,transcriber's ,notes ,text between underscores represents text printed in italics1 text between equal signs represents blackletter text4 ,d represents a subscript ,d4 ,small capitals have been transcribed as ,,all ,,capitals4 ,more ,transcriber's ,notes may be found at the end of this text4 ,,the ,,principles ,,of ,,leather ,,manufacture ,illustration3 ,frontispiece4 ,,plate ,i4 ,,section ,,of ,,calf-,,skin4 7,for key1 see ,fig4 #i47 ,,the ,,principles ,,of ,,leather ,,manufacture ,,by ,h4 ,r4 ,,procter1 ,f4,i4,c4 ,f4,c4,s4 ,,professor ,,of ,,leather ,,industries ,,at ,,the ,,yorkshire ,,college1 ,,leeds2 ,,past ,,president ,,of ,,the ,,international ,,association ,,of ,,leather ,,trades ,,chemists ,illustration ,london3 ,e4 ,f4 ,n4 ,,spon1 ,,limited1 #abe ,,strand ,new ,york3 ,,spon ,,chamberlain1 #abc ,,liberty ,,street #aijc ,dedicated to ,,professor ,f4 ,l4 ,,knapp ,,geheimen ,,hofrath1 ,,dr4 ,,phil4 ,,and ,,dr4 ,,ing4 ,,the ,,pioneer ,,of ,,scientific ,,research ,,in ,,leather ,,manufacture ,,preface4 ,the origin of the present work was an attempt to prepare a second edition of the little ,text-,book of ,tanning which the ,author published in #ahhe1 and which has been long out of print4 ,though persevered in for years1 the work was never brought to completion1 partly owing to the constant pressure of other duties1 but still more to the rapid advances which have been made in our knowledge of the subject1 and in the scientific thought which has been devoted to it4 ,for his share in the initiation of this work1 much credit is due to ,wilhelm ,eitner1 ,director of the ,imperial ,royal ,research ,institute for ,leather ,industries in ,vienna1 but the advance he began has been energetically carried forward not only in ,vienna1 but in the ,tanning ,schools and ,research ,institutes of ,freiberg1 ,leeds1 ,london1 ,lige1 ,copenhagen1 ,berlin and elsewhere1 and to a less extent in private laboratories4 ,under the pressure of this rapid growth1 as it was impossible to complete the work as a whole1 the ,author published an instalment dealing with the purely chemical side of the subject in #ahih1 under the title of the #8,leather ,industries ,laboratory ,book'2 which has been translated into ,german1 ,french and ,italian1 and of which the ,english edition is rapidly approaching exhaustion4 ,the present work1 which should by right have preceded the ,laboratory ,book 7and which frequently refers to it as 8,l4,i4,l4,b4071 attempts to deal with the general scientific principles of the industry1 without describing in detail its practical methods 7though incidentally many practical points are discussed74 ,to complete the subject1 a third volume ought to be written1 giving working details of the various methods of manufacture2 but apart from the difficulty of the subject1 and the weariness of 8making many books10 the methods of trade are so fluctuating1 and dependent on temporary conditions that they have not the same permanent value as the record of scientific advance4 ,as the present volume is intended to appeal both to the chemist and to the practical tanner1 it must to a certain extent fail in both1 since many matters are included which are already familiar to the former1 and it is to be feared1 some1 which may prove difficult to the latter4 ,for these and other imperfections the ,author claims the indulgence of his ,readers4 ,the ,author must here acknowledge his indebtedness to ,dr4 ,,tom ,,guthrie and to ,mr4 ,a4 ,b4 ,,searle for assistance in writing several of the chapters2 to ,dr4 ,a4 ,,turnbull and ,mr4 ,f4 ,a4 ,,blockey for much help in reading proofs and preparing the ,,ms4 for the press2 and to the many gentlemen who have furnished or allowed him to use their blocks and drawings in illustration4 ,,the ,,yorkshire ,,college1 ,,leeds4 ,,contents4 ,,chapter ,i4 ,,introductory ,,and ,,historical4 ,primitive methods of leather manufacture -- ,use of leather by the ancients -- ,progress of leather manufacture in ,england -- ,methods of production of leather -- ,vegetable tannages -- ,combination tannages -- ,use of aluminium1 iron and chromium -- ,oil- and fat-leathers -- ,difficulties of scientific treatment ,,page #a ,,chapter ,,ii4 ,,introductory ,,sketch ,,of ,,leather ,,manufacture4 ,the object of tanning -- ,washing and soaking -- ,removal of hair by liming -- ,unhairing by putrefaction -- ,unhairing and fleshing -- ,deliming -- ,bating1 puering and drenching -- ,the vegetable tanning process -- ,currying -- ,alum1 chrome and chamois leathers ,,page #g ,,chapter ,,iii4 ,,the ,,living ,,cell4 ,the structure of cells -- ,white blood-corpuscles -- ,the yeast-cell -- ,epidermis cells -- ,the building up of plants ,,page #aj ,,chapter ,,iv4 ,,putrefaction ,,and ,,fermentation4 ,the nature of ferments -- ,organised and unorganised ferments -- ,classification of organised ferments -- ,general properties of ferments -- ,the alcoholic fermentation -- ,the action of enzymes or unorganised ferments -- ,the destruction of ferments by heat and antiseptics -- ,the products of fermentation -- ,the fermentations of the tannery -- ,fermentation in bating and puering -- ,fermentation in the tanning liquors -- ,moulds and mildews -- ,control of fermentation ,,page #ae ,,chapter ,v4 ,,antiseptics ,,and ,,disinfectants4 ,distinction of antiseptics and disinfectants -- ,lime -- ,sulphur dioxide -- ,manufacture of sulphuric acid -- ,bisulphites and metabisulphites -- ,boric acid and borates -- ,mercuric chloride -- ,mercuric iodide -- ,copper sulphate -- ,zinc salts -- ,arsenic -- ,fluorides -- ,phenol -- ,use of carbolic acid -- ,eudermin -- ,creasote -- ,creolin -- ,salicylic acid -- ,benzoic acid -- ,cresotinic acid -- ,anticalcium -- 8,c4,t40 bate -- ,naphthalene sulphonic acid -- ,naphthols -- ,hydronaphthol -- ,oxynaphthoic acid -- ,carbon disulphide -- ,formaldehyde -- ,triformol -- ,camphor and essential oils ,,page #ba ,,chapter ,,vi4 ,,the ,,origin ,,and ,,curing ,,of ,,hides ,,and ,,skins4 ,marking of hides -- ,fellmongering of sheep-skins -- ,the use of salt -- ,salting of packer hides -- ,brining -- ,dry-salting -- ,indian plaster cures -- ,analysis of salt-earths -- ,salt- and iron-stains -- ,drying of hides and skins -- ,damage by insects -- ,the warble-fly -- ,damage by branding -- ,cockle ,,page #cc ,,chapter ,,vii4 ,,structure ,,and ,,growth ,,of ,,skin4 ,similarity of ,mammalian skins -- ,development of skin -- ,structure of calf-skin -- ,the epidermis -- ,the structure of hair -- ,the sebaceous glands -- ,the development of hair -- ,the hair-sheath -- ,the hair-muscle -- ,the hyaline layer -- ,the corium -- ,connective tissue -- ,fat cells -- ,striped muscle -- ,elastic fibres -- ,the unhairing process -- ,the sweating process ,,page #df ,,chapter ,,viii4 ,,the ,,chemical ,,constituents ,,of ,,skin4 ,the keratin tissues -- ,production of gelatine from connective tissue -- ,analyses of hide and gelatine -- ,constitution of gelatine -- ,analysis and ,reactions of gelatine -- ,decomposition of gelatine -- ,reactions of gelatine -- ,chondrin -- ,coriin -- ,hide-albumin -- 8,acid0 and 8alkali0 albumins -- ,egg-albumin -- ,vitellin -- ,casein -- ,keratins -- ,elastic fibres -- ,analytical methods -- ,kjeldahl process ,,page #ef ,,chapter ,,ix4 ,,the ,,physical ,,chemistry ,,of ,,the ,,hide-,,fibre4 ,causes of swelling and contraction -- ,the essentials of the tanning process -- ,the constitution of matter -- ,the nature of molecules -- ,vapour-pressure -- ,surface-tension -- ,solution-pressures -- ,jellies -- ,crystals -- ,osmotic pressure -- ,electrolytic dissociation -- ,electrolysis -- ,reactions of ions -- ,absorption of water by gelatine -- ,dehydration by alcohol -- ,action of acids1 alkalies and salts on gelatinous fibre -- ,physical explanation of swelling -- ,action of acids on gelatine -- ,action of alkalies on gelatine -- ,effect of salt -- ,the pickling process ,,page #gc ,,chapter ,x4 ,,water ,,as ,,used ,,in ,,the ,,tannery4 ,impurities of natural water -- ,hardness -- ,soap test -- ,temporary hardness -- ,clark's softening process -- ,archbutt and ,deeley's softening apparatus -- ,other appliances -- ,effect of temporary hardness in tanning and dyeing -- ,permanent hardness -- ,boiler scale -- ,mud -- ,iron -- ,alumina -- ,soda -- ,copper1 lead1 etc4 -- ,sulphuric acid -- ,nitrates and ,nitrites -- ,chlorine -- ,carbonic acid -- ,silicic acid -- ,effect of hardness on plumping -- ,peaty waters ,,page #ic ,,chapter ,,xi4 ,,soaking ,,and ,,softening ,,of ,,hides ,,and ,,skins4 ,washing of fresh hides -- ,danger of putrefaction -- ,soaking of salted hides and skins -- ,soaking and softening of dry and dry-salted hides -- ,american wash-wheel -- ,chemical methods -- ,difficulty of softening hides dried at high temperature ,,page #ajh ,,chapter ,,xii4 ,,depilation4 ,methods of depilation -- ,sweating process -- ,liming -- ,sources of lime -- ,quicklime -- ,slaking of lime -- ,solubility of lime in water -- ,analysis of lime -- 8,available0 lime -- ,action of lime on hide -- ,liming in pits -- ,suspension limes -- ,effect of warming limes -- ,quantity of lime required -- ,the ,buffalo method -- ,action of old limes -- ,solution of hide substance by limes -- ,sodium and potassium hydrates -- ,payne and ,pullman's process -- ,alkaline carbonates -- ,alkaline sulphides -- ,sodium sulphide -- ,calcium ,sulphydrate -- ,gas-lime -- ,tank-waste -- ,lufkin's liming preparation -- ,barium sulphydrate -- ,realgar1 or red sulphide of arsenic -- 8,inoffensive0 unhairing solution -- ,earp's patent -- ,unhairing on the beam -- ,unhairing machines -- ,vaughn machine -- ,leidgen machine -- ,unhairing in stocks and wash-wheel -- ,jones machine -- ,fleshing -- ,vaughn fleshing machine -- ,rounding ,,page #aai ,,chapter ,,xiii4 ,,deliming1 ,,bating1 ,,puering ,,and ,,drenching4 ,methods of removing lime and reducing swelling -- ,use of acids -- ,lactic1 acetic and formic acids -- ,boral -- ,sodium bisulphate -- ,boric 7boracic7 acid -- ,borax -- 8,pulling down0 process -- ,use of ammonium chloride and sulphate -- ,pickling solutions -- ,drenching with lactic acid -- ,metabisulphite of soda -- ,washing out lime1 ,french process -- ,nesbitt's process -- ,use of carbonic acid -- ,carbolic acid -- ,cresotinic acid -- ,oxynaphthoic acid -- 8,anticalcium0 -- 8,acrilene bating acid0 -- 8,c4,t4 ,bate0 -- ,use of sulphides and polysulphides -- ,babool pods -- ,bran-drenching -- ,bating and puering -- ,causes of bating effect -- ,pepsin -- ,trypsin1 or ,pancreatin -- ,wood's researches -- ,erodin -- ,palmer's experiments -- ,other artificial bates -- ,relative effect of dog- and pigeon-dung bates -- ,analysis of dungs -- 8,scudding10 or 8fine hairing0 -- ,preservation and use of dung ,,page #aeb ,,chapter ,,xiv4 ,,alum ,,tannage1 ,,or ,,tawing4 ,nature of leather -- ,mineral tanning substances -- ,salts of aluminium -- ,alums -- ,aluminium sulphate -- ,effect of salt in tawing -- ,basic alumina solutions -- ,tawing of skins for rugs -- ,calf-kid manufacture -- ,glove-kid -- ,green leather and other combination tannages ,,page #ahd ,,chapter ,,xv4 ,,iron ,,and ,,chrome ,,tannages4 ,iron tannages -- ,chrome tannages -- ,chemistry of chromium compounds -- ,knapp's method of chrome tannage -- ,cavallin -- ,swan -- ,heinzerling -- ,hummel's improvement -- ,schultz's method -- ,theory of the two-bath process -- ,practical management of the two-bath process -- ,dennis's chrome tanning liquor -- ,procter's liquors -- ,theory of basic process -- ,practical use of basic liquors -- ,washing and neutralisation -- ,effect of sulphur on chrome leather -- ,bluebacking -- ,fat-liquoring -- ,dyeing of chrome leather -- ,glazing and finishing ,,page #aih ,,chapter ,,xvi4 ,,principles ,,of ,,the ,,vegetable ,,tanning ,,processes4 ,methods of sole-leather tanning -- ,finishing of sole-leather -- ,theory of vegetable tannage -- ,deliming of sole-leather -- 8,mellowness0 of liquors -- ,penetration of tannage -- ,drying of sole-leather -- ,tanning of dressing leathers -- ,preparation for tannage -- ,avoidance of 8bloom0 -- ,tannage of moroccos and other skins ,,page #bbj ,,chapter ,,xvii4 ,,combination ,,of ,,vegetable ,,and ,,mineral ,,tannages4 ,early combination tannages -- ,respective effect of mineral and vegetable tannages -- ,use of fat-liquor -- ,action of mineral and vegetable tanning materials on each other -- ,danish and ,swedish glove leathers -- ,green leathers -- ,making of fat-liquors -- ,chrome combinations ,,page #bcf ,,chapter ,,xviii4 ,,vegetable ,,tanning ,,materials4 ,distribution of tannin in plants -- ,structure of barks -- ,botanical list of important tanning materials ,,page #bdb ,,chapter ,,xix4 ,,the ,,chemistry ,,of ,,the ,,tannins4 ,sources of tannins -- ,general qualities of tannins -- ,chemical constitution -- ,catechol- and pyrogallol tannins -- ,catechins -- ,tendency of ,catechol tannins to darken with light -- 8,physiological0 and 8pathological0 tannins -- ,presence of mordant colouring matters ,,page #bid ,,chapter ,,xx4 ,,the ,,sampling ,,and ,,analysis ,,of ,,tanning ,,materials4 ,the ,international ,association of ,leather ,trades ,chemists -- ,the ,american ,official ,association of ,agricultural ,chemists -- ,the sampling of material -- ,preparation of solution for analysis -- ,extraction of solid materials -- ,total soluble matter -- ,evaporations of solutions -- ,the weighing of residues -- ,the determination of non-tannins -- ,the hide-powder filter method -- ,the hide-powder shake method -- ,determination of moisture -- ,colour-measurement ,,page #cjj ,,chapter ,,xxi4 ,,the ,,grinding ,,of ,,tanning ,,materials4 ,primitive methods of grinding -- ,the bell mill or coffee mill -- ,disc mills -- ,disintegrators -- ,carr's disintegrator -- ,carter's disintegrator -- ,adjustment of disintegrators -- ,the ,williams pulveriser -- ,myrobalans and ,valonia crushers -- ,sawing mills -- ,shaving mills -- ,dyewood cutting machines -- ,screening of ground materials -- ,hatching of bark -- ,disintegrators and fire insurance -- ,dust from disintegrators -- ,chain conveyors -- ,belt conveyors -- ,vibrating conveyors ,,page #caf ,,chapter ,,xxii4 ,,the ,,extraction ,,of ,,tanning ,,materials1 ,,and ,,the ,,making ,,of ,,extracts4 ,leaching -- ,early forms of leaches -- ,the press-leach system -- ,handling of liquors -- ,distributing troughs and valves -- ,construction of leaches -- ,influence of temperature -- ,use of silent boiling jet -- ,closed extractors -- ,sprinkling leaches -- ,manufacture of extracts -- ,decolorisation of extracts -- ,soluble extracts -- ,concentration of extracts -- ,yaryan evaporator -- ,multiple effects -- ,the use of extracts in the tannery -- ,effect of temperature on extraction and colour ,,page #cbh ,,chapter ,,xxiii4 ,,fats1 ,,soaps1 ,,oils ,,and ,,waxes4 ,characteristics of fats and oils -- ,chemical constitution -- ,nature and production of soaps -- ,insoluble soaps -- ,distillation of fats -- ,solvents of oils -- ,drying oils -- ,saturated fatty acids -- ,non-drying liquid fatty acids -- ,less-saturated liquid fatty acids -- ,castor oil -- ,tallow -- ,neatsfoot oil -- ,wool fat -- ,holden fat -- ,distilled wool grease -- ,distilled stearine -- ,olive oil -- ,castor oil -- ,turkey-red oil -- ,linseed oil -- ,boiled oils -- ,japan for leather -- ,cottonseed oil -- ,sesame oil -- ,cod oil -- ,shark liver oil -- ,whale oil -- ,seal oil -- ,menhaden oil -- ,fish oils -- ,fish tallow -- ,dgras and ,sod oil -- ,waxes -- ,sperm oil -- ,beeswax -- ,carnauba wax -- ,japan wax -- ,volatile or essential oils -- ,birch oil -- ,wintergreen oil -- ,mineral oils and waxes -- ,vaseline and vaseline oil -- ,paraffin wax -- ,ozokerit -- ,resin oils -- ,resin ,,page #cej ,,chapter ,,xxiv4 ,,oil ,,tannages1 ,,and ,,the ,,use ,,of ,,oils ,,and ,,fats ,,in ,,currying4 ,primitive use of oil in leather manufacture -- ,chamoising and the production of washleather -- ,manufacture of ,moellon1 or ,dgras -- ,sod oil -- ,formaldehyde leathers -- 8,crown0 and 8,helvetia0 leathers -- ,theory of oil leathers -- ,processes of currying -- ,theory of the stuffing process -- ,hand-stuffing -- ,drum-stuffing -- ,stuffing of dry leather -- 8,spueing0 and its causes -- ,fat-liquoring ,,page #cgh ,,chapter ,,xxv4 ,,dyes ,,and ,,dyeing4 ,coal-tar colours -- ,acid and basic colours -- ,theories of dyeing -- ,fixation of colours on leather -- ,mordants and mordant colours -- ,curriers' inks -- ,glazes and finishes -- 8,assistants0 in dyeing -- ,bronzing -- ,fading of colours -- ,practical methods of leather dyeing -- ,use of dyewoods -- ,iron 8strikers0 -- ,tannin blacks -- ,staining -- ,theory of colour-mixtures -- ,finishing dyed leathers -- ,testing of dyes -- ,injurious effects of metals in dyeing ,,page #cid ,,chapter ,,xxvi4 ,,evaporation1 ,,heating ,,and ,,drying4 ,theory of evaporation -- ,boiling point and vapour-pressure -- ,consumption of heat in evaporation -- ,heat-units -- ,mechanical energy of heat -- ,evaporation by 8multiple effect0 -- ,vapour-pressure of atmospheric moisture -- ,wet and dry bulb thermometers -- ,heat and air required in leather-drying -- ,loss of heat by buildings -- ,quantity of heat given by steam and hot-water pipes -- ,screw-fans for drying -- ,centrifugal fans -- 8,turret0 dryer -- ,downward ventilation -- ,arrangement of steam-pipes -- ,hot water pipes ,,page #dbj ,,chapter ,,xxvii4 ,,construction ,,and ,,maintenance ,,of ,,tanneries4 ,selection of site -- ,arrangement of buildings -- ,fire insurance -- ,automatic sprinklers -- ,possibility of extension -- ,production and distribution of power -- ,electric motors -- ,shafts1 pulleys and belting -- ,balancing of machinery -- ,fire-risk from bark mills -- ,chain-conveyors -- ,lubricating oils -- ,construction of pits -- ,underground pipes and overhead troughs -- ,pumps and pumping appliances ,,page #ddd ,,chapter ,,xxviii4 ,,waste ,,products ,,and ,,their ,,disposal4 ,hair -- ,fleshings and glue-stuff -- ,fat -- ,bate-shavings -- ,horns -- ,spent tan -- ,tan-furnaces -- ,sewage and other waste liquids -- ,chemical purification of sewage -- ,settling tanks -- ,filter-presses -- ,bacterial purification of sewage -- ,tannery waste-liquors ,,page #dfj ,,appendix ,a4 ,,method ,,of ,,the ,,international ,,association ,,of ,,leather-,,trades ,,chemists ,,for ,,the ,,analysis ,,of ,,tanning ,,materials3 ,corrected to #aija4 ,sampling from bulk -- ,preparation for analysis -- ,preparation of infusion -- ,determination of tanning matters and non-tannins -- ,colour-measurement -- ,analysis of used liquors ,,page #dge ,,appendix ,b4 ,,the ,,decimal ,,system4 ,metrical weights and measures -- ,centigrade thermometer ,,page #dha ,,appendix ,c4 ,,method ,,of ,,analysis ,,of ,,tanning ,,materials ,,of ,,the ,,american ,,association ,,of ,,official ,,agricultural ,,chemists3 ,corrected to #aija4 ,preparation of sample -- ,quantity of material -- ,moisture -- ,total solids -- ,soluble solids -- ,non-tannins -- ,tannins -- ,testing of hide-powder -- ,testing non-tannin filtrate ,,page #dhb ,,appendix ,d4 ,,lists ,,of ,,coal-,,tar ,,dyes ,,suitable ,,for ,,dyeing ,,and ,,staining ,,leather1 furnished by ,mr4 ,m4 ,c4 ,,lamb4 ,colours for staining leather -- ,colours for dyeing vegetable-tanned leather -- ,dyeing and finishing chrome-leather -- ,list of colours suitable for chrome-leather ,,page #dhe ,,index ,,page #dii ,,principles ,,of ,,leather ,,manufacture4 ,illustration ,,chapter ,i4 ,,introductory ,,and ,,historical4 ,the origin of leather manufacture dates far back in the prehistoric ages1 and was probably one of the earliest arts practised by mankind4 ,the relics which have come down to us from palolithic times1 and the experience of the modern explorer1 alike tell us that agriculture is a later and a higher stage of development than the life of the hunter2 and since1 in the colder regions1 clothing of some kind must always have been a necessity1 we may conclude that it was first furnished by the skins of animals4#a #a ,see also ,gen4 iii4 #ba4 ,while wet skins putrefy and decay1 dry ones are hard and horny2 and nothing could be more natural to the hunter than to try to remedy this by rubbing the drying skin with the fat of the animal1 of which he must have noticed the softening effect on his own skin4 ,by this means a soft and durable leather may be produced1 and this process of rubbing and kneading with greasy and albuminous matters1 such as fat1 brains1 milk1 butter and egg-yolks1 is in use to this day1 alike by the ,tartars on ,asiatic steppes and the ,indians on ,american prairies2 and not only so1 but we ourselves still use the same principle in the dressing of our finest furs1 and in the manufacture of chamois1 and many sorts of lace- and belt-leathers4 ,such a process is described in the ,iliad 7xvii4 #chi-cic7 in the account of the struggle over the body of ,patroclus3 8,as when a man ,a huge ox-hide drunken with slippery lard ,gives to be stretched1 his servants all around ,disposed1 just intervals between1 the task ,ply strenuous1 and while many straining hard ,extend it equal on all sides1 it sweats ,the moisture out and drinks the unction in40 ,it must also have been early noticed that wood smoke1 which in those days was inseparable from the use of fire1 had an antiseptic and preservative effect on skins which were dried in it1 and smoked leathers are still made in ,america1 both by the ,indians and by more civilised leather manufacturers4 ,to this method the ,psalmist refers#b when he says1 8,i am become like a bottle in the smoke20 and such bottles1 made of the entire skin of the goat1 are still familiar to travellers in the ,east4 #b ,ps4 cxix4 #hc4 ,the use of vegetable tanning materials1 though prehistoric1 is probably less ancient than the methods ,i have described1 and may possibly have been discovered in early attempts at dyeing2 an art which perhaps had its origin even before the use of clothing6 ,the tannins are very widely distributed in the vegetable kingdom1 and most barks1 and many fruits1 are capable of making leather4 ,the employment of alum and salt in tanning was probably of still later introduction1 and must have originated in countries where alum is found as a natural product4 ,the art was lost or unknown in ,europe till introduced into ,spain by the ,moors4 ,leather manufacture reached considerable perfection in ancient ,egypt4 ,a granite carving1 probably at least #djjj years old1 is preserved in the ,berlin ,museum1 in which leather-dressers are represented4 ,one is taking a tiger-skin from a tub or pit1 a second is employed at another tub1 while a third is working a skin upon a table4 ,embossed and gilt leather straps have been found on a mummy of the ninth century ,b4,c41 and an ,egyptian boat-cover of embossed goat leather1 as well as shoes of dyed and painted morocco1 are still in comparatively good preservation4 ,the art is of very early date in ,china1 and was well understood by the ,greeks and ,romans4 ,in the ,grosvenor ,museum at ,chester is the sole of a ,roman caliga1 studded with bronze nails1 which is yet pretty flexible4 ,after the fall of the ,roman empire many arts were lost to ,europe1 and it was not until the ,moorish invasion of ,spain that the art of dyeing and finishing the finer kinds of leather was reintroduced4 ,england was very backward in this manufacture up to the end of the last century1 owing to the fossilising influence of much paternal legislation1 and of certain excise-duties1 which were only repealed in #ahcj4 ,since this time the art has made rapid strides1 especially in the use of labour-saving machinery1 and ,england may at the present moment be considered fairly abreast of any other country as a whole2 though in some special manufactures we are surpassed by the ,continent and by ,america4 ,in making comparisons of this kind1 it must1 however1 be remembered that1 especially in sole-leather tannage1 the most rapid progress has been made during the last few years in those countries which were more backward1 and that therefore our superiority is much less pronounced than formerly1 and in a few years will probably cease to exist unless marked improvements are introduced in the methods of production4 ,in the sketch of the development of leather manufacture which has just been given1 it has been implied that its object is to convert the putrescible animal skin into a material which is permanent1 and not readily subject to decay1 while retaining sufficient softness or flexibility for the purposes for which it is intended4 ,as these range from boot-soles to kid-gloves1 there are wide divergences1 not only in the processes employed1 but also in the materials used and in the principles of their application4 ,the most important method of producing leather is by the use of vegetable tanning materials1 and this is perhaps the only one which is really entitled to be called 8tanning10 though the distinction is not very strictly adhered to4 ,it includes the whole range--from sole leather1 through strap1 harness and dressing leather1 to calf and goat skins1 and the various sumach tannages which yield morocco and its imitations4 ,all of these products but the first and the last undergo1 after tanning1 the further processes of 8currying10 of which the most important operation consists in 8stuffing0 with oily and fatty matters1 both to increase the flexibility and to confer a certain amount of resistance to water4 ,sumach-tanned skins are not strictly 8curried0 but usually receive a certain amount of oil in the process of 8finishing40 ,next in importance to the vegetable tannages are the 8tawed0 leathers produced by the agency of alum and salt1 including the 8white leathers0 for belt laces and aprons1 and calf- and glove-kid4 ,a connecting link between tanning and tawing is found in the 8green leather10 8,dongola10 and 8combination0 tannages1 in which alum and salt are employed in conjunction with vegetable tanning materials1 and especially with gambier4 ,salts of several of the metals1 and particularly those of aluminium1 iron1 and chromium1 have the power of converting skin into leather2 and processes in which salts of chromium are used have recently attained very considerable commercial importance4 ,in the production of calf- and glove-kid1 in addition to alum and salt1 albuminous and fatty matters1 such as egg-yolk1 olive oil and the gluten of flour1 play a considerable part1 and are thus linked both to the primitive methods in use by the ,indians and ,kalmucks1 and to those by which 8crown0 and 8,helvetia0 leather1 and many other forms of belt- and lace-leathers are now produced by treatment with fats and albumens4 ,from these again the step is a short one to the 8chamois0 and 8buff0 leathers1 and the ,german 8fettgar0 leathers1 in which oils and fats only are used2 and these are probably again related chemically to leather produced by the aid of formaldehyde and other aldehydes4 ,in an attempt to view all these complex processes from the scientific standpoint1 the reader should constantly realise that the present methods of leather manufacture are the results of tens of centuries of experience1 and of innumerable forgotten failures1 and must not therefore expect that they can be easily superseded4 ,science must follow before it can lead1 and its first duty is to try to understand the reasons and principles of our present practice1 for we can only build the new on the foundation of what has been already learned4 ,another fact1 which is scarcely understood by the practical man in his demands on science1 is that in leather manufacture every question which is raised seems to rest on the most recondite problems of chemistry and physics2 the chemistry of some of the most complex of organic compounds1 and the physics of solution1 of osmose1 and of the structure of colloid bodies--problems which are yet far from completely conquered by the highest science of the day4 ,it may seem bold to attempt the scientific treatment of such a subject at all2 and1 indeed1 it must be admitted that our knowledge is still far from adequate for its complete accomplishment1 but enough has been done to lay a foundation for future work1 and this can at least be summarised and arranged in an available form4 ,the subject falls naturally into two sections1 in the first of which the processes of manufacture would only be described in general terms1 and with sufficient fulness to enable the reader to understand the scientific considerations on which they are based1 and the methods of investigation which can be applied to them2 while in the second an effort should be made to give working details of the various processes sufficient to enable those with a general knowledge of the trade to experiment successfully in its various branches4 ,it was at first intended that these two sections should be published in one book as a second edition to the ,author's #8,text-book of ,tanning1' but owing to the long delay in its publication1 it was decided to publish the first section under the present title #8,principles of ,leather ,manufacture1' leaving the latter section #8,processes of ,leather ,manufacture' to a later1 and ,i fear1 somewhat uncertain date2 while the strictly chemical portion has already appeared in the #8,leather ,industries ,laboratory ,book1' frequently referred to in the following pages under the abbreviation 8,l4,i4,l4,b40 ,where quantities and details are given1 they must not be taken as recipes to be blindly followed2 or even1 in every case1 as the best known methods2 but rather as mere guides to experiment1 which must be modified to suit varying conditions and requirements4 ,it is the special virtue of the scientific1 as opposed to the merely traditional way of looking at such questions1 that knowing the cause and effect of each part of the process1 it can so adjust them as to get over difficulties1 and to suit novel conditions4 ,it is needless to add that many methods are jealously preserved as trade secrets1 and full details are frequently unattainable4 ,after what has just been said1 it may be well to emphasise the great importance of practical knowledge and experience to the leather manufacturer4 ,even in trades which have reached the highest scientific development1 such1 for instance1 as the manufacture of the coal-tar colours1 the small experiments of the laboratory are not transformed into manufacturing operations without experience and sometimes even failure2 and this must still more often be the case in a trade like that of leather-making1 where our knowledge of the actual changes involved is still so incomplete4 ,on the other hand1 the cost of experiments on a manufacturing scale is usually so heavy that the least scientific must admit the advantage of learning all which the laboratory can teach before venturing on anything more2 while even our present imperfect knowledge of the chemical changes involved will often warn us off hopeless experiments1 and give us hints of the directions in which success may be attained4 ,a knowledge of chemistry will probably prove at least as important to the future of our trade as that of mechanics has been in the past4 ,,chapter ,,ii4 ,,introductory ,,sketch ,,of ,,leather ,,manufacture4 ,the object of tanning has been stated to be the rendering of animal skin imputrescible and pliable1 but as we now rarely require leather with the hair on1 preliminary processes are needed to remove it1 and to fit the skin for tanning1 and the nature of these processes has great influence on the subsequent character of the leather produced4 ,the first step is usually a washing of the skin to remove blood and dirt2 while1 where it has been salted or dried1 a more thorough soaking is needed to remove the salt1 and to restore the skin to its original soft and permeable condition4 ,the hair is then loosened by softening and partial solution of the epidermis structures 7see p4 #dg7 in which it is rooted4 ,this is most generally accomplished by soaking for some days in milk of lime1 which is occasionally assisted by the addition of caustic alkalies or of sulphides4 ,when the latter are used in concentrated solution1 the hair itself1 as well as the epidermis tissues1 is softened and destroyed in the course of a few hours4 ,the lime not only serves to loosen the hair1 but swells and splits up the fibre-bundles of which the hide tissue is composed1 and so fits it to receive the tannage 7cp4 p4 #abe74 ,for some purposes a regulated putrefactive process is substituted for the liming2 the hides or skins being hung in a moist and warm chamber 7see p4 #aai71 when the soft mucous layer which forms the inner part of the epidermis is disintegrated1 partly by direct putrefaction1 partly by the action of the ammonia evolved1 so that the hair can be scraped off4 ,in this case the hide-fibre is not swollen1 and the necessary swelling has to be obtained by subsequent processes4 ,in whatever way the hair has been loosened1 it is scraped off with a blunt and somewhat curved two-handled knife on a sloping rounded 8beam0 of wood or metal2 this operation being termed 8unhairing0 7see p4 #add74 ,this is generally followed by 8fleshing10 which is performed on the same beam with a somewhat similar knife1 which1 however1 is two-edged and sharp4 ,in this operation1 portions of flesh1 and the fat and loose tissue which underlie the true skin 7see p4 #adg7 are removed by scraping and cutting4 ,machines for fleshing are also largely in use for certain purposes 7see p4 #adh74 ,for sole leather1 the hide1 after some washing in soft water to cleanse from lime1 is then ready for the actual tanning process2 but for the softer leathers more thorough treatment is needed to remove the lime1 and to still further soften the skin by solution and removal of a portion of the cementing substance of the fibres4 ,this treatment is generally of a fermentive or putrefactive nature1 and the most common form is that known as 8bating10 which consists in steeping in a fermenting infusion of pigeon- or hen-dung4 ,the theory of its action is not yet thoroughly understood1 but the effect is largely due to the unorganised hydrolysing ferments produced by the bacteria present2 while at the same time the lime is neutralised and removed by the weak organic acids and salts of ammonia which are produced2 and the fibre which had been plump and swollen with lime1 becomes extremely relaxed and flaccid4 ,in the lightest leathers1 such as kid- and lamb-skins for gloves1 and goat and sheep for moroccos and the like1 dog-dung is substituted for that of fowls1 and the process is then called 8puering0 7see p4 #agj74 ,these processes are often followed by 8drenching10 which sometimes indeed takes their place1 the skins being soaked in a fermenting bran infusion4 ,in this1 the small quantities of acetic and lactic acid formed by fermentation are the active agents1 neutralising and dissolving the lime1 and cleansing and slightly plumping the pelt 7see p4 #aff74 ,the tanning process which follows consists in soaking the pelt in infusions of various vegetable products containing bodies of the class known as 8tannins10 which have the power of combining with skin-fibre and converting it into leather4 ,if at first strong infusions were used1 they would act too violently on the surface of the skin1 hardening and contracting it so that the subsequent tannage of the interior would be impeded1 and the 8grain0 or outer surface would be 8drawn0 and wrinkled4 ,this is avoided by the use at first of very weak infusions which have already been used on goods in a more advanced stage4 ,in the later part of the process much stronger solutions are employed1 and the hides are frequently 8dusted0 in them with ground tanning material4 ,in the case of sole leather1 these processes may require from two to twelve months for completion2 after which the leather is dried1 smoothed1 and compressed by mechanical means1 and is then ready for use4 ,dressing-leathers1 ranging from calf-skins to harness-hides1 receive a much shorter tannage1 and the subsequent treatment with fats and oils1 which1 together with mechanical manipulations1 constitute 8currying40 ,the thin film of grease distributed over the surface of the fibres renders them supple1 and to some extent waterproof4 ,the lighter fancy leathers1 such as morocco1 are dyed1 and undergo many complex processes to fit them for their required purposes and improve their appearance4 ,many skins such as calf1 glove1 and glac kid1 are not tanned1 but 8tawed0 by a solution of alum and salt1 which is often supplemented with mixtures of flour and egg-yolk to fill and soften the leather4 ,salts of chromium are also employed in place of alum and salt1 and produce an equally soft1 but more permanent and enduring leather4 ,lastly1 wash-leather1 or so-called 8chamois10 and buff-leather are produced by fulling the prepared pelt with fish or whale oil1 which converts the skin into leather by subsequent oxidation1 during which aldehydes are evolved4 ,,chapter ,,iii4 ,,the ,,living ,,cell4 ,the larger part of the materials employed in leather manufacture are organic in their origin1 and the skin itself is an organised structure1 while the life-processes of putrefaction and fermentation play a large part in the tannery4 ,some knowledge1 therefore1 of biological structures and processes is necessary to a full understanding of much which follows1 and a few words are not out of place with regard to the foundations of life itself4 ,the bricks of which all living structures are built are the living 8cells0 and their products1 and these first elements differ little1 if at all1 whether the life is animal or vegetable1 the distinction being produced rather by the way in which they are put together1 than by differences in the cells themselves4 ,this is so much the case that it is often difficult to decide in which of the two classes to place the simplest organisms1 since most of these forms are capable of active movement1 and their modes of nutrition and reproduction are common to both kingdoms4 ,in its simplest form1 the cell1 whether animal or vegetable1 is strictly speaking not a cell at all1 but consists merely of a minute mass of living jelly or protoplasm4 ,such is the amba found in water and damp soil1 such are the lymph-cells and white blood-corpuscles of our bodies1 and such also some stages at least of the lowest forms of fungi1 like the thalium septicum which is sometimes found on old tan-heaps as a crawling mass of yellow slime4 ,if a drop of saliva be examined with the microscope under a cover-glass1 with one-sixth objective and small opening of diaphragm1#c a few scattered semi-transparent objects will be found1 of the apparent size of a lentil or small pea1 and of rounded form4 ,these are lymph-corpuscles 7,fig4 #a74 ,their contents are full of small granules1 and if they be observed quickly1 or if the slide be kept at about the warmth of the body1 it will be noticed that these are in constant streaming motion4 ,if the warmth can be kept constant1 which is difficult without special apparatus1 and the cells can be observed from time to time1 it may be seen that they lose their circular form1 and put out protuberances 7pseudopodia1 8false feet07 one of which will gradually increase in bulk1 till it absorbs the whole cell1 which thus crawls about4 ,it will now readily be understood how these cells wander through all the tissues of the body1 passing through the smallest pores like the fairy who put her finger through a keyhole1 and grew on the other side till she was all through6 ,this independent vitality1 in a warm and suitable nutrient liquid1 may continue for more than a week1 and1 in the case of amba1 quite indefinitely4 #c ,for details of microscopic manipulation in this and the following chapter see ,l4,i4,l4,b41 p4 #bcd et seq4 ,illustration3 ,,fig4 #a4--,lymph-corpuscle of frog1 showing gradual change of form4 7,ranvier47 ,it is possible that by close attention1 a rounded or elongated body1 somewhat like an oil-globule1 may be seen within the cell1 though it is generally more obvious when the latter has been killed and stained with a weak solution of iodine4 ,this is the nucleus1 and within it is a still smaller speck called the nucleolus1 which bears an important1 and as yet little understood1 part in the life-history of the cell4 ,after a period1 it undergoes certain somewhat complicated changes1 and divides into two1 the nucleus elongates1 and also divides1 each half carrying with it a portion of the living protoplasmic jelly1 and thus forming two complete and independent cells4 ,this is the life-history1 not only of the lymph-cell1 but with more or less modification1 of every living cell or tissue4 ,illustration3 ,,fig4 #b4--,yeast-cells1 much magnified4 ,these cells1 like all living things1 feed on the nutriment which surrounds them1 and even enclose small particles of solid food1 which are gradually dissolved and disappear4 ,in this way the white blood-corpuscles are said to feed upon and destroy the still smaller organisms which gain access to the blood1 and which might otherwise cause disease4 ,the matter which cells consume is not1 of course1 destroyed1 but simply converted into other forms1 some of which are useless1 or even poisonous to the cells1 and which1 like the secretions of higher animals1 are discharged into the surrounding fluids2 while others are retained1 and contribute to the growth of the cell4 ,thus most vegetable cells secrete cellulose1 or plant-tissue1 which forms a wall enclosing the protoplasm1 and so justifies the name of cell4 ,if to warm water and a little sugar we add enough yeast to render it slightly milky1 and examine it like the saliva1 we shall have before us typical vegetable cells of the simplest form 7,fig4 #b74 ,there is the same granular protoplasm1 and there is the nucleus1 though it cannot be seen without special preparation1 the rounded spaces which look like one1 being simply filled with transparent fluid1 and called vacuoles4 ,there is1 however1 no motion1 as in the case of amba1 for the cells are enclosed in a tough skin of cellulose1 which will be evident if they are crushed by putting some folds of blotting paper on the cover-glass1 and pressing it with the handle of a needle or a rounded glass rod1 when the protoplasm will be forced out and the skin remain like a burst bladder4 ,this will be more obvious if the cells are previously stained with iodine or magenta1 which will stain the protoplasm1 but not the membrane4 ,it is easy to observe the multiplication of the yeast-cells1 which is somewhat different to that of the corpuscles4 ,instead of enlarging as a whole1 and dividing into two equal cells1 a small bud appears on the side of the parent-cell1 and enlarges till it becomes itself a parent-cell with buds of its own4 ,these do not break away at once1 and hence chains and groups of attached cells are formed which are easily noticed in growing yeast if a microscope be employed4 ,the principal nutriment of yeast is grape-sugar or glucose2 and much more of this is consumed than is needed to produce the cellulose wall and the substance of new cells2 just as in the animal1 sugar1 starch and fat are consumed to give heat and energy4 ,in the yeast1 this extra sugar is split up into carbon dioxide1 which escapes as gas1 and to which yeast owes its power of raising bread2 and into alcohol1 which in too large proportion is poisonous to the yeast itself4 ,illustration3 ,,fig4 #c4--;,epithelium-cells4 ,ranvier4 p1 pressure-marks2 g1 granular protoplasm4 ,in examining the saliva for lymph-cells1 it is probable that some much larger objects may have been noticed of irregular polygonal outline and with a well-marked nucleus4 ,these are cells from the lining epithelium of the mouth1 and only differ from those of the epidermis of skin in their form and size 7,fig4 #c74 ,note the markings caused by the pressure of overlapping cells4 ,in these cells the wall is formed of keratin or horny tissue1 which takes the place of the cellulose of the yeast4 ,illustration3 ,,fig4 #d4--,penicillium glaucum1 a common green mould4 ,other simple forms of cell are those of ,saccharomyces mycoderma or torula which forms a skin on the surface of old liquors1 and which much resembles a small yeast2 and of the various ferments which are found in liquors1 bates and drenches1 which will be more fully described in the chapter following4 ,many of these1 such as the acetic and lactic ferments1 which1 like all other bacteria1 multiply by division1 do not separate1 but remain connected in chains or chaplets1 like a string of beads4 ,from these1 the step is not a long one to the hyph or stems of the higher moulds1 which are too frequently found on leather which has been slowly dried1 and which consist simply of tubular cells which elongate and divide by the formation of septa or cross-partitions1 and thus build up a complicated plant-structure 7,fig4 #d74 ,as we proceed higher in the scale of plant and animal life1 the forms and products of the cells become more varied1 and instead of one single cell1 fulfilling all the functions of the plant or animal1 each class of cell has its own peculiar duties and properties1 while all work together for the maintenance of the complex structure of which they form a part4 ,,chapter ,,iv4 ,,putrefaction ,,and ,,fermentation4 ,the chemical changes produced by the unicellular plants1 such as yeasts and bacteria1 to which allusion has been made in the last chapter1 are known as fermentation and putrefaction1 and are of such importance to the tanner1 both for good and evil1 that the subject must be treated in some detail4 ,no scientific distinction exists between fermentation and putrefaction1 though it is customary to restrict the latter term to those decompositions of nitrogenous animal matter which yield products of disagreeable smell and taste4 ,the organisms which are the cause of both fermentation and putrefaction are known by the general term of 8ferments40 ,this term has also been extended in recent years so as to include the so-called 8unorganised ferments0 7enzymes1 zymases7 which are active products secreted by the 8organised ferments0 or living organisms4 ,these latter are again divided into three classes3-- #a4 ,moulds4 #b4 ,yeasts 7,saccharomycetes74 #c4 ,bacteria4 ,the members of one class are distinguished from those of another by their form1 and1 more especially1 by the substances they produce during their life-history4 ,all three classes are now considered to be fungi4 ,all ferments possess the following three properties3-- #a4 ,they are nitrogenous bodies4 #b4 ,they are unstable1 i4e4 they are destroyed by heat1 chemicals1 etc4 #c4 ,a relatively small quantity of the ferment is capable of producing great changes in the substances upon which it acts1 especially if the products of the change can be removed as they are formed4 ,the general character of fermentation will be best understood by a closer study of the yeast cell1 which has already been described 7p4 #ab71 and its life-history briefly sketched4 ,it has been shown that it is a growing plant of a very simple type1 belonging to the fungi4 ,these are devoid of the green colouring matter which enables the higher plants to utilise the energy of sunlight to assimilate the carbonic acid of the atmosphere1 exhaling its oxygen1 and employing its carbon for the building up of tissue2 and they must therefore1 like animals1 have their nutriment ready formed1 and capable of supplying energy by its oxidation4 ,for yeast1 as has been stated1 the appropriate nourishment is glucose1 or 8grape-sugar40 ,this is broken down1 in the main1 into the simpler compounds1 alcohol and carbonic acid1 while a small portion is utilised for the building up of the cell and the formation of secondary products4 ,the main reaction is represented by the following equation3 ,c,h,o #b;,c,h,o #b;,,co ,glucose ,alcohol ,carbon dioxide ,yeast cannot directly ferment ordinary cane-sugar 7,c,h,o71 but secretes a substance called invertase1 which so acts on the sugar as to break it up1 with absorption of one molecule of water1 into two molecules of fermentable glucose 7dextrose and levulose7 which serve as nourishment for the yeast4#d ,this invertase is the type of the series of bodies which are known as 8unorganised ferments10 enzymes1 or zymases1 differing from the organised ferments in being simply chemical products without life or power of reproduction1 but capable of breaking up an unlimited quantity of the bodies on which they act1 without themselves suffering change4 ,the way in which this is done is not clearly understood1 but some parallel may be found to it in the action of sulphuric acid on alcohol1 of which it will convert an unlimited quantity into ether1 without itself suffering any permanent change4 ,the action of enzymes is limited to breaking down complex bodies into simpler forms1 often with absorption of water1 as in the case of sugar1 while some of the products of living ferments are often complex1 a part of their nutriment being broken down into simple products such as carbonic acid1 marsh gas and ammonia1 to supply the necessary energy to elaborate the remainder4 #d ,compare ,o',sullivan and ,thompson1 ,jour4 ,chem4 ,soc41 #ahij1 p4 #hcd2 #ahia1 p4 #df4 ,very many different unorganised ferments are known to exist1 as they are not only produced by yeasts and bacteria1 but are formed by the cells of higher plants and animals2 thus the digestive principles1 pepsin1 trypsin1 ptyalin1 are of this character--ptyalin1 like diastase1 converting starch into sugar2 and such bodies fulfil many functions both in animal and vegetable economy4 ,in fermentation1 as in disease1 it is often difficult to distinguish what is due to the direct action of bacteria1 and what to the unorganised ferments which they produce1 and the question is further complicated by the fact that in most natural fermentations more than one ferment-organism is present4 ,sometimes the action of the unorganised ferments may be distinguished by the fact that the addition of chloroform has little effect on their activity while it paralyses that of the living organism4 ,by exposure to high temperature both are destroyed1 the bacteria1 yeasts and moulds being killed and the unorganised ferments coagulated like white of egg1 and so rendered inoperative4 ,many antiseptics also destroy the activity of both organisms and enzymes2 but others1 like chloroform1 have no action on the latter4 ,in some cases1 as in that of invertase1 the actual zymase can be precipitated by alcohol from its aqueous solution1 filtered off1 and restored to activity by transference into water4 ,since both classes of ferments are destroyed by high temperatures1 all fermentation-processes are completely and permanently arrested by exposure to sufficient heat1 and subsequent preservation in vessels so closed that no new ferment-germs can gain access4 ,a familiar instance is that of tinned meats4 ,all fully developed bacteria are destroyed by a very short exposure to a boiling temperature1 and most by #fj to #gj ,c41 but many species produce spores which are extremely difficult to destroy4 ,the thermophilic bacteria discovered by ,globig and further investigated by ,rabinowitsch1#e thrive at a temperature of #fj ,c4 ,about eight species are known1 and they take part in the heating of hay and similar fermentations where high temperatures are involved1 and are therefore presumably present in spent tan4 #e ,centr4 ,blatt fr ,bakt41 ,,ii4 ,abth4 vol4 i4 p4 #ehe4 ,for absolute sterilisation it is therefore necessary either to boil under pressure so as to raise the temperature to1 say #aaj ,c41 or to heat repeatedly for a short time to temperatures of #hj-ajj ,c4 at successive intervals of #bd hours1 in order to allow the spores to develop4 ,this process is frequently performed for bacteriological observation in flasks or test-tubes merely stopped with a plug of sterilised cotton-wool1 which has been found to efficiently filter the germs from the air which enters through it 7see ,l4,i4,l4,b41 p4 #bgj74 ,the ferment-organisms cannot thrive and multiply unless they have proper nourishment and conditions of growth1 the amount of moisture and the temperature being two of the most important of the latter4 ,use is made of this in the preservation of many articles of food1 etc41 since by ensuring that at least one of the conditions necessary for growth shall be absent1 these substances are prevented from decomposing4 ,for instance1 hides are preserved by drying them2 the absence of sufficient moisture hindering the growth of any organisms in them so long as they are dry1 but as soon as they become somewhat damp1 putrefaction commences at once4 ,the waste products of organisms are often poisonous to themselves1 and for this reason fermentations frequently come to an end before the whole of the substance is fermented4 ,thus neither beer nor vinegar can be obtained of more than a certain strength by direct fermentation1 the alcohol or acetic acid checking the growth of their respective ferments4 ,a solution of glucose 8set0 with the lactic ferment of sour milk will only produce lactic acid to the extent of about half a per cent42 but if chalk be added1 the lactic acid will be neutralised as produced1 and the fermentation will go on till the whole of the glucose is converted into insoluble calcium lactate4#f ,when this is accomplished the lactic ferment dies from want of nutriment1 and its place is taken by another organism1 of which some germs are sure to be present1 which ferments the calcium lactate into calcium butyrate4 ,if the nourishment fails1 or the conditions become less favourable for one ferment than for some other which exists even in small quantity in a liquid1 the former is quickly overgrown and killed1 and the latter takes its place4 ,thus the ordinary ferment of the bran drench will die out rapidly unless constantly transferred to fresh bran infusions4 #f ,for the practical preparation of lactic acid1 the solution may contain #g-aa per cent4 of glucose1 and some nitrogenous nourishment4 ,the solution should be slightly acid4 ,see ,journ4 ,soc4 ,ch4 ,ind41 #ahig1 p4 #eaf4 ,many of the products of bacteria 7like those of some of the higher plants7 are intensely poisonous both to animals and man4 ,many of the severe symptoms of disease are caused by these poisons produced in the body4 ,thus the tetanus-bacteria produce a poison similar in its effects to strychnine1 and quite as virulent4 ,not only are such poisons produced by disease-bacteria in the body1 but frequently also in the earlier stages of putrefactive fermentation4 ,the latter are known as ptomaines1 and when present in cheese and preserved foods are liable to cause poisoning4 ,such putrefactions are often unaccompanied by any disagreeable odour or flavour4 ,the fermentations which are most important in the tannery are1 firstly1 the ordinary putrefaction which attacks hides as well as other animal matter1 and which is usually a complicated process carried on by many sorts of bacteria and other micro-organisms4 ,this may be regarded as generally injurious to the tanner2 but it is utilised in the 8sweating0 process for depilation and in the 8staling0 of sheepskins1 in both of which advantage is taken of the fact that the soft mucous layer of the epidermis1 which contains the hair-roots1 putrefies more rapidly than the fibrous structure of the hide itself4 ,in soaking also1 use is made of the power of putrefactive ferments to dissolve the cementing substance of the hide1 though in this case with doubtful advantage to the tanner4 ,in the liming process putrefaction makes itself felt when the limes are allowed to become stale and charged with animal matter1 softening the hide and finally rendering the leather loose1 empty and inclined to 8pipe40 ,here the effect is in many cases useful if not carried too far4 ,in bating and puering1 the action is almost entirely due to the enzymes and other products of bacterial activity1 the original chemical constituents of the dung being apparently of minor importance4 ,naturally the liquid is adapted to the growth of many other organisms beside those acting most advantageously on the hide1 and injury in the bates from wrong forms of putrefaction is very common1 if indeed it is not always present in greater or less degree4 ,in drenching1 the effect is1 at first1 entirely due to the weak acids produced by bacterial fermentation of the bran1 but becomes complicated in its later stages by putrefactive and other fermentations which may be desirable or otherwise4 ,in the tanning liquors1 fermentation is not so marked1 but is of great importance owing to the production of acids by bacterial action from the sugars present in the material4 ,the acids themselves are apt to be fermented and destroyed1 principally by the oxidising action of ,saccharomyces mycoderma and the higher moulds 7see p4 #ad71 which also act destructively on the tannins4 ,the effect of these acids on the hides is to swell them and to neutralise any lime they may contain4 ,they also give to the liquors a characteristic sour taste1 as a consequence of which1 liquors containing acetic and lactic acids are usually known in the tannery as 8sour liquors40 ,it is doubtful whether the action of fungi is completely stayed even by the drying process4 ,the heating of leather in the sheds is due to bacteria and the higher moulds1 and ,eitner considers their growth one of the causes of the 8spueing0 or 8gumming0 of curried leathers4 ,from what has been said1 it is obvious that1 with regard to fermentations1 a double problem is presented to the leather manufacturer1 since he desires to utilise those which make for his advantage1 while controlling or destroying those which are injurious4 ,the first step to a solution of these problems is a more complete knowledge of the organisms which serve or injure us1 that we may1 as it were1 discriminate friends and enemies4 ,we may then approach the question in two ways4 ,taking the drenching process as an example1 we may on the one hand introduce a 8pure cultivation0 of the right ferment into a sterilised bran infusion1 and so induce only the one fermentation which we require2 or1 on the other hand1 as different ferments are affected in varying degrees by antiseptics1 we may perhaps choose such as permit the growth of the organism we want1 while killing or discouraging the rest4 ,we may also arrange the nutriment1 temperature1 degree of acidity and other conditions1 so as to favour one organism rather than another4 ,all three methods have been applied in brewing with good results4 ,,chapter ,v4 ,,antiseptics ,,and ,,disinfectants4 8,antiseptics0 are often defined as substances which check putrefaction without necessarily destroying bacteria and their spores1 while 8disinfectants0 are poisonous to ferment-organisms1 and actually destroy them2 great differences exist in the extent of their sterilising power1 and the whole distinction is one rather of degree than of kind1 and has little practical value4 ,thus common salt is incapable of killing most bacteria1 even in concentrated solution1 though it holds putrefaction in check both by withdrawing water from the hide and by directly preventing the multiplication of bacteria4 ,if the salt be washed out of the hide1 putrefaction is at once resumed by the organisms present4 ,hides1 on the other hand1 which have once been sterilised by powerful disinfectants1 such as phenol 78carbolic acid07 or mercuric chloride1 do not again putrefy till the organisms which are killed are replaced by fresh ones from outside4 ,the action of sodium sulphate1 and many other salts1 is similar to common salt in this respect1 while a large proportion of the aromatic compounds are permanently disinfectant1 though their efficiency varies with the species of bacteria involved4 ,biernacki and others have shown that some disinfectants when extremely diluted actually stimulate alcoholic fermentation1 and probably the growth of other ferments1 e4g4 mercuric chloride #a in #cjj1jjj1 salicylic acid #a in #fjjj1 and boric acid #a in #hjjj1 and in many cases organisms become habituated to antiseptics in doses which would at first have proved fatal4 ,the number of antiseptics available is now so great that it is impossible to give a detailed account of all1 but the following are among those which are best known and have been practically employed4 ,lime possesses some antiseptic properties1 and is largely used in the preservation of fleshings before they are sent off to the glue factory4 ,they are most conveniently stored in a large vat filled with a strong milk of lime4 ,dilute solutions of caustic alkalies have an effect similar to that of lime4 ,common salt1 sodium chloride1 ,na,cl1 acts to a certain extent by its solubility and a dehydrating effect on animal tissues common to chlorides1 which removes water from hides and other materials which it is used to preserve4 ,probably the latter characteristic has a good deal to do with its effect in checking the development of bacteria1 since many species thrive quite well in weak salt solutions1 and some even in brine1 and the dehydrating effect of the salt enables it to harden many animal tissues if used in sufficient quantity1 the water they contain running away in the form of brine4 ,ordinary rock salt frequently contains ferric chloride1 and this1 either originally present in the salt1 or in some cases derived from the action of the latter upon the iron contained in the blood1 is the cause of what is known as 8salt-stains40 ,these show but little during the liming of the hides1 unless sulphides are used1 when stains appear of a greenish black1 from the formation of sulphide of iron2 when1 however1 the hides come into the tanning liquors1 black or blue stains are produced by the action of the tannin1 which are partially removed by the acids of the liquors during the tanning process1 but generally show to some extent in the finished hide4 ,there is another species of salt-stain1 not apparently due to iron1 but to the colouring matter produced by some fungoid or bacterial growth1 which it is practically impossible to remove1 and which is stated to be sometimes caused by the use of old salt with which hides have been previously salted4 ,iron stains are most readily recognised by the use of a solution of potassium ferrocyanide or thiocyanate slightly acidified by hydrochloric acid4 ,if this be applied to the leather1 the stains will be changed from a blackish to a blue1 if the former1 or a red colour if the latter salt has been used4 ,a more absolutely conclusive proof is to lay a piece of filter paper soaked in dilute hydrochloric acid upon the stain1 and then to test for iron upon the paper with ferrocyanide or thiocyanate4 ,the freedom of the paper itself from iron must be ascertained before use4 ,iron-stains produced in the salted state are more difficult to discharge than those which are caused later in the tanning process1 since iron salts have distinct tanning power1 and attach themselves firmly to the untanned fibre4 ,on the ,continent1 where common salt is heavily taxed1 alum1 carbolic acid1 naphthalene and other materials are frequently added to it to 8denaturise10 or render it incapable of being used as food1 and these additions are often the cause of trouble to the tanner4 ,sodium sulphate1 ,na,,so1 has little if any disinfectant power in dilute solution1 but if used in the calcined form 7anhydrous sodium sulphate7 as proposed by ,eitner#g as a substitute for common salt in preserving hides1 it withdraws water from the hide and crystallises with #aj ,aq 7about #ef per cent474 ,this does not run away like brine1 but remains in the hide1 which retains its weight1 and remains plump and swells well in the limes and liquors1 which chlorides have a great tendency to prevent2 #aj-ae per cent4 on the weight of the hide is sufficient1 while salt must be used in nearly double this quantity4 ,care must be taken that the sulphate used is free from bisulphate1 ,na,h,s,o1 which has a powerful swelling effect upon the hide-fibre1 like sulphuric acid4 ,the neutral sulphate does not redden methyl orange or litmus4 ,pickled skivers may be in part preserved by the sodium sulphate formed by the action of sulphuric acid upon the salt employed in the pickling bath 7see p4 #ij74 #g ,gerber1 #ahhj1 p4 #ahe4 ,the stronger mineral acids have considerable antiseptic power1 and are of course especially fatal to such ferments as thrive best in alkaline solutions4 ,the use of sulphuric acid in pickling skivers has already been alluded to1 and a very dilute solution applied without salt to raw hides prevents putrefaction1 though the principal object in using it is to plump the hides and produce a fictitious weight and substance which disappear on tanning4 ,such hides of course have a powerful acid reaction to litmus4 ,sulphuric acid in small quantities has been used with advantage in soaking ,e4,i4 kips4 ,a very small excess of hydrochloric acid will sterilise putrid effluents1 and no doubt nitric or sulphuric acid would have the same effect4 ,the powerful effect of mineral acids on animal fibre1 and their solvent action on cements and iron1 preclude however1 their general use as antiseptics4 ,more important is the use of sulphurous acid and sulphur dioxide1 which1 from their mild acidity and great antiseptic powers1 are capable of a variety of useful applications4 ,considerable doubt has been raised as to the germicide power of sulphur dioxide1 and it is certain that the dry gas is less effective on dry objects than when applied in solution1 or to moist materials1 as is almost invariably the case in the tannery4 ,it may possibly be more efficient in its action on some moulds and putrefaction-ferments than on the pathogenic bacteria which have been most frequently used to test the power of disinfectants2 but in practice it is found extremely useful in the brewery and in gelatine manufacture1 and there is no reason that it should be less so in the tannery4 ,the gas is most conveniently produced by burning sulphur1 which produces double its weight of sulphur dioxide4 ,if used for 8stoving0 drying rooms and other places infested with moulds1 care must be taken to avoid risk of fire4 ,a shallow cast-iron pot set on bricks or sand is generally the most suitable vessel1 and the sulphur may be ignited by a piece of red-hot iron or a rag which has been previously dipped in melted sulphur4 ,it is corrosive to metalwork1 and bleaches many colours1 but does not produce any marked injurious effect on leather1 though the sulphuric acid formed by oxidation may1 if not removed1 ultimately make it tender4 ,for many purposes a solution of the gas is required1 and this is most easily made by burning the sulphur in a small metal or firebrick stove from which the fumes are sucked through a 8scrubber10 which1 on a small scale1 is conveniently made of large glazed sanitary pipes1 packed with coke or broken earthenware1 over which water is allowed to trickle4 ,the lowest pipe has an opening for a branch pipe1 which is connected with the stove and rests on three bricks in a tub1 which collects the acid solution and forms a water-seal to prevent the escape of gas4 ,above the inlet for the gases is fixed a wooden grating on which the coke rests4 ,the scrubber may be #aj-ae feet in height and connected at the top with a chimney or steam ejector to produce the draught4 ,the arrangement is illustrated in ,fig4 #e4 ,another method is to burn the sulphur in a closed cylinder and to force the products through water with an air-compressor or steam-jet injector4 ,in place of using a scrubber1 the fumes may be blown by a steam ejector direct into a tank4 ,this is a very good arrangement for washing and bleaching hair1 etc41 but where large quantities of solution are required is inferior to the scrubber4 ,ejectors of hard lead or regulus metal should be used1 and are less acted on by the dry gases than by the very dilute moist exhaust from the scrubber 7see p4 #cce74 ,illustration3 ,,fig4 #e--,sulphurous acid apparatus4 ,bisulphites have also strong antiseptic properties4 8,bisulphite of soda0 7hydric sodic sulphite7 solution may be made by supplying the scrubber with solution of soda-ash or washing soda2 bisulphite of lime1 by using milk of lime or packing the scrubber with chalk or limestone 7free from much iron7 in place of the coke4 ,in either case a much stronger solution is obtained than with water alone4 ,boakes' 8metabisulphite of soda0#h is a very convenient source of sulphurous acid when the latter is wanted in small quantities4 ,it is an anhydrosulphite1 ,na,o4#b7,,so71 and contains #fgd per cent4 of its weight of ,,so4 ,one molecule of the salt 7 #aij7 requires one molecule of ,h,,so 7 #ih7 to set free the whole of the sulphurous acid4 ,for many purposes the sulphate of soda formed may be neglected and the acidified solution used direct4 #h ,patented by ,boakes1 ,ltd41 ,stratford1 ,london1 ,e4 ,for analysis of sulphites and sulphurous acid solution1 see ,l4,i4,l4,b41 pp4 #af and #cg4 ,boric acid1 borax and other borates are not very powerful disinfectants4 ,they have no injurious action upon the skin1 but to be effective require to be employed in pretty strong solutions1 say #a per cent41 and their comparatively high cost unfits them for general use as antiseptics in the tannery1 though boric 7boracic7 acid is very useful as a drenching and deliming agent 7see pp4 #aef1 #bbi1 and ,l4,i4,l4,b41 p4 #cg74 ,mercuric chloride1 corrosive sublimate1 ,hg,cl1 is an extremely powerful antiseptic1 preventing the growth of some species of bacteria in solutions so dilute as #a in #cjj1jjj 7,koch74 #a in #ad1jjj is disinfectant 7,miquel71 but its power varies very much upon different organisms 7,jrgensen states that #a in #djj is required to kill ,penicillium glaucum71 and it is unsuited for most purposes in leather manufacture1 both from its extremely poisonous character1 and because it is rendered inactive by various substances present in the materials used4 ,mercuric iodide dissolved in iodide of potassium solution was patented by ,messrs4 ,collin and ,benoist as an antiseptic in tanning1 but it is ineffective for the same reasons as mercuric chloride2 although under favourable circumstances it is even more powerful than the latter4 ,copper sulphate1 zinc chloride and sulphate1 and many other metallic salts are powerful antiseptics1 but have only a limited application in leather industries1 and do not usually actually sterilise4 ,arsenic 7arsenious acid71 which has been used in curing hides1 is an excellent insecticide1 but not particularly effective as an antiseptic2 and sulphide of arsenic 7realgar7 when used in limes 7see p4 #aci7 seems to have but little antiseptic effect4 ,arsenious acid is easily soluble in alkaline solutions4 ,fluorides have been suggested as antiseptics in the tannery1 but do not seem of much practical value4 ,the most important antiseptics at present are those derived from coal tar1 and belonging to the aromatic series4 ,of these1 the phenols 7carbolic acid1 cresol1 etc47 are the most used4 ,pure phenol1 8pure crystallised carbolic acid10 is hydroxybenzene ,c,h7,,oh71 but the crude forms which are generally employed contain cresols and higher members of the series in which one or more of the atoms of hydrogen are substituted by ,,ch groups4 ,these are oily bodies scarcely soluble in water1 and even pure phenol is only soluble in cold water to the extent of some #g per cent4 ,crude carbolic acid should not be employed in the tannery1 since the insoluble oily particles stain the hide1 and render it unsusceptible of tanning4 ,suitable carbolic acid should be of a pale yellow colour when fresh 7though it will darken on exposure to air and light71 and it should be wholly soluble in a sufficient quantity of water4 ,its specific gravity should be #ajej to #ajfe4 ,for methods of chemical examination1 see ,l4,i4,l4,b41 p4 #dj4 ,a saturated solution of carbolic acid sterilises hide completely against most putrefactive organisms1 but has a sort of tanning effect1 adhering obstinately to the fibre so that it cannot be removed by washing2 and hides which have been cured with it cannot be unhaired by sweating1 though they may be limed in the usual manner1 if somewhat more slowly4 ,care should be taken in mixing with water or liquor1 as undissolved drops will produce the same effects as those of the crude acid4 ,hides are occasionally stained1 as has just been described1 by salt which has been denaturised with common sorts of carbolic acid4 ,eitner recommends the use of a solution of carbolic acid in an equal weight of crude glycerine1 which readily dissolves in water1 and seems to prevent any injurious effect on the hide4 ,an aqueous solution containing #a per cent4 of carbolic acid is sufficient for mere sterilising of hides1 but if it be desired to preserve them for a long period1 stronger solutions 7up to #d per cent47 may be employed4#i #i ,gerber1 #ahhi1 p4 #ih4 ,quantities so small as #a part per #ajjj control the fermentation of liquors1 and prevent the formation of moulds on the surface1 economising tannin1 and preserving vegetable acids already present1 but at the same time lessening their production by fermentation1 and therefore sometimes leading to difficulties in the early stages of tanning4 ,carbolic acid is not1 strictly speaking1 an acid1 but rather of the nature of an alcohol1 although it forms weak combinations with bases4 ,it is a powerful narcotic poison1 and if dropped on the skin in a concentrated form it produces severe burns2 these are best treated with oil1 while in cases of poisoning1 oil and chalk must be administered internally1 but if the quantity of carbolic acid taken has been large1 are not likely to be effective4 ,from its cheapness and efficiency1 carbolic acid is likely to be increasingly used1 although for special uses some of the newer antiseptics have great advantages4 ,eudermin is a tar-oil manufactured by ,speyer and ,grund1 of ,frankfort-on-,main1 which is intended as an antiseptic addition to stuffing greases to prevent mould and spueing4 ,it is recommended for the purpose by ,eitner#aj and can be used in proportions such as #aj per cent4 of the grease4 ,creasotes and cresols can be dissolved in oils and stuffing greases1 and act as antiseptics1 though less powerfully than in aqueous solution4 ,rosin oils and turpentine have also antiseptic properties4 #aj ,ibid41 #ahic1 p4 #da4 ,creasote1 8heavy coal oil10 or 8dead oil10 is a complex mixture of hydrocarbons1 phenols and cresols1 obtained by distillation of coal tar1 heavier than water1 and almost insoluble in it4 ,it is largely used as a preservative for timber4 ,carbolineum is an oil of this class1 boiling at over #cjj ,c41 and intended for application to wood4 ,one or more coats are applied to the dry wood at a temperature of #hj ,c4 ,the workman's hands must be protected by gloves1 as the hot creasote raises painful blisters4 ,eitner#aa recommends its use for preserving pits1 posts and other woodwork in tanneries4 ,wood-creasote is a somewhat similar product obtained from wood-tar4 #aa ,gerber1 #ahhi1 p4 #ahc4 ,the heavier cresols are so little soluble in water as to be valueless in their ordinary form as antiseptics1 but several preparations are made under the names of 8,creolin10 8,jeye's fluid10 8,lysol10 8,izal10 8,soluble phenyl10 etc41 in which they are treated with additions of soap or alkalies1 which cause them to emulsify or dissolve in water1 generally as milky liquids4 ,these are powerful germicides and have the advantage over phenol of being non-poisonous4 #ja to #je per cent4 solution of creolin will sterilise hides after bating so that no putrefaction takes place in the liquors4 ,mr4 ,j4 ,t4 ,wood specially recommends creolin for the general purposes of the tannery1 disinfecting pits and tubs1 and for checking the action of puers and drenches on goods which have gone a little too far1 by throwing them into a #jb per cent4 solution4 ,salicylic acid1 orthohydroxybenzoic acid1 ,c,h,,oh7,,cooh71 is now artificially prepared from phenol4 ,it is much less poisonous than the latter and has no smell1 which makes it valuable for certain purposes1 but is too dear for most technical applications4 ,many bacteria appear to become gradually habituated to its action1 and the same is true of phenol to a less degree4 ,salicylic acid is closely related to protocatechuic and gallic acids1 and1 like these1 gives a blackish colour with iron salts4 ,it is freely soluble in hot water1 but very sparingly in cold4 ,the addition of #a-b parts of sodium phosphate1 sulphate1 or potassium nitrate to each part of salicylic acid greatly increases its solubility4 ,it seems much more powerful in preventing the development of bacteria than carbolic acid2 a solution of #a part of salicylic acid in #fff of water is said to be equal in this respect to #a part of carbolic in #bjj4 ,benzoic acid1 ,c,h,,cooh1 though not much employed1 except in medicine1 is a still more powerful disinfectant1 and has the advantage of being non-poisonous to human beings4 8,cresotinic acid10 which is derived from the cresols as salicylic acid is derived from phenol1 is more soluble than salicylic acid4 ,it is not very poisonous1 and a powerful disinfectant4 ,in a crude form it has been introduced by ,hauff1 of ,feuerbach1 for bating or removing lime from hides4 ,this it does very well1 though without the softening action of a true bate4 ,it has a tendency to produce a pinkish stain1 and in some degree a sort of tanning of the fibre4 ,its price1 moreover1 is rather high for extensive technical use4 7,see also p4 #afb47 8,anticalcium0 is a more recent preparation introduced as a bate by the same firm4#ab ,it is a solution of mixed sulphonic acids derived from cresols1 and has considerable disinfectant powers4 ,it removes lime very effectively1 but from its acid character somewhat swells the skin4 ,it is used very successfully as a drench for thin skins 7p4 #afc74 #ab ,gerber1 #ahie1 p4 #acc4 8,c4,t40 7coal-tar7 bate is a grey crystalline pasty mass1 with a tarry smell1 and is chemically very similar to anticalcium if not identical with it4 ,naphthalene sulphonic acid has strong antiseptic properties4 ,its use in bating has been patented by ,burns and ,cross4 7,see p4 #afc47 ,naphthols1 ,c,h7,,oh74--,these bodies1 which have the same relation to naphthalene as the phenols to benzene1 are powerful antiseptics2 and naphthalene itself appears to have antiseptic power1 and is occasionally used for denaturising salt4 ,there are two naphthols1 varying in the position of the ,,oh group in the molecule1 and denominated and 1 of which naphthol is the more powerful antiseptic and the less poisonous1 though 1 being cheaper1 is the common commercial article4 ,it is said that quantities so small as #ja-jd grams of naphthol per liter are sufficient to prevent the development of microbes1 while of naphthol about ten times that quantity is required4 ,naphthols are not very expensive1 but their value is diminished by the fact that they are insoluble in water4 ,they are soluble in alkaline solutions1 but their compounds with bases are of much lower antiseptic value1 and the same is true of their alcoholic solutions2 when an alcoholic solution is added to water the naphthol is precipitated1 but if an addition of soap or camphor be made to the alcoholic solution1 the naphthol remains in a very finely divided condition1 if not dissolved4 ,adopting ,eitner's suggestion with regard to oxynaphthoic acid 7see below71 hides may no doubt be sterilised by treatment first with an alkaline naphthol solution1 and then with a very dilute acid to set the naphthol free4 8,hydronaphthol10 tetra-hydro-naphthol1 ,c,h,o1 is obtained by the reduction of naphthol by sodium 7,rideal74 ,it seems to be an excellent disinfectant4 ,oxynaphthoic acid1 hydroxynaphthoic acid1 ,c,h7,,oh7,,cooh1 which bears the same relation to naphthol as salicylic acid does to phenol1 is cheaper than salicylic acid1 and said to be a more powerful antiseptic4 ,its salts have no antiseptic power4 ,in its commercial form it is a reddish crystalline powder1 inodorous1 but with a burning taste1 and its dust causes violent sneezing4 ,it is scarcely soluble in water1 and is said to undergo some change on keeping which lessens its germicide power2 it is readily soluble in alcohol1 and the solution produces a milky fluid on mixture with water4 ,such a solution containing #ae grams of the acid in #d liters of water1 will sterilise a hide4 ,eitner recommends#ac that it should be dissolved in dilute soda solution1 and the hides1 after soaking in it1 passed through water slightly acidified with hydrochloric acid1 as has been suggested in the case of naphthol2 the method is also applicable to creosotinic acid1 the hides being permanently sterilised so that they cannot be unhaired by sweating1 though they will lime in the usual manner4 #ac ,gerber1 #ahhh1 p4 #aja2 #ahhi1 pp4 #ii et seq4 ,see also p4 #afc4 ,carbon disulphide4--,moret has suggested an aqueous solution of this compound as an antiseptic1 and it seems to have considerable sterilising powers1 but from its inflammability1 poisonous character1 and unpleasant smell1 it is not likely to come largely into use4 ,formaldehyde1 ,,coh1 has recently been introduced as an antiseptic in aqueous solution containing #dj per cent4 of formaldehyde together with a little formic acid1 under the names of 8formalin10 8formol10 etc4 ,it seems to have great disinfectant powers1 and may possibly be valuable in various processes of leather manufacture as it becomes cheaper1 but has a curious hardening tanning effect on hide fibre and gelatinous matters1 so that in very dilute solution it will produce leather4#ad ,the vapour of formaldehyde1 or of its condensation-product paraform1 may be employed to harden microscopic preparations4 #a part of formaldehyde1 and consequently #b parts of 8formalin0 in #ab1jjj parts of water1 is said to sterilise1 and this proportion would form a good disinfectant solution4 ,even in considerably larger proportion than the above1 it does not appear to be poisonous1 and thus possesses the bactericidal power of sublimate without the latter's poisonous properties4 ,formaldehyde has another advantage over most1 if not all other antiseptics1 in that it may be used as well in the gaseous as in the liquid state1 and on that account it is largely employed in the disinfection of rooms or of articles which would be spoiled if they were to be wetted1 as the gaseous formaldehyde1 though thoroughly disinfecting them1 will not injure the colours of materials of the most delicate fabrics4 #ad ,gerber1 #ahig1 p4 #fg2 ibid41 #ahii1 pp4 #aja1 #bje1 #bah4 ,on account of its capability of rendering gelatinous matters hard and insoluble in water1 formaldehyde requires to be employed with great care1 but #jb-jc per cent4 may be successfully used in admixture with egg-albumen in the preparation of 8seasoning0 in the finishing of morocco leather4 ,it is also used commercially to produce different varieties of white leather for soldiers' accoutrements and similar purposes 7p4 #chj74 ,triformol 7tri-oxymethylene1 8paraform07 is a product of the polymerisation of formaldehyde1 and is prepared by evaporating a solution of the latter to dryness on the water-bath4 ,it is said to be more powerful than formalin in its antiseptic properties1 but has not entered very largely into use as a disinfectant1 though considerable use is made of it to 8fix0 bacteria in gelatin for bacteriological purposes4 ,camphor and essential oils1 as well as oil of turpentine1 have considerable antiseptic powers1 and the cheaper essential oils such as those of winter-green1 black birch1 sassafras and aniseed are frequently employed1 especially in ,america1 in preserving pastes1 finishes and seasonings1 and at the same time covering offensive odours4 ,the odour of essential oils becomes much more powerful as they are diluted1 and very small quantities suffice for the purposes mentioned4 ,birch-tar oil1 such as is used to give the scent to ,russian leather 7p4 #cgb71 has considerable antiseptic effect4 ,,chapter ,,vi4 ,,the ,,origin ,,and ,,curing ,,of ,,hides ,,and ,,skins4 ,a considerable proportion of the hides and skins used in leather manufacture are those of animals killed by the butcher for food1 and these are frequently employed by the tanner without any preliminary curing4 ,domestic hides and skins are now generally sold by auction in weekly markets in the principal towns1 after sorting and classification in weight and quality4#ae ,this is in many respects an improvement on the old method of purchase direct from the butcher1 but it often leads to delay in delivery1 and in hot weather hides suffer from putrefaction4 ,in most cases1 the damage is not sufficient seriously to affect the durability of the leather1 but the delicate membrane of the 8grain0 is injured1 and the hide or skin unfitted for coloured leather1 or any purpose where small damages to appearance are important4 ,butchers are adverse to the use of salt1 because it withdraws water from the hide in the form of brine1 and so causes it to lose weight2 but much injury would be saved by a light salting1 and all hides or skins on which the hair is 8slipping0 should be regarded as damaged for fine leather manufacture4 #ae ,the weight of ,english market-hides as credited to the butcher is usually marked on the edge of the butt near the tail1 by cuts with a knife1 the mode of numeration being sufficiently explained by ,fig4 #f1 in which cuts crossing the horizontal line each represent #bj lb41 that above it #aj lb41 while less amounts are expressed in ,roman figures4 ,on the ,continent weights are usually given in pounds of half a kilogramme 7#ej kilos #aaj lb4 ,english74 ,in ,paris the marking is on the tail1 and is also shown on ,fig4 #f4 ,illustration3 ,,fig4 #f4--,method of marking weight on hides2 #ig lb4 ,sheep-skins are not usually bought direct by the tanner1 but by the fellmonger1 who removes the wool2 and as this is usually of much greater value than the skin1 the latter is frequently handled very carelessly1 and its quality sacrificed for the sake of real or fancied improvement to the wool4 ,in very many cases the skin is 8sweated0 or 8staled0 by hanging in a warm and moist chamber1 heavily charged with ammonia derived from the putrefaction of the skin1 until the wool is sufficiently loosened to be 8pulled40 ,if this treatment is conducted with extreme care the skin may escape serious injury1 but in most cases the grain is weakened1 and the foundation is laid of damage1 which makes itself felt throughout the tanning process4 ,for the purposes of the tanner1 a much better way is to lime the skins by painting with thick limewash on the flesh-side1 and after folding the skins down the back1 flesh-side in1 to prevent as much as possible the access of the lime to the wool1 to place them in a pit1 and cover them with water1 till the wool is loosened by the penetration of the lime through the skin4 ,a still more satisfactory method1 and one which is in general use in the ,american stockyards1 and to some extent also in ,europe1 is to wash the skins in water to free them from blood and dirt1 and then1 laying them in a wet condition1 flesh side up1 to paint them with a solution containing about #be per cent4 of sulphide of sodium1 thickened with lime4 ,the skins1 as they are painted1 are doubled down the back1 flesh-side in1 and laid on a floor1 overlapping each other like tiles on a roof1 for some hours1 or overnight1 till the wool is sufficiently loosened to pull1 after which the pelts are limed and treated in the ordinary way4 ,as a general rule the ,english fellmonger keeps his skins in lime till they are sold to the tanner1 and as in small yards some time is taken to accumulate a parcel1 the earlier skins may suffer great injury from overliming4 ,even sweet fresh limes dissolve the cementing substance of the fibre1 and increase the naturally loose texture of the sheep-skin1 but the injury is much more considerable when old and stale limes1 charged with ammonia and bacterial products1 are employed1 as is frequently the case4 ,in the ,american stockyards the skins are generally limed only for the necessary time to act upon the grease1 and to swell and differentiate the fibres1 and are then at once puered1 drenched and preserved by 8pickling40 ,for details of 8pickling0 see p4 #hi4 ,it is very probable that the ,pullman process of liming 7p4 #acg7 would answer well for fellmongered skins1 as goods will keep for a considerable length of time uninjured after treatment with calcium chloride4 ,where hides or skins cannot be used at once in the fresh state1 there is probably no better method of preserving them than the use of salt4 ,although salt is not fatal to bacteria1 it so slows bacterial growth1 partly by its direct antiseptic effect on many organisms1 and partly by withdrawing water from the skin1 that well-salted skins can be kept in good condition for almost an unlimited time4 ,where it is only required to preserve goods for a week or two1 a moderate sprinkling on the flesh side is efficient1 but if they are to be preserved for any length of time1 more thorough treatment is necessary4 ,it is said that however carefully hides are salted they deteriorate if kept in this condition above twelve months4 ,the method of salting employed in the ,chicago stockyards for 8packer0 hides may be taken as a good type of a thorough salting4 ,the hides are first trimmed from useless 8switches10 and any large portions of adhering fat are removed4 ,the curing takes place in large and cool cellars1 with concrete floors4 ,the detail is well given in the following extract from the #8,shoe and ,leather ,reporter'3-- 8,great care is taken to make the sides of a pack higher than the middle1 so that the brine which is made by the juices of the hide coming in contact with the salt will be retained4 ,the brine can only escape by percolation and hence the fibre of the hides is thoroughly cured4 ,the floor of a hide cellar is usually of concrete1 and a pack is from #ae to #bj feet long and as wide as the space between the posts which support the floor above4 ,the sides of a pack are built first to a height of from #d to #f inches2 the cross layers are then put on1 generally three on each side1 two being inside and one having the butts drawn out to the edge4 ,in a pack #bj feet long1 the side layers will contain about #be medium-sized hides each1 and a cross-layer #ab or #ad4 ,to begin a pack a truck-load of hides is run along to the front of the place selected1 one spreader grasps the butt and his partner the head of a hide1 and together they carry it to what is to be the rear of the bed4 ,the hide is then dropped1 so that the folded back is parallel to and from #ae to #bj inches from the inside line of the posts1 the head a trifle closer than the butt4 ,the front man takes the dewlap and front shank in his left hand1 and extends his right along the belly of the hide as far as is necessary to raise the edge1 the rear man holding the flank with one hand and the hind shank with the other4 ,they keep their legs well out of the way of the salt thrower1 who with a single throw covers the whole hide1 being particular that enough salt strikes against the edges held by the men to make a pronounced ridge when they are lapped down4 ,a little salt is thrown on the hair surface and the butt folded over about a foot4 ,the folded edge is then drawn out even with the outer line of the pack4 ,more hides are placed the same way until the corner is high enough4 ,after this1 each hide is put further forward to make a level surface from rear to front1 the heads at the front corner being folded back as the butts were at the starting place4 ,the other side is built the same way1 and then the cross layers are put on alternately until the pack is level1 when sides are again built as before4 ,in putting on the first hides of the cross layers1 they are thrown over the edge1 to lap back again when the salt is thrown on2 the layer is then continued on to the front4 ,the spreader who holds the butt does the guiding in every case4 ,he drops the butt down at exactly the proper place1 takes the upper flank and shank in each hand1 sets one foot on the lower shank to keep it firm1 and throws the one in his hands from him with considerable force4 ,the man at the head watches his partner1 keeps the folded hide taut1 and drops it at the same time as the latter4 ,he takes the fore-shank at the knee in the one hand and the upper head-piece in the other1 and setting his foot on the lower side1 throws the upper side forward simultaneously with the rear man4 ,two expert spreaders1 accustomed to working together1 spread a hide at a single throw1 but some little straightening has to be done by hand before the hide is ready for the salt4 ,a gang composed of two spreaders1 one salt thrower and a salt trucker put down forty hides an hour4 ,when gangs are doubled1 two men do all the spreading2 the other two place the hides where they can be got at conveniently4 ,a double gang put down eighty hides an hour4 ,the salt trucker brings the salt to the pack in box-trucks open at one end to permit the entrance of a shovel4 ,the salt thrower keeps the edges and corners of the pack full of salt4 ,he must see that every part of the flesh-side is well covered4 ,each hide takes two scoop shovelfuls of ground rock or coarse white salt1 mixed with an equal quantity of old or second salt4 ,the salt thrower throws the shovel forward and to one side and back again with a peculiar swinging jerk1 causing the salt to fall regularly over the entire surface of the hide4 ,the ease and rapidity with which a gang operates depends greatly upon the efficiency of the salt thrower4 ,when the pack gets too high to be comfortable for the men1 it is brought to a dead level and covered over with clean salt4 ,it then presents a very neat and workmanlike appearance4 ,spreaders and salt throwers receive #bj cents an hour1 and truckers get #ag cents4 ,when the temperature is kept at an even average1 two weeks is ample time to cure the hides4 8,in #8taking up1' two men strip the hides from the pack4 ,as they were put down from the rear to the front1 they are taken up in the reverse direction4 ,no matter how much loose salt is lying on the top1 the man knows exactly where to place his hand on a shank2 as the hides are moved forward1 the loose salt is thrown off toward the front4 ,one man takes away the salt as it accumulates and trucks it to the salt bins1 where it is mixed with new1 to be used again4 ,a #8horse' made of a network of scantling about #c feet wide by #f feet long1 and standing #b feet from the floor1 is placed in front of the pack1 on this the hides1 flesh side down1 are shaken to remove the salt that is clinging to them4 ,this process requires four men1 one at each corner4 ,the hide is brought down heavily on the horse twice1 and then spread on the floor flesh side up for examination by the inspectors1 of which there are two1 one representing the house and the other the buyer of the hides4 ,they sweep off any salt that may be left1 and examine for cuts1 sores1 brands1 manure and grubs4 ,they also see that the hide is properly weighed and classified4 ,if the contract calls for a special trim it is now done4 ,two men then roll the hide1 beginning by lapping over the shanks1 head and neck4 ,then the sides are folded over and lapped again1 leaving the roll #ae to #ah inches wide4 ,the ends are thrown inward1 slightly overlapping each other2 a final fold is then given1 and the hide is ready to be tied4 ,rope the size of clothesline is used for tying1 and is cut into lengths of about seven feet4 ,it takes three men to tie for a gang such as we have described4 ,after tying1 the neat bundles are weighed and loaded on the cars for shipment4 ,a small tare is allowed the buyer4 ,ordinary workmen in hide cellars get #ag cents an hour1 and inspectors #be cents an hour40 ,about #be per cent4 of salt on the green weight of the hide is required for thorough curing4 ,rock salt merely crushed is frequently employed1 but this is very liable to contain iron in the form of oxide and chloride1 which causes the peculiar marbled markings known as 8salt-stains40 ,it is therefore much better to use a white crystallised salt1 though it is possible even in this case that stains may arise from the iron present in the blood4 ,some salt-stains appear also to be due to the action of pigment-bacteria1 and not to contain iron4 ,a reddening of the flesh side is often noticed in hides which have been kept in salt long or under unsatisfactory conditions1 and is very frequent in wet-salted ,south ,american hides4 ,such hides are said never to produce so firm a leather as those which are sound4 ,hides are not unfrequently cured by steeping in salt brine1 instead of strewing with dry salt4 ,this method is principally resorted to in order to give fictitious weight4 ,brined hides do not plump well in tanning1 the leather is not so good in quality as from those salted with dry salt1 and the cure is much less efficient4 ,many hides are not only salted but also dried in order to preserve them4 ,not much detail has been published with regard to the methods used1 which no doubt vary much in different places1 but probably in some cases the hides are salted in pile and in others by brining1 and then hung up to dry4 ,the principal object of this drying is to economise weight and cost of transport1 but it makes the hides much more difficult to wash and soften for tanning1 and probably the crystallisation of the salt has a weakening effect on the fibre4 ,hides cured in this way are styled 8dry salted40 ,a large number of the hides of the small native cattle of ,india are imported into this country in a dry-salted condition4 ,the following particulars of their cure are taken from a paper by the ,author and ,mr4 ,w4 ,towse4#af #af ,journ4 ,soc4 ,ch4 ,ind41 #ahie1 p4 #ajbe4 ,dry-salted1 or1 as they are commonly called 8plaster cures10 such as those of ,dacca and ,mehapore1 are thickly coated with a white material1 which in the first instance is merely the insoluble portion of a saline earth used in the cure2 though in many cases it is applied in larger quantities than necessary1 with the simple object of giving weight4 ,the salting is thus described by ,mr4 ,w4 ,g4 ,evans1 who some years since had considerable experience as a tanner at ,cawnpore3-- 8,the salt used by the natives is a salt-earth2 and is so called by them4 ,it is found extensively in the districts of ,cawnpore1 ,agra1 ,delhi1 ,lucknow1 ,patna1 etc41 and has no doubt something to do with the localisation of the hide-curing and kindred industries in these places4 ,the mode of procedure used is pretty much as follows3--the salt-earth is mixed into a very thin paste1 and this is lightly brushed on to the flesh side one day1 and the hide allowed to remain over night under cover4 ,next day1 for best hides1 the same solution is again spread on the flesh side of the outstretched hide and rubbed into it with a porous brick1 and then for legitimate salting1 the hide is allowed to dry under cover4 ,if for export1 