,,pigments1 ,,paint ,,and ,,painting ,,pigments1 ,,paint ,,and ,,painting ,a ,,practical ,,book ,,for ,,practical ,,men ,,by ,,george ,,terry ,illustration3 colophon ,london ,e4 ,f4 ,n4 ,,spon1 #abe ,,strand ,new ,york ,,spon ,,chamberlain1 #ab ,,cortlandt ,,street #ahic ,,introduction4 ,in days gone by1 the painter who served the usual term of apprenticeship was deemed to have done all that was required to qualify him for his trade4 ,he may have learned little or much1 but he had 8served his time10 and that was all that was expected of him4 ,so far as it went1 the training was good1 because it was nothing if not practical1 and practice is an essential element of skill4 ,but nowadays such a training can only be considered partial2 mere practice1 without any scientific knowledge of the principles which underlie it1 is but half a qualification for the workman who aims at being really a master of his trade4 ,when competition was unknown1 and the low prices of raw material offered no inducement for passing off inferior or fraudulent substitutes1 there was less need for a high degree of knowledge4 ,but under modern conditions1 the painter who is unable to gauge the qualities of the materials he uses1 and who is ignorant of the rules which govern those qualities1 and of the principles which determine the use of this and the rejection of that article1 cannot long survive in the struggle for supremacy or even livelihood4 ,hence the need for a handbook such as this volume aims at being4 ,granted that our technical schools and colleges are affording a liberal and invaluable education to the workman who will avail himself of the opportunities given him1 still a man does not remain for ever at school1 and he needs a guide-book1 handy of reference and accessible in price1 to refresh his memory and supplement the information gained in the class-room and workshop4 ,to fulfil this useful purpose is the aim and object of this unpretending volume4 ,,contents4 ,,chapter ,i4 ,,preliminary4 ,,page ,colour #a ,pigments #c ,,chapter ,,ii4 ,,blacks4 ,general #e ,animal-black #f ,bone-black #f ,frankfort or ,drop-black #aa ,ivory-black #aa ,lamp-black #aa ,unimportant blacks--,aniline1 candle1 charcoal1 coal1 cork1 ,german1 iron1 lead1 manganese1 ,prussian1 prussiate1 ,spanish1 tannin #be ,,chapter ,,iii4 ,,blues4 ,cobalt blues--,cruleum2 ,cobalt blue2 smalts #bg ,copper blues--,bremen blue2 ,cruleum2 ,lime blue2 ,mountain blue or ,azurite2 ,pligot blue2 ,verditer #cd ,indigo #db ,manganese blue #di ,prussian blue--,general2 ,yellow prussiate2 ,combination of the cyanide and iron solutions2 ,antwerp blue2 ,bong's blue2 ,brunswick blue2 ,chinese blue2 ,paris blue2 ,saxon blue2 ,soluble blue2 ,turnbull's blue #di ,ultramarine #gj ,,chapter ,,iv4 ,,browns4 ,asphalt or ,bitumen #aja ,bistre #aja ,bone brown #ajb ,cappagh brown #ajb ,cassel earth #ajb ,chicory brown #ajb ,cologne earth #ajb ,manganese brown #ajc ,mars brown #ajc ,prussian brown #ajc ,rubens brown #ajd ,sepia #ajd ,ulmin #aje ,umbers #aje ,vandyke brown #ajg ,,chapter ,v4 ,,greens4 ,baryta #aji ,bremen #aab ,brighton #aab ,brunswick #aac ,chinese #aah ,chrome #aah ,cobalt #aai ,douglas #abj ,emerald #aba ,guignet's #abe ,lokao #abi ,malachite #abi ,manganese #acj ,mineral #acj ,mitis #acj ,mountain #aca ,paris #acb ,prussian #acb ,rinmann #acb ,sap #acb ,scheele's #acc ,schweinfurth #acd ,terre verte #acd ,titanium #ace ,verdigris #ace ,verditer #acf ,verona earth #acf ,victoria #acg ,vienna #acg ,zinc #acg ,,chapter ,,vi4 ,,reds4 ,antimony vermilion #ach ,baryta red #adc ,cassius purple #adc ,chinese red #add ,chrome orange #add ,chrome red #add ,cobalt pink #add ,cobalt red #add ,colcothar #ade ,derby red #ade ,indian red #adg ,lead orange #adg ,minium #adh ,orange mineral #aej ,oxide reds #aej ,persian red #aec ,realgar #aec ,red lead #aec ,rouge #aec ,venetian red #aec ,vermilion #aec ,victoria red #afi ,,chapter ,,vii4 ,,whites4 ,baryta white #agj ,blanc fixe #agb ,charlton white #agb ,china clay #agb ,enamelled white #ahc ,english white #ahc ,gypsum #ahc ,kaolin #ahc ,lead whites or ,white leads #ahc ,lime white #bde ,lithophone #bde ,magnesite #bde ,mineral white #bde ,orr's enamel white #bde ,paris white #bdf ,permanent white #bdf ,satin white #bdf ,spanish white #bdf ,strontia white #bdf ,terra alba #bdf ,whiting #bdf ,zinc whites #bdg ,,chapter ,,viii4 ,,yellows4 ,arsenic yellow #beg ,aureolin yellow #beg ,cadmium yellow #beh ,chrome yellows #beh ,gamboge #bgj ,king's yellow #bga ,naples yellows #bga ,ochres #bgb ,orpiment #bhj ,realgar #bhj ,siennas #bha ,,chapter ,,ix4 ,,lakes4 ,brazil-wood lake #bhc ,carminated lake #bhc ,carmine #bhc ,cochineal lake #bhd ,madder lake #bhd ,yellow lakes #bhe ,,chapter ,x4 ,,luminous ,,paints #bhf ,,chapter ,,xi4 ,,examination ,,of ,,pigments4 ,fineness #bic ,body or covering power #bic ,colour #bic ,durability #bid ,,chapter ,,xii4 ,,vehicles ,,and ,,dryers4 ,generalities #bie ,ground-nut oil #big ,hempseed oil #bih ,kukui or ,candle-nut oil #bih ,linseed oil #bii ,menhaden oil #cjc ,poppy-seed oils #cje ,tobacco-seed oil #cjf ,walnut oil #cjg ,wood or ,tung oil #cjh ,extraction of seed oils #cjh ,dryers #caf ,litharge #caf ,cobalt and manganese benzoates #cah ,cobalt and manganese borates #cah ,resinates #cah ,zumatic dryers #cah ,manganese oxide #cah ,guynemer's dryer #cai ,manganese oxalate #cai ,boiled oil #cbj ,,chapter ,,xiii4 ,,paint ,,machinery4 ,wright ,co's #cci ,hind and ,lund's #cde ,brinjes ,goodwin's #cdf ,,chapter ,,xiv4 ,,painting4 ,the surface #cea ,priming #ceb ,drying #cec ,filling #ced ,coats #cee ,brushes #cee ,water-colours #cef ,removing odour #cef ,discoloration #cef ,composition #ceh ,area covered #cfj ,measuring #cfj ,carriage and ,car painting #cfa ,woodwork painting #cfh ,iron painting #cfi ,fresco painting #cgh ,,index #chc ,,illustrations4 ,,figure ,,page #a1 #b4 ,,bone-,,black ,,furnace #h #c-aa4 ,,apparatus ,,for ,,making ,,lamp-,,black #ab-bb #ab4 ,,furnace ,,for ,,roasting ,,cobalt ,,ores #ca #ac4 ,,furnace ,,for ,,making ,,smalts #cc #ad-ag4 ,,yellow ,,prussiate ,,furnace #fj #ah-bj4 ,,hannay',s ,,white ,,lead ,,furnace #bag #ba-be4 ,,lewis',s ,,white ,,lead ,,furnace #bbf1 #bcj #bf1 #bg4 ,,macivor',s ,,white ,,lead ,,process #bcc1 #bci #bh4 ,,apparatus ,,for ,,making ,,zinc ,,oxide #bdh #bi4 ,,apparatus ,,for ,,making ,,zinc ,,sulphide #bec #cj-cb4 ,,furnace ,,for ,,roasting ,,ochres #bgh #cc-ci4 ,,apparatus ,,for ,,extracting ,,seed-,,oils #cji-cae #dj-dd4 ,,wright ,,co4',s ,,paint ,,mills #cdj-cdd #de4 ,,hind ,,lund',s ,,paint ,,mill #cdf #df-dh4 ,,brinjes ,,and ,,goodwin',s ,,paint ,,mills #cdg1 #cdh #di4 ,,noakes ,,co4',s ,,metallic ,,keg #cej ,,chapter ,i4 ,,preliminary4 ,colour4--,the term 8colour0 is inappropriately given by common usage to material substances which convey a sense of colour to the human eye1 but is properly restricted to that sense itself4 ,the material colour should be called 8pigment0 or 8dyestuff0 in the raw state1 and paint when compounded with other substances for application in the form of a coating4 ,the sense of colour is due to light4 ,in the absence of light there is no colour1 only blackness2 and black is really no colour1 but an absence of colour4 ,very many conditions combine to cause different colour sensations1 some of which are understood1 while others we are not able to explain4 ,for instance1 take the action of heat upon a solution of chloride of cobalt4 ,as soon as the liquid becomes warm1 the pink colour disappears and gives place to blue2 but on pouring water into it1 the blue vanishes and the pink reappears4 ,again1 on heating the blue crystals of sulphate of copper they become white1 but the blue colour comes back when water is added1 and the solution assumes a deeper tint as it dissolves more of the white powder4 ,if all the rays are cut off from an electric light except those which are in and beyond the violet1 and a flask containing a solution of sulphate of quinine is held in that portion of the spectrum1 it will become luminous4 ,the same thing will occur even more strikingly on placing a piece of uranium glass in the ultra-violet rays4 ,the explanation of this phenomenon is that beyond those rays which give light there are others which do not give light1 i4 e4 which do not cause us to experience the sensation of light2 the reason being that their vibrations are too rapid4 ,but when certain other substances1 such as sulphate of quinine1 or a thin slip of uranium glass1 are placed in the path of the rays1 this rapid motion is arrested and modified1 and these rays1 which in themselves are not luminous1 are reflected back to our eyes as luminous rays4 ,the rapidity of the vibrations being moderated1 our retinas become sensible to them as rays of blue light4 ,colour does not depend only upon chemical composition nor solely upon the aggregation of the particles1 but upon these and other things besides not yet explained4 ,all matter is in a state of motion4 ,if you heat a substance you communicate an increased activity of motion to the particles of which it consists4 ,when certain coloured rays of light are falling upon a substance1 these coloured rays of light have a motion peculiar to themselves4 ,it may be that the degree of motion in that substance1 either existing in it naturally without heating1 or communicated to it by artificial heating1 is such that these rays of light are precisely those which that substance is not capable of sending back to our eyes4 ,they are then absorbed or destroyed in some way1 by the particular state of that substance upon which they fall2 and those rays which the substance is capable of reflecting back are mainly sent back to our eyes4 ,certain colours1 such as blue1 yellow1 and green1 absorb certain rays more or less perfectly1 and reflect back in the main blue1 yellow1 and green to our eyes4 ,hence it is incumbent on those who are studying colour1 and who are interested in the purity and permanency of colour1 to comprehend at least the principles of that science of light which tells of the action of light upon various bodies that are used as pigments in painting4 ,if we put together two substances one of which destroys or modifies the chemical condition or state of the other1 then certainly one of those substances1 and very probably both1 will lose the colour which it had before it came into contact with the other4 ,it is therefore most important that all engaged in the preparation and use of colours should make a study of this science of light4 ,of almost equal value is a study of the science of heat4 ,we have seen what heat can do in changing the conditions of a substance4 ,to give another instance4 ,the black sulphide of mercury1 after sublimation by heat1 exhibits properties1 imparted to it by the heat1 which it did not possess before1 i4 e4 it can1 by trituration1 be brought to display a red colour4 ,on showing the spectrum on a screen1 if some solution of soda or other sodium salt be held in the course of the light1 almost all the coloured rays but one will be cut off1 and a little band is seen in the yellow part of the spectrum4 ,this is because the sodium flame is almost 8monochromatic10 or single-lined3 it cuts off all the colours but the yellow4 ,again1 if metallic thallium is held in the flame1 the only band remaining in the spectrum will be the green2 and if a lithium salt1 the only surviving colour will be red4 ,pigments4--,the term 8pigments0 is applied to those colouring matters which are mixed in a powdery form with oil or other vehicle for the purpose of painting4 ,they differ in this respect from the dyestuffs1 which are always employed in solution4 ,a very large proportion of the pigments in common use are derived from the mineral kingdom1 the most notable exceptions being found in the blacks and lakes4 ,all pigments are required to possess 8body10 or density and opacity2 to be insoluble in water and most other solvents1 except the stronger mineral acids2 and to be inert1 or incapable of exercising chemical or other influence on each other or on the vehicle or drier with which they are mixed prior to use4 ,they may be conveniently classified according to their colours in the first place1 reserving the consideration of their preparation for use for a later chapter4 ,the chief classes are ,blacks1 ,blues1 ,browns1 ,greens1 ,reds1 ,whites1 and ,yellows4 ,,chapter ,,ii4 ,,blacks4 ,all the black pigments in use owe their colour to carbon1 and all are produced by artificial means1 no natural form of carbon possessing the requisite qualities4 ,several manufactured carbonaceous substances are known in commerce under the generic name of 8,blacks40 ,the most important of these are animal-black1 bone-black1 ,frankfort-black1 ivory-black1 and lamp-black4 ,they are usually obtained by carbonising organic matter1 particularly bones1 in closed vessels or crucibles1 or by collecting the soot formed by the combustion of oily1 resinous1 and bituminous substances4 ,other blacks than those enumerated are manufactured1 but only on so small a scale as to be of no commercial importance4 ,carbon1 lamp1 and vegetable blacks consist almost entirely of carbon1 containing usually from #ih to #ii per cent4 of that substance1 the residue consisting of a little ash1 water1 and occasionally unburnt oil4 ,bone and ivory blacks1 on the other hand1 are chiefly composed of mineral matter1 which may amount to #fe or #ge per cent4 and is mainly represented by phosphate of lime4 ,their actual colouring matter1 the carbon1 only constitutes #ae to #cj per cent4 of the mass4 ,the balance is water and unburnt animal tissue4 ,blacks prepared from animal matters other than bone and ivory carry #dj to #hj per cent4 of carbon1 and their mineral matter is generally in the form of carbonates of lime and of the alkalies4 ,the principal impurity to be watchful of in the vegetable and lamp blacks is a small quantity of oily matter which may seriously interfere with their drying qualities4 ,they should leave very little ash after being burned in a crucible4 ,bone and ivory blacks are sometimes valued as much for their mineral matter as for their colouring matter4 ,the proportion of this mineral matter is ascertained by heating a certain weight of the black to red heat in a crucible till every trace of black has disappeared1 and then weighing the residue4 ,the residue should next be boiled in strong hydrochloric acid till it is dissolved2 if there is any which will not dissolve it is most probably barytes1 which has been added as an adulterant and to make the black weigh heavy4 ,when the solution is complete1 the addition of ammonia will throw down a precipitate of phosphate of lime1 which should equal #fj to #gj per cent4 of the original weight of mineral matter4 ,if much less than this1 it is likely that whiting or gypsum has been mixed with the pigment4 ,as carbon is not acted upon by acids or alkalies1 it follows that all pure carbon blacks are in themselves perfectly stable and permanent pigments1 and that they exert no influence on other pigments with which they may be mixed4 ,animal-black4--,this substance is almost identical with bone-black1 but is generally in a more finely divided state4 ,any animal refuse matter may be used in its preparation1 such as albumen1 gelatine1 horn shavings1 c4 ,these are subjected to dry distillation in an earthenware retort4 ,an inflammable gas is given off1 together with much oily matter1 ammonia1 and water1 while a black carbonaceous mass is left behind4 ,this is washed with water and powdered in a mill1 the product being animal-black4 ,it is largely used in the manufacture of paint1 printing ink1 and blacking4 ,bone-black4--,when bones are heated in a retort or crucible1 the organic constituents are decomposed and carbonised4 ,a mixture of combustible gases is given off2 some of these do not condense on cooling1 others condense in the form of a heavy oil1 called bone-oil4 ,also much water containing tarry water and ammoniacal salts in solution passes over4 ,the residue in the retort or crucible consists of finely divided carbon1 in intimate mixture with the inorganic constituents of the bones3 this mixture constitutes ordinary bone-black1 or animal charcoal1 as it is sometimes called4 ,the inorganic portion may1 if required1 be removed by washing the residue in dilute hydrochloric acid4 ,the process1 as worked on the large scale1 is carried on in different ways1 according as it is desired to collect the volatile condensable portion of the distillate1 or to allow it to escape4 ,in the latter case1 when it is required to obtain only bone-black1 the apparatus employed is of a very simple nature1 and the amount of fuel needed is comparatively small4 ,the carbonisation is effected in fire-clay crucibles1 #af in4 high and #ab in4 diameter4 ,these are to be preferred to crucibles made of iron1 which were much used at one time1 since they do not lose their round form when subjected to a high temperature2 in consequence of this1 they fit more closely together in the furnace1 less air can penetrate1 and therefore less of the charcoal is consumed by oxidation4 ,the furnace is an ordinary flat hearth1 having a superficial area of about #dj square yards1 and is covered in with a flat arch1 all of brickwork4 ,the fireplace is situate in the middle of the hearth2 the crucibles are introduced through doors in the front1 which are bricked up when the furnace is filled2 each furnace holds eighteen crucibles4 ,the crucibles1 filled with the coarsely broken bones1 are covered with a lid luted on with clay4 ,to economise fuel1 the furnaces should be in a row1 and placed back to back4 ,the arrangement of the furnace and pots is shown in ,figs4 #a and #b4 ,a is the fireplace2 ,b1 the crucibles1 eighteen in number1 spread over the floor of the furnace in a single layer2 c1 d1 e1 and f are the flues for conducting away the heated gases arising from the calcination of the bones1 as well as the waste heat itself2 the last portion of the flue is fitted with a damper g4 ,the furnaces are intended to be built in fours1 back to back1 the waste heat serving in a great measure to conduct the operation of the revivifying apparatus placed in the centre of the group1 and marked ,c4 ,illustration3 ,figs4 #a and #b4--;,,bone-,,black ,,furnace4 ,when the furnace is filled and the doors are bricked up1 the heat is slowly raised to redness1 at which point it is kept for six or eight hours4 ,the combustible gases are evolved and consumed in the furnace as the bones begin to decompose1 and by this means so much heat is produced that only a small quantity of fuel is needed to maintain the required temperature4 ,when the carbonisation is complete1 the doors are taken down and the crucibles are removed to cool1 their places being immediately filled with fresh ones4 ,the heat must be kept as uniform as possible throughout the process3 if it be not sufficiently high1 the bone-black will contain a portion of undecomposed organic matter1 which renders it quite unfit for use2 if1 on the other hand1 the temperature be raised too high1 the bone-black will become dense and compact1 whereby its efficacy as a decoloriser is much reduced4 ,when the charcoal in the crucible has become perfectly cool1 it is removed and crushed4 ,when required for decolorising or deodorising purposes1 it is only roughly broken up into small lumps1 in which form it is most readily applicable4 ,the crushing is effected by means of two grooved cylinders1 consisting of toothed discs1 alternately #aj and #ab in4 in diameter4 ,these are so placed that the #aj-;in4 discs of one cylinder are opposite the #ab-;in4 discs of the other1 and thus1 in revolving1 the carbonised bones are crushed to fragments between them1 but are not reduced to powder4 ,they are passed successively through six of these mills1 the cylinders of each couple being nearer to each other than the last4 ,finally the crushed bones are carefully sieved2 the powder is placed apart from the lumps1 again passed through finer sieves1 and sorted out into different sizes4 ,a furnace such as that described above will carbonise four charges of bones in one day1 each charge being more than half a ton in weight4 ,with careful work1 the bones will yield #fj per cent4 of bone-black1 or more than one ton daily4 ,if it be required to condense the volatile gaseous products of the carbonisation1 this process is conducted in retorts similar to those used in the manufacture of acetic acid from wood3 these are so arranged that the whole of the gaseous products are condensed and collected4 ,the aqueous portion of the distillate is usually evaporated down to obtain salts of ammonia2 the uncondensable gases may be employed for illuminating purposes4 ,the manufacture of bone-black is usually carried on in the neighbourhood of large towns1 where a good supply of bones may be readily obtained4 ,ordinary bone-black has about the following composition3 ,phosphate and carbonate of lime1 and sulphide or oxide of iron1 #hh parts2 charcoal1 containing a small quantity of nitrogenous matter1 #aj parts2 silicated carbide of iron1 #b parts4 ,the decolorising properties of bone-black are due solely to the presence of the charcoal4 ,when intended for use as a deodoriser or decoloriser1 bone-black should be kept carefully excluded from the air1 for by exposure it loses this power to a great extent1 and becomes almost inert4 ,that which has been freshly burned is therefore best for these purposes4 ,the cost of production of bone-black may be calculated as follows3-- s4 d4 #d tons fat bones at #ds4 per cwt #af #j #j #bg bushels coals #a #c #i #b firemen #j #d #i #d workmen #j #h #j #a carman #j #b #d #b horses #j #e #g ,breaking up the bones #a #e #d ,rent and taxes #j #h #j ,interest1 repairs1 and wear and tear #j #g #b ,contingencies and transports #j #b #d ------------- #bj #g #c ,produce3-- ,black1 #fj per cent41 say #ch cwt4 in grains1 at #ads4 #c;d4 #ac #aj #i #aj cwt4 fine1 at #es4 #f;d4 #a #g #h ,fat1 #f per cent41 say #e cwt41 at #cas4 #h;d4 #g #ah #d --------- #bb #af #i #bb #af #i -------- ,profit #b #i #f ,bone-black never has the depth or brilliancy of lamp-black1 but it mixes well with either water or oil1 and though a slow drier as an oil paint1 is permanent and not high priced4 ,frankfort-black or ,drop-black4--,this is a black powder obtained from dried vine-twigs carbonised to a full black and then ground very fine4 ,on a large scale it is prepared from a mixture of vine-twigs1 wine-lees1 peach-stones1 bone-shavings1 and ivory refuse4 ,it varies in shade according as the animal or vegetable charcoal is in excess2 when the latter predominates1 the powder is of a bluish colour2 but when there is an excess of animal charcoal1 it has a brownish tinge4 ,it is customary to wash the powder well when first made1 in order to remove any soluble inorganic impurities4 ,the finest ,frankfort-black is probably the soot obtained from the combustion of the materials mentioned above4 ,it makes an excellent pigment1 and is extensively used by copperplate engravers in the preparation of their ink4 ,drop-black is simply ,frankfort-black ground exceedingly fine1 mixed with a little glue water1 and dried in pear-shaped drops for sale4 ,ivory-black4--,ivory-black is a beautiful black pigment prepared by carbonising waste fragments and turnings of ivory4 ,these are exposed to a red heat for some hours in crucibles1 great care being taken to avoid overheating or burning4 ,when quite cold1 the crucibles are opened1 and the contents are pulverised1 the richest coloured fragments being kept apart for the best quality4 ,the powder is then levigated on a porphyry slab1 washed well with hot water on a filter1 and dried in an oven at a temperature not exceeding #bab ,f4 ,the product is of a very beautiful velvety black colour1 superior even to that obtained from peach-kernels1 and quite free from the reddish tinge which so often characterises bone-black4 ,ivory-black1 like ,frankfort-black1 is employed by copperplate printers in the preparation of their ink4 ,mixed with white lead1 it affords a rich pearl-grey pigment4 ,lamp-black4--,lamp-black is an exceedingly light1 dull-black powder1 formed by the imperfect combustion of oils1 fats1 resins1 c4 ,it may be prepared on a small scale by suspending a small tin-plate funnel over the flame of a lamp fed with oil1 tallow1 or crude naphtha1 the wick being so arranged that it shall burn with a large and smoky flame4 ,dense masses of this light carbonaceous matter gradually collect in the funnel1 and may be removed from time to time4 ,the funnel should be furnished with a metal tube to convey the gases away from the room1 but no solder must be used in making the connections4 ,illustration3 ,figs4 #c and #d4--;,,apparatus ,,for ,,making ,,lamp-,,black4 ,an especially fine quality of lamp-black is obtained from bone-oil1 deprived of the ammonia with which it is always contaminated4 ,it is manufactured on a commercial scale by means of the apparatus shown in ,figs4 #c and #d4 ,the oil is contained in the lamp ,a and kept at a constant level by means of the globular vessel ,b1 which is also filled with oil and inverted over ,a4 ,the oil flows from the lamp into the tube ,c1 which is bent upwards at the farther extremity on a level with the oil in the lamp4 ,a cotton wick is supplied to the bent end of the tube1 as well as a little spout ,d1 for conducting away any oil that may overflow into the receptacle ,e placed beneath4 ,a conical hood a surrounds the flame of the lamp and terminates in a tube b1 through which are conveyed the sooty products of the combustion of the oil into the wide lateral tube c1 arranged to accommodate the smoke from about a dozen such lamps placed at intervals of about #f feet1 as indicated in the figures4 ,the effect of this wide tube c is not only to cool the smoke1 but also to collect the water and other liquids condensed4 ,the smoke and vapours pass hence into d1 the first of a series of sacks made of closely woven linen1 about #aj or #ab feet long and #c feet in diameter1 closed at the bottom with a trap or slide e1 and formed at the upper and lower ends of sheet-copper tubing made funnel-shaped4 ,the upper one of these is prolonged into an additional pipe f1 by means of which the smoke arrives at the second sack g in the series1 thence finding its way to the third1 and so on till the last sack of the row is reached4 ,in connection with the last sack of each row is placed a horizontal flue ,f1 in which are arranged frames covered with wire gauze and mounted on hinges4 ,their purpose is to retain the small remaining portions of lamp-black passing out with the smoke from the sacks4 ,the meshes of the gauze are constantly getting filled up with soot1 which necessitates a periodical checking of the draught for its removal4 ,this is done by means of the rod ,g1 which1 when raised and allowed to fall suddenly1 jerks the accumulated mass off the gauze4 ,the current of air passing through the entire apparatus can be regulated by a damper placed at the entrance to the chimney in which the flue ,f embouches4 ,at regular intervals1 the mouthpieces in the lower ends of the sacks are removed1 and their contents are shaken out separately and collected according to their various qualities4 ,that gathered from the first sack in each row should always be kept apart from the remainder1 as it is much contaminated by the presence of resinous and tarry matters4 ,illustration3 ,fig4 #e4--;,,apparatus ,,for ,,making ,,lamp-,,black4 ,the old-fashioned method of preparing lamp-black from the incomplete combustion of gas tar is conducted in an apparatus resembling that shown in ,fig4 #e4 ,the furnace a1 lined with fire-brick1 contains a kettle b1 and is surmounted by a large thick cast-iron hood c1 communicating with a stone or brick condensing chamber1 divided by means of perforated partition walls into three unequal sized compartments d1 e1 f1 wherein the black is deposited4 ,a chimney g delivers uncondensed vapours into the atmosphere4 ,in working1 the furnace is first brought to a red heat1 then the kettle b1 charged with tar1 is introduced4 ,as a charge is finished1 more tar is added1 with occasional stirring1 till the kettle becomes inconveniently full of residue1 when it is withdrawn and a fresh one replaces it4 ,the residue is chipped out and used as fuel4 ,the black is removed weekly through the door h4 ,it is of good quality and colour so long as the combustion is conducted with a minimum of air1 admission of which is controlled at the furnace4 ,the yield is about #be per cent4 of the weight of the tar2 and one furnace should treat a ton of tar in a week4 ,one workman can manage several furnaces4 ,an improved process has been introduced by ,martin and ,grafton for the preparation of lamp-black from coal-tar1 which affords a very good product4 ,the coal-tar is first stirred up energetically with lime-water in any convenient vessel1 after which the mixture is allowed to stand until the coal-tar has subsided to the bottom1 when the lime-water is drawn off4 ,the tar is then well washed by decantation with hot water1 and rectified in the ordinary naphtha still4 ,afterwards it is run into a long iron cylinder1 which is placed over a furnace1 and supplied with numerous large burners4 ,each burner has a metal funnel placed immediately above it1 connected with a cast-iron pipe1 into which all the fumes from each burner are conducted4 ,the naphtha in the cylinder is heated almost to the boiling point by the furnace beneath4 ,a series of smaller pipes lead away the fumes from the main pipe into a row of chambers1 and thence into a series of large canvas bags1 placed side by side1 and connected alternately at top and bottom4 ,the bags vary in number from fifty to eighty1 the last one being left open to allow the smoke to escape1 after traversing some #djj yards since leaving the burners4 ,the best quality of lamp-black is found in the last bags1 that near the furnace being much coarser and less pure4 ,the bags are emptied whenever they contain a sufficient quantity4 ,the process employed in ,germany for the manufacture of lamp-black is to conduct the products of the combustion of any resinous matter in a furnace into a long flue1 at the end of which is placed a loose hood1 made of some woollen material1 and suspended by a rope and pulley4 ,the lamp-black collects in this hood1 and1 when a sufficient quantity has accumulated1 is shaken down and removed4 ,in this manner about #f cwt4 of lamp-black may be collected in twenty-four hours4 ,one form of the apparatus is shown in ,fig4 #f4 ,the circular structure a is lined inside with hanging cloths upon which the black can condense1 and is covered with a conical roof from which depends a movable sheet-iron cone b1 perforated at its apex to give egress to a current of air4 ,this cone b is supported by a rope g passing over a pulley c and accessible from the outside4 ,a fireplace d1 containing a small iron dish e for holding the resin1 is built against one of the side walls of the structure in such a manner that it can be fired externally4 ,the rate of combustion is regulated by a small sliding damper on the door of the fireplace4 ,when the black has accumulated in the chamber a to such an extent that operations must be suspended1 the fire is let out1 and the chamber is left to cool entirely1 so that the black may not ignite on contact with the air4 ,the cone b is then lowered1 and in its descent scrapes the walls of the chamber a and causes the black to collect on the floor1 whence it is removed through an iron door f which at other times is kept tightly luted4 ,illustration3 ,fig4 #f4--;,,apparatus ,,for ,,making ,,lamp-,,black4 ,in ,england1 an inferior variety is sometimes obtained from the flues of coke-ovens4 ,that known as ,russian lamp-black is made by burning chips of resinous deal or pine wood1 and collecting the soot formed2 but it is objectionable1 owing to its liability to take fire spontaneously when left for a long time moistened with oil4 ,a modified form of apparatus has been introduced by ,thalwitzer1 a ,german manufacturer1 and is shown in ,figs4 #g and #h4 ,a vertical tube is provided at its upper end with a funnel1 into which cooling water is poured and flows out through openings in the tube immediately above a circular plate of thin cast or wrought iron arranged horizontally and ,illustration3 ,figs4 #g and #h4--,,thalwitzer',s ,,lamp-,,black ,,apparatus4 secured at its centre to the tube4 ,round the periphery of this plate is a vertical rim of tin plate1 at the top of which is a pipe through which the cooling water runs into a gutter round the top of the cylindrical casing1 the water being carried off from this gutter by a pipe4 ,the vertical tube is carried near its upper end in a bearing1 and at that part is attached a worm-wheel geared into it by a worm driven by any suitable power4 ,at the underside of the circular plate is fixed a scraper1 the edge of which is formed with a strip of leather in contact with the lower surface of the plate4 ,opposite the scraper1 at the bottom of the casing1 is a burning lamp1 which sucks up the oil for its consumption by a flat wide wick4 ,the operation is as follows3--,the vertical tube is caused to revolve by the action of the worm-wheel1 the circular plate thereby receiving a slow rotary movement2 and a small stream of water being poured into the funnel at the top of the tube1 this water passes down the latter and through the openings on to the circular plate1 which is thus kept cool4 ,the burning lamp filled with paraffin or other oil is brought as near to the circular plate as is necessary for the cooling of the flame and the most perfect extraction of the carbon1 which1 in the form of soot1 attaches itself readily to the plate1 owing to its coldness and to the condensation of the steam produced4 ,the revolving plate presents continually to the flames a new and clean surface1 in consequence of the lamp-black being scraped away by the scraper as soon as deposited1 and brought away through a pipe or shoot into a collecting barrel4 ,the apparatus as shown in ,figs4 #g and #h consists of a round metal plate ,a1 provided with a flange a1 and fixed on a vertical shaft b supported by the bearing ,b1 and carrying at its upper end a worm wheel d set in motion by a worm4 ,the plate ,a is cooled by water admitted through a pipe g1 and the flange a is provided with a discharge pipe h1 through which the cooling water runs into the groove ,d1 surrounding the whole apparatus4 ,underneath the plate ,a a number of lamps ,j are applied1 which are fed with oil by a common pipe l4 ,h is an oblique scratcher or blade1 the working edge of which is formed by a strip of leather1 and touches the lower surface of the plate ,a4 ,for manufacturing lamp-black1 a slow rotary motion is imparted to the apparatus by means of the worm and worm-wheel1 and a slight current of water is directed upon the plate ,a through the pipe g4 ,the lamps ,j1 filled with paraffin oil derived from lignite1 or with any other suitable oil1 are ignited and approached to the plate ,a as far as is necessary for cooling the flame1 so as to deposit the greatest possible quantity of black4 ,the latter adheres to the cold surface of the plate1 which is also kept damp by the aqueous vapour formed during the combustion4 ,the revolution of the plate serves to bring the flame continually into contact with new and clean portions of the plate1 the black being continually scraped off by the blade or scraper placed opposite the flames1 and conducted through a channel into a collecting trough4 ,there is a risk of overburning1 causing a grey tint and a hard and granular texture4 ,a variety of lamp-black known as 8carbon black0 or 8gas black10 has of late years assumed an important position among black pigments4 ,it is produced in considerable quantities in the ,united ,states by the combustion of the natural gas issuing from the earth in the mineral oil regions4 ,the soot arising from the imperfect combustion of the gaseous hydrocarbon is made to deposit itself on cooled iron surfaces4 ,these at first were made stationary1 but now take the form of revolving discs or cylinders1 which are automatically cleansed of the black as fast as it is deposited4 ,this type of lamp-black is remarkably free from mineral impurities and unburned oil1 and of a full colour4 ,an improved lamp-black kiln has been introduced in which the use of water is dispensed with4 ,it is shown in ,figs4 #i and #aj4 ,the furnace ,a1 which is preferably built double1 as shown1 is constructed of brick lined with firebrick1 with a rear wall a that divides the furnace room from the condensing room1 side walls b1 front c1 and central dividing wall d1 that divides the furnace into two long and narrow fire ,illustration3 ,figs4 #i and #aj4--;,,american ,,lamp-,,black ,,kiln4 spaces4 ,the bottom of the fire spaces e is formed by a sheet iron plate f that is supported by the walls1 and the space below plate f serves as an air space through which air circulates by openings g in the front and side walls1 this circulation of air tending to keep the plate f cool4 ,the rear of the fire space e extends upward and communicates by an opening h through the wall with the condensing room4 ,in the front wall c is an opening to each fire space e and a door i to each opening4 ,the oil or other liquid is supplied by pipes k that enter from the outside near the rear of the fire spaces4 ,the outer end of each pipe k is fitted with a cup-shaped receptacle l1 into which the oil will run from the vertical branch of the main supply pipe m1 so that the amount of oil running into each pipe k may be observed1 and regulated by a cock4 ,the pipe m feeds the oil to one or more furnaces1 the supply of material to each furnace being separately regulated4 ,in the fire spaces beneath pipes k are placed shallow cast iron drip pans o to receive the oil1 and the oil running in faster than it will burn will drop while on fire into the pans o1 and be spattered into small particles4 ,these pans are changed frequently1 access to them being obtained by doors i4 ,a slide p is provided in each door i to allow of ventilation when required4 ,the slides and doors should close air-tight4 ,by constructing the fire space e long and narrow1 the plate f is more readily kept cool1 and the space in front of the point of combustion renders the smoke less liable to escape by the doors4 ,the products of combustion pass through the opening h to the condensing room1 which is lathed and plastered1 and if the room is sufficiently large a number of furnaces may be fitted to discharge into the same room4 ,this furnace is especially adapted for burning dead oil2 but by using burners of suitable construction other oils may be burned1 and a superior quality of lamp-black made from mitigated spirits4 ,a very large proportion of the lamp-black now made is derived from the combustion of creosote or anthracene oils from coal tar1 or of the residues of shale-oil distillation4 ,the form of combustion chamber varies in different works1 but is typified by the following rough sketch of that in use at the ,stampshaw ,chemical ,works 7,fig4 #aa74 ,illustration3 ,fig4 #aa4--;,apparatus for making ,lamp-black from ,creosote or ,shale ,oil4 ,at these works a horizontal brick flue a about #ah inches square and about #aj feet long is provided4 ,at one end it enters the black-house b1 and is here provided with a damper c to shut it off when not working4 ,the other end opens to the air1 and here is a sliding door d which1 when shut down1 leaves an opening round a small pipe e1 which enters in this situation from a main pipe that conveys oil in a similar manner to four burners of this description placed side by side4 ,at the bottom of the flue is an iron tray f to catch any liquid that falls from the tube1 and in this tray the oil is burned4 ,the burning of oil in one of these flues is not allowed to go on for more than three hours1 and1 when the combustion is over1 the communication with the black-house is closed1 the entrance door of the flue is opened1 and the cover is taken off the chimney g so that the flue may become cooled1 and another flue is taken into use4 ,the black-house is a brick chamber into which the smoke passes1 and where it deposits its sooty particles4 ,in some works there is only one undivided chamber2 in other works there are more than one1 and the chambers communicate by flues through which the smoke passes from one to another4 ,at other works the chamber is divided by vertical partitions1 springing alternately from the two ends1 so as to constitute one high zigzag flue1 along which the smoke must travel to its outlet from the black-house4 ,this chamber must needs have an opening somewhere to the outer air4 ,the opening is sometimes a small chimney in the roof1 and sometimes a short louvre tower4 ,this is necessary to produce a trifling draught1 just enough to carry the smoke into the chamber and no more4 ,in some works1 the black from the black-house is also calcined1 the object of the 8calcination0 being to get rid of all greasiness1 a point of great importance when the lamp-black is to be used for making fine pigment4 ,this process is conducted in circular iron pans1 usually about #b feet high and #b feet diameter1 which are provided with removable iron covers4 ,a pan of this size will hold about #b lb4 of lamp-black4 ,a bowlful is first put in and lighted by a red-hot iron2 more and more is added from time to time as the ignition proceeds4 ,when the pan1 being full1 leaves off smoking1 the calcination is known to be complete1 and the pan is then covered and its contents are allowed to cool4 ,the loss undergone in this process is about #be per cent4 ,the smoke which comes off is acrid and very irritating to the eyes1 like that proceeding from boiling oil1 and it is difficult for a person unaccustomed to it to remain many minutes in the chamber where calcining is going on4 ,this process is sometimes conducted within a chamber1 but frequently under a shed or even in a building freely open to the air4 ,there are three sources from which nuisance may arise in lamp-black making3 #a4 ,the smoke which issues from the chimney of the black-house1 small as it sometimes is1 often constitutes a nuisance to near neighbours2 but the nuisance is not a very serious one1 and it does not extend very far from the works1 never to a greater distance than about #ej yards4 ,the odour1 even when but little smoke escapes1 is oppressive and suffocating in character1 and resembles that diffused in a room by a smoking table-lamp4 ,it occasions headache1 but is not otherwise injurious to health4 #b4 ,a similar nuisance of suffocating smoke sometimes proceeds from the burners1 but this is when they are leaky or when there is a deficiency of draught through the black-house1 or when the doors of the burning chambers do not shut closely1 and when there is much wind blowing past them4 ,this nuisance chiefly occurs when the burners are open to the air and merely protected by an open shed4 #c4 ,the escape of acrolein and other offensive vapours from the calcining house4 ,the best mode of preventing nuisance from the black-house is so to elongate the chamber as to give abundant opportunity for the soot to deposit in the course of the smoke along it to the outlet1 and by taking means to consume by fire what little smoke escapes deposition4 ,a most effectual arrangement for the accomplishment of these ends is to have a black-house #aej feet long1 and so divided by partitions within as to cause the smoke to traverse a distance of altogether #ejj feet before it finds an exit2 the exit from the chamber communicating with a fire1 in which the last of the smoke is consumed1 and which serves to assist in regulating the draught through the chamber4 ,the regulation of the draught through the burner and black chamber is of importance in order to avoid the escape of smoke from the burners4 ,if the draught be too great1 too much black is lost from the chamber1 but if1 on the other hand1 it be too little1 the smoke instead of passing into the chamber will come out into the works and create a nuisance1 especially where the burners are erected in the open air1 under circumstances in which variation in the force of the wind cannot fail to interfere with due regulation of draught4 ,this part of the manufacture should be conducted within a building of some sort4 ,the best mode of preventing nuisance from calcination is in operation at ,shackell ,edwards' works1 in ,hornsey ,road1 ,islington4 ,at these works the black is calcined in a chamber #bj feet square and #be feet in greatest height1 with a paved floor and arched roof4 ,in the centre of the roof is the opening where a fire was formerly placed1 but which is now closed by a sky-light1 capable of being raised4 ,the calcining pots are ranged round this chamber1 and a fan1 employed to draw off the vapours from the oil-boiling pans1 is further utilised to draw off also1 from the upper part of the calcining-house1 the vapours arising from the calcination1 and to drive them into the boiler fire1 where they are consumed4 ,calcination should always be conducted in a closed building duly ventilated so as not to create nuisance4 ,the transport of lamp-black is effected in barrels or bags2 when in the latter1 these should be previously soaked in water containing some clay in suspension1 which stops up the pores of the sacking1 and thereby prevents loss4 ,the particular virtue of lamp-black as a pigment lies in its state of extremely fine division1 which could not possibly be attained by artificial means2 this quality renders it invaluable as the basis of black pigments1 all of which contain it in a greater or less quantity4 ,indian ink and printers' ink are also composed principally of this substance4 ,unimportant ,blacks4--,in addition to the recognised blacks already noticed there are a number of other sources of black pigment which have been drawn upon to a limited extent1 or have been suggested as substitutes for the standard articles4 ,they only merit a short description4 ,aniline black is prepared by adding an acidified 7sulphuric7 solution of bichromate of potash to an aqueous solution of hydrochlorate of aniline1 and washing the precipitate4 ,the cost is prohibitive4 ,candle black is candle smoke condensed on a cold plate4 ,charcoal black is finely-ground wood charcoal4 ,coal black has been suggested by grinding coal1 but lacks the requisite qualities of a pigment4 ,cork black is a very fine pigment prepared by calcining cork refuse4 ,limited supply4 ,german black is ,frankfort black4 ,iron black is ground black sulphide of iron4 ,lead black is prepared by boiling lead fume in sulphide of soda solution4 ,it would probably be unstable on account of oxidation4 ,manganese black is ground oxide of manganese4 ,it is costly1 and dries too quickly4 ,prussian black is calcined ,prussian blue4 ,it is not of a good colour1 nor economical4 ,prussiate black is the carbonaceous residue from making yellow prussiate of potash4 ,used chiefly for decolorising syrups1 c4 ,spanish black is cork black4 ,tannin black is proposed to be made by exhausting the tannin from refuse leather and tanning agents1 and adding alum and sulphate of iron4 ,the colour is blue-black1 weak1 and unstable4 ,,chapter ,,iii4 ,,blues4 ,cobalt ,blues4--,some of the compounds of cobalt with alumina1 phosphoric acid1 silica1 and tin1 are remarkable for possessing a fine blue colour of great permanency and indestructibility1 and still find a limited application4 ,they are chiefly as follows3-- ,cruleum--a mixture of the oxides of cobalt and tin4 ,cobalt blue--a mixture of the oxides of cobalt and alumina4 ,smalts--a double silicate of cobalt and potash4 ,c,,ruleum4--,this is a light-blue slightly greenish colour1 with no purple tendency in artificial light4 ,it is non-granular1 covers well1 mixes with water or oil1 and is a good artists' colour for sky effects4 ,it is permanent in strong sunlight and impure atmosphere1 and resists acids and alkalies at normal temperatures4 ,hot hydrochloric acid dissolves it1 and addition of water to the pale blue solution produces a violet red2 evaporation to dryness restores the original pigment4 ,the green tint of a nitric acid solution is due to iron and nickel impurites4 ,dilute sulphuric acid causes partial decomposition of cruleum1 but it is proof against caustic potash1 acetic acid1 and concentrated sulphuric acid4 ,its composition is given as ,cobalt oxide #ahff ,tin oxide #diff ,silica and sulphate of lime #cafh ------ #ajjjj ,there are several methods of preparing cruleum3-- 7#a7 ,a solution of stannate of potash is added to one of cobalt4 ,a blue precipitate is thrown down1 which1 on washing1 becomes first light-red and then brown4 ,when calcined at a white heat it assumes a blue colour4 7#b7 ,a solution of stannate of soda is mixed with a solution of nitrate of cobalt1 and the resulting precipitate calcined to bright redness forms a blue pigment4 7#c7 ,solutions of cobalt and tin are mixed and precipitated by soda1 the precipitate washed free from soda being calcined as in all the other cases4 ,the silicate of soda is the most satisfactory sodium salt for a precipitant4 ,,cobalt ,,blue4--,this rich pure blue pigment is not alone permanent1 but actually develops its full intensity only after exposure to the air4 ,with age1 however1 it acquires a greenish tendency1 and in artificial light it inclines to a violet tint4 ,it is proof against acids and alkalies1 and mixes particularly well with water4 ,in combination with other pigments it is unaltered and has no effect on them4 ,its tones are different from those of ultramarine4 ,it slowly decomposes when heated in strong sulphuric acid1 yielding a violet solution and a white precipitate1 which latter dissolves and affords a blue liquid on dilution with water4 ,it consists principally of about #hj per cent4 alumina1 and #ae per cent4 oxide of cobalt4 ,there are several ways of preparing it3-- 7#a7 ,by ,thnard's original process1 roasted cobalt1 from ,tunaberg1 ,sweden1 is dissolved under heat in an excess of nitric acid4 ,the solution1 evaporated nearly to dryness1 is boiled in water1 and the deposit of arseniate of iron is filtered out4 ,into the filtrate is poured a solution of basic phosphate of soda1 which throws down a precipitate of basic phosphate of cobalt1 varying in hue from violet to pink4 ,this precipitate is washed on a filter1 and1 while still gelatinous1 #a lb4 of it is intimately mixed with #h lb4 of hydrated alumina1 recently precipitated by ammonia from a solution of potash-alum4 ,the mass is first dried to brittleness and then calcined in a covered clay vessel for half an hour at a cherry-red heat4 ,the resultant blue pigment is stored in glass receptacles4 ,the preparation of the gelatinous alumina is conducted as follows4 ,the potash-alum is dissolved in at least three times as much water as is necessary1 and is then precipitated by an abundant excess of ammonia1 with frequent stirring4 ,when settled1 the supernatant liquor is siphoned off1 and the precipitate is thoroughly washed several times on a filter4 ,thnard blue will vary in tint according to the proportions of alumina used4 ,a pure colour is obtained with #d-e parts alumina to #a of phosphate of cobalt2 a greenish hue with equal parts of alumina and cobalt salt2 and almost any intermediate tone by varying the proportions between these limits4 7#b7 ,to #af parts of gelatinous alumina add #a part of arseniate of cobalt1 obtained by precipitating the solution of cobalt by arseniate of potash4 7#c7 ,a richer and more velvety blue is got by using oxide of cobalt and substituting phosphate of lime for the alumina 7,boullai-,marillac74 7#d7 ,binder's process is as follows3--,dissolve by boiling #f lb4 alum1 free from iron1 in a leaden or earthenware vessel1 and filter it into a vat #e ft4 high and #c ft4 across1 one-third full of clean water4 ,precipitate the alumina by solution of potash1 fill up the vat with water1 settle1 decant the clear liquor1 and wash repeatedly till barium chloride gives no precipitate4 ,dissolve lb4 sesquioxide of cobalt in #a lb4 hydrochloric acid at #bb ,b41 and evaporate to dryness4 ,dissolve the residue in #c lb4 hydrochloric acid1 and pass a stream of sulphuretted hydrogen through it1 to throw down any foreign metals4 ,filter clear1 evaporate again to dryness1 and dissolve the residue in enough water to produce #d-e lb4 of solution4 ,next precipitate the cobalt solution 7#c to #f lb41 according to depth of tint required7 by ammonia1 avoiding excess4 ,wash the precipitate1 and add it to the water1 holding the gelatinous alumina in suspension1 stirring thoroughly for an hour4 ,a reddish tint in the supernatant liquor shows that some of the cobalt has been dissolved4 ,add a little ammonia1 and allow the precipitate to settle4 ,decant and add new waters repeatedly4 ,finally collect on a fine filter cloth1 drain1 press1 stove dry1 and calcine for #b-b hours at red heat in clay crucibles3 then cool1 grind first in a mill and then on a slab1 and sift4 ,,smalts4--,this pigment has not maintained its position in competition with artificial ultramarine4 ,formerly it was very largely used to correct the yellow tone of cottons1 papers1 and pottery4 ,it has a pale violet-blue tint1 which1 however1 is not constant in artificial light4 ,being a silicate it is very permanent1 and proof against the action of acids1 alkalies1 and sunlight1 besides being inert when mixed with other pigments4 ,it can be used with either water or oil as a medium1 but is not a successful paint owing to its weak colouring power4 ,it is virtually a double silicate of cobalt and potash1 or a cobalt glass1 containing a few impurities1 of which the chief are aluminium1 iron1 and lead oxides4 ,the colour varies somewhat according as these impurities fluctuate1 and the finest ground sample is always the palest4 ,it is hardly ever adulterated1 and the chief point to secure is that it be ground to the finest possible degree4 ,its manufacture is most extensively and successfully carried on in ,saxony4 ,the raw materials used are cobalt speiss 7an arsenide of cobalt and iron71 potash1 and sand4 ,the ore is broken up into convenient sized pieces and roasted at red heat in a reverberatory furnace provided with a tall shaft for discharging the sulphurous and arsenical fumes at a high altitude4 ,when the evolution of these fumes has ceased and the mass begins to assume a pasty consistence1 the roasted ore is removed from the furnace1 cooled1 reduced to a fine pulverulent condition 7then known as 8zaffre07 and passed through a silken sieve4 ,should it be necessary1 ,illustration3 ,fig4 #ab4--;,,furnace ,,for ,,roasting ,,cobalt ,,ores4 the cobalt ore is first spalled and hand-picked to remove the ores of foreign metals which are associated with it2 and then reduced to a very fine state in an edge runner or mortar mill1 and freed from earthy impurities by washing4 ,the concentrated ore is then dried and dead-roasted in small charges at a time 7about #d cwt47 in a specially designed reverberatory furnace such as shown in ,fig4 #ab1 of which a is the hearth on which the ore is spread2 b1 the fireplace1 the products of combustion from which pass over the ore on the hearth1 and thence into the flues c1 which repeatedly circle round the furnace so as to provide abundant opportunity for the arsenious oxide derived from the combustion 7oxidation7 of the arsenic in the ore to condense2 this highly poisonous arsenious oxide is collected in a solid form from the flues at convenient intervals by means of the doors d4 ,the ore is charged and discharged at the door e4 ,the roasting should not be carried to such a point that the whole of the sulphur and arsenic are removed when making smalts1 as by leaving a portion of these substances in the ore at this stage1 the ultimate purification is better accomplished4 ,the next stage is to fuse the roasted ore with potash and silica so as to form a blue glass4 ,the proportions in which the ingredients are mixed depend upon the depth of colour in the zaffre operated upon and the tint desired in the finished smalts2 hence it is always determined by a preliminary experiment1 and is then most carefully adhered to1 each material being accurately weighed out4 ,only the best potash can be used1 as it must be quite free from soda1 and iron or other metal2 the effect of soda is to render the blue greenish tinted4 ,quartz affords the requisite silica1 and is hand-picked to ensure freedom from alumina1 iron1 and lime1 which import dullness into the colour1 and then ground to a fine powder in an edge runner mill4 ,the duly weighed quantities of the several ingredients are intimately mixed in wooden or cement lined vessels1 so as to preclude the possibility of any metallic iron finding its way in2 and as a further protection against this risk a little white arsenic is often added so that the iron may be carried down in the regulus which is formed during the fusion in the crucible4 ,these crucibles are of refractory earthenware quite free from lime1 and measure about #ah inches across at top1 gradually diminishing to #ad inches at bottom1 so that an ordinary charge is about cwt4 ,they are placed in rows in a furnace which generally bears a close resemblance to a glass furnace1 the operation being very similar4 ,the form of furnace common in ,saxony1 where most of the smalts is made1 is shown in ,fig4 #ac4 ,by means of a series of openings a in the walls of the furnace the pots b are introduced on to the hearth of the furnace1 whereupon the openings a are bricked up again and remain closed during the operation4 ,the ingredients are charged into the pots b ,illustration3 ,fig4 #ac4--;,,furnace ,,for ,,making ,,smalts4 by means of long iron ladles which are introduced through the small square apertures c1 which can be temporarily closed by a half-brick or other simple article4 ,the fire is then lit in the fireplace d1 and the products of combustion circulate around the pots b1 and finally escape at the orifices e at the top of the furnace into flues leading to the chimney f4 ,after about #h hours' firing fusion commences in the pots1 whereupon the contents are thoroughly stirred by rods inserted through the working holes c4 ,the temperature is then increased till a white heat is attained1 this being necessary for the formation of a glass4 ,the fused mass is repeatedly sampled1 and when it has become quite homogeneous1 and the regulus or speiss containing the iron1 antimony1 bismuth1 arsenic1 copper1 nickel1 sulphur and other impurities has completely separated itself and collected at the bottom of the pots1 the blue glass is ladled out and dropped at once into cold water1 by which it is disintegrated and rendered very brittle ready for the subsequent grinding4 ,the regulus is then drawn off from the pots through holes provided for the purpose1 and removed by the orifices g1 after which the pots are ready for another charge4 ,they ordinarily remain serviceable for about six months4 ,the grinding needs to be done with great thoroughness1 and is accomplished partly by stamps and partly by edge-runner mills in the presence of water4 ,the particles as reduced are floated off by the water to a series of settling tanks communicating one with another4 ,the portion which settles in the first of the series is too coarse for use1 and is returned to the edge-runner for further grinding2 while the portion in the last of the series possesses such a weak colour that it is rejected1 or put into the crucible to undergo a second fusion4 ,the selected portions are dried ready for the consumer4 ,copper ,blues4--,these form an unimportant class1 being unstable and not endowed with great colouring power4 ,their tint is pale and greenish1 and though opaque in water1 they are not particularly so when mixed with oil4 ,exposed to the action of sulphur or its compounds1 whether present as sulphuretted hydrogen in the air1 or in combination with a metal1 forming another pigment with which they may be mixed1 copper blues undergo an important chemical change1 the carbonates and oxides of copper being converted into the sulphide1 which is black4 ,under the influence of heat too the blue carbonate will lose its carbonic acid1 and be turned into the black oxide4 ,ammonia and the acids dissolve them1 but other alkalies are resisted until heat is applied4 ,the chief kinds of copper blue are ,bremen blue1 cruleum1 lime blue1 mountain blue1 ,pligot's blue1 and blue verditer4 ,,bremen ,,blue4--,this is a more or less pure hydrated oxide of copper1 varying in its qualities according to the method of preparation4 ,when made by precipitating a neutral salt of copper from solution1 it forms a dense and compact mass2 whereas a porous and pulverulent pigment results when basic and insoluble copper salts are treated with alkalies4 7#a7 ,the foundation of the manufacture of this colour was waste copper scrap1 such as ship's sheathing1 from which1 in various ways1 was prepared a basic chloride or oxy-chloride4 ,some of the methods adopted were3--7a7 #ajj lb4 scrap copper1 #ii lb4 powdered sulphate of potash1 and #ajj lb4 salt1 moistened with clean water2 7b7 #ajj lb4 copper fragments1 #fj lb4 salt1 and #cj lb4 diluted sulphuric acid 7#c volumes of water to #a of acid72 7c7 a solution of copper oxide 7scales7 in pure hydrochloric acid poured over the scrap copper4 ,the method 7a7 produces a chloride of copper which1 in contact with more metal1 becomes a sub-chloride2 this1 absorbing more oxygen from the air1 is converted into the basic green 8oxide0 of the factories4 ,by the 7b7 process1 the hydrochloric acid set free1 and the atmospheric oxygen produce the same result4 ,in the 7c7 process a similar effect is obtained4 ,it is of primary importance that no trace of this sub-chloride of copper shall be allowed to remain1 as it undergoes decomposition by caustic alkalies1 and throws down an orange-yellow sub-oxide of copper4 ,hence it has sometimes been the practice to prepare the basic oxy-chloride twelve months in advance1 and to stir it frequently before use4 ,complete oxidation1 however1 can be as satisfactorily accomplished by alternately wetting and completely drying the mass4 ,an interesting phenomenon takes place during the transformation of this green magma into a hydrated oxide of copper4 ,on this magma being introduced by degrees into a caustic potash or soda lye of about #bb ,b41 the thoroughly washed and dried product is exceedingly fine1 with great covering power1 and deepens on addition of a little water4 ,when the magma is diluted with an equal volume of water1 and the mixture at once poured into an excess of caustic lye1 with constant agitation1 a few minutes' rest will suffice for the mass to assume a most compact consistence4 ,the colour thus produced1 when washed and dried1 is much lighter in colour1 and has less body4 ,a blue derived from any of these products is unsatisfactory as regards freshness and intensity of colour2 whereas by adding a small quantity of concentrated solution of sulphate of copper to the magma before treating it with the alkaline lye1 apparently a highly basic sulphate of copper is produced which deepens the colour4 ,a pigment with good body can be made in the following manner4 ,to #ajj lb4 of the thick magma of basic oxychloride add a concentrated solution of #g lb4 sulphate of copper1 and then #dj lb4 of a concentrated caustic lye 7#cb-cf ,b171 with vigorous and rapid stirring1 finally adding about #aej lb4 of caustic lye at #bj ,b4 ,when the decomposition is quite complete1 the precipitate is carefully washed1 passed through a fine hair sieve1 and filtered4 ,drying is effected at a low temperature1 to ensure that the hydrated state of the oxide is not changed2 and the air of the drying chamber must be free from acid or sulphuretted vapours4 7#b7 ,if neutral nitrate of copper be decomposed by an insufficiency of potash carbonate solution1 the flocculent precipitate of copper carbonate resulting is by degrees transformed into a sub-nitrate of copper1 which goes down as a heavy green powder4 ,on treating this sub-nitrate with a potassic solution of zinc oxide1 a dark-blue coloured pigment is formed1 which is apparently a zincate of copper mixed with a very small proportion of a highly basic nitrate of copper4 ,though very light it has great covering power4 ,in practice the manufacture is conducted as follows4 ,calcine copper scales in a reverberatory or muffle furnace till the sub-oxide is entirely converted into protoxide1 or until it dissolves in nitric acid without evolving red nitrous fumes4 ,heat is applied to the solution of nitrate of copper1 which is decomposed by addition of a clear solution of potash carbonate4 ,after effervescence has subsided1 small doses of potash carbonate solution are added till but little undecomposed copper is left4 ,this residue is recovered by decanting the clear liquor1 and repeatedly washing the green precipitate with small quantities of clean water1 collecting all the washings1 and finally precipitating by potash solution4 ,on introducing the green carbonate of copper into a new solution of copper nitrate1 it is transformed into a basic salt4 ,crystals of nitrate of potash are obtained by evaporating the previous liquors4 ,to obtain an economic solution of zinc oxide1 clippings of metallic zinc are treated with a solution of caustic potash or soda in a cast-iron vessel4 ,the immediate result is a disengagement of hydrogen1 and saturation of the alkali with zinc oxide1 which behaves as an acid4 ,the cleared liquor serves for decomposing the basic nitrate of copper4 ,the pigment produced is a handsome blue1 and the potash liquor can be evaporated down till it yields crystals of saltpetre4 ,the economy of this method lies in producing nitric acid cheaply from soda nitrate and obtaining saltpetre as a bye-product4 7#c7 ,an inferior and cheaper pigment is made in the following manner4 ,to a solution of copper sulphate add one of barium or calcium chloride till a white precipitate ceases to go down1 and from the cleared blue liquor all the copper is precipitated by addition of fresh milk of lime4 ,usually the weight of quicklime required is #bj per cent4 of the copper sulphate4 ,the settled1 washed1 and dried precipitate is the pigment desired4 ,the cleared barium or calcium chloride solution may be used anew as a precipitant for the next batch4 ,c,,ruleum4--,this name has been given to the beautiful blue pigment used in ,egyptian and ,pompeian mural paintings1 and exhibiting the same bright blue after #ajjj years' exposure to the weather as when first used4 ,its composition has been given by ,fouqu as approximately #fc per cent4 silica1 #ba per cent4 copper oxide1 and #ad per cent4 calcium oxide1 and he regards it as a double silicate of copper and calcium4 ,it is supposed to have been produced by fusing together copper ore1 sand and lime1 but experiments have not yet resulted in a successful imitation of the pigment1 a difficulty being encountered in the fact that if too high a temperature be permitted1 destruction of the blue colour ensues1 and a green glass results instead4 ,this is unfortunate1 as its remarkably bright and stable hue would make it very popular if it could be manufactured at a moderate cost4 ,it withstands sulphuretted hydrogen1 and even prolonged boiling with any of the acids or alkalies4 ,,lime ,,blue4--,this pigment is essentially a mixture of hydrated oxide of copper and calcium sulphate4 ,it resists the action of alkalies in the cold1 but turns black when boiled in caustic soda1 and is completely soluble in hydrochloric acid4 ,ultramarine has largely1 if not entirely usurped its place4 ,there are several ways of making lime blue3-- #a4 ,any soluble copper salt the acid of which will make a soluble salt with lime is suitable1 the only precaution necessary being that if in the decomposition of the copper and lime salts1 the combination of the whole of the sulphuric acid with the lime is not attained1 there should be an excess of copper sulphate in the liquor rather than of the lime salt4 ,the resulting copper solution1 containing very little lime sulphate1 is settled in a cool place for #bd-cf hours1 filtered1 and diluted with clean water down to about #ah ,b4 ,meantime a milk of lime is prepared with very white and well-burned lime1 slaked and mixed with abundance of pure water1 and kept stirred for a long time in a lead-lined vat4 ,after a short rest to permit sand1 c41 to precipitate itself1 the milk is drawn off1 and left to settle in lead-lined or copper pans4 ,the deposit is collected1 ground in a mill where contact with iron is impossible1 and passed through a very fine sieve4 ,the mixture of lime and copper solution is made in the proportion of #ajj lb4 dry lime with #age dry copper salt1 if the most intense coloration is desired1 but the proportion of lime may be much increased without detriment to the pigment beyond lessening its intensity of colour4 ,after complete settlement of the precipitate1 the clear liquor is decanted2 the pigment is carefully washed with clean soft water1 and drained on filter cloths till it is of a convenient consistence forming a green paste4 ,a definite weight of this paste calculated on the dry pigment is taken for further incorporation1 consequently it is first necessary to ascertain how much water is in the paste4 ,usually it amounts to #ge per cent41 and on this basis #e lb4 of the paste are stirred up with #a gal4 clean water in a lead-lined vat1 with addition of lb4 wet lime under constant agitation4 ,subsequently pint of clear solution of best potash at #ae ,b4 is well stirred in1 and the mixture is immediately taken to the mill and most thoroughly ground4 ,further1 for each #aj gal4 of green paste is prepared a clear solution of #a lb4 pure salammoniac in #b gal4 water and another solution of #b lb4 copper sulphate in #b gal4 water4 ,the liquid paste is drawn off from the mill into a stoneware vessel1 and the two solutions of salammoniac and copper sulphate are immediately added4 ,after complete agitation and combination1 the mixture is left for #d or #e days to settle1 and turned into a lead-lined vat1 where it is repeatedly washed with clean waters until turmeric paper is not discoloured4 7#b7 ,precipitation of copper sulphate by excess of thin milk of lime in the cold1 followed by washing and drying1 will give a lime blue which will dry without turning black4 ,or #ajj lb4 of the copper sulphate may be treated with a milk of lime prepared from #cj lb4 quicklime and addition of #ab lb4 salammoniac4 ,when the liquor has become colourless1 the pigment is prepared from the precipitate2 but the lime should be ground after slaking1 and the milk of lime left to stand for some days1 before use4 ,the salammoniac seems to be essential to the production of a pure full blue4 ,milk of lime poured drop by drop into the ammoniacal copper solution gives a precipitate which redissolves on agitation1 and remains long in solution under heat1 but finally throws down a permanent precipitate1 while the liquor on standing gives beautiful blue crystals4 ,from experiments it appears that out of seven atoms of copper sulphate in the liquor1 five are precipitated by milk of lime and the last two are decomposed by ammonia4 ,a greater proportion of lime will produce a precipitate holding a certain quantity of less valuable pigment4 ,a smaller proportion of lime yields a finer coloured and more crystalline pigment1 because it crystallises partly in the excess of solution1 so that by incomplete decomposition a smaller yield of superior pigment is obtained4 ,the proportions necessary for formation of the colour are #g equivalents of copper sulphate1 #e of lime1 and #b of ammonia1 and if the #b equivalents of ammonia be replaced by #b of lime and #b of salammoniac1 the proportions furnishing the best colour will be #ajj lb4 copper sulphate1 #bd lb4 lime1 and #bb lb4 salammoniac4 ,both caustic soda and caustic potash produce a fine blue precipitate in a solution of ammoniacal copper sulphate with excess of ammonia1 but the liquor decolorises only on evaporation of the ammonia4 ,the precipitate becomes lighter-hued the more it is washed1 and consists of hydrated oxide of copper with a little carbonic acid2 it does not turn brown even when heated in presence of excess of potash or soda4 ,moreover the presence of ammonia renders the hydrated oxide of copper much more permanent4 ,the composition of this pigment is given by ,gentele as #cc per cent4 copper oxide1 #bc sulphuric acid1 #af lime1 and the remainder water1 c4 ,,mountain ,,blue ,,or ,,azurite4--,this natural blue pigment consists essentially of a basic carbonate of copper1 and is found in quartz rocks in ,england1 ,france1 ,bohemia1 ,hesse1 ,saxony1 the ,tyrol1 and ,siberia4 ,it affords a rich sky-blue paint of a permanent character1 but being comparatively costly is not largely employed4 ,its composition is about #fi per cent4 copper oxide1 #be carbonic acid1 and #e water4 ,the only preparation needed is exceedingly fine grinding4 ,p,,ligot ,,blue4--7#a7 ,whereas the hydrated oxide of copper precipitated from a solution of a salt of copper by excess of potash or soda rapidly blackens even though washed with cold water1 ,pligot obtains a blue hydrated oxide which resists boiling and heating at #bab ,f4 ,he uses any soluble copper salt1 but preferably the sulphate4 ,a very dilute solution of the copper sulphate is treated with ammonia in excess 7aqua ammoni or an ammoniacal salt7 and precipitated by soda or potash4 7#b7 ,on adding water in excess to a slightly ammoniacal solution of copper nitrate1 the same pigment is obtained4 7#c7 ,a mixture of #gc parts silica1 #af oxide of copper1 #h lime1 and #c soda1 is fused together at a temperature not much exceeding #hjj ,f4 ,at higher temperatures there is risk of the pigment turning black4 ,,verditer4--,this sky-blue and not very durable pigment1 used in water-colour painting1 closely resembles ,bremen blue 7see p4 #cd7 in composition and manufacture4 ,it consists chiefly of copper carbonate1 mixed with a lesser proportion of hydroxide1 sulphate1 or oxide1 and occasionally a small quantity of sulphate of lime2 and is most satisfactorily prepared from copper chloride or nitrate1 though almost any salt of copper may be used4 ,the mode of fabrication varies4 7#a7 ,to a solution of the nitrate or sulphate is added one of potash or soda carbonate so long as any precipitate is formed1 and this precipitate1 when filtered and washed1 is treated with a weak caustic soda solution4 7#b7 ,a hot solution of chloride of lime is added to a hot solution of sulphate of copper at #fb ,tw4 till the precipitate ceases to go down4 ,the solution of chloride of copper which constitutes the liquor is filtered off1 diluted with water to about #ca ,tw41 and treated with repeated small doses of slaked lime ground exceedingly fine in water till no more copper is precipitated4 ,the resulting green paste is drained1 filtered1 washed1 and put into wooden vats2 here #h lb4 of lime paste and #e pints of potash carbonate solution at #be ,tw4 are added for every #gj lb4 of dry colour contained in the green paste1 the whole mass being thoroughly agitated1 then allowed to rest till the development of the required shade is accomplished1 when it is filtered1 washed1 and dried4 7#c7 ,in some ,german works the final green paste as prepared in 7#b7 is put into air-tight vessels1 and a solution of #c lb4 ammonium chloride and #d lb4 sulphate of copper in #g gal4 of water is introduced for each #gj lb4 of dry colour in the green paste4 ,after complete admixture of all the ingredients1 the receptacles are fastened up for several days so that the reactions may proceed out of contact with the air1 and finally the pigment is removed1 washed1 and dried for use4 ,indigo4--,the well-known blue colouring matter termed indigo is produced by a great number and variety of plants1 distributed throughout all the tropical countries of the globe4 ,commercially1 it is obtained chiefly from species of ,indigofera1 as ,i4 tinctoria1 the cultivated species of ,india1 furnishing the chief article of commerce1 found also in ,madagascar1 ,st4 ,domingo1 c42 and ,i4 ,anil1 in the ,punjab1 ,w4 ,indies1 and on the ,gambia river4 ,some is also obtained from ,i4 argentea1 in ,africa and ,america3 ,i4 ,caroliniana2 ,i4 disperma1 the cultivated plant of ,spain1 ,america1 and some of the ,e4 ,indies2 ,i4 crulea1 the 8black indigo0 of ,india2 ,i4 glauca1 in ,egypt and ,arabia2 ,i4 pseudo-tinctoria1 cultivated in some parts of the ,e4 ,indies1 and said to yield the best dye2 ,i4 cinerea1 ,i4 erecta1 ,i4 hirsuta1 and ,i4 glabra1 in ,guinea4 ,considerable local supplies are obtained from the following plants3--,isatis tinctoria1 in ,europe and ,china 7see ,woad72 ,i4 indigotica1 cultivated in some parts of ,china2 ,amorpha fruticosa1 in ,carolina2 ,baptisia tinctoria1 wild1 in the ,united ,states2 ,gymnemia 7,asclepias7 tingens1 in ,burmah2 ,polygala tinctoria1 in ,arabia2 ,polygonum ,chinense1 ,p4 tinctorium1 ,p4 perfoliatum1 ,p4 barbatum1 ,p4 aviculare1 in ,china and ,japan1 and introduced into ,belgium2 ,ruellia indigotica1 largely cultivated in ,assam1 as well as in ,india1 and at ,che-king1 in ,china2 ,tephrosia tinctoria1 and ,t4 apollinea1 in ,india and ,egypt2 ,wrightia tinctoria 7,nerium tinctorium71 the ,palas indigo of the ,carnatic4 ,the cultivation of indigo 7chiefly ,indigofera tinctoria7 is very extensively carried on in ,india1 especially in the district included between #bj and #cj ,n4 lat4 ,the soil best suited for the culture is a rich loam1 with a subsoil which is neither too sandy nor too stiff2 alluvial soils give the best returns1 but good crops are sometimes raised on higher grounds4 ,the land is ploughed in ,october-,november1 after the rains2 the seed1 about #ab lb4 to the acre1 is sown in ,february-,april4 ,too rapid growth diminishes the yield of dye4 ,in ,july-,september1 the plants are in full blossom1 and the harvest takes place4 ,the preparation of the dyestuff may be performed in either of two ways1 which are distinguished as the 8dry-leaf10 and the 8green-leaf0 process4 ,the latter is considered the better1 and is the more general2 it is conducted as follows3--,the flowering plants are cut down at about #f in4 from the ground1 and immediately taken to the steeping vats1 within which they are spread out and pressed down by beams fitted to the side posts of the tanks4 ,enough water is then admitted to cover the plants2 if this be delayed1 fermentation may set in and spoil the product4 ,the duration of the steeping is liable to considerable modification1 and needs much judgment and experience2 with a temperature of #if ,f4 in the shade1 #aa-ab hours may suffice2 in cooler weather1 #ae-af hours may be necessary4 ,moreover1 very ripe plants require less time than young and unripe ones4 ,the following general conditions indicate the time for suspending the maceration3--7#a7 ,the sinking of the water in the vat2 7#b7 the immediate bursting of the bubbles that arise2 7#c7 an orange tint mingled with the green1 when the surface water is disturbed2 7#d7 the emission of a sweetish1 pungent odour1 quite distinct from the raw odour of the unripe liquor4 ,at this point1 men enter the vat1 and stir up its contents either by hand or by a wooden paddle4 ,the agitation is at first gentle1 but increases as the fecula begins to separate2 this is known by the disappearance of the froth1 and by the colour of the liquor changing from green to blue4 ,the 8beating10 as it is called1 is continued for #a-c hours1 the following conditions being a guide as to its sufficiency3--7#a7 ,the ready precipitation of the fecula from a sample of the liquor1 and the madeira-wine colour of the latter2 7#b7 a brownish colour observed on dipping a cloth into the liquor1 and wringing it out2 7#c7 the appearance of a glassy surface on the liquor1 and the subsidence of the froth with sparkling and effervescence4 ,next a little pure cold water1 or weak lime-water1 is sprinkled over the surface of the liquor1 to hasten the settlement of the fecula1 which occupies #c-d hours4 ,after this1 the water is drained away from the top1 by means of plug-holes in the side of the vat4 ,the precipitated fecula is then removed to a boiler4 ,here it is made to boil as promptly as possible1 and is kept boiling for #e-f hours2 it is constantly stirred1 and skimmed with a perforated ladle4 ,after boiling1 it is run off to a straining table1 where it stays for #ab-ae hours to drain2 next it is pressed for about #ab hours1 and then cut1 stamped1 and placed to dry4 ,the ordinary dimensions of a steeping-vat are #af ft4 by #ad ft4 by #d ft4 deep2 this will contain about #ajj maunds 7#hbjj lb47 of plants1 which may yield from #dj lb4 downwards of indigo4 ,the beating-vat is less deep4 ,such are the methods of cultivation and manufacture most generally in use throughout ,india4 ,in limited districts1 however1 some modifications are in vogue4 ,on land subject to inundation1 the plants last only one year4 ,south of the ,ganges1 the seed is sown at the beginning of the rains1 and the plants remain on the ground for two years1 thus giving a double crop1 the second of which is the larger and better4 ,in very strong land1 a third crop is sometimes secured4 ,occasionally1 sesame is sown on the same ground1 and harvested before the indigo is cut4 ,small quantities of indigo are grown on poppy lands1 and irrigated4 ,the seed is sown in ,march-,april1 and the crop is gathered at the end of the rains1 in time for an opium crop to be taken off the land4 ,indigo is sometimes manufactured by collecting the fecula1 and dropping it in cakes to harden in the sun2 this is 8gaud0 indigo1 of very inferior quality4 ,the fecula is improved by boiling it in coppers and pressing it into boxes4 ,the production of the indigo blue is the result of the decomposition of the colouring principle of the plant1 which exists as a glucoside4 ,plants grown on poor soils1 and in dry climates1 yield almost the whole of this glucoside to the ordinary process of steeping and beating described above2 but plants raised on rich alluvial soil1 and in damp heat1 contain an amount of glucoside which cannot be utilised by the ordinary process4 ,in order to prevent this waste1 which causes the richest plants to give the least return1 it is necessary either to prolong the fermentation1 and raise the heat to #ie-ajj ,f41 or to add a solution of sugar or glucose to the vat-liquor4 ,olphert adopts the use of steam1 to raise the temperature of the vat to #aaa ,f41 and thus obtains #be per cent4 more colouring matter4 ,japan possesses several large factories for preparing indigo from the native ,polygonum tinctorium4 ,the plants1 #b-c ft4 high1 are cut into three parts1 the uppermost being the most valuable4 ,the best dye is made from the leaves alone1 which1 after a few hours' exposure to air and sun1 are placed in straw bags4 ,they are afterwards removed from the bags and moistened with water1 which must be proportioned with the greatest exactitude4 ,they are then spread upon1 and covered by1 mats1 for a few days1 after which the sprinkling is repeated4 ,the process continues for about #hj days1 the moistening being renewed about #be times for the best leaves1 and #i for the inferior4 ,after this fermentation1 the leaves are pounded in wooden mortars for two consecutive days1 by which they are reduced to a pulp2 this is then formed into balls of dark-blue colour4 ,the central provinces of ,java yield large quantities of indigo1 which are exported to ,holland1 and thence widely distributed4 ,the indigo prepared by the natives is of an indifferent quality1 in a semi-fluid state1 and contains much quicklime2 but that prepared by ,europeans is of a very superior quality4 ,an inferior variety1 having smaller seeds1 and being of quicker growth1 is usually planted as a second crop on land where one rice crop has been raised4 ,in these situations1 the plant rises to a height of about #c ft4 ,it is then cut1 and the cuttings are repeated three1 or even four times1 till the ground is again required for the annual rice crop4 ,but the superior plant1 when cultivated on a naturally rich soil1 not impoverished by a previous heavy crop1 attains a height of #e ft41 and grows with the greatest luxuriance4 ,the plants intended for seed are raised in favourite spots1 on the ridges of rice-fields in the neighbourhood of the villages1 and the seed of one district is frequently exchanged for that of another4 ,that of the rich mountainous districts1 being esteemed of best quality1 is occasionally introduced into the lowlands1 and is thought necessary to prevent that degeneration which would be the consequence of cultivating for a long time the same plant upon the same soil4 ,the climate1 soil1 and state of society of ,java seem to offer peculiar advantages for the extensive cultivation of this plant4 ,the periodical droughts and inundations of the ,bengal provinces are unknown in ,java1 where the plant1 in favoured situations1 may be cultivated nearly throughout the whole year1 and where it would be secure of a prolonged period of that kind of weather necessary for the cutting4 ,the dye is prepared in a liquid state by the natives1 by infusing the leaves with a quantity of lime2 in this state1 it forms by far the principal dye-stuff of the country4 ,the indigos prepared in ,java by ,sayers's process are of unusually high and constant quality4 ,they contain an average of #gj per cent4 of indigotine1 and a minimum of #fe-ff per cent42 and an average of #bgg per cent4 of ash4 ,ordinary commercial indigos seldom attain #fe-ff per cent4 of indigotine2 and their ash averages about #af per cent4 ,the ,philippines produce considerable quantities of indigo1 the best coming from ,luzon4 ,the plants suffer from locusts and storms1 but the cultivation is very profitable4 ,the yield of indigotine is large1 but the preparation is conducted in such a primitive manner that the value of the product is much deteriorated4 ,in many parts of ,africa1 as ,sierra ,leone1 ,liberia1 ,abeokuta1 the ,niger valley1 ,natal1 ,cape ,colony1 ,tunis1 and the ,soudan1 species of indigo plants are found in a wild state1 and from them the natives prepare an inferior dye-stuff4 ,in some of the ,s4 ,states of ,america1 notably ,s4 ,carolina1 indigo culture has been attended with more or less success4 ,the method of preparation pursued here varies but very slightly from the ordinary ,indian process1 almost the only important modification being the addition of a little oil to the liquor in the beating-vat1 when the fermentation becomes too violent4 ,the precipitated fecula is placed in coarse linen bags1 and hung up to drain4 ,the drying is finished by turning it out of the bags upon a floor of porous timber1 and working it up4 ,it is frequently exposed to the sun for short periods at morning and evening1 and is then placed in boxes or frames1 to cure till it is fit for the market4 ,several of the ,central ,american ,states have figured conspicuously as indigo producers4 ,the dye is precipitated in the beating-vat by the sap contained in the bark of ,tihuilate 7,yonidium71 ,platanillo 7,myrosma ,indica71 or ,cuaja tinta4 ,the fecula is left during the night2 and1 on the following day1 is boiled1 filtered1 pressed1 and sun-dried4 ,in most districts1 the cultivation is declining1 partly owing to the carelessness exhibited in the preparation of the dye4 ,indigo is judged commercially by its lightness1 by a copper gloss on the surface1 and by exhibiting no foreign ingredients when broken4 ,there are several ways of testing it chemically1 to ascertain the exact proportion of indigotine present2 one method is as follows3--,finely pulverised indigo1 #a part2 green copperas1 #b parts2 and water containing #aj per cent4 of caustic soda1 #bjj parts2 are well boiled in a flask1 and left to cool4 ,the clear liquor is exposed in shallow vessels to the air1 when the soluble indigo is oxidised1 and precipitated as pure indigotine4 ,the residue in the flask is thus treated three times2 the whole indigotine is then collected on a filter1 dried1 and weighed4 ,the consumption of indigo is still very large4 ,artificial indigo has not1 as yet1 been manufactured on a commercial scale1 nor at a commercial price2 but it has been produced1 in the laboratory1 from coal-tar derivatives1 and further experiment may reveal a process for preparing the article at a sufficiently low price to compete with the natural colour4 ,several preparations of indigo are in use3--7#a7 ,sulphopurpuric acid1 phenicine1 or indigo-purple1 is made by mixing #a part of indigo with #d parts of sulphuric acid 7sp4 gr4 #ahde71 and heating for -#a hour2 the acid mass is thrown into #dj-ej parts of water1 when the purple falls down2 it is collected on a filter1 and washed with dilute hydrochloric acid4 7#b7 ,sulphindigotic acid is prepared by mixing indigotine1 #a part1 with sulphuric acid 7sp4 gr4 #ahde7 #f parts2 the operation must be performed in a leaden vessel1 cooled outside1 and the indigo must be added by degrees1 to avoid heating2 the mixture is then left for #h days1 when the conversion will be complete4 ,fuming or anhydrous acid may be used1 in less proportion1 but the reaction is more difficult to manage4 ,weaker acid will require a longer period1 say a month for 8brown acid0 7#ade ,tw474 7#c7 ,sulphindigotic acids are transformed into neutral paste1 or 8carmine10 by neutralising with carbonate of soda1 and washing the paste1 on a woollen filter1 with a solution of chloride of sodium 7common salt74 ,manganese ,blue4--7#a7 ,kuhlmann found a blue mass of manganate of lime in furnaces used for making calcium chloride by calcining a mixture of chalk and residues from chlorine making4 ,the formation of this beautiful coloured manganate he attributes to the decomposition of the calcium chloride by steam1 and to a certain solubility of the lime in undecomposed calcium chloride4 ,unsuccessful attempts to reproduce this result were apparently due to the lime not being under such favourable conditions for acting upon the manganese oxide as when it is in solution in the calcium chloride4 ,as accidentally produced in reverberatory furnaces1 the manganate of lime is of an ultramarine tint1 and is insoluble in water though not permanent under its influence2 it is acted upon by the weakest acids4 7#b7 ,bong has proposed several formul for making manganese blues1 the ingredients in each case being heated to redness in an oxidising atmosphere1 taking special care to avoid iron4 ,the following are his recipes3--7a7 #f parts soda ash1 #e of calcium carbonate1 #c of silica1 and #c of manganese oxide2 7b7 #h of barium nitrate1 #b of kaolin1 and #c of manganese oxide2 7c7 #h of barium nitrate1 #c of silica1 and #c