde ,carbon1 #dad gravimetric determination1 #daf in iron or steel1 #dbc ,carbonates1 #dbd ,carbonic acid in the air of mines1 #dbh ,caustic potash potassium hydroxide1 #fe ,caustic soda sodium hydroxide1 #ff ,cerium1 #cah ,chalybite1 iron in1 #bdc ,charcoal1 #ba1 #id ,check assays for gold1 #aed for silver1 #ajd1 #aac ,chlorine and chlorides1 #cei ,chromium1 #cjg gravimetric assay1 #cji in chrome iron ore1 #cjh volumetric assay1 #cji ,clays1 examination of1 #caf ,coals1 #dah ,cobalt1 #bei detection of1 #bei dry assay for1 #bea gravimetric determination1 #bfj in hardhead1 #bhh separation from nickel1 #ddb1 #bed1 #beh ,coke1 #be ,common salt1 examination of1 #ccf ,concentrates1 assay for gold of1 #adj ,colorimetric assays1 #dd ,copper1 #age ,copper1 bismuth in1 #bjh colorimetric assay for1 #aij1 #bjc commercial1 arsenic in1 #bjh1 #chh commercial1 copper in1 #aic commercial1 examination of1 #bje cyanide assay for1 #aid dry assay of1 #agf dry assay1 loss of1 in1 #agf electrolytic assay for1 #aij1 #bjc gold in1 #bjf iodide assay for1 #aii iron in1 #bji1 #bdi lead in1 #bjf separation of1 #ahc silver in1 #bje sulphur in1 #bjg ,copper ores1 solution of1 #ahc valuation of1 #aha ,copper pyrites1 copper in1 #agi1 #ahh1 #aih1 #bjb sulphur in1 #cgf ,culm1 #bb ,cupel1 #bc1 #adb ,cupellation1 loss1 corrections for1 #ajc loss in gold1 #ade loss in silver1 #aja of gold lead alloys1 #ahb of silver lead alloys1 #ih1 #aaj temperature of1 #adc ,cyanicides1 #afi ,cyanide assay for copper1 #aid for nickel1 #bee for tin1 #bgh ,cyanides1 alkalinity of1 #afg assay of1 #afg commercial1 #afj double1 #afa gold-dissolving power1 #afb prussic acid1 #afb volumetric determination of1 #afc1 #afe ,cyanide liquors1 alkalinity of1 #afg assay of1 #afd1 #afe assay of1 for gold1 #adj assay of1 for zinc1 c41 #afi ,daniell cells1 #ahe ,didymium1 #cai ,dollars to the ton1 #i ,dry assays1 #af ,drying1 #e1 #cc ,earths1 #cad the alkaline1 #cbj ,electrodes1 #ahg ,electrolysis for copper1 #ahd for nickel1 #bed ,equations1 #fi ,erbia1 #cai ,ferrous and ferric salts1 #bca ,filtration1 #ca ,finishing point1 #db ,flasks1 graduated1 #di ,flatting1 #adi ,fluorine and fluorides1 #cfc ,fluxes1 #af1 #ic1 #acf1 #ach1 #adj ,formul1 #fh ,furnaces1 #be ,galena1 lead in1 #bag1 #bah ,gangue1 #dje iron in the1 #bdd ,gas-measuring apparatus1 #eb ,gases1 measurement of1 #dd ,gay-,lussac's assay for silver1 #aai assay for silver modified1 #abc ,german silver1 copper in1 #aid nickel in1 #bee1 #bei ,gold1 #abf amalgamation of1 #abf in cyanide liquor1 #adj loss of1 in cupellation1 #ade loss of1 in parting1 #aed preparation of1 #fc silver in1 #aeg silver in1 after parting1 #aed test for1 #abf ,gold-lead alloys1 cupellation of1 #adb sampling of1 #aeh ,gold ores assay with cyanide solutions1 #ada calcination of1 #aci concentrates1 #adj fluxing1 #acf1 #ach1 #adj sampling of1 #abg size of assay charges1 #abg tailings1 #adj ,gold-parting1 #aej platinum in1 #ade1 #aed1 #agj1 #aga ,gold-zinc slimes1 #adb ,graduated vessels1 #di ,gravimetric methods1 #ae1 #bg ,halogens1 #ceh ,hardhead1 #bhg an analysis of1 #bhi ,hot plate1 #cj ,hydrogen1 preparation of1 #fb reduction by1 #bhj ,hydrometer1 #gg ,ignition1 #cb in hydrogen1 #bhj ,indicators1 #db ,inquartation1 #adf ,iodine and iodides1 #cfb ,iridium1 #aga ,iron1 #bca bichromate assay for1 #bcg1 #bdc1 carbon in1 #dbc colorimetric assay for1 #bdg ferrous and ferric1 #bca gravimetric determination1 #bcc permanganate assay for1 #bcf1 #bch phosphorus in1 #cii reduction of ferric solutions1 #bce1 #bda separation of1 #bcb stannous chloride assay for1 #bdd volumetric assays for1 #bcd ,iron ores1 iron in1 #bdd1 #bdg phosphates in1 #cii ,laboratory books1 #i ,lanthanum1 #cai ,lawrence ,smith's method for alkalies1 #ccc1 #dab ,lead1 #baa colorimetric assay for1 #bah detection of1 #baa dry assay for1 #baa gravimetric determination of1 #bac in commercial copper1 #bjf in commercial zinc1 #bad in galena1 #bag1 #bah separation of1 #baa1 #bac volumetric determination of1 #bad ,litharge1 use of1 in dry assays1 #bj1 #ic ,lithium1 #cch ,lime1 #cbj milk of1 #cba volumetric assays for1 #cbb ,limestone1 examination of1 #cbi lime in1 #cbd ,limewater1 #cba ,loths1 #i ,magnesia1 magnesium1 #cbh mixture1 preparation of1 #fd ,manganese1 #bih colorimetric assay1 #cjf detection of1 #bii gravimetric determination of1 #cjj separation of1 #bii volumetric determination of1 #cjj ,manganese peroxide1 ferrous sulphate assay for1 #cja iodine assay for1 #cjb manganese dioxide1 #bih ,manganese ore1 copper in1 #bjd manganese in1 #cjj peroxide in1 #cjb ,matte1 #ah ,measuring1 #di flasks1 #di gases1 #dd1 #eb gold buttons1 #acc1 #ddj1 liquids1 #di silver buttons1 #ajf ,mechanical methods1 #af ,mercury1 #aga dry assay1 #agb wet assay1 #agc ,metallic particles in ores1 gold1 #abi particles in ores1 silver1 #ajh particles1 tin1 #bgh1 #bhg ,micrometer1 #acc ,microscope1 measuring with the1 #ddj1 #acc ,mispickel1 arsenic in1 #abe1 #cib sulphur in1 #cgf ,moisture1 #g1 #cej ,molybdate separation for phosphates1 #cie solution1 preparation of1 #fj ,molybdenum1 #caa ,muffle1 #be ,nessler's solution1 #cdb ,nickel1 #bea dry assay for1 #bea electrolytic assay1 #bed gravimetric determination of1 #bed in ,german silver1 #bee1 #bei separation from cobalt1 #bed1 #beh1 #ddb separation from iron1 #beh separation from manganese1 #beh separation of1 #bec volumetric assay1 #bee ,niobium1 #big ,nitre1 #bb use of1 in dry assays1 #ie ,nitrogen and nitrates1 #djj ,nitrometer1 #djc ,normal acid1 normal solutions1 #cbc ,ores1 determining water in1 #e1 #cea drying1 #e powdering1 #d1 #aji1 #acj1 #ddh quantities of1 for an assay1 #aa1 #bg1 #abg sampling1 #a1 #abg1 #ddd with metallic particles1 #c1 #ajh1 #abi ,osmiridium1 #aga ,osmium1 #aga ,ounces to the ton1 long1 #ajg to the ton1 short1 #acb ,oxidation1 #cde ,oxides1 #cde determination of oxygen in1 #cdf ,oxidising agents1 #bb1 #ie1 #cde effect of nitre1 #ie effect of nitric acid1 #ef ,oxygen1 #cdd equivalent1 #ceh in natural waters1 #cdd1 #cef in ores1 #cdh ,palladium1 #aga ,parting1 #aej acids1 #aej in flasks1 #aea in glazed crucibles1 #aec in special apparatus1 #aef in test tubes1 #aeb ,phosphate1 assay of apatite for1 #cii assay of iron ore for1 #cii ,phosphates1 gravimetric assay1 #cif volumetric assay1 #cig ,phosphorus and phosphates1 #cid in iron1 #cii ,pipette1 #ej1 #abj ,platinum1 #agj in gold1 #ade1 #aed1 #agj ,potash1 commercial examination of1 #cch ,potassium1 #ccf gravimetric determination1 #ccg ,potassium cyanide1 #bb1 #fe1 #afj commercial assay of1 #afg commercial1 purity of1 #afa ,powdering1 #d1 #acj1 #ddh1 #aji ,precipitation1 #cj ,precipitates1 drying1 #cb igniting1 #cb1 #cd washing1 #ca ,preliminary assays1 #ajd1 #adg ,preparation of acids1 #ed of other reagents1 #ei ,prill1 #ajh1 #abi1 #bgh1 #bhg ,produce1 #h ,pyrarsenate of magnesia1 #chc ,pyrites1 iron in1 #bdd sulphur in1 #cgj1 #cgf ,pyrophosphate of magnesia1 #cig ,quantity to be taken for an assay1 #aa1 #bg1 #abg ,quartation1 #adf ,quartering1 #b ,reagents1 strength of1 #ed ,red lead for dry assays1 #bj1 #bb1 #id ,reducing agents1 #ba1 #id effects of charcoal1 c41 #id effect of mineral sulphides1 #ie1 #ig1 #ih ,reduction by hydrogen1 #bhj of ferric solutions1 #bce1 #bdb1 #bdd ,regulus1 #ah ,report form1 #ab ,results1 calculation of1 #g1 #ac1 #af1 #ch1 #ajg1 #aca1 #acb statement of1 #g ,rhodium1 #aga ,roasting1 #bb1 #cde ,rolling1 #adi ,rubidium1 #cdj ,ruthenium1 #aga ,sample book1 #i ,sampling1 #a effect of powdering on1 #ddi errors1 #ddg gold ores1 #abg metals1 #aeg theory of1 #ddd ,scorification of silver ores1 #hh ,scorifier1 #bc1 #hi ,selenium1 #cgi ,separation1 as sulphides1 #eg basic acetate1 #bcc molybdate1 #cie ,shales1 bituminous1 #dbj ,silicon and silicates1 #dje in iron1 #dad ,silica in rocks1 #dji in slags1 #dad ,silicates1 alkalies in1 #ccc1 #dab beryllia in1 #cbj examination of1 #dji titanium in1 #daa ,silver1 #hg correction for cupellation loss1 #ajc detection of1 #hg ,gay-,lussac's assay1 #aai ,gay-,lussac's assay modified1 #abc gravimetric determination of1 #aag in bullion1 #aac in burnt ore1 #aaf1 #aah in copper1 #aad1 #bje in galena1 #aad in lead1 #aac in oxide of lead1 #aac in silver precipitate1 #aae loss in cupellation1 #aja pure preparation of1 #ff ,volhard's assay1 #aba volumetric methods1 #aai1 #aba1 #abc ,silver lead alloys1 cupellation of1 #ih sampling of1 #aeg ,silver ore1 crucible assay of1 #ij metallic particles in1 #ajh scorification of1 #hh ,size of assay charges1 #aa1 #bg1 #abg ,slags1 #ai ,soda-lime1 #dbe ,sodium1 #ccd ,sodium cyanide1 #afj ,solution1 #bi ,solutions1 normal1 #cbc standard1 #cf ,specific gravity1 #ge1 #dcf ,speise1 #ai ,standard1 #cg solutions1 #cf ,standardising1 #cg ,steel1 carbon in1 #dbc chromium in1 #caj manganese in1 #cjj ,stoking1 #be1 #adc ,strength of reagents1 #ed ,strontium1 #cbd ,sulphates and sulphur1 #cfg gravimetric determination1 #cfi volumetric determination1 #cgj ,sulphides1 reducing action of1 #i1 #ie ,sulphocyanate assay for silver1 #aba ,sulphur in blende1 #cge in burnt ore1 #cgg in chalcocite1 #cgf in coal1 #dai in copper1 #bjg in copper pyrites1 #cgf in mispickel1 #cgf in pyrites1 #cgj1 #cgf ,sulphuretted hydrogen1 preparation1 #eg ,surcharge1 #aed ,system in assaying1 #bh ,table1 atomic weights1 #dcc comparing thermometers1 #dce ounces to the long ton1 #ajg ounces to the short ton1 #acb sp4 g4 ammonia1 #dch sp4 g4 hydrochloric acid1 #dcg sp4 g4 minerals1 #hf sp4 g4 nitric acid1 #dcf sp4 g4 sulphuric acid1 #dci sp4 g4 water1 #hc ,tantalum1 #big ,tartar1 #bj1 #id ,tellurium1 #cgi improved test for1 #aej ,thallium1 #bai ,thorium1 #cag ,tin1 #bga ,see also ,black tin assay for1 by vanning1 #bgc copper in1 #bjd ,cornish assay1 #bgf cyanide assay1 #bgh detection of1 #bgi gravimetric determination of1 #bha iron in1 #bej separation of1 #bhj volumetric assay for1 #bhb ,tin arsenide1 #bhd ,tin phosphide1 #bhd ,tin slag1 #bij an analysis of1 #bib tin in1 #bij ,titanium1 #bib detection of1 #bic in black tin1 #bgb1 #bhg in rocks1 #daa separation1 c41 #bid ,titration1 #ce indirect1 #dc1 #gb ,ton1 assay1 #ac1 #aca1 long1 #bbdj lbs4 #cb1fff4f oz41 #ajg short1 #bjjj lbs #bi1aff4f oz41 #acb ,tungsten1 #bie ,tungstic acid1 #bie gravimetric determination1 #bif in black tin1 #bhe in wolfram1 #bif ,uranium1 #cab ,valuation1 of copper ores1 #aha ,vanadium1 #caj ,vanning1 #bgc ,volhard's assay applied to arsenic1 #abd silver assay1 #aba ,volume-corrector1 #ec ,volumetric assay1 #ce1 #ch ,water1 #g1 #cej direct determination of1 #cea examination of1 #ceb expansion of1 #hc solids in1 #ced ,weighing1 #dg small gold buttons1 #aca ,weights1 #dg ,wolfram1 an analysis of1 #bif tungstic acid in1 #bif ,yttria1 #cai ,zinc1 #bfa commercial1 examination of1 #bfh commercial1 iron in1 #bdi commercial1 lead in1 #bad dry assay1 #bfa gasometric assay1 #bff gravimetric determination1 #bfb in blende1 #bff in cyanide liquors1 #afi in silver precipitate1 #bff separation of1 #bfb volumetric assay1 #bfc ,zirconia1 #cag ,printed by ,,ballantyne1 ,,hanson ,co4 ,london ,edinburgh4 ,a ,,selection ,,from ,,the ,,scientific ,,and ,,technical ,,works ,,published ,,by ,,charles ,,griffin ,,company1 ,,limited4 ,illustration ,,messrs4 ,,charles ,,griffin ,,company',s ,,publications may be obtained through any ,bookseller in the ,united ,kingdom1 or will be sent ,post-free on receipt of a remittance to cover published price4 ,to prevent delay1 ,orders should be accompanied by a ,cheque or ,postal ,order crossed ,,union ,,of ,,london ,,and ,,smith',s ,,bank1 ,chancery ,lane ,branch4 999999 ,for ,,index1 see next page4 ,transcriber's ,note3 ,no index on next page4 ,illustration ,,complete ,,technical1 ,,medical1 and ,,general ,,catalogues forwarded ,post-free on ,application4 ,,london3 ,,exeter ,,street1 ,,strand4 99 99 99 99 99 ,,third ,,edition1 ,revised1 with an ,additional ,chapter on ,foundations4 ,numerous ,diagrams1 ,examples1 and ,tables4 ,large #hvo4 ,cloth4 #afs4 ,,the ,,design ,,of ,,structures3 ,a ,practical ,treatise on the ,building of ,bridges1 ,roofs1 c4 ,,by ,s4 ,,anglin1 ,c4,e41 ,master of ,engineering1 ,royal ,university of ,ireland1 late ,whitworth ,scholar1 c4 ,students of ,engineering will find this ,text-,book ,,invaluable4--,architect4 ,the author has certainly succeeded in producing a ,,thoroughly ,,practical ,text-,book4--,builder4 ,we can unhesitatingly recommend this work not only to the ,student1 as the ,,best ,,text-,,book on the subject1 but also to the professional engineer as an ,,exceedingly ,,valuable book of reference4--,mechanical ,world4 99 99 99 99 99 ,,third ,,edition1 ,thoroughly ,revised4 ,royal #hvo4 ,with numerous ,illustrations and #ac ,lithographic ,plates4 ,handsome ,cloth4 ,price #cjs4 ,a ,,practical ,,treatise ,,on ,,bridge-,,construction3 ,being a ,text-,book on the ,construction of ,bridges in ,iron and ,steel4 ,,for ,,the ,,use ,,of ,,students1 ,,draughtsmen1 ,,and ,,engineers4 ,,by ,t4 ,,claxton ,,fidler1 ,m4 ,,inst4 ,c4,e41 ,prof4 of ,engineering1 ,university ,college1 ,dundee4 ,,general ,,contents4--,,part ,i4--,elementary ,statics4 ,,part ,,ii4--,general ,principles of ,bridge-,construction4 ,,part ,,iii4--,the ,strength of ,materials4 ,,part ,,iv4--,the ,design of ,bridges in ,detail4 ,the new edition of ,mr4 ,fidler's work will again occupy the same ,,conspicuous ,,position among professional text-books and treatises as has been accorded to its predecessors4 ,the instruction imparted is ,,sound1 ,,simple1 ,,and ,,full4 ,the volume will be found valuable and useful alike to those who may wish to study only the theoretical principles enunciated1 and 444 to others whose object and business is 444 practical4--,the ,engineer4 99 99 99 99 99 ,at ,press4 ,in ,large #hvo4 ,handsome ,cloth4 ,with ,copious ,plates and ,illustrations4 ,the ,principles and ,practice of ,,dock ,,engineering4 ,by ,,bryson ,,cunningham1 ,b4,e41 ,,assoc4,m4,,inst4,c4,e41 ,of the ,engineers' ,department1 ,mersey ,docks and ,harbour ,board4 ,,general ,,contents4 ,historical and ,discursive4--,dock ,design4--,constructive ,appliances4--,materials4--,dock and ,quay ,walls4--,entrance ,passages and ,locks4--,jetties1 ,wharves1 and ,piers4--,dock ,gates and ,caissons4--,transit ,sheds and ,warehouses4--,dock ,bridges4--,graving and ,repairing ,docks4--,working ,equipment of ,docks4--,,index4 999999 ,the object of the ,author has been to deal fully and comprehensively with the problems arising out of the construction and maintenance of ,docks and their appanages1 not simply as a record of works carried out1 but as a treatise on the principles underlying their construction and an investigation of the mathematical theories involved4 ,it is primarily intended for the student2 but it is hoped that the large amount of data and material collected from various sources1 and in many cases contributed specially for this book1 will render it useful to the expert engineer as a work of reference2 while1 at the same time1 of general interest to directors and others connected with the management and administration of seaports4 99 99 99 99 99 ,,third ,,edition4 ,in ,two ,parts1 ,published ,separately4 ,a ,,text-,,book ,,of ,engineering ,drawing and ,design ,vol4 ,i4--,practical ,geometry1 ,plane1 and ,solid4 #cs4 ,,vol4 ,,ii4--,machine and ,engine ,drawing and ,design4 #ds4 #f;d4 by ,,sidney ,h4 ,,wells1 ,,wh4,,sc41 ,a4,m4,,inst4,c4,e41 ,a4,m4,,inst4,,mech4,e41 ,principal of the ,battersea ,polytechnic ,institute1 and ,head of the ,engineering ,department therein2 formerly of the ,engineering ,departments of the ,yorkshire ,college1 ,leeds2 and ,dulwich ,college1 ,london4 ,with many ,illustrations1 specially prepared for the ,work1 and numerous ,examples1 for the ,use of ,students in ,technical ,schools and ,colleges4 ,a ,,capital ,,text-,,book1 arranged on an ,,excellent ,,system1 calculated to give an intelligent grasp of the subject1 and not the mere faculty of mechanical copying4444 ,mr4 ,wells shows how to make complete working drawings1 discussing fully each step in the design4--,electrical ,review4 ,the first book leads easily and naturally towards the second1 where the technical pupil brought into contact with large and more complex designs4--,the ,schoolmaster4 99 99 99 99 99 ,works by ,,bryan ,,donkin1 ,m4 ,inst4 ,c4,e41 ,m4 ,inst4 ,mech4 ,e41 c4 ,,third ,,edition1 ,revised and ,enlarged4 ,with additional ,illustrations4 ,large #hvo1 ,handsome ,cloth4 #bes4 ,,gas1 ,,oil1 ,,and ,,air ,,engines3 ,a ,practical ,text-,book on ,internal ,combustion ,motors without ,boiler4 ,,by ,,bryan ,,donkin1 ,m4 ,,inst4 ,c4,e41 ,m4 ,,inst4 ,,mech4 ,e4 ,,general ,,contents4--,gas ,engines3--,general ,description--,history and ,development--,british1 ,french1 and ,german ,gas ,engines--,gas ,production for ,motive ,power--,theory of the ,gas ,engine--,chemical ,composition of ,gas in ,gas ,engines--,utilisation of ,heat--,explosion and ,combustion4 ,oil ,motors3--,history and ,development--,various ,types--,priestman's and other ,oil ,engines4 ,hot-,air ,engines3--,history and ,development--,various ,types3 ,stirling's1 ,ericsson's1 c41 c4 ,the ,,best ,,book ,,now ,,published on ,gas1 ,oil1 and ,air ,engines4444 ,will be of ,,very ,,great ,,interest to the numerous practical engineers who have to make themselves familiar with the motor of the day4444 ,mr4 ,donkin has the advantage of ,,long ,,practical ,,experience1 combined with ,,high ,,scientific ,,and ,,experimental ,,knowledge1 and an accurate perception of the requirements of ,engineers4--,the ,engineer4 ,we ,,heartily ,,recommend ,mr4 ,donkin's work4444 ,a monument of careful labour4444 ,luminous and comprehensive4--,journal of ,gas ,lighting4 ,a thoroughly ,,reliable ,,and ,,exhaustive ,treatise4--,engineering4 99 99 99 99 99 ,in ,quarto1 ,handsome ,cloth4 ,with ,numerous ,plates4 #bes4 ,,the ,,heat ,,efficiency ,,of ,,steam ,,boilers 7,,land1 ,,marine1 ,,and ,,locomotive74 ,with many ,tests and ,experiments on different ,types of ,boilers1 as to the ,heating ,value of ,fuels1 c41 with ,analyses of ,gases and ,amount of ,evaporation1 and ,suggestions for the ,testing of ,boilers4 ,,by ,,bryan ,,donkin1 ,m4 ,,inst4 ,c4,e4 ,,general ,,contents4--,classification of different ,types of ,boilers--#dbe ,experiments on ,english and ,foreign ,boilers with their ,heat ,efficiencies shown in ,fifty ,tables--,fire ,grates of ,various ,types--,mechanical ,stokers--,combustion of ,fuel in ,boilers--,transmission of ,heat through ,boiler ,plates1 and their ,temperature--,feed ,water ,heaters1 ,superheaters1 ,feed ,pumps1 c4--,smoke and its ,prevention--,instruments used in ,testing ,boilers--,marine and ,locomotive ,boilers--,fuel ,testing ,stations--,discussion of the ,trials and ,conclusions--,on the ,choice of a ,boiler1 and ,testing of ,land1 ,marine1 and ,locomotive ,boilers--,appendices--,bibliography--,i ndex4 ,with ,plates illustrating ,progress made during recent years1 and the best ,modern ,practice4 ,a ,,work ,,of ,,reference ,,at ,,present ,,unique4 ,will give an answer to almost any question connected with the performance of boilers that it is possible to ask4--,engineer4 ,probably the ,,most ,,exhaustive rsum that has ever been collected4 ,a ,,practical ,,book by a thoroughly practical man4--,iron and ,coal ,trades ,review4 99 99 99 99 99 ,,third ,,edition1 ,revised and ,enlarged4 ,pocket-,size1 ,leather1 #abs4 #f;d42 also ,larger ,size for ,office ,use1 ,cloth1 #abs4 #f;d4 ,boilers1 ,marine and ,land3 ,,their ,,construction ,,and ,,strength4 ,a ,,handbook ,,of ,,rules1 ,,formul1 ,,tables1 ,c41 ,,relative ,,to ,,material1 ,,scantlings1 ,,and ,,pressures1 ,,safety ,,valves1 ,,springs1 ,,fittings ,,and ,,mountings1 ,c4 ,,for ,,the ,,use ,,of ,,engineers1 ,,surveyors1 ,,boiler-,,makers1 ,,and ,,steam ,,users4 ,,by ,t4,w4 ,,traill1 ,m4 ,,inst4 ,c4,e41 ,f4,e4,r4,n41 ,late ,engineer ,surveyor-in-,chief to the ,board of ,trade4 999999 ,to the ,second and ,third ,editions many ,new ,tables for ,pressure1 up to #bjj ,lbs4 per ,square ,inch have been added4 ,,the ,,most ,,valuable ,,work on ,boilers published in ,england4--,shipping ,world4 ,contains an ,,enormous ,,quantity ,,of ,,information arranged in a very convenient form4444 ,a ,,most ,,useful ,,volume 444 supplying information to be had nowhere else4--,the ,engineer4 99 99 99 99 99 ,third ,impression4 ,large ,crown #hvo4 ,with numerous ,illustrations4 #fs4 ,,engine-,,room ,,practice3 ,a ,handbook for ,engineers and ,officers in the ,royal ,navy and ,mercantile ,marine1 ,including the ,management of the ,main and ,auxiliary ,engines on ,board ,ship4 ,,by ,,john ,g4 ,,liversidge1 ,engineer1 ,r4,n41 ,a4,m4,i4,c4,e41 ,instructor in ,applied ,mechanics at the ,royal ,naval ,college1 ,greenwich4 ,contents4--,general ,description of ,marine ,machinery4--,the ,conditions of ,service and ,duties of ,engineers of the ,royal ,navy4--,entry and ,conditions of ,service of ,engineers of the ,leading ,s4,s4 ,companies4--,raising ,steam4--,duties of a ,steaming ,watch on ,engines and ,boilers4--,shutting off ,steam4--,harbour ,duties and ,watches4--,adjustments and ,repairs of ,engines4--,preservation and ,repairs of ,tank ,boilers4--,the ,hull and its ,fittings4--,cleaning and ,painting ,machinery4--,reciprocating ,pumps1 ,feed ,heaters1 and ,automatic ,feed-,water ,regulators4--,evaporators4--,steam ,boats4--,electric ,light ,machinery4--,hydraulic ,machinery4--,air-,compressing ,pumps4--,refrigerating ,machines4--,machinery of ,destroyers4--,the ,management of ,water-,tube ,boilers4--,regulations for ,entry of ,assistant ,engineers1 ,r4,n4--,questions given in ,examinations for ,promotion of ,engineers1 ,r4,n4--,regulations respecting ,board of ,trade ,examinations for ,engineers1 c4 ,the contents ,,cannot ,,fail ,,to ,,be ,,appreciated4--,the ,steamship4 ,this very useful book4444 ,,illustrations are of ,,great ,,importance in a work of this kind1 and it is satisfactory to find that ,,special ,,attention has been given in this respect4--,engineers' ,gazette4 99 99 99 99 99 ,in ,crown #hvo1 extra1 with ,numerous ,illustrations4 ,shortly4 ,,gas ,,and ,,oil ,,engines3 ,an ,introductory ,text-,book on the ,theory1 ,design1 ,construction1 and ,testing of ,internal ,combustion ,engines without ,boiler4 ,,for ,,the ,,use ,,of ,,students4 ,,by ,,prof4 ,w4,h4 ,,watkinson1 ,,whit4 ,,sch41 ,m4 ,,inst4 ,,mech4 ,e41 ,glasgow and ,west of ,scotland ,technical ,college4 99 99 99 99 99 ,,second ,,edition1 ,revised4 ,with numerous ,plates reduced from ,working ,drawings and #bhj ,illustrations in the ,text4 #bas4 ,a ,,manual ,,of ,,locomotive ,,engineering3 ,a ,practical ,text-,book for the ,use of ,engine ,builders1 ,designers and ,draughtsmen1 ,railway ,engineers1 and ,students4 ,,by ,,william ,,frank ,,pettigrew1 ,m4 ,,inst4 ,c4,e4 ,with a ,section on ,american and ,continental ,engines4 ,,by ,,albert ,f4 ,,ravenshear1 ,b4,,sc41 ,of ,his ,majesty's ,patent ,office4 ,contents4--,historical ,introduction1 #agfc-ahfc4--,modern ,locomotives3 ,simple4--,modern ,locomotives3 ,compound4--,primary ,consideration in ,locomotive ,design4--,cylinders1 ,steam ,chests1 and ,stuffing ,boxes4--,pistons1 ,piston ,rods1 ,crossheads1 and ,slide ,bars4--,connecting and ,coupling ,rods4--,wheels and ,axles1 ,axle ,boxes1 ,hornblocks1 and ,bearing ,springs4--,balancing4--,valve ,gear4--,slide ,valves and ,valve ,gear ,details4--,framing1 ,bogies and ,axle ,trucks1 ,radial ,axle ,boxes4--,boilers4--,smokebox1 ,blast ,pipe1 ,firebox ,fittings4--,boiler ,mountings4--,tenders4--,railway ,brakes4--,lubrication4--,consumption of ,fuel1 ,evaporation and ,engine ,efficiency4--,american ,locomotives4--,continental ,locomotives4--,repairs1 ,running1 ,inspection1 and ,renewals4--,three ,appendices4--,index4 ,likely to remain for many years the ,,standard ,,work for those wishing to learn ,design4--,engineer4 ,a most interesting and valuable addition to the bibliography of the ,locomotive4--,railway ,official ,gazette4 ,we recommend the book as ,,thoroughly ,,practical in its character1 and ,,meriting ,a ,,place ,,in ,,any ,,collection of 444 works on ,locomotive ,engineering4--,railway ,news4 ,the work ,,contains ,,all ,,that ,,can ,,be ,,learnt from a book upon such a subject4 ,it will at once rank as ,,the ,,standard ,,work ,,upon ,,this ,,important ,,subject4--,railway ,magazine4 99 99 99 99 99 ,in ,large #hvo4 ,handsome ,cloth4 ,with ,plates and ,illustrations4 #afs4 ,,light ,,railways ,,at ,,home ,,and ,,abroad4 ,,by ,,william ,,henry ,,cole1 ,m4 ,,inst4 ,c4,e41 ,late ,deputy-,manager1 ,north-,western ,railway1 ,india4 ,contents4--,discussion of the ,term ,light ,railways4--,english ,railways1 ,rates1 and ,farmers4--,light ,railways in ,belgium1 ,france1 ,italy1 other ,european ,countries1 ,america and the ,colonies1 ,india1 ,ireland4--,road ,transport as an alternative4--,the ,light ,railways ,act1 #ahif4--,the ,question of ,gauge4--,construction and ,working4--,locomotives and ,rolling-,stock4--,light ,railways in ,england1 ,scotland1 and ,wales4--,appendices and ,index4 ,mr4 ,w4,h4 ,cole has brought together 444 a ,,large ,,amount ,,of ,,valuable ,,information 444 hitherto practically inaccessible to the ordinary reader4--,times4 ,will remain1 for some time yet a ,,standard ,,work in everything relating to ,light ,railways4--,engineer4 ,the author has extended practical experience that makes the book lucid and useful4 ,it is ,,exceedingly well done--,engineering4 ,the whole subject is ,,exhaustively and ,,practically considered4 ,the work can be cordially recommended as ,,indispensable to those whose duty it is to become acquainted with one of the prime necessities of the immediate future4--,railway ,official ,gazette4 ,,there ,,could ,,be ,,no ,,better ,,book of first reference on its subject4 ,all classes of ,engineers will welcome its appearance4--,scotsman4 99 99 99 99 99 ,,third ,,edition1 ,revised and ,enlarged4 ,with ,numerous ,illustrations4 ,price #hs4 #f;d4 ,,valves ,,and ,,valve-,,gearing3 ,,including ,,the ,,corliss ,,valve ,,and ,,trip ,,gears4 ,,by ,,charles ,,hurst1 ,practical ,draughtsman4 ,,concise explanations illustrated by #aae ,,very ,,clear ,,diagrams and drawings and #d folding-plates 444 the book fulfils a ,,valuable function4--,athenum4 ,,mr4 ,,hurst',s ,,valves ,,and ,,valve-,,gearing will prove a very valuable aid1 and tend to the production of ,engines of ,,scientific ,,design ,,and ,,economical ,,working4444 ,will be largely sought after by ,students and ,designers4--,marine ,engineer4 ,,useful ,,and ,,thoroughly ,,practical4 ,will undoubtedly be found of ,,great ,,value to all concerned with the design of ,valve-gearing4--,mechanical ,world4 ,almost ,,every ,,type ,,of ,,valve and its gearing is clearly set forth1 and illustrated in such a way as to be ,,readily ,,understood and ,,practically ,,applied by either the ,engineer1 ,draughtsman1 or ,student4444 ,should prove both ,,useful and ,,valuable to all ,engineers seeking for ,,reliable and ,,clear information on the subject4 ,its moderate price brings it within the reach of all--,industries and ,iron4 ,mr4 ,,hurst',s work is ,,admirably suited to the needs of the practical mechanic4444 ,it is free from any elaborate theoretical discussions1 and the explanations of the various types of valve-gear are accompanied by diagrams which render them ,,easily ,,understood4--,the ,scientific ,american4 99 99 99 99 99 ,hints on ,steam ,engine ,design and ,construction4 ,by ,,charles ,,hurst1 ,author of ,valves and ,valve ,gearing4 ,in ,paper ,boards1 #hvo41 ,cloth ,back4 ,illustrated4 ,price #as4 #f;d4 net4 ,,contents4--,i4 ,steam ,pipes4--,,ii4 ,valves4--,,iii4 ,cylinders4--,,iv4 ,air ,pumps and ,condensers4--,v4 ,motion ,work4--,,vi4 ,crank ,shafts and ,pedestals4--,,vii4 ,valve ,gear4--,,viii4 ,lubrication4--,,ix4 ,miscellaneous ,details--,,index4 ,a handy volume which every practical young engineer should possess4--,the ,model ,engineer4 99 99 99 99 99 ,,just ,,out4 ,strongly ,bound in ,super ,royal #hvo4 ,cloth ,boards4 ,,bonus ,,tables3 ,for ,calculating ,wages on the ,bonus or ,premium ,systems4 ,for ,engineering1 ,technical and ,allied ,trades4 ,,by ,,henry ,a4 ,,golding1 ,a4,m4,,inst4,m4,e41 ,technical ,assistant to ,messrs4 ,bryan ,donkin and ,clench1 ,ltd41 and ,assistant ,lecturer in ,mechanical ,engineering at the ,northampton ,institute1 ,london1 ,e4,c4 ,the adoption of this system for the payment of workmen has created a demand for some handy table or series of tables1 by means of which the wages may be easily found without the necessity of any calculations whatever4 ,with the object of supplying this need1 the author has compiled the following tables1 which have been in practical use for some time past at a large engineering works in ,london1 and have been found of inestimable value4 ,not only are they of great value as a 'time saving appliance1' the computation of the bonus or premiums earned by a number of men taking only one-tenth the time by the aid of these tables compared with ordinary calculations1 but they possess the additional advantage of being less liable to error1 as there is practically no possibility of a mistake occurring4--,extract from ,preface4 99 99 99 99 99 ,large #hvo1 ,handsome ,cloth4 ,with ,illustrations1 ,tables1 c4 #bas4 ,lubrication ,lubricants3 ,a ,,treatise ,,on ,,the ,,theory ,,and ,,practice ,,of ,,lubrication ,,and ,,on ,,the ,,nature1 ,,properties1 ,,and ,,testing ,,of ,,lubricants4 ,,by ,,leonard ,,archbutt1 ,f4,i4,c41 ,f4,c4,s41 ,chemist to the ,midland ,railway ,company1 ,,and ,r4 ,,mountford ,,deeley1 ,m4,i4,m4,e41 ,f4,g4,s41 ,midland ,railway ,locomotive ,works' ,manager1 ,derby4 ,,contents4--,i4 ,friction of ,solids4--,,ii4 ,liquid ,friction or ,viscosity1 and ,plastic ,friction4--,,iii4 ,superficial ,tension4--,,iv4 ,the ,theory of ,lubrication4--,v4 ,lubricants1 their ,sources1 ,preparation1 and ,properties4--,,vi4 ,physical ,properties and ,methods of ,examination of ,lubricants4--,,vii4 ,chemical ,properties and ,methods of ,examination of ,lubricants4--,,viii4 ,the ,systematic ,testing of ,lubricants by ,physical and ,chemical ,methods4--,,ix4 ,the ,mechanical ,testing of ,lubricants4--,x4 ,the ,design and ,lubrication of ,bearings4--,,xi4 ,the ,lubrication of ,machinery4--,,index4 ,destined to become a ,,classic on the subject4--,industries and ,iron4 ,contains practically ,,all ,,that ,,is ,,known on the subject4 ,deserves the careful attention of all ,engineers4--,railway ,official ,guide4 99 99 99 99 99 ,,fourth ,,edition4 ,very fully ,illustrated4 ,cloth1 #ds4 #f;d4 ,,steam-,,boilers3 ,,their ,,defects1 ,,management1 ,,and ,,construction4 ,,by ,r4,d4 ,,munro1 ,chief ,engineer of the ,scottish ,boiler ,insurance and ,engine ,inspection ,company4 ,,general ,,contents4--,i4 ,,explosions caused 7#a7 by ,overheating of ,plates--7#b7 ,by ,defective and ,overloaded ,safety ,valves--7#c7 ,by ,corrosion1 ,internal or ,external--7#d7 ,by ,defective ,design and ,construction 7,unsupported ,flue ,tubes2 ,unstrengthened ,manholes2 ,defective ,staying2 ,strength of ,rivetted ,joints2 ,factor of ,safety7--,,ii4 ,,construction ,,of ,,vertical ,,boilers3 ,shells--,crown ,plates and ,uptake ,tubes--,man-,holes1 ,mud-,holes1 and ,fire-,holes--,fireboxes--,mountings--,m anagement--,cleaning--,table of ,bursting ,pressures of ,steel ,boilers--,table of ,rivetted ,joints--,specifications and ,drawings of ,lancashire ,boiler for ,working ,pressures 7a7 #hj lbs42 7b7 #bjj lbs4 per square inch respectively4 ,a valuable companion for workmen and engineers engaged about ,steam ,boilers1 ought to be carefully studied1 and ,,always ,,at ,,hand4--,coll4 ,guardian4 ,the book is ,,very ,,useful1 especially to steam users1 artisans1 and young ,engineers4--,engineer4 99 99 99 99 99 ,,by ,,the ,,same ,,author4 ,,kitchen ,,boiler ,,explosions3 ,why they ,occur1 and ,how to ,prevent their ,occurrence4 ,a ,practical ,handbook based on ,actual ,experiment4 ,with ,diagram and ,coloured ,plate4 ,price #cs4 99 99 99 99 99 ,,just ,,out4 ,in ,crown #hvo1 ,handsome ,cloth4 ,with ,numerous ,illustrations4 #es4 net4 ,,emery ,,grinding ,,machinery4 ,a ,text-,book of ,workshop ,practice in ,general ,tool ,grinding1 and the ,design1 ,construction1 and ,application of the ,machines ,employed4 ,,by ,r4,b4 ,,hodgson1 ,a4,m4 ,,inst4 ,,mech4 ,e41 ,author of ,machines and ,tools ,employed in the ,working of ,sheet ,metals4 ,,introduction4--,tool ,grinding4--,emery ,wheels4--,mounting ,emery ,wheels4--,emery ,rings and ,cylinders4--,conditions to ,ensure ,efficient ,working4--,leading ,types of ,machines4--,concave and ,convex ,grinding4--,cup and ,cone ,machines4--,multiple ,grinding4--,guest ,universal and ,cutter ,grinding ,machines4--,ward ,universal ,cutter ,grinder4--,press4--,tool ,grinding4--,lathe ,centre ,grinder4--,polishing4--,,index4 ,deals practically with every phase of his subject4--,ironmonger4 99 99 99 99 99 ,,fifth ,,edition4 ,folio1 strongly half-bound1 #ba_/4 ,,traverse ,,tables3 ,computed to ,four ,places of ,decimals for every ,minute of ,angle up to #ajj of ,distance4 ,for the use of ,surveyors and ,engineers4 ,,by ,,richard ,,lloyd ,,gurden1 ,authorised ,surveyor for the ,governments of ,new ,south ,wales and ,victoria4 999999 ,published with the ,concurrence of the ,surveyors-,general for ,new ,south ,wales and ,victoria4 ,those who have experience in exact ,,survey-,,work will best know how to appreciate the enormous amount of labour represented by this valuable book4 ,the computations enable the user to ascertain the sines and cosines for a distance of twelve miles to within half an inch1 and this ,,by ,,reference ,,to ,,but ,,one ,,table1 in place of the usual ,fifteen minute computations required4 ,this alone is evidence of the assistance which the ,tables ensure to every user1 and as every ,surveyor in active practice has felt the want of such assistance ,,few ,,knowing ,,of ,,their ,,publication ,,will ,,remain ,,without ,,them4--,engineer4 99 99 99 99 99 ,,works ,,by ,,andrew ,,jamieson1 ,m4 ,,inst4 ,c4,e41 ,m4,i4,e4,e41 ,f4,r4,s4,e41 ,formerly ,professor of ,electrical ,engineering1 ,the ,glasgow and ,west of ,scotland ,technical ,college4 99 99 99 99 99 ,,professor ,,jamieson',s ,,advanced ,,text-,,books4 ,in ,large ,crown #hvo4 ,fully ,illustrated4 ,,steam ,,and ,,steam-,,engines 7,a ,text-,book on74 ,for the ,use of ,students preparing for ,competitive ,examinations4 ,with #fjj pp41 over #bjj ,illustrations1 #f ,folding ,plates1 and numerous ,examination ,papers4 ,,thirteenth ,,edition1 ,revised4 #h_/f4 ,professor ,jamieson fascinates the reader by his ,,clearness ,,of ,,conception ,,and ,,simplicity ,,of ,,expression4 ,his treatment recalls the lecturing of ,faraday4--,athenum4 ,the ,,best ,,book yet published for the use of ,students4--,engineer4 ,,magnetism ,,and ,,electricity 7,an ,advanced ,text-,book on74 ,for ,advanced and ,honours ,students4 ,by ,prof4 ,jamieson1 assisted by ,david ,robertson1 ,b4,sc41 ,professor of ,electrical ,engineering in the ,merchant ,venturers' ,technical ,college1 ,bristol4 ,shortly4 ,,applied ,,mechanics 7,an ,advanced ,text-,book on74 ,vol4 ,i4--,comprising ,part ,i43 ,the ,principle of ,work and its applications2 ,part ,,ii43 ,gearing4 ,price #gs4 #f;d4 ,,third ,,edition4 ,,fully ,,maintains the reputation of the ,author4--,pract4 ,engineer4 ,vol4 ,,ii4--,comprising ,parts ,,iii4 to ,,vi43 ,motion and ,energy2 ,graphic ,statics2 ,strength of ,materials2 ,hydraulics and ,hydraulic ,machinery4 ,,second ,,edition4 #hs4 #f;d4 ,,well ,,and ,,lucidly ,,written4--,the ,engineer4 999999 ,each of the above volumes is complete in itself1 and sold separately4 99 99 99 99 99 ,,professor ,,jamieson',s ,,introductory ,,manuals4 ,crown #hvo4 ,with ,illustrations and ,examination ,papers4 ,,steam ,,and ,,the ,,steam-,,engine 7,elementary ,manual of74 ,for ,first-,year ,students4 ,,ninth ,,edition1 ,revised4 #c_/f4 ,should be in the hands of ,,every engineering apprentice4--,practical ,engineer4 ,,magnetism ,,and ,,electricity 7,elementary ,manual of74 ,for ,first-,year ,students4 ,,fifth ,,edition44 #c_/f4 ,a ,,capital ,,text-,,book4444 ,the diagrams are an important feature4--,schoolmaster4 ,a ,,thoroughly ,,trustworthy ,text-book4 ,,practical and clear4--,nature4 ,,applied ,,mechanics 7,elementary ,manual of74 ,specially arranged for ,first-,year ,students4 ,,fifth ,,edition1 ,revised4 #c_/f4 ,the work has ,,very ,,high ,,qualities1 which may be condensed into the one word ',,clear4'--,science and ,art4 99 99 99 99 99 ,,in ,,preparation4 #cjj pages4 ,crown #hvo4 ,profusely ,illustrated4 ,,modern ,,electric ,,tramway ,,traction3 ,a ,text-,book of ,present-,day ,practice4 ,for the ,use of ,electrical ,engineering ,students and those interested in ,electric ,transmission of ,power4 ,,by ,,prof4 ,,andrew ,,jamieson4 99 99 99 99 99 ,a ,,pocket-,,book of ,,electrical ,,rules and ,,tables4 ,for the ,use of ,electricians and ,engineers4 ,pocket ,size4 ,leather1 #hs4 #f;d4 ,,sixteenth ,,edition4 ,see p4 #di4 99 99 99 99 99 ,,works ,,by ,w4,j4 ,,macquorn ,,rankine1 ,,ll4,d41 ,f4,r4,s41 ,late ,regius ,professor of ,civil ,engineering in the ,university of ,glasgow4 ,,thoroughly ,,revised ,,by ,w4,j4 ,,millar1 ,c4,e41 ,late ,secretary to the ,institute of ,engineers and ,shipbuilders in ,scotland4 99 99 99 99 99 ,a ,,manual ,,of ,,applied ,,mechanics3 ,comprising the ,principles of ,statics and ,cinematics1 and ,theory of ,structures1 ,mechanism1 and ,machines4 ,with ,numerous ,diagrams4 ,crown #hvo1 cloth4 ,,sixteenth ,,edition4 #abs4 #f;d4 99 99 99 99 99 ,a ,,manual ,,of ,,civil ,,engineering3 ,comprising ,engineering ,surveys1 ,earthwork1 ,foundations1 ,masonry1 ,carpentry1 ,metal ,work1 ,roads1 ,railways1 ,canals1 ,rivers1 ,waterworks1 ,harbours1 c4 ,with ,numerous ,tables and ,illustrations4 ,crown #hvo4 ,cloth4 ,,twenty-,,first ,,edition4 #afs4 99 99 99 99 99 ,a ,,manual ,,of ,,machinery ,,and ,,millwork3 ,comprising the ,geometry1 ,motions1 ,work1 ,strength1 ,construction1 and ,objects of ,machines1 c4 ,illustrated with nearly #cjj ,woodcuts1 ,crown #hvo1 cloth4 ,,seventh ,,edition4 #abs4 #f;d4 99 99 99 99 99 ,a ,,manual ,,of ,,the ,,steam-,,engine ,,and ,,other ,,prime ,,movers3 ,with a ,section on ,,gas1 ,,oil1 and ,,air ,,engines1 by ,,bryan ,,donkin1 ,m4,inst4,c4,e4 ,with ,folding ,plates and ,numerous ,illustrations4 ,crown #hvo1 cloth4 ,,fifteenth ,,edition4 #abs4 #f;d4 99 99 99 99 99 ,,useful ,,rules ,,and ,,tables3 ,for ,architects1 ,builders1 ,engineers1 ,founders1 ,mechanics1 ,shipbuilders1 ,surveyors1 c4 ,with ,,appendix for the use of ,,electrical ,,engineers4 ,by ,professor ,,jamieson1 ,f4,r4,s4,e4 ,,seventh ,,edition4 #ajs4 #f;d4 99 99 99 99 99 ,a ,,mechanical ,,text-,,book3 ,a ,practical and ,simple ,introduction to the ,study of ,mechanics4 ,by ,professor ,,rankine and ,e4,f4 ,,bamber1 ,c4,e4 ,with ,numerous ,illustrations4 ,crown #hvo1 cloth4 ,,fifth ,,edition4 #is4 999999 ,the ,,mechanical ,,text-,,book was designed by ,professor ,,rankine as an ,,introduction to the above ,series of ,manuals4 99 99 99 99 99 ,,miscellaneous ,,scientific ,,papers4 ,royal #hvo4 ,cloth1 #cas4 #f;d4 ,part ,i4 ,papers relating to ,temperature1 ,elasticity1 and ,expansion of ,vapours1 ,liquids1 and ,solids4 ,part ,,ii4 ,papers on ,energy and its ,transformations4 ,part ,,iii4 ,papers on ,wave-,forms1 ,propulsion of ,vessels1 c4 ,with ,memoir by ,professor ,,tait1 ,m4,a4 ,edited by ,w4,j4 ,,millar1 ,c4,e4 ,with fine ,portrait on ,steel1 ,plates1 and ,diagrams4 ,no more enduring ,memorial of ,professor ,rankine could be devised than the publication of these papers in an accessible form4444 ,the ,collection is most valuable on account of the nature of his discoveries1 and the beauty and completeness of his analysis4444 ,the ,volume exceeds in importance any work in the same department published in our time4--,architect4 99 99 99 99 99 ,,shelton-,,bey 7,w4 ,vincent1 ,foreman to the ,imperial ,ottoman ,gun ,factories1 ,constantinople73 ,,the ,,mechanic',s ,,guide3 ,a ,hand-,book for ,engineers and ,artizans4 ,with ,copious ,tables and ,valuable ,recipes for ,practical ,use4 ,illustrated4 ,second ,edition4 ,crown #hvo4 ,cloth1 #g_/f4 99 99 99 99 99 ,,second ,,edition1 ,revised and ,enlarged4 ,in ,large #hvo1 ,handsome cloth1 #cds4 ,,hydraulic ,,power ,,and ,,hydraulic ,,machinery4 ,,by ,,henry ,,robinson1 ,m4 ,,inst4 ,c4,e41 ,f4,g4,s41 ,,fellow ,,of ,,king',s ,,college1 ,,london2 ,,prof4 ,,of ,,civil ,,engineering1 ,,king',s ,,college1 ,,etc41 ,,etc4 ,with numerous ,woodcuts1 and ,sixty-nine ,plates4 ,a ,book of great ,professional ,usefulness4--,iron4 99 99 99 99 99 ,in ,large #hvo1 ,handsome ,cloth4 ,with ,frontispiece1 several ,plates1 and over #bej ,illustrations4 #bas4 ,,the ,,principles ,,and ,,construction ,,of ,,pumping ,,machinery 7,,steam ,,and ,,water ,,pressure74 ,with ,practical ,illustrations of ,,engines and ,,pumps applied to ,,mining1 ,,town ,,water ,,supply1 ,,drainage of ,lands1 c41 also ,economy and ,efficiency ,trials of ,pumping ,machinery4 ,,by ,,henry ,,davey1 ,member of the ,institution of ,civil ,engineers1 ,member of the ,institution of ,mechanical ,engineers1 ,f4,g4,s41 c4 ,,contents--,early ,history of ,pumping ,engines--,steam ,pumping ,engines--,pumps and ,pump ,valves--,general ,principles of ,non-,rotative ,pumping ,engines--,the ,cornish ,engine1 ,simple and ,compound--,types of ,mining ,engines--,pit ,work--,shaft ,sinking--,hydraulic ,transmission of ,power in ,mines--,valve ,gears of ,pumping ,engines--,water ,pressure ,pumping ,engines--,water ,works ,engines--,pumping ,engine ,economy and ,trials of ,pumping ,machinery--,centrifugal and other ,low-,lift ,pumps--,hydraulic ,rams4 ,pumping ,mains1 c4--,,index4 ,by the 'one' ,english ,engineer who probably knows more about ,pumping ,machinery than ,,any ,,other4' 444 ,a ,,volume ,,recording ,,the ,,results ,,of ,,long ,,experience ,,and ,,study4--,the ,engineer4 ,undoubtedly ,,the ,,best ,,and ,,most ,,practical ,,treatise on ,pumping ,machinery ,,that ,,has ,,yet ,,been ,,published4--,mining ,journal4 99 99 99 99 99 ,royal #hvo1 ,handsome ,cloth4 ,with numerous ,illustrations and ,tables4 #bes4 ,,the ,,stability ,,of ,,ships4 ,,by ,,sir ,,edward ,j4 ,,reed1 ,k4,c4,b41 ,f4,r4,s41 ,m4,p41 ,,knight ,,of ,,the ,,imperial ,,orders ,,of ,,st4 ,,stanilaus ,,of ,,russia2 ,,francis ,,joseph ,,of ,,austria2 ,,medjidie ,,of ,,turkey2 ,,and ,,rising ,,sun ,,of ,,japan2 ,,vice-,,president ,,of ,,the ,,institution ,,of ,,naval ,,architects4 ,in order to render the work complete for the purposes of the ,shipbuilder1 whether at home or abroad1 the ,methods of ,calculation introduced by ,mr4 ,f4,k4 ,,barnes1 ,mr4 ,,gray1 ,m4 ,,reech1 ,m4 ,,daymard1 and ,mr4 ,,benjamin1 are all given separately1 illustrated by ,tables and worked-out examples4 ,the book contains more than #bjj ,diagrams1 and is illustrated by a large number of actual cases1 derived from ships of all descriptions4 ,sir ,,edward ,,reed',s ',,stability ,,of ,,ships' is ,,invaluable4 ,the ,,naval ,,architect will find brought together and ready to his hand1 a mass of information which he would otherwise have to seek in an almost