the saltings may be three or four1 and the hides are treated out in the open1 subject to the intense heat of the sun2 which accounts for the number of hides which go back in the soaks in ,england and elsewhere40 8,we had a clause in our agreement with hide-factors1 that any hides which did not come down to natural suppleness in two days in clean water were to be returned4 ,of arsenic curing ,i know nothing1 and it is not so much in vogue as formerly4 ,there is quite a trade in ,cawnpore1 ,lucknow1 ,allahabad1 etc41 in treating old and inferior hides with new for export1 and great efforts are made by native holders to get their stocks down before the rains commence1 as they say1 and rightly ,i think1 that hides are not worth so much after the rains by #cj per cent4 ,the peculiar latent moisture of the rains affects them very detrimentally40 ,under certain circumstances this mode of cure gives rise to extensive iron-staining of the skins1 and analyses of the material scraped off ,dacca and ,mehapore kips were undertaken with a view to elucidating the causes of this injury4 ,the following are the results of the analyses referred to1 which were made upon the residue after the rather considerable quantity of fibrous organic matter1 which had been scraped off with the cure1 had been destroyed by ignition1 together no doubt with traces of ammoniacal salts3-- ---------------------------------------- ----------- ---- ,dacca4 ,mehapore4 ,entire ,cure4,entire ,cure4 ---------------------------------------- ----- ,sand and silica #bjee #bgch ,fe,o #bgg #ahf ,al,o #bdh #bgd ,mn,o #jfj #jdj ,ca,o #bfj #cgj ,mg,o #cch #cfi ,na,o #bhig #bfhj ,,so #chij #ccge ,cl #jbb #jah ,h,,po and ,,co ,traces ,traces ------------------------ #ajjdg #ajjej ---------------------------------------- ----------- ,the soluble salts of the ,dacca cure were also analysed separately with the following result3-- ,ca,o #jgj ,mg,o #jfj ,na,o #bijj ,,so #cgij ,cl #bb ,insoluble #cbab ------ #ajjed ,it thus consisted exclusively of sulphates1 with the exception of a trace of chloride4 ,the cures1 after ignition1 were both neutral to phenolphthalein1 but before ignition the ,dacca was distinctly alkaline1 in consequence probably of the presence of ammonium salts1 and both showed considerably larger traces of carbonates before than after4 ,the most striking feature of these analyses is the absence of more than the smallest traces of chlorides4 ,the cures are thus practically free from common salt1 and owe their antiseptic power to the sodium sulphate which they contain1 and which indeed forms their principal constituent4 ,nitrates appear to be entirely absent4 ,sodium sulphate sometimes forms large crystals in pits used for soaking these kips4 ,the iron-staining of hides which has been mentioned appears to result only when the hides after cure are exposed for a lengthened period to a moist atmosphere1 in which the carbonic acid present probably also plays its part1 the iron passing into solution as hydric carbonate4 ,the analyses show a striking resemblance to those of the soda deposits of ,wyoming1 given by ,dr4 ,attfield1#ag except that their percentage of sodium carbonate is smaller1 which is quite intelligible in the light of ,mr4 ,brunner's abstract on the #8,probable origin of natural deposits of sodium carbonate1'#ah which supports the view that the sodium carbonate is derived from sodium sulphate by the reducing and carbonating action of low organisms4 #ag ,journ4 ,soc4 ,ch4 ,ind41 #ahie1 p4 #d4 #ah ,ibid41 #ahic1 p4 #aaf4 ,it may be noted here that the preservative properties of sodium sulphate are well known1 and the anhydrous sulphate has been recommended as a substitute for common salt 7see p4 #bc74 ,drying is a very common method of preserving hides as well as other putrescible matters4 ,it has no effect in killing bacteria1 but putrefaction can only go on in presence of a considerable amount of moisture4 ,as applied to hides1 it is1 to the tanner1 one of the least satisfactory modes of cure1 involving very considerable difficulties in bringing hides back to the moist and swollen condition which is necessary at the outset of his operations1 but it is the only practical method in districts far from the coast and with primitive modes of transit1 both on account of the cost of salt1 and the lessened weight of the dried hide4 ,great differences are found in the ease with which dried hides soften1 according to the way in which the drying has been accomplished1 the difficulty being greater the higher the temperature which has been used 7see p4 #aaa74 ,the best mode of drying is to hang in the shade in a good draught of cool air1 with the flesh side out4 ,hides or skins dried in a tropical sun are not only difficult to soften1 but are liable to damaged portions1 which either refuse to soften1 or blister and go to pieces in liming1 owing to the structure of the hide being destroyed by heat1 the outer surface drying first and forming an impervious layer which hinders evaporation from the inside1 so that the moist interior becomes melted1 while the outside appears quite sound4 ,such injuries are often only to be discovered by soaking and liming4 ,very similar damage may occur from putrefaction of the interior after the outside has become dry1 and to get good results1 the drying must be gradual1 but rapid1 especially in hot climates4 ,south ,american hides are mostly dried in the sun1 suspended by head and tail from stakes1 with the hair side out4 ,the risk of injury by putrefaction during drying is diminished by the use of antiseptics4 ,solutions of arsenic have been frequently used for this purpose1 and many of the dried ,indian kips are of what are known as 8arsenic cures10 although the writer has never been able to detect arsenic in any which he has examined1 and its use seems by no means general4 ,the arsenious acid is usually dissolved in soda solutions4 ,unless used pretty freely it has little antiseptic effect1 but is useful in preventing the attacks of insects1 which are often very destructive4 ,the larva of a small beetle1 ,dermestes vulpinus1 frequently devours the whole tissue of patches of the hide1 leaving only the epidermis4 ,it may be well here to say a few words about the injuries and defects to which hides and skins are liable1 although some of them are not strictly due to the cure4 ,the most serious1 and yet preventable injury is that due to butchers' cuts4 ,as the value of the hide bears only a small proportion to that of the meat1 many butchers do their work extremely carelessly1 and this is encouraged by the loose classification of 8damaged hides0 in some markets4 ,there is also an idea that the appearance of the meat is improved by a thin layer of the white skin-tissue being left on it1 and for this reason as well as mere carelessness1 butchers frequently score the flanks of the hide with shallow cuts which greatly diminish its value4 ,the 8packer hides0 of the ,united ,states1 and the products of the large saladeros or slaughtering 78salting07 establishments of ,south ,america1 such as ,liebig's1 show what can be done by skilled work in this respect4 ,in the ,united ,states1 much of the flaying is done by means of a wooden cleaver1 instead of a sharp knife4 ,another method to some extent in use1 and which may be recommended for calf and sheep skins1 is to inflate the carcase before skinning1 with air from a compressing syringe1 which tears the connecting tissue between the skin and the body1 and renders flaying much easier4 ,brands are a great source of damage to hides1 but where cattle roam at large on unfenced plains1 as on the prairies of ,texas and the ,pampas of ,south ,america1 it seems indispensable for the recognition of ownership2 no other mode of marking being sufficiently permanent and conspicuous4 ,it is unfortunate1 that as the animals crowd together1 and cannot be closely approached1 it is necessary that the brands should not only be large1 but placed on the most valuable part of the hide4 ,generally on the ,pampas an effort is made to keep them on one side only1 so that in ,south ,american hides it is possible to select clear and branded sides4 ,in the ,united ,states much land is now fenced with barbed wire1 which while it obviates the necessity of branding1 introduces another evil in the form of 8barbed wire scratches10 which are frequently troublesome in 8packer hides40 ,illustration3 ,,fig4 #g4--;,hypoderma bovis4 #a1 egg2 #b1 maggot2 #d1 chrysalis case2 #f1 fly1 magnified 7,brauer72 #c1 #e1 chrysalis and fly1 natural size 7,b4 ,clark74 ,illustration3 ,,fig4 #h4--,sac of warble1 showing growth of epidermis round aperture4 ,in countries where cattle are used for draught purposes1 goadmarks are a frequent source of injury1 and some of the large cattle-ticks do considerable damage to the hides of ,spain and ,south ,america4 ,from the tanners' point of view1 however1 the most injurious insects are the 8bot-flies0 or 8warble-flies0 7,hypoderma bovis and allied species1 ,fig4 #g74 ,there is still some controversy as to how the eggs of these insects are deposited4 ,in the horse-bot fly it is known that the eggs1 first deposited on the skin1 are licked off and swallowed by the animal1 and develop in the stomach1 where they pass their larval and pupal life hanging on to its interior coats1 and only drop off and are passed out with the dung before their final change to the complete fly4 ,fortified by this1 and by some direct observation1 some ,american naturalists are of opinion that the ,american species at least1 hatches in the stomach1 and as a minute larva wanders through all the intervening tissues till it reaches the skin1 where it undergoes its further development4 ,the late ,miss ,ormerod1 who has made a careful study of the ,english species1#ai states that the egg hatches on the hair1 and that the larva simply eats its way below the skin1 leaving a minute red puncture which it subsequently enlarges to obtain air for its spiracles1 which are in the tail4 ,as it grows it continues to irritate the lower part of the cavity with hooked mandibles1 and lives on the pus and matter so produced4 ,it grows to a length of fully inch1 and the cavity1 ,fig4 #h1 situated between the skin and the subcutaneous tissue is often as large as half a walnut4 ,it remains in the sac not only during its larval1 but its pupal stage1 which do not differ much in appearance1 and falls out on the ground before complete development4 ,in small numbers1 the warble seems to do little injury to the general health of the animal1 but cases have been known where animals have actually died of the inflammation produced4 ,some idea of the extent of the plague may be realised from the statement that an ,indian kip in the possession of the writer has not less than #fhj warble holes1 and that almost equal numbers have been counted in ,english hides4 ,preventive measures are the sheltering of the cattle during the summer months when the fly is most prevalent2 the application of mixtures of oil or grease with tar-oil and sulphur to the hair1 to prevent egg-laying2 and the destruction of the larva in its early stages1 in autumn and winter by smearing the breathing aperture with grease1 or better1 with mercurial ointment4 ,when this is done sufficiently early1 the hole heals up without permanent injury1 but when it is allowed to remain open during the period of growth1 its sides become partially coated by the growth of epidermis1 and this permanently prevents their proper union by skin-tissue4 ,it is believed that if the larv were systematically destroyed in a district1 they would soon become extinct1 as they are not supposed to travel far4 #ai #8,some ,observations on the strid1' ,e4 ,a4 ,ormerod1 ,simpkin and ,marshall1 ,london1 #ahhd1 price #d;d4 ,a very troublesome injury to the skins of lambs and sheep is the disease known as 8cockle10 in which the skin becomes thickly dotted with spots of thickened tissue1 which bear some fanciful resemblance in form to a cockleshell4 ,the affection is prevalent during the spring while the wool is thick1 and disappears almost immediately on shearing1 but little is known of its causes or mode of prevention4 ,climate and breed have a considerable effect on the quality of hides and skins4 ,as a rule the less highly bred races1 and those which are most exposed to the extremes of weather1 have the thickest hides1 and in most cases highly bred animals have had their meat-producing1 or in the case of sheep1 their wool-bearing qualities developed at the expense of the characteristics most valued by the tanner4 ,,chapter ,,vii4 ,,structure ,,and ,,growth ,,of ,,skin4 ,although1 at first sight1 the skins of different animals appear to have little in common1 a closer examination shows that all the ,mammalia possess skins which have the same general structure1 and thus an anatomical description of the skin of an ox applies almost equally to that of a sheep1 goat1 or calf1 though on account of the difference in texture and thickness the practical uses of these various materials may differ widely4 ,the skins of lizards1 alligators1 fishes and serpents differ from those of the higher animals1 chiefly in having considerable modifications in the epidermis1 so that it becomes harder and forms 8scales10 and the arrangement of the fibres presents considerable difference4 ,in many fish-skins for instance1 the fibres are in successive layers1 at right angles to each other and diagonal to the skin1 but not interlaced4 ,in its natural condition1 the skin is not merely a covering for the animal1 but at the same time an organ of sense and of secretion1 and hence its structure is somewhat complicated4 ,it consists of two principal layers1 the epidermis 7epithelium1 cuticle7 and the corium 7derma1 cutis or true skin74 ,these are totally distinct1 not only in structure and functions1 but in their origin4 ,in the egg of a bird and the ovum of a higher animal1 the living germ consists of a single cell1 which1 as soon as fertilised1 begins to multiply by repeated division4 ,the mass of cells thus formed early differentiates into three distinct layers1 from the upper of which the epithelium arises1 while the true skin1 together with the bones and cartilages1 is derived from the middle one4 ,this distinction of origin corresponds with a wide difference of both anatomical and chemical characteristics4 ,a diagrammatic section of calf-skin is shown in ,fig4 #i1 and a more correct representation of its actual appearance is given in ,plate ,i4 7,frontispiece74 ,the epidermis is very thin as compared with the true skin which it covers1 and is entirely removed preparatory to tanning2 it nevertheless possesses important functions4 ,it is shown in ,fig4 #aj at a and b1 more highly magnified4 ,its inner mucous layer b1 the rete malpighi1 which rests upon the true skin c1 is soft1 and composed of living nucleated cells1 which multiply by division and form cell-walls of keratin4 ,these are elongated in the deeper layers1 and gradually become flattened as they approach the surface1 where they dry up1 and form the horny layer a4 ,this last is being constantly worn away1 thrown off as dead scales of skin1 and as constantly renewed from below1 by the multiplication of the cells4 ,it is from the epithelial layer that the hair1 as well as the sweat and fat-glands1 are developed4 ,illustration3 ,,fig4 #i4--,vertical section of calf-skin1 magnified about #ej diameters4 a1 epidermis2 b1 grain or papillary layer2 c1 fibrous layer of skin2 d1 hairs2 e1 fat-glands2 f1 sweat-glands2 g1 opening of ducts of sweat-glands2 h1 hair-muscles4 ,each hair is surrounded by a sheath which is continuous with the epidermis1 and into which the young hair usually grows as the old one falls out4 ,the hair itself is covered with a layer of overlapping scales1 like the slates on a roof1 but of irregular form4 ,these give it a serrated outline at the sides1 and when strongly developed as in wool and some furs1 confer the property of felting4 ,within these scales1 which are called the 8hair cuticle10 is a fibrous substance which forms the body of the hair2 and sometimes but not always1 there is also a central and cellular pith1 which under the microscope frequently appears black and opaque1 from the optical effect of imprisoned air4 ,on boiling or long soaking in water1 alcohol1 or turpentine1 the air-spaces become saturated with the liquid1 and then appear transparent4 ,illustration3 ,,fig4 #aj4--;,epidermis layer4 ,the fibrous part of the hair is made up of long spindle-shaped cells1 and contains the pigment which gives the hair its colour4 ,the hair of the deer differs from that of most other animals in being almost wholly formed of polygonal cells1 which1 in white hairs1 are usually filled with air4 ,in dark hairs1 both the hair and sheath are strongly pigmented1 but the hair is much the most so1 and hence the bulb has usually a distinct dark form4 ,the dark-haired portions of a hide from which the hair has been removed by liming still remain coloured by the pigmented cells of the hair-sheaths1 which can only be completely removed by 8bating and scudding40 ,illustration3 ,,fig4 #aa4--;a1 sebaceous gland2 b1 hair2 c1 erector muscle4 ,mag4 #bjj4 ,illustration3 ,,fig4 #ab4--;a1 hair2 b1 hair cuticle2 c1 inner root-sheath2 d1 outer root-sheath2 e1 dermic coat of hair-sheath2 f1 origin of inner sheath2 g1 bulb2 h1 hair-papilla4 ,near the opening of the hair-sheath to the surface of the skin the ducts of the sebaceous or fat-glands pass into the sheath and secrete a sort of oil to lubricate the hair4 ,the glands themselves are formed of large nucleated cells arranged somewhat like a bunch of grapes2 the upper and more central ones being highly charged with fatty matter4 ,their appearance is shown in ,fig4 #aa4 ,the base of the hair is a bulb1 enclosing the hair papilla h 7,fig4 #ab71 which is a projecting knob of the true skin and which by means of the blood-vessels contained in it supplies nourishment to the hair4 ,the hair-bulb is composed of round soft cells1 which multiply rapidly1 and pressing upwards through the hair-sheath1 become hardened1 thus increasing the length of the hair4 ,the cells outside the bulb1 shown at f in ,fig4 #ab1 pass upwards as they grow1 and form a coating around the hair1 known as the 8inner root-sheath40 ,in embryonic development1 a small knob of cells forms on the under side of the epidermis1 over a knot of capillary blood-vessels in the corium1 and enlarges and sinks deeper into the latter1 while the root-bulb of the young hair is formed within it1 surrounding the capillaries from which it derives nourishment1 and which form the hair-papilla1 ,fig4 #ac4 ,in the renewal of hair in the adult animal the process is very similar4 ,the bulb of the old hair withers1 and the hair falls out1 and in the meantime a thickening takes place in the epidermal coating of the bottom of the sheath1 and the young hair is formed below1 and usually to one side of the old one1 growing into the sheath1 and taking the place of the old hair4 ,this is one cause of the difficulty of removing ground-hairs in the process of unhairing1 since they are not only short1 but deeper seated than the old ones4 ,the process of development of the sudoriferous or sweat-glands is very similar to that of the hairs4 ,they consist of more or less convoluted tubes with walls formed of longitudinal fibres of connective tissue of the corium1 lined with a single layer of large nucleated cells1 which secrete the perspiration4 ,the ducts1 which are exceedingly narrow1 and with walls of nucleated cells like those of the outer hair-sheaths1 sometimes open directly through the epidermis1 but more frequently into the orifice of a hair-sheath1 just at the surface of the skin4 ,each hair is provided with a slanting muscle called the arrector or erector pili 7see ,fig4 #aa71 which is contracted by cold or fear1 and causes the hair to 8bristle10 or stand on end2 by forcing up the attached skin1 it produces the effect known as 8goose-skin40 ,the muscle1 which is of the unstriped or involuntary kind1 passes from near the hair-bulb to the epidermis1 and just under the sebaceous glands1 which it compresses when it contracts4 ,beside the hair1 and hair-sheaths1 and the sebaceous and sudoriferous glands1 the epidermis layer produces other structures of a horny character1 including horns1 hoofs1 claws and finger-nails2 which both chemically and anatomically are analogous to exaggerated hairs1 such as the quills of the porcupine4 ,the whole of the epidermis1 together with the hairs1 is separated from the corium by an exceedingly fine membrane1 called the hyaline or glassy layer4 ,this forms the very thin buff-coloured 8grain-0 surface of tanned leather1 which is evidently of different structure from the rest of the corium1 since1 if it gets scraped off before tanning1 the exposed portion of the underlying skin remains nearly white1 instead of colouring4 ,the whole of the hair-sheath is enclosed in a coating of elastic and connective-tissue fibres1 which are supplied with nerves and blood-vessels1 and form part of the corium4 ,illustration3 ,,fig4 #ac4--;,development of young hair4 ,illustration3 ,,fig4 #ad4--;,connective-tissue fibres4 7,ranvier47 ,the structure of the corium or true skin is quite different from that of the epidermis which has just been described1 as it is principally composed of interlacing bundles of white fibres1 of the kind known as 8connective tissue0 7see ,fig4 #ad72 these are composed of fibrils of extreme fineness1 cemented together by a substance somewhat more soluble than the fibres themselves4 ,the fibres are not themselves living cells1 but are apparently produced by narrow spindle-shaped cells lying against them4 ,the felted fibre-bundles are more loosely interwoven in the middle portion of the skin1 but become compacter again near the flesh4 ,in the case of sheep-skins this is especially marked1 the middle part being full of fat-cells and very loose4 ,any ill treatment of the pelt during the wet-work is liable to still further loosen this middle layer so that grain and flesh may sometimes be torn apart4 ,the flesh-splits of sheep-skins must have this loose fatty layer frized off before chamoising1 and ,american 8waxed fleshes0 from ox-hides are levelled by splitting away this portion1 and finished on the flesh4 ,the outermost layer1 just beneath the epidermis1 is exceedingly close and compact1 the fibre-bundles that run into it being separated into their elementary fibrils1 which are so interlaced that they can scarcely be recognised4 ,this is the pars papillaris1 and forms the lighter-coloured layer1 called 7together with its very fine outer coating7 the 8grain0 of leather4 ,it is in this part that the fat-glands are embedded1 while the hair-roots and sweat-glands pass through it into the looser tissue beneath4 ,it receives its name from the small projections or papill1 with which its outer surface is studded1 and which form the characteristic grain of the various kinds of skin4#bj 7,see ,fig4 #i and ,plate ,i47 #bj ,it will be noted that the word 8grain0 is used by the tanner in at least three different senses1 which are productive of much confusion4 ,the extremely thin hyaline layer forms a natural glaze to the skin1 and might well be spoken of as such2 the form and arrangement of the papill and hair-pores might be called the 8pattern0 of the grain1 leaving the use of the word 8grain0 itself restricted to the pars papillaris4 ,illustration3 ,,fig4 #ae4--;,fat-cells in connective tissue4 a1 fat-globule2 p1 protoplasm2 n1 nucleus2 m1 cell-wall4 7,ranvier47 ,the study of the structure of the grain1 and especially of the arrangement of the hair-pores is very important1 as it is usually the readiest means of identifying the kind of skin of which a leather is made1 which in finished skins with artificially printed grain is often very difficult4 7,plate ,,ii47 ,the examination is facilitated by wetting and stretching the skin1 and by the use of a good lens1 or a low power of the microscope4#ba #ba ,under the microscope1 the skin is of course lighted from above by direct light from a window1 or by that of a lamp concentrated by a 8bullseye0 condenser4 ,the reversal of the image in the microscope often causes a pseudoscopic effect very puzzling to the beginner1 prominences appearing as hollows1 and vice versa till the real direction of the lighting is considered4 ,illustration3 ,,plate ,,ii4 ,,photo-,,micrographs ,,of ,,grain ,,of ,,various ,,skins 7,a4 ,seymour-,jones74 #a4 ,cow-hide2 #b4 ,calf-skin2 #c4 ,east ,india ,goat2 #d4 ,pig-skin2 #e4 ,east ,india ,sheep2 #f4 ,welsh ,sheep4 ,face p4 #eb4 ,illustration3 ,,fig4 #af4--,striped1 or voluntary muscular fibre4 7,ranvier47 ,as stated above1 the surface of skin which is next to the flesh is firmer than that in the centre1 and as the fibres run nearly parallel with the surface it has a more or less membranous character4 ,the skin is united to the body of the animal by a network of connective tissue 7panniculus adiposus71 which is frequently full of fat-cells and is then called adipose tissue4 ,this constitutes the whitish layer which is removed1 together with portions of actual flesh1 in the operation of 8fleshing40 ,if a minute portion of adipose tissue be examined microscopically1 it will appear to consist of a mere mass of fat-globules entangled in connective tissue4 ,if1 however1 it be stained with carmine or logwood it may be at once observed that each globule is contained in a cell1 of which the nucleated protoplasm1 by which the fat was secreted1 is pressed closely against the wall 7,fig4 #ae74 ,similar cells are contained in considerable quantities throughout the hide1 and especially in the loose tissue of the central part2 hence in leather manufacture it is impossible to expel or wash out the fat until the cells have been broken down by 8liming0 or in some other way4 ,many animals 7ox1 horse1 etc47 possess a thin layer of voluntary muscle 7red flesh7 spread over the inner side of the skin1 and used for twitching to drive off flies4 ,in rough fleshing this is sometimes left on and may be a cause of dark flesh in sole leather4 ,even in the finished leather its striped structure may be detected microscopically 7,fig4 #af74 ,besides the connective-tissue fibres1 the skin contains a small proportion of fine yellow 8elastic0 fibres4 ,if a thin section of hide be soaked for a few minutes in a mixture of equal parts of water1 glycerine1 and strong acetic acid1 and then examined under the microscope1 the white connective-tissue fibres become swollen and transparent1 and the yellow 8elastic0 fibres may be seen1 as they are scarcely affected by the acid4 ,the hair-bulbs and sweat- and fat-glands are also rendered distinctly visible by this treatment4 ,on the other hand1 the white gelatinous fibres are most easily seen by examining the section in a strong solution of common salt1 or in one of ammonium sulphate2 or by staining with some aniline dyes such as safranine4 ,sections are most readily cut for these purposes by the use of the freezing microtome1 or after previous hardening in alcohol4 ,for further details see ,l4,i4,l4,b41 p4 #bed4 ,ordinarily in the production of leather only the corium1 or true skin is used1 and in order to obtain it in a suitable condition for the various tanning processes1 the hair or wool1 together with the epithelium1 must be completely removed without damaging the skin itself2 and especial care must be taken that the grain1 or portion next to the epidermis1 does not suffer any injury during the treatment4 ,all the methods employed depend upon the fact that the epidermis cells1 especially the soft growing ones next to the corium1 and those of the epidermis layer which surround the hair-roots1 are more easily destroyed than the corium itself owing to their different chemical character4 ,the 8unhairing0 process consists essentially in breaking down these cells by chemical or putrefactive agents1 and removing the hair together with the rest of the epidermis by mechanical means4 ,of the various substances which may be used for this purpose1 lime is one of the most convenient1 as its solubility in water is so slight1 that a solution of such a strength as to injure the hide cannot be easily made4 ,caustic alkalies1 on the other hand1 are much more soluble1 and unless care be taken to use only the proper quantity1 a dangerously strong solution may be made with consequent damage to the skin4 ,the addition of small amounts of sulphides to the lime-solution accelerates the unhairing owing to their special solvent action on the epidermis-structures1 and also in the case of alkaline sulphides1 by the caustic alkali which is produced by their reaction with the lime4 ,even if used alone1 strong solutions of alkaline sulphides rapidly destroy both hair and epidermis1 converting them into a mass which may be swept off the skin like wet pulp1 and yet they have practically no injurious action on the true skin4 ,in the 8sweating0 process the epidermic cells are broken down by putrefactive organisms and their products1 so that the hair becomes loose and may then be either rubbed or scraped off4 ,ammonia1 which is produced during the putrefaction1 has also an important solvent action1 and its presence doubtless tends to quicken the processes both of unhairing and of destruction4 ,to obtain useful knowledge of the structure of any particular skin1 it is not necessary to have a very elaborate or expensive microscope1 and it is quite possible to obtain useful information merely by the use of a good pocket lens1 as for instance1 in the examination of various forms of 8grain10 and the embossing of one skin to imitate another4 ,for further details of the manipulation and selection of the microscope1 the reader must consult ,l4,i4,l4,b41 pp4 #bcd et seq4 ,,chapter ,,viii4 ,,the ,,chemical ,,constituents ,,of ,,skin4 ,the chemistry of the various constituents of skin is still very imperfectly understood1 but ,beilstein1 in his great handbook of organic chemistry1 places gelatin1 albumens and keratins in the 8aromatic0 series1 and implies therefore that they contain the 8benzene0 ring4 ,it is at least certain that all are very complex4 ,the epidermis structures belong to the class of keratins1 which are closely related to coagulated albumin2 while the white fibres of the corium 7or true skin7 are either identical with gelatin1 or only differ from it in their molecular condition or degree of hydration4 ,this gelatinous tissue constitutes the bulk of the corium1 but it also contains albumen as a constituent of the lymph and blood which supply its nourishment1 keratins in the epithelial structures of the blood and lymph vessels1 and 8yellow fibres10 which are perhaps allied to the keratins1 but which cannot well be isolated for analysis4 ,the white connective tissue of the corium is converted into gelatin 7glutin7 by boiling with water4 ,owing to the impossibility of obtaining unaltered hide-fibre free from the other constituents1 and still more to that of deciding to what point it should be dried to remove uncombined water1 it is impossible to prove by analysis whether its composition is identical with that of glutin2 but as the white fibre constitutes by far the largest part of the corium1 and the other constituents do not differ largely from it in their percentage composition1 an analysis of carefully purified corium is practically identical with that of the actual fibre4 ,the following analyses of hide and gelatin are therefore of interest4 ,the analyses of ,von ,schroeder and ,paessler#bb are of special importance as being the average of a large number of separate determinations4 ,their nitrogen determinations are by ,kjeldahl's method4 ,small amounts of ash and traces of sulphur are neglected1 and probably included in the ,o1 which is obtained by difference4 #bb ,ding4 ,polyt4 ,journ41 #ahic1 cclxxxvii4 pp4 #beh1 #bhc1 #cjj4 ,,analyses ,,of ,,purified ,,corium4 ---------------------------------------- ------------------------ ,analyst4 ,material4 ,c ,h ,n ,o ,s ---------------------------------------- ------------------------ ,stohmann and ,langbein 44 #dii #ehahjbfj #jc ,mntz ,ox-hide #eah #fgahcbcb 44 ,ox1 calf1 horse1 ,von ,schroeder and ,paesslercamel1 pig1 #ejb #fdaghbed 44 rhinoceros ,goat and deer #ejc #fdagdbei 44 ,sheep and dog #ejb #feagjbfc 44 ,cat 44 44 #eaa #feagabec 44 ---------------------------------------- ------------------------ ,,analyses ,,of ,,gelatin 7free from ,ash74 ---------------------------------------- -- ,analyst4 ,c ,h ,n ,o ---------------------------------------- -- ,von ,schroeder and ,paessler#eab #feahabdb ,mulder #eja #ffahcbej ,fremy #ejj #feagebfj ,schtzenberger #ejj #fgahcbej ,chittenden and ,solly#bc #did #fhahjbea ---------------------------------------- -- #bc ,contained also #jg sulphur4 ,journ4 ,physiol41 xii4 p4 #bc4 ,it will be noted that the above analyses of skin differ more widely among themselves than their average does from that of the gelatin analyses1 though on the whole the nitrogen is somewhat higher in the latter4 ,the molecular weight of gelatin must be very high1#bd and any empirical formula founded on ultimate analysis therefore quite hypothetical4 ,bleunard1#be ,schtzenberger and ,bourgois1#bf and ,hofmeister agree on the formula ,c,h,n,o1 which leads to the following percentage composition3-- per cent4 ,c #iab #dig ,h #abd #fh ,n #ccf #ahc ,o #dfd #beb ---- ----- #ahcf #ajjj #bd ,paal 7,berichte ,d4 ,ch4 ,ges41 xxv4 7#ahib7 pp4 #abjb-cf1 and ,ch4 ,soc4 ,abst41 #ahib1 pp4 #hie-g7 calculates a molecular weight of about #ijj from physical 7freezing1 boiling point7 methods4 #be ,annales de ,chimie #e xxvi4 p4 #ah4 #bf ,compt4 ,rend41 lxxxii4 pp4 #bfb-d4 ,the addition of a molecule of water would make a difference in the percentage composition indicated by these formul which would be less than their probable experimental error1 and the change may therefore be one of hydration4 ,gelatin certainly contains both carboxyl and amido-groups1 and is capable of combining with both acids and alkalies 7see p4 #hd74 ,reimer#bg obtained what he supposed to be pure unaltered fibre-substance by digestion of purified hide with per cent4 acetic acid for many days and subsequent neutralisation4 ,his analysis showed ,c #dhde per cent41 ,h #fff per cent41 ,n #ahde per cent41 ,o #bfdd per cent41 thus deviating considerably from direct analysis of unaltered skin4 ,it is obvious that little weight can be placed on this result1 ,reimer's precipitate being probably a mere decomposition product4 #bg ,ding4 ,polyt41 ccv4 p4 #afd4 ,hofmeister#bh notes that on heating gelatin it loses water and forms an anhydride which he considers identical with collagen or hide-fibre4 ,when gelatin is dried at a temperature of #acj ,c4 it becomes incapable of solution in water1 even at boiling temperature1 and can only be dissolved by heating under pressure4 ,it is certain that collagen 7hide-fibre1 ossein7 is less easily soluble in hot water than ordinary gelatin4 #bh ,bied4 ,centr41 #ahhj1 p4 #ggb4 ,so far as our present knowledge goes1 we may regard hide-fibre as merely an organised and perhaps dehydrated gelatin4 ,gelatin or glutin 7not to be confounded with the gluten of cereals71 when pure and dry is a colourless1 transparent solid of horny toughness and of sp4 gr4 #ac4 ,it begins to melt about #adj ,c41 at the same time undergoing decomposition4 ,it is insoluble in hydrocarbons1 in ether1 or in strong alcohol4 ,in cold water it swells to a transparent jelly1 absorbing several times its weight of water1 but does not dissolve4 ,in hot water it is soluble1 but a solution containing even #a per cent4 of good gelatin sets to a weak jelly on cooling4 ,gelatin jellies melt at temperatures which vary considerably with the quality or freedom from degradation products1 but which within pretty wide limits 7#e-aj per cent47 are little affected by the concentration4 ,a #aj per cent4 solution of best hard gelatin melts about #ch ,c41 while low glue may fail to set at #ae ,c4 ,a useful technical test for the setting power of gelatin1 based on this fact1 consists in placing an angular fragment of the jelly in a small tube attached to a thermometer1 and stirring in a beaker of water1 which is slowly heated till the jelly melts1 when the temperature is noted4 ,the exact point is perhaps more easily seen if the tube is drawn to a conical point4 ,the jelly may also be allowed to set in capillary tubes open at the bottom1 and the moment noted when water rises into the tube4 ,the temperature of fusion is raised by the addition of formaldehyde1 salts of chromium1 alumina and ferric salts1 which produce a tanning effect1 and in a less degree by sulphates1 tartrates1 acetates1 some other salts1 and diminished by iodides1 bromides1 chlorides and nitrates4#bi ,solutions of gelatin too weak or too warm to gelatinise possess considerable viscosity4 ,gelatin may therefore be estimated1 in the absence of other viscous matters1 by the viscosimeter1 an instrument which measures the time taken by a liquid in flowing through a capillary tube4#cj ,the firmness of a jelly1 which is often important for commercial purposes1 is frequently measured by ,lipowitz's method1 in which a slightly convex disc1 conveniently of exactly #a cm4 diameter1 and cemented to the bottom of a thistle-head funnel tube1 is loaded gradually with mercury till it sinks in the jelly4 ,the jelly 7#e or #aj per cent47 should be allowed to set some hours before the test is made4 #bi ,see ,pascheles1 #8,versuche ber ,quellung1' ,archiv fr ges4 ,path41 ,bd4 #ga4 #cj ,see ,prollius1 ,ding4 ,polyt4 ,journ41 ccxlix4 p4 #dbe1 who employs a #a per cent4 solution2 also ,sttzer1 ,zeit4 ,ann4 ,ch41 xxxi4 pp4 #eja-ae4 ,solutions of gelatin from skin and bone are powerfully lvorotatory to polarised light4 ,at #cj ,c4 7,a7,d -#acj1 but temperature and the reaction of the solution have much influence on the value found4 ,gelatin is precipitated from aqueous solution by the addition of strong alcohol and concentrated solutions of ammonium sulphate and some other salts4 ,many other colloid bodies such as dextrin and gums behave similarly4 ,in the absence of these substances1 precipitation by alcohol may be utilised for the technical analysis of gelatins and glues1 printers' roller compositions and gelatin confectionery4 #be c4c4 of the gelatinous solution1 which is preferably of about #aj per cent41 is placed in a small beaker tared together with a glass stirring rod1 and thrice its volume of absolute alcohol added4 ,on stirring1 the gelatin sets firmly on the rod and sides of the beaker1 and may be washed with dilute alcohol or even with cold water1 dried and weighed4 ,a very pure ,french gelatin gave #ihf per cent41 while a common bone-glue only yielded about #fj per cent4 precipitate4 ,absolute alcohol withdraws water from gelatin-jelly1 leaving a horny mass4 ,gelatin may also be precipitated completely by saturating its solution with sodium chloride1 and then acidifying slightly with sulphuric or hydrochloric acid2 and masses of jelly become hardened in acidified salt solution as in alcohol1 though a neutral solution has little effect4 ,the cause of this is difficult of explanation1 but its bearing on the pickling of sheep-skins 7p4 #hi7 and the production of white leather 7p4 #ahf7 is obvious4 ,decompositions4--,when aqueous solutions of gelatin are heated under pressure1 or in presence of glycerin and other bodies which raise the boiling-point1 or more slowly at lower temperatures1 they gradually lose the power of gelatinising on cooling1 the gelatin being converted into modifications soluble in cold water1 but still capable of being precipitated by tannin4 ,hofmeister#ca states that the gelatin takes up #c molecules water and is split up into hemicollin1 soluble in alcohol and not precipitated by platinic chloride solution2 and semiglutin1 insoluble in alcohol and precipitated by platinic chloride solution4 ,both are precipitated by mercuric chloride4 ,dry gelatin is soluble in glycerin at high temperatures1 but probably suffers a similar change4 ,hence high temperatures and long-continued heating must be avoided in gelatin manufacture2 and in making printers' roller compositions1 which are mixtures of gelatin and glycerin1 the gelatin must be swollen with water and melted at a low temperature with the glycerin4 #ca ,bied4 ,centr41 #ahhj1 p4 #ggb1 and ,ch4 ,soc4 ,abs41 #ahha1 p4 #bid4 ,gelatin is also converted into soluble forms 7peptones71 perhaps identical with the above1 by the action of heat in presence of dilute acids and alkalies4 ,these1 like gelatin1 are precipitated by tannin and by metaphosphoric acid4#cb ,heated for longer periods or to higher temperatures with aqueous solutions of the caustic alkalies1 baryta1 or lime1 gelatin is gradually broken down into simpler and simpler products1 ending in nitrogen or ammonia1 water and carbonic acid4 ,among the intermediate products may be mentioned various acids of the amido-acetic series1 as amido-acetic 7glycocine1 glycocoll71 amido-propionic 7alanine71 and amido-caproic 7leucine72 and of the amido-succinic series 7amido-succinic aspartic acid74#cc #cb ,lorenz1 ,pflger's ,arch41 xlvii4 pp4 #ahi-ie2 ,journ4 ,chem4 ,soc41 #ahia1 ,a4 p4 #dgg4 #cc ,compare ,schtzenberger1 ,comptes ,rend41 cii4 pp4 #abif-i2 ,journ4 ,chem4 ,soc41 #ahhf1 ,a4 p4 #hah4 ,treatment with acids produces very similar effects4 ,the first products are soluble peptones4 ,paal#cd on treating #ajj parts of gelatin on the water-bath with #afj parts water and #dj parts concentrated ,h,cl till the product was soluble in absolute alcohol1 obtained1 on purification1 a white hygroscopic mass of peptone salts containing #aj-ab per cent4 of hydrochloric acid4#ce #cd ,berichte1 xxv4 pp4 #abjb-cf2 ,journ4 ,chem4 ,soc41 #ahib1 ,a4 p4 #hie4 #ce ,see also ,buchner and ,curtius1 ,ber41 xix4 pp4 #hej-i2 ,journ4 ,chem4 ,soc41 #ahhf1 ,a4 p4 #fce4 ,the products of digestion of gelatin with gastric and pancreatic juice are peptones which do not differ materially from gelatin in ultimate composition1 and the action is probably mainly hydrolytic4#cf #cf ,chittenden and ,solly1 ,journ4 ,chem4 ,soc41 #ahia1 ,a4 p4 #hdi4 ,the earlier products of putrefaction are very similar4 ,many bacteria have the power of liquefying gelatin-jelly4 ,this has been shown by ,brunton and ,mc,fadyen#cg to be due not to the direct action of the bacteria1 but to a soluble zymase secreted by them which peptonises the gelatin4 ,its action is favoured by an alkaline condition1 and destroyed by a temperature of #ajj ,c4#ch ,as putrefaction progresses1 the solution becomes very acid from the formation of butyric acid1 and later on ammonia and amido-acids are formed4 #cg ,r4 ,s4 ,proc41 xlvi4 pp4 #edb-ec4 #ch ,compare pp4 #ag1 #aga2 also ,ch4 ,zeit41 #ahie1 p4 #adhg4 ,fahrion1#ci starting with the idea that albuminoids and gelatin were condensation products of a lactone character 7,l4,i4,l4,b4 p4 #ahe71 and that they might1 like lactones1 be depolymerised by saponification1 digested these bodies with alcoholic soda till they were dissolved1 and on neutralising the solution with hydrochloric acid1 of which the excess was driven off by repeated evaporation1 and removing the sodium chloride by treatment with alcohol1 obtained in each case bodies of acid reaction1 which from their composition he supposed to be identical with ,schtzenberger's proteic acid1 ,c,h,n,o1 which is soluble in water and alcohol1 insoluble in ether and petroleum1 uncrystallisable1 and forming uncrystallisable salts4 ,fahrion suggested that the nitrogenous character which ,eitner attributed to his 8dgras-former0 7p4 #cgj7 was probably due to contamination by this body2 and that its formation might be utilised in the analysis of leather and other proteid bodies4 ,these products have since been further investigated by ,prof4 ,paal and ,dr4 ,schilling1#dj who show that they contain hydrochloric acid1 to which their acid reaction is due1 and that they are identical with the peptone salts previously obtained by ,prof4 ,paal 7v4 s47 by digestion of proteids with hydrochloric acid4 ,the free peptones are strongly basic4 #ci ,ch4 ,zeit41 #ahie1 p4 #ajjj4 #dj ,ch4 ,zeit41 #ahie1 p4 #adhg4 ,by dry distillation of gelatin a mixture of pyrrol and pyridin bases are produced4 ,this is commercially obtained by the distillation of bones1 and is known as 8bone oil10 or 8,dippel's animal oil40 ,pyrrol1 ,c,h,n1 resembles phloroglucol in giving a purple-red colour to fir wood moistened with hydrochloric acid 7p4 #bii74 ,reactions of ,gelatin4--,gelatin is precipitated by mercuric chloride1 in this respect resembling peptones1 but not by potassium ferrocyanide1 by which it is distinguished from albuminoids1 and it differs from albumin in not being coagulated by heat4 ,solution of gelatin dissolves considerable quantities of calcium phosphate2 hence this is always present in bone-glues4 ,gelatin and some of its decomposition products are precipitated by metaphosphoric acid4#da ,the precipitate contains about #g per cent4 ,p,o1 but gradually loses it on washing4 ,various salts diminish the solubility of gelatin in hot water1 and especially those of the alum type4 ,chrome alum and basic chrome salts are especially powerful1 rendering it practically insoluble4 ,the addition of about #c per cent4 ammonium or potassium dichromate causes glue or gelatin to become insoluble by the action of light with the formation of basic salts of chromium1 and has been utilised in photography and as a waterproof cement4 ,other colloids besides gelatin are similarly affected4 #da ,lorenz1 ,pflger's ,archiv1 xlvii4 pp4 #ahi-aie4 ,gelatin is precipitated by all tannins1 even from very dilute solutions2 one containing only #jb grm4 per liter is rendered distinctly turbid by gallotannic acid or infusion of gall-nuts2 but some other tannins give a less sensitive reaction4 ,the precipitate is soluble to a considerable extent in excess of gelatin1 so that in using the latter as a test for traces of tannin care must be taken to add a very small quantity only4 ,the addition of a little alum renders the reaction more delicate4 ,whether the precipitate is a definite chemical compound has been disputed1 as its composition varies according to whether gelatin or tannin is in excess4 ,bttinger#db states that the precipitate produced by adding gelatin to excess of gallotannic acid contains #ajg per cent4 of nitrogen1 indicating the presence of #ff per cent4 of gelatin on the assumption that gelatin contains #afe per cent4 ,n 7see p4 #eg74 ,digested with water at #acj ,c41 the precipitate is decomposed1 yielding a solution which precipitates tannin1 and probably indicating the formation of a more acid compound4 ,gelatin with excess of oak-bark tannin gives a precipitate containing #ie per cent4 of nitrogen1 corresponding to #ege per cent4 of gelatin4 ,treated with water at #aej ,c41 this precipitate yielded three products3 one soluble in cold water1 another in hot only and one insoluble4 ,on addition of a solution of formaldehyde 7formalin7 to one of gelatin no visible action takes place in the cold1 unless the solution of gelatin be very concentrated and alkaline1 but on heating1 the gelatin is rendered insoluble owing to the formation of a compound with the formaldehyde4 ,from the very small amount of formalin which is required to produce formo-gelatin it is very doubtful if this is a definite compound4 #db ,liebig's ,ann4 der ,ch41 ccxliv4 pp4 #bbg-cb4 ,weiske#dc states that bone-gelatin1 carefully freed from all mineral matter1 is not precipitated by tannin till a trace of a salt 7e4 g4 sodium chloride7 is added4 ,so far as is known1 bone-gelatin is identical with that of skin4 #dc ,bied4 ,centr41 #ahhc1 p4 #fgc4 ,chondrin is the gelatinous body produced by the digestion of cartilage with water at #abj ,c4 for three hours4 ,in most of its physical properties it is identical with gelatin1 but differs from the latter in being precipitated from its solution in water by acetic acid1 lead acetate1 alum1 and the mineral acids when the latter are not present in excess4 ,chondrin also differs from gelatin in producing a substance capable of easily reducing cupric oxide when it is boiled for some time with dilute mineral acids4 ,it is extremely probable that chondrin is merely an impure gelatine4#dd #dd ,cp4 ,petri1 ,berichte1 xii4 p4 #bfg2 ,mrner1 ,skand4 ,archiv f4 ,physiol41 i4 pp4 #baj-bdc2 and ,journ4 ,chem4 ,soc41 #ahhi1 ,a4 p4 #gcf and ,zeit4 ,physiol4 ,chem41 #ahie1 xx4 pp4 #ceg-cfd2 and ,journ4 ,chem4 ,soc41 #ahie1 ,a4 i4 p4 #bed4 ,see also ,richter1 ,org4 ,chem41 i4 p4 #eei4 ,coriin4--,rollet#de has shown that when hide and other forms of connective tissue are soaked in lime- or baryta-water1 the fibres become split up into finer fibrils1 and as the action proceeds1 these again separate into still finer ones1 till the ultimate fibrils are so fine as to be only distinguished under a powerful microscope4 ,at the same time1 the alkaline solution dissolves the substance which cemented the fibres together1 and this may be recovered by neutralising the solution with acetic acid1 when the substance is thrown down as a flocculent precipitate4 ,this was considered by ,rollet to be an albuminoid substance2 but ,reimer#df has shown that it is much more closely allied to the gelatinous fibres1 and1 indeed1 is probably produced from them by the action of the alkaline solution4 ,reimer used limed calf-skin for his experiments1 and subjected it to prolonged cleansing with distilled water1 so that all soluble parts must have been pretty thoroughly removed beforehand4 ,he then digested it in closed glasses with lime-water for #g-h days1 and precipitated the clear solution with dilute acetic acid4 ,he found that the same portion of hide might be used again and again1 without becoming exhausted1 which strongly supports the supposition that the substance is merely a product of a partial decomposition of the hide-fibre1 and indeed that there is no distinct 8cementing substance10 but merely a difference in the hydration or physical condition of the fibre substance which causes it to split more readily in certain directions4 ,the dissolved substance1 which he called 8coriin10 was purified by repeated solution in lime-water and reprecipitation by acetic acid4 ,it was readily soluble in alkaline solutions but not in dilute acids1 though in some cases it became so swollen and finely divided as to appear almost as if dissolved4 ,it was1 however1 very soluble in common salt solution of about #aj per cent41 from which it was precipitated both by the addition of much water and by saturating the solution with salt4 ,reimer found that a #aj per cent4 salt solution was equally effective with lime-water in extracting coriin from the hide1 and that it was partially precipitated on the addition of acid1 and completely so on saturating the acidified solution with salt4 ,other salts of the alkalies and alkaline earths acted in a similar manner1 so that ,reimer was at first deceived when experimenting with baryta-water1 because1 being more concentrated than lime-water1 the coriin remained dissolved in the barium salt formed on neutralising with acid1 and it was necessary to dilute before a precipitate could be obtained4 ,the slightly acid solution of coriin gave no precipitate either in the cold or on boiling with potassium ferrocyanide1 being thus distinguished from albuminoids4 ,the neutral or alkaline solution showed no precipitate with iron or mercuric chloride1 copper sulphate1 or with neutral lead acetate2 but with basic lead acetate1 basic iron sulphate1 or an excess of tannin a precipitate was produced4 ,reimer's analysis showed3 ,carbon1 #deia2 hydrogen1 #feg2 nitrogen1 #aghb2 oxygen1 #bifj2 and he gives a formula showing its relation to the original fibre1 which does not seem supported by sufficient evidence4 ,in all probability coriin is merely an impure degradation-product of hide-fibre or gelatin4 #de ,sitz4 ,wiener ,akad41 xxxix4 p4 #cje4 #df ,ding4 ,polyt4 ,journ41 ccv4 p4 #aec4 ,hide ,albumin4--,the fresh hide contains a portion of actual albumin1 viz4 that of the blood-serum and of the lymph1 which is not only contained in the abundant blood-vessels1 but saturates the fibrous connective tissue1 of which it forms the nourishment4 ,this albumin is mostly removed from the skin by the liming and working on the beam1 which is preparatory to tanning4 ,probably for sole-leather1 the albumin itself would be rather advantageous if left in the hide1 as it combines with tannin1 and would assist in giving firmness and weight to the leather4 ,it is1 however1 for reasons which will be seen hereafter1 absolutely necessary to get rid of any lime which may be in combination with it4 ,the blood must also be thoroughly cleansed from the hide before tanning1 as its colouring matter contains iron1 which1 by combination with the tannin1 produces a bad colour4 ,the albumins form a class of closely allied bodies of which white of egg may be taken as a type4 ,they are also related to the casein of milk1 to fibrin1 and more distantly to gelatin4 ,a good deal of information on the class may be found in ,watt's ,dict4 of ,chem41 #bnd ed41 article #8,proteids1' and ,beilstein's article #8,albuminaten1' and in ,allen's #8,commercial ,organic ,analysis1' vol4 iv4 ,the most characteristic property of albumins is that of coagulation by heat4 ,the temperature at which this takes place differs somewhat in different members of the group1 egg and serum albumin coagulating at #gb-gc ,c4 ,dry albumins become insoluble if heated to #aaj ,c4 for some time4 ,traces of acid tend slightly to lower1 and traces of alkali to raise the temperature of coagulation4 ,sodium chloride and some other neutral salts favour coagulation4 ,solutions of albumin become opalescent at a temperature slightly below that at which flakes form4 ,albumins are also coagulated by alcohol and by strong mineral acids4 ,coagulated albumin is only soluble in strong acids and alkalies by aid of heat1 and strongly resembles keratin 7pp4 #ef1 #fh74 ,solutions of albumin are lvorotatory to polarised light4 8,acid0 and 8,alkali0 ,albumins are formed by the action1 in the cold1 of dilute acids 7such as acetic1 hydrochloric7 and alkalies on albumin solution4 ,they are uncoagulable by heat1 and are precipitated by careful neutralisation1 but are soluble in excess of either acid or alkali1 or alkaline carbonates4 ,they are thrown out of solution by saturation with sodium chloride or magnesium sulphate4 ,it is doubtful whether albumins combine with either acids or bases1 and it is probable that the 8acid0 or 8alkali0 albumins are identical with the parapeptones formed in the first stage of peptic digestion4 ,on putrefaction1 or on more severe treatment with acids and alkalies1 albumins break down in a way similar to gelatin1 and yield almost identical products 7see p4 #eg72 amido-acids of the acetic series1 and tyrosin 7para-oxy--amido-phenyl-propionic acid7 and aspartic 7amido-succinic7 acid1 being the most important4 ,treatment with alcoholic soda 7see p4 #fb7 yields peptones similar to those of gelatin4#dg #dg ,paal1 ,ch4 ,zeit41 #ahie1 p4 #adhg4 ,heated for some days with dilute nitric acid 7#a 3 #b7 all proteids1 including albumins1 gelatin and keratins1 yield yellow flocks of 8xantho-proteic acid10 a substance of somewhat indefinite composition1 soluble in ammonia and in fixed caustic alkalies with production of an orange-red or brownish-red colour4 ,millon's reagent gives an intense red coloration when heated with albumins1 keratins1 or gelatin4 ,the reagent is made by dissolving #be grm4 of mercury in #bj c4c4 of concentrated nitric acid1 adding #ej c4c4 of water1 allowing to settle and then decanting the clear liquid4 ,albumins1 previously purified by boiling with alcohol and washing with ether1 when dissolved in concentrated hydrochloric acid 7sp4 gr4 #aaif7 by aid of heat1 give a violet-blue coloration1 but the reaction is often somewhat indefinite4 ,gelatin1 chondrin and keratins do not give this reaction4 ,treated with a trace of cupric sulphate and excess of caustic potash solution1 albumins give a violet1 and gelatin and peptones a pink solution 7biuret reaction74 ,dissolved in glacial acetic acid and treated with concentrated sulphuric acid1 albumins and peptones give a violet and feebly fluorescent solution4 ,a somewhat similar reaction is obtained if sugar solution be substituted for acetic acid4 ,a solution of albumin rendered strongly acid with acetic acid is precipitated by potassium ferrocyanide1 salt1 sodium sulphate1 lead acetate1 mercuric chloride1 tannin and picric and tungstic acids4 ,egg-,albumin is contained in the whites of eggs in membranes which are broken up by beating with water and can then be removed by filtration4 ,when fresh its reaction is slightly alkaline1 and it is lvorotatory4 ,according to ,lehmann1 white of egg contains #hg per cent4 of water1 and #ac per cent4 of solid matter1 the latter being almost entirely composed of egg-albumin4 ,this latter coagulates and becomes insoluble in water on heating to #fj ,c4 ,vitellin 7the albumin or globulin#dh of the yolk7 is insoluble in water1 and is obtained as a white granular residue on extracting undried egg-yolk with large quantities of ether4 ,it closely resembles myosin1 the chief globulin of muscle1 but differs from other globulins in being soluble in a saturated solution of common salt4 ,a neutral solution of vitellin in very dilute brine coagulates at #gj-ge ,c4 #dh ,globulin is an albumin soluble in dilute salt solutions1 but insoluble in water4 ,yolks of eggs1 preserved by the addition of salt1 borax1 or formalin1 are used for dressing skins in the process of 8tawing0 7see p4 #aia74 ,for the analysis of such yolks1 see ,l4,i4,l4,b41 p4 #aei4 ,their most important constituent for the leather-dresser is egg-oil of which they contain about #cj per cent4 ,casein1 the principal proteid of milk1 may be mentioned here in connection with the albumins to which it is closely related1 since1 though in no way connected with the animal skin1 since it is used to some extent as a 8seasoning0 or glaze for leather1 for which it is well adapted1 and it is now to a considerable extent a waste product of butter manufacture4 ,it differs from albumins in being very incompletely if at all coagulated by boiling1 but separates at once in curdy flakes on the addition of acids 7hydrochloric1 acetic1 butyric71 and by the action of rennet4 ,the curd is easily soluble in small quantities of dilute alkalies1 lime-water1 and salts of alkaline reaction1 such as sodium carbonate and borax4 ,if no more than the necessary quantity of alkali is employed for solution1 the compound has an acid reaction to phenolphthalein1 and like the original milk1 is curdled by rennet and dilute acids4 ,casein may also be dissolved by digestion with diluted mineral or organic acids4 ,hair1 ,epidermis and ,glands4--,these are all derived from the epithelial layer1 and hence1 as might be inferred1 have much in common in their chemical constitution4 ,they are all classed by chemists under one name1 8keratin10 or horny tissue1 and their ultimate analysis shows that in elementary composition they closely resemble the albumins4 ,it is evident1 however1 that the horny tissues are a class rather than a single compound4 ,the keratins are gradually loosened by prolonged soaking in water1 and1 by continued boiling in a ,papin's digester at #afj ,c41 evolve sulphuretted hydrogen1 at the same time dissolving to a turbid solution which does not gelatinise on cooling4 ,keratin is dissolved by caustic alkalies2 the epidermis and the softer horny tissues are easily attacked1 while hair and horn require strong solutions and the aid of heat to effect complete solution4 ,the caustic alkaline earths act in the same manner as dilute alkaline solutions2 hence lime easily attacks the epidermis1 and loosens the hair1 but does not readily destroy the latter4 ,alkaline sulphides1 on the other hand1 seem to attack the harder tissues with at least the same facility as the soft ones1 the hair being often completely disintegrated1 while the epidermis is still almost intact2 hence their applicability to unhairing by destruction of the hair4 ,keratins give the xanthoproteic reaction with nitric acid1 and a red coloration with ,millon's reagent1 and also resemble albumin1 in the fact that they are precipitated from their solution in sulphuric acid by potassium ferrocyanide4 ,by fusion with potash1 or prolonged boiling with dilute sulphuric acid1 keratin is decomposed1 yielding leucin1 tyrosin1 ammonia1 etc4 ,the precipitate produced by the addition of acids to alkaline solution of keratin 7hair1 horns1 etc471 mixed with oil and barium sulphate1 has been employed by ,dr4 ,putz as a filling material for leather1 for which purpose it acts in the same way as the egg-yolks and flour used in kid-leather manufacture4 ,eitner attempted to use it for the same purpose with bark-tanned leather1 but without much success4 ,putz has also proposed to precipitate the material after first working its solution into the pores of the leather4 ,elastic ,fibres4--,the elastic or yellow fibres of the hide are of a very stable character4 ,they are not completely dissolved even by prolonged boiling1 and acetic acid and hot solutions of caustic alkalies scarcely attack them4 ,they do not appear to combine with tannin1 and are very little changed in the tanning process4 ,they are present in hide and skin to the extent of less than one per cent4 ,analytical ,methods4--,the reactions distinguishing the principal skin constituents are summarised in the following table3-- ---------------------------------------- ------------------------- ,reagent4 ,gelatin4 ,albumins4 ,keratins4 ---------------------------------------- ------------------------- ,cold water ,swells only ,soluble ,insoluble4 ,heated in water ,soluble ,coagulate at ,soluble only at #gbto #ge ,c4 temp4 over #ajj ,c4 ,acetic acid and potassium ferro- ,no precipitate,precipitate ,precipitate cyanide to aque- ous solution ,millon's reagent ,no reaction ,red coloration ,red coloration4 ,hot concentrated ,no coloration ,violet blue ,no coloration4 hydrochloric acid ---------------------------------------- ------------------------- ,there is no simple method for the quantitative separation of the different constituents of skin4 ,it is1 therefore1 customary to simply determine the amount of nitrogen which any particular portion of the material may contain1 and1 as gelatinous fibre1 which constitutes by far the greater portion of the true skin1 contains #agh per cent4 of nitrogen1 to base the estimation of the amount of skin present upon this figure 7see p4 #eg74 ,the most convenient process for the determination of the nitrogen is that devised by ,kjeldahl1 which is most easily carried out as follows3-- ,a known weight of the substance which contains about #ja gram of nitrogen 7#je gram of skin1 or a corresponding quantity of liquor7 is placed in a flask of ,jena glass1 capable of holding #ejj-gjj c4c4 together with #ae c4c4 of concentrated sulphuric acid4 ,the contents of the flask are then boiled over a small ,bunsen flame for #ae minutes1 or more1 until all the water has been driven off and the material is quite disintegrated2 and are then allowed to cool below #ajj4 #aj grams of dry powdered potassium persulphate is now added1 and the boiling continued till the liquid has become colourless4 ,the operation of boiling should be conducted in a good draught1 or in the open air4 ,before the substance has begun to char it is advisable to place a small funnel in the neck of the flask to prevent1 as far as possible1 spirting and loss of sulphuric acid4 ,illustration3 ,,fig4 #ah4--,kjeldahl ,apparatus4 ,the colourless liquid is allowed to cool thoroughly1 and the flask is then fitted with a tapped funnel and tube1 as shown in ,fig4 #ah4 ,this tube must not be less than #d mm4 in diameter1 and with the end in the flask cut diagonally to facilitate drops of liquid falling back again into the flask4 ,it rises obliquely for a height of #ab to #ae inches1 is then bent over as shown in the figure and connected by a rubber tube#di to a #ajj c4c4 pipette1 or similarly shaped tube1 the other end of which dips just below the surface of a volume of exactly #ej c4c4 of 8normal0 hydrochloric acid contained in a second flask4 ,about #ej c4c4 of distilled water is introduced into the flask containing the treated sample1 and after this #ajj c4c4 of a solution of #ej grams of caustic soda in #ajj c4c4 of water is carefully and slowly run into the flask by means of the tapped funnel with which it is provided4 ,the contents of the flask are now boiled for about half an hour1#ej the normal acid in the receiving flask being kept cool by immersing the latter in cold water4 ,the liquid in this second flask is then titrated with normal sodium carbonate1 using methyl orange as indicator4 ,the difference in c4c4 between #ej c4c41 the volume of acid used1 and the quantity of normal sodium carbonate required to neutralise it1 when multiplied by #jjad represents the amount of nitrogen 7in grams7 in the weight of the substance used for the determination2 or if multiplied by #jjghf shows the weight of hide-fibre in the same quantity of material4 ,some chemists add copper sulphate1 or a drop of mercury before boiling up the substance with the strong sulphuric acid1 but the use of such substances introduces complications in the process without1 in the case of gelatinous matter1 securing more accurate results4 ,it is absolutely necessary that the acids and alkali used should be free from ammonia1 and a blank experiment should be made using pure sugar which contains no nitrogen1 and a correction applied if necessary for the ammonia they contain4#ea #di ,the ends of the glass tubes should fit closely together1 so as to expose the rubber as little as possible to the action of ammoniacal vapour4 #ej 8,bumping0 is often very troublesome at this stage1 and may be prevented by passing a current of steam from another flask1 or ammonia-free air through a tube with a capillary opening into the boiling liquid2 fragments of pure zinc1 of platinum1 or broken tobacco-pipe are much less efficient4 ,it is an additional safeguard against the escape of ammonia to fix a small absorption-tube containing fragments of glass to the absorption-flask4 ,the normal acid is run through this tube into the flask1 so as to wet the broken glass1 and is finally rinsed into the absorption flask before titrating its contents4 #ea ,cp4 ,procter and ,turnbull1 ,jour4 ,soc4 ,chem4 ,ind41 #aijj1 p4 #acj2 also ,nihoul1 ,composition des ,cuirs ,belges1 p4 #ad 7,bourse aux ,cuirs de ,lige1 ,sept4 #aija71 who advocates the use of potassium permanganate in the oxidation2 and ,law 7,jour4 ,soc4 ,ch4 ,ind41 #aijb1 p4 #hdg74 ,in place of using #aj grm4 of potassium persulphate as described1 #aj grm4 of ordinary potassium sulphate may be used1 and potassium persulphate added in small quantities towards the end of the operation till a perfectly colourless solution is obtained4 ,,chapter ,,ix4 ,,the ,,physical ,,chemistry ,,of ,,the ,,hide-,,fibre4 ,the nature of the changes which take place in the conversion of raw hide into leather1 and the causes of swelling and 8falling0 in the various stages of the wet-work and tannage are among the most difficult problems with which we have to deal1 and no intelligible explanation can be given without taking into account facts which are among the most recent discoveries of physical chemistry2 and of which even yet our knowledge is by no means complete4 ,we know from our study of the structure of hide1 that it consists in its natural state of gelatinous fibres which are soft and swollen with water1 and easy putrescible4 ,when these are dried1 they contract and adhere to each other1 forming a hard and almost homogeneous mass1 resembling in degree1 a sheet of glue or gelatine4 ,after the tanning process1 the fibres are changed in character1 though not in form2 they no longer absorb water so freely1 and in drying they do not adhere together1 but remain detached and capable of independent movement4 ,the leather is therefore porous1 flexible1 and opaque on account of the scattering of light from the surfaces of the fibres1 although the individual fibres are translucent4 ,at the same time1 chemical changes have taken place which render the fibres incapable of ordinary putrefaction4 ,our first necessity1 therefore1 in the conversion of skin into leather is to dry the fibres without allowing them to adhere4 ,this is accomplished in the most primitive mode of leather dressing1 by mechanically working fatty substances into the skin as it slowly dries1 so as to coat and isolate the fibres1 which are loosened by kneading and stretching2 while at the same time the fat forms a waterproof coating which prevents them from again absorbing the water which is necessary to putrefaction4 ,similar results may be produced by causing chemical changes in the fibres themselves1 which render them insoluble in water1 and consequently non-adhesive2 and a sort of leather may even be made by merely replacing the water between the fibres with strong alcohol1 in which they are insoluble1 and which absorbs and withdraws the water from them1 allowing them to shrink and harden1 while preventing their adhesion4 ,the merit of having first clearly seen and expressed these cardinal principles in leather production belongs to the now venerable ,professor ,knapp1 who published in #aheh a short paper 7,natur und ,wesen der ,gerberei und des ,leders7 which is a model of clear explanation and practical experiment4 ,knapp1 however1 deals mainly with the changes in the condition of the fibre which are necessary to convert it into leather1 and not with their physical causes2 and before we can explain the means by which these changes are brought about1 we must be acquainted with certain facts and theories about solutions which have become much clearer since he wrote4 ,the particles 7molecules7 of all substances are drawn together by attractive forces somewhat of the same character as the attraction of gravitation which holds together the solar system1 and which is the cause of weight4 ,it is indeed even possible that these forces are identical4 ,like gravitation1 these molecular attractions increase rapidly in intensity as the distance of the attracting bodies diminishes1 so that in solids and liquids1 where the molecules are near together1 they are immensely powerful1 while in gases and vapours they are barely perceptible4 ,these attractions are opposed by the motion of heat1 which takes the same part in molecular physics which the energy of planetary motion does in the solar system4 ,in solids1 the attractive forces hold the molecules rigidly in position1 the motion of heat being limited to short vibrations round a fixed point1 the effects of which are visible in the expansion caused by rising temperature4 ,if the temperature is increased1 most substances become liquid1 a condition in which the particles can roll round each other1 but are still held together by their mutual attractions1 as the sun holds the earth from flying off into space4 ,if the temperature goes on rising1 the orbits of the molecules become greater1 the liquid expands1 and finally molecules fly off at a tangent out of reach of the attractions of the mass of liquid1 and are only diverted from their course by colliding with solids or with other flying molecules1 from which they rebound4 ,this constitutes the state of vapour or gas4 ,the molecules usually consist of groups of atoms4 ,thus in the vapour of water1 each molecule contains one atom of oxygen combined with two of hydrogen1 and it is only at immense temperatures that this inner grouping is broken up4 ,naturally1 the more complicated and heavier the molecular group1 the more easily it is broken up by outside causes into simpler groupings1 and molecules may exist in liquids or solids1 which break up before they reach the gaseous form4 ,of such substances the chemist says that they 8cannot be volatilised without decomposition40 ,in very rare instances does the gaseous molecule consist of a single atom2 even those of the most perfect gases1 such as hydrogen1 oxygen and nitrogen consist of pairs which are not broken up at any known temperature4 ,the pressure of a gas1 and its tendency to expand is due simply to the motion and impact of its flying molecules1 and it may be noted that at the same temperature and pressure equal volumes of all gases have the same number of molecules1 the lighter molecules making up for their want of weight by their greater velocity4 ,the average velocity of a molecule of oxygen 7,o7 at freezing point is #dfa meters per second or about that of a rifle-bullet4 ,it must not be taken however1 that in any given solid1 liquid1 or gas1 all the molecules at any temperature move at a uniform velocity1 but that each individual molecule may vary from moment to moment from rest up to a very high speed1 while the temperature of the mass only represents the average4 ,thus it happens that in all liquids1 and even in solids1 a certain proportion of the molecules at any temperature will have a speed sufficient to enable them to leave the surface1 and take the form of vapour1 while a certain proportion will fall back and be caught and retained4 ,thus every liquid1 and theoretically every solid1 has a 8vapour-pressure10 rising with the temperature1 and depending on it only1 and at the boiling temperature of the liquid equal to that of the atmosphere1 or about #ae lb4 per square inch1 and therefore able to form bubbles in the interior of the liquid4 ,if a little of a liquid is confined in a flask1 the flask will become filled with its vapour1 and so long as any of the liquid is present1 the pressure of the vapour will depend only on the temperature and not at all on the respective quantities of liquid or vapour4 ,neither will it be affected by the pressure of other vapours or gases present in the flask1 the total pressure in which will be the sum of the 8partial0 pressures of all the gases and vapours present4#eb #eb ,cp4 p4 #dba4 ,the behaviour of gases and vapours has been described in some detail because it possesses very close analogy to that of substances in solution4 ,the molecules of liquids are held together by attractions which are very powerful over the short distances which separate them1 amounting in most cases to many tons per square centimeter of sectional area1 but the range over which they act is very small4 ,in the interior of the liquid the attractions on one side of a molecule are of course exactly balanced by those on the opposite side1 so that it is free to move within the liquid without hindrance1 but at the surface a very small part of the force due to the attractions of the surface-layer is unbalanced and acts as a sort of elastic skin holding the liquid together1 and is called 8surface-tension40 ,familiar examples of this are found in the force which supports a drop on the end of a tube1 the possibility of laying a slightly oily needle on the surface of water without sinking1 and the ability of some flies to walk on water as if it were covered with a sheet of india-rubber4 ,many liquids will mix or dissolve in each other in any proportions1 e4g4 water and alcohol2 the attraction of the alcohol for the water-molecule being as great or greater than that of alcohol for alcohol1 or water for water4 ,in other cases1 such as water and oil1 or water and petroleum spirit1 practically no mixture takes place1 their mutual attraction being small2 and each retains a considerable surface-tension at the points of contact1 though less than that of the free surfaces1 since each exerts an attraction on the other4 ,there are also many intermediate cases1 such as water with chloroform1 carbolic acid1 or ether1 in which each solvent dissolves a portion of the other1 but the two solutions do not mix1 but form separate layers4 ,in these cases an equilibrium is attained1 in which there is just as much tendency for either of the liquids to pass into as out of the other layer4 ,in this there is an extraordinary resemblance to what has been said of vapour-pressures2 and the tendency to pass into solution is often called solution-pressure2 and it may be noted that when equilibrium has been reached1 not only is the solution-pressure1 but the vapour-pressure of each constituent equal in both solutions4 ,like vapour-pressures1 the solution-pressures usually increase with rise of temperature1 more of each constituent passing into the other1 till at last the composition of the two layers becomes identical1 their surface-tensions disappear1 and complete mixture takes place4 ,with phenol 7carbolic acid7 and water this takes place at about #gj ,c4 ,most of what has been said of the mutual solution of liquids is also true of the solution of solids1 but the latter may be divided into two very distinct classes1 colloids and crystalloids 7which1 however1 shade off into each other74 ,the colloid or gluey bodies are mostly miscible in any proportion with liquids in which they dissolve1 and there is no such thing as a definite point of saturation4 ,there are however some which form jellies which have great analogy to the partially miscible liquids2 there is a mutual solubility1 a portion of the solid dissolving to a liquid solution1 while the remainder of the liquid dissolves in the solid1 increasing its volume1 but still retaining the characteristics of the solid state4 ,as the temperature is raised1 this mutual solubility generally increases1 till at a given point the jelly melts1 and complete solution takes place1 as in the case of partially miscible liquids4 ,these phenomena are of prime importance in the theory of tanning1 but their further consideration must be deferred till a few words have been said about the crystalloids4 ,these are characterised by regular crystalline form1 indicating that the attractive forces of their molecules are exerted in definite directions1 giving them a tendency to attach themselves together in definite geometrical arrangements4 ,they dissolve in themselves no part of the solvent1 but are dissolved by it till an equilibrium is reached in which the tendency of further particles of the solid to pass into the solvent is balanced by that of those already dissolved to attach themselves to the remaining solid1 or 8crystallise out40 ,such a solution is 8saturated0 with respect to the solid residue1 but the word has no meaning unless solid crystals are present1 and where a body has1 as sometimes happens1 more than one crystalline form1 a solution may be saturated with regard to one of them1 and more or less than saturated with regard to another4 ,in 8supersaturated0 solutions1 crystallisation is at once started by the addition of a 8seed0 crystal of the proper form4 ,if a crystalloid substance1 such1 for instance1 as copper sulphate1 be placed in a solvent 7e4 g4 water71 the dissolved salt will gradually spread itself through the whole body of the solvent1 though in the complete absence of currents in the liquid1 the motion is extremely slow1 and years may be taken for the diffusion to rise through a few feet4 ,in many cases salts diffuse through aqueous jellies at the same speed as they would through still water4 ,colloid substances on the other hand have little or no power of diffusion and mostly cannot pass through jellies at all4 ,this is the reason why tannage with mineral salts is so much more rapid than with vegetable tannins which are of colloidal character1 and diffuse through the gelatinous fibres of the hide with extreme slowness4 ,all dissolved crystalloids do not pass through gelatinous membranes with equal ease1 and substances are known1 mostly gelatinous precipitates1 which do not permit the diffusion of dissolved salts1 though they allow water to pass freely4 ,thin layers of such precipitates form what are called 8semipermeable membranes40 ,the existence of such membranes affords us the possibility of direct measurement of the tendency to diffusion1 or as it is generally called the 8osmotic0#ec pressure of dissolved bodies4 ,thus a porous earthenware battery-cell may be immersed in a solution of copper sulphate1 and filled with one of potassium ferrocyanide4 ,in this way its pores will be filled with a gelatinous precipitate of copper ferrocyanide1 which is pervious to water1 but impervious to most dissolved substances4 ,if now the cell be filled with a dilute solution of some crystalloid1 say sugar1 and its top closed by a perforated cork fitted with a vertical tube1 and the cell be plunged in water1 the latter will pass into the cell1 and the dilute solution will rise in the tube to a height of many feet above the water outside4 ,by substituting a mercury pressure gauge for the vertical tube1 exact measures of the pressure in the cell can be made1 which is the osmotic pressure of the dissolved substance4 ,at first sight it is paradoxical that the water should flow into the solution1 apparently against a heavy pressure1 but the explanation is simple4 ,mention has already been made of the enormous internal pressures of liquids produced by the attractions of their molecules4 ,in the solution a portion of this is borne by the dissolved substance1 and the water flows in from the outside till an internal mechanical pressure is produced1 equal in amount to the osmotic pressure of the dissolved substance4 ,the resemblance of the phenomena of solution to those of vapour-pressure has already been mentioned1 and it is found to be even quantitative1 since the measured osmotic pressures are exactly equal in amount to those which the dissolved body would produce if it were in the state of vapour at the same temperature and occupying the same volume as the solution4 ,it acts1 in fact1 precisely as the 8partial pressure0 of a vapour4 ,there are several indirect ways of measuring the osmotic pressure of dissolved bodies1 as for instance1 from the lowering of the freezing point1 or the raising of the boiling point of the solution as compared to those of the pure solvent1 all of which confirm the direct measurements1 and show that in a given volume at the same temperature1 the same number of molecules will produce the same osmotic pressure whatever their nature1 or conversely1 that at the same osmotic pressure and temperature equal volumes of any solution must contain the same number of molecules4 ,the use of these facts in determining molecular weight is obvious4 #ec ,solution-pressure and osmotic pressure are really two names for the same force2 the former being employed to signify the tendency of a solid to dissolve1 and the latter the pressure produced by the dissolved body which tends to prevent further solution4 ,thus1 in a saturated solution in contact with its solid1 the two pressures are always equal1 but exerted in opposite directions4 ,a curious apparent deviation from this law is however noticed in solutions of salts1 acids1 and alkalies1 and indeed of electrolytes generally2 thus a dilute solution of sodium chloride produces an osmotic pressure nearly double that corresponding to the number of molecules of ,na,cl present2 and in fact behaves as if it were a solution of ,na and ,cl existing separately4 ,such a solution conducts a current of electricity very readily1 while at the same time the chlorine is carried to the positive1 and the sodium to the negative pole1 where they separate as ,na and ,cl 7the ,na decomposing the water present and forming ,na,o,h74 ,in fact1 the modern theory of electrolysis asserts that these dissociated atoms are not separated from each other by electricity1 but that they exist already separated in the solution of the electrolyte1 and merely act as carriers for the electricity1 and that the work done by the latter is not that of breaking up the salt-molecule1 but of giving its dissociated atoms fresh charges of electricity which enable them to combine as new molecules1 and escape from the electrolyte4 ,complex salts do not always break up into single atoms1 thus calcium sulphate dissociates into ,ca and ,,so1 hydrogen sulphate 7sulphuric acid7 into #b;,h and ,,so1 and so on4 ,these dissociated atoms and atom-groups are called 8ions10 and may be monovalent1 divalent1 and so on2 the divalent ion carrying double the electrical quantity or charge of the monovalent4 ,without discussing the ultimate nature of electricity itself1 the matter is most easily pictured by assuming that the molecule of the undissolved salt is made up of an ion with a charge 78kation10 e4g4 ,na71 and an ion with a - charge 78anion10 e4g4 ,cl71 by the electrical attraction of which charges they are held together4 ,in the solution these attractions are balanced by those of other ions1 so that they can wander freely within the liquid1 but in order to take the molecular form of free elements and escape1 say as ,na and ,cl1 the pair of kations must go to the - pole and give up one charge1 and at the same time a pair of anions must go to the pole and receive a charge4 ,thus the ,na and all other kations separate at the - pole1 and the ,cl and all other anions at the pole4 ,from what has been said1 it will be obvious that free ions can only exist in solution1 and can neither evaporate1 nor separate as solids2 but that in the liquid they act much like other dissolved molecules1 exerting their own osmotic pressure independently of each other or of the dissolved salt1 but with the limitation that a solution must always contain at the same time equal numbers of and - ions4 ,as a solution is diluted1 more ions are liberated2 as it is concentrated1 more recombine to form undissociated salt4 ,this will be made clearer by an example4 ,in a saturated solution of sodium chloride with solid salt present1 we have dissolved salt at the solution-pressure of the crystallised salt1 and ,na and ,cl ions at the dissociation-pressure of the saturated salt solution1 and neither affect the others4 ,if we now add hydrochloric acid1 it has no effect directly on the solubility of the salt1 but as ,h,cl dissociates largely into ,h and ,cl1 it increases the pressure of the ,cl ions1 and so compels the salt to recombine till the ,cl pressure is reduced to its normal amount4 ,this increases the concentration of the undissociated salt-solution1 and thus salt is precipitated or crystallises out till the solution is no longer super-saturated with respect to the salt-crystals4 ,most chemical reactions1 and especially those between acids and bases1 are really reactions of the ions4 ,thus ,na,o,h in dilute solution is mostly ionised into ,na and ,,oh1 while ,h,cl is similarly ionised into ,h and ,cl4 ,on the other hand1 water ionises only very slightly4 ,hence1 on mixture1 the ,h and ,,oh combine and form water1 with evolution of heat1 while no actual combination occurs between the ,na and ,cl1 so long as they remain in dilute solution4 ,for this reason1 the heat of neutralisation of all strong acids and bases is the same1 independent of their nature1 since strong acids1 bases and salts are almost completely ionised4 ,the rapidity of action1 and consequently what we call the 8strength0 or 8avidity0 of an acid or base depends on the number of its free ions in solution2 very weak acids and bases are very little ionised1 though their salts ionise almost completely in dilute solution4 ,on this depends the explanation of a fact of great practical importance4 ,hydrochloric acid1 a strong acid1 is almost completely ionised in solution2 acetic1 a weak one1 very little2 while sodium acetate and sodium chloride as salts are both almost completely ionised4 ,if we add hydrochloric acid to a solution of sodium acetate1 we shall have sodium-ions1 acet-ions1 chlorine-ions and hydrogen-ions in the solution4 ,as the pressure of the acet-ions and the hydrogen-ions will be greater than the dissociation-pressure of acetic acid1 they will combine to form it1 till the pressure is equalised1 and we shall have in the solution1 free acetic acid slightly ionised1 the sodium- and chlorine-ions of sodium chloride1 and the sodium- and acet-ions of any excess of sodium acetate left4 ,if the hydrochloric acid were just sufficient to combine with the whole of the sodium1 we should have an equilibrium containing much 7ionised7 sodium chloride and little sodium acetate1 together with much free acetic acid1 and little hydrochloric4 ,thus the 8strong0 acid would displace the weak one4 ,taking another example1 we add sodium acetate to a solution of acetic acid4 ,as the ionisation-pressure of the acetic acid is much less than that of sodium acetate1 and both have a common acet-ion1 the ionisation of the acetic acid will diminish1 and more undissociated acetic acid will form1 till by its concentration the two pressures are equalised4 ,the total quantity of free acetic acid will be unchanged1 but a less proportion of it will be ionised1 and it will act like a weaker acid4 ,this reduction of the activity of a weak acid by the addition of its neutral salt is often made use of by chemists4 ,instances in tanning practice are the use of excess of potassium dichromate with chromic acid in the chrome tanning process1 the effect of neutral salts in 8mellowing0 the action of tanning liquors1 and the use of salt in 8pickling40 ,let us now try to apply these facts to the physics of tanning1 taking first the simplest cases1 where electrolytic dissociation does not take place4 ,we may consider the wet hide as made up of a mass of fibres of gelatine-jelly1 with interspaces which are filled with water4 ,in fact1 for many purposes of experiment we may substitute for hide1 mere sheets of swollen gelatine1 so as to avoid the complications introduced by the water or solution mechanically retained between the fibres4 ,if we place a sheet of dry gelatine in water1 it swells1 absorbing perhaps seven or eight times its weight of water1 but does not appreciably dissolve4 ,a condition of equilibrium is reached when the attraction of the water-molecules for the gelatine is equal to the sum of the cohesive attraction of the gelatine for itself and the internal attraction of the water outside4 ,an increase of the cohesion of the gelatine would tend to make it contract and expel part of the water1 and this contraction would tend further to increase both the cohesion of the gelatine1 and its attraction on the diminished number of water molecules it contained1 and clearly these causes would act in opposing directions4 ,the equilibrium is therefore a very unstable one1 and slight causes might be expected to produce great changes in the degree of swelling1 which is indeed the case4 ,if we increase the temperature we diminish the cohesion of the gelatine1 till at a point it becomes less than its attraction for the water1 and the jelly suddenly loses its solid condition and dissolves4 ,the absorption of water by colloids 7including gelatine7 is accompanied by contraction of volume 7compression7 of the water absorbed1 and by evolution of heat1 and1 as has been pointed out by ,koerner1#ed it is opposed 7and swelling decreased7 by increase of temperature4 ,solution1 on the other hand1 absorbs heat1 and is therefore favoured by rise of temperature4 #ed ,beitrge zur wissenschaftlichen ,grundlage der ,gerberei1 ,freiberg1 #ahii4 ,if we place the swollen jelly in alcohol1 it parts with water and contracts4 ,the gelatine and alcohol are not mutually soluble1 the sum of the attraction of water for alcohol1 and the cohesive attraction of the gelatine is greater than the attraction of the latter for water1 and as the alcohol cannot pass into the gelatine1 the water passes out1 and the jelly contracts4 ,the greater the concentration of the alcohol1 the more completely is the jelly dehydrated1 and in strong alcohol it may become quite hard and solid4 ,if we like to express the same facts in language more familiar to the modern chemist1 but perhaps less clear to the non-chemical reader1 we may say that the alcohol exerts an osmotic pressure outside the gelatine1 but little or none inside it1 and therefore the water is squeezed out4 ,it would be equally true to say that the water passes out of the jelly till its osmotic pressure is equal in both the jelly and the alcohol4 ,the jelly is a true 8solid solution0 of water in gelatine1 and in a solution we may regard either of the two constituents as the solvent4 ,exact parallels may be found in the distribution of a third substance between two immiscible solvents 7see p4 #gf71 say alcohol between water and ether4 ,the osmotic pressure of water into alcohol may be demonstrated in a very simple way1 taking advantage of the fact that a film of jelly is permeable for water but not for alcohol4 ,if the experiment described on p4 #gh be made by placing alcohol in a cell previously washed out with a gelatine solution1 and the cell be placed in water1 the water will pass into the cell1 and the alcoholic solution will rise many feet in the vertical tube4 ,the insolubility of gelatine in alcohol may be made use of for its estimation4 ,if three times its volume of absolute alcohol be added to a solution containing gelatine1 the latter will separate as a solid mass on a stirring rod1 or on the sides of the beaker1 and may be washed with further portions of alcohol4 ,the method is useful in the analysis of gelatine lozenges and 8jelly squares10 roller compositions1 hectograph masses1 and the like2 and for the determination of true unaltered gelatine in glues1 and commercial gelatines 7see page #fj74 ,many other colloids are however also precipitated by alcohol4 ,if hide be treated with alcohol1 as in ,knapp's experiment 7p4 #gd71 the action is precisely the same as has been described with gelatine-jelly4 ,the water is withdrawn1 first from the spaces between the fibres1 and then from the fibres themselves1 and the skin dries with the fibres isolated and non-adherent1 and is in fact converted into a sort of leather1 which1 however1 returns to raw pelt on soaking in water4 ,the action of solutions of sugars1 glycerine1 and the like is in principle similar to that of alcohol1 but more complex1 since in general these bodies are soluble not only in the water1 but in the gelatine or hide-fibre1 so that their effect cannot be foretold1 though usually it tends towards contraction rather than swelling4 ,in general terms the equilibrium is a balance of the attraction of the water and the sugar for the gelatine1 against the sum of their mutual attraction in the solution outside and the resisting cohesive force of the gelatine2 and will depend not only on the nature of the substances1 but on temperature and concentration4 ,the action of acids1 alkalies and salts on gelatinous fibre is yet more complex1 since not only electrolytic dissociation1 but most probably actual chemical combination comes into the question4 ,the chemical constitution of gelatine is as yet quite uncertain1 but it is known that the molecule contains both amido-groups capable of linking with acids1 and carboxyls which will combine with bases 7see p4 #eh74 ,hence hide-fibre absorbs both acids and bases with great avidity1 so much so that the sulphuric acid of a decinormal solution may be completely removed by hide1 leaving only water without a trace of acid recognisable by litmus4 ,alkalies are absorbed in a similar way1 and in both cases the gelatine or gelatinous fibre acquires a greatly increased power of absorbing water1 and consequently of swelling4 ,familiar cases of this are the swelling of hide by acid1 and by lime1 and in neither case can the added substance be removed in any reasonable time by mere washing with water4 ,hence to free hides from lime or acids it is necessary to neutralise the alkali with acids 7see p4 #aec7 or the acid with chalk or alkalies 7p4 #ia74 ,no accurate determination has yet been made of the amount of acid or alkali with which gelatine or hide-fibre will combine1 since the matter is complicated by the volume of acid or alkaline solution which is absorbed mechanically1 and by the tendency of the compound to partially decompose on washing with water4 ,experiments made by the author lead to the conclusion that #a grm4 of air-dried gelatine will combine with about #jjbe grm4 of actual hydrochloric acid 7,h,cl7 when placed in a very dilute solution of the latter1 and this compound will absorb #dj or #de grm4 of water while still retaining the jelly state4 ,the maximum swelling1 with both acids and alkalies1 is obtained with dilute solutions2 and with the stronger acids1 the outside solution must be almost neutral when equilibrium is attained1 increasing quantities of acid diminishing the amount of water absorbed4 ,the same statement is true of the strong alkalies4 ,thus in both cases1 where swelling is desired1 the object is defeated by the use of too strong solutions1 and the quantity of acid or alkali should be rigidly adjusted to the weight of pelt1 and not to the volume of solution4 ,as regards a physical explanation of the effect of acid and alkaline solutions upon gelatine1 anything which can yet be said must be regarded rather as speculation than as actual scientific knowledge4 ,it must also be admitted that while the view that actual chemical combination takes place between the gelatine and acids 7or alkalies7 seems much the most probable1 difficulties arise from the fact that different acids apparently do not always combine in proportion to their equivalents1 though it is probable that these will prove only apparent anomalies when more accurate means are known of determining how much acid is really combined1 and how much merely mechanically absorbed4 ,leaving out of account for the moment the question of swelling1 a few words must be said about a property of these acid- 7and alkali-7 gelatine compounds1 a knowledge of which is essential to understanding the swelling process4 ,if a mass of acid-gelatine be suspended in pure water1 a certain portion of it will be decomposed into neutral gelatine and free acid1 and the latter will diffuse into the water4 ,thus acid-gelatine can only exist in presence of a certain amount of free acid4 ,this dissociation by water is a common property of all salts1 and necessarily follows from what has been said of ionisation2 but it is only where the combining affinity of the constituents is weak1 that it becomes practically perceptible4 ,water to a very small extent ionises to ,h and ,,oh4 ,if we imagine a salt dissolved in it1 such as ,na,cl1 which ionises almost completely to ,na and ,cl1 we see that a certain proportion of ,na,o,h and ,h,cl must be formed by combination with the water-ions4 ,in the case named the quantity is absolutely negligible1 since both sodium hydrate and hydrochloric acid are almost completely ionised themselves1 but if either the acid or the base is weak 7that is little ionised71 the process of combination must go on till the acid or basic solution is strong enough to have an ionisation-pressure equal to that of the salt4 ,as this acid or base is no longer in an ionised condition1 it may be removed from the solution by volatilisation or diffusion4 ,for instance1 if a solution of ferric chloride