of manganese oxide4 ,the tint can be varied from violet to green by altering the proportions4 ,prussian ,blue4--,this blue owes its colour to a combination of iron and ferrocyanogen4 ,the commercial products vary very much in tint1 depth of colour1 covering power1 and solubility4 ,they are used for a variety of purposes1 nearly all of which require the blue to have some property different from what it should have for other uses4 ,for some purposes a green shade blue is wanted1 for others a violet shade blue2 some users want the blue to be soluble in water1 others for it to be soluble in oxalic acid1 others require it to be insoluble4 ,ordinary ,prussian blue is insoluble in water1 acids1 and alkaline salts2 bleaching powder has no action on it1 and therefore it is largely used for tinting paper4 ,it is capable of resisting acids2 but alkalies1 such as caustic soda1 caustic potash1 the carbonates of the same metals1 lime and ammonia1 decompose it1 oxide of iron and a solution of a ferrocyanide of the alkali being formed1 the decomposition being shown by a change of colour from blue to a reddish brown4 ,on this account ,prussian blues cannot be used for colouring soaps and alkaline products1 or used as a pigment in distemper painting along with lime4 ,the change of colour1 from blue to brown1 by the action of alkalies1 distinguishes this blue from other blues4 ,prussian blues require to be tested for their solubility in oxalic acid1 by taking about #bj gr4 of the blue1 mixing with #a oz4 of water and #bj gr4 of oxalic acid1 in which a good blue ought to dissolve completely4 ,some brands are soluble in strong hydrochloric acid while others are not4 ,it is decomposed by boiling sulphuric acid1 and turned green by boiling nitric acid4 ,for all the ordinary uses of a pigment ,prussian blue is quite durable1 and possesses a depth of colour and a definite tint which is proof against the destructive agencies of light and air2 and though its covering powers are not great1 it is one of the most important blue pigments in use4 ,when a salt of the higher oxide of iron is added to a solution of yellow prussiate of potash 7or ferrocyanide of potassium7 a blue compound is formed which is called ,prussian blue4 ,but this is not the method adopted for its commercial manufacture4 ,in that case a ferrous salt1 the proto-sulphate of iron1 is added to a potassium ferrocyanide solution1 the result of which is that a dirty bluish white precipitate is thrown down4 ,on adding to this a little solution of bichromate of potash and sulphuric acid1 the full deep blue is obtained4 ,this is the industrial method of manufacturing ,prussian blue4 ,yellow ,prussiate4--,the first step is the preparation of the yellow prussiate of potash4 ,the manufacture of this substance1 although an industry of considerable importance1 is comparatively little understood1 either from a scientific or a practical point of view4 ,at all events1 many prussiate makers seem completely at sea with regard to the most favourable conditions for carrying on the manufacture1 and there can be no doubt that in many cases great waste occurs1 through ignorance of the various reactions which take place during the process4 ,the raw materials usually consist of carbonate of potash1 iron filings or turnings1 and organic matters containing carbon and nitrogen--such as dried blood1 woollen rags1 horn1 hair1 leather scraps1 c4 ,the most suitable substances for use are1 of course1 those containing the largest proportion of nitrogen4 ,the following are the percentages of nitrogen in various kinds of animal matter3-- ,horn #ae to #ag ,dried blood #ae to #ag ,woollen rags #aj to #af ,sheep shearings #af to #ag ,calves' hair #ae to #ag ,bristles #i to #aj ,feathers #af to #ag ,hide clippings #d to #e ,old shoes #f to #g ,horn charcoal #b to #g ,rag charcoal #b to #ab ,animal matters always contain more carbon than is necessary for the formation of cyanogen by combining with the nitrogen also present4 ,consequently1 when such substances are heated with pearlash1 the excess of carbon reduces a portion of the carbonate to the metallic state1 and this potassium combines with the cyanogen to produce potassium cyanide4 ,the manufacture of yellow prussiate of potash may be conveniently divided into three stages3 7#a7 ,the production of the molten mass technically known as 8metal02 7#b7 the lixiviation2 and 7#c7 the crystallisation4 7#a7 ,the 8metal0 is made by fusing animal matters with pearlash1 almost invariably with the addition of iron scrap4 ,the animal substances are sometimes used in their original condition1 whilst sometimes they are previously charred4 ,generally speaking1 however1 a judicious mixture of the fresh and charred materials has been found to give the best results4 ,the charcoal which is left on carbonising animal matters contains a certain amount of nitrogen1 decreasing in proportion as the temperature rises2 but a smaller quantity of charcoal is also thereby produced4 ,for example3 #ajj parts of rags carbonised at a certain temperature left #ge parts charcoal containing #ab per cent4 of nitrogen1 while the same rag carbonised at a higher temperature yielded #be parts of charcoal1 which contained only #b per cent4 of nitrogen4 ,the animal matters employed should not leave much ash on ignition1 as this would both thicken the mass and decompose a portion of the potash4 ,in this respect sand is specially objectionable1 for on ignition #a part will decompose #b of pearlash1 owing to formation of silicate of potash4 ,it is not necessary that the pearlash should be quite pure2 in fact1 a certain proportion of sulphate is stated to be useful1 as it is changed into sulphide by ignition with the carbonaceous materials4 ,the theory of the formation of yellow prussiate of potash may be briefly stated as follows3 ,the carbonate and sulphate of potash react with the carbon1 nitrogen1 and iron1 forming in the first instance sulphide of potassium1 which afterwards converts the iron into sulphide1 whilst potassium cyanide is simultaneously produced4 ,it should be here explained that ferrocyanide of potassium 7yellow prussiate7 is not formed during the ignition of the above mentioned materials1 but results from the lixiviation of the fused mass with water1 when the cyanide of potassium and iron sulphide decompose each other1 producing ferrocyanide and sulphide of potassium4 ,it is quite obvious that even if any ferrocyanide were produced during the process of fusion1 it would almost immediately be decomposed1 at the intense heat to which the mass is subjected1 into potassium cyanide1 iron carbide1 and nitrogen gas4 ,if any doubt were felt on this point1 the experiments of ,liebig conclusively prove that the formation of ferrocyanide takes place on dissolving the ignited mass in water1 but not previously4 ,liebig found that if the fused mixture be allowed to cool1 and then treated with moderately strong alcohol1 potassium cyanide alone is extracted1 and the residue when dissolved in water no longer yields ferrocyanide4 ,as ferrocyanide is not formed during the process of fusion1 the presence of iron in the preliminary stages may appear superfluous2 but such is not the case4 ,the presence of iron is necessary for two reasons1 firstly1 because the sulphate of potash which is generally present is converted into sulphide and bisulphide1 and these1 in the absence of iron1 would decompose some of the cyanide of potash into sulphocyanate1 thereby causing a loss of cyanogen so far as yellow prussiate is concerned2 and secondly1 because potassium bisulphide has a very corrosive action on the iron pot in which the fusion takes place4 ,when iron is present it readily decomposes any alkaline sulphides1 thereby preventing formation of sulphocyanate1 and being itself converted into iron sulphide1 which is again changed into prussiate by the action of the aqueous cyanide4 ,pear-shaped iron pots were formerly used for fusing the raw materials4 ,the arrangement now generally adopted in large ,english works consists of a series of iron pots almost hemispherical in shape1 set in brickwork1 and each heated by a separate fire and circular flue4 ,these vessels are closed by iron lids1 with apertures for the admittance of animal matters1 the aperture being at once closed by a slide after each addition4 ,through every lid there passes a vertical spindle1 carrying a set of blades for mixing the materials1 and set in motion by a suitable shaft worked by steam power4 ,instead of the ordinary iron pots1 reverberatory furnaces are often employed1 especially in ,germany4 ,the reason for this preference is1 that ordinary iron vessels are worn out in a comparatively short time1 the destructive action being greatest on the under surface of the muffle4 ,a much larger quantity of raw material can also be operated upon at one time if a reverberatory furnace be used4 ,the mode of procedure depends to some extent upon the condition of the organic materials employed4 ,if fresh1 the muffle or furnace must be left open1 so as to permit the mixture to be well and frequently stirred1 and additions to be made at intervals until eventually ammonia ceases to be evolved4 ,the furnaces are arranged in such a manner that when the carbonate of potash has once become fused the doors of the fire-place may be shut1 and no fresh firing is required during the introduction of the animal matters4 ,the molten mass is kept well stirred by means of a thick iron bar1 suspended by a chain1 and fixed in an aperture in the side of the furnace4 ,by the use of this arrangement the stirring is much more easily and thoroughly effected than is the case with the old fashioned pots4 ,ordinary reverberatory furnaces cannot be used for the fusion1 because the silica in the hearth would combine with the potash to form silicate of potash4 ,gas generators with air blast are now sometimes employed instead of ordinary fuel in the manufacture of yellow prussiate of potash4 ,several advantages are gained by operating in this manner1 especially that of permitting the regulation of temperature and the admission of oxygen1 so as to obtain an ordinary1 a neutral1 or a reducing flame1 according to requirements4 ,in the preparation of the 8metal10 for every #ajj parts of pearlash from #ajj to #abe parts of fresh animal substances are required1 together with #f or #h parts of iron in some form or other4 ,the pearlash1 or a mixture of #a part of pearlash with #b to #d parts 8blue salt0 or 8blue potash0 7this substance will be referred to later on71 is melted in the furnace and heated to bright redness1 so that the temperature of the mass may not be reduced too much by the addition of the animal matters4 ,these1 in their original condition1 or an equivalent quantity of carbonised materials1 together with the proper proportion of iron1 are then introduced--first pretty frequently1 afterwards at longer intervals4 ,each addition of animal matter causes a somewhat violent frothing and escape of combustible gases1 along with water and carbonic acid1 and the whole becomes thick--not so much owing to the introduction of solid substances as by the fall of temperature1 resulting from the production of such large quantities of gas4 ,in order to hasten the decomposition1 vigorous stirring must be applied4 ,when the reaction is at an end1 the semi-fluid mass is transferred to cast-iron dishes1 and the furnace is again filled with carbonate of potash and heated4 ,in this way four or five charges may be accomplished every day1 and the process carried on continuously4 ,the most favourable conditions for effecting the melting part of the process are attained when the heat approaches whiteness1 and a bright1 clear flame is produced as soon as the raw materials are introduced4 ,according to one authority1 woollen rags and good pearlash1 with a small proportion of waste iron1 have produced the largest yield of yellow prussiate1 although even in this case two-thirds of the total nitrogen present was lost in the form of ammonia4 7#b7 ,lixiviation4--,the fused mass1 if properly prepared1 should yield about #af per cent4 of prussiate on dissolving in water4 ,in this part of the process1 the 8metal0 when cold is broken into lumps and placed in cold water mixed with the weak lyes from former operations4 ,heat is then applied until the temperature rises to about #ahj-aij ,f41 and the liquid is stirred vigorously so as to promote rapid solution1 because some of the potassium cyanide is apt to be decomposed during lixiviation4 ,when the solution attains a density of #cj-dj ,tw4 it is left to clarify1 the heat being withdrawn4 ,the clear solution is decanted1 and evaporated in pans1 which are generally heated by the waste heat of the furnaces4 ,when it has a density of #ed ,tw4 it is run off into the crystallisers1 where it deposits the crude salt4 7#c7 ,crystallisation4--,this is a very important stage of the manufacture1 as it is the final process by which the crude prussiate is rendered sufficiently pure to be placed on the market4 ,the impure substance is dissolved in warm water until the solution stands at #ed ,tw42 after all insoluble matter has deposited1 the clear liquor is placed in the crystallising vessels4 ,these are occasionally made of wood2 but when such vessels are used1 the crystallised salt generally possesses a green colour1 which is believed to be due to the tannin present in the wood4 ,on this account cast-iron crystallisers are more frequently employed4 ,the crystallisation proceeds slowly--often going on for several weeks in large vessels4 ,the mother liquor is then drawn off1 and if not too impure is used for dissolving fresh quantities of the crude prussiate4 ,the ferrocyanide is deposited in crusts in the crystallisers2 but by hanging lumps of the solid salt in the solution1 long clusters of crystals may be obtained1 and by suspending these in fresh prussiate lyes immense crystals are produced4 ,from #ajj parts crude prussiate about #ij parts pure potassium ferrocyanide are obtained1 or sometimes in the case of purer materials #ig parts4 ,sulphate of potash is often present in commercial yellow prussiate4 ,the separation of this impurity is best effected on the large scale by evaporating the prussiate solution to a density of #fb ,tw41 at which point most of the sulphate will crystallise out4 ,if the clear liquor be then drawn off1 diluted to #eb ,tw41 and allowed to cool1 almost pure potassium ferrocyanide will gradually deposit4 ,this may be rendered absolutely pure by gently fusing the crystals1 dissolving in water1 and treating with a small quantity of acetic acid1 which will decompose any carbonates and cyanides4 ,on adding sufficient strong alcohol1 the ferrocyanide is precipitated1 and when crystallised once or twice more from water it may be regarded as chemically pure4 ,blue salt4--,this substance1 to which we have previously referred1 is a residue obtained in the manufacture of prussiate of potash4 ,the last mother-liquor contains a large quantity of carbonate of potash1 along with smaller amounts of hydrate1 silicate1 chloride1 and sulphocyanate4 ,it is concentrated until the liquid has a density of #ij ,tw41 when most of the chloride1 silicate1 c41 separates out1 and the strong liquor containing the greater proportion of the carbonate is evaporated to dryness1 and calcined in a reverberatory furnace4 ,the dry residue constitutes the 8blue salt0 or 8blue potash10 and contains from #gj to #hj per cent4 carbonate of potash4 ,it may be employed instead of pearlash1 or mixed with it1 for the next batch of yellow prussiate4 ,the composition and amount of the insoluble residue left on lixiviation of the 8metal0 vary according to the proportions and character of the raw materials used4 ,other conditions being equal1 horn gives the lowest percentage of insoluble matter on lixiviation4 ,the large proportions of potash and phosphates contained in the insoluble residues render them well suited for use in the manufacture of artificial manures4 ,as already mentioned1 when regarded from a scientific or economical point of view1 the yellow prussiate industry is carried on under very imperfect conditions4 ,in addition to the amount of potash1 there is a very considerable waste of nitrogen1 firstly1 because the larger proportion of that element present in the animal substances is not converted into cyanogen at all1 but passes off chiefly in the form of ammonia salts2 and1 secondly1 because part of the potassium cyanide which is actually produced is lost by decomposition1 and another portion is left in the mother liquor4 ,it has been calculated that out of every #ajj parts of ferrocyanide which should theoretically be obtained1 #d parts are lost when fairly pure materials have been employed1 and #ad in the case of impure ingredients4 ,the following analyses indicate the percentage composition of two samples of insoluble residue3-- ,no4 #a4 ,no4 #b4 ,sulphate of potash1 c4 #ijf #cba ,phosphates of lime1 magnesia and iron #acgd #fbd ,oxide of iron #accd #aieh ,lime and magnesia #ejh #gbc ,sand and silica #bcig #bibd ,charcoal and moisture #cdha #cdej ------ ------ #ajjjj #ajjjj ,according to ,karmrodt1 the following proportions of the nitrogen contained in various animal substances are actually converted into cyanogen during the manufacture of yellow prussiate of potash3-- ,per cent4 ,woollen rags #af ,horn #bj ,leather cuttings #cc ,cow hair #ad ,dried blood #af ,horn charcoal #ef ,rag charcoal #cc ,as is well known1 human excreta contain a considerable proportion of nitrogen1 and there seems no reason why this should not be employed in the manufacture of yellow prussiate4 ,it is quite possible that municipal bodies might find this a convenient and profitable plan of disposing of a portion of the sewage with which they have to deal4 ,it is obvious to all persons who have given this subject much consideration1 that the nitrogen required in the manufacture of yellow prussiate of potash might be obtained with comparative ease from the surrounding atmosphere4 ,indeed1 from a theoretical point of view this seems a charming process4 ,about fifty years ago the ,society of ,arts awarded ,lewis ,thompson a medal in connection with this very process4 ,thompson ignited a mixture of #b parts pearlash1 #b parts coke1 and #a part iron turnings in an open crucible for a considerable time at a full red heat4 ,the resulting black mass was found to contain a large quantity of ferrocyanide1 together with excess of carbonate of potash1 c4 ,this process1 or a similar one1 in which a current of air was passed over a mixture of charcoal and iron saturated with carbonate of potash1 was tried on a large scale for two years at ,bramwell's works at ,newcastle4 ,about #a ton of yellow prussiate was made daily by this process2 but it was not found to work profitably1 and was eventually abandoned1 chiefly1 it is said1 owing to the large amount of fuel required1 and because the cylinders1 whether of iron or fireclay1 were not able to stand for any length of time the intense heat to which they were subjected4 ,the annexed illustrations1 ,figs4 #ad to #ag1 show the arrangement of a prussiate of potash furnace at ,sir ,e4 ,buckley's works1 at ,clayton1 ,manchester1 which are well designed to prevent nuisance3 ,a1 iron pot2 ,b1 fire-place2 a1 cover of pot2 b1 stirrer2 c1 hinged pipe conveying vapours to the flues2 d1 flues surrounding the pot1 and leading to the chimney-shaft2 e1 chain to lift up cast-iron vapour hood4 ,brunquell1 a ,german manufacturer1 has criticised the present method of conducting operations1 and proposes that it is necessary as far as practicable to aid the secondary formation of cyanogen by ammonia and incandescent charcoal1 and to avoid loss of potash by using pure animal substances1 and preventing contact with the solid products of combustion from the furnace4 ,with this view he adopts a horizontal reverberatory furnace1 the hearth of which is a cast-iron tray about #d ft4 long1 #d ft4 wide1 and #c in4 deep4 ,the crown of the furnace is built as flat as possible1 the working space is limited1 and the charge is kept from contamination by the fire4 ,such a furnace1 despite certain drawbacks1 presents important advantages4 ,fuel is economised2 the process is hastened so that seven or eight charges can be dealt with in a day1 instead of only four2 and the furnaces cost less and endure longer4 ,the charge consists of #bbj lb4 potash1 of which two-thirds is from evaporated mother-liquors1 and one-third fresh2 #dd lb4 animal charcoal from the carbonisation of substances poor in nitrogen2 #adj-aej lb4 of pure animal matters as dry as practicable2 and #ag lb4 iron4 ,the firing is urged and the charge is stirred till all the potash is fused1 when the ash-pit is closed1 and the damper turned on for charging half the animal charcoal4 ,the firing and stirring are again pushed on till the proper consistency is attained1 and potassium vapour begins to burn off4 ,in this state the mass is ready to receive the animal ,illustration3 ,figs4 #ad1 #ae1 #af1 #ag4--,,yellow ,,prussiate ,,furnace4 substances1 those rich in nitrogen being first added in small portions at a time4 ,their effect is to render the mass hard1 dry1 and difficult of fusion1 whereupon the remainder of the animal charcoal should be promptly introduced4 ,after thorough agitation1 the working door is closed for a short time1 and the contents of the furnace are rapidly discharged into a covered iron pan4 ,the character of the animal matters employed varies so much that it is impossible to lay down hard and fast rules for the proportions of the several ingredients1 or the duration of the roasting4 ,nor is the value of a raw material always in proportion to its richness in nitrogen1 because the poorer material may waste less potash1 consume less fuel1 and require less labour4 ,the addition of iron filings or turnings is useful only in prolonging the life of the cast-iron crucibles4 ,combination of the ,cyanide and ,iron ,solutions4--,a great number of recipes are in vogue for combining the two solutions of ferrocyanide and an iron salt1 both with reference to their proportions1 and to the addition of foreign matters of various kinds4 ,these variations in the formul give rise to distinct names for some kinds of ,prussian blue1 which will be referred to below4 ,the ordinary common ,prussian blue has a greenish tendency1 and is chiefly made according to one or the other of the following directions3-- 7#a7 ,mix a solution of #ajj lb4 yellow prussiate with a solution of #ajj lb4 green copperas 7ferrous sulphate7 and #ah lb4 alum1 to which #i lb4 sulphuric acid has been added1 and let the mixture stand for #b-c hours1 or until the solid portion has completely settled out4 ,decant the clear supernatant liquor1 and well wash the precipitate with clean waters4 ,finally throw it on a filter and subject it to repeated disturbance1 so as to ensure the admission of air to every particle1 in order that the requisite oxidation may take place4 ,the proportion of alum used is subject to very great variation according to individual fancy2 it renders the subsequent grinding of the pigment a very much easier matter1 but it causes the shade of blue to be paler than it otherwise would be4 7#b7 ,the simple solutions of green copperas and yellow prussiate in equal proportions are mixed together without any other ingredient being added1 and the precipitate produced is washed1 filtered1 and arated as in 7#a74 ,it is1 however1 inferior by reason of the oxide of iron formed in the pigment spoiling the purity of the colour1 and necessitating the treatment of the wet mass with hydrochloric acid1 at some expense1 for removal of the iron oxide4 ,,antwerp ,,blue4--,this pale variety of ,prussian blue has but little importance now4 ,it is prepared by adding a solution of #d lb4 yellow prussiate in #e-f gallons of water to one of #b lb4 sulphate of iron1 and #a lb4 each of alum and sulphate of zinc in an equal quantity of water4 ,the resulting pigment consists of a mixture of the ferrocyanides of iron1 alumina1 and zinc2 it is washed1 filtered1 arated1 and dried as other forms of ,prussian blue4 ,,bong',s ,,blue4--,when cyanide of potassium is added to an acid solution of a copper salt1 a red colour is produced1 which has already been mentioned by different observers4 ,the substance formed is very changeable1 at least in the liquid where it is formed4 ,it is decomposed by acids1 alkalies1 cyanide of potassium1 and even decomposes spontaneously1 the colour changing to yellow4 ,it is precipitated by insoluble cyanides2 hence when a dilute acid is added to the red solution1 the dye is at once thrown down along with the cyanide of copper4 ,if the precipitate thus obtained is treated with sulphuretted hydrogen1 it is decomposed and the substance is set free4 ,this substance can combine with iron1 like cyanogen1 so as to conceal the properties of the iron4 ,this compound is very permanent1 and has lately been studied by ,bong1 who gives the following directions for its preparation3-- ,cyanide of potassium is added in excess to an acid solution of a copper salt until the red colour at first formed has disappeared1 when a ferric salt is at once added4 ,on the addition of the iron salt1 of course1 a copious precipitation of ,prussian blue takes place1 and the liquid again turns to a dark purple-red4 ,to separate the colouring substance from the alkaline salts in the liquid1 a dilute acid is added1 which precipitates it and the cyanide of copper4 ,this precipitate is combined with the ,prussian blue1 which also contains a considerable quantity of the colouring substance1 and then treated with a boiling solution of carbonate of ammonia1 in which it dissolves4 ,as the cyanide of copper also goes into solution1 it is separated by again precipitating it with an acid1 and treating the precipitate with sulphuretted hydrogen4 ,the colouring substance thus liberated now contains a certain amount of hydroferrocyanic acid1 which is removed after neutralisation by acetate of lead4 ,it is now filtered1 and the purification is completed by precipitating with a silver salt and treating the precipitate with sulphuretted hydrogen4 ,this purple-coloured compound crystallises very indistinctly4 ,to determine its composition1 ,bong precipitated it with acetate of copper4 ,when dried at #bab ,f41 the rose-coloured precipitate had the following composition3 ,carbon #bdca1 nitrogen #bhjd1 hydrogen #ahh1 iron #acff1 copper #agfg1 oxygen #addd4 ,total #ajjjj4 ,these numbers correspond to the formula ,cu1 ,fe ,cy#d 7,,ho7#d4 ,this substance is likewise precipitated by salts of zinc1 mercury1 and silver4 ,all these precipitates are pink or purple1 very beautiful1 and of remarkable brilliancy4 ,they are soluble in alkalies4 ,iron salts yield no precipitate1 nor do lead salts1 except in the presence of ammonia1 when a blue-violet precipitate is formed4 ,when treated with sulphuretted hydrogen1 these precipitates yield purple-red and acid liquids1 which undergo change in the air1 especially if warm1 forming ,prussian blue4 ,when these liquids are neutralised with alkali1 purple compounds are formed1 which are permanent in the air1 soluble in water1 slightly so in alcohol1 and insoluble in ether4 ,their colouring power is exceptionally great4 ,these pigments will unite with ferrocyanides1 and in its preparation such a compound is produced in considerable quantity2 it is likewise of a purple colour1 and gives a rose-coloured precipitate with acetate of lead4 ,both alone and in this compound it is very permanent2 it resists the action of sulphurous acid1 concentrated and boiling alkalies1 and dilute acids1 but is rapidly destroyed by chlorine and nitric acid4 ,if this pigment could be prepared cheaply enough1 it would probably be used with advantage in the arts1 on account of its resistance to chemical reagents and light1 the variety of its shades1 and its brilliancy4 ,it does not colour fibres directly1 but can readily be fixed on them from slightly acid solutions1 if they are previously mordanted with metallic oxides4 ,,brunswick ,,blue4--,this pigment is made in pale1 medium1 and deep shades1 and is an extremely useful colour1 being very fine1 requiring no grinding1 thoroughly permanent in light and air1 hardly acted upon by acids1 but turned brown by alkalies1 and liable on standing to separate into two portions--a white and a blue--the latter coming to the surface while the former sinks1 and necessitating a thorough stirring of the paint before use4 ,it generally consists simply of barytes1 or gypsum1 or china clay1 coloured by a small percentage of ,prussian blue1 with or without the addition of a lesser proportion of ultramarine4 ,the barytes or other base is very thoroughly agitated in water1 while a solution of green copperas and a solution of yellow prussiate are gradually added without ceasing the agitation4 ,when the incorporation of the ingredients has been completely accomplished1 the precipitate is settled1 washed1 filtered1 and dried4 ,following are a few recipes3-- ,pale4 7#a7 #a cwt4 barytes1 #a lb4 green copperas1 #a lb4 yellow prussiate4 ,pale4 7#b7 #a cwt4 china clay1 #b lb4 green copperas1 #b lb4 yellow prussiate4 ,pale4 7#c7 #a cwt4 gypsum1 #a lb4 green copperas1 #a lb4 yellow prussiate4 ,medium4 7#a7 #a cwt4 barytes1 #c lb4 green copperas1 #c lb4 yellow prussiate4 ,medium4 7#b7 #a cwt4 china clay1 #f lb4 green copperas1 #f lb4 yellow prussiate4 ,medium4 7#c7 #a cwt4 gypsum1 #d lb4 green copperas1 #d lb4 yellow prussiate4 ,deep4 7#a7 #a cwt4 barytes1 #e lb4 green copperas1 #e lb4 yellow prussiate4 ,deep4 7#b7 #a cwt4 china clay1 #aj lb4 green copperas1 #aj lb4 yellow prussiate4 ,deep4 7#c7 #a cwt4 gypsum1 #g lb4 green copperas1 #g lb4 yellow prussiate4 ,in each case about #ej-fj gallons of water are required4 ,to determine the amount of barytes present in a sample1 boil about #ej gr4 with caustic soda1 filter1 wash the residue free from soda1 treat with sulphuric acid1 well wash the insoluble residue1 dry1 and weigh4 ,,chinese ,,blue4--,this well-known and favourite form of ,prussian blue is prepared with great care1 and is usually sold in fine powder or little cubes4 ,its composition is virtually identical with that of ordinary ,prussian blue1 but it is more free from impurities1 and shows a fine bronze bloom or lustre on newly fractured surfaces4 ,being pure1 it is entirely dissolved by oxalic acid2 and its composition is about #eb per cent4 oxide of iron1 #dc cyanogen1 and #d water4 ,in dyeing and calico-printing it is extensively employed4 ,its tint varies from greenish to violet1 according to modifications in the method of manufacture1 the chief difference being that yellow prussiate gives a greenish tone and red prussiate a violet4 ,the process of preparation is mainly as follows4 ,in about #dj gallons of cold water dissolve #a cwt4 of green copperas selecting it carefully for freedom from insoluble oxide2 add about #e pints of sulphuric acid4 ,this liquor very rapidly undergoes oxidation1 by which oxide of iron is thrown down1 and the solution is rendered unfit for making the best quality pigment4 ,therefore it should be prepared only immediately before it is used4 ,in another vessel containing about #dj gallons of cold water1 dissolve #a cwt4 of yellow prussiate 7if a green shade is desired71 or of red prussiate 7if a violet tint is wished for74 ,even larger quantities of water may be used for the solutions1 as the more dilute they are the finer is the colour precipitated and the greater the lustre on the surface of the finished pigment4 ,when the two solutions of yellow or red prussiate and acidified green copperas are brought together1 a bluish-white precipitate is thrown down4 ,this is allowed to completely separate itself1 and then the clear supernatant liquid is drawn off4 ,the next step is to thoroughly oxidise the precipitate4 ,this cannot be satisfactorily accomplished by utilising the oxygen of the atmosphere1 as is done in other cases1 because that method entails the production of a certain amount of oxide of iron1 which prejudicially affects the purity of colour of the finished article4 ,of the chemical oxidising agents which are available1 the most satisfactory in point of cost and efficiency is chloride of lime 7bleaching powder74 ,for each cwt4 of green copperas1 mix about #bj lb4 of bleaching powder into a thin cream with water1 and add it1 in small quantities at a time1 to the precipitate1 constantly stirring so as to ensure the absorption of the whole of the chlorine by the blue4 ,without the addition be made gradually and under agitation1 the chlorine will be generated more quickly than it can be absorbed1 entailing a waste of gas and a noxious vapour to be breathed by the workmen4 ,sometimes the bleaching powder is added at an earlier stage1 viz4 to the green copperas solution1 and in that case the blue assumes a violet tone4 ,after the addition of the bleaching powder solution to the bluish-white precipitate1 it is acidified with hydrochloric acid1 which develops the blue4 ,when the whole has settled1 the supernatant liquor is drawn off1 and the blue powder is well washed and strained on a filter1 then placed in pans and dried very gradually indeed in the dark1 at a temperature never exceeding #acj ,f4 ,the slower the drying the better is the gloss of the pigment4 ,it is most essential that iron be excluded during the final grinding operation1 or it may cause ignition of the mass1 and its conversion into oxide of iron would speedily follow4 ,it has been proposed to treat the white precipitate 7obtained in the usual manner from green copperas and yellow prussiate7 by the chlorine contained in aqua regia 7nitro-hydrochloric acid74 ,the copperas1 however1 must be as free as possible from basic sulphate 7oxide71 which is ensured by keeping a little metallic iron in the acid solution of copperas4 ,it is also desirable to effect the precipitation with crude prussiate1 so as to avoid absorption of oxygen and premature development of the blue colour4 ,habich considers that the mistake is generally made of using too little copperas1 and he has found that when #ij lb4 of copperas have been added to #ajj lb4 of yellow prussiate1 a drop of iron solution in the filtered liquor produces no precipitate1 while the white precipitate has carried with it a certain proportion of prussiate1 which can be washed out4 ,he therefore proposes to avoid this waste by pouring the copperas solution into the prussiate solution1 with constant agitation1 till no further precipitate goes down1 then adding one volume of the copperas solution equal to one-ninth of that already used4 ,after fifteen minutes stirring1 it is certain that all the prussiate carried down is decomposed4 ,the drained precipitate is blued 7peroxidised7 by adding aqua regia prepared several days previously1 and in proportions depending on the strengths of the two acids4 ,generally1 the aqua regia mixture will be #ajj lb4 of commercial nitric acid at #cj ,b4 7containing #ced lb4 of anhydrous acid7 and #fbb lb4 commercial hydrochloric acid at #bc ,b4 7containing #bci lb4 of the anhydrous acid72 and #dj lb4 of this mixture will suffice for bluing the precipitate resulting from #ajj lb4 yellow prussiate4 ,the addition of the aqua regia should take place in a wooden vessel with constant agitation4 ,according to another modification1 the white precipitate obtained in the usual way is blued by adding a solution of perchloride of iron1 which may be made from a hematite ore free from clay and carbonate of lime1 or from rouge4 ,the iron oxide1 from whatever source1 is ground to a very fine state1 and treated with crude hydrochloric acid in a lead-lined tank1 where the mixture remains for several days1 and is constantly stirred4 ,when saturated with iron the clear liquid is withdrawn for use4 ,to receive it1 the white precipitate is rapidly heated to boiling in a copper vessel1 and is then transferred to a wooden vat1 and the iron perchloride solution is stirred in till the desired tint is produced4 ,the pigment is washed and dried in the ordinary way1 while the supernatant liquor 7essentially protochloride of iron7 is poured over old scrap iron and used instead of copperas for a fresh batch of yellow prussiate4 ,a solution of perchloride of manganese may be used instead of perchloride of iron4 ,inferior qualities of manganese ore can be employed1 and the residues left after treatment with hydrochloric acid may be washed and dried for sale as purified or peroxidised manganese4 ,,paris ,,blue4--7#a7 ,a synonym for the violet-tinted kind of ,prussian blue4 7#b7 ,a series of compounds described below4 a ,a thorough mixture of #b parts sulphur and #a part dry carbonate of soda is gradually heated in a covered crucible to redness or till fused2 a mixture of silicate of soda and aluminate of soda is then sprinkled in1 and the heat is continued for an hour2 the little free sulphur present may be washed out by water4 b ,an intimate mixture of #cg parts china-clay1 #ae parts sulphate of soda1 #bb parts carbonate of soda1 #ah parts sulphur1 and #h parts charcoal1 is heated in large crucibles for #bd-cj hours2 the mass is re-heated in cast-iron boxes at a moderate temperature till the desired tint appears1 and is finally pulverised1 washed1 and dried4 c ,gently fuse #ajge oz4 crystallised carbonate of soda in its water of crystallisation2 shake in #e oz4 finely-pulverised orpiment1 and1 when partly decomposed1 as much gelatinous alumina hydrate as contains #g oz4 anhydrous alumina2 add #ajj oz4 finely-sifted clay1 and #bba oz4 flowers of sulphur2 place the whole in a covered crucible1 and heat gently till the water is driven off1 then to redness1 so that the ingredients sinter together without fusing2 the mass is then cooled1 finely pulverised1 suspended in river-water1 and filtered4 ,the product is heated in a covered dish to dull redness for #a-b hours1 with occasional stirring4 ,colourless or brownish patches may occur1 and must be removed4 ,,saxon ,,blue4--,following is a recipe for the preparation of this pigment1 which possesses limited importance4 ,dissolve #h lb4 alum and #a lb4 green copperas in #af gallons of water4 ,add separate solutions of pearlash and yellow prussiate till precipitate ceases to go down4 ,collect the precipitate when it has completely settled2 wash thoroughly1 and dry4 ,,soluble ,,blue4--,this term is applied to a variety of ,prussian blue which1 while possessing no difference in the matter of chemical composition1 yet has the distinctive feature of being soluble in water1 which the other varieties are not4 ,it no longer enjoys the popularity it once had as a dye1 on account of the severe competition of the coal-tar colours4 ,below are some of the most satisfactory formul for its preparation4 7#a7 ,mix #aj lb4 of ,prussian blue thoroughly in about #aj gallons of cold water4 ,then add #e lb4 of yellow prussiate and let the whole mass boil steadily for several hours4 ,strain off the liquor and well wash the precipitate on a filter4 ,finally dry for use4 7#b7 ,dissolve about #a cwt4 of red prussiate in water and make the solution hot4 ,prepare another solution of about #gc lb4 of green copperas in hot water4 ,mix the two solutions together and boil them for about a couple of hours4 ,allow the solid matters to settle out1 then put them on a filter and wash with clean water until a blue coloration manifests itself in the drainings4 ,the blue residue is then dried as usual4 7#c7 ,make one solution of #aj lb4 of yellow prussiate1 and another of #h lb4 of green copperas1 water being the solvent in both cases4 ,mix these two solutions together and give them an hour's boiling4 ,add #c lb4 of a mixture of nitro-sulphuric acid1 containing #b parts of the former to #a of the latter4 ,boil for another hour4 ,let the solid pigment precipitate itself thoroughly1 and then filter1 wash1 and dry as in the other cases4 7#d7 ,dissolve about #a cwt4 of perchloride of iron and #aj lb4 of sulphate of soda in water4 ,also dissolve in another vessel #b cwt4 of yellow prussiate and #aj lb4 of sulphate of soda4 ,pour the first solution into the second 7never the contrary7 and take care that the prussiate solution is always preponderant4 ,the ,glauber's salt is useful in rendering the precipitation of the blue pigment more complete by reason of the insolubility of the latter in saline fluids4 ,when the blue sediment is all thrown down it is drained off on a filter1 and repeatedly washed till a blue tint appears in the wash-waters1 when it is dried for use4 ,,turnbull',s ,,blue4--,this is an old-fashioned name often applied1 like the term ,paris blue1 to the violet shades of ,prussian blue which have been prepared with red prussiate4 ,ultramarine4--,according to ,rowland ,williams1 ,f4,c4,s41 natural ultramarine is1 perhaps1 the most beautiful blue pigment known4 ,it was formerly1 and is now to a small extent1 manufactured 7chiefly for artists' use7 from lapis lazuli1 a blue mineral which occurs1 intermixed with limestone and iron pyrites1 in ,siberia1 ,thibet1 and ,china4 ,in order to obtain ultramarine from lapis lazuli1 the roughly pulverised mineral is ignited1 dipped into vinegar to remove carbonate of lime1 and then reduced to the finest possible state of division4 ,the powder is next mixed with a cement composed of rosin1 linseed oil1 white wax1 and ,burgundy pitch1 and the resultant paste is worked under water until all the ultramarine is separated4 ,the ultramarine is washed several times with water1 and afterwards with alcohol1 which removes any of the resinous compound which may have adhered4 ,when treated in this manner1 lapis lazuli yields from #b to #c per cent4 of ultramarine4 ,according to ,clement and ,desormes1 lapis lazuli has the following composition3-- ,per cent4 ,soda #bcb ,alumina #cdh ,silica #ceh ,sulphur #ca ,carbonate of lime #ca ----- #ajjj ,it will be seen1 therefore1 that ultramarine essentially consists of alumina1 silica1 soda1 and sulphur1 and may be regarded as a sodium aluminium sulphate1 in combination either with polysulphide of sodium alone1 or with a polysulphide and a polythionate of sodium4 ,clement and ,desormes believe that the iron in lazulite 7lapis lazuli7 is an accidental impurity1 and is neither essential to the mineral itself nor to the ultramarine derived from it4 ,there is still some doubt on this point1 however1 many eminent chemists holding the opinion that iron is a necessary constituent of ultramarine blue4 ,natural ultramarine has been almost entirely replaced by the artificial product1 since methods have been devised for the manufacture of the latter on a large scale4 ,the possibility of preparing artificial ultramarine suggested itself in a curious manner4 ,about seventy years ago a ,french alkali maker noticed the occasional appearance of a blue coloured substance in his soda furnace4 ,on analysis1 ,vauquelin found the substance to have the same chemical composition as lapis lazuli1 and this incident led him to believe that ultramarine might be built up from its elements4 ,several years passed away before ,guimet succeeded in manufacturing artificial ultramarine on anything like a large scale1 but ,gmelin is said to have prepared it in small quantity half a dozen years previously4 ,there are four varieties of artificial ultramarine3 7#a7 the pure deep blue1 equal in colour to average native ultramarine2 7#b7 pale blue2 7#c7 violet or pink ultramarine2 7#d7 green ultramarine4 ,the latter is obtained in the first stage of the ultramarine manufacture1 being the result of incomplete ignition of the materials employed4 ,ultramarine is generally manufactured by one of the following processes3--7a7 8,sulphate02 7b7 8,soda02 7c7 8,silica40 7a7 8,sulphate0 ,ultramarine4--,this may be prepared from sulphate of soda 7,glauber's salt71 charcoal1 and kaolin 7china clay74 ,the materials should be as free as possible from iron1 and it has been found that clay having approximately the formula ,al#b,o#b 7,si,o#b7b gives the best results4 ,the clay and sulphate of soda must be thoroughly calcined4 ,they are then intimately mixed with charcoal in the following proportions3-- ,per cent4 ,clay #dhc ,sulphate of soda #dce ,charcoal #hb ----- #ajjj ,sometimes a portion of the sulphate of soda is omitted1 and some carbonate of soda and sulphur added instead4 ,the composition of the mixture then becomes3-- ,per cent4 ,clay #dgb ,sulphate of soda #aic ,carbonate of soda #aic ,charcoal #ha ,sulphur #fa ----- #ajjj ,caustic soda is also sometimes used instead of carbonate4 ,these mixtures 7whether sulphate alone or sulphate and carbonate7 are made with a view to have the soda present in sufficient amount to combine with one-half the silica contained in the clay1 and to leave sufficient soda to form polysulphide of sodium with a portion of the sulphur4 ,there should then remain enough soda and sulphur to produce ordinary sulphide of sodium 7,na#b,s74 ,if either of the two mixtures be ignited out of contact with air1 a white compound is formed1 which is sometimes termed white ultramarine4 ,on leaving this exposed to the atmosphere for some time it becomes green1 and on further ignition1 with free access of air1 it is converted into ultramarine blue4 ,in actual working the carefully prepared mixture of the above mentioned materials is heated for several hours to a high temperature in fire-clay crucibles1 only a limited supply of air being allowed to enter1 and the temperature being eventually raised to a white heat4 ,the product of this operation1 when cool1 has a grey or yellowish-green appearance4 ,it is washed several times with water1 dried1 reduced to a fine powder1 and then represents the green ultramarine of commerce4 ,stlzel found that green ultramarine had the following composition3-- ,per cent4 ,alumina #cjaa ,silica #cgdf ,sodium #aiji ,sulphur #fjh ,iron #di ,calcium #de ,chlorine #cg ,oxygen #eai ,sulphuric acid #gf ,magnesia1 potash1 and phosphoric acid traces4 ------- #ajjjj ,green ultramarine is transformed into blue by heating with about #d per cent4 of sulphur at a low temperature1 with free access of air4 ,sulphur is afterwards added1 if necessary1 in small quantities at a time1 and the heating is continued until the desired shade of blue is obtained4 ,the mass is then powdered1 the soluble matter 7sulphide of soda1 c47 is removed by washing with water1 and the blue is dried and assorted according to quality4 7b7 8,soda0 ,ultramarine is sometimes made with soda alone 7either carbonate or caustic71 and at others with a mixture of soda and sulphate of soda4 ,rowland ,williams found the following proportions of the respective ingredients to answer satisfactorily3-- ,per cent4 ,china clay #cfh ,carbonate of soda #cfh ,sulphur #bbj ,coal #dd ----- #ajjj ,the proportions for soda and sulphate of soda ultramarine have been previously given under 8sulphate ultramarine40 ,the ignition is carried on in a manner similar to that already described4 ,the resultant green product1 owing to its avidity for oxygen1 is partially changed into ultramarine blue by simple contact with the air4 ,it is entirely converted into the blue variety by roasting with an additional quantity of sulphur4 ,with care1 ultramarine blue may be manufactured in one operation1 by increasing the proportions of soda and sulphur4 7c7 8,silica0 ,ultramarine is manufactured in the same way as soda ultramarine1 except that1 in addition to the other materials1 silica to the extent of #e or #aj per cent4 of the weight of clay is employed4 ,by this process1 ultramarine blue of a slightly reddish tint is obtained in one operation4 ,the method has1 however1 one decided drawback1 viz4 that the materials employed are rather liable to fuse during ignition4 ,the faintly reddish hue of 8silica0 ultramarine becomes more intense according to the proportion of silica present4 8,silica0 ultramarine is said by some to be less readily attacked by acids and by strong alum solutions than ultramarine prepared by the 8sulphate0 and 8soda0 processes2 but ,rowland ,williams' experience does not confirm this statement4 ,he mentions that good artificial ultramarine withstands the action of weak acids much better than is generally imagined4 ,he had occasion to test many samples which resisted the action of dilute acids to a remarkable degree4 ,most strong acids1 of course1 decompose both artificial and native ultramarine1 with evolution of sulphuretted hydrogen4 ,native ultramarine is1 however1 less susceptible to the influence of acids 7both strong and dilute7 than the artificial compound4 ,this difference of behaviour is probably due to the fact that the former contains considerably less sulphur than the latter1 and it is also possible that the constituents of natural ultramarine may be combined in a somewhat different manner from those of the artificial product4 ,notwithstanding the large amount of research with reference to the chemical composition of ultramarine1 the origin of its blue colour still remains in doubt4 ,according to ,wilkens 7,ann4 ,ch4 ,pharm41 xcix4 #ba71 ultramarine consists of two portions1 one of which is easily attacked by hydrochloric acid1 and is regarded by him as the essential constituent1 whilst the other portion is insoluble in hydrochloric acid1 and contains variable proportions of clay1 sand1 oxide of iron1 and sulphuric acid4 ,from his analyses of the pure blue1 ,wilkens deduces the formula 7#b;,al#b,o#c #c,si,o#b7 7,al#b,o#c #d,si,o#b7 ,na#b,s#b,o#c #c,na#b,s3-- ,per cent4 ,silica #cgf ,alumina #bgd ,sulphur #adb ,soda 7,na#b,o7 #bjj ---- #iib ,wilkens regards the blue colouring principle of ultramarine as a compound of hyposulphite and sulphide of sodium4 ,he considers the presence of iron is not necessary for the production of the blue2 whilst ,dr4 ,elsner1 in a paper published in #ahda1 states that about #a per cent4 of iron 7which he presumes to be in the state of sulphide7 is essential4 ,rowland ,williams asks whether it is not conceivable that the blue colour of ultramarine may be due to the presence of a small quantity of black sulphide of iron1 most intimately combined with a colourless or comparatively colourless compound 7such as white ultramarine71 the whole mass 7owing to the dilution of the black sulphide7 showing a blue reflection4 ,ultramarine is insoluble without decomposition in any known menstruum4 ,according to ,p4 ,ebell 7,ber4 #af71 ultramarine1 when in the most finely divided state1 will remain suspended in pure water for months4 ,the liquid may be filtered unchanged through several layers of ,swedish filter paper1 and appears perfectly clear when examined in a in4 layer1 and on evaporation deposits the ultramarine as a lustrous coating on the sides of the vessel4 ,rowland ,williams repeated the above experiment1 and can confirm ,ebell's statement4 ,this result shows the necessity of due precautions being taken during the washing of the ultramarine in the process of manufacture1 otherwise a considerable amount of the finely divided blue may be lost4 ,ultramarine is largely used in calico printing for pigment styles1 being fixed on the fibre by means of albumen4 ,it is also employed for blueing linen and cotton1 wax candles1 lump sugar1 c4 ,ultramarine is not adulterated to a large extent1 the chief sophistication being barium sulphate 7barytes71 and occasionally chalk and china clay4--7,rowland ,williams1 in ,industries47 ,another writer in ,industries says that the manufacture of ultramarine has perhaps hardly received the attention it deserves in ,england4 ,the importance of the industry has been recognised in ,germany1 however1 and though the palmy days of the trade1 when the whole production was in the hands of a few firms1 and the price was a matter of private friendly arrangement1 are gone for ever1 yet the business is in a flourishing state1 and should prove lucrative if properly managed4 ,it is a characteristically ,english failing to overlook branches of business not dealing with large quantities of staple commodities1 and thus many of the smaller but remunerative industries have passed out of our hands4 ,when one observes that almost every sheet of ordinary blue official paper is decolorised when accidentally brought into contact with an acid1 betraying the fact at once that its colouring matter is ultramarine1 one realises that a very considerable consumption for this and similar purposes must take place4 ,like most trades based upon chemical principles1 the manufacture of ultramarine has recently made rapid strides1 and some of the latest developments are recorded in a paper by ,j4 ,wunder1 appearing in a recent number of the ,chemiker ,zeitung1 which is worthy of some attention4 ,with most people not directly interested in it1 the term ultramarine is taken to mean the blue pigment known under that name1 the words being reckoned almost synonymous4 ,others1 more erudite1 recognise the existence of a green variety1 but that the production of such colours as red and violet is possible is scarcely suspected4 ,of course the blue is the most important1 but even that does not correspond to one specific substance1 products of different shade being prepared by modifying the process of manufacture4 ,as usually made1 ultramarine is formed by heating together carbonate of soda1 kaolin1 sulphur1 and charcoal1 with limited access of air1 the resulting pigment being green2 this1 on roasting with sulphur1 becomes blue4 ,if the operation be conducted with complete exclusion of air1 so-called ultramarine white 7in reality grey7 is produced1 which becomes green on further heating4 ,ultramarine blue capable of resisting the action of alum is sometimes required1 and may be obtained by the use of a highly silicious charge and much sulphur1 the burning being conducted in crucibles or in mass according to the purpose for which the pigment is required4 ,the former process is costly1 while the latter gives a product containing a good deal of free sulphur1 which is objectionable for such purposes as calico printing4 ,removal of the excess of sulphur by heat or caustic soda is not feasible1 as the colour suffers in either case1 but a certain amount of success has attended experiments with sodium sulphide1 the colour often brightening noticeably4 ,it is curious that chemically pure sodium carbonate1 or such as is made by the ammonia-soda process1 is not well fitted for the manufacture of ultramarine2 ,leblanc soda1 containing a little caustic1 is distinctly preferable4 ,sprinkling the soda with a strong solution of sodium sulphide before use is a good plan1 and one easy to adopt4 ,the more silicious the mixture the more difficulties are encountered1 but the product is a deeper1 richer colour1 and withstands the action of alum and weak acids better4 ,excess of oxygen must be guarded against2 many a manufacturer has had a batch turn out a hard cold blue1 instead of a soft rich colour1 solely on account of a too-excellent draught1 an accident especially liable to happen in winter time4 ,so much dreaded is this catastrophe that some makers habitually limit the air supply--smothering the neighbourhood with smoke1 and wasting coal4 ,the need for exact control here indicated points to a probable advantage from the use of gaseous fuel4 ,considerable economy has resulted from the use of the waste gases from one furnace serving for the preliminary heating of another2 a better plan would probably be the introduction of regenerative heating4 ,the crude ultramarine as it comes from the furnace contains a large proportion of soluble salts1 notably #bj to #bd per cent4 of sodium sulphate1 which have to be removed before it is merchantable4 ,usually1 after grinding1 it is simply stirred up repeatedly with hot water and the aqueous extract is siphoned off4 ,that such a crude method should be in vogue at the present time is very significant of the ample margin of profit that must exist4 ,by systematic extraction and filtration under pressure the washing may be effected with so little water that the solution is sufficiently concentrated to pay for evaporation by the heat of waste furnace gases1 the recovered sodium sulphate serving to replace part of the raw material4 ,the quality of ultramarine largely depending upon its fineness1 it is graded by levigation1 the coarser portions being filter pressed1 and the finest 8floating0 quality1 which remains in suspension for an inconveniently long time1 precipitated by the addition of a trace of an ammonium salt1 gypsum1 or even hard water1 and filtered by the aid of a suction tube on the principle of an ordinary ,bunsen pump4 ,the first successful attempt to produce ultramarine violet was made by ,professor ,leykauf in #ahei4 ,by heating ordinary ultramarine with calcium chloride in the presence of air and moisture1 he obtained a violet-toned pigment1 but it was not a full colour4 ,the active substance in this change was probably hydrochloric acid1 produced by the decomposition of the calcium chloride4 ,later experiments with other reagents1 such as chlorine and gaseous hydrochloric acid1 led to the following methods being devised4 ,in the first1 ultramarine blue is spread out on stoneware shelves in iron chambers and treated with a mixture of chlorine and steam at a temperature of #cjj ,f4 to #dhj ,f4 for about three hours4 ,in the second1 the plant is very similar1 but at the bottom of the chambers are stoneware dishes1 into which hydrochloric acid is poured from time to time4 ,as the temperature is raised1 copious vapours arise from these1 evaporation being aided by a strong draught1 and the ultramarine blue1 after being kept at #dbh-ddf ,f4 for some seven hours1 becomes converted into a dull violet1 which brightens on continuing the process with a temperature gradually falling to #cbj ,f4 ,the ultramarine violet produced by either of the above methods resists the action of lime1 and is of general applicability4 ,the pigment produced by a third and simpler process1 consisting merely in heating ultramarine blue mixed with salammoniac and a little sodium nitrate1 is unfortunately not so stable4 ,another shade of considerable interest is a pure bright light blue1 formed by heating the violet variety in hydrogen to about #ecf-eed ,f4 ,it has not yet been prepared on a commercial scale1 but certainly merits the attention of manufacturers4 ,an ultramarine red has been made by acting on the violet produced by either of the first two methods with the vapour of either nitric or hydrochloric acid at #bge-bic ,f41 the sole essential determining condition being the temperature4 ,iron vessels could be used in the case of nitric acid at this temperature1 but if hydrochloric acid were employed stoneware would have to be substituted4 ,in the manufacture of the violet the temperature is above the limit at which hydrochloric acid acts on iron4 ,it is now only necessary for some successful experimenter to put on the market yellow and orange shades of ultramarine for almost the whole of the spectrum to be represented4 ,the problem of the cause of the colour of ultramarine1 attempts to solve which have been repeatedly made1 seems increasingly difficult when its protean character is considered2 but this from the industrial point of view is of secondary importance1 provided all required shades can be produced with ease and economy4 ,nevertheless1 it is certain that here1 as in other cases1 substantial technical progress would follow from adequate scientific investigation4--7,industries47 ,ultramarine was also made the subject of a very interesting paper1 by ,herbert ,j4 ,l4 ,rawlins1 read before the ,society of ,chemical ,industry1 in ,december #ahhg4 ,after referring to the native form1 lapis lazuli1 ,rawlins goes on to observe that 8analysis could give no clue as to the cause of the blue colour4 ,to prepare it artificially became a great object1 and the efforts in this direction were stimulated by the offer of prizes1 amongst which was one of #fjjj francs1 offered by the #8,socit d',encouragement' of ,france1 to be awarded to the discoverer of a method of making ultramarine1 provided it did not cost more than #ijs4 per lb4 ,how strange it seems to think of this in these days when the value has fallen to less than half that price per cwt46 8,as early as #ahad1 two ,german chemists1 ,tessrt and ,kuhlmann1 had observed the formation of a blue product in soda kilns and calcination kilns1 but ,guimet1 in #ahbh1 first discovered how it was produced1 and gained the #fjjj francs prize4 ,he did not1 however1 publish his method1 and grew immensely rich1 although the price sank to about #afs4 per lb4 ,in #ahbh he was producing at the rate of #abj1jjj lb4 annually4 8,about the same time1 or1 as is positively asserted by some1 even prior to ,guimet1 ,gmelin made the same discovery and published his researches in full1 thus perhaps laying the foundation stone of the present supremacy of ,germany in this manufacture4 8,in spite of the valuable discoveries of ,hoffmann1 ,unger1 and others1 our knowledge of the chemical constitution of ultramarine is very limited and uncertain1 many different theories having been advanced regarding the cause of the blue colour4 8,according to ,wilkins1 ultramarine is composed of two portions1 one of which consists of two silicates of alumina with sulphite and sulphide of sodium1 and is constant in its composition2 the other being a mixture of variable quantities of sand1 clay and oxide of iron1 with sulphuric acid4 ,the blue colouring principle he considers to be a compound of sodium sulphite and sulphide4 ,another ingenious theorist1 ,stein1 in two papers published in the ,jahresberichte in #ahga and #ahgb1 concludes that blue ultramarine contains sulphurous1 and not thiosulphuric acid1 that neither sulphites nor thiosulphates are necessary to its composition1 and that it owes its colour to the presence of black sulphide of sodium1 which is formed at high temperatures by the action of sulphide of sodium on alumina--admitting1 therefore1 that it is not a chemical compound1 but merely a mechanical mixture1 the blue colour of which is due to the bodies composing it4 8,brunner considers ultramarine to be a compound of aluminium silicate1 with sodium sulphate and sulphide2 while ,brnlin regards it as a double silicate of aluminium and sodium1 in combination with pentasulphide of sodium4 ,green ultramarine he considers to be the same double silicate in combination with bisulphide of sodium4 8,again1 according to ,ritter1 ultramarine contains a double silicate1 not only associated with polysulphide1 but also with thiosulphate of soda2 and ,schlzenberger1 on the other hand1 considers that it is a mixture of a double silicate with sulphite and monosulphide of sodium4 8,endemann considers that the blue colour is due to a #8colour nucleus1' consisting of unchanging proportions of aluminium1 sodium1 oxygen and sulphur1 in each variety of ultramarine the proportion being different1 while the rest of the sodium and aluminium and the whole of the silica merely act as a vehicle necessary to the preparation and existence of the colour4 ,he considers that this #8colour nucleus1' in the case of white ultramarine1 which he calls the #8mother-substance in the manufacture of blue ultramarine1' has the formula ,al,na#d,o#b,s#b4 ,by the action on two molecules of this of sulphurous acid gas1 ,na#b,o is removed1 and green ultramarine ,al#b,na#f,o#c,s#d is formed1 which then1 by the action of oxygen1 which forms sodium sulphate1 passes into the pure green compound1 having the formula ,al#b,na#d,o#c,s#c4 ,in the #8indirect process' of manufacture1 green ultramarine is converted into blue by being burned with sulphur4 ,by this means ,endemann considers that more sodium and sulphur are removed1 and blue ultramarine ,al#b,na#b,o#c,s#c is formed4 ,he considers that the other portion1 not included in the #8colour nucleus1' differs in different samples4 ,in one which he mentions it has about the composition #c;,al#b,o#c4e,na#b,o4#af,si,o#b4 8,but of all chemists who have worked on this subject1 none has done more to increase our knowledge of #8the blue marvel of inorganic chemistry1' as he himself has called it1 than ,reinhold ,hoffmann4 ,his position of manager of the ,marienberg ,ultramarine ,works1 near ,benscheim1 in the ,grand ,duchy of ,hesse1 renders his acquaintance with the manufacture perfect1 and his untiring researches on the subject have been well rewarded by results both interesting and valuable4 ,he considers ultramarine to be a double silicate of sodium and aluminium1 together with bisulphide of sodium1 the variety poor in silica1 characterised by its paleness and purity of tint1 and easy decomposition by acids1 having the formula #d7;,al#b,na#b,si#b,o#h7 ,na#b,s#d2 while that rich in silica1 characterised by its dark and somewhat reddish tint1 and more difficult decomposition by acids1 has the formula #b7;,al#b,na#b,si#c,o#aj7 ,na#b,s#d4 ,he also considers it very doubtful whether green ultramarine is really a chemical compound1 and indeed it is now generally considered that the colour is only due to small traces of sodium salts in very intimate mechanical mixture with the blue variety1 for by heating the green body for some time at #afj with water in closed tubes1 it is converted into the blue product1 and small traces of sodium compounds are found in solution in the water2 and further1 on heating blue ultramarine strongly with sodium sulphate and charcoal--that is1 acting upon it with sodium sulphide--the green variety is formed4 8,in a paper by ,knapp1 an abstract of which appeared in the ,journal of the ,chemical ,society for ,march #ahhj1 there are some curious facts recorded with regard to the colouring agent4 ,it was noticed that when silicic acid was replaced by boracic acid1 a blue1 nearly as stable in its properties as that of ordinary ultramarine1 was produced4 ,it was found that a blue could be obtained without alumina being introduced4 ,hence silica without alumina1 and alumina without silica1 can be employed with a certain amount of success4 ,the blue1 however1 formed without silica1 is not so strong or stable as that formed with it4 8,one very curious property which ultramarine possesses is its power of giving up its sodium in exchange for other metals4 ,thus1 by heating blue ultramarine with a concentrated solution of silver nitrate in sealed tubes to #abj for fifteen hours1 a dark yellow silver ultramarine is produced1 containing about #dfe per cent4 of silver4 ,this corresponds to about #aee per cent4 of sodium1 which is just about the amount that the original body contained4 8,when this body is heated with an aqueous solution of sodium chloride to #abj in sealed tubes1 about three-quarters of the silver is replaced by sodium1 but the other quarter cannot be so replaced2 in fact1 blue ultramarine1 when heated with silver chloride1 takes up silver1 and becomes green4 ,but by heating silver ultramarine with sodium chloride in the dry way1 at rather a higher temperature1 the whole of the silver is replaced by sodium1 but the ultramarine thus regenerated does not equal the original body in colour4 ,the change is probably due to the loss of sulphur in the formation of the silver ultramarine4 8,if in the above experiment potassium chloride be substituted for the sodium salt1 and the temperature not allowed to exceed #djj1 a bluish-green potassium ultramarine is formed4 ,barium ultramarine is a yellowish-brown product1 zinc ultramarine is violet1 and magnesium ultramarine is grey4 ,these may all be obtained by acting on the yellow silver ultramarine with the corresponding metallic chloride4 8,from the experiments of ,dollfus and ,goppelsrder some very striking differences have been brought to light between the three types of colour which they examined--namely1 the blue1 green and violet--in their behaviour with various reagents4 ,thus1 an aqueous solution of caustic soda or potash does not act on the blue or green1 but turns the violet to blue1 and when heated with carbonic oxide the same result ensues4 ,many other reagents have the same effect on the violet variety1 but when acted upon with sodium sulphide1 the green turns grey1 and when heated with potassium chlorate becomes darker and loses its brightness of colour4 ,dollfus and ,goppelsrder attempt no explanation of these facts1 but simply state them as results of their observations1 and profess their inability to give any chemical formul for the three ultramarines1 though they consider that there is sufficient proof that each has its distinct constitution4 ,they give as their opinion1 however1 that they are double silicates of aluminium and sodium1 in which a part of the oxygen is replaced by sulphur4 8,violet and red ultramarines are more bodies of scientific interest than of any practical use1 as their colouring power is not sufficiently great4 ,the violet variety may be prepared by exposing the underground blue product to chlorine gas under a high temperature1 while the red may be obtained from the violet by acting on it1 under a low temperature1 by dilute nitric acid fumes4 8,the first artificial method of producing ultramarine was that known as the #8indirect process'--that is1 first the manufacture of green ultramarine2 and secondly1 its conversion into blue4 ,it was carried out as follows3-- 8,an intimate mixture of ,glauber's salts1 china clay1 and coal or rosin1 finely ground together1 was placed in crucibles and baked or burned in an oven for about six hours4 ,it was then transferred to iron trays1 and heated with flowers of sulphur to the point where the sulphur took fire1 when it was allowed to burn itself out4 ,by this second process the green was converted into blue4 ,it was then washed1 ground with water1 and settled out1 the first deposit being of a darker shade than the second1 and the colour becoming lighter as the powder settled was finer in grind4 ,this is essentially the method employed now at many ,german works--those at ,marienberg1 for instance--and produces what is known as 8sulphate ultramarine10 distinguished by its pale shade and almost greenish blue tint4 8,there are1 however1 some objections to the indirect process1 and it was considered advisable to find a plan by which ultramarine could be made in bulk in a muffle furnace4 ,the following is a method which is employed at the present time in some of the ,german works3-- 8,a mixture of china clay1 carbonate of soda1 sulphate of soda1 sulphur1 sand and charcoal or rosin1 finely ground together1 are placed upon the floor of a muffle furnace1 being pressed down so as to present an even surface4 ,the mixture is then entirely enclosed with fire-clay tiles1 the spaces between which are filled in with thin mortar4 ,when the oven is so charged1 the front is built up1 a small hole being left for watching the temperature of the flue between the tiles and the top of the furnace1 and for drawing samples during the process1 which is done through a corresponding hole in the front of the fire-clay tiles1 temporarily closed with a fire-clay stopper4 ,the oven is now heated1 slowly at first1 and afterwards more strongly1 so that at the end of eight or nine hours it is at a dull red heat4 ,it is kept at this temperature for about #bd hours1 when the heat is raised so that a clear red glow is obtained1 which is kept up to the end of the operation4 8,for the purpose of taking a sample1 an iron spoon borer is introduced through the hole left in the enclosing tiles1 turned round1 and pulled out4 ,the contents are laid on a clean tile1 and quickly covered with another tile1 on which a second quantity is placed1 and allowed to remain exposed to the air4 ,if the oven has been sufficiently heated the covered sample should appear of a bluish green1 and no longer brown or yellow1 while the second sample should be rather bluer4 ,if this be the case1 the oven is heated slowly for another hour1 and then all communication with the outer air is cut off4 ,it is allowed to cool and then opened1 when the contents should appear as a beautiful blue mass1 the lower portion of which1 however1 is of a greenish tinge4 ,both parts are now treated alike1 but worked up separately1 the greenish-blue portion making an inferior article4 ,the finishing process is as follows3-- 8,the raw ultramarine is ground in upright mills1 and then repeatedly boiled for about ten or fifteen minutes at a time in cast-iron boilers1 being all the time agitated by a mechanical stirring arrangement4 ,it is then allowed to settle1 and the water is drawn off with a siphon4 ,as soon as the powder settles into a hard compact mass1 it has been sufficiently washed1 and it is then dug out4 ,the part next to the bottom of the boiler is generally coarse and of poor quality4 ,it is carefully separated from the upper portion1 which is transferred to wet mills of the ordinary description1 and there ground for six to twelve hours1 during which time about #aej lb4 can be treated in each mill4 ,the ground colour from these mills is then collected in a large tub1 and allowed to settle for four hours1 during which time the coarsest particles fall to the bottom4 ,the liquid is then passed through a series of tubs1 in each of which it is allowed to stand for a period of time1 lengthening as the quality settled out becomes finer1 the last settling requiring about three weeks4 ,the various qualities are then dried and sifted1 when they are ready for the market4 8,the blue produced by this operation is of a good quality1 but there are some objections to the process1 which have given rise to another1 in which the ultramarine is produced direct in crucibles similar to those used in the indirect process4 8,this is conducted as follows3--,the mixture of raw materials consists of about #ajj parts of china clay1 #ij of carbonate of soda1 #aaj of sulphur1 #bj of charcoal1 and a quantity of infusorial earth1 varying according as the ultramarine produced is desired to be rich or poor in silica4 ,these are finely ground together1 in which process great care must be observed1 as much depends upon its being properly carried out4 ,the mixture is then filled loosely into crucibles provided with flat circular lids1 which are fixed on with mortar containing clay4 ,this is allowed to dry1 and the crucibles are then ready for firing1 which process is conducted in ovens1 generally constructed so as to contain several hundred crucibles1 which are arranged in rows one above another4 8,the mixture undergoes a very curious change of colour while in the ovens4 ,when put in it is greyish white1 and during the process of burning it becomes successively brown1 green1 blue1 violet1 red and white1 in the order named4 ,these changes are1 according to ,guimet1 due to oxidation4 ,the brown appears with the blue flames due to the combustion of the sulphur1 the green just after the sulphur flames have ceased1 and the blue is first formed at a temperature of about #gjj--;i4 e4 a bright red heat4 ,if1 after this1 heat be still applied and air freely admitted1 the mixture becomes first violet1 then red or rose coloured1 and finally white4 ,when this white body is heated to redness with carbon or other reducing agents1 the red1 violet1 blue1 green and brown colours 7according to the amount of reducing agent employed7 may sometimes be reproduced1 though the reaction is by no means a certain one4 8,if brown ultramarine be removed from the oven1 and allowed to remain exposed to the air1 it immediately takes fire and burns to an inferior blue colour4 ,the same thing occurs with the green body4 ,even if the brown product be completely cooled before being exposed to the air1 it will1 as soon as the air is allowed to reach it1 get hotter and hotter1 until it is glowing1 when it will burst into flame and become blue4 ,attempts have been made to preserve the brown colour1 which is of a beautiful chocolate tint1 but have always failed4 ,in one instance1 when this was tried1 the colour was put immediately into water1 and treated like the ordinary blue variety1 and as long as it was kept moist no change was apparent4 ,after being washed and wet ground the moist powder was put into a cask1 where for some time it was allowed to remain undisturbed4 ,at the end of about three weeks it was noticed that the mass was hot1 and on being turned out of the cask and broken up it was found to be at a glowing heat in the interior4 8,after the oven has been fired for several hours1 it is carefully closed at every point where air might enter1 and allowed to cool for four or five days4 ,the exact length of time during which the ovens are fired1 and the amount of air admitted1 depend upon various circumstances1 one important one being the state of the weather4 ,thus1 on a dull1 foggy day1 when the draught in the chimney is not good1 a longer time is required4 ,of course1 no rule can be given for this1 and it is the experience required in the management of the oven that makes the manufacture so difficult to carry out successfully1 the early efforts of a manufacturer not unfrequently resulting in the loss of a whole ovenful of raw material4 ,as soon as the oven has cooled1 the crucibles are taken out1 and the contents of each are turned out in a solid mass1 which must be carefully cleaned with a knife of any badly burned portions1 and afterwards broken up and thrown into a cask along with the contents of other crucibles4 8,this forms what is known as crude raw ultramarine4 ,it contains about #ae per cent4 of sulphate of soda1 which must be removed before the colour is fit for sale4 8,for this purpose it is washed with hot water in large tubs1 after which it is ground in wet mills to an impalpable powder1 and allowed to stand for about an hour in a large tub1 in order to remove the coarsest particles and dirt which are sure to be present4 ,it is then removed to another tub1 where it settles for four or five hours1 and from this it passes to others1 where it stands for various lengths of time1 increasing1 of course1 as the powder to be settled becomes finer1 the last settling occupying three or four weeks1 and producing the strongest quality that can be obtained--that is to say1 it will bear mixing with more of a reducing medium1 such as mineral white1 than would a former settling for the mixture in each case to be of the same depth of colour4 8,the water1 after the final settling1 still contains about #e per cent4 of ultramarine4 ,this would take five or six months to settle1 and as this time could not generally be given to it1 it is precipitated with lime water1 which has a sort of coagulating influence upon the particles1 which can then be removed by filtration4 ,it is a curious thing that this last quality is quite different from the one preceding it1 being very inferior in both colour and strength4 8,after settling1 all the various qualities are dried in kilns1 and sifted through fine brass wire sieves by means of a fan1 which breaks up the lumps and forces the particles through the meshes of the sieve1 which must be very close--about #ajj to the inch--in order that the ultramarine may be perfectly smooth and free from lumps or grit of any sort4 ,when finished1 it should be in the form of an impalpable powder--the finer qualities so fine1 indeed1 as to feel almost buttery when rubbed between the fingers4 ,after this process the different qualities and shades are mixed to certain standards1 and are then ready for sale4 8,the uses of ultramarine in the arts and manufactures are very numerous and important4 ,the most important1 from the point of view of quantity1 is the manufacture of #8square blue' for washing purposes4 ,in the preparation of this article the ultramarine is generally mixed with bicarbonate of soda and some glutinous material1 to help it to retain its shape1 and is then pressed into the well-known form of small square or oblong blocks4 8,it is also used largely in the manufacture of blue paint and printing ink1 and in the preparation of blue mottled soap4 ,the way in which it is employed in the last-named manufacture is worthy of remark4 ,it is added to the soap while it is in a molten state and just before it is allowed to cool1 and thoroughly mixed with it1 so that the whole mass is of a pale blue tint4 ,if a small quantity of this be removed from the boiler and cooled quickly1 it remains of a uniform tint1 but in the case of the whole boilerful1 where the cooling is very slow1 the action is entirely different4 ,just at the point of cooling1 when the soap is going to set hard1 the ultramarine--to use a technical expression--8strikes10 and goes into the form which gives to blue mottled soap its well-known appearance4 8,in the manufacture of paper1 ultramarine also plays an important part4 ,it is here used not only for producing blue shades1 but also as a bleaching agent1 to counteract the yellow when white paper is made4 8,another important use is in the calico manufacture1 where it is used both in the printing of blue patterns and in the finishing of goods4 ,in the case of calico printing1 it is mixed with albumen and printed on to the calico1 which is then subjected to the action of steam1 the albumen being by this means coagulated and each grain of ultramarine surrounded by an insoluble envelope1 so that it cannot be washed out of the calico4 8,the growth in the manufacture of ultramarine has been very remarkable1 especially when it is considered how little the process is understood chemically1 and what care and patience--to say nothing of the equally important item of capital--are required in the starting of a manufactory4 ,commencing less than #ej years ago in the works of ,guimet1 at ,lyons1 who produced #abj1jjj lb4 annually1 there are at the present day nearly #dj manufactories at work in various parts of the world--chiefly in ,germany--producing about #bj million lb4 per year4 ,the following figures will give some idea of ten years' growth of this industry--from #ahfb to #ahgb3-- #ahfb4 #ahgb4 ,number of manufactories #bd #cb ,men employed #ifd #aibi ,tons manufactured #ceef #hehe 8,from the above numbers it will be seen that in these ten years the manufacture more than doubled itself1 the fact being due1 however1 not so much to the increase in the number of works1 which was only one-third1 as to the enlarged capabilities of those existing in #ahfb4 ,thus1 in the works of ,dr4 ,leverkus1 near ,cologne--the first works ever started in ,germany--the number of men employed had1 during these ten years1 more than doubled1 while the output had trebled2 and in the case of the ,marienberg ,works the difference was even more striking1 the number of hands employed and the quantity turned out per annum having nearly quadrupled40 ,in reply to various questions which were asked in the discussion which ensued1 ,mr4 ,rawlins said that1 with regard to the use of ammonia soda1 it had frequently been used in the manufacture of ultramarine1 and was constantly used he understood1 but he himself had not much experience of it4 ,as far as he could make out1 it certainly produced ultramarine1 but of a darker shade than that made with ,leblanc soda4 ,it could not be supposed1 in works where the ,leblanc soda was used1 that ammonia soda could conveniently be substituted1 for of course a works when established had to adhere to its known standards and shades1 and it would not do to change the raw materials1 though the ammonia soda produced a very good ultramarine4 ,as regards the discovery of ultramarine1 the first works started anywhere were ,guimet's4 ,he had with him a little historical list containing the dates at which the various works established before #ahff or a little later had been started4 ,it was drawn out by ,hoffmann1 who1 as he stated before1 was the manager of large ultramarine works1 and he put down ,guimet's1 which were started in #ahbi1 first on the list4 ,dr4 ,leverkus started in #ahcd4 ,he knew that the discovery of ultramarine had been attributed to different people4 ,he had mentioned ,guimet because it had generally been considered1 as far as he had heard1 that ,guimet and ,gmelin were the two who discovered it from a manufacturing point of view4 ,he had heard of crystals of ultramarine1 but had never seen any1 and he knew they were very difficult to prepare1 and very rare4 ,he had mentioned that the grinding had to be done very thoroughly1 because the better it was mixed and the finer it was ground1 the better was the ultramarine produced4 ,if it was badly mixed it was quite fatal to getting a good result4 ,grinding lightens the colour4 ,raw ultramarine must be ground before it was practicable to use it at all4 ,for instance1 a coarse ultramarine could not be used for printing calico4 ,therefore it was necessary to grind it both for the sake of the colour and for the sake of the way in which it was applied4 ,it was increased in value by grinding because it made it stronger and finer4 ,before grinding it was of a dark colour1 but after grinding it became lighter and brighter4 ,the materials employed in ,mc,ivor's process for making ultramarine are kaolin or other suitable clay1 a solution of sulphide of sodium1 in which sulphur in the form of flowers of sulphur is dissolved to saturation1 and caustic or carbonate of soda4 ,the preparation of the solution is effected by adding the sulphur to boiling sulphide of sodium liquor of maximum strength until it ceases to be taken up4 ,the clay and soda are first roasted together at a red heat1 so as to effect a partial double decomposition1 and the product1 after grinding1 is made into a thick paste with 8sulphur liquor10 i4 e4 the sulphide of sodium solution of sulphur4 ,this latter operation may be carried out in an ordinary pug-mill4 ,the paste so formed is dried in an oven or other convenient way1 and the dried mass 7being broken into small pieces7 is roasted without access of air in a closed earthenware retort1 first at about #dhj-egj ,f4 for an hour1 then at a red heat for eight hours1 and finally at a moderate heat just below dull redness1 in presence of a slow current of air1 which enters through a series of holes or small openings in the front of the retort1 the current being regulated by means of a damper or an adjustable slide4 ,the retort should be allowed to become quite cold before being opened1 otherwise the tint of the product will be injured4 ,mc,ivor has found the following proportions of the raw materials used in the process to yield excellent results1 viz3-- ,sulphide of sodium #db lb4 ,sulphur #bj 8 ,kaolin 7china clay7 #aaj 8 ,soda 7as carbonate7 #ajf 8 or ,caustic soda #dj 8 ,these quantities yield about #b cwt4 of ultramarine blue4 ,the following communication from the pen of ,j4 ,b4 ,nejedly1 of ,vienna1 appeared in the ,chemiker ,zeitung1 during #ahhh3-- 8,animated by various articles and notes in your journal under the heading of #8,the ,present ,position of the ,manufacture of ,ultramarine1' ,i would like to draw out of obscurity a little work on this industry which contains much that is true1 and furnishes at the same time many comparisons with regard to the present position of the ultramarine industry in ,germany4 8,the work above referred to was printed in the year #ahdj and bears the title3-- 8#8,treatise on the chemico-technical preparation of ,ultramarine colours1 according to the discoveries of ,leykauf and ,heyne1 or on the importance of the manufacture of blue and green ,ultramarine for purposes of science1 art1 and industry4 ,by ,friedr4 ,wilh4 ,heyne1 president of the ,nrnberg ,ultramarine ,manufactory4 ,nrnberg3 #ahdj4 ,printed at the ,campe ,press4' 8,the preface1 which ,i consider to be well suited to present circumstances1 ,i reproduce verbatim1 while from the little work itself ,i will only quote such sentences as would seem to be suited to the present time1 and which are the most important as bearing on the subject4 8#8,preface4--,the incitement to this treatise was furnished by the utility of the discovery of ,leykauf1 instructor of chemistry at the technical schools in ,nrnberg1 of artificially preparing the well-known blue mineral colour styled ultramarine1 according to simple principles1 which discovery was supplemented by the production of the green ultramarine1 an equally genuine and beautiful green mineral colour1 by the technist ,heyne in ,nrnberg4 ,a short review of the importance of these two discoveries for mankind in general and for science1 art1 and industry in particular1 will form the main subject of this treatise1 which has no other object but that of arousing the attention of all high protectors and stimulators1 as well as friends of industry and art1 to a newly-born industrial branch4 ,at this moment we are living in a period when many industries have got into the stocks1 in consequence of far too severe competition1 combined with other influences2 indeed they are barely able to support those engaged in them4 ,if in consequence of this state of things it already becomes of the most vital importance that fresh sources of acquisition should be obtained1 it becomes all the more so when by their means at the same time materials come into requisition which the ,fatherland possesses in great superfluity1 and which otherwise possess no intrinsic value beyond just the expense of extracting them from their natural localities or deposits1 and the worth that attaches to their working up for industrial purpose4 ,a source of acquisition in this sense is met with in the manufacture of blue and green ultramarine colours1 which in course of time can be raised to an extremely valuable acquisition4 ,may the communications here made result in their being considered worthy of a thorough many-sided investigation and consideration4' 8,,regarding ,,the ,,work ,,itself4 8,page #ba4--#8,not long since a prize of #fjjj francs was offered by the 8,socit d',encouragement40 ,this prize was gained by ,guimet1 who has not published his process1 and who now furnishes ultramarine at the price of #be francs per oz41 whereas it otherwise cost #bjj francs per oz4 ,latterly1 in #ahci1 ,guimet reduced his price for ultramarine1 viz4 ,no4 #a1 for painting1 to #aj francs1 a lighter shade being #f francs per oz4 ,in addition1 this manufacturer furnishes lower qualities for carpet and paper manufacturers at #bj francs and #ab francs per lb4' 8,page #bc4--#8;,indeed1 if we are able to produce ultramarine by means of a polysulphide of sodium and common clay1 then the most beautiful and most lasting of all known blue colours would at the same time become the cheapest of them all4' 8,page #bg4--#8;,all faults which are known to exist in the old methods are obviated in the new invention of ,leykauf and ,heyne1 while the same offers the following advantages3-- 8#87#a7 ,the materials which are treated with it can be brought into use without any special previous chemical preparations1 indeed as supplied by ,nature1 while chemical treatment is entirely unnecessary4 ,in view of the unimportant cost of derivation of the raw material1 there cannot consequently be any questions raised