endless variety of publications1 and some of which he would possibly not be able to obtain at all elsewhere4--,steamship4 99 99 99 99 99 ,,the ,,design ,,and ,,construction ,,of ,,ships4 ,by ,,john ,,harvard ,,biles1 ,m4,,inst4,n4,a41 ,professor of ,naval ,architecture in the ,university of ,glasgow4 ,in ,preparation4 99 99 99 99 99 ,,second ,,edition4 ,illustrated with ,plates1 ,numerous ,diagrams1 and ,figures in the ,text4 #ahs4 net4 ,,steel ,,ships3 ,,their ,,construction ,,and ,,maintenance4 ,a ,manual for ,shipbuilders1 ,ship ,superintendents1 ,students1 and ,marine ,engineers4 ,,by ,,thomas ,,walton1 ,,naval ,,architect1 ,,author ,,of ,,know ,,your ,,own ,,ship4 ,,contents4--,i4 ,manufacture of ,cast ,iron1 ,wrought ,iron1 and ,steel4--,composition of ,iron and ,steel1 ,quality1 ,strength1 ,tests1 c4 ,,ii4 ,classification of ,steel ,ships4 ,,iii4 ,considerations in making choice of ,type of ,vessel4--,framing of ,ships4 ,,iv4 ,strains experienced by ,ships4--,methods of ,computing and ,comparing ,strengths of ,ships4 ,v4 ,construction of ,ships4--,alternative ,modes of ,construction4--,types of ,vessels4--,turret1 ,self ,trimming1 and ,trunk ,steamers1 c4--,rivets and ,rivetting1 ,workmanship4 ,,vi4 ,pumping ,arrangements4 ,,vii4 ,maintenance4--,prevention of ,deterioration in the ,hulls of ,ships4--,cement1 ,paint1 c4--,,index4 ,so thorough and well written is every chapter in the book that it is difficult to select any of them as being worthy of exceptional praise4 ,altogether1 the work is excellent1 and will prove of great value to those for whom it is intended4--,the ,engineer4 ,mr4 ,walton has written for the profession of which he is an ornament4 ,his work will be read and appreciated1 no doubt1 by every ,m4,i4,n4,a41 and with great benefit by the majority of them4--,journal of ,commerce4 99 99 99 99 99 ,,second ,,edition1 ,cloth1 #hs4 #f;d4 ,leather1 for the ,pocket1 #hs4 #f;d4 ,,griffin',s ,,electrical ,,price-,,book3 ,for ,electrical1 ,civil1 ,marine1 and ,borough ,engineers1 ,local ,authorities1 ,architects1 ,railway ,contractors1 c41 c4 ,edited by ,h4,j4 ,,dowsing4 ,the ,,electrical ,,price-,,book ,,removes ,,all ,,mystery about the cost of ,electrical ,power4 ,by its aid the ,,expense that will be entailed by utilising electricity on a large or small scale can be discovered4--,architect4 99 99 99 99 99 ,,griffin',s ,,nautical ,,series1 ,,edited ,,by ,,edw4 ,,blackmore1 ,master ,mariner1 ,first ,class ,trinity ,house ,certificate1 ,assoc4 ,inst4 ,n4,a42 ,,and ,,written1 ,,mainly1 by ,,sailors for ,,sailors4 ,,this ,,admirable ,,series4--,fairplay4 ,a ,,very ,,useful ,,series4--,nature4 ,the volumes of ,,messrs4 ,,griffin',s ,,nautical ,,series may well and profitably be read by ,,all interested in our ,,national ,,maritime ,,progress4--,marine ,engineer4 ,,every ,,ship should have the ,,whole ,,series as a ,,reference ,,library4 ,,handsomely ,,bound1 ,,clearly ,,printed and ,,illustrated4--,liverpool ,journ4 of ,commerce4 ,the ,british ,mercantile ,marine3 ,an ,historical ,sketch of its ,rise and ,development4 ,by the ,,editor1 ,,capt4 ,,blackmore4 #cs4 #f;d4 ,captain ,blackmore's ,,splendid ,,book 444 contains paragraphs on every point of interest to the ,merchant ,marine4 ,the #bdc pages of this book are ,,the ,,most ,,valuable to the sea captain that have ,,ever been ,,compiled4--,merchant ,service ,review4 ,elementary ,seamanship4 ,by ,d4 ,,wilson-,,barker1 ,master ,mariner1 ,f4,r4,s4,e41 ,f4,r4,g4,s4 ,with numerous ,plates1 two in ,colours1 and ,frontispiece4 ,,third ,,edition1 ,thoroughly ,revised1 ,enlarged1 and ,re-set4 ,with additional ,illustrations4 #fs4 ,this ,,admirable ,,manual1 by ,,capt4 ,,wilson ,,barker1 of the ',worcester'1 seems to us ,,perfectly ,,designed4 --,athenum4 ,know ,your ,own ,ship3 ,a ,simple ,explanation of the ,stability1 ,construction1 ,tonnage1 and ,freeboard of ,ships4 ,by ,,thos4 ,,walton1 ,naval ,architect4 ,with numerous ,illustrations and additional ,chapters on ,buoyancy1 ,trim1 and ,calculations4 ,,sixth ,,edition1 ,revised4 #gs4 #f;d4 ,,mr4 ,,walton',s book will be found ,,very ,,useful4--,the ,engineer4 ,navigation3 ,theoretical and ,practical4 ,by ,d4 ,,wilson-,,barker1 ,master ,mariner1 c41 and ,,william ,,allingham4 ,,second ,,edition1 ,revised4 #hs4 #f;d4 ,,precisely the kind of work required for the ,new ,certificates of competency4 ,candidates will find it ,,invaluable4--,dundee ,advertiser4 ,marine ,meteorology3 ,for ,officers of the ,merchant ,navy4 ,by ,,william ,,allingham1 ,first ,class ,honours1 ,navigation1 ,science and ,art ,department4 ,with ,illustrations1 ,maps1 and ,diagrams1 and facsimile reproduction of log page4 #gs4 #f;d4 ,quite the ,,best ,,publication on this subject4--,shipping ,gazette4 ,latitude and ,longitude3 ,how to find them4 ,by ,w4,j4 ,,millar1 ,c4,e41 late ,sec4 to the ,inst4 of ,engineers and ,shipbuilders in ,scotland4 ,,second ,,edition1 ,revised4 #bs4 ,cannot but prove an acquisition to those studying ,navigation4--,marine ,engineer4 ,practical ,mechanics3 ,applied to the requirements of the ,sailor4 ,by ,,thos4 ,,mackenzie1 ,master ,mariner1 ,f4,r4,a4,s4 ,,second ,,edition1 ,revised4 #cs4 #f;d4 ,,well ,,worth the money 444 ,,exceedingly ,,helpful4--,shipping ,world4 ,trigonometry3 ,for the ,young ,sailor1 c4 ,by ,,rich4 ,c4 ,,buck1 of the ,thames ,nautical ,training ,college1 ,h4,m4,s4 ,worcester4 ,,second ,,edition1 ,revised4 ,price #cs4 #f;d4 ,this ,,eminently ,,practical and reliable volume4--,schoolmaster4 ,practical ,algebra4 ,by ,,rich4 ,c4 ,,buck4 ,companion ,volume to the above1 for ,sailors and others4 ,price #cs4 #f;d4 ,it is ,,just ,,the ,,book for the young sailor mindful of progress4--,nautical ,magazine4 ,the ,legal ,duties of ,shipmasters4 ,by ,,benedict ,,wm4 ,,ginsburg1 ,m4,a41 ,,ll4,d41 of the ,inner ,temple and ,northern ,circuit2 ,barrister-at-,law4 ,,second ,,edition1 ,thoroughly ,revised and ,extended4 ,price #ds4 #f;d4 ,,invaluable to masters 444 ,we can fully recommend it4--,shipping ,gazette4 ,a ,medical and ,surgical ,help for ,shipmasters4 ,including ,first ,aid at ,sea4 ,by ,,wm4 ,,johnson ,,smith1 ,f4,r4,c4,s41 ,principal ,medical ,officer1 ,seamen's ,hospital1 ,greenwich4 ,,second ,,edition1 ,revised4 #fs4 ,,sound1 ,,judicious1 ,,really ,,helpful4--,the ,lancet4 99 99 99 99 99 ,introductory ,volume4 ,price #cs4 #f;d4 ,,the ,british ,mercantile ,marine4 ,,by ,,edward ,,blackmore1 ,,master ,,mariner2 ,,associate ,,of ,,the ,,institution ,,of ,,naval ,,architects2 ,,member ,,of ,,the ,,institution ,,of ,,engineers ,,and ,,shipbuilders ,,in ,,scotland2 ,,editor ,,of ,,griffin',s ,,nautical ,,series4 ,,general ,,contents4--,,historical3 ,from ,early ,times to #adhf--,progress under ,henry ,,viii4--,to ,death of ,mary--,during ,elizabeth's ,reign--,up to the ,reign of ,william ,,iii4--,the #ahth and #aith ,centuries--,institution of ,examinations--,rise and ,progress of ,steam ,propulsion--,development of ,free ,trade--,shipping ,legislation1 #ahfb to #ahge--,locksley ,hall ,case--,shipmasters' ,societies--,loading of ,ships--,shipping ,legislation1 #ahhd to #ahid--,statistics of ,shipping4 ,,the ,,personnel3 ,shipowners--,officers--,mariners--,duti es and ,present ,position4 ,,education3 ,a ,seaman's ,education3 what it should be--,present ,means of ,education--,hints4 ,,discipline ,,and ,,duty--,postscript--,the ,serious ,decrease in the ,number of ,british ,seamen1 a ,matter demanding the ,attention of the ,nation4 ,,interesting ,,and ,,instructive 444 may be read ,,with ,,profit ,,and ,,enjoyment4--,glasgow ,herald4 ,,every ,,branch of the subject is dealt with in a way which shows that the writer 'knows the ropes' familiarly4--,scotsman4 ,this ,,admirable book 444 ,,teems with useful information--,should be in the hands of every ,sailor4--,western ,morning ,news4 99 99 99 99 99 ,,third ,,edition1 ,thoroughly ,revised1 ,enlarged1 and ,re-set4 ,with ,additional ,illustrations4 ,price #fs4 ,a ,,manual ,,of ,,elementary ,,seamanship4 ,,by ,d4 ,,wilson-,,barker1 ,,master ,,mariner2 ,f4,r4,s4,e41 ,f4,r4,g4,s41 ,c41 ,c42 ,,younger ,,brother ,,of ,,the ,,trinity ,,house4 ,with ,frontispiece1 ,numerous ,plates 7,two in ,colours71 and ,illustrations in the ,text4 ,,general ,,contents4--,the ,building of a ,ship2 ,parts of ,hull1 ,masts1 c4--,ropes1 ,knots1 ,splicing1 c4--,gear1 ,lead and ,log1 c4--,rigging1 ,anchors--,sailmaking--,the ,sails1 c4--,handling of ,boats under ,sail--,signals and ,signalling--,rule of the ,road--,keeping and ,relieving ,watch--,points of ,etiquette--,glossary of ,sea ,terms and ,phrases--,index4 999999 ,the volume contains the ,,new ,,rules ,,of ,,the ,,road4 ,this ,,admirable ,,manual1 by ,,capt4 ,,wilson-,,barker of the ',worcester1' seems to us ,,perfectly ,,designed1 and holds its place excellently in ,,griffin',s ,,nautical ,,series4' 444 ,although intended for those who are to become ,officers of the ,merchant ,navy1 it will be found useful by ,,all ,,yachtsmen4--,athenum4 999999 ,for complete ,list of ,,griffin',s ,,nautical ,,series1 see p4 #ci4 99 99 99 99 99 ,,second ,,edition1 ,revised and ,illustrated4 ,price #cs4 #f;d4 ,,navigation3 ,,practical ,,and ,,theoretical ,,by ,,david ,,wilson-,,barker1 ,r4,n4,r1 ,f4,r4,s4,e41 c41 c41 ,,and ,,william ,,allingham1 ,,first-,,class ,,honors1 ,,navigation1 ,,science ,,and ,,art ,,department4 ,with ,numerous ,illustrations and ,examination ,questions4 ,,general ,,contents4--,definitions--,latitude and ,longitude--,instruments of ,navigation--,correction of ,courses--,plane ,sailing--,traverse ,sailing--,day's ,work--,parallel ,sailing--,middle ,latitude ,sailing--,mercator's ,chart--,mercator ,sailing--,current ,sailing--,position by ,bearings--,great ,circle ,sailing--,the ,tides--,questions--,appendix3 ,compass ,error--,numerous ,useful ,hints1 c4--,index4 ,,precisely the kind of work required for the ,new ,certificates of competency in grades from ,second ,mate to extra ,master4444 ,candidates will find it ,,invaluable4--,dundee ,advertiser4 ,a ,,capital ,,little ,,book 444 specially adapted to the ,new ,examinations4 ,the ,authors are ,,capt4 ,,wilson-,,barker 7,captain-,superintendent of the ,nautical ,college1 ,h4,m4,s4 ',worcester1' who has had great experience in the highest problems of ,navigation71 and ,,mr4 ,,allingham1 a well-known writer on the ,science of ,navigation and ,nautical ,astronomy4--,shipping ,world4 99 99 99 99 99 ,handsome ,cloth4 ,fully ,illustrated4 ,price #gs4 #f;d4 ,,marine ,,meteorology1 ,,for ,,officers ,,of ,,the ,,merchant ,,navy4 ,,by ,,william ,,allingham1 ,joint ,author of ,navigation1 ,theoretical and ,practical4 ,with numerous ,plates1 ,maps1 ,diagrams1 and ,illustrations1 and a facsimile ,reproduction of a ,page from an actual ,meteorological ,log-,book4 ,,summary ,,of ,,contents4 ,,introductory4--,instruments ,used at ,sea for ,meteorological ,purposes4--,meteorological ,log-,books4--,atmospheric ,pressure4--,air ,temperatures4--,sea ,temperatures4--,winds4--,wind ,force ,scales4--,history of the ,law of ,storms4--,hurricanes1 ,seasons1 and ,storm ,tracks4--,solution of the ,cyclone ,problem4--,ocean ,currents4--,icebergs4--,synchronous ,charts4--,dew1 ,mists1 ,fogs1 and ,haze4--,clouds4--,rain1 ,snow1 and ,hail4--,mirage1 ,rainbows1 ,coronas1 ,halos1 and ,meteors4--,lightning1 ,corposants1 and ,auroras4--,,questions4--,,appendix4--,, index4 ,quite the ,,best publication1 ,,and certainly the ,,most ,,interesting1 on this subject ever presented to ,nautical men4--,shipping ,gazette4 999999 ,for ,complete ,list of ,,griffin',s ,,nautical ,,series1 see p4 #ci4 99 99 99 99 99 ,,second ,,edition1 ,,revised4 ,with ,numerous ,illustrations4 ,price #cs4 #f;d4 ,practical ,mechanics3 ,applied to the ,requirements of the ,sailor4 ,by ,,thos4 ,,mackenzie1 ,master ,mariner1 ,f4,r4,a4,s4 ,,general ,,contents4--,resolution and ,composition of ,forces--,work done by ,machines and ,living ,agents--,the ,mechanical ,powers3 ,the ,lever2 ,derricks as ,bent ,levers--,the ,wheel and ,axle3 ,windlass2 ,ship's ,capstan2 ,crab ,winch--,tackles3 the ,old ,man--,the ,inclined ,plane2 the ,screw--,the ,centre of ,gravity of a ,ship and ,cargo--,relative ,strength of ,rope3 ,steel ,wire1 ,manilla1 ,hemp1 ,coir--,derricks and ,shears--,calculation of the ,cross-breaking ,strain of ,fir ,spar--,centre of ,effort of ,sails--,hydrostatics3 the ,diving-bell2 ,stability of ,floating ,bodies2 the ,ship's ,pump1 c4 ,,this ,,excellent ,,book 444 contains a ,,large ,,amount of information4--,nature4 ,,well ,,worth the money 444 will be found ,,exceedingly ,,helpful4--,shipping ,world4 ,,no ,,ships' ,,officers' ,,bookcase will henceforth be complete without ,,captain ,,mackenzie',s ',,practical ,,mechanics4' ,notwithstanding my many years' experience at sea1 it has told me how much more there is to acquire4--7,letter to the ,publishers from a ,master ,mariner74 ,i must express my thanks to you for the labour and care you have taken in ',,practical ,,mechanics4' 444 ,,it ,,is ,a ,,life',s ,,experience4 444 ,what an amount we frequently see wasted by rigging purchases without reason and accidents to spars1 c41 c46 ',,practical ,,mechanics' ,,would ,,save ,,all ,,this4--7,letter to the ,author from another ,master ,mariner74 99 99 99 99 99 ,,works ,,by ,,richard ,c4 ,,buck1 of the ,thames ,nautical ,training ,college1 ,h4,m4,s4 ',worcester4' ,a ,manual of ,trigonometry3 ,with ,diagrams1 ,examples1 and ,exercises4 ,price #cs4 #f;d4 ,,second ,,edition1 ,revised and ,corrected4 999999 ,mr4 ,buck's ,text-,book has been ,,specially ,,prepared with a view to the ,new ,examinations of the ,board of ,trade1 in which ,trigonometry is an obligatory subject4 ,this ,,eminently ,,practical and ,,reliable ,,volume4--,schoolmaster4 99 99 99 99 99 ,a ,manual of ,algebra4 ,designed to meet the ,requirements of ,sailors and others4 ,price #cs4 #f;d4 999999 ,these elementary works on ,,algebra and ,,trigonometry are written specially for those who will have little opportunity of consulting a ,teacher4 ,they are books for ,,self-,,help4 ,all but the simplest explanations have1 therefore1 been avoided1 and ,,answers to the ,exercises are given4 ,any person may readily1 by careful study1 become master of their contents1 and thus lay the foundation for a further mathematical course1 if desired4 ,it is hoped that to the younger ,officers of our ,mercantile ,marine they will be found decidedly serviceable4 ,the ,examples and ,exercises are taken from the ,examination ,papers set for the ,cadets of the ,worcester4 ,clearly arranged1 and well got up4444 ,a first-rate ,elementary ,algebra4--,nautical ,magazine4 99 99 99 99 99 ,,second ,,edition1 ,thoroughly ,revised and ,extended4 ,in ,crown #hvo4 ,handsome ,cloth4 ,price #ds4 #f;d4 ,,the ,,legal ,,duties ,,of ,,shipmasters4 ,,by ,,benedict ,,wm4 ,,ginsburg1 ,m4,a41 ,,ll4,d4 7,,cantab471 ,of the ,inner ,temple and ,northern ,circuit2 ,barrister-at-,law4 ,general ,contents4--,the ,qualification for the ,position of ,shipmaster--,the ,contract with the ,shipowner--,the ,master's ,duty in respect of the ,crew3 ,engagement2 ,apprentices2 ,discipline2 ,provisions1 ,accommodation1 and ,medical ,comforts2 ,payment of ,wages and ,discharge--,the ,master's ,duty in respect of the ,passengers--,the ,master's ,financial ,responsibilities--,the ,master's ,duty in respect of the ,cargo--,the ,master's ,duty in ,case of ,casualty--,the ,master's ,duty to certain ,public ,authorities--,the ,master's ,duty in relation to ,pilots1 ,signals1 ,flags1 and ,light ,dues--,the ,master's ,duty upon ,arrival at the ,port of ,discharge--,appendices relative to certain ,legal ,matters3 ,board of ,trade ,certificates1 ,dietary ,scales1 ,stowage of ,grain ,cargoes1 ,load ,line ,regulations1 ,life-saving ,appliances1 ,carriage of ,cattle at ,sea1 c41 c4--,copious ,index4 ,no intelligent ,master should fail to add this to his list of necessary books4 ,a few lines of it may ,,save ,a ,,lawyer',s ,,fee1 ,,besides ,,endless ,,worry4--,liverpool ,journal of ,commerce4 ,,sensible1 plainly written1 in ,,clear and ,,non-,,technical ,,language1 and will be found of much service by the ,shipmaster4--,british ,trade ,review4 99 99 99 99 99 ,,second ,,edition1 ,revised4 ,with ,diagrams4 ,price #bs4 ,latitude and ,longitude3 ,how to ,find them4 ,by ,w4,j4 ,,millar1 ,c4,e41 ,late ,secretary to the ,inst4 of ,engineers and ,shipbuilders in ,scotland4 ,,concisely and ,,clearly ,,written 444 cannot but prove an acquisition to those studying ,navigation4--,marine ,engineer4 ,young ,seamen will find it ,,handy and ,,useful1 ,,simple and ,,clear4--,the ,engineer4 99 99 99 99 99 ,,first ,,aid ,,at ,,sea4 ,,second ,,edition1 ,revised4 ,with ,coloured ,plates and ,numerous ,illustrations1 and comprising the latest ,regulations ,respecting the ,carriage of ,medical ,stores on ,board ,ship4 ,price #fs4 ,a ,,medical ,,and ,,surgical ,,help ,,for ,,shipmasters ,,and ,,officers ,,in ,,the ,,merchant ,,navy4 ,,by ,,wm4 ,,johnson ,,smith1 ,f4,r4,c4,s41 ,principal ,medical ,officer1 ,seamen's ,hospital1 ,greenwich4 999999 ,the attention of all interested in our ,merchant ,navy is requested to this exceedingly useful and valuable work4 ,it is needless to say that it is the outcome of many years ,,practical ,,experience amongst ,seamen4 ,,sound1 ,,judicious1 ,,really ,,helpful4--,the ,lancet4 99 99 99 99 99 ,,sixth ,,edition4 ,revised1 with ,chapters on ,trim1 ,buoyancy1 and ,calculations4 ,numerous ,illustrations4 ,handsome ,cloth1 ,crown #hvo4 ,price #gs4 #f;d4 ,,know ,,your ,,own ,,ship4 ,,by ,,thomas ,,walton1 ,,naval ,,architect4 ,,specially ,,arranged ,,to ,,suit ,,the ,,requirements ,,of ,,ships' ,,officers1 ,,shipowners1 ,,superintendents1 ,,draughtsmen1 ,,engineers1 ,,and ,,others4 ,this work explains1 in a simple manner1 such important subjects as3-- ,displacement1 ,deadweight1 ,tonnage1 ,freeboard1 ,moments1 ,buoyancy1 ,strain1 ,structure1 ,stability1 ,rolling1 ,ballasting1 ,loading1 ,shifting ,cargoes1 ,admission of ,water1 ,sail ,area1 c41 c4 ,the little book will be found ,,exceedingly ,,handy by most officers and officials connected with shipping4444 ,mr4 ,walton's work will obtain ,,lasting ,,success1 because of its unique fitness for those for whom it has been written4--,shipping ,world4 ,an ,,excellent ,,work1 full of solid instruction and ,,invaluable to every officer of the ,mercantile ,marine who has his profession at heart4--,shipping4 ,not one of the #bdb pages could well be spared4 ,it will admirably fulfil its purpose 444 useful to ship owners1 ship superintendents1 ship draughtsmen1 and all interested in shipping4--,liverpool ,journal of ,commerce4 ,a mass of ,,very ,,useful ,,information1 accompanied by diagrams and illustrations1 is given in a compact form4--,fairplay4 ,we have found no one statement that we could have wished differently expressed4 ,the matter has1 so far as clearness allows1 been admirably condensed1 and is simple enough to be understood by every seaman4--,marine ,engineer4 99 99 99 99 99 ,,by ,,the ,,same ,,author4 ,steel ,ships3 ,their ,construction and ,maintenance4 7,see page #ch47 99 99 99 99 99 ,fourteenth ,edition1 ,revised4 ,price #bas4 ,demy #hvo1 ,cloth4 ,with ,numerous ,illustrations1 reduced from ,working ,drawings4 ,a ,,manual ,,of ,,marine ,,engineering3 ,,comprising ,,the ,,designing1 ,,construction1 ,,and ,,working ,,of ,,marine ,,machinery4 ,by ,a4,e4 ,,seaton1 ,m4 ,inst4 ,c4,e41 ,m4 ,inst4 ,mech4 ,e41 ,m4 ,inst4 ,n4,a4 ,,general ,,contents4--,,part ,i4--,principles of ,marine ,propulsion4 ,,part ,,ii4--,principles of ,steam ,engineering4 ,,part ,,iii4--,details of ,marine ,engines3 ,design and ,calculations for ,cylinders1 ,pistons1 ,valves1 ,expansion ,valves1 c4 ,,part ,,iv4--,propellers4 ,,part ,v4--,boilers4 ,,part ,,vi4--,miscellaneous4 999999 ,this ,,edition includes a ,chapter on ,,water-,,tube ,,boilers1 with ,illustrations of the leading ,types and the ,revised ,rules of the ,bureau ,veritas4 ,in the three-fold capacity of enabling a ,student to learn how to design1 construct1 and work a ,marine ,steam-,engine1 ,mr4 ,seaton's ,manual has ,,no ,,rival4--,times4 ,by far the ,,best ,,manual in existence4444 ,gives a complete account of the methods of solving1 with the utmost possible economy1 the problems before the ,marine ,engineer4--,athenum4 ,the ,student1 ,draughtsman1 and ,engineer will find this work the ,,most ,,valuable ,,handbook of ,reference on the ,marine ,engine now in existence4--,marine ,engineer4 99 99 99 99 99 ,,seventh ,,edition1 ,thoroughly ,revised4 ,pocket-,size1 ,leather4 #hs4 #f;d4 ,a ,,pocket-,,book ,,of ,,marine ,,engineering ,,rules ,,and ,,tables1 ,,for ,,the ,,use ,,of ,marine ,engineers1 ,naval ,architects1 ,designers1 ,draughtsmen1 ,superintendents and ,others4 ,,by ,a4,e4 ,,seaton1 ,m4,i4,c4,e41 ,m4,i4,mech4,e41 ,m4,i4,n4,a41 ,,and ,h4,m4 ,,rounthwaite1 ,m4,i4,mech4,e41 ,m4,i4,n4,a4 ,,admirably ,,fulfils its purpose4--,marine ,engineer4 99 99 99 99 99 ,by ,b4 ,,cunningham4 ,,docks3 ,,their ,,construction ,,maintenance4 7,see page #bg47 99 99 99 99 99 ,,works ,,by ,,prof4 ,,robert ,h4 ,,smith1 ,assoc4 ,m4,i4,c4,e41 ,m4,i4,m4,e41 ,m4,i4,el4,b41 ,m4,i4 ,min4 ,e41 ,whit4 ,sch41 ,m4 ,ord4 ,meiji4 99 99 99 99 99 ,,the ,,calculus ,,for ,,engineers ,,and ,,physicists1 ,applied to ,technical ,problems4 ,,with ,,extensive ,,classified ,,reference ,,list ,,of ,,integrals4 ,by ,,prof4 ,,robert ,h4 ,,smith4 ,,assisted ,,by ,r4,f4 ,,muirhead1 ,m4,a41 ,b4,sc41 ,formerly ,clark ,fellow of ,glasgow ,university1 and ,lecturer on ,mathematics at ,mason ,college4 ,in ,crown #hvo1 extra1 with ,diagrams and ,folding-,plate4 #hs4 #f;d4 ,,prof4 ,r4,h4 ,,smith',s book will be serviceable in rendering a hard road ,,as ,,easy ,,as ,,practicable for the non-mathematical ,student and ,engineer4--,athenum4 ,interesting diagrams1 with practical illustrations of actual occurrence1 are to be found here in abundance4 ,,the ,,very ,,complete ,,classified ,,reference ,,table will prove very useful in saving the time of those who want an integral in a hurry4--,the ,engineer4 99 99 99 99 99 ,,measurement ,,conversions 7,english and ,french73 #bh ,,graphic ,,tables ,,or ,,diagrams4 ,showing at a glance the ,,mutual ,,conversion of ,,measurements in ,,different ,,units ,of ,lengths1 ,areas1 ,volumes1 ,weights1 ,stresses1 ,densities1 ,quantities of ,work1 ,horse ,powers1 ,temperatures1 c4 ,for the use of ,engineers1 ,surveyors1 ,architects1 and ,contractors4 ,in #dto1 ,boards4 #gs4 #f;d4 99 99 99 99 99 999999 ,prof4 ,,smith',s ,,conversion-,,tables form the most unique and comprehensive collection ever placed before the profession4 ,by their use much time and labour will be saved1 and the chances of error in calculation diminished4 ,it is believed that henceforth no ,engineer's ,office will be considered complete without them4 ,the work is ,,invaluable4--,colliery ,guardian4 ,ought to be in ,,every office where even occasional conversions are required4444 ,prof4 ,,smith',s ,,tables form very ,,excellent ,,checks on results4--,electrical ,review4 ,prof4 ,smith deserves the hearty thanks1 not only of the ,,engineer1 but of the ,,commercial ,,world1 for having smoothed the way for the ,,adoption of the ,,metric ,,system of ,,measurement1 a subject which is now assuming great importance as a factor in maintaining our ,,hold upon ,,foreign ,,trade4--,the ,machinery ,market4 99 99 99 99 99 ,in ,large #hvo4 ,handsome ,cloth4 #ajs4 #f;d4 ,,chemistry ,,for ,,engineers4 ,,by ,,bertram ,,blount1 ,f4,i4,c41 ,f4,c4,s41 ,a4,i4,c4,e41 ,consulting ,chemist to the ,crown ,agents for the ,colonies4 ,,and ,a4,g4 ,,bloxam1 ,f4,i4,c41 ,f4,c4,s41 ,consulting ,chemist1 ,head of the ,chemistry ,department1 ,goldsmiths' ,inst41 ,new ,cross4 ,,general ,,contents4--,introduction--,chemistry of the ,chief ,materials of ,construction--,sources of ,energy--,chemistry of ,steam-raising--,chemistry of ,lubrication and ,lubricants--,metallurgical ,processes used in the ,winning and ,manufacture of ,metals4 ,the authors have ,,succeeded beyond all expectation1 and have produced a work which should give ,,fresh ,,power to the ,engineer and ,manufacturer4--,the ,times4 ,,practical ,,throughout 444 an ,,admirable ,,text-,,book1 useful not only to ,students1 but to ,,engineers and ,,managers ,,of ,,works in ,,preventing ,,waste and ,,improving ,,processes4--,scotsman4 ,a book worthy to take ,,high ,,rank 444 treatment of the subject of ,,gaseous ,,fuel particularly good4444 ,,water ,,gas and its production clearly worked out4444 ,we ,,warmly ,,recommend the work4--,journal of ,gas ,lighting4 ,for ,companion ,volume by the same ,authors1 see ,,chemistry ,,for ,,manufacturers1 p4 #ga4 99 99 99 99 99 ,,works ,,by ,,walter ,r4 ,,browne1 ,m4,a41 ,m4 ,,inst4 ,c4,e41 ,late ,fellow of ,trinity ,college1 ,cambridge4 ,,the ,,student',s ,,mechanics3 ,an ,introduction to the ,study of ,force and ,motion4 ,with ,diagrams4 ,crown #hvo4 ,cloth1 #ds4 #f;d4 ,clear in style and practical in method1 ',,the ,,student',s ,,mechanics' is cordially to be commended from all points of view4--,athenum4 99 99 99 99 99 ,,foundations ,,of ,,mechanics4 ,papers reprinted from the ,engineer4 ,in ,crown #hvo1 #as4 99 99 99 99 99 ,demy #hvo1 with ,numerous ,illustrations1 #is4 ,,fuel ,,and ,,water3 ,a ,manual for ,users of ,steam and ,water4 ,,by ,,prof4 ,,franz ,,schwackh,,fer ,,of ,,vienna1 ,,and ,,walter ,r4 ,,browne1 ,m4,a41 ,c4,e4 ,,general ,,contents4--,heat and ,combustion--,fuel1 ,varieties of--,firing ,arrangements3 ,furnace1 ,flues1 ,chimney--,the ,boiler1 ,choice of--,varieties--,feed-water ,heaters--,steam ,pipes--,water3 ,composition1 ,purification--,prevention of ,scale1 c41 c4 ,the ,section on ,heat is one of the best and most lucid ever written4--,engineer4 ,cannot fail to be valuable to thousands using steam power4--,railway ,engineer4 99 99 99 99 99 ,,griffins ,,local ,,government ,,handbooks4 ,,works ,,suitable ,,for ,,municipal ,,and ,,county ,,engineers1 ,,analysts1 ,,and ,,others4 ,see also ,davies' ,hygiene1 p4 #ii1 and ,mac,leod's ,public ,health1 p4 #aaj4 ,gas ,manufacture 7,the ,chemistry of74 ,a ,handbook on the ,production1 ,purification1 and ,testing of ,illuminating ,gas1 and the ,assay of ,bye-,products4 ,by ,w4,j4,a4 ,,butterfield1 ,m4,a41 ,f4,i4,c41 ,f4,c4,s4 ,with ,illustrations4 ,,third ,,edition1 ,revised 7in preparation74 ,see page #gg4 ,water ,supply3 ,a ,practical ,treatise on the ,selection of ,sources and the ,distribution of ,water4 ,by ,,reginald ,e4 ,,middleton1 ,m4 ,inst4 ,c4,e41 ,m4 ,inst4 ,mech4 ,e41 ,f4,s4,i4 ,with ,four ,plates and ,numerous ,diagrams4 ,crown #hvo4 ,see page #gg4 ,central ,electrical ,stations3 ,their ,design1 ,organisation1 and ,management4 ,by ,c4,h4 ,wordingham1 ,a4,k4,c41 ,m4 ,inst4 ,c4,e4 ,price #bds4 net4 ,for details see opposite page4 ,sewage ,disposal ,works3 ,a ,guide to the ,construction of ,works for the ,prevention of the ,pollution by ,sewage of ,rivers and ,estuaries4 ,by ,w4 ,,santo ,,crimp1 ,m4 ,inst4 ,c4,e41 ,f4,g4,s4 ,,second ,,edition1 ,revised and ,enlarged4 ,large #hvo1 ,handsome ,cloth4 ,with #cg ,plates4 ,price #cjs4 ,see page #gf4 ,trades' ,waste3 ,its ,treatment and ,utilisation1 with ,special ,reference to the ,prevention of ,rivers' ,pollution4 ,by ,w4 ,,naylor1 ,f4,c4,s41 ,a4,m4 ,inst4 ,c4,e4 ,with ,numerous ,plates1 ,diagrams1 and ,illustrations4 #bas4 net4 ,see page #gf4 ,calcareous ,cements3 ,their ,nature1 ,preparation1 and ,uses4 ,with some ,remarks upon ,cement ,testing4 ,by ,,gilbert ,,redgrave1 ,assoc4 ,inst4 ,c4,e4 ,with ,illustrations1 ,analytical ,data1 and ,appendices on ,costs1 c4 #hs4 #f;d4 ,see page #gf4 ,road ,making and ,maintenance3 ,a ,practical ,treatise for ,engineers1 ,surveyors1 and others4 ,with an ,historical ,sketch of ,ancient and ,modern ,practice4 ,by ,,thomas ,,aitken1 ,assoc4 ,m4 ,inst4 ,c4,e41 ,m4 ,assoc4 ,municipal and ,county ,engrs42 ,m4 ,san4 ,inst4 ,with numerous ,plates1 ,diagrams1 and ,illustrations4 #bas4 ,see page #gi4 ,light ,railways at ,home and ,abroad4 ,by ,,william ,,henry ,,cole1 ,m4 ,inst4 ,c4,e41 late ,deputy ,manager1 ,north-,western ,railway1 ,india4 ,large #hvo1 ,handsome ,cloth1 ,plates and illustrations4 #afs4 ,see page #cj4 ,practical ,sanitation3 ,a ,handbook for ,sanitary ,inspectors and others interested in ,sanitation4 ,by ,,geo4 ,,reid1 ,m4,d41 ,d4,p4,h41 ,medical ,officer1 ,staffordshire ,county ,council4 ,with ,appendix on ,sanitary ,law1 by ,herbert ,manley1 ,m4,a41 ,m4,b41 ,d4,p4,h4 ,,tenth ,,edition1 ,revised4 #fs4 ,see page #gh4 ,sanitary ,engineering3 ,a ,practical ,manual of ,town ,drainage and ,sewage and ,refuse ,disposal4 ,by ,,frank ,,wood1 ,a4,m4 ,inst4 ,c4,e41 ,f4,g4,s41 ,borough ,surveyor1 ,fulham4 ,fully ,illustrated4 #hs4 #f;d4 net4 ,see page #gh4 ,dairy ,chemistry3 ,a ,practical ,handbook for ,dairy ,managers1 ,chemists1 and ,analysts4 ,by ,h4 ,droop ,richmond1 ,f4,c4,s41 ,chemist to the ,aylesbury ,dairy ,company4 ,with ,tables1 ,illustrations1 c4 ,handsome ,cloth1 #afs4 ,see page #gc4 ,milk3 ,its ,production and ,uses4 ,with ,chapters on ,dairy ,farming1 ,the ,diseases of ,cattle1 and on the ,hygiene and ,control of ,supplies4 ,by ,,edward ,f4 ,,willoughby1 ,m4,d4 7,lond471 ,d4,p4,h4 7,lond4 and ,camb471 ,inspector of ,farms and ,general ,scientific ,adviser to ,welford ,sons1 ,ltd4 ,see page #gc4 ,flesh ,foods3 ,with ,methods for their ,chemical1 ,microscopical1 and ,bacteriological ,examination4 ,a ,handbook for ,medical ,men1 ,inspectors1 ,analysts1 and others4 ,by ,c4 ,,ainsworth ,,mitchell1 ,b4,a41 ,f4,i4,c41 ,mem4 ,council ,soc4 of ,public ,analysts4 ,with numerous ,illustrations and a coloured ,plate4 #ajs4 #f;d4 ,see page #gc4 ,foods3 ,their ,composition and ,analysis4 ,by ,a4 ,,wynter ,,blyth1 ,m4,r4,c4,s41 ,f4,c4,s41 ,public ,analyst for the ,county of ,devon4 ,with ,tables1 ,folding ,plate1 and ,frontispiece4 ,,fifth ,,edition1 ,thoroughly ,revised4 #bas4 ,see page #gb4 ,,an ,,admirable ,,digest of the most recent state of knowledge4--,chemical ,news4 99 99 99 99 99 ,,electrical ,,engineering4 ,in ,large #hvo4 ,handsome ,cloth4 ,profusely ,illustrated with ,plates1 ,diagrams1 and ,figures4 #bds4 net4 ,,central ,,electrical ,,stations3 ,their ,design1 ,organisation1 and ,management4 ,,by ,,chas4 ,h4 ,,wordingham1 ,a4,k4,c41 ,m4 ,,inst4 ,c4,e41 ,m4 ,,inst4 ,,mech4 ,e41 ,late ,memb4 of ,council ,inst4 ,e4,e41 and ,electrical ,engineer to the ,city of ,manchester4 ,,abridged ,,contents4 ,introductory4--,central ,station ,work as a ,profession4--,as an ,investment4--,the ,establishment of a ,central ,station4--,systems of ,supply4--,site4--,architecture4--,plant 4--,boilers4--,systems of ,draught and ,waste ,heat ,economy4--,coal ,handling1 ,weighing1 and ,storing4--,the ,transmission of ,steam4--,generators4--,condensing ,appliances4--,switching ,gear1 ,instruments1 and ,connections4--,distributing ,mains4--,insulation1 ,resistance1 and ,cost4--,distributing ,networks4--,service ,mains and ,feeders4--,testing ,mains4--,meters and ,appliances4--,standardising and ,testing ,laboratory4--,secondary ,batteries4--,street ,lighting4--,cost4--,general ,organisation4--,mains ,department4--,installation ,department4--,standardising ,department4--,drawing ,office4--,clerical ,department4--,the ,consumer4--,routine and ,main ,laying4--,,index4 ,one of the ,,most ,,valuable ,,contributions to ,central ,station literature we have had for some time4--,electricity4 99 99 99 99 99 ,,electricity ,,control4 ,a ,treatise on ,electricity ,switchgear and ,systems of ,transmission4 ,,by ,,leonard ,,andrews1 ,m4,i4,e4,e41 ,ex-,member of ,council of the ,incorporated ,municipal ,electrical ,association2 ,consulting ,electrical ,engineer to the ,hastings ,corporation1 c41 c4 ,general ,principles of ,switchgear ,design4--,constructional ,details4--,circuit ,breakers or ,arc ,interrupting ,devices4--,automatically ,operated ,circuit ,breakers4--,alternating ,reverse ,current ,devices4--,arrangement of ',bus ,bars1 and ,apparatus for ,parallel ,running4--,general ,arrangement of ,controlling ,apparatus for ,high ,tension ,systems4--,general ,arrangement of ,controlling ,apparatus for ,low ,tension ,systems4--,examples of ,complete ,installations4--,long ,distance ,transmission ,schemes4 99 99 99 99 99 ,,sixteenth ,,edition1 ,thoroughly ,revised and ,enlarged4 ,a ,,pocket-,,book ,,of ,,electrical ,,rules ,,tables ,,for ,,the ,,use ,,of ,,electricians ,,and ,,engineers4 ,,by ,,john ,,munro1 ,c4,e41 ,,prof4 ,,jamieson1 ,m4 ,,inst4 ,c4,e41 ,f4,r4,s4,e4 ,with ,numerous ,diagrams4 ,pocket ,size4 ,leather1 #hs4 #f;d4 ,,general ,,contents4 ,units of ,measurement4--,measures4--,testing4--,c onductors4--,dielectrics4-- ,submarine ,cables4--,telegraphy4--,electro-,chemis try4--,electro-,metallurgy4-- ,batteries4--,dynamos and ,motors4--,transformers4--,electric ,lighting4--,miscellaneous4--,logarithms 4--,appendices4 ,,wonderfully ,,perfect4444 ,worthy of the highest commendation we can give it4--,electrician4 ,the ,,sterling ,,value of ,messrs4 ,,munro and ,,jamieson',s ,,pocket-,,book4--,electrical ,review4 99 99 99 99 99 ,by ,,professors ,j4,h4 ,,poynting ,j4,j4 ,,thomson4 ,in ,five ,volumes4 ,large #hvo4 ,sold ,separately4 ,a ,,text-,,book ,,of ,,physics4 ,,by ,j4,h4 ,,poynting1 ,,sc4,d41 ,f4,r4,s41 ,late ,fellow of ,trinity ,college1 ,cambridge2 ,professor of ,physics1 ,birmingham ,university4 ,,and ,j4,j4 ,,thomson1 ,m4,a41 ,f4,r4,s4 ,fellow of ,trinity ,college1 ,cambridge2 ,prof4 of ,experimental ,physics in the ,university of ,cambridge4 99 99 99 99 99 ,introductory ,volume1 fully ,illustrated4 ,,second ,,edition1 ,revised4 ,price #ajs4 #f;d4 ,,properties ,,of ,,matter4 ,,contents4--,gravitation4--,the ,acceleration of ,gravity4--,elasticity4--,stresses and ,strains4--,torsion4--,bending of ,rods4--,spiral ,springs4--,collision4--,compressibility of ,liquids4--,pressures and ,volumes of ,gases4--,thermal ,effects ,accompanying ,strain4--,capillarity4--,surface ,tension4--,laplace's ,theory of ,capillarity4--,diffusion of ,liquids4--,diffusion of ,gases4--,viscosity of ,liquids4--,,index4 99 99 99 99 99 ,,volume ,,ii4 ,,second ,,edition4 ,fully ,illustrated4 ,price #hs4 #f;d4 ,,sound4 ,,contents4--,the ,nature of ,sound and its chief ,characteristics4--,the ,velocity of ,sound in ,air and other ,media4--,reflection and ,refraction of ,sound4--,frequency and ,pitch of ,notes4--,resonance and ,forced ,oscillations4--,analysis of ,vibrations4--,the ,transverse ,vibrations of ,stretched ,strings or ,wires4--,pipes and other ,air ,cavities4--,rods4--,plates4--,membranes 4--,vibrations maintained by ,heat4--,sensitive ,flames and ,jets4--,musical ,sand4--,the ,superposition of ,waves4--,,index4 ,the work 444 may be recommended to anyone desirous of possessing an ,,easy ,,up-,,to-,,date ,,standard ,,treatise on ,acoustics4--,literature4 ,very clearly written4444 ,the names of the authors are a guarantee of the ,,scientific ,,accuracy and ,,up-,,to-,,date ,,character of the work4--,educational ,times4 99 99 99 99 99 ,,volume ,,iii4 ,at ,press4 ,fully ,illustrated4 ,,heat4 ,remaining ,volumes in ,preparation-- ,,light2 ,,magnetism ,,and ,,electricity4 99 99 99 99 99 ,,the ,,mean ,,density ,,of ,,the ,,earth3 ,an ,essay to which the ,adams ,prize was adjudged in #ahic in the ,university of ,cambridge4 ,by ,j4,h4 ,,poynting1 ,sc4,d41 ,f4,r4,s41 ,late ,fellow of ,trinity ,college1 ,cambridge2 ,professor of ,physics1 ,birmingham ,university4 ,in ,large #hvo1 with ,bibliography1 ,illustrations in the ,text1 and ,seven ,lithographed ,plates4 #abs4 #f;d4 ,an account of this subject cannot fail to be of ,,great and ,,general ,,interest to the scientific mind4 ,especially is this the case when the account is given by one who has contributed so considerably as has ,prof4 ,poynting to our present state of knowledge with respect to a very difficult subject4444 ,remarkably has ,newton's estimate been verified by ,prof4 ,poynting4--,athenum4 99 99 99 99 99 ,griffin's ,geological1 ,prospecting1 ,mining1 and ,metallurgical ,publications4 ,for ,works on ,,chemistry and ,,chemical ,,industries see p4 #fi4 ,,page ,geology1 ,stratigraphical1 ,r4 ,,etheridge1 ,f4,r4,s41 #eb ,physical1 ,,prof4 ,h4,g4 ,,seeley1 #eb ,practical ,aids1 ,,prof4 ,,grenville ,,cole1 #ec ,open ,air ,studies1 #ai ,griffin's ,new ,land ,series1 ,,ed4 ,,by ,,prof4 ,,cole1 #ed ,prospecting for ,minerals1 ,s4 ,,herbert ,,cox1 ,a4,r4,s4,m41 #ee ,food ,supply1 ,,robt4 ,,bruce1 #ee ,new ,lands1 ,h4,r4 ,,mill1 ,d4,,sc41 ,f4,r4,s4,e41 #ed ,building ,construction1 ,,prof4 ,,james ,,lyon1 #ed ,ore and ,stone ,mining1 ,,prof4 ,,le ,,neve ,,foster1 #ef ,elementary ,mining1 #ef ,coal ,mining1 ,h4,w4 ,,hughes1 ,f4,g4,s41 #ef ,practical ,coal ,mining1 ,g4,l4 ,,kerr1 ,m4,,inst4,m4,e41 #eh ,elementary #eh ,electrical ,coal ,mining1 ,d4 ,,burns1 #eh ,mine-,surveying1 ,,bennett ,h4 ,,brough1 ,a4,r4,s4,m41 #eg ,blasting and ,explosives1 ,o4 ,,guttmann1 ,a4,m4,i4,c4,e41 #eg ,mine ,accounts1 ,,prof4 ,j4,g4 ,,lawn1 #eg ,mining ,engineers' ,pkt4-,bk41 ,e4,r4 ,,field1 ,m4,,inst4,m4,m41 #fj ,petroleum1 ,,redwood ,,and ,,holloway1 #fa ,a ,handbook on ,petroleum1 ,j4,h4 ,,thomson ,,and ,,dr4 ,,redwood1 #fa ,the ,petroleum ,lamp1 #fa ,metallurgical ,analysis1 ,,macleod ,,and ,,walker1 #fj ,metallurgy 7,general71 ,,phillips ,,and ,,bauerman1 #fj 7,elementary71 ,,prof4 ,,humboldt ,,sexton1 #ff ,getting ,gold1 ,j4,c4,f4 ,,johnson1 ,f4,g4,s41 #eh ,gold ,seeking in ,south ,africa1 ,,theo ,,kassner1 #ei ,cyanide ,process1 ,,james ,,park1 ,f4,g4,s41 #ei ,cyaniding1 ,,smart ,,and ,,julian1 #ei ,electric ,smelting1 ,borchers and ,mc,millan1 #fg ,electro-,metallurgy1 ,w4,g4 ,mc,millan1 ,f4,i4,c41 #fg ,assaying1 ,j4,j4 ,c4 ,,beringer1 #ff ,metallurgical ,analysis1 ,j4,j4 ,,morgan1 ,f4,c4,s1 #ff ,griffin's ,metallurgical ,series ,,ed4 ,,by ,,sir ,w4 ,,roberts-,,austen1 #fb ,introduction1 ,,sir ,w4 ,,roberts-,,austen1 ,k4,c4,b41 #fc ,gold1 ,metallurgy of1 ,,dr4 ,,kirke ,,rose1 ,a4,r4,s4,m41 #fc ,lead and ,silver1 ,h4,f4 ,,collins1 ,a4,r4,s4,m41 #fd ,iron1 ,metallurgy of1 ,,thos4 ,,turner1 ,a4,r4,s4,m41 #fe ,steel1 ,f4,w4 ,,harbord1 #fe ,metallurgical ,machinery1 ,h4,c4 ,,jenkins1 ,a4,r4,s4,m41 #fd ,goldsmith and ,jeweller's ,art1 ,,thos4 ,b4 ,,wigley1 #fh ,precious ,stones1 ,,dr4 ,,max ,,bauer1 #fh 99 99 99 99 99 ,demy #hvo1 ,handsome cloth1 #ahs4 ,physical ,geology and ,palontology1 ,,on ,,the ,,basis ,,of ,,phillips4 ,,by ,,harry ,,govier ,,seeley1 ,f4,r4,s41 ,,professor ,,of ,,geography ,,in ,,king',s ,,college1 ,,london4 ,with ,frontispiece in ,chromo-,lithography1 and ,illustrations4 ,it is impossible to praise too highly the research which ,,professor ,,seeley',s ',,physical ,,geology' evidences4 ,,it ,,is ,,far ,,more ,,than ,a ,,text-,,book--it is a ,,directory to the ,student in prosecuting his researches4--,presidential ,address to the ,geological ,society1 #ahhe1 by ,rev4 ,prof4 ,bonney1 ,d4,sc41 ,,ll4,d41 ,f4,r4,s4 ,,professor ,,seeley maintains in his ',,physical ,,geology' the high reputation he already deservedly bears as a ,teacher4--,dr4 ,henry ,woodward1 ,f4,r4,s41 in the ,geological ,magazine4 ,,professor ,,seeley',s work includes one of the most satisfactory ,treatises on ,lithology in the ,english language4--,american ,journal of ,engineering4 99 99 99 99 99 ,demy #hvo1 ,handsome cloth1 #cds4 ,stratigraphical ,geology ,palontology1 ,,on ,,the ,,basis ,,of ,,phillips4 ,,by ,,robert ,,etheridge1 ,f4,r4,s41 ,,of ,,the ,,natural ,,hist4 ,,department1 ,,british ,,museum1 ,,late ,,pal,,ontologist ,,to ,,the ,,geological ,,survey ,,of ,,great ,,britain1 ,,past ,,president ,,of ,,the ,,geological ,,society1 ,,etc4 ,with ,map1 ,numerous ,tables1 and ,thirty-six ,plates4 ,no such compendium of geological knowledge has ever been brought together before4--,westminster ,review4 ,if ,,prof4 ,,seeley',s volume was remarkable for its originality and the breadth of its views1 ,mr4 ,,etheridge fully justifies the assertion made in his preface that his book differs in construction and detail from any known manual4444 ,must take ,,high ,,rank ,,among ,,works ,,of ,,reference4--,athenum4 99 99 99 99 99 ,,open-,,air ,,studies ,,in ,,geology3 ,an ,introduction to ,geology ,out-of-doors4 ,,by ,,professor ,,grenville ,,cole1 ,m4,r4,i4,a41 ,f4,g4,s4 ,for details1 see ,griffin's ,introductory ,science ,series1 p4 #he4 99 99 99 99 99 ,crown #hvo4 ,handsome ,cloth1 #bs4 #f;d4 ,,researches ,,on ,,the ,,past ,,and ,,present ,,history ,,of ,,the ,,earth',s ,,atmosphere4 ,including the latest ,discoveries and their ,practical ,applications4 ,,by ,,dr4 ,,thomas ,,lamb ,,phipson4 ,,part ,i4--,,the ,,earth',s ,,atmosphere ,,in ,,remote ,,geological ,,periods4 ,,part ,,ii4--,,the ,,atmosphere ,,of ,,our ,,present ,,period4 ,,appendices2 ,,index4 999999 ,dr4 ,phipson's work presents1 amidst much which is of interest to the ,scientist and the ,general ,reader alike1 a short rsum of his discovery of the origin of ,atmospheric ,oxygen1 the existence of which he attributes wholly to the action of ,solar ,radiation upon vegetable life4 ,the book will be found replete with much that is new1 curious1 and interesting1 both in connection with ,weather ,lore1 and with ,scientific ,meteorology4--,publisher's ,note4 ,the book should prove of interest to general readers1 as well as to meteorologists and other students of science4--,nature4 99 99 99 99 99 ,by ,,grenville ,a4,j4 ,,cole1 ,m4,r4,i4,a41 ,f4,g4,s41 ,professor of ,geology in the ,royal ,college of ,science for ,ireland1 and ,examiner in the ,university of ,london4 ,see also the two following pages 7#ed1 #ee71 and page #he4 99 99 99 99 99 ,,aids ,,in ,,practical ,,geology3 ,,with ,a ,,section ,,on ,,pal,,ontology4 ,,by ,,professor ,,grenville ,,cole1 ,m4,r4,i4,a41 ,f4,g4,s4 ,,fourth ,,edition1 ,thoroughly ,revised4 ,with ,frontispiece and ,illustrations4 ,cloth1 #ajs4 #f;d4 ,,general ,,contents4-- ,,part ,i4--,,sampling ,,of ,,the ,,earth',s ,,crust4 ,,part ,,ii4--,,examination ,,of ,,minerals4 ,,part ,,iii4--,,examination ,,of ,,rocks4 ,,part ,,iv4--,,examination ,,of ,,fossils4 ,prof4 ,cole treats of the examination of minerals and rocks in a way that has never been attempted before 444 ,,deserving ,,of ,,the ,,highest ,,praise4 ,here indeed are ',aids' ,,innumerable and ,,invaluable4 ,all the directions are given1 with the utmost clearness and precision4--,athenum4 ,that the work deserves its title1 that it is full of ',,aids1' and in the highest degree ',,practical1' will be the verdict of all who use it4--,nature4 ,this ,,excellent ,,manual 444 will be ,a ,,very ,,great ,,help4444 ,the ,section on the ,examination of ,fossils is probably the ,,best of its kind yet published4444 ,,full of well-digested information from the newest sources and from personal research4--,annals of ,nat4 ,history4 99 99 99 99 99 ,,griffins ,,new ,,land ,,series4 99 99 99 99 99 ,practical ,hand-,books for the ,use of ,prospectors1 ,explorers1 ,settlers1 ,colonists1 and all ,interested in the opening up and ,development of ,new ,lands4 ,,edited ,,by ,,grenville ,a4,j4 ,,cole1 ,m4,r4,i4,a41 ,f4,g4,s41 ,professor of ,geology in the ,royal ,college of ,science for ,ireland1 and ,examiner in the ,university of ,london4 99 99 99 99 99 ,in ,crown #hvo4 ,handsome ,cloth4 #es4 ,with ,numerous ,maps ,specially ,drawn and ,executed for this ,work4 ,,new ,,lands3 ,,their ,,resources ,,and ,,prospective ,,advantages4 ,,by ,,hugh ,,robert ,,mill1 ,d4,sc41 ,,ll4,d41 ,f4,r4,s4,e41 ,librarian to the ,royal ,geographical ,society4 ,,introductory4--,the ,development of ,new ,lands4--,the ,dominion of ,canada4--,canada1 ,eastern ,provinces4--,canada1 ,western ,provinces and ,territories4--,newfoundland4--,the ,united ,states4--,latin ,america1 ,mexico4--,latin ,america1 ,temperate ,brazil and ,chili4--,latin ,america1 ,argentina4--,the ,falkland ,islands4--,victoria4--,new ,south ,wales4--,queensland4--,south ,australia4--,tasmania4--,western ,australia4--,new ,zealand4--,the ,resources of ,south ,africa4--,southern ,rhodesia4--,,index4 ,,painstaking 444 ,,complete 444 of great ,,practical ,,assistance4--,the ,field4 ,a want admirably supplied4444 ,has the advantage of being written by a professed ,geographer4--,geographical ,journal4 99 99 99 99 99 ,,in ,,preparation4 ,,building ,,construction ,,in ,,wood1 ,,stone1 ,,and ,,concrete4 ,by ,,james ,,lyon1 ,m4,a41 ,professor of ,engineering in the ,royal ,college of ,science for ,ireland2 sometime ,superintendent of the ,engineering ,department in the ,university of ,cambridge2 and ,j4 ,taylor1 ,a4,r4,c4,s4,i4 99 99 99 99 99 999999 ,other ,volumes1 dealing with subjects of ,,primary ,,importance in the ,,examination and ,,utilisation of ,lands which have not as yet been fully developed1 are in preparation4 99 99 99 99 99 ,,third ,,edition1 ,revised4 ,with ,illustrations4 ,handsome ,cloth1 #es4 ,,prospecting ,,for ,,minerals4 ,a ,practical ,handbook for ,prospectors1 ,explorers1 ,settlers1 and all interested in the ,opening up and ,development of ,new ,lands4 ,,by ,s4 ,,herbert ,,cox1 ,assoc4 ,r4,s4,m41 ,m4 ,inst4 ,m4,m41 ,f4,g4,s41 c4 ,,general ,,contents4--,introduction and ,hints on ,geology--,the ,determination of ,minerals3 ,use of the ,blow-pipe1 c4--,rock-forming ,minerals and ,non-,metallic ,minerals of ,commercial ,value3 ,rock ,salt1 ,borax1 ,marbles1 ,lithographic ,stone1 ,quartz and ,opal1 c41 c4--,precious ,stones and ,gems--,stratified ,deposits3 ,coal and ,ores--,mineral ,veins and ,lodes--,irregular ,deposits--,dynamics of ,lodes3 ,faults1 c4--,alluvial ,deposits--,noble ,metals3 ,gold1 ,platinum1 ,silver1 c4--,lead--,mercury--,copper--,tin--,zin c--,iron--,nickel1 c4--,sulphur1 ,antimony1 ,arsenic1 c4--,combustible ,minerals--,petroleum--,general ,hints on ,prospecting--,glossary--,index4 ,this ,,admirable ,,little ,,work 444 written with ,,scientific ,,accuracy in a ,,clear and ,,lucid style4444 ,an ,,important ,,addition to technical literature 444 will be of value not only to the ,student1 but to the experienced ,prospector4444 ,if the succeeding volumes of the ,,new ,,land ,,series are equal in merit to the ,first1 we must congratulate the ,publishers on successfully filling up a gap in existing literature4--,mining ,journal4 ,this ,,excellent ,,handbook will prove a perfect ,vade-mecum to those engaged in the practical work of ,mining and ,metallurgy4--,times of ,africa4 99 99 99 99 99 ,with many ,engravings and ,photographs4 ,handsome ,cloth1 #ds4 #f;d4 ,,food ,,supply4 ,by ,,robert ,,bruce1 ,agricultural ,superintendent to the ,royal ,dublin ,society4 ,with ,appendix on ,preserved ,foods by ,c4,a4 ,mitchell1 ,b4,a41 ,f4,l4,c4 ,,general ,,contents4--,climate and ,soil--,drainage and ,rotation of ,crops--,seeds and ,crops--,vegetables and ,fruits--,cattle and ,cattle-,breeding--,sheep and ,sheep ,rearing--,pigs--,poultry--,horses--,the ,dairy--,the ,farmer's ,implements--,the ,settler's ,home4 ,,bristles ,,with ,,information4--,farmers' ,gazette4 ,the work is one which will appeal to those intending to become farmers at home or in the ,colonies1 and who desire to obtain a general idea of the true principles of farming in ,,all ,,its ,,branches4--,journal of the ,royal ,colonial ,inst4 ,a most ,,readable and ,,valuable book1 and merits an ,,extensive ,,sale4--,scottish ,farmer4 ,will prove of service in ,,any ,,part ,,of ,,the ,,world4--,nature4 99 99 99 99 99 ,,fourth ,,edition1 ,revised1 and brought thoroughly up-to-date by ,l4,h4 ,,cooke1 ,instructor in ,mine ,surveying1 ,royal ,college of ,science4 ,with ,frontispiece and #gaf ,illustrations4 ,price #cds4 ,,ore ,,stone ,,mining4 ,,by ,c4 ,,le ,,neve ,,foster1 ,d4,sc41 ,f4,r4,s41 ,,professor ,,of ,,mining1 ,,royal ,,college ,,of ,,science2 ,,examiner ,,in ,,mining ,,to ,,the ,,board ,,of ,,education4 ,,general ,,contents4 ,,introduction4 ,mode of ,occurrence of ,minerals4--,prospecting4--,boring4--,br eaking ,ground4--,supporting ,excavations4--,exploitation4--,haulage or ,transport4--,hoisting or ,winding4--,drainage4--,ventilation4--,l ighting4--,descent and ,ascent4--,dressing4--,principles of ,employment of ,mining ,labour4--,legislation affecting ,mines and ,quarries4--,condition of the ,miner4--,accidents4--,index4 ,dr4 ,foster's book was expected to be epoch-making1 and it fully justifies such expectation4444 ,a ,,most ,,admirable account of the mode of occurrence of practically ,,all ,,known ,,minerals4 ,probably stands unrivalled for completeness4--,the ,mining ,journal4 ,this ,,epoch-,,making work 444 appeals to ,,men ,,of ,,experience no less than to students4--,berg- und ,httenmnnische ,zeitung4 ,this ,,splendid ,,work4--,oesterr4 ,ztschrft4 fr ,berg- und ,httenwesen4 99 99 99 99 99 ,,elementary ,,mining ,,and ,,quarrying 7,an ,introductory ,text-book74 ,by ,prof4 ,c4 ,,le ,,neve ,,foster1 ,f4,r4,s4 ,with ,illustrations4 ,at ,press4 99 99 99 99 99 ,,fourth ,,edition1 ,revised and ,greatly ,enlarged4 ,with ,numerous ,additional ,illustrations1 mostly reduced from ,working ,drawings4 ,price #bds4 net4 ,a ,,text-,,book ,,of ,,coal-,,mining3 ,,for ,,the ,,use ,,of ,,colliery ,,managers ,,and ,,others ,,engaged ,,in ,,coal-,,mining4 ,,by ,,herbert ,,william ,,hughes1 ,f4,g4,s41 ,assoc4 ,royal ,school of ,mines1 ,general ,manager of ,sandwell ,park ,colliery4 ,,general ,,contents4 ,geology4--,search for ,coal4--,breaking ,ground4--,sinking4--,preliminary ,operations4--,methods of ,working4--,haulage4--,winding4--,pumpin g4-- ,ventilation4--,lighting4--,works at ,surface4--,preparation of ,coal for ,market4--,,index4 ,quite ,,the ,,best book of its kind 444 as ,,practical in aim as a book can be 444 ,the illustrations are ,,excellent4--,athenum4 ,we cordially recommend the work4--,colliery ,guardian4 ,will soon come to be regarded as the ,,standard ,,work of its kind4--,birmingham ,daily ,gazette4 99 99 99 99 99 ,,tenth ,,edition1 ,revised and ,enlarged4 ,with ,numerous ,diagrams4 ,cloth1 #gs4 #f;d4 ,a ,,treatise ,,on ,,mine-,,surveying3 ,for the use of ,managers of ,mines and ,collieries1 ,students at the ,royal ,school of ,mines1 c4 ,by ,,bennett ,h4 ,,brough1 ,f4,g4,s41 ,,assoc4,r4,s4,m41 ,formerly ,instructor of ,mine-,surveying1 ,royal ,school of ,mines4 ,,general ,,contents4--,general ,explanations4--,measurement of ,distances4--,miner's ,dial4--,variation of the ,magnetic-,needle4--,surveying4--,german ,dial4--,theodolite4--,traversing ,underground4--,surface-,surveys4--,plot ting the ,survey4--,calculation of ,areas4--,levelling4--,measuring ,distances by ,telescope4--,setting-out4--,problems4-- ,photographic ,surveying4--,appendices4 ,its ,,clearness of ,,style1 ,,lucidity of ,,description1 and ,,fulness of ,,detail have long ago won for it a place unique in the literature of this branch of mining engineering1 and the present edition fully maintains the high standard of its predecessors4 ,to the student1 and to the mining engineer alike1 ,,its ,,value is inestimable4 ,the illustrations are excellent4--,the ,mining ,journal4 99 99 99 99 99 ,in ,large #hvo4 ,,second ,,edition4 ,price #ajs4 #f;d4 ,mine ,accounts and ,mining ,book-keeping4 ,for ,students1 ,managers1 ,secretaries1 and others4 ,with ,examples taken from ,actual ,practice of ,leading ,companies4 ,,by ,,james ,,gunson ,,lawn1 ,assoc4,r4,s4,m41 ,assoc4 ,mem4 ,inst4 ,c4,e41 ,f4,g4,s41 ,professor of ,mining at the ,south ,african ,school of ,mines4 ,,edited ,,by ,c4 ,,le ,,neve ,,foster1 ,d4,sc41 ,f4,r4,s4 ,,general ,,contents4--,introduction4--,part ,i4 ,engagement and ,payment of ,workmen4--,part ,,ii4 ,purchases and ,sales4--,part ,,iii4 ,working ,summaries and ,analyses4--,part ,,iv4 ,ledger1 ,balance ,sheet1 and ,company ,books4--,part ,v4 ,reports and ,statistics4 ,it seems ,,impossible to suggest how ,mr4 ,,lawn',s book could be made more ,,complete or more ,,valuable1 careful1 and exhaustive4--,accountants' ,magazine4 99 99 99 99 99 ,in ,large #hvo1 with ,illustrations and ,folding-,plates4 #ajs4 #f;d4 ,,blasting3 ,,and ,,the ,,use ,,of ,,explosives4 ,a ,handbook for ,engineers and others ,engaged in ,mining1 ,tunnelling1 ,quarrying1 c4 ,,by ,,oscar ,,guttmann1 ,,assoc4 ,m4 ,,inst4 ,c4,e4 ,member of the ,societies of ,civil ,engineers and ,architects of ,vienna and ,budapest1 ,corresponding ,member of the ,imp4 ,roy4 ,geological ,institution of ,austria1 c4 ,this ,,admirable work4--,colliery ,guardian4 ,should prove a vade-mecum to ,mining ,engineers and all engaged in practical work4--,iron and ,coal ,trades ,review4 99 99 99 99 99 ,in ,crown #hvo4 ,handsome cloth4 ,with ,numerous ,illustrations4 #fs4 net4 ,,electrical ,,practice ,,in ,,collieries4 ,,by ,d4 ,,burns1 ,m4,e41 ,m4,,inst4,m4,e41 ,certificated ,colliery ,manager1 and ,lecturer on ,mining and ,geology to the ,glasgow and ,west of ,scotland ,technical ,college4 ,units of ,measurement1 ,conductors1 c4--,the ,theory of the ,dynamo4--,the ,dynamo1 ,details of ,construction and ,working4--,motors4--,lighting ,installations in ,collieries4--,pumping by ,electricity4--,electrical ,haulage4--,coal ,cutting4--,miscellaneous ,applications of ,electricity in ,mines4--,,index4 ,a clear and concise introduction to electrical practice in collieries4--,mining ,journal4 99 99 99 99 99 ,,second ,,edition4 ,large ,crown #hvo4 ,handsome ,cloth4 ,with over #ebj ,illustrations in the ,text4 #abs4 #f;d4 ,,practical ,,coal-,,mining3 ,a ,,manual ,,for ,,managers1 ,,under-,,managers1 ,,colliery ,,engineers1 ,,and ,,others4 ,with ,worked-out ,problems on ,haulage1 ,pumping1 ,ventilation1 c4 ,,by ,,george ,l4 ,,kerr1 ,m4,e41 ,m4,,inst4,m4,e4 ,an ,,essentially ,,practical ,,work1 and can be confidently recommended4 ,no department of ,coal-,mining has been overlooked4--,engineers' ,gazette4 ,this book ,,just ,,meets the wants of ,students preparing for the ,colliery ,managers' ,examinations4 ,i have decided to use it for our classes here4444 ,we have1 ,i believe the largest atining class in ,great ,britain4--,the ,principal of a ,training ,college4 99 99 99 99 99 ,,elementary ,,coal-,,mining3 ,for the ,use of ,students1 ,miners1 and others preparing for ,examinations4 ,by ,,george ,l4 ,,kerr1 ,m4,e41 ,m4,,inst4,m4,e41 ,author of ,practical ,coal-,mining4 ,in ,crown #hvo4 ,handsome ,cloth4 ,with #bjj ,illustrations4 #cs4 #f;d4 ,an abundance of information conveyed in a popular and attractive form4444 ,will be of great use to all who are in any way interested in coal mining4--,scottish ,critic4 99 99 99 99 99 ,,second ,,edition4 ,with ,illustrations4 ,cloth1 #cs4 #f;d4 ,,getting ,,gold3 ,a ,,gold-,,mining ,,handbook ,,for ,,practical ,,men4 ,,by ,j4,c4,f4 ,,johnson1 ,f4,g4,s41 ,a4,i4,m4,e41 ,life ,member ,australasian ,mine-,managers' ,association4 ,,general ,,contents4--,introductory3 ,prospecting 7,alluvial and ,general7--,lode or ,reef ,prospecting--,genesiology of ,gold--,auriferous ,lodes--,drifts--,gold ,extraction--,lixiviation--,calcination- -,motor ,power and its ,transmission--,company ,formation--,mining ,appliances and ,methods--,australasian ,mining ,regulations4 ,,practical from beginning to end 444 deals thoroughly with the ,prospecting1 ,sinking1 ,crushing1 and ,extraction of gold4--,brit4 ,australasian4 99 99 99 99 99 ,with ,plates and ,illustrations4 ,handsome ,cloth4 ,at ,press4 ,,the ,,cyanide ,,process ,,of ,,gold ,,extraction4 ,a ,text-,book for the ,use of ,metallurgists and ,students at ,schools of ,mines1 c4 ,,by ,,james ,,park1 ,f4,g4,s41 ,m4,,inst4,m4,m41 ,professor of ,mining and ,director of the ,otago ,university ,school of ,mines2 late ,director ,thames ,school of ,mines1 and ,geological ,surveyor and ,mining ,geologist to the ,government of ,new ,zealand4 ,,third ,,english ,,edition4 ,thoroughly ,revised and ,greatly ,enlarged4 ,with additional details concerning the ,siemens-,halske and other recent processes4 ,,contents4--,the ,mac,arthur ,process4--,chemistry of the ,process4--,laboratory ,experiments4--,control ,testing and ,analysis of ,solutions4--,appliances for ,cyanide ,extraction4--,the ,actual ,extraction by ,cyanide4--,application of the ,process4--,leaching by ,agitation4--,zinc ,precipitation of ,gold4--,the ,siemens-,halske ,process4--,other ,cyanide ,processes4--,antidotes for ,cyanide ,poisoning4--,cyaniding in ,new ,zealand4 ,mr4 ,park's book deserves to be ranked as amongst the ,,best ,,of ,,existing ,,treatises ,,on ,,this ,,subject4--,mining ,journal4 99 99 99 99 99 ,,at ,,press4 ,with ,numerous ,plates1 ,maps1 and ,illustrations4 ,,cyaniding ,,gold ,,silver ,,ores4 ,a ,practical ,treatise on the ,cyanide ,process2 its ,application1 ,methods of ,working1 ,design and ,construction of ,plant1 and ,costs4 ,,by ,h4 ,,forbes ,,julian1 ,mining and ,metallurgical ,engineer2 ,specialist in ,gold3 ,late ,technical ,adviser of the ,deutsche ,gold und ,silber ,scheide ,anstalt1 ,frankfort-on-,maine4 ,,and ,,edgar ,,smart1 ,a4,m4,i4,c4,e41 ,civil and ,metallurgical ,engineer4 999999 ,this book deals with the ,cyanide ,process from ,technical1 ,commercial1 and ,scientific points of view4 ,it is adapted for the ,use of ,directors1 ,managers1 and ,superintendents of ,mines and ,metallurgical ,works1 ,mining ,engineers1 ,metallurgists1 ,chemists1 ,assayers1 ,working ,cyaniders1 and ,students4 99 99 99 99 99 ,in ,crown4 #hvo4 ,illustrated4 ,fancy ,cloth ,boards4 #d;c4 #f;c4 ,,gold ,,seeking ,,in ,,south ,,africa3 ,a ,handbook of ,hints for intending ,explorers1 ,prospectors1 and ,settlers4 ,,by ,,theo ,,kassner1 ,mine ,manager1 ,author of the ,geological ,sketch ,map of the ,de ,kaap ,gold ,fields4 ,with a ,chapter on the ,agricultural ,prospects of ,south ,africa4 ,,abstract ,,of ,,contents--,history4--,geology4--,prosp ecting4--,the ,de ,kaap ,goldfields4--,komati and ,swaziland4--,cost of ,mining1 ,native ,labour1 c4--,lydenberg ,goldfields--,zoutspanberg4--,witwatersr and4--,other ,goldfields4--,general ,considerations--,conclusions4--,agricul tural ,prospects1 ,tables1 ,index1 c4 ,as fascinating in its way as anything ever penned by ,jules ,verne4 ,mr4 ,kassner manages to impart his information in a way that enables him to be understanded even of the dullest4--,african ,commerce4 99 99 99 99 99 ,,at ,,press4 ,large #hvo4 ,handsome ,cloth4 ,with ,illustrations4 ,,metallurgical ,,analysis ,,assaying3 ,a ,,three ,,years' ,,course ,,for ,,students ,,of ,,schools ,,of ,,mines4 ,by ,w4,a4 ,,macleod1 ,b4,a41 ,b4,sc41 ,a4,o4,s4,m4 7,n4,z471 ,formerly ,assist4-,director1 ,thames ,school of ,mines 7,n4,z471 and ,lecturer in ,chemistry1 ,university of ,tasmania2 ,director of ,queensland ,government ,school of ,mines1 ,charters ,towers2 ,,and ,,chas4 ,,walker1 ,f4,c4,s41 ,formerly ,assist4-,demonstrator in ,chemistry1 ,sydney ,university2 ,lecturer in ,chemistry and ,metallurgy1 ,charters ,towers ,school of ,mines ,,part ,i4--,,qualitative ,,analysis ,,and ,,preparation ,,and ,,properties ,,of ,,gases4 ,,part ,,ii4--,,qualitative ,,and ,,quantitative ,,analysis4 ,,part ,,iii4--,,assaying1 ,,technical ,,analysis 7,,gas1 ,,water1 ,,fuels1 ,,oils1 ,c474 999999 ,the aim of this work is to provide the student with a graded course of work leading from ,simple ,quantitative ,analysis up to the ,technical ,quantitative ,methods4 ,it has been specially prepared to meet the requirements of ,schools of ,mines1 and more especially1 of those in the ,colonies1 the subject matter having been selected to cover a three years' laboratory course4--,extract from ,author's ,preface4 99 99 99 99 99 ,,third ,,edition4 ,with ,folding ,plates and ,many ,illustrations4 #cfs4 ,,elements ,,of ,,metallurgy4 ,a ,,practical ,,treatise ,,on ,,the ,,art ,,of ,,extracting ,,metals ,,from ,,their ,,ores4 ,,by ,j4 ,,arthur ,,phillips1 ,m4 ,,inst4 ,c4,e41 ,f4,c4,s41 ,f4,g4,s41 c41 ,,and ,h4 ,,bauerman1 ,v4,p4,g4,s4 ,,general ,,contents4--,refractory ,materials4--,fire-,clays4--,fuels1 c4--,aluminium4--,copper4--,tin4--,antim ony4--,arsenic4--,zinc4--,mercury4-- ,bismuth4--,lead4--,iron4--,cobalt4--,ni ckel4--,silver4--,gold4--,platinum4 ,of the ,,third ,,edition1 we are still able to say that1 as a ,text-book of ,metallurgy1 it is ,,the ,,best with which we are acquainted4--,engineer4 ,a work which is equally valuable to the ,student as a ,text-book1 and to the practical ,smelter as a ,standard ,work of ,reference4444 ,the ,illustrations are admirable examples of ,wood ,engraving4--,chemical ,news4 99 99 99 99 99 ,,the ,,mining ,,engineers' ,,report ,,book ,,and ,,directors' ,,and ,,shareholders' ,,guide ,,to ,,mining ,,reports4 ,by ,,edwin ,r4 ,,field1 ,m4,,inst4,m4,m4 ,with ,notes on the ,valuation of ,mining ,property and ,tabulating ,reports1 ,useful ,tables1 c41 and provided with detachable blank pages for ,,ms4 ,notes4 ,an ,,admirably compiled book which ,mining ,engineers and ,managers will find ,,extremely ,,useful4--,mining ,journal4 99 99 99 99 99 ,,second ,,edition4 ,in ,preparation4 ,in ,two ,volumes1 ,large #hvo4 ,with ,numerous ,maps1 ,plates1 and ,illustrations in the ,text4 ,price #des4 ,,petroleum ,,and ,,its ,,products3 ,a ,,practical ,,treatise4 ,by ,dr4 ,,boverton ,,redwood1 ,f4,r4,s4,e41 ,f4,i4,c41 ,,assoc4,r4,c4,s41 ,hon4 ,corr4 ,mem4 of the ,imperial ,russian ,technical ,society2 ,mem4 of the ,american ,chemical ,society2 ,adviser to the ,home ,office and to the ,corporation of ,london under the ,petroleum ,acts1 c41 c4 ,,assisted ,,by ,,geo4 ,t4 ,,holloway1 ,f4,i4,c41 ,,assoc4 ,r4,c4,s41 ,and ,numerous ,contributors4 ,,general ,,contents4--,i4 ,historical4--,,ii4 ,geological and ,geographical ,distribution of ,petroleum and ,natural ,gas4--,,iii4 ,chemical and ,physical ,properties4--,,iv4 ,origin--,v4 ,production4--,,vi4 ,refining4--,,vii4 ,the ,shale ,oil and ,allied ,industries4--,,viii4 ,transport1 ,storage1 and ,distribution4--,,ix4 ,testing4--,x4 ,application and ,uses4--,,xi4 ,legislation at ,home and ,abroad4--,,xii4 ,statistics4--,,index4 ,the ,,most ,,comprehensive ,,and ,,convenient ,,account that has yet appeared of a gigantic ,industry which has made incalculable additions to the comfort of civilised man4--,the ,times4 ,a ,,splendid ,,contribution to our technical literature4--,chemical ,news4 99 99 99 99 99 ,with ,plates 7,one ,coloured7 and ,illustrations4 ,price #hs4 #f;d4 net4 ,a ,,handbook ,,on ,,petroleum4 ,,for ,,inspectors ,,under ,,the ,,petroleum ,,acts1 ,and for those engaged in the ,storage1 ,transport1 ,distribution1 and ,industrial ,use of ,petroleum and its ,products1 and of ,calcium ,carbide4 ,with suggestions on the ,construction and ,use of ,mineral ,oil ,lamps4 ,,by ,,captain ,j4,h4 ,,thomson1 ,h4,m4 ,chief ,inspector of ,explosives1 ,,and ,,dr4 ,,boverton ,,redwood1 ,author of ,petroleum and its ,products4 ,,contents4--,i4 ,introductory4--,,ii4 ,sources of ,supply4--,,iii4 ,production4--,,iv4 ,chemical ,products1 ,shale ,oil1 and ,coal ,tar4--,v4 ,flash ,point and ,fire ,test4--,,vi4 ,testings4--,,vii4 ,existing ,legislation relating to ,petroleum4--,,viii4--,,ix4--,precaution s ,necessary4--,x4 ,petroleum ,oil ,lamps4--,,xi4 ,carbide of ,calcium and ,acetylene4--,appendices4--,,index4 ,a volume that will enrich the world's petroleum literature1 and render a service to the ,british branch of the industry4444 ,reliable1 indispensable1 a brilliant contribution4--,petroleum4 99 99 99 99 99 ,,the ,,petroleum ,,lamp3 ,its ,choice and ,use4 ,a ,guide to the ,safe ,employment of ,mineral ,oil in what is commonly termed the ,paraffin ,lamp4 ,by ,,capt4 ,j4,h4 ,,thomson and ,dr4 ,,boverton ,,redwood4 ,popular ,edition1 ,illustrated4 #as4 net4 ,the book contains a great deal of interesting reading1 much of which is thoroughly practical and useful4 ,it is a work which will meet every purpose for which it has been written4--,petroleum4 99 99 99 99 99 ,griffin's ,metallurgical ,series4 99 99 99 99 99 ,,standard ,,works ,,of ,,reference ,,for ,metallurgists1 ,mine-,owners1 ,assayers1 ,manufacturers1 and all interested in the development of the ,metallurgical ,industries4 ,,edited ,,by ,sir ,w4 ,,roberts-,,austen1 ,k4,c4,b41 ,d4,c4,l1 ,f4,r4,s4 ,in ,large #hvo1 ,handsome ,cloth4 ,with ,illustrations4 99 99 99 99 99 ,,introduction to the ,,study of ,,metallurgy4 ,by the ,,editor4 ,,fifth ,,edition4 #ahs4 7,see p4 #fc47 ,,gold 7,the ,metallurgy of74 ,by ,,thos4 ,,kirke ,,rose1 ,d4,sc41 ,assoc4,r4,s4,m41 ,f4,i4,c41 ,chemist and ,assayer of the ,royal ,mint4 ,,fourth ,,edition4 #bas4 7,see p4 #fc47 ,,lead ,,and ,,silver 7,the ,metallurgy of74 ,by ,h4,f4 ,,collins1 ,assoc4,r4,s4,m41 ,m4,inst4,m4,m4 ,part ,i41 ,lead1 #afs2 ,part ,,ii41 ,silver1 #afs4 7,see p4 #fd47 ,,iron 7,the ,metallurgy of74 ,by ,t4 ,,turner1 ,a4,r4,s4,m41 ,f4,i4,c41 ,f4,c4,s4 ,,second ,,edition1 ,revised4 #afs4 7,see p4 #fe47 ,,steel 7,the ,metallurgy of74 ,by ,f4,w4 ,,harbord1 ,assoc4,r4,s4,m41 ,f4,i4,c41 with a ,section on ,mechanical ,treatment by ,j4,w4 ,,hall1 ,a4,m4,inst1 ,c4,e4 7,see p4 #fe47 ,ready shortly4 99 99 99 99 99 ,will be ,published at ,short ,intervals4 ,,metallurgical ,,machinery3 the ,application of ,engineering to ,metallurgical ,problems4 ,by ,,henry ,,charles ,,jenkins1 ,wh4,sc41 ,assoc4,r4,s4,m41 ,assoc4,m4,inst4,c4,e41 of the ,royal ,college of ,science4 7,see p4 #fd74 ,,alloys4 ,by the ,,editor4 999999 ,other ,volumes in ,preparation4 99 99 99 99 99 ,,fifth ,,edition1 thoroughly ,revised and considerably ,enlarged4 ,large #hvo1 with numerous ,illustrations and ,micro-,photographic ,plates of different varieties of ,steel4 #ahs4 ,an ,introduction to the ,study of ,,metallurgy4 ,,by ,sir ,w4 ,,roberts-,,austen1 ,k4,c4,b41 ,d4,c4,l41 ,f4,r4,s41 ,a4,r4,s4,m41 ,late ,chemist and ,assayer of the ,royal ,mint1 and ,professor of ,metallurgy in the ,royal ,college of ,science4 ,,general ,,contents4--,the ,relation of ,metallurgy to ,chemistry4--,physical ,properties of ,metals4--,alloys4--,the ,thermal ,treatment of ,metals4--,fuel and ,thermal ,measurements4--,materials and ,products of ,metallurgical ,processes4--,furnaces4--,means of ,supplying ,air to ,furnaces4--,thermo-,chemistry4--,typica l ,metallurgical ,processes4--,the ,micro-,structure of ,metals and ,alloys4--,economic ,considerations4 ,no ,english text-book at all approaches this in the ,,completeness with which the most modern views on the subject are dealt with4 ,professor ,austen's volume will be ,,invaluable1 not only to the student1 but also to those whose knowledge of the art is far advanced4--,chemical ,news4 99 99 99 99 99 ,,fourth ,,edition1 ,revised1 ,considerably ,enlarged1 and in part ,re-written4 ,including the most recent ,improvements in the ,cyanide ,process4 ,with ,frontispiece and numerous ,illustrations4 #bas4 ,,the ,,metallurgy ,,of ,,gold4 ,,by ,t4 ,,kirke ,,rose1 ,d4,sc4,lond41 ,assoc4,r4,s4,m41 ,chemist and ,assayer of the ,royal ,mint4 ,,general ,,contents4--,the ,properties of ,gold and its ,alloys4--,chemistry of ,gold4--,mode of ,occurrence and ,distribution4--,placer ,mining4--,shallow ,deposits4--,deep ,placer ,mining4--,quartz ,crushing in the ,stamp ,battery4--,amalgamation4--,other ,forms of ,crushing and ,amalgamating4--,concentration4--,stamp ,battery ,practice4--,chlorination3 ,the ,preparation of ,ore4--,the ,vat ,process4--,the ,barrel ,process4--,chlorination ,practice in ,particular ,mills4--,the ,cyanide ,process4--,chemistry of the ,process4--,pyritic ,smelting4--,the ,refining and ,parting of ,gold ,bullion--,the ,assay of ,gold ,ores4--,the ,assay of ,bullion--,economic ,considerations4--,bibliography4 ,a ,,comprehensive ,,practical ,,treatise on this important subject4--,the ,times4 ,the ,,most ,,complete description of the ,,chlorination ,,process which has yet been published4--,mining ,journal4 ,adapted for all who are interested in the ,gold ,mining ,industry1 being free from technicalities as far as possible1 but is more particularly of value to those engaged in the industry4--,cape ,times4 99 99 99 99 99 ,,edited ,,by ,,sir ,w4 ,,roberts-,,austen1 ,k4,c4,b41 ,f4,r4,s41 ,d4,c4,l4 ,in ,large #hvo4 ,handsome ,cloth4 ,with ,illustrations4 99 99 99 99 99 ,in ,two ,volumes1 ,each ,complete in ,itself and ,sold ,separately4 ,,the ,,metallurgy ,,of ,,lead ,,and ,,silver4 ,,by ,h4,f4 ,,collins1 ,,assoc4,r4,s4,m41 ,m4,,inst4,m4,m4 ,part ,i4--,,lead3 ,a ,complete and ,exhaustive ,treatise on the ,manufacture of ,lead1 with ,sections on ,smelting and ,desilverisation1 and ,chapters on the ,assay and ,analysis of the ,materials involved4 ,price #afs4 ,,summary ,,of ,,contents4--,sampling and ,assaying ,lead and ,silver4--,properties and ,compounds of ,lead4--,lead ,ores4--,lead ,smelting4--,reverberatories4--,lead ,smelting in ,hearths4--,the ,roasting of ,lead ,ores4--,blast ,furnace ,smelting2 ,principles1 ,practice1 and ,examples2 ,products4--,flue ,dust1 its ,composition1 ,collection and ,treatment4--,costs and ,losses1 ,purchase of ,ores4--,treatment of ,zinc1 ,lead ,sulphides1 ,desilverisation1 ,softening and ,refining4--,the ,pattinson ,process4--,the ,parkes ,process4--,cupellation and ,refining1 c41 c4 ,a ,,thoroughly ,,sound and useful digest4 ,may with ,,every ,,confidence be recommended4--,mining ,journal4 99 99 99 99 99 ,part ,,ii4 ,,silver4 ,comprising ,details regarding the ,sources and ,treatment of ,silver ,ores1 together with ,descriptions of ,plant1 ,machinery1 and ,processes of ,manufacture1 ,refining of ,bullion1 ,cost of ,working1 c4 ,price #afs4 ,,summary ,,of ,,contents4--,properties of ,silver and its ,principal ,compounds4--,silver ,ores4--,the ,patio ,process4--,the ,kazo1 ,fondon1 ,krhnke1 and ,tina ,processes4--,the ,pan ,process4--,roast ,amalgamation4--,treatment of ,tailings and ,concentration4--,retorting1 ,melting1 and ,assaying4--,chloridising-,roasting4--,t he ,augustin1 ,claudet1 and ,ziervogel ,processes4--,the ,hypo-,sulphite ,leaching ,process4--,refining4--,matte ,smelting4--,pyritic ,smelting4--,matte ,smelting in ,reverberatories4--,silver-,copper ,smelting and ,refining4--,,index4 ,the author has focussed ,a ,,large ,,amount ,,of ,,valuable ,,information into a convenient form4444 ,the author has evidently considerable practical experience1 and describes the various processes clearly and well4--,mining ,journal4 99 99 99 99 99 ,,in ,,preparation4 ,,metallurgical ,,machinery3 ,the ,application of ,engineering to ,metallurgical ,problems4 ,,by ,,henry ,,charles ,,jenkins1 ,wh4,sc41 ,assoc4,r4,s4,m41 ,assoc4,m4,inst4,c4,e4 99 99 99 99 99 ,,ready ,,shortly4 ,with ,numerous ,illustrations4 ,large #hvo4 ,handsome ,cloth4 ,,the ,,metallurgy ,,of ,,steel4 ,,by ,f4,w4 ,,harbord1 ,,assoc4,r4,s4,m41 ,f4,i4,c41 ,consulting ,metallurgist and ,analytical ,chemist to the ,indian ,government1 ,royal ,indian ,engineering ,college1 ,coopers ,hill4 ,with over #dj ,plates1 #ejj ,illustrations 7comprising nearly #ajj ,micro-,sections of ,steel71 ,diagrams of ,plant and ,machinery1 reduced from ,working ,drawings1 and a ,section on ,mill ,practice4 ,,by ,j4,w4 ,,hall1 ,a4,m4,,inst4,c4,e4 ,,abridged ,,contents4--,the ,plant1 ,machinery1 ,methods and ,chemistry of the ,bessemer and of the ,open ,hearth ,processes 7,acid and ,basic74--,the ,mechanical ,treatment of ,steel comprising ,mill ,practice1 ,plant and ,machinery4--,the ,influence of ,metalloids1 ,heat ,treatment1 ,special ,steels1 ,microstructure1 ,testing1 and ,specifications4 99 99 99 99 99 ,,second ,,edition1 ,revised4 ,price #afs4 ,,the ,,metallurgy ,,of ,,iron4 ,,by ,,thomas ,,turner1 ,,assoc4,r4,s4,m41 ,f4,i4,c41 ,professor of ,metallurgy in the ,university of ,birmingham4 ,in ,large #hvo1 ,handsome ,cloth1 ,with ,numerous ,illustrations 7many from ,photographs74 ,general ,contents4--,early ,history of ,iron4--,modern ,history of ,iron4--,the ,age of ,steel4--,chief ,iron ,ores4--,preparation of ,iron ,ores4--,the ,blast ,furnace4--,the ,air used in the ,blast ,furnace4--,reactions of the ,blast ,furnace4--,the ,fuel used in the ,blast ,furnace4--,slags and ,fluxes of ,iron ,smelting4--,properties of ,cast ,iron4--,foundry ,practice4--,wrought ,iron4--,indirect ,production of ,wrought ,iron4--,the ,puddling ,process4--,further ,treatment of ,wrought ,iron4--,corrosion of ,iron and ,steel4 ,a ,,most ,,valuable ,,summary of knowledge relating to every method and stage in the manufacture of cast and wrought iron 444 rich in chemical details4444 ,,exhaustive and ,,thoroughly ,,up-,,to-,,date4--,bulletin of the ,american ,iron and ,steel ,association4 ,this is ,a ,,delightful ,,book1 giving1 as it does1 reliable information on a subject becoming every day more elaborate4--,colliery ,guardian4 ,a ,,thoroughly ,,useful ,,book1 which brings the subject ,,up ,,to ,,date4 ,,of ,,great ,,value to those engaged in the iron industry4--,mining ,journal4 99 99 99 99 99 999999 ,for ,details of ,,works ,,on ,,mining1 see pages #ee-ei4 99 99 99 99 99 ,a ,,text-,,book ,,of ,,assaying3 ,for the use of ,students1 ,mine ,managers1 ,assayers1 c4 ,,by ,j4,j4 ,,beringer1 ,f4,i4,c41 ,f4,c4,s41 ,public ,analyst for1 and ,lecturer to the ,mining ,association of1 ,cornwall4 ,,and ,c4 ,,beringer1 ,f4,c4,s41 ,late ,chief ,assayer to the ,rio ,tinto ,copper ,company1 ,london4 ,with numerous ,tables and ,illustrations4 ,crown #hvo4 ,cloth1 #ajs4 #f;d4 ,,eighth ,,edition4 ,,general ,,contents4--,,part ,i4--,,introductory2 ,,manipulation3 ,sampling2 ,drying2 ,calculation of ,results--,laboratory-books and ,reports4 ,,methods3 ,dry ,gravimetric2 ,wet ,gravimetric--,volumetric ,assays3 ,titrometric1 ,colorimetric1 ,gasometric--,weighing and ,measuring--,reagents--,formul1 ,equations1 c4--,specific ,gravity4 ,,part ,,ii4--,,metals3 ,detection and ,assay of ,silver1 ,gold1 ,platinum1 ,mercury1 ,copper1 ,lead1 ,thallium1 ,bismuth1 ,antimony1 ,iron1 ,nickel1 ,cobalt1 ,zinc1 ,cadmium1 ,tin1 ,tungsten1 ,titanium1 ,manganese1 ,chromium1 c4--,earths1 ,alkalies4 ,,part ,,iii4--,,non-,,metals3 ,oxygen and ,oxides2 ,the ,halogens--,sulphur and ,sulphates--,arsenic1 ,phosphorus1 ,nitrogen--,silicon1 ,carbon1 ,boron--,useful ,tables4 ,a ,,really ,,meritorious ,,work1 that may be safely depended upon either for systematic instruction or for reference4--,nature4 ,this work is one of the best of its kind4--,engineer4 99 99 99 99 99 ,,third ,,edition1 ,revised4 ,handsome ,cloth4 ,with ,numerous ,illustrations4 #fs4 ,a ,,text-,,book ,,of ,,elementary ,,metallurgy4 ,including the ,author's ,practical ,laboratory ,course4 ,,by ,a4 ,,humboldt ,,sexton1 ,f4,i4,c41 ,f4,c4,s41 ,professor of ,metallurgy in the ,glasgow and ,west of ,scotland ,technical ,college4 ,,general ,,contents4--,introduction4--,properties of the ,metals4--,combustion4--,fuels4--,refrac tory ,materials4--,furnaces4--,occurrence of the ,metals in ,nature4--,preparation of the ,ore for the ,smelter4--,metallurgical ,processes4--,iron4--,steel4---,copper4- -,lead4--,zinc and ,tin4--,silver4--,gold4--,mercury4--,all oys4--,applications of ,,electricity to ,metallurgy4--,,laboratory ,,course4 ,just the kind of work for ,students commencing the study of ,metallurgy1 or for ,,engineering ,students4--,practical ,engineer4 ,,excellently got-up and ,,well-,,arranged4--,chemical ,trade ,journal4 99 99 99 99 99 ,in ,large #hvo4 ,handsome ,cloth4 ,price #ds4 ,,tables ,,for ,,quantitative ,,metallurgical ,,analysis4 ,,for ,,laboratory ,,use4 ,,on ,,the ,,principle ,,of ,,group ,,separations4 ,,by ,j4 ,,james ,,morgan1 ,f4,c4,s41 ,m4,s4,c4,i4 ,the ,author may be ,,congratulated on the way his work has been carried out4--,the ,engineer4 ,will ,,commend ,,itself highly in ,laboratory ,practice4 ,its ,,clearness and ,,precision mark the book out as a highly useful one4--,mining ,journal4 99 99 99 99 99 ,,second ,,edition1 ,revised1 ,enlarged1 and in part ,re-written4 ,with ,additional ,sections on ,,modern ,,theories ,,of ,,electrolysis ,,costs1 c4 ,price #ajs4 #f;d4 ,a ,,treatise ,,on ,,electro-,,metallurgy3 ,embracing the ,application of ,electrolysis to the ,plating1 ,depositing1 ,smelting1 and ,refining of various ,metals1 and to the ,reproduction of ,printing ,surfaces and ,art-,work1 c4 ,,by ,,walter ,g4 ,mc,m,i,l,l,a,n1 ,f4,i4,c41 ,f4,c4,s41 ,secretary to the ,institution of ,electrical ,engineers2 late ,lecturer in ,metallurgy at ,mason ,college1 ,birmingham4 ,with numerous ,illustrations4 ,large ,crown #hvo4 ,cloth4 ,this excellent treatise1 444 one of the ,,best and ,,most ,,complete manuals hitherto published on ,electro-,metallurgy4--,electrical ,review4 ,this work will be a ,,standard4--,jeweller4 ,any metallurgical process which ,,reduces the cost of production must of necessity prove of great commercial importance4444 ,we recommend this manual to ,,all who are interested in the ,,practical ,,application of electrolytic processes4--,nature4 99 99 99 99 99 ,in large #hvo4 ,with ,numerous ,illustrations and ,three ,folding-,plates4 ,price #bas4 ,,electric ,,smelting ,,refining3 ,a ,practical ,manual of the ,extraction and ,treatment of ,metals by ,electrical ,methods4 ,being the ,,elektro-,,metallurgie of ,,dr4 ,w4 ,,borchers4 ,translated from the ,second ,edition by ,,walter ,g4 ,mc,m,i,l,l,a,n1 ,f4,i4,c41 ,f4,c4,s 99 99 99 99 99 ,,contents4 ,,part ,i4--,,alkalies ,,and ,,alkaline ,,earth ,,metals3 ,magnesium1 ,lithium1 ,beryllium1 ,sodium1 ,potassium1 ,calcium1 ,strontium1 ,barium1 the ,carbides of the ,alkaline ,earth ,metals4 ,,part ,,ii4--,,the ,,earth ,,metals3 ,aluminium1 ,cerium1 ,lanthanum1 ,didymium4 ,,part ,,iii4--,,the ,,heavy ,,metals3 ,copper1 ,silver1 ,gold1 ,zinc and ,cadmium1 ,mercury1 ,tin1 ,lead1 ,bismuth1 ,antimony1 ,chromium1 ,molybdenum1 ,tungsten1 ,uranium1 ,manganese1 ,iron1 ,nickel1 and ,cobalt1 the ,platinum ,group4 ,,comprehensive and ,,authoritative 444 not only ,,full of ,,valuable ,,information1 but gives evidence of a ,,thorough ,,insight into the technical ,,value and ,,possibilities of all the methods discussed4--,the ,electrician4 ,dr4 ,,borchers' ,,well-,,known ,,work 444 must of ,,necessity ,,be ,,acquired by every one interested in the subject4 ,,excellently put into ,english with additional matter by ,mr4 ,,mcmillan4--,nature4 ,will be of ,,great ,,service to the practical man and the ,student4--,electric ,smelting4 99 99 99 99 99 ,in ,large #dto1 ,library ,style4 ,beautifully ,illustrated with #bj ,plates1 many in ,colours1 and #id ,figures in the ,text4 ,,precious ,,stones3 ,their ,properties1 ,occurrences1 and ,uses4 ,a ,treatise for ,dealers1 ,manufacturers1 ,jewellers1 and for all ,collectors and others interested in ,gems4 ,,by ,,dr4 ,,max ,,bauer1 ,professor in the ,university of ,marburg1 ,,translated ,,by ,l4,j4 ,,spencer1 ,m4,a4 7,,cantab471 ,f4,g4,s4 ,,general ,,contents4--,general ,properties of ,gems3 ,their ,natural ,characters1 ,occurrence1 ,application1 and ,uses4--,detailed ,description of ,particular ,gems3 ,the ,diamond1 ,rubies1 ,sapphires2 ,emeralds1 ,tourmalines1 and ,opals2 ,felspars1 ,amphiboles1 ,malachite4--,non-mineral ,gems3 ,amber1 c4--,optical ,features1 ,transparency1 ,translucency1 ,opacity1 ,refraction and ,dispersion1 c4--,,appendix3 ,pearls2 ,coral4 99 99 99 99 99 ,in ,large ,crown #hvo4 ,with ,numerous ,illustrations4 #hs4 #f;d4 ,the ,art of the ,goldsmith and ,jeweller ,a ,manual on the ,manipulation of ,gold and the ,manufacture of ,personal ,ornaments4 ,,by ,,thos4 ,b4 ,,wigley1 ,headmaster of the ,jewellers and ,silversmiths' ,association ,technical ,school1 ,birmingham4 ,,assisted ,,by ,j4,h4 ,,stansbie1 ,b4,,sc4 7,,lond471 ,f4,i4,c41 ,lecturer at the ,birmingham ,municipal ,technical ,school4 99 99 99 99 99 ,,general ,,contents4--,introduction4--,the ,ancient ,goldsmith's ,art4--,metallurgy of ,gold4--,prices1 c4--,alloys4--,melting1 ,rolling1 and ,slitting ,gold4--,the workshop and ,tools4--,wire ,drawing4--,rings4--,chains and ,insignia4--,antique ,jewellery ,work4--,,precious ,,stones4--,cutting4--,polishing and ,finishing4--,chasing1 and its ,revival4--,etruscan ,embossing1 and ,repouss ,work4--,colouring and ,finishing4--,enamelling4--,engraving4-- ,moulding and ,casting ,ornaments1 c4--,fluxes4 c4--,recovery of the ,precious ,metals4--,refining and ,assaying4--,gilding and ,electro ,deposition4--,hall-,marking4--,miscella neous4--,appendix4 99 99 99 99 99 ,griffin's ,chemical and ,technological ,publications4 99 99 99 99 99 ,for ,metallurgy and ,electro-,metallurgy1 see previous ,section4 ,,page ,inorganic ,chemistry1 ,,profs4 ,,dupr ,,and ,,hake1 #gj ,quantitative ,analysis1 ,,prof4 ,,humboldt ,,sexton1 #gj ,qualitative #gj ,chemistry for ,engineers1 ,,blount ,,and ,,bloxam1 #ga ,manufacturers1 #ga ,foods1 ,analysis of1 ,a4 ,,wynter ,,blyth1 #gb ,poisons1 ,detection of1 #gb ,tables for ,chemists and ,manufacturers1 ,,prof4 ,,castell-,,evans1 #gi ,agricultural ,chemistry1 ,,prof4 ,j4,m4,h4 ,,munro1 #ge ,dairy ,chemistry1 ,h4 ,d4 ,,richmond1 #gc ,milk1 ,e4,f4 ,,willoughby1 #gc ,flesh ,foods1 ,c4,a4 ,,mitchell1 #gc ,practical ,sanitation1 ,,dr4 ,g4 ,,reid1 #gh ,sanitary ,engineering1 ,f4 ,,wood1 #gh ,technical ,mycology1 ,,lafar ,,and ,,salter1 #gd ,ferments1 ,c4 ,,oppenheimer1 #gd ,brewing1 ,,dr4 ,w4,j4 ,,sykes1 #ge ,sewage ,disposal1 ,,santo ,,crimp1 #gf ,trades' ,waste1 ,w4 ,,naylor1 #gf ,cements1 ,g4,r4 ,,redgrave1 #gf ,water ,supply1 ,r4,e4 ,,middleton1 #gg ,road ,making1 ,,thos4 ,,aitken1 #gi ,gas ,manufacture1 ,w4 ,,atkinson ,,butterfield1 #gg ,acetylene1 ,,leeds ,,and ,,butterfield1 #gg ,fire ,risks1 ,,dr4 ,,schwartz1 #gg ,petroleum1 ,,redwood ,,and ,,holloway1 #fa ---- 7,handbook71 ,,thomson ,,and ,,redwood1 #fa ,oils1 ,soaps1 ,candles1 ,,dr4 ,,alder ,,wright1 #ha ,lubrication and ,lubricants1 ,,archbutt ,,and ,,deeley1 #cb ,india ,rubber1 ,,dr4 ,,carl ,o4 ,,weber1 #ha ,painters' ,colours1 ,oils1 and ,varnishes1 ,g4,h4 ,,hurst1 #hj ,painters' ,laboratory ,guide1 #hj ,painting and ,decorating1 ,w4,j4 ,,pearce1 #hj ,photography1 ,a4 ,,brothers1 #ba ,dyeing1 ,,knecht ,,and ,,rawson1 #hb ,dictionary of ,dyes1 ,,rawson1 ,,gardner1 ,,and ,,laycock1 #hb ,textile ,printing1 ,,seymour ,,rothwell1 #hc ,textile ,fibres of ,commerce1 ,w4,i4 ,,hannan1 #hc ,dyeing and ,cleaning1 ,g4,h4 ,,hurst1 #hd ,bleaching and ,calico-,printing1 ,,geo4 ,,duerr1 #hd 99 99 99 99 99 ,a ,,short ,,manual ,,of ,,inorganic ,,chemistry4 ,,by ,a4 ,,dupr1 ,ph4,d41 ,f4,r4,s41 ,,and ,,wilson ,,hake1 ,ph4,d41 ,f4,i4,c41 ,f4,c4,s41 ,of the ,westminster ,hospital ,medical ,school ,,third ,,edition1 ,revised1 ,enlarged1 and ,re-issued4 ,price #fs4 net4 ,a well-written1 clear and accurate ,elementary ,manual of ,inorganic ,chemistry4444 ,we agree heartily with the system adopted by ,drs4 ,dupr and ,hake4 ,,will ,,make ,,experimental ,,work ,,trebly ,,interesting ,,because ,,intelligible4--,saturday ,review4 ,there is no question that1 given the ,,perfect ,,grounding of the ,student in his ,science1 the remainder comes afterwards to him in a manner much more simple and easily acquired4 ,the work is ,,an ,,example ,,of ,,the ,,advantages ,,of ,,the ,,systematic ,,treatment of a ,science over the fragmentary style so generally followed4 ,,by ,a ,,long ,,way ,,the ,,best of the small ,manuals for ,students4--,analyst4 99 99 99 99 99 ,,laboratory ,,handbooks ,,by ,a4 ,,humboldt ,,sexton1 ,professor of ,metallurgy in the ,glasgow and ,west of ,scotland ,technical ,college4 99 99 99 99 99 ,,outlines ,,of ,,quantitative ,,analysis4 ,,for ,,the ,,use ,,of ,,students4 ,with ,illustrations4 ,,fourth ,,edition4 ,crown #hvo1 ,cloth1 #cs4 ,a ,,compact ,,laboratory ,,guide for beginners was wanted1 and the want has been ,,well ,,supplied4444 ,a good and useful book4--,lancet4 99 99 99 99 99 ,,outlines ,,of ,,qualitative ,,analysis4 ,,for ,,the ,,use ,,of ,,students4 ,with ,illustrations4 ,,fourth ,,edition1 ,revised4 ,crown #hvo1 ,cloth1 #cs4 #f;d4 ,the work of a thoroughly practical chemist4--,british ,medical ,journal4 ,compiled with great care1 and will supply a want4--,journal of ,education4 99 99 99 99 99 ,,elementary ,,metallurgy3 ,including the ,author's ,practical ,laboratory ,course4 ,with many ,illustrations4 ,see p4 #ff4 ,,third ,,edition1 ,revised4 ,crown #hvo4 ,cloth1 #fs4 ,just the kind of work for students commencing the study of metallurgy4--,practical ,engineer4 99 99 99 99 99 ,,chemistry ,,for ,,engineers ,,and ,,manufacturers4 ,a ,,practical ,,text-,,book4 ,,by ,,bertram ,,blount1 ,f4,i4,c41 ,f4,c4,s41 ,assoc4,inst4,c4,e41 ,consulting ,chemist to the ,crown ,agents for the ,colonies4 ,,and ,a4,g4 ,,bloxam1 ,f4,i4,c41 ,f4,c4,s41 ,consulting ,chemist1 ,head of the ,chemistry ,department1 ,goldsmiths' ,inst41 ,new ,cross4 ,in ,two ,vols41 ,large #hvo4 ,with ,illustrations4 ,sold ,separately4 99 99 99 99 99 ,the authors have ,,succeeded beyond all expectations1 and have produced a work which should give ,,fresh ,,power to the ,engineer and ,manufacturer4--,the ,times4 99 99 99 99 99 ,,volume ,i4 ,price #ajs4 #f;d4 ,,chemistry ,,of ,,engineering1 ,,building1 ,,and ,,metallurgy4 ,general ,content4--,,introduction--,chemistry of the ,chief ,materials of ,construction--,sources of ,energy--,chemistry of ,steam-raising--,chemistry of ,lubrication and ,lubricants--,metallurgical ,processes used in the ,winning and ,manufacture of ,metals4 ,,practical ,,throughout 444 an ,,admirable ,,text-,,book1 useful not only to ,students1 but to ,,engineers and ,,managers ,,of ,,works in ,,preventing ,,waste and ,,improving ,,processes4--,scotsman4 ,,eminently ,,practical4--,glasgow ,herald4 ,a book worthy of ,,high ,,rank 444 its merit is great 444 treatment of the subject of ,,gaseous ,,fuel particularly good4444 ,,water ,,gas and the production clearly worked out4444 ,altogether a most creditable production4 ,,we ,,warmly ,,recommend ,,it1 and look forward with keen interest to the appearance of ,vol4 ,,ii4--,journal of ,gas ,lighting4 ,,volume ,,ii4 ,price #afs4 ,,the ,,chemistry ,,of ,,manufacturing ,,processes4 ,general ,contents4--,sulphuric ,acid ,manufacture--,manufacture of ,alkali1 c4--,destructive ,distillation--,artificial ,manure ,manufacture--,petroleum--,lime and ,cement--,clay ,industries and ,glass--,sugar and ,starch--,brewing and ,distilling--,oils1 ,resins1 and ,varnishes--,soap and ,candles--,textiles and ,bleaching--,colouring ,matters1 ,dyeing1 and ,printing--,paper and ,pasteboard--,pigments and ,paints--,leather1 ,glue1 and ,size--,explosives and ,matches--,minor ,chemical ,manufactures4 ,certainly a ,,good and ,,useful ,,book1 constituting a ,,practical ,,guide for students by affording a clear conception of the numerous processes as a whole4--,chemical ,trade ,journal4 ,we ,,confidently ,,recommend this volume as a ,,practical1 and not overloaded1 ,,text-,,book1 of ,,great ,,value to students4--,the ,builder4 99 99 99 99 99 ,,just ,,out4 ,,fifth ,,edition1 ,thoroughly ,revised1 ,greatly ,enlarged and ,re-written4 ,with additional ,tables1 ,plates1 and ,illustrations4 #bas4 ,,foods3 ,,their ,,composition ,,and ,,analysis4 ,,by ,a4 ,,wynter ,,blyth1 ,m4,r4,c4,s41 ,f4,i4,c41 ,f4,c4,s41 ,barrister-at-,law1 ,public ,analyst for the ,county of ,devon1 and ,medical ,officer of ,health for ,st4 ,marylebone4 ,,and ,m4 ,,wynter ,,blyth1 ,b4,a41 ,b4,,sc41 ,f4,c4,s4 ,,general ,,contents4--,history of ,adulteration4--,legislation4--,apparatu s4--,ash4--,sugar4--,confectionery4-- ,honey4--,treacle4--,jams and ,preserved ,fruits4--,starches4--,wheaten-,flour4-- ,bread4--,oats4--,barley4--,rye4--,rice4 --,maize4--,millet4--,potato4--,peas4-- ,lentils4--,beans4--,milk4--,cream4--,bu tter4--,oleo-,margarine4--,cheese4-- ,lard4--,tea4--,coffee4--,cocoa and ,chocolate4--,alcohol4--,brandy4--,rum4- - ,whisky4--,gin4--,arrack4--,liqueurs4--, absinthe4--,yeast4---,beer4--,wine4-- ,vinegar4--,lemon and ,lime ,juice4--,mustard4--,pepper4--,sweet and ,bitter ,almonds4--,annatto4--,olive ,oil4--,water ,analysis4--,appendix3 ,adulteration ,acts1 c4 ,simply ,,indispensable in the ,analyst's laboratory4--,the ,lancet4 ,a new edition of ,mr4 ,wynter ,blyth's ,standard work1 ,,enriched ,,with ,,all ,,the ,,recent ,,discoveries ,,and ,,improvements1 will be accepted as a boon4--,chemical ,news4 99 99 99 99 99 ,,third ,,edition4 ,in ,large #hvo1 ,cloth1 with ,tables and ,illustrations4 ,price #bas4 ,,poisons3 ,,their ,,effects ,,and ,,detection4 ,,by ,a4 ,,wynter ,,blyth1 ,m4,r4,c4,s41 ,f4,i4,c41 ,f4,c4,s41 ,barrister-at-,law1 ,public ,analyst for the ,county of ,devon1 and ,medical ,officer of ,health for ,st4 ,marylebone4 ,,general ,,contents4 ,i4--,historical ,introduction4 ,,ii4--,classification--,statistics--,co nnection between ,toxic ,action and ,chemical ,composition--,life ,tests--,general ,method of ,procedure--,the ,spectroscope--,examination of ,blood and ,blood ,stains4 ,,iii4--,poisonous ,gases4 ,,iv4--,acids and ,alkalies4 ,v4--,more or less ,volatile ,poisonous ,substances4 ,,vi4--,alkaloids and ,poisonous ,vegetable ,principles4 ,,vii4--,poisons derived from ,living or ,dead ,animal ,substances4 ,,viii4--,the ,oxalic ,acid ,group4 ,,ix4--,inorganic ,poisons4 ,appendix3 ,treatment1 by ,antidotes or otherwise1 of ,cases of ,poisoning4 ,undoubtedly ,,the ,,most ,,complete ,,work on ,toxicology in our language4--,the ,analyst 7on the ,third ,edition74 ,as a ,,practical ,,guide1 we know ,,no ,,better work4--,the ,lancet 7on the ,third ,edition74 999999 ,in the ,,third ,,edition1 ,enlarged and partly ,re-written1 ,,new ,,analytical ,,methods have been introduced1 and the ,,cadaveric ,,alkaloids1 or ,,ptomaines1 bodies playing so great a part in ,food-poisoning and in the ,manifestations of ,disease1 have received special attention4 99 99 99 99 99 ,with ,numerous ,tables1 and #bb ,illustrations4 #afs4 ,,dairy ,,chemistry ,,for ,,dairy ,,managers1 ,,chemists1 ,,and ,,analysts ,a ,practical ,handbook for ,dairy ,chemists and others having ,control of ,dairies4 ,,by ,h4 ,,droop ,,richmond1 ,f4,c4,s41 ,,chemist ,,to ,,the ,,aylesbury ,,dairy ,,company4 ,contents4--,i4 ,introductory4--,the ,constituents of ,milk4 ,,ii4 ,the ,analysis of ,milk4 ,,iii4 ,normal ,milk3 its ,adulterations and and their ,detection4 ,,iv4 ,the ,chemical ,control of the ,dairy4 ,v4 ,alterations1 ,biological and ,sanitary ,matters4 ,,vi4 ,butter4 ,,vii4 ,other ,milk ,products4 ,,viii4 ,the ,milk of ,mammals other than the ,cow4--,appendices4--,tables4--,index4 444 ,in our opinion the book is the ,,best ,,contribution ,,on ,,the ,,subject ,,that ,,has ,,yet ,,appeared in the ,english language4--,lancet4 99 99 99 99 99 ,,at ,,press1 ,fully ,illustrated4 ,,milk3 ,,its ,,production ,,uses4 ,with ,chapters on ,dairy ,farming1 ,the ,diseases of ,cattle1 and on the ,hygiene and ,control of ,supplies4 ,,by ,,edward ,f4 ,,willoughby1 ,m4,d4 7,lond471 ,d4,p4,h4 7,lond4 and ,camb471 ,inspector of ,farms and ,general ,scientific ,adviser to ,welford and ,sons1 ,ltd4 99 99 99 99 99 ,crown #hvo1 ,handsome ,cloth4 ,fully ,illustrated4 #ajs4 #f;d4 ,,flesh ,,foods3 ,with ,methods for their ,chemical1 ,microscopical1 and ,bacteriological ,examination4 ,a ,practical ,handbook for ,medical ,men1 ,analysts1 ,inspectors and others4 ,,by ,c4 ,,ainsworth ,,mitchell1 ,b4,a47,,oxon71 ,fellow of the ,institute of ,chemistry2 ,member of ,council1 ,society of ,public ,analysts4 ,with ,numerous ,tables1 ,illustrations1 and a ,coloured ,plate4 ,,contents4--,structure and ,chemical ,composition of ,muscular ,fibre4--of ,connective ,tissue1 and ,blood4--,the ,flesh of ,different ,animals4--,the ,examination of ,flesh4--,methods of ,examining ,animal ,fat4--,the ,preservation of ,flesh4--,composition and ,analysis of ,sausages4--,proteids of ,flesh4--,meat ,extracts and ,flesh ,peptones4--,the ,cooking of ,flesh4--,poisonous ,flesh4--,the ,animal ,parasites of ,flesh4--,the ,bacteriological ,examination of ,flesh4--,the ,extraction and ,separation of ,ptomaines4--,,index4 999999 ,this work is a complete compendium of the ,,chemistry ,,of ,,animal ,,tissues4 ,it contains directions for the detection of morbid conditions1 putrefactive changes1 and poisonous or injurious constituents1 together with an account of their causes and effects4--,publishers' ,note4 ,a compilation which will be most useful for the class for whom it is intended4--,athenum4 ,a book which ,,no ,,one whose duties involve considerations of food supply ,,can ,,afford ,,to ,,be ,,without4--,municipal ,journal4 99 99 99 99 99 ,in ,large #hvo4 ,handsome ,cloth4 ,with numerous ,illustrations4 ,each ,volume ,complete in ,itself1 and ,sold ,separately4 ,,technical ,,mycology3 ,,the ,,utilisation ,,of ,,micro-,,organisms ,,in ,,the ,,arts ,,and ,,manufactures4 ,a ,practical ,handbook on ,fermentation and ,fermentative ,processes for the ,use of ,brewers and ,distillers1 ,analysts1 ,technical and ,agricultural ,chemists1 and all interested in the ,industries dependent on ,fermentation4 ,,by ,,dr4 ,,franz ,,lafar1 ,professor of ,fermentation-,physiology and ,bacteriology in the ,technical ,high ,school1 ,vienna4 ,with an ,introduction by ,,dr4 ,,emil ,,chr4 ,,hansen1 ,principal of the ,carlsberg ,laboratory1 ,copenhagen4 ,,translated ,,by ,,charles ,t4,c4 ,,salter4 ,vol4 ,i4--,,schizomycetic ,,fermentation4 #aes4 ,including the ,theory of ,fermentation1 the ,principles of ,sterilization1 and ,pure ,culture ,processes4 ,vol4 ,,ii41 ,part ,i4 ,,eumycetic ,,fermentation4 #gs4 #f;d4 ,the ,morphology1 ,chemistry1 ,physiology1 and ,fermentative ,processes of the ,eumycetes1 ,zygomycetes1 and ,saccharomycetes4 ,the first work of the kind which can lay claim to completeness in the treatment of a fascinating subject4 ,the plan is admirable1 the classification simple1 the style is good1 and the tendency of the whole volume is to convey sure information to the reader4--,lancet4 999999 ,the publishers trust that before long they will be able to present ,english readers with the whole of the second volume1 arrangements having been concluded whereby1 upon its appearance in ,germany1 the ,english translation will be at once put in hand4 ,this is now being done with ,part ,i41 which will be issued shortly1 and which will be followed by the two final parts4 99 99 99 99 99 ,in ,crown #hvo1 ,handsome ,cloth4 ,price #gs4 #f;d4 net4 ,,ferments ,,and ,,their ,,actions4 ,a ,text-book on the ,chemistry and ,physics of ,fermentative ,changes4 ,,by ,,carl ,,oppenheimer1 ,,ph4,d41 ,m4,d41 ,of the ,physiological ,institute at ,eilangen4 ,,translated ,,from ,,the ,,german ,,by ,c4 ,,ainsworth ,,mitchell1 ,b4,a41 ,f4,i4,c41 ,f4,c4,s4 ,,abridged ,,contents4--,introduction4--,definition 4--,chemical ,nature of ,ferments4--,influence of ,external ,factors4--,mode of ,action4--,physiological ,action4--,secretion4--,importance of ,ferments to ,vital ,action4--,proteolytic ,ferments4--,trypsin4--,bacteriolytic and ,hmolytic ,ferments4--,vegetable ,ferments4--,coagulating ,ferments4--,saccharifying ,ferments4--,diastases4--,polysaccharide s4--,enzymes4--,ferments which decompose ,glucosides4--,hydrolytic ,ferments4--,lactic ,acid ,fermentation4--,alcoholic ,fermentation4--,biology of ,alcoholic ,fermentation4--,oxydases4--,oxidising ,fermentation4--,bibliography4--,,index4 ,the present ,translation embodies ,notes and ,additions to the ,work made by the ,author subsequent to its ,publication in ,germany4 ,such a veritable multum in parvo has never yet appeared4 ,the author has set himself the task of writing a work on ,ferments that should embrace human erudition on the subject--,brewers' ,journal4 99 99 99 99 99 ,,second ,,edition1 ,revised4 ,in ,large #hvo4 ,handsome ,cloth4 ,with ,plate and ,illustrations4 ,price #bas4 ,,the ,,principles ,,and ,,practice ,,of ,,brewing4 ,,for ,,the ,,use ,,of ,,students ,,and ,,practical ,,men4 ,,by ,,walter ,j4 ,,sykes1 ,m4,d41 ,d4,p4,h41 ,f4,i4,c41 ,,editor ,,of ,,the ,,analyst4 ,,abstract ,,of ,,contents4 ,i4 ,physical ,principles involved in ,brewing ,operations4 ,chemistry with special reference to the materials used in ,brewing4 ,,ii4 ,the ,microscope4 ,vegetable ,biology4 ,fermentation4 ,,iii4 ,water4 ,barley and ,malting4 ,brewery ,plant4 ,brewing4 ,beer and its ,diseases4 ,appendices4 ,index4 ,a volume of ,brewing ,science1 which has long been awaited4444 ,we consider it one of ,,the ,,most ,,complete in ,,contents and ,,novel ,,in ,,arrangement that has yet been published4444 ,will command a large sale4--,the ,brewers' ,journal4 ,the appearance of a work such as this serves to remind us of the ,,enormously ,,rapid ,,advances made in our knowledge of the ,scientific ,principles underlying the ,brewing ,processes4444 ,dr4 ,sykes' work will undoubtedly be of the ,,greatest ,,assistance1 not merely to ,brewers1 but to all ,chemists and ,biologists interested in the problems which the ,fermentation ,industries present4--,the ,analyst4 ,the publication of ,,dr4 ,,sykes' ,,masterly ,,treatise on the art of ,brewing is quite an event in the ,brewing ,world4444 ,deserves our warmest praise4444 ,a better guide than ,dr4 ,sykes could hardly be found4--,county ,brewers' ,gazette4 99 99 99 99 99 ,in ,large #hvo4 ,handsome ,cloth4 ,,agricultural ,,chemistry ,,and ,,analysis3 ,a ,,practical ,,handbook ,,for ,,the ,,use ,,of ,,agricultural ,,students4 ,,by ,j4,m4,h4 ,,munro1 ,d4,sc41 ,f4,i4,c41 ,f4,c4,s41 ,professor of ,chemistry1 ,downton ,college of ,agriculture4 ,in ,preparation4 99 99 99 99 99 ,,second ,,edition1 ,,revised ,,and ,,enlarged4 ,with ,tables1 ,illustrations in the ,text1 and #cg ,lithographic ,plates4 ,medium #hvo4 ,handsome ,cloth4 #cjs4 ,,sewage ,,disposal ,,works3 ,a ,guide to the ,construction of ,works for the ,prevention of the ,pollution by ,sewage of ,rivers and ,estuaries4 ,,by ,w4 ,,santo ,,crimp1 ,m4,,inst4,c4,e41 ,f4,g4,s41 ,late ,assistant-,engineer1 ,london ,county ,council4 ,,part ,i4--,,introductory4 ,,part ,,ii4--,,sewage ,,disposal ,,works ,,in ,,operation--,,their ,,construction1 ,,maintenance1 ,,and ,,cost4 999999 ,from the fact of the ,author's having1 for some years1 had charge of the ,main ,drainage ,works of the ,northern ,section of the ,metropolis1 the chapter on ,,london will be found to contain many important details which would not otherwise have been available4 ,all persons interested in ,sanitary ,science owe a debt of gratitude to ,mr4 ,crimp4444 ,his work will be especially useful to ,,sanitary ,,authorities and their advisers 444 ,,eminently ,,practical ,,and ,,useful4--,lancet4 ,probably the ,,most ,,complete ,,and ,,best ,,treatise on the subject which has appeared in our language4444 ,will prove of the greatest use to all who have the problem of ,sewage ,disposal to face4--,edinburgh ,medical ,journal4 99 99 99 99 99 ,beautifully ,illustrated1 with ,numerous ,plates1 ,diagrams1 and ,figures in the ,text4 #bas4 net4 ,,trades' ,,waste3 ,,its ,,treatment ,,and ,,utilisation4 ,a ,handbook for ,borough ,engineers1 ,surveyors1 ,architects1 and ,analysts4 ,,by ,w4 ,,naylor1 ,f4,c4,s41 ,a4,m4,,inst4,c4,e41 ,chief ,inspector of ,rivers1 ,ribble ,joint ,committee4 ,,contents4--,i4 ,introduction4--,,ii4 ,chemical ,engineering4--,,iii4--,wool ,de-greasing and ,grease ,recovery4--,,iv4 ,textile ,industries2 ,calico ,bleaching and ,dyeing4--,v4 ,dyeing and ,calico-,printing1--,,vi4 ,tanning and ,fellmongery4--,,vii4 ,brewery and ,distillery ,waste4--,,viii4 ,paper ,mill ,refuse4--,,ix4 ,general ,trades' ,waste4--,,index4 ,there is probably no person in ,england to-day better fitted to deal rationally with such a subject4--,british ,sanitarian4 ,the work is thoroughly practical1 and will serve as a handbook in the future for those who have to encounter the problems discussed4--,chemical ,trade ,journal4 99 99 99 99 99 ,in ,crown #hvo1 ,extra4 ,with ,illustrations4 #hs4 #f;d4 ,,calcareous ,,cements3 ,,their ,,nature1 ,,preparation1 ,,and ,,uses4 ,with some ,remarks upon ,cement ,testing4 ,,by ,,gilbert ,r4 ,,redgrave1 ,,assoc4 ,,inst4 ,c4,e41 ,assistant ,secretary for ,technology1 ,board of ,education1 ,south ,kensington4 ,,invaluable to the ,student1 ,architect1 and ,engineer4--,building ,news4 ,will be useful to all interested in the ,,manufacture1 ,,use1 and ,,testing of ,cements4--,engineer4 99 99 99 99 99 ,just ,out4 ,with ,four ,folding ,plates and ,numerous ,illustrations4 ,large #hvo4 ,,water ,,supply3 ,a ,practical ,treatise on the ,selection of ,sources and the ,distribution of ,water4 ,,by ,,reginald ,e4 ,,middleton1 ,m4,,inst4,c4,e41 ,m4,,inst4,,mech4,e41 ,f4,s4,i4 ,,abridged ,,contents4--,introductory4--,requiremen ts as to ,quality4--,requirements as to ,quantity4--,storage ,reservoirs4--,purification4--,service ,reservoirs4--,the ,flow of ,water through ,pipes4--,distributing ,systems4--,pumping ,machines4--,special ,requirements4 99 99 99 99 99 ,,third ,,edition1 ,revised4 ,fully ,illustrated4 ,at ,press4 ,,the ,,chemistry ,,of ,,gas ,,manufacture3 ,a ,hand-,book on the ,production1 ,purification1 and ,testing of ,illuminating ,gas1 and the ,assay of the ,bye-,products of ,gas ,manufacture4 ,,by ,w4,j4 ,,atkinson ,,butterfield1 ,m4,a41 ,f4,i4,c41 ,f4,c4,s41 ,formerly ,head ,chemist1 ,gas ,works1 ,beckton1 ,london1 ,e4 ,,general ,,contents4--,i4 ,raw ,materials for ,gas ,manufacture4--,,ii4 ,coal ,gas4--,,iii4 ,carburetted ,water ,gas4--,,iv4 ,oil ,gas4--,v4 ,enriching by ,light ,oils4--,,vi4 ,final ,details of ,manufacture4--,,vii4 ,gas ,analysis4--,,viii4 ,photometry4--,,ix4 ,applications of ,gas4--,x4 ,bye-,products4--,,xi4 ,acetylene4--,,index4 ,the ,,best ,,work of its kind which we have ever had the pleasure of reviewing4--,journal of ,gas ,lighting4 99 99 99 99 99 ,,just ,,out4 ,with ,diagrams and ,illustrations4 #es4 net4 ,,acetylene3 ,,the ,,principles ,,of ,,its ,,generation ,,and ,,use4 ,,by ,f4,h4 ,,leeds1 ,f4,i4,c41 ,f4,c4,s41 ,member of the ,society of ,public ,analysts and of the ,acetylene ,association2 ,,and ,w4,j4 ,,atkinson ,,butterfield1 ,m4,a41 ,f4,i4,c41 ,f4,c4,s41 ,consulting ,chemist1 ,author of ,the ,chemistry of ,gas ,manufacture4 ,,general ,,contents4--,introductory4--,advantages of ,acetylene and other ,illuminants4--,chemistry and ,physics4--,general ,principles of ,acetylene ,generation4--,choice of a ,generator4--,statutory ,regulations4--,treatment of ,acetylene after ,generation4--,general ,properties4--,mains and ,service ,pipes4--,subsidiary ,apparatus4--,burners4--,incandescent ,burners4--,heating ,apparatus and ,motors4--,carburetted1 ,compressed1 and ,dissolved ,acetylene4--,mixtures with other ,gases4--,sundry ,uses4--,acetylene ,lamps4--,valuation and ,analysis of ,carbide4 99 99 99 99 99 ,,ready ,,immediately4 ,large #hvo4 ,handsome ,cloth4 ,price #afs4 net4 ,,fire ,,and ,,explosion ,,risks4 ,a ,handbook of the ,detection1 ,investigation1 and ,prevention of ,fires and ,explosion4 ,,by ,,dr4 ,,von ,,schwartz4 ,translated from the ,revised ,german ,edition ,,by ,c4,t4,c4 ,,salter4 ,,abridged ,,general ,,contents4--,fires and ,explosions of a ,general ,character4--,dangers arising from ,sources of ,light and ,heat4--,dangerous ,gases4--,risks ,attending ,special ,industries4--,materials ,employed4--,agricultural ,products4--,fats1 ,oils1 and ,resins4--,mineral ,oils and ,tar4--,alcohol1 c4--,metals1 ,oxides1 ,acids1 c4--,lightning1 ,ignition ,appliances1 ,fireworks4 99 99 99 99 99 ,,tenth ,,edition1 ,revised4 ,price #fs4 ,,practical ,,sanitation3 ,a ,,hand-,,book ,,for ,,sanitary ,,inspectors ,,and ,,others ,,interested ,,in ,,sanitation4 ,,by ,,george ,,reid1 ,m4,d41 ,d4,p4,h41 ,fellow1 ,mem4 ,council1 and ,examiner1 ,sanitary ,institute of ,great ,britain1 and ,medical ,officer to the ,staffordshire ,county ,council4 ,with an ,appendix on ,sanitary ,law4 ,,by ,,herbert ,,manley1 ,m4,a41 ,m4,b41 ,d4,p4,h41 ,medical ,officer of ,health for the ,county ,borough of ,west ,bromwich4 ,,general ,,contents4--,introduction--,water ,supply3 ,drinking ,water1 ,pollution of ,water--,ventilation and ,warming--,principles of ,sewage ,removal--,details of ,drainage2 ,refuse ,removal and ,disposal--,sanitary and ,insanitary ,work and ,appliances--,details of ,plumbers' ,work--,house ,construction--,infection and ,disinfection--,food1 ,inspection of2 ,characteristics of ,good ,meat2 ,meat1 ,milk1 ,fish1 c41 unfit for ,human ,food--,appendix3 ,sanitary ,law2 ,model ,bye-,laws1 c4 ,dr4 ,reid's very useful ,manual 444 ,,abounds ,,in ,,practical ,,detail4--,british ,medical ,journal4 ,a ,,very ,,useful ,,handbook1 with a very useful ,appendix4 ,we recommend it not only to ,,sanitary ,,inspectors1 but to ,,householders and ,,all interested in ,sanitary matters4--,sanitary ,record4 99 99 99 99 99 ,,companion ,,volume ,,to ,,reid',s ,,sanitation4 ,in ,crown #hvo4 ,handsome ,cloth4 ,profusely ,illustrated4 #hs4 #f;d4 net4 ,sanitary ,engineering3 ,a ,practical ,manual of ,town ,drainage and ,sewage and ,refuse ,disposal4 ,for ,sanitary ,authorities1 ,engineers1 ,inspectors1 ,architects1 ,contractors1 and ,students4 ,,by ,,francis ,,wood1 ,a4,m4,,inst4,c4,e41 ,f4,g4,s41 ,borough ,engineer and ,surveyor1 ,fulham2 late ,borough ,engineer1 ,bacup1 ,lancs4 ,,general ,,contents4 ,introduction4--,hydraulics4--,velocity of ,water in ,pipes4--,earth ,pressures and ,retaining ,walls4--,powers4--,house ,drainage4--,land ,drainage4--,sewers4--,separate ,system4--,sewage ,pumping4--,sewer ,ventilation4--,drainage ,areas4--,sewers1 ,manholes1 c4--,trade ,refuse4--,sewage ,disposal ,works4--,,bacteriolysis4--,sludge ,disposal4--,construction and ,cleansing of ,sewers4--,refuse ,disposal4--,chimneys and ,foundations4 ,the volume bristles with information which will be greedily read by those in need of assistance4 ,the book is one that ought to be on the bookshelves of ,,every ,,practical ,,engineer4--,sanitary ,journal4 ,a ,,veritable ,,pocket ,,compendium of ,sanitary ,engineering4444 ,a work which may1 in many respects1 be considered as ,,complete 444 ,,commendably ,,cautious 444 ,,interesting 444 ,,suggestive4--,public ,health ,engineer4 99 99 99 99 99 ,,vol4 ,i4 ,,now ,,ready4 ,,in ,,half ,,morocco1 #bd,s4 ,in ,two ,volumes1 each complete in itself4 ,,physico-,,chemical ,,tables ,,for ,,the ,,use ,,of ,,analysts1 ,,physicists1 ,,chemical ,,manufacturers1 ,,and ,,scientific ,,chemists4 ,volume ,i4--,chemical ,engineering1 ,physical ,chemistry4 ,just ,out4 ,volume ,,ii4--,chemical ,physics1 ,pure and ,analytical ,chemistry4 ,,by ,,john ,,castell-,,evans1 ,f4,i4,c41 ,f4,c4,s41 ,superintendent of the ,chemical ,laboratories1 and ,lecturer on ,inorganic ,chemistry and ,metallurgy at the ,finsbury ,technical ,college4 ,the ,tables may almost claim to be exhaustive1 and embody and collate all the most recent data established by experimentalists at home and abroad4 ,the volumes will be found invaluable to all engaged in research and experimental investigation in ,chemistry and ,physics4 ,the ,work comprehends as far as possible ,,all ,,rulles ,,and ,,tables required by the ,analyst1 ,brewer1 ,distiller1 ,acid- and ,alkali-,manufacturer1 c41 c42 and also the principal data in ,,thermo-,,chemistry1 ,,electro-,,chemistry1 and the various branches of ,,chemical ,,physics4 ,every possible care has been taken to ensure perfect accuracy1 and to include the results of the most recent investigations4 99 99 99 99 99 ,in ,large #hvo4 ,handsome ,cloth4 ,beautifully ,illustrated4 ,with ,plates and ,figures in the ,text4 #bas4 ,road ,making and ,maintenance3 ,a ,,practical ,,treatise ,,for ,,engineers1 ,,surveyors1 ,,and ,,others4 ,,with ,,an ,,historical ,,sketch ,,of ,,ancient ,,and ,,modern ,,practice4 ,,by ,,thos4 ,,aitken1 ,,assoc4,m4,,inst4,c4,e41 ,member of the ,association of ,municipal and ,county ,engineers2 ,member of the ,sanitary ,inst42 ,surveyor to the ,county ,council of ,fife1 ,cupar ,division4 ,,with ,,numerous ,,plates1 ,,diagrams1 ,,and ,,illustrations4 ,,contents4--,historical ,sketch4--,resistance of ,traction4--,laying out ,new ,roads4--,earthworks1 ,drainage1 and ,retaining ,walls4--,road ,materials1 or ,metal4--,quarrying4--,stone ,breaking and ,haulage4--,road-,rolling and ,scarifying4--,the ,construction of ,new1 and the ,maintenance of existing ,roads4--,carriage ,ways and ,foot ,ways4 ,the ,literary style is ,,excellent 444 ,a ,,comprehensive and ,,excellent ,modern ,book1 an ,,up-,,to-,,date work 444 ,should be on