be confined in a tray of parchment paper1 through which it has little power of diffusion1 and this tray floated upon water which is frequently changed1 the dissociated acid will diffuse through the membrane into the water1 and in this way the whole of it may be ultimately removed1 leaving nothing but a colloid solution of hydrated ferric oxide in the tray4 ,actions of this sort1 in which the gelatinous fibre of the hide plays the same part as the parchment-paper membrane1 have an important share in many of the phenomena of tanning4#ee ,thus1 in the case of hide swollen with acid1 the acid compound with the fibre is somewhat dissociated1 and if the hide be hung in water which is constantly changed1 the acid diffuses into it1 and the whole may be ultimately1 though slowly removed4 ,a similar effect is produced in the familiar operation of removing acid from pelt or chromed leathers by paddling with 8whitening0 7calcium carbonate74 ,the latter is insoluble in water1 and therefore cannot penetrate into the hide1 but as it instantly combines with any acid which diffuses out1 the acid-gelatine compound is rapidly decomposed1 since it is only permanent in a solution containing enough free acid to have an ionisation-pressure equal to that of the compound4 ,similar statements are true of the alkali-gelatine and lime-gelatine compounds4 #ee ,probably chrome1 aluminium and iron salts are decomposed in this way in mineral tanning1 and thus fixed in the hide as insoluble basic salts4 ,cp4 pp4 #ahf1 #bae4 ,it will be easier to follow the results of what has been said if we take a concrete case which has been carefully investigated by the author and others2 that of the action of hydrochloric acid solutions on gelatine4 ,if a weighed sheet of gelatine be placed in a very dilute solution of the acid1 it swells much more considerably than it does in water1 a maximum swelling being attained with a concentration of the outer solution of #ja to #jb grm4 of ,h,cl per litre4 ,the swollen jelly has then a volume of about #de c4c4 per gram of the air-dried gelatine1 and a concentration equal to about #jge grm4 of ,h,cl per litre of swollen jelly1 or at least about five times that of the outer solution4 ,as the concentration of the latter is increased1 the concentration in the jelly also increases1 but in a much smaller ratio1 while the volume of the jelly diminishes1 till1 with a concentration of #e grm4 of ,h,cl per litre in the outer solution1 the volume of the jelly is only about #ahe c4c41 and its concentration not quite #f grm4 per litre4 ,these facts cannot be accounted for by any theory of simple solution of the ,h,cl in the jelly1 since the law of such solutions is that the concentration in each maintains a constant ratio1 unless chemical change takes place4 ,it is possible that they might be explained by adsorption 7surface attraction71 but as it is known that gelatine contains both amido-groups capable of combining with acids1 and carboxyl-groups which can combine with bases1 it is much more likely that actual chemical combination takes place1 and that the apparent irregularities in the amount of acid fixed are due to partial hydrolysis of the compound4#ef #ef ,cp41 however1 ,walker and ,appleyard on the #8,absorption of ,acids by ,silk1' ,chem4 ,soc4 ,trans4 #ahif1 p4 #accd4 ,the following may be suggested as a working hypothesis4 ,as both water and hydrochloric acid can pass freely in and out of the jelly1 it must be in osmotic equilibrium with the outer solution in every respect1 and neither the un-ionised hydrochloric acid of the solution1 nor the small amount which may be formed by hydrolysis of the gelatine compound can have any effect on the swelling4 ,so long as the outer solution is very dilute1 by far the greater part of the acid present is absorbed and fixed by the gelatine1 and almost the whole of the outer acid will be ionised1 as well as a portion of that in combination with the gelatine4 ,in the latter case1 however1 the ions will be unable to pass out of the jelly1 and will therefore cause an internal osmotic pressure1 and the gelatine will swell till the ,cl-ions are in osmotic equilibrium with those of the outer solution4 ,at the same time1 this internal pressure of ,cl-ions will oppose the entry of the ,cl-ions 7and therefore also of their associated ,h-ions7 from the outer solution1 and the acid solution absorbed mechanically will be somewhat less concentrated than that outside4 ,as the concentration of the outer solution is increased1 the pressure of the outer ,cl-ions will repress the ionisation of the gelatine-chloride1 and at the same time its tendency to hydrolyse4 ,thus the acid actually combined with the gelatine should somewhat increase1 but the swelling should diminish1 as is actually the case4#eg ,it is impossible to carry the concentration of the hydrochloric acid much above #e grm4 per liter without causing solution of the gelatine1 but the addition of common salt to the outer solution should equally increase the pressure of its ,cl-ions1 and cause further diminution of swelling1 the ,na-ions in this case increasing the outside pressure in the same way as the hydrogen ions4 ,in fact the addition of salt in sufficient quantity will reduce the swelling till the gelatine becomes quite solid1 and retains only about its own weight of water1 while at the same time the apparently combined acid largely increases4 ,this cannot be attributed to any direct dehydrating action of the salt1 since concentrated sodium chloride solutions have no dehydrating1 but rather a swelling effect on gelatine in the absence of acid1 and the concentration of the salt in the outer solution and in the jelly proves precisely the same within the limits of experimental error4 ,several other facts may be noted1 tending to support the explanation which has been given4 ,the tendency to swell gelatine is common to all acids of appreciable strength1 and in all cases where the concentration of the acid could be increased to a moderate extent without causing solution of the jelly1 the effect of a maximum swelling1 diminishing as the concentration of the acid increased1 has been observed4 ,other salts also produce similar effects to sodium chloride2 thus the swelling caused by sulphuric acid is repressed by sodium sulphate4 ,sodium chloride seems to diminish the swelling caused by all acids1 but in presence of large excess of sodium chloride1 most of the acid in combination with the gelatine will probably be hydrochloric1 whatever the acid used to originally produce the swelling4 ,a curious fact observed by the author1 is that absolute alcohol1 which so effectually dehydrates neutral gelatine1 is almost powerless to remove either water or acid from gelatine swollen by hydrochloric acid4 ,h,cl is freely soluble even in absolute alcohol1 but ,h- and ,cl-ions can only exist in it to a very small extent1 so that we may conclude that the acid which causes the swelling and retains the water of the jelly exists either in actual combination with the gelatine1 or in an ionised condition4 #eg ,the acid retained by the gelatine1 as measured by deducting from the total contained in the jelly1 a quantity equivalent to the volume of solution absorbed1 at first rises rapidly to a maximum1 then slightly diminishes and remains practically constant4 ,on the theory suggested1 it is evident1 however1 that the absorbed solution must be more dilute than that outside1 and the actual combined acid greater than that shown by the above calculation4 ,the 8combined0 acid1 as determined by indicators1 shows slight but continuous increase4 ,it is acid to phenolphthalein1 but neutral to methyl orange4 ,solutions of caustic alkalies are in most respects analogous in their swelling action to those of strong acids4 ,a portion of the alkali is in some way fixed by the gelatine1 while another portion is simply absorbed as solution4 ,a maximum swelling effect is also noticed with dilute solutions1 which is diminished as the concentration increases4 ,swelling by alkalies is not diminished by chlorides so far as has been observed1 and especially it may be noted that the swelling produced by caustic soda is not diminished by sodium chloride4 ,on the theory which has been suggested there is no reason why alkaline swelling should be reduced by chlorides1 since the swelling agent has no ,cl-ion1 but it is somewhat singular that the sodium salt1 having a common ,na-ion should produce no repression of the swelling by caustic soda4 ,in the present state of our knowledge no definite explanation can be given1 but it is quite possible that the swelling in this case is not produced by the sodium-ion but by some more complex one1 or even by the hydroxyl-ion1 like most of the characteristic reactions of alkalies4 ,apparently the gelatin-alkali compound is still strongly alkaline1 affecting phenolphthalein indicator like uncombined alkali--an effect which is known to be due to the presence of free ,,ho-ions4 ,the effect of acids and alkalies has been studied by ,procter and others on actual pelt as well as on gelatine1 and has been found to be qualitatively1 if not quantitatively quite similar to that on gelatine1 though from the acid retained mechanically in the interfibrous spaces1 exact quantitative determination is more difficult4 ,the amount of swelling produced is not proportional to the strength of the acid1 some weak and little ionised acids such as lactic producing larger swelling than stronger acids such as hydrochloric and sulphuric1 of which the ionic pressure in the external solution is greater4 ,dilute solutions generally produce greater swelling than more concentrated1 so that where swelling is required without destructive effect on the fibre1 dilute solutions of such weak acids are to be preferred1 and the presence of neutral salts is to be avoided4 ,on the other hand1 where it is desired to remove lime1 or to bring the pelt into an acid condition without swelling1 the addition of neutral salts1 and especially of chlorides is advantageous4 ,a very important application of this principle is the 8pickling0 of sheep-skins1 and especially of sheep-grains1 in order to preserve them for export4 ,the principle of this operation is that the skins are first swollen slightly with sulphuric acid1 and the swelling is then reduced by salt1 either added1 or used in a subsequent bath4 ,in practice1 salt is now generally also added to the first bath to moderate the swelling4 ,a suitable strength for the 8rising solution0 is about #hj grm4 common salt1 and #ge grm4 sulphuric acid per litre4 #ajj c4c4 of this solution will therefore require about #ae c4c4 of ,n_/#a alkali to neutralise it1 and it should be tested after each lot of skins1 and maintained at the same strength by suitable additions of acid4 ,the acid absorbed by the skins is mainly hydrochloric1 sodium sulphate accumulating in the bath4 ,the salt is not absorbed by the skins in the same way as the acid1 but will be continually diluted by the water they bring in1 and occasional additions of salt must therefore be made1 the density being maintained at about #fe ,bkr4 7#ajfe sp4 gr47 ,after paddling or being stirred in this bath for about or hour the skins are transferred to saturated brine1 and stirred in it till fully fallen in thickness1 the density of the liquid being maintained by excess of salt4 ,they may be allowed to remain some hours in the saturated brine with advantage4 ,within moderate limits1 the strength of the rising liquor is not of great importance1 since the skins will only absorb a certain amount of acid 7increasing with the concentration of salt74 ,in the second or falling liquor the large excess of salt forces all the acid present into the skins1 none diffusing into the bath4 ,skins may be effectively pickled with very much smaller quantities of acid than those prescribed above1 or ordinarily used1 and are much easier to tan satisfactorily2 but it is said that they are more liable to suffer from mildew4 ,pickling may also be done by placing the skins in a concentrated brine-bath1 and adding a calculated quantity of acid1 not exceeding #ja grm4-molecule of sulphuric acid per kilo4 of dry hide substance1 but the method is not economical in practice from the dilution of the bath produced by the water brought in by the skins and the necessity of constant large additions of salt4 ,pickled skins must not be brought in contact with water1 which by diluting the brine they contain1 allows the excess of acid to act upon and destroy the fibre4 ,even drops of water1 accidentally sprinkled on the skins produce this effect1 and it is said that it spreads to parts which have not been wet4 ,for similar reasons1 it is necessary in tanning pickled skins1 at least to begin the process in liquors to which salt has been added1 the quantity required being dependent on the amount of acid used in pickling the skins1 and where this is reduced to a minimum1 it is even possible to tan without further addition of salt than that contained in the skins4#eh ,the pickling process converts the skins into a species of white leather1 and skins tanned in salted liquors after pickling1 or by addition of both acid and salt to sumach liquors give good colour1 and tough leather with a much diminished consumption of sumach4 ,the permanency of such leather is somewhat doubtful1 but the writer was unable to detect free sulphuric acid in a sample which he examined1 and it may be that when no acid is added to the later liquors1 that derived from the pickling is expelled by the tannin2 but this is very doubtful4 #eh ,instead of using salted liquors1 the skins maybe 8depickled0 by a bath of whitening and water1 borax1 or some other mildly alkaline solution before tanning4 ,the facts which have been discussed in the preceding pages offer a sufficient explanation of the causes which operate in those deliming processes which depend on the simple neutralisation of the alkaline matters present in the hide1 and of the swelling by means of acid which forms a step in the manufacture of many sorts of sole-leather1 but they by no means fully elucidate the causes of the much more complete depletion of the pelt brought about by the bacterial products of bates and puers4 ,it has been pointed out 7p4 #hb7 that gelatine and hide-fibre in a neutral condition are swollen by water1 but that the equilibrium so reached is an unstable one1 easily influenced by slight causes4 ,among these1 as has been pointed out by ,koerner1#ei the surface-tension between the water and the swollen fibre holds a place2 and surface-tensions of this sort are greatly influenced by many substances of the class to which bacterial ferments belong4 ,many salts also alter the water-absorption of gelatinous fibres1 sometimes causing swelling1 and sometimes contraction1 according to temperature1 concentration1 and the nature of the salt4 ,though most salts do not seem to be absorbed by hide-fibre1 it is possible1 as suggested by ,koerner 7loc4 cit471 that in some instances the base may combine with the acid-groups1 and the acid of the salt with the basic groups of the gelatine-molecule1 while other cases are known in which salts are actually dissociated1 and their acid fixed by the affinities of the hide-fibre4 ,an interesting case of this sort was recently proved by ,paessler and ,appelius1#fj who showed that sulphuric acid was absorbed from a solution of hydric sodic sulphate1 and the neutral sulphate left in the solution4 ,similar reactions undoubtedly occur with some salts of strong acids and weak bases1 but this point must be more fully discussed in connection with the theory of mineral tannages4 #ei ,beitrge zur wissenschaftlichen ,grundlage der ,gerberei1 ,jahresberichte der deutschen ,gerberschule zu ,freiberg1 #ahih-i and #ahii-aijj4 #fj ,wissenschaftliche ,beilage des ,ledermarkt1 #aija1 ii4 p4 #ajf4 ,,chapter ,x4 ,,water ,,as ,,used ,,in ,,the ,,tannery4 ,of all the materials employed in tanning1 none is of more indispensable importance than water1 and its quality has undoubtedly great influence on tanning1 though it is constantly blamed for faults and troubles which are really due to the mistakes of the tanner4 ,water is chiefly used in tanneries for soaking and washing hides and skins1 for making the limes1 the bates1 and the tanning liquors1 for steam boilers1 and in dyeing4 ,for all these purposes it should be as free as possible from impurities1 but since water is the most universal solvent in ,nature1 it is never found pure1 but always contains mineral matter derived from the rocks and soil through which it has flowed1 as well as organic impurities from decaying animal and vegetable matter4 ,associated with the latter are usually living organisms of putrefaction 7bacteria7 which may affect the quality of the water for tanning even more seriously than the mineral impurities4 ,the purest natural waters are those which have flowed only over hard sandstones and volcanic rocks4 ,water sufficiently pure for laboratory use can only be obtained by distillation4 ,the steam-water from heating pipes usually contains large quantities of dissolved iron1 and often also volatile organic matters from the oil1 etc41 which finds its way into the boiler4 ,it may sometimes be made fit for use by boiling 7which precipitates the ferrous carbonate present71 and subsequent settling or filtration4 ,the use of steam-water containing iron is a frequent source of stains and discolorations in the tannery which more than counterbalances the advantage of its softness4 ,the 8hardness0 of natural waters is mostly due to the salts of lime and magnesia which they contain1 which precipitate soap in the form of insoluble stearates and oleates1 which are useless for washing4 ,it is commonly estimated by determining the amount of a standard alcoholic soap solution which must be added in order to produce a permanent froth on shaking4 ,theoretically about #ab parts of soap 7sodium stearate or oleate7 are destroyed by #a part of calcium carbonate or an equivalent quantity of other lime salts1 with formation of insoluble lime soaps 7calcium stearate or oleate74 ,really1 the reaction is much more complicated1 owing to the dissociation of the soap into free alkali and acid-salts on solution in water4 ,teed#fa estimates that to more is required than the theoretical quantity1 and more in hot water than cold4 ,this uncertainty is partially overcome by testing the soap solution against a known solution of calcium chloride4 ,the presence of magnesia also complicates the test and leads to discrepant results4 #fa ,journ4 ,soc4 ,chem4 ,ind41 #ahhi1 p4 #bef4 ,cp4 also ,allen1 ibid4 #ahhh1 p4 #gie4 ,the methods of determining hardness originated by ,hehner 7see ,l4,i4,l4,b41 p4 #ai7 are simpler and more accurate than the soap-test1 and are to be preferred1 except for direct determination of the suitability of a water for scouring with soap4 8,degrees0 of hardness in ,england are calculated as parts of ,ca,c,o per #ajj1jjj1 or sometimes grains per gallon 7#gj1jjj grains74 ,hardness is of two kinds1 8temporary0 and 8permanent02 the former being removed by boiling1 while the latter is not so removed4 ,temporary hardness consists of the carbonates of alkaline earths held in solution by an excess of carbonic acid4 ,lime combines with #a molecule of carbon dioxide to form the ordinary normal carbonate 7chalk71 which is practically insoluble in water4 ,when1 however1 excess of carbonic acid is present1 hydric calcic carbonate 7bicarbonate7 which is fairly soluble is produced4 ,this is easily demonstrated by passing carbon dioxide into somewhat diluted lime-water1 which at first becomes turbid from precipitated chalk1 but soon clears by formation of soluble hydric carbonate4 ,if the solution be now boiled1 the hydric carbonate is decomposed1 and the excess of carbonic acid is driven off as ,,co1 and the chalk again precipitated4 ,the reactions are represented by the following equations3-- ,ca7,,oh7 ,,co ,ca,c,o ,,oh4 7#a7 ,ca,c,o ,ca,c,o ,,co ,,oh 7#b7 ,h,,co ,magnesia forms soluble double carbonates in a similar manner1 but on continued boiling gradually loses the whole of its carbonic acid1 and is precipitated as magnesium hydrate1 ,mg7,,oh74 ,one of the most important reactions in connection with temporary hardness is that caused by the addition of calcium hydrate 7slaked lime71 which forms the basis of ,clark's softening process4 ,when an equivalent amount of lime is added to a solution of hydric calcic carbonate1 it displaces the water of the 8half-bound0 carbonic acid1 forming a second molecule of calcium carbonate1 which is precipitated together with that originally present1 as is represented in the following equation3-- ,ca,c,o ,ca7,,oh7 #b;,ca,c,o #b,,oh4 7#c7 ,h,,co ,hydric magnesium carbonate is also precipitated by lime1 but the reaction is somewhat different1 the magnesia being removed as hydrate as follows3-- ,mg,c,o #b;,ca7,,oh7 #b;,ca,c,o #b,,oh ,mg7,,oh74 7#d7 ,h,,co ,it will be noted that #b equivalents of lime are required to precipitate #a of magnesia4 ,two molecules of sodium hydrate 7,na,o,h7 or potassium hydrate 7,,koh7 may be substituted for #a of ,ca7,,oh7 with similar results1 and in some cases it is practically advantageous to use the former1 as the sodium carbonate formed in precipitating the temporary hardness reacts again on the permanent1 throwing down the lime and magnesia as carbonates4 7,see p4 #aja47 ,illustration3 ,,fig4 #ai4--,plan of ,archbutt and ,deeley's ,apparatus4 ,the use of lime for softening temporary hard waters was originally proposed by ,thomas ,henry1 ,f4,r4,s41 of ,manchester1 but was first applied as a practical process by ,clark1 who1 after adding the requisite quantity of lime to the water in a mixing vat1 allowed it to stand in a large tank to clear by subsidence1 the precipitated carbonate of lime taking from #f to #ab hours to settle4 ,the process in its original form is a perfectly satisfactory one1 except for the capacious settling tanks which are required1 which in some cases are inconvenient and expensive4 ,messrs4 ,archbutt and ,deeley#fb have patented a modification of the ,clark process1 by which the time of subsidence is much shortened1 and according to which the precipitated carbonate of lime of previous operations is allowed to remain in the tank1 and the fresh charge of water and lime is mixed up with it by means of steam-injectors1 which blow in a current of air through perforated pipes at the bottom of the tank1 and at the same time very slightly warm the water4 ,the action goes on much more rapidly at a slightly raised temperature than in the cold2 and rather curiously1 the stirred up precipitate1 instead of increasing the time of clearing1 settles rapidly and carries down with it that formed in the new operation4 ,it is particularly suitable for treating waters containing magnesia1 from which a compound of lime and magnesia is apt to be precipitated in a colloid form which chokes filter-cloths and will not readily settle4 ,after softening1 the water is usually 8carbonated0 by passing the gases produced by burning coke into the floating exit-pipe through which it falls1 in order to retain any remaining traces of carbonates of lime and magnesia in a soluble form1 and prevent their subsequent precipitation in the pipes4 ,the apparatus is made by ,messrs4 ,mather and ,platt1 of ,manchester1 and its arrangement is shown in ,figs4 #ai and #bj4 #fb ,journ4 ,soc4 ,chem4 ,ind41 #ahia1 p4 #eaa4 ,illustration3 ,,fig4 #bj4 ,several modifications of the ,clark process have been introduced1 in which the precipitation is carried on continuously instead of intermittently4 ,the most important of these is the ,porter-,clark1 in which one portion of the water to be softened flows through an agitator containing excess of lime1 with which it forms saturated lime-water1 which is passed slowly up a cylinder where it deposits the excess of suspended lime4 ,the clear lime-water so produced is mixed with a fresh portion of the water to be softened in a second cylinder also provided with an agitator1 the proportion of the two liquids being regulated by cocks4 ,the carbonate of lime is at once precipitated1 and is removed by passage through a filter press4 ,this process is in successful operation on a considerable scale at ,messrs4 ,hodgsons' tannery at ,beverley4 ,several other forms of filter have also been employed with success1 and also methods in which the treated water traverses tanks with sloping partitions on which the carbonate of lime is deposited4 ,the latter plan was originally patented in ,france by ,gaillet-,huet1 and has been introduced into ,england by ,stanhope4 ,so far as is yet known1 from the tanner's point of view1 it is hardly necessary to make any distinction between lime and magnesia1 either or both of which may be considered simply as 8hardness40 ,a hard water probably softens dried hides more slowly than a purer water1 though it is possible that the observed difference in the time required may be due in many cases to the lower temperature of wells from which hard water is generally derived4 ,in the actual 8limes0 the hardness of the water can have no appreciable influence1 though if sodium sulphide be used alone for unhairing1 a certain waste occurs from temporary hardness which may render it advisable to add a little lime4 ,it is in washing the hides free from lime that the influence of hard water is first distinctly felt4 ,if limy goods1 after unhairing1 are placed in a water with much temporary hardness1 the same action occurs as in ,clark's water-softening process1 and chalk is deposited in the surface of the hides1 making them harsh and apt to 8frize0 or roughen the grain in 8scudding40 ,the common1 but not wholly satisfactory expedient is to add a little lime1 or better1 a few pailfuls of lime liquor to the water before putting in the hides4 ,the best plan is to use a properly softened water4 ,permanent hardness is not injurious in this way4 ,unfortunately it is not the grain alone which is injured by the use of hard water for washing the hides1 but on coming into the liquors the precipitated bases combine with the acids and tannins1 forming compounds which oxidise and darken when exposed to the air1 and which are the commonest causes of stains and markings on all descriptions of leather4 ,even when goods are drenched or bated before tanning the injury is not prevented1 since the weak organic acids which are capable of removing the lime 7as such7 from the hide have little effect on the precipitated carbonate1 which can only be dissolved by the use of stronger acids4 ,it must be noted that the same injurious effect on limed goods is produced by free carbonic acid1 which may be present even in soft waters4 ,when temporarily hard waters are employed for leaching tanning materials1 the carbonic acid is displaced by the tannins1 which form compounds similar to those just mentioned1 which are incapable of tanning1 and darken and discolour when exposed to the air4 ,though the amount of lime present in a liter of even the hardest water is very small1 yet in the aggregate of thousands of gallons used weekly in a good-sized yard it amounts to something very considerable1 and as the molecular weight of tannins is very high1 the quantity destroyed is many times that of the lime present4 ,this loss can be prevented 7a7 by the addition of sufficient mineral acid to convert the temporary into permanent hardness1 7b7 by the use of oxalic acid1 which precipitates the whole of the lime as oxalate1 or1 7c7 best of all1 by softening the water by suitable treatment before use4 ,each part of temporary hardness reckoned as ,ca,c,o 7,l4,i4,l4,b41 p4 #ai71 requires #abf parts of crystallised oxalic acid or #jih parts of ,h,,so1 or say one part of ordinary oil of vitriol of sp4 gr4 #ahdj per #ajj1jjj parts of water4 ,as the lime and magnesia of temporarily-hard water is thrown down by boiling1 it is deposited in steam boilers as a soft precipitate1 much of which can be blown out by suitable sludging2 but if oils or fats obtain access to the boiler1 a soft1 bulky1 adherent deposit is formed1 keeping the water from the plates1 which may become red hot1 and lead to collapse or explosion4 ,this effect is not produced by mineral oils1 which1 on the contrary1 tend to prevent adherence of scale to the plates1 and as suitable mineral oils are not only cheaper1 but much less injurious to the working parts of steam engines than animal or vegetable oils or tallow1 they should always be used in preference for cylinder purposes4 ,water which is temporarily hard owing to calcium and magnesium carbonates1 is unsuitable for dyeing1 as the carbonates react with basic dyes1 precipitating the colour-base1 and so rendering a part of the dye useless4 ,further1 as this precipitate is deposited on the skins it causes uneven dyeing and gives rise to spots and streaks4 ,in dyeing with basic dyes1 therefore1 it is advisable to add sufficient acetic acid to the water before use to exactly neutralise the carbonates present4 ,of course this treatment is quite unnecessary when acid dyes are employed1 as acid is usually added with the dye1 and with dyewoods the presence of a little calcium salt is advantageous4 ,as each 8degree0 of total hardness represents a soap-destroying power of at least #b oz4 of soap per #ajj gallons of water1 allowance must be made in making up 8fat-liquors0 with soap and oil for the loss of soap due to its precipitation by the mineral matter in the water4 ,the sticky lime-soaps are apt to adhere to the leather and interfere with glazing2 so that it is much better to employ a soft water4 ,permanent hardness of water is generally caused by sulphates of lime and magnesia1 and more rarely by chlorides and nitrates4 ,as none of these can be precipitated by lime1 permanent hardness cannot be removed by ,clark's process1 nor can it produce the injurious effect on limed hides which have been attributed to temporary hardness4 ,neither can the lime and magnesia present combine with the tannins if used for leaching1 since they are already fixed by stronger acids1 and at most can only act injuriously by slightly lessening the solubility of the tannins4 ,even this effect cannot be regarded as proved1 though it deserves further investigation4#fc ,permanent hardness is therefore of little moment as regards the ordinary uses of the tannery1 though it has considerable influence in some of the processes of dyeing1 and acts very injuriously where soap is used for scouring1 as in the washing of sheep-skins for wool mats1 since each part of lime reckoned as carbonate destroys at least twelve parts of pure soap 7sodium stearate or oleate71 producing a sticky and insoluble lime-soap which adheres to the fibre4 ,in sole-leather tanning1 permanent hardness is sometimes advantageous1 especially if it be due to calcium and magnesium sulphates1 and ,vignon recommended that sulphuric acid should be added to the water before use in quantity sufficient to exactly neutralise the carbonates which cause temporary hardness1 as magnesium and calcium sulphates are not injurious1 but tend to plump the hides4 ,it must be remembered1 however1 that the carbonic acid liberated may still have prejudicial effects on limed hides4 #fc ,recent investigations by ,nihoul 7#8,influence de la nature de l'eau sur l'extraction des matires tannantes1' ,bulletin de la ,bourse aux ,cuirs de ,lige1 ,sept4 #aija7 on the tanning waters of ,belgium seem to show that permanent hardness is more injurious in the extraction of tannin than has generally been supposed4 ,permanent hardness is most objectionable in waters employed for boiler-feeding1 and calcium sulphate is especially so1 as it becomes nearly insoluble in water at #aej ,c4 or #ee lb4 steam-pressure1 and is deposited on the plates as a hard crystalline scale which has to be chipped off with a hammer4 ,where many boilers have to be worked with a hard water1 it is much the most satisfactory to soften the water with caustic soda1 or with lime and soda together before it comes into the boiler1 but in cases where the plant required would be too costly1 boiler-compositions are sometimes used with good effect1 though considerable caution is advisable1 since some of them affect the plates injuriously4 ,the active constituent of many boiler-compositions is soda-ash or sodium carbonate1 which acts by double decomposition with the calcium sulphate1 forming sodium sulphate1 and precipitating calcium carbonate as a sediment which is easily washed out4 ,most tanning materials1 and even spent tan liquors1 will prevent or lessen incrustation if mixed with the feed water1 but sometimes corrode the plates if used too freely4 ,this danger is lessened if they are used in conjunction with soda4 ,heavy mineral oils1 either introduced in small quantity with the feed water1 or painted on the sides of the boiler when cleaned1 are useful in preventing the formation of a coherent scale4 ,the removal of permanent hardness from water is easily effected in most of the forms of apparatus employed for the softening of water by lime1 by using a calculated quantity of sodium carbonate in addition4 ,the reaction is represented in the case of calcium sulphate by the following equation-- ,ca,s,o ,na,,co ,ca,c,o ,na,,so4 ,the conversion of magnesium sulphate into carbonate may be similarly effected1 but as the latter is somewhat soluble1 an additional equivalent of lime must be used to precipitate it as hydrate4 ,magnesium salts1 from their solubility1 do not cause scale on boilers 7though the chloride is apt to produce corrosion71 but they are equally destructive of soap with the calcium salts4 ,caustic soda will remove temporary hardness1 and after becoming converted into carbonate will further react on any permanent hardness present2 and its use is therefore sometimes convenient in small softening plants1 but it is not more effective1 and considerably more costly than a suitable mixture of lime and sodium carbonate4 ,even with these1 ,archbutt states that the cost of softening permanent hardness is about ten times as great as that of removing temporary hardness with lime only4#fd #fd ,proceedings of ,inst4 of ,mech4 ,engineers1 #ahih1 pp4 #djd-ed1 in which much valuable information on water-softening is given4 ,as regards the influence of other impurities1 our knowledge is far from complete1 but the following are the most important matters likely to be present4 ,mud under any circumstances is objectionable4 ,it frequently contains organic slime and organisms which encourage the putrefaction of hides placed in it to wash or soften4 ,it also almost invariably contains iron as one of its constituents1 and hence stains leather and gives dark coloured liquors4 ,it is not easily removed by filtration1 as large filter-beds are expensive and difficult to keep in order1 and much space is required to clear water by subsidence4 ,some mechanical filter which can be easily cleaned1 and used under pressure1 offers the best chance of success4 ,the ,pulsometer ,company make one consisting of sponge tightly packed below a perforated piston4 ,to cleanse the filter a stream of water is passed the reverse way1 and the piston raised and worked up and down1 either by hand or power1 so as to loosen and knead the sponge4 ,filter-presses1 in which cloths1 or in some cases sand1 are used as the filtering medium1 are also well adapted for the purpose4 ,if a water be softened by ,clark's or other process the precipitated chalk carries down the mud with it1 together with most of the organisms4 ,iron is always an objectionable impurity in the tannery1 though it is less injurious to the quality than the appearance of the leather produced1 and indeed ,german sole-leather tanners frequently put old iron in the handlers to darken the colour of the leather1 and apparently1 if not really1 to quicken the tannage4 ,it must not be present in waters used for dyeing4 ,iron oxide is frequently present as a mud merely1 and in this case can be removed by filtration4 ,it is rarely in solution in any other form than that of acid carbonate1 since sulphate or chloride could not exist in presence of bicarbonate of lime4 ,in this form1 iron is precipitated at once by boiling or on the addition of lime1 like the temporary hardness due to other bases1 in the form of ferric hydrate1 and more slowly by oxidation on exposure to the air4 ,the mud produced by softening waters which contain iron must be completely removed by filtration1 or subsidence1 before the water is used for leaching1 or the iron will redissolve in the acids of the liquors4 ,iron is not perceptibly injurious in the limes1 but in the bates and wash-pits sometimes causes stains1 which are scarcely visible till blackened by the tanning liquors4 ,in presence of sulphur 7from sulphide of sodium or the decomposition of sulphates by the sulphur-bacteria nearly always present in bates and soaks71 the stains become bluish or greenish black1 and a black deposit is frequently produced on the sides of the pit1 in which the threads of sulphur-bacteria 7,thiothrix7 can often be recognised by the microscope4 ,as ferric salts not only combine with the tannins1 but are themselves tanning agents 7see p4 #aih71 they are rapidly absorbed by leather1 and iron is always present in leather ash4 7,for detection and estimation see ,l4,i4,l4,b41 p4 #bah47 ,alumina1 except as clay1 is rarely present in waters1 and probably harmless in any water likely to be used in tanning4 ,soda is sometimes present in considerable amount1 as sulphate1 chloride1 or carbonate4 ,the sulphate is probably inoperative4 ,the chloride1 if present in material quantities1 prevents plumping1 and may be the cause of thin and soft leather1 and in large amounts will greatly impede the proper exhaustion of many tanning materials4 ,sodium carbonate is sometimes present in considerable quantities1 as in some of the waters of the ,leeds district4 ,it may coexist with temporary hardness1 and produces similar injurious effects4 ,waters in which it is present cannot have any real permanent hardness4 ,it may be neutralised by the very cautious addition of an acid2 or by admixture of a permanent-hard water4 ,it tends to increased plumping in the limes1 but neutralises the free acids of the tan-liquors which are necessary in sole-leather tanning4 ,copper1 lead1 and other metallic bases are not likely to be present in any waters used for tanning in quantities sufficient to be injurious4 ,sulphuric acid rarely occurs free in water1 and then only in such traces as would be harmless for tanning1 though possibly injurious to steam boilers4 ,as sulphates it is most common4 ,alkaline sulphates are not known to have any deleterious action4 ,the sulphates of lime and magnesia are the principal cause of permanent hardness1 q4v4 ,iron sulphate is sometimes found in colliery waters4 ,nitrates and nitrites in water are usually the result of 8previous0 sewage contamination1 and are only important as an indication of the possible presence of the putrefactive ferments1 and are of little moment in waters only used for manufacturing purposes1 while they seem to be even useful in promoting the 8working0 of bran drenches1 by supplying the nitrogen required by the ferment4 ,chlorine is seldom or never present in water in the free state1 but only in the form of chlorides1 most frequently of sodium chloride 7common salt71 the effect of which has been referred to above1 and also at p4 #hh4 ,the action of other chlorides is probably similar as regards the swelling of hide4 ,magnesium chloride is very objectionable as a constituent of boiler-waters1 as it liberates hydrochloric acid at high temperatures1 and corrodes the plates at the surface of the water4 ,this injury can be prevented by addition of soda4 ,carbonic acid has been referred to under temporary hardness4 ,its presence in the free state is a matter of some importance to the tanner 7see p4 #ii74 ,silicic acid in a soluble form is present in some waters in considerable quantity4 ,such waters are said to harden leather1 but of this the writer has no personal experience4 ,few accurate researches have been made on the effect of the impurities of water on tanning1#fe and though1 from what has already been said1 it will be seen that they are not without effect it is probable that in many cases the water is blamed for troubles which are simply the result of mismanagement1 and credited with virtues which are really due to careful and skilful manufacture4 #fe ,see ,nihoul1 #8,influence de l'eau sur l'extraction des matires tannantes1' ,bulletin de la ,bourse aux ,cuirs de ,lige1 ,sept4 #aija4 ,the hardness of water1 and the dissolved carbonic acid which it contains1 are1 together with its temperature1 the principal factors which determine whether a hide will plump or fall in it4 ,almost the only accurate investigation of this point has been made by ,w4 ,eitner4#ff ,he placed pieces of hide1 unhaired by sweating1 and quite flat and fallen1 in water for four days at a temperature of #df ,f4 7#h ,c471 with the following results3-- #a4 ,in distilled water ,scarcely at all plumped4 #b4 water saturated with ,,co ,well plumped4 #c4 with lime bicarbonate1 #bj ,german ,tolerably plump4 scale of hardness #d4 magnesia bicarbonate1 #bj do4 #e4 lime sulphate #bj do4 ,well plumped4 #f4 magnesia sulphate1 #bj do ,best plumped4 #g4 magnesium chloride1 #bj do4 ,not at all plumped4 #h4 common salt1 #bj do4 7#a ,german degree of hardness corresponds to #a of ,ca,o in #ajj1jjj47 #ff ,gerber1 iii4 7#ahgg7 p4 #ahc4 ,the peculiarities which were shown by the hide pieces on removal from the water were maintained throughout the tanning1 which was conducted in imitation of the ,german method1 the hide being swollen and coloured through in weak birch-bark liquors1 made with distilled water and acidified in each case with equal quantities of lactic acid1 and finally laid away1 till tanned1 in a mixture of oak bark and valonia4 ,no4 #f1 from magnesium sulphate1 was the best2 then ,no4 #b2 ,no4 #c was less good1 but all the pieces from #a to #f were firm1 close and of good substance and texture1 ,no4 #a having swelled well in the sour liquor4 ,on the other hand1 #g and #h scarcely swelled in liquor1 but remained flat throughout1 and were looser1 thinner and of finer fibre4 ,from this experiment it is clear that while sulphates and carbonates exert a favourable influence on plumping1 chlorides do the reverse1 as they themselves not only do not plump1 but they place the hides in an unfavourable condition for the plumping action of acids in the liquors4 ,these experiments are quite borne out by the writer's experience in practice4 ,the water at the ,lowlights ,tannery1 which in dry weather was mostly obtained from beds of what was originally sea-sand1 and which consequently contained a very abnormal proportion of chlorides 7up to #fh pts4 ,na,cl per #ajj1jjj71 required special and very careful management to make thick leather1 notwithstanding the fact that it contained a considerable quantity of calcium and magnesium sulphates4 ,these facts also indicate the importance of the thorough removal of salt from hides intended for sole-leather4 ,plumping is not a desirable thing in leather intended for dressing purposes1 and it is possible that the use of a small percentage of salt in the liquors or wash waters might in some cases enable bating to be dispensed with4 ,like a bate1 salt would dissolve a small proportion of hide substance 7see p4 #fe74 ,there is no practicable means of removing chlorides from water1 but ,eitner suggests the addition of a small quantity of sulphuric acid to water containing much temporary hardness 7bicarbonates71 in order to convert it into permanent hardness 7sulphates71 which1 as stated above1 plumps better4 ,the amount required may be calculated from an acidimetric determination of temporary hardness 7see ,l4,i4,l4,b41 p4 #ai74 ,a simple but not very accurate guide1 is to add enough acid to purple1 but not to redden litmus paper even after moving the latter about in the water for some minutes4 ,in practice the acid must of course be very thoroughly mixed with the water by stirring and plunging4 ,it must be borne in mind that ,eitner's experiment was on sweated hides1 and that with limed hide1 which is kept plump by the dissolved lime retained in the hide1 different results as regards carbonic acid and bicarbonates would be obtained4 ,both these would convert the lime in the hide into chalk1 which is insoluble and inert1 and the hide would fall1 at any rate when the lime was completely carbonated1 while hides would remain plumpest in waters most free from substances capable of neutralising lime4 ,from this we may conclude1 what may be a priori expected1 that the purer the water1 the plumper limed hides remain in it4 ,in soft but peaty waters1 hides fall rapidly1 from the neutralisation of the lime by the weak organic acids of the peat4 ,such waters are dangerous for domestic use from their solvent action on lead1 but this danger can be entirely removed by storing the water in limestone reservoirs1 or allowing it to flow slowly through a limestone culvert before use4 ,in some towns in the north of ,england a small quantity of lime is added so as to neutralise the water as it leaves the reservoir and before it enters the mains4 ,wherever the conditions of putrefaction or decaying organic matter are present1 as in a bate1 hides fall rapidly1 and in extreme cases even the presence of the stronger acids will not maintain plumpness4 ,eitner mentions the case of a stream at ,vissoko in ,bosnia1 which was in special repute among the tanners from its power of pulling down hides rapidly1 and which took its rise in a common on which the pigs of the town were pastured4 ,the causes of this action are no doubt due to the products of putrefaction1 but are somewhat obscure4 ,bacteria present in water are a frequent source of injury in the soaks1 and probably in other stages of the tanning process4 ,rain water and the water of streams in mountain districts of hard igneous rock are generally nearly free from mineral constituents4 ,this is the case with the ,glasgow water from ,loch ,katrine1 and the ,thirlmere water which supplies ,manchester4 ,such water1 if cold enough1 and free from mud and organic impurity1 is the best for almost every purpose in the tannery4 ,most river-water contains material quantities of mineral matter1 though it is usually softer than that of springs or wells4 ,for further details as to the chemical examination of water1 and the methods of determining the amounts of its different constituents1 see ,l4,i4,l4,b41 pp4 #ah et seq4 ,,chapter ,,xi4 ,,soaking ,,and ,,softening ,,of ,,hides ,,and ,,skins4 ,as has been explained in the last chapter1 hides and skins come into the hands of the tanner either uncured 78green071 as they are taken off the animal1 preserved with salt or some other antiseptic1 dried1 or 8drysalted0 in which both methods are combined4 ,his object in each case is to remove blood and dirt1 and to restore the hide to its soft and natural condition2 but the treatment required varies much with the state of the hides4 ,fresh hides merely require cleansing from blood and dirt4 ,this is necessary because the blood causes bad colour1 and both blood1 lymph and adhering dung are sources of putrefaction1 which ultimately attacks the grain and fibrous structure of the hide4 ,hence washed hides keep better than unwashed4 ,cold water is most desirable1 as checking putrefaction4 ,if the water is much over #aj ,c41 or if it is charged with organic matter and ferment-germs2 or if1 as is too generally the case1 the hides are in a partially putrid state when received1 the time of soaking must be reduced as much as possible1 and it may be necessary to sterilise the water with carbolic acid or creolin 7pp4 #bf1 #bh74 ,in such cases the use of a wash-wheel1 or tumbler1 is very desirable1 rapidly cleansing the hides and removing adhering dung1 which interferes with the liming1 and is a serious cause of damaged grain4 ,the ,american pattern of wash-wheel shown in ,fig4 #ba is very suitable for the purpose4 ,in no case is it desirable to allow green hides to lie for more than a few hours in water2 and unwise treatment at this time is the cause of many troubles1 which are only detected at later stages1 and which are very difficult to trace to their source4 8,weak grain10 in which the hyaline layer 7p4 #ej7 is destroyed1 and which tans a whitish colour2 8pricking10 or perforation of the grain with small pinholes1 which may go on to 8pitting0 with larger holes1 and a general weakening of fibre1 with softening and needless loss of weight1 are among these results4 ,an instructive instance may be quoted4 ,a large tanner found that his curried leather was affected with small spots and rings of darker colour1 which rendered it quite unfit for staining1 and which reappeared even when the leather was buffed4 ,when finished as black grain1 these spots had a tendency to 8spue10 or rise as little pimples of resinous matter4 ,before the leather was stuffed no defect was noticeable to the eye1 but either then1 or on stripping the grease by a solvent1 they could be seen under the microscope as lighter patches of open and porous grain which absorbed more than their share of fat4 ,during the tanning process they could hardly be detected1 but in the first colouring they appeared for a few hours as blackish specks almost exactly like those caused by particles of iron or iron-rust4 ,by careful observation they were traced back to the limes2 specimens of the limed hide were submitted to ,director ,eitner1 who identified the defect as 8,stippen10 caused by a species of bacteria1 which cannot subsist in limes1 and which therefore must have been in the soaks4 ,these1 which had been somewhat neglected from pressure of work1 were cleaned out and sterilised with creolin solution1 and the mischief ceased4 ,it is worth noting that the tanner dated the beginning of the trouble from the soaking of some 8,spanish0 horse-hides1 which may have introduced the infection4 ,several very similar cases have come under the writer's notice4 ,it is not absolutely necessary to soak fresh hides or skins at all before liming1 and where the water is scarce or unfavourable1 or the skins tainted or 8slipping0 hair1 it is best to pass straight into a weak lime4 ,in this case the limes must be worked in shifts 7see p4 #aca7 and the whole of the oldest liquor run away and the hides rapidly changed into a fresh lime1 or the limes will become so charged with organic matter and bacteria that the hides will cease to plump1 and may even putrefy4 ,salted hides and skins require more soaking and more thorough washing than fresh ones1 as it is not only necessary to remove the salt1 but to soften and plump the fibre which has been dehydrated and contracted by salting4 ,if goods with salt in them are taken into limes1 they will not plump properly1#fg and creases and wrinkles 7drawn grain7 are formed which no after-treatment will remove4 ,this is especially important in sole leather4 ,in deciding on a method1 we must bear in mind that salt is easily soluble1 and diffuses rapidly into water or weaker solutions1 and that weak salt solutions tend to prevent the plumping of the fibre1 while those of about #aj per cent4 have considerable power of dissolving the cementing matter of the fibres 7p4 #fe7 and so lessening weight and firmness4 ,it may also be noted that though salt is not a true disinfectant 7p4 #bb71 salted hides are much less prone to putrefaction than fresh ones1 and therefore a longer soaking may be safely given4 #fg ,experiments mentioned on p4 #hi throw some doubt on the power of salt to prevent plumping in the limes1 though the opinion in the text is generally held by tanners4 ,these conditions point to the desirability of free exposure to water1 attained by suspending1 handling frequently1 or tumbling1 and repeated changes to remove the salt4 ,the degree of removal of salt is easily determined by the estimation of ,cl in the last wash-water 7,l4,i4,l4,b41 p4 #ah74 ,american tanners universally soak wet-salted hides three or four days with as many changes of water1 and frequently finish by a few minutes in a wash-wheel4 ,any washing tumbler may be used2 but the cheap and simple construction of the ,american wash-wheel will be easily understood from ,fig4 #ba4 ,the sides are open1 so that hides can be put in or removed between the spokes4 ,the rim of the wheel is generally perforated1 for the escape of water which is supplied by a pipe passing through the axis2 and the wheel is often driven by a chain or rope round its circumference4 ,no severe mechanical treatment1 such as 8stocking10 is necessary or desirable for green or salted hides4 ,dry and dry-salted hides require much longer soaking than wet-salted1 the amount naturally depending on the thickness of the hide and the character of drying4 ,even thin skins when strongly dried require considerable time to soften and swell the fibres1 although they soon become wet-through and flexible4 ,many different methods of soaking have been employed4 ,sometimes hides are suspended in running water2 sometimes laid in soaks which may be either renewed1 or allowed to putrefy2 sometimes in water to which salt1 borax or carbolic acid has been added1 to prevent putrefaction2 and more recently weak solutions of caustic soda1 sulphide of sodium or sulphurous acid have been used with much success4 ,illustration3 ,,fig4 #ba4--;,american ,wash-wheel4 ,the first of these methods1 were it desirable1 is rarely possible in these days of ,river ,pollution ,acts2 of the others1 it is difficult to say which is better1 since the treatment desirable varies with the hardness of the hide and the temperature at which it has been dried4 ,the great object is to thoroughly soften the hide without allowing putrefaction to injure it4 ,as dried hides are often damaged already from this cause1 either before drying1 or from becoming moist and heated on shipboard1 it is frequently no easy matter to accomplish this4 ,the fresh hide1 as has been seen1 contains considerable portions of albumin1 and if the hide is dried at a high temperature1 this may become wholly or partially coagulated and insoluble4 ,the gelatinous fibre and the coriin 7if indeed the latter exists ready formed in the fresh hide7 do not coagulate by heat1 but also become less readily soluble4 ,gelatin dried at #acj ,c4 can only be redissolved by acids1 or water at #abj ,c4 ,eitner#fh experimented with pieces of green calf-skin of equal thickness1 which were dried at different temperatures1 with results given in the following table3-- ---------------------------------------- ----------------------- ,sample4,temperature,remarks4 ,time of ,remarks4 ,coriin of ,drying4 ,softening ,dissolved by in ,water4 ,salt ,solution4 ---------------------------------------- ----------------------- ,i4 #ae ,c4 ,in vacuo #bd hours ,without #afh per cent4 mechanical ,,ii4 #bb ,c4 ,in sun #b days work #afb ,,iii4 #ce ,c4 ,in drying#e ,twice worked #jae closet ,refused to soften ,,iv4 #fj ,c4 sufficiently for traces tanning ---------------------------------------- ----------------------- #fh ,gerber1 #ahhj1 p4 #aab4 ,hence it is evident that1 for hides dried at low temperatures1 short soaking in fresh and cold water is sufficient1 and1 except in warm weather1 there would be little danger of putrefaction4 ,with harder drying1 longer time is required1 and more vigorous measures may be necessary4 ,a well-known tanner recommended a brine of #cj-ce barkometer 7sp4 gr4 #ajce1 or about #e per cent4 of ,na,cl74 ,this has a double action1 not only preserving from putrefaction1 but dissolving a portion of the hide-substance in the form of coriin1 which is undoubtedly a loss to the tanner1 though it is questionable if there is any process which will soften overdried hides without loss of weight2 since even prolonged soaking in cold water at a temperature which is too low to allow of putrefaction taking place will dissolve a serious amount of hide-substance4 ,chlorides1 however1 do not seem well adapted for the purpose in view1 from their weak antiseptic power and tendency to prevent swelling4 ,to prevent this ,jackson ,schulz advised the use of water at #hj ,f4 for soaking during the winter months4 ,water containing a small quantity 7#ja per cent47 of carbolic acid has been recommended for the purpose1 and will prevent putrefaction1 while it has no solvent power on the hide1 but1 on the contrary1 tends to coagulate and render insoluble albuminous matters4 ,borax has been proposed for the same purpose1 and1 in #a per cent4 solution1 certainly prevents putrefaction1 and has considerable softening power1 but is far too costly4 ,other methods of chemical softening are described on p4 #aae4 ,for some descriptions of hides1 and notably for ,india kips1 putrid soaks were formerly much employed1 the putrefactive action softening and rendering soluble the hardened tissue4 ,in ,india the native tanners soften their hides in very few hours by plunging them in putrid pools1 into which every description of tannery refuse is allowed to run4 ,putrefactive processes1 however1 are always dangerous1 as the action1 through changes of temperature1 or variation in the previous state of the liquor1 is apt to be irregular1 and either to attack one portion of the hide before another1 or to proceed faster than was expected4 ,hides are also frequently more or less damaged by putrefaction and heating during the process of cure1 and these damages are accentuated in a putrid soak4 ,hence hides in the soaks require constant and careful watching1 and the goods must be withdrawn as soon as they are thoroughly softened1 for the putrefaction is constantly destroying as well as softening the hides4 ,it is possible that putrefactive softening is less injurious to kips1 and such goods as are intended for upper-leather1 than to those for sole purposes1 as it is generally considered necessary in the former case that a good deal of the albumen and interfibrillary matter be removed1 and that the fibre be well divided into its constituent fibrils for the sake of softness and pliability2 and thus the putrid soak1 if acting rightly1 accomplishes part of the work which would afterwards have to be done by the lime and the bate1 as the actual fibre of the hide seems less readily putrescible than the softer cementing substance4 ,putrefaction is caused1 as we have seen1 by a great variety of living organisms1 each of which has its own special products and modes of action4 ,it is quite possible that1 if we knew what precise form of putrefaction was most advantageous1 we might by appropriate conditions be able to encourage it1 to the exclusion of others1 and obtain better results than at present4 ,putrid soaks 7in the old sense7 are1 however1 disused in the present day by all enlightened tanners1 as it is recognised that the risks outbalance the advantages1 and when drysalted hides are worked1 the soluble salts of the cure accumulate to an injurious extent4 ,the modern method1 where no chemicals are used1 is to give one fresh water at least to each pack of hides or skins4 ,even in this case considerable putrefaction takes place where the soaking occupies #g to #ad days1 as is the case with kips and hides1 and it is probable that the use of chemical and antiseptic methods of soaking will ultimately be generally adopted1 both on technical and sanitary grounds4 ,the use of dilute acids for softening has much to recommend it1 their power of causing the fibre to swell and absorb water being quite equal to that of the alkalies1 while few1 if any1 putrefactive bacteria can thrive in an acid liquid4 ,very dilute sulphuric acid has been used with success to dissolve the alkaline 8plaster0 of ,east ,india kips 7p4 #ci74 ,it has considerable disinfectant power 7p4 #bc71 but its action on the hide-fibre is undesirably strong4 ,sulphurous acid is much more suitable4 ,its use for this purpose was patented by ,maynard1 along with a number of other possible uses1 but the patent has now lapsed1 and he does not seem to have succeeded in introducing it into practice4 ,experiments at the ,yorkshire ,college1 and also at a tannery on a manufacturing scale1 have shown that the method is capable of excellent results4 ,the hides are soaked for #bd-dh hours in a solution of sulphurous acid containing about #b per cent4 of ,,so 7for manufacture1 compare p4 #bd2 for testing1 ,l4,i4,l4,b41 pp4 #af1 #cg71 and are then transferred to water1 where they swell freely to their full thickness4 ,they may be either limed at once1 or first neutralised with dilute caustic soda1 ammonia1 or sulphide of sodium1 which1 for dressing leather1 is perhaps desirable4 ,no putrefaction takes place1 even if they are retained for a considerable time in water1 and the acid has little or no solvent effect on the hide-fibre1 the strength of which is well preserved4 ,the liming1 however1 must either be conducted with the aid of sodium sulphide or in old limes1 since the sterile condition of the hides renders liming in fresh lime very slow 7cp4 p4 #acg74 ,for experimental purposes a per cent4 solution of ,boakes' 8metabisulphite of soda0 may be used1 to which per cent4 of concentrated sulphuric acid previously diluted with water is gradually added during the soaking1 the hides being first withdrawn4 ,for permanent work it will be found much cheaper to manufacture the acid on the spot by burning sulphur4 ,the use of solutions of caustic soda 7#a part per #ajjj71 or of sodium sulphide 7#a-c parts per #ajjj7 as suggested by ,eitner1 seems at present likely to supersede all other methods of softening from their simplicity and safety4 ,twenty-four to forty-eight hours in either of these solutions1 which may if necessary be followed by a short soak in plain water1 seem sufficient to soften either kips or hides4 ,experiments at the ,yorkshire ,college have shown that solutions of this strength have little or no solvent action on the hide-fibre1 but promote its swelling in water so effectively that no mechanical softening is needed 7though a slight drumming is advantageous71 while putrefaction is almost entirely prevented1 so that the solution may be repeatedly used if kept up to its original strength1 which is easily determined with standard acid and phenolphthalein 7see ,l4,i4,l4,b41 p4 #ag74 ,neither caustic soda nor sodium sulphide have any injurious effect on liming1 though it may prove somewhat slower than with the older methods1 where the epidermis was partially destroyed by the action of putrid ferments4 ,the dilute solutions used are not only less injurious to the hide than those of greater strength1 but they are also more effective in softening4 ,eitner 7,gerber1 #ahii1 p4 #ehd7 states that when using a solution of caustic soda of #a part in #ajjj strength1 the time required to soften some hides was only two days1 as against three days for a sodium sulphide liquor1 and four days for pure water1 and that with the soda solution only about #jf per cent of the hide-substance of the skin was dissolved out1 whilst when sodium sulphide was used it was #jg per cent41 and with pure water alone no less than #ai per cent4 was lost by solution4 ,the use of moderately warm water 7#dj ,c47 in a drum is quite successful in rapidly softening sound hides after they have previously been soaked for some days in cold water2 but if they are tainted in the cure1 it is very apt to intensify the mischief4 ,hides which have partially putrefied internally1 or which have been exposed to a hot sun while the interior is still moist1 are very apt to appear sound while dry1 but to blister or go to pieces from the destruction of the fibres as soon as they are limed1 and this in spite of even the most careful treatment4 ,for tainted hides1 caustic soda is probably preferable to sodium sulphide4 ,many chemicals have been patented for softening hides4 ,sulphide of arsenic is said to be in use1 and if dissolved in caustic soda solution would differ little in its effect from ordinary sulphide of sodium4 ,saltpetre has also been employed1 but its effect1 if any1 was probably merely antiseptic4 ,ordinary sodium carbonate has been used1 but is less effective than caustic soda4 ,gas liquor and mixtures of this with tar and water were patented by ,barron1 and probably the first would soften by virtue of its ammonia and sulphides1 while tar contains carbolic acid4 ,probably the most absurd mixture of all was patented by ,berry1 which consisted of bucket of slaked lime1 bucket of wood-ashes1 #ab lbs4 of potash1 #e lbs4 of oil of vitriol1 and #d lbs4 of spirit of salt6 ,illustration3 ,,fig4 #bb4--;,faller ,stocks4 ,beside merely soaking the hides1 it is sometimes necessary to work them mechanically1 to promote their softening2 this was formerly accomplished by 8breaking over0 the hides on the beam with a blunt knife4 ,this process is still in use for skins of many sorts1 but for the heavier classes of leather is now usually superseded or supplemented by the use of 8stocks10 or drums4 ,the former consist of a wooden or metallic box1 of peculiar shape1 wherein work two very heavy hammers1 raised alternately by pins or cams on a wheel1 and let fall upon the hides1 which they force up against the curved end of the box with a sort of kneading action4 ,the ordinary form of this machine is shown in ,fig4 #bb4 ,a more modern form1 which seems to possess some advantages1 is the ,american 8double-shover10 or 8hide-mill10 seen in ,fig4 #bc4 8,crank stocks10 similar in form to the faller stocks1 but driven by cranks1 are sometimes used for softening1 but are better adapted to lighter uses4 ,illustration3 ,,fig4 #bc4--;,american ,hide-,mill4 ,the number of hides which can be stocked at once naturally varies with the size of both hides and stocks1 but should be such that the hides work regularly and steadily over and over4 ,the whole number should not be put in at once1 but should be added one after another1 as they get into regular work4 ,the duration of stocking is #aj-cj min41 according to the condition and character of the hides4 ,hides should not be stocked until they are so far softened that they can be doubled sharply1 without breaking or straining the fibre4 ,after stocking1 they must be soaked again for a short time1 and then be brought into an old lime4 ,a small quantity of sodium sulphide added to the soaks or in the stocks has been recommended as of great value in softening obstinate hides1 and probably with justice1 from its well-known softening action upon cellular and horny tissues4 ,tumbler drums of various forms may also be used with good effect for softening purposes1 especially for skins1 and are much less detrimental than stocking1 both as regards the weight and quality of the goods4 ,for sole leather1 and even for kips1 the use of stocks has in recent years been entirely discarded by many of the more advanced tanners4 ,if mechanical work is required at all1 the drum is preferred1 and is sometimes employed after a few days' liming1 the goods being first merely softened in fresh water4 ,the use of caustic soda1 sodium sulphide1 or sulphurous acid renders mechanical softening almost unnecessary4 ,illustration3 ,,fig4 #bd4--;,drum for ,washing or ,tanning4 ,the drums employed are in principle like a barrel-churn1 and are large cylindrical wooden chambers #f to #ab feet in diameter1 and fitted inside either with shelves like the floats of a water-wheel1 or with rounded pegs on which the hides fall4 ,the ,american wash-wheel figured on p4 #aaa is a machine of this kind1 and one of a more elaborate description is shown in ,fig4 #bd4 ,drums are not only used for softening1 but for tanning1 dyeing1 and many other purposes in leather manufacture4 ,it is advantageous to be able to reverse the direction of their rotation to prevent the rolling up of the hides4 ,,chapter ,,xii4 ,,depilation4 ,after the softening and cleansing of the hide or skin is completed1 and before proceeding to tan it1 it is usually necessary to remove the hair or wool4 ,the earliest method of accomplishing this was by means of incipient putrefaction1 which attacks in the first instance the soft mucous matter of the epidermis1 and thus loosens the hair without materially injuring the true skin4 ,this loosening of the hair often takes place accidentally in hides which have been kept too long without salting1 and is known as 8slipping10 and is apt to be accompanied by some degree of injury to the grain4 ,the old method of loosening the hair by putrefaction1 or1 as it is generally called1 8sweating10 was to lay the hides in piles1 usually in some warm and damp place4 ,occasionally a slight preliminary salting was given to prevent too much putrefaction of the hide4 ,the action in this case1 however1 was very irregular1 and it has been quite abandoned in all civilised countries4 ,illustration3 ,,fig4 #be4--,sweat-,pit4 ,the method which is now used is to hang the hides in a closed chamber1 generally called a 8sweat-pit10 ,fig4 #be1 but usually constructed above the ground-level and protected from sudden changes of temperature by double walls1 or by mounds of earth4 ,the hides are hung in the sweat-pit1 in small chambers each capable of holding #ej or #ajj hides4 ,the temperature is kept at about #ae to #bj ,c41 the air being warmed1 if necessary1 by the admission of steam below a perforated floor1 or cooled by a shower of water from sprinklers1 so arranged as not to play directly on the skins1 and is thus always kept saturated with moisture4 ,little if any ventilation is allowed1 and a large quantity of ammonia is given off from the decomposition of the organic matter1 and no doubt contributes to the solution of the epidermis and the loosening of the hair1 as the writer has found that ammoniacal vapours alone very speedily produce this effect4 ,after #d-f days of this treatment1 the hair is sufficiently loosened to be removed by working the skin over the beam with a blunt knife1 or by means of the stocks or hide-mill 7see p4 #aaf74 ,great care and watchfulness are required to avoid injury to the grain by putrefaction4 ,the hide is in a slimy and completely flaccid and 8fallen0 condition1 and some trouble is occasioned by the hair being worked into the flesh by the hide-mill1 to obviate which1 a slight liming is frequently given after the sweating4 ,hides which have been unhaired in this way require to be swollen by acid in the liquors in order to produce a satisfactory sole-leather1 as the sweating process does not swell or split up the fibres4 ,in some ,european tanneries a similar process1 but at a higher temperature1 is employed1 and it is also largely used for sheep-skins under the name of 8staling10 but in this case is sometimes conducted in a very rude and primitive manner1 and frequently with the result of considerable injury to the pelt4 ,the great objection to the sweating process1 however carefully conducted1 is the liability of putrefaction to attack the skin itself1 causing 8weak grain40 ,its most advantageous use is for sole leather1 as1 although the solution of the hide-substance may not be very much less than in the case of liming1 the dissolved matter remains in the hide instead of being washed out1 and being fixed by the tannin1 contributes to the solidity of the leather4 ,in ,england1 lime is the agent almost universally employed for unhairing1 though every tanner admits its deficiencies and disadvantages4 ,it is hard1 however1 to recommend a substitute which is free from the same or greater evils1 and lime has one or two valuable qualities which will make it very difficult to supersede4 ,one of these is that1 though it inevitably causes loss of substance and weight1 it is also impossible1 with any reasonable care1 totally to destroy a pack of hides by its use2 which is by no means the case with some of its rivals4 ,another advantage is that1 owing to the very limited solubility of lime in water1 it is of comparatively small consequence whether much or little is used2 and even if the hides are left in a few days longer than necessary1 the mischief1 though certain1 is only to be detected by careful and accurate observation4 ,with all other methods1 exact time and quantity are of primary importance1 and it is not easy to get ordinary workmen to pay the necessary attention to such details4 ,again1 the qualities of lime1 its virtues and failings1 have been matter of experience for hundreds of years1 and so far as such experience can teach1 we know exactly how to deal with it4 ,a new method1 on the other hand1 brings new and unlooked-for difficulties1 and often requires changes in other parts of the process1 as well as in the mere unhairing1 to make it successful4 ,as our knowledge of the chemical and physical changes involved becomes greater1 we may look to overcoming these obstacles more readily4 ,the universal source of lime is chalk or limestone1 which consists of calcium carbonate1 and from which the carbon dioxide is driven off by burning in a kiln4 ,many limestones1 however1 are far from being pure calcium carbonate1 but contain large proportions of magnesia1 iron and alumina1 the latter perhaps originally deposited in the form of clay with the sediment from which the stone was formed4 ,such clay limestones when burnt yield natural cements1 like oolite and other 8hydraulic0 limes1 which are capable of setting even under water4 ,the presence of magnesia and clay is injurious not only by diminishing the amount of lime present1 but by making the lime much more difficult to slake2 and iron oxide1 though quite insoluble1 may become mechanically fixed in the grain of the hide1 and may be the cause of subsequent stains4 ,the burning of lime in the kiln is probably not quite so simple an operation as the equations of the text-books would suggest4 ,by mere heating1 the carbonate can1 it is true1 be decomposed1 but to do this completely a good white heat is required1 which is rarely attained in practical burning1 and it is probable that at least a part of the carbon dioxide present is reduced to carbon monoxide by the combustible fuel-gases1 and so separated from the lime1 for which it has no affinity4 ,carbon monoxide is the cause of the intensely poisonous character of limekiln gases1 the pure dioxide being irrespirable1 but not strictly poisonous4 ,quicklime1 ,ca,o1 on coming in contact with water1 combines with it with the evolution of considerable heat1 becoming slaked or converted into hydrate1 ,ca7,,oh74 ,this change takes place rapidly and easily when the lime is light and porous1 such as is obtained by the burning of chalk or good limestone at a low temperature2 but if it has been too intensely heated or 8over-burnt10 or contains silicates or other salts which fuse at the temperature of the kiln1 a compact lime is formed which slakes with difficulty and extreme slowness1 thus being lost to the tanner1 or leading to the still more serious result of burning holes in the hides by the heat produced by slaking in contact with them4 ,it is stated by ,le ,chatelier#fi that for dense limes #bd-dh hours is frequently required for complete slaking in the cold1 while magnesia is still more obstinate1 months being sometimes necessary for the complete hydration of hard-burnt samples2 and mixtures of lime and magnesia are intermediate in their character4 ,slaking is greatly assisted by heat1 even heavily burnt magnesia being hydrated in about six hours at #ajj ,c4 ,slaking is also much more rapid in a dilute solution 7#b per cent47 of calcium or magnesium chloride4 ,from these facts it is easy to deduce the reason why a suitable quantity of water1 neither too much nor too little1 is desirable for the rapid and effectual slaking of lime4 ,if too little is used1 the lime is only partially slaked1 and it is not easy for further portions of water to gain access to the interior of the powdery mass4 ,on the other hand1 if it is 8drowned0 by excess1 the temperature is lowered1 the process goes on slowly1 and the mass does not readily fall into powder1 and so fails to be utilised in the liming process4 ,of all methods of slaking lime1 the ordinary one of tipping it direct into the lime-pits is perhaps the most irrational1 leading to the formation of unslaked lumps which may burn the hides1 and which1 together with stones and dirt1 rapidly choke the pits with useless matter4 ,the best process is that adopted by builders and in many ,continental yards1 in which a large quantity of lime is slaked in a shallow tank by throwing on it sufficient water to thoroughly wet it1 and after allowing it to heat and fall for #bd hours1 adding enough water to convert it into a stiff paste4 ,in this form it may be kept for months without material deterioration4 ,when required for use1 a suitable quantity of the paste is dug out1 and well stirred with water in a tub or tank before running into the pit when the stones and sand remain in the tank4 ,in this way all nuisance from dust is also avoided4 ,if lime is stored unslaked1 it gradually absorbs moisture from the air1 falling1 and soon becoming dusty and difficult to slake completely1 while the traces of carbon dioxide in the air gradually convert it into useless carbonate4 #fi ,bull4 de la ,soc4 d',encouragement1 #ahie1 x4 pp4 #eb-fb2 ,journ4 ,soc4 ,chem4 ,ind41 #ahie1 p4 #ege4 ,the solubility of lime in water is very limited1 and the figures determined by different chemists do not agree very satisfactorily4 ,the following table gives the result of determinations made by ,mr4 ,a4 ,guthrie in the ,author's laboratory1 and is probably one of the most accurate#gj3-- #ajj c4c4 of saturated lime water at #e ,c4 contain #jacej grm4 of ,ca,o4 #aj #jacdb #ae #jacbj #bj #jabic #be #jabed #cj #jabai #ce #jaafa #dj #jaaai #ej #jjiha #fj #jjhgi #gj #jjgha #hj #jjgdj #ij #jjfif #ajj #jjeig #gj ,journ4 ,soc4 ,chem4 ,ind41 #aija1 p4 #bbd4 ,it will be noticed that unlike that of most substances1 the solubility of lime in water diminishes as the temperature is raised4 ,it is therefore necessary in employing lime-water as a standard solution to take care that it is saturated at a constant temperature4 ,the results given in the above table are those from pure marble lime4 ,where the ordinary impure limes from limestone are employed1 a somewhat stronger lime-water is often obtained4 ,this is difficult to explain1 but possibly some double hydrate of lime and magnesia is formed which is more soluble than either hydrate alone4 ,the results harmonise with the old belief of tanners that chalk-lime is milder in its action on skin than that made from less pure limestones4 ,the solubility of any given lime is easily determined by adding it in excess to water in a stoppered flask1 and shaking frequently until a solution of constant strength is obtained4 ,a known volume of this solution 7which must be clear and free from undissolved lime7 is then titrated with ,n_/#aj hydrochloric acid1 using phenolphthalein as the indicator4 ,saturated lime-water may be conveniently used as an alkaline standard solution for many purposes1 and if kept on excess of lime is always caustic1 and varies very little in strength at ordinary laboratory temperatures4 ,the solution is nearly normal1 but for accurate work its strength should be exactly determined with ,n_/#aj acid4 #a liter of pure lime-water at #ae ,c4 should require #dgad c4c4 of ,n_/#aj acid for neutralisation4 ,lime is much more soluble in sugar solutions than in water4 ,such solutions have been used as standard solutions1 and sugar has been added to limes to increase the action on the hides4 ,the following is the analysis of a lime used in a ,leeds tannery1 which was made by ,mr4 ,g4 ,w4 ,flower1 ,b4,sc41 in the ,leather ,industries ,laboratory of the ,yorkshire ,college#ga3-- ,per cent4 ,si,o and insoluble matter #aggj ,fe,o #fdb ,ca,o #dihf ,ca,c,o #adba ,ca,s,o #cja ,ca,cl #jcc ,mg,o #bji ,organic matter #jhj ,moisture by difference #eeh ------ #ajjjj #ga ,journ4 ,soc4 ,chem4 ,ind41 #aija1 p4 #bbd4 ,the sample only contained #cajb per cent4 of available lime1 the remainder being probably combined with the silica4 ,it also contained an appreciable quantity of iron oxide1 which might lodge mechanically in the pores of the skin and become dissolved in later processes1 darkening the colour of the leather4 ,the lime was also under-burnt1 judging from the amount of carbonate it contained4 ,for comparison with this1 the analysis of a good specimen of carboniferous-limestone lime from ,buxton may be given3-- ,per cent4 ,ca,o #iaie ,mg,o #acj ,,co and moisture #fge ------ #ajjjj ,determination of 8,available0 ,lime4--,the practical value of lime for the tanner is easily determined by drawing a sample by breaking off small pieces from a number of lumps of the bulk1 coarsely pulverising them in a mortar1 and then rapidly grinding a portion as fine as possible1 and transferring it at once to a stoppered bottle for weighing4 ,a portion of this1 not exceeding #a grm41 is shaken into a stoppered liter flask1 which is filled up roughly to the mark with hot and well-boiled distilled water1 and allowed to stand for some hours with occasional shaking4 ,when cold it is filled exactly to the mark with cold distilled water1 well shaken again and allowed to settle1 or rapidly filtered1 and #be or #ej c4c4 of the clear liquid withdrawn with a pipette and titrated with ,n_/#aj hydrochloric or sulphuric acid and phenolphthalein4 ,each cubic centimeter of ,n_/#aj acid equals #jjbh grm4 ,ca,o4 ,it is generally a very mistaken economy to make use of an inferior lime for tanning purposes1 as any saving in cost is discounted by the larger quantity required1 the more frequent cleaning of the pits1 and the danger of stains and of burns from imperfect slaking4 ,the action of lime on the hide has already been spoken of to some extent4 ,it is throughout a solvent one4 ,the hardened cells of the epidermis swell up and soften1 the mucous or growing layer and the hair-sheaths are loosened and dissolved1 so that1 on scraping with a blunt knife1 both come away more or less completely with the hair 7constituting 8scud0 or 8scurf10 ,ger4 ,gneist or ,grund74 ,the hair itself is very slightly altered1 except at its soft and growing root-bulb1 but the true skin is vigorously acted on4 ,the fibres swell and absorb water1 so that the hides become plump and swollen1 and1 at the same time1 the 8cement-substance0 of the fibres is dissolved1 and they become split-up into finer fibrils3 the fibrils themselves become first swollen and transparent1 and finally corroded1 and even dissolved4 ,a similar swelling of the fibres is produced by both alkalies and acids1 and is probably due to weak combinations formed with the fibre-substance1 which have greater affinities for water than the unaltered hide4#gb ,this swelling is useful to the tanner1 since it renders the hide easier to 8flesh0 7i4e4 to free from the adhering flesh7 on account of the greater firmness which it gives to the true skin4 ,it also assists the tanning1 by splitting up the fibre into its individual fibrils1 and so exposing a greater surface to the action of the liquors4 ,this is advantageous in dressing-leather which is afterwards tanned in sweet liquors1 and which must have the cement-substance of the fibres dissolved and removed for the sake of flexibility2 and1 in the case of sole-leather1 it is necessary for sake of weight and firmness that the hide be plumped at some stage of the process2 but it is probable that this effect is produced with less loss of substance and solidity by suitable acidity of the tanning-liquors4 ,another advantage of lime is that it acts on the fat of the hide1 converting it more or less completely into an insoluble soap1#gc and so hindering its injurious effects on the after tanning process1 and on the finished leather4 ,if strong acids whether mineral or organic are used later on1 this lime soap is decomposed1 and the grease is again set free4 ,in sweated or very low-limed hides this grease is a formidable evil1 causing darkening or grease spots on the finished leather4 #gb ,cp4 p4 #hd4 #gc ,this has been questioned1 but ,i have satisfied myself it is correct4 ,the customary method of liming is simply to lay the hides horizontally one at once in milk of lime in large pits1 taking care that each hide is completely immersed before the next is put into the pit1 so as to ensure a sufficiency of liquor between them4 ,every day1 or even twice a day1 the hides are drawn out 78hauled071 and the pit is well plunged up1 to distribute the undissolved lime through the liquor4 ,the hides are then drawn in again 78set071 care being taken that they are fully spread out4 ,how much lime is required is doubtful1 but owing to its limited solubility1 an excess1 if well slaked1 is rather wasteful than injurious4 ,great differences exist in the quantity of the lime used1 the time given1 and the method of working1 not only for various classes of leather1 but for the same kinds in different yards4 ,lime1 as we have seen1 is only soluble to the extent of about #abe grm4 per litre1 or 7as #a cub4 foot of water weighs about #ajjj oz47 say #a oz4 per cub4 foot1 or1 in an ordinary lime-pit1 not more than lb4 per hide4 ,only the lime in solution acts on the hide1 but it is necessary to provide a surplus of solid lime which dissolves as that in the liquor is consumed or absorbed by the hide2 and this is especially the case where1 as is generally customary1 the hides are laid flat in pits1 so that no circulation of liquor is possible4 ,where hides are suspended in lime-water1 which is constantly circulated and kept up to its full strength by agitation in another vessel with solid lime1 they unhair as quickly as with milk of lime1 but the method seems1 in the case of lime1 to present no special advantage over the ordinary one1 if in the latter the hides are hauled sufficiently often to keep the lime uniformly distributed4 ,the case is otherwise in dealing with more soluble depilatories4 ,various patents have been taken for methods of liming by suspending in liquors1 but the idea is now public property1 and is largely used on the ,continent4 ,it is necessary that the lime which settles to the bottom of the pit should be agitated and kept in suspension1 which may be effected either by moving the hides on a frame as in 8suspenders0 7p4 #bba71 or by agitators acting on the principle of pumps1 and raising the liquor and sludge from the bottom4 ,such agitators have been patented in ,germany1 but had been in use much earlier in the ,author's tanyard4 ,an agitator on the principle of the screw-propeller of a steamship1 placed near the bottom of the pit1 and protected by a lattice1 may also be usefully employed 7,fig4 #bf74 ,skins are frequently limed in paddles1 or stirred up by blowing air into the pit4 ,the latter method is neither effective nor economical in power4 ,illustration3 ,,fig4 #bf4--,suspension ,lime-,pit4 ,as has been noted1 the solubility of lime1 and consequently the strength of the lime-liquor1 is diminished by rise of temperature1 but its solvent action on hide-substance is much increased4 ,as a consequence1 the loosening of the hair proceeds much more rapidly in warm limes1 but the hides do not plump well1 and become loose1 hollow and inclined to 8pipe0 in the grain1 and to weigh out badly1 and for sole leather the method is therefore in every way disastrous4 ,in the few cases among the lighter leathers where a decided softening and loosening of the texture of the skin is required1 it is possible that useful advantage may be taken of this effect2 but it would be exceedingly difficult to regulate the temperature of an ordinary lime-pit with accuracy1 and better results could probably be obtained with suspenders in which the liquor could be constantly circulated4 ,when limes are very cold1 in spite of the greater strength of solution1 the action is very much checked1 and where goods are frozen into pits in severe weather1 there is but little danger of overliming1 although the usual time may be much exceeded4 ,it is generally best to work limes at about the ordinary summer temperature1 and this is better done in winter by warming the limeyard than by any direct heating of the limes4 ,if lime which has cooled after slaking is used1 the water with which limes are made may safely be warmed in midwinter to a temperature not exceeding #bj ,c4 ,the quantity of lime used by different tanners1 and for different sorts of hides and skins1 is very variable1 not only according to the effect which it is desired to produce1 and the way in which it is used1 but from the arbitrary fancy of the user1 since its limited solubility renders an excess comparatively innocuous4 ,for sole-leather1 the amount recommended varies from under #a per cent4 to #aj or #ab per cent4 on the green weight of the hide2 but probably #b-c per cent4 is all that can be really utilised1 the remainder being wasted4 ,in order1 however1 to utilise the whole of the lime1 very frequent handling or agitation is required to ensure its uniform distribution4 ,it must also be borne in mind that the strength of commercial limes varies from above #hj down to #cj per cent4 of available calcium oxide4 ,von ,schroeder has found that a strength of #f grams of calcium oxide 7,ca,o7 per liter was sufficient1 but1 in practice1 much more is generally added4 ,it is also noteworthy that a perfectly fresh milk of lime must be made much stronger than one which has been used4 ,this is partially due to the fact that some bacterial action takes place in an old lime and that ammonia is formed which assists unhairing1 in addition to the effect of the lime itself1 and partially because the lime in old liquors remains in suspension for a much longer time1 and is thus more evenly distributed4 ,a method of liming1 sometimes known as the 8,buffalo method10 has been largely adopted for sole-leather in ,america1 and is now used in many ,continental yards4 ,it consists in a very short liming and the subsequent use of warm water4 ,the limes are also often sharpened by the addition of a little sodium sulphide or of some other sulphide4 ,thus1 in one large yard in the ,states1 the hides for sole-leather 7salted 8packers07 are limed for #aj hours only with #b lb4 lime and #b oz4 of sulphide of sodium per side1 and after lying overnight in water of a temperature of #ce-de ,c41 are easily unhaired4 ,a ,continental firm lime two days in weak fresh limes with a little tank-waste1 and then treat with water at #cb ,c4 for #f-h hours1 when the hides are unhaired and returned to the warm water for two hours before scudding4 ,all sorts of combinations between liming and hot water treatment can be employed4 ,the longer and stronger the liming1 the lower temperature or shorter time in the water will suffice4 ,the method is much to be recommended for firm sole-leather1 but it does not saponify grease or swell the fibres thoroughly1 and usually vitriol is used for the latter purpose in a later stage4 ,the hide goes into the liquors practically free of lime1 and the loss of hide-substance is much less than in the ordinary method of liming4 ,a point of probably much greater importance than the quantity of lime used is the length of time during which a lime is worked without change of liquor4 ,an old lime becomes charged with ammonia and other products of the action of lime upon the skin1 such as tyrosin1 leucin 7amidocaproic acid71 and some caproic acid1 the disagreeable goaty odour of which is very obvious on acidifying an old lime-liquor with sulphuric acid1 by which considerable quantities of partially altered gelatin are at the same time precipitated 7compare p4 #fd74 ,lime has considerable antiseptic power1 and a new lime is practically sterile1 but very old limes1 especially in hot weather1 often contain large numbers of active bacteria1 which may be seen in the microscope under a good -inch objective4 ,their presence is always an indication that putrefaction is going forward1 and if their number be very excessive1 the leather out of such limes will generally prove loose1 hollow and dull-grained1 and in extreme cases hides may be totally destroyed4 ,spherical concretions of calcium carbonate may also be seen under the microscope1 resembling on a smaller scale those found in ,permian limestone1 and caused perhaps in both cases by crystallisation from a liquid containing much organic matter4 ,it is hardly probable that in many tanneries the ammonia would pay for recovery from the lime-liquors1 though it could be easily done by steaming the old limes in suitable vessels1 and condensing the ammoniacal vapours in dilute sulphuric acid4 ,its quantity rarely exceeds #ja per cent4 of ,,nh4 ,for methods of estimation of ammonia1 see ,l4,i4,l4,b41 p4 #cj4 ,up to a certain point1 it is found that old limes unhair much more readily1 and have a greater softening effect than new ones1 which is often advantageous for dressing goods2 though for sole leather1 where weight and firmness are of primary importance1 the use of stale limes must be kept within the narrowest limits4 ,in the finer leathers also1 such as kid and moroccos and coloured calf1 where a sound and glossy grain is desired1 the effects mentioned are generally better obtained in other ways1 such as by the use of sulphides4 ,on ,east ,india kips and other dried hides1 which are difficult to soften1 and which have great power of resistance to the action of lime1 old limes are distinctly useful1 but1 even there1 there are limits which should not be passed4 ,probably no lime ought to be allowed to go for more than three months at the outside limit without at least a partial change of liquor1 and the system of allowing all the limes in a yard to run for twelve months1 and then cleaning them all together1 is almost the worst which can be planned4 ,a very much better way is to clean the limes in regular rotation1 using1 if desired1 a portion of the old liquor in making the new lime1 so as to avoid a too sudden transition4 ,the old liquor is valuable1 if at all1 for the ammonia and organic matter which it contains1 as the amount of lime in solution is not worth considering4 ,the ammonia considerably increases the solvent and unhairing power1 while swelling the hide less than an equivalent amount of lime4 ,in some cases it may be desirable to add ammonia artificially for this purpose4 ,in this case it will be cheaper and more convenient to add it in the form of ammonium sulphate than as liquid ammonia4 ,if it be desired to retain ammonia1 the lime should be kept covered4 ,very old limes containing excess of ammonia and lime1 sometimes in hot weather cause a transparent swelling of the goods1 with destruction of the fibrous texture4#gd ,the writer has observed a similar phenomenon in very weak and old limes strengthened with sulphides1 in which hide was left experimentally for several weeks4 ,the principal effect of the dissolved animal matter is to enable bacteria to thrive in it1 which they will not do in a fresh lime1 but putrid limes probably also contain liquefying ferments produced by the bacteria present 7p4 #ag71 and which dissolve hide4 ,eitner has published researches on the amount of hide-substance dissolved by limes1#ge in which he shows that the loss of substance in liming sufficiently to unhair is materially greater in old limes than in fresh ones1 although during the first two days of liming the new limes are decidedly the most active4 ,as he remarks1 this justifies the wisdom of the method1 now largely adopted1 of working limes in shifts1 and beginning the operation in old limes and completing it in fresh ones4 7,see also p4 #aca47 #gd ,gerber1 #ahhd1 pp4 #aej1 #ahd4 #ge ,gerber1 #ahie1 pp4 #aeg-i1 #afi-gb4 ,for details of the analytical methods employed1 ,eitner's original paper must be consulted1 but the annexed table 7see next page7 summarises his results4 ,the letters heading the columns have the following meanings4 ,a4 ,hide substance precipitated by neutralisation of the lime with carbonic acid4 ,b4 ,a further precipitate obtained by slight acidification with hydrochloric acid4 ,c4 ,soluble peptones precipitated by hypochlorous acid or mercuric nitrate4 ,it is obvious that none of these figures represent the total dissolved organic matter1 and it is to be regretted that this was not determined4 ,it is1 however1 fairly safe to assume that the table correctly represents the relative solubility in the different liquors4 ,in each case #b liters of liquor were used for each kilo of green hide4 ,when old liquors were employed1 the hide-substance they originally contained was determined1 and deducted from the final result4 ---------------------------------------- -------------------------- ,hide ,description of ,days ,hide-substances in ,loss ,used4 ,lime ,liquor4 ,liming4 ,grams per ,liter4 per cent4 on --------------------- ,dry ,a4 ,b4 ,c4 ,total4,pelt4 ---------------------------------------- ---------------------- #a,ox- ,fresh lime #cj grm4 per #fgf #ajfhjcbdbcgj #cgfb #bce hideliter #b ,ditto #i #bgfdjedjcfbd #fibh #dad #c ,fresh lime #cj grm41 grm4 sulphide of #egf #jhebjagbahaf #bhdj #age sodium per liter #d ,ditto #h #abdjjeadchdf #efjj #ccf #e #e weeks old lime1 through which four #b #jahjjbabjihh #achj #jhg packs had passed #f ,ditto #egf #jhfhacahccef #eedb #cdf #g #e months old lime1 #b #jaifjahhjhfd #abdh #jgg with sodium sulphide #h ,ditto #egf #jibhaaihcjjd #eacj #cjf #i;,cow-,fresh lime as above #egf #aihbjdacdeja #fhif #dcj hide #aj ,ditto #h #cacbjfgbegda #iede #eid #aa ,fresh lime as above1 and grm4 sodium #egf #ajabjdjcbcae #dgcj #bif sulphide per liter #ab ,ditto #h #bebajfecejbf #hbjj #dhg #ac ,old disused lime #e #jcddjbiabcda #bigf #ahd #ad ,ditto #hgf #baaiafigfiebajgfh #fde #ae ,used sulphide of sodium lime #d weeks #egf 44 #afjjajdg #bebg #aeh old #af ,ditto #h #jgiajeaideib #ehib #cdc ---------------------------------------- ---------------------- #gf ,hides unhaired4 ,taking into account the liming necessary for unhairing only1 as shown in the table1 it will be noted that the percentage of loss is invariably greater in old limes than in new ones1 and less in limes sharpened with sulphide of sodium than where lime alone is used4 ,the only exception to this rule is in ,no4 #ae1 where a sulphide lime #d weeks old shows the least loss of any in the time required for unhairing2 and indeed sulphide limes if kept strengthened with the requisite addition of sulphide1 seem to deteriorate very slowly1 ,no4 #h1 with a lime #e months old1 showing a result which may still be considered good4 ,another point especially noted by ,eitner is the slight action of old limes during the first stages of liming1 as compared with their rapid solvent effect as the hair becomes loosened4 ,the loss in any case does not appear to be so great as the advocates of other unhairing processes have often claimed4 ,if we assume that all the dissolved hide-substance might have made leather1 the worst loss on oxhide only limed to the point of unhairing amounts to less than #c per cent4 on the possible total2 and it must be remembered that at least a part of this consists of dissolved epidermis matter1 which could not by any possible method have