with regard to waste4 8#87#b7 ,this method is so simple that any man of sound intellect can easily work it1 without possessing any special chemical knowledge beforehand4 ,as the labour can be easily grappled with1 errors can only occur when the grossest carelessness is shown in conforming to the instructions prescribed4 8#87#c7 ,according to the said method one can work according to any desired scale1 and1 what is best of all1 the larger this scale the more favourable are the results obtained1 lighter work and excellence of quality4 8#87#d7 ,if the process is carefully conducted1 everything is in your own power1 nothing depending on chance4 8#87#e7 ,consequently an equal product can invariably be obtained1 while this can at will be brought to the most complete stage of perfection at but little greater cost than lower qualities entail4 8#87#f7 ,according to this method you are master of the fire1 enabling a retention of colours in any desired shade1 of the deepest tone1 of the greatest permanency4 8#8,from this it appears3 ,that this process is the easiest1 the cheapest1 and the most complete4 ,worked according to this method the hope is likely soon to become a reality that ultramarine may yet become the cheapest of all mineral colours1 and as in the same everything rests upon simplicity1 the preparation of the article in future will be carried on somewhat after the fashion of baking1 brewing1 c4' 8,page #cb4--#8,moreover1 there is not only blue ultramarine1 but also a pure green1 and we may venture the hope that similar combinations in white1 black1 red1 and yellow will soon follow in equal perfection4 ,in consequence of these discoveries1 ,leykauf and ,heyne have erected a factory in ,nrnberg1 which1 according to a circular dated #aeth ,july1 #ahdj1 is in operation under the style of 8,leykauf1 ,heyne and ,co410 and are producing the two ultramarine colours referred to at the present time at the rate of #ej lb4 per day4' 8,page #cc4--#8;,all the mechanical appliances of the factory are at the present time exclusively worked by hand1 the number of persons employed being sixteen2 while the establishment upon completion of the buildings that are wanting is calculated to employ twenty operatives and two horses4 ,with this extension the factory will be able to turn out #e cwt4 blue and #e cwt4 green weekly1 consequently annually #ejj cwt4 of finished merchantable ultramarine will be brought on the market4' 8,page #ce4--#8,now1 as regards the prices ruling at present for ,nrnberg ultramarine1 these are1 as compared with those of the ,french1 more than #ejj per cent4 cheaper4 ,blue ultramarine costs1 namely1 in ,nrnberg1 quality ,no4 #j1 #aj florins per lb42 a lighter quality1 which is nevertheless darker than the darkest ,french at #ajj francs1 #e fl4 per lb42 a third quality likewise darker than the seconds ,french at #fj francs1 #c fl4 per lb4 ,green ultramarine1 #c fl4 #aj kr4 per lb4 8#8,how much further1 however1 these low prices will be yet reduced after the completion of the factory1 may be gathered from a detailed calculation of cost which the chief of this factory has made himself responsible for as being the highest estimate4 ,this calculation of cost is based upon the weekly production of #aj cwt41 which the factory will soon be able to turn out1 and upon a necessary cost of plant and working capital of #ij1jjj ,rhenish florins1 as follows3-- 8,page #cf4--#8;,calculation of cost of #ejj cwt4 blue and green ultramarine3-- ,fl4 7#a7 ,raw material and cost of transport #aj1jjj 7#b7 ,fuel1 including cost of transport of #gbjj cwt4 of coal at fl4 #a4cj #aj1hjj 7#c7 ,wages of #bj operatives at fl4 #bej per annum #e1jjj 7#d7 ,utensils and apparatus #c1bjj 7#e7 ,buildings and repairs #c1djj 7#f7 ,keep for two horses #fjj 7#g7 ,expense of factory #c1jjj 7#h7 ,cost of administration #b1jjj 7#i7 ,unforeseen matters and accidents #b1jjj 7#aj7 ,interest on building and working capital at #e per cent4 #d1ejj 7#aa7 ,public taxes1 insurance1 c4 #ejj ------ ,thus #ejj cwt4 will cost ,fl4 #de1jjj 8 #a 8 8 ,fl4 #ij 8 #a lb4 8 #dekr4 8#8,forty-five kreutzers1 therefore1 in accordance with the above1 will in future be the production cost of a colour which1 as is well known1 could not be obtained for several hundred guldens1 while in green it was not procurable at any price4' 8,i venture to hope that the foregoing communication may yet prove of some interest in chemical circles40 #a florin or gulden #bs4 #a kreutzer d4 ,ultramarine is by far the most commonly used of the blue pigments4 ,it is a chemical combination of silica1 alumina1 soda1 and sulphur1 but its exact chemical constitution is not known1 the proportions of its ingredients varying somewhat with different makes4 ,there are two principal varieties of ultramarine sold4 ,one is known as sulphate ultramarine the other as soda ultramarine1 from the materials used in the process of manufacture4 ,in the first1 silica1 china clay1 sulphate of soda1 and coal are used2 in the latter1 silica1 china clay1 carbonate of soda1 and sulphur are used4 ,the sulphate ultramarine is distinguished by its very pale greenish blue colour1 while the soda ultramarine is of a violet hue4 ,ultramarine is distinguished from other blues by the fact that acids completely decolorise it1 with the evolution of sulphuretted hydrogen and the formation of a white precipitate of sulphate4 ,the sulphate ultramarine is more easily decomposed by acids than the soda ultramarine1 and some makes of the latter more easily than others4 ,alkalies and heat have no action on this pigment4 ,boiled in strong nitric acid1 ultramarine is completely decolorised1 a colourless solution being formed1 and a gelatinous mass of silica being left as a residue4 ,it is not as a rule necessary to make an analysis of the pigment2 the above tests serve to distinguish it from other pigments4 ,an assay of ultramarine should include the following points3--#ast1 colour or tint2 #bnd1 covering power or body2 #crd1 acid resisting properties3 this can be tested by making a very weak solution of sulphuric acid--about #d oz4 in #ajjj oz4 of water--and adding a little of this to the pigment contained in a glass1 and noting how long it takes to bring about decolorisation2 #dth1 the power of resistance to the action of alum4 ,when ultramarines are boiled with a solution of alum1 they are more or less reddened thereby2 those which are made with a large excess of silica are found to resist this action of alum better than those containing a normal quantity of this compound4 ,such ultramarines are preferred by the paper maker1 who uses a large quantity of alum and sulphate of alumina in the sizing of his papers1 and therefore he wants an ultramarine which shall not change in shade when used for tinting alumina sized papers4 ,this point is easily tested4 ,a solution of alum is made1 and in a little of this a small quantity of ultramarine is boiled for a few minutes1 and it is noted whether any change of shade occurs4 ,if any sample is found to change much1 that sample must be rejected for paper tinting1 although it may be used by the painter or the laundress4 ,it may be worth pointing out here that ultramarine should not be used with any other colours which have a tendency to be acid1 as sooner or later the colour will be destroyed4 ,it should also not be used with lead or copper pigments1 as the sulphur it contains tends to react on those metals2 forming the black sulphides1 thus leading to the ultimate discoloration of the mixture4--7,chemical ,trade ,journal74 ,,chapter ,,iv4 ,,browns4 ,brown colouring matters are obtained from all three kingdoms--the animal1 the vegetable1 and the mineral--but in greatest abundance from the last named4 ,the natural mineral brown pigments afford almost every variety of tint1 and being largely composed of silica and metallic oxides they are remarkably permanent4 ,,asphalt ,,or ,,bitumen4--,these names are applied to a variety of black or brown resinous matters found in many parts of the world in a mineralised state1 though derived originally from organic sources4 ,the 8,bitumen of ,juda0 is supposed to be found on and around the ,dead ,sea1 but the bulk of the product going by that name really comes from ,trinidad4 ,all kinds of asphalt have a pungent and peculiar smell1 melt at a low temperature1 are very combustible1 and while dissolving in turpentine1 and more readily in coal tar naphtha1 are insoluble in water and in alcohol4 ,very little asphalt is now used as a pigment1 but it continues to find a limited application in varnish making1 notwithstanding the tendency of varnishes containing it to suffer from minute cracks with the lapse of time4 ,,bistre4--,this pigment is used exclusively in water-colour painting1 for which purpose it affords a fine warm yellowish tinted brown4 ,it is of vegetable origin1 being prepared from the soot which is deposited in the flues leading from fireplaces which consume wood fuel4 ,every wood1 however1 does not afford an equally good sample of bistre1 and beech occupies the foremost rank in this respect4 ,the brightest and blackest soot is selected1 and after careful grinding and sifting through a very fine sieve1 it is repeatedly stirred up1 for several hours at a time1 in a series of clean hot waters1 the object of which is to dissolve out all traces of tarry and other soluble matters1 which very seriously affect its permanence1 being oxidised on exposure to air and light1 and thus weakening the tint4 ,the washing is therefore a matter of the very first importance4 ,the solid pigment is allowed to settle out of each wash water1 and is collected and dried1 being mixed with a small proportion of gum water to give cohesion4 ,the drying is effected in a stove room4 ,,bone ,,brown4--,this unimportant pigment is simply underdone bone black 7see p4 #f71 and is obtained by stopping the calcination of the bones at a point which falls short of thorough charring4 ,in consequence it contains a proportion of unaltered animal matters1 which sooner or later may undergo decomposition1 and prejudicially affect the painting4 ,,cappagh ,,brown4--,a mineral pigment which is only a variety of umber1 and may best be described under that head 7see p4 #aje74 ,,cassel ,,earth4--,another name for ,cologne earth1 q4 v4 ,,chicory ,,brown4--,this vegetable pigment is rich-coloured but lacks permanence4 ,it is prepared by calcining roots1 such as those of chicory1 in vessels to which air is not admitted1 from which then results a fine brown powder4 ,this is boiled in water1 and the solution is evaporated to dryness1 yielding a brown pigment1 which1 being soluble in water1 is sometimes employed by water-colour artists4 ,,cologne ,,earth4--,this material1 which is also known as ,cassel earth or ,rubens brown1 is an earthy carbonaceous substance1 probably derived from the decomposition of lignite or brown coal1 readily undergoing combustion without emitting flame or smoke4 ,large deposits of it are worked in the vicinity of ,cologne1 whence its name4 ,it is blackish-brown in colour1 smooth and crumbling to the touch1 and very light4 ,to remove soluble impurities it is subjected to several washings in water1 and then collected1 mixed with a little gum-water1 and dried in small moulds4 ,the colour is used by artists1 but is very variable in composition and uncertain in durability4 ,,manganese ,,brown4--,one of the most durable brown pigments used by the ,romans is found to be oxide of manganese1 which discovery has led to the proposal to prepare the binoxide of that metal as a brown pigment4 ,the method suggested is as follows3-- ,the protochloride of manganese1 derived from the manufacture of chlorine1 or the protosulphate resulting from the calcination of the protoxide with iron sulphate1 is dissolved in warm water 7#he-aje ,f472 to this is added a sodium hypochlorite solution1 or a solution of potassium hypochlorite containing a small proportion of carbonate of soda1 the addition being continued until the precipitated manganese binoxide ceases to change colour1 marking the completion of the oxidation4 ,the supernatant clear liquor is drawn off1 and the precipitate is washed first with acidulated water 7containing #b per cent4 of sulphuric acid71 and then with pure water till all trace of the acid is removed4 ,the dark-brown impalpable powder of manganese binoxide is stove dried1 and forms a permanent and safe pigment with good covering power4 ,,mars ,,brown4--,one of the products obtained by the calcination of ,mars yellow 7q4 v47 at various temperatures and under different conditions is a full-tinted and durable brown due to sesquioxide of iron4 ,another method of preparing it is from alum1 sulphate of iron1 and chloride of manganese4 ,in either case the pigment is not superior to umber or oxide of iron1 while it cannot be produced as cheaply4 ,,prussian ,,brown4--,an artists' colour known by this name is prepared from ,prussian blue1 but as it has no superiority over ,vandyke brown or umber1 and is higher priced1 it is not in general use4 ,it consists essentially of carbon and ferric oxide1 resembles bistre in tone1 and possesses durability and good covering powers4 ,the operation of calcining the ,prussian blue should be conducted slowly1 and is best performed in a closed vessel1 though it may also be done in the open4 ,the pieces of blue should not be larger than a hazel nut4 ,they soon split1 scale off1 and become red1 when the heating should cease4 ,on breaking the cooled particles they will show a patchy coloration varying from yellowish-brown to black4 ,on grinding1 the mass assumes the desired brown hue4 ,,rubens ,,brown4--,another name for ,cassel brown or ,cologne earth 7q4 v474 ,,sepia4--,this is one of the few pigments derived from the animal kingdom4 ,it is produced by several sea-inhabiting creatures belonging to the class called ,cephalopoda1 and more particularly by two members of the genus ,sepia1 known respectively as ,sepia officinalis and ,sepia loligo4 ,a peculiarity of these cephalopods is that they are provided with what is commonly called an ink bag1 in other words a gland or sac filled with a blackish-brown liquid1 which possesses intense colouring power4 ,the object of the secretion is the protection of the creature from pursuit by its enemies1 a portion of fluid being discharged at will1 and so obscuring the surrounding water that escape is facilitated4 ,for the sake of this pigment the cuttle-fish are sought after by fishermen in the localities frequented by the animals1 notably in the warm waters of the ,mediterranean4 ,when the creatures are captured1 their glands are carefully extracted and sun-dried so as to solidify the contents4 ,in this state ink bags are sent into commerce4 ,the colourman subjects the sacs to boiling in a solution of soda or potash1 whereby the colour is dissolved out of the receptacle1 and being filtered clear of all fragments of the animal tissue1 is next precipitated by the addition of acid1 collected on a filter1 washed1 and dried4 ,it then forms an exceedingly useful pigment1 having1 according to ,prout1 the following average composition3-- ,per cent4 ,black pigment 7melanin7 about #gh ,calcium carbonate #aj ,magnesium carbonate #g ,alkaline chlorides and sulphates #b ,organic matter #a ,it is remarkably permanent for an organic substance1 suffering no alteration on being combined with other pigments1 and withstanding the effects of exposure to air and light4 ,though slightly transparent1 and not quite constant in tint1 it possesses very great colouring power4 ,being of extremely fine texture it can be worked up equally well as an oil colour or as a water colour1 but it is especially in the latter capacity that it forms an indispensable artists' colour1 and permits the production of a great range of shades and tints4 ,,ulmin4--,the pigments grouped under this name are also of organic origin2 but though they possess good colour1 mix well1 and flow readily from the brush1 they lack the durability which is essential to their successful use4 ,the following methods have been employed in their preparation3--7#a7 ,fused caustic potash is digested in alcohol1 and the liquor filtered and heated till a brown powder is thrown down1 which is filtered and washed with acidulated water2 7#b7 ,waste cotton1 peat1 or brown coal1 heated with an alkali2 7#c7 ,farinaceous matters carbonised by mineral acids4 ,,umbers4--,these form a large class of natural earths of a brown colour1 differing widely in the proportions of their chief constituents1 but closely allied to the ochres and siennas in general composition1 and owing their colour mainly to the presence of hydrated oxides of iron and manganese1 the latter prevailing in the umbers to a greater degree than in the ochres and siennas1 which consequently belong to the yellow group 7q4 v474 ,beds or veins of umber of varying thickness and extent are found in many places1 especially in connection with magnesian limestone 7dolomite74 ,apparently they are often derived from decomposition of this rock1 perhaps due to the infiltration of carbonated water1 which has acted upon the calcium and magnesium carbonates in the dolomite1 and left the silica and the iron and manganese as oxides1 forming the bulk of the umber4 ,usually these beds of umber are near the surface1 though covered by an overburden of vegetable soil1 and the operation of working them may be called quarrying rather than mining1 being of a superficial and simple character1 often only amounting to small pits4 ,as no umber is a definite body1 but rather a mixture of various substances1 so the composition of every kind is peculiar to itself1 and very wide differences are noticeable4 ,even the same bed will not necessarily produce always the same class of umber4 ,the following figures show the extent to which the proportions of the several ingredients may vary3-- ,per cent4 ,water given off at #bab ,f4 #d to #fe ,water in combination #e to #aa ,silica #d to #bi ,manganese dioxide #g to #bg ,ferric oxide #f to #cf ,calcium carbonate is sometimes present to the extent of #b to #f per cent41 and at other times is quite absent1 its place being taken by to #a per cent4 of lime 7calcium oxide72 some of the ,english umbers contain about #b per cent4 of calcium sulphate 7gypsum7 in addition to the carbonate4 ,alumina may occur to the amount of #b to #ab per cent41 or may be wanting altogether4 ,in a sample of ,derbyshire umber analysed by ,hurst there appears to have been over #cj per cent4 of barium sulphate 7barytes71 which looks suspiciously like adulteration4 ,almost every variety of shade may be found in umbers4 ,the darkest and richest in colour--a warm violet-brown--is the so-called ,turkey umber1 mined in ,cyprus1 and formerly shipped vi ,constantinople2 this is of very fine quality and commands the higher price in the market4 ,a reddish-brown ,irish umber1 known as ,cappagh brown1 obtained from the ,cappagh mines in ,cork county1 is much esteemed among artists1 both for water-colour and oil painting1 and especially for the latter when it has been subjected to a preliminary desiccation at a temperature of about #agj ,f4 ,heated to the boiling point its colour changes to a rich red1 resembling burnt sienna4 ,cornish umbers are of fairly good quality4 ,derbyshire umbers are poor1 and incline to a reddish tint1 besides being gritty4 ,sometimes they are adulterated with a little lamp black1 which renders the tone more like that of ,turkey umber1 and thus deceives the unwary buyer4 ,there are three conditions in which umbers come into commerce3 7#a7 as raw lump1 being the mineral just as it is mined2 7#b7 as raw powdered1 when it has been ground very fine and levigated or washed in flowing water1 whereby the particles get assorted according to their several degrees of fineness2 and 7#c7 as burnt1 being the powder after it has been subjected to calcination in a closed furnace4 ,some umbers are so soft that they can be washed without any previous grinding1 but this is not generally the case4 ,the apparatus used in grinding and levigating is common to all pigments where these processes are employed1 and will therefore be described once for all in a later chapter4 ,the calcination is conducted at a red heat1 and by this process the tint is made darker and warmer1 but it must not be pushed too far or the pigment will blacken4 ,while different samples of umber present differences of tone and shade1 from a yellowish to a violet brown1 they are alike in being very durable and proof against the injurious influences of air1 light1 and impure atmospheres2 ordinary acids and caustic soda have no appreciable effect4 ,they mix well with other pigments without provoking any change1 and are equally satisfactory as oil or water colours4 ,they do not admit of much adulteration1 except in the substitution of an inferior grade for a superior one1 and possibly the addition of barytes as a make-weight4 ,,vandyke ,,brown4--,what the original brown used so much by the great ,van ,dyke was no one can tell4 ,the pigments now sold under the name of ,vandyke brown are of varying composition1 some being simply mixtures of red oxide of iron and lamp black1 others are natural earthy substances after the character of ,cologne earth1 and others again are artificial products of the partial carbonisation of vegetable matters1 such as cork waste4 ,as it is uncertain what was the composition of the original ,vandyke brown1 no standard of chemical purity can be established4 ,probably the most general sources of ,vandyke brown are red oxide and lamp black1 and the quality of such a pigment will chiefly depend on securing a good black1 as any traces of unburned oily matter will make the paint difficult to dry4 ,almost any variety of shade can be produced by adjusting the proportions of lamp black and red oxide1 with sometimes the addition of a little ochre4 ,the pigment made in this manner forms the staple brown paint for industrial application1 mixing well with oil1 and being of a durable character1 but it does not mix so well with water4 ,vandyke browns of the ,cologne earth type1 from earthy lignites and peaty matter1 are much used in and around the localities where they are produced1 and entail nothing more than grinding and levigation to fit them for the market4 ,they are in general best adapted to water-colour painting4 ,warm and slightly reddish tints of ,vandyke brown are obtained by the partial carbonisation of ligneous material1 in other words by subjecting cork and bark waste to moderate calcination in closed retorts4 ,these mix equally well in water or oil4 ,all varieties of ,vandyke brown are stable pigments1 without any disturbing influence when used in admixture with other colours1 and quite proof against any change on exposure to air and light4 ,next to the umbers they are the most generally useful browns4 ,,chapter ,v4 ,,greens4 ,green pigments form an important and numerous class1 but many of those which possess the most brilliant and durable qualities contain highly poisonous ingredients1 and some of the most beautiful are not permanent4 ,all things considered they are perhaps the least satisfactory group of colouring matters4 ,the following list comprises all worth notice4 ,,baryta ,,green4--,it is said that the manganate of baryta makes an excellent green pigment1 which may with advantage replace for many purposes those greens which contain arsenic4 ,several methods of preparing it have been published3--7a7 ,one consists in igniting together the nitrate of baryta and manganese oxide or dioxide4 7b7 ,another consists in fusing a mixture of pyrolusite or black oxide of manganese1 caustic bartya1 and chlorate of potash4 7c7 ,according to a third method1 mix #b parts caustic soda and #a part chlorate of potash1 and gradually add #b parts very finely powdered manganese2 heat gradually up to dull redness1 then allow to cool1 powder1 and exhaust with water2 filter and cool1 and add a solution of nitrate of baryta to the filtrate2 a violet-coloured baryta precipitate forms2 this is carefully washed1 dried1 and treated with -#a part of caustic baryta1 hydrated1 and gradually heated up to redness1 with constant stirring4 ,the cooled mass is powdered1 and finally washed to remove any excess of baryta4 ,by either process a green mass is obtained1 but the second method seems to yield a more beautiful and homogeneous product4 ,in experimenting with other and more direct methods for preparing a baryta green of great purity and beauty1 ,fleicher has made several observations of its properties4 ,if a green solution of manganate of potash be precipitated1 while boiling1 by chloride of barium1 a heavy1 granular1 but not crystalline1 precipitate of manganate of barium is obtained4 ,this precipitate has a violet colour1 approaching blue1 can be washed by decantation at first1 and afterwards may be collected on a filter4 ,on drying the precipitate1 its colour grows lighter with the increase of temperature2 and on being heated to a dark red heat1 it looks almost perfectly white1 with only a shade of greyish blue4 ,if1 then1 it be heated still higher with free access of air1 or in an oxidising flame1 it gradually turns green2 by carrying the process farther the colour becomes a beautiful greenish-blue1 and finally1 at a very high heat1 a dirty greyish-brown mass is formed from the reduction of the manganic acid to binoxide of manganese4 ,on adding chloride of barium to a solution of the permanganate of potash1 and boiling1 a precipitate is slowly formed of a peach-blossom colour1 while the liquid retains a deep violet colour4 ,by decanting and bringing the mass1 diluted with water1 on a filter1 the precipitate is not decomposed1 and can be dried at #bab ,f4 without changing colour4 ,when the dry permanganate of barium is gradually heated1 its colour also grows paler1 but does not1 like the manganate of baryta1 acquire a green colour at a still higher temperature2 for after the colour has once vanished1 an increase of temperature soon converts it into the greyish-brown mixture of the binoxide of manganese and baryta or carbonate of baryta4 ,hence it is impossible to prepare the green manganate of baryta from the permanganate4 ,in regard to the colour itself1 experiments have shown that the most beautiful green is that formed by igniting the manganate as described above4 ,the green prepared by ,rosenstiehl's process--fusing together caustic baryta1 chlorate of potash1 and binoxide of manganese--is less beautiful than the above2 while that attained from nitrate of baryta and binoxide of manganese is far inferior to either of the others4 ,perhaps1 however1 this colour could be improved by preparing it in a reverberatory furnace with a strong oxidising flame4 ,the blue-green baryta pigment has different shades1 according to its preparation1 some being almost pure blue with only a shade of green1 and resembling the light blue quill feathers of many parrots4 ,the greener the colour the more it gains in intensity1 but it loses in fineness1 although still surpassing the green manganate of baryta4 ,the production of the blue or bluish-green baryta is due entirely to the alkaline property of the mass4 ,whether each definite colour is due to a definite composition is doubtful1 since the temperature1 which must not exceed that of a bright red heat1 exerts a greater influence on the colour4 ,this much is however certain1 that both manganic acid as well as the permanganate of baryta1 when mixed with about #bj per cent4 of hydrate of baryta and ignited at a red heat1 will always produce this blue-green colour4 ,it is evident that the blue-green colour is dependent entirely on its basic character2 for on placing this powder in weak acids1 it first turns green and is then gradually decomposed4 ,the baryta pigment is quite permanent1 and may be subjected to the action of strong sulphuric acid for hours1 at the ordinary temperature1 before the colour will be destroyed4 ,boiling potash solution has no perceptible effect upon it4 ,the permanence1 especially of the blue shade1 is increased by adding a little baryta1 which increases its alkalinity4 ,it is also worthy of remark that the pigment prepared from the nitrate of baryta is much less permanent1 because the nitrous acid present will after a time exert a reducing action4 ,the baryta pigments seem especially adapted to fresco painting1 because they appear very bright and lively on stone1 and especially on lime1 where many other pigments lose their beauty or are entirely destroyed4 ,,bremen ,,green4--,this old-fashioned pigment is a basic carbonate of copper1 and has been produced in several ways4 ,at first a basic chloride or oxychloride was used1 its mode of preparation varying somewhat but without affecting the character of the result1 the great essential being that no subchloride of copper should be present4 ,therefore1 in some factories1 it was the practice to prepare the magma of basic oxychloride even a year in advance2 or1 to subject it to repeated wetting and drying in order to ensure prefect oxidation4 ,the method has now become obsolete1 and is superseded by the following3-- ,when neutral nitrate of copper is decomposed by an insufficiency of a potash carbonate solution1 the flocculent precipitate of copper carbonate formed at first is gradually changed into a subnitrate of copper which is precipitated as a heavy green powder4 ,in practice the operation is conducted as follows3--,copper scales are calcined in a reverberatory or muffle furnace1 till all the suboxide is converted into protoxide1 or until a sample dissolves in nitric acid without evolution of red nitrous vapours4 ,the copper nitrate solution is heated and decomposed by a clear solution of potash carbonate1 and when the effervescence subsides1 small doses of potash carbonate solution are added1 till but little undecomposed copper remains in the solution4 ,to recover this last portion1 the clear liquor is decanted1 and the green precipitate is washed several times with small quantities of water4 ,all the liquors are collected1 and the remaining copper is precipitated by potash solution4 ,the green carbonate of copper is introduced into a new solution of copper nitrate1 in which it is transformed into a basic salt4 ,the previous liquors are evaporated till they afford crystals of nitrate of potash1 which is a valuable secondary product4 ,,brighton ,,green4--,the following recipe has been published for making this pigment4 ,dissolve separately #g lb4 sulphate of copper and #c lb4 sugar of lead1 each in #e pints of water2 mix the solutions1 stir in #bd lb4 of whiting1 and when the mass is dry grind to powder4 ,,brunswick ,,green4--7a7 ,old process4 ,the ,brunswick green of former days was closely allied to ,bremen green1 essentially consisting of a basic chloride or oxychloride of copper1 and possessing all the faults incidental to that class of copper salt4 ,while having fairly good covering power1 and capable of being used either as a water colour or an oil colour1 it was tedious and therefore expensive to prepare1 and not thoroughly durable under exposure to air and sunlight4 ,nevertheless it was a useful bluish-green pigment4 ,following are some of the many methods by which it has been prepared3-- 7#a7 ,poor oxidised copper ores are moistened with hydrochloric acid1 and spread out exposed to the air4 ,the metal is thus rendered very susceptible to the action of chlorine1 and is even attacked by solutions of ammonium chloride and of common salt4 ,the sub-chloride produced is rapidly transformed into oxy-chloride1 and forms a fine light-green pigment4 7#b7 ,place #b parts by weight of copper-filings in a vessel capable of being tightly closed1 and over them pour #c parts by weight of salammoniac in the form of a saturated aqueous solution4 ,keep the mixture in a warm place for some weeks and thoroughly agitate it occasionally4 ,in due time the newly formed oxychloride is removed from the vessel1 and separated from the non-oxidised copper by washing on a sieve4 ,this washing must be continued until all traces of alkali have been destroyed1 when the pigment is drained1 and very slowly dried at a low temperature to avoid decomposition4 7#c7 ,copper scrap is covered with a concentrated solution of chloride of copper and allowed to remain until the chloride has undergone conversion into basic chloride4 ,the latter is then subjected to the straining1 washing1 and drying treatment prescribed in 7#b74 7#d7 ,in a lead-lined vessel1 place a quantity of copper filings or waste1 and add to it two-thirds of its weight of common salt1 and one-third of its weight of concentrated sulphuric acid1 the latter being however first diluted by admixture with three times its volume of water4 ,the mass is left to stand1 with occasional stirring till all the copper has been transformed into oxychloride1 when it is strained1 washed1 and dried as in 7#b74 7#e7 ,a modification of 7#d7 is to put the copper scrap into a wooden vessel1 and cover it with an equal weight of common salt and an equal weight of sulphate of potash dissolved in water4 ,after standing and agitation as before1 the oxychloride is formed1 and the straining1 washing1 and drying are repeated4 7#f7 ,a solution of crude carbonate of ammonia is added to a mixed solution of alum and blue vitriol so long as any reaction takes place4 ,when it is completed1 the precipitate is collected1 washed1 and dried as in the other cases4 7#g7 ,lighter shades are produced by the addition of alum1 or of sulphate of baryta4 7b7 ,new process4 ,the modern ,brunswick greens1 which are made in a variety of shades1 and sometimes known as chrome greens1 ,prussian greens1 ,victoria greens1 and by other fancy names1 really consist of a white pigment as a basis--usually sulphate of baryta 7barytes71 but occasionally also sulphate of lime 7gypsum7 and sulphate of lead--coloured green of varying intensity and depth by addition of a blue pigment in the shape of ,prussian blue1 and a yellow in the guise of chrome-yellow4 ,there are what may be called four distinct standard shades recognised by colour-makers1 viz4 8pale10 8medium10 8deep10 and 8extra deep02 but inasmuch as every manufacturer adopts a formula of his own1 there may be appreciable differences among colours of the same nominal standard if by different makers4 ,taken as a whole1 about three-fourths of their total weight consists of the foundation white pigment1 usually barytes2 about #a to #f per cent4 is ,prussian blue1 according to the shade2 and #ad to #ah per cent4 chrome yellow2 but there are brands occasionally met with which depart considerably from these average figures4 ,the actual ingredients employed to form these green pigments are essentially different1 according as the wet or the dry method of combining them be adopted4 ,in selecting the various ingredients the following points must be borne in mind4 ,the ,prussian blue of every maker is not the same in quality1 and while the character of the blue is not of the foremost importance when dark greens are being made1 for light shades of green1 on the other hand1 it is essential to select only the best and brightest brands4 ,in the same way the tint and quality of the chrome yellow are liable to considerable fluctuation1 and it is almost impossible to ensure two lots having exactly the same characteristics1 consequently the only way in which a certain shade of green can be ensured is by experimental trial with small quantities for each batch4 ,middle chromes can be used for deep greens1 but only the lemon chromes for pale shades4 ,regarding the barytes which forms the basis of the pigment1 there are no special precautions to be observed2 and the same may be said of the gypsum1 should that be adopted as a substitute for the barytes1 except that #a part by weight of gypsum takes the place of about #b parts of barytes4 ,the latter1 however1 is much the more commonly used4 ,for the dry method of compounding ,brunswick greens1 the above named ingredients are all that are required4 ,in the wet method there is this essential difference1 that it is sought to precipitate the blue and yellow colours upon the inert base by bringing about certain reactions1 and therefore while the base remains the same as in the dry method1 the colouring media are totally distinct1 consisting of lead acetate1 bichromate of potash1 sulphate of iron1 and yellow or red prussiate of potash4 ,the chief condition to be observed with regard to the lead acetate is that it shall be in the proportion of slightly more than three to one of the bichromate of potash2 in other words1 the bichromate should be a trifle less than one-third the weight of the lead acetate4 ,as to the iron salt1 if commercial acetate or nitrate of iron could be bought of constant quality or purity1 that would be the most convenient form2 but failing that1 recourse is had to freshly made and good quality sulphate of iron 7green copperas74 ,it is found that the best results are secured when the weight of the sulphate of iron is exactly the same as that of the prussiate of potash4 ,on the score of economy1 the yellow prussiate of potash 7ferrocyanide7 is employed1 but the red prussiate 7ferricyanide of potassium7 gives better and more certain results1 and should be adopted when making a superior paint which will command a higher price4 ,as to the comparative merits of the wet and dry systems of mixing the ingredients of ,brunswick greens1 preference must be given to the former on the score of quality of the pigment produced1 but on the other hand it entails much more trouble and skill1 and there never can be the same degree of control over the conduct of the operation or the shade of colour developed4 ,the dry method1 however1 though much more easily carried out1 and enabling the exact shade desired to be obtained to a nicety by adding a little more of either the blue or the yellow during the process of manufacture1 is seldom adopted1 because the quality and fineness of the tints thus secured are much inferior4 ,the modus operandi with the wet method is as follows3--,the barytes1 in the requisite fine state of subdivision1 is very thoroughly stirred up with water in a capacious vessel fitted with an agitator1 the water being in sufficient quantity to make quite a fluid mass4 ,in convenient proximity to the barytes tank1 and elevated above it1 provide three other tanks of lesser capacity furnished with means of discharging their contents into the barytes tank4 ,in one of these smaller tanks dissolve the green copperas in cold water2 in another1 the sugar of lead2 and in the third the bichromate and prussiate of potash together4 ,when all the salts are thoroughly dissolved1 and while the barytes is kept in constant agitation1 admit first of all the copperas solution1 then the lead acetate solution1 and finally the combined bichromate and prussiate solution1 never allowing the stirring to slacken till after the last drop of these solutions has been introduced4 ,when the commingling of all the ingredients is judged to be complete1 the green pigment formed is allowed to subside1 and the clear supernatant fluid is siphoned off4 ,the pigment is washed several times by admitting clean water1 agitating and settling1 and finally is removed1 drained on a filter1 and slowly and carefully dried4 ,many ways of arranging the apparatus will suggest themselves1 the chief point to keep in mind being to economise labour as much as possible4 ,the dry method of mixing is simplicity itself in comparison with the above1 and merely entails putting the component materials--barytes1 chrome-yellow and ,prussian blue--through an edge-runner mill simultaneously1 in the proportions adapted for producing the shade required4 ,in giving formul for compounding these ,brunswick greens1 it must be understood that they are not absolute1 as every manufacturer adopts his own particular proportions for a certain shade1 but they form a sufficiently approximate basis from which to work4 ,they are all computed for #ajj lb4 of barytes forming the body of the new pigment3-- ,pale3 ,wet--#a lb4 each copperas and prussiate1 #ab lb4 lead acetate1 #c lb4 bichromate4 ,dry--#hj lb4 chrome yellow1 #a lb4 ,prussian blue4 ,medium3 ,wet--#a lb4 each copperas and prussiate1 #ab lb4 lead acetate1 #d lb4 bichromate4 ,dry--#cj lb4 chrome yellow1 #b lb4 ,prussian blue4 ,deep3 ,wet--#b lb4 each copperas and prussiate1 #ac lb4 lead acetate1 #d lb4 bichromate4 ,dry--#cj lb4 chrome yellow1 #d lb4 ,prussian blue4 ,extra deep3 ,wet--#c lb4 each1 copperas and prussiate1 #ad lb4 lead acetate1 #d lb4 bichromate4 ,dry--#cj lb4 chrome yellow1 #g lb4 ,prussian blue4 ,the ,brunswick greens are in the front rank of green pigments so far as covering power is concerned1 and1 when made from reliable materials1 are reasonably durable under the influence of air and light1 in which respect1 however1 they vary considerably4 ,they can be used as water colours1 but are superior in oil paints4 ,precautions are necessary in mixing them with other pigments4 ,by the action of sulphuretted hydrogen1 or sulphur in any form1 the colour is darkened to a notable degree2 by the action of acids1 the chrome is destroyed and the green becomes blue2 by the action of alkalies1 both the blue and the yellow constituents are affected1 and the green gives place to a reddish hue4 ,the pale and medium shades are yellow greens2 the deep and extra deep are blue greens4 ,these colours can be distinguished by heating them with caustic soda1 which turns them brownish in tone1 owing to the destruction of the ,prussian blue4 ,if the residue be filtered1 and to the filtrate some acid and ferric chloride be added1 a blue precipitate will be obtained1 indicative of the presence of ,prussian blue4 ,on washing the residue with water and treating with hydrochloric acid1 the brown colour disappears1 and1 in most cases1 only a white residue of barytes is left2 sometimes the residue may have a faint yellowish colour4 ,the solution in hydrochloric acid will give the characteristic tests for iron4 ,the yellow element can be recognised by boiling in hydrochloric acid1 filtering1 and allowing the filtrate to cool1 when crystals of lead chloride will deposit2 these1 separated out and dissolved in boiling water1 will give the characteristic tests for lead1 such as a white precipitate with sulphuric acid1 and yellow precipitate with bichromate of potash4 ,the filtrate will have a green colour1 indicative of chromium4 ,,chinese ,,green4--,another name for the vegetable pigment known in ,china as ,lokao 7q4v47 ,,chrome ,,green4--,this name is often applied to any green in which chrome enters as an element1 but more particularly to the modern ,brunswick greens described on pp4 #aad-aah2 and to the green which bears the name of its first maker1 ,guignet1 and described under the title of ,guignet's ,green1 see p4 #abe4 ,,cobalt ,,green4--,this remarkably stable1 but somewhat costly1 pigment is also known by the names of ,rinmann green and zinc green1 the former after the name of the chemist who first prepared it1 and the latter because it contains a large proportion of zinc4 ,it is in fact a combination of the oxides of cobalt and zinc1 and was originally produced in the following manner3- lb4 pure cobalt ore was dissolved in #d lb4 concentrated nitric acid1 and added to a solution of #a lb4 zinc in #e lb4 nitric acid2 the mixture was diluted with water1 and a solution of potash carbonate was added1 throwing down a pinkish precipitate1 which was washed on a filter1 dried1 and calcined at a high temperature4 ,wagner found that an indispensable condition was to have a protoxide of cobalt as free as possible from foreign metals1 with which object he practised the following method3--,cobalt oxide is dissolved in three equivalents of hydrochloric acid1 and the solution is evaporated to dryness2 the residue is dissolved in six equivalents of water1 and through the solution is passed a current of sulphuretted hydrogen gas1 so long as any precipitate is formed4 ,this precipitate consists of sulphides of the foreign metals4 ,the clear solution is siphoned off1 evaporated to dryness1 and the residue is dissolved in water4 ,as required1 this solution is treated with carbonate of soda1 and the precipitate1 washed1 and while still wet1 is mixed with zinc white4 ,the reddish mass produced in this way is dried and calcined4 ,the best tone is attained by combining #i to #aj parts of zinc oxide with #a to #a parts of cobalt protoxide4 ,louyet has shown that if the cobaltic solution be precipitated by the phosphate or the arseniate of potash1 the corresponding salt of cobalt thus produced possesses the property of imparting a green colour to zinc white at a much lower temperature than is required in the case of ordinary protoxide of cobalt3 moreover1 the pigment gains in body1 and the colour gains in purity and brightness4 ,if a small quantity of arsenious acid is added to the ordinary mixture before calcination1 the calcined mass will assume a remarkably bright green colour2 and its structure being loosened by the disengagement of fumes of arsenious acid1 it will be easy to grind4 ,according to ,barruel and ,leclaire's method1 #a lb4 of pure dry sulphate of cobalt1 dissolved in hot water1 is mixed with #e lb4 of zinc oxide4 ,the mixture is dried1 and calcined for three hours at a clear red heat in a muffle2 when cooled1 it is thrown into water1 washed1 and dried4 ,the composition of cobalt green has been shown by ,wagner to vary considerably1 as is to be expected from the methods of its preparation4 ,the proportion of zinc oxide ranges from #ga to #hh per cent41 and the cobalt protoxide from #aa to #ai per cent42 in addition1 there will be fluctuating percentages of phosphoric acid1 soda1 oxide of iron1 c41 according to the process followed4 ,with the single exception of its costliness1 cobalt green possesses advantages over most other green pigments4 ,it has a bright colour1 sometimes inclining to a yellowish tint1 or1 when phosphates are used in its preparation1 leaning to a blue shade4 ,but it is always permanent1 not only under the influence of air and light1 but also in the presence of alkalies and any but concentrated acids2 thus it may safely be compounded with other pigments4 ,,douglas ,,green4--,this pigment1 which is fairly permanent1 and possessed of considerable covering power1 owes its name to the chemist who proposes its use1 and its colour to the oxide of chromium4 ,the method by which it is prepared is as follows3--,solutions of barium chloride and potassium chromate are mixed together4 ,to the barium chromate thus produced is added one-fifth of its weight of concentrated sulphuric acid1 whereby partial decomposition is brought about1 resulting in a mixture of barium chromate1 barium sulphate1 and chromic acid4 ,this mixture is dried1 and calcined in a crucible at bright red heat1 the effect of which is that the chromic acid is converted into green oxide of chromium1 and1 being scattered throughout the mass1 imbues it with a green colour4 ,,emerald ,,green4--,this is quite an old-fashioned pigment1 having been in use some #hj years4 ,it is a combination of acetate and arsenite of copper1 and varies in tint from a dark to a pale green1 always with a bluish cast4 ,it possesses good covering power1 and can be used either as an oil-or as a water-colour1 but particularly as the latter1 and is much used in paper staining4 ,in composition it varies considerably1 as there are some half-dozen industrial methods of making it2 but in general terms it usually contains over #ej per cent4 of arsenious acid1 and about #cj per cent4 of oxide of copper1 together with various impurities4 ,following are some of the processes by which it is manufactured4 7#a7 ,according to the method introduced by ,liebig1 #a part of verdigris is heated in a copper kettle with sufficient distilled vinegar to effect its solution1 and to this is added a solution of #a part of arsenious acid in water4 ,the result is a precipitate of a dirty green colour1 which is dissolved in a new quantity of vinegar and boiled for some time4 ,in this way is obtained a new precipitate1 granular and crystalline1 and exhibiting a splendid green colour4 ,when this has been filtered off1 washed1 and drained1 it is boiled with one-tenth of its weight of commercial potash1 in order to deepen and brighten the colour and destroy the bluish tint4 ,should the waste liquor obtained after the filtration of the pigment from the second boiling in vinegar contain any remaining copper1 arsenious acid is added2 and if arsenious acid be present1 copper acetate is added2 while if acetic acid survives it may be used again for dissolving another lot of verdigris4 7#b7 ,form a paste with #a part verdigris in sufficient boiling water1 pass it through1 a sieve to remove lumps1 and gradually add it to a boiling solution of #a part arsenious acid in #aj parts water1 the mixture being constantly stirred until the precipitate becomes a heavy granular powder1 when it is filtered through calico1 and dried very carefully4 7#c7 ,acetate of copper is mixed with a sufficient quantity of water heated to #abb ,f41 to make a homogeneous and liquid paste4 ,to #aj parts of acetate of copper in this condition is added a solution of #h parts of arsenious acid in #ajj parts of boiling water1 the whole being then kept in a state of ebullition4 ,the addition of a little acetic acid helps to develop the beauty of the colour4 ,when precipitation is complete1 the clear liquor is drawn off1 and forms a convenient solvent for the next charge of arsenic1 the operation being facilitated by adding a little carbonate of potash1 forming an arsenite of potash4 ,the precipitate constituting the desired green pigment is filtered off and dried at the lowest effective temperature4 7#d7 ,dissolve #e lb4 of sulphate of copper in water1 and add to it a solution of #a lb4 of lime in #b gallons of vinegar4 ,mix #e lb4 of white arsenic with sufficient water to form a paste4 ,add the arsenic paste to the copper and lime mixture1 and leave the whole at rest in a moderate degree of heat4 ,mutual decomposition slowly ensues1 with consequent formation of the green pigment1 which is filtered off1 washed1 and dried with the same precaution as before4 ,when sulphate of copper is used in the production of emerald green1 it is very desirable that it shall be free from sulphate of iron1 which is a common impurity in the commercial article1 and greatly detracts from the purity and brilliance of the pigment4 ,a good method of eliminating this iron is to add to the sulphate of copper solution a small quantity of a gelatinous precipitate of carbonate of copper1 produced by decomposing a copper sulphate solution by a soda carbonate solution1 and washing4 ,on adding the gelatinous carbonate of copper1 with agitation1 the iron is soon thrown down in flakes of oxide1 and pure sulphate of copper may be filtered off4 7#e7 ,braconnot proceeds as follows3--,a solution of #c lb4 of sulphate of copper is made in a small quantity of hot water2 and a second solution of #c lb4 of arsenious acid and #d lb4 of commercial carbonate of potash in boiling water4 ,when the evolution of carbonic acid gas has ceased1 the two liquors are mixed together while being kept continuously stirred2 the result is an abundant precipitate of a dirty yellowish-green colour4 ,on adding a slight excess of acetic acid1 a fine crystalline green is developed2 this is washed with boiling water on a filter1 and dried very slowly and carefully4 7#f7 ,a rough and ready process is to mix white arsenic with water1 and then stir in an equal weight of verdigris1 allowing the mixture to be at rest for a time in a moderately warm temperature till the pigment is completely precipitated1 when it is washed on a filter1 and dried very gradually4 7#g7 ,a method due to ,kchlin is described in the following terms3--,an aqueous solution of sulphate of copper is made by adding #ajj grammes of the salt to #ejj cc4 of water4 ,to this1 when solution is complete1 is added #ahg cc4 of a solution of arsenite of soda1 which is of the strength represented by #ejj grammes of arsenite in #a litre of water4 ,the result is that a precipitate of arsenite of copper is thrown down4 ,this precipitate is treated with #fb cc4 of acetic acid at #aa to #ab ,tw41 or half that quantity of pure formic acid1 for one hour1 at a temperature ranging from #ajd to #abb ,f4 ,the pigment thus produced is of good colour1 but its superiority would not seem to justify the use of such an expensive article as pure formic acid1 nor the minute adjustment of the proportions of the ingredients1 in an operation to be conducted on a commercial scale4 7#h7 ,another complicated process has been invented by ,prof4 ,galloway1 which1 under skilled supervision1 and when the correct proportions of the several ingredients have been ascertained by careful experiment1 may give good results1 but several precautions have to be observed which cannot be entrusted to ordinary factory hands4 ,the principle of the process is that when a quantity of sulphate of copper is dissolved in water1 sufficient carbonate of soda is added to throw down one-fourth of that copper sulphate as carbonate of copper1 and then so much acetic acid is introduced as will convert that copper carbonate into acetate4 ,in order to convert the balance of the copper sulphate into arsenite1 a solution of arsenic in boiling carbonate of soda is made and added to the copper acetate solution1 both solutions being at a boiling temperature4 ,emerald green is a pigment which possesses considerable stability in dry pure air1 but in damp atmospheres it becomes brown2 in the presence of acid or ammoniacal vapours it turns blue1 and under the influence of sulphuretted hydrogen it blackens2 moreover1 strong alkalies destroy it4 ,consequently it cannot be used in many situations1 nor in association with such pigments as contain sulphur compounds4 ,in decorative painting it is difficult to apply on large flat surfaces1 and necessitates stippling in order to get it to lie well2 but when stippled on a ground of proper green it develops an exceedingly beautiful bloom-like appearance4 ,its peculiar shade distinguishes it from all other green pigments1 none of which approaches it in the paleness and brightness of its colour4 ,it can be distinguished by the fact that it is soluble in acids and ammonia1 to a blue solution which does not change on boiling4 ,in caustic soda it also dissolves with a blue colour3 on boiling1 a red precipitate of cuprous oxide falls down4 ,no other green pigment answers to all these tests4 ,there are a good many imitation emerald greens on the market1 some of which are offered as genuine emerald greens1 others as 8emerald tint0 green1 which is much more honest4 ,the composition of these greens necessarily varies greatly1 some are prepared from coal tar greens1 others by careful admixture of various green1 blue1 and yellow pigments4 ,if the tint of these substitutes is right and they are sold for what they are1 there is no reason why they should not be used in place of the real article1 over which they have the advantage of not being poisonous1 which is a great disadvantage of the genuine emerald green4 ,although one authority disputes this point1 certainly the poisonous action of emerald green varies very considerably with different individuals4 ,the genuine emerald green may be distinguished from the spurious by being perfectly soluble in acids and alkalies1 which the imitations are not2 the character of the latter must be inferred by the application of a few special tests1 the nature of which will be readily deduced from what is said as to the properties of other green pigments4 ,emerald green should be assayed for purity and tint2 this is important1 as pure emerald green has a tint of its own1 which is difficult to imitate1 and sometimes really pure emerald green offered for sale is of a defective tint1 due to some fault in the process of manufacture4 ,such samples should be rejected4 ,,guignet',s ,,green4--,the greens of this class1 which owe their colour to chromium oxide1 are also known as 8chrome greens10 a name which they share with a totally different group into whose composition chrome yellow enters as a constituent1 and which have been already described under the synonym 8,brunswick greens10 on pp4 #aad-aah4 ,though one of the simplest of chemical products1 a great many ways of preparing chromium oxides have been proposed4 ,one of the earliest for industrial application was that of ,guignet1 who has given his name to the pigment1 and this may fitly commence the long list4 7#a7 ,the first method adopted by ,guignet consisted in mixing bichromate of potash with three times its weight of boracic acid and moistening the mass with just sufficient water to form it into a thick paste4 ,this paste is put on the hearth of a reverberatory furnace1 which is carefully heated to a point never exceeding a dark red heat2 if this precaution is neglected1 the mass1 instead of becoming porous1 will fuse entirely1 and the anhydrous oxide will be produced1 which has a pale-green colour4 ,the heated paste1 while still red hot1 is thrown into cold water and washed with boiling water1 in order to remove borate of potash in solution2 and this solution1 when boiled down and treated with hydrochloric acid1 can be made to yield up most of the boracic acid it contains4 ,the filtered and washed residue is the hydrated oxide of chromium4 7#b7 ,a modification of 7#a71 followed by ,guignet1 was to replace the bichromate of potash by chromate of soda1 prepared by dissolving in boiling water #fa parts of neutral chromate of potash and #ec parts of nitrate of soda4 ,for the neutral chromate of potash1 also1 may be substituted a mixture of #ib parts of bichromate of potash and #hi parts of crystallised carbonate of soda1 the nitrate of soda remaining as before4 ,on cooling1 in either case1 the solution deposits much nitrate of potash1 which is commercially valuable4 ,the chromate of soda present in the mother liquors is obtained by evaporating to dryness4 ,the pigment produced by the chromate of soda process is lighter in colour than that obtained with bichromate of potash4 ,it may be still further paled by adding a little alumina1 baryta1 or other white pigment to the bichromate and boracic acid mixture before calcining4 7#c7 ,equal quantities of potash bichromate and potato starch are thoroughly mixed and then calcined in a crucible at a high temperature4 ,the product is washed with boiling water1 to remove the potash carbonate formed1 and any remaining undecomposed bichromate4 ,the precipitated chromium oxide is filtered1 dried1 and again calcined to drive off the water4 ,the final result is a handsome pigment which flows well from the brush4 7#d7 ,on heating in a crucible a mixture of #c parts of neutral chromate of potash with #b parts of salammoniac1 the two salts are decomposed1 the result being formation of chromium oxide mixed with potassium chloride1 which latter is removed by several washings with hot water4 ,the brilliancy of the chromium oxide is enhanced by calcination at a dull red heat4 7#e7 ,fuse together #c parts of boracic acid and #a part of potash bichromate at a dull red heat on the hearth of a reverberatory furnace4 ,thus is formed a borate of chromium and potash1 with evolution of oxygen4 ,the mass is repeatedly washed with boiling water1 which causes decomposition1 and consequent separation of hydrated oxide of chromium1 and a soluble borate of potash4 ,the chromium oxide is washed1 and ground very fine4 7#f7 ,when a solution of potash bichromate is poured into a neutral solution of mercury proto-nitrate1 it forms an orange-coloured precipitate1 which is washed and gently dried1 then powdered1 and heated in a stoneware retort provided with an arm dipping into cold water1 by which the mercury is distilled and condensed4 ,the residue in the retort is a highly comminuted chromium oxide1 of a fine dark-green colour4 7#g7 ,on calcining potash bichromate in a crucible at a very high temperature1 it is decomposed1 and results in chromium oxide and potash1 the latter of which can be washed out4 ,the chromium oxide thus obtained is very dense and of a dark-green colour resembling 7#f74 7#h7 ,equal quantities of flowers of sulphur and bichromate of potash are thoroughly mixed1 and heated to redness in a crucible1 producing a mixture of oxide of chromium with sulphide and sulphate of potash4 ,the latter are dissolved out by washing repeatedly with hot water1 leaving the chromium oxide as a finely comminuted dense powder of an intense green colour4 7#i7 ,a modification of 7#h7 consists in adding small successive quantities of flowers of sulphur to a boiling concentrated solution of potash bichromate4 ,from this results a gelatinous oxide of chromium1 which is washed with boiling water1 dried1 and calcined in a crucible at a red heat4 7#aj7 ,hydrochloric acid decomposes bichromate of potash1 forming a soluble chloride of potash which can be removed by washing1 and a residue of chromium oxide1 which is washed on a filter and dried4 ,there remain for description two or three processes in which phosphoric acid plays a part1 but the greens made by these methods do not possess the freshness of the others1 and it is difficult to see what advantages can attend this modification4 7#aa7 ,according to ,arnaudon1 #adi parts of bichromate of potash are thoroughly incorporated with #abh parts of crystallised neutral phosphate of ammonia1 and the mixture is heated in thin layers to a temperature between #cch and #cef ,f41 which brings about intumescence1 change of colour1 and disengagement of water and ammonia2 the heating is continued for half an hour1 but must not be allowed to exceed #cib ,f4 ,when the development of the green colour is complete1 the product is washed with hot water to remove soluble salts1 and the residue constitutes an impalpable powder of chromium oxide1 forming a leaf-green pigment4 7#ab7 ,dissolve #aj lb4 of bichromate of potash and #ah lb4 of phosphate of soda in boiling water1 and add to the boiling mixture #aj lb4 of thio-sulphate of soda solution and a little hydrochloric acid4 ,a precipitate of phosphate of chromium is gradually thrown down as the boiling is maintained4 ,for general utility no class of pigments can exceed the several forms of ,guignet's green4 ,it is capable of affording a great variety of tints1 all absolutely permanent under reasonable conditions4 ,no ordinary agent will decompose them1 and they will stand almost any test to which they may be subjected without losing colour4 ,they are quite insoluble in acids and alkalies1 and are not affected even by the extreme heat of the glass furnace4 ,they possess good covering power1 do not suffer in brightness or purity under artificial light1 and are equally useful as oil or water colours1 besides being admirably adapted for fresco and silicious painting1 and employed in making green glass and in calico printing4 ,they can be mixed with any other pigment4 ,adulteration with ,brunswick or ,prussian greens is often practised1 but may be discovered by a portion being dissolved on boiling with caustic soda1 the solution giving a precipitate of chrome yellow on adding acetic acid1 and 7a separate portion1 of course7 ,prussian blue with hydrochloric acid and perchloride of iron4 ,,lokao4--,this pigment1 which is also known as 8,chinese green10 was first met with as a sediment left after dyeing cotton cloths with the barks of one or more species of buckthorn1 notably ,rhamnus chlorophorus and ,r4 utilis1 and passing in ,china under the general name of ,lo-,kao4 ,this sediment is spread on blotting paper and thus dried1 forming thin cakes4 ,latterly1 the juice afforded by the berries of the same trees is extracted by pressure1 absorbed by alum1 and dried in the same form of little cakes4 ,when first introduced into ,england it was highly valued as affording a pure green1 even in artificial light4 ,its price on the ,london market in #ahfa was #gs4 #f;d4 an ounce4 ,so long ago as #ahec it was imported into ,france and used for dyeing silk4 ,the colouring principle appears to consist of a glucose 7lokaose7 and an acid 7lokaonic acid74 ,in #ahfd1 ,chauvin obtained an identical colouring matter from ,rhamnus catharticus1 or the common buckthorn1 a shrub which grows wild in most parts of ,europe1 and found a ready market for the pigment at #cgs4 a pound4 ,this was simply the article known as sap green 7see p4 #acb47 ,,malachite4--,this is one of the names applied to mountain green 7q4v474 ,,manganese ,,green4--,several formul have been published for making a green pigment from manganese1 as follows3-- 7#a7 ,an intimate mixture of #hj parts of nitrate of barium1 #ad parts of oxide of manganese and #f parts of sulphate of barium1 is placed in a crucible and heated to bright redness until the green colour is thoroughly developed4 ,the fused green mass is poured out of the crucible1 cooled1 and ground wet to a fine condition4 7#b7 ,to #c or #d parts of caustic baryta moistened with water are added #b parts of nitrate of barium and #b parts of oxide of manganese2 the whole mass is most intimately mixed1 then put into a crucible in a furnace1 and subjected to a dull red heat so long as may be necessary for securing complete decomposition4 ,when the green colour is satisfactorily produced1 the mass in a state of fusion is poured out1 cooled1 pulverised1 digested in boiling water1 then washed with cold water1 and finally dried in an atmosphere which is free from carbonic acid4 7#c7 ,the oxide of manganese may be replaced by the nitrate1 when the quantities are #df parts nitrate of barium1 #cj parts of sulphate of barium1 and #bd parts of nitrate of manganese2 the fusion1 grinding and washing are repeated as before4 ,according to some recipes the powdery pigment1 consisting essentially of manganate of barium1 is mixed with a little dextrine to make sure of its stability1 but it is not clear whether this is really essential4 ,,mineral ,,green4--,this is only another name for the green made from copper carbonate1 and described under mountain green1 see p4 #aca4 ,,mitis ,,green4--,this pigment is an arseniate of copper1 and bears a very close relationship to the emerald green made according to ,braconnot's formula1 and described in the fifth paragraph of that section1 see p4 #abc4 ,mitis green is prepared by dissolving arseniate of potash in five times the quantity of hot water and adding a solution of an equal weight of sulphate of copper1 keeping the whole in constant agitation4 ,a pulverulent precipitate is formed1 possessing a grass green colour4 ,this is washed and dried4 ,the tint can be varied by altering the proportions of the arseniate and sulphate4 ,the arseniate of potash is made by boiling arsenious acid in concentrated nitric acid1 filtering1 and saturating with carbonate of potash4 ,the arseniate is allowed to crystallise out of the liquor4 ,,mountain ,,green4--,this pigment is also known by the names of malachite and mineral green4 7#a7 ,in its native form the mineral malachite or green carbonate of copper is very widely distributed in ,europe1 ,asia1 ,america1 and ,australia1 but on a commercial scale it is chiefly produced in the ,ural mountains of ,siberia and in the ,banat of ,hungary4 ,it only needs to be picked clean from adhering rock and to be ground to a very fine powder in order to render it ready for use4 ,it is much superior to any of the artificial substitutes referred to below1 but its cost confines its application to artistic work4 7#b7 ,sometimes a little orpiment or chrome yellow is ground up with the malachite4 7#c7 ,a very simple formula for making the artificial pigment is to add solution of carbonate of soda or potash to a hot mixed solution of alum and bluestone 7sulphate of copper74 7#d7 ,other recipes for making mountain greens have been published which bear no relation to the composition of the original article1 e4 g4 by mixing a solution containing potash and arsenic with a solution of bluestone2 or1 as a much more complicated example1 treating a solution of bluestone first with slaked lime1 then with a solution of arsenic and soda obtained by boiling in water1 and finally with tartaric acid4 ,the advantages attendant on so much trouble in producing what is at best an unstable pigment are not very apparent4 ,,paris ,,green4--,this is another name1 used especially in ,america1 for the emerald greens described on p4 #aba4 ,,prussian ,,green4--,a name often applied to class b of the ,brunswick greens 7see p4 #aad71 or in other words those which are prepared from ,prussian blue4 ,,rinmann ,,green4--,the first cobalt green 7see p4 #aai71 put on the market was made by ,rinmann1 and hence it is still often called by his name4 ,,sap ,,green4--,this vegetable pigment or lake is closely allied to the ,chinese green or lokao1 described on p4 #abi4 ,it consists of the solidified juice extracted from the berries of the common buckthorn shrub 7,rhamnus catharticus71 which is obtained either by allowing the berries to undergo slight fermentation for about a week in wooden tubs1 then pressing and straining2 or by boiling the berries1 and straining off the juice4 ,in either case the clean juice is boiled down to a syrupy consistence1 and a little alum 7about oz4 to the pint of thickened juice7 is added1 the liquor being then evaporated to dryness1 or very nearly to that point1 the drying being left to complete itself after the pigment has been ran into bladders4 ,the quality of this green is liable to serious fluctuation1 owing to the neglect or ignorance of certain simple precautions4 ,thus1 for a true green the berries should be selected before they have quite reached maturity4 ,the more nearly ripe the berries are1 the more yellow will be the tint of the green afforded by them4 ,the boiling of the berries1 if followed1 and the evaporation of the juice1 must be done at a low temperature1 and the final stages of the evaporation cannot safely be done with direct fire heat1 but should be effected in a water bath4 ,the only substance incorporated with the juice should be potash alum4 ,sometimes it is replaced by carbonate of magnesia 7which destroys the transparency of the pigment72 or by carbonate of potash 7which introduces a stickiness or viscosity74 ,sap green possesses too little body and is too translucent for use as an oil paint2 but being non-poisonous1 and in fact perfectly harmless1 it finds many useful applications outside of water colour and pastel painting1 viz4 in colouring alimentary substances such as drinks and sweets4 ,its true colour is a leaf green1 glossy and translucent4 ,in durability it is not remarkable4 ,,scheele',s ,,green4--,for more than a century has ,scheele's green been a familiar pigment1 but the reputation it enjoyed in its early days has long since departed1 and it is now to be classed among the inferior green colouring matters4 ,it consists essentially of a basic arsenite of copper1 and contains from #h to more than #dj per cent4 of arsenic1 according to the mode of preparation1 of which there are several1 as follows3-- 7#a7 ,a mixture of #b parts of commercial carbonate of potash and #a part of powdered arsenious acid 7white arsenic71 are dissolved in #ce parts of boiling water2 the solution is filtered clear1 and then added gradually and while still warm to a filtered solution of #b parts of sulphate of copper until no further precipitate goes down4 ,this latter is collected1 washed with warm water on a filter1 and slowly dried without excess of heat4 7#b7 ,the preceding formula is modified by making one solution of the arsenic and the sulphate of copper1 and precipitating by adding the carbonate of potash solution till the colour is fully developed1 agitation being constantly maintained4 7#c7 ,another variation is to mix the arsenic with soda crystals in boiling water1 and to pour the arsenite of soda solution thus formed into the bluestone solution1 the boiling being kept up for a few minutes4 ,scheele's green has a pale yellowish cast1 and mixes well with either water or oil1 but it lacks brightness1 durability1 and covering power1 in addition to being highly poisonous1 and though once much employed in staining wall papers1 is now generally discarded4 ,,schweinfurth ,,green4--,this is an old-fashioned name for emerald green1 which has been described on pp4 #aba-abe4 ,,terre ,,verte4--,rendered into ,english1 the name terre verte means 8green earth40 ,it is applied to a number of green-coloured earths found widely distributed in rocks of various ages1 but especially in those of a basaltic or porphyritic character4 ,in commercial quantity it occurs notably in ,cyprus and near ,verona in ,italy2 the latter locality is so important that the pigment is often known as 8,verona earth40 ,notwithstanding minor points of dissimilarity in samples from different sources1 there is a great family likeness among them1 sufficient to indicate that the essential constituent is a silicate of iron and magnesia4 ,the other ingredients vary with the locality producing the mineral4 ,the same may be said of the physical characteristics1 some specimens being soft and earthy1 while others are hard and glassy4 ,all possess the peculiar soapy touch of the magnesian earths1 and a clay-like odour4 ,analysis of a ,verona earth gave3-- ,per cent4 ,silica #eaba ,iron protoxide #bjgb ,magnesia #faf ,water #ddi ,alumina #gbe ,soda #fba ,manganese protoxide trace4 ,while a ,cyprus earth showed3-- ,per cent4 ,silica #eae ,iron protoxide #bje ,magnesia #ae ,water #hj ,potash #ahj ,the presence of copper would point suspiciously to adulteration1 and in any case should suffice to condemn the sample for use4 ,naturally there is considerable variety of tint among the many kinds of terre verte1 but they all belong to the pale greyish class1 and are more or less translucent1 consequently their covering power is small4 ,their value lies in their durability1 and the resistance they offer to the injurious effects of strong light and impure atmosphere4 ,they can be employed either as oil or water colours4 ,the only preparation to which the natural pigments are submitted is fine grinding and washing4 ,,titanium ,,green4--,an excellent dark green pigment1 though rather costly1 can be prepared from rutile or any titaniferous iron ore by the following method3-- ,the ore is dressed clean1 and fused with twelve times its weight of acid sulphate of potash in a crucible4 ,when cool1 it is reduced to fine powder1 and digested at #abj ,f4 in dilute hydrochloric acid 7half water7 until solution is complete4 ,the hot solution is filtered off from the residue and carefully evaporated down to a syrupy consistence1 when the nearly pure titanic acid is allowed to cool in the dish and thrown on a filter4 ,when sufficiently drained1 it is boiled in a large volume of water containing a little ammonia1 and the precipitated titanic acid is filtered and washed4 ,if an ore is used containing carbonate of lime1 it must first be treated with dilute hydrochloric acid before the sulphate of potash is applied4 ,the titanic acid on the filter is next mixed with a concentrated solution of sal ammoniac1 and again filtered4 ,then it is digested in dilute hydrochloric acid at #abj to #adj ,f4 till the solution is complete4 ,on adding ferrocyanide of potassium to the acid liquor1 and bringing quickly to a boil1 a precipitate of ferro-cyanide of titanium is thrown down4 ,this is very carefully and slowly dried1 at a temperature never exceeding #bjj ,f4 ,,verdigris4--,the chemical examination of verdigris shows it to be a basic hydrated acetate of copper1 containing variable proportions of the bibasic and tribasic acetates4 ,commercially it is prepared in districts where acetic or pyroligneous acid can be had at small cost4 ,thin pieces of scrap copper are subjected to the action of fermenting grape skins in mass1 or cider refuse1 for a fortnight or three weeks2 or to the influence of pyroligneous acid for four or five days4 ,by this means the copper surfaces are attacked by the acetic acid being generated or liberated1 and become coated with acetate of copper4 ,at intervals the pieces are removed1 and surfaces are cleaned of the accumulated acetate or verdigris and this is repeated till the metallic copper has thus been completely converted4 ,the collected verdigris is washed1 and carefully dried at a very low temperature4 ,its composition is subject to many irregularities1 and the colour varies from green to bluish green according to the proportion of sesquibasic acetate present4 ,it is one of the least permanent pigments1 especially in the presence of water1 and is exceedingly poisonous4 ,at one time it was largely used as a pigment1 but is now gradually going1 if indeed it has not already gone1 out of use4 ,it can be distinguished by its solubility in acids and ammonia1 the latter giving a deep azure blue solution4 ,on being heated1 it turns black1 owing to its parting with acetic acid and leaving the black oxide of copper behind4 ,this should be entirely soluble in nitric acid1 the solution giving the characteristic tests for copper4 ,the solution should give no precipitate with chloride of barium or nitrate of silver1 and the original pigment should be freely soluble in any acid and in ammonia without effervescence4 ,,verditer4--,green verditer is another of the copper greens which has practically disappeared from the modern painter's list of pigments4 ,it is a yellow tinted very fugitive colour1 consisting of a basic carbonate of copper1 and is manufactured by treating copper solutions with carbonate of soda1 or of potash4 ,,verona ,,earth4--,one kind of terre verte 7see p4 #acd71 is known by this name because it is produced in the neighbourhood of ,verona4 ,,victoria ,,green4--,this is a fancy name for the ,brunswick greens compounded from ,prussian blue1 and already described on p4 #aad4 ,,vienna ,,green4--,the aceto-arsenite of copper described under the heading of emerald green 7see pp4 #aba-abe71 is sometimes called by this name4 ,,zinc ,,green4--,the pigments described under cobalt green 7see p4 #aai71 as often pass by the name of zinc greens1 and in fact they contain much more zinc than cobalt4 ,a handsome but not permanent green may be made by combining zinc with iron instead of cobalt1 in the form of a double cyanide4 ,the process is as follows3--,finely powdered ,prussian blue is stirred into a concentrated solution of chloride of zinc1 and put by to allow the decomposition to take place4 ,after some time1 the precipitated ferro-zinc cyanide is thoroughly washed1 and dried out of reach of the light4 ,,chapter ,,vi4 ,,reds4 ,though the red pigments are an important class1 they are not numerous1 and1 with the exception of a few lakes1 they are drawn from the mineral kingdom4 ,the most useful are compounds of the several metals1 iron1 lead1 and mercury4 ,,antimony ,,vermilion4--,this useful pigment is prepared by several methods1 as follows3-- 7#a7 ,one of the earliest successful processes was that introduced by ,mathieu ,plessy1 which gives a scarlet product4 ,he obtains the pigment1 a modified sulphide of antimony1 by decomposition of hyposulphite of soda in the presence of chloride of antimony4 ,the two solutions of hyposulphite of soda and chloride of antimony1 each at #be ,b41 being prepared1 the next step is to pour into a stoneware vessel #d gals4 of the antimony chloride solution1 #f gals4 of water1 and #aj gals4 of soda hyposulphite solutions4 ,the precipitate caused by the water is rapidly dissolved in the cold by the hyposulphite4 ,the stoneware vessel is then placed in a hot water bath1 and the temperature of the contents is thus gradually raised4 ,at about #hf ,f4 the precipitation of the sulphide commences1 showing orange yellow at first1 but becoming darker subsequently4 ,when the temperature has reached #acj ,f41 the vessel is removed from the water bath1 and the deposition of the precipitate proceeds rapidly4 ,the supernatant liquor is siphoned off1 and the solid residue is washed first with water acidulated by adding to it one fifteenth of its bulk of hydrochloric acid1 and then with clean water4 ,finally the residue is collected on a filter1 and dried4 ,it is exceedingly brilliant while wet1 but loses a portion of its brightness when dried4 ,provision must be made for disposing of the sulphurous oxide gas driven off during the process of manufacture4 7#b7 ,kopp found certain disadvantages in working by the above method1 and adopted instead the reaction of antimony chloride upon a dilute solution of hyposulphite of lime4 ,experiencing much difficulty in the decomposition of antimony sulphide by hydrochloric acid on an industrial scale1 he experimented on roasting the sulphide at a moderate temperature in contact with air and steam1 whereby most of the antimony sulphide is converted into oxide1 while the sulphurous acid driven off is utilised for making the hyposulphite of lime4 ,this proved a most successful plan1 and the resulting antimony oxide is readily dissolved by commercial hydrochloric acid4 ,during the oxidation of the antimony sulphide1 a certain proportion of antimonious acid may be produced4 ,this is but slightly soluble in hydrochloric acid4 ,it may be collected1 however1 by saving the residues from the treatment by hydrochloric acid1 and washing them with chloride or hyposulphite of lime1 which will dissolve the adherent antimony chloride2 they are then dried1 and melted with a little antimony sulphide and quicklime1 so as to transform the whole into antimony green1 the quicklime having the effect of decomposing any small residue of antimony chloride4 ,the preparation of the hyposulphite of lime is cheaply effected by the action of sulphurous acid on sulphides of lime1 the sulphurous acid being derived either from the roasting of the antimony sulphide1 or from pyrites or brimstone in the usual way4 ,calcium polysulphide is prepared by boiling finely powdered sulphur and newly slaked lime in water4 ,certain advantages arise from the addition to this solution of a little powdered calcium oxysulphide1 or some quicklime4 ,in the reaction of sulphurous acid on calcium sulphide and oxysulphide1 sulphur is set free and forms a sulphite of lime1 which1 in the presence of sulphur and undecomposed sulphide1 is soon transformed into hyposulphite1 the reaction being facilitated by the rise of temperature which takes place in the apparatus4 ,as soon as the liquor has become slightly acid1 it is drawn off into a large settling tank4 ,if1 after agitating for some time1 the liquor has not become neutralised by the undecomposed calcium oxysulphide contained in it1 this is brought about by addition of a little calcium sulphide1 and is recognisable by the appearance of a black precipitate of sulphide of iron4 ,after due settlement1 the clear liquor is decanted1 and forms a solution of nearly pure hyposulphite of lime4 ,the production of antimony vermilion is effected from the foregoing solutions of antimony chloride and hyposulphite of lime1 in apparatus consisting simply of a series of wooden tanks raised conveniently above the floor1 holding about #ejj gals4 each1 and provided with steam coils for heating their contents4 ,sufficient hyposulphite of lime solution is run into the tanks to fill about seven-eighths of their depth2 and then into the first tank is poured the chloride of antimony solution1 in quantities of a few pints at a time4 ,a white precipitate is formed1 and rapidly dissolves at first2 when it is slow in going into solution1 even though stirred1 the addition of antimony chloride should be stopped1 as an excess of hyposulphite of lime is essential4 ,the liquor in the tank must be perfectly clear and limpid1 and should any white precipitate remain it must be dissolved by making small additions of hyposulphite4 ,at this stage steam is admitted into the coils1 and thereby the temperature of the solutions is gradually raised to #abj or #adj ,f41 or even to #afj ,f41 while stirring is unceasingly carried on4 ,the reaction is soon manifested by the successive colours of the liquor1 passing from straw-yellow to lemon-yellow1 orange-yellow1 orange1 orange-red1 and lastly a very deep and brilliant red4 ,the steam is shut off from the coil before the desired tint is arrived at1 as the acquired heat and the agitation complete the development of the colour4 ,if the heating is carried too far1 the red gradually passes to a brown and later to nearly black4 ,with experience1 almost any desired shade of red can be produced4 ,when the precipitate has attained the required colour1 it is allowed to settle1 and the tank is covered4 ,the clear and limpid liquor1 having a strong sulphurous odour1 is let out through tap holes at various levels in the sides of the tanks1 and run by wooden gutters or leaden pipes into a large reservoir holding a quantity of sulphide and oxysulphide of lime4 ,here the sulphurous liquor regenerates a certain amount of hyposulphite of lime4 ,the antimony chloride solution always contains a large proportion of chloride of iron1 which provides an easy means of guiding the progress of this latter operation4 ,all the iron remains soluble in the mother liquors of the antimony sulphide1 and as soon as they are brought into contact with the calcium sulphide1 an insoluble black precipitate of iron sulphide is formed4 ,so long as this remains1 the mother liquors charged with sulphurous acid have not been added in excess2 but when it disappears by conversion into soluble hyposulphite of iron1 that is a sign that the sulphurous solution is in excess4 ,the contents of the reservoir are then well stirred1 and calcium sulphide is introduced if necessary1 until the precipitate of iron sulphide returns and remains4 ,it is also needful to ensure that a certain proportion of hyposulphite of iron shall remain in solution4 ,the clear liquor decanted off when all the precipitate has gone down is a neutral solution of hyposulphite of lime1 containing some calcium chloride and hyposulphite of iron4 ,another requisite precaution in this regeneration of hyposulphite of lime is that no excess of calcium sulphide be left1 or it will give an orange-yellow tint to the vermilion2 and if the hyposulphite of lime solution is alkaline and yellow1 sulphurous acid liquor must be run in till all alkalinity is destroyed4 ,this regenerated solution of hyposulphite of lime is used like the first4 ,the mother liquors charged with sulphurous acid are again neutralised in the large reservoir by new proportions of calcium sulphide and oxysulphide1 until so much calcium chloride is present that they are useless for the purpose1 say after #be to #cj operations4 ,the antimony vermilion precipitated on the bottom of the first tank is received into a conical cloth filter1 and the liquor drained off is passed to the reservoir4 ,the first tank is then washed out with warm water1 which also passes through the filter4 ,the precipitate of red sulphide cannot be too carefully or completely washed1 and finally is filtered and slowly dried below #adj ,f4 7#c7 ,wagner's method of making a scarlet pigment is to dissolve #f lb4 of tartaric acid and #h lb4 of tartar emetic in #d gallons of water at #adj ,f41 adding a solution of hyposulphite of soda at #dj ,tw41 and heating the whole mixture to #ahj ,f41 whereby the red pigment is gradually precipitated4 ,it is collected on a filter1 well washed and dried4 7#d7 ,the process adopted by ,murdoch1 in which a solution of antimony chloride 7prepared by dissolving black sulphide of antimony in hydrochloric acid7 is acted on by a current of sulphuretted hydrogen gas1 has disadvantages in the apparatus necessary1 in the limited range of tints which can be produced1 and in the almost certain presence of free sulphur in the finished pigment4 ,antimony vermilion forms an exceedingly useful pigment1 which can be prepared in every shade of red1 from orange to red-brown4 ,it is produced in the condition of a very fine powder1 requiring no grinding1 and mixes readily with water or oil1 especially the latter1 and moreover does not interfere with the drying of the oil4 ,it possesses great covering powers1 and can be made at a low price4 ,it undergoes no change in strong light and impure air1 and is insoluble in water1 alcohol1 essential oils1 weak acids1 ammonia1 and alkaline carbonates2 but it is destroyed by high temperatures1 strong acids1 and caustic alkalies4 ,it cannot be mixed with other pigments which are intolerant of sulphur1 nor with alkaline vehicles4 ,when pure1 it should consist of nothing but antimony sulphide and a little water2 the presence of iron or lead indicates adulteration4 ,,baryta ,,red4--,an orange red may be prepared1 according to ,wagner1 in the form of a sulpho-antimonite of barium1 by calcining in a clay or graphite crucible at red heat for several hours a mixture of #b parts of finely powdered barytes1 #a part of native antimony sulphide1 and #a part of powdered charcoal4 ,the calcined mass is not removed until the crucible is quite cold1 as it is liable to undergo combustion4 ,when cold1 it is boiled in water and filtered4 ,the residue1 containing some undecomposed sulphate and sulphide of barium1 is utilised in the next batch4 ,the pale-yellow filtrate is treated with dilute sulphuric acid1 by which sulphuretted hydrogen is driven off1 and an orange precipitate is thrown down4 ,this is collected1 washed on a filter1 and dried1 constituting the pigment4 ,,cassius ,,purple4--,this costly pigment is a stannate of protoxide of gold1 much used in painting on porcelain and for miniatures4 ,it is the precipitate which is thrown down when solutions of gold and tin chlorides are mixed under proper conditions1 according to one of the following methods3-- 7#a7 ,buisson prepares three solutions3 a a neutral solution of protochloride of tin by dissolving #a part of tin in hydrochloric acid2 b a solution 7bichloride7 of #b parts of granulated tin in an aqua regia containing #c parts of nitric to #a of hydrochloric acid1 removing the excess of acid2 c a neutral solution of #g parts of gold in an aqua regia composed of #a part of nitric and #f parts of hydrochloric acid4 ,the gold chloride solution is largely diluted with water1 and to it is added the solution b of bichloride1 and finally the solution a of protochloride is introduced1 a drop at a time1 until the desired colour is produced in the precipitate4 ,this last is rapidly washed by decantation1 and finally dried away from the light4 7#b7 ,figuier prepares a gold bichloride solution by dissolving #bj grammes of gold in #ajj grammes of an aqua regia containing #d parts of hydrochloric to #a of nitric acid4 ,the solution is evaporated to dryness in a water bath1 and the residue is dissolved in #gej grammes of water4 ,into this solution1 when duly filtered1 pure granulated tin is introduced1 and the whole is left for some days1 at