the reference shelf of every ,municipal and ,county ,engineer or ,surveyor in the ,united ,kingdom1 and of every ,colonial ,engineer4--,the ,surveyor4 99 99 99 99 99 ,,third ,,edition1 ,revised and ,enlarged4 ,with ,illustrations1 #abs4 #f;d4 ,painters' ,colours1 ,oils1 ,varnishes3 ,a ,,practical ,,manual4 ,,by ,,george ,h4 ,,hurst1 ,f4,c4,s41 ,member of the ,society of ,chemical ,industry2 ,lecturer on the ,technology of ,painters' ,colours1 ,oils1 and ,varnishes1 the ,municipal ,technical ,school1 ,manchester4 ,,general ,,contents4--,introductory--,,the ,,composition1 ,,manufacture1 ,,assay1 and ,,analysis of ,,pigments1 ,white1 ,red1 ,yellow and ,orange1 ,green1 ,blue1 ,brown1 and ,black--,,lakes--,colour and ,paint ,machinery--,paint ,vehicles 7,oils1 ,turpentine1 c41 c47--,driers--,,varnishes4 ,a ,,thoroughly ,,practical book1 444 the ,,only ,english work that satisfactorily treats of the manufacture of oils1 colours1 and pigments4--,chemical ,trades' ,journal4 999999 ,,for ,,mr4 ,,hurst',s ,,garment ,,dyeing ,,and ,,cleaning1 see p4 #hd4 99 99 99 99 99 ,in ,crown #hvo4 ,handsome ,cloth4 ,with ,illustrations4 #es4 ,,the ,,painter',s ,,laboratory ,,guide4 ,a ,student's ,handbook of ,paints1 ,colours1 and ,varnishes4 ,,by ,,george ,h4 ,,hurst1 ,f4,c4,s41 ,m4,s4,c4,i4 ,,abstract ,,of ,,contents4--,preparation of ,pigment ,colours4--,chemical ,principles ,involved4--,oils and ,varnishes4--,properties of ,oils and ,varnishes4--,tests and ,experiments4--,plants1 ,methods1 and ,machinery of the ,paint and ,varnish ,manufactures4 ,this ,work has been designed by the ,author for the ,laboratory of the ,technical ,school1 and of the ,paint and ,colour ,works1 and for all interested or engaged in these industries4 99 99 99 99 99 ,,second ,,edition1 ,revised4 ,in ,crown #hvo4 extra4 ,with ,numerous ,illustrations and ,plates 7some in ,colours71 including ,original ,designs4 #abs4 #f;d4 ,painting and ,decorating3 ,a ,complete ,practical ,manual for ,house ,painters and ,decorators4 ,,by ,,walter ,,john ,,pearce1 ,,lecturer ,,at ,,the ,,manchester ,,technical ,,school ,,for ,,house-,,painting ,,and ,,decorating4 ,,general ,,contents4 ,introduction--,workshop and ,stores--,plant and ,appliances--,brushes and ,tools--,materials3 ,pigments1 ,driers1 ,painters' ,oils--,wall ,hangings--,paper ,hanging--,colour ,mixing--,distempering--,plain ,painting--,staining--,varnish and ,varnishing--,imitative ,painting--,graining--,marbling--,gildin g--,sign-,writing and ,lettering--,decoration3 ,general ,principles--,decoration in ,distemper--,painted ,decoration--,relievo ,decoration--,colour--,measuring and ,estimating--,coach-,painting--,ship-,pa inting4 ,a ,,thoroughly ,,useful ,,book 444 ,,good1 ,,sound1 ,,practical ,,information in a ,,clear and ,,concise ,,form4--,plumber and ,decorator4 ,a ,,thoroughly ,,good ,,and ,,reliable ,,text-,,book4444 ,so ,,full and ,,complete that it would be difficult to imagine how anything further could be added about the ,painter's craft4--,builders' ,journal4 99 99 99 99 99 ,in ,large #hvo4 ,handsome ,cloth4 ,with #d ,plates and ,several ,illustrations4 #afs4 net4 ,,the ,,chemistry ,,of ,,india ,,rubber4 ,a ,treatise on the ,nature of ,india ,rubber1 its ,chemical and ,physical ,examination1 and the ,determination and ,valuation of ,india ,rubber ,substitutes4 ,including the ,outlines of a ,theory on ,vulcanisation4 ,,by ,,carl ,,otto ,,weber1 ,,ph4,d4 ,,abstract ,,of ,,contents4--,introduction4--,the ,chemistry of ,india ,rubber4--,the ,examination and ,valuation of ,india ,rubber4--,examination of ,india ,rubber ,substitutes4--,inorganic ,filling ,materials4--,vulcanisers and ,sulphur ,carriers4--,india ,rubber ,solvents4--,colouring ,matters and ,pigment ,colours4--,constructive ,components of ,india ,rubber ,articles4--,analysis of ,manufactured ,india ,rubber4--,sanitary ,conditions in ,india ,rubber ,works4--,,index4 ,replete with scientific and also with technical interest4444 ,the sub-section on the physical properties is a complete rsum of every thing known to-day on the subject4--,india-rubber ,journal4 99 99 99 99 99 ,,new ,,edition4 ,in ,large #hvo4 ,handsome ,cloth4 ,with #add ,illustrations4 ,,oils1 ,,fats1 ,,butters ,,waxes3 ,,their ,,preparation ,,and ,,properties1 ,,and ,,manufacture ,,therefrom ,,of ,,candles1 ,,soaps1 ,,and ,,other ,,products4 ,,by ,c4,r4 ,,alder ,,wright1 ,d4,sc41 ,f4,r4,s41 ,late ,lecturer on ,chemistry1 ,st4 ,mary's ,hospital ,medical ,school2 ,examiner in ,soap to the ,city and ,guilds of ,london ,institute4 ,thoroughly ,revised1 ,enlarged1 and in ,part ,rewritten ,,by ,c4 ,,ainsworth ,,mitchell1 ,b4,a41 ,f4,i4,c4 ,dr4 ,,wright',s work will be found ,,absolutely ,,indispensable by every ,chemist4 ,,teems with information valuable alike to the ,analyst and the ,technical ,chemist4--,the ,analyst4 ,will rank as the ,,standard ,,english ,,authority on ,,oils and ,,fats for many years to come4--,industries and ,iron4 99 99 99 99 99 ,,the ,,textile ,,industries4 99 99 99 99 99 ,in ,two ,large ,volumes1 #ibj pp41 with a ,supplementary ,volume1 containing ,specimens of ,dyed ,fabrics4 #des4 ,a ,,manual ,,of ,,dyeing3 ,,for ,,the ,,use ,,of ,,practical ,,dyers1 ,,manufacturers1 ,,students1 ,,and ,,all ,,interested ,,in ,,the ,,art ,,of ,,dyeing4 ,,by ,e4 ,,knecht1 ,ph4,d41 ,f4,i4,c41 ,head of the ,chemistry and ,dyeing ,department of the ,technical ,college1 ,manchester2 ,editor of ,the ,journal of the ,society of ,dyers and ,colourists2 ,,chr4 ,,rawson1 ,f4,i4,c41 ,f4,c4,s41 ,late ,head of the ,chemistry and ,dyeing ,department of the ,technical ,college1 ,bradford2 ,member of ,council of the ,society of ,dyers and ,colourists2 ,and ,,richard ,,loewenthal1 ,ph4,d4 99 99 99 99 99 ,,general ,,contents4--,chemical ,technology of the ,textile ,fabrics--,water--,washing and ,bleaching--,acids1 ,alkalies1 ,mordants--,natural ,colouring ,matters--,artificial ,organic ,colouring ,matters--,mineral ,colours--,machinery used in ,dyeing--,tinctorial ,properties of ,colouring ,matters--,analysis and ,valuation of ,materials used in ,dyeing1 c41 c4 ,the ,,most ,,valuable and ,,useful ,,work on ,dyeing that has yet appeared in the ,english language 444 likely to be the ,,standard ,,work ,,of ,,reference for years to come4--,textile ,mercury4 ,this authoritative and exhaustive work 444 the ,,most ,,complete we have yet seen on the subject4--,textile ,manufacturer4 ,the ,,most ,,exhaustive ,,and ,,complete ,,work on the subject extant4--,textile ,recorder4 99 99 99 99 99 ,companion ,volume to ,knecht ,rawson's ,dyeing4 ,in ,large #hvo4 ,handsome ,cloth1 ,library ,style4 #afs4 net4 ,a ,,dictionary ,,of ,,dyes1 ,,mordants1 ,,other ,,compounds ,,used ,,in ,,dyeing ,,and ,,calico ,,printing4 ,with ,formul1 ,properties1 and ,applications of the various substances described1 and concise directions for their ,commercial ,valuation4 and for the ,detection of ,adulterants4 ,,by ,,christopher ,,rawson1 ,f4,i4,c41 ,f4,c4,s41 ,consulting ,chemist to the ,behar ,indigo ,planters' ,association3 ,co-,author of ,a ,manual of ,dyeing2 ,,walter ,m4 ,,gardner1 ,f4,c4,s41 ,head of the ,department of ,chemistry and ,dyeing1 ,bradford ,municipal ,technical ,college2 ,editor of the ,journ4 ,soc4 ,dyers and ,colourists2 ,,and ,w4,f4 ,,laycock1 ,,ph4,d41 ,f4,c4,s41 ,analytical and ,consulting ,chemist4 ,turn to the book as one may on any subject1 or any substance in connection with the trade1 and a reference is sure to be found4 ,the authors have apparently left nothing out4 ,considering the immense amount of information1 the book is a cheap one1 and we trust it will be widely appreciated1--,textile ,mercury4 99 99 99 99 99 ,in ,large #hvo1 ,handsome ,cloth1 with ,numerous ,illustrations4 #is4 net4 ,,textile ,,fibres ,,of ,,commerce4 ,a ,,handbook ,,of ,the ,occurrence1 ,distribution1 ,preparation1 and ,industrial ,uses of the ,animal1 ,vegetable1 and ,mineral ,products used in ,spinning and ,weaving4 ,,by ,,william ,i4 ,,hannan1 ,lecturer on ,botany at the ,ashton ,municipal ,technical ,school1 ,lecturer on ,cotton ,spinning at the ,chorley ,science and ,art ,school1 c4 ,with ,numerous ,photo ,engravings from ,nature4 999999 ,the subjects discussed in this volume are1 in order to facilitate reference1 arranged in alphabetical order under their respective heads4 ,the work may thus be regarded as a ,dictionary of ,textile ,fibres4 ,a feature of the work is the wealth of botanical description which accompanies the ,section dealing with ,vegetable ,fibres4--,publishers' ,note4 ,,useful ,,information4444 ,,admirable ,,illustrations4444 ,the information is not easily attainable1 and in its present convenient form will be valuable4--,textile ,recorder4 99 99 99 99 99 ,,textile ,,printing3 ,a ,,practical ,,manual4 ,including the ,processes ,used in the ,printing of ,,cotton1 ,,woollen1 ,,silk1 and ,,half-,,silk ,,fabrics4 ,by ,c4,f4 ,,seymour ,,rothwell1 ,f4,c4,s41 ,mem4 ,soc4 of ,chemical ,industries2 late ,lecturer at the ,municipal ,technical ,school1 ,manchester4 ,in ,large #hvo1 with ,illustrations and ,printed ,patterns4 ,price #bas4 ,,general ,,contents4--,introduction4--,the ,machinery ,used in ,textile ,printing4--,thickeners and ,mordants4--,the ,printing of ,cotton ,goods4--,the ,steam ,style4--,colours ,produced ,directly on the ,fibre4--,dyed ,styles4--,padding ,style4--,resist and ,discharge ,styles4--,the ,printing of ,compound ,colourings1 c4--,the ,printing of ,woollen ,goods4--,the ,printing of ,silk ,goods4--,practical ,recipes for ,printing4--,appendix4--,useful ,tables4--,patterns4 ,,by ,,far ,,the ,,best and ,,most ,,practical ,,book on ,,textile ,,printing which has yet been brought out1 and will long remain the standard work on the subject4 ,it is essentially practical in character4--,textile ,mercury4 ,,the ,,most ,,practical ,,manual of ,,textile ,,printing which has yet appeared4 ,we have no hesitation in recommending it4--,the ,textile ,manufacturer4 99 99 99 99 99 ,large #hvo4 ,handsome ,cloth4 #abs4 #f;d4 ,,bleaching ,,calico-,,printing4 ,a ,short ,manual for ,students and ,practical ,men4 ,,by ,,george ,,duerr1 ,director of the ,bleaching1 ,dyeing1 and ,printing ,department at the ,accrington and ,bacup ,technical ,schools2 ,chemist and ,colourist at the ,irwell ,print ,works4 ,,assisted ,,by ,,william ,,turnbull 7of ,turnbull ,stockdale1 ,limited74 ,with ,illustrations and upwards of ,one ,hundred ,dyed and ,printed ,patterns designed specially to show various ,stages of the ,processes described4 ,,general ,,contents4--,,cotton1 ,composition of2 ,,bleaching1 ,new ,processes2 ,,printing1 ,hand-,block2 ,flat-,press ,work2 ,machine ,printing--,,mordants--,,styles ,,of ,,calico-,,printing3 ,the ,dyed or ,madder ,style1 ,resist ,padded ,style1 ,discharge and ,extract ,style1 ,chromed or ,raised ,colours1 ,insoluble ,colours1 c4--,thickeners--,natural ,organic ,colouring ,matters--,tannin ,matters--,oils1 ,soaps1 ,solvents--,organic ,acids--,salts--,mineral ,colours--,coal ,tar ,colours--,dyeing--,water1 ,softening of--,theory of ,colours--,weights and ,measures1 c4 ,when a ,,ready ,,way out of a difficulty is wanted1 it is ,,in ,,books ,,like ,,this that it is found4--,textile ,recorder4 ,mr4 ,,duerr',s ,,work will be found ,,most ,,useful4444 ,the information given is of ,,great ,,value4444 ,the ,recipes are ,,thoroughly ,,practical4--,textile ,manufacturer4 99 99 99 99 99 ,,second ,,edition4 ,revised and ,enlarged4 ,with ,numerous ,illustrations4 #ds4 #f;d4 ,,garment ,,dyeing ,,and ,,cleaning4 ,a ,practical ,book for ,practical ,men4 ,,by ,,george ,h4 ,,hurst1 ,f4,c4,s41 ,member of the ,society of ,chemical ,industry4 ,,general ,,contents4--,technology of the ,textile ,fibres--,garment ,cleaning--,dyeing of ,textile ,fabrics--,bleaching--,finishing of ,dyed and ,cleaned ,fabrics--,scouring and ,dyeing of ,skin ,rugs and ,mats--,cleaning and ,dyeing of ,feathers--,glove ,cleaning and ,dyeing--,straw ,bleaching and ,dyeing--,glossary of ,drugs and ,chemicals--,useful ,tables4 ,an ,,up-,,to-,,date hand book has long been wanted1 and ,mr4 ,hurst has done nothing more complete than this4 ,an important work1 the more so that several of the branches of the craft here treated upon are almost entirely without ,english ,manuals for the guidance of workers4 ,the price brings it within the reach of all4--,dyer and ,calico-,printer4 ,mr4 ,hurst's work ,,decidedly ,,fills ,a ,,want 444 ought to be in the hands of every ,,garment ,,dyer and cleaner in the ,kingdom--,textile ,mercury4 99 99 99 99 99 ,boys ,,could ,,not ,,have ,a ,,more ,,alluring ,,introduction to scientific pursuits than these charming-looking volumes4--,letter to the ,publishers from the ,headmaster of one of our great ,public ,schools4 ,handsome ,cloth1 #gs4 #f;d4 ,gilt1 for ,presentation1 #hs4 #f;d4 ,,open-,,air ,,studies ,,in ,,botany3 ,,sketches ,,of ,,british ,,wild ,,flowers ,,in ,,their ,,homes4 ,,by ,r4 ,,lloyd ,,praeger1 ,b4,a41 ,m4,r4,i4,a4 ,illustrated by ,drawings from ,nature by ,s4 ,rosamond ,praeger1 and ,photographs by ,r4 ,welch4 ,,general ,,contents4--,a ,daisy-,starred ,pasture--,under the ,hawthorns--,by the ,river--,along the ,shingle--,a ,fragrant ,hedgerow--,a ,connemara ,bog--,where the ,samphire grows--,a ,flowery ,meadow--,among the ,corn 7a ,study in ,weeds7--,in the ,home of the ,alpines--,a ,city ,rubbish-,heap--,glossary4 ,a ,,fresh ,,and ,,stimulating book 444 should take a high place4444 ,the ,illustrations are drawn with much skill4--,the ,times4 ,,beautifully ,,illustrated4444 ,one of the ,,most ,,accurate as well as ,,interesting books of the kind we have seen4--,athenum4 ,redolent with the scent of woodland and meadow4--,the ,standard4 99 99 99 99 99 ,with #ab ,full-,page ,illustrations from ,photographs4 ,cloth4 ,second ,edition1 ,revised4 #hs4 #f;d4 ,,open-,,air ,,studies ,,in ,,geology3 ,an ,introduction to ,geology ,out-of-doors4 ,,by ,,grenville ,a4,j4 ,,cole1 ,f4,g4,s41 ,m4,r4,i4,a41 ,professor of ,geology in the ,royal ,college of ,science for ,ireland1 and ,examiner in the ,university of ,london4 ,,general ,,contents4--,the ,materials of the ,earth--,a ,mountain ,hollow--,down the ,valley--,along the ,shore--,across the ,plains--,dead ,volcanoes--,a ,granite ,highland--,the ,annals of the ,earth--,the ,surrey ,hills--,the ,folds of the ,mountains4 ,the ,,fascinating ',,open-,,air ,,studies' of ,,prof4 ,,cole give the ,subject a ,,glow ,,animation 444 cannot fail to arouse keen interest in geology4--,geological ,magazine4 ,a ,,charming ,,book1 beautifully illustrated4--,athenum4 99 99 99 99 99 ,beautifully ,illustrated4 ,with a ,frontispiece in ,colours1 and ,numerous ,specially ,drawn ,plates by ,charles ,whymper4 #gs4 #f;d4 ,,open-,,air ,,studies ,,in ,,bird-,,life3 ,,sketches ,,of ,,british ,,birds ,,in ,,their ,,haunts4 ,,by ,,charles ,,dixon4 ,the ,spacious ,air4--,the ,open ,fields and ,downs4--,in the ,hedgerows4--,on ,open ,heath and ,moor4--,on the ,mountains4--,amongst the ,evergreens4--,copse and ,woodland4--,by ,stream and ,pool4--,the ,sandy ,wastes and ,mud-flats4--,sea-laved ,rocks4--,birds of the ,cities4--,,index4 ,enriched with excellent illustrations4 ,a welcome addition to all libraries4--,westminster ,review4 99 99 99 99 99 ,twentieth ,annual ,issue4 ,handsome cloth1 #gs4 #f;d4 7,to ,subscribers1 #fs474 ,,the ,,official ,,year-,,book ,,of ,,the ,,scientific ,,and ,,learned ,,societies ,,of ,,great ,,britain ,,and ,,ireland4 ,,compiled ,,from ,,official ,,sources4 ,comprising 7together with other ,official ,information7 ,,lists of the ,,papers read during the ,session #aijb-aijc before all the ,,leading ,,societies throughout the ,kingdom engaged in the following ,departments of ,research3-- #a4 ,science ,generally3 i4e41 ,societies occupying themselves with several ,branches of ,science1 or with ,science and ,literature jointly4 #b4 ,mathematics and ,physics4 #c4 ,chemistry and ,photography4 #d4 ,geology1 ,geography1 and ,mineralogy4 #e4 ,biology1 including ,microscopy and ,anthropology4 #f4 ,economic ,science and ,statistics4 #g4 ,mechanical ,science1 ,engineering1 and ,architecture4 #h4 ,naval and ,military ,science4 #i4 ,agriculture and ,horticulture4 #aj4 ,law4 #aa4 ,literature4 #ab4 ,psychology4 #ac4 ,archology4 #ad4 ,medicine4 ,,fills ,a ,,very ,,real ,,want4--,engineering4 ,,indispensable to any one who may wish to keep himself abreast of the scientific work of the day4--,edinburgh ,medical ,journal4 ,the ,,year-,,book ,,of ,,societies is a ,record which ought to be of the greatest use for the progress of ,science4--,lord ,playfair1 ,f4,r4,s41 ,k4,c4,b41 ,m4,p41 ,past-,president of the ,british ,association4 ,it goes almost without saying that a ,handbook of this subject will be in time one of the most generally useful works for the library or the desk4--,the ,times4 ,british ,societies are now well represented in the ',year-,book of the ,scientific and ,learned ,societies of ,great ,britain and ,ireland'--7,art4 ,societies in ,new ,edition of ,encyclopdia ,britannica1 vol4 xxii47 99 99 99 99 99 ,copies of the ,,first ,,issue1 giving an ,account of the ,history1 ,organization1 and ,conditions of ,membership of the various ,societies1 and forming the groundwork of the ,series1 may still be had1 price #g_/f4 ,also ,copies of the ,issues following4 ,the ,,year-,,book ,,of ,,societies forms a complete ,,index ,,to ,,the ,,scientific ,,work of the sessional year in the various ,departments4 ,it is used as a ,,handbook in all our great ,,scientific ,,centres1 ,,museums1 and ,,libraries throughout the ,kingdom1 and has become an ,,indispensable ,,book ,,of ,,reference to every one engaged in ,scientific ,work4 ,,ready ,,in ,,october ,,each ,,year4 ,griffin's ,metallurgical ,series4 ,edited by ,,sir ,w4 ,,roberts-,,austen1 ,k4,c4,b41 ,f4,r4,s41 ,d4,c4,l4 99 99 99 99 99 ,fifth ,edition1 ,thoroughly ,revised and ,considerably ,enlarged4 #ahs4 ,,introduction ,,to ,,the ,,study ,,of ,,metallurgy4 ,by ,sir ,w4,c4 ,,roberts-,,austen4 ,with additional ,illustrations and ,micro-,photographic ,plates of ,different ,varieties of ,steel4 ,fourth ,edition1 ,thoroughly ,revised and ,enlarged4 #bas4 ,,the ,,metallurgy ,,of ,,gold4 ,by ,t4 ,,kirke ,,rose1 ,d4,sc41 ,assayer of the ,royal ,mint4 ,including the most recent ,improvements in the ,cyanide ,process4 ,with new ,frontispiece and additional ,illustrations4 ,in ,two ,volumes1 each complete in itself4 ,,the ,,metallurgy ,,of ,,lead ,,and ,,silver4 ,by ,h4,f4 ,,collins1 ,assoc4 ,r4,s4,m41 ,m4,inst4,m4,m4 ,part ,i4--,,lead4 ,with ,sections on ,smelting and ,desilverisation1 and the ,assay and ,analysis of the ,materials ,involved4 #afs4 ,part ,,ii4--,,silver4 ,sources and ,treatment of ,ores1 with ,descriptions of ,plant1 ,machinery1 c4 #afs4 ,second ,edition1 ,revised4 ,with numerous ,illustrations4 #afs4 ,,the ,,metallurgy ,,of ,,iron4 ,by ,,thomas ,,turner1 ,f4,i4,c41 ,assoc4 ,r4,s4,m4 ,professor of ,metallurgy at the ,university of ,birmingham4 ,large #hvo4 ,profusely ,illustrated with ,plates and ,diagrams4 ,,the ,,metallurgy ,,of ,,steel4 ,by ,f4,w4 ,,harbord4 ,with a ,section on the ,mechanical ,treatment of ,steel4 ,by ,j4,w4 ,,hall4 #bes4 net4 99 99 99 99 99 ,,assaying4 ,by ,j4,j4 ,,beringer1 ,f4,i4,c41 ,f4,c4,s41 and ,c4 ,,beringer1 ,f4,c4,s4 ,,ninth ,,edition1 ,revised4 ,with ,diagrams1 #ajs4 #f;d4 ,,getting ,,gold4 ,a ,practical ,treatise for ,prospectors and ,,miners4 ,by ,j4,c4,f4 ,,johnson1 ,a4,i4,m4,e44 ,f4,g4,s41 ,life ,member ,australian ,mine ,managers' ,association4 ,numerous ,illustrations4 ,,second ,,edition4 #cs4 #f;d4 ,,gold ,,seeking ,,in ,,south ,,africa4 ,a ,handbook of ,hints for ,intending ,explorers1 ,prospectors1 and ,settlers4 ,by ,,theo4 ,,kassner4 ,with a ,chapter on ,agriculture4 ,crown #hvo1 ,fancy ,cloth ,boards4 ,illustrated4 #ds4 #f;d4 net4 ,,the ,,cyanide ,,process ,,of ,,gold ,,extraction4 ,by ,,james ,,park1 ,f4,g4,s41 ,m4,inst4,m4,m41 late ,geological ,surveyor and ,mining ,geologist to the ,new ,zealand ,government4 ,,new ,,edition1 ,revised and ,enlarged from the last ,new ,zealand ,edition4 ,with ,frontispiece1 ,plates and ,illustrations4 #fs4 net4 ,,prospecting ,,for ,,minerals4 ,a ,practical ,handbook4 ,by ,s4 ,,herbert ,,cox1 ,assoc4 ,r4,s4,m41 ,m4,inst4,m4,m41 ,f4,g4,s41 c4 ,with ,illustrations4 ,,second ,,edition1 ,revised4 ,cloth1 #es42 ,leather1 #fs4 #f;d4 ,,tables ,,for ,,quantitative ,,metallurgical ,,analysis ,,for ,,laboratory ,,use4 ,by ,j4 ,,james ,,morgan1 ,f4,c4,s4 ,large #hvo1 strongly bound1 cloth1 #ds4 ,,electric ,,smelting ,,and ,,refining4 ,by ,dr4 ,w4 ,,borchers4 ,translated by ,,walter ,g4 ,,mcmillan1 ,f4,i4,c41 ,f4,c4,s41 from the ,second ,german ,edition4 ,with numerous ,illustrations and ,three ,folding ,plates4 #bas4 ,,mine ,,accounts ,,and ,,mining ,,bookkeeping4 ,from the ,,actual ,,practice of leading ,mining ,companies4 ,by ,,james ,g4 ,,lawn1 ,assoc4 ,r4,s4,m41 ,a4,m4,inst4,c4,e4,f4,g4,s4 ,edited by ,sir ,,le ,,neve ,,foster1 ,d4,sc41 ,f4,r4,s4 ,large #hvo4 ,,third ,,edition4 #ajs4 #f;d4 99 99 99 99 99 ,large #hvo4 ,handsome ,cloth4 ,illustrated1 #abs4 #f;d4 net4 ,,metallurgical ,,analysis ,,and ,,assaying3 ,a ,three ,years' ,course for ,students4 ,by ,w4,a4 ,,macleod1 ,b4,a41 ,b4,sc41 ,a4,o4,s4,m4 7,n4,z471 and ,,chas4 ,,walker1 ,f4,c4,s4 ,part ,i4--,qualitative ,analysis1 and ,preparation and ,properties of ,cases4 ,part ,,ii4--,qualitative and ,quantitative ,analysis4 ,part ,,iii4--,assaying1 ,technical ,analysis 7,gas1 ,water1 ,fuels1 ,oils1 c474 99 99 99 99 99 ,london3 ,charles ,griffin ,co41 ,ltd41 ,exeter ,street1 ,strand4