been converted into leather4 ,it will be noted in ,nos4 #b1 #d1 #aj1 #ab and #af1 what considerable losses are produced by plumping limes after unhairing1 but it must be borne in mind that1 in the case of dressing-leather1 solution of at least a part of the cementing matter is essential to produce the necessary softness and flexibility4 ,eitner calculates the dry pelt-weight from that of the green hide on the assumption1 based on experiment1 that #ajj parts of the original skin corresponds to #cb parts of dry pure pelt in green oxhide1 #be parts in green calf-skins1 and #ef parts in dried calf-skins4 ,in some of the smaller skins1 such as kid worked for glove leather1 where great softness and stretch is required1 the loss is necessarily much greater than in ordinary dressing-leathers1 amounting1 in the case of kid1 to from #bj to #bg per cent4 ,the parts taken by the purely chemical activity of the lime1 and by the action of bacteria and bacterial ferments in the unhairing process must still be regarded as uncertain4 ,the late ,professor von ,schroeder#gg carried out a series of experiments on liming and sweating which were characterised by his usual care and thoroughness1 and which tend to prove that the chemical action is far more important than the bacterial4 ,he had fresh hides well washed in a tannery immediately after slaughter1 and fleshed4 ,the butts were then cut into pieces of about #aj cm4 7#d inches7 square1 and salted in brine repeatedly changed1 and finally preserved for use in glass jars in saturated salt solution4 ,he found that when washed free from salt1 and placed in a moist chamber at a temperature of #af ,c41 the hair was sufficiently loosened by bacterial action in four to five days4 ,pieces placed in the moist chamber without previous removal of the salt only showed signs of sweating after about ten weeks' exposure4 ,liming experiments were made with similar pieces of salted hide1 both after three days' washing to free them from salt1 and unwashed1 and in both cases the pieces unhaired freely in three to four days4 ,these experiments were varied by using #f1 #ah and #cj grms4 of lime per liter of water in which about #bjj grms4 of hide were placed1 but neither in the washed1 nor unwashed portions was there any material difference in the time required to loosen the hair4 ,addition of #a vol4 of used lime-liquor to #c vols4 of water in making up the limes was equally without perceptible influence1 and careful bacteriological examination of hide and liquors showed that the former was almost sterilised by the intense salting1 and that the lime-liquors were practically free from bacteria4 #gg ,gerberei-,chemie1 ,berlin1 #ahih4 p4 #fdf4 ,von ,schroeder's conclusion that no gain arises from the use of excessive quantities of lime1 so long as the solution is kept saturated1 is fully justified both by experience and scientific reasoning1 but his results with regard to the effect of old liquors and bacteria contradict the conclusions both of practical tanners and of other scientific experimenters4 ,the different effects of old and new limes are too well known to practical tanners to be discounted by laboratory experiments1 even if they were not confirmed not only by ,eitner's results1 but by a considerable amount of work done in the ,author's laboratory and elsewhere2 while the necessity of bacterial action is at least rendered probable by the fact that soda solutions1 which are completely sterile to bacteria1 fail to unhair hides which have not previously undergone some putrefaction 7see p4 #acg74 ,in some experiments undertaken at the suggestion of the ,author it was found that a perfectly fresh and sterilised calf-skin which was not unhaired after ten days' liming in sterilised lime-liquor unhaired rapidly on the addition of a bacterial culture to the lime4 ,it is extremely difficult to exclude bacteria1 and even where perfectly fresh skins treated with chloroform or carbon disulphide were employed1 bacteria were always to be recognised when the skin was ready for unhairing4 ,von ,schroeder's work1 is1 however1 so painstaking and reliable1 that these divergent results must be explained as other than experimental errors4 ,with regard to old liquors1 it is known that ammonia is a powerful aid to the unhairing process1 and it is not certain to what extent the liquors he used were charged with it4 ,it is also certain that old limes containing much organic matter1 support bacterial life freely1 while #be per cent4 of a possibly not very old liquor would probably be sterilised by the addition of lime and #ge per cent4 water4 ,in order to test the matter fairly under exact tannery conditions1 the lime should have been made up entirely with old lime-liquor well charged with ammonia and organic matters1 instead of with water4 ,it is also probable that the hides had undergone a sufficient amount of bacterial change in the tannery before they came into ,von ,schroeder's salt solutions1 and it is not at all unlikely that the salt solution itself exercised some specific effect on the unhairing4 ,it is also possible that his bacterial cultures were made on gelatine media unsuitable for the growth of alkaline bacteria1 and therefore gave blank results4 ,under these circumstances it is scarcely possible to arrive at any very definite conclusions1 and it is obvious that further experiments on these points are extremely desirable4 ,sodium and ,potassium ,hydrates4--,from the earliest antiquity1 wood-ashes1 consisting mainly of potassium carbonate1 have been used for unhairing1 either alone or in conjunction with lime1 and indeed the ,german name of the process 7,aeschern7 is derived from the fact4 ,in more recent times1 caustic soda1 either ready formed1 or causticised on the spot by the addition of lime1 has often been recommended as a substitute for lime4 ,its action is very similar to lime1 but1 from its greater solubility1 is far more powerful1 and probably this has hitherto formed one of the greatest obstacles to its use1 since a solution of the strength of lime-water is almost immediately exhausted1 while a much stronger one is too violent in its action on the hides4 ,experiments made in the ,author's laboratory show that caustic soda1 in solutions of the same strength as lime-water1 dissolve considerably less hide substance than the latter1 but it is more antiseptic than lime1 and does not unhair readily without the aid of bacterial action 7cp4 p4 #acg74 ,it also swells more violently1 and it is difficult to keep the grain smooth and unwrinkled4 ,caustic soda has the great advantage that from its solubility1 and that of its carbonates in water1 it is much more easily and completely removed by washing than is the case with lime4 ,it has been successfully applied in some instances to soften skins of which the texture is naturally too compact for moroccos and the softer leathers2 and is usefully employed in softening dried goods 7p4 #aae74 ,where caustic soda is required merely to 8sharpen0 limes1 it is best added in the form of sodium carbonate 7soda-ash or crystals71 which are causticised by the lime in the pits4 ,one-quarter or one-half per cent4 on the weight of hides added in this way decidedly increases the plumping power of the lime4 ,it may be noted that in the use of sodium sulphide in conjunction with lime1 caustic soda is one of the products of its decomposition1#gh and is probably one great cause of the difference of effect of this material for sharpening limes as compared with red arsenic4 #gh ,this has been denied1 but is probably correct1 though the actual reaction is not easy to prove analytically2 but the effect on the hide is practically what is stated4 ,an indirect method of liming has recently been patented by ,messrs4 ,payne and ,pullman of ,godalming1#gi which is of both scientific and practical interest4 ,from the difficult solubility of lime1 and the consequently weak solutions which must be employed1 the ordinary process of liming is a slow one4 ,caustic soda1 however1 can be used in much stronger solutions without producing injury to the hide1 or larger solution of hide substance1 and from its great diffusibility1 it penetrates very rapidly4 ,used alone1 however1 the hide becomes too much swollen for most purposes1 and for certain classes of leather at least 7e4g4 buff and chamois leather7 the presence of a portion of lime in the hide appears to be necessary for successful work4 ,if a hide which has been swollen with caustic soda be afterwards treated with a solution of calcium chloride1 double decomposition takes place1 and caustic lime is formed actually in the interior of the fibre of the hide1 while the sodium unites with the chlorine to form common salt4 ,both solutions may be used in any convenient way1 and by the employment of drums1 the whole liming process may be accomplished in five or six hours4 ,it is found1 however1 that perfectly fresh hides treated in this way cannot be unhaired1 and the explanation appears to be that in the ordinary liming process1 the epidermis is made soluble by the joint action of bacterial ferments and of the alkaline solutions4 ,if sodium sulphide be added to the caustic soda used for unhairing1 the goods will unhair without the use of putrefactive means1 but the process is difficult to manage without destruction of the hair1 and ,messrs4 ,pullman now recommend that all hides or skins for unhairing by their process should be soaked for forty-eight hours in winter1 and twenty-four hours in summer in a really putrid stale soak4 ,this necessity constitutes for very many purposes a serious weakness in the method1 as putrid soaking is always extremely dangerous to the grain of the hide1 and especially so in hot weather4 ,for certain purposes1 however1 advantage may be taken of the fact that the hide or skin can be fully limed by ,pullman's process and the fibres swollen so as to be prepared for tanning without any loosening of the hair1 and the ,author has seen deerskins which have been treated in this way1 on which the hair was perfectly firm1 while they possessed a softness and fulness which could not be attained without liming4 #gi ,eng4 ,pat4 #bhgc1 #ahih4 ,messrs4 ,pullman now recommend that the treatment with their solutions should take place in pits1 in preference to drums or paddles1 and that the caustic soda should not exceed a strength of one pound in ten gallons 7#a per cent474 ,the hides or calf-skins remain in this for about forty-eight hours1 during which they are once drawn and returned1 by which time1 if the putrid soaking has been properly done1 the hair should be fully loosened4 ,the hides are then drained for two hours1 and passed into another pit containing a solution of calcium chloride1 which should be slightly stronger than the caustic soda1 say of about one and a half pounds per ten gallons4 ,the goods remain in this for about forty-eight hours1 during which they are drawn once1 and are then well washed in soft water 7free from temporary hardness7 in which they may be kept for some time without injury4 ,as both the caustic soda and the calcium chloride solutions are quite sterile to ordinary putrefactive bacteria1 both can be used for an almost unlimited time1 and they are conveniently kept up to strength by the addition of strong stock-solutions4 ,these may be made of a sp4 gr4 of #ad 7#hj deg4 ,tw47 which gives a strength of about #e lb4 of caustic soda and #e lb4 of calcium chloride per gallon4 ,in addition to the advantage of considerable saving of time1 the effects can be much more easily regulated than in ordinary liming1 and the amount of soda 7and subsequently of lime7 absorbed by the hide can be exactly determined by titration of the liquors4 ,grease is better removed than by ordinary liming1 as soda-soaps are soluble in water1 but if this result is to be obtained1 the soap must be worked out before passing into the calcium chloride solution1 which would otherwise convert it into an insoluble lime-soap4 ,a great gain in many districts is that the process yields practically no effluents and no lime slab1 both of which are frequently very difficult to dispose of4 ,the serious disadvantages of the stale soaking1 however1 have already been mentioned4 ,in place of applying the caustic soda first1 and the calcium chloride subsequently1 hides may be first treated with calcium chloride solution1 and then with caustic soda1 or the caustic soda may be applied to the flesh side of the hide by painting4 ,these modifications are covered by ,messrs4 ,pullman's patent1 but they are willing to grant licences for experiments at a nominal fee4 ,alkaline carbonates are much milder in their action on hide than the corresponding hydrates1 and although they will unhair hides1 in absence of lime1 their action is somewhat uncertain and slow4 8,polysulphin0 7,polysulphin ,co41 ,keynsham7 owes its unhairing power principally to the sodium carbonate1 and not to the small traces of sulphur compounds which it contains4 ,sodium carbonate occurs in commerce in three forms3 8soda ash10 a more or less pure dry sodium carbonate2 8soda crystals10 or washing soda1 ,na,,co#aj;,aq1 containing #fbie per cent4 of water of crystallisation1 and efflorescing in the air2 and ,gaskell and ,deacon's 8crystal soda10 ,na,,co#a;,aq1 containing only #ade per cent4 of water of crystallisation4 ,it must be remembered that where carbonate is used in conjunction with lime it becomes causticised and converted into ,na,o,h4 ,sulphides4--,the practice of using realgar1 or red sulphide of arsenic 7,ger4 ,rusma7 as an addition to limes for fine leathers is one of considerable antiquity4 ,it has the property of loosening the hair and epidermis structures with less solution of cement-substance than lime alone1 and hence produces a leather of fuller and closer texture4 ,it will1 however1 be convenient to defer the consideration of this agent till after that of some of the more modern and simpler substitutes1 such as the sulphides of sodium and calcium4 ,sulphides of the alkalies and alkaline earths1 if used in strong solution1 say #e per cent4 or upwards1 have the effect of very rapidly reducing the harder keratin-structures1 such as hair and wool1 to a pulp1 attacking first the interior cells1 so that the hair crumples up like a string of sausages1 and in a few hours1 or even1 with very strong solution1 in a few minutes1 the whole mass becomes so completely disintegrated that it can be swept off the hide with a broom1 or washed off in a tumbler4 ,at the same time1 the action on the substance of the hide1 and especially on the cementing substance1 is very slight1 though the grain is swollen and temporarily rendered somewhat tender4 ,on the other hand1 when used in weak solutions1 say per cent4 and under1 in conjunction with lime1 the hair is but little injured1 while the hair-roots and dirt are rapidly loosened1 and results are obtained very similar to those with arsenic4 ,sodium ,sulphide 7,na,s#i,,oh74#hj--;,for the methods of valuation and determination of sodium sulphide1 see ,l4,i4,l4,b41 p4 #bh4 #hj ,in the ,laboratory ,book the water of crystallisation is given as #aj ,aq4 ,later researches show that pure crystals of the commercial sulphide only contain #i ,aq41 or #fge per cent4 of water4 ,hides suspended in solutions of sulphide of sodium of #b to #c per cent4 strength unhair rapidly4 ,for the commoner classes of sole-leather1 hair is frequently removed by painting on the hair side with a #ae-bh ,tw4 7#cj-dj per cent47 solution of 7crystallised7 sulphide of sodium thickened with lime1 applied with a fibre-brush1 and folding the hide in cushions in a damp place1 or packing in a tub4 ,the hair is reduced to paste in a few hours4 ,the same effect is produced by drawing the hides through a similar solution without lime1 of which sufficient is retained by the hair to destroy it4 ,the workmen must be provided with indiarubber gloves to prevent the caustic effect of the solution on the skin and nails4 ,skins and lighter hides are conveniently unhaired by painting the mixture on the flesh side1 when it will loosen the hair or wool in a few hours without destroying it4 ,for dressing-leathers and the finer sorts of sole it is best employed as an addition to ordinary limes to the extent of - per cent4 on the weight of the hides or skins1 when the hair is loosened more rapidly than with lime alone1 and with less loss of hide substance4 ,good samples of sulphide of sodium consist of pale-brown1 almost colourless crystals1 containing #bh to #cb per cent4 of dry sodium sulphide1 which readily deliquesce on exposure to air4 ,fused sodium sulphide can now be obtained1 which contains nearly twice as much actual sulphide as the crystalline form4 ,the dark green colour possessed by many samples of sodium sulphide is due to the presence of iron sulphide4 ,if carefully used no serious harm can accrue from its presence4 ,if allowed to stand a short time in solution the iron sulphide will settle out4 ,calcium sulphydrate1 ,ca7,,sh71 sometimes called ,bttger's ,grnkalk1 is a powerful depilatory1 while it has probably less destructive action on the hide-fibre than even the sulphide of sodium1 and would no doubt be largely used but for its unstable character4 ,it is probably the principal active product produced by the use of sulphide of arsenic in conjunction with lime1 though it is possible that a sulpharsenite may be formed4 ,it may be produced by passing hydrogen sulphide 7,,sh71 into milk of lime4 ,according to von ,schroeder1 it is not formed by the reaction of sodium sulphide on lime solutions 7see note1 p4 #acf74 ,it may be obtained crystallised1 and is soluble in water1 but is decomposed on boiling4 ,the sulphide1 ,ca,s1 is insoluble in water1 but by the action of steam under pressure it is said to be converted into a mixture of equivalent parts of hydrate and sulphydrate4 ,it may also be dissolved in a solution of hydrogen sulphide1 forming a solution of sulphydrate4 ,in this way it might be formed on a large scale from the 8tank waste0 of the ,leblanc soda process4 ,gas-lime is principally active on account of the calcium sulphide which it contains1 but is very variable in its strength1 as both sulphydrate and sulphide are decomposed by the carbon dioxide always present in the gas1 forming carbonates4 ,lime has nearly gone out of use for purifying gas1 its place being now taken by iron oxide1 but formerly gas-lime was a good deal used for unwooling the small lambskins used for the commoner sort of glove-kid1 usually by painting a cream of it on the flesh side1 but sometimes by immersing in a strong solution1 which of course destroyed the wool4 ,its place is now taken by a solution of sodium sulphide of #ae-ah ,tw4 7approximately #cj-ce per cent4 crystals71 thickened with lime to a soupy consistence1 the use of which is much to be recommended for unwooling sheep-skins4 ,the tank-waste from the ,leblanc process1 consisting principally of calcium sulphide1 is1 when fresh1 quite insoluble1 and has no depilatory powers2 but when exposed to air and moisture1 decompositions take place1 resulting in the formation of sulphydrates and polysulphides1 which form a solution which has been the subject of several patents for unhairing4#ha ,polysulphides alone have probably no unhairing effect1 but in conjunction with lime1 sulphydrates are formed which rapidly loosen the hair4 ,this fact was the basis of an ingenious and effective unhairing process used very many years ago by ,mr4 ,john ,muir1 of ,beith1 who1 after liming for #bd hours in the usual way1 submitted the hides to a pretty strong solution of weathered tank waste for #bd hours1 and finally to water for #bd hours1 to remove the surplus lime and sulphides4 ,the sulphydrates formed in the hide attacked the hair-roots with little injury to the hair itself1 and the hides contained so little lime that they could be tanned for dressing without bating1 and made about #aj per cent4 more weight than those treated in the ordinary way4 ,some trouble was occasioned by stains caused by impurities in the tank-waste4 #ha ,squire1 ,e4 ,p41 #gef1 #ahee2 ,claus1 ,e4 ,p41 #aijf1 #ahee4 ,a somewhat similar unhairing mixture to that obtained from tank-waste1 which is now seldom to be got1 was patented by ,prof4 ,lufkin1#hb who mixed equal parts of sulphur and soda-ash with a little water till combined1 and then added #h to #aj parts of lime1 slaked and still hot4 ,schultz#hc states that such a mixture containing #aj lb4 of sulphur1 will unhair fifty hides in the same way1 and in about the same time as an ordinary lime1 the pelt being little plumped and easily reduced without bating by a few minutes' wheeling in warm water4 ,by boiling lime and sulphur with water a yellow solution is obtained which can be used in the same way as that from the tank-waste4 ,a further quantity of water can be boiled on the same materials1 more lime and sulphur being added as required4 ,polysulphides appear to have a marked effect in preventing plumping4 #hb ,eng4 ,pat4 #bjec1 #ahfj4 #hc #8,leather ,manufacture1' p4 #ce4 ,barium sulphydrate has been put on the market experimentally as an unhairing agent1 in the form of a strong solution containing yellow polysulphides1 and which deposits crystals of sulphydrate in cold weather4 ,it is more stable than calcium sulphydrate1 but1 on the whole1 does not seem to present any advantages over sodium sulphide4 ,realgar or red sulphide of arsenic1 ,as,s1 is made by fusing arsenious acid and sulphur4 7,orpiment is ,as,s1 but its action is different from that of realgar47 ,mixed with lime it produces calcium sulphydrate and possibly hyposulpharsenite4 ,to produce a rapid and complete reaction it must be mixed with hot lime1 and the hotter the mixture is made the more powerful is its unhairing action4 ,milder forms may be made by mixing cold1 or with the aid of hot water only4 ,it is used with great advantage in conjunction with lime in varying proportions for unhairing lamb- and kid-skins for glove-kid and other fine leathers1 to which it gives the necessary stretch and softness and cleanness of grain1 without the loosening of texture and loss of hide-substance which would be caused by an equivalent amount of ordinary liming4 ,for glove-kid about #ja-jc per cent4 of realgar and #e per cent4 of lime is used1 reckoned on the green weight of the skin4 ,for painting the flesh side of calf- and lamb-skins #a part of realgar is mixed with #aj parts of hot lime1 made into a paste with water4 ,calf will unhair in #h or #aj hours4 8,inoffensive0 unhairing solution contains a large quantity of arsenic sulphide apparently dissolved in caustic soda1 although ,moret's original patent claimed the use of wool-sweat potash only6 ,w4 ,r4 ,earp#hd has suggested the use of compounds of sulphur and arsenic 7thio-arsenates1 thio-arsenites1 etc471 in #e per cent4 alkaline solution4 ,he prefers to add the compounds to the ordinary lime-liquors1 or to manufacture them in situ by adding the proper quantities of arsenious or arsenic acid mixed with one-third of its weight of sulphur to a solution of an alkaline sulphide in lime-liquor4 ,the pelt is not bated or drenched in the ordinary way1 but1 after unhairing1 is passed directly into the tanning liquor to which sulphurous acid has been previously added4 #hd ,eng ,pat41 ,no4 #bjeb1 ,feb4 #ab1 #ahhf4 ,there is more danger of injury to the hide from the very prolonged action of weak solutions of sulphides1 which tend ultimately to destroy the structure and reduce the fibre to a gelatinous condition1 than there is from too concentrated solutions4 ,no danger need1 however1 be apprehended in the course of any ordinary liming4 ,arsenical limes are not suited for tainted skins1 and they should not be made so strong as to destroy the hair or wool4 ,for methods of analysis of both old and new lime-liquors1 see ,l4,i4,l4,b41 pp4 #bg to #cd4 ,whichever method of loosening the hair be adopted1 the actual removal must be effected by placing the hide on a sloping beam with a convex surface1 and then scraping it with a blunt two-handled knife 7,fig4 #bg71 the workman pushing the hair downward and away from himself4 ,the beam may be either of cast iron or of wood1 usually covered with zinc to increase its wearing capacity4 ,the hides after being removed from the lime-pits1 are allowed to drain for half an hour or so before the hair is removed1 and immediately this operation has been completed1 they should be placed in soft water4 ,it is of great importance that the limed hides should not be exposed to the air longer than is absolutely necessary for the removal of the hair1 as the carbonic acid present in the atmosphere quickly carbonates any lime contained in the surface of the skin1 forming chalk1 and leading to uneven tanning at a later stage4 ,when hide has been insufficiently limed it is often easy to remove the longer hair but excessively difficult to get rid of the short under-growth of the young hairs1 which even in properly limed skins can often only be removed by shaving them with a sharp handknife4 ,this difficulty is caused partly by the small resistance which the short hairs offer to the unhairing-knife1 and partly by their being more deeply rooted in the skin than the older hairs 7see p4 #di74 ,illustration3 ,,fig4 #bg4--,unhairing 7,penketh ,tannery74 ,various machines have been devised to accomplish the removal of the hair1 but owing to the rapidity with which it may be worked off by hand1 and the fact that the work is not difficult1 no machine has as yet come into general use4 ,hand-work has the further advantage that in those portions of skin where the hair is tighter than usual it may be removed by greater pressure of the knife or by hand-shaving1 whereas after goods have been unhaired by machine they must always be examined and any patches of hair removed by hand on the beam4 ,the edges invariably require to be gone over by hand4 ,several machines with spiral knives have been introduced for the purpose4 ,that made by the ,vaughn ,company 7,peabody1 ,mass47 for fleshing is one of the most satisfactory for unhairing1 though any other machine of a similar type1 and provided with spiral knife-blades1 purposely kept blunt1 may be used4 ,the ,leidgen unhairing machine1 shown in ,figs4 #bh and #bi1 is one of the latest and most ingenious4#he #he ,e4 ,h4 ,munkwitz1 ,milwaukee4 ,illustration3 ,,fig4 #bh4--,leidgen ,unhairing ,machine4 ,occasionally goods are unhaired by fulling in the 8stocks02 but it is very doubtful whether the saving in labour is not more than counteracted by the loss of weight caused by submitting the hide1 while its gelatin is in a partially dissolved condition1 to such rough usage4 ,the use of the wash-wheel 7see pp4 #aaa1 #aah7 for the same purpose is much more satisfactory1 and may be profitably employed for common goods1 especially when the hair has been loosened by painting with a sulphide mixture4 ,after being unhaired1 the hides are 8fleshed0 on the beam4 ,this work1 which consists in removing any small pieces of flesh and fat left by the butcher on the inner side of the skin1 should be carefully and thoroughly done2 but the closeness of the fleshing required is dependent on the purpose to which the hides or skins are to be applied4 ,illustration3 ,,fig4 #bi4--,leidgen ,unhairing ,machine4 ,it is necessary not only to remove those portions of fat which are easily visible1 but also to force out that contained in the loose areolar tissue4 ,the form of knife used in ,england in fleshing is shown in ,fig4 #cj4 ,it differs from the one used for unhairing in being somewhat broader and heavier1 and both its edges are sharp1 so that where the flesh is too tight to remove by mere friction of the knife1 it may be actually cut away by holding the knife almost flat on the beam1 and using the convex sharp edge4 ,the strokes in cutting must not be too broad1 or1 from the convexity of the beam1 the substance of the hide will be cut into in the middle1 or flesh will be left at the edges of the stroke4 ,this difficulty is avoided by the flexible knife commonly used in ,germany1 but in other ways its work is less rapid and effective4 ,illustration3 ,,fig4 #cj4--;,fleshing4 ,machines have long been used for fleshing and scudding light goods1 such as lamb-1 kid-1 and goat-skins1 and their use for fleshing dressing hides has now become very general in the ,united ,states1 and is gradually gaining ground in ,england4 ,the type of machine used for these heavier leathers1 varies considerably from that used for light skins1 but the general principle is the same4 ,in most cases the working tool of the machine is a cylinder with spiral blades1 which are generally arranged right-handed on one half1 and left handed on the other1 so as not only to scrape the hide in the direction in which the cylinder works1 but also to extend it sideways4 ,much of the efficiency of these machines depends on the exact adjustment of the pitch of the spiral1 and in the ,vaughn machine1 which is probably most in practical use1 the blades are so arranged as to form two intersecting spirals1 one of steeper pitch than the other4 ,the great difference in the machines for skins and for heavy work1 consists in the means adopted to support the skin1 and to carry it under the spiral blades4 ,illustration3 ,,fig4 #ca4--;,jones ,fleshing ,machine4 ,in the machine invented by the late ,j4 ,meredith ,jones1 the skins are supported upon an india-rubber blanket stretched over two rollers1 so that the knife-cylinder works on that part of the blanket which is between them1 by which great elasticity is obtained1 and this machine has proved most successful in treating delicate skins4 ,in some other forms of machine1 cylinders thickly covered with rubber have been substituted for this arrangement4 ,the ,jones machine is shown in ,fig4 #ca4 ,for heavy hides the ,vaughn machine is most generally used1 and may be taken as the type of the rest1 as the ,vaughn ,company certainly originated the semi-cylindrical 8beam10 which forms a very important feature4 ,its construction will be seen from ,fig4 #cb4 ,illustration3 ,,fig4 #cb4--,vaughn ,fleshing ,machine1 front view4 ,it will be easily noticed that if a hide be thrown over the half-cylinder so that one half hangs outside it1 and the other half falls in its hollow1 and it be then rotated1 the hide is first caught firmly by a spring-clamp1 which has been supported above the edge of the half-cylinder by blocks attached to the frame4 ,as the edge rises1 it lifts this clamp off the blocks1 and thus carries the hide under the spiral knife-cylinder4 ,the blades of this spiral knife-cylinder are ground to a sharp rectangular edge1 and partly scrape and partly cut the loose tissue of the flesh4 ,when the half-cylinder has made a semi-revolution1 it returns to its original position1 and the sizes of the driving pulleys are so arranged that the cylinder travels downwards more rapidly than it rises1 in order to economise time1 though in both cases the hide is worked upon by the knife-spiral which is rotated at a still higher speed4 ,the hide is of course turned on the beam-cylinder and the other half is similarly fleshed4 ,the beam-cylinder reverses automatically1 or may be reversed by hand1 and its nearness to the spiral knife is also under control4 ,it is usually covered with a thick sheet of rubber4 ,it is obvious that machines of this type can not only be used for fleshing1 but for unhairing and scudding1 by the substitution of suitable knife-cylinders1 and in the case of light skins1 cylinders fitted with slates are frequently employed for the latter operation4 ,the slate for the purpose must be of a peculiarly fine and even grain1 and is mostly obtained from a single quarry in ,wales4 ,the ,vaughn machine is frequently used in ,america for fleshing hides after soaking but before they go into the limes1 and much is to be said in favour of this method1 as the removal of the flesh permits even and uniform action of the lime4 ,it is1 however1 a distinct disadvantage to the method that the flesh appears rough-looking after tanning1 and the method is most suitable in conjunction with the ,american system of splitting the tanned leather4 ,in the production of sole-leather1 fleshing machines have not as yet come into very general use4 ,this may be accounted for by the fact that if used before liming a rough flesh is produced1 which is unsightly on sole-leather1 and which cannot well be afterwards improved1 while something of the same objection attaches to fleshing after liming1 with the added disadvantage that the hide is too much pressed1 and is not easy to plump again1 so as to make a satisfactory sole-leather4 ,in ,america1 both sole- and dressing-leathers are usually tanned in sides1 the hide being cut down the centre of the back4 ,in ,england1 the hide is usually 8rounded0 for sole-leather into 8butts0 or 8bends0 and 8offal10 as shown in ,fig4 #cc4 ,the rounding is done by hand with a sharp knife on a table1 and in some of the best tanneries frames made of wood or metal are employed1 to mark the sizes required4 ,the chief advantage of rounding before tanning is that the different parts of the hide can be differently tanned1 and appropriated to the purposes for which they are most suitable4 ,the offal is now frequently split and worked up for light leather1 or in other cases is tanned with a cheaper and more rapid tannage than the butts4 ,illustration3 ,,fig4 #cc4--;,diagram of ,hide4 ,dressing leather is more frequently rounded after tanning1 according to the purposes for which it may be required4 ,,chapter ,,xiii4 ,,deliming1 ,,bating1 ,,puering ,,and ,,drenching4 ,although lime is in many respects the most useful and satisfactory means of loosening hair from hides and skins1 it is of the greatest importance that it should be completely removed when it has done its work1 since its action on tannins is most injurious1 and it is often harmful in tawing4 ,for soft leathers it is also necessary that the skin should be brought from a swollen to a soft and flaccid condition4 ,in practice this is mainly accomplished for dressing leathers by bating1 puering and drenching2 while sole-leather and strap-butts are only too frequently left to chance1 and to the natural acidity of the tanning liquors4 ,bating consists in handling1 or steeping the goods in a weak1 fermenting infusion of pigeon- or hen-dung for a time usually extending over some days1 and is applied to the heavier classes of dressing leather1 such as 8common0 and shaved hides1 kips and calf-skins4 ,puering is a very similar process1 applied to the finer and lighter skins1 such as glove- and glac-kids and moroccos1 in which dog-dung is substituted for that of birds1 and1 as the mixture is used warm and the skins are thin1 the process is generally complete in a few hours at most4 ,neither bating nor puering are very effective in removing lime1 and seem to act principally by some direct effect of the bacterial products on the swelling of the pelt4 ,drenching is occasionally used 7e4g4 on calf-kid7 as a substitute for bating or puering1 but more frequently follows the latter1 and serves to cleanse and slightly plump the skins before tanning1 and complete the removal of lime4 ,the drench-liquor is an infusion of bran made with hot water1 and allowed to ferment under the influence of special bacteria1 which are always present in vats used for the purpose1 and which develop lactic and acetic acids4 ,it will be noted that all these methods are fermentative1 and their effect is not simply the chemical one of removing the lime1 but the bacterial action leads also to solution of the cementing substance of the hide-fibres1 and produces a marked softening effect on the leather1 together with considerable loss of hide-substance4 ,in the manufacture of the softer leathers this effect is generally desired1 and no process would be satisfactory which did not produce it2 but in other cases1 such as harness- and strap-butts1 firmer and heavier weighing leathers would be preferred1 if it were known how to make them4 ,the putrefactive processes would be gladly relinquished1 if satisfactory substitutes could be found1 not only on account of their offensive character1 but because of their uncertainty and danger to the goods2 and even if lime only were removed1 the necessary softness could often be obtained by appropriate liming and tanning4 ,it will be best1 therefore1 to deal first with the purely chemical methods which aim only at removal of lime1 before considering those involving bacterial action4 ,unfortunately1 the chemical problem is not so simple as it might at first sight appear4 ,the alkaline lime clings obstinately to the hide-fibre1 and can only be removed very slowly1 if at all1 by mere washing4 ,on the other hand1 the use of any excess of strong acid is absolutely precluded1 because of its powerful swelling effect on the pelt1 in the tanning of which it would prove even more injurious than the lime1 making dark-coloured and brittle1 or tender1 leather4 ,this effect is not to be avoided by the use of even very dilute solutions of strong acids1 since the affinity of hide-fibre for them is so strong that it will abstract practically all the acid from even a decinormal solution1 leaving it quite neutral4 ,what is required is an acid of extremely weak affinities1 forming soluble lime salts1 and obtainable at a low cost2 or1 on the other hand1 a salt of some weak base which could be displaced by lime1 and which would not act injuriously on the pelt4 ,with certain precautions1 and in special cases1 however1 the stronger acids may be used successfully4 ,in the cases of sole- and belting-leather no softening is desired1 and formerly tanners usually contented themselves with a very perfunctory washing in water1 trusting to the acids present in the liquors to complete the removal of the lime4 ,even pure distilled water effects this removal very slowly and imperfectly1 owing to the strong attraction of the lime for the fibre2 and if 8temporary hard0 water is used1 the lime present in the hide combines with that present in the water and is precipitated as chalk in the surface of the hide4 ,this may be prevented by previously adding a small quantity of lime or lime-liquor to the water before use to soften it 7see p4 #ie72 but unless this is very carefully done1 the free lime present in the water prevents it from removing any from the hide4 ,the safest way is not to add lime direct to the water1 but to change the latter gradually1 so as to allow the lime already present to soften the new portion of water4 ,a much more efficient method is to suspend the butts in water to which small portions of diluted acid are successively added till the lime is nearly1 but not quite1 neutralised4 ,if carefully used1 sulphuric acid#hf is perhaps as good as any1 but1 of course1 any excess will spoil the colour or 8buff0 of the leather4 #hf ,the use of sulphuric acid for this purpose was patented by ,h4 ,belcher of ,wantage 7,no4 #ad1idc71 but was used some years previously in several tanneries known by the author4 ,acetic1 formic1 and lactic acids are safer than sulphuric1 but are somewhat costly1 and must not be used in appreciable excess4 ,crude pyroligneous acid may be used1 and it has a considerable antiseptic effect owing to the phenols1 etc41 which it contains4 ,hydrochloric acid is not suitable for sole-leather1 on account of the bad effect of chlorides on plumping4 ,sulphurous acid#hg is perhaps the best1 and its acid properties are so weak that slight excess does little harm1 but the neutral calcium sulphite is insoluble1 and to actually dissolve the lime the hydric sulphite must be formed1 which can only occur in presence of excess of the acid4 ,unless such excess is used1 the colour of the pelt in the early liquors is apt to be somewhat greyish4 ,probably a very good method would be to suspend the butts in a solution of sulphurous or some other acid of about ,n_/#bj strength1 sufficiently long to remove all lime from the surface and slightly to plump it but not to penetrate to the centre of the hide1 which should then be suspended in water until any excess of acid had been taken up by the unneutralised lime still present in the middle of the butt1 which at the end of the operation should be rather alkaline than acid4 ,the course of this1 or any other bating operation can be followed by cutting the hide1 and moistening the cut surface with alcoholic solution of phenolphthalein1 which is turned red1 or pink1 by the least trace of free lime4 #hg ,manufacture of sulphurous acid1 see p4 #bd2 testing1 see ,l4,i4,l4,b41 p4 #cg4 ,in using mineral acids it is of great importance that they should be perfectly free from iron1 and that the vat employed should contain no iron which could become dissolved1 since1 if present in the bating liquid1 it is sure to be fixed by the hide1 especially if the quantity of acid used is insufficient to neutralise the whole of the lime4 ,besides the direct use of mineral acid which has been described1 sulphuric1 or still better1 oxalic acid may be very advantageously employed in precipitating lime from used bating liquids containing weak organic acids1 or other lime solvents1 so as to restore their original activity4 ,not only is the bate economised by being used repeatedly1 but some of the organic products dissolved from the hide have themselves considerable power of removing lime4 ,putrefaction should not be allowed to take place2 but many of the organic acids which have been proposed for bating belong to the aromatic series1 and have considerable antiseptic power4 ,where organic acids are employed1 the presence of their neutral lime-salts in the liquor1 resulting from previous operations1 will reduce the swelling action of the acid on the skin1 without diminishing its power of removing lime 7cp4 p4 #ha74 ,in place of sulphuric acid1 some tanners have employed a material advertised under the name of 8boral40 ,this substance consists simply of sodium anhydrosulphate melted up with about one-seventh of its weight of boric acid1 the quantity of which is1 however1 too small to have appreciable influence as an antiseptic1 while it is said to form insoluble borates with the lime present1 which are sometimes a source of subsequent trouble4 ,there is no reason why ordinary sodium bisulphate should not be used for the purpose1 and its action is more mild than that of sulphuric acid itself1 but great care must be taken that no nitric acid is present1 as is frequently the case in the crude product obtained in the manufacture of nitric acid from sodium nitrate1 and known in commerce as 8nitre-cake40 ,the presence of a trace of sodium chloride would not be disadvantageous for dressing leather1 but would tend to prevent plumpness in sole4 ,paessler and ,appelius#hh have recently shown that raw hide absorbs sulphuric acid from sodium bisulphate1 leaving the neutral sulphate in solution4 #hh #8,wissenschaftlich-,technische ,beilage des ,ledermarkt1' #aija1 p4 #ajg4 ,boric 7boracic7 acid1 though used to a slight extent for a number of years past1 has recently come much into favour as a deliming agent1 for which purpose it is in many respects particularly suitable4 ,sole-leather may be improved in colour by giving a short bath in #a-b per cent4 boric acid solution to remove surface-lime4 ,in this case the acid is best applied just before the hide enters the suspenders4 ,boric acid may also be suitably employed on hides which have been bated4 ,it then acts as a drench and removes traces of lime still left in the hides1 so that the liquors have a more even effect on them4 ,experience has shown that the skins should never be allowed to lie for any length of time in the boric acid solution in a motionless condition1 as this tends to produce patches of partially delimed skin1 which cause irregular colour4 ,it is best to keep the skins in fairly constant motion in a paddle or by frequent handling4 ,boric acid has considerable influence in preventing drawn grain in the early liquors1 but if it gets into the forward liquors it renders the leather loose and light 7cp4 p4 #bbi1 and ,l4,i4,l4,b4 p4 #cg74 ,borax has also been suggested as a deliming agent1 and as it is chemically an acid salt1 it has naturally some deliming effect1 but it cannot compare with boric acid in either price or efficiency4 ,both boric acid and borax are antiseptics 7see p4 #be74 ,in the employment of either sulphuric1 boric1 or any other acid forming calcium salts of limited solubility1 it must be borne in mind that if the solution is repeatedly re-strengthened1 it will become saturated with the lime-salt1 and although the acid will still combine with the lime and render it neutral1 it will no longer remove it from the hide4 ,under these conditions1 sulphuric acid may cause the deposition of crystalline calcium sulphate in minute nodules between the fibres4 ,calcium borate may be similarly deposited1 and has the further disadvantage of becoming decomposed by the tanning liquors1 which form dark compounds with the lime4 ,in using sulphuric acid alone it is therefore best to renew the water each time4 ,when it is used in conjunction with some other acid1 forming very soluble lime salts1 this danger is not to be apprehended1 while oxalic acid precipitates the lime almost completely from the solution4 ,it is to be borne in mind that in all cases of using acids1 any carbonate of lime present on the pit sides or elsewhere will be decomposed1 and the carbonic acid will become dissolved in the liquor1 and unless acid is used in sufficient quantity to remove the whole of the lime1 may tend to fix the remainder as carbonate4 ,in the case of dressing leather there is less danger of this1 as warm water is generally used1 in which little carbonic acid dissolves4 ,it is probable that some of the coal-tar acids which have been advertised for bating dressing leather might be advantageously employed for sole4 ,hauff's 8anticalcium0 7see pp4 #bi1 #afc71 would appear to be very suitable for this purpose1 and if the liquor were regenerated by the addition of sufficient sulphuric acid to neutralise the lime dissolved from the hide1 might be used repeatedly1 and would not then prove expensive2 while its sterilising power would be very advantageous to the proper swelling of the butts in the handlers1 since nothing tends to check plumping so much as putrefactive action4 ,turning from sole to dressing leather1 mineral acids are very successfully employed for 8pulling down10 the goods being thrown into a paddle containing warm water of about #cj-ce ,c41 and the calculated quantity of sulphuric or hydrochloric acid1 previously largely diluted with water1 is then added in two or three successive portions at intervals of perhaps ten minutes4 ,the acid must in no case be sufficient to neutralise quite the whole of the lime4 ,goods treated in this way can be further bated1 puered1 or drenched as required by the ordinary methods1 if they are not sufficiently soft4 ,if too much acid has been used1 and the skins show signs of swelling1 they may be brought down by the addition of a little ammonia1 borax1 or even soda4 ,in many cases the addition of salt in small quantity to the acid liquor will tend to deplete the hides1 and at the same time prevent any injurious action of the acid4 ,ammonium chloride may also be used with advantage 7see p4 #aei74 ,a solution containing about #ae per cent4 of salt and #jc per cent4 of sulphuric acid1 with some molasses1 has been a good deal used in the ,states as a bate1 and seems to answer well on some classes of goods1 but the acid and salt are apt1 ultimately1 to find their way into the liquors and destroy tannin4 ,the process is well suited for chrome-leather1 and may also be usefully applied in cases where goods have become 8wind-blasted0 or otherwise impregnated with carbonate of lime1 since in presence of salt the acid can be used in sufficient excess to dissolve the carbonate4 ,vegetable acids may1 of course1 be used in conjunction with salt in the same way4 ,the salt does not neutralise the acid1 but simply controls the swelling of the skin1 and if acid has been used in any material excess1 the first part of the tanning must be done in salted liquors1 or the acid neutralised with ammonia1 sodium carbonate1 or chalk1 previous to tanning1 as1 otherwise1 the goods will plump up in the liquors1 and be tender when tanned 7cp4 p4 #ia74 ,lactic acid has recently come largely into use as a deliming agent4 ,it is best known as the acid which gives a characteristic taste to sour milk1 and is the chief product of the lactic ferment4 ,it may be very successfully used for neutralising the lime left in the skins after the depilation1 but1 if used in excess1 it tends to plump or swell the leather very strongly1 being one of the best plumping agents known4 ,when used for deliming1 a solution of #b lbs4 in #ajj gallons is very suitable4 ,it may1 in many cases1 be substituted for the bran-drench with advantage1 and is much more rapid and less dangerous in hot weather1 but the effect is not in all respects identical4#hi #hi ,on the manufacture of lactic acid by fermentation1 see ,claflin1 ,journ4 ,soc4 ,chem4 ,ind41 #ahig1 p4 #eaf4 ,campbell states that practically pure cultures of the lactic bacteria are obtained by continued culture in milk4 ,these cultures employed as a ferment for drenches have given good results in the ,yorkshire ,college ,experimental ,tannery4 ,when lactic acid is used for bating1 or drenching1 the operation should always be conducted in a paddle1 and the liquid works more satisfactorily if it is at a temperature of #cj-ce ,c4 ,as regards cost1 it will be found that in practice it is not appreciably more expensive than dung or bran4 ,about an hour's paddling will generally suffice1 if the right quantity of acid has been used1 but in some cases it is best to add the acid in several portions and take more time4 ,the estimation of the amount of lactic acid in the commercial article may be carried out by diluting exactly #i grms4 with about ten times its volume of water1 and then titrating it with normal caustic soda as described in ,l4,i4,l4,b41 p4 #af1 for acetic acid4 ,as each c4c4 of normal alkali is equivalent to #jij grm4 of lactic acid it will represent one per cent4 of real lactic acid in the sample4 ,if other acids are present1 they are of course included4 ,commercial lactic acid is usually of about #ej per cent4 ,it is important that the lactic acid should be free from iron1 a dilute solution should give no blue coloration on addition of either potassium ferrocyanide or ferricyanide4 ,acid perfectly free from iron is now easily obtained4 ,formic acid in #fj per cent4 solution1 formed synthetically by the combination of carbon monoxide with caustic soda and the subsequent decomposition of the sodium formate so produced1 has recently been brought into commerce at a cheap rate1 and will probably form a satisfactory substitute for acetic acid in the deliming of hides and many other technical operations4 ,instead of acids1 many neutral salts may be used to neutralise lime1 and in sole-leather1 it is not generally disadvantageous to leave the lime in the hide1 so long as it is in an insoluble and fixed condition1 and combined with an acid which cannot be displaced by tannin4 ,thus phosphates1 or oxalates of sodium or ammonium will convert the lime into insoluble phosphate1 or oxalate1 setting free sodium- or ammonium-hydrate which form soluble tannates and other salts which are easily washed out of the hide4 ,zinc sulphate will form sulphate of lime and zinc oxide in the hide1 and seems worth further experiment for sole-leather1 but must be free from iron4 ,alum1 or sulphate of alumina1 would similarly form calcium sulphate and alumina1 but the tanning effect of alumina salts is too great to admit of their general use for bating4 ,ammonium sulphate will form calcium sulphate with liberation of ammonia4 ,for dressing leather1 the use of ammonium chloride would be still more advantageous1 and it is a powerful bating material1 converting the lime into calcium chloride with the evolution of ammonia1 which has but little plumping power1 and which is easily washed out4 ,ammonium chloride has been very successfully used in calf-kid manufacture as a preparation for drenching1 instead of puering1 which was formerly in vogue4 ,as1 however1 only about oz4 per dozen skins was employed1 the cleansing must have mainly depended on the warm water with which it was used1 and the free ammonia evolved4 ,the use of ammonium chloride as a bate was patented by ,zollickoffer in #ahch4 ,a bating liquor which was proposed by the writer1 and which has been used with some success on harness-leather1 is made up with a lb4 of good white ammonium chloride 7sal ammoniac7 and a lb4 of ,boakes' 8metabisulphite of soda0 per hide1 and for successive packs sufficient sulphuric acid to neutralise the ammonia formed1 together with a small quantity of metabisulphite and ammonium chloride to restore that carried out by the hides is added4 ,it is probable that this would also answer well for deliming sole-leather as it entirely removes lime without pulling down the hides much1 and they would remain still plumper if ammonium sulphate were substituted for ammonium chloride1 while the sulphuric acid might be safely increased till the liquor was but slightly alkaline when the bating was finished4 ,about #b-d oz4 of good white oil of vitriol is required per hide1 but the exact quantity will depend on the mode of liming1 and the amount of washing the hides receive before going into the bate1 and can therefore be only ascertained by experience4 ,as no free sulphuric acid can exist in the liquor so long as the quantity of metabisulphite is maintained1 there is no practical danger of spoiling the leather if the acid be in slight excess4 ,the quantities given may in most cases be advantageously diminished1 since it is not always advisable in practice to remove the whole of the lime1 which in small quantity renders tannage and penetration of the liquor much more rapid1 either by acting as a mordant to the tannin1 or by temporarily neutralising it and diminishing its astringent action on the hide-fibre4 ,turning to dressing leather1 we find that the use of cold water alone has been practically abandoned in this country1 though the finest ,french calf is produced by repeated soakings in cold water with alternate workings over the beam1 sometimes extending to nine or more4 ,in this case1 from the lengthened exposure to waters which are only gradually renewed it is probable that putrefactive action takes place1 and that a sort of bating is effected by the decomposing products of the hide itself2 in fact1 in many ,french yards1 bran-drenches have been introduced to supplement the action of the water alone4 ,waters differ greatly in their power of removing lime from skin4 ,slightly acid and peaty waters1 and those in general which contain much organic matter1 are much more powerful in reducing than those which are purer 7cp4 p4 #ajg74 ,warm water has much more effect in removing lime than cold1 since the heat lessens the risk of dissolved carbonic acid1 and seems to have a direct depleting effect on the pelt4 ,a good tumbling in warm soft water will remove a great deal of lime1 and is an excellent preparation for bating1 but heat must be used cautiously1 and should never exceed #cj-ce ,c42 some skins1 such as seals1 being very readily tendered by its action1 while others1 especially sheep-skins1 will stand a comparatively high temperature4 ,the use of a solution of carbonic acid for removing lime has been patented by ,nesbitt1#ij who takes advantage of the fact that calcium carbonate is soluble in excess of carbonic acid 7p4 #id74 ,the gas1 which he generates1 as for soda water1 by the action of acids on chalk1 or limestone1 is received in a gasholder1 and forced by a compressing pump into the vessel containing the hides1 which is preferably a rotating drum lined with copper1 and capable of bearing a pressure of about three atmospheres4 ,the invention excited considerable interest on its introduction1 as the gas is1 certainly1 quite uninjurious to the hides1 and it was claimed that it enabled the grease and dirt to be better removed than by the ordinary methods4 ,further experience has shown1 however1 that the removal of the lime is far from complete1 since1 for success1 it is not only necessary to bring it into solution1 but to wash it out with carbonic acid solution under pressure1 as on exposure to the air1 solutions of lime in excess of carbonic acid rapidly deposit calcium carbonate4 ,at the present time1 the only tannery in which to my knowledge the process is in use is that of ,messrs4 ,mossop and ,garland1 of ,capetown1 who state that it answers very well for harness-leather when a pure lime made by calcining sea-shells is used for liming1 but is not satisfactory with ordinary stone lime4 ,it is difficult to account for this on chemical grounds4 ,gluestuff may be treated very satisfactorily by simply blowing carbon dioxide1 or washed and cooled lime-kiln- or furnace-gases1 into an open pit in which the material is kept agitated4 ,in this case1 however1 there is no need for the actual removal of the lime1 so long as it is carbonated and its caustic character destroyed4 ,carbonic acid does not decompose lime-soap1 and hence sets free no fatty acids1 which1 together with grease1 are the main cause of the turbidity of glue1 and the process therefore yields a more brilliant though darker coloured glue than does treatment with sulphurous acid4 #ij ,eng4 ,pats4 #ggdd and #ab1fha1 #ahhf4 ,several acids of the aromatic series have been from time to time recommended as deliming agents1 and generally possess the merit of acting at the same time as powerful antiseptics4 ,in this connection it may be well to mention the solution of #a per cent4 of phenol and #b per cent4 of boric acid used by ,dr4 ,parker and the writer for preparing and preserving skins for colour tests 7,l4,i4,l4,b41 p4 #acc74 ,this answers very well as a bate even when much diluted1 and may be rendered cheap enough for use in practice by the employment of a good commercial carbolic acid instead of pure phenol1 and the use of sulphuric acid to remove lime from the solution and render it capable of repeated employment4 ,the carbolic acid should not be too dark in colour1 and should be carefully dissolved1 or 8carbolic0 stains will result4 8,cresotinic acid10 a mixture of impure acids obtained from cresols in the same way as salicylic acid is manufactured from pure phenol1 was introduced as a bate and unhairing and deliming agent by ,j4 ,hauff1 of ,feuerbach4#ia ,he also claims the use of hydrochloric acid to liberate the acid after it has been combined with lime in the deliming process4 ,it is only soluble to the extent of about #a in #hjj of water1 so that1 even if used in excess1 no dangerously strong solution is formed1 but it has a tendency to slightly swell1 and somewhat harden1 the hides or skins1 so that it is perhaps more suitable for sole than dressing leather4 ,it has also powerful disinfectant properties 7see p4 #bi74ib #ia ,eng4 ,pat4 #ad1hhi1 #ahhh4 #ib ,compare also ,journ4 ,soc4 ,chem4 ,ind41 #ahhi1 p4 #ied4 ,hauff states that a solution of #ah lb4 of cresotinic acid in #ejj gallons of water at #cj ,c4 will bate one lot of #ej heavy hides1 and that the same liquor may be used continuously1 by adding #d-e lb4 more cresotinic acid for each successive #ej hides4 ,for bating glove-leather1 ,hauff recommends the use of #e kilos4 cresotinic acid dissolved in #ajjj liters of warm water for every #ejj kilos4 of wet skins1 to which is added ammonia nearly sufficient to neutralise the cresotinic acid1 leaving the solution still slightly acid to litmus paper2 and he also advises the addition of #e kilos4 of ammonium chloride or sulphate4 ,the goods are paddled in this solution for about half an hour4 8,oxynaphthoic acid10 the corresponding mixed acids of the naphthols 7p4 #cj71 has also been patented by ,hauff as a bate1 since cresotinic acid sometimes acts too powerfully on light skins4#ic ,he mentions that mixtures of this and cresotinic acid1 or salicylic acid1 may also be used4 ,oxynaphthoic acid requires for its solution #bj1jjj to #cj1jjj parts of water4 #ic ,eng4 ,pats4 #aj1aaj and #ab1eba4 ,journ4 ,soc4 ,chem4 ,ind41 #ahhi1 pp4 #abd1 #hji2 #ahij1 p4 #he4 ,a mixture of the and mono- and di-sulphonic acids of naphthalene has also been patented for bating1#id under the name of 8,acrilene bating and puering acid40 #aej calf-skins1 weighing #hhj lb41 were pured in a #c per cent4 solution of the acid1 and gave #bff lb4 of leather as against #bee lb4 from a lot of similar weight treated with hen-dung1 and this gain was more than maintained on stuffing1 while the shoulders were plumper and fuller4 ,this patent appears to anticipate a part of ,hauff's claim mentioned in the next paragraph4 #id ,burns and ,hull1 ,eng4 ,pat4 #hjif1 #ahia2 ,journ4 ,soc4 ,chem4 ,ind41 #ahib1 p4 #dh4 ,more recently ,hauff has patented1 under the name of 8anticalcium10 a mixture of impure sulphonic acids of various cresols and hydrocarbons4 ,this is cheaper than cresotinic acid1 and like it1 possesses considerable antiseptic powers4 ,one-half to one-quarter per cent4 solution will keep hides uninjured for a considerable time1 but at this strength it plumps considerably1 and seems more suitable as a deliming agent for sole-leather than as a bate for dressing-leather1 though it may replace drenching4 ,no doubt1 by the use of warm water1 and avoidance of excess of acid1 skins could be pulled down satisfactorily1 or the plumping could be controlled by addition of salt1 but the disinfectant powers of the acid would render further treatment with an ordinary bate or puer very difficult4#ie #ie ,j4 ,hauff1 ,eng4 ,pat4 #bb1edf1 #ahid2 ,journ4 ,soc4 ,chem4 ,ind41 #ahie1 p4 #agj1 ,gerber1 #ahie1 p4 #acc4 ,the 8,c4 ,t4 ,bate10 manufactured by the ,martin ,dennis ,chrome ,company1 is of a very similar character2 and is in the form of a greyish crystalline paste1 consisting mainly of sulphonic acids of naphthalene and probably other hydrocarbons4 ,it is very possibly made by sulphonating coal-creasote oils1 which contain much naphthalene and phenanthrene4 ,the following directions are given by the company for its use4 8#a4 ,after unhairing and fleshing from the lime1 the skins should be thoroughly washed with water 7preferably warm7 so as to remove as much lime as possible4 #b4 ,if1 in the liming process1 the sulphide of sodium is used in combination with the lime1 it will render the lime more soluble and therefore more easily removed with water4 #c4 ,the more completely the skins are cleansed with warm water the less will be the quantity of bate required4 #d4 ,after washing1 the skins should be thoroughly worked on the beam1 especially on the grain4 #e4 ,a solution of ,c4 ,t4 ,bate is now prepared in the proportion of from one-half pound to one pound of bate in #ajj gallons of warm water 7#ij ,f474 ,in making the solution do not have the water over #adj ,f4 ,under no circumstances boil it4 #f4 ,if the hides or skins have been treated as above indicated1 one pound of bate should be sufficient for #djj pounds wet hide1 washed from the limes4 ,the hides or skins are placed in the bating solution and worked for an hour4 ,they are then allowed to rest in the solution with occasional stirring for some hours or over night4 #g4 ,the length of time that the bating should continue will depend upon the degree of softness and pliability required in the leather4 ,for instance1 for sole-leather fifteen minutes is sufficient2 for satin leather thirty minutes2 for glove-leathers four to six hours or even longer4 #h4 ,on removing the skins from the bating solution it is sometimes desirable1 especially for the finer grades of leather1 to wash them in warm water and again work them over the beam4 ,they are then ready to be placed in the tanning liquors4 #i4 ,in preparing the bating solution for the second pack1 draw down the old solution one-third and replace with fresh water2 then add in solution just one-half the quantity of bate used at first1 and so on with each succeeding pack4 #aj4 ,when fresh white limes are used toward the end of the liming process1 and a manure bate is deemed necessary to reduce the harshness of grain caused by the fresh lime1 it is very beneficial to give the skins from the manure bate a drench of ,c4 ,t4 ,bate1 thereby arresting the bacterial action of the manure bate1 preserving the grain1 besides cleansing1 bleaching and neutralising the skins preparatory to placing them in the tanning liquors4 #aa4 ,again1 when it is considered desirable to use a manure bate1 it is good practice to treat the skins as above indicated 7down to item ,no4 #g71 and then place them in the manure bate4 ,by this previous treatment the antiseptic action of the ,c4 ,t4 ,bate tends to arrest the destructive bacterial action of the manure bate1 thereby lessening the risk of damage to the grain4 ,in all cases where the value of the leather is dependent on the quality and perfection of the grain1 this is an important advantage to gain40 ,all these coal tar 8bates0 are rather suitable to replace drenching than bating or puering1 as their effect is mainly that of removing lime4 ,from their antiseptic character they are very useful in stopping the effects of putrefaction1 and preventing ferments being carried into the tanning liquors1 and skins may safely be kept at least for some days in weak solutions1 but any necessary fermentive puering or bating should usually be done before and not after their use4 ,a writer in the #8,gerber1' #ahge1 p4 #bgi1 recommends the use of dilute solution of sulphide of sodium as a bating agent4 ,possibly it removes lime as sulphydrate1 and the writer named seems to have obtained good results with glove lamb-skins4 ,in experiments made at the ,yorkshire ,college1 a solution of #d grm4 per litre used on #dj grm4 of pelt was found to plump it considerably1 but probably a much weaker solution might be sufficient and more satisfactory4 ,polysulphides1 such as 8liver of sulphur10 or the yellow solution obtained by boiling dilute sodium sulphide or sodium hydrate solution with excess of sulphur1 have great power of 8bringing down0 the pelt1 and seem well worthy of experiment as bating agents4 ,in ,india1 the pods of the babool 7,acacia arabica7 are much used as a bate1 the infusion being allowed to ferment4 ,in their dry state they contain about #ab per cent4 of an easily changeable tannin1 which does not precipitate lime-water1 and which by fermentation is very probably converted into gallic acid4 ,the use of gallic acid itself as a bate has been patented by ,albert ,hull1#if and would undoubtedly accomplish the removal of the lime if used in sufficient quantity2 but as he only uses a solution of #be mgr4 per litre 7one part in #dj1jjj7 any effect must be mainly due to the washing with water4 ,gallic acid forms dark oxidation products with lime4 #if ,eng4 ,pat4 #ad1eie1 #ahhi4 ,of the fermentive methods of removing lime1 8drenching0 with fermenting bran-infusions is the simplest in theory1 and has been very carefully investigated by ,mr4 ,j4 ,t4 ,wood4#ig ,it will1 therefore1 be convenient to consider this process first1 although it is frequently employed as a means of cleansing and slightly plumping the skin after the lime has been removed by puering or bating4 ,in calf-kid manufacture1 however1 it is now used without previous puering1 and in some other cases it is substituted for the use of dung bates4 ,the most important of the active ferments are two species of bacteria1 named by ,wood ,bacterium furfuris and 1 which are very similar in their form and action 7see ,l4,i4,l4,b41 p4 #bfd71 but produce a somewhat better fermentation together than separately4 ,they are shown in ,figs4 #cd and #ce4 #ig ,journ4 ,soc4 ,chem4 ,ind41 #ahij1 p4 #bg2 #ahic1 p4 #dbb2 #ahig1 p4 #eaj2 ,brit4 ,assoc4 ,rep41 #ahic1 p4 #gbc4 ,illustration3 ,,fig4 #cd4--;,bacterium furfuris 4 ,illustration3 ,,fig4 #ce4--;,bacterium furfuris 4 ,neither species has any direct action on the hide substance1 but ferments the glucose produced by the action of the cerealin of the bran on the starch which is present4 ,a considerable quantity of hydrogen1 with carbon dioxide1 nitrogen and small quantities of hydrogen sulphide1 are produced during the fermentation1 together with lactic and acetic1 and traces of formic and butyric acids and amines4 ,active drenches contain #a-c grm4 of mixed acids per liter1 to which they owe their action1 a perfectly satisfactory drenching being produced by an artificial drench containing #je grm4 of glacial acetic acid and #a grm4 of lactic acid 7sp4 gr4 #abaj7 per liter in which the skins were worked for #a-b hours1 while #ab-af hours would have been required in the ordinary drench4 ,an experimental drench gave the following results on analysis3-- ,formic acid #jjcjf grm4 per litre ,acetic acid #jbdjb ,butyric acid #jjacd ,lactic acid #jgijg ------ ,total #ajgdi ,it is probable that other organisms are capable of producing similar fermentations1 and it is not certain that in all tanneries the same ferments are present4 ,mr4 ,a4 ,n4 ,palmer states that at the ,cambrian ,leather ,works at ,wrexham1 he has been unable to detect lactic acid in the drenches1 all the acids present being of the acetic series4 ,the drench-ferments investigated by ,wood are incapable of attacking or injuring the hide1 and1 in his opinion1 when the skin is attacked1 it is generally due to putrefactive and gelatine-liquefying organisms introduced from the bates1 or from the air in hot sultry weather4 ,drenching takes place most safely and satisfactorily at temperatures not exceeding #cj-ce ,c41 when the process is usually complete in #ab-bd hours4 ,in hot sultry weather a butyric fermentation of an active character sometimes suddenly takes the place of the normal one 7,ger4 ,umschlagen71 the skins swell rapidly1 become translucent 7glasig7 and finally dissolve to a jelly4 ,if tanned in the swollen condition1 tender and useless leather results1 and the injury1 once begun1 proceeds with alarming rapidity1 skins being sometimes completely ruined in a few hours4 ,prompt action is therefore necessary1 and the first step to take is to add salt1 which checks the fermentation1 and acts in the same way as in the pickling process1 controlling the action of the acid1 and producing a sort of tawing4 ,such skins will yield sound leather1 though the grain is apt to be somewhat drawn4 ,if the skins can be immediately got out of the drench1 the acid may be neutralised by the cautious addition of ammonia1 soda1 or whitening to the water in which they are placed1 preferably in a paddle1 and if they are insufficiently drenched they may then be paddled in tepid water1 though this is hardly likely to be needed1 as the effect of the acid is to remove the lime very completely4 ,the objection to the use of whitening1 which otherwise is the safest and best material to employ for removing acid from pelt1 is that it is apt to become mechanically fixed in the grain1 and1 thus1 to produce bad colour with vegetable tans4 ,for white or chrome leather it would do no harm4 ,precautions to prevent the recurrence of the injury are to keep the temperature of the drench low1 and to free the bran from flour by washing in two or three cold waters1 before adding to it the hot water with which the actual drench-liquor is made1 since the flour1 or at least its starch1 is the source from which the butyric acid1 as well as the lactic1 is formed4 ,in cold weather1 where drenching is proceeding in a normal way1 the flour is useful1 since it is the natural nutriment of the drench-ferment2 and1 in ,england1 flour is frequently added purposely to the bran to increase the activity of the drench4 ,to retain the flour1 the bran may be washed first with boiling water1 which gelatinises the starch and makes it adhere to the bran1 and1 according to ,eitner1 removes a sticky fatlike matter from it1 and fits it better to remove the fat of the skin4 ,after soaking in hot water for two hours1 it is washed in several cold waters and infused at about #dj ,c4 for use4#ih ,many tanners use the bran without previous washing1 but if much flour is present it rises to the top with the gas evolved by the fermentation1 and forms a pasty mass on the skins1 which interferes with even drenching4 #ih ,gerber1 #ahhb1 p4 #bdf4 ,the quantity of bran used in ordinary drenching is very variable1 but about #d parts per #ajjj of water used and from #e to #aj per cent4 on the weight of pelt may be taken as an average quantity1 more being frequently employed4 ,the temperature may vary from #aj up to about #cj-ce ,c41 and the time inversely from days or weeks down to two or three hours1 according to the temperature of the drench1 the amount of ferment present1 and the thickness and character of the skins4 ,the skins are usually thrown into the freshly prepared drench1 to which a few pailfuls of old drench-liquor is frequently added as a ferment4 ,fermentation soon sets in1 and the gas evolved causes the skins to float to the surface2 this is called the 8working0 of the drench4 ,thin skins may be sufficiently drenched after once rising1 while thick ones require to be put down two or three times4 ,a certain sign of sufficient drenching is the appearance of small blisters on the grain1 caused by the evolution of gas in the substance of the skin4 ,when these are seen the drenching should be at once discontinued1 as otherwise the blisters will increase in number and burst through the grain1 causing minute holes or 8pricks0 7one of the many forms of the complaint called in ,german ,pikiren or ,piquieren74 ,when a bubble of air is enclosed in a fold of the sufficiently drenched skin and pressed1 it raises the grain without actually separating it from the substance of the skin4 ,the properly drenched skin also falls easily in folds when held between the hands either lengthways or crossways1 and if thin1 the skin tightly stretched over the hand shows grains of bran underneath it as little lumps1 round which the skin clings to the hand4 ,the drenched skin should not be transparent1 but white and soft2 and when pressed should retain the mark of the finger4 ,some experience is required to determine certainly the point of sufficient drenching1 which1 of course1 varies with the character of the skins1 and the kind of leather which is to be produced2 and the feel of the skin to a practised hand is one of the most important criteria4 ,a writer in the #8,gerber'#ii divides drenching into three classes--8sweet10 8alcoholic0 and 8sour40 ,sweet drenching is done in a bath of tepid bran-water1 made by infusing in hot water and drawing the clear liquor off the bran1 which settles to the bottom4 ,the skins are only allowed to remain in #b-c hours1 or not long enough for fermentation to set in4 ,the process is only suited for very thin or soft skins1 which will not stand any further loosening4 ,the use of bran-water has the advantage of saving the labour of 8branning10 or removing adhering bran with the knife on the beam1 but it is doubtful if unfermented bran has much actual effect4 ,bran-water can1 however1 be used for drenching by fermentation1 and for small glove-lamb has largely superseded the older method4 ,the mechanical action of the bran in cleansing the pelt is however often useful4 ,in sour drenching the bran is allowed to steep and soften in cold water for many hours1 and boiling water is then added till the temperature is raised to #ge ,c41 and it is allowed to infuse with frequent stirring for some hours1 and after cooling to #de a considerable quantity of old drench-liquor is added as a ferment4 ,if the drench is used warm 7#cj-ce1 or1 in cold weather1 even #dj ,c471 the skins only remain in #a-c hours1 but if cold the drenching can be extended over a period of #b-c days1 the skins being frequently handled4 ,this modification is suitable for glac-kid and the harder sorts of skins1 but glove-lamb are always treated by the warm and rapid process4 ,what the writer in the #8,gerber' describes as the 8alcoholic0 bran-drench is probably the method of fermentation investigated by ,mr4 ,wood1 in which ordinary inflammable gases1 but no alcohol1 are produced4 #ii ,gerber1 #ahhh1 p4 #beg4 ,a normal drench plumps the goods slightly1 but if it contains much of the putrid ferments carried in from the bate or puer the skins fall in it as they would do in a bate4 ,to increase this effect1 putrid soak-liquor is sometimes added to the drench1 but with doubtful advantage4 ,in drench-liquors the total acidity may be determined by titration with lime-water or ,n_/#aj caustic soda1 with phenolphthalein as indicator2 and the volatile acids may be distilled off as described under the analysis of tanning liquors 7,l4,i4,l4,b41 p4 #abf74 ,for more complete methods of analysis the reader is referred to ,messrs4 ,wood and ,willcox's paper on the 8,nature of ,bran ,fermentation40#ajj #ajj ,journ4 ,soc4 ,chem4 ,ind41 #ahic1 p4 #dbb4 ,drenches are said to 8work0 somewhat better if made with water containing nitrates1 and this is quite probable2 but the necessary nitrogen can easily be supplied if required by the addition of a very small quantity of saltpetre4 ,wood is of the opinion that the ferments found in bran do not originate in the drench itself1 but come from the bated skins1 as the drench-bacteria soon die out without finishing the fermentation1 and constant renewing of the nutrient material is necessary 7cp4 p4 #ah74 ,bating and puering1 though differing practically in many ways1 are identical in theory1 and most of what follows applies to both of them4 ,the action is much more complex than that of the drench1 involving both chemical reactions and those of organised and unorganised ferments1 and it is a matter of no little difficulty to say what proportion of the observed effect should be ascribed to each of these agencies4 ,formerly1 the principal effect was attributed to organic salts of ammonia and its homologues1 and to amido-acids which combine with lime4 ,phosphoric acid is also present1 and if any exists in the form of soluble salts1 it will combine with lime1 and render it insoluble and inactive4 ,it is probable1 however1 that most if not all the phosphoric acid is already in the form of tricalcium phosphate1 and therefore without effect4 ,it is now1 however1 recognised that the effects of these chemicals are of no importance as compared with the products of bacterial action1 and the researches of ,j4 ,t4 ,wood have cleared up much that was until recently quite inexplicable4#aja #aja ,journ4 ,soc4 ,chem4 ,ind41 #ahid1 p4 #bah2 #ahie1 p4 #ddi2 #ahih1 pp4 #hef1 #ajaj2 #ahii1 pp4 #aag1 #iij4 ,much effect has been ascribed to the digestive ferments1 such as pepsin and trypsin1 which are present in fresh dung4 ,it is known that the animal organism secretes these in considerable excess of its requirements1 but it is doubtful whether any exist undecomposed1 even in fresh dung2 though they are apparently more resistant to putrefaction and decomposition than would a priori have been expected of such complex organic compounds1 and there is therefore a possibility of their existence in the dung1 even as it comes to be used in the tannery4 ,both pepsin and trypsin are enzymes 7see p4 #af71 and belong to the great class of albuminoids4 ,they are soluble in water1 but insoluble in alcohol1 and hence are precipitated by the addition of the latter to their solution1 but are not altered by it1 and regain their activity on solution in water4 ,by heat they are coagulated and decomposed1 and their activity permanently destroyed4 ,pepsin is the active principle of the secretion of the glands of the stomach1 and large quantities are prepared for medical use as an aid to digestion from the stomachs of pigs4 ,pepsin only acts in slightly acid solution1 and1 though fresh bate liquor is slightly acid to litmus1 it speedily becomes alkaline from the lime of the skins and the ammonia present1 so that the action of pepsin in a bate can only be a very limited one4 ,wood#ajb compared the action of a #a per cent4 solution of pepsin1 acidified with #jb per cent4 of hydrochloric acid1 with that of a dogs' dung puer liquor1 both at the temperature of #dj ,c4 ,at the end of one hour the skin in the pepsin-solution was considerably fallen1 but that in the puer-solution was almost dissolved4 ,since the solution here employed was much stronger than is likely to occur in practice1 and the conditions much more favourable to its action1 it may be assumed that the practical effect of traces of pepsin in the bate may be neglected4 #ajb ,journ4 ,soc4 ,chem4 ,ind41 #ahid1 p4 #bbj4 ,trypsin or pancreatin#ajc if present1 is more likely to have an effect1 since it is active in neutral and in alkaline solutions4 ,it is the product of the pancreas1 and is largely concerned in intestinal digestion4 ,chemically it much resembles pepsin1 but is more resistant to heat1 retaining its power of digestion after heating to a temperature of #afj ,c4 in a dry condition4 ,its warmed solution dissolves fibrin almost instantly1 and in large quantity1 and peptonises gelatin and hide-fibre1 so as to render them soluble in water4 ,wood found that a #a per cent4 solution of pancreatin acted far more rapidly than a solution of pepsin of equal strength4 ,at #dj ,c4 in neutral solution1 the skin fell rapidly1 and the action continued even in the cold4 ,in #ae hours the liquid was swarming with minute bacteria4 ,at the suggestion of the ,author1 the experiment was therefore repeated1 with the addition of #ae per cent4 of chloroform1 which prevented the development of bacteria1 while it did not stop the action of the pancreatin4 ,the skin fell as before1 but in neither case had it the peculiar touch of puered skin1 nor were the characteristics of the leather produced from it the same4 ,we may therefore conclude that1 though trypsin may contribute to the action of the bate or puer1 it can only do so in a minor degree1 and that the principal effect of the bate or puer is due to other causes4 ,it is certain1 however1 that fresh bird-dung1 and probably that of all animals1 contains ferments capable of liquefying gelatin4 ,an instance of this is found in the observation1 common in glue manufacture1 that if the dropping of a sparrow falls on a cooler full of solidified gelatine size1 it will liquefy a track quite down to the bottom of the cooler4 ,trypsin1 or at least the secretion of the pancreas1 as well as the gall from the liver1 have great power of wetting and emulsifying fats1 and this has possibly something to do with the action of the bate in enabling the skins to be cleansed of fat4 #ajc ,loc4 cit4 and ,beilstein1 iii4 p4 #acjh1 #bnd ed4 ,bacterial fermentation and its products are however the main factor in the action of puers and bates1 and on this subject we owe most of our knowledge to the work of ,j4 ,t4 ,wood1 since1 though ,popp and ,becker have worked over much of the same ground1 they have not nearly so freely published their results4 ,wood showed that a fresh puer liquor1 even when boiled for half an hour and so freed from living organisms and albuminoid ferments1 has still considerable action on a limed skin1 though much less than the unboiled puer4 ,he found that this action was principally due to amines and their compounds with organic acids1 which removed lime1 but did not remove the interfibrillary substance or give the proper feel of puered skin4 ,a very similar result was obtained with aniline 7phenyl-amine7 hydrochloride in #a per cent4 solution4 ,a considerable variety of bacteria from dung and other sources were cultivated in various media and their puering power tested1 but though greater than that of the unorganised chemical compounds such as amine salts and organic acids1 it was in no case equal to that of an ordinary puer1 or sufficient for practical use4 ,when1 however1 a small quantity of the amine salts obtained from the puer were added to a mixed bacterial culture the effect on the skin was almost as rapid and considerable as with an actual puer4 ,in order to determine whether the puering effect was due to the direct action of the bacteria or to their enzyme-products1 the latter were separated from a filtered puer solution by adding it to a large volume of #ih per cent4 alcohol in which the enzymes are insoluble4 ,when redissolved in water1 they had a decided puering effect1 and a solution of #je grm4 of the mixed enzymes and #je grm4 of the mixed amine hydrochlorides in #ajj c4c4 of water at #cej ,c4 brought down a piece of limed sheep-skin in thirty minutes exactly like a puer4 ,the action is therefore dependent on the mutual action of the enzymes and amine salts1 but as the separation of these would be too costly for practical use1 and the puering proved more effectual when they were formed in contact with the skin by active bacteria1 ,wood adopted the method of preparing a suitable sterilised nutritive liquid1 which was inoculated before use with a mixed culture of suitable bacteria4 ,for laboratory purposes a suitable culture-medium was obtained by digesting #aj grm4 of gelatine with #e grm4 of lactic acid 7reckoned water-free7 and #ajj c4c4 of water for three hours in a closed vessel on the water-bath4 ,the resultant solution was neutralised with sodium carbonate and diluted to #a litre with addition of a small quantity of potassium phosphate4 ,the bacteria of fresh dog-dung were not found to possess a satisfactory puering effect1 but those from dung which had been fermented a month 7as in practice7 gave a result nearly equal to actual puer4 ,a still better result was obtained by a mixed culture from the roots of wool loosened by sweating4 ,the bacteria were principally of two species1 of which neither separately was capable of satisfactory puering2 but which together acted more rapidly than an actual puer4 ,these bacteria do not liquefy gelatine4 ,during the course of his experiments1 ,wood found that filtered puer solutions were less active than turbid ones and that their activity was increased even by the addition of inert substances1 such as kaolin4 ,wood attributes the differences in action between dog-dung and bird-dung not only to different bacteria1 but to the fact that in the latter case the urinary products1 and especially uric acid are contained in the dung4 ,from the results of these and similar researches1 ,wood in ,england1 and ,popp and ,becker in ,germany succeeded in producing a practical artificial puer1 which they now manufacture in conjunction under the name of 8,erodin40 8,erodin0 consists of a solid nutrient medium and a liquid 8pure culture0 of the bacteria necessary to effect the required bating or puering4 ,the following are the directions for working with erodin bate1 as supplied by the manufacturers3-- 8,for #ajj lb4 of wet skin washed ready for bating1 about #a lb4 of erodin is required4 ,or in the metric system1 #a kilo4 wet skin requires about #aj grm4 erodin4 ,the strength or concentration of the bate must not fall below #c grm4 per litre of bate liquor1 i4e4 oz4 per gallon4 ,for preparing the bate a sufficiently large cask or tub carefully cleaned and steamed out is placed near the bating paddle4 ,the cask should be fitted with a steam pipe easily screwed on and off1 and also furnished with a clean cover4 ,the requisite quantity of erodin is weighed out and put into the tub with fifty times its weight of water1 and the whole brought up to a temperature reaching but not exceeding #dj ,c4 7#ajd ,f47 by direct admission of steam1 thoroughly stirred1 and the pure culture of ,bacillus erodiens added to the mixture4 ,the temperature must not be allowed to fall below #be;,c4 7#hg ,f471 and a little steam should be admitted first thing in the morning1 again at noon1 and in the evening1 to bring the temperature up to #dj ,c4 7#ajd ,f474 ,a practical mode of procedure is as follows3--,on ,friday make up and start fermenting twice as much erodin as will be required for a day's work4 ,this is allowed to remain under the above-mentioned conditions until ,monday4 ,on ,monday half the amount will be used for bating2 this is replaced by an equivalent amount of fresh erodin powder1 dissolved in fifty times its weight of water1 which is added to the already fermented erodin in the tub4 ,proceed in this way each day until the following ,friday1 when there will be left in the tub sufficient erodin for one day4 ,this is put into a smaller tub for use on ,saturday1 and the cycle of operation begun again4 ,one pure culture of ,bacillus erodiens should be used for every #aa lb4 7#e kilos47 erodin powder or less quantity4 ,suppose the amount of erodin required for a day's work to be #aa lb4 7#e kilos471 then on ,friday #bb lb4 7#aj kilos47 erodin must be mashed as above described in #aaj galls4 7#ejj litres7 water1 #b pure cultures added1 and allowed to ferment until ,monday4 ,on ,monday half of this is used1 and to the remainder #aa lb4 7#e kilos47 erodin and #ee galls4 7#bej litres7 water is added4 ,this is repeated on ,tuesday1 ,wednesday and ,thursday2 and on ,friday half is used and the remainder put into a separate cask for use on ,saturday1 and in the mashing cask a fresh quantity of #bb lb4 7#aj kilos47 erodin with #aaj galls4 7#ejj litres7 water is made up for use next week4#ajd #ajd ,mr4 ,wood has found that in many cases it is unnecessary to start afresh at the end of each week1 but that additional quantities of erodin solution with the accompanying bacterial culture may be added continuously to the stock-tub as required4 ,in puering1 the concentrated solution from the tub may be diluted with #d to #f times its volume of warm water4 ,the diluted liquor should usually only be used for one pack of skins4 ,on ,saturday the remainder of the old mash is used up4 ,in case this mode of procedure is for any reason not suited to the conditions of work1 erodin may be used by making up every day a fresh quantity with fifty times its weight of water1 adding the pure culture1 and allowing it to ferment three days before use40 ,in some cases the solution may be used for several consecutive packs1 merely adding water and a small quantity of erodin without a new culture4 ,erodin is being used most successfully in several large works both in ,england and abroad1 and on calf-skins and sheep-skins has proved quite as effective and much safer than dog-dung2 the skins coming out clean and free from stains4 ,it has been a good deal used in the experimental tannery of the ,yorkshire ,college1 and has proved a satisfactory substitute for puer1 but with the present bacterial cultures can only be employed warm1 and does not answer used cold like the ordinary pigeon-dung bate4 ,no doubt a suitable bacterial medium and culture can be found for cold bating1 which for thicker leathers is often preferable to puering1 and experiments in this direction are being undertaken4 ,from the multiplicity of germs present1 and the adaptability of the dung infusion as a nutrient medium for any putrefactive organisms which may gain access to it1 the bating and puering process is necessarily a dangerous one for the goods1 always leading to loss of weight1 and1 if the process is carried on too long1 to the more or less complete destruction of the skins4 ,loss of weight1 however1 in greater or lesser degree is inevitable1 and indeed necessary where a soft leather is to be produced4 ,if the skins are allowed to lie in the bate or puer liquor1 mud1 containing organisms1 and zoogla-forms of bacteria settle in the folds1 and produce marbled markings1 streaks and lines by the destruction of the grain surface 7hyaline layer74 ,black or bluish stains are also often produced1 known as bate-stains1 and either due to bacterial pigments1 or in some cases1 to the action of evolved hydrogen sulphide on iron present from salting or other sources4 ,frequent change of position is therefore necessary1 especially when the liquor is active from being used at a high temperature1 but it does not seem to be desirable to keep the skins in constant motion1 and if puering is done in a paddle1 it should only be run at intervals4 ,t4 ,palmer#aje determined in experiments on pigeon-dung bates that there is considerable loss of nitrogen during the process1 and recommended bating in pits from which the air was excluded as much as possible1 both as effecting a considerable economy in the dung1 and in excluding false ferments1 which1 he concludes1 are mostly aerobic4 ,it is not improbable that the method is advantageous1 since it has been shown by ,roscoe and ,scudder that liquefaction of gelatin only takes place in presence of oxygen1 and its partial exclusion would therefore lessen the risk of overbating1 and consequent damage and loss of weight4 #aje ,leather ,trade ,circular1 #bbnd ,sept41 #ahia2 #ahhg1 p4 #ffg2 and ,sanford1 ,journ4 ,soc4 ,chem4 ,ind41 #ahic1 p4 #ecj4 ,starting from the presumption that bating and puering are1 in the main1 bacterial processes1 more or less successful attempts had been made previous to those of ,wood1 ,popp and ,becker1 to substitute other fermenting substances for dung2 and probably these efforts failed in many cases1 not so much because they were wrong in principle1 as from want of knowledge of the necessary details1 such as the use of proper ferments1 and the provision of suitable culture-media4 ,guano1 prepared horse-flesh1 urine1 yeast1 and fermenting vegetables have all been tried4 ,a solution of glucose or treacle of about #aj per cent41 to which #c per cent4 of pasty dog-puer is added about a week before use1 was tried many years since in a morocco-factory1 at the suggestion of the writer1 as at least a partial substitute for puer1 and is still in use there4 ,the mixture keeps for some time in an active state1 and is added to the puer liquors in the same way and in approximately the same proportions as the dung paste4 ,similar in principle is the solid bate supplied by an ,american firm1 in which glucose is mixed with a small amount of nitrogenous matter and phosphates1 together with a lactic ferment1 and which only requires dissolving in warm water some little time before use4 ,its results are good for some purposes1 but rather resemble those of a drench than a bate4 ,in a similar way1 puer may be added to bran-drench liquors1 and induces in them a fermentation which brings the skins down much lower than the ordinary drench4 ,it is probable that a weak glucose solution1 with traces of mineral constituents similar to ,cohn's solution 7see ,l4,i4,l4,b41 p4 #bfi7 and 8set0 with sour milk1 or fermenting drench-liquor1 might in some cases be used with advantage for drenching1 with a saving of cost4 ,a writer in #8,hide and ,leather' describes a bate in which two parts by weight of glucose are dissolved in about #be parts of water1 and fermented1 for about three days1 till a foam gathers on the top1 with about one part of old bran drench-liquor1 or #ja part of pressed yeast1 and then made up with water to #ajjj parts4 ,the goods are bated #bd-cf hours at a temperature of about #ce ,c1 and the bate is strengthened for a second pack with about one-fifth of the original glucose1 a new bate being made at the end of a week1 and set with one part per thousand of the old one4 ,a short bating of say #aj hours produced very nice harness-leather1 but the general tendency was to make the goods looser and more spongy than a dung-bate4 ,it is obviously not a matter of indifference whether old drench1 or yeast1 is used to start the fermentation1 since in the latter case only alcohol could be produced directly by the ferment introduced1 though this might be fermented later1 by other accidental organisms1 into acetic acid4 ,these mixed bates1 containing glucose1 are however probably wrong in principle1 since the true puering and bating bacteria will not thrive in presence of acids1 and require nitrogenous nutriment4 ,as regards the relative effect of dog- and hen- or pigeon-dung bates1 the chief of the published experiments are those made by ,w4 ,j4 ,salomon at the ,vienna ,versuchsanstalt fr ,lederindustrie1#ajf in which he determined the relative solvent power of equal quantities as being1 for dog-dung #b1 for pigeon-dung #b1 and for hen-dung #a4 ,it is obvious that these figures1 though interesting1 must be taken with some reserve1 as the composition even of pure dungs is by no means constant1 depending on the feeding of the animals1 and adulteration is common4 ,the writer has heard stories of a certain dealer who used to fabricate his product from clay by the aid of a popgun1 though he does not vouch for the statement6 ,it is generally held that the action of bird-dung is more penetrating1 but less softening and loosening than that of dog-dung1 which is thus generally used for descriptions of leather where great softness and stretch are required4 ,it is to be remembered in this connection that bird-dung bates are generally used cold1 and hence are much slower in their action1 which allows them time to penetrate thicker hides more uniformly4 ,few analyses of the dungs used in leather manufacture have been published1 and these mostly with a view to manurial value4 ,schulze#ajg gives the result of forty analyses of pigeon-dung as follows3-- ,min4 ,max4 ,mean4 per cent4 per cent4 per cent4 ,water #chj #djjj #bajj ,nitrogen #adg #ejd #bec ,phosphoric acid #ajj #bgg #agi ,potash #jga #beg #adf ,one sample contained #dcc per cent4 of sand6 #ajf ,tech4 ,quart41 #ahib1 v4 p4 #ha4 #ajg ,der ,landwirt1 #ahie1 li4 p4 #cja4 ,wood#ajh quotes the following3-- ,hen-,dung4 ,per cent4 ,water #fjhh ,organic matter#aji #aibb ,phosphates #ddg ,calcium carbonate and sulphate #ghe ,alkaline salts #aji ,silica and sand #ffi ,dog-,dung4 ,water #caj ,ca #dcj ,na1 ,k1 ,mg #jh ,,po #cd ,,co #ge ,organic matter #adb ,traces ,fe1 ,cl1 ,si1 loss #ja #ajh ,journ4 ,soc4 ,chem4 ,ind41 #ahid1 p #bbj4 #aji ,containing nitrogen equal to #jgd per cent4 of ammonia4 ,this was apparently a sample from a dog fed on bones2 that from the kennels1 which is more commonly used in leather manufacture1 contains much less lime2 a sample analysed by ,wood gave #dg per cent4 mineral matter1 #ig per cent4 organic1 and #hef per cent4 of water1 part of which was no doubt added4 ,analysis4--,little or no attention has been paid to the analysis either of dungs for bating purposes1 or of the bating liquors1 and although the total cost of manure bates is a high one1 it is evident that such low- priced and irregular articles will not pay for elaborate analysis4 ,probably in some cases it would be worth while to make a determination of moisture and organic and mineral constituents by drying and ignition4 ,where a further investigation is desired1 the determination of the soluble matter by filtering and evaporating a portion of the solution to dryness1 and that of the nitrogen by ,kjeldahl's method 7see p4 #gj71 would be advisable1 and of course in the future1 when the subject is better understood1 a bacteriological examination may be useful4 ,if it is desired to estimate the solution of hide-substance in the