the end of which time all the gold will be in the state of stannate of protoxide2 it is collected on a filter1 carefully washed1 and gently dried4 ,the residues contain some gold1 and should be preserved for subsequent operations4 ,,chinese ,,red4--,one of the many names of the chromate of lead pigment1 described under ,derby red1 see p4 #ade4 ,,chrome ,,orange4--,a popular name for the group of yellow-red pigments consisting essentially of lead chromate1 and described under ,lead orange1 on p4 #adg4 ,,chrome ,,red4--,another of the synonyms for ,derby red1 see p4 #ade4 ,,cobalt ,,pink4--,this costly and permanent artists' colour is a combination of oxide of cobalt with magnesia4 ,it is prepared by treating carbonate of magnesia with a concentrated solution of nitrate of cobalt2 the resulting paste is dried in a stove1 calcined in a porcelain crucible1 and finally ground to a fine powder4 ,,cobalt ,,red4--,a very deep-coloured and permanent red pigment used in oil painting is the arseniate of cobalt1 which is found native in admixture with other substances in cobalt mines1 or may be artificially produced4 ,the native mineral is treated with boiling nitric acid2 the solution is filtered clear1 and small portions of potash are added till all the iron has been thrown down as arseniate4 ,after this is completed1 the mass is allowed to settle1 and the clear liquor is poured off4 ,on adding further small portions of potash1 the cobalt is also precipitated as arseniate4 ,to prepare artificial cobalt arseniate1 grey cobalt ore 7sulph-arsenide of cobalt71 reduced to a powder1 is mixed with a little sand and twice its weight of potash1 and fused in a crucible4 ,the slag of mixed sulphides which is formed is removed1 and the remaining white arseniate of cobalt is pulverised and subjected to another fusion with potash4 ,the slag is again removed1 and the button of pure arsenide of cobalt remaining is finely powdered and again roasted to effect conversion into arseniate of cobalt4 ,lastly1 it is ground very fine4 ,,colcothar4--,a fancy name for a kind of iron oxide pigment1 described under oxide reds 7see p4 #aej74 ,,derby ,,red4--,as a basic chromate of lead1 often known as chrome red1 ,derby red is closely allied to chrome yellow1 the preparation of which is described in a subsequent chapter4 ,it has been asserted that all the chrome reds1 from the darkest cinnabar red to a lustreless minium red1 are distinguishable simply by the size of the crystals composing the powder1 as may be easily determined under the microscope1 and that if various chrome reds of the same hue1 but with different intensities of colour1 are reduced by grinding to the same degree of comminution1 the several powders will possess exactly the same degrees of intensity of coloration1 though they lose in brightness4 ,therefore the conditions which give brilliancy and intensity of colour are those which favour crystallisation4 ,on this supposition it is recommended by ,riffault to adopt a plan which dispenses with agitation1 and he supports the following method3-- 7#a7 ,chrome yellow is precipitated in the usual manner1 as described in a later chapter1 without sulphuric acid1 and is carefully washed4 ,after draining1 the mass is well stirred1 and six or eight equal samples are drawn from it and put into glass vessels of equal size and thickness of structure4 ,to each sample is added a different volume of caustic soda or potash lye1 marking about #bj ,b4 ,for instance1 to #e volumes of paste are added #b1 #b1 #c1 #c1 #d1 #e1 c41 volumes of lye4 ,the different mixtures are rapidly and thoroughly agitated1 but the chemical reaction is allowed to take place without any disturbance4 ,after examination of the quality of the products1 the relative proportions of pulp and lye are noted down for the best hues obtained4 ,too much lye will fail to deepen the red colour2 in fact1 ,derby red is entirely soluble in an excess of lye1 and forms needle-like crystals holding potash when the caustic solution has absorbed carbonic acid from the air4 ,on the industrial scale the operation is conducted in a large tub1 which receives the mixture of pulp and caustic lye in precisely the proportions found by experiment to give the best results4 ,the changes in colour soon manifest themselves1 and the whole reaction is completed in about #ab hours4 ,at the end of that time1 the lye is drawn off1 and carries with it much of the chromic acid4 ,the precipitated pigment is carefully washed with pure water once in the tub1 and the mass is gently stirred4 ,the washing is continued in the filters by throwing water upon the pulp1 and in this manner there is less friction between the crystals1 which retain their deep colour4 ,of course a highly crystalline dark red cannot possess great covering power4 7#b7 ,prinvalt mixes together #ajj lb4 of lead carbonate and #cj lb4 of potash bichromate neutralised with caustic potash1 in #ej gallons of water1 leaving them in contact for a couple of days under repeated agitation4 ,about half an hour's boiling then suffices to develop the red colour4 ,after settling1 the supernatant liquor is drawn off1 and the precipitated pigment is washed twice with pure water and finally with acidulated water 7#a lb4 sulphuric acid in #aj gallons of water71 and dried4 ,there are several other recipes published which differ in detail from 7#b71 but they do not demand a lengthy description4 7#c7 #ajj lb4 of lead carbonate 7white lead7 made into a paste with water1 then added to and boiled with a solution of #ej lb4 of potash bichromate and #ae lb4 of caustic soda of #gg per cent4 ,remainder of process as before4 7#d7 #d cwt4 of lead monoxide 7litharge7 and #fj lb4 of salt dissolved in #ej gallons of water1 and left with agitation for #d or #e days2 then boiled for #b hours with solution of #aej lb4 of potash bichromate4 7#e7 #ajj lb4 of lead carbonate 7white lead7 made into a paste with water1 then added to a solution of #cj lb4 of potash bichromate and #ab lb4 of caustic soda at #gg per cent41 and boiled4 ,derby red possesses great covering power and considerable brilliancy2 but if not very carefully washed it is liable to retain a little alkali1 which renders it unstable4 ,otherwise1 it well resists damp1 strong light1 and impure air so long as sulphuretted hydrogen is absent4 ,taken altogether it is not one of the best red pigments1 and its consumption is declining4 ,,indian ,,red4--,this is one of the names for the red pigments due to oxide of iron1 and is described under oxide red1 p4 #aej4 ,,lead ,,orange4--,equally well known as chrome orange1 this pigment may be regarded as a ,derby red in which the reactions have been curtailed4 ,that is to say1 the yellow normal lead chromate being in excess1 the red chromate formed by the action of the alkali combines with that excess of the yellow salt and forms a yellow-red1 i4e4 orange4 ,obviously1 therefore1 a great variety of tints can be produced by altering the proportions of the alkali1 and this is further regulated by the duration of the boiling1 while the tint can also be weakened by admixture of barytes or gypsum4 ,the better kinds of lead orange are prepared with the aid of caustic potash or soda as the alkali1 while the cheaper sorts depend on lime4 ,the operations are practically identical with those adopted in the case of ,derby red 7see p4 #ade71 the chief differences lying in the proportions of the ingredients4 ,thus3-- 7#a7 ,pale4--,add a thin cream made from #aj lb4 of quicklime to a chrome yellow made from #ajj lb4 of lead acetate1 #cj lb4 of soda or potash bichromate1 and #ba lb4 of soda sulphate4 ,boil4 7#b7 ,pale4--,add a thin cream of #aj lb4 of quicklime to a chrome yellow made from #bjj lb4 of baryta sulphate1 #ajj lb4 of lead acetate1 and #ce lb4 of potash bichromate4 ,boil4 7#c7 ,deep4--,precipitate a chrome yellow by adding #ce lb4 of soda or potash bichromate to #ajj lb4 of lead acetate2 settle4 ,draw off supernatant liquor and admit solution of #i lb4 of caustic soda at #gg per cent4 7#d7 ,deep4--,add a cream of #aj lb4 of quicklime to a chrome yellow made from #ajj lb4 of lead acetate1 #ge lb4 of baryta sulphate1 and #ce lb4 of potash bichromate4 ,boil4 ,in characters the lead oranges resemble ,derby red 7see p4 #ade47 ,,minium4--,the important red pigment known as minium or red lead is composed of two oxides of lead in combination1 viz4 about #fe per cent4 of protoxide and #ce per cent4 of binoxide4 ,in its preparation1 metallic lead is first converted by roasting into protoxide 7termed 8massicot10 8dross10 or 8casing07 and this protoxide is further subjected to heat in a reverberatory furnace whereby a portion of it is changed into binoxide4 ,it is also possible to produce red lead by the decomposition of the carbonate of lead 7white lead7 at a high temperature1 but this does not seem to be an industrial process4 ,the following methods are recognised3-- 7#a7 ,the practice in ,france1 as carried on near ,tours1 at the white lead works using the ,thnard process1 is to calcine the best metallic lead in reverberatory furnaces built in the rock4 ,these furnaces are five in number1 with double fireplaces1 four being constantly in operation1 dealing with about #djjj lb4 at a charge1 and using bituminous coal as fuel4 ,each furnace is nearly circular in shape and about #aa feet in diameter1 with a fire-place on each side of the hearth4 ,the latter is constructed of fire-brick containing as little silica as possible1 and is made hollow so as to retain the metallic lead when the heat has rendered it fluid4 ,the products of combustion from the side fire-places1 having heated the hearth and its contents1 pass through an aperture in front of the charging door of the hearth1 and thence go to furnish heat to an upper hearth where the conversion of the oxide into red lead takes place4 ,a period of about #ab hours is occupied in the oxidation of a charge1 which is repeatedly 8rabbled40 ,even then a considerable amount of the metallic lead remains unoxidised and is returned to the calciner with the next charge4 ,half the oxide is utilised for making white lead1 as described in a later chapter1 and the other half is converted into red lead by the method detailed hereunder4 ,the crude oxide is pulverised in a small mill and separated from the unconverted metal4 ,the mill takes the form of a flat circular cast-iron plate on which rotates a cast-iron muller4 ,water and an agitating arrangement are also provided4 ,as the muller revolves the material undergoes comminution1 and the small particles of oxide as formed are disturbed by the agitator and kept in suspension in the water1 by the overflow of which they are continuously carried away into settling pits4 ,the residual metallic lead is not pulverised1 and of course never becomes suspended in the water1 consequently it accumulates at the bottom of the mill1 whence it is occasionally withdrawn for re-calcination4 ,sufficient oxide having collected in the settling pits1 it is transferred to a shallow pan heated by the waste heat from the furnaces and is there rendered almost dry4 ,in this state it is put into small square dishes made of sheet iron1 and adapted to hold about #cj lb4 each4 ,a charge consists of a hundred of these dishes1 which are placed in the heated furnaces at the end of each day4 ,the roasting is repeated several times1 and the product is accordingly known as 8two fires10 8three fires10 c4 ,the material at this stage is lumpy and coarse1 and has to undergo dry pulverisation1 the fine particles as they are produced being drawn off by means of a pneumatic fan1 and collected4 7#b7 ,what may in contradistinction be called the ,english method of making minium does not differ materially from the preceding4 ,the 8drossing0 furnace1 where the metallic lead is first oxidised1 receives a smaller charge as a rule1 and perhaps greater care is given to the rabbling1 and to the regulation of the temperature so that it is only just above the melting point of the metallic lead1 and not sufficient to fuse the massicot4 ,minium or red lead is one of the most important and useful red pigments1 as it mixes well with oil1 has good covering power1 dries quickly1 and is permanent except in presence of sulphur or sulphides4 ,,orange ,,mineral4--,the pigment known as orange mineral or orange lead is simply minium which has been imperfectly calcined4 ,consequently it is almost identical with red lead in composition1 qualities1 and method of manufacture1 the only exception being that1 as the calcination is not carried quite so far1 therefore the colour is not so fully developed1 and is an orange rather than a red4 ,as with minium1 practically the only adulterant is iron oxide red1 which may be detected by boiling the pigment to a colourless solution with nitric acid1 when addition of prussiate of potash will give a blue precipitate4 ,,oxide ,,reds4--,under various names--such as ,persian red1 light red1 ,indian red1 scarlet red1 rouge1 colcothar1 red oxide1 purple oxide1 c4--many pigments1 of which the base is the ferric oxide ,fe#b,o#c1 are now made4 ,these vary in shade from a deep scarlet red to a dark violet4 ,they are obtained both from natural and artificial sources4 ,oxide of iron occurs naturally as the mineral hematite1 and some varieties of this are bright enough and soft enough to be used as pigment when ground up4 ,these are usually nearly pure oxide of iron4 ,then the ochres1 when calcined1 yield red pigments known as light red1 ,indian red1 c41 and a good many reds are obtained from this source4 ,the composition of these is variable1 being dependent upon that of the ochres from which they are made1 and these1 as has already been pointed out1 vary very much4 ,then1 in preparing fuming sulphuric acid from copperas1 oxide of iron which is specially sold as rouge1 is obtained4 ,colcothar is produced as a residue2 this is nearly pure oxide of iron1 and usually has a red colour4 ,in the manufacture of sulphuric acid from pyrites1 a dark violet oxide of iron is left as a residue1 and much of this is used as a pigment under the name of purple oxide4 ,then a large quantity of oxide of iron reds are made artificially from waste liquors obtained in copper refining1 galvanising iron1 c4 ,the composition of the oxide of iron reds1 therefore1 is very variable4 ,the whole group of oxide reds is of foremost importance1 by reason of their good colour1 covering power1 and durability1 besides which1 being mostly bye-products of much more important manufactures1 their cost is reasonable4 ,the methods of preparation of oxide reds vary slightly in detail according to the material from which they are made1 but the general features of the processes are almost identical and eminently simple4 ,the principal sources are impure native oxides of iron1 such as the ochres1 various waste liquors containing iron salts in solution1 and copperas 7protosulphate of iron74 7#a7 ,native oxides4 ,the iron present in the ochres and similar native earths exists in the form of hydrated oxide1 and has a brown red colour4 ,for many purposes this hue is satisfactory1 and the preparation of such a pigment consists simply in grinding the mineral in a wet mill1 subjecting it to levigation till all grit is removed1 and drying4 ,in order to obtain a brighter red from the native oxides they must be calcined to effect dehydration4 ,this can be accomplished in the most rudimentary forms of furnace1 and many kinds are in use4 ,the colour produced depends on the degree and duration of the heat to which the material is exposed1 the shade becoming deeper as the roasting is prolonged or the temperature increased4 ,as no two samples of ochre are just alike it is impossible to fix a precise time for the length of the operation1 and therefore it is necessary to repeatedly draw samples in order to judge of the progress of the dehydration and development of the colour desired4 ,when the requisite shade is attained1 the charge is drawn and allowed to cool4 7#b7 ,waste ,products4 ,the pyrites cinders from sulphuric acid works afford an abundance of oxide of iron4 ,when the pyrites has contained no copper1 the cinders merely require grinding and levigating1 the iron being present as oxide4 ,but when the pyriteshas been treated for the recovery of the copper1 by a second roasting with salt1 the liquors contain the iron as chloride and sulphate1 and lime has to be added to precipitate the oxide4 ,this last is dried and calcined in the same manner as the native oxides1 and grinding and levigation can be dispensed with4 ,the liquors from galvanising works contain acid sulphate of iron 7green copperas7 in solution4 ,to correct the acidity1 more iron is added in the form of scrap4 ,then lime or other alkaline substance is introduced to throw down the iron as oxide1 and this last is filtered out1 dried1 and calcined in the usual way4 7#c7 ,copperas4 ,where beds of common iron pyrites occur1 the iron sulphide is converted into sulphate by exposure to the oxidising influence of the air4 ,the result is an acid sulphate of iron1 which is leached out and neutralised by addition of more iron in the form of scrap4 ,the neutral sulphate is crystallised out of the liquor1 and calcined in a muffle furnace1 the shade of the ultimate product being governed by the degree or duration of the roasting4 ,the sulphurous acid liberated in the roasting is sometimes utilised for making sulphuric acid1 but is more often wasted1 because1 to be commercially successful1 the sulphuric acid manufacture must be conducted on a large scale1 demanding #ajjl4 of capital for every #al4 necessary for the copper and red oxide fabrication4 ,,persian ,,red4--,a name which is used somewhat indiscriminately both for ,derby red 7p4 #ade7 and for oxide red 7p4 #aej74 ,,realgar4--,the native mineral realgar is a yellow-red bisulphide of arsenic1 often called also ruby of arsenic1 or arsenic orange4 ,it occurs native in very limited quantities in some of the older rocks1 and then only requires to be ground and levigated4 ,but for painters' purposes it is prepared artificially by heating a mixture of sulphur and arsenic in such a way that they are melted in company and react on each other to form the arsenic sulphide4 ,the heating takes place in crucibles1 and the proportions are two parts by weight of arsenious acid 7white arsenic7 to one of flowers of sulphur4 ,when the reaction has ceased1 the contents of the crucible are allowed to cool1 and then reduced to very fine powder4 ,the pigment is exceedingly poisonous and not remarkably durable1 besides which1 it cannot be mixed with any other pigment which is affected by sulphur4 ,,red ,,lead4--,a common name for minium1 see p4 #adh4 ,,rouge4--,one of the names for a particular shade of the oxide reds1 see p4 #aej4 ,,venetian ,,red4--,a fancy name for a special shade of oxide red1 see p4 #aej4 ,,vermilion4--,this old pigment is gradually going out of use2 the newer reds1 which are more brilliant in colour and cheaper1 are gradually displacing it1 although it is doubtful whether it will ever go completely out of use4 ,it is the mercuric sulphide ,hg,s4 ,when pure1 it is not attacked by acids or alkalies2 only aqua regia1 a mixture of hydrochloric and nitric acids1 is capable of dissolving it1 when it forms a clear solution4 ,heated in the flame of a ,bunsen burner1 it is completely volatile1 a property possessed by no other pigment in common use1 therefore any adulteration can be readily detected by simply heating a little vermilion in a crucible2 if a known weight is taken and the residue is weighed1 the amount of adulteration can be ascertained4 ,vermilion is chiefly adulterated with oxide of iron and orange lead4 ,from the character of the residue left on heating in a crucible1 the kind of adulteration can be readily ascertained4 7#a7 ,the following notes are taken from ,christy's translation of a brochure on the ,imperial ,quicksilver ,works at ,idria1 ,krain3-- ,in the oldest times of the existence of the present works1 vermilion was manufactured4 ,in the beginning it was merely pure pulverised cinnabar ore1 then later it was a product made by sublimation from this substance2 and there were formerly other works for vermilion manufacture than those for quicksilver production4 ,when the ,venetians and ,dutch began to produce better wares1 the production here sank steadily4 ,the researches of ,christofoletti1 #afha1 and of ,baron ,richtenfels1 #agbf1 for the improvement of ,idrian vermilion1 met with as little success as those of some ,venetian women--#agdj-agda--who had lost their husbands in the ,venetian works and had offered themselves to manufacture vermilion according to the ,venetian method4 ,after ,hacquet had strongly urged the manufacture of vermilion1 ,oberhttenmeister ,ignaz v4 ,passetzky succeeded1 with the ,dutchman ,gussig assisting him1 in making beautiful cake cinnabar in #aghb1 and in #aghe vermilion also1 in the newly-built works on the right bank of the ,idriza4 ,in #agif ,oberhttenverwalter 7manager of the works7 ,leopold v4 ,passetzky introduced the sublimate and precipitate manufacture1 but it was abandoned as unprofitable in #ahbd4 ,the many foreign attempts to manufacture vermilion in the wet way caused similar ones here1 as those of ,fabriks-,controlor ,rabitsch in #ahch1 and later of ,httenverwalter ,m4 ,glowacki1 which brought large amounts of the vermilion so manufactured into the market4 ,still this manufacture came to no full development1 and became forgotten1 until1 finally1 in the years #ahgg and #ahgh1 experiments led to its being discontinued on account of the costliness and uncertainty of the method4 ,a new set of experiments in #ahgh and #ahgi1 by ,assayer ,e4 ,teuber and ,director of ,works 7,httenverwalter7 ,h4 ,langer1 under the direction of the ,imperial ,agricultural ,ministry1 led to favourable results4 ,a new manufactory1 set in operation in #ahhj1 furnishes three sorts of vermilion manufactured in the wet way4 ,the arrangements of the works for the manufacture of vermilion in the dry way consist of3--,one sulphur stamp battery4 ,one amalgamating plant with eighteen small barrels2 both pieces of apparatus being driven by a two horse-power water-wheel4 ,four sublimation furnaces1 each with six retorts of cast iron4 ,four vermilion mills1 each driven by a water-wheel of #be horse-power4 ,kettles and vats for heating1 digesting1 and refining the ground cinnabar4 ,one drying hearth4 ,the preparation of vermilion as an article of commerce1 falls into several separate operations1 viz43 #a4 ,amalgamation2 i4 e4 preparation of the raw mohr4 #b4 ,sublimation2 i4 e4 preparation of the cake cinnabar4 #c4 ,grinding of the cake cinnabar1 refining and drying of the vermilion4 ,for the preparation of the raw mohr1 for each charge of eighteen kegs there are taken #hjfd kg4 7#aag lb47 powdered and sifted sulphur1 and #dbccf kg4 7#gca lb47 of quicksilver4 ,the amalgamating kegs each contain #bh kg4 7#fa lb47 of the charge1 and are given intermittent rotating motion by a rack and pinion driven by a water-wheel4 ,after an average of two and three-quarter hours1 the amalgamation is complete1 and the raw mohr is taken from the casks4 ,for the sublimation1 four furnaces are used1 each with six pear-shaped cast-iron retorts of considerable thickness4 ,each is charged with #eh kg4 7#abg lb47 of mohr1 the mouth covered with a loosely placed sheet-iron helmet1 the furnace being slowly fired2 the combination of the sulphur and the quicksilver then results in about fifteen minutes1 with a detonation4 ,as soon as this operation 7das ,abdampfen7 is over1 a clay helmet is placed over the retort1 and the firing is increased1 so that after two hours and twenty minutes the excess of sulphur evaporates from the tube4 ,the condenser is now added 7,stckperiode--,cake-period7 and luted1 then the firing is still more urged1 whereupon the cinnabar volatilises and deposits itself upon the glazed earthenware condensation apparatus 7tube1 helmet1 c474 ,after four hours1 the sublimation is complete1 and there is furnished by the helmet #fi per cent41 by the tubes #bf per cent41 by the condenser 7,vorlage7 #b per cent41 cinnabar4 ,the grinding of the cake cinnabar takes place in four mills driven by an undershot water-wheel4 ,these mills have a fixed under and upper movable stone1 and the grinding is done with water4 ,the vermilion which leaves the spout and runs into glazed clay vessels has a temperature of about #ajj ,f41 that of the air being #ei ,f4 ,the millstones make forty revolutions per minute1 and after each passage of the charge are placed nearer together4 7#b7 ,a ,german chemist named ,fleck has discovered that when a warm solution of hyposulphite of soda is added to a double salt of mercury1 such as chloride of mercury and sodium1 the solution becomes acid1 and black sulphide of mercury is deposited4 ,but if the hyposulphite solution is added in excess1 and the temperature is not allowed to rise beyond #adj ,f41 the solution remains neutral1 and red sulphide of mercury1 or vermilion1 is deposited4 ,the least quantity of acid causes the production of the black sulphide4 ,the presence of a salt of zinc facilitates the production of the vermilion4 ,the best method is as follows3--,to four equivalents of hyposulphite of soda mixed with four equivalents of sulphate of zinc in diluted solution1 is added1 drop by drop1 a solution containing one equivalent of corrosive sublimate4 ,the whole is gently heated for #fj hours1 at a temperature of #aab to #acj ,f4 7#c7 ,the following account of vermilion manufacture in ,china appeared over the initials ,t4 ,i4 ,b41 in the ,chemical ,news4 ,the ,chinaman has no knowledge whatever of chemistry1 and of the principles of natural philosophy and statics generally his notions are of the most rudimentary and primitive description4 ,how1 then1 in the face of these obvious disadvantages have the ,chinese contrived to place themselves in the front rank amongst nations in the matter of certain chemical manufactures1 one of the most important of which is the subject of this article--,vermilion8 ,we have seen with what ingenuity and pertinacity in carrying out his ends the ,chinaman has succeeded in making perhaps the most delicate and perfect iron castings in the world4 ,he has succeeded in that instance1 not by any deep researches into the hidden mysteries of ,nature1 by no process of thought involving an enquiry into the 8reason why02 to this the ,chinaman is averse1 the whole tendency of his education1 such as it is1 tends to make him satisfied with observing effects2 it is sufficient to him to know that things are so1 without going into troublesome or elaborate investigations into those changeless laws of ,nature into which his philosophy teaches him that1 as he cannot alter or control1 research is fruitless3 but that he has in his own small1 ingenious1 patient way observed effects to very good purpose1 the unrivalled excellence of some of his manufactures testifies4 ,we will now enter a vermilion manufactory and watch the process from the first stage of mixing its two ingredients--mercury and sulphur--to the final process of weighing and packing this costly and beautiful pigment for the market4 ,the first objects to attract the visitor's attention on entering the yard attached to the works will probably be large piles or stacks of charcoal1 crates or baskets of broken crockery ware1 and numerous rusty old iron pans of somewhat similar shape to rice pans1 but considerably thicker and heavier4 ,there will also probably be a few broken and disused cast-iron mortars4 ,all these articles are the cast off or worn out implements of the manufacture1 and will be described in their proper order4 ,on entering the factory proper1 scores of little stone mills1 each being turned by one man1 and other long rows of workmen weighing out and wrapping up the vermilion1 will be seen4 ,the furnaces are then arrived at3 there may be a score or more in number1 and may be ten or twelve in each furnace room1 five or six on each side4 ,after passing these1 the stores of quicksilver1 sulphur1 alum1 glue1 new spare iron pans1 serviceable crockery ware1 and sieves and other utensils used in the factory are arrived at1 and this completes the view of the works4 ,the iron pans in which the vermilion is sublimed are those referred to above2 they are circular and hemispherical in shape2 all are of the same size and weight2 they are cast upside down1 and in the casting1 a runner or lump of iron1 two and three-eighths inches in diameter by from six-eighths to one inch in depth1 is purposely left on every pan in order to enable the workman the more readily to handle the pan when stirring up its contents4 ,the size of the pans proved by actual measurement to be #bi inches in diameter1 by #h inches deep1 and the weight #dj catties1 or say about #ec lb4 ,these pans are set in rows of #e or #f on each side of a small rectangular room1 in size some #ab feet by #ae feet2 the door of this room is of wood and contains an aperture a few inches square in order to enable the workman to watch the progress of his operation1 from time to time1 without the necessity of lowering the temperature of the apartment by opening the door4 ,the pans are set in brickwork1 each pan having beneath it a grate to hold the charcoal used as fuel4 ,there is no communication between the grates or furnaces under each pan1 and no chimney1 the flames and products of combustion finding exit from the front of the grate1 which is left wholly open at all stages of the operation4 ,the process of manufacture is as follows3--,taking an iron pan which is of #d inches smaller diameter than those described1 and also in all other respects proportionally less1 except the runner1 which is of the same size1 a skilled workman proceeds to weigh out #ag lb4 of sulphur4 ,this he places in the pan1 and adds about half the contents of a bottle of quicksilver4 ,the pan with its contents is then put upon a small earthen brazier or portable furnace1 the fuel used in which is charcoal4 ,when the sulphur is sufficiently melted1 the workman1 taking an iron spatula or stirrer1 rapidly stirs up the quicksilver with the sulphur1 and gradually adds the remaining contents of the bottle of quicksilver1 stirring the two ingredients together meanwhile until the mercury has wholly disappeared1 or 8been killed10 as the ,chinese put it4 ,when this takes place1 the pan is removed from the fire1 a small quantity of water is added1 and rapidly stirred up with the contents of the pan1 which have now assumed a dark blood-red appearance and semi-crystalline structure4 ,this mass is then turned out of the pan into an iron mortar1 and then broken up into a coarse powder4 ,this forms a charge for one of the large pans previously described1 and when sufficient material has been prepared to charge all the pans in one furnace chamber the sublimation is proceeded with as follows3-- ,all the pans having received their quantum of crude vermilion1 this is covered with a number of crockery-or porcelain-ware plates1 of tough1 strong manufacture1 each about #h inches in diameter2 some of these plates1 however1 are broken up1 and are in a more or less fragmentary condition4 ,when these plates have been piled up into a dome-shaped heap of the same shape as the bottom of the upper pan1 to which they should extend1 the whole is covered with one of the smaller pans previously described4 ,now it will be remembered that the smaller pan was of #d inches less diameter than the larger one2 there will consequently be a circular space two inches all round between the circumferences of the pans4 ,consequently the rim of the upper or covering pan will be about #b inches lower than the rim of the lower pan2 there will also be some #d inches space horizontally between the rim of the large lower pan and that portion of the smaller pan which is at the same height as the rim of the larger one4 ,this space is carefully filled with a clay luting into which some holes1 generally about four in number1 are pierced1 extending down to the rim of the smaller pan or cover2 this is done in order to allow the heated air and other matters to escape4 ,all the pans in one furnace chamber being thus charged and covered1 the fires are lighted4 ,the flames from the charcoal should occasionally play several feet above the mouths of the furnaces4 ,the door of the chamber is kept closed1 except when it is open for a moment in order to enable the workmen to replenish the fires1 which must be kept up at a fierce heat for eighteen hours4 ,during this process a blue lambent flame is seen to play above each of the four holes which are pierced through the clay luting of the pans1 so it is evident that a considerable quantity of either one or probably both the ingredients is wasted4 ,after eighteen hours the fires are allowed to go out1 and the contents of the pan cool down4 ,when this is accomplished1 the greater portion of the vermilion will be found adhering to the lower surface of the broken-up porcelain plates with which the crude product is covered4 ,the vermilion is then carefully removed from the porcelain by means of chisels1 and is now ready for the elutriating mills4 ,another portion of vermilion of not so good quality is found adhering to the upper iron pan1 and that obtained by washing the clay luting in a cradle1 as diggers wash dirt for gold4 ,this1 together with the wipings and scrapings generally1 is mixed up with alum and glue-water into cakes1 and1 after drying on a brick surface heated beneath by means of wood or charcoal1 is powdered up on a mortar1 and re-sublimed when a sufficient quantity has accumulated4 ,the vermilion which was removed from the porcelain plates is of a blood-red colour and crystalline structure4 ,this is then powdered up in a mortar and removed to the levigating mills4 ,these are the ordinary little horizontal stone mills used by ,chinese and other natives of the ,east to grind rice and other grain into flour or pulp1 as the case may be4 ,each stone is about #b feet in diameter2 the lower stone is stationary1 the upper is turned by a direct-acting piece of wood having a hole in it which works a wooden peg affixed to the upper stone1 which is made to revolve by a backward and forward movement of the piece of wood1 or handle1 some #c or #d feet long1 previously mentioned4 ,one man turns each mill4 ,the upper stone has a small hole in it near its centre1 down which the workman from time to time pours a little spoonful of the powdered vermilion1 which he washes down into the mill with water2 as he turns the mill1 the workman keeps continually ladling little spoonfuls of water down the aperture or hole in the upper stone2 the ground and thus elutriated vermilion1 as it escapes from between the stones1 is washed down by the water into a vessel placed beneath to receive it4 ,when work is suspended for the evening1 the ground vermilion is carefully stirred up with a solution of glue and alum in water1 in the proportion of about an ounce of each to the gallon4 ,the glue has been made to mix with the water by previously heating it with a small quantity of water2 the earthen pots in which this process is effected each hold about #f gallons4 ,the mixture is then left to settle4 ,in the following morning the mixture of glue and alum is poured off the vermilion1 and the upper portion of the cake of vermilion at the bottom of the vessel--that is1 the portion which remained longest suspended in the liquid--will be found to be in a much finer state of subdivision than the lower portion1 which requires to be again elutriated as on the previous day3 this separation of the more finely divided vermilion from that which was coarser1 by suspension in a dense medium1 is a really most ingenious process1 for which we should give the ,chinaman every credit4 ,the process of grinding1 elutriation1 and separation of the coarsely ground from the fine vermilion1 sometimes requires to be several times repeated1 in order to fully bring out the colour4 ,as a final process the damp cake of finely ground vermilion is stirred up with clean water1 and allowed to settle down until the next morning1 when the water is carefully poured off into large wooden vats to still further deposit a small quantity of vermilion yet remaining in suspension1 and the vermilion is dried in the open air on the roof of the premises4 ,when quite dried1 the cakes of now full-coloured pigment are carefully powdered1 and sifted by means of square muslin-bottomed sieves1 contained in a covered box some #b feet high by #b wide1 in which the sieves1 which slide on a framework inside the box1 are jerked backwards and forwards by means of a handle on the outside of the box or case containing them4 ,the now fully-prepared vermilion is removed to the packing house1 where may be seen rows of workmen1 men and boys1 seated before a series of tables4 ,between every two workmen is a third1 with a small pair of scales1 which he holds in his left hand2 and as the workmen on either side place before him the little pieces of paper in which the vermilion is to be wrapped up1 he weighs into each paper one tael 7about an ounce and a third avoirdupois7 weight of vermilion2 the papers are two in number1 the inner a black or prepared paper1 and the outer a piece of ordinary white paper4 ,after being wrapped up1 the packets are placed in rows before another workman1 who stamps them with a seal containing in ,chinese characters the name and address of the manufactory in which the article has been made1 and the quantity and quality of vermilion contained in the packet4 ,the rapidity and deftness of the ,chinese workmen at this employment is really surprising2 the stamping1 for instance1 is effected at the average rate of sixty impressions per minute1 and the wrapping up is carried on with proportionate rapidity4 ,the mixture of alum1 which is the ordinary aluminium potassium sulphate1 with the vermilion1 in one of its stages of manufacture as described above1 is not added1 as at first sight we thought it might be1 merely to assist in clarifying or purifying the water by causing it to deposit its sediment1 but seems to have some peculiar effect upon the colour1 although what may be the rationale of the process1 or how it acts1 we cannot quite clearly see4 ,the glue is added as described above merely to favour separation of the finely elutriated vermilion by holding it longer in suspension than the coarser particles1 which sink first1 and may therefore be separated in their order of stratification4 ,the actual composition of vermilion is #ajj parts of mercury to #af of sulphur1 when both these ingredients are in a perfectly pure state2 the excess of #e lb4 of sulphur added by the ,chinese is probably volatilised and lost in the process of sublimation1 or1 as the sulphur used is generally not quite pure1 a part may go for foreign matter contained in the sulphur2 the balance being probably the raison d'tre of the blue lambent flame seen playing over the apertures in the luting during the sublimation process4 ,for a people having1 like the ,chinese1 no acquaintance with even the first rudiments of chemistry1 the proportion of ingredients taken--#ef catties to #ac catties1 or say #ge lb4 to #ag lb4--shows wonderfully accurate powers of observation and a knowledge of combining proportions only to be gained by much experience and a long extended series of careful observations highly creditable to the manufacturers4 ,the entire process is one of the most ingenious and interesting to be seen in any part of the world4--7,t4 ,i4 ,b47 ,another and briefer account of the ,chinese vermilion manufacture is given by ,h4 ,maccallum1 in the ,proceedings of the ,pharmaceutical ,society4 ,he says there are three vermilion works in ,hong ,kong1 the method of manufacture being exactly the same in each4 ,the largest works consume about #fjjj bottles of mercury annually1 and it was in this one that the following operations were witnessed3-- ,first ,step4--,a large1 very thin iron pan1 containing a weighed quantity1 about #ad lb41 of sulphur1 is placed over a slow fire1 and two-thirds of a bottle of mercury added2 as soon as the sulphur begins to melt1 the mixture is vigorously stirred with an iron stirrer until it assumes a black pulverulent appearance with some melted sulphur floating on the surface2 it is then removed from the fire and the remainder of the bottle of mercury is added1 the whole being well stirred4 ,a little water is now poured over the mass1 which rapidly cools it2 the pan is immediately emptied1 when it is again ready for the next batch4 ,the whole operation does not last more than ten minutes4 ,the resulting black powder is not a definite sulphide1 as uncombined mercury can be seen throughout the whole mass2 besides1 the quantity of sulphur used is much in excess of the amount required to form mercuric sulphide4 ,second ,step4--,the black powder obtained in the first step is placed in a semi-hemispherical iron pan1 built in with brick1 and having a fireplace beneath1 covered over with broken pieces of porcelain4 ,these are built up in a loose porous manner1 so as to fill another semi-hemispherical iron pan1 which is then placed over the fixed one and securely luted with clay1 a large stone being placed on the top of it to assist in keeping it in its place4 ,the fire is then lighted and kept up for sixteen hours4 ,the whole is then allowed to cool4 ,when the top pan is removed1 the vermilion1 together with the greater part of the broken porcelain1 is attached to it in a coherent mass1 which is easily separated into its component parts4 ,the surfaces of the vermilion which were attached to the porcelain have a brownish red and polished appearance1 the broken surfaces being somewhat brighter and crystalline4 ,third ,step4--,the sublimed mass obtained in the second step is pounded in a mortar to a coarse powder1 and then ground with water between two stones1 somewhat after the manner of grinding corn4 ,the resulting semi-fluid mass is transferred to large vats of water and allowed to settle1 the supernatant water is removed1 and the sediment is dried at a gentle heat2 when dried1 it is again powdered1 passed through a sieve1 and is then fit for the market4--,proc4 ,pharm4 ,soc4 7#d7 ,firmenich describes a process which he declares gives better results in the beauty of colour than any other4 ,it consists in using sulphide of potassium1 which must be in a state of great purity4 ,of the various methods for preparing potassium sulphide1 ,firmenich rejects those in which caustic potash lye is boiled with excess of flowers of sulphur1 on account of the simultaneous formation of a hyposulphite or sulphate of potash1 which interferes in the preparation of the vermilion4 ,the process adopted by ,firmenich for making pure potassium sulphide is to reduce sulphate of potash by heating with charcoal1 and subsequently saturating the lye with sulphur to the necessary degree4 ,usually about #bj parts by weight of potassium sulphate and #f parts by weight of charcoal are reduced to very fine powder and thoroughly incorporated4 ,placed in a ,hessian crucible1 the mass is covered1 luted1 and strongly heated4 ,as considerable ebullition takes place the crucible should be of such a size that the charge only occupies two-thirds of its capacity4 ,after fusion is complete1 the mass1 which is now potassium sulphide1 is allowed to cool2 it presents a reddish-brown crystalline appearance1 and is very hygroscopic4 ,it is put into a cast-iron pan1 with addition of soft water in the proportion of #g parts of water to every #b parts of the potassium sulphide2 after boiling1 it is filtered and on cooling1 the undecomposed sulphate of potash collects in crystals attached to the sides of the pan4 ,the thus purified lye is boiled a second time with flowers of sulphur1 added in small doses until saturation is indicated by bubbling and effervescence4 ,the simple 7monosulphide7 potassium sulphide in this manner takes up four additional atoms of sulphur1 and becomes the pentasulphide4 ,the preparation of the vermilion then proceeds in the following manner3--,into a series of large flasks are put #aa lb4 of mercury1 #e lb4 of the potassium sulphide lye1 and #b lb4 of sulphur4 ,the contents are subjected to a moderate heat1 and the flasks are then agitated in a curious manner by arranging them in pairs in baskets suspended from strings1 over a straw mattress1 on which the baskets bump each time they descend4 ,occasionally the flasks are turned about1 and after about two hours of this agitation they commence to grow hot1 and the contents assume a greenish-brown colour4 ,the lye is robbed of its sulphur by the mercury1 and replenishes itself from the excess added4 ,complete combination of the mercury and sulphur is accomplished in about three and a half hours1 when the colour of the mass becomes dark brown4 ,the next step is to cool the compound1 an operation which must proceed very slowly1 and should occupy about five hours4 ,development of the colour is effected by heat1 for which purpose the flasks are placed in a stove room or water bath1 and subjected to a temperature which does not fluctuate beyond #aac and #abb ,f41 under the influence of which the red colour appears4 ,the greatest care is necessary in this heating process1 as it determines the success or failure of the colour4 ,it lasts several days1 during which the flasks should be shaken three or four times daily4 ,in order to separate the vermilion from the excess of sulphur1 water is added to the contents of each bottle1 and1 after thorough shaking1 the whole is turned out into a filter4 ,the clear liquor escapes1 and the residual vermilion is mixed with caustic soda lye in stoneware jars1 and thus the remaining free sulphur is dissolved out4 ,subsequently the lye is poured off as completely as possible1 and the deposit is repeatedly washed1 first by decantation and finally on a filter4 ,the whole operation of filtering and washing cannot be completed in less than two or three days4 ,when this is finished1 the drying must be carried on at a very low temperature1 till the vermilion can readily be broken and is dry to the touch1 when it is put into iron basins and repeatedly stirred1 while the temperature is allowed to reach #adc ,f41 but never beyond that4 ,the final desiccation occupies about five hours4 ,vermilion made in this way is reputed more permanent and less costly than by the usual methods4 7#e7 ,dutch vermilion has a good name1 and one method adopted in ,holland is as follows3--,a mixture of #b lb4 of mercury and #a lb4 of sulphur is thoroughly ground1 and to #ajj lb4 of the mixture are added #b lb4 of minium or of granulated lead4 ,about #b cwt4 of the compound is put into each sublimation pot1 which is duly heated4 ,when the operation is finished1 the pots are allowed to cool for eighteen to twenty hours1 when they are broken1 and their contents are ground in a mill4 ,the lead remains as a sulphide in the bottom of the pots4 7#f7 ,a modification of the ,dutch method consists in making an intimate mixture of #ed lb4 of mercury squeezed through chamois leather and #g lb4 of flowers of sulphur1 which is then moderately heated on a shallow iron dish1 and the resulting black sulphide 78ethiops07 is coarsely broken1 ground1 and kept in pots4 ,to convert the ethiops into vermilion1 the former is put into large clay crucibles in a furnace1 and heated to dark-redness1 whereupon the mass takes fire4 ,as soon as the flame has subsided1 the crucibles are covered with a close-fitting iron plate1 and the firing is continued for thirty-six hours4 ,the mass is stirred every half-hour with an iron rod1 and fresh additions of ethiops are made at four or five hours' intervals4 ,the vermilion is sublimed1 and condenses on the cool portion of the interior of the crucibles1 whence it is collected by breaking the crucibles when cold1 and is finally ground and levigated4 7#g7 ,kirchoff's method requires special care1 and consists in grinding #cjj lb4 of mercury with #fh lb4 of flowers of sulphur in a mortar1 the sulphur being first moistened with a few drops of caustic potash4 ,the resulting black sulphide of mercury is added to #afj lb4 of caustic potash dissolved in very little water1 and the whole is heated for half an hour on a sand bath1 with occasional addition of water to make up for loss by evaporation4 ,gradually the mass1 under constant agitation1 becomes brown and gelatinous1 and finally red4 ,thereupon it is carried to the stove room and still agitated at intervals4 ,after several washings it is drained1 and dried very gently4 7#h7 ,weshle mixes finely powdered cinnabar with #a per cent4 of antimony sulphide1 and boils the mixture several times with three parts of potassium sulphide in a cast-iron pot4 ,the precipitate is water-washed1 digested with hydrochloric acid1 washed again1 and finally dried4 7#i7 ,jacquelin takes #ij lb4 of mercury1 #cj of sulphur1 #cj of water1 and #bj of hydrated potash2 the mercury and sulphur are put into a shallow cast-iron dish1 dipping into cold water1 and the potash solution is added by degrees while the mass is kept in agitation4 ,then the mixture is heated for an hour at #agf ,f41 the evaporated water being replenished4 ,the vermilion is washed in an excess of boiling water1 and again several times in cold water1 and finally filtered and dried4 ,,victoria ,,red4--,one of the fancy names for ,derby red4 7,see p4 #ade47 ,,chapter ,,vii4 ,,whites4 ,in the whole range of pigments there is no more important class than those to be described in this chapter4 ,not only are the white pigments largely employed for the sake of their distinctive colour1 but they are probably even more extensively applied as a basis of other pigments1 both as an ingredient in the composition of the other coloured paints and for ground coats where the final coat is to be of a delicate shade4 ,they are among the cheapest and most permanent pigments1 and possess as a whole remarkably good covering powers4 ,,baryta ,,white4--,barytes or sulphate of baryta1 the most important of the salts of barium1 is found native in large quantities1 forming the species of mineral termed barites or barytes1 and commonly known as heavy-spar1 on account of its weight 7sp4 gr4 from #dc to #dg74 ,it is found in ,derbyshire and ,shropshire1 and often occurs in fine tabular crystals4 ,the massive variety found in the mountain limestone of the above counties is sometimes called 8cawk02 it is more frequently found in white or reddish-white masses4 ,in ,saxony it occurs as the mineral stangen-spath1 in a columnar form2 and at ,bologna1 a nodular variety is found1 called ,bologna stone1 which is notable for its phosphorescent powers when heated4 ,the pure salt may be prepared artificially for use as a pigment1 by adding dilute sulphuric acid to a solution of chloride of baryta1 when a white precipitate is formed2 this is well washed and dried4 ,it is a heavy1 white powder1 insoluble in water and nearly insoluble in all other menstrua4 ,it may also be prepared by heating the native mineral1 grinding it to powder1 and well washing it1 first in dilute sulphuric acid1 in order to remove any traces of iron1 and afterwards in water2 the white powder is afterwards thoroughly dried4 ,this process is employed at several works in the neighbourhood of ,matlock ,bath1 in ,derbyshire1 but much larger quantities could be produced in different parts of the country if the demand for the article rendered its production more profitable4 ,the principal use of sulphate of baryta is to adulterate white lead1 and to form the pigment known as blanc fixe1 or permanent white4 ,for these purposes1 the native mineral1 ground and washed as described above1 is commonly employed4 ,improvements in machinery and in the process of treating natural barytes have overcome many of the objections which formerly existed to its utilisation1 and considerable attention is now being given to the localities in the ,united ,states where it is found4 ,the mineral1 in order to be available for the uses to which it is put1 must be fairly free from quartz grains1 the stain of iron rust1 and other impurities4 ,if the barytes is stained to any extent1 it is practically valueless1 as a good white colour is essential to its usefulness4 ,quartz grains or other hard substances with which it is apt to be associated injure the machinery in grinding4 ,the purest barytes so far produced in ,america comes from ,missouri1 though a very fair grade is now being mined in considerable quantities in ,virginia4 ,the returns from all producers of crude varieties show a product in the ,united ,states1 for #ahhi1 of #ba1fdj short tons1 valued at #ajf1cac dols41 against #bj1jjj short tons in #ahhh1 valued1 approximately1 at #aaj1jjj dols4 ,the product was limited to four ,states1 as shown in the following table3-- ,short tons4 ,value4 ,illinois #bjj #a1cjj ,missouri #g1eeh #cb1gae ,north ,carolina #c1jjj #ae1jjj ,virginia #aj1gjb #eg1bih ------ -------- ,total #ba1dfj #ajf1cac ,,blanc ,,fixe4--,this name is given to baryta white when it has been artificially prepared by adding sulphuric acid to a solution of chloride of barium4 7,see p4 #agj47 ,,charlton ,,white4--,one of the names applied to a white pigment1 containing zinc oxide and sulphide1 and described under zinc whites1 p4 #bed4 ,,china ,,clay4--,this substance is also known as kaolin1 porcelain clay1 and ,cornish clay4 ,it arises from the natural decomposition of felspar in soft disintegrating granite1 gneiss1 and porphyry1 the rocks which are rich in soda-felspar yielding it most abundantly4 ,the main supplies of this country are derived from ,cornwall and ,devon2 in continental ,europe1 beds of good quality exist in ,france1 ,bavaria1 ,saxony1 ,prussia1 ,bohemia1 ,bornholm island1 and ,hungary2 in ,china1 it is very plentiful2 and in the ,united ,states1 it occurs in many localities4 ,the approximate composition of china clay may be stated as silica1 #dgb2 alumina1 #cia2 water1 #acg per cent4 ,often a little iron1 lime1 and potash or soda are left in the prepared article by the imperfection of the cleansing process4 ,the most important characters are colour1 plasticity1 and a capacity for hardening under the influence of heat4 ,the china-clay industry of ,cornwall and ,devon has been admirably described by ,j4 ,h4 ,collins1 ,f4,g4,s41 in a paper recently read before the ,society of ,arts4 ,occurrence4--,the natural clay rock is almost always covered with a thick layer of stones1 sand1 or impure and discoloured clay1 known as 8overburden40 ,this capping often much resembles glacial drift2 but it never contains any scratched or glaciated stones1 or travelled blocks4 ,it varies in thickness from #c feet to #dj feet1 and must1 of course1 be removed before the clay can be wrought4 ,the clay rock1 being a decomposed granite1 consists of china-clay1 irregular crystals of quartz1 and flakes of mica1 with sometimes a little schorl and undecomposed felspar4 ,extraction and ,preparation4--,the following descriptions apply1 with more or less accuracy1 to a majority of the larger works of the present day1 turning out from #bejj to #hjjj tons of clay each1 yearly4 ,two somewhat different methods are employed1 according to the situation of the 8bed0 of clay in relation to the surface contour of the immediate neighbourhood4 ,the most general case is that in which the clay has to be raised from a veritable pit1 the bottom of which is lower than the ground on all sides4 ,the exact situation of the clay is first determined by systematic 8pitting10 to a depth of several fathoms1 or occasionally by boring4 ,a shaft is then sunk either in the clay itself1 or1 preferably1 in the granite close to the clay4 ,from the bottom of this shaft1 a level is driven out under that part of the clay which it is intended to work first1 and a 8rise0 is put up to the surface1 which should1 by this time1 be partially cleared of its overburden4 ,a common depth for such a shaft will be from ten to twelve fathoms4 ,as soon as the rise is completed to surface1 a 8button-hole0 launder is placed in it1 and the remainder of the rise is again filled up with clay4 ,in the meantime1 a column of pumps has been placed in the shaft1 with an engine to work them1 unless water-power is obtainable4 ,for water1 many works are almost entirely dependent upon that met with in sinking the shaft and in driving levels2 but1 of course1 this may be1 and is1 eked out by catching the rain-water in reservoirs1 and by making use of such small streams as may happen to be available4 ,a small constant supply is sufficient even for a large work1 as it is used over and over again4 ,the operation is begun by digging a small pit in the clay1 around the upper end of the button-hole launder1 and running a stream of water over the exposed clay1 or 8stope10 which is broken up with picks4 ,a very large quantity of sand is constantly disturbed1 and as constantly shovelled out of the way1 while the water1 holding the clay and finer impurities in suspension1 runs down the launder1 along the level1 and into the bottom of the shaft1 from whence it is pumped up by the engine or water-wheel4 ,as the excavation becomes larger and deeper1 more overburden is removed1 and the upper portions of the launder are taken away1 until at last the stopes reach the level1 when the launder is1 of course1 no longer required4 ,at first1 the sand is thrown out by one or two 8throws10 but very soon it becomes necessary to put in an inclined road1 for pulling up the sand in waggons2 these are worked by a horse-whim1 or by winding gear attached to the engine or water-wheel4 ,as there are from three to eight tons of sand to each ton of clay1 its removal in the cheapest possible manner is a matter of great importance4 ,any veins or lodes of stone1 or discoloured portions of clay1 are raised from the 8bottoms0 in the same way as the sand4 ,the stream of water1 holding in suspension clay1 fine sand1 and mica1 is1 in well-arranged works1 lifted at once high enough to allow of all subsequent operations being carried out by the aid of gravity4 ,the stream is first led into one or two long channels1 the sides of which are built of rough stone4 ,in these channels1 called 8drags10 the current suffers a partial check1 and the fine sand and rougher particles of mica are deposited4 ,from these drags1 the stream passes on into other channels1 much resembling them1 but of greater number1 so as to divide the stream still further4 ,this second series of channels1 known as 8micas10 are often built of wood1 but sometimes of stone4 ,they differ in no essential respect from the drags1 but are more carefully constructed and better looked after1 and1 as the stream is greatly divided and very gentle1 the fine mica is deposited in them4 ,the micas are often about #aa inches wide1 ten or a dozen in number1 and #ajj feet or more long4 ,provision is made1 by underground channels and plug holes1 for the periodical cleansing of the drags and micas4 ,this may have to be done twice a day1 but generally only once4 ,the deposit in the drags is worthless at present1 and is always thrown away2 but that from the micas is often saved1 and sold as inferior or 8mica0 clay4 ,the refined stream of clay then passes on to the 8pits10 which are circular1 #cj to #dj feet diameter and #g to #aj feet deep4 ,these pits are built of rough masonry1 and have an outlet at the bottom1 opposite the point at which the stream of clay-water is admitted4 ,this outlet is stopped by a gate or 8hatch10 or by a plug1 and is kept closed until the pit is full of clay4 ,in each outlet1 however1 is fixed an upright launder some #d inches square1 provided with 8pin-holes0 and wooden pins set close together4 ,as the stream of clay enters on one side1 it is constantly depositing its burden1 and the water is as constantly drawn off nearly or quite clear from the pin holes1 the pins being put higher and higher as the clay rises in the pit4 ,the effluent water is conducted directly to small storage reservoirs1 and thence over the clay stopes1 whence it does its work over again4 ,when the stream of clay-water enters the pits1 it contains from #a to #c per cent4 of clay2 and what is called a good washing stream will carry about one ton of clay an hour4 ,when the pit is full1 the 8hatch0 is drawn1 and the clay is 8landed0 into the tank4 ,the upper portion is sufficiently fluid to run in of itself2 but that near the bottom has to be helped out by men using 8shivers0 of wood or iron1 which resemble large hoes2 they are assisted by a small stream of water4 ,the tanks are commonly1 but not always1 rectangular1 built of stone1 and paved with stone at bottom1 often #fj feet by #cj feet by #f feet or larger4 ,once in the tank1 the clay is left to settle1 until it has the consistency of cream cheese1 the water being drawn off from time to time2 it is then ready to be trammed into the 8dry40 ,the 8dry0 is a large building erected in immediate proximity to the tanks4 ,it is always composed of two parts1 the dry proper and the 8linhay40 ,the floor or 8pan0 of the dry is composed of fire-clay tiles #ah inches square1 #e or #f inches thick at the fire end1 and gradually thinning off to #b or #b inches at the stack end4 ,the flues are built of fire-brick1 about #ae inches wide1 #b feet deep at the fire end1 and #i inches deep at the stack end4 ,each flue should be supplied with a damper4 ,the furnaces are built in and arched over with best fire-brick2 the fire bars run longitudinally1 and are about #f feet long4 ,the grate surface is about #b feet #f inches wide in front1 and #d feet #f inches to #f feet at back1 according as each furnace supplies three or four flues4 ,the clay1 brought in from the tanks in tram-waggons holding about half a ton1 is tipped on to the tiles1 and spread in a layer from #i inches thick at the fire end to #f inches thick at the stack end4 ,the fire end is loaded and cleared every day2 the other end perhaps twice or thrice a week1 according to the length of the dry1 thickness of tiles1 perfection of draught1 c4 ,an average size for a first-class dry is perhaps #ae feet wide and #abj feet long2 but some have been constructed considerably larger than this4 ,the pan of the dry should be #f or #h feet above the linhay whenever possible1 so as to afford storage space for the dry clay1 without expending labour in piling4 ,the tiles should be as porous as possible1 for very much more water passes through the tiles and into the flues than is driven upwards in the state of steam4 ,the temperature should never be allowed to rise so high that the workmen cannot walk on the tiles1 otherwise the clay may become baked and damaged4 ,in cases where there are no means of artificial drying1 as at some old-fashioned works1 the thick clay is at once transferred from the original settling pit to shallow depressions in the ground1 called 8pans40 ,ten or twelve of these1 each holding from #dj to #ej tons1 should be provided for each settling pit2 they measure from #bj to #dj feet square1 and #b feet deep1 and are enclosed by granite walls1 the interstices of which are rendered impervious by plugging with moss4 ,the clay1 filling two-thirds of their depth1 is here left exposed to the sun and wind1 by which it is partially deprived of its moisture4 ,in order to complete its desiccation1 the clay is removed from the pans after three or four months' exposure4 ,a number of parallel incisions are made lengthwise in the clay1 by means of a knife attached to a long handle2 the strips are next divided transversely1 by men with spades1 who throw the blocks on to a board1 upon which they are borne by women and children to the sandy drying yard1 where1 in fine summer weather1 they soon become dry4 ,they are then collected1 and piled away in sheds1 under a number of thatched gates or 8reeders10 or are placed in some sheltered position where air can circulate around them without their becoming wet from rain4 ,when required1 the blocks are scraped by women armed with hoes1 before being despatched from the works4 ,the transport is often effected in small casks1 holding about half a ton4 ,a few years since1 a machine for drying china-clay was invented by a mechanical engineer named ,leopoldo ,henrion1 of ,sampierdacena1 near ,genoa4 ,it is said that1 by its use1 the operation can be effected in a few hours1 at a relatively small cost4 ,collins was first led to adopt his arrangement in consequence of the formation of the ground2 but he is inclined to recommend it in most cases if practicable4 ,very large quantities of stone are required in the dry pits1 tanks1 c4 ,very often this is got1 in part or entirely1 in the process of excavating the pits1 c42 but if it cannot be so obtained1 a very serious expense will be incurred1 in some instances amounting to several thousand pounds4 ,the total cost of the works may even be doubled from this cause1 if stone has to be fetched from a distance of several miles4 ,two modes of building with rough stone are adopted2 they are known as 8lime building10 and 8dry stone walling40 ,the first needs no special remark1 but the second is very ingenious and very effectual4 ,the wall is built up double1 with a batter of about inch or #a inch to the foot4 ,moss is placed between the joints of the wall1 and the space between is filled in with sharp sand1 the refuse of that or some other clay works4 ,a small stream of water is then made to flow over the sand1 which is well beaten in with rammers1 or by treading with the feet4 ,this process is continued1 a foot at a time1 till the wall reaches the required height1 when it is either paved with rough stones set on edge1 or turfed4 ,a wall properly built1 in the manner just described1 is quite impervious to moisture1 and will stand for fifty years or more4 ,it is1 where the proper kind of sand is abundant1 much cheaper than lime walling1 and is always preferred for the walls of pits and tanks4 ,where the bed of clay is situated on a hill-side1 with plenty of space below1 a tunnel is driven in from the hill-side or from the valley to the required depth1 and a rise is put up as before4 ,this rise is then divided off into two parts4 ,in the smaller1 a button-hole launder is placed as before1 and packed around with clay2 but the larger is left open4 ,a stream of water1 obtained by pumping or otherwise1 is made to run over the stope1 and down the button-hole launder4 ,it then flows along a launder placed in the bottom of the level1 until it makes its exit in the valley4 ,it may then be purified1 settled1 and dried exactly as already described--the works being laid out at a lower level than the adit2 or1 if the clear water is wanted to flow over the stope1 or it is1 for any reason1 necessary to place the pits and tanks at a higher level than the stopes1 the water is pumped up after partial or complete purification4 ,the main difference in this mode of working is that instead of pulling the sand and rubbish up over an incline1 it may be tipped down the pass into waggons1 run out through the level1 and tipped over the hill-sides4 ,in cases where waste water is abundant1 it may even be washed out at night1 thus saving the expense of tramming4 ,of course1 when the workings have reached their full depth1 the rise and the launder are dispensed with1 and the adit level communicates directly with the 8bottoms40 ,by this mode of working a considerable economy may be effected1 especially when it is not necessary to pump the clay water for settling or repeating4 ,cost of ,production4--,where the conditions of production vary so greatly1 there must necessarily be great differences of cost2 but1 after having been at some pains to determine the cost under average conditions1 ,collins thinks the following figures and statements may be relied upon4 ,a work capable of producing say #djjj tons of clay yearly will cost from #bejjl4 to #ejjjl4 ,to get the clay in the linhay ready for the market will cost about #is4 a ton1 of which about #bs4 #f;d4 must be expended in fuel for pumping and drying1 #as4 in removing overburden1 #as4 in removing sand1 and #as4 for management and office expenses1 leaving #cs4 #f;d4 as the net labour cost of washing and drying a ton of clay4 ,to the #is4 net cost of clay must be added an average of #cs4 for royalties1 #ds4 for transit and placing on board ship1 and #as4 for agencies1 commission1 bad debts1 and sundries1 making the average actual cost amount to #ags4 ,some favourably situated works can no doubt save #bs4 or even #cs4 on this account2 in others1 the cost may amount to #bjs4 or even #bbs4 ,as to the selling price1 this varies much more widely than the cost of production1 ranging from #ads4 to #ces4 f4o4b4 ,clays sold at the lower rate are unremunerative4 ,nature and ,utilisation of ,waste ,products4--,besides the clay proper1 there are certain waste or pseudo-waste substances produced in very large quantities4 ,these are as follows3-- ,fine ,mica4--,this is deposited in the 8micas02 a few years since it was thrown away1 or rather washed away1 as is still the case in many works4 ,sometimes1 however1 it is collected1 dried in the manner of clay proper1 and sold to the makers of soft paper1 paste-board1 inferior pottery1 c41 at a low price4 ,coarse ,mica4--,this is invariably washed away1 or thrown away1 there being at present no demand for it4 ,it1 however1 contains a very beautiful material1 which might be applied to many ornamental purposes4 ,sand4--,this consists of broken quartz crystals1 mostly white or pale brownish2 when washed clean1 it is the finest building sand known1 as the angles are all sharp4 ,mixed with one-eighth of ,portland cement1 it forms a concrete as hard as stone4 ,discoloured ,clay4--,this has to be dug out from among the good white clay in many places4 ,it has been successfully used in the manufacture of white bricks for building purposes4 ,in some instances1 a quantity of the sand already mentioned is mixed with the refuse clay1 and produces an excellent fire-brick4 ,the same material is used in the manufacture of the tiles used as a floor for drying the clay4 ,the manufacture of bricks and tiles from this debris is a growth1 it is believed1 of the last twelve years4 ,overburden4--,the upper part of this consists of soil1 or 8meat earth02 this is usually removed and carefully preserved4 ,underneath is a hard1 often stony or sandy layer1 which1 in districts where tin is worked1 often contains enough tin to pay for washing4 ,with this stony or sandy layer1 is usually a considerable thickness of discoloured clay suitable for brick-making4 ,branches4--,these are stony veins which run through the clay stopes in various directions4 ,sometimes they are quite worthless2 but in a few instances they are veritable tin lodes1 and contain enough tin to pay for stamping and dressing4 ,thus at ,carclaze1 near ,st4 ,austell1 each #ajjj tons of clay yields something like one ton of oxide of tin1 and formerly the proportion was much greater4 ,the proportions of these waste materials1 as compared with the fine clay procured1 are thus stated3-- ,for every #a ton of fine clay there is removed--from #c to #g tons of sand1 average about #c tons2 from #b to #e cwt4 of coarse mica1 average #c cwt42 from #a to #c cwt4 of fine mica1 average #b cwt42 from #j to #a cwt4 of stones1 average cwt4 ,a cubic fathom of clay rock1 of average quality1 will yield about #b tons of fine clay2 and about half a fathom of overburden must be removed to get it4 ,suggested ,improvements in ,preparing4--,collins thinks that there is still much room for improvement in the preparation of china clay1 but that such must be a growth of time and circumstances4 ,at the present time1 about one ton of water has to be driven off from each ton of clay in the 8dry10 and this uses at least #b cwt4 of coals on an average1 and costs from #h;d4 to #aj;d4 in labour4 ,in a few modern drys1 a small economy in fuel has been effected1 by lengthening the kiln2 but in none has it been brought so low as #a cwt4 to the ton of clay4 ,stocker1 in #ahfb1 suggested the use of filter beds1 and also devised a centrifugal dryer2 but neither of these contrivances has come into use1 and the first would seem quite inapplicable on account of the extreme fineness of the particles of clay1 and the impermeability of even a thin layer of that substance4 ,some economy might perhaps result from the use of hydraulic filters of calico1 such as are used in the potteries for drying the slip2 but it is very doubtful if any saving would be effected1 as the labour would be about the same1 and1 against the #bs4 a ton for fuel1 would have to be placed the wear and tear of the calico4 ,in washing the clay from the stope1 some benefit might accrue from the use of a jet of water under a pressure of from #ej to #ajj lb4 per square inch1 as in the so-called hydraulic mining4 ,this could only be applied to stopes of even quality1 where very little picking out of inferior portions was required2 but it would supersede the services of the 8breakers0 on the stope1 and greatly lessen the labour of the washers4 ,it is but rarely that a natural head of water is obtainable equal to the required pressure2 but where machinery is used for pumping1 the additional cost of pumping1 say #bej gals4 a minute to a height of #aej feet in a standpipe1 would be very slight1 as the extra power required is little more than that of one horse4 ,statistics4--,from statistics obtained from many sources1 it is evident that the production has very largely increased from #ahji to #ahgd--biai tons against #bbf1cji4 ,in #ahaj1 ,trethosa 7one of the largest works7 produced #cjj tons per annum1 and employed thirteen persons1 viz4 eight in removing burden and raising 7breaking7 clay 7at per fathom71 three washing1 two attending ponds and packing4 ,in #ahgd1 one of the works near ,st4 ,austell produced #ijjj tons1 employing about thirty men4 ,many works produced #fjjj tons1 employing twenty men4 ,the quantity sent annually from ,cornwall must average at least #aej1jjj tons4 ,it goes not only to ,staffordshire1 but also largely to ,france1 ,belgium1 and other countries4 ,the extensive clay works recently opened in several departments of ,northern ,france have done much to curtail the export of ,cornish clay to that country1 and the large deposits of the island of ,bornholm have lately been worked upon to supply the needs of ,denmark1 ,sweden1 and ,germany2 while similar utilisation of native clays has been carried out in ,america4 ,nevertheless1 the growth of home industries which depend in a measure upon this article will1 doubtless1 counteract the influence of decreasing exports4 ,artificial ,china ,clay4--,the principal supplies of china clay are obtained1 as has been described1 through the agency of natural decomposing influences in granite rocks4 ,in one instance1 however1 at ,betleek1 ,county ,fermanagh1 it is procured by calcining the red orthoclase granite of the district4 ,the felspar is whitened by the process1 and the iron becomes separated in a metallic state1 and is removed by magnets4 ,characters4--,being virtually a hydrated silicate of alumina1 china clay is a remarkably stable pigment4 ,not only is it unaffected by prolonged exposure to strong light and impure air1 but is insoluble in water1 weak acids1 and alkalies4 ,it is moreover very much lighter in weight than any other white pigment1 an advantage on the score of cost when buying by weight4 ,its covering power in distemper work and as a water colour is good2 but the addition of oil reduces its capacity4 ,the best qualities are exceedingly fine in grain and pure in tint1 but inferior samples sometimes have their yellowness 8corrected0 by the addition of a little ultramarine4 ,,enamelled ,,white4--,another name for the finest kinds of baryta white1 see p4 #agj4 ,,english ,,white4--,a synonym for whiting1 see p4 #bdf4 ,,gypsum4--,this very common and abundant mineral is a hydrated sulphate of lime1 occurring in several forms1 of which only the opaque white variety is useful as a pigment4 ,the native mineral is quarried1 dressed1 ground1 and levigated1 in all which operations there is nothing special to be noted4 ,whether obtained in this way1 or prepared artificially1 or formed as a bye product in other industries1 gypsum affords a permanent and neutral white pigment1 mixing well with oil or water1 and possessing a covering power which ranks between white lead and zinc white4 ,it has a bluish tint1 but less so than ordinary white lead4 ,,kaolin4--,one of the names applied to china clay1 see p4 #agb4 ,,lead ,,whites1 ,,or ,,white ,,leads4--,on the grounds of the quantity in which it is produced and the extent to which it is applied1 probably no pigment can compare with white lead1 including in that term the various white pigments having lead as a basis4 ,in its commonest form white lead is lead carbonate4 ,there are many ways in which it is made commercially1 all dependent upon certain chemical reactions4 ,when a solution of normal plumbic acetate is attacked by carbonic acid1 no precipitate is produced4 ,that normal solution is formed by the action of acetic acid or hydric acetate upon oxide of lead4 ,it consists of a certain weight of lead to a certain weight of acid1 which converts it into the acetate4 ,carbonic acid has no power to separate out from it the lead1 and form carbonate of lead4 ,but this acetate of lead has the power of dissolving a considerable quantity of oxide of lead in addition to that which was used in its first formation1 and when this additional quantity of oxide of lead is dissolved by the acetate1 a substance is formed which is termed a basic acetate1 that means an acetate which contains more of the base 7the lead oxide7 than the normal acetate itself does4 ,from such a solution we are able to precipitate1 by means of carbonic acid1 a white substance1 which white substance is a carbonate of lead4 ,thnard1 a ,french chemist1 proposed to make white lead in this way1 but it was found that although the colour was pure and good1 yet the lead had not sufficient body to satisfy the wishes of artists and painters4 ,white lead has been made for years past according to what is called the ,dutch method4 ,lead is cast into plates1 and these plates1 in some factories1 are rolled into coils4 ,these coils then are immersed in earthen pots2 the pots are placed in a row1 and a small quantity of vinegar is put into each pot4 ,on the top of one row of pots a board is placed1 and then other pots above1 and so a stack is made4 ,between the interstices of the pots is put spent tan1 or some other substance which by oxidation will evolve heat1 and also carbonic acid gas4 ,now the heat which is evolved in oxidation of the spent tan is useful in volatilising the acid from the vinegar1 and in the presence of this acetate the oxygen of the air oxidises the lead4 ,the oxide of lead is dissolved by the acid1 and the normal acetate of lead is formed4 ,more oxide is produced1 and this is dissolved by the normal acetate1 and then you have basic acetate4 ,when substances containing carbon are oxidised1 carbonic acid is the product of the oxidation when the oxygen is in excess1 as in this particular case4 ,carbonic acid is then formed by the oxidation of the spent tan4 ,the carbonic acid then unites with the oxide of lead which was dissolved in the normal acetate1 and a thin film of lead carbonate is formed4 ,these thin films go on forming in succession1 until at last nearly the whole of the lead is converted into carbonate1 which retains the shape of the original lead4 ,in some cases1 gratings of lead are used4 ,when the lead is converted into carbonate1 it is ground in water and reduced to a fine powder1 and is then made up into the sort of pigments required1 either with water or with oil4 ,this is1 or rather was1 an operation attended with considerable danger to the workmen1 who were subjected to what is termed lead-poisoning1 to which1 unfortunately1 many painters1 from want of cleanly habits1 are subject now4 ,dutch ,process4--,in the words of ,mr4 ,carter ,bell1 who has read a most interesting paper on the subject before the ,society of ,chemical ,industry1 the manufacture of white lead is a most ancient proceeding1 and has been pursued with but little variation in the mode of manufacture for some hundreds of years4 ,the ,dutch seem to have been the originators of this method of making white lead1 which is now so largely conducted in this and other countries4 ,in this process metallic lead is piled in stacks1 and submitted to the action of acetic acid1 watery vapour1 air1 and carbonic acid for some time1 by which means the metallic lead becomes gradually converted into white lead4 ,this method is called the 8stack0 or ,dutch process4 ,the construction of a stack is a very simple and rude operation4 ,layers of dung or tan1 or a mixture of the two1 are so arranged as to imbed a large number of earthenware pots1 each containing some acetic acid4 ,these pots are about #d or #e inches in diameter1 and about #g or #h inches high2 a coil of lead is placed in each pot1 and buckles or gratings of lead supported on oaken bearers are laid across and on top of the pots2 boards are laid to cover the whole1 and form a floor4 ,the stack is composed of a number of such layers of pots1 bearers1 and buckles or gratings1 raised one upon another4 ,a stack chamber is a brick enclosure #aj or #ab feet square1 and #bj or #be feet high2 such a chamber will contain about #gj tons of lead when stacked and piled4 ,in a white lead factory several of these chambers are built side by side1 and when they are in full operation a set of chambers will contain as much as #gjj or #ajjj tons of lead4 ,only the purest kind of lead will be suitable for conversion in this stack process of making white lead1 the common varieties being inadmissible4 ,messrs4 ,pontifex and ,wood have furnished the following analyses of lead used for white lead making4 ,copper4 ,antimony4 ,iron4 ,spelter4 ,silver4 ,lead4 ,a #jjjgjj #jjjdij #jjjbjj #jjjjhj #jjjajj #iiihdcj ,b #jjgehj #jjjcbj #jjjbbj #jjjcbj #jjjbjj #iiiacfj ,c #jjjcdj #jjjdfj #jjjabj #jjjjgj #jjjcej #iiihffj ,d #jjebfj #jjjgdj #jjjaej #jjjahj #jjjdjj #iiicbgj ,e #jjjidj #jjjbaj #jjjafj #jjjajj #jjjjge #iiiheae ,f #jjbcfj #jjjehj #jjjbaj #jjjahj #jjjajj #iiifegj ,the presence of silver1 copper and iron in the lead would damage the colour of the white lead resulting1 and other admixtures retard or prevent the progress of conversion4 ,in olden times horse dung was the only imbedding material used in the stack arrangement4 ,this material when heated evolves gases which seriously interfere with the colour of the resulting corrosion4 ,dung has been almost superseded in this country by tanners' refuse2 in ,belgium dung is yet employed1 and in some places a mixture of dung and tan4 ,where dung is used1 the process of corrosion of the lead goes on more quickly than when tan alone is employed1 but the use of tan offers great advantages1 especially this one3 that it does not give off gases that damage the white lead4 ,the operations of charging and discharging these chambers are principally the work of women1 and are most laborious and fatiguing4 ,in emptying the chambers and stripping the stacks1 the women are fully exposed to the heated gases which are yielded by the decomposing tan1 and the heated and corroded lead4 ,these gases1 in themselves most injurious to health1 are not to be compared in this respect to the dust which pervades the air and fills the chamber in which these women work4 ,when a stack is charged1 the chamber containing it is enclosed4 ,the tan or dung within soon commences heating1 and the heat soon causes the acetic acid in the pots1 and the water in the tan or dung1 to rise in vapour and penetrate the stack4 ,air is admitted to the stack through openings left for that purpose1 and carbonic acid is evolved from the heated decomposing tan or dung1 and this gas also penetrates the stack1 and the process of converting blue lead into the white lead gradually proceeds1 and the blue metal becomes corroded and incrusted with a white crust or covering4 ,as to the exact chemical changes and combinations proceeding in the working of a stack1 differences of opinion exist1 but we may fairly conclude that the process resolves itself into this--first1 the formation of sub-acetate of lead1 which1 decomposed by the agency of the carbonic acid gas1 becomes reduced to the condition of normal acetate by loss of a portion of its basic oxide of lead4 ,the reduced sub-acetate then again takes up an additional molecule of oxide of lead1 and is re-converted into its original subsalt state1 to be again attacked and reduced by the carbonic acid gas1 and so on continually during the working of the stack4 ,it will be evident that the 8nascent0 state of the various substances disengaged during the chemical changes which are proceeding in the stack is an important factor in this process1 and must be taken into account in considering the philosophy of the operation4 ,it will also be evident that the mode of proceeding in white lead making by the stack process is most crude and clumsy1 and a most uncertain method1 one governed by rule of thumb1 and1 by no element of certainty or science4 ,white lead makers1 as a rule1 know nothing of the chemistry of their subject4 ,this absence of chemical knowledge of the subject1 by those who are engaged in this manufacture1 may explain the curious circumstance that for hundreds of years this industry has been pursued in the same old-fashioned and uncertain way1 and the stack1 or ,dutch process1 still holds its ground and displays little or no advance in knowledge or improvements in its method of proceeding1 even in the present age of precision in almost every branch of manufacture4 ,the uncertainty of the stack process is shown most clearly in this3 ,that stacks may work and some do not work4 ,in the latter case all the time and labour spent in forming the stacks1 and all the acid they contained1 is lost4 ,no amount of foresight will avail to determine beforehand which stack shall accomplish the conversion of its contained metallic lead1 and which will not4 ,the stacks are generally allowed to remain in operation1 after they are charged1 three or four months2 in this time it is presumed all profitable action in the stack has ceased4 ,the temperature of the stack1 which had risen gradually from the normal temperature to #ajj or #aej ,f41 will have gradually fallen1 and this falling temperature is the indication that the corrosion of the lead in the stack has terminated4 ,after the three months' action of the stacks1 they are stripped and pulled to pieces4 ,some will be found to be done better than others1 and one part of the same stack will be done more perfectly than another4 ,the coating on the lead will also differ2 some will be smooth1 regular1 and equal in formation1 some will be rough and blistered1 and far from uniform4 ,the rough blistered casting is rejected as unfit for white lead making3 the workmen call it 8dross40 ,the smooth laminated coating is the one preserved for the after manufacture4 ,it is a curious fact connected with the consideration of the total want of educated guidance in these matters that prevails1 that in all factories of this description some chambers are noted as always working well1 and others are equally well known to always do their work the reverse of well4 ,no one knows why6 ,no one stays to seek the reason4 ,the factory way goes on filling and emptying these white lead chambers whether the stacks be working well or no4 ,the incrustation that is most esteemed by the manufacturers of white lead in this old-fashioned style is a hard1 china-like material1 formed of thin deposits1 layer upon layer1 in a slow1 continuous1 regular way4 ,it is at once conceivable that in the rough-and-ready manner of stack manufacture most irregular action must proceed4 ,it would be almost impossible for the contents of the pile or stack to be submitted to the same action of the gases throughout4 ,some parts of the stack and its contents will be under more favourable conditions than others1 hence the reason why1 in practice1 it is invariably found that some stacks1 and some parts of a stack1 work better than others4 ,under the microscope1 this good crust of white lead1 the proper incrustation from which to prepare white lead1 will be readily seen to consist of very thin coatings or layers of white lead1 which have been slowly formed on the metallic lead and piled one upon another to the thickness of an eighth or a quarter of an inch4 ,this formation constitutes the hard1 china-like substance1 which alone possesses the chemical constitution and the properties to form good white lead paint4 ,white lead makers1 recognising this peculiar incrustation as the only one capable of fulfilling their desired purpose of making good white lead paint1 do not even recognise any other as of any service for that purpose1 be it good or bad4 ,such a material1 if obtained1 however good1 would be outside their experience and beyond their philosophy4 ,after the stacks have been stripped1 the gratings or buckles with their adhering coating of white lead are moistened with water and are passed through crushing rollers to separate the unconverted lead2 then the crust which has been detached is ground under heavy edge runners with water4 ,this detached crust of white lead will vary much in colour3 it will be white in some parts1 yellowish or greyish in others4 ,these discolorations arise from various causes1 but they are principally caused by the contact of the moist wood and tan4 ,the white lead is now a rough crushed material1 very hard1 and requiring to be ground to the finest powder4 ,it contains1 also1 small fragments of blue lead which have passed the crushing rolls1 and a quantity of acetate of lead4 ,the presence of acetate of lead is always found in larger or smaller quantities1 which vary with every operation1 and which invariably accompany white lead produced in the stack4 ,to remove discolorations--to separate the fragments of metal and to dissolve out the acetate salt--much water and washing are employed4 ,the material is ground with water under the heavy edge runner stones1 it then proceeds to a series of horizontal mills1 each succeeding mill set closer than its fellow1 and is further and further ground to fineness with water4 ,from these mills it runs as a milky liquid to a series of settling tanks1 where it is allowed to subside1 and the clear fluid is run off to waste1 or into tanks to be used over again4 ,this waste water will now contain the colouring matter removed from the incrustation1 and the principal portion of the acetate of lead which the incrustation previously contained1 and any other soluble matters removed from the washed and ground material4 ,the small fragments of lead which passed the crushing roll and edge runner mills will have been previously removed by subsidence in water4 ,the white lead deposited in the tanks is in some factories ladled out into skips and agitated by a 8dolly10 which further enables the heavy powder to get free from the water in which it is entangled4 ,the moist powder is next placed on trays or dishes1 and is conveyed to the stove or drying chamber4 ,women always perform this work4 ,the drying or stoving room is a large enclosed space heated by a 8cockle0 arrangement2 rough scaffoldings are erected within this chamber1 on which women mount to stow the trays on shelves fitted for the purpose4 ,the trays and their contents remain in the heated atmosphere of this chamber for two or three weeks1 by which time they become dry and ready for removal1 to be packed in lumps for certain markets1 or ground to dry powder and packed in barrels for others4 ,women are employed to fill and also to empty the drying or stoving chamber1 and during this work they are fully exposed to its contaminating atmosphere4 ,hot and dry1 and charged with fine dusty particles of white lead1 it becomes a dangerous trap1 and contaminates the blood of those engaged with its deadly poison4 ,it is in this part of the manufacture that the principal damage to health occurs4 ,this is the most laborious work2 heat makes it very fatiguing1 the atmosphere within this chamber being always much above the exterior air4 ,recent ,government regulations have sought to curtail these and other evils in this manufacture4 ,women engaged in these stoves are ordered to wear overclothing1 headdress and respirators4 ,the general experience of their practice1 notwithstanding ,government regulations1 is this2 that they cannot work in them with ease and convenience1 and more often wear the respirator around their necks than in front of nose and mouth4 ,the excessive mortality in women who work in these stacks and stoving houses scarcely requires assertion4 ,few1 even of those who employ them1 know the extent of the deadly operation4 ,recently1 medical men have made public that cases are within their knowledge of children born already contaminated with lead poison4 ,woman labour should surely be restricted by ,government enactments in all such deadly occupations4 ,we may sum up the whole matter as regards white lead making by the stack or ,dutch method in a few brief words3 ,it is a most tedious and uncertain operation2 it is a most dangerous occupation for all concerned2 it is founded upon no true principles of any kind2 and of science its whole course is ignorant4 ,white lead making is ruled by a 8happy-go-lucky0 philosophy4 ,the representatives of this manufacture are completely ignorant of the scientific details relating to it1 and hence we may not be surprised to find amongst them an enormous amount of ignorance and prejudice4 ,good white lead will not differ materially in its composition by whatever process it may be made1 but it may differ seriously in its physical character1 and in its fitness to produce a substance adapted to the uses to which white lead paint is applied4 ,good white lead is a compound which contains hydrate and carbonate of the metal1 in the proportions either of one molecule of hydrate of lead combined with two of carbonate1 or is made up of one molecule of hydrate with three of carbonate of lead4 ,if we consider the first compound roughly ,pb,h#b,o#b1b,pb ,,co#c white lead will be made up of one part of hydrate and two parts of carbonate of lead4 ,the second compound roughly estimated ,pb ,h#b,o#b1c,pb ,,co#c will be one part of hydrate1 combined with three parts of carbonate or lead4 ,the latter will be in the proportion of #ge per cent1 of carbonate and #be per cent1 of hydrate of lead1 and this represents the composition which has been assigned to good white lead by those most acquainted with the subject4 ,the amount of hydrate contained in white lead should never exceed the proportion above named of #be per cent41 nor should its amount be much below the #be per cent4 ,the hydrate contained in the substance serves to unite with the oil in the paint2 it forms therewith a drying white and elastic varnish which embraces and holds the particles of white carbonate and prevents their subsidence and separation in the paint4 ,there is a chemical action of a much more intimate character between the components of good white lead when mixed with oil which neither of the constituents of this compound can alone produce4 ,for instance1 hydrate of lead and linseed oil produce a varnish-like substance1 semi-transparent and of no covering capability4 ,carbonate of lead and linseed oil produce a compound which is opaque1 but has no body or covering power1 and in which the white solid carbonate is held in feeble mechanical suspension4 ,neither of them constitutes a paint1 but when together as white lead they are mixed with oil1 combination takes place1 and serviceable paint of good body and covering power and enduring quality is produced4 ,good white lead is a dense1 perfectly amorphous powder of perfect whiteness1 possessed of great body and covering power when combined with oil4 ,when mixed with linseed oil and used as paint it rapidly dries in the air and assumes a varnish-like1 glossy1 hard surface1 and is capable when once dry of resisting the action of air and water for any length of time4 ,it does not weep when laid on a surface with a brush1 that is1 the oil does not separate from the solid material of the paint4 ,attempts have been made to produce white lead quickly and cheaply by precipitating processes1 but in all such methods the resulting compound is deficient in certain special qualities absolutely necessary to white lead proper and to its uses4 ,the precipitated white lead is always of a crystalline structure1 and crystalline lead can never furnish a good body paint--no amount of pulverising and grinding of this crystalline material will correct this defect in its nature1 and deprive it of its crystalline form4 8,once a crystal always a crystal0 has an especial application to this point of our philosophy4 ,pulverising a crystal will not alter its structure1 but simply reduces the size of the crystals4 ,crystals of white lead are unable to effect the necessary combination with the oil and form the true varnish which white amorphous lead so readily produces4 ,paint made with the precipitated white lead lacks body and covering power1 and this because of the absence of this chemical union with the oil4 ,the manufacture of white lead by process of precipitation1 even were the resulting preparation suitable1 does not correct the evils of the present method by ,dutch or stack process of making white lead4 ,a solution of lead may be precipitated in a few minutes1 but it cannot be made so quickly4 ,the white lead1 after its precipitation1 has to be filtered or separated1 washed and dried1 and ground to powder1 which processes cannot occupy less time than a few weeks for completion4 ,precipitated white lead has been made in ,france and ,germany for some years1 and it is now manufactured in those countries4 ,it is now made in ,england by one patent process1 but the product lacks certain qualities1 and is consequently still open to the objections already noted4 ,substitutes for white lead of a non-poisonous nature1 or of such a nature as not to produce such deadly effects in their preparation or use as white lead does1 have been proposed2 their introduction has not1 however1 been a great success4 ,a mixture of sulphate1 sulphide and oxide of zinc is a patent white made by subliming galena in an oxidising furnace or hearth4 ,this compound lacks body4 ,all of these so-called substitutes are very inferior to white lead1 not only as to quality but as to cost4 ,they cannot compete with white lead4 ,a committee of enquiry on these substitutes for white lead1 reporting the result of their enquiry and examination1 stated that they found that these were mostly prepared with varnishes before they were sold for use1 and that in most instances they were mixed with a large quantity of driers1 and that the drier invariably was a compound of lead4 ,the principal consumption of white lead is for paint2 to produce this paint it is ground with oil in varying proportions1 about #h to #ae per cent4 ,this produces the ordinary white lead in oil1 and is worth from #ail4 to #bjl4 a ton1 but often more than this amount4 ,dry powdered white lead is chiefly made for and used by grinders and mixers1 who combine with it a variety of other cheaper materials--chalk1 clay1 sulphate of lime1 and sulphate of baryta1 but principal use is made of chalk and barytes4 ,these are mixed with the white lead1 and then the mixture is ground with oil and formed into paint1 sold under various names according to quality3 thus--guaranteed white lead1 firsts1 seconds1 thirds1 and fourths1 the proportion of white lead diminishing1 and that of the adulterant increasing1 as we descend from the pure material4 ,guaranteed and best white lead is not pure1 and does not mean pure white lead4 ,pure white lead can be purchased at some makers1 but its price1 if pure1 can never fall below #ail4 or #bjl4 per ton4 ,to sophisticate white lead1 and produce the various inferiors named1 dry powdered white lead is needed as a starting point1 and for this purpose principally arises the necessity for its production4 ,if ground in oil the adulterants cannot be properly incorporated with it4 ,dry white lead is used for nothing else that could ever give rise to any great demand for it4 ,we have already observed that the production of this dry and powdered white lead is the most dangerous proceeding connected with this industry4 ,grinding in oil is unattended with any important consequence to the health and comfort of those employed4 ,a serious drawback to the 8stack0 production1 the china-like incrustation to which reference has already been made1 is that it requires crushing1 grinding1 washing1 and drying1 and a second course of dry grinding after it is dried--the most objectionable step in its preparation4 ,could the corrosion of the blue lead be effected in such a way as to prevent any discoloration of the material by the tan and wood--could the corrosion be so produced as to be easily separated from the buckle or grating on which it has formed--could this separation be so effected as to prevent the breaking up of the lead skeleton1 and the presence of small pieces of metal in the detached crust of white lead1 two principal reasons for washing and drying are removed4 ,there is yet another consideration1 that is1 the presence of acetate of lead1 always found in varying quantities in the incrustation produced1 and remaining at the close of the operation and conversion4 ,to remove this1 careful washing1 and after-stoving and drying must be accomplished4 ,the amount of this salt present is found to differ with each operation1 and in various portions of the same make4 ,the washing out of the acetate is never perfect1 and it involves a large amount of labour4 ,opinions differ as to the effect of this acetate if allowed to remain in the product4 ,white lead makers on the 8stack0 principle aver that it should and must be washed out1 lest it should damage the qualities of the paint4 ,this is questionable1 and not one can produce practical evidence of its being the cause of any damage if still contained in white lead4 ,facts seem to deny its harmfulness in this respect1 inasmuch as the best prepared samples1 those washed and dried from the most careful makers1 will be found upon analysis to contain more or less of acetate of lead4 ,a large proportion of this salt in white lead may not be beneficial for many reasons1 but a small percentage can do no harm2 nay1 for many purposes it may be good4 ,there is no substance used for driers for white lead that is more esteemed than this acetate of lead1 commonly known as 8sugar of lead40 ,a small amount of this salt present in white lead would communicate drying properties1 and this alone is what it could do4 ,granting that we can discover a method of producing white lead of amorphous character1 of good density1 free from all discoloration1 free from all particles of metallic lead1 and free from all but a small percentage of acetate of lead1 then washing will not be needed4 ,stoving and drying become unnecessary4 ,the work of women1 their deadly occupation1 so burdensome to the operatives and to all with whom they are concerned1 is done away with4 ,condy's ,process4--,an improvement in the manufacture of white lead was patented by ,condy1 of ,battersea1 in #ahha1 which1 though giving perfectly satisfactory results when carefully conducted1 necessitated special precautions1 and led to his substituting in practice the following additions and modifications1 which are of great consequence in rendering the process more certain in the quality of its product1 and more valuable as a commercial manufacture on the practical scale1 by virtue of its offering greatly increased facility and economy in production4 ,the results of numerous and repeated experiments on the larger scale induced ,condy to qualify the recommendation contained in his first patent1 viz4 that of employing a solution of tribasic acetate of lead and bicarbonate of soda in proper proportion to precipitate nearly the whole of the lead1 and further stating that he preferred to employ 8a slight excess of tribasic lead salt rather than find carbonate of soda in excess40 ,though1 when carefully conducted1 if the greatest nicety is observed1 a satisfactory result is obtained2 in practice1 the least variation from the exact composition of the two substances is attended with the drawback that the white lead is liable to a slight uncertainty of tint after it is ground in oil1 whereas by the process hereinafter described a positive and reliable result can be obtained1 as the white lead produced will be of a uniform white colour1 and not liable to turn when ground in oil4 ,though the earlier process was in itself complete for the manufacture of white lead from oxide of lead1 it afterwards occurred to ,condy that a great object would be attained in rendering the process more valuable and more practical1 if a method were devised1 worked out1 and described for the manufacture of tribasic acetate of lead to be made entirely from metallic lead by the action of acetic acid or neutral acetate of lead on metallic lead1 and not to be dependent on the employment in any way of previously manufactured oxide of lead4 ,this portion of ,condy's invention relating to the manufacture of tribasic acetate of lead may be described as follows3 he melts1 and1 after skimming carefully1 feathers the metallic lead by dropping it into water2 he places this granulated lead in wooden vessels or vats previously fitted with perforated false bottoms under which are fixed taps for drawing the liquor off into other vats or tanks placed on a lower level4 ,having filled with granulated lead the vessels fitted with the false bottoms1 he fills up the interstices with a dilute acetic acid composed of one part1 by weight1 of acid 7specific gravity #ajde at #fj ,f47 and #ab parts of water1 and after allowing the dilute acid to stand for two hours1 draws it off through the taps into the lower tanks4 ,this allows access of atmospheric air to the lead1 which has the effect of heating the lead so that oxidation takes place4 ,after a time 7about three or four hours71 this oxidation begins to slacken1 when he pumps up a second time the acid solution from the lower vat on to the granulated lead1 and allows them to stand in contact for one hour2 he then again draws off the liquid into the lower tank1 and again exposes the metallic lead to atmospheric oxidation1 allowing three or four hours for the latter operation2 and if the solution of lead has not already attained the specific gravity of #ajdj1 at #fj ,f41 he again repasses the liquor over the metallic lead partially oxidised1 until it has attained that specific gravity1 when he places the dissolved lead with fresh granulated lead and recommences the manufacture in the same way4 ,this operation succeeds much better on the large scale than on a laboratory scale4 ,in vats containing upwards of one ton of lead1 the result is all that can be desired1 and can be obtained by passing the liquor from twice to three times over the metallic lead partially oxidised4 ,a little practice enables the operator so to control the process that he can obtain the solution of the desired specific gravity with perfect ease4 ,this plan of manufacturing tribasic acetate of lead possesses the advantage of producing that substance wholly or nearly wholly free from the impurities contained in metallic lead1 such as copper and silver1 which are not taken up1 or soluble1 in the presence of metallic lead4 ,in consequence of the circumstance that foreign matter is left almost untouched1 it is practicable to make white lead of a fine quality from old lead such as lead piping1 roofing1 and worn out lead generally1 which can thus be utilised to greater advantage than in any other way4 ,having obtained this solution of basic acetate of lead of the specific gravity of #ajdj at #fj ,f41 ,condy proceeds as follows3--,to the solution produced by each #fj lb4 of acid and #gej lb4 of water previously pumped up into another vat or tank1 he adds bicarbonate of soda in the proportion of #cj lb4 for each #fj lb4 by weight of acid originally employed1 and agitates the mixture4 ,this will generally precipitate all the white lead1 but it is necessary to test the filtrate to ascertain the exact point when all the lead is thrown down4 ,sufficient bicarbonate of soda should be added to do this completely1 and it would be better to use bicarbonate of soda in excess rather than leave any lead unprecipitated1 as by this means greater certainty is obtained in securing on the large and practical scale a white lead capable of standing the effect of light and grinding in oil without changing4 ,the white lead after precipitation can be washed1 pressed1 and dried in the usual way4 ,the following variation may be made from the method described of making tribasic acetate of lead1 thus3--,to each #fj lb4 of acid and #gej lb4 of water may be added sufficient of the tribasic solution to make neutral acetate of lead1 with which to recommence the manufacture of tribasic acetate of lead by the process described4 ,vague reference has been made in works on technical chemistry to the possibility of using metallic lead in the manufacture of sugar of lead1 but such references have been practically worthless1 as they contain no information of a practical nature even for the manufacture of neutral acetate of lead1 and no process at all has ever been described for the manufacture of basic acetate of lead from metallic lead acted on by acetic acid or acetate of lead4 ,gardner's ,process4--,the conditions observed and fulfilled in the arrangements adopted by ,prof4 ,e4 ,v4 ,gardner1 are founded upon a study of the nature1 properties and behaviour of the substances concerned1 under certain methods of treatment4 ,there are several oxides of lead which may be formed under special conditions4--7#a7 ,pb#b,o1 and the same oxide combined with water ,pb#b;,h#b,o#b2 7#b7 ,pb,o1 and the same oxide combined with water ,pb,h#b,o#b4 ,in the hydrated form these oxides combine readily with carbonic acid1 but they do not combine readily with carbonic acid when dehydrated4 ,the hydrates are most readily formed at about #abj-acj ,f41 and are decomposed after they are formed if heated to #bab ,f4 ,these oxides and their hydrates combine with acetic acid to form acetate and sub-acetate of lead1 and with nitric acid to form nitrate and sub-nitrate of lead4 ,lead1 submitted to the action of air1 watery vapour1 and acetic or nitric acid1 or a mixture of these acids1 with air or oxygen1 with proper precautions1 forms sub-acetate or sub-nitrate of lead1 and this sub-acetate or sub-nitrate of lead readily absorbs carbonic acid and forms carbonate and sub-carbonate of lead4 ,sufficient acetic or nitric acid1 or a mixture of these and air or oxygen1 and watery vapour1 must be constantly supplied to form the subsalts of lead1 to carry on the operation of converting blue lead into white lead2 but an excess or an insufficiency of these agents will in either case prevent the formation of sub-acetate or sub-nitrate1 and consequently of the sub-carbonates4 ,thus--too little air1 acetic acid and aqueous vapour prevents the formation of the hydrated sub-acetate and consequently sub-carbonate of lead4 ,too much acetic acid and aqueous vapour1 and too little air forms an acetate on the surface of the lead1 which1 by the excess of water1 dissolves and wastes1 and washes the lead2 it also varnishes the surface of the lead with a coating of acetate1 and checks1 if it does not completely prevent1 the formation of sub-acetate of lead1 and consequently the formation of carbonate and sub-carbonate of lead4 ,similar rules hold good in the case of nitric acid and the formation of nitrate and sub-nitrate4 ,the process of forming the hydrated sub-acetate or sub-nitrate of lead is most energetic at a temperature of #abj-acj ,f4 ,in a lower temperature1 a much longer time is occupied in carrying out the process of conversion2 while at a higher temperature the delicate sub-acetate or sub-nitrate of lead first formed suffers loss of water1 until1 at #bab ,f41 it is completely dehydrated4 ,at a temperature about #ace ,f41 the power of forming carbonate and sub-carbonates is lessened1 and at #bab ,f4 is considerably diminished4 ,the carbonate itself is dehydrated at #bab ,f41 and is decomposed at a higher temperature4 ,to obtain a white lead of excellent quality for its various uses1 it is necessary to produce a substance which possesses sufficient body to cover surfaces to which it may be applied as paint1 and it must possess sufficient base to combine with the oil of the paint to form a vehicle or varnish to retain and hold the body on the surface4 ,this is found to be the case with sub-carbonate of lead1 or especially with a compound constituted of two or three equivalents of carbonate of lead1 with one equivalent of hydrated oxide of that metal4 ,lead1 to be attacked by chemical agents1 should possess a clean surface4 ,if the surface of the lead is chemically clean1 so much the better4 ,the surface of the lead should be extended as much as possible1 and exposed to the action of the gases and vapours at a certain heat for its conversion into white lead4 ,if the most favourable conditions are sought1 the temperature should be between #abj and #acj ,f42 and to carry on the chemical action most satisfactorily1 the lead during its conversion should present a granular coating--that is1 the coating formed by the chemical agents should be granular and not smooth and continuous in character4 ,it should be porous1 and not of a continuous varnish-like or vitreous character4 ,to rapidly carry on the chemical action1 the chemical agents should be well diffused and commingled throughout each other1 and the blue lead should be so exposed as to be open to their attack on all parts of its surface equally1 and all should be at1 and kept at1 a proper temperature and a proper degree of humidity4 ,too dry a heat prevents the process of conversion4 ,too moist an atmosphere wastes the materials and arrests their action4 ,the conditions1 therefore1 which are most favourable will be a certain humid atmosphere of well diffused and commingled vapours or gases1 acting on metallic lead exposed to them under the physical conditions described1 and at a temperature between #aaj and #ace ,f4 ,these favourable conditions can be further augmented by certain electrical arrangements in connection with them4 ,again1 in the sources from which the carbonic acid is derived1 and in the arrangement of the apparatus for applying the carbonic acid1 favourable and unfavourable conditions can be imported4 ,thus1 by using paraffin1 petroleum1 benzine1 or light oil of paraffin or petroleum1 or similar carbonaceous substances free from sulphur1 or mixtures of such carbonaceous substances either alone or mixed with air or other oxidising substance1 comparatively pure carbonic acid may be furnished without at the same time producing any objectionable compounds4 ,as a result of his researches and experiments1 ,prof4 ,gardner has proposed 7,eng4 ,pat4 #ahhb1 ,no4 #gca7 certain improvements in the method of converting blue lead into white lead1 in the apparatus employed1 and in the method of making and applying the carbonic acid used in the process4 ,some of these improvements are applicable to the open stack or chamber process1 while others relate to closed chambers4 ,preferably1 for the conversion of blue lead into white lead1 ,prof4 ,gardner adopts a closed1 but not air-tight1 chamber4 ,this chamber is ventilated or relieved so as to enable the incoming gases and vapours to enter it without hindrance1 and to escape by means of an exit valve and pipe1 or an exit shaft1 connected with the chamber1 communicating with the exterior air1 and regulated by a valve or damper4 ,the gases and vapours within the chamber can find their way out by this exit shaft only1 by slight pressure on expansion from within the chamber2 thus the interior of the chamber is preserved from disturbance1 by preventing the formation of currents within its atmosphere1 and yet a perfect circulation of the gases and vapours is kept up4 ,to warm the interior of this chamber1 which is constructed of any material that will resist the action of the vapours and gases1 and which is not too absorbent1 ,prof4 ,gardner makes the bottom of the chamber of such a shape as to form a heating vessel to hold water or steam1 this water or steam1 or both1 being kept at the required temperature by means of a steam coil4 ,matters are so arranged that the contents of this coil are protected from any excess of pressure1 and consequently the temperature seldom or never exceeds about #bab ,f41 unless for any special reason it is desired to raise it to a higher point4 ,sometimes the sides are constructed similarly to the bottom4 ,the materials of which these chambers are constructed must be capable of resisting the heated and acidified vapours within them4 ,cast or wrought iron faced with glass1 slate1 tiles1 pewter1 or glazed bricks2 tinned copper1 tinned brass1 or pewter2 timber1 whether green or after carbonising by heat or sulphuric acid2 all are more or less suitable4 ,means of observing the progress of the conversion1 and means of lifting the contents in or out1 must also be provided1 as well as thermometers to indicate the temperature prevailing inside4 ,the gases and vapours which effect the conversion of the blue lead into white lead are generated outside the chamber just described1 and are conducted into it by means of pipes1 being first raised to such a temperature in excess of that which should exist inside the converting chamber as to allow for the cooling effect arising from the friction and loss of heat in passing through the various pipes and distributors attached to the converting chamber4 ,owing to this extra heating1 the gases and vapours are expanded1 diffused1 and commingled1 and do not rob the interior of the converting chamber of any heat on entering it1 so that the heat inside the converting chamber is kept constant1 and can operate to further expand and diffuse the gases and vapours in contact with the blue lead inside the chamber4 ,in practice it is found that the temperature of the converting chamber cannot be suitably controlled if any portion of the gases or vapours be generated within that chamber4 ,the blue lead is arranged in the converting chamber in trays1 or on shelves or frames1 so as to allow it to be completely surrounded and attacked by the vapours or gases1 and thereby be converted into white lead1 at the same time preventing the formation of direct currents or eddies4 ,framed supports resembling a dinner waggon serve well for holding the lead1 and may easily be arranged to lift bodily in and out of the chamber with their burden of blue or white lead4 ,the surface on which the blue lead is directly supported is made of graphitic carbon1 hard coke1 platinum1 or carbonised or platinised material1 such as is used for plates in electric batteries1 or of other material standing in a similar electrical relationship to lead1 or capable of generating with it an electric current4 ,in applying this development of electrical energy to the ordinary 8stack10 as for instance the ,dutch process1 the pots containing the acetous liquid and blue lead are made of1 or lined with1 such electrical carbon1 or contain a portion of it in suspension1 by which the same effect is realised4 ,advantage may also be derived from furnishing a supplementary supply of carbonic acid to the stack beyond that due to the decomposing dung1 c42 as well as from injecting a current of air or oxygen at suitable temperatures1 and from the admission of steam in a coil throughout the stack4 ,the generation or production of the acetic or nitric acid vapours is attained by heat in a vessel so arranged that its contents are kept at a certain temperature for vaporising1 by having the boiling acid solution at about #ajjc sp4 gr41 procured by mixing water with vinegar or acetic or nitric acids4 ,the supply pipes conveying the air or oxygen and the carbonic acid1 or either of them1 can easily be made to emit their contents close to the boiling acid solution1 whereby the vapours arising from the latter are mixed and intermingled with them1 and all pass together through the pipes and distributors into the converting chamber or stack4 ,in preparing the carbonic acid it is necessary to observe certain precautions1 especially that it shall be pure and that no carbonic oxide shall gain admission to the chamber4 ,if the ordinary chalk and carbon method be employed1 the furnace must be provided at the uptake with a series of air inlets1 so as to ensure that the gases passing from the furnace to the delivery tube shall be most thoroughly oxidised4 ,the purification of the carbonic acid may be effected in the usual way by passing it through a vessel containing water2 or1 if requisite1 it may be cleansed1 expanded1 and heated in one operation by passing it through or over hot water1 or over a hot aqueous solution of carbonate of soda1 all of which1 however1 incur considerable cost in plant and manipulation4 ,owing to these difficulties in purifying carbonic acid1 ,prof4 ,gardner prefers to prepare a practically pure carbonic acid in the first place1 and this he does by allowing petroleum1 benzine1 paraffin1 or other hydrocarbon or carbonaceous liquid to gradually fall into a retort containing chalk or other suitable carbonate at a high temperature1 whereby relatively pure carbonic acid gas is generated2 and while still in a highly heated state it encounters a stream of air or oxygen1 ensuring its complete combustion before entering the converting chamber4 ,another method of procuring fairly pure carbonic acid is by the combustion and oxidation of any of the liquid hydrocarbons mentioned above1 in suitable lamps2 and when carbonic acid gas of exceptional purity is required1 it may be obtained by heating bicarbonates to a sufficient degree to drive off one molecule of carbonic acid1 reducing the bicarbonate to carbonate1 from which it can be reproduced by treatment with carbonic acid gas obtained from cheaper sources4 ,the modus operandi adopted by ,prof4 ,gardner is as follows3 ,the lead is granulated and prepared for conversion in one operation1 thus--an iron or a slate slab about #b-c inches thick is placed in a tank containing acetic or nitric acid solutions rising about #c inches above the upper surface of the slab4 ,the lead is melted at low red heat and poured from a height of #d to #f feet into the acid solution1 through which it falls till it encounters the slab1 and thereupon passes away into the surrounding solution1 being thus converted into a spongy condition4 ,in this condition the lead is spread on frames or trays1 which are then lifted bodily into their places in the converting chambers4 ,the latter is closed and heated to #abj ,f4 for #c-d hours1 or until the whole contents have assumed a uniform temperature4 ,thereupon the acid vapours and air are admitted and distributed1 taking care that the temperature is not thereby reduced below #aaj ,f4 nor increased above #abe ,f41 steam being temporarily shut off if necessary4 ,this treatment is continued for #bd hours4 ,the admission of aqueous vapour should be so regulated that while a dry atmosphere is avoided1 yet there is no appreciable condensation of moisture in the chamber4 ,while ensuring this condition1 the temperature may reach as high as #acj ,f4 for a second period of #bd hours1 but must not overstep the limits of #abj ,f4 minimum and #ace ,f4 maximum4 ,after #dh hours' treatment1 the supply of duly warmed carbonic acid gas is admitted for a period of two hours1 without discontinuing the introduction of acid vapours1 air and steam2 and this addition of carbonating gas is repeated for two hours at a time with intervals of four hours during which it is cut off4 ,when1 after four or five days1 efflorescence or exfoliation appears on the lead1 the supply of carbonic gas is increased to two hours in every four1 or four in every six2 and the admission of acid vapours1 air and steam may also be augmented so long as the temperature is not allowed to exceed #acj-ace;,f4 ,the whole operation is completed in seven to fourteen days4 ,of this process1 ,mr4 ,carter ,bell1 in his paper before referred to1 speaks in the highest terms4 ,no washing or drying is necessary4 ,no women are engaged in the manufacture1 and but few men4 ,the white lead thus produced by the aid of electricity is deposited in a peculiar state of disintegration1 it is perfectly amorphous and non-crystalline1 of the purest quality2 its density is #eh4 ,when ground in oil and made into paint1 it possesses great body and a covering power inferior to no other paint1 if not superior to them all4 ,painters who have used the paint1 practical men1 and amongst these we may observe coach painters1 have pronounced its excellence and superiority to the best ordinary white lead paint4 ,by this electrical process of manufacture1 not only is the time consumed in the making and in the preparation of this material greatly shortened1 but the cost of preparation is reduced1 and added to this is the important fact1 the vital factor in our consideration4 ,the labour of women is unnecessary4 ,no lives are sacrificed to its working requirements4 ,prof4 ,e4 ,v4 ,gardner1 who has been for some years occupying his attention with the subject of white lead making1 with a view especially to remedying its existing evils1 has invented his electrical chamber process of manufacture1 and an entirely new course of after treatment4 ,he has for the last seven or eight years been more or less occupied perfecting his conception1 and accommodating it to practical and commercial claims4 ,chamber processes are not new1 there have been several patents enrolled for making white lead in closed chambers1 but none has proved commercially convenient or practically successful in its adaptation1 and none has survived to the present time4 ,in ,germany1 white lead is made in chambers at the present day4 ,the lead in gratings or sheets is supported on wooden rods1 saddle fashion1 the chamber is then filled1 and its contents are submitted to currents of acetic acid vapour1 air1 steam1 and carbonic acid gas2 the time needful for conversion is six or seven weeks4 ,the after steps in the separation of the incrustation1 and its preparation for trade purposes are much the same as in the 8stack0 product preparation4 ,it is washed1 stoved1 dried1 and ground4 ,the white lead made on the ,german plan does not differ in any material degree1 save it be in price1 from the best ,english commodity4 ,we may assume that the washing and drying in ,germany consumes a like period of time to that process in ,english works1 viz4 two or three weeks4 ,we then see that the ,german plan of making white lead cannot be perfected in less than eight or ten weeks' time from the commencement of the corroding action in the chamber4 ,to compare these facts and the efficiency of the different plans described3-- ,the time required to complete the corrosion in the stack is at least #ad or #af weeks4 ,the ,gardner's electric process requires for the same purpose only #ad days4 ,as to point of time1 the ,german plan excels the stack1 and can be carried out in one-half the time required in the stack method of conversion4 ,the ,gardner's electrical method excels the ,german1 and can be perfected in one-third the time needed for the ,german chamber operation1 and one-sixth the time required the stack4 ,these figures open out a most important matter when we regard the capital invested and lying dormant in stack lead works4 ,it is well known that we have in electricity a most powerful agent by which to effect the chemical combination of various substances on the one hand1 or on the other1 by its means to break up and disrupt a chemical compound4 ,professor ,gardner's main principle of action in his new process is founded upon these facts1 and he takes advantage of electrical power to cause the combination of the lead with the necessary elements to build up white lead in his chambers4 ,he either employs electrical discharges to energise and render active in their chemical affinities the various materials engaged1 or he so disposes of them as to form an electric or galvanic combination in the chamber4 ,in the latter arrangement the chamber and its contents represent a gas battery on an extensive scale4 ,in practice he prefers the latter plan2 it is more simple1 more manageable in the hands of the ordinary workmen4 ,the original plan was to have graphite or graphitic carbon plates or supports for the buckles or gratings of lead within the converting chamber4 ,these carbon plates and the lead to be converted1 were so placed as to form a collection of galvanic 8couples0 or 8pairs10 and in this condition were submitted to the gases entering the chamber from without4 ,it will be understood that various modes of arrangement would occur without departing from the principle concerned4 ,in practice this method answered very well1 but presently a difficulty arose2 not only were the graphitic carbon or graphitic plates expensive1 but they were easily broken1 and became friable in use4 ,carbon plates of an especial kind were manufactured to meet these failures and remedy these defects1 not without success1 but still open to objection4 ,in looking round for some substitute to replace the carbon1 two points were to be kept in view1 to seek some electro-negative to lead like the carbon1 and some electro-conductive like it1 and some material that would bear rough handling such as workmen give1 and be practically convenient in its adaptation to a working chamber4 ,gold or platinum would excel in these particulars1 but there are considerations which debar their use4 ,pure tin presented itself1 and tin was tried with great success4 ,tin would at first be thought1 on account of its close electrical relationship to lead1 far from favourable to the purpose4 ,graphite or carbon would appear far more suitable4 ,practice pronounced the tin to act as efficiently as carbon4 ,this may at first seem contradictory and strange1 but if we consider that while the carbon is certainly more highly electro-negative to lead than tin1 yet the tin is the more conductive1 and offers the less resistance to the electric current of the two2 in this manner the tin compensates by its conductive power all it may lack1 as compared with carbon1 in electrical energy when coupled up with lead4 ,tin plate is now used as the electric-negative element in the chamber of the ,gardner plan4 ,tin plate means pure tin4 ,ingot tin is rolled out into plates1 the bottom of the chamber is covered with this pure tin plate1 so are the bearers and the shelves1 or supports which are to hold the lead during its conversion4 ,tin pipes and tin fittings1 which resist the action of acetic acid1 are also used to conduct the gases to the chamber to carry on the converting operation1 and to preserve the product from any source of discoloration4 ,when a chamber is prepared for the converting operation1 the whole of the lead it contains will be in metallic communication with the tin supports1 and these with the tin covered bottom of the chamber4 ,the chamber when working is kept at a certain temperature by a steam coil beneath the floor of the chamber4 ,the process is simple4 ,the lead buckles or gratings are placed on tin-covered stands1 somewhat in form and make like a dinner-waggon4 ,the whole is hauled up and dipped into a bath of acetic acid and acetate of lead2 it there remains for one or two minutes1 it is then hauled out1 drained and lifted bodily through the top into the chamber4 ,other stands filled with buckles are so dipped and so placed till the space of the chamber is fully occupied4 ,this dipping cleanses the surface of the metal1 and when it is exposed to the air it is speedily coated with a hydrated oxide of lead4 ,this is the first step in the process of conversion4 ,the chamber when filled is closed1 and its temperature is brought to about #ajj ,f42 then vapour of acetic acid and vapour of water and air are supplied from without to the interior of the chamber4 ,this is continued for #ae or #bj hours4 ,the lead buckles within the chamber will now possess a whitish coating1 consisting of subhydrate and subacetate of lead1 and they will present a uniform colour4 ,carbonic acid generated in any convenient manner is next passed into the acid generator2 it mixes with the other gases and vapours1 and with them goes on its way to supply the chamber4 ,speedily the action of the carbonic acid is observed1 the surface lead becomes quite white and presents the appearance of a snow shower having fallen within the chamber4 ,the formation of white lead is now speedily effected4 ,this treatment is continued throughout the space of #ac days2 at the end of this time the supply of acetic acid vapour is stopped1 and the supply of air1 steam and carbonic acid is continued1 according as it is desired to obtain white lead rich in oxide or in carbonate4 ,after a short further period1 steam and air only are sent into the chamber1 which is varied in temperature to #abj or #acj;,f41 and lastly the steam supply is stopped2 air alone enters the chamber1 which is kept heated by the coils beneath the floor4 ,the contents of the chamber are now in a dry state1 and the operation is terminated4 ,it will occur to most readers that these terminal proceedings amount in effect to a convenient method of washing and drying the white lead while it is still attached to the parent lead1 and this it is in fact4 ,the contents of the converting chamber are lifted out through the opened top1 and the buckles or gratings with their crust of white lead are turned into the agitator4 ,this agitator is an iron cage revolving inside a closed chamber of the same material4 ,during the revolution of this cylinder or cage1 the contained lead gratings fall from side to side1 and the incrustation on their surfaces becomes detached and broken up4 ,it falls in1 this broken state through the bars of the cage or cylinder into a receptacle beneath4 ,the denuded buckles or gratings are retained in the cylinder and are removed4 ,these gratings or buckles are cast of such a thickness as to withstand two or three converting operations in the chamber before they are recast4 ,this crude white lead is carried by an elevator1 or it falls into the hopper of a pair of granite crushing rolls1 also enclosed2 and from these it passes into the mixer or incorporator from which it can be removed in a dry state or mixed with oil4 ,the incrustation of white lead will be found upon examination to be possessed of some peculiarities1 the result of the electrical action which has been going on within the chamber4 ,it is quite white4 ,it falls from the lead buckle or grating which it coats1 if the grating be struck against a piece of wood with but a slight blow4 ,it is easily friable1 and can be rubbed to the finest powder between the thumb and finger1 or on the palm of the hand4 ,now1 we may explain1 as we conceive it1 the philosophy of its production in this state of disintegration4 ,we know that a feeble and prolonged current of electricity will in time deposit metals from their solutions in a crystalline condition1 and that if we quicken the current of electricity and cause it more energetically to act on the same solution1 we can precipitate the metal from that solution in a state of powder4 ,it is to similar action of electricity as that to which we last refer that we ascribe the formation of the crust on the gratings of lead in the non-adherent and disintegrated condition in which it is produced1 and by reason of which it is so easily detached from the lead and broken up to powder4 ,no edge runner grinding1 such as is required by the stack process1 is in this case necessary4 ,the crude white lead and crushed material1 whether in a dry state1 or incorporated with oil1 is finished and ground in a granite roller paint mill1 from which it issues as dry white lead1 or as white lead in oil4 ,paint made from this electric white lead has been sent to ,america1 to ,france1 to ,belgium1 to ,germany for trial1 and has also been largely tested in this country by painters1 engineers1 and others unacquainted with its precise nature1 and it has been productive of good results4 ,of its density1 body1 and covering power1 there can be no doubt1 and never once have these qualities been called in question4 ,the cost of the manufacture of white lead by the stack process is about #cl4 to #cl4 #ajs4 per ton4 ,by the ,german method1 the cost is about the same as by the stack4 ,by ,gardner's electric process1 the cost of conversion is #ajs4 a ton4 ,to this #ajs4 must be added the cost of labour expended in preparation1 an item which cannot be well estimated on the present limited scale of manufacture2 it could not exceed an additional #aes4 a ton4 ,this would bring the cost of manufacture of electric white lead to #bes4 a ton4 ,in this electric process inferior lead can be operated upon with success4 ,brands of that metal such as white lead makers by the stack method dare not employ1 may be successfully converted in an electric chamber1 and with fair results as to the quantity and quality of the white lead produced4 ,by the use of ,gardner's electric process it would appear that we not only preserve health1 but save lives2 we not only save time1 but interest on large capitals1 which lie idle for long periods at a time2 and we can economise and simplify the whole manufacture and preparation of white lead1 divesting it of all its present cumbersome and unhealthy stages4 ,gardner's process1 we believe1 must take a prominent position as one of the most necessary1 valuable1 and scientific inventions of modern times4 ,hannay's ,process4--,mr4 ,j4 ,b4 ,hannay1 whose name is well known in connection with various chemical and engineering inventions and processes1 has recently brought out a process for the manufacture of white lead4 ,the old method of producing white lead or carbonate of lead is one involving much time and labour1 together with no small risk to the health of the workpeople4 ,by the new process brought out by ,mr4 ,hannay1 sulphate of lead is manufactured direct from galena or lead ore1 without the necessity of the intermediate process of the reduction of the ore and the extraction of metallic lead4 ,it is said that the sulphate of lead produced by the new process is whiter and more permanent than the carbonate4 ,the process is described as follows3--,a furnace1 #cf in4 by #cj in41 and #dh in4 deep1 contracting to a narrow chamber about #cf in4 long by #ad in4 wide1 communicating with the main flue1 is charged with coke and brought to a red heat4 ,the bed of coke is so thick as to be almost up to the level of the sill of the furnace door4 ,the lead ore is not charged in large quantity and left for an indefinite time1 but is thrown in in quantities of a few shovelfuls at a time1 the object being to effect extremely rapid volatilisation and consequent oxidation4 ,the proportion of ore to fuel is #a ton to #a ton1 and the result is said to be the conversion of #ie per cent4 of the charge into its equivalent in white lead4 ,in the first or wide chamber1 the coke is oxidised1 carbonic oxide being the resulting gas1 the rapid volatilisation of the galena or sulphide of lead also taking place in the same chamber4 ,on entering the inner portion of the furnace1 the volatilised sulphide of lead and the carbonic oxide are converted into carbonic acid and sulphate of lead4 ,forced blast has been employed to cause the high temperature necessary for the volatilisation of the ore2 but it has been found unnecessary1 admission of air at atmospheric pressure through tuyere holes being quite adequate4 ,after leaving the inner chamber of the furnace1 the gases pass into a flue1 level with the furnace1 and about #dj feet long by #af square feet in sectional area4 ,from this flue the gases pass into a tower about #bj feet high1 and from thence into wrought-iron flues #c feet in diameter4 ,these flues terminate in a wrought-iron chest1 in which are fitted two steam injectors4 ,the gases are forced by these injectors into the central chambers of the condensers4 ,these condensers are two in number1 and contain a central chamber1 #af feet by #ab inches1 into which the gases are forced as described4 ,the gases escape through interstices into the outer chambers of the condenser1 and are there condensed1 a continuous stream of water occupying the lower part of the condenser4 ,the waste gases escape by a downcast leading to a tall chimney4 ,the temperature of the gases as they enter the condenser is about #hdj ,f4 ,the product is pumped from the condensers to a settling vat4 ,here it settles for an hour1 the deposit being pumped into a second vat and washed with dilute sulphuric acid1 in order to remove impurities4 ,the resulting product is washed several times with water1 and is then passed through a filter press4 ,from the press it drops into bogies1 which carry the pulp to the drying house1 where it is dried by hot air4 ,the process would thus appear an extremely simple and practical one4 ,several chemical authorities of repute1 as well as manufacturing firms and others who have used the new white lead1 have expressed themselves strongly as to its merits4 ,one point immensely in favour of sulphate of lead as opposed to carbonate1 is that the former is almost entirely innocuous1 whereas the poisonous properties of the other are well known4 ,it is claimed that the sulphate is not acted upon by coal gas or by the atmosphere of towns1 which is always more or less impregnated with gases such as sulphuretted hydrogen1 whose reactions with various metals have only too good reason to be known4 ,according to the patent specification bearing the names of ,french and ,hannay1 they employ lead ores1 lead fume1 or lead slags containing sulphur2 and when these materials do not contain sufficient sulphur to form a sulphate with all the lead which sublimes in the process1 they add to them pyrites or other sulphur-yielding substance to make up the deficiency4 ,they heat the materials mixed with a suitable proportion of coke in an air-blast cupola furnace1 which is by preference of an improved and special construction shown in ,figs4 #ah to #bj1 and hereinafter described2 and they thereby produce sulphite of lead as a sublimate1 provided that there are no chlorides such as common salt present in the charge1 in which case sulphate and chloride of lead will be formed4 ,the sublimate is carried forward with the current of gases through flues to a fume condenser1 which is by preference of the kind known as ,wilson's and ,french's4 ,as the gases and sublimate pass through the flues1 hydrochloric acid is mixed ,illustration3 ,fig4 #ah4 ,fig4 #ai4 ,fig4 #bj4 ,,french ,,and ,,hannay',s ,,white-,,lead ,,furnace4 with them1 being by preference formed in a chamber in connection with the flue1 by introducing a solution of chloride of sodium in spray1 and by providing a sufficient excess of sulphurous acid beyond that required for forming the sulphite of lead4 ,air is also present1 and a well known reaction takes place1 yielding hydrochloric acid and sulphate of soda1 the operation taking place at a part of the flue near enough to the furnace to be always at a red heat4 ,the hydrochloric acid thus mixed with the gases and sublimate causes the formation of chloro-sulphite of lead1 or other combinations of lead1 sulphur1 oxygen1 and chlorine of variable constitution1 depending on the proportions of the several constituents1 but in most cases the product is a body which forms a white pigment of extremely good quality4 ,fig4 #ah is an elevation of their improved cupola furnace2 ,fig4 #ai is a corresponding vertical section2 and ,fig4 #bj is a horizontal section as at the level of the principal tuyeres4 ,this cupola furnace is formed with a deep hearth a 7like the ,american lead smelting cupola7 having a siphon outlet b1 for withdrawing molten lead when necessary4 ,at a level a little above the siphon outlet b1 an outlet c for slag and scoria is provided1 and the main blast tuyeres d enter at about the same or a slightly higher level4 ,with this arrangement1 a considerable depth of melted lead is constantly maintained1 and the choking of materials is thereby avoided at the level of the tuyeres4 ,for a short distance above the main tuyeres d1 the interior of the furnace is made with the sides e moderately and gradually widening upwards1 and is afterwards continued upwards of uniform diameter or width4 ,the charging door f is between #c and #d feet above the main tuyeres d1 and the space above the charging door is crossed by two or more arched diaphragms g h1 of brickwork1 having irregular openings in them1 there being doors i k in the side of the furnace above each diaphragm1 for inspection and cleaning4 ,the purpose of these diaphragms is to cause the air1 gases1 and sublimate to become thoroughly intermixed and to ensure the complete combustion of any black smoke and the oxidation of any sulphide of lead that may be present4 ,an upper series of small tuyeres or jet pipes l is provided for admitting air a little below the lowest diaphragm g1 these jet pipes l being supplied by a branch pipe m from the main air blast pipe n1 it being found that the introduction of the air and the production of heat can be best regulated by supplying a portion at the upper part of the furnace in this way1 in addition to that supplied by the main tuyeres d2 and a tap or valve o is fitted on the branch pipe m for adjusting the supplementary supply thus admitted4 ,above the highest perforated diaphragm h1 the interior of the furnace communicates with a lateral flue p1 through which the gases and sublimate pass2 and at a part of this flue p1 sufficiently near the surface for the gases to be still hot enough1 an enlargement or chamber r forming a descending part of the flue1 is constructed4 ,into this chamber r a solution of chloride of sodium is introduced as a spray from a number of jet pipes s1 for the purpose hereinbefore explained4 ,this chamber r is provided with a door t at its lower part1 for periodically removing matters that become deposited in it4 ,the continuation u of the flue communicates with the lower part of the chamber r4 ,preferably the spray of chloride of sodium is fine enough to allow of all or nearly all of the water being instantly evaporated1 so as to leave the salt in fine particles1 and in a favourable condition for being acted upon by the sulphurous acid1 steam1 and oxygen present in the gaseous currents4 ,the temperature of the chamber r should not be allowed to fall below red heat4 ,the proportion of chloride of sodium used will depend on the amount of chlorination of the lead that may be desired1 in addition to what is necessary for converting the zinc and other metals into chlorides4 ,in practice a proportion of salt #b to #e per cent4 of the weight of the sublimate formed answers the purpose and yields a good product1 but a larger proportion may be used without injury4 ,it is of great importance to keep the temperature of the upper part of the furnace steadily at a red heat and flaming1 as the colour of the sublimate will be inferior if the temperature is either too high or too low4 ,to facilitate the proper regulation of the temperature1 a pyrometer 7which may be similar to the kind used in ironworks7 is employed1 which pyrometer is placed in the flue at a distance from the furnace where it cannot be injured2 and by a few trials is ascertained what temperature should be indicated by the pyrometer when the temperature in the furnace is what it should be4 ,this point having been ascertained1 a glance at the pyrometer will at any time show whether the furnace is working properly or not4 ,the inventors also provide for rapidly cooling the upper part of the furnace without interfering with the lower part1 in the event of the heat becoming too great1 by arranging a water pipe w1 with a set of jets1 round the top of the furnace1 so that on turning a tap on the supply pipe a spray of water may be applied to the outside of the furnace2 and as it is desirable that water applied in this way should not run down to the lower part of the furnace they build gutter plates x into the sides of the furnace just above the charging door f1 to lead off any surplus water to a drain pipe4 ,sufficient hydrochloric acid may be formed or introduced1 as hereinbefore described1 not only for forming chloro-sulphite of lead in the condenser1 but also for saturating all the free oxide of lead1 and for combining with and rendering soluble any iron1 zinc1 antimony1 silver1 or other metals4 ,the chlorides thus formed become dissolved in the water of the condenser1 and the solution1 separated from the insoluble white pigment1 may be treated by known processes for recovery of the metals4 ,when the lead ores or other lead-yielding materials contain silver to a greater extent than #e oz4 per ton1 a notable quantity of the silver is volatilised1 and if it is left in the white pigment it renders the latter sensitive to sunlight2 whereas if rendered soluble in the manner hereinbefore described1 and separated by any of the known processes1 it becomes a source of profit4 ,the white pigment is washed in the ordinary way2 and when chloride of zinc is not completely removed by washing1 a small quantity of sulphuric acid may be mixed with the pigment1 by adding the same to the last washing water1 to convert the chloride of zinc into sulphate1 which is not hygroscopic4 ,the white pigment made as hereinbefore described is a very good and economical material for manufacturing into chrome yellow1 this being done by mixing a solution of any suitable chromate or bichromate with the wet pigment2 whilst the chrome yellow thus obtained may be converted into chrome orange or red by treating it in the usual way4 ,italian ,process4--,the precise period of the introduction of white-lead manufacture in ,italy is unknown1 but it was certainly previous to the beginning of the present century4 ,prior to #ahha1 the ,dutch process was exclusively used in ,italy4 ,in #ahha the so-called ,brumlen and ,dahn process was introduced into ,liguria4 ,somewhat later the ,rhenish process was introduced4 ,the ,rhenish process is one in use in nearly all the ,italian white-lead manufactories4 ,it is employed in a large manufactory at ,cogoleto1 as follows3--,lead in thin sheets of about #c feet in length1 and #d inches in width are placed in a clay chamber having the form of a cube1 of about the capacity of #ehjj cubic feet4 ,in this chamber there is a wooden framework1 upon which are hung the sheets of lead4 ,three of these sheets weigh together about #d lb41 and as the capacity of the chamber is about #bj tons1 it can hold about #cj1jjj sheets of lead4 ,on the floor of the chamber are placed twenty-four copper receptacles1 each having four circular apertures4 ,these receptacles are all in direct communication with a large pipe of masonry1 which1 by means of a copper tube1 receives the gas coming from a boiler and furnace placed under the chamber4 ,in the boiler1 which is also of copper1 is placed a mixture of #ijj parts of water1 and #hj parts of acetic acid concentrated to #dj1 and the capacity of the boiler is about equivalent to #be1hhb gallons4 ,the furnace serves the purpose of producing carbonic acid4 ,the gaseous mixture1 consisting of volatilised acetic acid1 carbonic acid1 and aqueous vapour1 is admitted from the boiler and furnace into the chamber in quantity and proportions best adapted to each stage of the work4 ,the chemical reactions resulting are analogous to those which take place in the ,dutch process1 and the ,brumlen and ,dahn process4 ,each operation lasts six weeks1 and gives a product of about #bj tons of white lead1 with a consumption of #g per cent4 of acetic acid1 and #i tons of coke4 ,the residuum of lead is about #aj per cent4 of the quantity placed in the chamber4 ,at the end of each operation the white lead taken from the chamber is washed and purified in large tubs1 some of which are furnished with filters4 ,finally1 it is packed in earthen vessels1 and dried1 when it is ready for the market1 and is sold either in cakes or powder4 ,the establishment at ,cogoleto1 above referred to1 is able to produce annually about #bjjj tons of white lead1 of which #abjj tons are produced by the ,rhenish process1 and #hjj tons by the ,brumlen and ,dahn process4 ,there is also in a manufactory in ,milan1 the process of revolving heaters4 ,the process of precipitation has not yet been used in ,italy4 ,the ,rhenish process1 as above described1 furnishes the greater part of ,italian white lead4 ,the smaller manufacturers still use the ,dutch process1 but the ,brumlen and ,dahn process is generally regarded as unsatisfactory4 ,it is believed that the production of white lead in ,italy during the first ten years of this century was about #cjj tons per annum4 ,the total annual production at present is1 in round numbers1 about #cejj tons1 of which #bhjj are produced in the ,ligurian manufactories1 and about #cjj in those of ,naples4 ,milan also produces about #cjj tons4 ,the product finds a market almost exclusively in ,italy4 ,the annual amount exported is about #cjj tons1 and goes chiefly to ,constantinople4 ,of the quantity of #bjjj tons per annum produced at ,cogoleto1 about #cjj tons is sold mixed with oil4 ,no exact statistics are attainable as to the total amount of ,italian white lead which is annually sold other than in the dry state1 but it is believed to be little1 if any1 larger than #cjj tons4 ,when the price of white lead was high1 sulphate of baryta was mixed with carbonate of lead to produce white lead of inferior quality1 but in consequence of the present price of white lead the use of sulphate of baryta has almost entirely ceased4 ,no other methods of adulteration are known to be in use4 ,in ,italy1 white lead is universally known as 8biacca0 when it is sold in cakes4 ,when sold in powder it is known as 8carbonato di piombo0 7carbonate of lead74 ,the lead from which all the white lead made in ,italy is manufactured comes from the lead mines of the island of ,sardinia1 with the exception of a very small quantity of argentiferous lead coming from ,spain4 ,the acetic acid used in the process of manufacture comes from ,france4 ,the market price of white lead in ,italy is now about #de lire the quintal 7equivalent to #ahs4 per cwt474 ,lewis's ,process4--,many attempts have been made to substitute for carbonate of lead--the ordinary poisonous white lead1 that slowly but surely induces paralysis in those who come in contact with it for any considerable period--some less deleterious pigment4 ,zinc white has often been put forward as a substitute1 and is indeed largely employed2 but it is open to the objection of not possessing sufficient body or opacity4 ,sulphate of lead is not poisonous2 but1 when prepared in the ordinary way by precipitation1 is of a crystalline nature1 and1 therefore1 wanting in both these qualities4 ,a sulphate of lead has1 however1 been produced by ,john ,t4 ,lewis1 of ,philadelphia1 by sublimation1 which1 when treated by the ,freeman process1 is stated to possess a body and colour superior to the best white lead made by the ordinary process1 with the additional merit of being cheaper1 while it is also non-poisonous4 ,in the smelting of lead ore into pig lead1 #ae per cent4 goes off in fumes1 and #aj per cent4 are all that it has hitherto been found possible to recover2 by this process1 however1 the whole #ae per cent4 are recovered4 ,the sulphate may also be produced from a low quality of galena1 or lead ore1 which is not suited for smelting into metallic lead1 and from the slag formed in the process of smelting4 ,the plant consists of simple subliming furnaces1 iron cooling pipes1 suction fans1 and a series of flannel or calico bags1 arranged vertically in a building1 well ventilated1 so as to allow the filtered gases to escape1 leaving behind the sublimed white lead1 which is then merely shaken down from the bags into barrels placed beneath them4 ,the manufacture is carried on at ,joplin1 ,missouri1 with four subliming furnaces1 about #ejj feet of cooling pipes and towers1 with suction fans1 which drive the fumes into #cjj bags1 #bj inches in diameter1 and #ch feet long1 arranged vertically4 ,about #ej tons weekly of white lead are now being produced from waste fumes1 slag1 and poor ore1 by this establishment alone1 at a cost not exceeding that given in the following figures3-- s4 d4 #bj cwt4 of galena 7with #hb per cent1 of ore7 #h #j #j ,cost of subliming and catching1 including repairs1 labour and all expenses #a #aj #j ,casks #j #f #j ------------ #i #af #j ,freeman's process 7see p4 #bed7 consists of grinding together1 in a dry state1 under great pressure1 and consequently with great friction1 sulphate of lead and sulphate of zinc4 ,while neither of these two substances alone possesses good body or opacity1 when treated by this process they are so changed in character that the new substance is stated to be superior in these respects to the best form of ordinary white lead4 ,the white lead thus obtained mixes well with oil1 and has also the advantage of not becoming blackened when exposed to the fumes of sulphuretted hydrogen1 and of not peeling off in a saline atmosphere4 ,as a basis for coloured paints1 it is recommended on the ground that1 being decomposed with greater difficulty1 it can be mixed with almost any colouring substance2 and1 being free from acid1 it does not change the tints of other substances4 ,the details of ,lewis's process1 and the plant employed1 are more fully set forth below4 ,heretofore the manufacture of dry white lead from galena or the native sulphurets has been effected by roasting or desulphurising the galena1 and then mixing the residue1 after roasting1 with carbon1 and subjecting the mixture to the action of heat in a compound reducing or subliming and oxidising furnace1 and collecting the resulting fumes in textile bags4 ,lewis's process1 however1 is based upon the discovery that by subliming unroasted galena1 or the native or raw sulphuret of lead1 and then oxidising the volatile products1 cooling the fumes1 and collecting them by means of a textile fabric1 a superior basis of a pigment can be obtained4 ,the admixture of carbon with the raw ore will facilitate the subliming process1 or it may be carried on in a muffle or reverberatory furnace without the previous admixture of carbon4 ,the furnace1 which has been found to answer well for the purposes above mentioned1 is commonly known as the ,wetherill furnace1 and is represented in plan1 in ,fig4 #ba2 in front and back elevations1 in ,figs4 #bb1 #bc2 and in central longitudinal section1 in ,fig4 #bd4 a represents the main chamber1 the bottom b of which is composed of iron bars perforated with small holes of about inch in diameter and about #a inch apart1 and preferably made slightly conical1 with the larger diameter downward1 that is to say1 the said holes are of such a size as to prevent ,illustration3 ,fig4 #ba4 ,fig4 #bb4 ,fig4 #bc4 ,fig4 #bd4 ,,lewis',s ,,white ,,lead ,,plant4 the escape of the crushed ore and coal4 ,these perforated bars are suitably sustained at the ends on the front and back walls of the furnace4 ,the ash pit below the perforated bottom is of equal area therewith1 and is provided with a door e in front1 and with a hole f at the back for the reception of a pipe from suitable blowing apparatus4 ,the walls g1 and arch on the top should be built of some refractory substance1 such as fire-brick4 ,the front of the furnace is entirely open1 and is provided with sliding doors i1 by which it can be closed when working1 and opened to remove the residuum4 ,at the back of the furnace there are two slides j1 to permit access to the main chamber1 for stirring the charge and for inspection4 ,at the back1 near the arch1 there is a hole k1 governed by a sliding damper leading to a chimney1 for carrying off smoke and impure gases at the commencement of the operation upon a new charge4 ,in the centre of the roof there is an aperture l1 governed by a damper or sliding door m1 the said aperture leading to a suitable apparatus for the collection of the oxidised vapours of lead4 ,the exterior walls n o p q may be built up to form two feeding troughs r1 one on each side of the arch or roof1 and each provided with an aperture or passage s1 communicating with the inside or main chamber1 and each aperture or passage is provided with a cover to be put on after the furnace has been charged4 ,in working with this furnace1 crushed ore 7native sulphuret of lead7 and carbon1 preferably in the state of pea or dust anthracite coal1 are mixed in equal proportions2 the mixture is ignited1 and the fumes are oxidised by the blast through the mixture1 which also promotes the combustion4 ,dense white vapours or fumes pass off1 and are conveyed to a separate chamber1 where they are strained by passing through a screen or series of screens of muslin or other textile fabric4 ,lime may also be employed in the furnace1 in the proportion of #bjj lb4 of lime to #djj lb4 of galena1 although the addition of the lime is not necessary in all cases4 ,instead of the furnace above described1 a muffle furnace may be employed1 in which the heat is applied indirectly to the ore1 with the precaution of constructing the sole or bottom of this furnace of a material not rapidly acted on by the constituents of the ore2 or a reverberatory furnace may be used in which the heat is directly applied4 ,in both of these two cases reducing carbon may or may not be mixed with the ore4 ,sometimes1 generated gas is employed in place of coal1 to effect the same result4 ,in a later specification ,lewis remarks that when white lead pigment is manufactured from galena or other lead ores1 in the raw state1 or even in the roasted state1 by subjecting them to the joint action of heat and air1 either with or without reducing means1 according to the quality of the lead ores used1 the fumes are discoloured by particles of carbon or sulphuret of lead1 or both1 when they are caught in bags of textile fabric1 and are unfit when in this state for use as a white pigment4 ,the fumes which are produced by this action of heat and air on galena or other lead ore are cooled and then collected in bags1 and ,lewis prefers to expose the so-collected products to the joint action of heat and air1 to destroy or to burn out all the particles of carbon or sulphuret of lead1 or both1 by either throwing the said fumes on a bright clean anthracite or coke fire1 with a blast from the sides or from below1 or by throwing them over such fires or into a cupola furnace1 or by throwing or blowing them into a generator gas flame1 or through externally heated retorts4 ,he then in either case collects the escaping fumes from the furnace or retort in bags or screening chambers4 ,the best process to be adopted depends upon the kind of fuel in the locality where the fumes are refined1 and also upon the purity of the lead fumes4 ,if they contain iron1 clay1 or the like1 it is best to throw them into a coal fire2 but if they are pure1 one process is about as effective as the other1 and the degree of purity of the fuel decides the kind of heating apparatus to be used4 ,there being such great difference in the purity of fuels1 and this irregularity not allowing of uniform results1 ,lewis prefers to use a furnace in which the flame and heat are produced by burning gaseous fuel with air1 which is forced into the furnace with the fumes which have been collected in a previous process4 ,fig4 #be represents a furnace which may be advantageously employed for the purpose when gas is used as fuel4 a represents a blower1 into which the fumes are fed from the hopper b4 ,the fumes1 being thoroughly mixed with air in this blower1 are forced into a chamber c1 and then through a series of tuyeres d4 ,at the same time1 gas from a generator or producer is admitted by the flue e1 and is burned by the incoming blast from the tuyeres d2 the volatile fumes produced in the furnace f pass through it and out of the flue g1 and are collected in bags or screening chambers4 ,by using gas fuel1 which is easily and fully burned1 and clean to handle1 a fine white pigment is produced4 ,mac,ivor's ,processes4--,the name of ,mac,ivor is a familiar one in improvements in manufacturing chemistry1 and not the least in connection with the subject of pigments1 sometimes in conjunction with other inventors4 ,in #ahhi ,mac,ivor and others introduced some modifications in the process of producing white lead or carbonate of lead1 by the treatment of oxide of lead 7litharge or massicot7 with a solution of acetate of ammonia1 whereby the oxide of lead is transformed into hydrate and acetate1 which are subsequently converted into carbonate of lead by the injection of carbonic acid4 ,the hydrate and acetate of lead1 in presence of free ammonia formed in the reaction1 are quickly decomposed by ,illustration3 ,fig4 #be4--,,lewis',s ,,white ,,lead ,,plant4 the carbonic acid1 yielding the final product1 namely carbonate of lead1 and re-forming the acetate of ammonia4 ,the rapidity with which the conversion of oxide of lead into hydrate can be effected depends upon the strength of the acetate of ammonia solution employed1 that is to say1 the weaker the solution the slower will be the conversion4 ,it has been found that1 for commercial purposes1 the solution of acetate of ammonia may be used with advantage of a strength which need not be more than #be per cent4 nor less than #e per cent4 ,a strength of #be per cent1 operates in a comparatively short space of time2 but a strength as low as per cent4 will effect the hydration if there be a sufficient quantity of the weak solution1 the lead oxide being in a fine state of division1 and time of no object4 ,this per cent4 strength1 however1 or any strength below #e per cent41 is not recommended for commercial purposes1 having regard to the time required for completing the operation4 ,the conversion of the oxide of lead into the hydrate and acetate of lead is effected in the cold 7heat may be used1 but for commercial operation it is not recommended74 ,the conversion is facilitated by employing a mechanical arrangement1 similar in many respects to that adopted in a previous specification1 but modified by connecting the digesting vat with a cistern or vat containing acetic acid1 whereby any free ammonia carried over during the operation may be absorbed4 ,also by introducing carbonic acid to the mass of hydroxide and acetate of lead formed by the oxide of lead and acetate of ammonia1 either by a series of concentric rings perforated with small holes in the bottom of the vat itself1 or by passing carbonic acid down a hollow shaft to which are attached stirrers1 and through perforated tubes attached to the blades of the stirrers1 or by any other means that may ensure the thorough saturation of the hydroxide and acetate of lead so as to form carbonate of lead4 ,the solution of acetate of ammonia may be recovered from the white lead1 and be repeatedly used1 for the conversion of further quantities of oxide of lead into hydrate and acetate of lead1 which hydrate and acetate are converted into carbonate of lead by the injection of carbonic acid4 ,theoretically1 a given weight of acetate of ammonia in solution1 used in conjunction with carbonic acid1 should be capable of converting an unlimited quantity of oxide of lead into carbonate of lead2 but during the manufacture of white lead by this process1 it may be reckoned that there will be a loss of ammonia acetate varying with the strength of the solution employed1 but it should not exceed #aj per cent4 on each charge4 ,this loss arises in the washing of the final product1 and through the escape of some ammonia during the process4 ,fig4 #bf is a vertical section of the apparatus employed4 a is a vat1 which may be made of wood or other material capable of resisting the chemicals employed2 it may conveniently be #f feet in diameter and #d feet deep1 and it is provided with a closely fitting cover1 b is a cistern situate at a higher level1 and intended to contain a solution of acetate of ammonia1 c is a pipe by which the solution can be drawn down from the cistern b into the vat a2 a cock is provided upon this pipe1 as the drawing indicates4 ,there is a man-hole d in the cover of the vat1 and the vat contains an agitator e1 with a vertical shaft which can be turned by gearing f as shown1 or the agitator may be driven by any suitable motor4 ,the shaft of the agitator e is hollow1 and pipes g1 which stand immediately behind the stirring tines1 are connected with the hollow shaft1 to deliver the carbonic acid gas into the vat2 or this may be effected by means of coils of pipe laid at the bottom of the vat1 and pierced with small holes4 ,the pipes g are open at their lower ends4 h is a cock by which the liquor can be drawn off from the vat into the receiver i4 ,a pump k is provided upon the cover of the receiver1 by which the liquor may be returned into the vat a4 l are outlets by which the white lead is discharged from the ,illustration3 ,fig4 #bf4--,,macivor',s ,,white ,,lead ,,plant4 vat into the washing cisterns m and n4 o is a man-hole1 which may be opened to facilitate the emptying of the vat4 p is a plug which is removed to let the white lead run out of the vat4 r is an ammonia catch box1 charged with acetic acid4 ,all the metal-work of the apparatus with which the acetate solution comes into contact should be of such a character as to resist corrosion1 or should be coated with a material capable of withstanding attack by the chemicals employed in or formed during the process4 ,the operation is by preference conducted in the following manner1 but the details admit of variation4 ,the charge of monoxide of lead for an apparatus of the dimensions indicated may weigh about #aabj lb4 ,the monoxide should be in fine powder1 and may be either moist or dry4 ,having received this charge1 which is introduced by the upper man-hole d1 the vat a is closed1 and a solution of acetate of ammonia is let down upon the charge from the cistern b1 or pumped out of the receiver i4 ,the vat a should be charged with the solution of acetate of ammonia in the proportion of three parts of said solution to one part of lead monoxide by weight4 ,it is convenient to employ a solution containing #e per cent4 of acetate of ammonia1 and the quantities above stated are suited to a solution of this strength2 but the strength of the acetate solution may be varied within wide limits1 as hereafter explained4 ,the charge of monoxide of lead and acetate of ammonia in the vat should be kept constantly stirred by the agitator until it becomes whitish in colour1 when it will be found that the monoxide of lead has become converted into hydrate and acetate4 ,the workman will know that this change is complete when the reddish or yellowish appearance of the monoxide of lead disappears1 and the mass in the vat becomes whitish in colour4 ,the hollow axis of the agitator is connected with a pipe1 by which carbonic acid gas is supplied to it under pressure sufficient to cause the gas to pass through the contents of the vat4 ,this gas escapes at the lower ends of the pipes g1 and ascends through the liquid in which the hydrate and acetate of lead are held suspended4 ,a free flow of this gas should be maintained1 and some excess allowed to pass away by a pipe on the cover into the ammonia catch box r4 ,the pipe dips down into the acetic acid which this box contains1 and any ammonia passing off with the carbonic acid gas is caught by the acid1 and forms acetate of ammonia4 ,when the hydrate and acetate of lead are completely converted into basic carbonate 7and this the workman will know by its changed appearance71 the motion of the agitator is caused to cease1 and the white lead is allowed to settle4 ,there is a gauge glass on the side of the vat a1 and in this glass the changes of appearance can be recognised by which the workman regulates the process4 ,when the white lead is deposited1 the liquor is drawn off into the receiver i by opening the cock h4 ,the plug p is then displaced1 and the white lead is allowed to descend into the washing cistern m4 ,below the cock h is another cock or cocks1 in order that any further quantity of liquor may be drawn off into the cistern i if required4 ,the taper plug p is then raised1 by being pushed up from underneath the vat a1 through pipe l4 ,the white lead requires to be well washed with clean cold water4 ,when a fresh charge of monoxide of lead has been placed in the vat a1 the liquor is pumped up on to it from the receiver i1 and then a further quantity of solution is drawn from the cistern b1 and also from the ammonia catch box r1 until the proper quantity has been supplied1 which is determined by the gauge4 ,quite recently1 in conjunction with ,mr4 ,watson ,smith1 ,mr4 ,mac,ivor has introduced further improvements in the production of 8white lead0 or basic carbonate of lead1 by the treatment of oxide of lead 7litharge or 8massicot07 with a heated solution of acetate of ammonium1 in a closed vessel 7called the digestor71 with agitation and under pressure1 so that the oxide of lead is transformed with exceeding rapidity into basic acetate of lead1 chiefly consisting of the tribasic acetate1 ammonia being set free2 and the subsequent treatment of the basic acetate thus obtained1 after filtering or otherwise removing insoluble impurities1 and after cooling with carbonic acid gas in a separate vessel 7called the carbonator74 ,the acetate of ammonium is by preference first charged into the digestor1 and then the oxide of lead 7litharge or massicot7 in fine powder1 and in the equivalent proportions calculated to be at least somewhat slightly in excess of the quantity necessary to form with the acetic acid of the acetate of ammonium the tribasic acetate of lead ,pb7,c#b;,h#c,o#b7b #b ,pb,o or ,pb#c,o#b 7,c#b;,h#c,o#b7b1 is added 7this being in allowance for the certain amount of insoluble and unconvertible matters in the litharge71 the acetate of ammonium liquor of a strength preferably not below #e per cent41 though it may be stronger1 being first1 before the addition of the oxide of lead1 set in vigorous agitation and circulation by the pump1 and heat having been applied by means of a steam heater as shown in the drawing and as will be explained later on4 ,the digestor is closed1 and the temperature rises4 ,as the temperature rises1 and approaches #bab ,f41 and as the pressure1 due more especially to the tension of vapour of ammonia set free during the reaction with the litharge1 increases1 so is the rapidity of the conversion of the oxide into basic acetate increased1 and more and more of this basic acetate becomes dissolved1 whilst at or about #bab ,f4 it is entirely in a state of solution4 ,the degree of heat1 or the prolongation of the heat1 depend of course upon the state of dilution of the acetate of ammonium used4 ,something more specific will be said later on regarding this question of degree of heat4 ,the clear liquor1 together with extraneous coloured particles1 red lead1 dirt and undissolved matters1 is pumped out through a suitable filter to one of the carbonators1 being carried en route through a cooling-pipe system1 and being let cool further if necessary in the carbonator itself4 ,after cooling thoroughly1 the cold basic acetate1 which may now have crystallised or separated out more or less1 according to the strength of the solution1 is treated with carbonic acid gas1 whereby the basic acetate1 in the presence of the ammonia set free1 is converted into basic carbonate of lead of exceptionally white colour1 and with high basicity and covering power1 proper care being taken as specially indicated later on4 ,there are several reasons why greater whiteness of the product is secured1 the principal one being that filtration from solid and insoluble coloured impurities has taken place previous to the carbonating process4 ,the advantages of the employment of heat and pressure for the formation of the basic acetate of lead from oxide of lead1 and the advantage of thus carrying out the conversion of oxide into basic acetate of lead separately from the conversion of that basic acetate of lead into basic carbonate or white lead1 are-- ,firstly--,that separation by filtration from impurities and so forth left by the oxide of lead used1 and insoluble in the acetate of ammonium1 is made possible1 and thereby a pigment of exceeding whiteness and purity can be obtained1 besides high basicity1 with corresponding body and covering power4 ,secondly--,that the rapidity of the conversion of oxide of lead into basic acetate of lead is immensely increased--it becomes in fact almost instantaneous1 much time being saved4 ,thirdly--,that the conversion is effected quickly and in a perfectly closed vessel2 no chance of the escape of ammonia occurs1 and1 in the carbonating stage of the process1 the free ammonia present in the liquid assists in securing the formation of basic carbonate of lead1 and the maintenance of this basicity throughout the conversion4 ,this free ammonia is converted by the carbonic acid into the less volatile but still alkaline carbonate1 and1 later on1 this ammonium carbonate reacts upon the basic acetate of lead1 converting it into basic carbonate of lead1 acetate of ammonium1 still less volatile1 being simultaneously produced1 ready for use over again4 ,it must be understood then1 that as the carbonic acid passes into and through the ammoniacal mixture in the carbonator1 it continually precipitates or forms basic carbonate of lead1 in presence of more or less of the volatile alkali1 which however continually diminishes in quantity as the conversion proceeds4 ,were no ammonia present1 but only tribasic acetate of lead1 as in the case of the earlier methods of precipitating white lead1 unless a very slow current of carbonic acid gas were passed through1 some of the first formed basic carbonate of lead would be in danger of being over-carbonated and losing its basicity1 being converted into mono-carbonate of lead4 ,this danger is much lessened1 and consequently a much greater possibility of rapidity of carbonating is conferred1 in the case of the process as above described1 and by virtue of the ammonia which is present4 ,nevertheless the carbonic acid gas must not be passed1 even into the ammoniacal liquid containing the tribasic acetate of lead1 with such rapidity that distinct alkalinity to the usual tests ceases to be maintained1 and the process must be terminated whilst the liquid is still alkaline4 ,if a little lead salt on the one hand1 and a little ammonia on the other1 be left in the mother liquors ultimately obtained on filtering from the white lead1 they will be returned and circulated4 ,fig4 #bg shows an elevation 7partly in section7 of the apparatus employed4 a is an iron vessel made of boiler plate1 and lined internally with lead4 ,it may be here added that all the apparatus is thus lined1 or is constructed of material invulnerable to the action of lead salts1 ammonia1 or acetate of ammonia4 ,the vessel a1 which is termed the digestor1 should be furnished with1 a thermometer1 pressure gauge1 safety valve1 charging hole b1 and suitably arranged sampling pipe with cock4 ,illustration3 ,fig4 #bg4--,,macivor',s ,,white ,,lead ,,plant4 ,agitation of the contents of the vessel is effected by means of the circulating pump c1 which1 drawing off supernatant liquor along with air and ammonia vapour from the upper part of the digestor a1 by the pipe d1 forces it through the pipe e to the heater f1 consisting of a coil suitably heated by steam in a steam vessel g1 or by similar means1 and then is forced through a pipe h1 leading to the bottom of the digestor a1 where it terminates in a cone-spreader i1 provided with a regulating valve j4 ,by means of this spreader1 the liquid is forced through the heavy and dense mixture containing the oxide of lead1 which it vigorously agitates and keeps more or less in circulation as indicated4 ,the charges of litharge and acetate of ammonium will vary according to the strength of the latter4 ,for a #e per cent4 strength of acetate of ammonium solution1 however1 it will be best to calculate the proportions as follows1 viz4 about #abjj gallons of #e per cent4 acetate of ammonium liquor for #a ton of litharge1 which should be finely ground4 ,the temperature of the liquor may vary between #adj ,f4 and #bab ,f42 but within these limits1 the lowest temperature consistent with the sufficiently rapid conversion and solution of the litharge is preferable4 ,the reason of this is simply that the less the heat employed1 the less is the tension of the ammonia1 and the chances of the loss of ammonia are thus minimised2 in addition to this1 less delay is involved and less refrigeration or cooling is needed before carbonating4 ,the object of the violent agitation of the litharge amongst the heated acetate of ammonium in the digestor a1 is that caking of the former may be prevented1 and a most rapid conversion of the oxide of lead into basic acetate of lead1 with minimum expenditure of heat1 be secured4 ,the effect of the heat in the closed space is greatly aided by that of the pressure due to the tension of the ammonia and aqueous vapour at the increasing temperatures4 ,when the litharge is converted into tribasic acetate of lead1 and brought into solution1 the liquor and sludge of insoluble matters