use of bate or drench liquors1 the determination of the nitrogen in a measured quantity by ,kjeldahl's method will afford the best basis of calculation1 allowance being made for the nitrogen present in the original bate liquor4 ,hide-substance contains about #agh per cent4 of nitrogen4 ,in many cases1 simple weighing of the solid residue1 left on evaporating the liquor to dryness and drying for several hours at #ajj ,c41 with subsequent ignition to determine lime and other mineral matters1 will suffice4 ,the quantity of hen- or pigeon-dung used in bating hides is very variable1 but may be stated at from #ab to #fj litres per #ajjj kilos of raw hide1 in at least #bjjj litres of water4 ,the bate is generally used cold1 the hides remaining in it #d-h days1 with frequent handling2 but some tanners1 especially in the ,united ,states1 prefer bating in a paddle or drum at a temperature of about #ce ,c41 in which case the time must be diminished to a few hours4 ,the dung is best infused with warm water in a separate vessel1#aaj and allowed to ferment for at least a week without use1 when it will be found to swarm with micrococcus-chains4 ,only the clear liquor should be run into the bate-pit1 the sediment and dirt being thrown away1 or used as manure4 ,in this way the danger of stains and flaking is much reduced4 ,bates may be mended with fresh portions of dung-infusion for several successive packs of hides1 but should not be used too long1 as they gain in solvent power by the dissolved hide-substance and the increased fermentation1 and the method is not without risk4 #aaj ,this seems to have been first suggested by ,t4 ,palmer1 ,eng4 ,pat4 #ac1fcf1 #ahhf4 ,after bating1 the hides are usually 8worked0 78scudded10 8fine-haired07 on the beam1 to remove dirt and grease1 but in ,america a wash in the wash-wheel is often considered sufficient4 ,goods are occasionally 8stocked0 7p4 #aaf7 from the bates1 but this is not to be recommended1 as it is likely to drive out much of the partially dissolved hide-substance and produce undue looseness and loss of weight4 ,it is difficult to give any definite marks of sufficient bating other than the soft and fallen feel of the hides1 which is easily recognised by a practised hand4 ,one of the earliest signs of commencing overbating is the occurrence of bluish patches1 or a bluish tinge somewhat similar to an iron-stain1 which1 if slight1 generally disappears in a few days after the hides are taken into the liquors4 ,hen- and pigeon-dung is probably best kept air-dried1 though1 if very wet1 or for convenience for immediate use1 it may be kept in paste like dog-dung4 ,dog-dung should never be allowed to lie exposed to the air1 or it putrefies and turns black1 the bating ingredients are destroyed1 and it will not puer the goods which turn black and putrid without softening4 ,dung should1 therefore1 be mixed to a paste with water and kept in tanks1 so as to be but little exposed to the air1 when it will retain its puering properties for a long time unaffected4 ,fresh dung should be allowed to ferment for at least a week before use4 ,no accurate statement can be made as to the quantities required4 ,eitner states that #a-a pails of dung-paste 7say #ad-bj litres7 is sufficient for #bjj medium to large lamb-skins for glove-kid4 ,it should be sufficient to make the water quite turbid1 but not thick or soupy4 ,for lamb-skins a temperature of #ah-bj ,c4 is suitable1 which may be raised in very cold weather to #be ,c41 to allow for cooling4 ,the time required is from two hours for the thinnest slink skins1 to #ab-ad hours for strong ones4 ,it is well to use wooden1 and not iron1 utensils for handling the dung1 and it should be strained through a coarse cloth after diluting with water4 ,as has been remarked1 it is not desirable to keep the skins in constant motion in the puer2 they should be stirred or paddled for the first #bj-cj minutes1 and then for #aj minutes every hour for five or six hours1 after which they can be allowed to lie for a longer period without injury4 ,puering is sufficient when the skins feel quite soft and flaccid1 hanging in folds in any direction and allowing the flesh to be scraped off with the finger-nail4 ,wood recommends that1 for the puering of sheep-skins1 dung should be allowed to ferment one month before use1 and states that it deteriorates if kept over three months4 ,the puering products are the result of the successive action of many sorts of bacteria1 and ,wood is of opinion that those actually concerned in puering originate from the air1 or from the vessels in which the dung is stored1 and are not present in it when excreted4 ,borgman#aaa advises that the dung should be kept in a dry condition1 and only made into a paste between a fortnight and three weeks before use1 by covering in a clean cask with cold water1 and on the following day mixing to a smooth paste with a clean wooden 8poss-stick10 made from wood free from tannin4 ,the cask should then be covered up1 and allowed to rest undisturbed till required4 ,clean extract-casks are very suitable for the purpose1 if carefully and repeatedly steamed out1 and ,borgman advises that a regular series should be arranged1 so as to supply the dung required1 the date of mixing being carefully marked on each cask4 ,throughout the process the utmost cleanliness should be observed1 and the casks should be carefully steamed out as soon as emptied4 ,immediately before use the dung-paste should be heated by steaming nearly but not quite to boiling point1 care being taken to avoid the introduction of condensed water containing iron1 and the dung thoroughly mixed with a large quantity 7say #ajj gallons7 of water at #de-ej ,c41 allowed to settle1 and drawn off through a basket1 and strained into the puering paddle through a second basket lined with coarse open canvas 7such as is used by plasterers to cover windows while the plaster is drying74 ,a further quantity of warm water should be poured on the residue in the mixing tub1 and used for diluting that in the paddle to the proper volume4 ,the temperature of the liquor may reach #db ,c4 before the skins are introduced4 ,the liquor should be of a light colour1 greenish to brownish yellow2 if darker1 it indicates decomposition of the dung by improper storing1 or too long fermentation1 and will be liable to cause staining and injury to the skins4 ,about #cc liters of dry dung is required per #ajj kilos4 of wet skin prepared for puering 7#cc gallons per #ajjj lb474 ,dry dung should be of yellow to brown colour1 dark brown or black dung is spoiled and unsuitable for use4 ,wet dung is more difficult to judge1 but very dark brown or black should be rejected1 as well as that with a very strong smell1 indicating that it has already fermented4 ,borgman's directions bear the stamp of experience and common sense1 and the book as a whole repays study4 #aaa #8,die ,feinleder-,fabrikation1' ,berlin1 #aija1 p4 #fi4 ,borgman recommends that the skins should be warmed by paddling for some time in water of about #dj ,c4 to which a couple of pails of puer-paste have been added1 before bringing them into the puer1 the temperature of which they should reduce to perhaps #ch ,c4 ,the puered skins should feel silky on the grain1 and even somewhat slippery1 and when pressed between the finger and thumb a dark impress should be left1 and the flesh should be tender and easily scraped off4 ,the requisite condition will1 however1 vary somewhat with the kind of skins1 and the purpose for which they are intended4 ,after puering1 the skins may be paddled for half an hour in water of about the same temperature as the puer4 ,,chapter ,,xiv4 ,,alum ,,tannage ,,or ,,tawing4 ,we have now followed the raw material up to the final stage of preparation for its actual conversion into leather1 and it remains to consider the means by which that important change is produced4 ,though as yet the vegetable tanning process is most largely used1 and possesses the greatest commercial importance1 the use of mineral salts has long been known1 and1 through the advent of chrome tanning1 has placed the permanent supremacy of the vegetable tannins in considerable doubt4 ,not only the importance of mineral tanning processes1 but their greater simplicity from the scientific side1 justify their consideration before those of vegetable origin4 ,in the previous chapters it has been shown that to produce a permanent leather1 it is not only necessary to dry the fibres in a separate and non-adherent condition1 but so to coat them or alter their chemical character that they are no longer capable of being swelled and rendered sticky by water4 ,all salts which produce a contraction or dehydration of the fibre similar to that caused by alcohol are capable of the first effect in a greater or less degree4 ,many sulphates1 and particularly those of sodium and magnesium1 though they will not alone produce leather1 will so far contract the fibres as to greatly hasten tanning by vegetable tanning materials1 and they are therefore capable of useful application in quick tanning processes1 especially where tough and light-weighing leathers are aimed at1 which may be subsequently weighted and solidified by further treatment4 ,strong solutions of ammonium sulphate are almost as strongly dehydrating as alcohol1 and will produce white leathers very similar to those formed by pickling1 a fact which is certainly of considerable commercial importance4 ,none of these salts1 however1 can form a complete leather in themselves1 but require the assistance of metallic salts which will permanently fix themselves in the fibre1 and diminish or destroy its attraction for water4 ,many substances have this power in a greater or less degree1 but all those of commercial importance belong to the group of which aluminium1 iron and chromium are representative1 and which are capable of producing salt-forming oxides of the formula ,m,o 7e4g4 alumina1 ,al,o74 ,manganese1 of which the salts of this type are very unstable1 has very slight tanning power1 while titanium1 which in many ways is allied to the group1 though it does not strictly belong to it1 has recently been patented as a tanning agent4 ,for the present1 however1 we may limit our attention to the three metals first named4 ,alumina and its salts demand the first attention1 not only as having been used for leather manufacture in very early times1 but as being still important commercially4 ,the metal aluminium is now well known1 and its oxide1 alumina1 ,al,o is abundant in nature1 combined with silica in the form of clay and bauxite1 as fluoride in combination with sodium fluoride in cryolite1 and in some cases as a native sulphate4 ,alum-shale1 which was formerly the principal source of alum1 is a bituminous clay containing much iron sulphide1 and which when calcined yields aluminium sulphate4 ,as aluminium sulphate does not crystallise readily1 and was difficult to free from iron1 potassium sulphate was added to the liquor obtained by leaching the calcined shale1 from which1 after concentration by boiling1 potash-alum1 a double sulphate of potassium and aluminium1 ,al7,,so71,k,,so1#bd;,aq1 was easily crystallised out4 ,alum is now usually made by decomposing clay or bauxite with sulphuric acid1 and ammonium sulphate is generally substituted for the potassium salt1 yielding ammonia-alum1 a double sulphate of aluminium and ammonium of similar constitution to potash-alum4 ,ammonium alum is easily distinguished from the potassium salt1 by the strong smell of ammonia which it evolves on the addition of caustic soda or lime4 ,so far as is known1 there is no practical difference in tanning effect between the two salts1 and ammonium alum is cheaper1 and slightly stronger1 its molecular weight being #ijf1 as against #idh for the potassium salt4 ,either alum dissolves readily in cold water to the extent of about nine parts in #ajj of water1 and more easily1 and to a much larger extent in hot water1 from which the excess crystallises on cooling4 ,it is said that for purposes of leather manufacture1 alum solutions should not be boiled1 and1 though it is improbable that this produces any change1 it must be remembered that chrome alum on boiling really does undergo decomposition to free acid and a more basic salt1 indicated by change of colour from violet to green1 from which it slowly returns to the violet form on cooling4 ,alums are only valuable in leather manufacture in proportion to the aluminium sulphate which they contain1 the potassium or ammonium sulphate taking no part in the reaction1 and since improved methods have rendered possible the production of aluminium sulphate practically free from iron1 it has largely taken the place of alum1 than which it is both cheaper and stronger4 ,crystallised aluminium sulphate1 ,al7,,so71 #ah;,aq1 has a molecular weight of #fff1 which is of equal value to #ijf of ammonia-alum1 and #idh of potash-alum4 ,iron is the most objectionable impurity in both alums and aluminium sulphate1 and may be detected by the addition of potassium thiocyanate1 which will produce a red colour1 or potassium ferrocyanide 7yellow prussiate of potash71 which will produce a blue4 ,as the iron may be present in the ferrous condition1 it is safer first to boil the alum solution with a few drops of nitric acid or bromine water4 ,for more accurate determination of iron see ,l4,i4,l4,b41 pp4 #bj1 #acf4 ,no satisfactory leather can be produced with a solution of alum or aluminium sulphate alone1 the skin drying horny1 and incapable of softening by stretching4 ,in practice1 salt is always used in addition1 the proportion being very variable1 but averaging about half the weight of alum1 or two-thirds the weight of sulphate of alumina employed4 ,the mode of action of the salt has long puzzled chemists1 and it has been supposed that its use was to convert the aluminium sulphate into chloride1 a reaction which takes place to some extent1 but which fails to explain the production of a soft leather1 since aluminium chloride1 though freely taken up by the skin1 produces no more satisfactory leather than aluminium sulphate4 ,the real explanation is found in ,chapter ,,ix4 ,alumina is a weak base1 which readily gives up its acid to the pelt1 becoming converted into a basic salt 7see p4 #ahg74 ,the acid not only swells the pelt1 and renders it incapable of producing a soft leather1 but the swollen pelt is less ready to absorb the alumina salt1 and so remains undertanned4 ,the addition of salt prevents the swelling effect of the acid1 and produces a partial pickling of the skin 7p4 #hi71 which1 in conjunction with the tanning effect of the basic alumina salt formed1 yields a satisfactory leather1 though one which is readily affected by washing4 ,if instead of adding common salt to the alum solution1 an alkali such as soda is added1 it combines with a portion of the acid1 forming sodium sulphate1 while the alumina remains in solution as a 8basic salt40 ,as the term 8basic salt0 must be frequently employed in connection with mineral tannage1 it may here be explained4 ,basic salts are compounds intermediate between the normal salt1 in which the whole of the base is combined with acid1 and the hydrated oxide in which the whole is combined with ,,oh groups4 ,thus aluminium chloride1 ,al,cl1 is a normal salt1 in which the whole of the combining powers of the aluminium are saturated with chlorine3 aluminium hydrate1 ,al7,,oh71 is the hydrated oxide1 and ,al,cl,,oh1 ,al,cl7,,oh71 and so on are basic salts in which successively more of the ,cl is substituted by ,,oh4 ,generally1 as a salt becomes more basic1 its solution in water becomes more unstable1 and very basic salts are either insoluble1 or are precipitated from their solutions by very trifling causes1 such as boiling1 dilution1 or the attraction of animal or vegetable fibres2 separating into free acid and either hydrate or a still more basic and insoluble salt4 ,on this property depends their importance in tanning and dyeing1 many of the metallic mordants being solutions of basic salts4 ,basic salt solutions are formed in various ways1 the most common being the direct solution of a hydrated oxide in a solution of the normal salt1 or the neutralisation of a part of the acid of the normal salt by the addition of a stronger base4 ,this is what takes place on the addition of soda to an alum solution4 ,if the soda is added in excess1 the whole of the alumina is precipitated as hydrate1 or as an insoluble basic salt1 but if a proportion not exceeding about four parts of crystallised sodium carbonate be dissolved separately1 and added slowly with constant stirring to the ten parts of alum dissolved in water1 no precipitation will take place4 ,in this solution leather can be tanned1 either with or without addition of salt1 the alumina is taken up more freely than from the normal alum1 and the leather is more easily softened1 and more resistant to water4 ,in fact such leather bears a strong resemblance to the chrome tannages1 standing a great deal of washing1 and considerable temperatures without returning to a pelty condition4 ,the more basic the solution that is used1 the fuller and softer is the leather produced4 ,the alumina-salt taken up by the skin from such basic solutions is always basic1 while that absorbed from alum or alumina sulphate is apparently the normal aluminium sulphate4 ,it is probable however that the actual tanning salt is in both cases basic1 and that the acid is fixed as free acid1 as in the pickling process1 as the proportions of acid and base found in the residual liquor are somewhat variable4 ,basic alumina solutions have hardly taken the place in practice which they deserve1 though they were described by ,knapp in #ahehaab and have since been patented by ,hunt1 but the patent 7probably invalid7 has been allowed to lapse4 ,a good stock solution for practical use is made by dissolving #aj lb4 of sulphate of alumina in #aj gallons of water1 and #d lb4 of washing soda in #d gallons1 and gradually mixing the latter with the former4 ,salt can be used in addition if desired1 and flour and egg-yolk may also be added4 #aab #8,natur und ,wesen der ,gerberei1' ,braunschweig1 #aheh4 ,in curing small skins1 where it is not desirable for the fur to come in contact with the liquid1 or in the tawing of wool rugs1 it is often convenient1 after freeing the skin as much as possible from blood and dirt1 and adhering flesh1 to stretch it on a frame1 or nail it out on a board1 and apply a strong alum-and-salt solution1 as hot as the hand will bear1 with a sponge1 repeating the operation till the skin is struck through4 ,about #a lb4 of alum and lb4 of salt per gallon is a suitable strength4 ,in place of applying the solution1 powdered alum and salt is sometimes rubbed into the wet skin4 ,alumed goods should generally be dried out rapidly1 and finally at a good temperature1 as this tends to fix the tannage1 which is also made more permanent and resistant to water by keeping the skins for a month or more in the alumed condition1 an operation known as 8ageing40 ,when first dried1 alumed goods are invariably stiff and horny1 and1 to give them softness1 must first be damped back to a half-dry condition1 and then gradually softened by mechanical means4 8,staking10 and 8perching0 are the usual methods1 the first consisting in drawing the goods vigorously over a bluntish blade fixed on the top of a post1 and the second in fixing the skins on a horizontal pole 7the 8perch071 and working them with the 8crutch stake10 a tool formed somewhat like a small shovel with a semicircular blade1 in place of which a 8moon-knife0 7a round blade somewhat like a broad thin quoit7 is often fixed in a wooden crutch4 ,the tools1 and mode of using them are shown in ,figs4 #cf and #cg4aac ,machines1 described on p4 #aib1 are now generally used for these operations4 ,after the first staking or softening1 the skins are allowed to become nearly dry1 and are then staked a second time4 ,some judgment is required as to the precise degree of moisture in each case3 in the first instance the skins must be sufficiently damp to yield without injury to the mechanical stretching1 but in this state they retain sufficient moisture to enable the fibres again to adhere on drying2 and at the second staking or perching1 they must be damp enough to allow these fibres to be again loosened without violence1 and dry enough to prevent their again adhering4 #aac ,the process shown in ,fig4 #cg is not actually 8perching10 but 8grounding10 in which a moon-knife with a sharp turned edge is used to reduce the thickness of the skin on the perch1 at the same time as it stretches and softens it4 ,illustration3 ,,fig4 #cf4--,staking ,white ,leather4 ,illustration3 ,,fig4 #cg4--;,grounding with the ,moon-knife4 ,the following slight sketch of the manufacture of calf-kid will serve to illustrate the practical manufacture of the finer alumed or 8white0 leathers4 ,the raw material is in ,england mostly large market-calf1 though salted and dried skins are sometimes employed4 ,after sufficient soaking or washing in water1 they are limed without arsenic or other sulphides1 in limes which must not be allowed to grow stale or putrid1 until the hair can be easily removed4 ,after unhairing and fleshing in the usual way1 they receive a few days in a pretty fresh lime1 in order to plump them1 and are then freed from lime gradually but as completely as possible1 by successive steepings and washings in water softened by a mixture of that already used on other goods and by working on the beam4 ,this acts as a partial substitute for puering with dung1 which is now no longer used on calf-kid4 ,the goods are next drenched in the ordinary way1 #c-d of bran being used1 and the goods allowed to rise two or three times in the drench1 which should be conducted with the usual precautions 7p4 #afg7 to avoid the danger of butyric fermentation in hot weather4 ,the goods should come out of the drench free from lime1 and unswollen by acid1 but full1 white1 and soft4 ,the tanning 7or 8tawing0 as it is usually called in the case of alumed goods7 is done in a rotating drum with a mixture of alum or sulphate of alumina1 salt1 flour1 egg-yolk1 and olive oil4 ,about #e per cent4 of flour1 #be per cent4 of alum1 #a per cent4 of salt1 the yolks of #be eggs1 or #a lb4 of preserved egg-yolk1 #b oz4 of olive oil1 and #a-a gallon 7#ab-ae lb47 of water are required per #ajj lb4 of wet pelt4 ,the flour is first made into a smooth paste with a little water1 the egg-yolk1 somewhat diluted with warm water and strained1 is mixed in together with the oil1 and finally the alum and salt solution is added at such a temperature as to bring the whole mixture to blood-heat 7#ch ,c474 ,the length of drumming depends on the thickness of the skins1 several hours being required for very thick ones1 but care must be taken to stop and ventilate the drum at frequent intervals1 so as to prevent the skins becoming hot by friction4 ,this part of the process was formerly accomplished by treading with bare feet in a tub4 ,after tawing1 the goods are allowed to lie in piles over-night1 or are sometimes laid in tanks for a day or so with any that remains of the tawing paste1 to complete the absorption of the salt and alum1 and are then frequently split with the band-knife machine1 though it would be better1 as is often done on the ,continent1 to split them before tawing1 the materials of which are not only costly1 but unfit the splits for many purposes for which they might be employed4 ,the drying should be rapid1 but is best done first at a moderate temperature1 or in the open air1 and then in a rather hot stove4 ,they may now be allowed to 8age0 from one to three months1 but it is usually better before ageing to do the first part of the finishing process1 consisting of damping back1 staking1 and if necessary1 shaving4 ,machines are now almost invariably used for the staking1 the principle of which may be described as that of a pair of tongs1 carrying one or generally two staking blades on one limb1 and a roller on the other which closes on the skin1 and presses it against and between the blades1 while the tongs are drawn backwards1 allowing it to slip through4 ,fig4 #ch illustrates the ,slocomb1 one of the most popular machines of this type4 ,after staking and ageing1 the skin is soaked in water till thoroughly wet in all parts4 ,this not only softens the skin1 and prepares it for dyeing1 but takes out the superfluous alum and salt1 and at the same time a good deal of flour and egg4 ,to replace these1 8re-egging0 is necessary1 and while some manufacturers give egg-yolk1 or egg-yolk and flour only1 many add a proportion of salt1 and sometimes also of alum4 ,this is done before dyeing1 if the skins are to be blacked on the table1 but as tray-dyeing 7see p4 #djf7 would again wash out the egg1 the re-egging is deferred till after dyeing if this process is resorted to4 ,before dyeing1 the skins receive an alkaline mordant to overcome greasiness1 and enable them better to take the colour4 ,in former times this was usually stale urine1 but this has mostly been superseded by solutions of 8hydroleine0 7a washing powder71 or of soap rendered more or less alkaline with ammonia4 ,eitner gives the following recipe1 viz4 lb4 ,marseilles soap dissolved in boiling water1 #e or #f egg-yolks added1 and the whole made up to #d gallons with water and lb4 potash bichromate4 ,the colour used is infusion of logwood or its extract1 or two-thirds logwood and one-third fustic1 which is best extracted without alkali1 a small quantity of soda or ammonia being afterwards added4 ,it is fixed and darkened by a wash of iron-liquor or a solution of #a of ferrous sulphate in #ge of cold water4 ,after being again dried1 the skins are sometimes grounded with the moon-knife1 softened again by staking or perching1 for which a machine with inclined or spiral blades attached to a drum and working on a sort of leather apron is often preferred to machines of the ,slocomb type1 and rubbed over on the grain with a composition containing oil1 wax1 etc41 and are finally ironed with a heavy flat-iron1 to give them a fine and smooth surface4 ,eitner gives a recipe for the gloss3--#a kilo gum arabic1 kilo yellow wax1 kilo beef-tallow1 kilo ,marseilles soap1 #a liter strong logwood infusion1 and #e liters water4 ,the water is brought to a boil in an earthen pot1 and then the soap1 wax1 gum1 and tallow are added successively1 each being stirred till dissolved before adding the next1 and lastly the logwood4 ,after boiling for an hour1 it is allowed to completely cool1 being incessantly stirred during the whole process4 ,after ironing the goods are rubbed over with a final gloss1 for which ,eitner gives the following recipe3--#h liters olive oil1 #ejj grm4 tallow1 #ejj grm4 yellow wax1 #ejj grm4 rosin1 #ejj grm4 gum arabic4 7,no water is given in the recipe1 but the gum arabic is presumably softened in water47 ,the mixture is cooked for two hours in an earthen pot till the water is evaporated1 and allowed to cool with constant stirring4 ,the skins are then rubbed with a flannel with a very small sprinkling of ,french chalk1 and are ready for sale4 ,illustration3 ,,fig4 #ch4--,the ,slocomb ,staking ,machine4 ,the manufacture of glove-kid is quite similar in principle to that just described1 but varied in detail to suit the softer and more delicate skins employed1 to give greater softness1 and especially the quality of stretching in any direction without springing back1 which is so characteristic of the leather4 ,lamb-skins are the principal raw material1 though genuine kid is also employed for the best qualities4 ,the manufacture varies much with the quality and character of the goods4 ,the skins1 which are mostly dried1 are soaked in clean and cool water for three to four days1 according to age and thickness4 ,common qualities 7small imported slink lambs7 are often unhaired by dipping in or painting with a paste of gas-lime1 lime and sulphide of sodium1 or lime and red arsenic1 so as to destroy the wool4 ,better skins are sometimes unhaired by painting on the flesh with lime alone or in mixture1 and in other cases ordinary lime-pits are used1 with limes1 which are most usually strengthened with red arsenic1 which is added to the lime while hot from slaking 7cp4 p4 #adb74 ,the calcic sulphydrate 7and perhaps sulpharsenite7 thus formed hastens the unhairing1 and preserves the gloss of the grain4 ,well conducted glove-kid establishments avoid as much as possible the use of old limes1 which produce a loose1 porous leather1 with a rough1 dull grain4 ,the liming lasts on the average ten days1 and is of the greatest importance4 ,it is essential that the inter-fibrillary substance should be dissolved1 that the leather may have the quality known in ,germany as ,stand1 that is to say1 may be strongly stretched in either length or breadth without springing back4 ,it also depends upon the liming 7and this is of special importance in the case of lamb-skins71 whether the tissue of the fat-glands is well loosened1 so that the fat1 either as such1 or as lime- or ammonia-soap1 may be readily and completely worked out4 ,skins in which this is neglected can never be properly dyed4 ,when the hair 7or wool7 is well loosened1 the skins are rinsed in water1 and then unhaired on the beam with a blunt knife4 ,the water employed in washing should not be much colder than the limes1 or it will prevent the hair from coming away readily4 ,the wool or hair is washed and dried for sale4 ,the skins are thrown into water1 to which a little lime-liquor has been added1 to prevent precipitation of the lime in the skins by the free carbonic acid of the water1 which would have the effect of making them rough-grained4 ,next comes the first fleshing 7,vergleichen7 or 8levelling40 ,by this1 the loose cellular tissue on the flesh-side is removed1 together with the head1 ears1 and shanks2 and the flanks are trimmed4 ,the skins are then again thrown into water softened with lime-liquor as above described1 and then into a puer of dogs'-dung4 ,this is prepared by stirring up white and fermented dogs'-dung with boiling water1 and straining it through a sieve or wicker basket4 ,the puer must be used tepid1 and not too strong4 ,the skins 8fall0 7lose their plumpness7 in it rapidly1 and become extremely soft and fine to the touch2 and the fat-glands1 remaining hairs1 and other dirt1 can now be very readily scudded out4 ,too strong puers1 or too long continuance in them1 produce evident putrefactive effects on the skins4 7,see also p4 #aha47 ,when the skins come out of the puer1 they are stretched and worked on the flesh with a sharp knife1 and any remaining subcutaneous tissue is removed4 ,this constitutes the second fleshing4 ,they are then rinsed in warm water1 and beaten with clubs in a tub1 or worked in a tumbler-drum1 in either case with a very little water only2 and finally brought into a tank of water1 not too cold1 and kept in constant motion with a paddle-wheel4 ,the skins are next cleansed on the grain-side by working on the beam with plates of vulcanite set in wooden handles1 so as to remove fat1 lime- and ammonia-soaps1 and other lime compounds1 together with all remaining hair or wool4 ,the skins are now a second time washed in the 8paddle-tumbler10 first in cold1 and then in tepid water2 and after allowing the water to drain from them1 they are transferred to the bran-drench4 ,this is prepared by soaking wheaten bran in water at about #ej ,c41 and diluting with warm water4 ,sometimes the mixture is strained1 and the bran-water only used1 to save the trouble and cost of removing adhering particles of bran from the delicate skins4 ,sufficient of the liquid must be employed to well cover the skins1 and the temperature may range from #ej ,f4 7#aj ,c47 to #fh ,f4 7#bj;,c474 ,these conditions are favourable to bacterial activity1 which comes into play1 and1 on the one hand1 evolves acetic and lactic acids1 which dissolve any remaining traces of lime1 and on the other1 loosens and differentiates the hide tissue1 so as to fit it to absorb the tawing solution4 ,much care is required in the management of the bran-drench1 especially in summer1 since the lactic readily passes into the butyric fermentation 7see also p4 #afg74 ,the tawing mixture is composed 7like that employed in the fabrication of calf-kid1 q4v47 of alum1 salt1 flour and egg-yolks1 in a quite thin paste4 ,a small quantity of olive oil is also generally used4 ,the skins are either trodden in it with the feet1 or more generally put into a tumbler-drum with it4 ,kathreiner pointed out1 some years ago1#aad that a mixture of olive-oil and glycerine might be partially substituted for the egg-yolks1 in both the tanning and dyeing of glove-kid leather4 #aad ,gerber1 i4 7#ahge7 p4 #agj2 ii4 7#ahgf7 p4 #ffd4 ,the tawed skins are now dried by hanging on poles1 grain inwards4 ,rapid drying in well-ventilated1 but only moderately heated rooms is essential to the manufacture of a satisfactory product4 ,the dry leather is rapidly passed through tepid water1 and after being hung for a very short time1 to allow the water to drain off1 is trodden tightly into chests1 and allowed to remain in them for about #ab hours1 so that the moisture may be uniformly distributed4 ,it is then trodden on hurdles 7,german ,horden7 composed of square bars of wood1 joined corner to corner1 so as to make a floor of sharply angular ridges4 ,the next operation is stretching with the 8moon-knife02 after which the leather is dried nearly completely1 and staked again4 ,this completes the tawing process4 ,the goods are now 8aged0 as in calf-kid manufacture4 ,before dyeing they are washed with tepid water to remove part of the tawing mixture1 and especially1 superfluous alum and salt1 and are re-egged much like calf-kid1 before dyeing if the latter is done by brushing1 and after if in the dye-tray or paddle4 ,aniline colours are more used than formerly1 especially for topping and brightening the natural colours1 but the dyewoods and other mordant colours are still largely employed4 ,the leather is first prepared with an alkaline mordant 7stale urine1 ammonia1 etc47 7cp4 p4 #dac71 then repeatedly brushed with or dipped in the dyewood liquor1 and a wash 78striker10 ,german ,ueberstrich7 containing some metallic salt is generally applied1 with the object either of bringing out the special tone required1 or of making the colour more lively and permanent4 ,the striker is usually a solution of one of the so-called 8vitriols03 8white vitriol0 7zinc sulphate71 8blue vitriol0 7copper sulphate71 8green vitriol0 7iron sulphate71 or occasionally other salts4 ,after the dyeing1 the skins1 if dipped1 are wrung out and re-egged2 if brush-dyed1 sleeked out with a brass or ebonite sleeker to get rid of superfluous water4 ,they are then dried in an airy room4 ,before staking 7stretching71 the skins are laid or hung in a damp cellar1 or in moist saw-dust4 ,they are staked twice3 once damp1 and once nearly dry2 and are finished by glassing or ironing4 ,skins which are much damaged on the grain1 or otherwise faulty1 are smoothed with lump pumice on the flesh side1 or fluffed with fine emery on the fluffing wheel4 ,they are then dyed on the flesh side1 mostly by dipping1 but occasionally with the brush1 in which case1 the method described is slightly modified4 ,tawing with alum and salt is frequently employed for commoner and stronger leathers1 such as aprons 7of sheep-skin71 leather for whip-lashes1 laces for belts1 and 8skivers0 for capping chemists' bottles4 ,the process is practically the same as for calf-kid1 except that no egg1 and little flour is used4 ,often flour is entirely omitted1 and the goods may then be alumed in tubs1 in which they are merely handled1 as the alum solution penetrates quickly4 ,goods which are required white are frequently handled or tumbled with a milk of 8whitening10 both to improve the colour1 and to neutralise any acid present1 and fix the alum by rendering it more basic4 ,alumed goods can be stuffed with greases1 either by hand or in the drum1 after thorough softening by staking4 ,alum1 and other salts of alumina are frequently used in combination-tanning with vegetable materials 7see ,chap4 ,,xvii474 8,green0 leather for laces1 8dongola10 and 8dog-skin0 glove-leathers are made in this way4 ,glazed kid for ladies' shoes must be slightly vegetable-tanned on the surface1 or it will not glaze1 but this is frequently accomplished by the use of materials in the dye-liquor containing tannins4 ,,chapter ,,xv4 ,,iron ,,and ,,chrome ,,tannages4 ,iron tannages may be very shortly dismissed1 as their practical interest is at present either historical or prospective1 but iron salts enter in so many ways into the chemistry of leather manufacture1 that their properties must be briefly considered4 ,iron exists in salts in two states1 the ferrous1 and the ferric1 in the first of which it is divalent1 and in the second trivalent4 ,thus ferrous chloride is ,fe,cl2 ferrous oxide1 ,fe,o2 ferrous sulphate1 ,fe,s,o2 ferrous hydrate1 ,fe7,,oh74 ,the compounds of ferrous iron are mostly green1 like ferrous sulphate 78green vitriol10 8copperas073 exposed to air and moisture1 they easily absorb oxygen1 and pass into the ferric form4 ,ferric chloride is ,fe,cl 7or1 as it is sometimes written without much reason1 ,fe,cl71 ferric hydrate ,fe7,,oh71 ferric oxide ,fe,o1 ferric sulphate ,fe 7,,so71 and so on4 ,the atomic weight of iron is #ef4 ,ferric salts are mostly yellow or orange1 ferric hydrate is yellow-brown1 and on ignition is converted into deep red ferric oxide1 which is very difficultly soluble in acids4 ,ferric salts in contact with more easily oxidisable matters1 readily give up oxygen1 and pass into the ferrous state2 and especially does this happen in the presence of organic matter1 under the influence of sunlight4 ,thus iron-salts often act as carriers of oxygen1 and oxidisers of organic matter1 absorbing oxygen from the air1 and giving it up again under the influence of light or heat4 ,there are several other oxides of iron which do not form salts1 and there is a ferric acid1 apparently corresponding to chromic acid1 which is so unstable that it has been very imperfectly investigated4 ,ferric salts correspond in structure to those of alumina1 and like these are powerful tanning agents1 and readily form basic salts1 while the ferrous salts have no tanning effect until they become oxidised1 when they form basic ferric salts4 ,ferric salts are characterised by giving blue-black or green-black compounds with tannins1 and with many other allied bodies1 while the corresponding ferrous compounds are mostly colourless1 though they rapidly oxidise and darken4 ,ferric iron1 like alumina1 forms an 8alum10 a double sulphate of iron and potassium1 ,fe7,,so7,k,,so1 #bd;,aq1 forming fine pale-violet crystals1 but dissolving to a yellow-brown solution4 7,it must be distinctly understood that iron-alum and chrome-alum contain no alumina1 but are simply called alums because of their similarity of constitution1 iron or chrome taking the place of the aluminium4 ,iron-alum1 in conjunction with salt1 can be used for tanning1 giving a pale buff-coloured leather very similar to an ordinary alum leather4 ,thus the presence of a small quantity of iron in an alum used for tawing is of no consequence1 except as affecting the colour of the leather4 ,in impure sulphate of alumina such as 8alumino-ferric10 it1 however1 generally exists in the green ferrous state1 and only acquires tanning properties on oxidation4 ,without common salt iron-salts are still less satisfactory tanning agents than those of alumina under the same conditions1 as the acid is yet more loosely held1 and though basic ferric salts are taken up in considerable quantities by hide1 the leather produced is thin1 and usually brittle4 ,professor ,knapp devoted much study to the production of a commercial sole-leather by basic iron-salts2 and took several patents1 which did not prove practically successful1 though the brittleness was to some extent overcome by the incorporation of compounds of iron with organic materials such as blood and urine1 of iron-soaps1 and of rosin and paraffin in the leather4 ,like most mineral tannages1 the process was far more rapid than that with vegetable materials4 ,knapp's basic tanning liquor was made by the oxidation of ferrous sulphate with a small quantity of nitric acid4 ,patents have also been taken for the oxidation of ferrous sulphate by peroxide of manganese in presence of sulphuric acid1 which produces basic ferric sulphate in mixture with manganese sulphate1 which has also some tanning properties4 ,attempts have also been made to tan by treatment of the hide with solutions of ferrous sulphate1 and subsequent exposure to the air1 in order to oxidise the iron on the fibre and convert it into a basic ferric salt1 but have not proved of any commercial value4 ,the principal use of iron at present in leather manufacture is in dyeing blacks 7see p4 #dac71 but in this case1 its feeble hold upon acids in the ferric state1 and its tendency to act as an oxidising agent1 or oxygen carrier1 renders the blacks somewhat unstable1 and is frequently injurious to the leather4 ,there is also little doubt that the presence of ferric salts in leather blacks has a great tendency to cause the resinification of the oil1 known as 8spueing10 by promoting its oxidation4 ,chrome tannages1 from a practical point of view1 stand on a very different footing to those which have just been mentioned2 having established their position in the manufacture of almost all sorts of light leathers1 in competition with all the older methods1 and making a serious claim to a share in the production of belting and even of sole leathers4 ,chromium is a grey1 and very infusible metal1 which chemically much resembles iron in its compounds1 and has an atomic weight of #eb1 or a little over4 ,like iron1 it possesses a divalent and a trivalent form1 but the divalent has so strong an affinity for oxygen1 and passes so readily into the trivalent form1 that until easier means are found for its preparation1 it is of little practical interest4 ,its salts are blue4 ,on the other hand1 salts of the trivalent form1 corresponding to the ferric salts of iron1 are very stable1 and powerful tanning agents4 ,they are mostly green1 but violet modifications are known1 corresponding to the violet crystals of iron-alum1 but of a much deeper tint4 ,there is also a hexavalent form1 probably corresponding to that of iron in the unstable ferrates1 but in the case of chromium1 of considerable stability4 ,its oxide is chromic anhydride1 ,cr,o1 commonly called chromic acid1 which combines with bases1 and especially with the alkalies to form yellow or orange-red salts1 and the anhydride itself is almost crimson in the solid form1 though dissolving to orange or yellow solutions4 ,chromic acid though it hardens and preserves animal tissues1 has no tanning properties till it becomes reduced to chromic oxide4 ,there is also a higher1 but very unstable oxide1 perchromic acid1 possibly corresponding to persulphuric acid1 which is soluble in ether to an intensely blue solution4 ,the name chromium is derived from the intense colour of many of its compounds4 ,our supplies of chromium are derived from chrome-iron-ore1 a mineral which contains oxides both of chrome and iron4 ,this is furnaced with a mixture of lime1 and soda or potash1 when it absorbs oxygen from the air1 the chromium becoming converted into chromic acid which combines with the alkali present1 while the iron remains undissolved as ferric oxide4 ,lixiviating the mass1 and evaporating the solution1 lime and potassium or sodium chromates are obtained1 according to the alkali used1 and on adding sufficient sulphuric acid to combine with half the base1 potassium or sodium dichromate 7or as it is commonly called 8bichromate07 can be crystallised out4 ,potassium dichromate is most commonly made1 because it crystallises well1 and is not deliquescent1 but sodium dichromate is somewhat cheaper1 though less convenient4 ,dichromates1 at least in the crystallised state1 are not hydric salts like bisulphates1 but anhydrochromates corresponding to the potassium anhydrosulphate obtained by fusing ordinary bisulphate1 and to fuming sulphuric acid4 ,thus the formula of potassium dichromate is ,cr,o,,ok ,o 1 ,cr,o,,ok or ,cr,k,o and its molecular weight is #bid1 while that of sodium dichromate1 which is similar in constitution1 but crystallises with #b;,aq1 is #bih4 ,the molecular weight of ,cr,o is #ajj4 ,chromic acid1 and acidified potassium dichromate are powerful oxidising agents1 and are used as such in many processes1 and especially in the manufacture of alizarine4 ,if sulphuric acid be used in molecular proportions1 the product of the reaction is chrome-alum3 #d;,h,,so ,cr,k,o #c,o #d,,oh ,k,cr7,,so74 ,this1 like ordinary alum1 crystallises with #bd;,aq1 and hence has a molecular weight of #iih4 ,it forms dark purple1 almost black crystals1 which are a fine garnet-red by transmitted light4 ,in cold water it dissolves to a violet solution1 which becomes green on boiling1 but very slowly resumes the violet condition when cold4 ,this change1 which is not uncommon in chrome solutions1 is probably due to a partial decomposition into free acid and a basic salt1 the basic salts of chromium being generally green4 ,it has been noticed that raw pelt swells much more in the green1 than in the violet solution4 ,being derived from waste products1 chrome-alum is often a cheap and valuable source of chromium for chrome tanning4 ,for the analysis of chrome compounds see ,l4,i4,l4,b41 p4 #ada et seq4 ,chrome oxide1 and basic chrome salts1 when strongly ignited1 become insoluble even in concentrated acids1 and their analysis is therefore attended with some difficulty4 ,if1 however1 the ignited residue 7for instance a leather-ash7 be finely powdered1 and intimately mixed with a fusion-mixture consisting of equal parts of pure calcined magnesia and pure dry sodium carbonate1 and ignited 7preferably over a ,teclu burner71 in a platinum crucible1 in which it is occasionally stirred with a platinum wire1 it will be quantitatively converted into chromate1 which may be dissolved in acid1 and estimated with potassium iodide and thiosulphate in the usual way4 ,if it is desired at the same time to estimate sulphuric acid1 it is sometimes preferable to substitute lime or calcium carbonate for the magnesia1 which is apt to be contaminated with sulphates4 ,chrome is not only of importance in tanning1 but in dyeing2 on account of its power of forming insoluble colour-lakes with many mordant colouring matters4 ,for this purpose normal or basic chromic salts are sometimes used1 sometimes chromic acid or dichromates1 the latter acting not only by yielding chrome-oxide on reduction1 but as oxidising agents to the colouring matters4 ,most of the colours produced with chrome mordants are of dark shades1 that with logwood being deep violet or black4 ,the mordanting power of chromium is important in the dyeing of chrome leather4 ,bichromate of potash is often used in dilute solution for darkening the shade of leather dyed with other materials1 but is not to be recommended on account of its destructive action on the leather4 ,numerous patents have been taken for processes of chrome tannage4 ,the first practical method was described by ,professor ,knapp in #aheh 7see p4 #baj71 though he did not recognise its value4 ,some of the patents have a historical interest1 though of no importance4 ,among these may be mentioned that of ,cavallin1 a ,swedish apothecary1 whose object was dyeing rather than tanning1 but who treated raw hide with a solution of bichromate1 which was afterwards reduced on the fibre by one of ferrous sulphate4 ,the leather produced is dark reddish brown1 and tender from the amount of basic ferric salt formed at the same time4 ,mr4 ,j4 ,w4 ,swan1 well known in connection with photographic processes1 and electric lighting1 also patented a process of chrome tannage 7as an addendum to a patent on carbon printing71 in which the chromic acid first fixed in the pelt was reduced by 8oxalic1 or other suitable acid40 ,although it is possible to produce leather within the lines of the patent1 the strongly acid reaction of the reducing agent renders it unsuitable for practical use4 ,the first chrome tanning process which made any show of practical success1 was that patented in #ahgi by ,heinzerling1 which was acquired in this country by the ,eglinton ,tanning ,company1 and also worked under their license for a short time by the ,yorkshire ,tanning ,company at ,leeds4 ,though the process was not commercially successful on any considerable scale1 it possesses points of interest which make a brief description desirable4 ,the hides or skins1 after preparation in the usual way1 were treated in a mixed solution of salt1 alum 7or aluminium sulphate71 and potassium bichromate1 but no systematic attempt was made to reduce the chromic acid to a tanning form1 the product being1 at first at least1 merely an alum tannage1 coloured1 and perhaps somewhat hardened with chromic acid1 though on keeping for a length of time1 reduction gradually took place at the expense of the hide-fibre1 and of the fats employed in currying1 so that the leather internally became greyish-green1 and really chrome-tanned4 ,specimens of the early products of the process1 preserved in the museum of the ,leather ,industries ,department at ,leeds1 have now all undergone this change1 but are still tough and flexible1 showing that the rapid tendering of the ,heinzerling leather1 which was one of the causes of its failure1 must have been due to some error in manufacture1 and was not inherent in the process4 ,interesting1 historically1 is the fact1 that at an early stage in the life of the patent1 a specimen of the leather was submitted to the late ,professor ,hummel1 in order that he should suggest some means of overcoming the disagreeable yellow colour of the product4 ,he reduced it with a bisulphite1 and coloured it with an aniline dye1 and a piece is still in the possession of the ,yorkshire ,college1 and in perfectly sound condition4 ,if legal publication of this experiment could have been proved1 it would have invalidated the important ,schultz patents under which most of the chrome-kid of the ,united ,states has been manufactured4 ,as bearing on modern chrome-tanning1 the most important reaction in the process is that of the alum with the bichromate4 ,it has been shown by ,heal and ,procter#aae that pelt absorbs practically no chromic acid from bichromate1 unless it has been previously set free by acidification4 ,when however alum1 or sulphate of alumina is added1 its sulphuric acid liberates the chromic acid1 leaving a basic alumina salt in solution1 and this fact has been utilised in some modern tanning processes4 #aae ,journ4 ,soc4 ,chem4 ,ind41 p4 #bea1 #ahie4 ,the first really important advance in practical chrome tanning was made by ,augustus ,schultz1 in #ahhd4 ,schultz was not a tanner1 but a chemist1 employed by a ,new ,york firm of aniline colour merchants1 and his attention was accidentally drawn to leather by a friend who asked him if it were possible to produce a leather for covering corset steels1 which would not rust them as ordinary alumed leathers do4 ,the process which he adopted was probably suggested by a method then recently patented for the mordanting of wool by chrome oxide1 and depended on the power of the pelt to absorb free chromic acid 7as it does all other free acids71 and the subsequent reduction of the latter on the fibre to a basic chrome salt1 which produced the tannage4 ,the reducing substance employed was the free sulphurous or thiosulphuric acid of an acidified solution of sodium thiosulphate 7hyposulphite71 and as it was not certain which of the two acids was the really active agent1 ,schultz duplicated his patent1 so as to cover both4 ,though he made no claim in his patent to having discovered the best proportions of his ingredients1 those which he specified have proved practically useful after allowing for the modifications required by different skins1 and slightly different methods of working4 ,his first bath consisted of a solution of #e per cent4 of bichromate of potash1 and #b per cent4 of concentrated hydrochloric acid 7or #abe per cent4 of concentrated sulphuric acid71 reckoned on the wet weight of the prepared pelt1 and dissolved in sufficient water for convenient use in the paddle or drum which was to be used in the process4 ,in this bath the skins were worked till they took a uniform yellow colour throughout1 but without any tanning effect being produced4 ,they were now freed from superfluous chrome liquor by draining or 8putting out10 and transferred to the second bath1 which consisted of #aj per cent4 of 8hypo0 and #e per cent4 of hydrochloric acid similarly dissolved4 ,in this1 they rapidly took a duck-egg green colour from the reduction of the chromic acid2 and when this was uniform throughout the skin1 the tannage was complete4 ,the exact quantity of water is not of great importance1 and good results can be obtained with anything varying from #bj to #ej gallons per #ajj lb4 of pelt 7#bjj to #ejj per cent47 if time be allowed for the weaker solution to act4 ,the quantities of 8hypo0 and hydrochloric acid given for the second bath are often somewhat insufficient1 and have to be slightly increased to complete the reduction4 ,the reactions which take place are represented by the following formul1 in which the weights of the materials taking part in the reaction are also given below the symbols4 ,in the first bath-- ,potassium ,hydrochloric ,potassium ,chromic ,water4 dichromate4 acid4 chloride4 acid4 ,k,cr,o #b;,h,cl #b,k,cl #b;,cr,o ,,oh #bid #gc #adi #bjj #ah ,as ordinary concentrated hydrochloric acid does not contain more than about #cj per cent4 of actual ,h,cl1#aaf about #be parts would be required to completely decompose #bid parts of dichromate1 while in ,schultz's formula #be parts of hydrochloric acid are used to #e parts of dichromate4 ,this excess has been found useful in the production of a good leather1 both to prevent accidents from an overdose of hydrochloric acid1 and because of the modifying effect of an excess of neutral salt on the action of the chromic acid 7cp4 p4 #hb74 #aaf ,acid of ,s4,g4 #aaf 7#cb ,tw47 contains #cae per cent4 of ,h,cl by weight or #cff grm4 per liter1 and therefore is practically #aj normal strength4 ,acid of ,s4,g4 #ab 7#dj ,tw47 contains #cia per cent4 or #dfi grm4 per liter4 ,the reactions which take place in the second bath are somewhat complicated4 ,eitner1 in a valuable series of articles on chrome tannage1 which have been appearing in the #8,gerber' since ,january #aijj1 states that even better results are obtained by using the hydrochloric acid in slight excess1 as the action of chromic acid 7in the presence of the potassium chloride of the chrome-bath7 is not swelling but hardening to the skin1 and the slight swelling action of the hydrochloric acid tends to counteract this1 and also to facilitate the subsequent reduction4 ,the two views are not contradictory1 as the excess of bichromate behaves to the hide as an alkaline salt1 which also produces a slight swelling effect1 and it is quite probable that better results are attained when the solution is either alkaline or acid1 than when the potassium chromate is exactly decomposed4 ,eitner recommends the use of four parts by weight of bichromate1 and four parts of the strongest hydrochloric acid1 dissolved in #djj parts of water1 for each #ajj parts of wet pelt1 which should yield about #dj parts of dry leather4 ,he states that if such a bath be used1 it may be safely and economically exhausted by a second pack of skins1 which is impossible in a bath containing excess of unacidified bichromate4 ,he gives#aag the following explanation of the successive changes which take place when acid is gradually added during the reduction1 but points out that in practice the reactions always to some extent go on simultaneously4 #aag ,gerber1 p4 #big1 #aijj4 ,in the first stage1 very slight acidification is required1 and if the skins have been chromed with excess of hydrochloric acid1 may be altogether dispensed with4 ,the skins become brownish from the conversion of the chromic acid into so-called 8chromium dioxide0 7probably really a basic chromic chromate1 ,cr,cr,o7,,oh71 which on ignition leaves ,cr,o72 no sulphurous acid is liberated1 or sulphur deposited1 but sodium tetrathionate is formed in the bath1 and the reaction may be represented as follows3 7#a7 #c;,cr,o #f;,h,cl #f,na,s,o #c,na,s,o #f,na,cl #c,,oh ,cr,o4 ,further addition of hydrochloric acid brightens the colour of the skins1 while the liquid still remains clear1 and chromium chloride is formed instead of chromic chromate1 the main reaction being3 7#b7 #b;,cr,o #ab;,h,cl #f,na,s,o #c,na,s,o #b;,cr,cl #f,na,cl #f,,oh4 ,on still further addition of hydrochloric acid1 sulphur is separated according to the following equation1 and is deposited partly in the skins1 and partly in the bath3 7#c7 #b;,cr,o #f;,h,cl #c,na,s,o #c,na,,so #c,s #b;,cr,cl #c,,oh4 ,after complete reduction1 and consumption of the free hydrochloric acid1 further reactions take place at the expense of the excess of thiosulphate which should be present1 resulting in the production of basic chromic salts1 and the further deposition of sulphur1 mostly within the skin1 as shown in the following equations3 7#d7 ,cr7,,so7 ,na,s,o ,,oh #b;,cr,o,h4,,so ,,so ,s ,na,,so4 7#e7 #b;,cr,cl ,na,s,o ,,oh #b;,cr,o,h4,cl ,,so ,s #b,na,cl4 ,the thiosulphate bath therefore not only reduces1 but precipitates sulphur in the skin1 and reduces the chromic salt to a basic state4 ,in boiling solution1 thiosulphate precipitates the whole of the chromium as chromic oxide1 but in the cold1 and in presence of free sulphurous acid1 it only reduces to a basic salt4 ,eitner does not consider the possibility1 which certainly requires investigation1 that instead of basic salts1 sulphite-sulphates are formed at least in the first instance4 ,such salts of one base and two acids are quite possible1 and it is very probable that in the use of chroming baths containing organic acids1 they have considerable influence on the tannage4 ,the free sulphur which is liberated is partially deposited on and among the fibres of the leather1 and adds to its softness1 and also acts chemically on the oils used in 8fatliquoring10 so that it is probably one of the main causes of difference between the products of the ,schultz or 8two-bath0 method1 and the 8one-bath0 processes subsequently to be described4 ,it does not fall within the scope of this book to describe in detail the working methods for the production of the different kinds of chrome leather1 but a few precautions common to all forms of the process may be named4 ,it is not absolutely important in all cases that goods should be completely freed from lime before chrome-tannage1 but in this case a sufficiency of acid must be allowed in the first bath to neutralise the lime introduced4 ,pretty thorough liming is generally advisable1 to plump and separate the fibres1 but as a rule the bating or puering of goods for chroming should not be excessive1#aah but should be planned not to remove more than is absolutely necessary of the hide-substance1 as the chrome tannage is in its nature soft and light1 and does not lend itself to artificial fillings1 such as the flour and egg-yolk of the calf-kid process4 ,skins are sometimes freed from lime by 8pickling0 7p4 #hi71 and pickled skins may be chromed without depickling1 which will be done by the dichromate1 but in this case the acid contained in the skins must be considered in the composition of the chroming bath4 ,skins1 indeed1 which are pickled with a sufficiency of acid may be chromed in a neutral dichromate bath1 and this is sometimes a convenient mode of procedure4 ,to prevent drawing of the grain during tanning1 skins not unfrequently receive a preliminary tannage with alum1 or sulphate of alumina1 and these materials1 together with salt1 may be introduced into the chroming bath1 in which case they will liberate a portion of the chromic acid1 as has been mentioned in connection with the ,heinzerling process4 ,alum1 chrome-alum1 and acid salts1 such as sodium bisulphate1 may be substituted for the acid in the chrome bath1 but organic acids must not be used1 as they would reduce the chromic acid4 ,the quantity of free chromic acid in the chrome bath is of the most vital importance to success1 as it1 and not the dichromate 7which may be present in considerable excess71 regulates the amount of chrome taken up by the skin1 and the subsequent degree of tannage4 ,it is very possible to injure leather by overchroming1 rendering it rough1 harsh and even tender4 ,if a bath containing excess of bichromate is to be re-strengthened1 it may be assumed as a rule that all the free chromic acid has been absorbed by the skins1 and while it is merely necessary to restore the strength of the dichromate to its original amount1 the full quantity of acid must be used which would be required in preparing a new bath4 ,where1 as in ,eitner's acid chrome bath1 the whole of the chromic acid is liberated1 the bath may be exhausted by a second pack of skins4 ,many tanners1 in order to avoid the complications of remaking a bath1 run away their chrome liquors after once using1 containing all the excess of dichromate which has been used4 ,with proper chemical control1 this should not be necessary1 and is objectionable1 not only from its wastefulness1 but on account of the very poisonous character of the unreduced bichromate4 ,even weak dichromate solutions1 especially if warm1 are liable to cause painful and obstinate eruptions on the hands1 but this rarely occurs to tanners1 as the poisonous action of the solution is removed on reduction4 ,it is well1 however1 to arrange that men who handle skins in the chrome bath1 should subsequently also work in the reducing bath4 ,methods of analysis of used chrome liquors are given1 ,l4,i4,l4,b41 pp4 #adb et seq4 ,those for the determination of acidity are not however easily applicable in the presence of alum and salts of chromic oxide4 #aah ,goat-skins for glac kid need thorough puering to produce a smooth grain4 ,the skins1 on coming from the chroming bath may be allowed to lie for some time without serious injury1 but should be carefully protected from the action of light1 which reduces the chrome at the expense of the skin1 and renders the subsequent tannage irregular4 ,it is found that skins1 if brought into a weak or neutral reducing bath1 are apt to 8bleed0 or lose chromic acid1 which is reduced wastefully in the bath4 ,on the other hand a strong 8hypo0 bath is apt to draw the grain and contract the skins1 owing to the tannage taking place too suddenly4 ,a somewhat strong 8hypo0 bath is therefore often employed as a preparatory 8dip10 the skins being simply drawn through it to fix the chrome on the surface1 piled on a 8horse0 and subsequently reduced in a bath of ordinary strength4 ,the tendency to bleed is lessened1 but at the expense of the pelt1 by the reduction which takes place if the skins are allowed to lie overnight in the chromed state4 ,eitner states that skins chromed in an acid bath 7i4e4 where the whole of the chromic acid is in a free state7 show little tendency to bleed4 ,after reduction1 the skins are well washed with warm water1 and their subsequent treatment is the same as that of skins tanned by the one-bath process1 which is subsequently described 7see p4 #baa74 ,naturally in practical work1 the reduction cannot be made to proceed rigidly in the definite steps described by ,eitner on p4 #bjf1 but all go on in different proportions together1 though by supplying the acid in proper quantities1 and at proper intervals1 they may be made in the main to follow in the given order4 ,both on this account1 and because neither the exact amount of chromic acid in the skins1 nor the sulphurous acid lost by escape into the air can be exactly determined1 the reduction cannot be conducted on theoretical principles1 but the best conditions must be empirically determined4 ,eitner states that #ab parts of thiosulphate dissolved in #djj parts of water1 and #f parts of 7#dj per cent47 hydrochloric acid are sufficient for #d parts of bichromate per #ajj of wet pelt employed in the chrome bath1 of which not more than one-half to two-thirds is absorbed2 and that if equal parts of bichromate and acid are employed in chroming1 the acid used in reducing may be lessened to #e parts4 ,in this case it must not be forgotten1 that if the partially exhausted chrome-bath is used for a second pack of skins1 which are afterwards finished in a bath of full strength1 nearly the whole quantity of bichromate used in making up one bath will be absorbed by the skins4 ,the amount of acid consumed in reduction will be greater1 the more rapidly it is added1 owing to increased escape of sulphurous acid4 ,it is better to add the acid1 previously diluted with water1 in #h or #aj successive portions1 more rapidly at first1 and more slowly during the latter half of the operation1 each portion of acid being added as soon as no further change of colour appears to be caused by that already given4 ,these changes are the more rapid the lighter the goods4 ,the colour darkens at first to olive-brown1 then gradually becomes green1 and finally blue1 and when this colour is uniform throughout the thickness of the goods1 no further acid need be added4 ,for goods which have been chromed in an acid bath1 ,eitner states that no acid will be needed for the first twenty to thirty minutes4 ,it is important to have a sufficient excess of thiosulphate in the bath when reduction is complete1 in which case the goods may be left for some hours or overnight in the bath1 to complete 8neutralisation10 but ,eitner prefers to use a fresh bath of #a parts of thiosulphate in #djj parts of water for this purpose1 the bath being used1 after settling1 for making up the reduction bath for the next lot of goods1 for which #a parts less thiosulphate is used4 ,the goods must be kept in motion during reduction1 either in a drum or a covered paddle4 ,in a paper on 8,die ,natur und ,wesen der ,gerberei0 published by ,professor ,knapp1 in #aheh1 he describes clearly a chrome tanning process with basic chromic chloride1 formed by the addition of sodium carbonate to a solution of the normal salt1 but he expressly states that the product was not more resistant to water than the ordinary alum tannages4 ,how he fell into this error is hard to explain1 for leathers produced according to his directions1 resist not merely washing in cold but boiling water4 ,as soon as the ,schultz process proved successful1 many attempts were made to evade the patent by the use of other reducing agents than the 8hypo10 and other salts of sulphurous acid which it covered4 ,among these1 the use of hydrogen sulphide1 and acidified solutions of alkaline sulphides1 and especially of polysulphides1#aai proved capable of practical use1 though less convenient than thiosulphate1 but were soon acquired by a combination1 the ,patent ,tanning ,company1 together with ,schultz's original patents4 #aai 8,liver of sulphur0 or solutions1 made by boiling sodium sulphide or soda with excess of sulphur4 ,under these circumstances1 ,martin ,dennis1 either by fresh discovery1 or otherwise1 revived the original process of ,knapp1 which he patented#abj almost word for word1 and offered a basic chrome tanning liquor for sale1 without further restrictions on its use4 ,this liquor was made by dissolving precipitated and washed chromic hydrate 7easily prepared by precipitating chrome-alum solution with excess of alkali7 in hydrochloric acid to saturation1 and adding washing soda until the solution was rendered sufficiently basic4 ,such a solution may be used on skins prepared in the ordinary way1 by diluting with water1 and strengthening as the tannage proceeds1 like a vegetable tan-liquor4 ,it is doubtful if the patent is a valid one1 as it was known that the use of such a solution was not new1 and it was only granted in ,america on the representation1 which has since been found to be mistaken1 that chlorides alone were applicable for tanning1 while ,knapp had not restricted his statement to these salts4 ,in reality chlorides and sulphates seem equally suitable1 but to produce similar results the former must be made more basic than the latter4 ,in any case the patent cannot cover the general principle of basic tanning1 but only the particular liquor and mode of preparation specified4 ,it was soon afterwards shown by the writer1#aba that a good chrome tanning liquor might be prepared by direct reduction of dichromate with sugar in presence of such a limited quantity of hydrochloric acid as to produce a basic salt4 ,suitable proportions are #e mol4 ,h,cl to #a mol4 potassium dichromate1 which produces a salt approximately ,cr,cl7,,oh74 ,the solution is easily made by dissolving three parts of dichromate in a convenient quantity of water1 adding six parts by weight of concentrated hydrochloric acid1 and then cane-sugar gradually till a green solution is obtained1 when the whole may be made up to one hundred parts1 and will be approximately of the same strength as a #aj per cent4 solution of chrome-alum4 ,a little heat may be needed to start the reaction1 but too much should be avoided1 as considerable heat is evolved by the oxidation2 and as much carbonic anhydride is produced1 which causes the solution to effervesce briskly1 the vessel used should be of ample size4 ,in place of cane-sugar1 a good quality of glucose may be used1 but some samples contain some impurity which produces a violet solution which will not tan satisfactorily4 ,this liquor is in regular use in many tanneries1 producing a good quality of chrome calf1 but is somewhat variable in its effects according to the temperature employed in its preparation1 and it appears to have no real advantage over a simple solution of chrome-alum1 rendered basic by soda and with some addition of salt4 ,a somewhat similar preparation is ,eberle's 8chromalin10#abb in which some organic substance1 probably crude glycerine1 is used to reduce the bichromate4 ,the organic matters1 and especially the organic acids which result from the oxidation of the sugar or glycerine1 are not without influence on the tanning properties of the liquor4 ,of course these solutions may be rendered still more basic by the addition of sodium carbonate4 ,a good stock-liquor1 of approximately the same strength as that above described1 is made by dissolving #aj parts of chrome-alum in #hj parts of tepid1 but not hot water1#abc and adding with constant stirring a solution of #b to #c parts of washing soda in #aj parts of water4 ,the chrome alum dissolves somewhat slowly without the aid of heat1 and the solution is best made either in a small drum driven by power1 or by suspending the crystals in a basket near the surface of the liquor1 so that the saturated solution can descend4 #abj ,martin ,dennis1 ,u4,s4,a4 ,pat4 #diejbh1 #ahic2 and #eaadaa1 #ahic1 #ggcb1 #ahic4 ,e4 ,pat4 ,gallagher4 #aba ,leather ,trades ,review1 ,jan4 #ab1 #ahig4 #abb ,compare ,eberle's ,german patents1 #aaijdb1 #ahih1 and #acjfgh1 #ahii4 ,the last of these appears to be anticipated1 at least as regards the use of glucose1 sugar and starch1 by the writer's publication in #ahig above cited4 #abc ,leather ,trades ,review4 ,later investigations have shown that the temperature of the water is unimportant if alkali be added1 but chrome-alum dissociates to some extent in hot water1 and comparative experiments have shown that solutions of the normal salt made with the aid of heat act on skin as if more acid than those made in the cold4 ,eitner#abd has pointed out the important effect that differences of basicity have on the tanning properties of chrome solutions4 ,normal chrome sulphate or chrome-alum colours the leather quickly and equally throughout1 and swells the pelt on account of its practically acid character1 but gives a thin and lightly tanned leather1 from which much of the chrome washes out1 unless it is at once 8neutralised0 in alkaline solutions4 ,as the chrome solution is made more basic1 the tannage penetrates more slowly1 but is heavier and more thorough1 the colour is darker and bluer1 and much less of the chromic salt is removed by washing with water4 ,when the basicity becomes excessive1 the solution becomes unstable1 and decomposes on dilution with water into a very basic salt which is precipitated1 and a more acid solution than that given by a moderately basic salt4 ,the effect of such solutions on the leather is very unsatisfactory1 producing the bad effects both of too acid and too basic salts4 ,the pelt is apt to be swollen and lightly coloured by the more acid salt1 but at the same time the actual tannage proceeds very slowly1 and in extreme cases it is difficult to tan through1 while the surface becomes over-tanned1 and the grain often tender and even brittle from the incrustation of precipitated basic salt4 ,eitner likens the effect of the more acid liquors to the quickly penetrating and lightly tanning vegetable tans1 such as gambier1 and that of the more basic to the heavier tannages1 such as valonia2 and within limits1 advantage may be taken of these facts in adjusting the liquors to the character of the leather it is desired to produce4 ,in sulphate liquors1 he considers the salt ,cr,o,h4,,so as most suited to general use1 and in the case of chrome-alum1 this is produced by the use of #bhf parts of soda-crystals1 or #ajf parts of dry sodium carbonate 7#a molecule7 to #iih 7or practically #ajjj7 parts by weight 7#a mol47 of chrome-alum4 7,in using washing soda1 care must be taken to employ clear crystals of the salt1 and not those which have become white by loss of water47 ,in place of soda1 ,eitner makes a similar basic liquor by boiling #ajjj parts of chrome-alum with #bdh parts 7#a mol47 of sodium hyposulphite until the whole of the liberated sulphurous acid is driven off1 and the sulphur deposited4 ,in comparative experiments by the ,author1 no difference could be detected between the tanning effects of the two solutions1 and that with soda is both cheaper and more easily made4 ,if the solution with hyposulphite is not boiled1 a more acid liquor results1 in which part of the chromium is combined with sulphurous acid1 forming an unstable compound which may prove useful in certain cases4 #abd ,gerber1 #aija1 pp4 #c et seq4 ,eitner states that he has made chrome-solutions of various types1 containing organic compounds in combination with the chrome-salt1 which combine with the leather1 producing a fuller and softer tannage1 but he gives no details as to their preparation1 as they are made commercially by the 8,erste ,oesterreichische ,soda-,fabrik0 at ,hruschau4 ,the writer has found that in some cases by the addition of say #c parts of sugar1 or still better of glucose1 to #aj parts of the chrome-alum in making up the basic liquor1 a much fuller and plumper leather is produced1 which dries perfectly soft1 even without staking or fat-liquoring2 and it is probable that many other organic compounds may be found which produce similar effects4 ,the addition of very small quantities of even neutral tartrates or lactates1 and probably of many other organic salts or acids1 have a remarkable effect in lowering the apparent basicity of the solution1 and it is possible that these may also be usefully employed in combination with very basic liquors4 ,it is highly probable that the unsatisfactory tanning liquors produced by direct reduction with some samples of glucose are due to the presence of small quantities of some organic acid produced during the oxidation4 ,it has been found that these solutions may be made to tan by the liberal addition of soda4 ,it is probable that more satisfactory results in chrome-tanning will be attained by the direct addition of known organic substances to basic liquors of definite constitution1 than by the somewhat uncertain products of organic oxidations4 ,the quantity of salt to be added depends on the qualities desired in the leather1 and upon whether chloride or sulphate liquors are employed2 salt in chloride-liquors increasing the softness of the leather1 but in excess tending to flatness1 while in sulphate-liquors it practically diminishes their basicity by converting the chromium sulphate into the equivalent chloride1 which1 as ,eitner points out1 behaves as a less basic salt1 and hence but little advantage is to be gained from its use4 ,it is best to begin with a very weak liquor1 to avoid drawn grain1 and for the same purpose a preparatory tannage with alumina salts1 or an addition of alum or sulphate of alumina and salt may be made to the first liquor1 as the attraction of the chrome salt for the fibre is sufficient to produce a chrome tannage1 even in presence of excess of alumina salts4 #aj lb4 of chrome alum will tan about #ajj lb4 of wet pelt1 but more must be used for the first parcel2 as to avoid loss of time1 the skins may be tanned out in a pretty strong liquor4 ,the bath has a tendency to become acid by use1 and before strengthening1 it may be necessary to add some more soda solution4 ,very little additional salt is required1 as it is only absorbed by the skins to a small extent1 probably as chromic chloride4 ,as the liquors gradually become charged with sulphates1 it is best to work them out like bark liquors1 and not to go on strengthening the same liquor indefinitely4 ,if old liquors are used for green goods1 it is not necessary to neutralise them with soda before use1 as ,eitner has shown that less basic liquors colour more evenly and with less tendency to produce drawn grain4 ,basic chrome liquors1 such as have been described1 may also be used in chrome combination tannage4 ,it is generally best to let the light vegetable tannage precede the chrome1 and lightly tanned skins1 such as 8,persians0 and ,east ,india kips1 acquire many of the qualities of chrome-tanned leather by the treatment4 ,the effect is still further increased by a previous detannisation of the leather with alkaline solutions 7see p4 #bda74 ,several firms beside ,dennis now supply basic chrome liquors ready prepared for use4 ,the time of tannage will of course vary with the thickness of the goods1 and for calf-skins will usually extend over some days1 though it can be much quickened by drumming4 ,the tannage is generally best accomplished in the paddle1 but can be carried out by frequent handling in pits or tubs1 or1 where very smooth grain is important1 by suspension4 ,when the goods come out of the final liquor1 they may be allowed to lie in pile for twenty-four hours1 or even for some days1 with advantage1 as the surplus chrome liquor is pressed out1 and the tannage becomes more complete4 ,they are then washed with plenty of warm water1 till it ceases to be coloured with chrome4 ,they may be kept for an almost unlimited time in a wet condition1 as they do not bleed1 and have little tendency to heat even in pile4 ,they have now reached the stage at which we left the 8two-bath0 leather1 and the subsequent treatment may be the same in both cases4 ,although by both processes1 the chrome-salt fixed in the fibre is of a decidedly basic character1 it still contains enough acid to act injuriously on the leather in course of time1 and to lead to serious inconveniences in its subsequent treatment4 ,before proceeding further1 this access of acid must be removed or neutralised1 and it is not too much to say that most of the troubles experienced in the fat-liquoring arise from neglect or mistake in the washing and neutralisation4 ,the difficulty in the process arises from the fact that while the acid should be reduced to a mere trace1 it must not be entirely removed1#abe as chromic oxide itself does not seem capable of tanning1 and at any rate the effect of excess of strong alkalies is at once to render the leather hard and pelty4 ,borax is one of the safest neutralising materials1 about #c per cent4 on the wet weight of the pelt being required1 in not more than per cent4 solution4 ,eitner recommends the use of silicate of soda1 which1 sold as a solution of ,s4,g4 #ae1 is somewhat stronger and much cheaper than borax4 ,hyposulphite of soda and whitening together neutralise more rapidly and completely than either alone4 ,other salts of weak acids may also be used1 the acids exercising a regulating influence which prevents neutralisation going too far4 ,sodium carbonate or bicarbonate1 or ammonia may also be used1 but with these it is difficult to get even 8neutralisation10 or to avoid the risk of carrying the process too far4 ,even a thorough drumming with a milk of 8whitening0 7calcium carbonate7 is effective4 ,with the latter there is no danger of overdoing the process1 but in some cases the adhering whitening and precipitated calcium sulphate are troublesome in later operations4 ,in any case the neutralising should only be carried so far that the skins show no acid reaction to litmus paper4 #abe ,procter and ,griffith1 ,journ4 ,soc4 ,chem4 ,ind41 #aijj1 p4 #bbc4 ,it is probable that one of the great causes of difference between 8one-bath0 and 8two-bath0 leathers is the presence of free sulphur in the latter4 ,this may also be introduced into 8one-bath0 leather1 by treating it in the wet chromed state1 without washing out the chrome liquor1 with excess of a solution of hyposulphite1 or of an alkaline polysulphide1 which at the same time will neutralise the skin4 ,the more acid the chrome liquor1 the greater the quantity of sulphur which will be introduced4 ,the simplest means of distinguishing 8two-bath0 from 8one-bath0 tannages is to test for the presence of sulphur1 by wrapping up a silver coin1 with a piece of the leather in paper1 and leaving the parcel for an hour in the water-oven1 or some other warm place1 when the presence of sulphur will be shown by the blackening of the coin4 ,of course a sulphurised 8one-bath0 leather will give the same reaction4 ,the leather must now be dyed and fat-liquored4 ,which of these two operations should be first undertaken will depend on circumstances4 ,most leathers dye more easily before fat-liquoring1 but as many dyes are soluble in the alkaline fat-liquor1 a good deal of colour is often lost4 ,this may be compensated by dissolving a suitable aniline 7acid7 colour in the fat-liquor4 8,bluebacking0 is generally done before fat-liquoring by drumming with methyl-violet1 or some other aniline colour 7with or without logwood1 which gives alone a very dark violet74 ,any shaving or splitting required must of course be done before bluebacking4 ,the fat-liquor is an emulsion of soap and oil1 which for chrome leather should be as neutral as possible1 if the neutralising has been thorough2 but if any acid be left on the skins1 a neutral fat-liquor will be precipitated as a greasy mass4 ,this can sometimes be remedied by the addition of a little ammonia or borax1 or by re-fat-liquoring with soap solution only1 but if the washing of the skins has been incomplete1 and soluble chrome-salts remain1 the mischief is almost irretrievable1 as sticky chrome-soaps are formed1 often coloured with the aniline violet1 which adhere to the skins1 and which can scarcely be removed by any solvent which does not injure the leather4 ,as regards the soaps and oils used1 there is considerable latitude3 #a per cent4 of castor-oil soap1 and per cent4 of castor or olive oil on the wet weight of the pelt has done good service in my hands1 but many manufacturers employ soft soaps1 curd soaps1 etc41 with castor1 olive1 cod or neatsfoot oil1 and sometimes sod-oil or degras4 ,eitner considers olive-oil and olive-oil potash soap the most suitable1 and particularly warns against the use either of drying oils or of oils containing tallow 7such as neatsfoot71 which are not only apt to cause a white efflorescence1 but to give the leather a disagreeable rancid smell4 ,fish-oils are unsuitable1 but mineral oils are often useful constituents of fat-liquors4 ,wool-fat also makes a good fat-liquor1 but is unsuitable for goods which are to be glazed4 8,turkey-red oil0 7which is sulphated castor7 may be used as a fat-liquor1 simply mixed with warm water1 without soap1 and has been recommended where delicate colours are to be dyed after fat-liquoring2 but it is said to have an unsatisfactory after-effect1 hardening and tendering the leather4 ,some soaps made from the saponifiable part of wool grease1 such as 8,lanosoap10 also act well in conjunction with olive1 castor1 or other oils4 ,where leather is to be glazed1 the amount of fat-liquoring must be kept very moderate4 ,fat-liquors should be thoroughly emulsified1 and are generally used warm4 ,they penetrate better if the leather is partially dried by sleeking out1 or pressing1 or cautious 8samming10 but the leather must not be completely dried out before fat-liquoring and dyeing1 unless it has been previously treated with glycerine1 glucose1 treacle or some deliquescent salt1 which will enable it to be wet back4 ,chrome leathers are not 8waterproof10 as has often been stated1 unless rendered so by treatment with soaps and greases1 and are apparently easily wetted1 but the fibre will no longer absorb water after thorough drying1 and consequently will neither dye nor stuff satisfactorily4 ,in order to enable chrome leather to be kept in an undyed condition1 glycerine or syrup is sometimes mixed with the fat-liquor1 but as the watery portion of this is not generally completely absorbed1 the process is somewhat wasteful4 ,mr4 ,m4 ,c4 ,lamb avoids this difficulty by applying a solution of glycerine to the grain-side with a sponge after fat-liquoring4 ,in this case the leather may be dried sufficiently for staking or shaving without risk4 ,chrome leather can be dyed by many of the acid aniline colours without a mordant4 ,basic colours are only fixed when the leather has been first prepared with a vegetable tannin1 gambier1 or a mixture of gambier and sumach being the most suitable4 ,considerable care must be employed in the application of tannins to chrome leather1 as they have a tendency to harden it and diminish its stretch1 or even to render it tender1 but traces of tannin in the dye probably facilitate glazing4 ,before dyeing1 it is advantageous to fix the tannin with tartar emetic1 or for browns and yellows1 with titanium potassium oxalate solution1 which itself gives a good yellow-brown with tannin4 ,in place of employing the tannin and titanium salt in two separate baths1 they may be combined1 using a weight of the gambier or tanning extract 7oakwood1 chestnut1 etc47 about equal to that of the titanium salt1 or titanium tanno-oxalate solution may be used4 ,chrome leather may be dyed with the various dye-woods1 which are mordanted by the chromium present1 but the colours are mostly dull1 that of logwood being nearly black4 ,a good black of a very permanent character is obtained by dyeing with logwood1 and saddening with a hot solution of titanium oxalate in the drum4 ,a little iron-alum added to the chrome liquor in tanning will facilitate dyeing the skins black with logwood and help it to penetrate through the leather1 which is sometimes desired4 ,several aniline blacks1 and notably the 8corvolines0 of the ,badische ,anilin und ,soda ,fabrik1 ,casella's 8leather black ,c10 and ,claus ,re's chrome-black give very satisfactory blacks by brushing or dyeing4 ,chrome skins may be glazed in the ordinary way with blood or albumen mixtures under glass or agate1 but require good pressure and repeated seasonings and glazings1 and much care is required in fat-liquoring4 ,the glazing is often assisted by the previous application of barberry juice 7pine vinette7 or of lactic or tartaric acid solution with a trace of sugar4 ,much of the difficulty which has been experienced in glazing chrome leathers is due either to the natural fat of the skin1 or to oils used in fat-liquoring in excessive quantity or of unsuitable character4 ,,chapter ,,xvi4 ,,principles ,,of ,,the ,,vegetable ,,tanning ,,processes4 ,the processes employed in the production of leather with the vegetable tanning materials vary extremely according to the class of leather which is being produced1 both in the materials selected and in the time required4 ,in sole-leather tanning1 where thick hides are used1 and where diffusion is the only force acting to carry the tannin into the hide1 many months are frequently needed1 while with thin skins1 and with the aid of mechanical motion1 which circulates the tanning liquid between the fibres1 the process is often complete within a few hours4 ,differences in the strength of the liquors according to whether hard or soft leathers are to be produced1 and the mutual action of the acids naturally present in the liquors1 and of the tan1 have also a determining effect upon the quality of the product4 ,the simplest form of tanning in principle is probably the old-fashioned method of sole-leather manufacture4 ,for this purpose1 the hides are usually 8rounded0 or trimmed after liming1 unhairing and fleshing1 so that the most valuable part1 the 8butt10 can be tanned separately from the 8offal40 ,the butts are usually washed in water to remove a portion of the lime1 considerable care being required at this stage to avoid carbonation and fixation of chalk by means of free carbonic acid1 or hydric calcium carbonate 7temporary hardness7 in the water employed1 or by the free carbonic acid of the air4 ,this somewhat primitive process can at best only remove a small portion of the lime1 since so long as the lime remains in the caustic condition1 it is very obstinately held by the hide-fibre4 ,advanced tanners now frequently employ weakly acid baths1 in addition to washing1 in order to produce more complete deliming1 and this effects a very considerable improvement of colour in the early liquors4 ,the use of lactic acid 7free from iron7 or boric 7boracic7 acid in solutions of about #d lb4 per #ajj gallons1 in which the butts are kept in motion1 are among the safest and most satisfactory ways of removing surface-lime and improving the colour1 but even the stronger mineral acids may be used successfully with caution 7see ,chap4 ,,xiii474 ,whether acid be used or not1 the butts are now usually suspended in deep pits containing old and nearly exhausted tan liquors4 ,these liquors contain a certain amount of lactic and acetic acids1 derived by fermentation from the sugary matters of the tanning materials1 and also in some cases1 weak acids originally present in the materials themselves4 ,these acids are most important to successful tannage1 and their effect is twofold2 in the first place1 they neutralise and remove any lime which still remains in the butts2 and1 secondly1 they bring the butt into a slightly acid condition1 in which it remains plump and swollen in the liquors1 while the tannin gradually penetrates and tans the fibre4 ,if1 as frequently happens1 especially in modern yards where extracts are very largely used1 the natural acid of the liquors is not sufficient for this purpose1 the lime combines with the tanning matters1 and the butts either become discoloured at once1 or darken by exposure and oxidation1 when they come to be dried1 while the pelt remains flat and insufficiently swollen4 ,to avoid this trouble1 resort is sometimes had to artificial acidification of the liquors4 ,as a general rule1 it may be stated that it does not answer to mix the stronger mineral acids directly with the liquors1 but lactic and acetic acids may be used1 or even oxalic acid may be added to the suspenders in such quantities as to precipitate and remove the lime which they contain1 setting free the organic acids with which it had been combined4 ,the use of oxalic acid should never be pushed further than this1 as it has a most powerful swelling action on the hide2 and goods which are too much swollen by acids tan dark and brittle4 ,after the hides have remained from ten days to a fortnight in the suspenders1 they are usually laid in pits called 8handlers0 which are worked in series of #f1 #h1 or #aj pits1 containing the same number of packs of goods4 ,the weakest liquor from the youngest pack is run to the suspenders daily1 a new and stronger liquor is run to the pit1 which now becomes the head of the series1 into which the oldest and most tanned pack of butts is moved2 and the next takes its place and liquor1 and so on down the series1 the youngest pack finally occupying the place which had previously been taken by the last but one4 ,in this way each pack receives a change of liquor of regularly graduated strength2 and during the time which it remains in the handlers1 passes from a strength of perhaps #bj ,bkr4 7sp4 gr4 #ajbj7 to one of about #dj ,bkr4 7sp4 gr4 #ajdj74 ,during this part of the process the butt is completely or nearly coloured through1 and is then ready for the 8layers40 ,in the forward handlers1 dustings of ground bark or other tanning material are very frequently given1 and the layers only differ from these in having much heavier dusting1 stronger liquors1 and being allowed to remain undisturbed for greater lengths of time1 ranging from a week up to a month or even six weeks1 as the tannage progresses4 ,the handler-liquors are principally from the old layers1 though they are frequently made up with weak liquors from the leaches1 and strengthened with extracts or gambier4 ,very varied materials are used in the manufacture of sole-leather4 ,oak-bark is one of the oldest1 and as regards quality one of the most satisfactory1 but it is costly1 not only on account of its weakness in tannin but from the light weight of leather which it gives4 ,valonia is one of the favourite materials1 giving heavy weight and a solid leather1 in which it deposits a great deal of bloom4 ,oakwood1 chestnut-wood1 and hemlock-bark extracts are now very largely consumed1 principally in strengthening the layer-liquors2 the great object being not only to lessen the cost in material1 but to save time1 and produce greater weight and firmness4 ,the layer-liquors in some yards where extract is used1 reach strengths of even #abj to #aej ,bkr4 7sp4 gr4 #aab to #aae71 while in pure oak-bark yards it is difficult to get above #cj or #ce ,bkr42 and even these figures are only reached by repeatedly strengthening the same liquor1 in which large quantities of non-tanning substances accumulate4 ,the opinion of the most intelligent tanners is1 however1 that better results are attained by a regular change of liquor1 even if the apparent strength is less4 ,when the leather has remained a sufficient time in the layers to have attained all the weight and solidity of which it is capable1 it is washed up in a clear and somewhat weaker liquor or even in warm water1 and taken into the shed to be dried and finished4 ,as this finishing is almost purely mechanical1 and scarcely comes within the scope of the present volume1 a very brief sketch must suffice4 ,illustration3 ,,fig4 #ci4--,wilson's ,striking ,machine4 ,the mode of finishing which was formerly1 at least1 in vogue in ,lancashire and ,cheshire may be taken as a type of the best work4 7,in the present day1 the various methods are so widely known that they have ceased to be local1 and are varied according to the quality and tannage of the goods47 ,the butts1 which in earlier times were largely bark-tanned1 are taken wet from the pits1 and scoured on a rounded beam or 8horse0 with stone and brush1 till the bloom is completely removed1 and are then lightly oiled on the grain1 half dried 78sammed071 laid in pile to temper1 and 8struck out0 with the 8pin10 a two-handled tool of triangular section shown in ,fig4 #bi4 ,the use of this tool has now been largely superseded by ,wilson's striking machine ,fig4 #ci1 in which knives or sleekers 7or stones and brushes71 held in jointed arms1 are made to work on the butt1 which is extended over a slowly rotating cylinder4 ,the object of the pinning is not so much to remove bloom or dirt1 which has been previously effected by the scouring1 as to smooth and flatten the grain4 ,after further drying1 a second pinning is generally given1 and the goods are then twice rolled1 first with a light weight1 and somewhat moist grain1 and then more heavily with the grain nearly dry4 ,this was formerly accomplished by a sort of box or car1 heavily loaded with weights1 supported on a smooth brass roller of about #e inches diameter and #i inches long1 and manipulated with a long wooden handle on a floor of hard wood1 or zinc plates4 ,one type of the machines which have now almost entirely replaced this primitive contrivance is shown in ,fig4 #dj1 but is principally used for offal and common classes of goods4 ,for better work1 traversing rollers1 such as ,wilson's ingenious double bed roller shown in ,fig4 #da1 are to be preferred4 ,after rolling1 the goods are dried pretty rapidly by the aid of moderate heat1 and1 after polishing with a brush 7hand1 or machine1 ,fig4 #db71 are ready for sale4 ,it may be pointed out that although the tools are different1 the process is almost the same as that used for 8vache lisse0 in ,france and ,belgium1 and closely resembles that of currying harness leather except that the 8stuffing0 with fats and oil is omitted4 ,illustration3 ,,fig4 #dj4--,offal ,roller4 ,in contrast with the rather elaborate method just described1 we may place the ,american finish of red hemlock sides1 which are tanned throughout with a material which yields no bloom4 ,on these1 the scouring and 8striking0 is altogether omitted3 the goods are completely dried out from the pits1 which is found to fix the dark-coloured liquor1 and result in better colour2 they are then damped back1 and tempered1 and heavily rolled under a rapidly moving pendulum roller1 which polishes at the same time that it smooths the leather4 ,the saving of cost by so simple a process is not inconsiderable4 ,illustration3 ,,fig4 #da4--,wilson's ,double-bed ,butt ,roller4 ,in the ,west of ,england1 much heavy leather is still manufactured from ,south ,american hides1 which are tanned with a large proportion of valonia2 and which consequently are heavily bloomed4 ,no attempt is made to remove this bloom1 which would too much lessen the weight and firmness1 but the goods1 after a light oiling to preserve the colour1 are hung up and partially dried1 and are then laid in pile to temper4 ,the grain side is now wet with soap and water1 with which a little oil is often mixed1 and the bloom is 8struck in0 with the pin or machine2 a somewhat blunt pin being used1 or a blunt tool in the striking machine2 which is held at such an angle as to smooth and compress the grain without taking too much hold on it4 ,after a little further drying1 the striking is generally repeated1 the goods are washed over with water1 and rolled 8on40 ,they are now coloured with a mixture of pigment colour1 generally containing a large proportion of whitening1 or sometimes of ,french chalk coloured with ochres1 chrome-yellow and