is preferably pumped through pipe k1 by means of the filter-press pump l1 and forced through the filter-press m1 which removes and retains the insoluble matter1 allowing the clear liquor to pass to the cooler n1 and through this to the carbonator o1 similar in construction to the digestor a4 ,here the cooled liquid is circulated by means of pump p 7in a similar manner to that adopted in the digestor process already described71 carbonic acid being simultaneously pumped in through the pipe q1 which is perforated as shown1 or introduced in any other way4 ,when carbonated to the desired extent1 the white magma1 consisting of basic carbonate of lead and mother liquor1 is drawn through the pipe r1 by the pump s1 into the filter press t4 ,the clear liquid flows through u1 into the covered mother liquor tank v1 whilst the press-cakes of white lead1 after sufficient washing with water1 are removed and dried in a suitable manner4 ,the washings are run off to a weak liquor tank 7not shown7 for concentration for use over again4 ,any inert gases accompanying the carbonic acid1 or the latter alone in excess1 pass from the carbonator through pipe w1 into the catch-box or other condensing and absorbing apparatus x1 containing either dilute acetic acid or cold water1 in order to retain any ammonia carried over1 and furnished with perforated trays or baffle-plates4 ,this catch-box is1 if necessary1 also connected with a further condenser1 so as to remove all ammonia from the displaced air1 or inert gases 7if impure carbonic acid has been used7 of the carbonator4 ,it is a lead lined vessel preferably4 ,the ammonia carried from each charge thus is tested by measuring the volume of the solution from the catch-box or other condensing and absorbing apparatus1 and estimating the ammonia present in the solution4 ,this amount of ammonia in a sufficiently concentrated form is then added to the charge in the carbonator1 when cold1 so as to produce a completely neutral solution4 ,the ammonia in the catch-box is either added to the ammonia stock in the ammonia department1 used for dilution of strong ammonia in making fresh acetate1 or strengthened up to further absorption in the catch-box or condenser1 until strong enough to add to a freshly run and cooled charge in the carbonator1 to replace any ammonia driven off by heat4 ,the sludge in the filter-press m is washed with water to remove acetate liquors and ammonia1 the weak liquors being run to a separate closed vessel similar to the carbonator o1 but smaller1 and not shown in the drawing4 ,here white lead is precipitated by carbonic acid1 and the product is passed into the filter-press t1 the weak liquors associated with it serving to give a preliminary washing to a freshly received charge of white lead already in the press4 ,the weak filtrate liquors thus obtained are preferably sent to the weak liquor tank already mentioned1 for subsequent concentration1 instead of to the stronger liquor tank v4 ,the sludge-cakes from the filter-press m1 connected with the digestor1 are suitably treated for the recovery of lead therefrom4 ,the mother liquors contained in tank v from the white lead filter-press t1 are directly returned to the ammonium acetate tank y1 by the pump z1 for use over again4 ,the carbonators may be operated singly as described1 or two or three may be connected together so as to be worked in rotation1 the partially absorbed carbonic acid from one carbonator being completely1 or more or less completely1 absorbed in the one1 or two1 with which it is connected4 ,the last of such series of carbonators would of course be connected with the catch-box arrangement previously described1 or other condensing and absorbing apparatus4 ,characters4--,the advantages and disadvantages in the employment of white lead have been described pretty fully by ,prof4 ,barff in one of the ,cantor series of lectures which form such an important feature in the publications of the ,society of ,arts4 ,probably the fact that white lead possesses the body it has is the reason why it has been so largely used1 and why so many paintings which have been painted with it have come to a most untimely end4 ,prof4 ,barff says he knows of no pigment so liable to change of colour as white lead4 ,in saying this he expects that there are many who will not agree with him4 ,they know that white lead works well and easily1 and they like it because it covers down well2 but then he points out some of the great defects under which it labours4 ,if you take some oil1 and if to that you add lime-water1 the oil will mix with the lime-water1 and form a kind of emulsion4 ,again1 if you boil oil or fat with soda1 a kind of soap is formed1 and the process of manufacturing soap is termed the process of saponification4 ,now if1 instead of boiling fat with soda or alkali1 we boil it with plumbic oxide or oxide of lead1 we shall form a soap1 and that soap goes by the name1 amongst medical men1 of emplastrum plumbi1 or lead plaster4 ,this is a substance made by the saponification of oil with the oxide of lead4 ,because this oxide and carbonate of lead have the power of saponifying oils1 you get in white lead that peculiarly smooth easy working which you do not get with any other white pigment2 and it is on this account1 for one reason1 that it is liked by artists and painters4 ,taking a piece of paper coated with some of this lead plaster1 if you throw a light upon it1 you will see that the substance is semi-transparent4 ,this is a peculiarity of lead that it will saponify and form this sort of transparent substance4 ,the famous landscape painter1 ,mr4 ,wilson1 made an addition to a room in his house4 ,the old part of the room had been painted a dark colour2 the new part1 of course1 when it left the workman's hands1 was perfectly white1 and therefore the painters painted down the dark colour with white lead1 until the whole room displayed one uniform tint4 ,after a while1 however1 it was found that the part which was originally painted dark became dark again2 the dark paint1 in fact1 showed through the white lead4 ,sometimes1 possibly1 when an artist wishes to put in figures upon a dark background that he has painted1 he uses white lead1 and the figures will stand out well and brilliantly at first1 but after a time the dark colour upon which they are painted strikes through the lead1 and the figures of course recede4 ,now1 this striking through is owing to a slight process of saponification1 no doubt owing to an interchange between the carbonic acid of the lead carbonate and the stearic and oleic acids of the oil with which the lead is mixed2 so that1 in time1 the white lead1 which has a body which makes it so great a favourite with artists1 loses that body1 and becomes a transparent or semi-transparent substance1 something like lead plaster4 ,here is a reason why white lead should not be used unless the ground has previously been brought to a light colour4 ,there is another objection to the use of white lead1 and really a very valid one it is4 ,persons go on year after year laying out sums of money for having their houses painted with white lead1 when other pigments which will keep their colour might well be employed4 ,a house painted with white lead after some time darkens in tint considerably2 the colour is changed by some influence that is acting upon it through the air1 and that influence is sulphuretted hydrogen gas4 ,if you paint with white lead doors placed near a drain from which this gas escapes1 those doors will become browned and blackened4 ,white lead is very often1 particularly that procured at ordinary shops1 adulterated with a substance called sulphate of baryta1 or1 commonly1 barytes4 ,this is much more transparent when ground with oil than white lead itself1 and it will materially impair that property for which white lead is valued1 viz4 that of covering down well and solidly4 ,white lead adulterated with barytes has1 generally speaking1 a bluish sort of look2 it is semi-transparent4 ,it has not that opacity that pure white lead has4 ,if you take a small piece of white lead and put it into a test-tube1 and add to it a little nitric acid1 or aquafortis1 and some water1 if the lead is pure the whole of it will dissolve in the liquid1 and you will have a pure solution4 ,if it does not dissolve there is a white precipitate1 which will fall down to the bottom of the tube1 and that precipitate is sulphate of baryta4 ,sulphate of baryta is insoluble in aquafortis1 but carbonate of lead1 and most lead salts1 are soluble in it4 ,there is another excellent test for the purity of white lead1 which is this4 ,if you take a small portion1 and grind it up with a little carbonate of soda into a small pellet about the size of a pea1 and then put it upon a piece of charcoal and hold it in the middle flame of a blow-pipe for some short time1 the sulphate of baryta becomes decomposed1 and you get sulphide of sodium formed4 ,if this sulphide of sodium be acted upon by an acid liquid1 sulphuretted hydrogen is given off1 which could not be formed from carbonate of lead1 for in it there is no sulphur at all2 and inasmuch as sulphate of baryta is the impurity for which we have to look1 the presence of sulphide after this treatment indicates that it was with the white lead which was examined4 ,,lime ,,white4--,a name sometimes given to the white pigment prepared from sulphate of barium4 ,see baryta white1 p4 #agj4 ,,lithophone4--,this is a fancy title for one of the several varieties of white pigment having the metal zinc as a basis1 and described under zinc whites on p4 #bdg4 ,,magnesite4--,the mineral known by this name is a natural carbonate of magnesia1 just as limestone is a natural carbonate of lime4 ,where sufficiently abundant it is quarried1 ground1 and levigated much in the same manner as barytes1 which it greatly resembles in its qualities as a pigment1 and for which it constitutes a suitable substitute4 ,it is very white1 heavy1 and opaque2 permanent in ordinary situations2 neutral with other pigments1 mixes equally well with oil or water1 and possesses good covering power4 ,,mineral ,,white4--,one of the names applied to the pigment prepared from gypsum1 see p4 #ahc4 ,,orr',s ,,enamel ,,white4--,a name derived from the maker of a certain variety of the zinc sulphide pigments1 described under zinc whites1 p4 #bed4 ,,paris ,,white4--,another name for the best brands of whiting1 see below4 ,,permanent ,,white4--,this name is often bestowed upon baryta white 7see p4 #agj71 on account of its durability as compared with white lead4 ,,satin ,,white4--,there is a certain amount of confusion in the application of this term1 for while it is sometimes referred to baryta white 7p4 #agj71 it is also a synonym for fine gypsum 7see p4 #ahc74 ,,spanish ,,white4--,the most carefully prepared samples of whiting 7see below71 are often known by this name4 ,,strontia ,,white4--,though much less common than the closely similar sulphate of barium1 the natural sulphate of strontium is equally suitable for employment as a pigment1 and is prepared in exactly the same way as baryta white 7see p4 #agj74 ,the artificial product is also used4 ,both possess qualities remarkably akin to those of baryta white4 ,,terra ,,alba4--,an old-fashioned name for levigated gypsum 7see p4 #ahc74 ,,whiting4--,this material is simply prepared chalk4 ,it should be soluble in hydrochloric acid with effervescence1 leaving at the most but a small residue4 ,sometimes samples of whiting are found which are more or less alkaline or caustic in their properties4 ,this is a serious defect for many purposes4 ,it can be detected by treating the sample with water1 and adding to the liquor a little phenolphthalein4 ,if a brilliant red colour is obtained1 caustic lime is present1 and the sample should be rejected1 if to be used for mixing with chromes or ,brunswick greens1 where a neutral product is required4 ,chalk itself is too familiar to need any description beyond saying that it essentially consists of carbonate of lime1 with always a small percentage of silica associated with it4 ,its preparation consists in hand selection to exclude the silica which1 occurs in the more pronounced form of flints1 then grinding in several stages1 levigation and drying4 ,the levigation is effected by having a series of settling pits into which the ground material flows with water1 and deposits according to its degree of fineness4 ,the drying is performed in chambers provided either with pipes carrying steam or heated air1 or by fires beneath the floor1 and thoroughly ventilated so that the moist air can escape as fast as it is saturated4 ,finally the dried whiting is again ground very fine4 ,the drying must be done with great care and at a low temperature1 so as to ensure avoiding calcination1 whereby the carbonate of lime is changed into oxide 7quicklime74 ,whiting is a permanent and useful pigment mixed with water in distempers1 but is not applicable as an oil colour4 ,,zinc ,,whites4--,originally and properly the term zinc white was reserved for the white pigment consisting of zinc oxide2 but latterly many kinds of white pigment have been introduced containing a large proportion of sulphide of zinc1 sometimes associated with more or less oxide1 and sometimes without any oxide1 and these are also by many people called zinc whites1 to which name they are perhaps as well entitled as the original zinc oxide4 ,it will therefore be convenient to arrange them all under the same general heading of zinc whites4 7#a7 ,oxide4--,under the influence of a white heat metallic zinc is volatilised1 and if the vapour is thus brought into contact with oxygen1 either in the pure state or as air1 combustion takes place1 and the oxygen unites with the metal to form zinc oxide4 ,on this very simple principle is based the manufacture of zinc oxide white4 ,the operation is conducted in plant similar to that shown in ,fig4 #bh1 which consists essentially of two departments1 that in which the zinc is volatilised and that in which the oxidised vapour is deposited for collection4 ,the volatilising process takes place in a series of oblong fire-clay retorts a1 varying somewhat in form but always with a contracted and rising neck4 ,ordinary dimensions are about #b feet long and #i inches in diameter each way1 with walls about #a inches thick4 ,these are heated to whiteness and then charged with ingots of metallic zinc4 ,the retorts are arranged in double rows in reverberatory furnaces b1 two furnaces being arranged back to back so as to economise heat4 ,the furnaces are fired at the side1 and the heat is conveyed around the retorts by means of the flues c1 the products of combustion of the fuel finally escaping by the chimney stack d4 ,illustration3 ,fig4 #bh4--;,,apparatus ,,for ,,making ,,zinc ,,oxide4 ,as the vaporised zinc is emitted at the mouths of the retorts a in a partially ascending current1 it immediately encounters a plentiful supply of air1 and thereupon takes fire 7undergoes combustion or oxidation74 ,in this condition it enters the lower and funnel-shaped end of the sheet-iron flue e1 by which it is conveyed into the series of settling compartments f4 ,while the bulk of the zinc oxide thus formed passes into the settling chambers1 a portion of it is too heavy to do so2 its specific gravity is such that the force of the draught is not sufficient to carry it up4 ,this portion falls at once into a receptacle placed beneath the mouth of the flue e4 ,in order to obtain the necessary draught1 the conduits h are open to the outside atmosphere1 and introduce a supply of air just below the mouths of the retorts a1 so that it impinges against the current of escaping zinc vapour4 ,after passing through the settling chambers f1 the superfluous air finds an outlet at i into a sufficiently capacious flue k1 which communicates with the chimney stack d4 ,thus the draught created by the fuel consumed in the reverberatory furnaces is made to assist the current through the settling chambers4 ,these settling chambers f1 are constructed of wood1 and are usually about three in number1 intercommunicating of course4 ,the zinc oxide enters the first compartment through an aperture in the top of the side to which the discharge end of the iron flue e is attached4 ,after traversing the first chamber1 the stream of air and such oxide as has not yet settled passes into the second chamber through the orifice l1 near the bottom of the partition dividing the two chambers4 ,to reach the next compartment1 the stream has to ascend again1 the aperture being at the top of the partition1 and this alternation is carried on to the end of the series1 thus checking the through draught and facilitating the settlement of the zinc oxide4 ,the floors of all the chambers are made funnel-shaped1 with a door at the lowest point1 so that the discharge of their contents may be as automatic as possible4 ,the flue k contains screens hung at intervals for the purpose of hindering1 as far as possible1 the escape of minute particles of zinc oxide into the chimney1 and thence into the outer air1 whereby they would be lost4 ,a description of the process as conducted in ,belgium1 says that ingot zinc is placed in a series of retorts within one furnace1 and the oxide is formed in an exhaust chimney1 and then passes through a long series of passages and condensing chambers1 in which are ranged tanks of sheet iron or cloth to collect deposits4 ,at a certain hour of the day it is collected into casks1 and after being tested as to quality it is ready for delivery4 ,according to the purity of the metal various qualities are produced4 ,the best is called 8blanc de neige10 or snow white1 and is of a very superior quality2 ,no4 #a white is the most used1 the ores for this quality being selected and purified by remelting2 ,no4 #b white is the common variety4 ,in the process of manufacture there is more or less waste material1 imperfectly oxidised1 deposited in the retorts and passages4 ,this residuum is carefully ground1 washed and dried1 and is employed in painting in the place of lead4 ,in the ,american method of making zinc white they use the ore direct4 ,this is cheaper than the ,lige method1 but its product is of inferior quality to that produced by sublimation4 ,there are but two works in ,belgium for making zinc white1 the ,vieille ,montagne ,company 7at the ,valentine ,cocq works71 which produce yearly #cjjj tons by sublimation2 the other is at ,ougree1 near ,lige1 where the ,american method is employed1 but at present it is idle4 ,there are many other modifications in detail in different works4 ,one may be noticed here as it is claimed for it that the pigment is gifted with greater covering power or body1 the limited degree of which is the only drawback to zinc oxide whites4 ,the plan consists in this1 that the oxide is allowed to collect in the condensing chambers till it is of such a depth that a man entering stands waist deep in the pigment4 ,the latter is gathered in pieces of sacking1 which are drawn together and squeezed up tightly1 so that the oxide1 when newly prepared1 is pressed into hard dense masses4 7#b7 ,sulphide4--,prof4 ,phipson1 in a paper read before the ,international ,health ,congress1 at ,paris1 remarked that for several years efforts had been made to discover some white substance to replace white lead for painting buildings1 ships1 c4 ,he himself had devoted several months to this important subject1 but without success4 ,there has been found1 it is true1 in oxide of zinc a substance less poisonous than lead1 and serving very well as a white pigment in oil painting2 but its production is very expensive1 and its mechanical properties as a colour in oil are not pronounced enough to allow it to compete in commerce with white lead4 ,such is not the case1 however1 with an invention of ,mr4 ,thomas ,griffiths1 of ,liverpool1 who has succeeded in obtaining a very interesting product4 ,this new preparation1 which is being manufactured at the present time on a pretty extensive scale1 has for its base sulphide of zinc 7or an oxysulphide of that metal71 the properties of which as an oil colour are of the most remarkable character4 ,it is prepared by precipitating one of the salts of zinc by a soluble sulphide1 and washing and drying the precipitate4 ,the latter is then calcined at a red heat1 with some precautionary measures1 then taken from the furnace1 and1 while still warm1 thrown into cold water4 ,it is afterwards levigated and dried4 ,the result is a white pigment1 very fine1 and of great beauty4 ,regarded from a hygienic point of view1 ,griffiths' new white is infinitely superior to white lead1 as it also is in its practical bearing2 it possesses no injurious qualities2 its manufacture and use do not affect the health of workmen2 its durability in climates of the most diverse kinds is1 so to speak1 illimitable2 it is altered neither by gaseous emanations nor by dampness2 and its price is comparatively low4 ,the most remarkable thing about this new white is that it covers as well as white lead1 while it withstands the effects of all kinds of weather1 so that its use is not only deprived of all danger to health1 but it is much more economical than white lead4 ,prof4 ,phipson stated to the ,congress that he regarded this new chemical preparation as being among the most ingenious and useful products that have been discovered in our time4 ,a later method1 introduced by ,griffiths and ,cawley1 consists in making an artificial sulphide of zinc by bringing the vapours of zinc and sulphur into intimate contact4 ,in carrying out this process1 sulphur is melted in a jacket pan heated preferably by high pressure steam4 ,the melting vessel is connected with a cast-iron still by means of a jacketed pipe1 and the connection is regulated by means of a valve in the bottom of the melting pan4 ,the latter should be at such a height above the still that the pressure due to the column of sulphur in the conduit pipe may be greater than the tension of the sulphur vapour in the still1 so that when the valve is opened1 the sulphur in the melting pans may descend into the still4 ,the still is kept during the process at a temperature of incipient redness1 so that when the sulphur reaches it1 the sulphur is immediately vaporised and the resulting current of vapour passes to the chamber described below4 ,metallic zinc is melted in a retort or crucible1 heated preferably by means of a furnace on the ,siemens or a similar principle1 and raised to such a temperature that it begins to volatilise freely4 ,when this takes place1 the resulting zinc vapour is met by a current of sulphur vapour obtained as above described1 and in excess of that required to form with the zinc sulphide of zinc4 ,the reaction takes place according to the chemical equation ,zn ,s ,zn,s4 ,the sulphide of zinc is in the form of white extremely light powder1 which is carried along by the current of sulphur into the collecting chamber1 such as is used for the manufacture of oxide of zinc4 ,this allows of the separation of the different constituents of the products into different qualities2 those parts that are carried the farthest are the whitest and best generally4 ,those portions nearest to the part of the apparatus where combination takes place may sometimes contain metallic zinc1 if the sulphur supply has not been carefully attended to1 but this may be separated from the sulphide by levigation4 ,the collecting apparatus should be kept at a temperature slightly superior to that of the boiling point of sulphur1 in order that sulphur1 which is necessarily in excess1 may not be deposited with the sulphide of zinc1 but may pass on in the vaporous form to a suitable condenser1 where1 after condensation1 it may be collected and used again4 ,before the sulphur vapour reaches the condenser1 the last traces of sulphide carried along with it are collected by the interposition of metallic screens or sieves1 placed between the sulphur condenser and the apparatus4 ,in carrying out the process1 care must be taken to keep the collecting apparatus as cool as possible consistently with the fulfilment of the conditions above mentioned1 viz4 that no sulphur be condensed therein4 ,in practice1 this object can be effected with little difficulty4 ,impurities in the zinc and sulphur are of little consequence provided they are not volatile1 and not of such a nature that they would detract from the whiteness of the sulphide of zinc formed4 ,illustration3 ,fig4 #bi4--;,,apparatus ,,for ,,making ,,zinc ,,sulphide4 ,the accompanying diagram1 ,fig4 #bi1 is given as an example of a plant that may be employed with good results4 a is the sulphur melting pan with its steam jacket b1 and steam pipe c2 d is a cast-iron still1 arranged within a gas furnace e2 f is a crucible for melting and volatilising zinc1 the said crucible being contained in a gas furnace g2 h is an automatic apparatus for freeing the mouth of the zinc vessel from deposited sulphide of zinc2 i is the collecting apparatus2 and k1 the condensing apparatus4 7#c7 ,mixtures4--,there are a number of compound pigments commonly known as zinc whites1 which only deserve the name in so far as they contain a proportion1 greater or smaller1 of some zinc salt4 ,at the same time it must be admitted that some of these combinations possess very good qualities1 and that the foreign ingredients largely correct the weak points of the zinc compounds4 ,freeman's4--,this pigment1 when ground with oil in the customary way1 forms a paint equal in body and covering power to the best white lead1 while it is superior in colour1 permanence1 and density1 and is free from odour and noxious qualities4 ,it is produced by grinding together 8zinc white0 7either oxide or sulphide71 lead sulphate and barium sulphate1 in certain proportions1 in the dry state1 in an edge-runner mill4 ,by thus grinding the several pigments together1 their particles become intimately incorporated and undergo changes in character4 ,the barium sulphate not only cheapens the product by reason of its low cost1 but also imparts a distinct feature in rendering the paint more free working4 ,the proportions generally adopted1 calculated by weight1 are #e parts lead sulphate1 #b of zinc white1 and #a of barium sulphate4 ,the duration of the grinding will necessarily vary in accordance with various governing conditions1 but it should be continued until the mixture has a density of about #bjj lb4 per cubic foot4 ,orr's4--,the pigment known as ,orr's enamel or ,charlton white1 is a compound of oxide and sulphide of zinc and sulphate of strontia1 or of baryta4 ,it is prepared in two ways4 7a7 ,barytes is calcined for some hours at white heat with charcoal1 and the calcined mass is lixiviated with water to wash out the barium sulphide2 to one-half of this solution is added zinc chloride1 which produces a precipitate of zinc sulphide1 leaving barium chloride in solution4 ,to this mixture of zinc sulphide and barium chloride is added the remaining half of the barium sulphide and some zinc sulphate1 the result of which is a double precipitate of zinc sulphide and barium sulphate4 ,this is water-washed1 filter-pressed1 dried1 calcined at red heat1 thrown immediately into cold water1 ground very fine1 and finally dried4 7b7 ,the second process closely resembles the first1 but celestine takes the place of the barytes4 ,either form of ,orr's enamel is a good useful white pigment1 very permanent1 mixing well1 of excellent covering power1 and pure in colour4 ,characters4--,zinc oxide1 being an expensive pigment1 is liable to adulteration2 fortunately1 all such adulterations are easily detected1 and their nature ascertained by a few simple tests4 ,zinc oxide1 if pure1 should dissolve entirely without effervescence in nitric acid2 any residue would indicate adulteration with barytes or china clay2 the former may be distinguished by its weight and the yellowish green colour it imparts to the ,bunsen flame1 the latter is lighter and gives no colour to the ,bunsen flame4 ,boiled with strong sulphuric acid1 barytes is not acted on1 while china clay is4 ,if1 after cooling1 the mass be diluted with water1 and ammonia be added to the liquor1 if barytes is present no precipitate will be obtained1 while if china clay is present a white precipitate is produced4 ,if the zinc oxide dissolves with effervescence1 white lead or whiting may be present2 the solution should give no precipitate of black sulphide of lead on passing sulphuretted hydrogen through it4 ,on neutralising the solution in nitric acid with sufficient ammonia1 and adding ammonia sulphide to precipitate all the zinc 7the precipitate should be white1 any other colour would show some impurity71 filtering off and adding a little oxalate of ammonia1 no white precipitate of calcium oxalate should be obtained2 such a precipitate would show presence of whiting or gypsum4 ,the white pigments having as a base the sulphide of zinc1 also contain barytes1 oxide of zinc1 sulphate of strontium1 c4 ,they can be distinguished by evolving sulphuretted hydrogen gas1 recognisable by its odour1 on treatment with an acid4 ,they are not entirely soluble in acids1 the residue being mostly barytes1 but may also be sulphate of strontium2 it is immaterial whether the two be distinguished or not4 ,,chapter ,,viii4 ,,yellows4 ,the yellow pigments do not form a large or important group1 and beyond a few organic colouring matters which have a limited use in artistic painting1 they are chiefly confined to the ochres of natural origin and to the chromes1 and one or two other kinds artificially prepared from mineral substances4 ,,arsenic ,,yellow4--,another name for ,orpiment 7see p4 #bhj74 ,,aureolin ,,yellow4--,this colour is prepared by precipitating carbonate of cobalt from a solution of a cobalt salt with carbonate of potash2 this precipitate is dissolved in acetic acid1 and to it is added nitrite of sodium2 nitrite of potassium and cobalt are thrown down as a yellow powder4 ,experiments made on the freshly-precipitated colour prepared in this way1 have proved it to be invariably destroyed by caustic potash2 but aureolin yellow prepared in another way1 put into a flask with some caustic soda1 has remained unchanged for several days1 and proved to be perfectly stable under this treatment4 ,samples of the same yellow1 exposed to the action of ammonia1 soda1 and potash for a considerable length of time1 have not changed4 ,this is really a most important fact1 because aureolin yellow is so beautiful a pigment that one wishes it would stand for ever4 ,it is1 in fresco and silicious painting1 a great desideratum to have colours that will stand the action of lime and caustic alkalies4 ,our colours for fresco painting are very limited1 and if aureolin will stand the action of caustic alkalies1 it may be safely used both for fresco and silicious painting4 ,,cadmium ,,yellow4--,the pigment known as cadmium yellow is important on account of its permanence and brilliance4 ,it is prepared by passing a stream of sulphuretted hydrogen gas through a slightly acid solution of a salt of cobalt1 usually the nitrate or sulphate1 whereby the sulphide of cadmium is precipitated as an impalpable powder4 ,it is filtered off1 well washed with water1 and finally dried at a low temperature4 ,by this method there is considerable difficulty in producing any precise1 shade of yellow1 which is dependent on the proportion of precipitant used1 and can only be controlled after long practical experience4 ,therefore some modifications have been introduced with the object of securing definite tints4 ,the ordinary colour is a pure chrome yellow4 ,for a lemon-yellow shade1 a solution of yellow sulphide of ammonium is added to one of sulphate of cadmium4 ,for an orange tint1 the cadmium solution 7chloride or sulphate7 is made very acid by addition of hydrochloric acid before passing the sulphuretted hydrogen2 or the cadmium solution1 as for lemon-yellow1 is boiled1 and receives the ammonium sulphide solution while still boiling4 ,but none of these modifications results in a really durable pigment1 on account of the presence of traces of free sulphur or acid4 ,the best brands of this pigment being somewhat expensive1 there is great inducement for adulteration1 which usually takes the form of orpiment or of chrome4 ,the former can be detected by the ordinary tests for arsenic1 and the latter by the process described on p4 #bff4 ,,chrome ,,yellows4--,a very important family of yellow pigments are the 8chromes10 consisting mainly of chromic acid in combination with lead1 iron1 or zinc4 ,chromates of lead1 says ,prof4 ,barff1 are produced by precipitating a lead salt with a salt of chromic acid1 and the difference in tint is owing to the different quantity of the chromic acid which is present in the salt4 ,the orange chrome is a basic chromate of lead1 and basic chromate of lead contains more of the chromic acid than is present in the lemon chrome4 ,the lightest chrome contains some sulphate of lead precipitated with the chromate4 ,all these colours contain lead1 and are therefore liable to the influence of sulphuretted hydrogen4 ,now1 if a chromate of lead is bought hap-hazard anywhere1 it may or may not be pure1 but generally speaking1 unless the chromates are obtained from makers who are careful in the preparation of their colours1 they contain many other substances besides chromate of lead4 ,for instance1 they contain a quantity of the solution1 in a dry state1 from which they have been precipitated1 and are by no means pure4 ,obviously1 also1 there is an inducement to men who sell cheap colours to adulterate them1 to bring them down with whiting1 and so forth4 ,in that case the chrome loses its body2 if it is brought down with lead sulphate it has more body2 but when chrome yellows are prepared and mixed with good oils1 and put on carefully1 and those oils have time allowed them to become oxidised1 perfectly dry in fact--not dry in the sense in which an artist considers a painting dry1 but perfectly hard--then the action of sulphuretted hydrogen in the atmosphere will not be of such great moment as if the colours are impure1 or if they are submitted to the influence of that deleterious gas before they have become perfectly hard4 ,another objection to the chromes1 on the authority of ,prof4 ,barff1 is that they are soluble in alkali1 and so are many other colours4 ,if a painting is painted with chromes1 and if that painting be washed with an alkaline soap1 it is quite certain that some of the chromates will be dissolved4 ,consequently the minute and delicate touches1 upon which the artist depended for some of the best effects of his picture1 are removed with soap and water4 ,no painting should ever be washed with soap and water at all2 but there are certain colours which will withstand the action of soap1 even if it is intensely alkaline1 while others will not4 ,taking a precipitate of lemon chrome1 if we act upon this with potash or soda1 it dissolves up the yellow precipitate1 and destroys it altogether4 ,according to ,weber1 the preparation of chrome yellow presents difficulties in practice1 because products differing in shade and structure1 although of uniform chemical composition1 are obtained according to modifications of the method of manufacture or nature of materials employed4 ,a special difficulty is the turning of colour1 whereby a 8turned0 yellow has a dirty orange-yellow colour1 which when mixed with barytes gives a yellowish-brown leather-coloured shade and not a light pure yellow4 ,other derived colours are similarly affected4 ,lead ,chromates4--,the acetate and nitrate of lead are the soluble lead salts generally used4 ,basic carbonate of lead 7white lead7 is also much used1 the yellows prepared from this material being cheaper1 having a large covering capacity1 and being particularly adapted for ordinary greens2 but these have not the smoothness and lightness so much prized in some of the yellows obtained from soluble lead salts4 ,the oxide1 sulphate1 and chloride of lead have been proposed for the manufacture of chrome yellow1 but their treatment would be very tedious and the products obtained only of medium quality4 ,in the manufacture of chrome yellow from acetate of lead and bichromate of potash1 different proportions of these materials are given by different authorities1 but some of these are obviously wrong where an excess of bichromate is to be used1 for every light chrome yellow is liable to turn by the action of chromic acid or a chromate and thereby become of little value4 ,proportions should be used1 whereby the acetate of lead remains in excess1 and the reaction should take place in a solution as cold and dilute as possible4 ,in this way a brilliant yellow tint is obtained4 ,for the lighter chrome yellows1 lead sulphate is precipitated simultaneously with the chromate by adding sulphuric acid or a soluble sulphate to the solution of the bichromate2 these yellows have less tendency to change colour than the pure chromate of lead1 if the above precautions are observed4 ,chrome yellow1 precipitated from an excess of lead acetate solution1 by means of potassium bichromate1 corresponds to the formula ,pb,cr,o#d4 ,when dried it forms light pieces1 which show a conchoidal fracture4 ,a still more voluminous product corresponds to the formula ,pb,cr,o#d1 ,pb,s,o#d4 ,the yellow having the composition ,pb,cr,o#d1 #b,pb,s,o#d1 is very heavy and shows a smooth fracture4 ,lightness is often imparted to chrome yellow by the addition of magnesium carbonate4 ,nitrate of lead offers no advantages over the acetate1 and is generally more expensive to use4 ,free nitric acid is more objectionable than free acetic acid1 because it may act as a solvent on chrome yellow and liberate free chromic acid1 which is liable to 8turn0 the yellow4 ,when using lead nitrate it is preferable to neutralise potassium bichromate with soda1 to avoid the presence of free nitric acid4 ,the yellows mostly in demand are the inferior qualities1 prepared by mixing pure chrome yellows with white mineral matters1 generally barytes1 gypsum1 and kaolin1 usually stirred in with the bichromate solution before adding the lead salt4 ,barytes injures the colour least1 but kaolin has the advantage that it does not increase the weight of the colour so much4 ,gypsum occupies an intermediate position2 it is much more voluminous than barytes1 and does not injure the colour so much as kaolin1 but it is generally used together with barytes4 ,it is not advisable to use this combination1 for the reason that the colour on drying forms very hard pieces1 which offer difficulties in grinding4 ,gypsum1 too1 from being more easily acted on by reagents than barytes or kaolin1 tends to take part in the reaction by decomposing the potassium bichromate before the addition of the lead salt1 and this is objectionable4 7,weber47 ,a writer in the ,chemical ,trade ,journal gives the following formula for the production of various yellows3-- 7#a7 ,for soluble lead salts3-- ,kilos4 ,lead acetate #ajj ,potassium bichromate #ah ,sulphuric acid 7#ff ,b47 #ab ,this mixture yields a yellow of the formula ,pb,cr,o#d1 ,pb,s,o#d4 ,to obtain good shades1 the amount of water employed should not be less than #ajjj litres1 or double as much with the nitrate4 ,in the latter case1 it is better to neutralise the lead nitrate and to replace the acid by the sulphate of an alkali or of magnesium1 or preferably of aluminium2 for the neutralisation of the bichromate1 the best substance is magnesite4 ,the formula thus becomes--,lead acetate and bichromate as before2 magnesite1 #f kilos42 aluminium sulphate1 #bg kilos4 7#b7 ,the ,basic ,acetate ,method4--,litharge1 #gf kilos42 acetic acid 7#cj per cent471 #db2 bichromate1 #bae2 sulphuric acid1 #bae2 water1 #bjjj to #cjjj litres4 ,to obtain a denser chrome1 #aj kilos4 of soda should be added to the acetate1 and #e of the sulphuric acid replaced by #aj of aluminium sulphate4 ,for the production of an orange chrome1 the following formula is given3 ,litharge1 #gf kilos42 acetic acid 7#cj per cent471 #db2 bichromate1 #bd2 ,solvay's soda1 #ae2 and caustic soda 7#ajj per cent471 #e4 ,care must be taken that the temperature does not rise sufficiently high to spoil the shade4 7#c7 ,the ,white ,lead ,method4--,in this case the white lead must be in the finest state of subdivision possible1 and suspended in the water3 ,white lead1 #ajj kilos42 nitric acid 7#cf ,b471 #ab2 bichromate1 #ac2 and aluminium sulphate1 #aj3 or nitric acid 7#dj ,b471 #dd2 bichromate1 #bd2 sulphate1 #bj1 the latter giving the more fiery shade4 ,for the production of an orange3 white lead1 #ajj kilos42 nitric acid 7#cf ,b47 #ah2 bichromate1 #bh2 and caustic soda1 #h1 the latter being best added to the bichromate before precipitation1 and the temperature kept between #aej and #afe ,f4 7#d7 ,the ,basic ,chloride ,method4--,the same proportions and temperature are suitable here as in the case of the white lead4 7#e7 ,the ,sulphate ,method4--,lead sulphate1 #ajj kilos42 bichromate1 #bd to #be2 ,solvay's soda1 #hge to #af2 ammonia 7#bd per cent471 #a to #b2 and acetic acid 7#cj per cent471 #e to #aj4 ,the sulphate1 in the form of a cream1 is gradually added to the other ingredients after solution4 ,a new and improved process for manufacturing from galena chemically pure chrome yellow having great colouring power1 according to the ,paper ,trade ,journal1 consists in first dissolving pulverised galena with nitric acid to produce liquid nitrate of lead1 and then precipitating the chromate of lead by subjecting the nitrate of lead to the action of bichromate of potash1 neutral chromate of potash or chromate of potash-soda4 ,the galena 7sulphide of lead7 is first pulverised by suitable means1 and in case it contains foreign minerals or other impurities1 it is washed or otherwise treated in a suitable manner to remove these substances4 ,the pulverised galena is then placed in acid-proof vessels and is dissolved by adding nitric acid diluted with water1 the entire mass being well stirred4 ,a slow dissolving takes place at the ordinary temperature2 but when the mass is heated artificially1 either by heating the vessel1 or by using hot water added to the nitric acid1 or by the use of steam1 more rapid solution is effected4 ,the product obtained is nitrate of lead in a liquid state4 ,the quantity of nitric acid necessary for dissolving a certain quantity of galena depends on the percentage of lead contained in the ore1 and to a certain extent on the amount and nature of impurities present in it1 and also on the length of time in which the dissolving takes place4 ,in treating #ajj lb4 of galena having #hj per cent4 of metallic lead1 about #ij to #ajj lb4 of nitric acid of #cf to #ch ,b4 are used1 and the nitric acid is diluted with #ajj to #bjj lb4 of water4 ,this mixture is left for about #bd to #cf hours1 and is stirred up occasionally1 as above stated4 ,after the galena is dissolved by the nitric acid1 and the sulphide of lead is changed into liquid plumbic nitrate1 then the sulphur which floats occasionally on the surface of the solution is removed1 and the substance which remains undissolved is washed out and is also removed4 ,the liquid nitrate is then passed through filters of felt1 linen1 hemp1 flannel1 c41 or is left standing for about #ab to #ah hours for settling and clearing4 ,now in order to produce the chrome yellow from this nitrate of lead1 bichromate of potash is dissolved in water1 and a sufficient quantity of this solution is poured into the plumbic nitrate solution until all the plumbic nitrate is changed into chromate of lead1 called 8chrome yellow40 ,instead of the bichromate of potash1 neutral chromate1 or chromate of soda may be used1 and for the purpose of obtaining lighter tints they may be tempered with sulphuric acid or any other compound of sulphur4 ,the liquid nitrate of lead is placed1 preferably1 in large open receptacles of wood1 clay1 earthenware1 or other suitable material1 and the chromate of potash solution is put into similar vessels1 and then placed above the receptacles containing the plumbic nitrate4 ,the chromate of potash can then easily be run into the lower receptacles containing the liquid nitrate of lead1 and this mixture is constantly agitated by similar means until all the plumbic nitrate is changed into chromate of lead1 which is precipitated on the bottom of the larger receptacles4 ,the chemical action which takes place by this changing of nitrate of lead into chromate of lead is that the chromic acid of the potash assumes the place of the nitric acid1 which parts from the lead and combines with the potassium1 so that the lead as chromate of lead is precipitated on the bottom of the receptacle1 while the nitric acid of the plumbic nitrate remains with the potassium1 which latter has parted with its chromic acid1 and a quantity of water as solution above the chromate of lead4 ,to change the nitrate of lead recovered out of the #ajj lb4 of galena above mentioned into chromate of lead1 about #ef lb4 of bichromate of potash are used4 ,this change usually takes place in from about #aj to #cj minutes1 after which the chrome yellow 7chromate of lead7 is left for a few hours to settle1 and then the solution standing on top of the chrome yellow is drawn off by suitable means1 or run out of the vessel by opening a cock placed above the level of the chromate of lead4 ,the latter is then washed by adding pure water1 which is poured upon the chrome yellow1 and the mixture is stirred up1 so that all the remaining liquid nitrate of potash is removed4 ,after this is accomplished1 the mass is left to settle1 and the water is again drawn off from the precipitate1 which then settles on the bottom of the receptacle4 ,this washing is repeated as often as is deemed necessary4 ,the chrome yellow is next placed in suitable receptacles1 and dried in the open air or in specially constructed drying rooms1 after which it is packed in boxes1 kegs1 c41 and is then ready for use4 ,the liquid nitrate of potassium1 or saltpetre lye1 removed from the receptacles in which the chrome yellow is precipitated1 and the first water used for washing the chrome yellow1 as above described1 are placed in large open flat receptacles or excavations1 so as to be exposed to the action of the air and sun2 or the liquids may be operated on by a small graduation work1 so that a great portion of water evaporates4 ,the residue is then heated in suitable vessels or troughs by a slow heat until a salt crust is formed1 which1 when cooled off and left to dry1 is nitrate of potassium or saltpetre in a pure state4 ,from #ajj lb4 of galena having #hj per cent4 metallic lead1 some #bh to #cj lb4 of pure and dry saltpetre are produced by the above described process4 ,the sulphur produced by the dissolving of the galena by nitric acid is melted in a small stove or furnace in the usual manner1 and then refined1 so as to produce bars of sulphur called 8brimstone40 ,about #aj lb4 of such sulphur are produced from #ajj lb4 of such galena treated in the manner described4 ,the chrome yellow thus produced is said to be chemically pure1 and of great covering power1 equal to the best chrome yellow in the market4 ,the process is very simple1 and the crude lead ore is transformed into chrome yellow in from three to four days4 ,characters4--,pure chromate of lead has an orange-yellow colour1 and in whatever manner it be made it always has this tint4 ,commercially1 chromes are made of a great variety of tints1 from a pale-lemon chrome to a deep scarlet1 through all the intermediate shades of yellows and oranges2 in fact1 most colour makers produce not less than eight1 and some more shades of chromes1 whence it is obvious that they cannot be chemically pure1 but must be mixed with some other bodies4 ,in commerce1 chromes are distinguished as 8pure0 and 8common03 the distinction between them is that the 8pure0 chromes are made from a lead base1 and consist of chromate of lead mixed to a larger or smaller amount with sulphate of lead1 the paler shades containing most of the latter2 while the 8common0 chromes are mixed with china clay1 barytes1 gypsum1 or similar bodies4 ,to distinguish the two kinds of chromes1 treat with boiling hydrochloric acid4 ,if pure1 the chrome will completely dissolve1 the solution usually having a green colour4 ,on cooling1 crystals of lead chloride separate out4 ,the liquor will give a white precipitate with barium chloride4 ,by taking a weighed quantity of chrome1 dissolving in hydrochloric acid1 adding excess of barium chloride1 filtering1 thoroughly washing the precipitate with boiling water1 drying and weighing it1 and making the necessary calculations1 every one part of the precipitate being equal to #ac parts of sulphate of lead1 the quantity of the latter in the chrome is obtained4 ,the 8common0 chromes1 which mostly contain barytes1 are not completely dissolved on boiling in hydrochloric acid1 the barytes they hold being left as an insoluble residue4 ,by taking a weighed quantity of the chrome1 and filtering off1 drying and weighing the residue1 the amount of barytes present can be ascertained2 the solution can be tested for sulphate of lead1 which they sometimes contain1 as described above4 ,chrome yellows and oranges should be assayed for colour and tint1 care being taken to compare them with a thoroughly reliable standard sample4 ,their colouring power and body should also be assayed4 ,another property which should be tested is the colour that they yield on mixing with ,prussian blue4 ,a great deal of chrome is used for making greens by mixing with ,prussian blue1 and as there is a very considerable difference between them in the shade of green they give1 it is rather important to test this property1 which can readily be done by mixing #ajj grains of the chrome with #aj grains of ,prussian blue1 grinding them together in a mortar1 and observing the shade of the green which is produced thereby2 if the green is not bright and pure1 the chrome is not fit to be made into greens1 and should be rejected for that purpose4 ,iron ,chromate4--,if a solution of chloride of iron acidulated with hydrochloric acid be added to neutral chromate of lead1 a light orange powder is precipitated1 which is chromate of iron4 ,dried at #ajd ,f41 it is found to consist of #fe to #feaa chromic acid1 and #cdeh to #cdgh oxide of iron4 ,chromate of iron is insoluble in water1 dissolves easily in hydrochloric1 nitric1 and sulphuric acids1 and decomposes when mixed with soda lye4 ,under strong heat1 it melts into a brownish mass4 ,it may be used in painting in oils1 as a substitute for chromate of lead4 ,although inferior to the latter in brilliancy1 it has certain advantages over it--it does not blacken with exposure to sulphuretted hydrogen1 is not injurious to the user1 and withal is cheaper4 ,zinc ,chromates4--,the before-quoted writer in the ,chemical ,trade ,journal1 speaking of zinc chromates1 says that although it is possible to prepare lead chromates having shades varying imperceptibly from the palest lemon to a deep granite red1 in the case of the zinc compounds scarcely any variation from the normal is possible1 this being1 however1 different from anything obtainable with lead4 ,zinc yellows fall considerably below the ordinary chromes in their colouring power1 but they are faster in light and are less poisonous4 ,more than #hj per cent4 of the amount annually made in ,germany is used for the production of zinc green by mixing with ,prussian blues1 of which substance ,holland1 ,switzerland1 and ,hungary are the greatest consumers4 ,the zinc yellows met with in commerce vary in their constitution considerably1 being usually acid chromates of zinc and potassium1 basic zinc chromates being rare4 ,ordinary salts of zinc invariably contain small amounts of iron1 which must be removed before they are used in the manufacture of colours4 ,the simplest method is to heat them with the quantity of permanganate theoretically necessary to convert all the iron present into the ferric state1 adding zinc hydrate1 which need not be free from iron2 after thorough stirring1 the whole is allowed to settle1 and filtered1 when the liquid will be found to contain not a trace of iron4 ,on the addition of chromate to such solutions1 a yellow precipitate 7,zn,cr,o#d7 falls1 but owing to its great solubility in the liquid this process is valueless4 ,by using an excess of bichromate1 the zinc chromate combines with some of the alkaline salt1 forming the compound 7,zn,cr,o#d7c4,k#b;,cr#b,o#g1 which may be washed without loss2 but on drying yields an extremely hard1 sandy powder1 possessing1 in spite of its fine colour1 no value as a pigment4 ,by neutralising the two solutions before precipitating1 a much higher yield of chromate is obtained1 but still so much chromic acid is lost as to make the process too expensive to pay4 ,formerly an addition of calcium chloride was made to the neutral solutions1 so as to precipitate as calcium chromate some of the acid which remained mixed with the zinc salt4 ,the best results1 both in regard to yield and colour1 are obtained by adding to the zinc salt sufficient alkali to decompose one-quarter of it1 so that the chrome may have the formula 7,zn,cr,o#d7c4,zn,o4 ,to the bichromate1 enough alkali should also be added to convert it into the normal salt4 ,it is to be remarked that the nature of the metal combined with the chromic acid has the greatest influence on the shade of the zinc yellow1 so much so that in manufacturing 8acid0 zinc yellow1 the use of sodium bichromate is inadmissible4 ,a basic zinc yellow prepared from the sodium salt has a redder and more cloudy shade than one made from the potassium compound1 but the difference is hardly noticeable when sodium-potassium chromate is employed4 ,modern zinc yellows are invariably prepared from acid solutions1 and consist of a double salt of zinc chromate and potassium bichromate1 mixed with a varying amount of unchanged zinc oxide1 which must not be regarded as an adulteration of the pigment1 for its presence gives the substance 8body40 ,as previously stated1 sodium bichromate is inadmissible1 as it does not form similar double salts4 ,the raw material is usually zinc oxide1 which is met with in a state of great purity2 by the addition of sulphuric acid1 this is converted into basic zinc sulphate2 potassium bichromate solution is added1 and the whole is stirred vigorously for an hour4 ,at the end of this time1 the zinc chromate1 which was previously in a state of partial solution1 begins to separate out in the form of a brilliant yellow scum on the surface of the liquid1 consisting of 7,zn,cr,o#d7c4,k#b;,cr#b,o#g1 while the solution rapidly becomes almost colourless4 ,suitable proportions are3--,zinc oxide1 #ajj parts2 sulphuric acid 7#ff ,b47 #fj2 and potassium bichromate1 #ajj4 ,although it is hardly possible that any hydration takes place1 it is found advisable to soak the zinc oxide in water for #bd hours before the other reagents are added1 the sulphuric acid after dilution being added gradually4 ,great care must be taken that the solutions are all cold1 and the stirring is continuous1 to avoid the pigment being deposited in a hard sandy form4 ,zinc yellows thus prepared are not liable to change during washing in a manner analogous to the lead compounds4 ,zinc chrome is not much used1 partly because it is expensive1 partly because it cannot compete with the lead chromes in brilliance1 depth of colour1 and body4 ,still1 owing to the fact that it can be mixed with sulphur pigments without change1 it is often employed in the place of the lead chromes4 ,pure zinc chrome is completely soluble in sulphuric acid without any effervescence1 but a slight effervescence may be disregarded4 ,any residue may be put down as adulteration1 and its character can be ascertained by a few simple tests3 it may be chrome yellow1 barytes1 c4 ,,gamboge4--,gamboge is a product of several trees of ,eastern ,asia3 viz4 ,garcinia ,morella var4 4 pedicellata ,g4 ,hanburyi1 a native of ,cambodia1 the province of ,chantibun in ,siam1 the islands on the east coast of the ,gulf of ,siam1 and the south parts of ,cochin ,china2 ,g4 ,morella1 growing in the moist forests of ,ceylon and ,southern ,india2 and ,g4 pictoria1 of ,southern ,india1 by some considered identical with ,g4 ,morella4 ,g4 travancorica1 of the southern forests of ,travancore and the ,tinnevelly ,ghts1 is capable of affording small supplies of the pigment for local use1 but not for export4 ,when the rainy season has set in1 parties of natives start in search of gamboge-trees1 and select those which are sufficiently matured4 ,a spiral incision is made in the bark on two sides of the tree1 and joints of bamboo are placed at the base of the incision so as to catch the gum-resin as it exudes with extreme slowness during a period of several months4 ,it issues as a yellowish fluid1 but gradually assumes a viscous and finally a solid state in the bamboo receptacle4 ,it is very commonly adulterated with rice-flour and the powdered bark of the tree1 but the latter imparts a greenish tint4 ,sand is occasionally added4 ,the product from a good tree may fill three bamboo joints1 each #ah to #bj inches long and #a inches in diameter4 ,the trees flourish on both high and low land4 ,annual tapping is said to shorten their lives1 but if the gum-resin is only drawn in alternate years1 the trees do not seem to suffer1 and last for many years4 ,dr4 ,jamie1 of ,singapore1 who has gamboge-trees growing on his estate1 says that they flourish most luxuriantly in the dense jungles4 ,he considers the best time for cutting to be ,february to ,april4 ,the filled bamboos are rotated near a fire till the moisture in the gamboge has evaporated sufficiently to permit the bamboo to be stripped from the hardened gum-resin4 ,the gamboge is secreted by the tree chiefly in numerous ducts in the middle layer of the bark1 besides a little in the dotted vessels of the outermost layer of the wood1 and in the pith4 ,it arrives in commerce in the form of cylinders1 #d to #h inches long and #a to #b inches in diameter1 often more or less rendered shapeless4 ,when good1 it is dense1 homogeneous1 brittle1 showing conchoidal fracture1 scarcely translucent1 and of rich brownish-orange colour4 ,inferior qualities show rough1 granular fracture1 and brownish hue1 and are sometimes still soft4 ,the pigment consists of a mixture of #ae to #bj per cent4 gum with #he to #hj per cent4 resin4 ,its chief uses are in water-colour painting1 and in varnishes4 ,,king',s ,,yellow4--,a familiar name for the trisulphide of arsenic1 also known as orpiment 7see p4 #bhj74 ,,naples ,,yellows4--,this group of pigments embraces several combinations of the oxides of lead and antimony1 derived from various sources1 and prepared by sundry methods4 ,two of the most useful formul are as follows3-- 7a7 ,mix #c lb4 powdered metallic antimony1 #a lb4 oxide of zinc1 and #b lb4 red-lead2 calcine1 grind fine1 and fuse in a closed crucible2 grind the fused mass to fine powder1 and wash well4 7b7 ,grind #a part washed antimony with #b parts red-lead to a stiff paste with water1 and expose to red heat for #d or #e hours4 ,there are a great many modifications both in the ingredients and the processes1 and a great variety of shades in consequence4 ,taken as a whole1 the ,naples yellows are unsatisfactory pigments1 very prone to deteriorate in impure air1 and necessitating great care in their preparation to avoid contact with iron1 which turns them green4 ,they cover well1 are fairly brilliant1 and mix readily with water or oil1 but their application is declining rapidly4 ,,ochres4--,the large class of mineral pigments known collectively as ochres or sienna earths possess considerable importance1 notably on account of their remarkable durability and their reasonable price4 ,they all consist essentially of an earthy base coloured by oxide of iron or of manganese1 or of both4 ,some authorities differentiate between ochres and siennas1 and ascribe the latter name only to those earths which contain manganese1 but this seems to be an arbitrary proceeding1 because the term sienna1 or more properly ,siena1 is derived solely from the name of the ,italian province in which these minerals are worked4 ,they are of widespread occurrence1 both geographically and geologically1 and the methods of mining and preparing them are not subject to much variation4 ,consul ,colnaghi1 in his report on the mineral products of the province of ,siena1 says that ,siena earths1 known also under the names of ochre1 bole1 umber1 c41 are considered by some mineralogists to be ferruginous clays1 by others1 minerals of iron4 ,they are chiefly found in large quantities in the communes of ,castel del ,piano and ,arcidosso4 ,the yellow earths and bole found on the western slopes of ,monte ,amiata are true lacustrine deposits found amid the trachytic rocks1 of which it is principally composed4 ,they lie under1 and are entirely covered by1 the vegetable soil4 ,varying in compactness and colour1 they are termed yellow earths when of a clear ochreous tint1 and terra bolare1 or bole1 when of a dark chestnut colour4 ,each deposit consists for the greater part of yellow earth1 beneath which bole is found in strata or small veins4 ,the mineral being very friable1 its excavation is easy1 and is generally conducted in open pits4 ,the different qualities are separated during the process1 the bole1 which has the higher commercial value1 being the more carefully treated4 ,after the first separation the bole is further classed into first1 second1 third1 and intermediate qualities--boletta1 fascia1 cerchione1 c4 ,its most important characteristic is termed1 in commercial language1 punto di colore1 or tint4 ,the value of the bole rises as its tint deepens4 ,thus bole of the third quality is lighter than that of the second1 and the second than that of the first4 ,after the third quality comes the terra guilla4 ,the yellow earths1 after excavation1 are exposed to the open air for about a year1 by the pit side1 without classification4 ,the bole1 on the contrary1 is placed in well-ventilated storehouses to dry for about six months4 ,this diversity of treatment is owing to the fact that exposure to the elements brightens the colour of the yellow earths1 and raises their value1 while it would damage the bole by turning its darker tint first into an orange yellow1 and1 if continued1 into an ordinary yellow earth4 ,it also loses in compactness and crumbles up under exposure4 ,in addition to the punto di colore1 the size of the pieces influences the commercial value of the bole1 which increases with their volume4 ,thus the classification is bolo pezzo1 bolo grapolino1 and bolo polvere4 ,the yellow earths are classed as giallo in pezzo1 giallo commune1 and giallo impalpabile1 the impalpable being worth more than the common yellow4 ,the production of the ,siena earths is estimated at about #fjj tons per annum1 of which amount about #ej tons are calcined1 and the rest sold in the natural condition4 ,the value of the trade is estimated at from #djjj to #fjjj4 ,the ,european trade in these earths is very large4 ,rouen exports some #ejjj tons yearly1 and ,havre about #aejj tons4 ,similar deposits occur in ,america1 where they are known as 8paint-beds10 and the earths are called 8metallic paints40 ,a prominent example is the paint-bed at ,lehigh ,gap1 ,carbon ,county1 ,pennsylvania1 which was originally opened as an ironstone mine4 ,the mineral proved valueless metallurgically1 but remarkably useful as a pigment1 since it contains about #bh per cent4 of hydraulic cement1 which hastens the drying and causes the paint to set without any addition of artificial dryers1 thereby making it eminently fitted for all outdoor application4 ,along the outcrop of the paint1 the beds are covered by a cap or overburden of clay1 and by the decomposed lower portion of the ,marcellus slate1 which is #ej feet thick at the ,rutherford shaft4 ,beginning with the ,marcellus slate1 the measures occur in the following descending order3-- a4 ,hydraulic cement 7probably ,upper ,helderberg71 very hard and compact4 b4 ,blue clay1 about #f inches thick4 c4 ,paint-ore1 varying from #f inches to #f feet in thickness4 d4 ,yellow clay1 #f feet thick4 e4 ,oriskany sandstone1 forming the crest and southern side of the ridge4 ,east of the ,rutherford shaft the sandstone forms the top-rock of the bed4 ,this is due to an overthrow occurring between the ,rutherford tunnel and shaft4 ,the paint-bed is not continuous throughout its extent4 ,it is faulted at several places2 sometimes it is pinched out to a few inches and again increases in width to #f feet4 ,a short distance south of ,bowman's there is a fault striking2 north-east in the ,marcellus slate1 which has produced a throw of about #bjj feet4 ,the measures dip from #aj to #ij4 ,the dip at the ,rutherford shaft is about #gi south1 whereas at the tunnel it is #de north4 ,the ore is bluish-gray1 resembling limestone1 and is very hard and compact4 ,the bed is of a lighter tint1 however1 in the upper than in the lower part1 and this is probably due to its containing more hydraulic cement in the upper strata4 ,the paint-ore contains partings of clay and slate at various places4 ,at the ,rutherford shaft there are fine bands of ore1 alternating with clay and slate1 as follows--,sandstone 7hanging-wall71 clay1 ore1 slate1 ore1 clay1 ore1 clay1 ore1 slate1 ore1 cement1 slate 7foot-wall74 ,these partings1 however1 are not continuous1 but pinch out1 leaving the ore without the admixture of clay and slate4 ,near the outcrop the bed becomes brown hematite1 due to the leaching out of the lime and to complete oxidation4 ,occasionally1 streaks of hematite are interleaved with the paint-ore4 ,in driving up the breasts1 towards the outcrop1 the ore is found at the top in rounded1 partially oxidised and weathered masses1 called 8bombshells10 covered with iron oxide and surrounded by a bluish clay4 ,in large pieces the ore shows a decided cleavage4 ,the method used in mining is a variation of panel-work4 ,nearly the same system of working is employed by all of the companies who have developed their mines either by means of tunnels or shafts4 ,tunnels are preferred whenever equally convenient1 because they involve no expenses for pumping and hoisting machinery1 fuel1 repairs to machinery1 c4 ,the following description of the operation of the ,rutherford mines is typical of all the workings in the vicinity4 ,the ,rutherford tunnel is #f feet high and #fjj feet long4 ,the gangways are driven along the foot-wall of the cement side1 #f feet high1 and are heavily timbered and lagged at the top and on the clay side4 ,the sets of timbers are #c feet apart1 and usually of #i-;inch timber4 ,the width at the top is #c feet1 with a spread of #e feet at the bottom1 the extra width being cut from the clay4 ,where the cement-rock is firm1 the collar is hitched #f inches into it and supported by a leg on the clay side4 ,the cost of the timber is #ed cents 7#bs4 #c;d47 per set1 including the lagging4 ,the monkey gangway1 which carries the air along the top of the breast from the air-shaft1 is #b feet high1 #a feet wide at the top1 with a spread of #b feet at the bottom4 ,wooden rails with a gauge of #ah inches are spiked to the cross-ties4 ,the gangway is not driven continuously1 but after being driven about #ee feet on either side of the shaft1 the breasts are started #be feet from the shaft1 a pillar being left to protect it4 ,the breast is then opened up to the face of the gangway1 and when one ore-breast is worked out1 the gangway is driven ahead about #cj feet1 and a new breast is opened and worked out before commencing a third4 ,the air-hole is first driven to the surface1 then the breast is opened to its full width of #f feet4 ,the thickness of the bed of ore here varies from #d to #f feet1 depending upon the thickness of the partings of clay and slate4 ,the clay and slate are left on the bottom1 which is made sloping to allow the ore to roll down to the shute2 this is #f feet wide and #d feet long and heavily timbered4 ,small props or sprags are hitched into the cement1 and wedged with a lid on the clay side to prevent falls of rock4 ,the holes are drilled by hand in the clay-partings4 ,they vary in depth from #a to #d feet1 and the charge of dynamite is varied correspondingly1 according to the amount of ore it is desired to throw down4 ,the loose ore is wedged down with crowbars and picks1 and is then freed from any adhering clay and thrown down the shute4 ,it is there loaded into boxes holding about half a ton each1 which are pushed to the shaft on a truck4 ,the ore-boxes have four rings at the corners1 to which are attached four chains1 suspended from the wire hoisting-rope4 ,at the top of the shaft the boxes are detached and placed on a truck1 which is run to the dump4 ,thirty cars1 averaging #ae tons1 are extracted in a day of two shifts1 the day-shift working nine hours and the night-shift eleven4 ,the pay of the miners is #es4 per shift4 ,the cost of mining the ore averages #gs4 per ton4 ,the ore1 as it comes from the mines1 is free from refuse1 great care having been taken to separate slate and clay from it in the working places4 ,it is hauled in #b-ton wagons to kilns1 which are situated on a hill-side for convenience in charging4 ,the platform upon which the ore is dumped is built from the top of the kiln to the side of the hill4 ,the ore is first spalled to fist-size and freed from slate1 and is then carried in buggies to the charging-hole of the kiln4 ,the slate1 when burned1 has a light yellowish colour1 which would change the colour of the product4 ,figs4 #cj to #cb represent a front elevation of the kiln and two sections at right angles to each other4 ,the kiln is #bb feet high and #af feet square on the outside4 ,the interior is cylindrical1 #e feet in diameter1 with a fire-brick lining a of the best quality4 ,the interior lining slopes from the fire-place b to the door c1 by which the charges are withdrawn2 this facilitates the removal of the calcined ore4 ,the casing d is of sandstone1 #e feet thick1 and tied together with the best white-oak timber e4 ,when charged1 a kiln holds #af tons of ore1 and the kiln is kept constantly full4 ,the heat passes from the fire-places b--of which there are two1 placed diametrically opposite each other--through a checker-work f of brick into the centre of the charge4 ,the charge enters at g and is withdrawn by a door c in the front wall1 #b feet long and #ah inches high4 ,the ashpit is at i4 ,the fire is kept at a cherry-red heat1 and about one cord of wood is burned every twenty-four hours4 ,the kiln works continuously1 calcined ore being withdrawn and fresh charges made without interruption4 ,the ore is subjected for forty-eight hours to the heat1 which expels the moisture1 sulphur and carbon-dioxide4 ,about #a tons of calcined ore are withdrawn every three hours during the day4 ,the outside of the lumps of calcined ore has a light brown colour1 while the interior shows upon fracture a darker brown4 ,great care is necessary to regulate the heat ,illustration3 ,figs4 #cj1 #ca1 #cb4--,,rutherford ,,and ,,barclay ,,kiln4 so that the ore is not over burned4 ,when this happens1 the product has a black scoriaceous appearance1 and is unfit for the manufacture of metallic paint1 as it is extremely hard to grind4 ,the calcined ore is carried from the kiln in wagons to the mill1 where it is broken to the size of grains of corn in a rotating crusher4 ,the broken ore is carried by elevators to the stock-bins at the top of the building1 and thence by shutes to the hoppers of the mills1 which grind it to the necessary degree of fineness4 ,elevators again carry it to the packing-machine by a spout1 and it is packed into barrels holding #ejj1 #cjj1 or #ajj lb4 each4 ,characters4--,ochres owe their colour to hydrated oxide of iron1 besides which body they contain clayey matter 7silicate of alumina71 earthy matters1 barytes1 carbonate and sulphate of calcium1 c41 dependent upon the locality from whence they are obtained2 thus ,derbyshire ochres contain mostly calcareous earthy matters1 barytes1 gypsum1 c41 while ,oxford ochres and ,french ochres contain clayey matter2 ,welsh ochres are variable1 and usually contain a good deal of silicious matter4 ,crude ochres should first be assayed for actual colouring matter and grit or refuse4 ,this can be done by a kind of levigation method3 #bjj grains of the crude ochre are crushed in a mortar2 the grinding must not be too well done1 or otherwise faulty results will be obtained4 ,the crushed ochre is put into a tall conical glass2 a long glass funnel passes to the bottom of the glass1 and the whole is arranged in a large glass basin or dish4 ,a current of water is now caused to flow down the glass funnel2 this washes the fine particles of ochre away from the grit1 and they are carried over the sides of the glass into the dish4 ,here they are allowed to settle1 and are collected and weighed after drying1 an operation which gives the amount of ochre in the crude material4 ,levigated and prepared ochres can be tested for colour and covering power1 by the usual methods4 ,these are the most important points about ochres to which attention should be paid4 ,,orpiment4--,orpiment1 king's yellow1 or trisulphide of arsenic1 is a lemon or orange-yellow coloured substance1 found native in ,hungary1 the ,hartz1 and other places4 ,the finest samples used by artists 7golden orpiment7 come from ,persia4 ,the commercial article is artificially prepared for use as a pigment in the following way3-- ,a mixture of arsenious acid and sulphur is placed in an iron subliming-pot1 similar to those used in the preparation of crude white arsenic4 ,the mixture is then heated until the sublimate which immediately forms upon the rings fixed above the pot begins to melt4 ,the proportions of the two ingredients used vary largely1 the best colours being probably produced when the mixture contains from one-third to one-fifth of sulphur2 for the lighter colours1 a smaller proportion of sulphur is employed4 ,orpiment made in this manner consists of a mechanical mixture of sulphide and oxide of arsenic4 ,orpiment is also employed as a dye1 in the preparation of fireworks1 and in some depilatories4 ,the native sulphide is preferred to the artificial variety by artists and dyers1 by reason of its richer colour2 but it is a colour which in reality is hardly ever used now4 ,sometimes it is employed in water-colours1 but as a pigment it is worthless4 ,if it comes in contact with white lead it is decomposed in time1 and a brown or black sulphide of lead is formed4 ,while it endures it is a very brilliant colour4 ,,realgar4--,realgar or disulphide of arsenic1 is a deep orange-red substance1 soluble in water1 and highly volatile and poisonous4 ,it is found native in some volcanic districts1 especially in the neighbourhood of ,naples2 but the commercial article is made by distilling1 in earthenware retorts1 arsenical pyrites1 or a mixture of sulphur and arsenic1 or of orpiment and sulphur1 or of arsenious acid1 sulphur1 and charcoal1 in the proper proportions2 it has not the brilliant colour of the native mineral1 and is much more poisonous4 ,on a large scale1 the manufacture is carried on in the following way3--,the ingredients are mixed together in such proportions that the mixture shall contain #ae per cent4 of arsenic1 and from #bf to #bh per cent4 of sulphur1 in order to make allowance for the volatilisation of a portion of the latter substance4 ,the mixture is then placed in a series of earthenware retorts1 which are charged every twelve hours with about #fj lb42 this quantity should fill them three parts full4 ,these are then gradually heated to redness for from eight to twelve hours1 during which time the realgar distils off1 and is collected in earthen receivers1 similar to the retorts1 but perforated with small holes to permit the escape of these gases4 ,after the operation1 the receivers are emptied1 and the crude product is remelted4 ,this is performed in cast-iron pots1 the contents being well agitated1 and the slag carefully removed4 ,the requisite amount of sulphur or arsenic is then added1 according to the colour of the mixture1 or else a proper quantity of realgar containing an excess of the required constituent1 and the mass is again stirred4 ,when1 on cooling1 it exhibits the correct colour and compactness1 it is run off into conical moulds of sheet iron1 cooled and broken up2 it is sometimes refined by re-sublimation4 ,the chief use of realgar is as a pigment2 and in pyrotechny in the preparation of white fires4 ,as a pigment it possesses the same features and faults as its close ally orpiment4 ,,siennas4--,another name for ochres1 described on p4 #bgb4 ,,chapter ,,ix4 ,,lakes4 ,organic colouring matters for use as pigments are mostly made in the form of 8lakes10 by one of the three following methods3-- 7a7 ,to a filtered solution of the colouring matter is added a solution of alum2 the whole is agitated1 and the colour is precipitated by a solution of carbonate of potash4 7b7 ,a solution of the colouring matter is made in a weak alkaline lye1 and precipitated by adding a solution of alum4 7c7 ,recently-precipitated alumina is agitated with a solution of the colouring matter as before1 until the liquid is nearly decolorised1 or the alumina assumes a sufficiently deep tint4 ,the first method is generally adopted for acidulous solutions of colouring matter1 or those injured by alkalies2 the second for those not injured by alkalies2 the third1 for those whose affinity for gelatinous alumina enables them to combine with it by mere agitation4 ,alumina in a state suitable for the preparation of the pigments known as 8lakes0 may be produced in the following manner3--,dissolve #a lb4 of alum in gallon of water1 and add #ge grains of sulphate of copper1 and about lb4 of zinc turnings2 leave the mixture for three days in a warm place1 renewing the water lost by evaporation4 ,the copper is first deposited upon the zinc1 the two metals thus forming a voltaic couple sufficiently strong4 ,hydrogen is disengaged1 sulphate of zinc is formed1 and the alumina gradually separates in the state of a very fine powder2 the action is allowed to continue until there is no more alumina left in solution1 or until ammonia ceases to give a precipitate4 ,if the reaction is prolonged beyond this point1 oxide of iron will precipitate if present4 ,the alumina washes easily1 and does not contract upon drying4 ,,brazil-,,wood ,,lake4--7a7 ,digest #a lb4 ground ,brazil-wood in #d gal4 water for #bd hours1 boil hour1 and add #a lb4 alum dissolved in a little water2 mix1 decant1 strain1 add lb4 tin solution1 again mix well1 and filter2 to the clear liquid cautiously add a solution of carbonate of soda while a precipitate forms1 avoiding excess2 collect1 wash1 and dry4 ,the shade will vary according as the precipitate is collected4 7b7 ,add washed and recently-precipitated alumina to a strong filtered decoction of ,brazil-wood4 ,,carminated ,,lake4--7a7 ,the cochineal residue left in making carmine is boiled with repeated portions of water till exhausted2 the liquor is mixed with that decanted off the carmine1 and at once filtered2 some recently-precipitated alumina is added1 and the whole is gently heated1 and well agitated for a short time4 ,as soon as the alumina has absorbed enough colour1 the mixture is allowed to settle1 the clear portion is decanted1 and the lake is collected on a filter1 washed1 and dried4 ,the decanted liquor1 if still coloured1 is treated with fresh alumina till exhausted1 and thus a lake of second quality is obtained4 7b7 ,to the coloured liquor obtained from the carmine and cochineal as just stated1 a solution of alum is added1 the filtered liquor is precipitated with a solution of carbonate of potash1 and the lake is collected and treated as before4 ,the colour is brightened by addition of tin solution4 ,,carmine4--,boil #a lb4 cochineal and #d dr4 carbonate of potash in #g gal4 water for hour4 ,remove from the fire1 and stir in #h dr4 powdered alum1 and allow to settle for #bj to #cj minutes4 ,pour the liquid into another vessel1 and mix in a strained solution of #d dr4 isinglass in #a pint water2 when a skin has formed upon the surface1 remove from the fire1 stir rapidly1 and allow to settle for hour1 when the deposited carmine is carefully collected1 drained1 and dried4 ,,cochineal ,,lake4--7a7 ,digest #a oz4 coarsely powdered cochineal in #b oz4 each water and rectified alcohol for a week2 filter1 and precipitate by adding a few drops of tin solution every #b hours1 till the whole of the colouring matter is thrown down2 wash the precipitate in distilled water1 and dry4 7b7 ,digest powdered cochineal in ammonia water for a week2 dilute with a little water1 and add the liquid to a solution of alum as long as any precipitate 7lake7 falls4 7c7 ,boil #a lb4 coarsely powdered cochineal in #b gal4 water for #a hour2 decant1 strain1 add solution of #a lb4 cream of tartar1 and precipitate with solution of alum4 ,by adding the alum first and precipitating the lake with the tartar1 the colour is slightly changed4 ,,madder ,,lake4--7a7 ,tie #b oz4 madder in a cloth1 beat it well in a pint of water in a stone mortar1 and repeat the process with about #e pints of fresh water till it ceases to yield colour2 boil the mixed liquor in an earthern vessel1 pour into a large basin1 and add #a oz4 alum dissolved in #a pint boiling water2 stir well1 and gradually pour in #a oz4 of strong solution of carbonate of potash2 let stand until cold1 pour off the yellow liquor from the top1 drain1 agitate the residue repeatedly in #a qt4 boiling water1 decant1 drain1 and dry4 7b7 ,add a little solution of acetate of lead to a decoction of madder1 to throw down the brown colouring matter2 filter1 add solution of tin or alum1 precipitate with solution of carbonate of soda or potash1 and proceed as before4 7c7 ,macerate #b lb4 ground madder in #a gal4 water for #aj minutes2 strain and press quite dry2 repeat a second and third time1 and add to the mixed liquors lb4 alum dissolved in #c qt4 water2 heat in water-bath for #c-d hours1 adding water as it evaporates2 filter first through flannel1 and when cold enough through paper2 add solution of carbonate of soda as long as precipitate falls2 wash the latter till the water comes off colourless1 and dry4 ,,yellow ,,lakes4--7a7 ,boil #a lb4 ,persian berries1 quercitron-bark1 or turmeric1 and #a oz4 cream of tartar1 in #a gal4 water till reduced to half2 strain the decoction1 and precipitate by solution of alum4 7b7 ,boil #a lb4 of the dyestuff with lb4 alum in #a gal4 water1 and precipitate by solution of carbonate of potash4 7c7 ,boil #d oz4 annatto and #ab oz4 pearlash in #a gal4 water for hour2 strain1 precipitate by adding #a lb4 alum dissolved in #a gal4 water till it ceases to produce effervescence or a precipitate2 strain and dry4 ,for information concerning the numerous coal-tar colours now largely manufactured into lakes1 the reader is referred to 8,spon's ,encyclopdia of ,industrial ,arts40 ,,chapter ,x4 ,,luminous ,,paints4 ,the luminosity of minerals has an obvious practical value in the case of such substances as can be conveniently applied in the form of a paint to surfaces which are alternately exposed to light and darkness1 such exposed surfaces emitting at one time the light which they have absorbed at another4 ,familiar illustrations are street plates1 buoys1 and interiors of railway carriages having to traverse many tunnels4 ,the light absorbed may be either daylight or powerful artificial light4 ,with this object1 several compositions are prepared under the generic name of luminous paints4 ,they are chiefly as follows3-- 7#a7 ,balmain's4--,this consists of a phosphorescent substance introduced into ordinary paint4 ,the phosphorescent substance employed for the purpose is a compound obtained by simply heating together a mixture of lime and sulphur1 or substances containing lime and sulphur1 such as alabaster1 gypsum1 c41 with carbon or other agent1 to remove a portion of the oxygen present2 or by heating lime in a vapour containing sulphur4 ,in applying this phosphorescent powder1 the best results are obtained by mixing it with a colourless varnish made from mastic and turpentine2 drying oils1 gums1 pastes1 sizes1 c41 may1 however1 also be used4 7#b7 ,a ,french compound4--#ajj lb4 of a carbonate of lime and phosphate of lime produced by the calcination of sea-shells1 and especially those of the genus ,tridacna and the cuttle-fish bone1 intimately mixed with #ajj lb4 of lime rendered chemically pure by calcination1 #be lb4 of calcined sea-salt1 #be-ej per cent4 of the whole mass of sulphur1 incorporated by the process of sublimation1 and #c-g per cent4 of colouring matter in the form of powder composed of monosulphide of calcium1 barium1 strontium1 uranium1 magnesium1 aluminium1 or other mineral or substance producing the same physical appearances1 i4 e4 which1 after having been impregnated with light becomes luminous in the dark4 ,after having mixed these five ingredients intimately1 the composition obtained is ready for use4 ,in certain cases1 and more especially for augmenting the intensity and the duration of the luminous effect of the composition1 a sixth ingredient is added1 in the form of phosphorus reduced to powder1 which is obtained from seaweed by the well-known process of calcination4 ,as to proportion1 it is found that the phosphorus contained in a quantity of seaweed1 representing #be per cent4 of the weight of the composition formed by the five above-named ingredients1 gives very good results4 ,the phosphorescent powder thus obtained and reduced to paste by the addition of a sufficient quantity of varnish1 such as copal1 may serve for illuminating a great number of objects1 by arranging it in more or less thick coatings1 or by the application of one or more coatings of the powder incorporated in the varnish1 or by varnishing previously and sprinkling the dry powder upon the varnish4 ,the amount of powder applied should not exceed the thickness of a thin sheet of cardboard4 ,the dry phosphorescent powders are also converted into translucent flexible sheets of unlimited length1 thickness1 and width1 by mixing them with about #hj per cent4 of their weight of ether and collodion in equal parts in a close vessel1 and rolling the product into sheets1 with which any objects may be covered which are intended to be luminous in the dark4 ,the powders may also be intimately mixed with stearine1 paraffin1 rectified glue1 isinglass1 water glass1 or other transparent solid matter1 in the proportion of #bj to #cj per cent4 of the former with #ej to #hj per cent4 of either of these substances1 and this mass is then reduced into sheets of variable length1 width1 and thickness1 according to their intended applications4 ,a luminous glass is also manufactured by means of the powders1 by mixing them in glass in a fused state in the proportions of #e to #bj per cent4 of the mass of glass4 ,after the composition has been puddled or mixed1 it is converted into different articles1 according to the ordinary processes2 or after the manufacture of an object still warm and plastic1 made of ordinary glass1 it is sprinkled with the powders1 which latter are then incorporated into the surface of the article by pressure exerted in the mould1 or in any other suitable way4 ,it has been observed1 after various trials1 that the passage of an electric current through the different compositions augments their luminous properties or brilliancy to a great extent2 this peculiarity is intended to be utilised in various applications too numerous to describe1 but of which buoys form a good example4 ,the current of electricity is furnished by plates of zinc and copper mounted on the buoy itself1 when the latter is used at sea2 but in rivers and fresh-water inlets the battery will be carried in the interior of the buoy4 ,to secure the full effect1 #aj to #bj per cent4 of fine zinc1 copper1 or antimony dust is added to the phosphorescent powder described4 7#c7 ,take oyster-shells and clean them with warm water2 put them into the fire for hour2 at the end of that time take them out and let them cool4 ,when quite cool1 pound them fine1 and take away any grey parts1 as they are of no use4 ,put the powder in a crucible with alternate layers of flowers of sulphur4 ,put on the lid1 and cement with sand made into a stiff paste with beer4 ,when dry1 put over the fire and bake for an hour4 ,wait until quite cold before opening the lid4 ,the product ought to be white4 ,you must separate all grey parts1 as they are not luminous4 ,make a sifter in the following manner3--,take a pot1 put a piece of very fine muslin very loosely across it1 tie around with a string1 put the powder into the top1 and rake about until only the coarse powder remains2 open the pot1 and you will find a very small powder4 ,mix it into a thin paint with gum water1 as two thin applications are better than one thick one4 ,this will give paint that will remain luminous far into the night1 provided it is exposed to the light during the day4 7#d7 ,sulphides of calcium1 of barium1 of strontium1 c41 give phosphorescent powders when duly heated4 ,each sulphide has a predominant colour1 but the temperature to which it is heated has a modifying effect on the colour4 ,calcine in a covered crucible1 along with powdered charcoal1 sulphate of lime1 sulphate of baryta1 or sulphate of strontia2 there is produced in each case a greyish white powder1 which1 after exposure to strong light 7either sun-light or magnesium light71 will be phosphorescent1 the colour depending on the sulphate used and the degree of heat employed4 7#e7 ,five parts of a luminous sulphide of an alkaline earth1 #aj of fluorspar1 cryolite1 or other similar fluoride1 #a of barium borate2 powdered1 mixed1 made into a cream with water1 painted on the glass or stone article1 dried1 and fired in the usual way for enamels4 ,if the article contains an oxide of iron1 lead1 or other metal1 it must be first glazed with ground felspar1 silica1 lime phosphate1 or clay1 to keep the sulphur of the sulphide from combining with the metal4 ,the result is an enamelled luminous article4 7,heaton and ,bolas47 7#f7 ,boil for #a hour #b oz4 caustic lime1 recently prepared by calcining clean white shells at a strong red heat1 with #a oz4 pure sulphur 7flowers7 and #a qt4 soft water4 ,set aside in a covered vessel for a few days2 then pour off the liquid1 collect the clear orange-coloured crystals which have deposited1 and let them drain and dry on bibulous paper4 ,place the dried sulphide in a clean graphite crucible provided with a cover4 ,heat for hour at a temperature just short of redness1 then quickly for about #ae minutes at a white heat4 ,remove cover1 and pack in clay until perfectly cold4 ,a