orange1 or whatever may suit the tint preferred by the tanner1 or best imitate the colour of a clean-scoured tannage1 and usually mixed with size and oil1 or sometimes with oil and tan liquor4 ,this mixture is well rubbed in1 and smoothed over with a cloth1 and then polished by brushing1 when the goods are 8rolled off10 rapidly dried1 and again brushed4 ,if the work has been well done1 it is not easy to distinguish from clean scouring1 and is much cheaper4 ,illustration3 ,,fig4 #db4--;,brushing ,machine4 ,a method intermediate between this and the first described1 and which was formerly much used in ,london1 was to proceed as above1 but using more water and holding the pin in the first striking so as to scour out as much bloom as possible1 and assisting this by the free use of water and the brush4 ,instead of using an opaque pigment-colour1 the goods were generally coloured either between striking and the first rolling1 or between the two rollings1 with a transparent colour1 such as dissolved annatto1 or a mixture of aniline dyes1 so as to conceal the traces of bloom1 and to render slight damages to the grain less conspicuous4 ,the principles of the manufacture have been fully explained in previous sections1 up to the time when the goods are taken into the tanning liquors4 ,at this stage complicated reactions take place between the lime in the butts1 the free vegetable acids in the liquors1 and the tannins2 and on the right adjustment of these three factors much of the success of the operation1 and indeed of the whole manufacture depends4 ,if the lime is in excess of the acids present1 it forms insoluble compounds with the tannins in the surface of the hide4 ,if these are protected from the air1 they are generally redissolved as they advance into more acid liquors1 but they readily become oxidised into dark-coloured matters1 which can no longer be removed4 ,their presence in the finished leather is one of the great causes of darkening in drying4 ,if the hide in the limy condition has been exposed either to the carbonic acid of the air1 or to free carbonic acid1 or acid calcium carbonate dissolved in water 78temporary0 hardness1 p4 #id71 a precipitate of calcium carbonate will be formed in the surface1 which is much more difficult to remove than free lime1 and which is perhaps the most common cause of the stains and discolorations which are so serious a source of loss to the sole-leather tanner4 ,these stains may1 if not too much oxidised1 be removed by treatment of the tanned leather with weak warm sulphuric acid1 but this remedy brings other evils in its train1 and should not be required4 ,the great remedy is to keep the goods from the time of unhairing till they go into the liquors1 under water in which there is always a trace of caustic lime1 or which at any rate are free from carbonic acid4 ,in deliming sole-leather with acids1 it is best to give the full dose of acid required1 at once1 and not gradually1 so that it may act most powerfully on the exterior1 and remove any carbonates present1 before it penetrates to and becomes neutralised by the excess of lime in the interior4 ,this is exactly the reverse of what is advisable with dressing leather1 where the object of the tanner is to remove lime as uniformly and completely as possible1 without excessive acidity of any part4 ,of course hides should not1 even in the case of sole-leather1 be allowed to go into the liquors while any acid swelling of the surface remains1 but this will soon disappear if the goods are suspended for a time in cold water after deliming1 unless excess of acid has been used 7cp4 p4 #aec et seq474 ,if the proportion of free acid in the suspender liquors is as it ought to be1 it is probably rather advantageous than otherwise for a little lime to remain in the interior of the hide1 as it keeps the pelt in a plump condition during the first stages of colouring1 quickens the penetration of the tannin1 and lessens the tendency to 8drawn0 or wrinkled grain1 which arises when the goods go into the liquors in a flat or fallen condition4 ,the causes of drawn grain are often a little obscure4 ,of course that case needs no elucidation in which the hides are submitted to the tanning liquor in a creased or wrinkled condition1 which is simply fixed and made permanent4 ,this may arise1 either from carelessness in handling the goods before taking into the suspenders1 or from the way in which they are slung to the sticks1 which often draws them into long wrinkles1 afterwards difficult to remove4 ,drawn grain in general1 however1 arises from the grain-surface becoming tanned and fixed in area1 while the substance of the hide is in a more extended condition than that which it assumes as tannage proceeds4 ,hides in a flat and unswollen condition are thinner1 the fibres are slenderer and looser than when swollen1 and consequently the hide has a larger area4 ,if1 after the grain is tanned1 the substance of the hide becomes contracted in the liquor1 either by swelling with acids1 or by the direct action of the tannin on the interior fibres1 the grain is certain to be shrivelled1 like the skin of a dried apple4 ,a similar effect1 produced in a mechanical way1 may always be noted where a hide has been coloured hanging grain-side out over a pole1 so that the surface is extended at the bend1 on which long wrinkles are formed as soon as it is straightened4 ,a hide in a slightly alkaline condition colours1 and even tans more quickly than one which is acid4 ,in presence of a trace of lime1 and deficiency of free acid in the suspender liquor1 tannages of valonia and bark give the butt a sort of lemon-yellow colour1 which is not in itself injurious1 and which disappears as the hides advance into more acid liquors1 but which is a sign of danger1 as showing that no excess of acid exists in the suspender-liquors4 ,gambier gives pelt perfectly free from lime a pale buff colour1 but where lime is present1 the colour is always reddish1 and much darker1 and this coloration does not disappear so readily as that with valonia1 so that if gambier is to be used in the first liquors1 care should be taken to remove all lime from the surface4 ,the only known tannin which gives no insoluble compound with lime is that of the babool pod 7sometimes called 8gambia-pod071 which is frequently used in ,india as a bate1 and which would probably prove very useful in colouring liquors 7pp4 #afe1 #bhh74 ,when sole-leather first goes into liquors1 it is generally swollen with lime to some extent4 ,if the liquors contain1 as they usually do1 sufficient free acid 7acetic1 lactic7 in addition to the tannins1 these combine with and neutralise the lime1 and the pelt1 without absolutely becoming flat and thin1 loses its firmness1 and becomes soft and spongy4 ,this is a favourable condition for the absorption of tannin1 but care should be taken not to allow the pelt to be squeezed or pressed1 or water will be squeezed out1 and the pelt will not easily resume its plumpness4 ,as the tannage proceeds1 both the tannin and the acid of the liquors penetrate deeper into the pelt1 the former tending to contract and the latter to swell the fibres4 ,thus a given quantity of acid will cause the greater swelling1 the less tannin is present2 and therefore in strong tanning liquors more acid is required4 ,the presence of certain products of bacterial putrefaction has a great but unexplained effect in preventing hide from swelling with acids2 and in hot weather1 much better swelling is obtained by sterilising and deliming the hides with one of the coal-tar products mentioned on pp4 #cj1 #afb4 ,boric acid may also be satisfactorily used for this purpose1 but should not be allowed to get into sole-leather liquors1 as it tends to produce a soft and loose tannage1 and from its inorganic and indestructible character1 is apt to accumulate in a yard in which it is used4 ,the same reasons render unadvisable its introduction into any liquors which are to be returned to the leaches even in the tannage of dressing leather1 though its presence in the colouring liquors is otherwise very useful in lessening the astringency of the tannins 78mellowing the liquors071 and making a fine grain4 ,its mode of action is by no means clearly explained1 but is in some way connected with its tendency to produce 8conjugated acids0 7,l4,i4,l4,b41 pp4 #cg1 #df74 ,the so-called 8mellowness0 of old liquors requires a word of comment4 ,it is well known to practical tanners1 that old liquors are much less liable to produce drawn grain1 and a harsh surface1 when used to colour green goods1 than liquors1 even equally weak1 which have been made from fresh materials4 ,this is probably due1 in part at least1 to more than one cause4 ,most natural tanning materials contain tanning matters of varied degrees of astringency and power of attaching themselves to the leather-fibre4 ,it is obvious that if a tanning liquor is used1 the most astringent and energetic tannins will be first removed from it1 leaving those of a milder character4 ,it is also known that the presence of neutral alkaline salts of weak acids has considerable influence in producing mellowness2 the addition1 for instance1 of sodium acetate has a marked effect4 ,this effect is probably due in the first place to the action of neutral salts in diminishing the energy of weak acids 7see p4 #ha71 and secondly to the fact1 that their bases combine to some extent with the tannins2 and that1 as was perhaps first pointed out by the writer1 such tannins are1 as it were1 partially paralysed in their action on hide 7p4 #cci74 ,sodium sulphite acts powerfully in this way1 and may perhaps prove of technical value in temporarily diminishing the astringency of liquors in quick tannage4 ,borax has a similar effect1 but is too alkaline1 and1 unless used with extreme caution1 spoils the colour of the liquors by causing oxidation4 ,it is probable that similar causes explain the mellowness of palmetto extract1 which contains large quantities of alkaline salts1 and of some extracts which have been treated with sulphites1 when used undiluted in drum tannage4 ,the addition of free acid will generally restore these tannins to an active condition4 ,as the tannage proceeds and penetrates further into the hide1 the liquors are used stronger1 as the outside1 once tanned1 is to a large extent protected from their action1 and it is only by continuously increasing the strength of the liquors that more tannin can diffuse into the interior1 since diffusion only takes place from a stronger into a weaker liquor4 ,the liquor in the interior of the butts is always exhausted of tannin so long as any part of the hide-fibre remains untanned1 but as the layer of tanned fibre between this and the outside gets thicker1 a greater difference is required to maintain a reasonable rate of exchange1 just as a greater head of liquor is required to maintain a flow of liquor through an increased number of percolation-leaches4 ,if the strength of the liquor outside be allowed to fall off1 this graduation of strength from the outside to the inside of the butt is disturbed1 and takes some time to re-establish4 ,as the liquors become stronger in tannin1 they may also become somewhat stronger in acid1 since1 as has been stated1 the two act to some extent in opposition to each other4 ,the acid-swollen fibre absorbs the tannin more slowly than if it were in more neutral condition1 but it absorbs it apparently in larger quantity1 and at any rate1 makes a firmer1 solider1 and less flexible leather4 ,it has been mentioned that in the latter stages of the process1 solid tanning materials are generally strewed between the butts in the tanning liquor4 ,it may be pointed out that many materials vary in their tanning effect1 according to whether they are used in solid form or merely in liquors4 ,it has been shown by ,youl and ,griffith#abf that such materials as valonia1 oakwood and chestnut extracts1 and myrobalans1 which contain both gallotannic and ellagitannic acids1 lose strength rapidly when kept in the form of liquor1 the ellagitannic acid becoming decomposed with separation of insoluble ellagic acid4 ,now it is just this ellagic acid1 which deposited in or on the leather1 gives weight1 solidity and bloom1 and the investigation points out not only an important source of loss in the tanning industry1 but also1 why valonia1 which in sole-leather tannage is known to give hard and heavy leather1 can be used in large quantities on dressing leathers in ,yorkshire1 with gambier1 in the form of liquor1 giving a soft and mellow leather almost destitute of bloom4 ,if weight and solidity are required from the use of such materials1 it is obvious that they must be brought into immediate contact with the leather to be tanned1 so that as large a part of the bloom as possible is deposited in1 and not outside the leather4 ,with many other materials1 such as hemlock1 quebracho1 and mimosa1 which yield no bloom1 but 8difficultly soluble0 tannins 7reds or phlobaphenes71 the same rule holds1 since in contact with the hides1 the small proportion of these materials which is soluble in the liquors1 is replaced from the materials as rapidly as it is absorbed by the leather1 while1 when liquors or extracts only are used1 the greater part of these solidifying and weight-giving constituents remain unutilised in the spent tanning materials4 ,at the same time1 the long 8layers0 afford an opportunity for the acetic and lactic fermentations to go on which are the principal source of the natural acidity of liquors4 ,it must be understood that what are called layers in ,england1 are not to be identified with the ,stze1 but rather with the ,versenke of the ,german tanner1 the former being layers given in much the same manner as was current in ,england #aej years ago2 in which the leather1 with thick layers of tanning material between it1 is laid into the empty pit1 which is afterwards filled up with liquor1 often of a comparatively weak character4 ,in such layers1 the acidification1 and the solidification of the leather both go on to a still greater degree2 the acid formed1 apparently gradually penetrating to the heart of the leather-fibres1 and producing a solidity1 and cheesy texture which can hardly be obtained by layers of the ,english kind2 which nevertheless have the advantage in rapidity and cheapness4 #abf ,journ4 ,soc4 ,chem4 ,ind41 #aija1 p4 #dbh4 ,in drying sole-leather1 one of the great objects which must be aimed at is to remove the dark coloured liquor1 with which the goods are saturated1 from the surface1 and to prevent further portions of it from finding their way there from the interior4 ,if a strip of filter-paper be allowed to rest with one end in a basin containing a little liquor1 and be placed in a draught of air1 the exposed end of the paper will rapidly become dark brown or black1 the liquor which evaporates there being constantly replaced by fresh portions sucked up by capillary attraction from the basin4 ,a similar action is constantly seen1 when filtering liquors through paper1 if the latter be allowed to project above the edge of the funnel4 ,precisely the same effect occurs1 perhaps increased by the oxidation of the tannins1 on the edges and other parts of a butt which are most exposed to draughts of air4 ,the use of oiling the grain is not only1 to a certain extent to protect it from oxidation1 but also to check evaporation1 and the consequent accumulation there of the dark-coloured solids contained in the liquor4 ,a very similar result is attained by wetting the grain-side1 and allowing as much of the evaporation as possible to take place from the flesh4 ,the process of sole leather tanning has been discussed in considerable detail on account of its simplicity and importance4 ,it is now time to point out in what respects the tannage of the lighter leathers differs from it in principle4 ,taking the case of ordinary dressing leathers1 such as kips and shaved hides1 the first point to remember is that these goods come into the liquors not merely almost entirely deprived of lime by bating1 but in a very flat and fallen condition from the action of the bacterial ferments of the bate4 ,as a general rule in this country the colouring is done in paddles1 but where a very smooth grain is required1 the use of suspenders is to be recommended1 and in ,america is largely adopted4 ,indeed in the ,states the entire tannage of much of the cheaper leather is done in suspension1 and the sides are only removed from the laths to which they have been nailed1 when they are required for splitting4 ,it is obvious1 from what has been said of sole leather1 that as the hides are brought into liquors in a very fallen and extended condition1 the grain will be likely to be wrinkled2 and indeed this is sure to be the case unless1 by suspension1 the hide is more or less kept in tension till its fibres are fixed by tanning4 ,the free motion in the paddle favours the formation of a 8pebbled0 grain1 since the hide is bent now this way1 now that1 and minute wrinkles and creases are formed in all directions4 ,for many purposes1 and especially if a grain is afterwards to be raised by 8boarding0 the curried leather1 this graining in the paddle is not disadvantageous1 so long as it is not excessive4 ,in some other cases it causes much trouble and labour to the currier before it is removed1 and if the ,english tanner and currier are ever to compete with the ,american in smooth grain finishes1 it will be necessary for them to obviate this source of wasted labour4 ,the graining is the less considerable1 and the easier to remove1 the weaker and more mellow are the liquors employed in colouring and the more gradually their strength is increased4 ,the production of a soft leather depends on the fibre being tanned in a fallen and unswelled condition4 ,it is for this reason that bating is in many cases essential1 though where somewhat firmer leathers are required1 mere reduction of the swelling by removal of the lime is sufficient4 ,for the same reason1 no acid-swelling is permissible either before tanning1 or in the liquors1 and though liquors for soft leathers must be rather acid than alkaline1 they are incapable of removing any large quantity of lime1 and for the best results1 the deliming must be complete before tanning4 ,as mere bating or puering is mainly designed to reduce swelling by the action of bacterial products 7p4 #agb71 and is not a very efficient means of removing lime1 it is desirable where it is employed1 to supplement it by some more active deliming process4 ,in the lighter leathers1 drenching 7p4 #aff7 generally fulfils this purpose and many of the more intelligent tanners now give bated hides a bath in boric acid before tanning1 which not only removes the last traces of lime without acid-swelling1 but checks the bacterial fermentation1 and prevents its introduction into the liquors4 ,in gambier tannages1 a decidedly better colour is obtained by this treatment 7p4 #bbh74 ,in most cases the production of bloom is not desired in dressing leather tannage1 and is prevented by relying chiefly on liquors1 and avoiding the use of bloom-giving solid materials1 which include most pyrogallol tannins4 ,dressing leather tannages can frequently be advantageously hastened by drumming3 which by continuously bending the leather in all directions1 constantly widens and contracts the spaces between the different fibres1 and1 as it were1 pumps the liquor through the skin4 ,the softness of dressing leathers is increased1 and the hardening action of acids present in the liquors is prevented by the addition of salt1 or of some sulphates 7sodium1 magnesium1 ammonium7 which exercise a sort of pickling action on the fibre1 and prevent its swelling1 but at the same time tend to light weight and a somewhat empty tannage4 ,it by no means follows that a hide or skin which is thoroughly coloured through1 is really fully tanned2 as1 though the fibres may be actually tanned or coated on the surface1 time is required for the tannins to penetrate them to the centre4 ,this incompleteness of saturation is often found in drum tannages4 ,such leathers are generally tough1 and gain weight and softness in currying4 ,in order to 8carry grease0 well1 that is1 to absorb a large quantity without appearing greasy1 it is essential that the fibre-bundles should be thoroughly split up or differentiated2 and the degree to which this is attained largely depends on the extent of liming4 ,there is also considerable difference in different tannages1 as to the amount of grease which they will carry4 ,it is now not uncommon to combine a degree of alum or chrome tannage with vegetable tannage in the finer dressing leathers4 ,for further information on this the reader must be referred to the next chapter4 ,the finest sorts of leather such as goat1 calf1 sheep and seal for bookbinding1 upholstery and the like1 are mostly tanned with sumach2 paddles and drums being largely used to quicken the operation4 ,leather tanned with sumach has been proved by the researches of the committee of the ,society of ,arts on the decay of bookbinding leathers#abg to be the most durable leather for this purpose1 some other tanning materials of the pyrogallol class coming near it in this respect1 while all catechol tannages are found peculiarly liable to destruction by the action of sunlight1 dry heat1 gas fumes1 and traces of sulphuric acid from other sources1 although in many cases more durable than the pyrogallol tannages when exposed to mechanical wear and moisture1 as is the case with shoe-leather 7p4 #bih74 ,east ,india sheep- and goat-skins 7so-called 8,persians07 are tanned with the catechol tannin of turwar or cassia bark4 #abg ,soc4 of ,arts ,journ41 #aija1 p4 #ad4 ,illustration3 ,,fig4 #db;a4--,interior of ,light ,leather ,tannery4 ,the finer leathers of which we are now speaking are almost invariably prepared for tanning by puering with dog-dung1 and drenching with bran1 as colour and softness are the special characteristics aimed at4 ,a somewhat interesting style of tannage is occasionally used for sheep-skins 7roans71 and calf-skins1 in which the skin is sewn into a bag1 flesh side out1 with only a small aperture left for filling at one of the shanks4 ,it is then turned grain-side out1 and filled with strong sumach liquor1 and a little leaf sumach1 and floated in a bath of warm sumach liquor4 ,after a short immersion1 the skins are piled on a stage1 so that the liquor is pressed through them by their weight2 and when partially empty1 they are refilled and the process repeated4 ,the time of tannage is very short1 not exceeding about twenty-four hours1 and the leather produced is very soft4 ,,chapter ,,xvii4 ,,combination ,,of ,,vegetable ,,and ,,mineral ,,tannage4 ,in very early times leathers were produced1 which were partly tanned with alum1 and partly with vegetable materials4 ,one of the earliest of these was probably the ,swedish or ,danish glove-leather4 ,the principle has long been applied to the production of certain very tough and flexible leathers known as 8green leather10 and used for 8picker-bands0 for looms1 laces for belting1 8combing-leathers0 and some other purposes where softness and toughness are of principal importance4 ,about twenty-five years since1 it was applied in ,america by ,mr4 ,kent to the manufacture of an imitation of glazed kid1 which he named ,dongola leather2 and since that time1 the method in various modifications1 has taken a considerable place in the manufacture of the finer leathers for shoe purposes1 especially in the ,united ,states4 ,alum-tanned leathers1 as has been already stated1 are remarkable for softness and toughness1 and the mineral 7crystalloid7 tannages have the power of penetrating and isolating the individual fibrils of the skin in a much greater degree than the vegetable tannins1 and hence are less dependent than the latter on a previous isolation produced by liming4 ,on the other hand1 they give much less plumpness and solidity1 and more liability to stretch1 and are less resistant to the action of water2 and are1 as a general rule 7to which some chrome-tannages are an exception71 incapable of producing a soft leather without mechanical softening 7staking7 after the tannage is completed4 ,purely mineral tannages have always a woolly fibrous structure1 and never the firm and compact flesh which is required in leathers which are to be 8waxed10 or finished on the flesh side to a smooth surface1 and as they communicate more or less of these peculiarities to combination-tannages1 the latter are mostly used1 either for grain-finish1 or for uses where a soft and velvety flesh-side is required1 as in the case of 8ooze-0 or 8velvet-0 calf4 ,on the other hand1 the partial use of vegetable tannage communicates to them a degree of plumpness1 fulness and resistance to water which is not possible to alum-tannages pure and simple1 and a softness which is not easily obtained in vegetable tannage without the use of large quantities of fats or oils4 ,a preliminary mineral tannage also greatly increases the rapidity of the penetration of the vegetable tans1 by isolating the fibres1 and rendering them less gelatinous4 ,once a leather is thoroughly tanned by vegetable materials1 it is little affected by subsequent treatment with alumina1 or even with chrome2 and on the other hand1 though chrome and alumina leathers are still capable of absorbing considerable quantities of vegetable tannins1 they always retain1 in a degree1 the qualities which the mineral tannage has communicated to them4 ,the resulting leathers are thus not only modified by the different proportion of vegetable and mineral tannages which have been given1 and by the properties of the particular vegetable tannage used2 but by the order in which the several treatments have been given1 and always retain1 to a considerable extent1 the characteristics of that which has been first applied4 ,we have thus in our hands a powerful means of modifying the character of our leather to suit the special requirements which it is to fulfil4 ,so long as tanners were restricted on the one hand1 to the ordinary methods of stuffing tanned leathers with oils and fats1 and on the other to the use of egg-yolk1 which had long been common in alum-tannages1 combination-tannage remained of but secondary importance1 and it was the application of the method of 8fat-liquoring0 by ,james ,kent to his ,dongola leather1 which gave them the place they now possess1 by providing a cheap substitute for egg-yolk1 and enabling the tanner to obtain softness and resistance to water1 without producing the greasy feel which is common to curried leathers4 ,the process of fat-liquoring has already been mentioned in connection with chrome leathers1 to which it was subsequently applied1 and we shall return to it1 after having given some further details of the methods of tannage4 ,in the first place we must consider briefly the mutual action of the mineral and vegetable tannages on each other4 ,it has been pointed out by ,eitner1 and also mentioned 7p4 #cci7 in connection with the decolorisation of extracts1 that the addition of say per cent4 of alum1 or aluminium sulphate to tanning liquors1 lightened their colour1 not only by giving a degree of acidity to the solution1 but by precipitating a portion of the less soluble and more darkly coloured tannins4 ,chrome-alum1 and basic chrome salts produce a similar effect1 though from their marked colour1 the lightening of the solution is not so easily observed4 ,it is therefore advisable if these salts are to be used in actual mixture with the vegetable tans1 to allow the solution time to subside1 or to filter off the dark-coloured precipitated matters4 ,larger quantities than per cent4 of the alum do not appear materially to increase the effect just described4 ,a second effect produced by these mineral salts on vegetable tannins1 is in many cases to develop mordant colouring matters which are present2 and thus1 since most of these colouring matters are yellow1 to produce a yellower leather than would be obtained with the vegetable material alone4 ,this effect is very marked in the cases of sumach1 gambier and quebracho4 ,the compounds which these colouring matters form with chrome are mostly of a darker shade than those with alumina1 tending to olive1 and therefore chrome-combination leathers are generally dull in colour4 ,potassium dichromate1 especially if acidified1 generally oxidises and precipitates tannins1 and darkens their colours1 so that it is not practical to follow a vegetable tannage by the two-bath chrome process2 and though the reverse order may be pursued1 the single-bath chrome process1 and that following and not preceding the vegetable tannage1 generally gives the best results4 ,if lightly tanned leathers1 such for instance as the imported ,east ,indian tannages1 with babool or turwar barks1 be treated with a basic chrome tanning liquor1 such as is described on p4 #bae1 so large a proportion of chrome will be absorbed1 that the leather will possess most of the characteristics of a genuine chrome leather4 ,combination-tannages for glove-leathers1 such as the ,danish and ,swedish leathers already alluded to1 are generally first tawed with alum and salt1 with or without addition of flour and egg-yolk1 and are then coloured1 and more or less tanned with vegetable materials4 ,that employed on the original ,danish leather was willow bark 7of ,salix arenaria74 ,in ,france1 where this willow is not found1 the bark of the commoner ,salix caprea was substituted2 and as it is much weaker in tannin1 additions of oak-bark or sumach to supply the deficiency1 and of madder to give a redder colour were made to it4 ,the dyeing of these leathers is frequently combined with the tannage1 dyewoods or dyewood liquors being mixed with the tanning liquors4 ,in the manufacture of glazed ,french kid1 indeed1 the process is so arranged1 by brushing on dye-liquors mixed with tannins1 as merely to tan the grain-surface1 which is necessary to enable it to be glazed by friction1 leaving the substance of the leather of purely alum tannage4 ,on the other hand1 in the 8green leathers0 7so-called from their greenish-yellow colour1 and largely made in the ,west ,riding of ,yorkshire71 the hides usually receive a light gambier tannage1 extending over a week or so in weak gambier liquors in handlers1 and are then 8cured0 by handling in hot and strong solution of salt and alum1 in which they are finally left all night1 and then dried rapidly without washing out the alum1 much of which consequently crystallises on the surface4 ,this is slicked off1 and the leather damped back1 and heavily stuffed with sod-oil4 ,if1 however1 the combination-tannage is properly carried out1 it will stand liberal washing without losing the necessary alum1 and of course a tougher and more satisfactory1 though somewhat lighter weighing leather results4 ,it is in many cases a better plan to combine the two tannages in one bath1 mixing the alum and salt with the gambier1 and handling or paddling the goods in the mixture4 ,this is the plan usually adopted for ,dongola leather1 in the ,united ,states4 ,for skins which are to be glazed1 it is important that the surface should be tanned with the vegetable material1 and the goods are therefore worked into gambier liquors1 to which the salt and alum are only added after the tannage has made some little progress2 while for dull ,dongola1 intended rather to imitate calf-kid1 it is best for the alum and salt tannage to begin first4 ,for goat-skins for glazed ,dongola kid1 about #d lb4 of block gambier1 lb4 of alum1 and lb4 of salt are used per dozen1 and the tannage occupies in all about twenty-four hours4 ,after the skins are tanned1 they are thoroughly washed out with tepid water1 to remove loose alum and gambier1 and are then ready for fat-liquoring4 ,as in the case of chrome leather1 it is of great importance that this washing should be done thoroughly1 as any remaining alum which diffuses into the fat-liquor1 will cause it to curdle4 ,if the washing is thorough1 the more neutral the fat-liquor and the better2 but a somewhat alkaline soap-solution is less liable to curdle4 ,the original fat-liquor used by ,mr4 ,kent was the alkaline liquor which had been used in washing the surplus oil from chamois leather 7see p4 #chj71 but now soap- and oil-solutions are generally made specially for the purpose4 ,most of the remarks in the chapter on chrome tannages are applicable in this case1 but probably fat-liquoring is somewhat easier than in the case of chrome4 ,mixtures of either soft soap or curd soap with cod1 sod1 and olive oil are frequently employed4 ,sesame oil also seems well adapted for the purpose4 ,the better these are emulsified1 and the more satisfactory is the result2 a cylinder of zinc or copper fitted with a plunger1 something like that of a 8,lightning ,egg ,beater10 but covered with perforated zinc1 or wire gauze1 does very good service as an emulsifier on a small scale4 ,another method is to melt the soap with just sufficient water to make it pasty1 and to incorporate the oil thoroughly with the mass1 which is afterwards dissolved in hot water4 ,oils are the most easily emulsified when they are somewhat acid4 ,for this reason rancid olive oils are often used for the ,turkey-red process1 but a similar effect can be obtained by adding a small quantity of candlemaker's oleic acid to the oil before mixing4 ,the addition of sulphated castor oil 7,turkey-red oil7 also helps emulsification1 and is in itself a very good softening agent4 ,one of the commonest mistakes in fat-liquoring is the employment of too strong an emulsion--even so small a quantity as per cent4 of soap1 and half that quantity of oil1 reckoned on the wet weight of the well-drained leather1 will produce a very notable softening effect4 ,of course1 for dull finishes1 much larger proportions may be used4 ,not only combination-tannages1 but those entirely vegetable1 can be fat-liquored with excellent effect1 and the process is now largely used for coloured calf1 and other leathers1 which are required soft and nourished1 but without any appearance of greasiness4 ,leathers absorb the fat-liquor most readily if put into it in a sammed or partially dried condition1 but even if quite wet1 they soon take up the whole of the oil and soap on drumming1 leaving only a little clear water in the drum4 ,goods may be blacked while still wet with fat-liquor1 but should generally 7except in the case of chrome leathers7 be dried out before dyeing1 as this fixes the oil and soap in the fibres4 ,many coloured leathers are now made by a process which may be considered a combination of the ,dongola process itself with the ordinary process of vegetable tanning1 the goods being coloured and partially tanned as if for a vegetable tannage1 and then finished in ,dongola liquors with alum1 salt and gambier4 ,very good leathers are made in this way in the ,united ,states1 with a tannage begun in suspension in hemlock bark liquors4 ,imitations of ,dongola leather are made by treating ,east ,india sheep or goat with alum liquors1 and afterwards fat-liquoring 7if necessary7#abh and finishing like genuine ,dongola leather4 ,the treatment is most effective1 if a portion of the original tan be removed by washing with warm water1 with a little borax1 ammonia1 or even soda1 and the goods then alumed with a 8neutralised0 or basic alum solution such as that described on p4 #ahg4 ,goods treated with a basic chrome-liquor1 like that used for the one-bath chrome process1 p4 #bab1 are almost converted into chrome-tanned goods1 and will even stand some degree of boiling4 ,the use of a liquor made like the ,martin-,dennis liquor1 by dissolving chromic oxide in hydrochloric acid1 was the subject of an ,american patent#abi which in this country is owned by ,wichellow and ,tebbutt1 but which expires in #aijc4 #abh ,east ,india sheep and goat are generally so heavily oiled with sesame oil 7up to #cj per cent4 of their weight71 that it is desirable in many cases rather to diminish than increase the oil1 which may be done by washing with soap solutions1 preferably before aluming4 #abi ,eng4 ,pat4 ,jensen #acabf1 #ahhi4 ,chrome-combinations may also be made by retanning goods tanned by either of the chrome processes with vegetable materials1 of which gambier seems the most suitable4 ,the use1 even of very weak liquors of sumach and most other tanning materials1 deprives chrome leather of its stretch1 and if carried to excess1 readily makes it hard and tender4 ,,chapter ,,xviii4 ,,vegetable ,,tanning ,,materials4 ,as has been stated in the previous chapter1 our knowledge of the chemistry of tannins is not sufficiently advanced to render possible any strictly chemical classification1 while an additional complication arises from the fact that very different tannins may coexist in the wood1 bark1 fruit1 galls1 etc4 of the same plant4 ,it therefore seems best to follow the example of ,prof4 ,bernardin in his #8,classification de #cej matires tannantes1'#acj and arrange the plants under the orders of the natural system of botany1 as has already been done by von ,hhnel#aca and ,a4 de ,lof4#acb ,in the following pages1 only those materials which from their high percentage of tannin1 or from some other cause1 are of commercial interest or value1 are included1 as the tannins are so widely distributed in the vegetable kingdom1 that any exhaustive list would be quite out of the question4 #acj ,gand1 #ahhj4 #aca #8,die ,gerberinden1' ,berlin1 #ahhj4 #acb #8,matires tannantes1' ,halle aux ,cuirs1 ,paris1 #ahij4 ,see also #8,agricultural ,ledger1' #aijb1 ,no4 #a 7,government ,printing ,office1 ,calcutta1 #f;d471 by ,mr4 ,d4 ,hooper1 which contains much valuable information4 ,tannins are not confined to any particular part of the plant1 though they are usually most abundant in barks and fruits4 ,insect-galls are often very rich in tannin1 usually gallotannic acid2 while in several cases woods are of commercial importance from their cheapness1 though the percentage of tannin they contain is not generally high4 ,the function of tannins in the vegetable economy is not well understood4 ,in some cases they are probably a waste product of plant-life1 and may help to ward off attacks of insects4 ,they usually exist as cell-contents1 and as vegetable cells have frequently thick and impermeable walls1 and the diffusive power of tannins is low1 much time is required for extraction1 unless the cells have been previously crushed or broken4 ,it would be beyond the scope of this text-book to describe in detail the structures of the tannin-yielding parts of plants2 but barks are of such general importance1 that some particulars seem desirable4 ,the detailed structure of bark varies greatly in different trees1 though its general principles remain unaltered4 ,one of the best short accounts of these is given by ,prof4 ,h4 ,marshall ,ward on page #aii of his little book on #8,timber and some of its ,diseases1'#acc and further information may be found in ,van ,tieghem's #8,trait de ,botanique' and other works on structural botany4 #acc ,macmillan ,co4 ,with regard to detailed structure of various tanning barks1 #8,die ,gerberinden' of von ,hhnel#acd is one of the best authorities4 #acd #8,die ,gerberinden1' ,berlin1 #ahhj4 ,the inner surface bark of a young tree1 or twig1 consists of a layer of soft and living cells resting on the outer surface of the wood1 and called the cambium4 ,these cells multiply by division 7cp4 p4 #ab7 and produce from their inner surface the successive annual layers of wood1 and on their outer a fibrous tissue called the bast 7phloem71 consisting of lengthened cells1 and tubes with perforated divisions 7sieve-tubes7 which convey sap1 and mostly run in the direction of the branch1 but are crossed transversely by cells in a line with the medullary rays of the wood4 ,all these cells when first produced in the cambium-layer have thin and soft cellulose walls1 but the inner layer forming the wood becomes lignified1 or hardened1 by deposits of lignine on the interior of the cell-walls1 while their contents of living protoplasm disappear4 ,the outer layer forming bast remains much softer and more fibrous1 and retains its vitality longer4 ,the outer surface of the young branch is covered by a thin layer of flat cork-like cells forming the epidermis1 developed from the growing tissue of the bud1 beneath which is a layer of growing cells frequently called the cork-cambium4 ,this produces1 on its inner side1 a layer of soft1 juicy1 thin-walled cells 7parenchym71 which are living and capable of growth1 and contain protoplasm and often chlorophyll1 to which the green colour of young twigs is due4 ,this layer at first rests on the bast4 ,on the outer side1 the cork-cambium produces corky layers beneath the epidermis4 ,the section of an oak-twig is shown in ,fig4 #dc4 ,illustration3 ,,fig4 #dc4--,section of ,oak ,twig1 drawn by ,prof4 ,bastin3 c1 corky layer2 t1 tannin-cells2 ,st1 stone-cells2 ,ca1 cambium2 ,mr1 medullary ray2 ,p1 pith4 ,as the tree grows1 it is obvious that the corky epidermis which grows in thickness1 but not in breadth1 must become distended and finally ruptured4 ,in some cases the surface is renewed by fresh corky layers constantly developed below it1 and then the bark remains smooth and unfurrowed1 as in the beech and young oak1 or in the birch1 from which thin corky layers are continually peeling2 or it may produce a thick layer of cork1 as in the cork-oak4 ,in many cases1 and especially in older trees1 the outer or primary layer of cork-cambium ultimately dies for want of nourishment1 and a fresh cork-producing layer is developed in the still living parenchym4 ,as cork is practically air- and water-proof1 the new layer cuts off from its source of nourishment and kills all the parenchym exterior to it4 ,in some cases this peels off1 as in the ,oriental plane 7,platanus71 but usually it forms a constantly increasing coat of dead tissue forming the 8ross0 or 8crap0 7,ger4 ,borke71 which as it cannot increase in breadth1 becomes deeply fissured as the tree becomes old4 ,in some cases the new growing layer or secondary cork-cambium forms a complete coating parallel with the first1 but more often it consists of a series of arcs convex towards the tree and cutting the primary cork-cambium at various places1 so as to divide the tissue outside itself into scales4 ,later on the process repeats itself1 new arcs forming inside the first1 and cutting off further portions of the parenchym4 ,in this way the cork-forming layer gradually sinks deeper and deeper into the bark1 till it frequently passes even into the bast-layer1 and very complicated arrangements of tissue result1 in which corky layers from the secondary cork-cambium are interspersed with bast-cells and sieve-tubes4 ,as a rule the outer and dead part of the bark contains but little tannin1 though to this there are exceptions1 as1 for instance1 in the hemlock and ,aleppo pines4 ,it always contains a large proportion of dark colouring matters 7reds1 phlobaphenes1 p4 #big74 ,cork consists of thin1 and often roughly cubical cells1 which are filled with air1 while tannin is usually contained in somewhat similar cells with thicker walls4 ,the walls of many vegetable cells are perforated with fine holes1 and become thickened by internal deposits of hard ligneous matter which sometimes almost fill the entire cell 78stone-cells074 ,bark-cells often contain starch-granules1 frequently of peculiar and characteristic forms 7which are easily recognised by the blue colour produced on treating the preparation under the microscope with a drop of a solution of iodine in potassium iodide71 as well as crystals of oxalate of lime and other matters4 ,these1 and the form and arrangement of the cells as seen in sections under the microscope1 form useful marks of recognition of the various barks4 ,tannin is most easily detected by staining1 before cutting sections1 with a solution of ferric chloride in absolute alcohol4 ,apart from microscopic characteristics1 the external appearance of barks1 both to the naked eye and by the aid of a lens1 forms a valuable means of recognition4 ,the arrangement of the bast and corky layers1 the remains of epidermis1 or the form and character of the fissures1 and of the lenticels or small corky protuberances which take the place of stomata in the epidermis1 should be observed4 ,space does not permit of any detailed account of the structure of fruits1 wood and leaves1 which are also cellular structures in many respects resembling the bark4 ,the cuticles of leaves1 and especially the stomata or breathing pores1 and the hairs are often very characteristic4 7,cp4 ,plates ,,iii4 and ,,iv41 and p4 #bgb47 ,valuable hints may also be obtained from the chemical reactions which are described on p4 #gj et seq41 ,l4,i4,l4,b4 ,,botanical ,,list ,,of ,,tanning ,,materials4#ace #ace ,the percentage of tannin given where the source of information is not stated must in many cases be regarded as uncertain1 many analyses having been made before the introduction of modern methods1 but those quoted as having been done in the author's laboratory are of recent date and have been made by the latest methods4 ,,conifer1 ,pines1 ,cypresses1 mostly containing ,catechol tans1 yielding reds4 ,abies excelsa1 ,lam4 7,pinus ,abies1 ,pinus ,picea1 ,picea vulgaris1 ,link471 ,norway ,spruce4 ,fr4 ,faux sapin2 ,ger4 ,fichte1 ,rottanne4 ,the source of the so-called larch-extract1 and a principal tanning material of ,austria4 ,contains #g-ac per cent4 of a catechol-tannin and much fermentable sugar1 and on this account is useful for swelling and colouring1 but does not tan heavily4 ,english and ,scandinavian bark does not seem much utilised4 ,best bark #b-h mm4 thick2 smooth1 yellow inside1 with reddish-brown ross outside4 ,for detailed description of structure see von ,hhnel1 #8,die ,gerberinden1' p4 #ce4 ,abies pectinata1 ,silver ,fir4 ,fr4 ,sapin2 ,ger4 ,edeltanne1 ,silbertanne1 ,weisstanne4 ,used to a limited extent1 but apt to be confused with spruce4 ,contains #f-ae per cent4 iron-blueing tannin4 ,used in ,styria1 ,austria1 ,russia4 ,without 8ross10 but silver-grey and smooth outside4 7,von ,hhnel1 #8,die ,gerberinden1' p4 #dj2 #8,gerber1' #ahge1 p4 #cge47 ,abies 7,pinus1 ,tsuga7 canadensis1 ,hemlock ,fir 7,fig4 #dd74 ,the principal ,american tanning material1 and source of hemlock extract2 averages #h-aj per cent4 of a catechol-tannin1 but variable1 #ah per cent4 reported1 possibly from a different species4 ,abundant in ,canada and the ,northern and ,north-western ,states of ,america4 ,the bark of old trees1 which is principally used for tanning and extract-making1 is #b-d cm4 thick1 smooth and yellow within1 greyish and deeply fissured without4 ,the ross1 which is red and thick1 contains a considerable quantity of tannin1 with much dark-red phlobaphen4 ,it does not differ in structure from the inner living and yellow 8flesh40 ,the bark is easily recognisable by its well-marked concave lamell of cork1 cutting off successive layers of 8ross0 of several millimetres in thickness4 7,von ,hhnel1 ibid41 p4 #db47 ,illustration3 ,,fig4 #dd4acf--;,hemlock ,fir 7,tsuga canadense74 #acf ,bastin and ,trimble's ,american ,conifer1 ,american ,journal of ,pharmacy4 ,abies alba 7,picea alba71 ,white ,spruce1 ,north ,america4 ,in character of tree and bark very similar to ,norway spruce4 ,larix europa ,d4,c4 7,abies or ,pinus ,larix71 ,larch4 ,fr4 ,mlze2 ,ger4 ,lrche4 ,contains #i-aj per cent4 pale catechol-tannin1 mild and suitable for light leathers4 ,used1 especially in ,scotland1 for basil tannage4 ,pinus halepensis1 ,aleppo ,pine4 ,an important tanning material of the ,mediterranean coasts4 ,the outer bark1 stripped like cork from the living tree 7,scorza or ,cortegia rossa71 is a deep red tannage1 and contains about #ae per cent4 of tannin very similar to hemlock4 ,it is largely used in the island of ,syra4 ,the inner and fleshy part of the bark1 only obtained when the tree is cut1 is ,snoubar or ,snobar bark1 containing up to #be per cent4 of lighter coloured tannin4 ,this bark is reddish brown1 and pretty smooth on both sides1 except for shell-like depressions on the outer surface4 ,the 8scorza rossa0 is dark red-brown internally1 grey and irregular outside1 frequently very thick1 and divided into successive layers of #a-b mm4 thickness by cork lamell4 7,von ,hhnel1 ibid41 p4 #dd47 ,in appearance the tree resembles the ,scotch fir4 ,pinus tda1 ,america2 ,p4 ,laricio1 ,austrian ,pine2 ,p4 maritima1 ,mediterranean2 ,p4 ,cembra1 ,alps1 ,tyrol1 #c-e per cent42 ,p4 sylvestris1 ,scotch ,fir4 ,ger4 ,kiefer2 ,fr4 ,pin sauvage1 #d-e per cent4 ,p4 longifolia ,roxb41 ,india1 #aa-ad per cent4 ,juniperus communis1 ,juniper4 ,bark used in ,russia4 ,podocarpus elongata and ,thunbergii1 ,cape of ,good ,hope2 ,geelhout1 ,yellow woods4 ,phyllocladus trichomanoides1 ,new ,zealand2 ,tanekahi1 ,tarsekahi1 ,kiri-toa-toa1 8,golden ,tan40 ,used in dyeing glove-leather4 ,tannin1 #cj per cent41 gives green blacks with iron4 ,p4 asplenifolia1 ,tasmania1 ,celery-topped ,pine2 #bc per cent4 ,phyllocladus belongs to ,yew family4 ,,liliace4 ,scilla maritima1 ,squill4 ,tannin stated from #b-bd per cent4 ,more valuable for pharmacy4 ,,palm4 ,areca catechu1 ,betel-,nut ,palm of ,india4 ,yields a species of cutch of no importance for tanning4 ,sabal serrulata1 ,saw ,palmetto of ,florida 7,trimble74 78,dwarf0 palmetto is ,s4 ,adansonia47 ,palmetto root has been much talked of as a tanning material2 and makes a light-coloured leather4 ,an extract is now made from the roots of the ,saw ,palmetto1 which grows freely in the ,southern ,states of ,america1 and is especially abundant on the east coast of ,florida4 ,the plant is an evergreen1 the stem growing flat along the ground1 being held in place by numerous roots each the size of a pipe-stem4 ,the leaves are fan-shaped and ribbed1 and two to three feet in diameter4 ,in its hardihood the palmetto resembles a weed1 as the leaves may be cut off quite close to the stem without damaging the plant1 which will grow freely on poor sandy land which is worthless for other purposes4 ,the average yield is stated to be about #aj cwt4 to the acre1 but in good seasons and with rich land1 over a ton per acre has been obtained4 ,the air-dried leaves contain about #ac per cent4 of tannin1 but the results obtained by different chemists vary from #e to #bj per cent4 ,possibly these variations are caused by the different amounts of moisture in the various samples4 ,the leaves must be treated with a solution of caustic soda1 to remove the glossy siliceous shield which covers them and prevents their being easily extracted4 ,after the tanning matter has been extracted the remaining fibre can be profitably disposed of to paper and rope manufacturers4 ,as the supply of palmetto is very large it is likely that it will1 to a considerable extent1 substitute the employment of gambier1 and in the ,united ,states the extract has already met with a considerable sale4 ,samples of the extract examined by the ,author analysed from #af-bb per cent4 of tanning matter1 and several per cent4 of mineral matter1 and produced a very soft and mellow leather of good colour4 ,the extract contains noticeable quantities of common salt1 and organic salts of soda which leave sodium carbonate on ignition4 ,cocos nucifera1 the ,cocoa-nut ,palm1 also contains tannin in roots4 ,,casuarin4 ,casuarina equisetifolia ,l4 7laterifolia ,lam472 ,filao bark1 ,reunion2 ,tjamara laut1 ,java2 ,casagha or ,tinian ,pine1 ,ceylon4 ,widely distributed in ,southern ,asia1 bark used for tanning and dyeing4 ,tannin gives blue-blacks with iron4 ,several other species very similar in structure and properties4 7,von ,hhnel47 ,hooper found #aa-ah per cent4 of tannin4 ,,myricace4 ,myrica ,gale1 ,sweet ,gale1 or bog-myrtle4 ,myrica 7,comptonia7 asplenifolia1 ,u4,s4,a42 8,sweet ,fern40 ,covers millions of acres in ,michigan4 ,yields #dj per cent4 of 8extract40 ,leaves #d-e per cent41 roots #d-f per cent4 tannin1 according to season 7,trimble74 ,has been much talked of1 but in ,prof4 ,trimble's opinion is not likely to prove of much importance4 ,myrica nagi 7,hind4 ,kaiphal71 ,india1 contains #ac-bg per cent4 of tannin in the bark1 and a colouring matter1 myricetin1 identical with that of sumach4#acg ,leather tanned with it is of a somewhat reddish colour which is much brightened by sumaching1 and converted into a pale yellow by treatment with alum4 ,it promises to be a valuable tanning material4 #acg ,perkin and ,hummel1 ,trans4 ,chem4 ,soc41 #ahif1 p4 #abhg4 ,,betulace4 ,alnus glutinosa1 ,common ,alder4 ,fr4 ,aulne2 ,ger4 ,erle4 ,contains #af-bj per cent4 iron-green tannin1 with much red colouring matter2 old barks as low as #aj per cent4 ,colour develops during and after tannage4 ,used alone it gives a red1 hard and brittle leather1 but with galls1 valonia1 etc4 it produces a satisfactory tannage4 ,its principal use is to furnish gunpowder-charcoal1 and it is possible the bark might be obtained from powder-factories1 if the use of gunpowder is not superseded by nitro-compounds4 7,von ,hhnel47 ,alnus maritima1 ,hannoki1 ,japan2 and ,a4 firma1 ,minibari4 ,fruits 7yashi7 contain #be per cent4 tanning matter 7iron-blueing71 and little colouring matter4 ,used in ,japan for dyeing and tanning4 ,a4 nepalensis and ,a4 nitida used in ,india4 ,several other species of ,alnus contain tannin4 ,betula alba1 ,white or ,common ,birch4 ,fr4 ,bouleau blanc2 ,ger4 ,birke4 ,inner bark used in ,scotland 7in conjunction with larch for tanning sheep-skins71 ,norway1 ,russia1 etc4 ,it contains only #b-e per cent4 of iron-greening tannin1 and much fermentable sugar4 ,by far the most important use of birch bark in tanning is to produce the birch-bark tar used to give scent and insect-resisting power to 8,russia0 leather 7,youft2 ,ger4 ,juchten74 ,the outside bark consists of thin layers of cork1 often white with a crystalline deposit of betulin1 which when distilled yields the odorous oil4 ,the distillation is a dry one1 and tarry products accompany the true oil1 and at first give a strong empyreumatic smell to the leather1 which it loses by keeping1 while the true 8,russia0 odour remains4 ,this 8ageing0 may be hastened by hanging the leather in a hot stove4 ,if the oil is distilled in a current of steam1 or with petroleum ether1 the tarry matter passes over1 while the matter giving the true odour remains in the retort 7p4 #cgb74 ,betula lenta1 ,american ,black ,birch4 ,the bark and twigs distilled with water yield an essential oil1 which is almost pure salicylate of methyl1 and largely substituted for oil of wintergreen 7,gaultheria procumbens71 with which it is chemically identical4 ,used for perfumery1 and as a rheumatism remedy4 ,often erroneously spoken of as the source of 8,russia0 oil4 ,a mixture of a trace of wintergreen oil with sandal-wood oil considerably resembles the 8,russia0 scent 7p4 #cgc74 ,,cupulifer4 ,castanea vesca1 ,true or ,spanish ,chestnut4 ,fr4 ,chtaignier2 ,ger4 ,kastanie4 ,abundant in ,italy1 ,south of ,france and ,corsica1 where it forms great forests4 ,bark said to be nearly as strong in tannin as oak 7up to #ag per cent41 de ,lof71 but not much used in tanning4 ,wood only contains #c-f per cent4 tannin1 but is the source of the valuable chestnut extract1 first employed for dyeing1 and introduced as a tanning agent by ,aim ,koch4 ,the strength of extract is of course very variable1 even for the same density 7see p4 #cci71 but it usually contains from #bh to #cb per cent4 of tannin4 ,the tannin gives blue-black with iron1 but is not identical with either oak-bark or gall tannins1 but apparently a mixture1 or possibly a methylated derivative of the latter1 and identical with oakwood tannin1 or so nearly so as to be indistinguishable2 it may also be identical with divi tannin4 ,decolorised chestnut extracts1 sometimes mixed with quebracho and other materials1 are often sold as 8oakwood0 or 8oak-bark0 extracts4 ,the extract gives a firm leather1 with a good deal of bloom if used strong1 and a more reddish tint than valonia4 ,the extract often contains dark colouring matters1 and the colour of leather tanned with it is readily darkened by traces of lime derived from calcareous waters or imperfectly delimed hides4 ,like all wood-extracts it tans rapidly1 the colour penetrating first1 and the tan following1 but1 according to ,eitner1 it does not1 alone1 make full or solid tannage1 perhaps from want of acid-forming matters1 but answers particularly well in combination with spruce-bark4 ,it is largely used in ,england for sole-leather in combination with valonia1 myrobalans and other materials4 ,the higher the temperature of extraction1 the more colouring matter is contained in the extract in proportion to tannin matter and the greater is its viscosity4 ,much colouring matter remains undissolved if the extract is dissolved in cold water1 but there is1 in addition1 a loss of tanning power1 the colouring matter being also capable of combining with hide4 ,it has in fact been used for tanning by dissolving it in solutions of borax or alkaline salts4 ,by improved methods of manufacture the colouring matter has been much reduced4 ,the chestnut is an important food tree1 the nuts forming a considerable part of the food of the inhabitants of ,corsica and ,sardinia1 and even of ,italy4 ,oaks4 ,almost all species of oak contain useful quantities of tannin in the bark1 and probably in the wood4 ,most if not all oaks yield catechol-tannins with1 probably1 some mixture of ellagitannic acid4 ,quercus robur1 ,common ,oak4 ,fr ,chne2 ,ger4 ,eiche4 ,it is frequently separated into the two subspecies3-- ,quercus pedunculata4 ,commonest oak of lowlands1 ,england1 ,ireland and ,scotland4 ,acorns in bunches or spikes on a stalk inch long1 hence ,ger4 name1 ,stiel-,eiche4 ,leaves sessile or short-stalked4 ,in favourable situations1 said to yield about #b per cent4 more tannin than ,q4 sessiliflora1 but this is doubtful4 ,it is the commonest oak in ,slavonia1 and the source of commercial oakwood-extract4 ,q4 sessiliflora1 ,ger4 ,traubeneiche4 ,common in hilly districts1 and scattered throughout the country4 ,acorns in bunch on the branch1 or with very short stalk2 leaves on stalk -#a inch long4 ,of ,english barks1 ,sussex and ,hampshire are considered the best1 and contain up to #ab-ad per cent4 of tanning matter2 a coppice bark from ,wastdale1 ,cumberland1 is however1 recorded to have yielded #ai per cent4 tanning matter 7,hellon74 ,probably each of the two varieties of oak gives best bark where it thrives best 7v4 ,hhnel74 ,belgian bark is sometimes equal to ,english1 and contains #aj-ab per cent4 tanning matter4 ,dutch bark as exported is generally inferior and not cleaned2 ,swedish is bright1 but very poor4 ,oak-bark contains a tanning matter1 quercitannic acid1 giving green-blacks with iron salts1 and possibly containing both catechol and pyrogallol groups1 but its constitution is not fully understood4 ,it yields both red anhydrides and ellagic acid2 and gallic acid has been obtained by the action of hydrochloric acid1 though not by fermentation in the tannery4 ,the tannin is not a glucoside1 but the fact that a sugar1 lvulose1 is also present in the bark has led some observers to erroneous conclusions regarding the constitution of the tannin4 ,the unpurified infusion of the bark of ,q4 robur gives a blue-black with iron-salts1 from the presence of a colouring matter2 but those of most other oaks give green-blacks4 ,most tannin is contained in the living part of the bark4 ,the yield diminishes in trees over twenty-five years1 and coppice barks1 from absence of ross1 are often strong1 and also contain less colouring matter and more fermentable sugar4 ,warm and rich soils seem to yield the best barks4 ,the brighter the colour of the fresh cut 8flesh10 the better the bark4 ,dark brown inner side shows that bark has been exposed to rain1 which deteriorates strength and colour2 but a very light colour is thought by some to indicate poorness in tannin4 ,white lichen is said to be a mark of poor bark1 and probably indicates a damp and unfavourable situation4 ,oaks are generally cut when the sap is rising 7#aeth ,april to #aeth ,june71 and the buds open and new soft cells begin to grow1 for the bark is then more easily detached4 ,experiments in ,france have shown that the bark of timber felled at other seasons may be loosened by steaming1 and it is said there is no practical loss of tannin4 ,superheated steam1 produced in a small boiler in the woods1 is used4 ,the bark is peeled with tools of various forms1 the branch and knotted places being loosened by beating with a mallet4 ,the bark must be peeled immediately the tree has been felled4 ,the peeled bark1 in pieces up to three feet long1 is laid on hurdles sloped in such a way that the rain runs off as much as possible1 and in this way it is dried1 but in wet seasons is much damaged4 ,bark so dried in the woods often retains #dj-ej per cent4 water1 and must be stacked or stored so as to allow of further drying4 ,english bark is sometimes sold in 8long rind10 and sometimes 8hatched0 or chopped in pieces about four inches long4 ,belgian and ,dutch barks are generally hatched4 ,belgian tree bark is 8cleaned0 7and cleanings often mixed back with bulk71 ,dutch bark is not cleaned4 ,much sand and dirt is contained in most ,continental bark3 screenings of ,belgian bark yielded a black liquor1 and contained so much sand that they would not even burn6 ,oak-bark extract is occasionally offered for sale1 but is not usually genuine or of good quality1 except that of the ,american chestnut-oak1 ,q4 prinus1 from which an excellent extract has been manufactured in the ,alleghanies4 ,factitious extracts often contain myrobalans and quebracho4 ,illustration3 ,,fig4 #de4--,turkey ,oak 7,quercus cerris74 ,oakwood contains only a very small percentage 7from #b-d per cent47 of a tannin1 practically identical with that of chestnut1 but different to that of oak-bark4 ,it is stated by de ,lof to reach #i-ad per cent4 in old heart-wood2 but this is doubtful4 ,the wood retains the tannin in its interior for a long time4 ,wood of a ,roman bridge built at ,mainz #ee ,b4,c4 is stated by de ,lof to have still contained #bad per cent4 tannin in #ahha ,a4,d4 ,a good deal of imitated oakwood extract is undoubtedly made from chestnut wood1 and unfortunately no very satisfactory way of distinguishing it is known1 though oak-bark extract can be distinguished from oakwood by giving a precipitate at once1 even in dilute solution1 with bromine-water1 while the wood gives a brown precipitate only after long standing4 ,precipitation by bromine-water is a general characteristic of catechol tannins1 and hence a mixture of quebracho 7a cheap catechol tan7 with chestnut would simulate oak-bark in this respect4 ,if a few drops of the non-tannin solution or an alcoholic extract from the 8total soluble0 of extracts containing quebracho or other catechol tannins be treated with concentrated sulphuric acid in a test-tube1 a deep crimson will be produced1 especially at the surface of the acid1 which remains pink on dilution with water4 ,with pyrogallol derivatives1 such as genuine oakwood1 a yellow or brown only is produced 7,j4 ,hughes74 ,the test is very delicate4 ,another distinction is that bark extracts contain perceptible traces of manganese1 but this cannot be relied on as many wood extracts also contain some1 probably derived from the twig and branch bark which is used along with the wood4 ,oakwood extract is now manufactured on an enormous scale in ,slavonia1 and is used both by sole- and dressing-leather tanners1 chiefly to increase the strength of the layer liquors4 ,the extract is also used to increase the weight of leather after tannage by mopping on the flesh-side4 ,all the best oakwood extract manufacturers contract to sell on analysis and colour estimation1 and good ,slavonian oakwood extract generally contains #bf-bh per cent4 of tanning matter1 giving a tintometer measurement of #d-e red1 and #bj-be yellow1 when a solution containing per cent4 of tanning matter is measured in a #a cm4 cell4 ,for particulars of the manufacture of concentrated extracts see p4 #ccg4 ,illustration3 ,,fig4 #df4--;,cork ,oak 7,quercus suber74 ,q4 cerris1 ,turkey ,oak4 ,ger4 ,zerreiche4 ,common in southern ,europe1 a fine tree1 but bark inferior to ,q4 robur4 ,fig4 #de4 ,q4 pubescens4 ,fr4 ,chne velu2 ,ger4 ,weiss- or ,schwarzeiche4 ,in mountain districts and scattered in ,southern ,europe1 about equal to ,q4 robur4 ,q4 ilex1 ,evergreen ,oak4 ,fr4 ,chne vert1 ,chne yeuse2 ,ger4 ,grneiche1 ,steineiche2 ,span4 and ,ital4 ,encina4 ,south ,europe1 ,algeria4 ,said to be somewhat stronger in tannin than common oak1 yielding #e-aa per cent4 of a rather darker coloured tannin1 but well adapted to sole-leather4 ,good bark is smooth outside1 without fissures1 short in fracture4 ,q4 ,suber1 ,cork ,oak4 ,f4 ,chne lige2 ,ital4 ,sughero1 ,suvero4 7,figs4 #df1 #dg47 ,the outer bark is cork2 the interior bark contains #ab-ae per cent4 of tannin which is redder than that of ordinary oak4 ,trees at first produce an irregular cork1 sold as 8virgin cork0 for ferneries1 etc4 ,after this is stripped1 later growths are more uniform1 and fit for use2 tanning bark is only obtained when the tree is cut down4 ,bark is rough but pale-coloured on both sides and about #a cm4 thick2 interior like ordinary oak1 but more strongly furrowed4 ,produced chiefly on ,mediterranean coasts1 and formerly largely used in ,ireland4 ,illustration3 ,,fig4 #dg4--,section of ,cork ,oak1 showing cork1 inner bark and wood4 ,q4 pseudosuber1 ,african ,oak4 ,fr4 ,chne faux lige4 ,algeria4 ,not stronger than ,english oak1 but with more colouring matter1 hence strikes quickly through leather4 ,bark very thick4 ,q4 ,mirbecki4 ,fr4 ,chne ,zeen4 ,algeria4 ,rapid growth4 ,bark contains #h per cent4 of tannin4 ,q4 ,toz4 ,fr4 ,chne tauzin4 ,pyrenees and ,s4 ,france4 ,bark contains #ad per cent4 of tannin4 ,q4 coccifera1 ,kermes ,oak4 ,fr4 ,kermes1 ,garouille 7,fig4 #dh74 ,south ,europe and ,algeria4 ,root bark is called 8rusque0 or 8garouille02 averages #aj-ah per cent4 tannin1 but trunk bark does not exceed #aa per cent4 ,this tree is the food of the kermes insect1 used for dyeing scarlet before the introduction of cochineal4 ,garouille is principally used in the south of ,france1 giving a firm sole-leather of a disagreeable odour and dark brown colour4 ,illustration3 ,,fig4 #dh4--,kermes ,oak 7,quercus coccifera74 ,q4 gilops 7and probably other species--,q4 macrolepis1 grca1 ,ungeri1 coccifera71 ,valonia4 ,fr4 ,valone2 ,ger4 ,valonea1 ,ackerdoppen1 ,orientalische ,knoppern4 ,best ,smyrna contains up to #dj per cent41 ,greek #ai-cj per cent41 ,candia valonias up to #da per cent41 and ,caramanian 7probably not ,q4 gilops7 #ag-bb per cent4 of tannins which are at least principally pyrogallol derivatives and which give blue-blacks with iron1 no precipitate with bromine-water1 and which deposit a great deal of bloom consisting of ellagic acid4 ,illustration3 ,,fig4 #di4--,valonia ,oak 7,q4 gilops74 ,q4 gilops 7,fig4 #di7 is said to be most abundant in the highlands of ,morea1 ,roumelia1 ,greek ,archipelago1 ,asia ,minor and ,palestine1 while macrolepis forms large forests in many parts of ,greece1 and especially on the lower slopes of ,mount ,taygetos4 ,in ,asia ,minor the fruit ripens in ,july-,august1 when the trees are beaten and acorns left on the ground to dry4 ,they are afterwards gathered1 and carried on camels to stores in the towns1 and thence by camel and rail to ,smyrna1 where they are placed in heaps #e-f feet deep in large airy stores1 and allowed to ferment and heat for some weeks1 when the acorn1 which contains but little tannin1 contracts and falls from the cup1 and is used for feeding pigs4 ,this fermentation is risky1 and if carried too far the cups become dark-coloured and damaged4 ,the acorn contains a considerable amount of fermentable sugar4 ,when ready for shipment1 the valonia is hand-picked1 the largest and finest cups 7prima7 going to ,trieste1 the second selection to ,england 7,inglese71 and the remainder1 known as 8natural10 also coming largely to ,england4 ,the 8,inglese10 although inferior in appearance to the very large selected cups1 is1 of course1 less costly1 and gives an equal yield of tannin4 ,in #ahhg1 ,smyrna exported about #bc1jjj tons to ,england1 and #af1jjj tons elsewhere1 principally to ,austria1 ,germany and ,italy4 ,the largest known crop is stated at #gj1jjj tons in ,asia ,minor1 and #ad1jjj in ,greece1 but the average yield is considerably less than this4 ,the beard contains considerably more tannin than the cups1 sometimes over #dj per cent4 ,it is often sold separately at the same or a lower price1 and in ,smyrna is known by the ,turkish name tirnac 7,ital4 trillo74 ,in ,greece the best valonia is collected 7in ,april87 before the cup is matured and while it still encloses the acorn1 and is known as chamada 7,it4 camata and camatina74 ,the colour of these kinds is excellent and the percentage of tannin high4 ,mainly used by dyers1 but often worth attention for tanning where colour is important4 ,in camatina the acorn is completely covered in the cup1 while in camata it is partly exposed4 ,the next quality1 rhabdisto1 is beaten down by sticks in ,september-,october 7hence name71 while after the first rains the fruit falls and turns black1 and is called charcala4 ,it contains but little tannin1 and is not generally collected4 ,sometimes valonia is attacked by a sort of honeydew1 probably caused by an aphis1 which renders it very sticky1 and perhaps more liable to heat1 but does not in itself damage its tanning properties4 ,the lighter the colour1 the heavier the weight1 and the thicker the scales of the beard1 the better the quality usually proves1 but analysis is the best guide4 ,caramanian valonia is very inferior4 ,the tannin contained in valonia is especially suitable in the manufacture of sole-leather4 ,it deposits much bloom1 and if used as a dusting material1 has the characteristic of making the leather solid and compact1 but leaves the grain somewhat rough and hard to work4 ,in mixture with gambier and other materials1 it is an excellent tannage for dressing leather1 and with proper management deposits little or no bloom 7cp4 p4 #bca74 ,q4 infectoria 7,fig4 #ej7 is the source of the 8,turkish0 or ,aleppo galls4 ,galls are caused by insects1 principally of the genus ,cynips1 or gall-wasps1 which lay their eggs in different parts of plants1 and in some way cause an abnormal growth of the bud1 leaf1 or other part4 ,illustration3 ,,fig4 #ej4--;,gall ,oak 7,q4 infectoria74 ,aleppo galls are developed from the young shoot of the oak1 are best before the insect has escaped1 and contain in this stage up to #ej or #fj per cent4 of gallotannic acid4 ,when the insect has developed and escaped1 the galls are of course perforated1 much lighter1 and more porous4 ,these galls and those of ,rhus semialata are the principal sources of the tannin of commerce4 ,the ,q4 infectoria also bears a large gall like an apple1 8,apples of ,sodom10 or 8rove10 caused by a different insect4 ,this1 in a crushed condition1 has been somewhat largely used as a tanning material1 and contains #bd-cd per cent4 gallotannic acid4 ,english oaks have several species of galls and oak-apples1 but they do not seem to be of much value for tanning4 ,illustration3 ,,fig4 #ea4--;,chestnut ,oak 7,q4 prinus74 ,knoppern are galls produced on the immature acorns of various species of oaks1 principally ,q4 ,cerris in ,hungary1 and were formerly largely used there for tanning1 as they contain up to #ce per cent4 gallotannic acid4 ,they are now less abundant1 and have been largely replaced by valonia1 sometimes called orientalische ,knoppern4 ,like all purely gallotannic materials1 they naturally give a soft and porous tannage1 ill-adapted for sole-leather purposes1 which has led to the ,austrian practice of drying1 or rather stewing1 the leather in very hot and damp stoves1 which make it hard and brittle4 ,chinese and ,japanese galls are the product of the action of an aphis on a species of sumach1 and will be mentioned again under sumachs 7,rhus74 ,djaft1 dchift1 jift1 or jaft is a material apparently of ,eastern origin1 and said to be derived from an oak of ,kurdistan4 ,dark red scales or fragments1 origin uncertain1 very astringent and darkish tannage1 liquor when spilt dries whitish1 apparently from crystallisation of some sort4 ,it contains a large amount of tannin4 ,it appears very irregularly in commerce and the writer would be glad to obtain further samples and details of origin4 ,he once used #f or #g tons successfully in sole-leather tannage4 ,it has also been attributed to a shrub allied to the ,csalpinias 7p4 #bhf74 ,the most important ,american oaks are--,q4 prinus 7castanea1 monticola71 the ,chestnut or ,rock ,oak 7,fig4 #ea74 ,about equal to our oak in strength1 bark very thick1 and infusion strongly fluorescent1 especially in presence of ammonia4 ,source of chestnut-oak extract4 ,the most important tanning oak-bark of the ,united ,states4 ,q4 alba1 or 8white oak10 is perhaps the most widely distributed and abundant of any of the ,american oaks1 and very closely resembles the ,european ,q4 robur4 ,q4 tinctoria or nigra1 ,black or ,quercitron ,oak4 ,poor as a tanning material1 but used for dyeing yellow1 and for modifying the colour of hemlock tannages4 ,the dyestuff1 quercetin1 is closely allied to that of fustic1 and gives yellows with alum and tin mordants4 ,a good deal of information is given by ,trimble#ach on ,american oaks and other tanning materials4 #ach #8,the ,tannins1' vol4 ii41 ,lippincott1 ,philadelphia1 #ahid4 ,important ,indian oaks are ,q4 glauca1 ,q4 lamellosa and ,q4 incana2 bark of last said to yield #bb per cent4 of tannin4 ,,salicace1 ,willows4 ,the bark of various willows1 especially ,salix arenaria and ,russeliana1 is used for tanning in ,russia1 and for ,danish glove-leather4 ,some contain up to #ab-ad per cent4 of an iron-blueing tannin4 ,they impart a strong odour to leather1 but different to that of birch-tar oil1 and the scent of genuine ,russia leather is due to a combination of both4 ,in many cases the bark peeled off osiers for basket-making is employed4 ,a ,russian willow 7species unknown71 in the form of thin bark of osiers or small branches1 gave #ie per cent4 tannin when examined in the ,leather ,industries ,laboratory of the ,yorkshire ,college2 and willow barks certainly demand more attention than they have received in ,england as tanning materials for fine leathers4 ,salix caprea has been used in ,france for glove leathers1 but is weaker than ,s4 arenaria4 ,poplars belong to the same natural order1 and have been used for tanning1 but their barks at the most contain #b-c per cent4 ,,polygonace1 ,docks4 ,most members of this family contain tannin4 ,rumex hymenosepalum1 ,canaigre1 ,gonagra 7,cana agria71 ,red ,dock1 wild pie-plant 7,fig4 #eb74 ,common in sandy alluvial plains of ,mexico and ,texas1 and considerably resembling rhubarb4 ,its tuberous roots resemble those of the dahlia1 and contain1 when air-dried1 #be-cj per cent4 of a catechol tannin1 probably allied to that of mimosa4 ,undried1 the roots contain about #fh per cent4 of water and only #h per cent4 of tannin4 ,when well harvested by slicing thin and rapidly drying1 it gives leather a bright orange colour1 and1 it is said1 considerable weight and firmness1 and is thus specially suitable for use in retanning and finishing light goods and harness leather4 ,besides tannin1 the root contains a yellow colouring matter1 and about #h per cent4 of starch1 of which the granules are very variable in form and size1 but mostly oval or elongated4 ,they do not stain readily with iodine till they have been well washed1 or treated with dilute sulphuric acid4 ,both the starch and tannin are contained in large and somewhat thin-walled cells1 and the sliced material is easily extracted at low temperatures4 ,greater heat gelatinises the starch1 and extracts a darker colour4 ,the best temperature for extraction is between #cj and #ej ,c4 7see p4 #cdh74 ,illustration3 ,,fig4 #eb4--;,canaigre 7,rumex hymenosepalum74 #8,new ,commercial ,drugs and ,plants1' ,t4 ,christy4 ,the root is most readily grown from tubers or portions including the crown1 as the plant seeds sparingly4 ,sandy soils1 subject to inundation or irrigation1 seem best suited to its culture4 ,in ,california and ,arizona the growth begins in ,october or ,november with the winter rains1 blooming about the end of ,january1 while the leaves die down in ,may and the roots remain dormant during the summer4 ,it is not important at what time the roots are harvested1 and they seem to improve in percentage of tannin up to the second year1 after which they become darker and deteriorate4 ,the harvested crop should be sliced into thin pieces and rapidly dried at a low temperature1 or still better1 converted at once into extract4 ,this is already done on a considerable scale at ,deming1 ,new ,mexico4 ,the residue after extraction is used in ,america as cattle-food2 and might no doubt be also applied to the production of alcohol4 ,planting takes place in autumn1 in rows1 say #cj inches apart1 with #aj inches between each root4 ,roots for 8seed0 should be kept in the ground or stored in dry sand4 ,this should yield a crop of #aj tons per acre in an average season4 ,references4--,report ,u4,s4 ,commissioner of ,agriculture1 #ahgh1 pp4 #aai et seq42 ,trimble1 ,am4 ,jour4 of ,pharmacy1 p4 #cie1 #ahhi2 ,canaigre1 ,bull4 ,no4 #g1 ,arizona ,agr4 ,expt4 ,station1 #ahic2 #8,canaigre or ,tanner's ,dock1' ,bull4 ,no4 #aje1 ,university of ,california1 ,berkeley1 ,cal42 #8,canaigre ,tannin1' ,trimble and ,peacock1 ,philadelphia1 #ahic2 #8,report to the ,german ,leather ,trades ,association1' by ,v4 ,schroeder1 #ahid2 #8,il ,canaigre1' ,e4 ,andrieis1 ,turin1 #ahii4 ,rumex maritima1 or maritimus4 ,central ,europe1 ,england1 ,ireland4 ,it is said by de ,lof to be found in ,california1 where it is used by the ,indians for tanning2 but he probably confounds it with canaigre4 ,de ,lof found its roots1 wet1 to contain #f per cent4 and after drying1 #bb per cent4 of tannin1 together with starch and an acid allied to malic4 ,several ,english docks contain tannin2 the writer had a sample of leather tanned with dock-root 7very possibly ,r4 aquaticus71 many years old1 but still soft and close in texture1 and of excellent quality4 ,polygonum amphibium4 ,said to grow on thousands of acres 787 on the lower ,missouri4 ,roots contain #bb per cent41 branches #ag per cent4 of tannin4 ,p4 amphibium is a common ,english and ,european plant1 with spikes of pink flowers1 growing in marshes and ponds4 ,probably this is the ,polygonum analysed by ,fraas1 who found #bj-bf per cent4 tannin4 ,polygonum ,bistorta4 ,common in damp places in ,england4 ,bistort1 ,snakeweed1 called 8,eastermer giants0 in ,cumberland1 where the young leaves are used for making herb-puddings4 ,fraas found #af-ba per cent4 tannin in the roots4 ,other species are known to contain much tannin4 ,perkin found a red colouring matter in ,p4 cuspidatum1 a native of ,india and ,china1 commonly grown in gardens as a foliage plant 7,journ4 ,chem4 ,soc41 #ahie1 p4 #ajhd74 ,p4 tinctorium1 used as a source of indigo in ,china and ,japan4 ,coccoloba uvifera1 ,seaside ,grape of ,west ,indies2 source of ,west ,indian kino4 ,whole plant rich in tannin4 ,,laurace1 ,bay ,family4 ,persea1 or ,laurus lingue4 ,bark used in ,chili for tanning ,valdivia leather4 7,according to ,arata1 ,laurus caustica47 ,a tree #be-cj feet high and #b feet in circumference4 ,bark rough outside1 and whitish1 with an aromatic smell and taste1 brittle and easily ground1 contains #ag-ai per cent4 of a catechol-phloroglucol tannin1 greening iron salts 7,journ4 ,chem4 ,soc41 #ahha1 p4 #fjj74 ,about #fj1jjj heavy hides are tanned yearly with this bark in ,valdivia and district1 and mostly sent to ,hamburg4 ,the hides are thick and scarcely tanned through1 colour fair1 leather soft and porous4 ,persea ,meyerina ,n4 and ,laurus ,pneumo4 ,said to be also used in ,chili4 ,,santalace4 ,osyris compressa 7,fusanus compressus1 ,colpoon compressum1 ,thesium ,colpoon71 8,cape ,sumach10 8,pruim ,bast10 leaves and bark1 ,cape of ,good ,hope4 ,leaves contain about #bc per cent4 of tannin and form a useful substitute for sumach2 but the tannin is not identical1 and is of the catechol class1 resembling gambier4 ,o4 arborea4 ,northern ,india4 ,leaves rich in tannin4 ,fusanus acuminatus 7,santalum acuminatum71 8,quandony40 ,australia4 #ah-ai per cent4 tannin1 dark coloured4 ,exocarpus cupressiformis4 ,australia4 ,bark contains #ae per cent4 tannin4 ,,daphnoid1 ,spurge ,laurels4 ,daphne ,cnidium ,l41 8,garou40 ,algeria4 ,used for dyeing and tanning4 ,,proteace4 ,banksia serrata1 ,heath ,honeysuckle4 ,australia4 ,specimen examined contained #aa per cent4 tannin2 according to ,maiden it reaches #bc per cent4 ,banksia integrifolia4 ,queensland4 ,bark contains #aa per cent4 tannin4 ,grevillia striata4 ,australia4 ,bark contains #ah per cent4 tannin4 ,leucospermum conocarpum4 ,kruppelboom4 ,knotted ,tree4 ,cape of ,good ,hope4 ,said by de ,lof to contain #bb per cent4 of tannin2 but a specimen examined by the ,author yielded #aji per cent4 on analysis4 ,protea mellifera4 ,sugarbush4 ,suikerbosch4 ,cape of ,good ,hope4 ,contains #be per cent4 tannin1 according to de ,lof2 but ,palmer found #ahh per cent4 ,protea grandiflora4 ,waagenboom4 ,cape4 ,contains #be per cent4 tannin 7de ,lof72 #aei per cent4 7,palmer72 #aef per cent4 7,procter74 ,protea speciosa4 ,cape of ,good ,hope4 ,leucadendron argenteum1 ,silver ,tree1 ,silverboom1 ,witteboom ,cape of ,good ,hope4 ,bark said to contain #af per cent4 tannin 7de ,lof72 a specimen examined by the ,author yielded #ib per cent4 ,brabium stellatifolium1 ,wilde ,amandelboom1 ,wild ,almond4 ,,plumbagin4 ,plumbago ,europea1 ,leadwort4 ,fr4 ,dentelaire4 ,a garden plant in ,england1 native in ,france2 contains much tannin1 especially in the root-bark4 ,statice coriaria1 ,marsh ,rosemary4 ,south of ,russia4 ,roots up to #c metres long and #b-ab cm4 thick2 used by ,kalmucks for tanning sheep-skins2 contain #bb per cent4 of tannin 7de ,lof74 ,statice limonum1 ,sea ,lavender4 ,coasts and salt marshes of ,europe and ,america4 ,richer in tannin than ,s4 coriaria2 used in ,france1 ,spain and ,portugal4 ,several other species contain tannin4 ,these plants are allied to 8,thrift0 7,armeria74 ,,malpighiace4 ,byrsonima spicata1 ,antilles1 8,tamwood40 ,byrsonima coriacea1 ,jamaica1 8,golden ,spoon40 ,byrsonima chrysophylla1 etc4 ,malpighia punicifolia1 ,nicaragua1 8,nancite02 8,mangrutta40 ,bark contains #bj-cj per cent4 of light-coloured tannin4 ,,polygalace1 ,milkwort ,family4 ,krameria triandria1 ,rhatany1 ,peru4 ,the root is used in medicine1 and is stated to contain #dj per cent4 of tannin4 ,wittstein found only #bj per cent4 of an iron-greening catechol-phloroglucol tannin allied to tormentil tannin1 in the root-bark1 the only active part of root4 ,,anacardiace4 ,loxopteryngium ,lorenzii4 ,span4 ,quebracho colorado4 ,south ,america1 especially ,argentine ,republic2 the highest proportion of tannin occurring in the wood from ,gran ,chaco district4 ,wood contains on an average about #bj per cent4 of a red1 difficultly-soluble tannin1 yielding 8reds10 and containing catechol and phloroglucol4 ,the tannin is not very soluble in water1 and hence can only be used in weak liquors1 but is very astringent1 and gives a firm1 reddish leather4 ,the wood also contains a catechin#aci and a colouring matter1 fustin1 identical with that of 8young fustic40 ,it is imported into ,england1 and more largely to ,havre and ,hamburg1 in logs1 which are there chipped like logwood1 and either used direct for tanning1 or made into extract4 ,a very cheap tan4 ,with alum it gives a yellow colour4 ,the extract usually dissolves to a fawn-coloured turbid solution4 ,many quebracho extracts are now made completely soluble by treatment with alkalies or sulphites 7cp4 p4 #cch74 #aci ,see ,p4 ,arata1 ,journ4 ,chem4 ,soc41 #ahgh1 ,a1 p4 #ihf2 #ahha1 ,a1 p4 #aaeb2 and ,perkin and ,gunnell1 ,trans4 ,chem4 ,soc41 #ahif1 #acjc4 8,quebracho0 means 8axebreaker10 and is consequently applied to a variety of hard woods4 ,its specific gravity is #abg-ach1 and it therefore sinks in water4 ,pistacia lentiscus1 ,ital4 ,pistacio1 ,fr4 ,lentisque4 ,sicily1 ,cyprus1 ,algeria4 ,small myrtle-like leaves contain from #ab-ai per cent4 of a catechol-tannin1 and are very largely used in the adulteration of sumach4 ,leather tanned with sumach adulterated with this material darkens and reddens on exposure to light and air1 and for this reason its use in many cases is decidedly injurious4 ,in ,cyprus and the ,east it is known as 8,skens10 ,ital4 ,schinia1 ,fr4 ,poudre de ,lentisque1 in ,england1 often called ,cyprus sumach4 7,cp4 p4 #bgb47 ,p4 orientalis1 terebinthus1 vera1 etc41 ,india1 ,mediterranean4 ,various aphis galls1 #cj-dj per cent4 tannin4 ,a sample of galls of ,pistacia vera1 8,gool-i-pista10 ,india1 recently examined in the ,author's laboratory1 contained #cj per cent4 of a light-coloured tannin4 ,schinus molle1 8,molle10 ,buenos ,ayres4 ,leaves only used2 said to contain #ai per cent4 tannin4 ,s4 ,aroeira1 ,brazil4 ,said to contain #ad per cent4 tannin4 ,rhus coriaria1 ,sicilian sumach4 ,ital4 ,somacco4 7,fig4 #ec47 ,a shrubby bush1 of which leaves and small twigs are used4 ,illustration3 ,,fig4 #ec4--,sicilian ,sumach 7,rhus coriaria74 ,mostly propagated by suckers from older plants1 which are planted in rows about two feet apart in early spring1 and pruned to #f-h inches4 ,bushes begin to bear the year after planting1 though the strength is not so good as from more mature plants4 ,cropping is either by pruning off shoots1 or gathering leaves by hand2 in the latter case shrubs are pruned in winter4 ,the leaves are dried either in the fields1 or on covered threshing floors1 where they are afterwards separated from the stems by beating4 ,some is exported in this state1 as 8leaf0 or 8baling0 sumach1 but most is ground to fine powder under edge-runners4 8,ventilated0 sumach is winnowed to remove dust and sand1 which often contains iron4 8,mascolino0 is the best sumach from ,palermo and district2 8feminella0 consists of weaker sorts from other parts1 and is generally used for mixing4 ,the different varieties of sumach are classed as follows3-- ,relative ,market ,value4 ,sumach for baling #be grinding #bc from yearling plants #ae ends of branches collected in autumn #aj ,to prepare these different grades for ultimate consumption1 they are ground in mills similar to those employed for crushing olives1 that is1 in which two large stone wheels follow each other1 revolving upon a circular bed1 the whole construction being about the same as the ,spanish or ,mexican arrastre4 ,the sumach thus pulverised is passed through bolting-screens to separate the finer from the coarser particles4 ,after the sumach leaf has been subjected to the first process of trituration1 the coarse remaining portions are re-ground and the product added to that which has been already obtained4 ,the still unpulverised residue known as peduzzo is sifted1 and the coarser and ungrindable parts are used as fuel1 while the finer are mixed with the partially-ground1 small1 leaf-bearing branches 7gambuzza1 gammuzza71 and ground again4 ,palermo is the principal seat of the sumach trade4 ,the material is generally bought from the small growers by middlemen1 who hold it till market conditions are favourable4 ,the quotations are always in tar of #dbe centimes per cantar of #gicdb kilos1 which are obsolete even in ,sicily1 and have to be reckoned into lire 7francs7 and kilos4 ,consequently #a tar per cantar equals #jecefe lira per #ajj kilos4 ,in #ahid1 the prices delivered at the mills were about #da-db tar for mascolino1 #cg-ch tar for femminello1 #ad-ah tar for brusca1 and #aj tar for stinco1 per cantar2 the lira being worth about #i;d4#adj #adj ,cf4 #8,kew ,bulletin1' ,no4 #ajg1 pp4 #bic-f4 ,sumach has been introduced into ,australia1 and is said to thrive well in the dry plains of the ,wimmera district4 ,sumach often contains much sand1 and sometimes particles of magnetic iron ore1 which cause black stains1 and may be collected by a magnet1 and which dissolve in dilute hydrochloric acid without evolution of hydrogen1 to a yellow solution4 ,metallic iron1 which is also attracted by the magnet1 dissolves in hydrochloric acid with effervescence to a colourless or green solution4 ,good sumach contains at least #be-bg per cent4 of tannin4 ,the ,author has analysed samples of undoubted genuineness containing as much as #cb per cent4 of a tannin1 principally gallotannic1 with some ellagitannic acid1 and a colouring matter 7myricetin7 identical with that of ,myrica nagi 7p4 #bej71 which gives yellows with alumina and tin mordants1 and is fugitive to light4 ,sumach is the best tanning material known for pale colour and soft tannage1 and is hence used for moroccos1 roans1 skivers1 etc41 and also for brightening leathers of darker tannages1 such as mimosa1 gambier1 the colouring matters of which warm sumach liquors seem able to dissolve4 ,in the report of the ,society of ,arts ,committee on bookbinding leathers1#ada it is stated on abundant evidence1 that sumach-tanned leathers are less affected by light and gas-fumes1 and less liable to decay than those of any other known tannage4 #ada ,soc4 ,arts4 ,journ41 #aija1 p4 #ad4 ,sumach is frequently adulterated with the ground leaves and twigs of ,pistacia lentiscus 78schinia0 or 8skens071 ,coriaria myrtifolia 78stinco071 ,tamarix africana 78brusca071 ,ailantus glandulosa1 ,vitis vinifera 7leaf of the common grape vine7 and some other species of the ,rhus family1 but ,pistacia lentiscus is used to a much larger extent than any of the others4 ,pistacia1 coriaria1 and tamarix all contain considerable quantities of tannin1 though less than genuine sumach1 and of a different chemical constitution4 ,the most satisfactory method of detecting these adulterants is by microscopic examination1 none of the chemical methods proposed being very satisfactory2 though1 as many of the added matters contain catechol tannins1 while those of sumach are purely pyrogallol derivatives1 the method proposed by ,hughes for the detection of quebracho in oakwood by the reaction of concentrated sulphuric acid 7p4 #bif7 might render good service1 and any sumach infusion which was rendered turbid by bromine-water would at least be open to grave suspicion4 ,illustration3 ,,plate ,,iii4 ,ailantus glandulosa4 ,coriaria myrtifolia4 ,colpoon compressa4 ,rhus cotinus4 ,illustration3 ,,plate ,,iv4 ,pistacia lentiscus4 ,rhus metopium4 ,rhus coriaria4 ,tamarix ,africana4 ,the most important work on the microscopic structure of the tissues of sumach and its adulterants was done by ,andreasch1 when during the later stages of his last illness he was obliged to winter in ,sicily4#adb ,his work will well repay study1 but unfortunately does not admit of useful abstraction here4 ,a very useful investigation was also made in the ,author's laboratory by ,messrs4 ,m4 ,c4 ,lamb and ,w4 ,h4 ,harrison1#adc as regards the treatment and examination of the leaf-cuticles1 which renders the detection of mixture comparatively easy4 ,for details1 the original memoir must be consulted1 but if the suspected sumach be gently warmed for a few minutes with strong nitric acid1 its more delicate leaf structure is entirely destroyed1 and after washing and neutralising with sodium carbonate the strong cuticles of the leaves of the more common adulterants1 8schinia0 7,pistacia lentiscus71 8stinco0 7,coriaria myrtifolia71 8brusca0 7,tamarix africana71 and ,ailantus glandulosa are uninjured1 and easily recognised4 ,examination is rendered easier by dyeing the cuticles2 safranine1 acid green1 ,bismarck brown1 and naphthol yellow being suitable for the purpose4 ,mr4 ,lamb's photographs of the cuticles are reproduced on ,plates ,,iii4 and ,,iv41 but if possible1 it is most satisfactory to compare the suspected sample direct with known specimens of the adulterants4 #adb #8,sicilianischer ,sumach und seine ,verfalschung1' ,wien1 #ahih4 #adc #8,sumach and the ,microscopic ,detection of its ,adulterants1' ,journ4 ,soc4 ,dyers and ,colorists1 ,march #ahii4 ,illustration3 ,,fig4 #ed4--;,american ,sumach 7,rhus glabra74 ,r4 glabra1 ,southern ,states1 ,u4,s4,a4 7,fig4 #ed74 ,very largely used in the ,states to take the place of ,sicilian sumach4 ,a sample collected by the late ,professor ,trimble1 and analysed in the ,leather ,industries ,laboratory1 contained #be per cent4 of tannin and produced a leather of very much darker colour than ,sicilian4 ,r4 typhina1 8staghorn0 or ,virginian sumach1 contains #aj-ah per cent4 of tannin4 ,a sample from same source as above contained #ac per cent4 ,r4 cotonoides1 ,u4,s4,a4 ,the analysis of a sample of this material gave #ba per cent4 of tanning matter1 and leather tanned with it was almost equal in colour to that from ,r4 glabra4 ,other sorts found in ,states3 ,r4 semialata 7#e per cent4 tannin72 ,r4 aromatica 7#ac per cent4 tannin72 ,r4 metopium 7#h per cent472 ,r4 copallina1 ,r4 pumila1 ,r4 canadensis2 ,r4 toxicodendron is the well-known 8poison ivy10 a climbing plant which causes a severe and irritating eruption if touched4 ,r4 glabra and ,r4 copallina are chiefly recommended for extended cultivation in the ,united ,states4 ,in ,virginia1 the leaves are collected and cured by the country people1 and sold and delivered to owners of mills for grinding4 ,their particular object being to secure the largest possible quantity of product at the lowest cost1 little attention is given to the quality obtained1 or the manner of collecting4 ,the most intelligent dealers in the raw material urge upon collectors to observe the following particulars3--,to ensure a maximum value for tanning purposes1 the leaf should be taken when full of sap1 before it has turned red1 has begun to wither1 or has been affected by frost4 ,either the leaf-bearing stems may be stripped off1 or the entire stalk may be cut away1 and the leaves upon it allowed to wither before being carried to the drying shed2 but care must be observed that they are neither scorched nor bleached by the sun4 ,when wilted1 they are carried to a covered place1 and spread upon open shelving or racks to dry1 avoiding the deposit in any one place of a quantity so great as to endanger the quality of the product by overheating and fermentation4 ,sumach should be allowed to remain in the drying-house for at least one month before sending to the market2 in case of bad weather1 a longer period may be required4 ,when ready for packing for shipment1 it should be perfectly dry and very brittle1 otherwise it is likely to suffer injury in warehouses from heating and fermentation4 ,buyers of sumach leaves for grinding depend largely upon colour for the determination of the value2 the leaves should1 therefore1 when ready for market1 present a bright-green colour1 which is evidence that they have suffered neither from rain after being gathered1 nor from heating during the process of drying4 ,leaves having a mouldy odour or appearance are rejected4 ,the ,virginian crop reaches #gjjj-hjjj tons1 and is collected at any time between ,july #ast and the appearance of frost4 ,there is an important difference in the value of the ,european and ,american products4 ,the proportion of tannic acid in the latter is generally lower than that found in the former1 which is much preferred by tanners and dyers4 ,by using ,sicilian sumach it is possible to make the finest white leathers1 while by the employment of the ,american product1 the leather has a disagreeable yellow or dark colour1 apparently due to a colouring matter1 which exists in larger quantity in the ,american variety than in the ,sicilian4 ,experiments upon the presence of colouring matters made by treating an infusion of sumach with a solution of gelatine1 gave the following results3-- ,virginia1 mixed1 collected in ,june1 gave ,a nearly white precipitate4 ,july1 ,a decidedly yellowish- white precipitate4 ,r4 copallina ,august1 ,a dirty- yellow precipitate4 ,r4 glabra ,a very dirty- white precipitate4 ,fredericksburg1 mixed ,a dirty- yellow precipitate4 ,sicilian ,a slightly yellowish- white precipitate4 ,for the purpose of tanning white and delicately coloured leathers1 therefore1 the collection should be made in ,june2 while for tanning dark-coloured leathers1 and for dyeing and calico-printing in dark colours1 where the slightly yellow shade will have no injurious effect1 the collection may be made in ,july4 ,it appears that for all purposes1 the sumach collected after the #ast of ,august is inferior in quality4 ,experimental results as regards percentage of tannin obtained by collecting sumach at different seasons showed3-- ,per ,cent4 of ,tannic ,acid4 ,virginia1 mixed1 collected in ,june1 gave #bbge ,july1 #bgch ,r4 glabra ,august1 #bcef ,r4 copallina #afii ,sicilian1 ,r4 coriaria #bdbg ,it is evident1 therefore1 that in order to secure the maximum amount of tannic acid1 the sumach should be collected in ,july1 but the colouring matter of the leaves has an important influence upon the value of the product4 ,the leaves of the upper extremities of the stalks are always richer in tannic acid than those of the base2 and the increase of age of the plant is accompanied by a general diminution of this acid4 ,the mill used for grinding sumach leaves consists of a heavy1 solid1 circular1 wooden bed1 #ae feet diameter1 with a depression around the edge a few inches deep and #a foot wide1 for the reception of the ground sumach from the bed1 and two edge-rollers1 weighing about #bejj lb4 each1 #e-f feet diameter1 and provided with numerous teeth of iron or wood1 thickly inserted4 ,in ,europe and in some parts of the ,southern ,states1 sumach is still ground by stones revolving on a stone bed1 and the sifting is often done by hand4 ,illustration3 ,,fig4 #ee4--,venetian ,sumach 7,rhus cotinus74 ,r4 cotinus1 ,venetian sumach4 ,fr4 ,arbre perruques2 ,ger4 ,perrukenstrauch 7,fig4 #ee74 ,more important as a dyeing than as a tanning material1 its twigs and wood1 8young fustic10 containing a large proportion of a colouring matter 7fisetin71 which with tin and alumina mordants dyes bright yellows2 and much resembles1 but is not identical with the myricetin present in ,r4 coriaria4#add ,its leaves1 known as ,turkish or ,venetian sumach1 contain about #ag per cent4 of tannin1 and are used for tanning4 #add ,perkin and ,allen1 ,trans4 ,chem4 ,soc4 #ahif1 #abii4 ,r4 pentaphylla1 8,tezera10 ,algeria1 is used by the ,arabs for tanning goat-skins4 ,r4 ,thunbergii1 ,kliphout1 ,cape of ,good ,hope4 ,a sample of the bark analysed in the ,author's laboratory contained #bh per cent4 of tanning matter4 ,a valuable tanning material1 of reddish colour4 ,the tannin is of the catechol class4 ,several other species of ,rhus are used in tanning4 ,r4 semialata yields ,chinese and ,japanese galls1 containing