small quantity of pure calcium fluoride is added to the sulphide before heating it4 ,it may be mixed with alcoholic copal varnish4 7,boston ,jl4 ,chem47 ,the luminous calcic sulphide 7also called sulphide of calcium71 now obtainable in the market1 has a yellowish white tint1 which considerably limits its direct application as a paint4 ,on the other hand1 the calcic sulphide1 or the luminous paint obtained therefrom1 loses its luminous property1 if it is directly mixed with the ordinary commercial paints4 ,schatte1 of ,dresden1 produces durable white or coloured paints1 containing a luminous substance which causes them to shine in the dark1 without changing or neutralising in daylight the tint of the colouring substance or substances contained in such paints4 ,for this purpose1 ,zanzibar or cowrie copal is melted over a charcoal fire1 #ae parts of this melted mass are dissolved in #fj parts of ,french turpentine1 and the resulting mixture is filtered1 whereupon #be parts of pure linseed oil are added1 which linseed oil has been previously boiled and allowed to cool a little4 ,the lake varnish thus obtained is carefully treated in a paint mill with granite rollers1 and worked into a luminous paint by one of the processes hereinafter described4 ,iron rollers capable of giving off under great pressure small particles of iron1 which might affect the luminous power1 should not be used4 ,lake varnish as obtained in commerce contains nearly always lead or manganese1 which would destroy the luminous power of the calcic sulphide4 ,the proportions given are as follows3-- ,pure ,white3 ,by mixing #dj parts of lake varnish obtained as described with #f parts of prepared baric sulphate1 #f parts of prepared calcic carbonate1 #ab parts of prepared zinc sulphide white1 and #cf parts of calcic sulphide in a luminous condition1 in an oil vessel1 and worked into a coarse emulsion1 which is then ground fine between the rollers4 ,red3 #ej parts of the said lake varnish are mixed with #h parts of prepared baric sulphate1 #b parts of prepared madder lake1 #f parts of prepared realgar 7diarsenious disulphide71 and #cd parts of calcic sulphide in a luminous condition1 and the mixture is worked in the same way as described for white4 ,orange3 #df parts varnish are mixed with #age parts prepared barium sulphate1 #a part prepared ,india yellow1 #ae parts prepared madder lake1 and #ch parts luminous calcium sulphide4 ,yellow3 #dh parts varnish are mixed with #aj parts prepared barium sulphate1 #h parts barium chromate1 and #cd parts luminous calcium sulphide4 ,green3 #dh parts varnish are mixed with #aj parts prepared barium sulphate1 #h parts chromium oxide green1 and #cd parts luminous calcium sulphide4 ,blue3 #db parts varnish1 #ajb parts prepared barium sulphate1 #fd parts ultramarine blue1 #ed parts cobalt blue1 and #df parts luminous calcium sulphide4 ,violet3 #db parts varnish1 #ajb parts prepared barium sulphate1 #bh parts ultramarine violet1 #i parts cobalt arsenate1 and #cf parts luminous calcium sulphide4 ,grey3 #de parts of the varnish are mixed with #f parts prepared barium sulphate1 #f parts prepared calcium carbonate1 #je part ultramarine blue1 #fe parts grey zinc sulphide4 ,yellowish-brown3 #dh parts varnish1 #aj parts precipitated barium sulphate1 #h parts auripigment1 and #cd parts luminous calcium sulphide4 ,luminous colours for artists' use are prepared by using pure ,east ,india poppy oil1 in the same quantity1 instead of the varnish1 and taking particular pains to grind the materials as fine as possible4 ,for luminous oil-colour paints1 equal quantities of pure linseed oil are used in the place of the varnish4 ,the linseed oil must be cold-pressed and thickened by heat4 ,all the above luminous paints can be used in the manufacture of coloured papers1 c41 if the varnish is altogether omitted1 and the dry mixtures are ground to a paste with water4 ,the luminous paints can also be used as wax colours for painting on glass and similar objects1 by adding1 instead of the varnish1 #aj per cent4 more of ,japanese wax and one-fourth the quantity of the latter of olive oil4 ,the wax colours prepared in this way may also be used for painting upon porcelain1 and are then carefully burned without access of air4 ,paintings of this kind can also be treated with water glass4 ,,chapter ,,xi4 ,,examination ,,of ,,pigments4 ,besides the chemical tests for purity and adulteration1 which necessarily must vary with each pigment1 there are certain other examinations which partake rather of a mechanical nature1 and which are applicable to practically all pigments without any modification4 ,they are directed chiefly to ascertaining fineness1 body1 colour1 and durability4 ,,fineness4--,fineness may be tested for as follows3--,a tall glass cylinder is filled with clean water1 and about oz4 of the pigment under examination is well shaken in the water2 the glass is placed on one side to settle out1 and the length of time taken to settle may be noted for future reference4 ,the finer the sample1 the longer the time it takes to settle out2 and the time in seconds may be taken as an approximate estimate of the fineness of the sample4 ,,body ,,or ,,covering ,,power4--,an equal and exact quantity1 say #ej gr41 of the sample under examination and of a standard sample of the same degree of fineness is weighed out1 and placed on two separate sheets of paper4 ,to each sample is added an equal quantity1 say #ae gr41 of vegetable black or of very finely ground barytes1 according as the pigment is a light or a dark-tinted kind4 ,the ingredients of each sample are most intimately and completely mixed1 and the tints of the two mixtures are compared by observation with the naked eye4 ,the pigment which most nearly retains its own colour1 possesses the greatest body or covering power4 ,,colour4--,the colour or tint of a pigment can only be estimated by comparing it with a standard sample2 this is done as follows3--,a sheet of black paper1 with1 a dead surface1 is spread out on a table in front of a window1 a small heap of the standard is placed on the paper1 and next to it a similar heap of the sample to be compared2 by means of a palette knife the surface of the two heaps is flattened out2 on now carefully looking at the two heaps1 the one which has the purest colour can readily be picked out4 ,the heaps should be looked at from several points of view before a final judgment is arrived at4 ,if the pigment is dark-coloured1 it should be spread on white paper1 taking care that the same kind of paper is used for the two samples4 ,durability4--,durability is not a difficult point to test1 but it takes some time to make a complete test4 ,the best method is to mix a small quantity of the pigment in question with raw linseed oil1 cover a piece of glass with the mixture1 and expose it outside to the action of the sun and air for some time1 noting at intervals how it behaves4 ,it is well for the sake of comparison to coat a second piece of glass with the mixture1 and keep this in a dark place4 ,the difference between the two from time to time will show how the pigment behaves under the influence of light and air4 ,as the durability of pigments is decidedly different according as they are used in oil or water-colour painting1 the oil in the former case acting as a protective agent1 it is well to use a similar test1 using a little gum water as a vehicle to mix the pigment with4 ,it will take from two to three months at least to properly test the durability of a pigment in summer1 while in winter the time will be increased considerably4 ,glass is the best substance to use1 as it is quite neutral1 and does not of itself introduce into the test any injurious element1 as wood or paper might do1 although these bodies may be used if thought desirable4 ,,chapter ,,xii4 ,,vehicles ,,and ,,dryers4 ,paint consists essentially of two parts1 the pigment 7see ,chapters ,i4 to ,,viii471 and the vehicle or medium4 ,in the case of oil paints1 a third substance termed a dryer becomes necessary1 to facilitate the 8drying10 or solidification of the vehicle4 ,a perfect vehicle should mix readily with the pigment1 forming a mass of about the consistency of treacle4 ,it should itself be colourless1 and have no chemical action upon the pigments with which it is mixed4 ,when spread out in a thin layer upon a non-porous substance1 it should solidify1 and form a film not liable to subsequent disintegration or decay1 and sufficiently elastic to resist a slight concussion4 ,unfortunately1 we possess no vehicle which complies with all these conditions2 those which most nearly approach them are the drying oils4 ,oils are compound bodies containing acids and a base4 ,some oils oxidise very rapidly1 while others do not oxidise at all4 ,when oils oxidise they change their colour1 and however white they may be at first1 they gradually turn yellow and finally brown4 ,the advantages of oils are that they mix kindly with most pigments1 can be dissolved in turpentine1 and can be used in almost any desired state of fluidity4 ,against these have to be set the disadvantage of the oxidation of the oil1 to which oxidation the use of oil in paint is entirely due4 ,the use of oil in painting is said to have been invented in the #adth century1 and1 in a short time1 it reached a considerable degree of perfection4 ,we have only to compare a ,van ,eyck with a painting by a modern master--,turner1 for instance--to see that even the best of recent painters have not succeeded in giving to their works that durability which the originators of the method attained4 ,all organic substances are liable to a more or less rapid oxidation1 especially if exposed to light and heat4 ,oil is no exception to this rule2 but it seems that1 in its pure state1 it is much more durable than when mixed with other substances4 ,although ground-nut-and poppy-oils are sometimes employed by artists where freedom from colour is essential1 yet linseed-oil is the vehicle of by far the larger proportion of paints used both for artistic and general purposes4 ,oil-paint appears to have been unknown to the ancients1 who used various vehicles1 chiefly of animal origin4 ,one of these1 which was in high repute at ,rome1 was the white of eggs beaten with twigs of the fig-tree4 ,no doubt the india-rubber contained in the milky juice exuding from the twigs contributed to the elasticity of the film resulting from the drying of this vehicle4 ,pliny was aware of the fact that when glue is dissolved in vinegar and allowed to dry1 it is less soluble than in its original state4 ,many suggestions have been made in modern times for vehicles in which glue or size plays an important part4 ,in order to render it insoluble1 various chemicals have been added to its solution1 such as tannin1 alum1 and a chromic salt4 ,none of these vehicles1 however useful for special purposes1 has become sufficiently well known to warrant description here4 ,substitutes which do claim attention are wax and dammar gum1 or paraffin wax1 dissolved in turpentine4 ,the colours must then be ground in turpentine and not in oil4 ,such a vehicle is very pleasant to work with1 and gives good results2 moreover1 it permits alterations or corrections to be made by rubbing out with turpentine4 ,nevertheless1 both the wax and the turpentine undergo oxidation to some extent1 and are therefore not altogether free from the same objections as oils4 ,but benzol1 especially when carefully prepared1 answers all the purposes of turpentine without undergoing oxidation4 ,the only drawback that can be urged against benzol is its odour1 which some people have an aversion to2 but it really has very little smell1 and it evaporates away completely in a very short time4 ,a mixture of wax1 dammar1 and benzol forms an excellent vehicle4 ,the wax may be replaced by paraffin wax with advantage4 ,it is desirable to be able to ascertain whether the oil intended for use is1 or is not1 adulterated with non-drying oil4 ,the distinction of non-drying oils is that they solidify when acted upon by peroxide of hydrogen1 or by sub-nitrate of mercury--the oleic acid is concreted1 and a substance called elaidin is formed4 ,this does not take place with the drying oils4 ,the oils used in paint making are chiefly-- ,ground-nut4 ,hempseed4 ,kukui or candle-nut4 ,linseed4 ,menhaden4 ,poppy-seed4 ,tobacco-seed4 ,walnut4 ,wood or ,tung4 ,,ground-,,nut ,,oil4--,the ground-nut or pea-nut 7,arachis hypoga7 is very widely cultivated in the tropics for the sake of its oily seeds4 ,in ,java1 the oil is extracted by drying the seeds in the sun1 and then subjecting them to pressure4 ,in ,european mills1 the nuts are first cleaned1 then decorticated and winnowed1 by which the kernels are left perfectly clean4 ,these are crushed like any other oil seed1 and put into bags1 which are introduced into cold presses2 the expressed oil is refined by passing through filter-bags4 ,the residual cake is ground very fine1 and pressed under #c tons to the inch1 in the presence of steam-heat2 this affords a second quantity of oil1 inferior in quality to the cold pressed4 ,the usual product is #a gal4 of oil from #a bush4 of nuts by the cold process1 besides the extra yield by the hot pressing4 ,in ,france1 where the oil is most largely prepared1 three expressions are adopted1 as with some sorts of gingelly3 the first gives about #ah per cent4 of superfine oil1 fit for alimentary purposes2 the second1 after moistening with cold water1 affords #f per cent4 of a fine oil1 suitable for lighting and for woollen-dressing2 the third1 after treating with hot water1 yields #f per cent4 of rabat1 or oil applicable only to soap-making4 ,in ,india1 the total mean yield is #cg per cent4 at ,pondicherry1 and #dc in ,madras4 ,the cold-pressed oil is almost colourless1 of agreeable faint odour1 and bland olive-like flavour4 ,the best has a sp4 gr4 of about #jiah1 or #jiafc at #ei ,f42 it becomes turbid at #cg ,f41 concretes at #bf-be;,f41 and hardens at #ai ,f4 ,by exposure it changes very slowly1 but thickens with time1 and assumes a rancid odour and flavour4 ,it is not a good oil for paint4 ,,hempseed-,,oil4--,the seeds of the hemp plant1 so well-known as a fibre-producer1 are valued for their oil4 ,it is from ,russia and ,lorraine that the seed for expressing mostly comes4 ,when the fibrous stems are tied in bundles1 the seed is rudely threshed out1 and spread in thin layers under cover to dry4 ,the extraction of the oil is performed in the same manner as with other seed oils1 described on p4 #cjh4 ,the proportion of oil contained in the seed is about #cd per cent4 on an average2 the yield varies from #be to #cj per cent4 ,the oil is at first greenish or brownish-yellow1 deepening with exposure to the air2 the flavour is disagreeable1 and the odour is mild4 ,it has a sp4 gr4 of #jibeb at #ei ,f42 it thickens at #e ,f41 and solidifies at-#ac to-#ah ,f42 it dissolves in #cj parts of cold alcohol and any proportion of boiling2 it saponifies with difficulty1 forming a soft soap1 but less soft than that from linseed oil4 ,it is inferior for the painter's purposes4 ,,kukui ,,or ,,candle-,,nut ,,oil4--,an oil bearing a multitude of names is obtained from the candle-nut 7,aleurites moluccana74 ,it is the most important product of the tree1 and constitutes about two-thirds of the entire weight of the kernel of the nut4 ,a great obstacle to its wider development is the difficulty encountered in extracting the kernels from the shells1 both on account of the extreme hardness of the latter1 and the obstinacy with which the two adhere4 ,boiling is out of the question1 as the kernels are cooked long before the shells are affected2 but there is every reason to suppose that a slight roasting would have the desired effect1 inasmuch as this plan seems to be adopted successfully by the ,samoans4 ,the weight of the shells necessitates this treatment being performed on the spot1 and1 as the kernels quickly become rancid and dark-coloured after liberation1 they must also be operated upon without removal4 ,the local cheapness of labour is an additional argument in favour of preparing the oil at the places where the nut grows4 ,the extraction of the oil is very simple4 ,in ,jamaica1 ,polynesia1 and the ,east ,indies1 #ej per cent4 is obtained by boiling the kernels in water2 by reducing the kernels to meal1 heating in a water-bath1 and placing the mass in bags under hydraulic pressure1 the yield is about #fj-ff per cent4 ,the shells are themselves excellent fuel4 ,the oil is completely clarified by mere filtration4 ,as ordinarily prepared1 it is amber-coloured1 tasteless and odourless2 slightly viscid at the temperature of the air in ,england1 congealing at #cb ,f42 its sp4 gr4 is #jibc2 it is insoluble in alcohol1 and saponifies readily1 giving a very soft soda-soap4 ,it dries less rapidly than linseed oil1 and is used for mixing paints and making oil-varnishes4 ,it is said to corrode tin plate and even platinum4 ,,linseed-,,oil4--,the flax plant1 so well known as yielding a textile fibre1 affords a valuable oil-seed4 ,the supplies of linseed for crushing are furnished chiefly by ,russia and ,india4 ,it is found that1 as a general rule1 the colder the climate in which the seed is grown1 the greater are the drying properties of the oil1 but the worse is its colour4 ,in ,india1 preference is given to white seed1 as yielding #b per cent4 more oil1 affording it more freely1 and giving a softer and sweeter cake1 than the red seed2 the latter1 moreover1 always comes to market largely mixed with rape-seed1 which is very difficult of separation1 and greatly depreciates the market value4 ,oil from unripe seed is watery4 ,the seed should always be kept for #c-d months in a dry place1 as the oil furnished after this lapse of time is much more abundant than when the expression takes place immediately after the harvest4 ,the seed is crushed and pressed in the manner described on p4 #cjh4 ,the best and finest oil is that which is 8cold-drawn02 it is paler1 less odorous1 and less flavoured1 but the yield is only #ba-bb per cent4 of the seed4 ,by the aid of a temperature not exceeding #bjj ,f41 and powerful and long-continued pressure1 as much as #bh per cent4 of very good oil can be obtained4 ,the cake forms a valuable cattle food4 ,the ,italian variety is said to have a much more highly oleaginous seed than the ,russian4 ,linseed-oil has a faint colour1 and mild odour and flavour when pure1 but the commercial article is dark-yellow1 with sharp repulsive flavour and odour4 ,its sp4 gr4 is #jicj2 at #j ,f41 a little solid fat separates out2 at-#d ,f41 it solidifies4 ,by exposure to the air1 after heating with oxide of lead1 it rapidly dries up to a transparent varnish4 ,the fresh oil saponifies readily1 giving a yellow and very soft soap with soda2 by saponification1 it yields #ie per cent4 of fatty acids1 chiefly linoleic1 with a little oleic1 palmitic1 and myristic acids4 ,it dissolves in #af parts of ether1 and in #cb parts of alcohol at #jhbj sp4 gr4 ,the oil is very extensively used in the manufacture of paint and oil-varnishes4 ,for artists' use it is purified by shaking up with whiting1 and warming4 ,linseed-oil is never met with in commerce really pure1 nor even the seed itself4 ,previous to the ,crimean ,war1 it was a recognised custom at the ,black ,sea ports to add one measure of hemp or other seed to every #ci of linseed4 ,since then the proportion has advanced to #a in #ai1 in addition to which the ,indian seed is grown mostly as a mixed crop with mustard and colza3 pure linseed oil can only be obtained by picking out the seeds individually4 ,linseed-oil1 to be suitable for painting1 must dry well4 ,a reliable test is to cover a piece of glass with a film of the raw oil1 and to expose it to a temperature of about #ajj ,f4 ,the time which the film requires to solidify is a measure of the quality of the oil4 ,if the oil has been extracted from unripe or impure seed1 the surface of the test-glass will remain 8tacky0 or sticky for some time1 and the same will happen if the oil under examination has been adulterated with either an animal or vegetable non-drying oil4 ,until recently1 linseed oil was frequently adulterated with cotton-seed oil1 extracted from the waste seeds of the cotton plant4 ,where the admixture was considerable1 it could easily be detected by the sharp1 acrid taste of the cotton-seed oil4 ,now1 however1 means have been found for removing this disagreeable taste1 and the consequence has been that cotton-seed oil is so largely used for adulterating olive-oil1 or as a substitute for it1 that its price has risen above that of linseed oil4 ,another adulterant which is rather difficult to detect is rosin4 ,oil containing this substance is thick1 and darker in colour than pure oil4 ,when the proportion of rosin is considerable1 its presence may be ascertained by heating a film of the oil upon a metallic plate1 when the characteristic smell of burning rosin will be perceptible4 ,when the percentage of rosin is too small for detection in this manner1 a film of the oil should be spread upon glass and allowed to dry4 ,when quite hard1 the film should be scraped off1 and treated with cold turpentine1 which will dissolve any rosin which may be present1 without materially affecting the oxidised oil4 ,the presence of rosin may also be detected by the following simple chemical test4 ,the oil is boiled for a few minutes with a small quantity of alcohol 7sp4 gr4 ,o#i71 and is allowed to stand until the alcohol becomes clear4 ,the supernatant liquid is then poured off1 and treated with an alcoholic solution of acetate of lead4 ,if the oil be pure1 there will be but a very slight turbidity1 while the presence of rosin causes a dense flocculent precipitate4 ,should linseed oil be adulterated with a non-drying oil1 it will remain sticky for months when spread out in a thin film upon glass or any other non-absorbent substance4 ,the sp4 gr4 of linseed oil is1 in some cases1 of value in estimating its quality2 but as the variations are slight1 it would be difficult to detect them in so thick a liquid by means of an ordinary hydrometer4 ,a simple method of obtaining an approximate result is to procure a sample of oil of known good quality1 and to colour it with an aniline dye4 ,a drop of this tinted oil will1 when placed in the oil to be tested1 indicate1 by its sinking or swimming1 the relative density of the liquid under examination4 ,freshly-extracted linseed oil is unfit for making paint4 ,it contains water and organic impurities1 respecting the composition of which little is known1 and which are generally termed 8mucilage40 ,by storing the oil in tanks for a long time1 the water and the greater part of the impurities are precipitated1 forming at the bottom of the cistern a pasty mass known as 8foots40 ,to accelerate the purification of the oil1 and to remove at least a portion of the colouring matter1 various methods are in use4 ,the action of sulphuric acid upon linseed-oil is not so favourable as upon other oils4 ,it is1 however1 sometimes employed1 in the proportion of two parts of a mixture of equal volumes of commercial sulphuric acid and water to #ajj parts of oil4 ,the dilute acid is poured gradually into the oil1 and the mixture is violently agitated for several hours4 ,it is then run into tanks1 and allowed to settle4 ,a concentrated solution of chloride of zinc has been substituted for sulphuric acid in the proportion of about #a per cent4 of the weight of the oil4 ,when the reaction is complete1 steam or warm water is admitted into the liquid1 in order to clarify it4 ,oil treated in this way loses a considerable proportion of the colouring matter which it originally contained4 ,when the oil is to be used for white paint1 it is sometimes bleached by exposing it to the action of light4 ,on a large scale1 this is done by placing it in shallow troughs1 lined with lead and covered with glass4 ,the lead itself appears to have some influence upon the bleaching of the oil1 for the decoloration is not so rapid if the troughs be lined with zinc4 ,for small quantities1 a shallow tray of white porcelain or earthenware1 similar to those in use for photographic purposes1 gives very good results1 the white surface increasing the photo-chemical action4 ,it is not quite clear whether the presence of water accelerates the bleaching of oil by this method2 some manufacturers consider its presence necessary1 others omit it4 ,various salts are added to the water1 the one most in use being copperas4 ,however the oil may have been prepared1 it will1 if kept a long time1 deposit a sediment4 ,at first this contains mucilage2 but the sediment from old oil consists chiefly of the products of decomposition of the oil itself4 ,the presence of oxygen is not necessary for this decomposition2 but it is increased by the action of light4 ,raw linseed-oil dries more slowly than boiled2 but the resulting film is more brilliant and durable4 ,raw and boiled oil are therefore usually mixed in proportions varying according to the time which can be allowed for the paint to dry1 or to the properties required of the film4 ,for the ordinary kinds of paint1 equal parts of boiled and raw oils are customary4 ,linseed-oil heated to a temperature of #cej-djj ,f4 dries much more rapidly than in its raw state4 ,,menhaden ,,oil4--,a fish eagerly sought for its oil on the ,atlantic coast of ,america' is the 8,menhaden0 or 8porgie0 7,alosa ,brevoordia ,menhaden71 a member of the herring family1 about #h-ad in4 long4 ,the fishery is carried on all along the coast from ,maine to ,maryland4 ,the fish leave the ,gulf ,stream and strike the coast of ,new ,jersey in ,april1 reaching the coast of ,maine in ,may-,june1 and remaining till ,october-,november4 ,they migrate in enormous schools1 and are caught in seines1 carried by the fastest and smartest yachts4 ,very few of the fish are sent to the table2 nearly all are boiled down for their oil4 ,this is performed in the following manner3--,the fish are shot into receiving-tanks situated outside the building2 thence a sliding door opens into the boiling-tanks1 which are long1 watertight1 uncovered boxes1 of varying capacity1 provided with a coil of perforated pipe for the admission of steam1 and a plug-hole for the exit of the liquid after boiling4 ,some water is put into the tanks ready for the fish1 and as soon as the latter have been introduced1 steam is turned on1 and the whole mass is boiled for #bj-dj minutes4 ,when the cooking is completed1 the liquor1 containing a portion of the oil of the fish1 is drawn off into settling tanks1 for the recovery of the oil4 ,the 8pomace0 or cooked fish is raked into 8curbs10 perforated cylinders fitted with hinged bottoms1 and these1 when full1 are placed under hydraulic presses4 ,pressure is applied so long as water and oil continue to escape from the mass4 ,the remaining solid matters1 called 8scrap10 are treated for the preparation of a fertilising compost4 ,the oil and water pass by gutters into settling tanks1 where the oil soon rises to the surface1 and is skimmed off1 or allowed to escape over a separating partition4 ,the oil is still crude1 and requires clarifying and bleaching before it becomes a saleable commodity4 ,this is effected in several ways4 ,it is first boiled1 to free it completely from water4 ,it is purified from solid matters by running it into filter-bags suspended over casks1 and then subjecting it to pressure in bags1 the oil escaping while the sediment remains in the bags4 ,this refuse1 termed 8foots10 is bleached and used for soap-making4 ,the oil thus refined is termed 8traits10 and is ready for barrelling4 8,bank0 is an inferior grade4 ,bleaching is sometimes performed by exposure to the sun in shallow tanks1 having glass covers to exclude dust when a superior quality is desired4 ,its principal application in ,america is for tanning and currying purposes4 ,in ,france1 it is largely employed as a substitute for cod-liver oil4 ,in this country1 it is often passed off as olive-oil1 and considerable quantities of it are mixed with linseed-oil for painters' use4 ,the rapidity with which it oxidises1 and its good body1 render it not unsuitable as a vehicle for paint4 ,,poppy-,,seed ,,oils4--,oil is yielded by the seeds of three kinds of poppy--the opium-poppy 7,papaver somniferum71 the spiny-poppy 7,argemene mexicana71 and the yellow-horn poppy 7,glaucium luteum74 ,in ,asia ,minor and ,persia1 after the collection of the opium from the poppy-heads1 the latter are gathered1 and the seed is shaken out and preserved4 ,it is black1 brown1 yellow1 or white2 some districts produce more white seed than others4 ,the seed is pressed in wooden lever presses to extract the oil1 which is used by the peasants for culinary and illuminating purposes4 ,some of the seed is also sold to ,smyrna merchants1 who ship it to ,marseilles1 where it is employed in soap-making1 and as a substitute for linseed-oil4 ,the average yield of oil is #ce-db per cent41 the white seed being considered the richest4 ,the same economy takes place in ,india1 where the plant is also grown for the sake of its seed alone in some districts4 ,in this latter case1 the sowing takes place in ,march-,april1 about #b lb4 of seed being sown broadcast to one acre4 ,the seed vessels ripen in ,august2 the heads are then cut off1 sun-dried1 sorted1 and trodden out in bags1 or threshed4 ,the seed is immediately crushed and pressed1 the yield of oil being in proportion to the freshness of the seed1 and amounting to #ad oz4 from #d lb4 under favourable conditions4 ,the oil readily bleaches by exposure to the sun in shallow vessels1 and is then transparent and almost tasteless4 ,the natives use it very largely for cooking purposes1 and as a lamp-oil4 ,the cake is consumed as food by the poorer classes4 ,the unpressed seed is largely exported from ,india4 ,france grows a large quantity of poppy-seed at home1 over #ajj1jjj acres having been returned as under this crop some few years since4 ,the ,french oil is of two kinds1 a white cold-drawn oil1 and a coarser oil obtained by a second expression and from inferior seed1 the total yield being #dj per cent4 ,the finer oil is fit for alimentary purposes1 and is largely used to adulterate olive-oil2 it is also employed as a lamp-oil1 and very extensively by artists for grinding light pigments1 as1 though possessing less strength and tenacity than linseed-oil1 it keeps its colour better4 ,the pure oil has a golden-yellow tint and agreeable flavour2 its sp4 gr4 is #jibd at #ei ,f42 it solidifies at #j ,f41 and remains long in this state at #bh ,f41 is slow to become rancid1 and saponifies readily2 dissolves in #be parts cold and #f parts boiling alcohol1 and dries in the air more rapidly than linseed oil4 ,glaucium luteum is a common plant on the sandy shores of the ,mediterranean1 the western coast of ,europe as far as ,scandinavia1 and some parts of ,north ,america4 ,it is very hardy and cultivated with little trouble4 ,it prefers stony and chalky soils1 where few other plants will thrive1 and has therefore been recommended for culture on such otherwise waste land4 ,under cultivation1 it affords about #aj bush4 of seed per acre4 ,the seed contains #db per cent4 of oil1 and yields about #cb per cent4 by pressure4 ,the oil obtained by cold expression is devoid of odour and flavour1 and has a sp4 gr4 of #jiac4 ,it is applicable to culinary and illuminating purposes1 as well as for soap-making and paint4 ,the cake is a good phosphatic manure4 ,it seems to have been very little utilised1 probably on account of the comparatively small yield of seed4 ,,tobacco-,,seed ,,oil4--,the seeds of the tobacco-plant contain about #cj per cent4 of a fatty oil1 which is extracted by powdering them1 kneading them into a stiff paste with hot water1 and pressing hot4 ,the oil is clear1 limpid1 golden-yellow in colour1 inodorous1 and mild flavoured2 its density is #jibc at #ei ,f42 it remains liquid at #f ,f41 dissolves in #afh parts of alcohol at #jhaa sp4 gr41 and saponifies readily4 ,one authority excludes it from the drying oils2 another considers its drying quality to be unusually developed1 and recommends it for paints and varnishes4 ,,walnut ,,oil4--,the common walnut 7,juglans regia7 is found native from ,greece and ,asia ,minor1 over ,lebanon and ,persia1 along the ,indu ,kush to the ,himalayas1 and from the ,caucasus almost throughout ,china1 besides having been introduced generally throughout temperate ,europe4 ,in portions of the ,alps and ,apennines1 it is very abundant1 and is fairly plentiful in the forests of ,lazistan1 on the ,black ,sea1 but is perhaps most common in ,cashmere1 whence come the walnuts imported into the plains of ,india4 ,the albuminous kernel of the walnut affords some #ej per cent4 of oil4 ,it is said that it furnishes one-third of all the oil made in ,france2 it is extensively prepared in the central and southern departments1 notably ,charente1 ,charente-,infrieure1 and ,dordogne1 where it is commonly met with in barrels of #ej kilo4 ,in both ,spain and ,italy1 outside the olive-region1 walnut-oil is largely expressed4 ,it is of considerable importance in the hill districts of ,india1 but is seldom seen in the plains4 ,cashmere and ,circassia also include it among their industrial products4 ,the oil should not be extracted from the nuts until #b-c months after they have been gathered4 ,this delay is absolutely necessary to secure an abundant yield1 as the fresh kernel contains only a sort of emulsive milk1 and the oil continues to form after the harvest has taken place2 if too long a period elapse1 the oil will be less sweet1 and perhaps even rancid4 ,the kernels are carefully freed from shell and skin1 and crushed into a paste1 which is put into bags and submitted to a press2 the first oil which escapes is termed 8virgin10 and is reserved for feeding purposes4 ,the cake is then rubbed down in boiling water1 and pressed anew2 the second oil1 called 8fire-drawn10 is applied to industrial uses4 ,the exhausted cake forms good cattle-food4 ,the virgin oil1 recently extracted1 is fluid1 almost colourless1 with a feeble odour1 and not disagreeable flavour4 ,its sp4 gr4 is #jibf at #ei ,f41 and #jhga at #bja ,f42 it thickens to a butter-like consistence at #e ,f41 and solidifies to a white mass at-#ag ,f4 ,in the fresh state1 it is largely used in ,nassau1 ,switzerland1 and other countries1 as a substitute for olive-oil in salads1 c41 but is scarcely to be considered as a first-class alimentary oil4 ,the fire-drawn oil is greenish1 caustic1 and siccative1 surpassing linseed-oil in the last respect and exhibiting the property more strongly as it becomes more rancid4 ,on this account it is preferred by many artists before all other oils4 ,,wood-,,oil ,,or ,,tung-,,oil4--,this fatty oil is a product of the so-called 8oil tree0 of ,china1 ,cochin ,china1 and ,japan 7,aleurites cordata ,elococca vernicia1 ,dryandra cordata71 and must not be confounded with the ,malayan article1 which is an oleo-resin4 ,the fruit capsules of the t'ung are filled with rich oil-yielding kernels1 from which #ce per cent4 by weight of oil may be obtained by simple pressure in the cold4 ,the sp4 gr4 of the oil is #jicfb at #ei ,f4 ,it possesses several remarkable properties3 heated to #bab-cib ,f4 out of contact with the air1 it retains its original limpidity after cooling1 but in contact with the air it solidifies almost instantaneously1 melting again at #ic ,f1 and exhibiting the same elementary composition2 the cold expressed oil rapidly solidifies by light in the absence of air2 and its drying qualities exceed those of any other known oil4 ,it is devoid of colour1 odour1 and flavour4 ,the oil is produced in immense quantities in ,china2 in the provinces of ,ichang and ,szechuen1 it is one of the principal articles of native manufacture4 ,in ,china the oil is universally employed for caulking and painting junks and boats1 and for varnishing and preserving woodwork of all kinds4 ,the oil is unknown to ,european commerce1 but an attempt to naturalise the tree in ,algeria has been projected4 ,its industrial value has been too long neglected4 ,,extraction ,,of ,,seed-,,oils4--,the old-fashioned crude apparatus for extracting oil from seeds1 which answered the purposes of our forefathers1 has had to give way to modern improved machinery1 such as that manufactured by ,rose1 ,downs ,thompson1 of ,hull1 and shown in the subjoined illustrations4 ,illustration3 ,fig4 #cc4--,,seed-,,oil ,,mill4 ,the arrangement of the mill is shown in plan in ,fig4 #cc and in elevation in ,fig4 #cd4 ,the seed or other material passes through the following course3--,it runs from an upper floor through the roll frame ,a1 by which it is crushed three or four times2 it is then taken by the elevators ,b to the kettle ,c1 where it is heated and damped4 ,from beneath the kettle1 it is drawn1 in quantities sufficient to make a cake1 by a box which conveys it to the moulding machine ,e4 ,here it undergoes preliminary compression1 the objects of which are 7#a7 to increase the number of cakes which may be inserted in the presses at one time1 enabling #ah #ab-lb4 cakes to be made where #d #h-lb4 cakes were formerly made1 and 7#b7 to ensure uniform size and weight1 and uniform density or consistence throughout4 ,illustration3 ,fig4 #cd4--,,seed-,,oil ,,mill4 ,the cakes are removed from the moulding machine1 and put into the press ,f1 #c or #d of which are required to each moulding machine4 ,the pressure is applied either by means of hydraulic pumps1 or by a high and low pressure accumulator2 but unless extreme care is used with the latter1 it gives too rapid a pressure1 squirting out the seed at the side of the plates1 and exercising a destructive effect upon the cloth employed4 ,the pulsation caused by the pumps working directly to the press cylinder is more akin to the action of a wedge1 and seems to extract the oil better than the dead pressure given by the accumulator4 ,if the latter is used1 a small cylinder may be applied to give the preliminary pressure in the moulding machine1 in lieu of a cam4 ,after remaining under pressure about #be minutes1 the cakes are withdrawn1 and after being stripped of the cloth1 are pared by the machine ,h1 which completes the manufacture of the cakes4 ,the parings fall under a very small pair of edge-running stones ,j1 which automatically discharge them when sufficiently ground1 into an elevator conducting to the kettle1 where they are worked up with fresh seed4 ,in a mill with #d presses1 #b men and a boy in the press room can make #f tons of cake in #aa hours1 a rate of production requiring #f men by the old process4 ,the saving in steam power is about #cj per cent41 chiefly due to the absence of the heavy edge runners1 which also effects an economy of space4 ,about #b per cent4 more oil is extracted1 and the cakes are improved in appearance by not having the structureless texture caused by the trituration of the seed under edge-runners4 ,illustration3 ,fig4 #ce4--,,seed-,,crushing ,,rolls4 ,having described the general routine of the process1 some details may be added concerning the working of the several machines4 ,the roll-frame1 ,fig4 #ce1 consists of #d or #e chilled-iron rolls1 each #c ft4 #f in4 long by #af in4 in diameter1 placed one above the other4 ,these rolls are used for crushing all the seed that passes through one set of presses1 making #e-f tons linseed-cake per spell of #aa hours4 ,the seed passes into the hopper in the usual manner1 and is distributed to the crushing-rolls by a fluted feed roll the same length as the crushing-rolls1 placed at the bottom of the hopper4 ,when the seed passes the feed roll1 it falls on a guide-plate that carries it between the #ast and #bnd roll4 ,after passing between these rolls and being partly crushed1 it falls on a guide-plate on the other side1 which carries it back between the #bnd and #crd rolls1 where it is crushed more fully4 ,it then falls on another guide-plate1 which carries it between the #crd and #dth rolls1 where it is ground more fully4 ,then it falls on a #dth guide-plate1 and is conveyed between the #dth and #eth rolls to receive the finishing touch4 ,it is thus crushed four times4 ,the kettle is shown in ,fig4 #cf1 which represents one capable of heating sufficient seed to keep four #af-plate presses occupied1 or to make #f tons of cake per #aa hours4 ,it is steam jacketed and furnished inside with a damping apparatus4 ,the inside diameter is #e ft41 and the depth #b ft4 #f in4 ,the seed introduced is kept in motion by the stirring gear1 and when sufficiently heated and damped1 is withdrawn by the box ,a in quantities to form one cake1 and transferred at once to the moulding machine1 attached or separate4 ,this machine is illustrated in ,figs4 #cg1 #ch4 ,its purpose is to measure the quantity of seed required to make each cake1 to shape it as required1 and to press it so much1 without extracting any oil1 as will enable the greatest number of cakes to be put into the press4 ,the measure of seed is placed on a strip of woollen cloth1 spread upon a thin iron tray1 sliding on the guides ,b2 the bottomless hinged mould ,c1 having the exact shape of the intended cake1 is closed upon it1 and the measure ,a 7,fig4 #cf71 which is also bottomless1 is drawn over guides in the upper surface of the mould ,c1 thus accurately distributing the seed4 ,the mould is next thrown upon its hinge 7,fig4 #cg71 and the ends of the strip of cloth are folded over the seed1 the thickness of which is about #c in4 ,the thin iron tray1 with the mould of seed upon it1 is then pushed along the guides ,b1 beneath the die ,d4 ,this action gives motion to a cam1 shown above in the illustrations1 but which may be placed beneath if necessary4 ,this cam brings down the die and compresses the mould of seed to a thickness of #a in42 its revolutions are so timed that the seed is under pressure long enough 7about one-third of a minute7 to let the workman have another cake ready4 ,illustration3 ,fig4 #cf4--,,seed-,,boiling ,,kettle4 ,when the die of the moulding-machine rises1 the cake and tray are removed and placed in the press 7,fig4 #ci71 the tray being withdrawn4 ,the plates of the press are slightly thickened towards the edges1 and bear the name of the ,illustration3 ,fig4 #cg4--,,oil-,,cake ,,moulding ,,machine4 ,illustration3 ,fig4 #ch4--,,oil-,,cake ,,moulding ,,machine4 manufacturer in reverse4 ,the press is suitable for extracting oil from linseed1 rape-seed1 cotton-seed1 hemp-seed1 niger-seed1 sunflower-seed1 gingelly-seed1 castor-seed1 ground-nuts1 coco-nuts1 olives1 c4 ,it is made in various sizes4 ,the ,no4 #a ,illustration3 ,fig4 #ci4--,,oil-,,seed ,,press4 double press 7not shown7 is furnished with #d cake boxes1 suitable for making #d tapered cakes at one pressing1 each about #b ft4 #e in4 long1 by #aj in4 wide at one end1 and #g in4 at the other1 when using linseed1 #dh lb4 of ,bombay seed being required to charge the press1 and giving a cake weighing about #h lb42 the maximum and minimum weights of its charges are #fj lb4 and #dj lb41 of the cakes1 #ac lb4 and #f lb4 ,the charges vary from #c to #f an hour1 being #d for cotton-seed and #e for linseed2 most other seeds are worked the same as linseed1 but rape and gingelly are worked twice4 ,by using #b presses for the first time and #c for the second1 #c presses will crush as much seed as #e4 ,these presses are made of a capacity to take #bgj-cbj lb4 of seed at a charge1 giving cakes of #i-ae lb41 and requiring #cj-de minutes for the operation4 ,in all these presses1 the hair wrappers1 weighing some #bf lb41 used in the old process1 are dispensed with4 ,a very complete account of oils and fats will be found in ,spon's #8,encyclopdia of the ,industrial ,arts1' to which the reader is referred for further information4 ,,dryers4--,the maximum of drying power in oils is obtained by the addition of certain metallic oxides1 which not only part with some of their own oxygen to the oil1 but also act as carriers between the atmospheric oxygen and the heated liquid4 ,this heating of the oil with oxides is known as boiling1 although the liquid is not volatilised without decomposition1 as is the case with water4 ,at about #ejj ,f41 bubbles begin to rise in the oil1 producing acrid1 white fumes on coming into contact with the air4 ,the gas thus given off consists chiefly of vapour of acrolein mingled with carbonic oxide4 ,there is no advantage in heating the oil to a higher temperature than #cej ,f4 ,accurate experiments have shown that the drying properties of the oil are not increased by heating it beyond this point1 while its colour is considerably darkened4 ,for the finer qualities of boiled oils1 it is essential that the raw oil should have been stored for some time1 so that it may be free from mucilage4 ,this mucilage is the chief source of the dark colour of some boiled oils2 when heated1 it forms a brown substance1 which is soluble in the oil itself1 and extremely difficult to remove4 ,the oxides usually added to the oil during boiling are litharge or red-lead1 the former being preferred on account of its lower price4 ,about #b-e per cent4 by weight of the oxides or dryers is gradually stirred into the oil after it has been slowly raised to a temperature of about #cjj ,f4 ,the stirring should be continued until the litharge is dissolved1 or it would cake on the bottom of the pan1 and cause the oil to burn4 ,litharge may even be reduced to a cake of metallic lead when the fire is brisk4 ,some pans are furnished with stirrers and gearing by which the latter can be worked1 either by hand or steam4 ,the material of which the pans are made is either wrought or cast iron4 ,copper pans are sometimes used with the object of improving the colour of the oil4 ,little is known respecting the chemical reactions which take place during the boiling of oil4 ,even when the air is excluded during the process1 the drying properties are greatly increased1 and1 if boiled long enough1 the oil is converted into a solid substance4 ,the loss of weight which ensues is dependent upon the temperature and the time during which the operation continues4 ,it is less when the air is freely admitted than if the pan is covered with a hood4 ,the vapours given off by the oil are of an extremely irritating character1 and should be destroyed by passing them through a furnace4 ,as their mixture with air in certain proportions is explosive1 this furnace should be situated at some distance1 and the gases be conducted into it by means of an earthenware pipe4 ,since zinc oxide has been introduced as a substitute for white lead in painting1 researches have been made to replace litharge as a dryer1 because it is not logical to discard the lead pigment and then use a lead dryer with a zinc pigment4 ,several metallic oxides and salts1 especially zinc sulphate1 manganese oxide1 and umber1 have the property of combining with oils1 which they render drying4 ,to these may be added the protoxides of the metals of the third class1 i4 e4 iron1 cobalt1 and tin4 ,but these oxides are very unstable and difficult of preparation2 hence it became desirable to discover some means by which they might be combined with bodies which would enable them to be prepared cheaply1 and at the same time leave unimpaired their desiccating powers4 ,moreover1 it is acknowledged that dryers in the dry state are preferable in many respects to drying oils4 ,following are some of the recently introduced dryers3-- ,cobalt and ,manganese ,benzoates4--,benzoic acid is dissolved in boiling water1 the liquid being continually stirred1 and neutralised with cobalt carbonate until effervescence ceases4 ,excess of carbonate is removed by filtration1 and the liquor is evaporated to dryness4 ,the salt thus prepared is an amorphous1 hard1 brownish material1 which may be powdered like rosin1 and kept in the pulverulent state in any climate1 simply folded in paper4 ,painting executed with a paint composed of #c parts of this dryer with #ajjj of oil and #abjj of zinc-white1 dries in #ah to #bj hours4 ,manganese benzoate is prepared in the same way1 substituting manganese carbonate for that of cobalt4 ,applied under similar circumstances1 it dries a little more rapidly1 and a little less is required4 ,urobenzoic 7hippuric7 acid is equally efficacious4 ,cobalt and ,manganese ,borates4--,these salts also1 in the same proportions1 are found to be of equal efficacy4 ,the latter is extremely active1 and requires to be used in much smaller proportions4 ,resinates4--,if an alkaline resinate of potash or soda be dissolved in hot water1 and this solution be precipitated by a solution of a proportionate quantity of a cobalt or manganese chloride or sulphate1 an amorphous resinate is formed1 which1 after being collected on cloth filters1 washed1 and dried1 forms an excellent drier4 ,zumatic 7,transparent7 ,dryer4--,take zinc carbonate1 #ij lb42 manganese borate1 #aj lb42 linseed-oil1 #ij lb4 ,grind thoroughly1 and keep in bladders or tin tubes2 the latter are preferable4 ,zumatic 7,opaque7 ,dryer4--,manganese borate1 as a dryer1 is so energetic that it is proper to reduce its action in the following way3--,take zinc-white1 #be lb42 manganese borate1 #a lb4 ,mix thoroughly1 first by hand1 then in a revolving drum2 #a lb4 of this mixed with #bj lb4 paint ensures rapid drying4 ,manganese ,oxide4--,purified linseed-oil is boiled for #f or #h hours1 and to every #ajj lb4 boiled oil are added #e lb4 of powdered manganese peroxide1 which may be kept suspended in a bag1 like litharge4 ,the liquid is boiled and stirred for #e or #f hours more1 and then cooled and filtered4 ,this drying oil is employed in the proportion of #e to #aj per cent4 of the zinc white4 ,guynemer's4--,take pure manganese sulphate1 #a part2 manganese acetate1 #a part2 calcined zinc sulphate1 #a part2 white zinc oxide1 #ig parts4 ,grind the sulphates and acetate to impalpable powder1 sift through a metallic sieve4 ,dust #c parts of this powder over #ig of zinc oxide1 spread out over a slab or board1 thoroughly mix1 and grind4 ,the resulting white powder1 mixed in the proportion of or #a per cent4 with zinc-white1 will enormously increase the drying property of this body1 which will become dry in #aj or #ab hours4 ,manganese ,oxalate4--,a writer in the ,moniteur de ,produits ,chimiques draws attention to the properties possessed by manganese oxalate as a drier4 ,this salt has hitherto not had any important industrial uses1 but it can be readily prepared in a state of purity from the native carbonate by the action of oxalic acid2 the author is of the opinion that it will be found of use for this purpose4 ,if prepared from carbonate free from iron and lime1 it can be obtained as a fine crystalline white powder1 and two-fifths per cent4 suffices to bring about the change4 ,the oxalate is resolved by heat into manganese oxide1 carbonic acid and carbon monoxide1 and in the presence of fatty acids the manganese oxide formed combines with them1 the decomposition taking place at about #acj4 ,the operation is carried out by mixing in a mortar the oxalate with two or three times its weight of oil1 and then adding the mixture to the main portion of the oil4 ,the heat should be applied gradually1 and the decomposition is known to be complete when there is no further evolution of gas4 ,the boiled oil1 under this treatment1 preserves its limpidity and also remains colourless4 ,manganese oxalate has the advantage over oxide of lead1 which is commonly employed for this purpose1 in causing the oil to remain transparent when exposed to sulphur vapours4 ,manganese acetate has also been used1 but it likewise causes a darkening in the colour of the oil1 and the nitrate is dangerous owing to the possible action of nitric acid on the fats present in the oil4 ,manganese borate appears to be next in value to the oxalate as an oil drier4 ,in a paper recently read before the ,society of ,arts1 ,prof4 ,hartley remarked that paint1 such as is used for ordinary purposes1 is essentially composed of three materials1 without taking into account the coloured pigments4 7#a7 ,white lead1 or sublimed zinc-white4 7#b7 ,an oil1 generally linseed or poppy oil1 which is ground up with the white lead or zinc-white until it becomes a soft paste4 ,this is mixed with variable preparations of linseed oil and spirit of turpentine4 7#c7 ,a substance called dryers1 or siccative materials2 it may be linseed oil in which litharge is dissolved1 or it may be linseed oil containing a compound of manganese4 ,paint owes to the dryers its property of drying more rapidly than it would do without it2 and it is considered indispensable in buildings in all cases where paint applied to wood1 stone1 or metal1 would not be quite dry in #dh hours1 or at most in #gb hours1 after the first application4 ,the first question which requires an answer is1 what chemical process takes place when a paint dries4 ,,boiled ,,oil4--,linseed oil absorbs oxygen2 and1 when the oil contains manganese1 it absorbs oxygen much more greedily2 and when a manganese oil--that is to say1 a boiled oil containing manganese--is mixed with linseed oil1 the substance absorbs oxygen1 from a limited supply of air contained in a closed space1 until no trace of any other gas but nitrogen remains4 ,the power of absorbing oxygen possessed by #ajj volumes of linseed oil1 compared with that of #ajj volumes of a mixture of linseed oil and so-called manganese oil1 is as #id to #ajj4 ,this may be termed the measure of its drying power4 ,a mixture of linseed oil1 with a little more than one-fourth of its volume of manganese oil1 has a power of absorbing oxygen four and a half times greater than either of the components of the mixture taken separately4 ,in this case ,chevreul argues that linseed oil may be considered as a 8dryer0 to manganese oil4 ,linseed oil1 without any addition whatever1 if boiled for three hours1 becomes a better drying oil than it was previous to the action of heat4 ,oil boiled with #aj per cent1 of litharge for three hours1 is a much better dryer than when heated without this oxide4 ,oil boiled alone for five hours is an inferior drying oil to one heated for only three hours4 ,oil previously boiled alone for five hours1 and boiled alone again for three hours1 is scarcely altered in drying power1 but it becomes a better drying oil if it is boiled the second time with litharge4 ,it is inferior to a drying oil which has been boiled only three hours with litharge1 without being submitted to a previous boiling4 ,oil boiled alone for five hours1 boiled for a further period of three hours with manganese dioxide which has already been used for one operation1 is very nearly as strong a dryer as that which has been boiled with litharge under the same conditions2 but it is superior to an oil which has been boiled with manganese dioxide for eight hours4 ,this no doubt arises from the longer boiling with manganese having caused a larger quantity of manganese to dissolve1 and that the quantity dissolved is in excess of that which yields the best result4 ,finally1 oil boiled for five hours1 and then boiled alone once more for eight hours1 becomes viscous1 and the first coat requires a considerable time to dry4 ,we thus see that the oxides of lead and of manganese in certain proportions concur with heat in increasing the drying power of linseed oil4 ,this drying of oils is a process of slow oxidation4 ,the following points of ,chevreul's appeared to be difficult of satisfactory explanation1 and suggested to ,prof4 ,hartley an examination de novo of the facts1 as well as an investigation of the chemistry of the subject generally3-- #a4 ,linseed oil not boiled acted as a dryer to the same oil boiled with manganese dioxide4 #b4 ,linseed oil1 boiled with either litharge or manganese dried more rapidly when mixed with turpentine4 #c4 ,oil1 mixed with white lead1 zinc white1 antimony white1 and arseniate of tin1 acts differently1 thus3--,the white lead dries most rapidly1 the zinc white next1 but antimony white and arseniate of tin are incapable of acting as dryers1 in fact1 they retard the drying process4 #d4 ,oil boiled alone for five hours1 and boiled for a further period of three hours with manganese dioxide becomes a superior drying oil to one which has been boiled with manganese dioxide for eight hours4 ,from a series of experiments1 which were continued for two years1 on twenty-five weighed quantities of raw linseed oil1 ,prof4 ,hartley draws the following deductions3-- #a4 ,the chemical action of a manganese compound1 when dissolved in linseed oil1 is that of a carrier of oxygen from the atmosphere to the oil4 ,manganese oxide takes up oxygen from the air1 and transfers it to the oil1 and in so doing it suffers alternately the opposite processes of oxidation and reduction4 #b4 ,to obtain the best result1 the amount of manganese present must not exceed a certain small proportion of the oil4 #c4 ,oil to which turpentine has been added dries more rapidly than oil without such addition1 because the oil being diluted and rendered thinner1 it spreads over a larger surface1 and is in contact1 therefore1 with a much larger quantity of oxygen4 #d4 ,turpentine does not act as a dryer1 that is1 as a carrier of oxygen to linseed oil4 #e4 ,different white pigments behave differently when drying1 because the more powerfully basic the properties of the pigment1 the more powerful is its action as a dryer4 ,lead oxide and white lead 7basic lead carbonate7 combine more easily with the acids of linseed oil than zinc oxide does4 ,but zinc oxide dries better than antimony oxide1 because it is a stronger base1 while arseniate of tin has no basic properties1 therefore does not act as a dryer4 ,different substances1 that is to say1 those without chemical action on oil1 such as lamp-black1 sulphate of baryta1 and sulphate of lead1 cannot act as 8dryers40 ,linseed oil is a glyceride of a peculiar acid1 called linoleic acid4 ,whatever the exact constitution of linoleic acid may be1 linseed oil for the most part is composed of trilinolein4 ,raw linseed oil contains the following constituents3-- #a4 ,glyceride of linoleic acid or trilinolein ,c#ah;,h#ca,o,o#c4 ,c#c;,h#e #b4 ,water4 #c4 ,mucilage1 with the composition n7,c#f;,h#aj,o#e74 ,on boiling with dilute acids this yields a gum and a sugar4 #d4 ,an essential oil1 present in minute proportions1 and of unknown composition4 #e4 ,a mixture of colouring matters of intense tinctorial power1 viz4 blue and yellow chlorophylls and erythrophyll4 ,the only useful and desirable substance is the trilinolein4 ,the effect of oxidation upon linseed oil is to destroy all the glycerine1 and to produce therefrom carbonic1 formic1 and acetic acids1 together with some acrolein4 ,when boiled at a high temperature without the addition of any metallic oxide1 the glyceride is decomposed1 acrolein is formed1 and linoleic acid is set free4 ,in fact1 whether oil is oxidised by air or by metallic oxides1 or whether it be simply heated1 the action in each case first leads to the destruction of the glycerine and the liberation of linoleic acid4 ,but linoleic acid very readily absorbs oxygen1 and the oxidised substance becomes a tough elastic solid1 which is essentially a varnish4 ,in fact1 the process which an oil undergoes in drying is not desiccation1 or depriving it of moisture or of glycerine1 but solidification1 and the technical term 8drying0 is a misnomer4 ,that1 however1 is of little consequence if we really know what is the chemical action of the 8drying0 process4 ,when oxidised even at a low temperature1 the glycerine is destroyed1 and the oxidised products form a tough varnish4 ,there are various methods of converting linseed oil into a drying oil or varnish3-- #a4 ,heating it to a high temperature with litharge4 #b4 ,heating with red oxide of lead4 #c4 ,heating with metallic lead4 #d4 ,heating to a high temperature with manganic oxide4 #e4 ,heating with manganese borate4 #f4 ,heating with manganese oxalate4 #g4 ,by the joint action of air and heat upon the oil and manganous oxide1 or a solution of manganese dioxide or manganous oxide in the oil4 ,in the processes #a1 #b1 #c1 there can be no doubt that a lead of linoleic acid is produced1 and that this facilitates further oxidation in air1 by forming salts with some of the acid products of such oxidation1 while the oxidation of the linoleic acid continues4 ,heating with red lead favours oxidation1 by the compound itself conveying oxygen to the oil4 ,in the case of metallic lead1 it must be noted that the metal is dissolved4 ,under certain circumstances1 metals become dryers to oils2 thus sheets of metallic lead are capable of acting as dryers to linseed oil4 ,linseed oil is pre-eminent in its capacity for absorbing oxygen4 ,this action of metallic lead as a dryer is due to the metal becoming oxidised at the expense of the glycerine of the oil1 and so passing into solution by combining with the linoleic acid1 or with acetic or formic acid1 caused by the oxidation of the glycerine4 ,it is the destruction of the glycerine with concurrent oxidation of the fatty acid which causes the drying or hardening of the oil4 ,when a drying oil which has been treated with metallic lead1 or with litharge1 is shaken up with a solution of zinc sulphate1 all the lead is precipitated from the oil1 and zinc passes into solution therein4 ,by manganese sulphate or copper sulphate1 the lead is removed by manganese or copper4 ,oil charged with lead dries in #bd hours when spread out in a thin layer on glass2 it will dry completely in #e or #f hours if charged with manganese1 in #cj or #cf hours with copper1 zinc1 or cobalt2 and it requires more than #dh hours with nickel1 iron1 chromium1 c4 ,although solidification of a drying oil charged with manganese takes place in from #e to #f hours when spread in thin films1 the solidification of thicker films requires a longer time4 ,a temperature of #abb to #adj ,f4 accelerates the oxidation of the drying oils1 partly because the oil becomes more fluid1 and partly because the oxygen is more active at a higher temperature4 ,hence1 oil which has been mixed with an equal volume of turpentine1 or a light hydrocarbon1 such as benzene1 dries more rapidly than oil without such admixture4 ,when a boiled oil1 prepared with manganese1 is dissolved in an equal volume of benzene1 and shaken up with air in a bottle1 rapid absorption of oxygen occurs1 especially about #abj ,f4 ,if fresh air is repeatedly provided1 the oxidation is sufficient to cause the liquid to become thick1 and1 on distilling off the sapient1 a perfectly dry and elastic solid remains4 ,an oil containing manganese is a very superior drying oil to one which has been prepared with lead4 ,this fact1 however1 is to be noted1 that though a large proportion of manganese in an oil may hasten its drying1 yet it is disadvantageous1 because it does not form so tough a film4 ,this arises from the film becoming hard upon the surface1 and so protecting the oil underneath from absorbing oxygen from the air4 ,though the oils containing large quantities of dryers dry1 they afterwards lose weight1 and become viscous under the same conditions4 ,pure linoleates of lead and of zinc are not dryers2 but if heated until it has turned brown1 or begun to blacken1 a lead dryer becomes effective1 although it contains less of the lead compound4 ,in this case1 some compound of lead is formed by absorption of oxygen1 which either itself actually oxidises or causes the oxidation of ordinary linseed oil4 ,having treated of the materials used for producing boiled oil1 and of their action upon the oil1 let us now consider how the operation is brought about4 ,process #a4--,oil is boiled at a high temperature1 that is to say1 it is heated until frothing and bubbles of gas escape1 when litharge or a manganese compound is added4 ,process #b4--,oil is boiled at a steam heat1 with litharge or a manganese compound1 in conjunction with a blast of air4 ,process #a4--,the chemical action in the first process is doubtless one which takes place in three stages4 ,it commences by depriving the oil of water2 in the second stage1 it destroys the mucilage1 by charring it2 in the third1 it destroys1 in part1 the glycerine1 and sets free the fatty acids4 ,after the litharge or manganese compound is added1 there is formed in the oil a solution of lead salts of the fatty acids1 or a manganese salt of the fatty acids4 ,the oil then1 at the high temperature1 loses glycerine by oxidation caused by the air1 such oxidation being greatly facilitated by the presence of manganese compounds1 which are repeatedly oxidised by the air and reduced by the oil1 that is to say1 they absorb oxygen and pass it over to the oil with great facility4 ,it matters little1 so long as the ultimate action is oxidation1 what salt of manganese or what oxide is used1 if it be capable of undergoing processes of an alternate character called oxidations and reductions4 ,it is1 however1 certain that some manganese compounds are more suitable than others1 owing to their more or less complete solubility in the oil1 and their more readily undergoing the two different processes of oxidation and reduction in presence of air and of oil4 ,process #b4--,the credit of being the first to boil oil without resorting to the dangerous expedient of using an open fire and a high1 temperature in the manufacture1 is due to ,vincent4 ,he used manganese compounds1 or both manganese salts and litharge4 ,his method of boiling oil for the manufacture of printing inks is1 with some modifications in technical details1 carried out on a large scale at the present time in the preparation of ordinary boiled oil4 ,the essential parts of the plant are a steam-jacketed close boiler with agitating gear1 and a pipe for conducting a current of air into the oil by means of a blowing engine4 ,from the head of the boiler there passes a funnel under the back of the furnace fire1 by which the disagreeable products of the chemical action are conducted to a place where they are destroyed4 ,these products1 as already mentioned1 are volatile fatty acids and acrolein4 ,oil boiling1 as ordinarily carried out1 is conducted by means of litharge along with compounds of manganese2 in some processes these are mixed with salts of alumina and zinc4 ,the oil so produced is brown and not clear1 but it is clarified by keeping4 ,many samples of such boiled oil deposit insoluble matter when stored for some time1 even although they may have become clear previously4 ,this is not a desirable property4 ,sometimes rosin is added to hasten its drying4 ,the defects to be noticed1 even in the best samples of boiled oil1 are the following3-- #a4 ,the oil causes a brownish or yellow colour to be communicated to white lead or zinc white4 #b4 ,the oil darkens pigments containing brilliantly coloured metallic sulphides1 such as vermilion1 cadmium yellow1 and ultramarine blue4 #c4 ,delicate colours are darkened by the oil when exposed to ordinary town air1 that is to say1 air which1 is not quite pure4 ,this is the case even when the oils themselves may not injure the paints4 ,the causes of such alterations is1 in nine cases out of ten1 the use of lead dryers4 #a4 ,in the first place1 boiled oil which contains litharge or other lead compounds takes a permanent brown colour1 which affects the purity of white lead1 zinc white1 and delicate pale tints4 #b4 ,lead forms1 with extreme ease1 lead sulphide1 which1 in very minute proportions1 is yellow or brown2 in larger quantity its colour is black4 ,the lead sulphide is readily formed by contact with other sulphides1 as1 for instance1 vermilion1 cadmium yellow1 and ultramarine4 #c4 ,boiled oil1 containing lead1 is coloured brown by exposure to air1 owing to the presence of minute quantities of sulphuretted hydrogen1 which causes the formation of lead sulphide4 ,the remedy is obvious3 no oil should be used which has been boiled with dryers containing lead4 ,in other words1 oil should be boiled with pure manganese compounds only4 ,in cases where it is desirable to have information of the presence or absence of lead in a boiled oil1 the following test will be found most useful3--,a mixture is made of #d oz4 of glycerine with #a oz4 of ammonium sulphide1 the liquid being kept in a stoppered bottle4 ,or glycerine is mixed with an equal volume of water1 and saturated with sulphuretted hydrogen4 ,half an ounce of the oil to be tested is placed in a white basin1 with the addition of two or three drops of the glycerine solution4 ,the two liquids are thoroughly incorporated1 by stirring with a strip of glass4 ,a brown or black colour1 which gradually appears1 indicates the presence of lead4 ,a pure manganese oil simply becomes slightly yellow4 ,it is true that1 if iron is present1 a black colour might appear1 but iron is also an undesirable impurity4 ,should it be required to ascertain that the coloration is or is not caused by iron1 two or three drops of glacial acetic acid may be stirred into the oil1 when1 if the black colour remains1 it is certainly not caused by iron4 ,under the old process of oil-boiling at a high temperature1 the brown colour of the oil was1 to some extent1 an indication that the oil had been sufficiently heated--that is to say1 properly boiled2 but in the modern processes1 so largely used1 in which oxidation is aided by a blast of air1 this coloration is no indication whatever of the excellence of the oil2 it may be1 in fact1 the very reverse4 ,this fact appears to be unknown1 or1 at any rate1 is not a matter of common knowledge among practical men in this country1 who1 being uninformed as to the methods of preparing the oils1 consider that a brown colour is desirable1 if not essential4 ,when oil-boilers were compelled to adopt some expedient to give a reddish-brown colour to the oil1 they added a small amount of litharge1 the introduction of which actually spoils the oil1 and makes it unsuitable for many purposes to which it is otherwise applicable4 ,of late years1 pale boiled oils have been more largely manufactured for special purposes4 ,it is obvious that1 for decorative house painting1 in which delicate tints are a leading feature1 they may be advantageously employed4 ,notwithstanding that some of the brown oils1 when mixed with white lead1 do not entirely retain the brownish tint1 but1 to some extent1 lose it upon drying1 yet they never preserve the whiteness of white lead4 ,it follows1 therefore1 that a pale colour in the oil1 provided it is not the yellow colour of raw oil1 is greatly to be preferred4 ,moreover1 when paints are mixed with zinc white1 no trace of lead should be contained in the oil1 otherwise1 one of the valuable properties of zinc white pigments is destroyed1 namely1 its power to retain its whiteness in the atmosphere of a town1 because its colour is not affected by sulphuretted hydrogen4 ,very generally1 zinc white and white lead paints are not mixed with drying oils1 but with refined linseed or bleached oil4 ,this1 at any rate1 is the practice on the ,continent4 ,that is to say1 the pigments are mixed with an oil from which the impurities1 and the natural yellow and red colouring matter1 have been removed1 so that the colour of the paint is white4 ,if ordinary oil be used1 the paint is more or less yellow4 ,in order to render such paint quick drying1 a certain amount of dryers1 in a solid or liquid form1 is added4 ,these dryers almost invariably contain lead1 so that zinc white paint is contaminated by lead in another way1 which may not be suspected1 or which is overlooked4 ,now as to the chemical action of dryers on oils4 ,raw oil contains water and mucilage2 the former can be absorbed by anhydrous zinc salts and by dried alum1 and solutions of the salts and the salts themselves are capable of precipitating mucilage from the oil2 hence these substances cause the impurities to become insoluble1 so that they are carried down as 8foots40 ,heat greatly facilitates this action1 particularly by causing the oil to become more fluid2 and by the action of the anhydrous salts water is withdrawn from the oil4 ,on the 8drying0 or oxidation of the oil1 they exert no chemical action whatever4 ,zinc linoleate and lead linoleate do not act as dryers when simply added to the oil4 ,though the former is soluble in hot oil it is insoluble in cold oil1 and it therefore separates from the oil as it cools4 ,the latter is very soluble in linseed oil1 but only adds to its drying power when heated therewith4 ,in conjunction with a high temperature1 lead dissolves in oil at the expense of the glycerine1 which is decomposed into acrolein1 while lead linoleate is formed4 ,when litharge is heated with linseed oil1 the action is somewhat similar1 the substances formed being acrolein1 lead linoleate1 and linoleic acid4 ,if we consider the action of red lead on trilinolein1 we have not only the formation of these lead linoleates1 but an excess of oxygen available for the oxidation of glycerine to acrolein and acrylic acid1 or to acetic and formic acids4 ,these equations serve to show the effect of lead and lead oxides in what may be termed the initiation of the chemical action upon the oil4 ,subsequent changes1 no doubt1 depend upon the conditions which obtain at the time1 notably upon the temperature and upon access of air to the oil4 ,it is probable that acid linoleates are formed1 and that compounds formed from the polymerisation of linoleic acid result eventually4 ,whatever doubt there may be as to the action of lead salts1 there can be none whatever as to that of manganese compounds4 ,in the first place1 manganous oxide is a powerful base1 which readily dissolves in oil2 manganic oxide is also readily soluble1 yielding fatty acid salts of manganese1 and causing oxidation of glycerine4 ,manganese borate and manganese oxalate are both soluble in oil1 the former much more readily than the latter1 but they are both salts of little stability at high temperatures in contact with oils4 ,they both dissolve by the aid of heat1 forming fatty acid salts of manganese4 ,borate liberates boric acid under these circumstances1 but oxalate yields a mixture of carbon monoxide and carbon dioxide4 ,of manganese oleate and linoleate nothing more may be said than that both are extremely soluble in oil1 and both easily oxidised from colourless to brown compounds when submitted to the action of air4 ,the chief adulterants of linseed oil and of boiled oil are cotton-seed oil1 rosin oil1 and linoleic acid4 ,cotton-seed1 which is to some extent a drying oil1 can act as such when mixed with linseed1 but when added to olive oil1 it behaves as a non-drying oil4 ,in fact1 its behaviour is anomalous1 and of such a character that it greatly facilitates its extensive use as an adulterating material for the more expensive oils4 ,rosin oil is a deleterious adulterant1 but one which may be more readily detected than cotton-seed oil4 ,rosin is added to boiled oil to hasten its drying2 this also is an injurious substance4 ,of late years glycerine has become an article of greater value than formerly1 and this may account for the manufacture of linoleic acid and its use as an adulterant of oleic acid and of linseed oil4 ,lastly1 it may be mentioned that certain samples of 8pale boiled oil0 have been found to contain what is practically a raw oil mixed with dryers4 ,although such oils will dry1 their efficiency is nothing like so great as that of an oil 8boiled0 with a blast of air at a suitable temperature1 and1 moreover1 such oils are deficient in body4 ,in bleaching vegetable oils1 it is necessary to consider the nature of the colouring matters naturally contained in them4 ,these consist of a mixture in varying proportions of the colouring matters known to exist in the leaves of plants1 but which1 in the case of oils1 are derived from the fruit or seeds from which the oils are expressed4 ,there can be no doubt that these substances are closely allied in chemical constitution2 they all possess an intensely powerful colouring property1 by which is meant that though the colour of some of them may not be dark1 yet a very minute weight is capable of imparting a tint to a very large quantity of material4 ,the names of these substances are3-- ,xanthophyll--yellow4 ,yellow chlorophyll--yellow4 ,blue chlorophyll--blue4 ,erythrophyll--red4 ,in some oils only the xanthophyll and yellow chlorophyll are present2 in others1 such as olive oil1 the yellow and blue chlorophylls occur1 and give the liquid a green tint2 while in linseed erythrophyll is always present with more or less of the yellow and blue chlorophylls1 and some xanthophyll4 ,according to the different proportions of these colouring matters the oil varies in colour4 ,for instance1 linseed oil1 when brown1 contains a mixture of erythrophyll with yellow and blue chlorophylls2 when greenish brown1 the yellow and blue chlorophylls are present in somewhat larger proportion1 but mixed with erythrophyll2 while1 generally speaking1 a bright yellow or pale yellow oil contains xanthophyll only4 ,these substances appear to be combined with the oils1 or to be substances of a fatty nature4 ,they are neither dissolved nor acted upon by water1 nor by acids diluted with water1 when naturally contained in the oils4 ,they are freely soluble in alcohol1 and an alcoholic solution is not only susceptible of being destroyed by the joint action of air and water1 but by very dilute aqueous solutions of mineral acids1 and by acetic acid4 ,in aqueous and alcoholic solutions1 light speedily modifies the blue1 and eventually destroys all these colours4 ,a solution in turpentine of the isolated colouring matters is also easily destroyed4 ,but1 on the other hand1 a solution of the colours in melted paraffin wax is comparatively stable4 ,zinc hydroxide1 copper hydroxide1 baryta1 potash1 and soda easily combine to form metallic salts with blue chlorophyll1 less readily1 though readily enough with yellow chlorophyll1 but far less readily with xanthophyll and erythrophyll4 ,the following facts will serve to show that this is the case4 ,when a solution of the colouring matters contained in green leaves is made by extracting dry1 but freshly-gathered1 leaves with absolute alcohol1 an addition of a saturated solution of baryta water1 to the intensely green extract1 precipitates first the compound of blue chlorophyll with baryta1 then a further addition precipitates the yellow chlorophyll1 also as a baryta salt2 but xanthophyll and erythrophyll either remain in solution1 or require a much larger addition of the base in order to be precipitated4 ,a crystalline compound of blue chlorophyll with soda is comparatively stable4 ,this substance is1 no doubt1 formed in green vegetables when they are boiled in water to which some carbonate of soda has been added to maintain their fresh appearance4 ,the addition of a small trace of copper sulphate to peas and to pickles forms a very permanent copper compound with the colouring matter1 which gives an attractive appearance to these articles4 ,such being an outline of the chief chemical properties of the natural colouring matters contained in oils1 the facts mentioned will serve to render the processes for removing the colour from oils more intelligible than they otherwise would be4 ,vegetable oils are decolorised1 either partially or completely1 by the application of one of the following processes3-- #a4 ,by the action of light1 or by the joint action of light and air4 #b4 ,by acids4 #c4 ,by saponification4 #d4 ,by the action of chlorine4 #a4 ,by exposing raw linseed oil to the action of sunlight1 it slowly becomes pale in colour1 and finally colourless4 ,it is in the highest degree probable that1 as oxygen is absorbed by the oil and acid substances are thereby produced1 these acids effect the destruction of the colouring matters4 ,in such wise castor oil is bleached4 #b4 ,by treating linseed oil with moderately strong sulphuric acid4 ,as the oil and sulphuric acid are of very different specific gravities1 it is essential that they be very rapidly and thoroughly mixed by violent agitation4 ,the impurities1 such as mucilage and albuminous matters1 are thus deprived of water1 and more or less charred1 and along with them the colouring matters are destroyed by the acid4 ,it is essential for the success of the process that the oil and the acid be not long in contact without undergoing dilution1 otherwise the oil itself may become charred4 ,it is1 however1 possible to obtain oil by this process in a fairly colourless condition1 after it has been thoroughly washed with water and allowed to settle4 #c4 ,both rape oil and cotton oil may be rendered of a pale yellow1 and even almost colourless1 by a process of partial saponification with caustic alkali of a suitable strength4 ,the colouring matters are saponified1 and the resulting soap is of a dark yellow or brown colour1 from the colouring matter having combined with the alkali4 #d4 ,by the action of chlorine produced in contact with the oil when1 for instance1 an aqueous solution of bleaching powder is acidified with a cheap mineral acid1 such as dilute sulphuric4 ,in this case rapid mixing and violent agitation are essential to the success of the process1 otherwise chlorinised products are retained in the oil1 which not only confer upon it a distinct flavour and odour1 but also cause the oil to solidify with a very moderate lowering of the normal temperature4 ,it is very questionable whether drying oils can with advantage be submitted to such treatment4 #e4 ,a variety of methods may be merely mentioned1 such as treatment with sulphurous acid1 with ferrous sulphate 7green vitriol71 and potassium dichromate and sulphuric acid4 #f4 ,lastly1 the method of ,binks1 to which reference will be made farther on4 ,prof4 ,hartley next gives an account of certain improvements in the process of oil-boiling1 designed with the object of producing a drying oil absolutely free from lead1 and1 as compared with ordinary oils1 absolutely free from colour4 ,the operations have been carried out1 on a manufacturing scale1 by ,mr4 ,w4 ,e4 ,b4 ,blenkinsop and himself1 and there is no doubt of the practicability of the process4 ,the process consists in1 first1 refining the oil1 by the removal therefrom of water and mucilage2 second1 boiling and bleaching the oil at one operation4 ,it is a fact that water and mucilage can be removed from linseed oil by the action of certain dehydrating substances and solutions of metallic salts1 as1 for instance1 by alum1 by strong sulphuric acid1 and by a solution of zinc chloride4 ,there are certain objections to each of these methods1 which are of a practical nature3 thus1 in treating the oil with strong sulphuric acid1 there is too frequently a charring of something1 either the oil itself1 or of some impurity therein1 and this charring1 though it may be very slight1 has the effect of giving a pale brownish tinge to the oil1 which cannot be completely removed by the bleaching process to which the natural colouring matters in the oil are amenable4 ,it is quite true that this brown colour separates sometimes1 but it is only after storage for a long period1 when a finely divided flocculent matter separates by subsidence4 ,treatment with zinc chloride is satisfactory but expensive4 ,perfectly pure manganese sulphate1 which is a neutral salt1 has been used by ,hartley and ,blenkinsop in very strong solution1 and where there is an objection to using an acid4 ,for ordinary purposes1 perfectly satisfactory results are obtained by the use of a dilute sulphuric acid containing about #cj per cent4 of ,h#b,,so#d1 since1 though it possesses the power of withdrawing water from the oil1 it may remain in contact therewith without causing any charring1 and at the same time it causes the precipitation in a complete and rapid manner of all the mucilage4 ,a purified linseed oil is thus produced which is bright1 clear1 and slightly yellowish in colour1 though somewhat paler than the ordinary oil4 ,it is important that the strength of the oil should not exceed that degree of concentration which is sufficient for the purpose for which it is intended4 ,the oil having been so treated1 and the impurities separated by subsidence or otherwise1 it is next submitted to the bleaching and oxidising treatment4 ,binks bleached oils with oxides of manganese dissolved in the oil1 but difficulty was experienced in carefully regulating the quantity of the manganese compounds which were to be introduced into the oil4 ,for instance1 he precipitated manganous hydroxide in contact with oil1 and added the mixture to the bulk of the material1 and he also modified the treatment by dissolving manganous hydroxide in ammonia1 and added the solution to the oil4 ,hartley and ,blenkinsop prepare manganese linoleate1 and dissolve this in a hydrocarbon1 and add a sufficient quantity of the solution to the oil1 whereby it dissolves easily and mixes completely4 ,by this treatment1 the colouring matter of the oil forms a compound with the manganese which1 while it remains in solution1 is very speedily oxidised in contact with air1 especially when a current of air or oxygen is blown through4 ,the oxidation destroys the colouring matter1 and the manganese compound is deoxidised2 subsequently it undergoes oxidation again1 and the products of such oxidation taking place in the oil are acrolein1 formic and acetic acids4 ,after1 or concurrently with1 the oxidation of the colouring matters1 the oil is oxidised1 and1 at a suitable temperature below #acb ,f41 the oil is bleached1 increased in density1 and converted into a pale drying oil4 ,by limiting the amount of the manganese linoleate to that which is capable of just oxidising the colouring matters1 oils may be bleached with very little further oxidation4 ,excellent drying oils have been produced by this process1 of a very pale colour4 ,the oil has been used for decorative house painting1 for both indoor and outdoor work1 on wood and on metal4 ,it has also been used as a coating for iron work1 without the addition of a pigment4 ,the plant used in its production is the same as that employed in oil-boiling by the usual processes when a blast of air is used4 ,the advantages of a pale boiled oil1 containing no lead1 are the following3-- #a4 ,zinc white retains its pure white colour4 #b4 ,delicate tints1 and colours containing sulphides1 are not darkened in course of time4 ,it may be suggested that for indoor decoration1 for the painting of ships1 railway carriages1 railway semaphores1 signs1 and stations1 such oil is free from liability to alter the colours with which it is mixed1 owing to its freedom from lead1 which is darkened by traces of sulphuretted hydrogen in the air to which such paints are exposed4 ,gasometers in gas-works may be painted an unalterable white with such oil and zinc white4 ,but in this case also the zinc white must be free from lead carbonate or oxide4 ,in commenting on ,prof4 ,hartley's paper1 ,mr4 ,laurie said he had never used linoleate of manganese for boiling with oil1 but by the use of borate one did get a boiled oil paler than the oil with which one started4 ,if you take linseed oil which has been already bleached in the sun to a golden yellow1 and convert it into boiled oil with manganese1 a further bleaching process undoubtedly takes place4 ,an oil prepared with manganese salts1 spread on a glass plate1 and allowed to dry in the dark1 will remain almost colourless1 whereas if it were boiled with a lead salt it quickly darkens1 even if it is kept away from impure air4 ,even in a dark room1 in pure air1 a picture painted with oil boiled with lead will darken4 ,that is another argument in favour of manganese1 and he should say it ought always to be used in preparing oil for artistic purposes4 ,,chapter ,,xiii4 ,,paint ,,machinery4 ,in ,fig4 #dj is shown a complete set of paint grinding and mixing machinery1 made by ,wright ,co41 #aeg ,southwark ,bridge ,road1 ,london1 ,s4,e41 which has given highly satisfactory results in efficiency and economy4 ,it has a set of three granite rollers #cj inches by #ae1 and two mixing cylinders or pugs1 #bd inches in diameter by #be inches deep1 the whole mounted on a strong cast-iron frame4 ,it is made in the following five sizes3-- ---------------------------------------- -------------------------------- ,work turned out per day4 ,no4 #c-roller ,mills4 ,diam4 of ,speed of ,weight4 ------------------------ ,size of ,roller4 ,pulleys4 ,pulleys4 7,approx47 ,ordinary ,white ,colours4 ,lead4 ---------------------------------------- ------------------------------- in4 in4 in4 cwt4 tons4 tons4 #a #af #i #ah #gj #ab to #a #b #bb #ab #bd #fj #af #a 8 #b #d #c #bb #ad #bf #ee #bb #c 8 #d #h #d #cj #ae #cj #ej #cj #d 8 #e #aj #e #cf #af #cj #ej #ce #e 8 #f #ab ---------------------------------------- ----------------------------- ,the utility of having the pug mills placed above the granite rollers is to save labour and space1 and the roller mill is kept constantly at work4 ,there are two pugs1 one of which is always ready to deliver to the rollers1 whilst the other is getting ready by the time the first is being emptied2 by this means the output is always going on1 and hence great saving both of time and labour4 ,the pugs are ,illustration3 ,fig4 #dj4--,,wright',s ,,paint ,,mill4 easily fed from a wooden stage fixed to the frame at the back of pugs4 ,the drawing shows the gear driven by a cog-wheel1 but if required it can be driven by fast and loose pulleys4 ,the whole of the machine is very compact4 ,a handy little grinding machine by the same well-known firm is shown in ,fig4 #da2 a liquid-paint mixer1 in ,fig4 #db2 and a single pug mill for paint or putty1 in ,fig4 #dc4 ,neither of these machines requires any special description1 as the mode of application is evident from the illustrations4 ,illustration3 ,fig4 #da4--,,wright',s ,,small ,,paint ,,mill4 ,this firm are also the manufacturers of ,clark's patent paint mill1 illustrated in ,fig4 #dd4 ,this mill differs from the ordinary mills in having five instead of three rollers4 ,the material is fed in between the two uppermost rollers1 being prevented from spreading too much by means of wooden cheeks shaped so as to fit between the rollers and form a kind of hopper in which the material to be ground is placed4 ,from these two rollers it passes to a third and ,illustration3 ,fig4 #db4--,,liquid-,,paint ,,mixer4 fourth placed below1 and receives a final grind from the fifth roller in front of the machine1 from which it is delivered to the spout as shown4 ,the rollers are all of granite turned truly cylindrical4 ,they are #ae inches in diameter and are mounted on strong steel spindles4 ,these spindles run on bearings working in guides1 by means of which the distance ,illustration3 ,fig4 #dc4--,,single ,,pug ,,mill4 apart of the rollers and the fineness of the grinding can be adjusted4 ,it will be seen that the driving-shaft of the machine is the lowest of the six shown4 ,it drives by means of spur gearing roller number three1 and through it the other rollers of the mill4 ,no two rollers working together revolve at the same speed1 and hence one rubs over the other1 and they thoroughly grind the material between them4 ,in the common three-roller mills it is necessary to pass the material to be ground through the mill twice1 but in this machine one passage is sufficient1 so that both time and floor space are saved1 as the machine1 it is claimed1 does the work of two ordinary mills4 ,another noteworthy feature of this mill is that on ,no4 #b roller is a ,illustration3 ,fig4 #dd4--;,,clark',s ,,patent ,,granite-,,roller ,,mill4 lateral motion giving a sidewise movement of inch4 ,this is also applied to ,no4 #d roller1 and gives the same movement4 ,each roller can be separately and easily adjusted by means of adjusting screws4 ,the fifth roller is the delivery roller4 ,the weight of ,no4 #b roller is carried by a strong spring fixed between the bearings of rollers ,nos4 #b and #c1 so that by the movement of the adjusting screw1 the ,no4 #b roller can be brought down upon ,no4 #c with the required pressure4 ,the principle of mounting the rollers of most machines1 is that the centre roll shall revolve in fixed bearings1 and the two outer ones shall revolve in bearings made to slide backward and forward in grooves in the framework4 ,there is no means of adjusting the rollers in order to keep them in perfect parallel plane1 or to compensate for the wear of the brasses4 ,the consequence is1 that immediately the bearings begin to wear1 the rolls are not then in parallel plane with each other1 and the longer they work the worse they get2 until they only grind a small distance in the centre of the roll1 causing the machine not only to perform imperfect work1 but the rolls to wear hollow in the centre4 ,hind and ,lund1 ,limited1 of the ,atlas ,works1 ,preston1 ,lancashire1 claim that in their machine 7,fig4 #de7 these defects are entirely obviated4 ,the centre roll is mounted in a similar manner to other machines1 but the two outer rolls are hung upon excentric studs at each side4 ,should the journals wear at all unevenly1 this is at once detached1 and by a single turn of the excentric stud at either one side or the other as the case may be1 the rolls are kept always in perfect parallel plane4 ,this machine is fitted with relieving apparatus for throwing the two outer rolls apart whilst working1 in case of accident1 or for cleaning purposes4 ,thus the machine may be run for an indefinite period without the granite touching1 hence no wear can take place2 while the rollers may be instantly put back to their working distances1 just exactly as they were before the rolls were thrown apart4 ,as will be readily understood1 this is a very valuable improvement1 as the machine can be put in and out of actual grinding work as often as may be desired1 without once altering the pressure upon the springs or the grinding distances4 ,illustration3 ,fig4 #de4--;,,hind ,,and ,,lund',s ,,patent ,,paint ,,mill4 ,the bearings are all self-lubricating1 and the most delicate colours or white lead can be ground without fear of being deteriorated4 ,the machine too is almost noiseless4 ,many of them can be seen at work1 and giving great satisfaction4 ,brinjes and ,goodwin's machine is shown in ,figs4 #df1 #dg1 and #dh4 ,the oil and pigments1 having been measured or weighed1 are placed in the trough h4 ,this is provided with ,illustration3 ,figs4 #df and #dg4--;,,brinjes ,,and ,,goodwin',s ,,paint ,,mill4 ,illustration3 ,fig4 #dh4--;,,brinjes ,,and ,,goodwin',s ,,paint ,,mill4 stirrers1 similar to those in a pug-mill1 which are driven by means of the pulley l1 m being a loose pulley2 by shifting the strap on to this1 the machine can be stopped at once4 ,when the oil has been thoroughly incorporated with the pigment1 the mixture is allowed to run through the spout g on the roller a4 ,working against a is a second roller b1 and this in its turn bears upon a third roller c4 ,in order to prevent the grooving of the faces of the rollers1 which always takes place when they revolve in the same plane1 there is an arrangement by which a slight lateral motion is communicated to b1 in addition to the rotary motion4 ,a pin fixed upon the rigid bracket k works in the grooved cam i1 which is keyed on the shaft of the roller b4 ,the grinding power of the machine is considerably increased by this modification4 ,the rollers are worked from the pulley d2 the loose pulley e receives the strap when a pause in the working of the machine becomes necessary4 ,the details of the construction of the grinding machine are given in ,fig4 #dh4 ,the rollers a b c are constructed of granite or porcelain2 for fine grinding1 the latter substance is preferable4 ,they are adjusted by means of the screws g h4 ,these are furnished with spiral springs1 so that should a nail or other hard substance get between the rollers1 these can rise in their bearings1 letting the nail fall down at the back4 ,the 8doctor0 or scraper f removes the paint from the surface of the roller c2 a b are also provided with smaller scrapers1 which remove any paint that may cake upon their surfaces4 ,where extreme fineness is requisite1 the paint is again passed through the machine1 and this operation is sometimes repeated several times4 ,in working these or any other form of grinding rollers1 great care must be taken to clean them thoroughly immediately after use4 ,if the paint be allowed to dry upon the surface of the rollers it is difficult of removal1 and interferes with the perfect action of the machine4 ,should the working parts become clogged with solidified oil1 a strong solution of caustic soda or potash will remove it4 ,by means of the same solutions1 porcelain rollers may be kept quite white1 even if used for mixing coloured paints4 ,although the colour of most pigments is improved by grinding them finely in oil1 yet there are some which suffer in intensity where their size of grain is reduced4 ,chrome red1 for instance1 owes its deep colour to the crystals of which it is composed1 and when these are reduced to extremely fine fragments1 the colour is considerably modified4 ,,packing4--,when paint is not intended for immediate use1 it is packed in metallic kegs4 ,the construction of these1 as made by ,b4 ,noakes ,co41 is shown in ,fig4 #di4 ,for exportation to hot climates1 the rim of the lid is sometimes soldered down1 a practice which effectually prevents access of atmospheric oxygen4 ,white-lead paint is frequently packed in wooden kegs2 these prevent the discoloration sometimes caused by the metal of iron kegs4 ,when paint is mixed ready for use1 it will1 if exposed to the air1 become covered with a skin1 which soon attains sufficient thickness to exclude the atmospheric oxygen1 and prevent any further solidification of the oil4 ,the paint may be still better protected by pouring water over it1 or it may be placed in air-tight cans4 ,if it has been allowed to stand for some time1 it must be well stirred before using1 as the pigments have a tendency not only to separate from the oil1 but also to settle down according to their specific gravity4 ,illustration3 ,fig4 #di4--,,paint ,,keg4 ,,chapter ,,xiv4 ,,painting4 ,the successful application of paint1 whether for artistic or preservative purposes1 necessitates careful attention to a number of considerations1 some of a mechanical and others of a chemical character4 ,the ,surface4--,of whatever the surface may be to which the paint is to be applied1 great care must be taken that it is perfectly dry4 ,wood especially1 even when apparently dry1 may on a damp day contain as much as #bj per cent4 of moisture4 ,a film of paint applied to the surface of wood in this condition prevents the moisture from escaping1 and it remains enclosed until a warm sun or artificial heat converts it into vapour1 which raises the paint and causes blisters4 ,moisture enclosed between two coats of paint has the same effect4 ,paint rarely blisters when applied to wood from which old paint has been burnt off2 this is probably due to the drying of the wood during the operation of burning4 ,when the surface to be painted is already covered with old paint1 this should be either removed or rubbed down smooth before applying the new4 ,when the thickness of the old coat is not great1 rubbing down1 accompanied by a careful scraping of blisters and defective parts1 will suffice4 ,when the thickness of the old paint necessitates its removal1 it may either be burned off1 or softened by a solution of caustic alkali1 and afterwards scraped4 ,the burning process is the most effective1 and leaves the wood in a fit condition to receive the fresh coat of paint2 but it is not applicable in the case of fine mouldings4 ,when caustic potash or soda is used1 the paint is left in contact with1 it for some time1 when the linoleic acid of the oxidised linseed-oil becomes saponified1 and can easily be scraped or scrubbed off the surface of the wood4 ,whenever an alkali is employed1 it is of the greatest importance that the wood should afterwards be thoroughly washed several times with clean water1 in order to remove every trace of the solvents4 ,any soda or potash remaining in the pores of the wood would not only retain moisture and cause blistering1 but would also have an injurious action upon the vehicle of the paint subsequently applied1 and in many cases upon the pigment itself4 ,the remarks already made as to the necessity of an absolutely dry surface should be borne in mind in this instance4 ,when the surface of the paint is to be protected by a coat of varnish1 the latter should not be applied until the whole of the oil contained in the paint has solidified4 ,the wrinkling of varnish upon paint is frequently erroneously attributed to the bad quality of the varnish1 when the real cause is the incomplete oxidation of the paint itself4 ,priming4--,the first coat of paint applied to any surface is termed the 8priming-coat40 ,it usually consists of red lead and boiled and raw linseed-oil4 ,experience has shown that such a priming not only dries quickly itself1 but also accelerates the drying of the next coat4 ,the latter action must be attributed to the oxygen contained in the red lead1 only a small portion of which is absorbed by the oil with which it is mixed4 ,kali1 of ,heidelberg1 prepares a substitute for boiled oil by mixing #aj parts whipped blood1 just as it is furnished from the slaughter-houses1 with #a part of air-slaked lime sifted into it through a fine sieve4 ,the two are well mixed and left standing for #bd hours4 ,the dirty portion that collects on top is taken off1 and the solid portion is broken loose from the lime at the bottom2 the latter is stirred up with water1 left to settle1 and the water is poured off after the lime has settled4 ,the clear liquid is well mixed up with the solid substance before mentioned4 ,this mass is left standing for #aj or #ab days1 after which a solution of potash permanganate is added1 which decolorises it and prevents putrefaction4 ,finally the mixture is stirred up1 diluted with more water to give it the consistence of very thin size1 filtered1 a few drops of oil of lavender are added1 and the preparation is preserved in closed vessels4 ,it is said to keep a long time without change4 ,a single coat of this liquid will suffice to prepare wood or paper1 as well as lime or hard plaster walls1 for painting with oil colours4 ,this substance is cheaper than linseed oil1 and closes the pores of the surface so perfectly that it takes much less paint to cover it than when primed with oil4 ,drying4--,the drying of paint is to a great extent dependent upon the temperature4 ,below the freezing point of water1 paint will remain wet for weeks1 even when mixed with a considerable proportion of dryers2 while1 if exposed to a heat of #abj ,f4 the same paint will become solid in a few hours4 ,the drying of paint being a process of oxidation1 and not evaporation1 it is essential that a good supply of fresh air should be provided4 ,when a film of fresh paint is placed with air in a closed vessel1 it does not absorb the whole of the oxygen present2 but after a time the drying process is arrested1 and the remaining oxygen appears to have become inert4 ,considerable quantities of volatile vapours are given off during the drying of paint2 these are due to the decomposition of the oil4 ,when the paint has been thinned down by turpentine1 the whole of this liquid evaporates on exposure to the air4 ,there must1 therefore1 be a plentiful access of air1 to remove the vapours formed1 and afford a fresh supply of active oxygen4 ,the presence of moisture in the air is rather beneficial than injurious at this stage4 ,especially in the case of paints mixed with varnish1 moist air appears to counteract the tendency to crack or shrink4 ,under the erroneous impression that the drying of paint is a species of evaporation1 open fires are sometimes kept up in freshly-painted rooms4 ,it is only when the temperature is very low that any benefit can result from this practice2 as a rule1 it rather retards than hastens the solidification of the oil1 which cannot take place rapidly in an atmosphere laden with carbonic acid4 ,the first coat of paint should be thoroughly dry before the second is applied4 ,acrylic acid is formed during the oxidation of linseed-oil1 and unless this be allowed to evaporate1 it may subsequently liberate carbonic acid from the white lead present in most paints1 and give rise to blisters4 ,sometimes a second priming-coat is given2 but usually the second coat applied contains the pigment4 ,this1 as soon as dry1 is again covered by another coat1 and subsequently by two or more finishing coats1 according to the nature of the work4 ,filling4--,before the first coat is applied to wood1 all holes should be filled up4 ,the filling usually employed is ordinary putty2 this1 however1 sometimes consists of whiting ground up with oil foots of a non-drying character1 and when the films of paint are dry1 the oil from the putty exudes to the surface1 causing a stain4 ,the best filling for ordinary purposes is whiting ground to a paste with boiled linseed-oil4 ,for finer work1 and for filling cracks1 red lead mixed with the same vehicle may be employed4 ,for porous hard woods1 use boiled oil and corn starch stirred into a very thick paste2 add a little japan1 and reduce with turpentine4 ,add no colour for light ash2 for dark ash and chestnut1 use a little raw sienna2 for walnut1 burnt umber and a slight amount of ,venetian red2 for bay wood1 burnt sienna4 ,in no case use more colour than is required to overcome the white appearance of the starch1 unless you wish to stain the wood4 ,this filler is worked with brush and rags in the usual manner4 ,let it dry #dh hours1 or until it is in condition to rub down with ,no4 #j sand-paper without much gumming up2 and if an extra fine finish is desired1 fill again with the same materials1 using less oil1 but more japan and turpentine4 ,the second coat will not shrink1 being supported by the first4 ,when the second coat is hard1 the wood is ready for finishing up by following the usual methods4 ,this formula is not intended for rosewood4 ,coats4--,there is no advantage in laying on the paint too thickly4 ,a thick film takes longer to dry thoroughly than two thin films of the same aggregate thickness4 ,paint is thinned down or diluted with linseed-oil or turpentine4 ,the latter liquid1 when used in excess1 causes the paint to dry with a dull surface1 and has an injurious effect upon its stability4 ,sometimes the last coat of paint is mixed with varnish1 in order to give it greater brilliancy4 ,in this case1 special care must be taken that the previous coats have thoroughly solidified1 or cracks in the final coat may subsequently appear4 ,the same remark applies when the surface of the paint is varnished4 ,the turpentine with which the varnish is mixed has a powerful action upon the oil contained in the paint1 if the latter is not thoroughly oxidised4 ,the exterior of the paint is thus softened1 and the varnish is enabled to shrink and crack1 especially in warm weather4 ,brushes4--,the bristles are frequently fastened by glue or size1 which is not perceptibly acted upon by oil1 and if brought into contact with this liquid alone1 there would be no complaints of loose hairs coming out and spoiling the work4 ,it is a common practice to leave the brushes in a paint-pot1 in which the paint is covered with water to keep it from drying4 ,the brushes are certainly kept soft and pliant in this way2 but at the same time the glue is softened1 and the bristles come out as soon as the brush is used4 ,after use1 brushes should be cleaned1 and placed in linseed-oil until again required1 when they will be found in good condition4 ,treated in this way1 they will wear so much better that the little additional trouble entailed is amply repaid4 ,when brushes will not again be required for some time1 the oil remaining in them should be washed out by means of turpentine1 after which they may be dried without deterioration4 ,on no account should oil be allowed to dry in a brush1 as it is most difficult to remove after oxidation has taken place4 ,the best means are steeping in benzoline for a few days1 or in turpentine1 with occasional washing in soda-water and with soft-soap1 avoiding too violent rubbing4 ,water-colours4--,the manufacture of water-colour paints is more simple than that of oil paints1 the pigments being first ground extremely fine and then mixed with a solution of gum or glue4 ,the paste produced in this manner is allowed to dry1 after having been stamped into the form of cakes4 ,as soon as the hardened mass is rubbed down with water1 the gum softens and dissolves1 and if the proportion of water be not too great1 the pigment will remain suspended in the solution of gum1 and can be applied in the same manner as oil-paint4 ,to facilitate the mixing with water1 glycerine is sometimes added to the cake of paint1 which then remains moist and soft4 ,removing ,odour4--7#a7 ,place a vessel of lighted charcoal in the room1 and throw on it #b or #c handfuls of juniper berries2 shut the windows1 the chimney1 and the door close2 #bd hours afterwards the room may be opened1 when it will be found that the sickly1 unwholesome smell will be entirely gone4 7#b7 ,plunge a handful of hay into a pail of water1 and let it stand in the room newly painted4 ,discoloration4--,light-coloured paints1 especially those having white lead as a basis1 rapidly discolour under different circumstances4 ,thus white paint discolours when excluded from the light2 stone colours lose their tone when exposed to sulphuretted hydrogen1 even when that is only present in very small quantity in the air2 greens fade or darken1 and vermilion loses its brilliancy rapidly in a smoky atmosphere like that of ,london4 ,ludersdorf thinks that the destructive change is principally due to a property in linseed-oil which cannot be destroyed4 ,the utility of drying oils for mixing pigments depends entirely on the fact that they are converted by the absorption of oxygen into a kind of resin1 which retains the colouring pigment in its semblance2 but during this oxidation of the oil--the drying of the paint--a process is set up which1 especially in the absence of light and air1 soon gives the whitest paint a yellow tinge4 ,ludersdorf therefore proposes to employ an already formed but colourless resin as the binding material of the paint1 and he selects two resins as being specially suitable--one1 sandarach1 soluble in alcohol2 the other1 dammar1 soluble in turpentine4 ,the sandarach must be carefully picked over1 and #g oz4 is added to #b oz4 ,venice turpentine and #bd oz4 alcohol of sp4 gr4 #jhcc4 ,the mixture is put in a suitable vessel over a slow fire or spirit-lamp1 and heated1 stirring diligently1 until it is almost boiling4 ,if the mixture be kept at this temperature1 with frequent stirring for an hour1 the resin will be dissolved1 and the varnish is ready for use as soon as cool4 ,the ,venice turpentine is necessary to prevent too rapid drying1 and more dilute alcohol cannot be employed1 because sandarach does not dissolve easily in weaker alcohol1 and1 furthermore1 the alcohol1 by evaporation1 would soon become so weak that the resin would be precipitated as a powder4 ,when this is to be mixed with white lead1 the latter must first be finely ground in water1 and dried again4 ,it is then rubbed with a little turpentine on a slab1 no more turpentine being taken than is absolutely necessary to enable it to be worked with the muller2 #a lb4 of the white lead is then mixed with exactly lb4 of varnish1 and stirred up for use4 ,it must be applied rapidly1 because it dries so quickly4 ,if when dry the colour is wanting in lustre1 it indicates the use of too much varnish4 ,in such cases1 the article painted should be rubbed1 when perfectly dry1 with a woollen cloth to give it a gloss4 ,the dammar varnish is made by heating #h oz4 dammar in #af oz4 turpentine oil at #afe to #aij ,f41 stirring diligently1 and keeping it at this temperature until all is dissolved1 which requires about an hour4 ,the varnish is then decanted from any impurities1 and preserved for use4 ,the second coat of the pure varnish1 to which half its weight of oil of turpentine has been added1 may be applied4 ,it is still better to apply a coat of sandarach varnish made with alcohol1 because dammar varnish alone does not possess the hardness of sandarach1 and when the article covered with it is handled much1 does not last so long4 ,composition4--,the composition of paints should be governed-- 7#a7 ,by the nature of the material to be painted3 thus the paints respectively best adapted for wood and iron differ considerably4 7#b7 ,by the kind of surface to be covered3 a porous surface requires more oil than one that is impervious4 7#c7 ,by the nature and appearance of the work to be done3 delicate tints require colourless oil1 a flatted surface must be painted without oil 7which gives gloss to a shining surface71 paint for surfaces intended to be varnished must contain a minimum of oil4 7#d7 ,by the climate and the degree of exposure to which the work will be subjected3 for outside work1 boiled oil is used1 because it weathers better than raw oil2 turps is avoided as much as possible1 because it evaporates and does not last2 if1 however1 the work is to be exposed to the sun1 turps is necessary1 to prevent the paint from blistering4 7#e7 ,the skill of the painter affects the composition3 a good workman can lay on even coats with a smaller quantity of oil and turps than one who is unskilful2 extra turps1 especially1 are often added to save labour4 7#f7 ,the quality of the materials makes an important difference in the proportions used3 thus more oil and turps will combine with pure than with impure white lead2 thick oil must be used in greater quantity than thin when paint is purchased ready ground in oil1 a soft paste will require less turps and oil for thinning than a thick4 7#g7 ,the different coats of paint vary in their composition3 the first coat laid on to new work requires a good deal of oil to soak into the material2 on old work1 the first coat requires turpentine to make it adhere2 the intermediate coats contain a proportion of turpentine to make them work smoothly2 and to the final coats the colouring materials are added1 the remainder of the ingredients being varied according as the surface is to be glossy or flat4 ,the exact proportions of ingredients best to be used in mixing paints vary according to their quality1 the nature of the work required1 the climate1 and other considerations4 ,the composition of paint for different coats also varies considerably4 ,the proportions given in the following table must only be taken as an approximate guide when the materials are of good quality3-- ,,table showing the ,,composition of the different ,,coats of ,,white ,,paint1 and the ,,quantities required to cover #ajj yd4 of ,,newly-,,worked ,,pine4 ---------------------------------------- ------------------ ,red ,white ,raw ,boiled,turp4,dryers,,remarks lead lead4 ,lins4,lins4 7see oil oil footnotes7 ---------------------------------------- ------------------ ,inside work1 #d coats not ,a flatted4 lb4 lb4 pt4 pt4 pt4 lb4 ,priming #af #f -- -- #bnd coat ,b #ae #c -- #a #crd coat -- #ac #b -- #a #dth coat -- #ac #b -- #a ,inside work #d coats flatting4 ,priming #a #af #f -- #a-h #bnd coat -- #ab #d -- #a #a-aj #crd coat -- #ab #d -- #j #a-aj #dth coat -- #ab #d -- #j #a-aj ,flatting -- #i #j -- #c #a-aj ,outside work ,c #d coats not flatted4 ,priming #b #ah #b #b -- #a-h #bnd coat -- #ae #b #b #a-aj #crd coat -- #ae #b #b #a-aj #dth coat -- #ae #c #b #j #a-aj ---------------------------------------- ----------------------- ,a ,sometimes more red lead is used and less dryer4 ,b ,sometimes just enough red lead is used to give a flesh-coloured tint4 ,c ,when the finished colour is not to be pure white1 it is better to have nearly all the oil boiled oil4 ,all boiled oil does not work well4 ,for pure white a larger proportion of raw oil is necessary1 because boiled oil is too dark4 ,area ,covered4--,for every #ajj sq4 yd41 besides the material enumerated in the foregoing1 #b lb4 white lead and #e lb4 putty will be required for stopping4 ,the area which a given quantity of paint will cover depends upon the nature of the surface to which it is applied1 the proportion of the ingredients1 and the state of the weather4 ,when the work is required to dry quickly1 more turpentine is added to all the coats4 ,in repainting old work1 two coats are generally required1 the old paint being considered as priming4 ,sometimes another coat may be deemed necessary4 ,for outside old work exposed to the sun1 both coats should contain #a pint turpentine and #d pints boiled oil1 the remaining ingredients being as stated in the foregoing table4 ,the extra turpentine is used to prevent blistering4 ,in cold weather1 more turpentine should be used to make the paint flow freely4 ,according to another authority1 it is found that in painting wood1 one coat takes #bj lb4 lead and #d gal4 oil per #ajj sq4 yd42 the second coat1 #dj lb4 lead and #d gal4 oil2 and the third the same as the second2 say #ajj lb4 lead and #af gal4 oil per sq4 yd4 for the three coats4 ,the number of square yards covered by one gallon of priming colour is found to be #ej2 of white zinc1 #ej2 of white lead paint1 #dd2 of lead colour1 #ej2 of black paint1 #ej2 of stone colour1 #dd2 of yellow paint1 #dd2 of blue colour1 #de2 of green paint1 #de4 ,measuring4--,surface painting is measured by the superficial yard1 girting every part of the work covered1 always making allowance for the deep cuttings in mouldings1 carved work1 railings1 or other work that is difficult to get at4 ,where work is very high1 and scaffolding or ladders have to be employed1 allowances must be made4 ,the following rules are generally adopted in ,america in the measurement of work3--,surfaces under #f in4 in width or girt are called #f in42 from #f to #ab in41 #ab in42 over #ab in41 measured superficial4 ,openings are deducted1 but all jambs1 reveals1 or casings are measured girt4 ,sashes are measured solid if more than two lights4 ,doors1 shutters and panelling are measured by the girt1 running the tape in all quirks1 angles or corners4 ,sash doors measure solid4 ,glazing1 in both windows and doors1 is always extra4 ,the tape should be run close in over the battens1 on batten doors1 and if the stuff is beaded1 add #a in4 in width for each bead4 ,venetian blinds are measured double4 ,dentels1 brackets1 medallions1 ornamented iron work1 balusters1 lattice work1 palings1 or turned work1 should all be measured double4 ,changing colours on base boards1 panels1 cornices1 or other work1 one-fourth extra measurement should be allowed for each tint4 ,add #e per cent4 to regular price for knotting1 puttying1 cleaning1 and sand-papering4 ,for work done above the ground floor1 charge as follows3--,add #e per cent4 for each story of #ab ft4 or less1 if interior work2 if exterior work1 add #a per cent4 for each foot of height above the first #ab ft4 ,,carriage ,,and ,,car ,,painting4--,the following is the substance of an address delivered by ,mc,keon1 secretary and treasurer of the ,master ,car-,painters' ,association of the ,united ,states3--,a first-class railway coach costs1 when complete1 about #abjjl4 ,to protect this work1 the painter expends #fjl4 to #abjl4 ,the latter figure will make a first class job4 ,the car has been completed in the wood-shop1 and is turned over to the painter1 who is responsible for the finish4 ,he is expected to smooth over all rough places or defects in the wood1 which requires both patience and skill to make the work look well4 ,twelve weeks should be the time allowed to paint a car1 and it cannot be done in any less time1 to make a good job that will be a credit to the painter and all other parties interested in the construction and finish of the car4 ,too much painting is done in a hurry3 proper time is not given the work to dry or become thoroughly hardened before it is run out of the shop1 and consequently it does not always give the satisfaction it should2 nor can it be expected that hurried work will be so lasting or durable as that which has the necessary time given to finish it4 ,priming ,paint4--,the priming coat of paint on a car is of as much importance as any succeeding one1 and perhaps more4 ,good work is ruined in the priming by little or no attention being given by the painter to the mixing and application of the first coat4 ,the foundation is the support1 and on that rests success or failure4 ,the priming should be made of the proper material1 mixed with care from good lead and good oil1 and not picked up from old paints which have been standing mixed1 and must necessarily be fat and gummy1 for such are unfit for use on a good job1 and will have a decided tendency to spoil the whole work4 ,special care should be exercised1 both in mixing and applying the priming1 and it should be put on very light1 so that it may penetrate well into the wood4 ,too much oil is worse than not enough4 ,good ground lead is by far the best material for the undercoats on a car4 ,two coats should be given to the car before it is puttied1 as it is best to fill well with paint the nail-holes and plugs1 as well as defects in the wood1 so that moisture may not secure a lodgment1 which otherwise will cause the putty to swell1 although sometimes unseasoned lumber will swell the putty2 and as it shrinks1 the nail remains stationary1 and of course the putty must give way4 ,best ,putty4--,in mixing putty1 which may be a small matter with some1 take care to so prepare it that it will dry perfectly hard in #ah hours4 ,use ground lead and japan1 stiffening up with dry lead1 and whatever colouring you may require in it to match your priming coats4 ,the next coats1 after the work is well puttied1 should be made to dry flat and hard4 ,two coats should be applied1 and1 for all ordinary jobs or cheap work1 sand-papering is all that is necessary for each coat2 but when a good surface is required1 ,i would recommend one coat to be put on heavy enough to fill the grain2 and before being set1 scrape with a steel scraper4 ,the plain surface is all that requires coating and scraping with the heavy mixture4 ,for this coat1 which is called filling1 use one-half ground lead and any good mineral which experience has shown can be relied on4 ,this scraping of the panel work will fill the wood equal to two coats of rough stuff1 and saves a great amount of labour over the old process1 when so much rubbing with lump pumice was done4 ,sand-paper when the filling is thoroughly hard1 and apply another coat of paint of ordinary thickness1 when1 after another sand-papering1 you have a good surface for your colour4 ,rough-coating on cars has gone almost out of use1 and few shops are now using it to any extent4 ,my experience is that paint has less tendency to crack where rough stuff is left off4 ,i do not claim that the filling was the principal cause of the cracking1 if it was properly mixed2 but ,i believe the water used in rubbing down a car with the lump pumice injures the paint1 as it will penetrate in some places1 particularly around the moulding plugs4 ,finishing ,colour4--,the car being ready for the finishing colour1 this should be mixed with the same proportion of dryer as the previous coat1 or just sufficient to have it dry in about the same time4 ,a great error with many car painters is using a large portion of oil in the under coats1 and then but little1 if any1 in the finishing coats2 this has a decided tendency to crack1 the under coats being more elastic4 ,always aim to have colour dry in about the same time1 after you have done your priming2 by this plan you secure what all painters should labour to accomplish--namely1 little liability to crack4 ,work will of course crack sometimes after being out a few months1 or when it has repeated coatings of varnish2 and using a quick rubbing varnish on work will cause it to give way in fine checks quicker than anything else4 ,many of the varnishes used are the cause of the paint cracking1 and no painter has been wholly exempt from this trouble4 ,cause of ,cracking4--,the most common cause of cracking is poor japan1 which is the worst enemy that the car-painter has to contend with4 ,the greater part of the japan is too elastic1 and will dry with a tack1 and the japan gold size has generally the same fault1 although the ,english gold size is generally of good quality2 but its high price is an objection to its use4 ,a little more care in the manufacture of japans would give a better dryer1 and few would object to the additional cost4 ,japan frequently curdles in the paint2 it will not mix with it1 but gathers in small gummy particles on the top4 ,work painted with such material cannot do otherwise than crack and scale1 and the remedy lies only in getting a good pure article of turpentine japan4 ,in regard to using ground lead1 car-painters differ1 as some prefer to grind their own in the shop4 ,i use the manufactured lead1 and my reasons for doing so are that it is generally finer than any shop can grind it with present facilities1 and it has age after grinding1 which improves its quality4 ,you can also get a purer lead and one with more body than you can by grinding in the shop1 which is a fact that ,i think most painters must admit4 ,i have tested it very fully1 and am convinced on this point4 ,mixing the ,paints4--,permit me to make a few suggestions here in regard to the mixing of paint1 which may not fully agree with others' views4 ,there is just as much paint that cracks by putting it on too flat as by using too much oil4 ,some painters mix their finishing colour so that it is impossible to get over a panel of ordinary size before it is set under the brush1 and consequently the colour will rough up4 ,colour should be mixed up so that it will not flat down for some time after leaving it1 and then you have got some substance that will not absorb the varnish as fast as it is applied to the surface4 ,this quick drying of colour is not always caused by want of oil in it1 but because there is too much japan1 and a less quantity of the latter will do better work1 and make a smoother finish4 ,give your colour #dh hours to dry between coats2 always give that time1 unless it is a hurried job1 and experience has fully demonstrated that it is poor economy to hurry work out of the shop before it is properly finished4 ,oils1 ,dryers1 and ,colours4--,in car-painting1 both raw and boiled oils are used1 and good work may be done with either1 but ,i recommend oil that is but slightly boiled1 in preference to either the raw or the boiled4 ,after it is boiled1 if it is done in the shop1 let it stand #bd hours to settle1 then strain off carefully2 this takes out all the impurities and fatty matter from the oil1 and it will dry much better1 nor will it have that tack after drying that you find with common boiled oil4 ,use the proper quantity of dryer in mixing your paint1 and a good reliable job will be the result4 ,in car-painting1 never use prepared colours which are ground in oil1 as nine-tenths of such colours are ground in very inferior oil1 and they may have been put up for a great length of time1 in which case they become fatty1 and will invariably crack4 ,these canned colours do not improve with age1 as lead and varnish do4 ,finishing colours should all be ground in the shop1 unless special arrangements can be made with manufacturers to prepare them2 and the colour should be fresh1 not over #f or #h days old after being mixed1 and open to the air4 ,enough may be prepared at a time to complete the coating on a job2 but when colour stands over a week it is not fit to use on first-class work1 as it becomes lifeless1 and has lost that free working which we find in freshly-mixed colours4 ,such colour may1 however1 be used upon a cheap class of work1 or on trucks1 steps1 c41 so that nothing need be wasted in the shop4 ,varnishing4--,three coats of varnish over the colour are necessary on a first-class coach4 ,the first coat should be a hard drying varnish put on the flat colour2 the quick rubbing that some use ,i would not recommend1 but one that will dry in five days 7in good drying weather7 sufficiently hard to rub1 is the best for durability4 ,after striping and ornamenting the car1 and when thoroughly washed1 give a coat of medium dry varnish4 ,let this stand #h days2 then rub lightly with curled hair or fine pumice1 and apply the finishing coat1 which is 8wearing body20 this will dry hard in about #aj days1 after which the car may be run out of the shop4 ,it should then be washed with cold water and a soft brush1 and is ready for the road4 ,in varnishing1 many will apply the varnish as heavy as they can possibly make it lie1 when1 as a consequence1 it flows over and runs or sags down in ridges1 and of course does not harden properly2 this also leaves a substance for the weather to act on4 ,it is better to get just enough on at a coat to make a good even coating which will flow out smooth1 and this will dry hard1 and will certainly wear better than the coat that is piled on heavily4 ,varnishing1 we claim1 can be over-done1 despite some painters' opinions to the contrary4 ,we have heard of those who put #b gal4 on the body of a #ej-;foot car at one application1 and we have also listened to the declaration1 made by a member of the craft1 that he put #b gal4 on the body of a locomotive tank4 ,such things are perhaps possible1 and may have been done2 but if so1 we know that the work never stood as well as it would if done with one-half the quantity to a coat4 ,in varnishing a car1 care should be taken to have the surface clean2 water never injures paint where it is used for washing2 and a proper attention to cleanliness in this respect1 and in the care of brushes used for varnishing1 will ensure a good-looking job4 ,perhaps your shop facilities for doing work are none of the best1 but do the best you can with what you have4 ,select if possible1 a still1 dry day for varnishing1 especially for the finishing coat4 ,keep your shop at an even temperature2 avoid cold draughts on the car from doors and windows2 wet the floor only just sufficient to lay the dust1 for if too wet1 the dampness arising will have a tendency to destroy the lustre of your varnish4 ,of course we cannot always do varnishing to our perfect satisfaction1 especially where there are #be or #cj men at work in an open shop1 and #f or #h cars are being painted1 when more or less dirt and dust are sure to get on the work4 ,a suggestion might here be made to railroad managers1 which is that no paint-shop is complete where the entire process of painting and finishing a car is to be done in one open shop4 ,a paint-shop should be made to shut off in sections by sliding doors1 one part of the shop being used exclusively for striping and varnishing4 ,i know from experience that nine-tenths of the railroad paint-shops are deficient in this particular1 and still we are expected to turn out a clean job1 no matter what difficulties we are compelled to labour under4 ,importance of ,washing ,cars4--,in regard to the care of a car after it has left the shop1 more attention should be given to this than is done on many roads4 ,the car should not be allowed to run until it is past remedy1 and the dirt and smoke become imbedded in the varnish1 actually forming a part of the coating1 so that when you undertake to clean the car you must use soda or soap strong enough to cut the varnish before you succeed in removing the dirt4 ,cars should be washed well with a brush and water at the end of every trip4 ,this only will obviate the difficulty1 and these repeated washings will harden the varnish as well as increase its lustre4 ,we know that1 in washing a car1 where soap is required to remove the dirt and smoke1 it is almost impossible to get the smoke washed off clean2 and if it is not quite impossible1 the hot sun and rain will act on the varnish and very soon destroy it4 ,re-varnishing4--,cars should be taken in and re-varnished at least once in #ab months2 and if done once in #h months it is better for them1 and they will require only one coat2 but where they run a year1 they will generally need two coats4 ,those varnished during the hot months will not stand as well as if done at any other time4 ,painting done in extremely cold weather1 or in a cold shop1 is more liable to crack than if done in warm weather4 ,how to ,dry ,paint4--,paint dried in the shop where there is a draught of dry air passing through1 will stand better than that dried by artificial heat2 and you will find1 by giving it your attention1 that work which has failed to stand1 and which cracked or scaled1 was invariably painted in the winter season1 or in cool1 wet weather4 ,i have paid some attention to this matter1 and know the result4 ,,woodwork ,,painting4--,one of the attendant drawbacks of houses that are newly built1 or have been hastily finished for letting1 is the inferior painting of the woodwork1 and its speedy destruction4 ,the wood is not thoroughly dry1 and the consequence is the preparatory coat does not adhere2 the pores being full of dampness1 it is impossible for the oil to sink into them1 especially as oil and water are unmiscible4 ,another equally injurious condition is the gum-resin which exudes from the knots of new pine and other timber4 ,painted over before it has time to come to the surface1 the coat is destroyed by the action of the gum4 ,now1 these evils have to be endured so long as the wood has no time to get seasoned4 ,the painter follows the carpenter without any interval of time1 and before the action of the weather can bring out the moisture and resinous substances4 ,a coating of shellac is usually given to the knots1 though this is often so thin as to be worthless4 ,crude petroleum1 as a preservative coat1 is found to be an admirable preparation for the painting4 ,the petroleum is thin1 and penetrates the wood1 filling up the pores1 and giving a good ground for the coats of paint4 ,according to one ,american authority1 the preparation is of great value4 ,the priming coat should be thin and well rubbed in1 and it is better to use a darker colour than white lead as a base4 ,white lead forms a dense covering to the surface1 though it has its disadvantages4 ,when petroleum has formed the first coat1 two other coats will suffice1 one being the priming coat1 and a third coat may be given after the work has stood for a season4 ,it is a very desirable plan to leave the painting1 or rather finishing coats1 for a time1 so that any imperfections in the wood or work may be discovered2 it also allows time for any change of colour that may be made4 ,after the priming coat1 it is usual in good work to stop all cracks1 nail-holes1 and other defects with putty2 but in the commoner class of paintings1 the coats are laid on quickly1 the preceding coat has hardly time to dry before the next is put on1 and all the defects of wood1 bad seasoning1 exudation of gum1 c41 quickly begin to show themselves through and disfigure the work4 ,a good paint ought to possess body1 power of covering1 and flow evenly from the brush1 and become hard4 ,though zinc white has less body than white lead1 it is more durable1 and will stand sulphur acids without blackening4 ,some colours stand better than others2 the ochres1 ,indian and ,venetian reds1 burnt and raw umber1 are reliable1 and may be used without scruple4 ,it is also worthy of notice that salt air acts injuriously on white lead1 and zinc white is therefore preferable in situations exposed to the sea-air4 7,english ,mechanic47 ,,iron ,,painting4--,the decay of iron becomes very marked in certain situations1 and weakens the metal in direct proportion to the depth to which it has penetrated2 and although where the metal is in quantity this is not very appreciable1 it really becomes so when the metal is under inch in thickness4 ,the natural surface of cast iron is very much harder than the interior1 occasioned no doubt by its becoming chilled1 or by its containing a large quantity of silica1 and this affords an excellent protection4 ,but should this surface be at all broken1 rust immediately attacks the metal and soon destroys it4 ,it is very desirable that the casting be protected1 and a priming coat of oil or paint should be applied for this purpose2 the other coats1 though requisite1 can be given at leisure4 ,the following is a process to which all cast-iron water pipes should be submitted4 ,it was introduced by ,dr4 ,smith1 and is equally applicable to any other casting that can be manipulated3--,each casting is thoroughly dressed1 and made clean and free from the earth and sand which cling to the iron in the moulds1 hard brushes being used in finishing the process to remove the loose dust4 ,every casting must be likewise free from rust when the paint is applied4 ,if the casting cannot promptly be dipped after being cleansed1 the surface must be oiled with linseed oil to preserve it until it is ready to be dipped4 ,no casting is on any account to be dipped after rust has set in4 ,the coal-tar pitch used as a paint in this process is made from coal-tar distilled until the naphtha is entirely removed and the material is deodorised4 ,in ,england it is distilled until the pitch is about the consistence of wax4 ,the mixture of #e or #f per cent4 of linseed oil is recommended by ,dr4 ,smith4 ,pitch which becomes hard and brittle when cold will not answer for this use4 ,pitch of the proper quality having been obtained1 it must be carefully heated in a suitable vessel to a temperature of #cjj ,f41 and must be maintained at not less than this temperature during the time of dipping4 ,the material will thicken1 and deteriorate after a number of pieces have been dipped2 fresh pitch must1 therefore1 frequently be added1 and occasionally the vessel must be entirely emptied of its old contents and refilled with fresh pitch4 ,the refuse will be hard and brittle like common pitch1 and consequently worthless for the purpose4 ,every casting must attain a temperature of #cjj ,f41 either by previous heating or during the immersion before being removed from the vessel of hot pitch4 ,it may then be slowly removed1 and laid upon skids to drip4 ,in the case of water pipes1 all those of #bj inches diameter and upwards will have to remain at least #cj minutes in the hot fluid to attain this temperature4 ,the coating when cold should be tough and tenacious1 and not brittle nor have the slightest tendency to scale off4 ,in considering the painting of wrought iron it must be noticed that when iron is oxidised by heating in contact with the atmosphere1 two or three distinct layers of scale form on the surface1 and1 unlike the skin upon cast iron1 can be readily detached1 as by bending or by hammering the metal4 ,the outer layer of this scale is more highly oxidised than the inner1 and is slightly redder in tinge from the presence of a variable excess of ferric oxide over that contained in the inner layer4 ,the oxide occurring in the outer scale is fusible only at a high temperature1 is strongly magnetic1 and slightly metallic in lustre2 while the inner layers are more porous1 dull1 and non-metallic in lustre1 less brittle1 and also less powerfully magnetic4 ,it will be seen that the iron has a tendency to rust from the moment it leaves the hammer or rolls1 and that the scale above described must come away4 ,one of the plans to preserve the iron has been to coat it with paint when still hot at the mill2 and although this answers for a while1 it is a very troublesome method1 which iron-masters cannot be persuaded to adopt1 and the subsequent cutting processes to which it is submitted leave many parts of the iron bare4 ,besides1 a good deal of the scale remains1 and until this has fallen off1 or has been removed1 any painting over it will be of little value4 ,the only effectual way of preparing wrought iron is to effect a thorough and chemical cleansing of the surface of the metal upon which the paint is to be applied1 that is1 it must be immersed for three or four hours in water containing from #a to #b per cent4 of sulphuric acid4 ,the metal is afterwards rinsed in cold water1 and1 if necessary1 scoured with sand1 put again into the acid bath or pickle1 and then well rinsed4 ,the real value of any paint depends upon the quality of the linseed oil1 the quality and character of the pigment1 and the care bestowed on the grinding and mixing1 and as all this is entirely a matter of expense1 cheap paints are not to be relied upon4 ,the superiority of most esteemed paints is due to the above causes rather than to any unknown process or material employed in the manufacture4 ,the following excellent article on the preservation of iron and steel structural work appeared in the #8,illustrated ,carpenter and ,builder4' ,it conveys the most recent ,american opinion4 ,one of the most important economic questions of the present day is the preservation of iron and steel structures4 ,in ,america many millions of dollars are annually spent in the erection and construction of these1 and the amount is increasing in rapid proportion4 ,bridges1 buildings1 viaducts1 ships1 and machinery are now being made of these materials1 to almost the entire exclusion of others4 ,from their very nature iron and steel are peculiarly subject to decay from atmospheric and other influences4 ,the question of preserving them is not merely one of finance1 but1 especially in the case of railroads1 one affecting the lives and property of a large portion of the community4 ,what1 then1 is the best method of preserving them8 ,the almost universal method is by means of paints1 or the application of substances to their surfaces which will resist or retard the influence of air1 water1 and other destructive agencies4 ,the requisites of a good paint for this purpose are that it shall adhere firmly to the surface1 and not chip or peel off1 thereby leaving portions of the surface exposed4 ,it must not corrode the iron1 else the remedy may only aggravate the disease4 ,it must form a surface hard enough to resist influences which would remove it by friction1 yet elastic enough to conform to the expansion and contraction of the metal by heat and cold4 ,it must be impervious to and unaffected1 as far as possible1 by moisture1 atmospheric and other influences to which the structure may be exposed4 ,the paints that have been used for this purpose are principally asphalt and coal-tar paints1 consisting of mineral and artificial asphalt or coal-tar1 either applied alone or combined with each other1 and1 more or less1 with metallic bases1 and iron oxide paints and lead oxide paints1 especially red lead1 in all of which the pigment is held to the surface of the iron or steel by combination with linseed oil4 ,the choice of paints must lie1 so far as our present practical experience goes1 between these three classes1 zinc oxide being found to be entirely unsuitable on account of a propensity to peel off4 ,what1 then1 is found to be the experience in actual practice with these8 ,asphalt and coal-tar paints 8run0 when exposed to the sun and other sources of heat1 which is a serious matter with vertical surfaces2 and after a time become extremely brittle and scale off entirely1 leaving the under surface exposed1 unless the paint is constantly renewed4 ,in the meantime the exposed iron and steel are being corroded by rust4 ,iron oxide paints1 including 8metallic brown10 are paints made from iron ore1 or by some chemical process with an iron base4 ,these are invariably iron in a greater or less degree of oxidation1 or in other words1 rusted iron4 ,now it is well known that one of the most active promoters of rust or decay in iron is the rust itself4 ,under the combined influences of the moisture and carbonic acid of the atmosphere1 iron oxide or iron rust becomes a carrier of oxygen from the air to the metal1 rust begetting rust4 ,it is therefore evident that this material alone has no preserving effect on iron2 in fact1 it promoted its decay4 ,how is it when combined with linseed oil in the form of paint8 ,in the economy of nature1 iron oxide is a great disinfectant4 ,when in contact with organic matter and moisture1 even at a low temperature1 under favourable conditions1 it readily gives up oxygen1 destroying more or less the organic matter1 and being itself reduced to a lower oxide4 ,when thus reduced1 with equal readiness it absorbs oxygen from the atmosphere1 and again passes it on1 thereby promoting and eventually ensuring the destruction or transformation of the organic matter with which it may be in contact1 either in the soil or elsewhere4 ,the same process appears to take place when combined with linseed oil in the form of paint and exposed to atmospheric influences1 the oil being the organic matter4 ,if linseed oil in drying formed an air-and water-proof film1 it might be urged that the oxide of iron would be entirely protected from the direct influences of oxygen of the air and moisture4 ,such however is not the case4 ,the most eminent authorities have recently shown that the dried film of linseed oil1 unless united with a pigment that combines chemically and forms a water-proof coating with it1 actually absorbs water very much like a sponge4 ,where water will go air will also go1 and we thus have in direct contact with the iron oxide of the paint1 which does not combine chemically with oil1 those elements1 air1 moisture1 and organic matter1 which cause the iron to become a carrier of oxygen and a destroyer of what it is in contact with4 ,it is well known that iron paint darkens with age2 this is caused largely by the iron oxide losing oxygen1 which is partly transferred to the oil1 burning it up and destroying its tenacity1 as may be seen by examining iron structures painted for some time with iron paint or metallic brown1 the paint being found extremely brittle and in feathery scales4 ,this is not all the damage that is done4 ,the iron oxide in the paint becomes a carrier of oxygen to the very metal it was designed to protect1 and the process of corrosion is commenced and carried on under the paint1 which eventually peels or scales off1 the surface of the metal being found more or less oxidised and corroded4 ,asphalt and iron oxide being thus shown to be entirely incapable of preserving the iron1 it remains for us to consider the effect of red lead4 ,this pigment has the property of forming with linseed oil a hard elastic coating1 clinging with great tenacity to the metal4 ,it has no oxidising effect on iron1 and does not act as a carrier of oxygen from the atmosphere after the paint has set1 neither does it render the oil brittle nor promote rust4 ,when red lead fails1 it is principally by gradual wear or friction from the outside4 ,it does not scale or blister1 which both asphalt and iron oxide paints will do1 thereby requiring a thorough scraping and removal of old material before a new coat can be applied4 ,any red lead pigment adhering to the metal forms a permanent base for subsequent paintings1 and is utilised in further preserving the metal4 ,the ,u4,s4 ,government specifications for ironwork in the new ,library ,building of ,congress provide that 8all the work not ,bower-,barffed must be given one coat of pure red lead paint--not metallic paint of any kind1 but pure red lead--before leaving the shop and becoming rusted40 ,the experiments of the ,u4,s4 ,navy ,department on the preservation and fouling of plates covered with different pigments may be interesting4 ,a plate of iron covered with asphalt paint was immersed in sea-water for eight months and six days at the ,u4,s4 ,navy ,yard1 ,portsmouth1 ,n4,h4 ,at the end of that period it was found to be covered with scum and mud1 and very badly rusted4 ,a plate coated with iron paint1 immersed at ,key ,west1 ,fla41 was found to be covered with branch shell and coral1 but little paint remaining1 and very badly pitted and rusted4 ,a plate with two coats of red lead1 at the ,norfolk ,navy ,yard1 was found to have a few barnacles attached1 but to be in fair condition1 with no rust whatever on the iron after the paint was removed4 ,it will be seen that not only did the red lead protect the iron better than the other pigments referred to1 but that the plates were in far better condition as regards barnacles and fouling4 ,the superiority of red lead being thus established1 it is adopted for use on hulls of ,u4,s4 ,government warships4 ,on the ,dutch ,state railroads a series of experiments extending over a period of three years were made with the above pigments on scrubbed plates1 as well as those which had been pickled in acid to remove the scale4 ,it was found that the red lead was superior in each case to the others4 ,if red lead is thus proved to be the best pigment for preserving iron and steel structures1 what is the proper method for applying it8 ,we have seen above that the value of red lead depends upon its forming certain combinations with the oil1 and actually setting very much the same as plaster of ,paris or cement sets when mixed with water4 ,to successfully work with the latter substances1 it is necessary to put them in shape as quickly as possible after mixing with water before the setting takes place4 ,if the chemical action of setting has partly taken place1 the material may be moulded1 but it is known that good results will not be obtained4 ,red lead1 like these substances1 must be applied to the work before it sets with the oil4 ,it is on this point that failures in the use of pigment have generally occurred1 because if it be applied after the combining or setting process has taken place1 the hard1 elastic1 clinging coating will not be formed on the iron surface4 ,the following is the practice of one of the largest shipbuilding establishments in applying red lead to the hulls of vessels4 ,the plates are first pickled in a dilute solution of muriatic acid2 then passed between rapidly revolving wire brushes1 which remove all scale and dirt1 leaving the iron with a bright1 smooth surface2 then thoroughly washed with pure water1 and rubbed entirely dry2 and immediately coated with red lead and pure raw linseed oil4 ,the red lead is first thoroughly mixed with just enough linseed oil to form a very thick1 tough paste1 which will keep for several days without hardening4 ,this paste1 as wanted for use1 is thinned down to the proper consistency for spreading with pure linseed oil1 and applied at once1 care being taken to leave paint-pots empty at night4 ,a gallon of paint thus prepared contains about #e lb4 of oil and #ah lb4 of red lead1 and will cover on first coat about #ejj square feet4 ,in this way the red lead and oil get their initial set on the surface of the iron1 and the closer the pigment is brought to the iron the more durable will it be found4 ,some parties prime iron with iron oxide paint or metallic brown before applying red lead1 which appears to be a mistake1 as this paint readily scales from iron1 and1 of course1 carries the lead with it4 ,others coat the iron with oil before applying the red lead4 ,this1 too1 prevents the adhering paint from coming in contact directly with the surface1 and should be avoided1 provided the iron is properly prepared by thorough cleaning and removal of any scale and moisture1 which is a matter of the greatest importance4 ,in priming wood surfaces which are absorbent of oil1 the best practice favours the putting on of a coat of pure oil1 or oil thinned with turpentine1 which shall penetrate the surface1 and form a binder for the subsequent coats4 ,with iron1 the case is quite different1 provided we have a paint which1 from its very nature1 can attach itself firmly to the surface1 because it is out of the question for it to hold on to the surface of iron by any process of absorption into the pores of the metal1 as linseed oil will not penetrate to any extent4 ,such a paint should be put directly on the surface of the clean1 dry metal1 as is done in the cases of ,government vessels referred to1 without the intervention of a coat of oil or other substances4 ,the rusting of iron before the application of paint1 which is sometimes recommended1 should by all means be avoided1 as it not only prevents the contact of the paint with the metal1 but induces a chemical action which may go on with its corroding work under the applied paint4 ,as to the relative cost of iron oxide paints and red lead1 there is no doubt that the first cost of painting structures with iron oxide is somewhat less than with red lead4 ,the best railroad authorities state1 however1 that labour in painting structural work costs twice as much as material4 ,the true economy must therefore be sought in the durability of the paint as well as the preservation of the structure from rust4 ,actual experiments have shown that structures painted with iron paint had to be repainted in the third or fourth year1 those with red lead not until the sixth year4 ,in the second painting with iron paint1 the old material must be entirely removed before a fresh coat can be properly applied1 entailing considerable increased cost1 whereas with the red lead no such expense is necessary1 but1 as before stated1 a portion of the pigment remains on the iron1 continuing to protect the surface1 and is the very best base for the new coat1 besides contributing materially towards it1 lessening the expense of each repainting4 ,it will therefore be easily seen that1 although in first cost red lead may be slightly dearer than the iron paint1 yet in the long run it will be greatly cheaper1 besides giving assurance1 for the reasons above stated1 that the structure is not deteriorating from the effects of the atmosphere and paint4 ,before closing1 it might be well to allude to the effect of lampblack when mixed in small quantities1 say an ounce to the pound of red lead4 ,it changes the colour to a deep chocolate1 a possible advantage in some cases1 and also prevents the red lead from taking its initial set with linseed oil as quickly as when mixed with oil alone4 ,experiments recently made showed that this compound would remain mixed in paste form with linseed oil some thirty days without hardening4 ,thorough mixture is of the greatest importance1 and should be done in the dry state before adding the oil4 ,if rapid drying is desired1 ,japan dryer can be mixed with the oil used in thinning the paste before application with the brush4 ,too much stress cannot be laid on the great importance of having the metallic surface perfectly clean and as free as possible from scale and rust before the application of the paint4 ,where pickling with acid is impracticable1 as is frequently the case in railroad and other structural work1 thorough brushing with wire brushes should be resorted to4 ,,fresco ,,painting4--,the following observations are due to ,prof4 ,barff1 who dealt with the subject in one of the ,cantor ,lectures given at the ,society of ,arts4 ,the ground upon which fresco is painted is a lime ground2 and in order to have a permanent picture1 it is clear we must have a firm and stable ground4 ,in order to prepare that ground1 first of all the wall must be absolutely dry2 there must be no leakage of moisture from behind4 ,lime which has been 8run0 7as it is technically called by builders7 for a year or a year and a half is best to be employed1 for in proportion as the lime has been carbonated 7though it must not be so to too great an extent7 by the action of the carbonic acid of the air it makes a better and a harder mortar4 ,with this lime must be mixed sand1 and a great deal depends on the selection of the sand4 ,it must be river sand1 and it should be of even grain2 the sand should be mixed with water1 and allowed to pass along down a small stream1 so that in the centre of the stream you would have sand grains pretty nearly equal in size4 ,this is a point of considerable importance4 ,the reason why new lime cannot and ought not to be used is because it blisters2 small blisters appear on the surface1 and that of course would be ruinous to a picture4 ,a well-plastered wall should not have a blister or crack in it1 and this is secured by having your lime run for some time1 of good quality to start with1 and mixed with good sand4 ,there is no chemical process that takes place in fresco painting other than this1 that silicates are formed by the action of the lime upon the sand1 and carbonates by the action of the carbonic acid of the air upon the lime4 ,in painting a fresco picture1 inasmuch as there is no retouching the work when it is finished1 the artist must make his drawing very carefully4 ,the cartoon is made upon ordinary paper1 then it is fixed against the wall where the picture is to be painted4 ,the part where the artist decides to begin his work is uncovered1 that is to say1 a portion of the paper is turned down and cut away1 but in such a manner that it may be replaced4 ,then the plasterer puts fresh plaster1 about an eighth of an inch thick1 upon the uncovered portion of the wall1 and the plasterer's work is of the utmost importance in fresco painting4 ,the workman ought to practise it well before he attempts to prepare the ground for a large picture1 and it is of the greatest importance to allow the man to practise for several weeks before he is allowed to prepare any portion of the ground1 even for decorative3 painting4 ,in this way he becomes accustomed to the suction of the wall1 and upon the suction of the wall depends the soundness of the ground and the success of fresco painting4 ,when the plaster is first put on1 of course it is very soft2 the piece of cartoon is replaced upon it1 and the lines of the picture are gone over with a bone point1 so that an indentation is made1 and then the artist begins his painting4 ,at first he finds his colours work greasy2 you cannot get the tint to lie on1 it works streaky2 but you must not mind that1 you must paint on1 but you must only paint on for a certain time1 for if you go on painting too long you will interfere with the satisfactory suction of the ground1 which is so necessary to produce a good fresco painting4 ,of course1 nothing but practice can tell any one the period at which he ought to stop4 ,after some practice1 you know perfectly well by the feel when you ought to stop4 ,if you feel your colour flowing from your brush too readily1 you ought to stop at this period4 ,you must then leave your work for a time1 and go back to it again4 ,and then you will find1 as the plaster sucks in the colour which you have first laid on1 that there will be--it may be in the course of half-an-hour1 it may be an hour1 that depends upon the temperature of the atmosphere--a pleasant suction from your brush1 the colour going from it agreeably1 and you will find that it will cover better4 ,now is the time to paint rapidly1 and complete the work you have in hand4 ,when the colour leaves your brush as though the wall was thirsty for moisture1 you should cease painting2 every touch that is applied after that will turn out grey when it dries1 and the colour will not be fast upon the wall4 ,you will see1 then1 how impossible it is1 with such materials1 to paint in the same style in which you paint a picture in oil-colour4 ,fresco painting involves the adoption of an entirely different style from oil painting4 ,the frescoes of the old masters are not highly wrought up1 highly-finished works4 ,they depend for their effect upon the juxtaposition of tints1 the shadows being intensified by lines and cross-hatching4 ,if you look at those reproductions of some of the most valuable fresco paintings of the old masters1 you will see the method adopted by them depended upon the juxtaposition of tints1 not upon covering over1 and over1 and over again4 ,that juxtaposition of tints produces roundness1 transparency1 and has a very pleasing effect upon the eye4 ,if two tints are put against one another1 they do not appear to us as if they were single1 but each adds something to the effect of the other1 and together they produce a pleasurable and agreeable effect1 if they have been properly selected4 ,we all know how tempting it is to go back to a piece of painting and do something to it that ought to have been done before4 ,we think that a touch will improve it1 and we go and make it3 but in fresco painting the temptation must be resisted1 for it will be absolutely fatal to the permanency of the work4 ,,index ,african indigo1 #dg ,alkali for removing old paint1 #cea ,alumina for lakes1 #bhb ,american indigo1 #dg ---- lamp-black furnace1 #bj ,aniline black1 #be ,animal black1 #e1 #f ---- matters1 nitrogen in1 #ea ,anthracene oil black1 #ba ,antimony vermilion1 #ach ,antwerp blue1 #fb ,area covered by paint1 #cei1 #cfj ,arnaudon's green1 #abh ,arsenic from cobalt ores1 #ca ---- orange1 #aec ---- yellow1 #beg1 #bhj ,asphalt brown1 #aja ---- for painting iron1 #cgc ,aureolin1 #beg ,azurite blue1 #dj ,balmains luminous paint1 #bhf ,baryta blue1 #aaa ---- green1 #aji ---- red1 #adc ---- white1 #agj ,barytes1 #agj ,benzoates as dryers1 #cah ,benzol vehicles1 #bif ,binder's cobalt blue1 #bi ,bistre1 #aja ,bitumen1 #aja ,blacks1 #e-bf ---- adulterations1 #f ---- aniline1 #be ---- animal1 #e1 #f ---- anthracene oil1 #ba ---- bone1 #e1 #f ---- bone-oil1 #ab ---- candle1 #be ---- 8carbon10 #ai ---- charcoal1 #be ---- coal1 #be ---- coal tar1 #ad1 #ae1 #ba ---- coke-oven1 #af ---- composition1 #e ---- cork1 #be ---- creosote oil1 #ba ---- drop1 #aa ---- fat1 #aa1 #ab1 #ba ---- ,frankfort1 #aa ---- 8gas10 #ai ---- gas-tar1 #ad1 #ae1 #ba ---- ,german1 #bf ---- impurities1 #e ---- iron1 #bf ---- ivory1 #e1 #aa ---- lamp1 #e1 #aa ---- lead1 #bf ---- manganese1 #bf ---- mineral gas1 #ai ---- ---- matter in1 #f ---- natural gas1 #ai ---- oil1 #aa1 #ab1 #ba ---- oily matter in1 #e ---- organic1 #e ---- paraffin1 #af ---- peach-stone1 #aa ---- ,prussian1 #bf ---- prussiate1 #bf ---- resin1 #aa4 #ae1 #af ---- shale oil1 #ba ---- ,spanish1 #bf ---- tannin1 #bf ---- tar1 #ad1 #ae1 #ba ---- testing1 #f ---- unimportant1 #be ---- vegetable1 #e1 #aa1 #be1 #bf ---- vine twig1 #aa ---- wine lees1 #aa ,blanc fixe1 #agb ,bleaching oils1 #ccb ,blenkinsop and ,hartley's dryer1 #cce ,blood in priming coat1 #ceb ,blue luminous paint1 #bia ---- potash1 #ed1 #ef ---- salt1 #ed1 #ef ---- washing1 #ij ,blues1 #bg-ajj ---- ,antwerp1 #fb ---- azurite1 #dj ---- baryta1 #aaa ---- ,binder's cobalt1 #bh ---- ,bong's1 #fb ---- ,bremen1 #cd ---- ,brunswick1 #fd ---- cruleum1 #bg ---- ,chinese1 #fe ---- cobalt1 #bg1 #bh ---- cruleum1 #cg ---- copper1 #cd ---- indigo1 #db ---- lime1 #ch ---- manganese1 #di ---- mountain1 #dj ---- ,paris1 #fh ---- ,pligot1 #da ---- ,prussian1 #di ---- ,saxon1 #fi ---- smalts1 #bg1 #cj ---- soluble1 #fi ---- ,thnard's cobalt1 #bh ---- ,turnbull's1 #gj ---- ultramarine1 #gj ---- verditer1 #da ---- zaffre1 #cj ,body of pigments1 #bic ,boiled oils1 adulterants of1 #cca ---- ---- defects1 #cbg ---- ---- substitute for1 #ceb ---- ---- testing for lead in1 #cbh ,boiling oil1 #caf1 #cbj ,bole1 #bgb ,boletta1 #bgc ,bologna stone1 #agj ,bone black1 #e1 #f ---- ---- composition1 #aj ---- cost of production1 #aj ---- ---- furnaces1 #g ---- ---- qualities1 #aj ---- brown1 #ajb ---- oil black1 #ab ,bones1 carbonising1 #g ---- gases from1 utilising1 #i ,bong's manganese blue1 #di ---- ,prussian blue1 #fb ,borates as dryers1 #cah ,braconnot's green1 #abc ,bramwell's prussiate1 #eh ,brazil-wood lake1 #bhc ,bremen blue1 #cd ---- green1 #aab ,brighton green1 #aab ,brinjes and ,goodwin's paint mill1 #cdf ,brown luminous paint1 #bia ,browns1 #aja1 #ajh ---- asphalt1 #aja ---- bistre1 #aja ---- bitumen1 #aja ---- bone1 #ajb ---- cappagh1 #ajb ---- ,cassel earth1 #ajb ---- chicory1 #ajb ---- ,cologne earth1 #ajb ---- manganese1 #ajc ---- ,mars1 #ajc ---- ,prussian1 #ajc ---- ,rubens1 #ajb ---- sepia1 #ajd ---- ulmin1 #aje ---- ultramarine1 #hh ---- umbers1 #aje ---- ,vandyke1 #ajg ,brunquell on prussiate1 #ei ,brunswick blue1 #fd ---- green1 #aac ---- ---- characters1 #aah ---- ---- dry method1 #aag ---- ---- testing1 #aah ---- ---- wet method1 #aae ,brushes1 #cee ---- keeping1 #cee ,buckley's prussiate works1 #ei ,cadmium ,yellow1 #beh ,cruleum1 #bg ,calcining lamp-black1 #bc ,calcium hyposulphite1 preparing1 #aci ---- polysulphide1 preparing1 #aci ,candle black1 #be ,candle-nut oil1 #bih ,cappagh brown1 #ajb1 #ajf 8,carbon0 black1 #ai ---- pigments1 #e ,carbonising bones1 #g ,carminated lake1 #bhc ,carmine lake1 #bhc ,carriages1 painting1 #cfa ---- varnishing1 #cfe ,cars1 painting1 #cfa ---- re-varnishing1 #cfg ---- washing1 #cfg ,cassel earth1 #ajb ,cassius purple1 #adc ,cawk1 #agj ,central ,american indigo1 #dg ,cerchione1 #bgc ,chalk1 #bdf ,charcoal black1 #be ,charlton white1 #agb1 #bed ,chicory brown1 #ajb ,china clay1 #agb ---- ---- artificial1 #ahb ---- ---- characters1 #ahb ---- ---- drying1 #age1 #aha ---- ---- waste products1 #agi ---- ---- works1 #agc ,chinese blue1 #fe ---- green1 #aah1 #abi ---- red1 #add1 #ahe ---- vermilion1 #aeg ,chromates1 iron1 #bfg ---- lead1 #bfj ---- zinc1 #bfh ,chrome greens1 #aac1 #aah1 #abe ---- orange1 #add ---- red1 #add1 #ade ---- yellows1 #beh ,chromes1 characters1 #bff ,clark's paint mill1 #cda ,coaches1 painting1 #cfa ---- re-varnishing1 #cfg ---- varnishing1 #cfe ---- washing1 #cfg ,coal black1 #be ,coal-tar black1 #ad1 #ae1 #ba ,coats of paint1 #cee ,cobalt benzoate1 #cah ---- blues1 #bg1 #bh ---- borate1 #cah ---- greens1 #aai ---- ore furnace1 #ca ---- oxide blue1 #bh ---- pink1 #add ---- red1 #add ,cochineal lake1 #bhd ,cruleum blue1 #cg ,coke oven black1 #af ,colcothar1 #ade1 #aej ,cologne earth1 #ajb ,colour and aggregation of particles1 #b ---- ---- chemical composition1 #b ---- ---- light1 #a ---- causes1 #a ---- defined1 #a ---- destruction1 #b ---- of pigments1 testing1 #bic ---- sense1 #a ,condenser1 fume1 #baf ,condensing smoke1 #ac1 #ae1 #ag ,condy's white lead1 #aig ,copper blues1 #cd ---- carbonate1 #dj ---- greens1 #aba1 #acj1 #aca ---- hydrated oxide1 #cd1 #da ---- nitrate1 #cf ---- sulphate dryer1 #cbe ,cork black1 #be ,cornish umber1 #ajg ,cotton seed oil in linseed oil1 #cja ,covering power of pigments1 #bic ,cracking1 causes1 #cfc ,creosote oil black1 #ba ,crucibles for roasting smalts1 #cb ,cuttle fish brown1 #ajd ,cyanogen in prussiate making1 #eh ,cyprus earth1 #acd ,dammar vehicles1 #bif ,derby red1 #ade ,derbyshire umber1 #ajf ,discoloration of paint1 #cef ,douglas green1 #abj ,drop black1 #aa ,dryers1 #bie-cch1 #cfe ,dryers1 benzoates1 #cah ---- ,blenkinsop and ,hartley's1 #cce ---- borates1 #cah ---- chemical action of1 #cbb ---- ---- ---- in oils1 #ccj ---- cobalt benzoate1 #cah ---- copper sulphate1 #cbe ---- ,guynemer's1 #cai ---- lead1 #cbe ---- litharge1 #caf ---- manganese benzoate1 #cah ---- ---- oxalate1 #cai ---- ---- oxide1 #cah ---- ---- sulphate1 #cbe ---- red lead1 #caf ---- resinates1 #cah --- zumatic1 #cah ,drying china clay1 #age1 #aha ---- paint1 #cec1 #cfg ---- white lead1 #aia ,durability of pigments1 #bid ,dutch vermilion1 #afg ---- white lead1 #ahe ,dyestuff defined1 #a1 #c ,egyptian cruleum1 #cg ,emerald green1 #aba ---- ---- characters1 #abd ---- ---- testing1 #abd ---- tint greens1 #abd ,enamel white1 #bde1 #bed ,enamelled white1 #agj1 #ahc ,english white1 #ahc1 #bdf ,extraction of oils1 #cjh ,eye1 colour effect on1 #a ,fascia1 #bgc ,fat-black1 #aa1 #ab1 #ba ,ferric oxide reds1 #aej ,figuier's red1 #add ,filling before painting1 #ced1 #cfb ,fineness of pigments1 testing1 #bic ,finishing painting1 #cfc ,firmenich's vermilion1 #afe ,fleck's vermilion1 #aef ,frankfort black1 #aa ,freeman's white1 #bbd1 #bed ,french and ,hannay's white lead1 #baf ,fresco colours1 #beg ---- painting1 #aaa1 #cgh ,fume condenser1 #baf ,furnaces1 bone-black1 #g ---- cobalt ore1 #ca ---- galena1 #bbe ---- lamp-black1 #ab1 #ad1 #af1 #ag1 #ah1 #ai1 #bj1 #ba ---- ochre1 #bgg ---- prussiate1 #ec1 #ei1 #fj ---- smalts1 #cb1 #cc ,galena1 chromates from1 #bfc ---- white lead from1 #bbe ,galloway's green1 #abc ,gamboge1 #bgj ,gardner's white lead1 #bjj 8,gas0 black1 #ai ,gases from bones1 utilising1 #i ,gas-tar black1 #ad1 #ae1 #ba ,gaud indigo1 #de ,german black1 #bf ---- lamp-black1 #ae ,gmelin's ultramarine1 #ha ,green luminous paint1 #bia ,greens1 #aji ---- ,arnaudon's1 #abh ---- baryta1 #aji ---- ,braconnot's1 #abc ---- ,bremen1 #aab ---- ,brighton1 #aab ---- ,brunswick1 #aac ---- ,chinese1 #aah1 #abi ---- chrome1 #aac1 #aah1 #abe ---- cobalt1 #aai ---- copper1 #aba1 #acj1 #aca ---- ,cyprus earth1 #acd ---- ,douglas1 #abj ---- emerald1 #aba ---- ---- tint1 #abd ---- ,galloway's1 #abc ---- ,guignet's1 #abe ---- ,kchlin's1 #abc ---- lokao1 #abi ---- malachite1 #abi1 #aca ---- manganese1 #acj ---- mineral1 #acj1 #aca ---- mitis1 #acj ---- mountain1 #aca ---- ,paris1 #acb ---- ,prussian1 #acb ---- ,rinmann's1 #acb ---- sap1 #abi1 #acb ---- ,scheele's1 #acc ---- ,schweinfurth1 #acd ---- terre verte1 #acd ---- titanium1 #ace ---- ultramarine1 #gc ---- verdigris1 #ace ---- verditer1 #acf ---- ,verona earth1 #acd1 #acf ---- ,victoria1 #acg ---- ,vienna1 #acg ---- zinc1 #acg ,grey luminous paint1 #bia ,griffith's zinc white1 #bea ,grinding ,chinese blue1 #fg ---- smalts1 #cd ,ground-nut oil1 #big ,guignet's green1 #abe ,guimet's ultramarine1 #ha ,guynemer's dryer1 #cai ,gypsum1 #ahc ,hannay's white lead1 #bad ,hartley ,blenkinsop's dryer1 #cce ---- on dryers1 #cbb ,hempseed oil1 #bih ,hind and ,lund's paint mill1 #cde ,hyposulphite of lime1 preparing1 #aci ,idrian vermilion works1 #aed ,indian indigo1 #dc ---- red1 #adg1 #aej ,indigo1 ,african1 #dg ---- ,american1 #dg ---- blue1 #db ---- carmine1 #dh ---- ,central ,american1 #dg ---- cultivation1 #dc ---- gaud1 #de ---- ,indian1 #dc ---- ,japanese1 #de ---- ,javan1 #df ---- maceration1 #dc ---- manufacture1 #dc ---- ,philippine1 #dg ---- plants1 #db ---- preparations1 #dh ---- qualities1 #dh ---- testing1 #dh ,irish umber1 #ajf ,iron black1 #bf ---- chromates1 #bfg ---- decay1 #cfi ---- oxide for painting1 #cgc ---- ---- reds1 #aej ---- painting1 #cfi ---- ---- experiments1 #cge ---- pitching1 #cfi ,italian white lead1 #bba ,ivory black1 #e1 #aa ,jacquelin's vermilion1 #afh ,japanese indigo1 #de ,javan indigo1 #df ,kaolin1 #agb1 #ahc ,keeping brushes1 #cee ,kegs1 paint1 #cdi ,kilns1 #g1 #ab1 #ad1 #af1 #ag1 #ah1 #ai1 #bj1 #ba1 #ca1 #cb1 #cc1 #ec1 #ei1 #fj1 #bbe1 #bgg ,king's yellow1 #bga1 #bhj ,kirchoff's vermilion1 #afh ,kchlin's green1 #abc ,kukui oil1 #bih ,lakes1 #bhb ---- alumina1 #bhb ---- ,brazil-wood1 #bhc ---- carminated1 #bhc ---- carmine1 #bhc ---- cochineal1 #bhd ---- madder1 #bhd ---- yellow1 #bhe ,lamp-black1 #e1 #aa ---- ---- anthracene oil1 #ba ---- ---- apparatus1 #ab1 #ad1 #ae1 #af1 #ag1 #ai1 #bj1 #ba1 #bb ---- ---- calcining1 #bc ---- ---- creosote oil1 #ba ---- ---- gas tar1 #ad1 #ae1 #ba ---- ---- ,german1 #ae ---- ---- in iron painting1 #cgh ---- ---- ,martin ,grafton's1 #ae ---- ---- natural gas1 #ai ---- ---- nuisance in making1 #bc ---- ---- paraffin1 #af ---- ---- qualities1 #be ---- ---- ,russian1 #af ---- ---- ,shackell ,edwards' ,works1 #bd ---- ---- shale oil1 #ba ---- ---- transport1 #be ,lapis lazuli1 #gj ,lead black1 #bf ---- chromates1 #bfj ---- dryers1 #cbe ---- for white lead making1 #ahf ---- in boiled oil1 testing for1 #cbh ---- orange1 #adg ---- red1 #adh ---- sulphate1 #bbc ---- whites1 #ahc ,levigating ultramarine1 #gi ,lewis's white lead1 #bbc ,light and colour1 #a ,lime blue1 #ch ---- hyposulphite1 preparing1 #aci ---- manganate1 #di ---- polysulphide1 preparing1 #aci ---- white1 #agj1 #bde ,linseed oil1 #bii ---- ---- adulterants1 #cca ---- ---- bleaching1 #cjc ---- ---- impurities1 #cja ---- ---- purifying1 #cjb ,litharge as a dryer1 #caf ,lithophone1 #bde1 #bdg ,lokao1 #abi ,luminous paints1 #bhf ,mac,ivor's ultramarine1 #ic ---- white lead1 #bbi ,madder1 lake1 #bhd ,magnesite1 #bde ,malachite green1 #abi1 #aca ,manganese benzoate1 #cah ---- black1 #bf ---- blue1 #di ---- borate1 #cah ---- brown1 #ajc ---- green1 #acj ---- linoleate1 #ccf ---- oxalate dryer1 #cai ---- oxide dryer1 #cah ---- sulphate dryer1 #cbe ,manure from prussiate residue1 #eg ,mars brown1 #ajc ,martin ,grafton's lamp-black1 #ae ,massicot1 #adh ,measuring painting1 #cfj ,menhaden oil1 #cjc ,metallic paints1 #bgd ,mica1 #agi ,mills1 oil1 #cji ---- paint1 #cci1 #cda1 #cde1 #cdf ,mineral gas black1 #ai ---- green1 #acj1 #aca ---- matter in blacks1 #f ---- orange1 #aej ,minium1 #adh ,mitis green1 #acj ,mixer for paint1 #cda ,mixing paint1 #cfd ,mountain blue1 #dj ---- green1 #aca ,murdoch's antimony red1 #adb ,naples yellows1 #bga ,natural gas black1 #ai ,nitrogen converted into cyanogen in prussiate making1 #eh ---- in animal matters1 #ea ,nuisance from making lamp-black1 #bc ---- prevention1 #bd ,ochres1 #bgb ---- characters1 #bgi ---- kilns1 #bgg ---- working1 #bgd ,odour of paint1 removing1 #cef ,oil-black1 #aa1 #ab1 #ba ---- cake1 moulding1 #cac ---- mill1 #cji ---- seed crushing rolls1 #caa ---- ---- kettles1 #cab ---- vehicles1 #bie ,oils1 bleaching1 #ccb ---- boiled1 defects1 #cbg ---- ---- substitute for1 #ceb ---- ---- testing for lead in1 #cbh ---- boiling1 #caf1 #cbj ---- ---- chemistry of1 #cbf ---- candle-nut1 #bih ---- chemical action of dryers on1 #ccj ---- drying and non-drying1 #big ---- extraction1 #cjh ---- ground-nut1 #big ---- hemp-seed1 #bih ---- kukui1 #bih ---- linseed1 #bii ---- menhaden1 #cjc ---- pea-nut1 #big ---- poppy1 #cje ---- porgie1 #cjc ---- refining1 #cce ---- tobacco1 #cjf ---- tung1 #cjh ---- walnut1 #cjg ---- wood1 #cjh ,oily matter in blacks1 #e ,old paint1 removing1 #cea ,orange1 chrome1 #add ---- lead1 #adg ---- luminous paint1 #bia ---- mineral1 #aej ,organic blacks1 #e ,orpiment1 #bhj ,orr's white1 #bde1 #bed ,oxide reds1 #aej ,oxygen in making ultramarine1 #gh ,packing paint1 #cdi ,paint beds1 #bgd ---- composition1 #ceh ---- covering power1 #cei1 #cfj ---- cracking1 #cfc ---- defined1 #a ---- discoloration1 #cef ---- drying1 #cfg ---- estimating quantity required1 #cei1 #cfj ---- machinery1 #cci ---- mills1 #cci1 #cda1 #cde1 #cdf ---- mixer1 #cda ---- mixing1 #cfd ---- old1 removing1 #cea ---- packing1 #cdi ---- priming1 #ced1 #cfb ,painting1 #cea ---- brushes1 #cee ---- carriages1 #cfa ---- coats1 #cee ---- drying1 #cec ---- filling1 #ced1 #cfb ---- finishing1 #cfc ---- fresco1 #cgh ---- iron1 #cfi ---- measuring1 #cfj ---- plaster1 #cgh ---- priming coat1 #ceb1 #cfb ---- removing odour1 #cef ---- surface1 #cea ---- walls1 #cgh ---- water-colours1 #cef ---- woodwork1 #cfh ,paraffin black1 #af ---- wax vehicles1 #bif ,paris blue1 #fh ---- green1 #acb --- white1 #bdf ,peach-stone black1 #aa ,pea-nut oil1 #big ,pligot blue1 #da ,permanent white1 #agj1 #bdf ,persian red1 #ade1 #aej1 #aec ,philippine indigo1 #dg ,phosphorescent paints1 #bhf ,pigments1 carbon1 #e ---- defined1 #a1 #c ---- examining1 #bic ---- requirements1 #c ---- testing body1 #bic ---- ---- colour1 #bic ---- ---- covering power1 #bic ---- ---- fineness1 #bic ,pink1 cobalt1 #add ,pitching iron1 #cfi ,plaster painting1 #cgh ,pompeian cruleum1 #cg ,poppy seed oils1 #cje ,porgie oil1 #cjc ,potash1 blue1 #ed1 #ef ---- prussiate1 #ej ,prevention of nuisance1 #bd ,priming coat1 #ceb ---- paint1 #cfb ,prussian black1 #bf ---- blue1 #di ---- ---- ,bong's1 #fb ---- ---- common1 #fa ---- ---- qualities1 #di ---- ---- recipes1 #fa ---- ---- testing1 #ej ---- brown1 #ajc ---- green1 #acb ,prussiate1 #ej ---- black1 #bf ---- ,bramwell's works1 #eh ---- ,brunquell on1 #ei ---- ,buckley's works1 #ei ---- crystallisation1 #ee ---- formation1 #eb ---- furnaces1 #ec1 #ei1 #fj ---- metal1 lixiviation1 #ee ---- of potash1 #ej ---- pots1 #ec ---- residue as manure1 #eg ---- separating3 impurities1 #ef ,pug mill1 #cda ,purple of ,cassius1 #adc ,putty1 #ced1 #cfb ,puttying1 #ced1 #cfb ,realgar1 #aec1 #bhj ,red lead1 #adh ---- ---- as a dryer1 #caf ---- ---- for painting iron1 #cgd ---- luminous paint1 #bia ---- ultramarine1 #gg1 #hj ,reds1 #ach-afi ---- antimony vermilion1 #ach ---- baryta1 #adc ---- ,cassius purple1 #adc ---- ,chinese1 #add1 #ade ---- chrome1 #add1 #ade ---- ---- orange1 #add ---- cobalt1 #add ---- ---- pink1 #add ---- colcothar1 #ade1 #aej ---- ,derby1 #ade ---- ,indian1 #adg1 #aej ---- iron oxide1 #aej ---- lead orange1 #adg ---- minium1 #adh ---- orange mineral1 #aej ---- oxides1 #aej ---- ,persian1 #ade1 #aej1 #aec ---- realgar1 #aec ---- rouge1 #aej1 #aec ---- tin1 #add ---- ,venetian1 #aej1 #aec ---- vermilion1 #aec ,refining oils1 #cce ,removing old paint1 #cea ,resin black1 #aa1 #ae1 #af ,resinates as dryers1 #cah ,rinmann green1 #acb ,roller mills for paint1 #cci1 #cda1 #cde1 #cdf ,rosin in linseed oil1 #cja ,rouge1 #aej1 #aec ,rubens brown1 #ajb ,ruby of arsenic1 #aec ,russian lamp-black1 #af ,rutherford ,barclay kiln1 #bgg ,sap green1 #abi1 #acb ,satin white1 #bdf ,saxon blue1 #fi ,schatte's luminous paint1 #bij ,scheele's green1 #acc ,schweinfurth green1 #acd ,seed-crushing rolls1 #caa ---- kettles1 #cab ---- oils1 extracting1 #cjh ,sepia1 #ajd ,shackle and ,edwards' lamp-black works1 #bd ,shale oil black1 #ba ,ships' hulls1 painting1 #cgf ,siena earths1 #bgb ,siennas1 #bgb ,silica ultramarine1 #gd ,smalts1 #bg1 #cj ---- crucibles1 #cb ---- furnace1 #cb1 #cc ---- grinding1 #cd ,smith's pitching process for iron pipes1 #cfi ,smoke1 condensing1 #ac1 #ae1 #ag ,soda for making ultramarine1 #gh1 #ib ---- sulphate from ultramarine1 #gi ---- ultramarine1 #gd ,soluble blue1 #fi ,spanish black1 #bf ---- white1 #bdf ,square blue1 #ij ,stack white lead1 #ahe ,stampshaw lamp-black furnace1 #ba ,stangen-spath1 #agj ,strontia white1 #bdf ,sulphate ultramarine1 #gb ,surface for painting1 #cea ,tannin black1 #bf ,tar black1 #ad1 #ae1 #ba ,terra alba1 #ahc1 #bdf ---- bolare1 #bgc ---- guilla1 #bgc ,terre verte1 #acd ,thalwitzer's lamp-black apparatus1 #af ,thnard's cobalt blue1 #bh ---- white lead1 #ahd ,tin red1 #add ,titanium green1 #ace ,tobacco-seed oil1 #cjf ,transport1 lamp-black1 #be ---- paint1 #cdi ,tung oil1 #cjh ,turkey umber1 #ajf ,turnbull's blue1 #gj ,ulmin1 #aje ,ultramarine1 #gj ---- adulterations1 #gf ---- ancient treatise on1 #id ---- artificial1 #ga ---- brown1 #hh ---- ,brunner on1 #hb ---- chemistry1 #ha ---- colouring principle1 #ge ---- composition1 #ha ---- direct crucible process1 #hg ---- ,dollfus on1 #hd ---- effect of silica1 #hc ---- ,endemann on1 #hb ---- faults1 #ajj ---- ,german process1 #hf ---- ,gmelin's1 #ha ---- ,goppelsrder on1 #hd ---- green1 #gc ---- ,guimet's1 #ha ---- ,heyne on1 #id ---- history1 #hj ---- ,hoffmann on1 #hc ---- indirect process1 #he ---- levigating1 #gi ---- ,leykauf process1 #id ---- ,mc,ivor's1 #ic ---- natural1 #gj ---- ,nejedly on1 #id ---- oxygen in making1 #gh ---- properties1 #gf ---- red1 #gg1 #hj ---- removing soluble salts1 #gh ---- resisting alum1 #ge1 #gg ---- ,ritter on1 #hb ---- ,schlzenberger on1 #hb ---- silica process1 #gd ---- soda for1 #gh1 #ib ---- ---- process1 #gd ---- ---- sulphate from1 #gi ---- statistics1 #ia ---- ,stein on1 #ha ---- sulphate process1 #gb ---- testing1 #ii ---- uses1 #gf1 #ij1 #ii1 #ajj ---- varieties1 #ii ---- violet1 #gg1 #gi ---- ,wilkins on1 #ha ,umbers1 #aje1 #bgb ,vandyke brown1 #ajg ,varnishing coaches1 #cfe1 #cfg ,vegetable blacks1 #e1 #aa1 #be1 #bf ,vehicles1 #bie-cch1 #cfe ,venetian red1 #aej1 #aec ,verdegris1 #ace ,verditer1 #acf ---- blue1 #da ,vermilion1 #aec ---- antimony1 #ach ---- ,chinese1 #aeg ---- ,dutch1 #afg ---- ,firmenich's1 #afe ---- ,fleck's1 #aef ---- ,jacquelin's1 #afh ---- ,kirchoff's1 #afh ---- ,weshle's1 #afh ---- works at ,idria1 #aed ,verona earth1 #acd1 #acf ,victoria green1 #acg ,vienna green1 #acg ,vine-twig black1 #aa ,violet luminous paint1 #bia ---- ultramarine1 #gg1 #gi ,wagner's antimony red1 #adb ,wall painting1 #cgh ,walnut oil1 #cjg ,washing blue1 #ij ,water-colour painting1 #cef ,wax vehicles1 #bif ,weshle's vermilion1 #afh ,wetherill furnace1 #bbe ,white lead1 #ahc ---- ---- adulterations1 #aie ---- ---- characters1 #bdb ---- ---- chemistry of1 #ahg1 #aib1 #aic1 #bjj ---- ---- ,condy's1 #aig ---- ---- cost1 #bac ---- ---- dangers of1 #aia ---- ---- dry1 #aie ---- ---- drying1 #aia ---- ---- ,dutch1 #ahe ---- ---- ,french ,hannay's1 #baf ---- ---- from galena1 #bbe ---- ---- ,gardner's1 #bjj ---- ---- ,hannay's1 #bad ---- ---- ,italian1 #bba ---- ---- lead for1 #ahf ---- ---- ,lewis's1 #bbc ---- ---- ,mac,ivor's1 #bbi ---- ---- powdered1 #aie ---- ---- precipitated1 #aid ---- ---- stack1 #ahe ---- ---- substitutes1 #aid ---- ---- testing1 #bdd ---- ---- ,thnard's1 #ahd ---- luminous paint1 #bhf1 #bij ,whites1 #agj-bef ---- baryta1 #agj ---- blanc fixe1 #agb ---- chalk1 #bdf ---- ,charlton1 #agb1 #bed ---- china clay1 #agb ---- enamel1 #bde1 #bed ---- enamelled1 #agj1 #ahc ---- ,english1 #ahc1 #bdf ---- ,freeman's1 #bbd1 #bed ---- ,griffith's1 #bea ---- gypsum1 #ahc ---- lead1 #ahc ---- lime1 #agj1 #bde ---- lithophone1 #bde1 #bdg ---- magnesite1 #bde ---- mineral1 #ahc1 #bde ---- ,orr's1 #bde1 #bed ---- ,paris1 #bdf ---- permanent1 #agj1 #bdf ---- satin1 #bdf ---- ,spanish1 #bdf ---- strontia1 #bdf ---- terra alba1 #ahc1 #bdf ---- whiting1 #bdf ---- zinc1 #bdg ,whiting1 #bdf ,wilson's fume condenser1 #baf ,wine-lees black1 #aa ,wood charcoal black1 #be -- oil1 #cjh ,woodwork1 painting1 #cfh ,working ochre beds1 #bgd ,wright's paint machinery1 #cci ,yellow luminous paint1 #bia ---- prussiate1 #ej ,yellows1 #beg-bha ---- arsenic1 #beg1 #bhj ---- aureolin1 #beg ---- hole1 #bgb ---- cadmium1 #beh ---- chrome1 #beh ---- gamboge1 #bgj ---- ,king's1 #bga1 #bhj ---- lakes1 #bhe ---- ,naples1 #bga ---- ochres1 #bgb ---- orpiment1 #bhj ---- realgar1 #bhj ---- umbers1 #bgb ,zaffre1 #cj ,zinc chromates1 #bfh ---- green1 #acg ---- oxide1 #cg1 #bdg ---- sulphide1 #bej ---- whites1 #bdg ---- ---- characters1 #bee ,zumatic dryer1 #cah ,,london3 ,,printed ,,by ,,william ,,clowes ,,and ,,sons1 ,,limited1 ,,stamford ,,street ,,and ,,charing ,,cross4