up to #gj per cent4 gallotannic acid4 ,they are caused1 not by a fly1 but by the attack of an aphis1 as are those of the allied ,pistacia4#ade ,the aphides pass their asexual stage inside the gall1 which is large and thin-walled4 ,a similar aphis-gall is found on the ,american sumach4 ,a specimen of the leaves examined at the ,yorkshire ,college yielded only #e per cent4 of tannin4 #ade ,see ,flckiger and ,hanbury1 #8,pharmacographia4' ,mangifera indica1 ,mango1 widely distributed in the ,tropics4 ,bark and leaves rich in tannin1 which gives green-blacks with iron4 ,,coriariace4 ,coriaria myrtifolia1 ,french sumach 7of which there are four kinds--fauvis1 douzre1 redoul or redon1 and pudis74 ,a poisonous shrub of ,south of ,france2 leaves used for tanning1 and as a sumach adulterant under the name of 8stinco02 contain about #ae per cent4 tannin4 7,cp4 p4 #bgb47 ,coriaria ruscifolia bark1 the tutu of ,new ,zealand1 contains #af-ag per cent4 of tannin4 ,other ,coriarias merit examination1 and are known to contain much tannin4 ,,rubiace4 ,rubia1 ,madder1 allied to ,galiums1 which are almost the only ,english representatives of the family4 ,the coffee- and cinchona-plants are foreign representatives4 ,nauclea1 or ,uncaria gambir4 ,east ,indies4 7,fig4 #ef47 ,a climbing shrub1 source of 8gambier10 or 8,terra ,japonica02 also called 8,catechu10 in common with several other solid extracts4 ,gambier is first described by the ,dutch trader ,couperus1 in #aghj2 plant introduced in ,malacca1 #ageh2 plantations established in ,singapore in #ahai4 ,culture is mainly by ,chinamen1 and is very rude2 it yields rapid return1 but under the treatment to which it is subjected a plantation is worn out in ten to fifteen years4 ,cropping commences three years after planting1 and is continued two to four times annually1 with little regard to fitness of shrubs1 the plant being cropped till it has barely leaves left to support existence4 ,it is found advantageous to combine pepper-culture with that of gambier1 the spent leaves form a good protection for the pepper-plant roots1 but they have little actual manurial value4 ,illustration3 ,,fig4 #ef4--;,gambier ,shrub 7,nauclea gambir74 ,cropping is done with a knife called a parang1 while a larger knife is used for chopping the leaves and twigs before they are put in a boiler1 in which they are heated with water till the liquid1 which is constantly stirred during the operation with a wooden five-pronged stirrer1 becomes syrupy4 ,the leaves are then brought out with a wooden fork1 and allowed to drain on a tray1 so that the liquor runs back into the boiler4 ,the coarser matter still remaining in the boiler is removed with a strainer like a racquet1 and the finer by straining the liquor through a perforated cocoanut shell into small shallow tubs1 where it is allowed to cool with constant stirring with a cylindrical wooden bar1 which is worked up and down with a rotary motion until the catechin crystallises4 ,when quite cool the pasty mass is turned out of the tub1 cut into cubes with sides #a inch long with a hoop-iron knife1 and dried on bamboo trays in racks under sheds1 or sometimes smoke-dried with wood fires4 ,good cube gambier is an earthy-looking substance and is dark outside1 but pale within from crystallisation of catechin4 ,catechin is not itself a tanning material1 but is apparently converted into a tannin by drying at #aaj-abf ,c41 when it parts with a molecule of water4 ,it is very probable that a similar change occurs in the tannery4 ,the tannin is a catechol-phloroglucol derivative1 less astringent than most of this series1 and of pale colour4 7,see p4 #big47 ,a commoner quality1 called 8block-gambier10 instead of being cut into cubes1 is run into large oblong blocks of about #bej lb4 weight1 which are wrapped in matting and exported in a pasty condition4 ,these contain #ce-dj per cent4 of tannin1 as estimated by the hide-powder method1 while the best cubes reach #ej-fe per cent4 ,besides the forms named1 various others are made1 principally for native use in chewing with betel-nut in the form of small biscuits1 or in thin discs 78wafer gambier07 by running the pasty mass into bamboos and cutting the cylinder so formed into thin slices4 ,these forms are usually light in colour1 and very rich in catechin4 ,for details of the chemistry and employment of gambier1 see pp4 #bbh1 #bca1 #bci1 etc4 ,,apocynace4 ,aspidospermum quebracho4 ,sp4 ,quebracho blanco4 ,brazil4 ,bark contains aspidospermin1 an alkaloid used in medicine1 but both bark and wood are poor in tannin4 ,quebracho colorado1 see ,,anacardiace1 p4 #bfi4 ,,ericace1 ,heath ,family4 ,arctostaphylos 7or ,arbutus7 uva-ursi1 ,bearberry4 ,used in ,russia1 ,finland2 twigs and leaves said to contain #ad per cent4 tannin4 ,often adulterated with leaves of ,vaccinium vitis-id or ,cowberry4 ,arbutus unedo1 ,common ,arbutus4 ,leaves1 fruit and bark used on ,mediterranean coasts4 ,,vaccini4 ,vaccinium ,myrtillus1 ,bilberry4 ,used in ,piedmont4 ,,saxifrage4 ,weimannia glabra ,l41 8,curtidor0 bark4 ,venezuela4 ,weimannia macrostachys ,d4,c4 ,reunion4 ,weimannia racemosa1 ,new ,zealand ,towai or ,tawheri bark4 ,these species contain #aj-ac per cent4 of iron-blueing tannin1 and have been practically used1 but are not of much importance4 ,,tamariscini4 ,most of the members of this group are poor in tannin1 but several species have galls which are rich4 ,tamarix africana2 ,egypt1 ,algeria4 ,galls containing #bf-ef per cent4 tannin4 ,the small twigs are collected in ,tunis1 and when dried and ground are imported into ,sicily to be used for the adulteration of sumach under the name of 8,brusca10 and contain about #i per cent4 of tannin4 7,cp4 p4 #bgb47 ,t4 articulata1 ,morocco1 yields galls produced by aphides1 called in ,arabia ,takout1 and stated by ,vogel to contain #dc per cent4 of tannin4 ,tamarix gallica1 used in ,spain and ,italy4 ,,oxalide4 ,oxalis gigantea1 source of churco bark1 ,chili4 ,a thin1 brittle1 dark red bark1 mostly about #b mm4 thick1 cork and ross entirely absent4 ,the bark is brittle1 and the cells thin4 ,it contains about #be per cent4 of an easily extracted1 dark red tannin1 giving green-blacks with iron4 ,the bark has been incorrectly attributed to ,fuchsia macrostemma4 7,cp4 ,von ,hhnel1 #8,die ,gerberinden1' p4 #abe1 and this book1 p4 #bhd47 ,,combretace4 ,several families of this genus contain trees rich in tannin1 but most important are the ,myrobalans 7often1 but incorrectly1 written ,myrabolams or ,myrabolans71 the unripe fruit of various species of ,indian ,terminalia4 ,illustration3 ,,fig4 #eg4--,myrobalan ,tree 7,terminalia ,chebula74 ,t4 ,chebula 7,fig4 #eg71 a tree #dj-ej feet high1 and yielding good timber1 is the source of all the ordinary varieties1 which differ only in the district from which they are obtained1 and the state of maturity of the fruit4 ,the nuts contain from #cj to #dj per cent4 of tannin4 ,of the various sorts1 probably those known as ,bombays are least unripe1 while 8lean greens0 are the most so4 ,the unripe fruit is the richest in tannin4 8,bombays0 have a smooth skin in coarse wrinkles1 and when cut are porous and light coloured4 8,j's0 7,jubbalpores7 and 8,v's0 7,vingorlas71 have finer and shallower wrinkles1 and are harder1 solider and consequently darker looking1 but do not give a darker liquor1 while 8lean greens0 are greener1 have less yellow colouring matter1 and consequently more nearly approach in character to sumach1 which the tannin in many respects resembles1 though probably containing more ellagitannic acid in proportion to gallotannic acid than the latter4 ,the 8nuts0 should be bright in colour1 not worm-eaten1 nor 8waxy0 or soft4 ,if kept in a damp place they rapidly absorb moisture1 and fall into the 8waxy0 condition1 in which they are very difficult to grind1 sticking to and choking the cutters or beaters of the mill4 ,neither the large hard stones nor their kernels contain tannin1 but the latter have an oil which gives a peculiar odour to leather4 ,the tannin exists in large and rather thickly-walled cells1 and is not very easily extracted2 the skin is wrinkled1 but the uncrushed nuts swell up to their original plum-like form when placed in water for some time4 ,the bark is almost as rich as the fruit1 and the tree also yields galls4 ,t4 ,belerica yields ,beleric or 8,bedda nuts10 which are downy1 rounder and larger than ordinary myrobalans1 and contain about #ab per cent4 of tannin1 used as adulterant of ground myrobalans4 ,a sample of solid extract made from the bark of ,t4 ,belerica contained #gj per cent4 of tannin4 ,t4 tomentosa has downy nuts1 containing about #aj per cent4 of tannin1 bark stated by de ,lof to contain #cf per cent4 of tannin4 ,a sample of solid extract contained #ef per cent4 of tannin4 ,the bark contains about #aa per cent4 ,there are several other ,indian species4 ,t4 ,catappa1 8,badamier bark0 of ,mauritius1 contains #ab per cent4 of tannin4 ,t4 mauritiana1 8,jamrosa bark10 said to contain #cj per cent4 of tannin4 ,t4 ,oliveri1 ,malay ,archipelago1 yields 8,thann leaves10 from which an extract is made as a cutch substitute4 ,a sample of the extract from ,burmah examined recently in the ,author's laboratory1 contained #fb per cent4 of tannin4 ,the tannin is a catechol derivative1 differing from that of ,acacia catechu in containing no phloroglucol 7p4 #big74 ,a sample of bark from ,mandalay contained #ca per cent4 of tannin1 while the leaves from the same tree contained #ad per cent4 ,emblic myrobalans1 see p4 #bic4 ,,rhizophorace1 ,mangles or ,mangroves4 ,rhizophora ,mangle1 and other allied species1 ,mangrove or ,mangle1 ,manglier1 ,paletuvier1 ,cascalote1 grows on tropical coasts all round the world4 ,the barks vary much in strength1 from #ae up to #dj per cent4 in different species 7see ,ceriops74 ,leaves1 used in ,havana1 are said to contain #bb per cent4 tannin4 ,according to ,eitner1 the younger plants contain the highest proportion of tannin4 ,r4 ,mangle seems to yield a bark inferior to several other species4 ,all trees growing in swamp1 and of the same character of growth as mangrove1 are called 8,bakau0 in the ,east ,indies 7,anglice1 mangrove7 and various species of ,ceriops yield the best tanning bark4 ,a tidal mangrove swamp at low water is a tangle of arched roots like inverted branches on which the trees are supported4 ,the catechol-tannin1 which is easily extracted1 is of deep red colour and allied to that of the mimosas4 ,in admixture with other materials the red colour has a much smaller effect1 and mangrove bark is now largely used in combination with pine1 oak and mimosa4 ,several other species are also rich in tannin1 and used in different parts of the world under the name of mangle1 as are also several species of ,conocarpus belonging to the ,combretace4 ,rhizophora mucronata4 ,india and ,burmah4 ,bark varies considerably2 ,david ,hooper1 ,indian ,museum1 ,calcutta1 gives #bfi per cent4 of tannin4 ,dr4 ,koerner 7,deutschen ,gerberschule1 ,freiberg7 analysed two samples in #aijj1 one containing #dh per cent4 and the other #ba per cent4 of tannin2 two samples from the ,british ,imperial ,institute recently examined by the ,author showed only #de and #fa per cent4 of tannin respectively4 ,ceriops ,candolleana1 ,bakau or ,tengah ,bark1 ,east ,indies4 ,goran1 ,bengal4 ,contains up to #bg per cent4 of tannin and yields an extract which promises well as a substitute for cutch1 to which1 for dyeing purposes it is nearly or quite equal4 ,the solid extract contains up to #fe per cent4 tannin1 making a good but dark red leather4 ,ceriops ,roxburghiana1 a somewhat larger tree1 also growing in the ,sunderbans1 bark very similar in strength and character to the above4 ,,onagrace1 the nothera ,family4 ,fuchsia excorticata1 the only deciduous tree of ,new ,zealand4 ,contains #e per cent4 tannin4 ,fuchsia macrostemma1 ,chili4 ,yields ,tilco or ,chilco bark4 ,churco bark has been incorrectly attributed to this plant1 but it is certainly derived from an oxalis1 as stated by the ,kew authorities4 7,cp4 von ,hhnel1 #8,die ,gerberinde1' p4 #abe47 ,,gunnerace4 ,gunnera scabra 7,pangue871 ,pauke1 ,chili4 ,used occasionally in the tanning of goat-skins4 ,,myrtace4 ,eucalyptus globulus1 and other species of ,e4 common in ,australia1 and introduced into ,algeria and ,southern ,europe 7gum-trees71 are more or less rich in catechol-tannins1 their sap being the source of ,botany ,bay or ,australian kinos1 which contain up to #gi per cent4 tannin4 ,several species of ,eucalyptus afford astringent extracts2 those from the 8red10 8white10 or 8flooded0 gum 7,e4 rostrata71 the 8blood-wood0 7,e4 corymbosa71 and ,e4 citriodora1 being quite suitable for replacing the officinal kind4 ,the gum is chiefly obtained by woodcutters1 being found in a viscid state in flattened cavities in the wood1 and soon becoming inspissated1 hard and brittle4 ,minor quantities are procured by incising the bark of living trees2 a treacly fluid yielding #ce per cent4 of solid kino on evaporation is thus obtained4 ,the gum is imported from ,australia1 but there are no statistics to show in what quantity4#adf #adf ,compare ,journ4 ,soc4 ,chem4 ,ind41 #aijb1 p4 #aei4 ,eucalyptus longifolia bark1 the 8woolly-butt0 of ,australia1 contains #hc per cent4 of tannic acid1 and #bh of gallic4 ,the 8peppermint0 tree contains #bj per cent4 of tannic acid in its bark4 ,the 8stringy-bark0 7,e4 obliqua7 gives #ac per cent4 of kinotannic acid4 ,the ,victorian 8iron-bark0 7,e4 leucoxylon7 contains #bb per cent4 of kinotannic acid1 but is available only for inferior leather4 ,myrtus communis1 and several other myrtle species1 contain a considerable amount of tannin in the bark and leaves4 ,,granatace4 ,punica ,granatum1 ,pomegranate4 ,peel of fruit employed in ,spain and the ,east as substitute for sumach1 containing up to #be per cent4 of tannin4 ,bark said to contain #bb per cent4 tannin4 ,balaustines1 wild pomegranates1 ,east ,indies4 ,fruit1 said to contain #df per cent4 tannin4 ,,rosace4 ,tormentilla erecta1 ,potentilla tormentilla4 ,root variously stated to contain #bj-df per cent4 tannin4 ,red coloured leather1 formerly used in ,orkneys1 ,shetland1 and ,faroe ,islands1 and in some parts of ,germany4 ,sorbus or ,pyrus ,aucuparia1 ,mountain ,ash4 ,bark said to be stronger than oak4 ,many other plants of the family contain tannin1 among others the strawberry4 ,,papilionace4 ,butea frondosa4#adg ,this 7with ,pterocarpus marsupium7#adh furnishes ,east ,indian kino4 ,the flowers are used in ,india as a dye1 under the name of ,tesu4 ,bark fairly rich in tannin4 #adg #8,dictionary of ,economic ,products1' ,i4,b41 p4 #idd2 ,hummel and ,cavallo1 ,proc4 ,chem4 ,soc4 #ahid1 p4 ii4 #adh ,agricult4 ,ledger1 #aija1 ,no4 #aa1 ,gov4 ,printing ,office1 ,calcutta4 ,pterocarpus or ,drepanocarpus senegalensis is the source of ,african kino1 which contains up to #ge per cent4 of tannin4 ,csalpinia coriaria1 ,divi-divi4 ,a tree of #bj-cj feet1 native in ,central ,america1 introduced successfully in ,india1 but principally imported from ,maracaibo1 ,paraiba and ,rio ,hache4 ,the dried pods contain #dj-de per cent4 of a pyrogallol-tannin1 mainly ellagitannic acid1 and would be a most valuable tanning material1 but for a liability to fermentation and sudden development of a deep red colouring matter4 ,the causes are not well understood1 but apparently the risk can be materially lessened by use of antiseptics4 ,if used in strong liquors it gives a heavy and firm leather1 but is principally employed as a partial substitute for gambier on dressing leather4 ,used in rapid drum-tannage for light leathers1 an excellent colour may be obtained4 ,it is said to give an especially firm and glossy flesh4 ,leather tanned with it1 even when of outwardly good colour1 has often a blueish-violet shade within1 perhaps due to the development of a colouring matter allied to that of logwood4 ,the seeds do not contain tannin1 which lies almost free in the husk of the pod4 ,the pods are about #c-d cm4 long1 dark outside1 and curl up in drying to an ,s-shape4 ,c4 digyna1 ,tari or teri pods4 ,occurs in ,prome1 ,toungoo1 ,bassin1 ,mynang and other parts of ,india and ,burmah1 where it is used as a drug4 ,the pod-case is said to yield over #ej per cent4 of tanning matter4 ,a sample from ,burmah1 kindly sent by the ,imperial ,institute1 examined by the ,author in #aijj1 contained #bd per cent4 of tannin1 but after removing the seeds the remaining pod-cases yielded #dd per cent4 of tannin on analysis4 ,c4 digyna promises to become a valuable tanning material if it proves free from the tendency to ferment which is so troublesome in divi-divi4 ,it has been introduced into ,england under the name of 8white tan10 which yields a leather quite as white as sumach2 but the supply seems at present uncertain4 ,c4 cacolaco1 ,cascalote1 ,mexico4 ,pods rich in tannin 7up to #ee per cent41 ,eitner74 ,pods larger and fleshier than divi1 seeds smaller1 tannin similar4 ,the pods of several other ,csalpinias are used in tanning1 sometimes under the name of 8,algarobilla10 which is simply a diminutive of ,algaroba1 the carob1 or locust-bean1 derived from ,arabic al ,kharroba1 and applied to several small pods4 7,see ,balsamocarpon and ,prosopis47 ,c4 7or ,balsamocarpon7 brevifolia1 ,chili1 ordinary ,algarobilla4 ,fig4 #eh4 ,one of the strongest tanning materials known1 containing an average of #de per cent4 of a tannin very like that of divi1 but less prone to discoloration4 ,the tannin lies loose in a very open skeleton of fibre1 and is easily soluble in cold water2 the seeds contain no tannin4 ,if not allowed to ferment it produces a very bright-coloured leather4 ,algarobilla has been attributed to ,prosopis pallida1 but this appears incorrect4 ,several species of ,p4 are known to yield tanning pods2 those of ,p4 ,stephaniana of the desert of ,kaschan1 in ,persia1 are dschigh dschighe1 perhaps identical with dchift or jaft4 7,see p4 #bfc47 ,bark of ,p4 spicigera used in ,punjab4 ,c4 7or ,hmatoxylon7 campechianum1 ,logwood1 ,central ,america4 ,in addition to colouring matter1 and a glucoside which it yields on oxidation1 this wood contains about #c per cent4 tannin4 ,its principal use is in dyeing blacks with iron or chrome mordants4 7,see p4 #dac47 ,illustration3 ,,fig4 #eh4adi--;,algarobilla 7,csalpinia brevifolia74 #adi #8,new ,commercial ,drugs and ,plants1' ,no4 #e1 ,t4 ,christy4 ,c4 echinata yields 8,brazil-wood40 7,see p4 #dac47 ,c4 ,sappan1 ,sappan-wood1 ,india4 ,cassia auriculata1 ,turwar or ,tanghadi bark1 ,southern ,india4 ,used for tanning so-called 8,persian0 sheep- and goat-skins1 contains about #ag per cent4 of a catechol tannin4 ,leather tanned with it is of a pale yellow colour1 but rapidly reddens in sunlight4 ,cp4 p4 #bce4 ,c4 fistula1 ,india4 ,husk of pod1 #ag per cent4 tannin4 ,the pulp of pod is used as an aperient4 ,c4 elongata and lanceolata4 ,senna leaves4 ,upper ,egypt4 ,c4 ,sophora1 8,bali-babilan40 ,illustration3 ,,fig4 #ei4--;,babool 7,acacia arabica74 ,,mimose1 a ,tribe of ,leguminos4 ,acacia arabica1 8,babool10 8,babul10 ,india1 ,egypt4 ,fig4 #ei4 ,bark contains about #ab-bj per cent4 of catechol tannin2 one of the principal ,indian tanning materials1 used for kips and heavier leathers4 ,pods1 used in ,india for bating1 contain about same amount of tannin as bark1 but of a different kind1 that of the bark being a catechol-tannin1 with a good deal of red colouring matter1 while the pods contain a paler tannin allied to divi1 which is not precipitated by lime-water4 ,in ,egypt the pods are called bablah1 a name which is also applied to pods of ,a4 cineraria and ,a4 vera1 and others4 ,they are used for dyeing glove-leathers4 ,a4 nilotica1 ,egypt4 ,pods called neb-neb or bablah4 ,illustration3 ,,fig4 #fj4--;,cutch ,tree 7,acacia catechu74 ,a4 catechu1 ,india4 ,the wood yields cutch or 8dark catechu40 ,a lighter coloured variety called kath1 containing much crystallised catechin1 is also made in ,india1 and principally used for chewing with betel4 ,a4 catechu is a tree #cj-dj feet high1 common in ,india and ,burma1 and also in tropical ,east ,africa1 where1 however1 it is not utilised4 ,in ,southern ,india1 ,a4 suma is also used for the same purpose4 ,trees of about #a foot diameter are cut down1 and the wood 7some state the heart-wood only7 is reduced to chips1 and boiled with water in earthen jars over a mud-fireplace4 ,as the liquor becomes thick and strong1 it is decanted into another vessel1 and the evaporation continued till the extract will set on cooling1 when it is poured into moulds made of leaves or clay1 the drying being completed by exposure to the sun and air4 8,kath10 or pale cutch1 is made in ,northern ,india1 by stopping the evaporation at an earlier point1 and allowing the liquor to cool1 and crystallise over twigs and leaves thrown into pots for the purpose4 ,it contains a large proportion of catechin1 apparently identical with that of gambier1 but its tannin is much redder4 ,good cutch contains about #fj per cent4 tanning matter1 but is principally used for dyeing browns and blacks with chrome and iron mordants4 ,it contains quercetin1 a yellow colouring matter 7p4 #bfc74 ,a4 leucophlea1 ,india and ,java 8,pilang40 ,pods and bark equal to ,a4 arabica4 ,australia abounds in acacias 7mimosas71 many of which are used in tanning1 but vary greatly in strength1 not only according to species1 but probably also by situation and growth4 ,probably the best information is to be found in a pamphlet on #8,wattles and ,wattle-,bark1' by ,j4 ,h4 ,maiden1 ,f4,l4,s41 published by the ,department of ,public ,instruction at ,sydney1 #ahij4 ,his analyses were made by the ,lwenthal process1 and can only be roughly compared with those by the hide-powder method4 ,the analyses given are by the ,i4,a4,l4,t4,c4 method1 and mostly on samples furnished by ,mr4 ,maiden4 ,a peculiarity largely developed in the mimosa family is the tendency for the true leaves to be suppressed1 and their place taken by the flattened and expanded midrib 7phyllode74 ,thus leaves of two very distinct forms are common in the genus1 and some acacias1 as ,a4 heterophylla1 may have both forms on the same branch4 ,compare ,a4 pycnantha and ,a4 decurrens4 ,the ,australian mimosas have been naturalised in ,india1 and grow freely in the ,nilgiri ,hills1 but the bark does not appear to be utilised4 ,the most important species are as follows3-- ,a4 pycnantha4 7,fig4 #fa47 8,broad-leaved0 or 8,golden ,wattle10 ,south ,australia4 ,one of the strongest tanning barks known4 ,a sample marked 8special10 analysed in the ,yorkshire ,college1 contained #ej per cent4 of tannin2 another sample marked 8ordinary0 contained #dj per cent4 ,illustration3 ,,fig4 #fa4--;,broad-leaved ,wattle 7,acacia pycnantha74 ,illustration3 ,,fig4 #fb4--;,green ,wattle 7,acacia decurrens74 ,a4 longifolia1 the ,golden ,wattle of ,new ,south ,wales1 only contains half as much tannin as ,a4 pycnantha4 ,a4 mollissima1 with its two varieties ,a4 decurrens 7,fig4 #fb7 and ,a4 dealbata1 are among the most important of the ,wattle family commercially4 ,two samples of the former marked 8,green ,wattle0 showed #cf-ci per cent4 of tanning matter2 another sample marked 8,sydney ,green ,wattle10 contained #da per cent4 ,a sample of ,a4 decurrens1 the second variety1 was much weaker1 showing only #ab per cent4 on analysis4 ,a4 penninervis 7,hickory bark7 is said to be particularly hardy1 but its strength seems to vary4 ,a sample from ,bateman's ,bay contained #ch per cent4 of tanning matter4 ,a4 binervata1 another 8,black ,wattle0 contains up to #cj per cent4 tanning matter1 as does also the 8,weeping ,willow10 ,a4 saligna4 ,the latter is poisonous1 and is said to be used for killing fish4 ,a4 prominens1 the bark of which resembles that of the ,golden ,wattle1 ,a4 longifolia1 in appearance contains only #ad per cent4 tannin4 ,the cultivation of wattles in ,australia has been somewhat neglected1 but would render possible the utilisation of many acres of land lying waste1 or which have already been exhausted and rendered unfit for the growth of cereals4 ,it requires so little attention as to make it very profitable1 and wattle-growing and sheep-grazing can be combined satisfactorily after the first year1 when the young trees in the plantation have reached the height of #c-d feet4 ,in ,natal the ,australian wattles1 especially ,a4 mollissima1 have been acclimatised and cultivated with success1 and large quantities of excellent bark are now exported to ,england4 ,african wattle-barks usually contain about #cj per cent4 of tannin4 ,wattles grow in almost any soil1 even the poorest1 but their growth is most rapid on loose1 sandy patches1 or where the surface has been broken for agricultural purposes4 ,when the soil is hard and firm1 plough-furrows should be made at a regular distance of #f-h feet apart1 and the seeds dropped into these4 ,the seed should be sown in ,may1 having been previously soaked in hot water1 a little below boiling temperature1 in which they may be allowed to remain for a few hours4 ,it should be dropped at an average distance of #a foot apart along the furrow1 in which case1 about #gbjj seeds would suffice for one acre of land4 ,the seed should not be covered with more than about inch of soil4 ,on loose sandy soil1 it might even be unnecessary to break up the ground in any way2 the furrows may be dispensed with1 and the seed sown broadcast after the land has been harrowed4 ,after the plants have come up1 they should be thinned so that they stand #f-h feet apart4 ,when the young trees have attained the height of #c-d feet1 the lower branches should be pruned off1 and every effort afterwards made to keep the stem straight and clear1 in order to facilitate the stripping1 and induce an increased yield of bark4 ,it is advisable that the black and broad-leaved kinds should be grown separately1 as the black wattle1 being of much larger and quicker growth1 would oppress the slower-growing broad-leaved one4 ,care should be taken to replace every tree stripped by re-sowing1 in order that there should be as little variation in the yield as possible4 ,in ,victoria1 the months of ,september-,december are those in which the sap rises without intermission1 and the bark is charged with tannin4 ,analysis proves that the bark from trees growing on limestone is greatly inferior in tannin to that obtained from other formations1 differing #aj-be per cent4 ,the following are ,south ,american mimosas3-- ,a4 cavenia1 ,espinillo4 ,bark1 contains #f per cent41 pods1 #ah-ba per cent41 or more of tannin4 ,a4 cebil1 ,red ,cebil4 ,bark1 contains #aj-ae per cent42 leaves1 #f-g per cent4 tannin4 ,argentine ,republic4 ,a4 ,guarensis1 ,algarobilla of ,argentine ,republic4 ,bark1 pods and flowers said to be used for tanning4 ,a4 timbo1 ,buenos ,ayres4 ,a4 curupi1 ,curupy bark4 ,a4 angico1 or ,piptadenia macrocarpa1 ,brazil1 yields 8angica bark10 a sample of which contained #bj per cent4 of tanning matter when analysed recently in the ,author's laboratory4 8,white ,bark10 ,south ,america1 probably an acacia1 bark internally very similar to angica1 if not identical4 ,a4 horrida1 8,doornbosch10 ,cape of ,good ,hope1 contains #h per cent4 of tannin4 ,inga feuillei1 8,paypay10 ,peru4 ,pods said to contain #ab-ae per cent4 of tannin 7doubtful74 ,several other species of ,inga known to contain tannin4 ,elephantorrhiza ,burchellii1 ,elandsboschjes1 ,tugwar1 or ,tulwah1 ,south ,africa2 a papilionaceous plant4 ,the air-dry root contains #ab per cent4 of tannin1 and a great deal of red colouring matter4 ,the roots are several feet long1 and about #b inches in diameter1 growing by the sides of rivers4 ,the following additions may be made to the above list3-- ,,euphorbiace4 ,cleistanthus collinus1 8,kodarsi10 ,deccan4 ,bark stated to contain #cc per cent4 of tannin4 ,phyllanthus emblica1 ,india1 yields emblic myrobalans1 which in immature condition contain considerable tannin4 ,leaves 7#ah per cent47 and bark used for tanning4 ,phyllanthus distichus and nepalensis both yield tanning barks4 ,,combretace4 ,anogeissus latifolia1 ,india4 ,bark and leaves rich in tannin4 ,,guttifer4 ,garcinia mangostana1 ,india4 ,the rind of the mangosteen fruit contains much tannin4 ,,chapter ,,xix4 ,,the ,,chemistry ,,of ,,the ,,tannins4 ,the essential constituents of tanning materials are members of a large group of organic compounds known as 8tannins0 or 8tannic acids10 which are widely distributed throughout the vegetable kingdom1 and said to have one representative among animals1 in the body of the corn-weevil4 ,their use in vegetable physiology is as yet uncertain1 and indeed they appear in some cases to be waste products of organic change4 ,the tannins1 though varying considerably in their chemical constitution1 and in many important characteristics1 are all marked by the power of precipitating gelatine and some allied bodies from their solutions1 of converting animal skin into the imputrescible material known as leather1 and of forming dark-coloured compounds with ferric salts which are often utilised as inks4 ,they are also precipitated by lead and copper acetates1 stannous chloride1 and many other metallic salts1 and form insoluble compounds with many organic bases1 such as quinine1 and with the basic aniline colours4 ,they are possessed of feeble acid character4 ,all tannins are soluble in water to a greater or less degree2 they are also soluble in alcohol1 in mixtures of alcohol and ether1 in ethyl acetate1 acetone1 and a few similar solvents1 but are not dissolved by dry ether alone1 nor by chloroform1 petroleum spirit1 carbon disulphide1 nor benzine4 ,as the tannins are uncrystallisable1 and incapable of being distilled without decomposition1 they are exceedingly difficult to obtain in a state of purity1 and1 owing to the considerable differences in their character1 no one method is equally applicable to the whole group4 ,as their successful separation requires considerable chemical training1 and experience1 detailed description is outside the scope of the present work1 but some particulars of the more important methods employed are given on p4 #dc1 ,l4,i4,l4,b4 ,their chemical constitution is complex and in most cases imperfectly understood1 but all the natural tannins which have been investigated prove to be derivatives of the trihydric phenol1 pyrogallol1 or of the dihydric phenol1 catechol1 the latter of which is often accompanied by a trihydric phenol1 phloroglucol1 which is isomeric with pyrogallol4 ,the phenols are1 themselves1 a class of derivatives of benzene1 ,c,h1 in which one or more of the hydrogen atoms are replaced by ,,oh groups4 ,common phenol or 8carbolic acid0 is their simplest representative4 ,many of them1 including pyrogallol and catechol1 are used as photographic 8developers40 ,the phenols on replacing another hydrogen by carboxyl 7,,co4,,oh7 form true acids1 of which salicylic corresponds to common phenol1 protocatechuic to catechol1 and gallic to pyrogallol2 and the tannins are apparently complicated acids1 in which one of the two latter acids is linked to a second molecule of the same or another acid as an anhydride1 in some cases possibly with the addition of phenols or other organic groups4 ,for more detailed information1 see ,l4,i4,l4,b41 p4 #de4 ,gallotannic acid is apparently digallic acid1 in which two molecules of gallic acid are linked together after giving up the elements of a molecule of water4 ,natural gallotannic acid and many other tannins are glucosides1 or at least contain glucose1 which in many cases can be removed by purification4 ,from what has just been said1 it is obvious that a classification of the tannins according to constitution1 is at present impracticable1 not only from our imperfect knowledge1 but from the difficulty of separating and determining the products of their decomposition4 ,it is not1 however1 difficult to distinguish the catechol- from the pyrogallol-tannins by their chemical characteristics1 apart from actual separation of the phenols1 and the division is important as it is marked by certain broad differences in their properties which affect their use in tanning4 ,the catechol-tannins1 dissolved in water1 yield a precipitate when bromine-water is added till the solution smells strongly of it4 ,the precipitate is occasionally crystalline1 but generally amorphous1 and of yellowish or brownish colour4 ,when the infusion of tannin is very weak1 the precipitate is sometimes only slight1 or forms slowly4 ,pyrogallol-tannins give no precipitate with bromine-water4 ,another reaction1 which is generally characteristic of catechol-tannins1 is that if concentrated sulphuric acid is added to a single drop of the infusion in a test-tube1 a dark red1 or crimson ring is formed at the junction of the two liquids1 and on dilution with water1 the solution is generally pink4 ,pyrogallol-tannins on the other hand give a yellow1 or at most a dark brown ring1 which dilutes to a yellowish solution4 ,this reaction is of great delicacy1 which may be further increased by the use of an alcoholic instead of an aqueous extract4 ,it is often given also by the non-tannin residue of catechol-tannins which is left after treatment with hide-powder1 in which case it is probably due to the presence of catechins allied to the tannins4 ,with ferric salts 7preferably a solution of iron-alum71 pyrogallol-tannins give blue-blacks1 while catechol-tannins generally give greenish blacks1 though the reaction is apt to be rendered uncertain by the presence of colouring matters1 or perhaps in some cases by the constitution of the tannin4 ,thus aqueous infusions of common oak-bark 7,quercus robur7 give a decidedly blue black with iron1 though the tannin is a catechol one1 and the purified tannin gives a green-black4 ,most of the barks of ,american oaks1 such as ,q4 prinus1 give green-blacks without purification4 ,the ,australian mimosas generally give dull purple-blacks with iron-salts1 though they all contain catechol-tannins4 ,the iron test was first proposed by ,stenhouse as a means of classification4 ,trimble has shown that while the purified pyrogallol-tannins only contain about #eb per cent4 of carbon1 the catechol-tannins have about #fj per cent4#aej #aej #8,the ,tannins1' ii4 p4 #aca4 ,only two tannins of the pyrogallol group have been definitely distinguished1 though it is very possible that more exist4 ,these are ordinary tannic acid of gall-nuts 7probably digallic acid71 which yields gallic acid when heated with dilute acids1 or by the action of certain unorganised ferments or zymases 7p4 #af7 which are generally present in tanning materials2 and ellagitannic acid 7usually present in greater or less proportion in mixture with the gallotannic acid71 which1 under the same conditions yields 8bloom0 7an insoluble deposit of ellagic acid71 as one of its products4 ,hence it happens that most pyrogallol tannins deposit 8bloom0 on leather1 though in very different proportions1 gall-nuts and sumach giving very little1 and myrobalans1 valonia and divi-divi a great deal4 ,english oak-bark deposits a good deal of 8bloom0 on leather1 though it is certain that its principal tannin is a catechol one1 but it is possible that the blue-black which it gives with iron salts may be due to the presence of ellagitannic acid1 though gallotannic acid is known to be absent4 ,the tannins of oakwood1 chestnut and valonia are principally if not entirely pyrogallol derivatives1 closely allied to1 if not identical with the two just named1 but1 if so1 very difficult to obtain in a pure condition4 ,it is noteworthy that so wide a difference exists between the various products of the oak2 galls1 bark1 fruit and wood yielding tannins of very varied properties4 ,the tannin of other galls1 such as those of the sumach and pistacio1 generally contain gallotannic acid1 even when1 as in the last case1 the remainder of the plant yields catechol-tannins4 ,the tannins of the catechol group appear to present much more variety than the pyrogallol-tannins1 though it is possible that many apparent differences may be due to the presence of impurities4 ,it is1 however1 at least certain that the tannins of gambier and cutch contain phloroglucol as one of their constituents1 while it is absent from most other tanning materials4 ,its presence is easily detected by moistening pine-wood 7a deal shaving7 with an infusion of the tannin in question1 and applying a little concentrated hydrochloric acid1 when after a few minutes1 a bright red or purple stain is produced4 ,the catechol-tannins1 on boiling with acids1 yield no gallic acid1 or bloom1 but generally a deposit of 8reds10 insoluble in water but soluble in alkaline liquids1 and in alcohol1 and which are closely allied to resins1 and especially to the red resin known as 8dragon's blood40 ,these reds are anhydrides of the tannins1 that is1 are produced from them by the abstraction of water2 and are consequently formed by any agency which tends to remove water1 such as long boiling or high temperature4 ,the lower anhydrides 7that is1 those from which least water has been abstracted7 are not wholly insoluble1 but form the 8difficultly soluble0 tannins which are naturally present in many materials4 ,they are much more readily soluble in hot than in cold water1 which is one of the causes why liquors made by the aid of heat generally give darker colour to leather than those extracted cold4 ,they exist in large quantity in hemlock extract and quebracho4 ,attempts have been made to utilise their alkaline solutions for tanning1 but without much success2 though alkalies or alkaline sulphites are frequently used to obtain 8soluble0 quebracho extracts 7p4 #cch74 ,many catechol tanning materials1 and especially gambier1 cutch and quebracho1 contain in addition to the tannin1 considerable portions of colourless bodies called catechins1 which are only slightly soluble in cold water1 but readily in hot1 and which crystallise out on cooling4 ,these bodies do not tan1 but are in a sense the source of the tannins1 which appear to be their first anhydrides1 the reds being formed by the successive loss of further molecules of water4 ,these bodies very probably ultimately become converted into tannins by changes in the tanyard4 ,the change may be brought about very rapidly by heating to a temperature of #ajj to #abj ,c4#aea ,the catechin of gambier1 by crystallising on and in the leather1 is the cause of a trouble known as 8whites10 which is common where gambier is largely used4 #aea ,some doubt exists as to the exact temperature at which catechins become converted into anhydrides1 and ,perkin puts it higher than that stated4 ,an unfortunate peculiarity1 apparently common to all catechol-tannins1 is that1 however light-coloured the leather produced by them1 it darkens and reddens rapidly by exposure to strong light1 and ultimately becomes quite friable and rotten4#aeb ,cp4 pp4 #bcd1 #bgb4 #aeb ,cp4 ,report of ,committee on ,leathers for ,bookbinding1 ,journ4 ,soc4 of ,arts1 #aija1 p4 #ad4 ,wagner1 a ,german chemist1 attempted to classify the tannins into 8physiological0 tannins1 which were produced in the natural growth of the plant1 and 8pathological0 which were caused by the attack of insects such as the gall-wasps1 and he further ventured the assertion that only the former class were capable of producing leather4 ,it has since been shown that the tannins produced in galls are identical with some of those found in healthy plants1 and galls themselves have been used in tanning from very ancient times4 ,it is only necessary to remind the reader of the use of ,turkish gall-nuts1 in place of sumach1 which was common in the ,east in the tannage of moroccos1 and of the 8,knoppern10 or oak-galls formerly so largely used in ,austria as a tanning material for sole leather4 ,it is true that the tannin of galls is not very suitable for the latter purpose1 consisting as it does mostly of gallotannic acid1 which1 giving no solid deposit of bloom or reds1 is incapable of making a heavy or solid leather4 ,pure gallotannic acid itself produces a very white and soft leather4 ,the class to which the tannins of the different tanning materials belong is mostly mentioned in the ,botanical ,list 7,chap4 ,,xviii471 but it may be well here to specify a few of the most common4 ,galls and sumach contain gallotannic acid with a little ellagitannic2 myrobalans1 valonia1 divi-divi1 algarobilla1 oakwood and chestnut are all pyrogallol-tannins giving ellagic and gallic acid among their decomposition products4 ,all the pine barks1 including the ,american hemlock1 and the larch1 all the acacias and mimosas1 including the ,indian ,babul 7,acacia arabica71 the oak barks 7though not the oak wood1 fruits1 or galls71 quebracho wood1 cassia#aec and mangrove barks1 canaigre1 cutch and gambier are catechol-tannins1 and the two last contain phloroglucol1 of which minute traces are also present in many other catechol-tannins 7p4 #big74 #aec ,cassia auriculata1 or 8turwar0 bark1 is the ordinary tannage of the ,east ,indian or 8,persian0 sheep- and goat-skins1 largely used in bookbinding1 but which redden and decay very rapidly4 ,gallotannic acid1 and several artificial tannins with the characteristic reactions of the class have been produced in the laboratory1 but there is no present prospect of their manufacture at prices which can in the faintest way compete with those of natural production4 ,tanning materials frequently contain mordant colouring matters1 often derived from the same phenols as the accompanying tannins4 ,they also usually contain gums1 starch and glucose4 ,oak bark contains lvulose which is not combined with the tannin4 ,many tannins1 however1 exist in nature in combination with the sugars as glucosides1 which are easily decomposed by the action of acids or by fermentation4 ,these sugary matters are important as furnishing by fermentation the acetic and lactic acids of tanning liquors4 ,,chapter ,,xx4 ,,the ,,sampling ,,and ,,analysis ,,of ,,tanning ,,materials4 ,although the analysis of tanning materials falls more properly within the scope of a book for chemists than one intended primarily for tanners1 and though it has been treated at considerable length in the #8,leather ,industries ,laboratory ,book1' a slight sketch must now be given of the methods in general use1 since it is of great importance that at least the principles on which they are based should be understood by all to whom they are of practical interest1 and also because an approximate analysis of a tanning material by the hide-powder method is within the scope of any intelligent tanner who will provide himself with the necessary implements4 ,much attention has been paid to the subject area by the ,international ,association of ,leather ,trades ,chemists1 and also by the ,american ,official ,association of ,agricultural ,chemists1 and as the methods prescribed by one or other of these are with very little exception employed by all qualified chemists throughout the world1 their directions1 corrected up to date1 are given in ,appendices ,a and ,c4 ,as1 however1 these directions are addressed to chemists already familiar with the usual course of analysis1 a somewhat fuller explanation must here be given4 ,it must specially be insisted on1 that absolute adherence to the methods given is essential to obtaining concordant results1 and little points of manipulation which appear in themselves unimportant1 are frequently the result of long experience and careful discussion4 ,the members of the ,international ,association1 especially1 are bound by their rules to make note in their analytical reports of any deviation1 however small1 from the prescribed process4 ,the first step in the analysis of any material is to draw a sample truly representing the bulk1 which is often by no means easy1 while failure to accomplish it is probably the cause of more errors and disputes than any inaccuracy of the method of analysis itself4 ,in very many cases1 chemists are blamed for discrepancies which really exist in the samples supplied to them4 ,the chemists of the ,international ,association only hold themselves responsible for the accuracy of their analyses when the sampling has been done strictly according to the rules prescribed by their ,association4 ,on this account1 all important samples should be drawn in the presence of a principal1 or some other responsible person4 ,in liquid extracts1 the thorough mixing of the liquid is of the greatest importance4 ,most extracts contain a portion of 8difficultly soluble0 tannins 7see p4 #big71 which slowly settle to the bottom1 or adhere to the sides of the cask2 from which such expedients as merely rolling a full cask are quite inefficient to dislodge them4 ,in fact nothing but taking the heads out of a sufficient number of casks1 and actually stirring them with a suitable plunger1 which should be specially applied to the sides and bottom1 or emptying the entire contents of the casks into a tank in which the whole can be adequately mixed1 is really thoroughly reliable1 though at times it is necessary to be content with less satisfactory methods4 ,in any case1 when it is probable that samples must be submitted to more than one chemist1 the whole should be drawn at once1 thoroughly mixed and divided1 and sealed in separate bottles1 and in dividing a sample the same care must be taken to ensure complete mixture1 as in drawing the original sample4 ,solid and pasty extracts1 such as quebracho1 cutch and gambier1 are still more difficult to sample fairly1 as the outside is almost invariably much drier than the interior4 ,generally the only way is to select such portions as are thought fairly to represent the bulk1 to chop them into moderately small pieces1 mix and seal in an air-tight tin1 leaving it to the chemist to draw from these the smaller sample required for analysis4 ,gambier is best sampled with a tubular tool like a cork-borer1 designed by ,mr4 ,kathreiner1 ,fig4 #fc1 which should be passed completely through the bale1 or the cylindrical sample of gambier cannot be withdrawn4 ,the same tool may also be used for sampling sumach in bags1 if the damage to the bag is not objected to4 ,if such a tool is not available1 the only fair way to sample gambier is to cut slices completely through the bale with a clean fleshing knife4 ,in any case it is of the utmost importance that the sample once drawn1 should be mixed as rapidly as possible1 and at once enclosed in an air-tight box or jar1 sealed and labelled4 ,illustration3 ,,fig4 #fc4--,kathreiner's ,sampling ,tools4 ,a1 strong cross-handle2 ,b1 guard-disc2 ,c ,c1 brass tube sharpened at ,c2 ,d1 brass or wooden plunger4 ,dry tanning materials1 such as bark and valonia1 require judgment in selecting samples which fairly represent bulk4 ,if they are of a nature which do not readily separate into dust and fibre1 a good method is to grind a sufficient quantity in an ordinary bark-mill1 and after well mixing1 to draw the sample from the ground portion4 ,in other cases it is best to empty a sufficient number of bags one upon another in layers on a smooth floor1 and to take out a section down to the floor4 ,in such materials as valonia and divi-divi1 the dust or beard is usually much stronger than the average of the pods or cups4 ,the same sort of precautions are required in drawing the still smaller sample required for analysis from the larger original sample1 but these are sufficiently detailed in the directions of the ,i4,a4,l4,t4,c4 given in the ,appendix4 ,as materials usually require finer grinding than can be managed with the mills employed in the tannery1 a suitable mill must be provided1 and one of the simplest1 at a moderate price1 is a ,no4 #d drug-mill made by ,a4 ,kenrick and ,sons1 ,limited1 ,west ,bromwich1 ,fig4 #fd4 ,coffee mills are seldom strong enough for the purpose1 but if nothing better is available1 the sample must be thoroughly dried before grinding1 and its loss of weight noted1 and taken into account in calculating the analysis1 care being taken that the sample after grinding is so preserved that it cannot re-absorb moisture4 ,valonia1 myrobalans and even barks1 may before grinding be broken with a flat-faced hammer1 on a thick cast-iron plate1 with raised edges to prevent loss from flying fragments4 ,illustration3 ,,fig4 #fd4--,kenrick's ,drug-,mill4 ,preparation of solution for analysis4--,as the method of analysis only gives satisfactory results when the quantity of tanning matter in the solution is within certain limits1 the ,international ,association prescribes that it must be such as to contain between #ce and #de grms4 of tanning matter per liter1 or as near as possible1 on the average1 to #d grms4 ,if1 as will rarely happen1 the strength of a material is quite unknown1 it may be necessary to make a trial test to ascertain the quantity of substance to be used1 but the following table gives the quantity with sufficient accuracy for most ordinary materials4 ,,table ,,showing ,,the ,,amount ,,of ,,different ,,materials ,,to ,,be ,,weighed ,,out ,,for ,,analysis ,,to ,,make ,,up ,,one ,,liter ,,of ,,solution4 ,barks1 etc4 ,grams4 ,algarobilla #i ,canaigre #ae ,divi-divi #i ,hemlock bark #af ,mimosa bark #aa ,myrobalans #ae ,oak-bark #cj ,oak-wood #ajj ,quebracho wood #bj ,sumach #ae ,valonia #ae ,valonia beard #aa ,extracts4 ,oak-wood1 sp4 gr4 #ab or over #ae ,chestnut ditto #ad ,quebracho 7solid7 #f 7liquid7 #i to #ac ,gambier 7block7 #aj 7cube7 #g ,the best method of weighing out exact quantities may be here described for those to whom it is not already known1 as much time may be wasted by attempting it unsystematically4 ,the material is of course weighed in a basin1 which together with the weight which is desired of the material1 is exactly counterpoised by weights in the other pan4 ,where many weighings of the sort have to be made1 it saves time to keep one particular basin for the purpose1 which should be properly marked#aed2 and to make a counterpoise of lead or brass exactly equal to it in weight1 so that it is only necessary to add weights corresponding to the quantity required to be weighed out4 ,supposing now1 that it is a liquid extract which is to be weighed1 a sufficient quantity is introduced into the basin with a pipette1 to slightly exceed the required weight4 ,the pipette is now emptied1 and a small quantity is withdrawn with it from the basin4 ,if the basin is still too heavy1 the pipette is emptied1 and the process repeated until the basin is too light4 ,the true weight now lies between that in the basin and the small quantity retained in the pipette1 from which extract is added till the basin is again over-weighed1 and the same process is repeated1 each time reducing the margin1 till a sufficient approximation is obtained4 ,it is not necessary in weighing out the sample1 to be accurate to a single milligram2 but with practice1 this amount of accuracy is easily attained4 ,if the material is solid1 a spatula is substituted for the pipette4 ,the weighing of liquid or pasty extracts should be as rapid as possible1 as they lose weight on the balance by evaporation4 #aed ,porcelain basins may be indelibly marked by writing on them with an ordinary iron ink1 and heating strongly with a blowpipe4 ,liquid extracts are most easily dissolved by placing a large funnel in the neck of a liter flask1 and after pouring a little boiling water into the flask1 holding the basin inclined in the funnel1 and washing out its contents with boiling distilled water from a glass wash-bottle1 or a perfectly clean copper kettle1 till the flask is filled to the mark4 ,the flask is now covered with a small beaker1 which must hang loose on its neck1 without resting on its shoulders1 and is rapidly cooled by placing it under a cold water tap1 to a temperature as little above #ae ,c4 as possible1 and is then filled up to the mark on the neck with cold water1 and well mixed by shaking very thoroughly4 ,solid or pasty extracts are dissolved in a beaker by stirring with successive quantities of boiling water1 which are poured off into the flask1 leaving the undissolved matter in the beaker4 ,when the flask is nearly full1 if any small portions remain undissolved or insoluble1 they may be rinsed into it with the last portions of hot water1 and the flask is now cooled and mixed as already described4 ,illustration3 ,,fig4 #fe4--,procter's ,extractor4 ,extraction of solid materials1 such as barks1 or valonia1 is more difficult1 but the following is a convenient method1 which has been recognised as official by the ,international ,association4 ,an ordinary beaker1 of about #bjj c4c4 capacity1 but which may be varied in size according to the weight of the material which it is necessary to treat1 is placed in a water-bath1 as shown in ,fig4 #fe4 ,a thistle-headed funnel1 the stem of which is bent twice at right angles1 and of which the head is covered with a piece of fine silk gauze 7such as is used by millers7 to act as a strainer1 is placed in the beaker and held in position by a clamp as shown in the figure4 ,to the free end of its stem a piece of glass tube1 six or eight inches long1 is attached by indiarubber tube1 which is provided with a pinchcock to regulate the flow of liquid4 ,fine silver-sand1 freed from iron and soluble matters by washing first with hydrochloric acid1 and then very thoroughly with water1 is now poured into the beaker1 so as to surround the head of the funnel to about half an inch in depth2 and the weighed quantity of tanning material is next introduced4 ,it is best to cover the material with cold water1 and allow it to stand all night1 but in case of haste1 water of #cj to #ej may be used1 and the extraction proceeded with after the material is thoroughly soaked4 ,percolation is started by sucking the syphon1 and allowing the liquid to drop slowly into a liter flask1 the temperature of the water-bath being maintained by a ,bunsen burner1 and the beaker being refilled as it requires it with water at the desired temperature4#aee ,at least #ejj c4c4 must be percolated before the temperature is allowed to exceed #ej1 after which1 except in the case of sumach and canaigre1 which should be begun about #cj1 and at no time allowed to rise above #ej1 the temperature may be raised to boiling point4 ,at least #a hour should be employed in percolating #hjj to #ijj c4c4 and if the material is not then practically exhausted1 the liter flask must be withdrawn1 and an ordinary ungauged flask substituted1 into which the percolation is continued till the material is exhausted4 ,the very dilute liquor in the second flask is now boiled down till its volume is sufficiently small to be added to that in the liter flask1 a small funnel being placed in its neck during ebullition1 to prevent spirting and the access of air4 ,under no conditions must the stronger liquor of the first part of the percolation be boiled down1 as this would involve destruction of tannin4 ,the solution is now cooled1 and made up to the mark as has been before described4 ,most ordinary materials may be practically exhausted by the liter of water if percolation is slow1 and the trouble of evaporation may thus be avoided4 #aee ,the material should be kept in an even layer1 and if necessary the surface may be stirred at intervals with the thermometer or a glass rod4 ,total soluble matter4--,the solution of which the preparation has been described1 must now be filtered1 the size and kind of paper1 and exact method of filtration prescribed by the ,international ,association being strictly adhered to4 ,all papers and methods of filtration absorb traces of tanning matters1 and but few will give a clear filtrate with such solutions as those of quebracho and hemlock extracts2 and to obtain uniform results exact uniformity of method is essential4#aef ,deviations from the exact method1 in the case of quebracho1 easily cause discrepancies of several units per cent4 in the result4 ,the object of rejecting the first portions of the filtered solution is to prevent1 as far as possible1 errors which would arise from the absorption of tannin by the paper1 and to insure a clear filtrate4 #ej c4c4 of the clear filtrate is now measured by an accurate pipette1 and evaporated to dryness in a weighed porcelain basin1 on a steam-bath1 in order to determine the 8total soluble40 ,this and succeeding operations should be done in duplicate1 even if this has not been the case in making up the original solution1 which is certainly desirable4 #aef ,methods of correction for absorption of filter-papers have been worked out in the ,author's laboratory1 and adopted by the last conference of the ,international ,association4 ,cp4 ,collegium1 pp4 #ade-aeh1 #aijb1 and ,app4 ,a1 p4 #dgg4 ,ordinary light porcelain basins1 generally of about three inches diameter1 are employed for evaporation1 which takes place somewhat more rapidly if they are flat-bottomed 7saucer-shaped74 ,in place of porcelain1 thin glass basins of hemispherical form may be used1 and1 but for the cost1 platinum would be better than anything else4 ,aluminium and nickel basins have been tried1 but are slightly attacked by some liquors1 and hence are more liable to vary in weight1 though they have the advantage in rapidity of evaporation4 ,evaporation takes place most quickly if the steam-bath can be placed in a draught of air1 so as to rapidly carry away the vapour formed1 but the basins must be protected from dust4 ,under favourable circumstances1 evaporation of #ej c4c4 in porcelain basins occupies one to one and a half hour4 ,an ordinary pan fitted with a lid of thin copper perforated with holes of two and three-quarter inches in diameter1 makes a useful water-bath2 but where much work is done1 it is desirable to have a rectangular bath of thin sheet copper1 taking a single1 or at most a double row of basins1 and fitted with the usual appliance for keeping the water at constant level2 or with a supply of steam from a boiler1 and an overflow for condensed water4 ,as soon as the contents of the basins appear completely dry1 they may be transferred to the drying oven4 ,the most satisfactory form is one in which the basins are placed in a closed chamber1 surrounded by steam at the atmospheric pressure1 and at the same time subjected to a vacuum maintained by a water-jet air-pump2 but as this apparatus is somewhat costly1 it will probably only be provided in laboratories which make a speciality of such work4 ,next to the vacuum-oven1 an air-oven1 heated by a gas-burner1 and with its temperature controlled by a mercurial regulator to #ajj-aje ,c41 gives the best results1 and it is also the cheapest2 but considerable care and some scientific knowledge are required to work it satisfactorily4 ,in intelligent hands good results may be got from the small 8breakfast cooker0 gas ovens made by ,fletcher of ,warrington1 which are placed on an iron plate heated by a gas burner1 the supply of gas to which is regulated by a thermostat1 or mercurial gas-regulator1 inserted1 together with a thermometer1 through holes drilled in the top4 ,the basins must not be placed too near the bottom of the oven1 which must be protected by a perforated metal plate supported perhaps one inch above it1 to prevent radiation and to distribute the hot air4 ,any cold air required for ventilation should be admitted below this plate1 and care should be taken to exclude the products of the burning gas4 ,contact of the basins with any heated part of the metal-work should be carefully avoided1 and they are best supported on grid-shelves covered with wire gauze or perforated metal1 so as to allow of free circulation of air4 ,if perforated zinc is used1 it must be well supported1 as it is much softened at the temperature used4 ,the least satisfactory appliance in skilled hands1 but probably the most easy to work by the inexperienced1 is the ordinary water- or steam-oven4 ,it is impossible1 in this apparatus1 to raise the temperature of the interior fully to boiling point1 and below this gambier1 quebracho1 and other solutions containing catechins 7p4 #bih71 dry very slowly4 ,on the other hand1 so long as it is kept boiling and supplied with water1 the temperature is necessarily constant1 and there is no danger of overheating1 which easily occurs in ovens heated directly by gas4 ,such ovens are often fitted with openings at the top for use as a steam-bath4 ,to get the best results1 the basins must be as freely exposed as possible to the air in the interior of the oven 7in no case must basins be set one inside another1 except in the exsiccator for cooling71 and little or no ventilation from the outside is required1 as only traces of moisture remain after evaporation on the steam-bath2 so that1 after an hour's drying1 any ventilators may safely be closed4 ,as a good deal of cooling takes place through the door1 it is best to protect it with some non-conducting material1 such as asbestos millboard1 which may be attached with rivets1 or even with ordinary paper-fasteners4 ,one to one and a half hours will be required to dry to constance in the vacuum-oven2 two to three in the air-oven at #aje2 and probably about four hours in the water-oven1 except in the case of gambiers1 which may require somewhat longer4 ,too long heating is disadvantageous1 as the residues begin to oxidise and gain in weight4 ,as soon as it is judged that the basins will be constant in weight1 they are withdrawn from the drying oven1 and at once placed in an exsiccator 7a glass vessel with an accurately fitted lid1 which should be slightly greased1 in the bottom part of which is placed either dry calcium chloride or concentrated sulphuric acid1 to absorb the moisture of the air it contains74 ,in this they are left till thoroughly cold1 which if several basins are put in together1 may require half an hour4 ,they are then weighed accurately1 but as rapidly as possible2 returned to the drying oven for half an hour2 and replaced in the exsiccator4 ,the exact weight of each basin1 as it comes in turn to be weighed1 is now placed on the balance before removing the basin from the exsiccator1 so that it can be seen instantly if there is loss or gain of weight1 before it has time to absorb any moisture from the air4 ,the weight should not be more than a milligram or so less than at the first weighing2 if weight has been gained1 it is caused by oxidation1 and the first weight should be taken as correct if it is certain that the basin was then perfectly cold2 a very slight amount of warmth easily reducing the apparent weight by several milligrams4 ,if material loss has occurred1 the basin must of course be returned to the oven1 and re-weighed in another half hour2 but with experience1 this should rarely be needed4 ,it is necessary that the balance used should weigh accurately to milligrams2 and it must carry at least #ej grm4 on each pan2 while it is more convenient that it should carry #ajj or more1 it is always possible with a little ingenuity1 to manage within #ej grm42 and if a cheap balance must be used1 the smaller size will probably be more accurate4 ,balances of this sort can now be got for two or three pounds1 though it is in all respects better to obtain one of first rate quality1 which should cost about ten pounds4 ,the balances of ,verbeek and ,peckholdt1 of ,dresden1 from their simplicity and rapidity of weighing1 have given great satisfaction in technical work in the ,yorkshire ,college4 ,whatever economy be exercised in the choice of the balance1 it is essential that the set of weights should be of the greatest accuracy1 and especially that all the weights of one denomination 7#aj grm41 #a grm41 etc471 should accurately balance each other4 ,even after all precautions are taken1 it is desirable that those weights which are in duplicate should receive distinguishing marks 7e4g4 with a centre-punch71 and should always be placed on the scale in the same order2 and1 not only on account of possible inaccuracy1 but to save time1 it is desirable to reject basins which are so nearly of an even weight 7#bj1 #be1 #cj grm47 that when weighed with the residue 7#jc-jd grm471 a change of the larger weights may be required1 since it is to be remembered that any error of the weights employed is concentrated on the small weight of the residue4 ,after deducting the weight of the empty basins1 the weight in milligrams of the two residues of #ej c4c41 which should be practically alike1 are added together1 and the sum divided by the weight in grams of tanning material used2 which gives the percentage of 8total soluble matter40 ,illustration3 ,,fig4 #ff4 ,hide-powder ,filter4 ,non-tannins4--,it is now necessary to determine the proportion of the 8total soluble0 which consists of 8non-tanning matters10 that is1 of substances not removed from the solution by treatment with hide-powder4 ,the so-called 8tanning matters0 removed1 include colouring matters and some other substances1 which though absorbed by hide1 are certainly not tannins in a strictly chemical sense4 7,see note1 p4 #dhj47 ,according to the method of the ,international ,association1 the apparatus shown in ,fig4 #ff is employed for this purpose4 ,the glass bell is carefully and uniformly stuffed with hide-powder1 care being taken that no channels are left1 especially at the sides1 through which the liquor can reach the syphon without traversing the hide-powder4 ,before filling the bell1 the short leg of the syphon-tube should be loosely plugged with cotton-wool 7of which a little is allowed to project from the end71 in order to prevent the powder from gaining access to the tube4 ,the powder is retained in its position in the bell by a piece of muslin held by an indiarubber band1 and the bell is then placed in a beaker or tumbler as shown in the figure2 and filtered liquor is gradually added1 as it is absorbed by the powder1 till the whole is uniformly wetted4 ,the liquor which was first filtered through the paper1 and rejected for 8total solubles10 may be used for this purpose1 and it is not necessary that it should be absolutely clear4 ,the syphon is now gently sucked1 and the filtrate is allowed to fall1 drop by drop1 into a gauged cylinder4 ,the first #cj c4c4 which collects is rejected1 since it contains traces of dissolved hide-substance even from the purest hide-powder2 and the next #ej c4c4 should give no turbidity if a few drops are mixed either with clear tannin solution 7absence of dissolved hide-substance71 or with the first #cj c4c4 7absence of tannin74 ,this #ej c4c4 is used for determination of non-tannins1 by evaporation and drying precisely as has been described in the case of 8total soluble40 ,some chemists1 with very accurate balances1 prefer to evaporate only #be c4c41 which effects a little saving of time in evaporation2 but in any case the whole of the #ej c4c4 must be allowed to run through the filter before it is measured1 as the filtrate varies somewhat in solid contents as the filtration proceeds4 ,the filtration and evaporation should be done in duplicate4 ,the weight of the residue is calculated into percentage as 8soluble non-tanning matters0 precisely as has been described for the 8total soluble02 and when subtracted from the latter1 the remainder is the percentage of 8tanning matters40 ,if the hide-powder now employed by the ,english members of the ,international ,association 7manufactured by ,messrs4 ,mehner and ,stransky in ,freiberg in ,sachsen71 be employed1 no difficulty will be found in the filtration4 ,this powder is quite neutral1 and contains between #aj and #bj per cent4 of cellulose to render it more absorbent4 ,it does not swell in the filter1 and hence should be stuffed into the bell almost as tightly as possible1 about #aj grm4 being required4 ,if the bell is properly filled1 the filtration should altogether take about one hour1 but if the liquid runs too fast1 it must be regulated by a pinchcock on the indiarubber tube of the syphon4 ,if other powders are used1 which often contain acid1 and swell very much in the bell1 the filling is much more difficult1 and while the sides of the bell must be closely packed1 great care is requisite to keep the powder loose in the centre1 or the filter will not run4 ,one point requires mention with regard to neutral hide-powders4 ,if an extract which has been rendered soluble by the addition of alkalis or sulphites 7p4 #chh7 be analysed with a perfectly neutral powder1 it has been shown by ,paessler and ,appelius#aeg that a part of the tannin combined with the alkali will not be absorbed1 while with acid powders1 the whole will be estimated4 #aeg ,wissenschaftliche ,beilage des #8,ledermarkt1' #aija1 p4 #ajg4 ,illustration3 ,,fig4 #fg4 ,american ,milk-shaker4 ,the 8shake-method0 adopted by the ,american ,association of ,official ,agricultural ,chemists1 possesses some advantages1 especially in the analysis of used liquors which1 from the acids they contain1 are apt to give somewhat too high results by the filter method 7see ,app4 ,b1 page #dhj74 ,it has the further advantage of being much less dependent than the filter-method on the quality of the hide-powder employed4 ,it has therefore been accepted by the ,international ,association as permissive for all tanning materials1 and as compulsory for used liquors 7see ,app4 ,a71 and must therefore be briefly explained4 ,it can be carried out successfully with somewhat inferior hide-powders to those required for the filter1 but generally gives results #a or #b per cent4 lower in tannins than the latter4 ,a special shaking machine must be employed1 capable of thoroughly agitating a mixture of hide-powder and the liquor to be analysed2 and if many analyses have to be done1 it is convenient that it should be driven by power1 as otherwise the work becomes somewhat laborious4 ,a machine called a 8milk-shaker10 ,fig4 #fg1 employed in the mixing of summer drinks1 is generally used4 ,the quantity of powder required for the analyses to be made 7about #h grm4 of ordinary air-dried powder for each determination1 with say #e grm4 added71 is stirred in a large beaker with #be times its weight of distilled water1 and allowed to soak for #bd hours1 #ae per cent4 of chrome-alum previously dissolved in water being added at the beginning of the operation1 and #ae per cent4 more not less than #f hours before its end4 ,the powder is then washed by squeezing through linen1 and the washing is continued till the wash-water no longer gives a precipitate with barium chloride2 and is then well squeezed out in linen1 preferably with the aid of a press4 ,the damp squeezed powder is now roughly weighed1 to determine approximately what quantity it is necessary to take1 to give #ge grm4 of the original dry powder to each estimation 7air-dried powder contains about #ae per cent4 of moisture71 and a portion is accurately weighed in a basin1 and dried1 first on the water-bath1 and then in the drying oven1 to determine its moisture by loss4 ,the approximate amount of powder required for each determination--if possible a round number of grams--is now weighed into as many bottles of about #cjj c4c4 capacity as determinations are to be made1 #ajj c4c4 of the filtered liquors1 prepared as before described1 are introduced into each bottle1 and the bottles are then each shaken for #aj minutes 7,mr4 ,alsop states that in his experience #e minutes is sufficient74 ,the contents of the bottles are now filtered through funnels1 the stems of which are plugged with pure cotton-wool1 and the liquor is returned till a clear filtrate is obtained1 of which #ej c4c4 is evaporated as in the ,international method4 ,it is now necessary to accurately correct the residue obtained1 for the amount of water carried in by the wet powder4 ,the loss of weight of the powder which has been dried1 divided by its wet weight1 gives the water contained in each gram of wet powder1 and this multiplied by the weight of wet powder added to the liquor1 gives the weight in grams 7or volume in c4c47 of water which has been added to each #ajj c4c4 of liquor4 ,consequently1 if the residues found be multiplied by this weight plus #ajj1 and the product divided by #ajj1 the weight will be obtained which should have been given by #ej c4c4 of undiluted but detannised liquor2 and from this the non-tannins are calculated exactly as in the case of the residues from the filter process4 ,of course1 in practice1 a factor is found1 by which it is simply necessary to multiply all the residues1 to correct them to undiluted weight4 ,the process sounds somewhat complicated1 but in reality1 where a large number of determinations have to be made1 is quite as quick1 if not quicker than the filter method2 which it is quite possible it may ultimately supersede1 as much attention is being devoted to its improvement4 ,having determined the tanning1 and soluble non-tanning matters of the materials1 it remains to determine the moisture1 and the insoluble which make up the whole4 ,to determine moisture1 a quantity1 not exceeding two or three grams of dry solid materials1 or half a gram of moist or liquid extracts1 is weighed into a basin1 and dried in the same way as has been described for the residues1 only that a considerably longer time will be required before constancy is attained4 ,the object of employing so small a quantity of liquid extracts is to abridge this time1 and the consequent oxidation1 as much as possible1 as the extract soon forms a hard skin on the exterior1 which renders further drying very tedious4 ,it is advantageous to add a little alcohol to liquid and semi-liquid extracts1 and so dilute them that by inclining the basin they can be distributed in a thin layer over its sides1 while at the same time the alcohol facilitates the evaporation of the water4 ,the weight of the dried residue in the basin is the 8total solids10 while the loss is the 8water02 and these can be converted into percentages by multiplying by #ajj and dividing by the weight of substance originally taken4 ,an alternate method1 which is frequently convenient with extracts1 is to pipette off #ej c4c4 7in duplicate7 of the dissolved and well-mixed extract-solution before filtration1 and dry exactly in the same way as for 8total soluble40 ,the sum of the two residues in milligrams1 divided by the weight of extract taken for analysis1 gives the 8total solids02 subtracting this from #ajj leaves the 8water10 while the difference between the 8total solids0 and the 8total soluble0 is the percentage of insoluble matter4 ,two further points must be noted4 ,if the total solids are determined by the first method1 and the total soluble in the ordinary way1 in an extract which contains no insoluble matter1 it frequently happens that they differ by #ja or #jb per cent41 owing either to the difficulty of driving off the whole of the water1 or to slight oxidation of the total soluble residue4 ,on the other hand1 if the second method is adopted1 a small amount of 8insoluble0 is invariably found1 even in perfectly soluble extracts1 which is due to the absorption of tannin or colouring matter by the filter paper4 ,on the correction of this error1 see ,collegium1 #aijb1 pp4 #ade-aeh1 and ,app4 ,a1 p4 #dgg4 ,as the value of a tanning material often depends very much on the paleness of its colour1 it has become customary to specify in contracts the intensity of colour of a solution of it containing one-half per cent4 of tanning matter 7as measured by the ,i4,a4,l4,t4,c4 method of analysis71 in a glass cell of one centimeter thick1 by comparison with standard coloured glasses in the tintometer4 ,on the method of making the measurement see ,l4,i4,l4,b41 p4 #aca4 ,,note4--,all the apparatus named in this chapter can be obtained of ,messrs4 ,reynolds and ,branson1 ,commercial ,street1 ,leeds2 or of ,messrs4 ,portway1 ,jamaica ,road1 ,s4,e42 and of most other dealers in chemical apparatus4 ,,chapter ,,xxi4 ,,grinding ,,of ,,tanning ,,materials4 ,before the tannin they contain can be extracted1 most materials require to be ground1 almost the only exceptions to this rule being divi-divi and algarobilla1 in which the tannin is very loosely contained4 ,extracts1 whether solid or liquid1 merely require to be dissolved in water or liquor1 in which they are1 for all practical purposes1 perfectly soluble4 ,with the less soluble extracts it is generally preferable to dissolve at a temperature of #ej to #fj ,c4 with vigorous stirring4 ,the actual method of grinding1 and consequently the machinery employed for the purpose1 vary not only with the material to be ground1 but with the method of leaching adopted1 as it is essential that the mass of ground material should be completely permeated by the liquor employed in leaching2 and if it be ground too finely1 or subjected to too much pressure on account of the height to which it is piled in the leaches1 it is apt to form a compact and clay-like mass1 the interior of which remains unextracted4 ,illustration3 ,,fig4 #fh4--;,cone-,mill4 ,in the laboratory1 where thorough extraction must be completed in a few hours1 the material can hardly be too fine2 but on the larger scale a much coarser product must be used1 and leaching requires days1 or sometimes even weeks1 and is then seldom successful in removing all the tannin4 ,it is probable1 however1 that in the future these mechanical difficulties of extraction will be overcome2 and the material will then be as finely divided1 and as completely extracted on the large scale1 as it is in the laboratory at the present time4 ,one of the earliest methods of grinding oak-bark1 and which is still used for sumach 7p4 #bga7 consists in crushing it under large circular edge-stones1 frequently turned by a horse4 ,this process was very slow and inefficient for barks1 and both it and horizontal millstones similar to those used for wheat were long ago superseded by iron or steel mills on the same principle as the ordinary coffee-mill4 ,these mills1 ,fig4 #fh1 consist of a 8bell0 or inner cone1 covered with blades or teeth arranged at a slight angle to the vertical section of the cone1 and which are made finer and increased in number towards its lower and wider part4 ,this cone rotates within an outer hollow cone or casing1 also provided with blades or teeth which are sloped slightly in the opposite direction to those of the inner cone1 so as to meet them at an angle1 like the cutting-blades of a pair of scissors1 and the angles of the cone are so chosen that the blades approach each other more closely towards their base4 ,the outer cone is fixed1 and is provided with a hopper like a coffee-mill1 while the inner cone is so rotated on its axis that bark placed in the hopper is screwed down between the two1 and cut finer and finer till it reaches the lower edge1 when it drops out4 ,the blades or teeth are usually cast in one piece with the metal cones1 and sharpened when required by chipping with cold chisels4 ,this operation should not be conducted in the mill-house1 or small chippings of iron may get mixed with the bark1 and cause stains on the leather4 ,this form of mill1 which is run in ,england at about #cj revolutions per minute1 and at nearly three times this speed in ,america1 works very well with dry material1 but clogs badly if it be appreciably damp4 ,on this account it is always well to run the mill with a fairly slack belt which will slip before exerting sufficient pressure to break the machine1 as in such operations as grinding1 safety clutches are of but little use4 ,a type of mill varying somewhat from the above1 consists of a pair of discs or very obtuse cones1 the inner one of which runs on a horizontal axis4 ,the teeth are generally arranged in concentric rings and interlock with each other4 ,the material to be ground is fed at or near the centre of the fixed disc1 and escapes at the edges4 ,the construction of this class of mill will be easily understood from ,fig4 #fi4 ,very small pieces of iron or steel which get caught between the teeth will often result in the breaking of the latter1 and the formation of iron dust1 which is a serious objection to the employment of this type of mill 7to which the ,schmeija 8,excelsior10 the ,glaeser 8,favorita10 and the 8,devil ,disintegrator0 of the ,hardy ,patent ,pick ,co4 belong7 for grinding barks4 ,illustration3 ,,fig4 #fi4--8;,excelsior0 ,mill4 ,myrobalans and mimosa-barks have proved especially troublesome to grind1 the former from the hardness of the stones of the fruit1 and a tendency to clog the mill1 and the latter from their combined hardness and toughness4 8,disintegrators0 of various patterns are now made1 which are capable of grinding both these materials satisfactorily1 and but for their liability to cause fire1 and the large proportion of fine dust which they make1 are usually to be preferred to toothed mills4 ,in spite of their disadvantages1 however1 they have come very largely into use1 on account of their efficiency in grinding obstinate materials4 ,disintegrators work on the principle of knocking or beating the material to powder1 by means of very rapidly revolving beaters1 which1 in the smaller machines1 are driven at #bejj to #cjjj revolutions per minute4 ,the first disintegrator was made by ,carr and consisted of two concentric cylinders or baskets of steel bars1 rotating in opposite directions at a very high speed4 ,the material was fed between these and was dashed to pieces by being thrown against the bars and the outer casing4 ,illustration3 ,,fig4 #gj4--;,disintegrator4 ,a simpler form was soon introduced by ,carter1 in which only one axis was employed1 carrying radial beaters which dashed the material against the serrated outer casing1 a portion of the circumference of which was fitted with gratings1 through which the ground material was thrown as soon as it was sufficiently reduced in size1 the fineness of the grinding being regulated by changing the grates as required4 ,this type of disintegrator is1 with slight variations1 made by all the leading makers of tanners' machinery2 and one form is shown in ,fig4 #gj1 and a similar but smaller machine1 opened to show construction1 in ,fig4 #ga4 ,in the more modern machines the sides as well as the circumference of the casing are frequently corrugated in order to increase the action on the material4 ,mills running at such high rates of speed as #cjjj revolutions per minute will grind most hard substances1 such as stone or brick1 without injury1 but pieces of iron among the tanning material are apt to cause damage1 and various magnetic devices have been employed for separating this metal1 but with only partial success4 ,in the best mills1 therefore1 the beaters and inner casings are constructed so that they can be easily replaced1 and the damage is then rarely serious4 ,illustration3 ,,fig4 #ga4--;,disintegrator opened1 showing construction4 ,in order to avoid vibration1 the discs and beaters of all these high-speed mills must be balanced with great accuracy4 ,this is best accomplished by removing the spindle from the mill1 and allowing it to roll on two levelled straight-edges1 and then filing or chipping the beaters on the heavy side until it will remain indifferently in any position4 ,a new form of disintegrator has been recently brought out in ,america by the ,williams' ,patent ,crusher and ,pulveriser ,company1 in which a series of discs are keyed to the main shaft1 to the circumference of which a number of sets of 8hammers0 are suspended by means of hinge-bolts4 ,each of these steel bars1 or hammers1 has a free arc movement of #abj1 and when the machine is in motion take a position divergent from the centre on account of the centrifugal force4 ,after striking a blow against any material fed on to a plate serving as an 8anvil10 the hammers recoil1 and1 after passing any material which is not shattered by the blow1 again resume their normal position1 leaving the next set of hammers to beat against the unground material4 ,the hinged suspension of the hammers imparts a degree of flexibility to the mill which is not found in any other machine of this character1 and lessens the risk of serious damage to the machine by the introduction of pieces of metal along with the bark4 ,the makers claim that this machine can be repaired more rapidly and with less expense than any other disintegrator of equal power on the market4 ,considerable improvements have recently been made in the details of its construction4 ,fig4 #gb shows a section of this mill4 ,of course only the end hammers of each set can be seen in the figure4 ,illustration3 ,,fig4 #gb4--,section of ,williams' ,crusher4 ,when myrobalans or valonia is to be used for leaching1 it is generally better to crush it between toothed or fluted rollers1 rather than to grind it finely1 as the cellular structure is just as completely broken up1 and the flakes formed by crushing allow of much freer percolation than when the material is powdered by the disintegrator1 while the consumption of power is also less4 ,the general construction of the machine will be easily understood from ,fig4 #gc1 and it is only necessary to point out that the small upper roller acts mainly as a 8feed0 to the larger crushing rolls4 ,in the best mills1 the rollers are made up of a series of toothed steel discs on a square axis1 and are on this account easily replaced or sharpened when they have become broken or worn4 ,illustration3 ,,fig4 #gc4--,myrobalans ,crusher4 ,several mills have been introduced in ,america in which the bark is sawn or rasped by toothed discs like circular saws1 but these are only capable of dealing with barks of a brittle nature1 and are immediately choked by tough materials like the bark of the mimosa or oak4 ,a better form of mill1 but one which is1 to some extent1 subject to the same disadvantage1 is the 8shaving-mill10 in which blades are fixed like plane-irons upon a disc1 cones or cylinder1 and are rotated at a high speed against the material which is fed against them by toothed rollers at such an angle that the shavings are cut diagonally to the grain4 ,these shaving-mills are largely in use in ,america for hemlock-bark1 with which they are particularly successful4 ,the principle of the machine is exactly the same as that of the machines used in cutting oakwood1 quebracho1 and the different dye woods4 ,one type of shaving-mill is illustrated in ,fig4 #gd4 ,illustration3 ,,fig4 #gd4--,shaving ,mill4 ,it frequently happens that the material is delivered from the mill in a very unequal state of division1 and it is sometimes necessary to screen it and thus separate the coarser portion either for use in the leaches or for re-grinding1 while the finer portion is more suitable for 8dusting40 ,with disintegrators1 which deliver the bark with considerable impetus1 the screening can be accomplished by placing a screen diagonally below the mill1 through which the finer parts are projected4 ,it is1 however1 essential that this screen should be quite smooth on its upper surface and very strong1 as ordinary wire gauze is immediately cut through by the impact of the material4 ,what are called 8locked wire screens0 in which the wires are supported by being actually twisted round the transverse bars are very suitable4 ,where the circumstances will not permit of screening in this way1 cylindrical rotating screens1 or nearly horizontal screens vibrated by an eccentric may be used4 ,the latter are cheaper to erect and have the advantage that they take up less room1 and by having lengths of wirework or perforated steel of different coarseness1 the material may be separated into more than one degree of fineness4 ,illustration3 ,,fig4 #ge4--;,bark-,breaker4 ,oak-bark as it is taken off the trees is usually in lengths of perhaps three feet1 and it is necessary to cut or break it into smaller fragments before it can be ground in most of the machines just described4 ,this is frequently done by hand by chopping the bark into pieces about four inches long1 and the operation is known as 8hatching40 ,machines on the principle of the chaff-cutter1 consisting of a fly-wheel with curved blades radially attached to it1 are sometimes used4 ,instead of 8hatching0 it1 the bark is frequently broken by passing through toothed rollers fitting into each other1 and often attached to the mill2 the construction of this machine will be readily understood from ,fig4 #ge4 ,in ,belgium1 and some other bark-producing districts1 the adhering moss and dead outside bark are usually removed before hatching1 but apparently these impurities are frequently re-mixed with the bark after the hatching is completed6 ,as such barks often also contain much clay and dirt1 it is generally expedient to pass the hatched bark over a coarse screen before letting it enter the mill1 so as to remove the greater part of such rubbish1 since1 if left in the bark1 it produces black and unsatisfactory liquors4 ,in drawing up policies for fire insurance1 it is usual to charge a higher rate where disintegrators are used to grind the tanning material1 as owing to the amount of dust and the production of sparks by the striking of the steel parts of the machine on any chance piece of flint or metal which may get into it1 there is a greater liability to fire than with toothed mills1 although with proper precautions the risk is really small4 7,cp4 p4 #ddf47 ,all disintegrators act like ventilating fans1 and suck in air with the material1 blowing it out again with great force at the periphery4 ,this air is heavily laden with dust from the tanning material which is extremely irritating to the lungs4 ,the difficulty is to some extent remedied by an air-channel or flue 7generally cast in the casing of the machine7 connecting the discharge with the feed-opening so as to convey the air back to the disintegrator4 ,the air is thus circulated through the arrangement1 but some is always drawn in from the external atmosphere and driven out with the ground material1 and it is advisable that the chamber into which it is discharged should be provided with some means of filtering the air before it escapes4 ,one convenient method is to have a large flannel bag which is blown out by the air like a balloon and out of which the dust can be shaken when the machinery has stopped4 ,another efficient method is to have one of the walls or the ceiling of the chamber made of canvas or of sacking2 but in any case the air should be allowed an escape where a little dust will not cause annoyance4 ,chain-,conveyors4--,while1 in ,england1 the ground material is usually carried from the mill to the leaches in barrows or baskets1 in ,america the use of conveyors is practically universal1 and there is no doubt that they effect a great saving of labour at a comparatively small cost4 ,the most practical conveyor for tanning materials consists of a trough through which an endless chain passes1 carrying scrapers4 ,the chain generally used for this purpose is one consisting of square links fitting into each other and capable of running over toothed wheels4 ,these chains are made by several firms in ,america1 and in ,england by the ,ewart ,chain ,conveyor ,co41 of ,derby1 who supply not only plain links but also those having projections to which buckets1 scrapers and a variety of attachments may be fixed4 ,illustration3 ,,fig4 #gf4--;,chain-,conveyor4 ,in many cases the trough is ,v-shaped with the chain running in the angle2 in others flat-bottomed as in the illustration1 or rectangular4 ,the scrapers may consist either of metal or of wood2 and where materials have to be carried up a steep incline buckets instead of scrapers should be employed4 ,the arrangement of such a conveyor is illustrated by ,fig4 #gf4 ,a useful form of conveyor for dry materials consists in a woven cotton belt running in a smooth trough and with laths riveted across it at intervals4 ,these laths should project slightly beyond the edges of the belt so as to prevent wear4 ,care must be taken with belts of this sort that the material does not get between the belt and the pulley4 ,chain-carriers are often used for conveying the spent tan to the furnaces from the leaches1 and occasionally for carrying skins4 ,several other kinds of conveyor are in use in corn-mills1 spiral or worm conveyors which work on the screw principle being very largely used for carrying corn4 ,they are not very suitable for tanning materials on account of the coarseness of the latter1 by which the friction is greatly increased2 they are however occasionally used4 ,those built up of separate blades are specially to be avoided4 ,an ingenious form of conveyor has been recently introduced from ,germany1 and consists of a light trough supported on steel springs and vibrated longitudinally by means of an eccentric in such a way as to shake the material from one end of the carrier to the other2 the velocity of motion of the trough being less in the outward than the return stroke1 so that the material is carried with it as it moves forward and slides over it in its return4 ,it is obvious that the principle may also be applied to screening or sifting4 ,,chapter ,,xxii4 ,,the ,,extraction ,,of ,,tanning ,,materials1 ,,and ,,the ,,making ,,of ,,extracts4 ,leaching4--,the material1 having been reduced to a suitable state of fineness1 is ready for extraction4 ,this requires a considerable amount of time1 as the tannin is contained in cells whose walls are of a wood-like substance 7cellulose and lignine71 through which the water diffuses but slowly4 ,hence1 unless the material be very finely ground1 a long soaking will be necessary before it becomes 8spent40 ,it should be the aim of the tanner to have his barks1 etc4 ground so finely that they may be extracted as rapidly as possible1 and yet not be so fine that they settle to a compact mass in the leaches and so prevent circulation4 ,using the present methods of extraction on the large scale it is necessary to have the material only somewhat coarsely ground or crushed1 so as to render its percolation practicable2 but it is quite possible that in the near future some better mechanical means will be found of treating the dust and other excessively finely ground matter so as to bring about a very rapid extraction4 ,up to perhaps #aej years ago1 no attempt was made to leach the tanning material1 which was simply strewed in layers between the hides1 and moistened with water4 ,leaching originated in ,england1 and was first applied merely to complete the exhaustion of the material which had been already used for layers2 but the use of even weak liquors instead of water in the layers was found so advantageous1 that new material was soon applied to make stronger infusions4 ,the earliest form of leach was simply a pit with a perforated wooden 8eye0 or shaft down one corner1 in which a pump could be placed to remove the liquor without being choked with solid matter4 ,this was considerably improved by the addition of a perforated 8false bottom0 to the pit1 with which the eye communicated4 ,the perforations of the latter were found unnecessary1 and it now serves simply for pumping through1 or for the manipulation of a plug in a hole communicating with an underground 8trunk0 leading into a pump-well4 ,the false-bottom is best made of laths about #a inch thick and #b inches wide1 cut slanting so as to be wider on the upper than the lower surface1 which makes the spaces between them less liable to choke4 ,the laths are nailed on cross-battens with copper nails1 which should be long enough to clinch1 -inch to -inch spaces being allowed between the laths according to the fineness of the ground material4 ,the lattice-bottom should be in at least two sections1 so as to allow of its easy removal for cleaning1 and should rest on detached blocks1 which are best nailed to the underside of the battens4 ,a space of #b inches to #c inches below the false bottom will prove sufficient if it is cleared every time the pit is emptied1 but not otherwise4 ,clearness from obstruction both below the bottom and between the laths themselves is very important in securing free running in the 8press leach0 system about to be described4 ,a section of the latticed bottom is shown in ,fig4 #gg4 ,the laths are easily cut by employing a circular saw with a tilted table1 and turning the board at each cut4 ,no advantage is gained by planing them4 ,illustration3 ,,fig4 #gg4--,section of ,leach-,bottom4 ,as a strong liquor cannot be made by the use of a single leaching-pit1 a series of pits are now always employed1 and it is the leaching1 systematic or otherwise1 which determines how much of the total tannin will be thrown away and lost in the 8spent tan40 ,in the case of properly extracted materials the 8spent tan0 will not contain more than one per cent4 of tanning matter1 but the degree of extraction which is profitable is dependent on the tanning material employed and the class of leather to be produced4 ,the system of leaches now considered to be the best is based on the 8continuous0 process of extraction4 ,of its different forms1 the 8press-leach0 is the simplest and in most cases is all that is required4 ,illustration3 ,,fig4 #gh4--,plan and ,section of ,battery of ,press-,leaches4 ,a plan and vertical section of the leaches is shown in ,fig4 #gh4 ,assuming that the leaches have been working for some time and that the liquor in the strongest leach has been run off to the tan-pits1 or in the case of manufacturing extracts to the decolorising tanks or evaporator1 the last vat in the series is now filled with water or spent liquor1 which may be heated by steam if desired1 and this water1 which completes the exhaustion of the material in this vat1 forces the liquor forward in the whole series1 so that it gets stronger and stronger as it passes from vat to vat4 ,the very weak liquor remaining in the last vat is now pumped into a spare pit1 or on to the next stronger vat1 pressing the liquor forward as before2 the vat is emptied of the spent material and refilled with new1 and now becomes the head leach2 and the strongest liquor is pressed on to it by running water or weak liquor on the weakest vat4 ,as regards the construction of such a 8battery0 of leaches1 details will differ according to whether the usual ,english square sunk pits1 or the ,american form of circular tub-leaches is employed4 ,in the former case the vertical spouts connected with the space under the false bottoms are usually made of wood1 like the old fashioned 8eye10 and placed at one side or corner of each pit1 and connected with the top of the next pit by a short trough which may be open above or covered as preferred4 ,both eyes and cross troughs must be of ample size1 so as not to check the running of the liquor1 and for a set of six or eight leaches1 the bottom of the cross trough should be at least #aj or #ab inches below the actual top of the leach1 which should not be filled with material above that level4 ,the object of this is to allow of a sufficient fall from the first to the last leach4 ,means must be provided for the temporary closing of the cross-trough between the vats which form the first and last leach4 ,on a very small scale1 this may be done with a plug2 sliding wooden doors are convenient1 but difficult to keep tight4 ,a hinged or sliding door held against an indiarubber facing by a wedge or toggle-joint would seem a practicable device4 ,if round tub-leaches are employed1 the vertical connection may be similarly made with a wooden trough1 but copper tubes are almost essential for the cross connections4 ,if a vertical copper eye in the centre of the leach be provided for boiling1 or for emptying the leach 7p4 #ccd71 it may be utilised for the upflow by connecting it with the cross pipe with a thin copper pipe of large diameter1 which must be movable for the purpose of casting the leach4 ,a joint like that of a stove-pipe will probably prove sufficiently tight1 but if necessary may be made tighter by rolling an indiarubber ring over it4 ,six to eight leaches is generally a sufficient number to form a press-leach 8battery40 ,if more are connected in one series it will usually be necessary to assist the circulation1 either by pumping an intermediate leach1 or by one or more pumps on the ,holbrook system1 in which a power-driven pump of simple construction is fitted in the eye of the leach4 ,it is hardly necessary to note that the liquor must run downward through the leaches1 and up through the vertical pipes1 in order to prevent mixture of the weaker with the stronger liquor4 ,several additions and modifications to the system have been made with a view of obviating the so-called 8channel difficulty40 ,there is always a fear on the part of some tanners that the liquid in the leaches may push the material aside and form channels through it1 thus preventing proper extraction of the tanning matter4 ,in the author's opinion this evil has been greatly exaggerated1 as1 unless the liquid be pumped from the leaches at a very rapid rate while they are in circulation1 it is not at all easy for the formation of such channels to take place4 ,in any case it can be entirely avoided by turning over the material in the leaches occasionally1 so as to lighten it somewhat and rearrange it a little4 ,it may also be pointed out that the provision of a proper system for pressing or circulating leaches does not prevent their being pumped off as frequently as desired1 though this is generally to be avoided1 since when the leach is emptied of liquor1 the material tends to settle into a compact mass1 which is not easy to percolate1 and which is liable to shrink from the sides of the pit1 thus causing the very trouble which it is desired to avoid4 ,there are some advantages in taking the first and strongest liquors off the material in a separate tank1 and then finishing the exhaustion in the press leaches1 since many materials swell1 and pack tightly when they are first wetted1 but on the whole the method hardly pays for its added cost4 ,the press-leach system as above described is well adapted for the requirements of tanners1 as its first cost is very small in addition to that of the construction of the leaches themselves2 it extracts the bark well1 and saves much labour in pumping1 and greatly lessens the tendency of the pumper to miss pits in the series1 to save time1 when the master's eye is not on him4 ,another advantage which is often important1 is that when the leaches are full1 much more than a single liquor can be run from the head-leach without pumping on2 and similarly when they are run down to their lowest level1 much more than a single liquor can be pumped on to the worst leach before it overflows4 ,as the leaches flow slowly in comparison to the rate at which liquors can be pumped by a good steam pump1 it is very advantageous to allow the pump to discharge into a liquor-tank raised to such a height that the liquor can be run from it into any leach at a suitable rate for the circulation1 and it also enables liquors to be pumped without waiting till room has been found for them in the leaches4 ,similar tanks are very useful in running liquors for the yard1 and especially for the suspenders in a sole-leather yard1 enabling circulation to be kept up during the night1 and at other times when the pumps are not running4 ,they may also be used as filters for the suspender liquors by fitting them with false bottoms covered with a layer of nearly spent tan4 ,the liquors may be distributed to the different pits and leaches by means of canvas hose-pipes1 or1 what is often more convenient1 by overhead troughs1 carefully levelled1 and fitted with discharge valves where required4 ,the latter are conveniently made of lead in a hemispherical form1 resting on an indiarubber washer supported by a light brass casting1 or a suitably turned rebate in a block of wood4 7,cp4 p4 #deg and ,fig4 #gi47 ,such valves if good indiarubber is used1 wear well1 and are absolutely tight4 ,illustration3 ,,fig4 #gi4--,valve for ,liquor-,troughs4 ,in ,england1 leaches are usually sunk in the ground1 and are frequently made of brick and cement1 or of large ,yorkshire flagstones4 ,such leaches are somewhat costly but very durable4 ,square wooden pits1 puddled outside with clay1 are also used1 and last well with cold1 or even warm liquors1 but will not stand direct steaming1 the wood gradually bending1 and allowing the clay to leak into the liquor1 causing black stains4 ,the large round vats of thick pine1 and often holding #aj or #ab tons1 which are generally used in the ,united ,states1 stand boiling much better1 and are frequently supported above a tramway or conveyor1 into which the spent bark can be discharged through a manhole in the bottom4 ,if this method is adopted1 it must be remembered that bark1 and indeed most other tanning materials1 will not run through a hole like corn1 but must be cast into it1 so that unless the vat is of great depth1 it is simpler and almost as easy to cast over the top4 ,if the manhole is used1 a central hole must be made in the false bottom1 and this must be surmounted by a copper pipe made in sections of two or three feet1 and reaching to the top of the leach4 ,when the pit is to be emptied1 the top length is removed1 and the tan shovelled down the hole until the second length is reached1 and the process repeated4 ,the central pipe serves also for the circulation of the liquor when the pits are boiled1 and may be used as the ascending pipe for circulating on the press-leach system4 ,the question of the influence of temperature on extraction is discussed on p4 #cdd1 but except where a pale colour is all important1 it is generally profitable to use a moderate degree of heat in extraction4 ,in the opinion of the writer 7which is supported by a vast amount of careful experiment7 only the nearly exhausted leaches should be heated1 not merely to avoid discoloration1 but to extract the maximum amount of tannin4 ,in ,american tanneries the boiling is frequently done by copper coils fixed below the false bottoms of the vats1 but such coils are very costly1 and1 where weak liquors only are to be heated1 seem to present no advantage over a well-arranged system of heating by direct steam in which care is taken that dry steam only is used1 and that all water condensed in steam pipes1 and usually containing iron1 is removed by effective steam-traps4 ,if steam is blown into cold liquor through an open pipe1 a very disagreeable rattling and vibration is produced1 which is not only annoying1 but is very injurious to the leaches4 ,this evil may be avoided by the use of 8silent boiling jets0 on the principle of the steam-jet water-raiser2 and1 following a suggestion of the writer1 these jets may be used at the same time to circulate the water through the tanning material of the nearly exhausted vat1 and so wash out the last traces of tan4 ,the simplest way to accomplish this is to lower the boiling jet1 directed upwards1 and connected with a movable steam-pipe1 into the eye of the leach 7which is preferably central7 so that the heated water flows over its top1 and percolates downwards through the material to be washed4 ,two forms of these boiling and mixing jets made by ,messrs4 ,krting are shown in ,figs4 #hj and #ha4 ,illustration3 ,,figs4 #hj and #ha4--;,boiling and ,mixing ,jets4 ,batteries of closed copper extractors1 worked on the press system1 and similar to those used in extracting sugar from beetroot1 have frequently been advocated1 but are very costly1 and have no other advantage over open vats than that the liquor can be forced through the series by pressure1 instead of circulating by gravity4 ,no advantage is gained by boiling under pressure1 since even boiling in open vats has been shown to destroy tannin1 darken the colour of the liquor1 and increase the amount of insolubles1 and higher temperatures are still more injurious4 ,heating the weakest leach in the press-leach system promotes the even circulation of the liquor1 since the warm weak liquor is much lighter than the colder and stronger liquors in the forward leaches1 and so floats on the top1 and presses the stronger liquor uniformly downwards4 ,it also has the advantage that the liquors are cooled before they are strong enough for the yard1 while in tanneries where all the leaches are heated1 expensive tubular coolers are often employed4 ,as the liquor cools1 much of the colouring matters and reds dissolved in the hot liquor separate1 and are filtered out by the tanning material1 so that much brighter and lighter coloured liquors are obtained4 ,illustration3 ,,fig4 #hb4--,sprinkler-,leach4 ,sprinkler-,leaches1 ,fig4 #hb1 were formerly used in many tanneries and extract factories1 especially in the ,united ,states4 ,they were introduced by ,allen and ,warren1 and yield a liquor which is at first very strong1 but which becomes very rapidly weaker as the running is continued4 ,these leaches are similar in principle to the mashing-tub and sparger of the brewer1 but the process is not well adapted for tanners' use1 as the material is left too much exposed to the air1 which is apt to cause oxidation and loss of tannin4 ,it is also extremely difficult to completely exhaust the material without using an impracticably large volume of water4 ,sprinkler-leaches are arranged so as to spray the liquor1 or water1 on to the top of the solid material which is to be extracted at such a rate that it flows out just as rapidly as it flows into the vat4 ,some idea of the great amount of oxidation and consequent loss of tannin which takes place in this form of extractor may be obtained when it is remembered that this same method is now used for the destruction of sewage matter by spraying it on to beds of coke so that it may be mixed with as much air as possible before it is attacked by the bacteria of the coke-beds 7see p4 #dgc71 and also to oxidise weak alcohol to acetic acid in the 8quick vinegar process40 ,so far as extraction is concerned1 there is no difference in principle between the methods adopted by the tanner and the extract manufacturer1 though the latter usually works on a larger scale1 and not unfrequently1 in order to increase his output1 or the gravity of his extract1 employs a higher temperature4 ,this is probably justified by practical considerations in the manufacture of extracts from very low-grade materials1 such as oakwood1 which only contains #b to #c per cent4 of tanning matter1 or even of chestnut wood which is somewhat stronger1 but it is one of the causes why decoloration of the battery liquor is generally necessary4 ,dried blood is chiefly used as the decolorising agent1 but a paste of blood-albumen has been recently placed on the market1 which is said to be free from several of the disadvantages attending the use of the crude material4 ,the liquor to be decolorised is run into a mixing vat fitted with a steam coil capable of raising the temperature of the liquid to at least #hj ,c41 and usually provided with a simple rotary stirring gear4 ,the liquor1 as run into the mixing vat1 must not have a temperature of more than #dh ,c4 7#aah ,f47 nor a strength of more than about #bj ,bkr4 7sp4 gr4 #ajbj74 ,the blood or albumen dissolved in a little water1 is added to the contents of the vat1 which are then well mixed1 and the temperature is raised to #gj ,c4 when the albumen coagulates and carries down much of the colouring matter4 ,the solution is run into another tank where the precipitate is allowed to settle1 and the clear liquor is then drawn off for the evaporation4 ,the muddy portion1 about #h inches in depth1 is pumped through filter-presses 7which can be cheaply constructed of wood71 the clear liquors going to the evaporators and the press-cakes being dried for manure4 ,in addition to blood-albumen1 several other substances1 such as lead acetate 7sugar of lead71 salts of alumina1 casein and other albuminous matters have been employed in the decoloration of extracts1 but they are by no means so efficient as albumen4 ,decolorising always causes a loss of tanning matter1 some of this being carried down with the precipitated colouring matter2 and is for this reason to be dispensed with whenever its use is not really necessary4 ,it may often be avoided by careful extraction at moderate temperatures1 and this is especially to be aimed at in the case of strong tanning materials1 which easily yield battery liquors of much greater strength than #bj ,bkr41 and which thus1 if they can be sent direct to the evaporator1 save cost in evaporation1 which is often an important consideration4 ,another method which is frequently used to brighten the colour of extracts1 is treatment with sulphurous acid4 ,dilute sulphurous acid solution may be used for extraction1 but a more common method is to pass sulphur dioxide gas into the liquor before concentration4 ,sulphurous acid acts partly as a weak acid1 in decomposing compounds of the tannins and colouring matters with bases1 such as lime1 iron1 copper1 but more actively by reducing oxygen compounds and preventing oxidation4 ,bleaching in this way does not actually destroy or remove the colouring matters1 which are apt to reappear on exposure to the air1 either in the liquor1 or perhaps more often in the leather tanned with it1 so that the gain is frequently more apparent than real4 ,if present in any considerable quantities1 sulphurous acid may also cause inconvenience by its swelling action on the pelt1 but is mostly expelled in concentration4 ,another process should perhaps also be mentioned here1 though not strictly a means of bleaching4 ,several tanning materials1 and notably quebracho and hemlock1 contain large quantities of 8difficultly soluble tannins10 which render the liquors made from their extracts turbid on cooling4 ,these tannins form soluble compounds with alkalis and with alkaline sulphites1 in the latter case probably setting free the sulphurous acid and combining with the base4 ,this has been taken advantage of in a recent patent#aeh in which quebracho and other extracts are rendered soluble by heating in closed vessels with bisulphites1 sulphites1 sulphides1 or even caustic alkalis2 and many 8soluble quebracho extracts0 made on this principle are now on the market4 ,in this case1 even where bisulphites are used1 the greater part of the sulphurous acid1 after serving its purpose in preventing oxidation1 escapes in course of manufacture1 and the extracts remain neutral or alkaline4 ,there is no reason that such extracts should not prove serviceable in tanning1 but it has recently been shown by ,paessler that the alkaline tannin is not absorbed by neutral hide-powder1 and it therefore may lead1 not only to discrepancies in analysis1 but in case of drum-tannage1 where no acid is naturally present1 to failure to utilise the whole of the tannin1 though1 when added to ordinary liquors1 the acids contained in the latter will set free the tannins4 #aeh ,lepetit1 ,dollfus1 and ,gansser1 ,eng4 ,pat4 #hehb1 #ahif4 ,the use of ferrocyanides has been suggested as a means of precipitating iron and copper present in extracts1 and it may also be pointed out1 that with many red-coloured tanning materials1 such as hemlock and quebracho1 the addition of small quantities of alum to the tanning liquor effects considerable improvement in colour1 not only by precipitating a part of the difficultly soluble 8reds10 but by developing the yellow colour of certain colouring matters 7quercetin1 myricetin1 etc47 which may be present4 ,such an addition does no harm in the case of soft leathers1 but would probably be injurious in a sole-leather tannage4 ,the liquors1 whether direct from the leaches or from the decolorising vats1 must next be concentrated by evaporation 7,chap4 ,,xxvi471 to sirupy consistency for liquid extracts1 or until they will become nearly solid on cooling1 if a solid extract is required4 ,as has already been stated1 the action of heat tends to cause a loss of tannin and a darkening of colour by decomposition and the formation of insoluble reds4 ,to reduce this loss to a minimum1 the weak liquors are evaporated with as little access of air and at as low a temperature as possible1 and these conditions are best obtained by the use of steam-heated vacuum pans4 ,illustration3 ,,fig4 #hc4--,triple-effect ,yaryan ,evaporator4 ,for concentration to gravities not exceeding #abjj1 the ,yaryan apparatus made by ,mirrlees1 ,watson and ,yaryan1 of ,glasgow1 is that most employed4 ,the general arrangement of a 8triple effect0 machine of this make is shown in ,fig4 #hc1 and the internal construction in ,fig4 #hd4 ,each body consists of a strong casing into which steam is admitted1 and which is traversed by copper tubes which terminate in a separating chamber at the further end1 which is maintained at a low pressure by an air-pump4 ,the liquid to be evaporated is admitted into the tubes1 and is immediately converted into spray by the steam generated from it1 and swept forward into the separating chamber1 from which it is withdrawn by a pump4 ,the steam before going to the air-pump 7or1 in the case of 8multiple effects10 to the next body71 is passed through a 8catch-all10 to separate any spray still retained in the steam4 ,thus the liquor to be evaporated will pass through the entire apparatus in four or five minutes1 and may be concentrated from a gravity of #ajb or #ajc to that of #abj without ever having been heated above #gj ,c4 7#afj ,f474 ,unless fuel is very cheap1 which is often the case where the spent tanning material can be used to raise steam1 it is advisable to use a double or triple effect1 in which the steam from the evaporation of the weakest liquor in the first body is used to heat the second1 which is maintained at a lower vacuum1 and so on4 ,in this way the steam is made to do nearly double or triple duty4 ,as the steam from the extract-liquors contains acids which corrode iron1 it is necessary to have the casing as well as the tubes made of copper in all bodies in which it is employed4 ,iron must1 in fact1 be carefully avoided in every part of apparatus which comes in contact with extract-liquor or its vapour4 ,besides the ,yaryan1 there are several other evaporators in which the spray principle is more or less completely employed4 ,the simplest of these consists in substituting for the heating coil of an ordinary vacuum-pan a copper steam-box traversed by vertical tubes open at both top and bottom4 ,this is immersed in the liquid to be evaporated1 which enters at the bottom of the tubes and is sprayed out at the top4 ,paul ,neubcker1 of ,danzig1 constructs a pan on this principle with a very ingenious arrangement for the destruction of foam1 which seems worth attention4 ,illustration3 ,,fig4 #hd4--,section of ,yaryan ,evaporator4 ,it is unfortunately impossible to carry the evaporation of extracts much further than sp4 g4 #ab with spray apparatus1 as thicker liquors are apt to clog the tubes1 which are then difficult to clean1 so that even liquid extracts are usually finished in vacuum-pans of the ordinary type1 which may also be arranged in multiple effect4 ,in the case of a solid extract1 the evaporation must be carried on until it is as thick as can be run from the apparatus4 ,to do this satisfactorily1 stirrers must be provided to keep the extract in motion so long as it is in the pan4 ,the thick1 hot1 liquid extract is then run into boxes lined with paper1 or other suitable material1 where it is allowed to cool and to solidify4 ,the pan for the final evaporation of solid extracts should be planned so as to allow of easy cleaning and ready access to its interior1 so that if accidentally the evaporation is carried so far that the liquid will not run out1 the clearing of the pan may be a comparatively easy matter4 ,it is also important that the extract-exit should be of large size4 ,probably a broad and somewhat shallow pan1 heated merely by a steam jacket1 and fitted with rotating stirrers1 is the most suitable4 ,the ,use of ,extracts in the ,tannery4--,one of the great attractions of extracts is that they save the trouble and cost of leaching1 and as the extract manufacturer makes this his specialty1 he can often extract more tanning matter from a material than the tanner who has no means of concentrating his weak liquors4 ,the extract manufacturer also can employ methods of decoloration which would be impracticable to the tanner1 and so enable the latter to obtain better colour than if he employed the raw material4 ,by the use of extracts a tanner can strengthen weak liquors without trouble1 and with definite quantities of materials2 and by using extracts for this purpose the tanner is enabled to use up the weaker liquors of his leaches and so employ more water and obtain better extraction of his solid materials than if he used them alone4 ,in the case of very weak materials like oakwood1 the difficulties of making liquors of sufficient strength for tanning without evaporation are so great as to render such materials useless to the tanner for his own extraction1 and their carriage even for short distances may amount to more than their total value4 ,even with much richer materials1 extraction effects a saving if the carriage is a long one1 as it rarely pays to import any material containing less than about #be per cent4 of tanning matter4 ,even when the strength of the natural material is considerable1 as in the case of quebracho1 extraction may be profitable if from its hardness1 or other reasons1 the material is difficult for the tanner to handle4 ,for long voyages1 and especially from the tropics1 solid extracts are more suitable than liquid1 as the expense of casks is saved1 and the danger of fermentation is lessened4 ,as it is impossible for the tanner to judge by appearance or consistency of the strength or value of extracts1 they should always be bought and sold on the analysis of the particular shipment or parcel by a competent chemist4 ,for directions for sampling see pp4 #cja1 #dge4 ,extracts simply require to be dissolved in a suitable quantity of water or weak liquor at an appropriate temperature1 to obtain a liquor of any required strength4 ,some extracts are completely soluble in cold water or liquor1 but most dissolve better by the aid of heat4 #dj-fj ,c4 7#ajj-adj ,f47 is generally sufficient1 and probably no advantage can arise from temperatures over #hj 7#ahj ,f474 ,boiling should be avoided1 as it facilitates the formation of insoluble 8reds0 with consequent loss of tanning matter and darkening of colour4 ,the extract should be run into the vat in a thin stream1 and continuously plunged up2 where large quantities of extract are to be dissolved1 a mechanical agitator is advantageous4 ,a 8silent boiling jet0 7p4 #cce7 may be used1 fitted into a small casing immersed in the liquor and open at both ends1 and the extract run into the current it produces4 ,whether in the manufacture of extracts1 or for direct use in the tannery1 the temperature at which tanning materials are extracted is of prime importance4 ,it is a common mistake to assume that the largest amount of tannin is extracted by boiling4 ,mr4 ,a4 ,n4 ,palmer has pointed out that this is by no means the case1 but that each material has an optimum temperature of extraction1 at which more tannin is extracted than at any other2 and the question has been carefully investigated by ,j4 ,g4 ,parker and the author1#aei with results which are given in the following tables4 ,for many purposes the colouring matter which accompanies the tannin is a serious disadvantage1 and it is usually most extracted at the higher temperatures2 and on this account it is necessary for the tanner who will work his leaches economically to ascertain at what temperature he can extract the largest amount of tannin combined with no more colouring matter than he can permit to enter his leather4 ,most materials are satisfactorily extracted at #ej-fj ,c41 but as a general rule it is best to begin cold or nearly so1 and only raise the temperature as the extraction proceeds4 ,the tables show the percentages of tanning matter1 and the amount of colour 7as measured by ,lovibond's tintometer71 obtained by extracting materials in a ,procter's extractor 7p4 #cjf and ,l4,i4,l4,b41 p4 #ajb7 so long as any colour or tannin could be obtained4 #aei ,journ4 ,soc4 ,ch4 ,ind41 #ahie1 #fce4 ,,belgian ,,oak ,,bark4 ---------------------------------------- ------------------------ ,temperature ,tanning ,soluble ,per cent4 ,colour of ,per cent4 of ,matters ,non-tanningof ,tannin per cent4 of ,colour ,extraction4absorbed ,matters4 on ,solution in on by ,hide4 ,maximum inch ,cell4 ,maximum ,yield4 -------------- ,yield4 ,red4 ,yellow4 ---------------------------------------- ----------------------- ,c4 per cent4 per cent4 deg4 deg4 #ae #ei #ea #fai #hf #bca #egd #ae-cj #fh #ee #gjg #ib #bfd #fde #cj-dj #hj #ee #hce #aaf #cjd #gfa #dj-ej #hb #eg #hdb #abj #cba #hjj #ej-fj #he #eh #hgf #abe #cfj #hdj #fj-gj #ia #ei #iee #aca #cha #ibg #gj-hj #ib #fj #ieg #adg #chi #ihg #hj-ij #if #fj #ajjj #adj #cfi #icb #ij-ajj #if #fa #ajjj #adj #dab #idf ,boiled hour #ia #ff #icg #aej #dbf #ajjj ---------------------------------------- ----------------------- ,,myrobalans4 ---------------------------------------- --------------------- ,temperature ,tanning ,soluble ,per cent4 ,colour of ,per cent4 of ,matters4 ,non- of per cent4 of ,extraction4 ,tannins4 ,tannin on solution in ,colour on ,maximum inch ,cell4 ,maximum ,yield4 ------------- ,yield4 ,red4 ,yellow4 ---------------------------------------- -------------------- ,c4 per cent4per cent4 deg4 deg4 #ae #bhe #abh #gib #aji #di #igd #ae-cj #cja #acf #hcf #ajj #da #hbe #cj-dj #cbc #adc #hih #ajc #da #hbg #dj-ej #cce #acf #icj #ajc #db #hdd #ej-fj #cdg #add #ifd #ajc #dd #hgf #fj-gj #cdh #add #iff #ajc #de #hic #gj-hj #cdi #adi #ifh #aaj #dg #ida #hj-ij #cea #aej #igd #aaf #dh #ifg #ij-ajj #cfj #adi #ajjj #aab #di #igj ,boiled #ced #aee #iha #abf #di #ajjj ---------------------------------------- -------------------- ,,smyrna ,,valonea4 ---------------------------------------- ------------------------- ,temperature ,tanning ,soluble ,per cent4 ,colour of ,per cent4 of ,matters4 ,non- of per cent4 of ,extraction4 ,tannins4 ,tannin on ,solution in ,colour on ,maximum inch ,cell4 ,maximum4 ,yield4 ---------------- ,red4,yellow4,blue4 ---------------------------------------- ----------------------- ,c4 per cent4per cent4 deg4 deg4 deg4 #ae #bee #aia #gje #be #fj #jc #gdf #ae-cj #bia #ahc #gde #be #fd #jc #ghj #cj-dj #ccf #aha #hfb #bc #fd #jc #gfb #dj-ej #cee #aha #hfb #bc #fe #jc #gdf #ej-fj #cia #aff #ajjj #bj #fj #jc #gfb #fj-gj #chf #agj #iij #bj #fh #jc #hdg #gj-hj #chh #age #iie #ba #gd #jd #hdg #hj-ij #cfi #agb #iej #bb #gf #jd #hdg #ij-ajj #cff #agj #idj #bd #gh #je #ijf ,boiled #ced #agf #ijf #cj #hb #jf #ajjj ---------------------------------------- ----------------------- ,,greek ,,valonea4 ---------------------------------------- ------------------------- ,temperature ,tanning ,soluble ,per cent4 ,colour of ,per cent4 of ,matters4 ,non- of per cent of ,colour ,extraction4 ,tannins4 ,tannin on ,solution in in ,maximum inch ,cell4 per cent4 ,yield4 ----------------of ,tannin ,red4,yellow4,blue4,solution4 ---------------------------------------- ----------------------- ,c4 per cent4per cent4 deg4 deg4 deg4 #ae #afj #acj #fdj #bi #fc #jc #fgc #ae-cj #aha #abf #gbd #cj #ff #jc #gjj #cj-dj #baa #abj #hdd #bh #fe #jc #fhj #dj-ej #bcf #aba #idd #bd #ff #jc #fei #ej-fj #bdh #abd #iib #bg #gj #jd #gaf #fj-gj #bej #abf #ajjj #bi #gc #je #geh #gj-hj #bdf #abe #ihd #ca #gi #jf #hbc #hj-ij #bdj #abe #ifj #cd #ha #jf #heh #ij-ajj #bcf #abf #idd #ce #hh #jg #ibj ,boiled #bbf #acj #hhh #ci #id #jh #ajjj ---------------------------------------- ----------------------- ,,natal ,,mimosa4 ---------------------------------------- ---------------------- ,temperature,tanning ,soluble ,per cent4 ,colour of ,per cent4 of ,matters4 ,non- of per cent of ,extraction4 ,tannins4 ,tannin on ,solution in ,colour on ,maximum4 inch ,cell4,maximum4 ------------- ,red4 ,yellow4 ---------------------------------------- --------------------- ,c4 per cent4per cent4 deg4 deg4 #ae #bab #aaf #ffb #bf #da #eaa #ae-cj #bij #ih #ijf #cj #da #edb #cj-dj #cja #ih #idj #cj #dd #efe #dj-ej #cjb #ih #idd #ca #ej #fah #ej-fj #cjd #ajd #iej #ci #fe #gii #fj-gj #cae #ajf #ihd #db #fe #haf #gj-hj #cbj #ajh #ajjj #db #gj #hee #hj-ij #cjh #aab #ifb #di #gd #ich #ij-ajj #cja #aah #idj #ec #gh #ajjj ,boiled #bid #abj #iah #eg #gb #ihd ---------------------------------------- --------------------- ,,sumach4 ---------------------------------------- --------------------- ,temperature,tanning ,soluble ,per cent4 ,colour of ,per cent4 of ,matters4 ,non- of per cent of ,extraction4 ,tannins4 ,tannin on ,solution in ,colour on ,maximum4 inch ,cell4 ,maximum4 ------------- ,red4 ,yellow4 ---------------------------------------- -------------------- ,c4 per cent4per cent4 deg4 deg4 #ae #adb #agh #gjj #af #ed #fcf #ae-cj #agf #aha #hfg #ad #dc #eah #cj-dj #ahe #aha #iaa #ac #dd #eah #dj-ej #bja #ahe #iij #ad #dd #ebi #ej-fj #bjc #aia #ajjj #ae #dg #efe #fj-gj #aij #aid #icf #ag #ef #fff #gj-hj #ahj #aii #hia #ai #fb #gbh #hj-ij #afi #baa #hcb #bc #fh #hbg #ij-ajj #aff #bbc #hag #bf #gj #hgg ,boiled #aeb #bdj #gdh #cc #gg #ajjj ---------------------------------------- -------------------- ,,quebracho ,,wood4 ---------------------------------------- --------------------- ,temperature,tanning ,soluble ,per cent4,colour of ,per cent4 of ,matters4 ,non- of ,tannin per cent of ,extraction4 ,tannins4 on ,solution in ,colour on ,maximum4 inch ,cell4,maximum4 ------------- ,red4 ,yellow4 ---------------------------------------- -------------------- ,c4 per cent4per cent4 deg4 deg4 #ae #gf #bb #cej #hi #ada #gac #ae-cj #aja #bd #dfe #fd #ajg #fhg #cj-dj #aah #bd #edd #ei #if #feb #dj-ej #aea #bd #fie #ec #hd #fjj #ej-fj #afe #bd #gfj #ed #he #fjd #fj-gj #agd #bd #hjj #ef #hb #eii #gj-hj #aia #bg #hhj #fd #hf #fgd #hj-ij #bag #cj #ajjj #fd #id #gdc #ij-ajj #aie #cj #hih #ff #ih #ajjj ---------------------------------------- -------------------- ,,mangrove ,,bark 7,ceriops74 ---------------------------------------- --------------------- ,temperature ,tanning ,soluble ,per cent4 ,colour of ,per cent4 of ,matters4 ,non- of ,tannin per cent4 of ,extraction4 ,tannins4 on ,solution in ,colour on ,maximum4 inch ,cell4 ,maximum4 ------------- ,red4 ,yellow4 ---------------------------------------- -------------------- ,c4 per cent4per cent4 deg4 deg4 #ae #acj #ajd #faf #adb #bjh #fdg #ae-cj #afa #ajd #gfc #afa #bag #fih #cj-dj #agd #abe #hbd #aeh #bcj #gag #dj-ej #ahe #aad #hgg #afe #cce #gch #ej-fj #bjc #ajc #ifb #afj #bcd #gbh #fj-gj #bjj #aad #idg #age #cab #ijj #gj-hj #bjd #aab #ifg #afe #bhc #hbh #hj-ij #baa #ajh #ajjj #aed #bdf #gch #ij-ajj #bjb #aad #ieg #bcj #cda #ajjj ---------------------------------------- -------------------- ,,canaigre ,,root 7three years old74 ,effect of ,different ,temperatures4 ---------------------------------------- ------------------------ ,temperature ,tanning ,soluble ,per cent4 ,colour of per ,per of ,matters ,non- of ,tannin cent4 ,solution in cent4 ,extraction4 absorbed ,tanning on -inch ,cell4 of by ,hide4 ,matters4 ,maximum ----------------- ,colour ,yield4 ,red4,yellow4,total4 on ,maximum ,yield4 ---------------------------------------- ---------------------- ,c4 per cent4per cent4 deg4 deg4 deg4 #ae #baa #acj #ghg #af #da #ei #dae #ae-cj #bfb #abe #hef #af #ch #dd #chj #cj-dj #bha #abe #iah #ad #cg #ea #cei #dj-ej #cje #aca #iif #ba #db #fc #ddc #ej-fj #cjf #acf #ajjj #bd #dh #gb #ejg #fj-gj #bgb #ada #hhh #be #ej #ge #ebg #gj-hj #bfd #adf #hfb #bh #fa #hi #fbf #hj-ij #bcb #adh #geh #ca #fi #ajj #gjd #ij-ajj #bbh #adh #gde #dc #gd #aag #hbd ,boiled hour #aib #abc #fbg #ef #hf #adb #ajjj ---------------------------------------- ---------------------- ,,cube ,,gambier4 ,effect of ,different ,temperatures4 ---------------------------------------- ------------------------ ,temperature ,tanning ,soluble ,per cent4 ,colour of per ,per of ,matters ,non- of ,tannin cent4 ,solution in cent4 ,extraction4 absorbed ,tanning on -inch ,cell4 of by ,hide4 ,matters4 ,maximum ----------------- ,colour ,yield4 ,red4,yellow4,total4 on ,maximum ,yield4 ---------------------------------------- ---------------------- ,c4 per cent4per cent4 deg4 deg4 #ae #dfh #bah #ghj #be #gh #ajc #egb #ae-cj #dhh #baj #hac #ag #hj #ig #edi #cj-dj #ejb #bbj #hcg #ag #hf #ajc #egb #dj-ej #eai #bcj #hfe #ag #hh #aje #ehc #ej-fj #eaa #bjc #iai #ag #hi #ajf #ehh #fj-gj #eef #bjc #ibg #ai #id #aac #fbg #gj-hj #eeg #bjc #ibh #bb #aja #abc #fhc #hj-ij #eeh #bab #ica #bc #ajf #abi #gaf #ij-ajj #efa #bbj #icc #bh #aaf #add #hjj ,boiled hour #fjj #bjj #ajjj #cb #adh #ahj #ajjj ---------------------------------------- ---------------------- ,,block ,,gambier4 ,effect of ,different ,temperatures4 ---------------------------------------- ------------------------ ,temperature ,tanning ,soluble ,per cent4 ,colour of per ,per of ,matters ,non- of ,tannin cent4 ,solution in cent4 ,extraction4 absorbed ,tanning on -inch ,cell4 of by ,hide4 ,matters4 ,maximum ----------------- ,colour ,yield4 ,red4,yellow4,total4 on ,maximum ,yield4 ---------------------------------------- ---------------------- ,c4 per cent4per cent4 deg4 deg4 #ae #cja #bgd #eja #bf #ha #ajg #cce #ae-cj #cdh #bfb #fif #bd #hj #ajd #cdj #cj-dj #djh #bgb #haf #bj #ij #aaj #eej #dj-ej #ddh #bgf #hif #bd #ih #abb #faj #ej-fj #dfh #bgh #icf #bd #aja #abe #fbe #fj-gj #dgc #bgf #idf #be #ajf #acb #ffj #gj-hj #dgd #bgf #idg #bh #aji #acg #fce #hj-ij #dgf #bgc #ieb #cb #aaf #adh #gdj #ij-ajj #dhb #bga #ifd #ch #abh #aff #hcj ,boiled hour #ejb #bfd #ajjj #ej #aej #bjj #ajjj ---------------------------------------- ---------------------- ,,chapter ,,xxiii4 ,,fats1 ,,soaps1 ,,oils ,,and ,,waxes4 ,fats and oils constitute a large class of substances1 of animal or vegetable origin1 which may be solid1 pasty or more or less viscous liquids1 but which in the latter case are commonly known as 8fixed0 or fatty oils1 to distinguish them from the volatile1 or essential oils1 which may be distilled without decomposition1 and which are the source of most of the odours of plants1 and of quite different chemical constitution4 ,the term 8oil0 is also applied to various products of mineral origin1 and especially to those derived from petroleum1 on account of their similarity in appearance and physical properties to the fixed oils1 though1 chemically1 they form a very distinct class4 ,the waxes are another group somewhat closely allied to the fats2 and there are certain fixed oils1 such as sperm oil1 which though very similar in appearance and properties to the fatty oils1 are chemically members of the group of waxes4 ,as it is obvious that there is no chemical distinction between the fats and fatty oils1 except that of melting-point1 it will be convenient to treat them together2 especially as what is a solid fat in one climate may be an oil in another4 ,palm and cocoa-nut oils are cases in point1 as the first is buttery1 and the second a hard fat in this country1 though they are both liquid in tropical climates4 ,for more detailed information on the chemistry of fats and oils1 the reader must be referred to the #8,leather ,industries ,laboratory ,book1' sect4 xviii41 or to the larger manuals devoted specially to the subject by ,lewkowitsch1 ,jean1 and others1 or the very excellent section on oils in ,allen's #8,commercial ,organic ,analysis1' vol4 ii42 but a few general facts must be recapitulated4 ,the true fats contain carbon1 hydrogen and oxygen1 but no nitrogen4 ,they are all compounds of glycerin with organic acids which are generally termed 8fatty acids10 and which resemble in many of their characteristics the fats themselves4 ,glycerin is a very weak base1 of the nature of an alcohol1 and consequently1 when a fat is heated with a solution of one of the caustic alkalis1 the fatty acid combines with the latter1 and the glycerin is set free4 ,the salts thus formed are denominated 8soaps40 ,the reaction with stearin 7glycerin stearate71 the principal constituent of hard animal fats1 is shown in the following equation4 ,stearin ,sodium ,sodium ,glycerin hydrate stearate 7,c,h,,co4,o7,c,h #c,na,o,h #c;,c,h,,co4,o,na ,c,h7,,oh74 ,if a soap is treated with an acid stronger than its own1 the latter is set free1 while the new acid combines with the base4 ,the following equation1 for instance1 shows the action of hydrochloric acid on the stearic soap4 ,sodium ,hydro- ,stearic acid ,sodium ,stearate chloric chloride acid ,c,h,,co4,o,na ,h,cl ,c,h,,co4,,oh ,na,cl4 ,if any soap be dissolved in hot water1 and sufficient hydrochloric or sulphuric acid added to render the solution acid1 the latter will turn first milky1 and 7if it be kept warm7 the fatty acid will finally rise in an oily layer to the surface1 which in many cases will harden1 as it cools1 to a solid mass4 ,the amount of fatty acid in a soap may be roughly determined by weighing #be grm41 dissolving in #ej c4c4 of boiling water1 and adding excess of acid1 and allowing the reaction to take place in a graduated cylinder1 or a flask with a graduated neck1 in a vessel of boiling water4 ,when the fatty acid has risen to the top1 its volume may be noted1 and each c4c4 may be roughly reckoned as #ji grm4 7,for more detailed methods cp4 ,l4,i4,l4,b41 ,sect4 ,,xvii474 ,soaps are insoluble in strong caustic alkaline solutions1 and therefore saponification 7as the decomposition of fats by alkalis is called71 does not readily take place in them1 and for this reason the soap-boiler generally dilutes his caustic soda solutions to a strength not exceeding #ah ,tw4 7sp4 gr4 #ajij7 in gravity1 and separates the soap at the end of the operation1 by the addition of brine1 in which it is insoluble4 ,an easier method1 and one which is often useful for the preparation of small quantities of special soaps for fat liquors and the like1 is as follows4#afj #aj lb4 of a good caustic soda1 free from common salt1 is dissolved in #d gallons of water1 and #ge lb4 of oil or fat is warmed to about #be ,c4 or just sufficiently to render it liquid1 and the soda solution is added in a thin stream1 with constant stirring1 which must be continued until the mass becomes too pasty4 ,it is now set aside in a warm place for at least twenty-four hours1 during which saponification gradually takes place4 ,for leather purposes1 a neutral soap1 with a slight excess of fat1 is generally advantageous1 so that the fat may be increased to #hj lb42 or1 in place of this1 the operation will be facilitated by the addition of #e lb4 of commercial oleic acid4 ,if soft soap is desired1 #ad lb4 of caustic potash may be used in place of the #aj lb4 of caustic soda4 ,the hardness or softness of soaps varies to some extent with the fat used1 but potash soaps are always much softer than the corresponding soda soaps4 ,it is obvious that with soaps made in this way1 all the glycerin remains mixed with the soap4 ,if1 on testing1 the soap does not prove to be free from caustic1 it may be re-melted1 which will generally complete the reaction4 ,before attempting to work with large quantities1 a laboratory experiment is desirable1 using #aj grm4 of soda in #dj c4c4 of water1 and #ge to #hj grm4 of oil or fat4 ,the neutrality or freedom of the soap from caustic alkali may be tested by touching a freshly cut surface with an alcoholic solution of phenolphthalein1 which the least trace of caustic soda or potash will render pink4 #afj ,carpenter1 #8,soap1 ,candles and ,lubricants1' p4 #add4 ,if solutions of soaps are mixed with those of salts of the heavy metals or of the alkaline earths1 a mutual decomposition takes place1 the acid of the salt combining with the alkali of the soap2 and the fatty acid with the metallic base1 to form a metallic soap4 ,most of these soaps are sticky masses1 insoluble in water1 but not unfrequently soluble in turpentine or petroleum spirit1 if previously thoroughly dried1 so that some of them have been applied to the production of varnish4 ,alumina soaps are occasionally used to thicken mineral oils1 or render them more viscous4 ,the general reaction of the stearin soap with calcium sulphate is shown in the following equation1 though in practice it is sometimes more complex3 ,stearin soap ,calcium ,sodium ,calcium sulphate sulphate stearate #b;,c,h,,co4,o,na ,ca,s,o ,na,,so 7,c,h,,co4,o7,ca ,this is the reaction which causes the curdling of soap by hard water1 page #ic4 ,true fats cannot be distilled alone without decomposition4 ,when distilled in a current of steam1 some undecomposed fat passes over1 but the greater part is broken up into free fatty acid and glycerin2 and hydrocarbons practically identical with mineral oils are also formed4 ,fats and oils are insoluble in water1 and in most cases only sparingly soluble in alcohol1 but freely soluble in ether1 petroleum spirit1 benzene1 and most other hydrocarbons1 as well as in chloroform1 carbon tetrachloride1 and carbon disulphide4 ,petroleum spirit1 often called benzine1 is largely used for their extraction1 and for de-greasing leather1 and removing grease from clothes4 ,in the laboratory1 carbon disulphide1 or carbon tetrachloride is to be preferred4 ,castor oil is an exception to the rule1 owing to the large proportion of oxygen which it contains1 being readily soluble in alcohol1 and very sparingly in petroleum-spirit2 and other oils1 when oxidised1 usually become more soluble in alcohol1 and less so in hydrocarbons4 ,oils vary much in their tendency to 8dry10 or become converted into solid or sticky resin-like substances4 ,this tendency is greatest in some of the seed oils1 and least in olive oil1 and the oily part of animal fats 7tallow oil1 neatsfoot oil74 ,sperm oil1 a 8liquid wax10 is also very free from this tendency1 but all fish oils possess it in a greater or less degree4 ,it is not due to evaporation1 but to the absorption of oxygen by the fatty acid4 ,the tendency to oxygen-absorption1 and consequently to drying 7and1 in the case of leather-oils1 to 8spueing071 is measured analytically by the 8iodine-value10 the absorption of iodine being proportional to that of oxygen1 while it is much more easily measured4 ,there are no simple tests by which the purity of oils can be determined1 though in a few cases the presence of particular oils can be detected4 ,the mixing and adulteration of oils is now a science1 and those who practise it are well acquainted with the customary tests1 and take care to adjust their mixtures so as to meet them4 ,taste and smell however1 with practice1 often furnish useful indications4 ,natural oils and fats are invariably mixtures of the glycerides of several fatty acids1 and their qualities depend simply on the character of these glycerides and the proportions in which they are mixed4 ,the fatty acids form several groups1 differing in their degree of 8saturation10#afa or1 inversely1 in their power of taking up oxygen1 on which their tendency to drying depends4 ,the members of any one of these groups resemble each other strongly1 differing principally in melting points1 density1 and other physical characteristics4 #afa ,a 8saturated0 compound is one1 the constituents of which are present in such proportions that all the combining affinities of each are satisfied by the others4 ,iodine value1 see ,l4,i4,l4,b41 p4 #agf1 and ,jour4 ,soc4 ,ch4 ,ind41 #aijb1 p4 #ded4 ,saturated ,fatty ,acids4--,stearic acid1 ,c,h,o4,,oh1 and palmitic acid1 ,c,h,o4,,oh1 are the most important4 ,at ordinary temperatures they are hard1 white1 crystalline bodies1 and melt at #fi and #fb ,c4 respectively4 ,they do not1 under ordinary circumstances1 absorb any oxygen1 nor iodine1 and are very little liable to chemical change4 ,together with oleic acid1 they are the principal acids of tallow and other animal fats1 while palmitic acid and some lower members of the same group are more common in vegetable oils4 ,free stearic acid is an important constituent of the 8distilled stearines0 used in currying2 while 8oleostearine0 consists mainly of the neutral fats or glycerides of stearic and palmitic acids4 ,liquid ,fatty ,acids1 ,non-drying4--,of these1 oleic acid is much the most common and important2 its glyceride1 olein1 forming the liquid part of animal fats1 and being the principal constituent of vegetable non-drying oils4 ,olive oil consists almost entirely of olein1 with a little palmitin4 ,the formula of oleic acid is ,c,h,o4,,oh1 thus differing from stearic acid in having two less atoms of hydrogen4 ,the 8bonds0 or affinities corresponding to these two atoms are linked together1 but can separate1 and attach two atoms of iodine1 bromine1 or chlorine1 or one of oxygen4 ,the iodine-value of pure olein is #hci 7that is1 #ajj grm4 absorb #hci grm4 iodine72 and that of olive oil about #hc4 ,any oil with a higher 8iodine-value0 than olein must contain drying oils1 though a lower value does not necessarily indicate their absence1 if palmitin or other saturated acids are also present4 ,unsaturated ,liquid ,fatty ,acids4--,of these there are several groups1 differing in their degree of saturation1 and also probably in their structure4 ,their glycerides1 together with olein1 and sometimes palmitin1 are the constituents of the seed oils1 the drying tendency of which depends on their proportion of unsaturated acids1 and the particular group to which they belong4 ,the fish oils contain a peculiar group of unsaturated acids1 together with olein1 and usually stearin and palmitin1 like the other animal fats4 ,linolenic acid1 ,c,h,o4,,oh1 one of the acids of linseed oil1 has six hydrogen atoms less than stearic acid1 and therefore three double linkings1 and will take up six atoms of iodine4 ,its theoretical iodine-value is #bgd1 while linseed oil itself often has an iodine-value exceeding #ahj4 ,the iodine-value of cod-liver oil is sometimes nearly as high4 ,both oils therefore contain other acids less unsaturated than linolenic4 ,the 8spueing0 of leather is due to the absorption of oxygen and consequent resinification of the oils1 and therefore all drying oils1 however pure1 are capable of producing it1 though some are more liable to do so than others 7cp4 pp4 #cfc1 #cfe1 #cff1 #cfh1 #cij74 ,linolenic acid1 and probably other allied acids1 become converted by absorption of oxygen into solid varnish-like substances1 which are important to the tanner1 as furnishing the principal constituents of japans for leather4 ,the unsaturated acids of fish oils seldom give hard varnishes1 though menhaden oil 7page #cfg7 is sometimes used as paint-oil for outside work4 ,most fats are liable to become rancid by exposure to the air1 acquiring a disagreeable taste and smell1 and an acid reaction from the liberation of the fatty acids4 ,the changes which take place are somewhat complex4 ,the fatty acid of castor oil is of peculiar constitution1 being an oleic acid in which one of the hydrogen-atoms is replaced by a 8hydroxyl0 or ,,oh group4 ,the solubility of castor oil in alcohol has already been alluded to4 ,it does not dry1 and is an excellent oil for lubricating heavy machinery4 ,it is sometimes adulterated with 8blown0 oils1 which are made from non-drying1 or slightly drying seed oils1 like cotton-seed or rape1 by blowing air through them in a warmed condition4 ,under this treatment they increase greatly in viscosity and density and in their solubility in alcohol1 but do not acquire the other valuable properties of genuine castor oil4 ,the 8foots0 or sediments which oils deposit on standing1 sometimes consist of animal or vegetable fibres1 or mucilage combined with water1 but often are simply the harder fats1 stearin1 palmitin1 etc41 which crystallise from the oil on cooling4 ,in this case they are re-dissolved on warming the oil4 ,such oils1 which like neatsfoot and tallow oils become turbid in cold weather1 are styled 8tender40 ,,non-,,drying ,,fats ,,and ,,oils4 ,tallow 7,fr4 ,suif2 ,ger4 ,talg7 is the fat of various mammalia1 principally of the ox and sheep1 but occasionally also of the goat4 ,the mixed fat obtained from all parts of the carcass is known as 8rendered tallow10 while that obtained from the region of the kidneys 7suet7 is harder4 ,a substance commonly referred to as 8pressed tallow0 or 8oleo-stearine0 is obtained by pressing ordinary tallow1 in cloths1 in the hydraulic press4 ,the more liquid portion which is expressed is tallow-oil1 the finer qualities of which are used in making margarine4 ,oleo-stearine must not be confounded with the 8distilled stearine10 obtained from ,yorkshire grease by distillation and pressure 7page #cei71 nor with candlemakers' 8stearine10 which is a mixture of free stearic and palmitic acids4 ,pure tallow is white and tasteless1 but much of that sold is yellowish and of a disagreeable1 slightly rancid flavour4 ,mutton tallow is usually harder and whiter than that of beef4 ,goat tallow has a characteristic odour1 as have the recovered stearines and other waste greases from glue-works4 ,buck tallow1 which is particularly hard1 has now been largely replaced by oleo-stearine4 ,beef tallow melts at about #dj ,c42 mutton tallow at #de4 ,in chemical composition1 tallow consists chiefly of a mixture of the tri-glycerides of palmitic1 stearic and oleic acids2 its hardness diminishing with the increase of the last4 ,tallow should1 when melted1 be perfectly clear1 turbidity indicating the presence of water or other foreign matters1 due either to carelessness in the manufacture or1 possibly1 adulteration4 ,traces of phosphate of lime1 or fragments of animal tissue1 may be present as accidental impurities2 lime1 on the other hand1 is sometimes added to thicken the tallow and enable it to retain more water2 starch1 china clay1 whiting1 heavy spar1 etc41 are also occasionally employed4 ,tallow has been not infrequently adulterated with the distilled fatty acids from wool grease4 ,when this is the case1 crystals of cholesterol 7see ,l4,i4,l4,b41 p4 #aha7 may be detected by examination of the unsaponifiable matter of the mixture under a microscope4 ,it would also give the tallow an unusually high 8acid-value40 ,methods for the proximate analysis of tallow are given in the #8,laboratory ,book1' pp4 #ahi et seq4 ,the fats produced by the boiling of fleshings for glue1 and by the pressing of sheep-skins1 are of the nature of soft tallows4 ,if the fleshings are delimed with acid1 and boiled fresh1 the grease is generally of good colour1 and with little unpleasant odour1 but contains traces of free fatty acids derived from the decomposition of the lime-soaps4 ,if the fleshings have been dried and the lime carbonated1 the grease will generally be brown1 and more or less rancid2 but the lime-soaps are not decomposed1 unless the 8scutch0 or refuse be treated with acid1 when a further yield of grease is obtained4 ,the grease from sheep-skins is generally somewhat brown1 and often smells of the volatile acids and other constituents of the tan-liquors1 especially if larch bark has been used4 ,these greases are usually much improved in appearance and odour1 if well washed by boiling or steaming on water1 or by blowing a mixture of air and steam through them1 or sometimes even by mere heating to a sufficient temperature to evaporate the water and drive off the volatile matters4 ,by allowing the grease to cool slowly1 so as to favour crystallisation1 till it is of a soupy consistency1 and then pumping through a filter press with woollen cloths1 the more liquid is separated easily from a more solid portion1 and both may in many cases be used in leather manufacture1 the tallow for currying1 and the oil in place of neatsfoot oil4 ,horse-fat1 and especially that from the fatty portions of the neck 7,ger4 ,kammfett71 as well as various other animal greases1 are used in the manufacture of leather4 ,they differ from tallow chiefly in that they have a lower melting-point1 and contain more olein in proportion to the stearin and palmitin than true tallow1 and are consequently somewhat softer4 ,though often almost white1 these greases are sometimes darkened in colour by the products of putrefying animal matter1 but this does not1 as a rule1 interfere with the oil being used for leather dressing4 ,they are usually so cheap that they are but little adulterated2 means of determining their purity are1 however1 given in ,l4,i4,l4,b41 p4 #aia4 ,neatsfoot oil is a yellowish1 nearly odourless oil1 of bland taste1 which is largely employed in the dressing of calf-kid4 ,it has a similar composition to tallow oil and the other oils obtained by subjecting the soft animal fats to great pressure at a low temperature4 ,it is often adulterated with bone oil1 lard oil and cotton-seed oil1 and occasionally with mineral oil and recovered wool-grease4 ,as neatsfoot oil is somewhat costly1 curriers may with advantage often use ordinary animal greases 7horse-fat1 etc47 after they have had the harder tallow extracted by cooling and pressure1 the product thus obtained being1 chemically1 the same as neatsfoot oil1 and in every respect as suitable1 while it is much less liable to adulteration4 ,the true neatsfoot oil is prepared by boiling the feet of cattle1 and sometimes of sheep and horses1 with water1 and skimming off and clarifying the oil which is thus obtained4 ,the physical and chemical characteristics of this oil are described in ,l4,i4,l4,b41 p4 #aib4 ,wool-,fat 7,fr4 ,suint1 oesype2 ,ger4 ,wollschweissfett7 is a grease of high specific gravity1 exsuded from the sebaceous glands of the sheep1 together with organic salts of potassium4 ,it is obtained by extracting wool with solvents2 or by washing with alkaline solutions1 from which it is recovered by precipitation with acid1 and subsequent hot-pressing of the 8magma10 or1 more recently1 by evaporating the scouring liquor to small bulk1 and centrifugating4 ,wool-fat is characterised by its low percentage of glycerides1 the fatty acids which it contains being mainly combined with higher alcohols 7bodies of alcoholic structure1 but of a waxlike consistency71 and chemically it is rather a wax than a true fat4 ,among the alcohols which it contains is included a marked percentage of cholesterol and isocholesterol4 ,it is difficultly saponifiable1 requiring to be heated to #aje-aaj ,c4 with alcoholic potash under pressure2 and even then about #dd per cent4 of alcohols remain1 which are incapable of further saponification4 ,care must therefore be taken not to assume that unsaponifiable matter in greases which may contain wool-fat is necessarily mineral oil4 ,for details of analysis see ,l4,i4,l4,b41 p4 #aid4 ,pure wool-fat is nearly white1 of salve-like consistency and very slight smell1 with a density of #jigc at #ae ,c4 ,crude wool-fat is yellow or brown1 with an unpleasant and very persistent characteristic smell4 ,both the pure and the crude wool-fat have an extraordinary power of emulsifying with water1 which makes them very valuable as substitutes for dgras in stuffing greases4 ,lanoline 7and several other preparations under different names7 are mixtures of purified wool-fat and water1 of which lanoline contains about #bb per cent4 8,yorkshire grease0 differs from crude wool-fat1 in being recovered from the waters employed in scouring woollen cloths1 as well as wool1 and hence contains the free fatty acids of soaps used in scouring1 as well as the 8oleines10 etc41 used in oiling the cloth1 and although it often contains much wool-fat1 it is occasionally destitute of this substance4 ,holden ,fat consists of ordinary wool-grease mixed with fish oil1 and is used either as a substitute for1 or in admixture with dgras 7q4 v474 ,distilled ,wool ,grease is produced by distilling crude ,yorkshire grease with steam4 ,most of the glycerides are broken up1 but many of the free fatty acids1 alcohols and waxes distil over unchanged1 though a considerable part is decomposed into volatile hydrocarbons strongly resembling mineral oils4 ,the distillate is separated by cooling and pressure into a liquid 8oleine0 and a solid 8stearine40 ,the latter forms a very valuable stuffing-grease which1 in ,england1 largely takes the place of the 8oleo-stearine0 used in the ,united ,states--with which1 however1 it must not be confounded4 ,distilled ,stearine1 prepared as above described1 is a pale yellow-to-brown fat1 which varies in hardness and in its melting point according to the conditions of its preparation4 ,it has a characteristic odour which is very persistent1 and it consists largely of free stearic and palmitic acids2 most of the liquid hydrocarbons formed by distillation being removed with the 8oleine40 ,olive ,oil 7,fr4 ,huile d'olive2 ,ger4 ,olivenoel1 ,baumoel7 finds extensive use in leather dressing1 and especially in the manufacture of 8fat-liquors0 7pp4 #bag1 #bdj74 ,it is extracted from the fruit of the olive tree by pressure1 and of late years from the residues by extraction with carbon disulphide4 ,although it chemically resembles tallow and lard oils very strongly1 its adulteration with these substances may usually be detected1 at any rate roughly1 by the taste and odour of the oil4 ,it is principally characterised1 from a chemical point of view1 by containing the glyceride of palmitic but not that of stearic acid1 and by having a much larger proportion of olein to solid glycerides than most of the non-drying animal oils4 ,at low temperatures1 olive oil solidifies to a product which can be separated by pressure into a solid tallow-like fat1 and a fluid oil consisting essentially of tri-olein4 ,olive oil is the type of a non-drying vegetable oil1 but though it does not thicken materially on exposure1 it becomes rancid somewhat rapidly1 and is thus rendered unsuitable for lubrication4 ,unless the acidity is excessive it does not appear to spoil the oil for leather manufacture1 and for some purposes is actually an advantage as aiding emulsification4 ,free acids in oils may be removed by shaking with sodium carbonate solution4 ,olive oil always contains some free acid2 which is of importance in the preparation of fat-liquors1 as it facilitates the production of an emulsion4 ,this quality may be increased by the addition1 when necessary1 of a little oleic acid4 ,olive oil is frequently adulterated with other vegetable oils4 ,probably the most useful criterion is the iodine-value1 which is raised by the addition of any seed oil4 ,examination in the refractometer also affords useful indications4 ,cotton-seed1 sesame and arachis 7earth-nut7 oils are the most frequent adulterants of the better qualities1 and in many cases may be recognised by special tests4 ,castor ,oil 7,fr4 ,huile de ricin2 ,ger4 ,ricinusoel7 is the oil expressed from the seeds of ,ricinus communis1 and is a transparent1 colourless or pale yellowish liquid1 having a faint odour and a disagreeable taste4 ,at a low temperature it thickens and deposits slightly1 and at -#ah ,c4 it solidifies to a pale yellow mass4 ,castor oil is distinguished from all other natural fixed oils by its high density 7#jifj to #jifd7 and viscosity1 and by its solubility in alcohol and its insolubility in petroleum ether4 ,genuine castor oil is completely soluble in an equal volume of absolute alcohol1 or in four times its volume of 8rectified spirit0 at the ordinary temperature4 ,it is practically insoluble in petroleum ether1 but can dissolve an equal measure of that liquid4 ,for the purpose of the leather manufacturer1 the ordinary hot-pressed oil1 such as is used for lubricating machinery1 is quite as good as the more costly cold-pressed oil which is used for medicinal purposes4 ,it is generally imported in tins holding about #dj lb4 of oil4 ,castor oil1 and castor-oil soap made as described on p4 #ceb1 are very good for fat-liquors1 seeming to interfere with dyeing and glazing less than most other oils4 ,boots oiled with castor oil may be blacked at once1 and will take a good polish4 ,the only oils which are usually mixed with castor oil are 8blown0 or oxidised seed oils1 or resin oil4 ,any other oils would so seriously lower the specific gravity as to render their use impracticable4 ,for the detection and estimation of these the #8,laboratory ,book' should be consulted1 or if fuller details are required the reader is referred to ,benedikt and ,lewkowitsch's #8,oils1 ,fats and ,waxes1' or to ,allen's #8,commercial ,organic ,analysis1' vol4 ii4 ,sulphonated castor oil or ,turkey-red oil is now largely used for 8fat-liquoring10 for which it was probably first employed by the author1 about #ahij4 ,this material--which must be carefully distinguished from the olive oil preparation which is also used for dyeing cotton a ,turkey-red colour--is made by treating castor oil with one-quarter of its weight of strong sulphuric acid 7specific gravity #ah71 adding the latter in very small quantities at a time1 and taking care that the temperature of the mixture at no time exceeds #ce ,c4 ,the mixture is then allowed to stand for twenty-four hours1 with occasional stirring1 and is washed with its own volume of water1 allowed to stand until the water has all separated1 and the oil is then syphoned off4 ,if desired1 the oil may be further washed once or twice with a solution of strong brine1 but this is of doubtful advantage1 and should in no case be excessive4 ,the washed oil is finally neutralised by the cautious addition of one-hundredth of its volume of strong ammonia solution 7sp4 gr4 #jhhj74 ,if properly prepared1 ,turkey-red oil 7sulphonated castor oil7 will1 when largely diluted with water1 bear the addition of ammonia to alkaline reaction without showing any turbidity even on standing several hours4 ,if a turbidity is produced1 it indicates that the castor oil used was impure and contained some oil rich in stearin4 ,the alcohol test described on p4 #cfj may also be applied1 as the oily layer will be entirely soluble if castor oil alone was used in the preparation of the red oil4 ,turkey-red oil usually contains about #ej per cent4 of fatty acids 7,allen74 ,linseed ,oil 7,fr4 ,huile de lin2 ,ger4 ,leinoel7 is used by leather manufacturers in the preparation of the japan for making 8patent leather10 and to some extent also in currying1 for oiling off levants and moroccos1 though for these purposes it has been largely superseded by mineral oils4 ,it is obtained from the seeds of the flax plant1 ,linum usitatissimum1 chiefly grown in ,russia and ,india4 ,the ,russian oil is usually mixed with the oil from hemp to the extent of about #bj per cent41 while that from ,india1 being grown as a mixed crop with mustard and rape1 is never perfectly pure4 ,the ,baltic oil is considered best for japans1 and is improved by storing for a considerable time in tanks in a warm place4 ,when obtained by cold pressure of the seeds1 linseed oil is of a bright yellow colour2 if a higher temperature be used in the extraction the oil is more or less brown1 and tastes much more acrid4 ,on exposure to air1 linseed oil turns easily rancid1 absorbs oxygen1 and if spread out in a sufficiently thin film it dries to a neutral substance 7linoxyn71 which is insoluble in ether4 ,this property is the one on which the chief value of linseed and other 8drying oils0 depends4 ,linseed oil is chiefly adulterated with other seed oils1 cottonseed being the most often used for this purpose1 though menhaden and various other fish oils are occasionally employed4 ,as the density of raw linseed oil varies between #jicb and #jicf at #ae ,c41 the addition of other seed oils or of mineral oil would cause an appreciable lowering of this figure1 whilst rosin or rosin oil would raise it4 ,a judicious admixture of both mineral and rosin oils would give a product of normal density4 ,fish oils can be detected by their characteristic smell1 especially on warming4 ,various methods have been proposed for judging the quality of linseed oil1 but none of them are perfectly satisfactory4 ,the best oil is that which dries the most perfectly2 but the rapidity of the drying1 and the consistency of the dried product1 are most important factors which must also be taken into account4 ,the iodine-valve1 which is a measure of the drying power1 should not fall much below #ahj4 ,a satisfactory practical test1 recommended by ,allen1#afb consists in mixing the oil with three times its weight of genuine white lead1 and covering a perfectly clean glass surface with the paint4 ,an exactly similar experiment is made simultaneously with a standard sample of linseed oil1 and the rates of drying and the characters of the coating of paint compared4 #afb ,commercial ,organic ,analysis1 ii4 p4 #abb4 ,j4 ,muter has simplified this test by merely flooding a plate of glass with the oil and then exposing it to a temperature of #ch ,c4 7#ajj ,f47 in a good current of air4 ,the time required for drying1 to such an extent that the coating will not come off when lightly touched1 is noted1 and compared with standard samples of oil4 ,by applying the finger at intervals to different parts of the film surface the progress of the drying can be readily observed4#afc #afc ,kathreiner states that this method is a useful test for fish and liver oils1 those which dry most rapidly being specially liable to 8spue40 ,boiled ,oils4--,its capacity for thus drying is much enhanced by heating1 with addition of 8driers10 to a temperature of #acj ,c4 and upwards1 while passing a current of air through the oil and then increasing the temperature until the oil begins to effervesce 78boil074 ,large quantities of linseed oil are now treated in this way for use in the arts4 ,the driers used are metallic salts1 principally those of lead and manganese1 which apparently act as oxygen-carriers4 ,litharge was formerly most commonly used1 but its place has been taken to a considerable extent by acetate1 borate and resinate of manganese4 ,from #a to #b per cent4 of either litharge or manganese borate may be used1 though less quantities produce a marked effect4 ,apparently litharge gives the most rapid drying1 and manganese a much paler colour4#afd ,linseed oil is usually darkened by boiling1 and increases both in actual weight and in specific gravity and viscosity4 ,the chemical reactions which take place in boiling are not well understood1 but it is in the main a process of oxidation and polymerisation1 perhaps accompanied by the formation of anhydrides of the fatty acids1 and a portion of the drier remains dissolved in the boiled oil4 ,these driers may be detected by boiling an ounce or so of the oil with dilute hydrochloric acid1 allowing the mixture to separate into two layers and then syphoning off the lower into another vessel1 and testing for metals 7lead1 manganese1 zinc7 or acids 7boric1 oxalic1 etc474 #afd ,cp4 ,f4 ,h4 ,thorpe1 ,abst4 ,jour4 ,soc4 ,chem4 ,ind41 #ahij1 #fbh1 from ,technology1 ,quart41 iii4 pp4 #i-af4 ,black japan for patent leathers is made by boiling linseed oil1 without blowing air through it1 for at least seven or eight hours1 with ,prussian blue1 or with oxides of iron4 ,the japan is brownish rather than blue in colour1 and it is probable that the ,prussian blue serves merely as a source of iron oxide1 which acts both as a colouring matter and a drier4 ,other driers1 such as litharge1 are sometimes added1 and for coloured enamels other pigments are substituted for the ,prussian blue4 ,cotton-seed ,oil 7,fr4 ,huile de coton2 ,ger4 ,cottonoel or ,baumwollensamenoel7 is now expressed in enormous quantities in the ,united ,states1 on the continent of ,europe and in ,great ,britain4 ,the crude oil contains a very characteristic colouring matter which1 though naturally ruby red1 is sometimes so intense as to make the oil appear to be nearly black4 ,this colouring matter causes the oil to produce stains1 and is therefore removed by a process of refining1 and a product of a straw- or golden-yellow colour is thus obtained4 ,the refining is usually effected by shaking the crude oil with a cold #e per cent4 solution of caustic soda1 using about ten times as much oil as soda solution4 ,cotton-seed oil is1 on account of its price1 seldom or never adulterated1 but is itself frequently employed as an adulterant of olive and neatsfoot oils4 ,it is a semi-drying oil1 and unsuitable for most purposes in leather manufacture4 ,for a description of its characteristic properties1 both chemical and physical1 the reader is referred to ,lewkowitsch's #8,oils1 ,fats and ,waxes1' or to ,allen's #8,commercial ,organic ,analysis1' vol4 ii4 ,sesam ,oil 7,fr4 ,huile de ssam2 ,ger4 ,sesamoel2 ,teel oil1 ,gingeli oil7 is another seed oil1 usually of paler colour than cotton-seed oil1 but resembling it in having scarcely any odour1 and possessing a bland and agreeable1 though not very characteristic taste4 ,it is often used as an adulterant of olive oil4 ,sesam oil is a non-drying oil1 which does not easily turn rancid4 ,when present in other oils1 it may be detected by agitating #aj c4c4 of the sample with #e c4c4 of concentrated hydrochloric acid in which #ja grm4 of white sugar has previously been dissolved4 ,after shaking together for at least ten minutes1 the oil and acid are allowed to separate1 when1 if sesam oil be present1 the acid layer will have a marked rose colour1 the intensity of which increases with the amount of sesam oil in the sample 7,baudouin's test74 ,sesam oil is largely used in ,india for oiling tanned sheep- and goat-skins 78,persians071 and has the characteristic property of being assimilable in large quantities by leather without the latter appearing oily4 ,east ,india tanned skins often contain #be and even #cj per cent4 ,the oil is applied to them in the wet condition before they are dried4 ,it is easily detected in the oils extracted from these skins by ,baudouin's test4 ,the oil seems well adapted for many purposes in leather manufacture4 ,cod ,oil 7,fr4 ,huile de morue2 ,ger4 ,leberthran7 is by far the most important oil used by leather manufacturers1 and is obtained from the liver of the common cod-fish 7,gadus ,morrhua7 and several other members of the genus ,gadus4 ,the chief seats of the cod fishery are the coasts and banks of ,newfoundland1 ,nova ,scotia1 the ,gulf of ,st4 ,lawrence1 the coasts of ,norway1 ,denmark and ,germany1 the ,dogger ,bank in the ,north ,sea1 and the shores of ,alaska in the ,pacific ,ocean4 ,the oil was formerly obtained by keeping the livers of the fish in large wooden vats1 stirring constantly until so much decomposition has taken place that the cells containing the oil burst1 and the oil thus released rises to the surface and is skimmed off with wooden ladles4 ,the crude oil is allowed to deposit any suspended matters by sedimentation in a tank1 and is then poured into casks ready for sale4 ,the 8brown oil0 so often used by tanners is obtained by boiling the solid matter left after extracting the oil as above in iron tanks until all the water has evaporated2 the oil thus liberated is then strained off1 clarified and put into barrels4 ,the purer qualities of cod-liver oil are now obtained by boiling the livers with water and skimming off the oil which rises to the surface4 ,three grades are on the market at the present time3 medicinal1 or ordinary bright2 an inferior 8light brown02 and 8dark-brown10 or 8tanners' oil40 ,it is probable that these steam-extracted oils are much more liable to 8spue0 than those extracted by the old method at a higher temperature1 since ,eitner#afe has shown that seal oils extracted at a low temperature spue badly1 but lose the tendency if heated for some time to #bej-cjj ,c4 #afe ,gerber1 #ahhj1 p4 #bdd4 ,genuine cod oil1 as suitable for use in leather manufacture1 is always more or less brown in colour1 of specific gravity about #jibh1 and refractive index #adhb4 ,at present prices it can only be adulterated with other fish oils1 rosin1 or mineral oil1 or with water1 gelatine or mucilage4 ,of these1 rosin oil and petroleum are the most frequently employed in sophistication4 ,an inferior variety of oil1 known as 8coast cod10 made from the livers of various fish1 such as ling1 haddock and hake1 is also sold1 but1 as it is frequently mixed with oils from other fish refuse1 it has a very poor reputation4 ,cod oil1 together with most of the other oils obtained from fish livers1 has the property of producing an intense reddish-violet colour when a drop of strong sulphuric acid is dropped upon ten or fifteen drops of the oil contained in a white porcelain tray or saucer4 ,the reaction succeeds still better1 if1 instead of the oil itself1 its solution in chloroform1 carbon disulphide or tetrachloride is employed4 ,this test1 although very useful for the detection of liver oils when they are present in oils of a totally different character1 such as rape or olive oils1 does not in any way indicate whether a sample of fish oil is pure or otherwise4 ,a very similar reaction is given by cholesterol which is present in wool-fat4 ,shark-liver ,oil 7,fr4 ,huile de requin2 ,ger4 ,haifischthran7 is obtained from the liver of the 8basking shark10 or 8ice-shark10 chiefly caught off the coast of ,norway2 but the livers of the dog-fish and several allied fish also are sometimes substituted4 ,shark oil has been employed in tanneries as a substitute for cod-liver oil1 but1 according to ,lewkowitsch1 and to ,allen1 it is no longer employed in ,england4 ,from its pale colour it is probably principally used to improve the appearance of darker oils4 ,according to ,eitner1#aff its use causes leather to 8spue0 badly if not previously heated4 #aff ,gerber1 #ahhf1 p4 #bff4 ,shark oil is characterised by the very notable proportion of unsaponifiable matter which it contains1 which is of the same character as that of sperm oil1 and not easily removed from its soap solution by petroleum ether4 ,it gives a strong violet-blue coloration with concentrated sulphuric acid1 the reaction being even more marked than with cod-liver oil itself1 and of a bluer violet4 ,whale ,oil 7,fr4 ,huile de baleine2 ,ger4 ,wallfischthran7 is extracted from the blubber of various species of whale1 and often contains traces of spermaceti1 the substance which characterises the oil from the sperm whale4 ,this yields on saponification higher alcohols1 which are found in the unsaponifiable matter2 but in ordinary whale oil the total unsaponifiable matter seldom exceeds #a to #b per cent4 ,whale oil is largely used on the ,continent for 8chamoising0 7q4v471 and is consequently a constituent of dgras4 ,it is much less oxidisable than cod4 ,seal oil 7,fr4 ,huile de phoque2 ,ger4 ,robbenthran7 is obtained from the common rough-coated seal1 abundant in the ,arctic regions4 ,it bears a strong resemblance to both whale and fish oils1 and cannot be detected in mixtures of these4 ,the ,swedish 8,dreikronenthran0 7,three ,crown ,oil7 is a mixture of seal and fish oils4 ,as genuine seal oil only contains about per cent4 of unsaponifiable matter1 its adulteration by mineral or resin oils may be detected by a determination of the matter extracted by petroleum ether after saponification of the oil 7see ,l4,i4,l4,b41 p4 #agh74 ,there is no simple test by which the purity or otherwise of a sample of oil can be determined1 as the dealers know all the best tests which the users could try1 and fake up their oils accordingly4 ,for instance1 if petroleum is to be added surreptitiously to a cod oil1 the decrease in specific gravity of the oil caused by this addition would be corrected by the addition of a suitable quantity of soap or rosin oil1 which would scarcely affect the colour1 taste or odour of the sample4 ,the only satisfactory method of detecting adulteration is to submit the oil to a complete chemical examination1 and for this purpose ,l4,i4,l4,b41 pp4 #aef et seq41 or the larger text-books already named may be suitably consulted4 ,menhaden ,oil 7,porgie oil1 ,straits oil7 is largely used in certain districts as an adulterant or substitute for cod oil4 ,it is obtained from the ,alosa ,brevoordia or menhaden1 a member of the herring family1 about a foot long4 ,the fish is caught on the ,atlantic coast of ,america1 and is so plentiful that it is very doubtful whether cod oil can ever compete with it successfully in price4 ,the fish are boiled in steam kettles1 the oil squeezed by hydraulic presses1 clarified1 and bleached by exposing to the sun in shallow glass-covered tanks4 ,an inferior grade is known as 8,bank oil40 ,menhaden oil is chiefly characterised by its very high 8specific temperature reaction0 7,l4,i4,l4,b41 p4 #afi7 which is about #cjf4 ,it is not a good leather-oil1 being very liable to 8spue40 ,many other varieties of oil extracted from the bodies1 and not from the livers only of fishes1 are classed as fish oils4 ,menhaden oil is the principal of these2 but ,japanese oil1 sardine and herring oils1 and those obtained from the refuse of other fish are scarcely less important1 though as they are derived from such different sources it is not possible to quote any definite characteristics by which they may be identified when mixed with more valuable oils4 ,they are usually very liable to 8spue40 ,fish ,tallow1 which1 according to ,eitner1 is a good and cheap substitute for dgras1 is the solid grease obtained from different kinds of fish oil by subjecting them to a low temperature and separating the matter which is thus precipitated1 or 7as in ,china and ,japan7 the solid fat which is extracted at the same time as the oil from the body of the fish4 ,formerly fish tallow was only obtained from and with ,japanese train oil1 but it is now obtained from whale blubber4 ,this latter yields a very pure form of the tallow1 which does not need any rectification2 but the ,japanese variety1 which is obtained from fish of the herring family1 contains a sort of fish glue1 which greatly deteriorates the quality of the product4 ,by careful purification1 however1 this glutinous matter may be removed1 and the refined product has none of the leather-staining properties so characteristic of the crude tallow4 ,the refined tallow is sold in square flat cakes1 melts at #db and is not quite so stiff as ox tallow4 ,dgras and ,sod ,oil are products of chamois-leather dressing 7p4 #cgh7 which are used in currying4 ,skins are treated with marine animal oils1 and submitted to oxidation1 and the surplus and partially altered oil is recovered4 ,in the ,french method1 whale and seal oils as well as liver oils are used1 and the oxidation is slow and gradual1 and the residual oil1 being liquid1 is recovered by pressure1 and constitutes moellon1 of which the first pressing 7premire torse7 is the best4 ,this is never sold for currying in its original purity2 but1 mixed with further quantities of fish oils1 tallows1 and sometimes wool-fat1 it constitutes the ordinary dgras of commerce4 ,the additions1 though they lower the value1 are not to be considered as simple adulterations1 since the moellon alone would be less suitable for the purpose4 ,after removal of as much oil as is possible by dipping in hot water and pressing1 a further quantity is recovered by washing with solutions of potash or soda1 from which it is separated by addition of acid1 and constitutes a lower quality of degras4 ,the moellon is of such value as a currying material1 that factories are run in which chamoising is carried on solely for its production1 the skins being oiled and oxidised repeatedly1 till reduced to rags4 ,in the ,english method of chamoising1 liver oils are almost exclusively used1 and the oxidation is much more rapid and intense1 the skins being packed in boxes or piled1 and allowed to heat4 ,the product obtained in this way is much more viscous1 and can only be recovered by scouring with alkalis2 and the product1 recovered with acid1 constitutes sod oil4 ,in many ,english factories1 a modified method is now adopted1 and a product recovered by pressure1 which scarcely differs from moellon4 ,an important peculiarity of dgras and sod oil is its ready emulsification with water1 which from its mode of preparation1 it always naturally contains1 and which should be present in a good dgras to the extent of not less than #bj per cent4 ,such a mixture1 containing water1 is a sort of natural fat-liquor and is absorbed much more perfectly by the skins than an oil alone4 ,sod oils1 however1 are frequently 8evaporated10 or deprived of water by heating above #ajj1 with the object not only of effecting a fancied improvement1 but of getting rid more completely of the sulphuric acid which the water is apt to contain4 ,this makes them more homogeneous1 and consequently much darker in colour4 ,it is not easy to neutralise the acid in an aqueous sod oil by direct addition of alkali2 possibly ammonia is best adapted for the purpose2 or a suggestion1 ,i think due to ,eitner1 may be adopted1 of incorporating a small quantity of a suitable soap4 ,in any case1 very complete mixture is required4 ,if the sulphuric acid used in recovery has been insufficient for complete neutralisation of the alkali1 the dgras or sod oil will naturally contain soaps1 and sometimes also free alkali4 ,free acid and free alkali are both injurious to leather1 the former if anything the more so1 darkening the colour1 and even rendering the leather tender4 ,when dgras is used in mixture with other fats1 care should be taken not to raise the temperature of the mixture so high as to drive off the water1 to which a good deal of its special efficacy is due4 ,the chemical changes which take place during the chamoising process are as yet incompletely understood4 ,a large proportion of the glycerine is dehydrated during the 8heating10 forming acrolein 7acrylic aldehyde71 to the action of which it is very possible that the actual conversion of the skin into leather is due1 while the fatty acids also undergo oxidation4 ,dgras therefore always contains considerable quantities of oxidised fatty acids1 which are sometimes associated with nitrogenous products from the skins1 and which are soluble in alcohol1 but insoluble in petroleum ether4 ,to these products ,simand gave the name of ,degrasbildner 7dgras-former1 ,fr4 dgragne71 and it has been considered a measure of the quality of the degras1 but its exact value and function is rather doubtful4 ,according to ,simand1 a genuine dgras should contain not less than #ae to #bj per cent4 of the dgras-former as estimated by his method1 calculated on the dry oil1 and a smaller percentage is also present in the original fish oils4 7,for method of estimation see ,l4,i4,l4,b41 p4 #ahb74 ,as the process of dgras manufacture is obviously mainly one of oxidation1 many attempts have been made to produce it by direct oxidation of fish oils1 without the agency of skins1 both by blowing air through the oil1 and by addition of oxidising agents such as nitric acid4 ,eitner states that such oxidised oils are more liable to 8spue0 than the original oils1 as they already contain large quantities of resinised products2 but this is certainly not true of all artificial dgras1 some of which answers its purpose perfectly as a currying material1 though it is very probably justified in other cases4 ,of course the methods of successful manufacturers are kept as profound secrets4 ,dgras and sod oil1 when deprived of water1 are dark and viscous oils1 of high specific gravity 7#jide-jiee71 and therefore heavier than the oils which have been employed in their manufacture4 ,,waxes1 as has already been stated1 differ in their chemical character from true fats1 in that their fatty acids1 which are mostly of high molecular weight1 are combined1 not with glycerine1 but with alcohols1 also of high molecular weight and of wax-like consistency4 ,most waxes are solid bodies of high melting point1 but some oils1 especially sperm and bottlenose oils1 are chemically liquid waxes2 woolfat contains a considerable proportion of waxes2 and many marine oils1 such for instance as shark-liver oil 7p4 #cff71 contain waxes in smaller quantity in mixture with true fatty oils4 ,sperm ,oil 7,fr4 ,huile de cachalot2 ,ger4 ,spermacetioel1 ,walratoel7 is obtained from the sperm whale1 an inhabitant of the ,antarctic seas4 8,arctic sperm0 7,ger4 ,doeglingthran7 is a very similar oil obtained from the 8,bottlenose whale40 ,these oils are very fluid1 do not dry1 and are excellent lubricating oils for light machinery1 and also good lamp oils4 ,they contain little if any glycerides1 and about #dj per cent4 of unsaponifiable solid alcohols1 which are soluble in ethyl-alcohol1 and must not be confused with ordinary unsaponifiable mineral oils1 which are frequently used as adulterants in mixture with fatty oils to adjust gravity and the 8saponification value40 ,mineral oils are liquid1 and insoluble in alcohol4 ,sperm oil is the lightest of ordinary oils1 its gravity being only about #jhhj at #ae ,c4 ,from its price it is particularly liable to sophistication4 ,it is used in leather manufacture in the finishing of some fine leathers1 and sometimes as a constituent of fat-liquors4 ,spermaceti1 a wax also obtained from the sperm whale1 is an occasional constituent of leather polishes4 ,beeswax 7,fr4 ,cire des abeilles2 ,ger4 ,bienenwachs7 is one of the most important waxes for the leather-dresser4 ,as is well known1 it is obtained from the honeycomb of the ordinary bee4 ,it is a yellowish solid body1 fairly plastic when fresh1 and of 8waxy0 feel4 ,at low temperatures it is brittle and of fine granular texture1 and when pure is almost tasteless4 ,it is often bleached by repeated melting and exposure to sunlight4 ,as wax always contains a considerable amount of pollen it may be identified when in admixture with other substances by means of the microscope4 ,beeswax is almost insoluble in cold alcohol1 but boiling alcohol dissolves out the contained cerotic acid1 which crystallises from it on cooling4 ,wax is saponified by alcoholic potash1 but the resulting myricyl alcohol 7about #ed per cent47 is not capable of further saponification4 ,beeswax is frequently adulterated4 ,water and mineral matters 7ochre1 gypsum1 etc47 also flour1 starch1 tallow1 stearic acid1 ,japan wax1 carnaba wax1 resin and paraffin-wax are among the substances most commonly used in its sophistication4 ,the detection of these1 and especially of the other waxes1 is so difficult that it will not be described here4 ,the reader is1 however1 referred to ,benedikt and ,lewkowitsch's #8,oils1 ,fats and ,waxes1' for further information4 ,carnaba ,wax 7,fr4 ,cire de carnauba2 ,ger4 ,cearenwachs1 ,carnaubawachs7 has come largely into use recently owing to the advent of the coloured leather shoe4 ,as it is a very hard wax it has become very popular with boot polish makers1 its low price being also in its favour4 ,carnaba wax is an exudation from the leaves of ,copernica cerifera1 a palm indigenous to ,brazil1 and is1 on this account1 often known as ,brazilian wax4 ,it is difficult to saponify1 and with different experimenters has yielded very varied results on analysis2 it is generally agreed1 however1 that it is a complicated mixture of several of the higher alcohols and acids4 ,japan ,wax is not a true wax1 but a fat consisting of glycerides4 ,it is a pale yellow1 hard1 waxy substance obtained from the berries of a sumach 7,rhus succedanea1 etc474 ,at ordinary temperatures its specific gravity is exactly that of water1 and it melts at #ef ,c4 ,any admixture with other fats would lower the melting point1 but japan wax is often adulterated with #ae to #cj per cent4 of water4 ,it is chiefly valuable to leather dressers as a substitute for beeswax on account of its lower price4 ,,volatile ,,or ,,essential ,,oils4 ,these oils are distinguished from those described in the previous section in that they are capable of distillation without undergoing any serious amount of decomposition4 ,they occur to some considerable extent in nature1 but those of most importance to the leather trade are produced by the decomposition of more complicated materials4 ,birch ,oil is by far the most important of this class of oils so far as the leather-dresser is concerned1 since it is the substance which gives to 8,russian leather0 its characteristic odour4 ,the oil is obtained by destructive distillation1 and the process by which the peasants conduct this is one of the rudest that can be imagined4 ,a cauldron is filled with dry birch-bark1 closed1 and heated over a fire4 ,the vapours which are evolved are carried1 by means of a pipe1 to another vessel which is buried in the ground1 and are there condensed4 ,the dark-brown liquid 7birch-tar7 is allowed to cool1 and the liquor which rises to the surface skimmed off4 ,the tar is sometimes distilled1 and an oil is thus obtained which does not give the true birch-oil scent very strongly though occasionally sold as a refined oil4 ,the true odorous substance is evidently of very high boiling point and remains mainly in the tar4 ,the birch tar is almost entirely used for giving leathers a 8,russian0 odour1 for although it smells somewhat strongly of tarry products1 the oils causing this smell are far more volatile than the birch scent itself1 and therefore disappear on storing the leather a short time4 ,tar obtained from various species of pine is sometimes substituted for birch tar1 but it may readily be distinguished from the latter by the odour and the difference in the specific gravity4 ,birch tar has a specific gravity of #jibe to #jide1 whilst fir tar has one of #ajb to #aje2 thus the former floats on water while the latter sinks if it be entirely free from enclosed air4 ,fir tar1 too1 gives up a yellow colouring matter to water shaken up with it1 while birch tar leaves the water colourless4 ,birch tar has a distinctly acid reaction1 and must not be kept in iron vessels4 7,see p4 #bea74 ,the leaves and twigs of ,american black birch when distilled with water or steam1 yield an oil which is practically identical with that of ,gaultheria procumbens 7wintergreen71 and consists almost entirely of methyl salicylate4 ,it is clarified1 and to some extent decolorised1 by filtration through woollen blankets and redistillation4 ,a ton of brushwood is said to yield about four pounds of oil4 ,this oil has quite a different odour to that of the real ,russian oil1 and cannot be used in the scenting of 8,russia0 leather4 ,sandalwood oil with a little black birch or wintergreen oil is sometimes employed for scenting small fancy articles and bears considerable resemblance to the true 8,russia0 leather odour4 ,black birch1 aniseed1 sassafras and various other essential oils are occasionally used in small quantities as preservatives1 and to cover disagreeable odour in blood-seasonings1 cements and other products used in the leather trade4 ,the methods employed for their detection and estimation do not1 however1 come within the scope of a work such as the present one4 ,most essential oils have considerable power as antiseptics1 and in preventing mildew and the attacks of insects4 ,,mineral ,,oils ,,and ,,waxes4 ,this class of bodies is totally different in chemical constitution from the true oils and waxes1 containing neither glycerides1 fatty acids nor alcohols1 but consisting of carbon and hydrogen only1 approximately in the proportion of one atom of the former to two of the latter4 ,they occur in underground lakes1 from which they are obtained by springs or borings2 or in shales1 from which they are separated by distillation4 ,it is commonly supposed that they have been formed1 at some remote period of the earth's history1 by the decomposition of animal and vegetable matters1 at a high temperature and under great pressure4#afg #afg ,oils from wells or springs are technically called 8petroleum oils10 those from shale1 8paraffin0 oils1 but chemically1 there is no definite distinction4 ,the mineral oils and waxes are largely capable of being distilled without decomposition1 but if heated to high temperatures1 are readily 8cracked0 or broken up into simpler and generally more volatile compounds--a fact which is employed in the production of gas1 and the utilisation of some of the heavier products4 ,they differ greatly in their gravity and boiling-point1 but not much in their ultimate composition1 consisting largely of saturated or nearly saturated hydrocarbons 7cp4 p4 #ced71 and hence are little liable to oxidation1 and acted on by few chemical reagents4 ,from their constitution they are of course unsaponifiable1 and in this way can be separated from fats and oils with which they have been mixed4 7,for particulars of the method see ,l4,i4,l4,b41 p4 #agh47 ,the heavier mineral oils are a good deal used in mixture with other oils and fats1 for stuffing leathers1 those of a specific gravity of #jhhj-jijj being usually most suitable4 ,they are quite incapable of 8spueing10 and are useful in lessening that tendency in other oils with which they are mixed4 ,they have not1 however1 the same affinity for the leather fibre as some of the true oils1 and are to a certain slight extent volatile1 and should generally be used in mixture1 rather than alone4 ,most mineral oils1 when held so that a strong light 7daylight or electric light rich in ultra-violet rays7 falls upon them1 show a green or violet fluorescence or 8bloom40 ,this is very persistent1 even when the oil is mixed with a large volume of other oils1 and is often relied upon as a means of detecting them when used as adulterants4 ,the test is1 however1 not infallible1 since the effect is due to impurities which may be removed by purification1 or masked by the addition of such substances as nitrobenzene or nitronaphthalene1 and it also occurs in the hydrocarbon products produced in the distillation by steam of animal oils1 and is occasionally seen to some extent even in oils which have not undergone distillation4 ,vaseline and ,vaseline ,oil are the most viscous and densest of the petroleum oil products4 ,they probably differ from the solid paraffins in chemical constitution1 though their ultimate composition is almost the same4 ,they are often useful constituents of stuffing greases4 ,paraffin ,wax consists of a mixture of hydrocarbons similar in chemical constitution to the paraffin and petroleum oils1 but of higher boiling point1 and solid at ordinary temperatures4 ,its hydrocarbons are mostly saturated1 and hence very stable bodies1 and little liable to oxidation4 ,they are completely unsaponifiable1 and unaffected by boiling with alcoholic potash1 and in most cases by boiling with strong sulphuric acid1 by which they may be separated from animal and vegetable waxes or fats with which they have been mixed4 ,they are quite incapable of resinising by oxidation1 or of causing 8spueing0 in leather4 ,they are soluble in petroleum spirit1 carbon disulphide and most of the ordinary solvents of fats1 but insoluble in alcohol4 ,paraffin wax separates from the liquid oils by crystallisation on cooling1 and the remaining liquid which adheres is removed by hydraulic pressing1 as in the case of tallow4 ,the hardness and melting point vary according to the extent to which the pressing has been carried1 and the temperature at which it has been done4 ,the paraffins of higher melting point are as a rule the more costly4 ,pure paraffin wax is a white1 more or less hard and brittle substance which does not melt so easily as ordinary fats1 and is on this account used in stuffing certain kinds of leather1 hardening the stuffing grease1 and making the leather feel less oily4 ,when melted1 paraffin wax forms a thin liquid1 more resembling an ordinary petroleum lamp oil than the viscous vaselines and leather oils4 ,on ignition it burns with a bright somewhat smoky flame1 and leaves no ash behind4 ,it is found on analysis when mixed with other waxes or oils in the 8unsaponifiable matter0 7see ,l4,i4,l4,b41 p4 #agh74 ,ozokerit is a natural paraffin material used for the manufacture of cerasin candles1 which sometimes occurs in the vicinity of petroleum springs1 especially in ,galicia4 ,it is of pale yellow colour when pure1 and has then a melting point of about #gj ,c4 ,its chief impurities are petroleum oils1 water and clay4 ,these are removed by melting the ozokerit1 decanting off the clear oil1 and filtering it through fine animal charcoal4 ,if liquid oils are present the material is treated with alkali or with strong sulphuric acid1 and is pressed before filtering through charcoal4 ,the refined product is termed 8cerasin10 and is of a more waxy and less crystalline texture than ordinary paraffin wax4 ,the ,resin ,oils are derived from resins1 and mainly from colophony or common pine rosin1 by destructive distillation4 ,their specific gravity ranges from #jif to #jii1 but their chemical composition is very imperfectly understood1 and appears to be by no means constant4 ,like the mineral oils they are 8unsaponifiable10 but often contain small amounts of soap-forming material 7resin acids74 ,the detection and estimation of resin oils is often a matter of considerable difficulty1 but further particulars on this point will be found in ,l4,i4,l4,b41 p4 #ahj4 ,from their cheapness1 they are considerably employed as adulterants of other oils1 and their high gravity makes them convenient to adjust the gravity of mineral oils when used for this purpose1 as the latter are usually lighter than the fatty oils4 ,as currying oils1 they are not particularly suitable1 though often employed in stuffing picker bands1 and other heavily greased leathers4 ,they have considerable antiseptic powers1 and for this reason are useful in leather greases1 preventing heating1 and checking mildews4 ,resin itself is occasionally used as an addition to stuffing greases1 and is said to increase the waterproofness of the leather1 and to give it a drier feel4 ,in mixture with about half its weight of paraffin wax1 and with a little grease if necessary to soften the mixture1 it is often used in waterproofing mixtures1 which can be made to melt at #ej to #fj ,c4 ,leather will bear immersion in the melted mixture without scalding if thoroughly dried in a hot stove at a temperature of not less than #ej ,c4 before dipping4 ,any great increase of the proportion of paraffin wax causes the rosin to separate4 ,rosin consists mainly of free acids which easily combine with alkalies and alkaline carbonates in boiling4 ,it is hence largely used in the manufacture of soaps on account of its cheapness1 and to render them more soluble in water4 ,the rosin acids are not so strong as many of the fatty acids1 and rosin soaps are therefore somewhat strongly alkaline4 ,rosin soap1 precipitated among the ground paper pulp in the rag engine1 by addition of alum or sulphate of alumina1 is largely used as a sizing for common papers4 ,,chapter ,,xxiv4 ,,oil ,,tannages1 ,,and ,,the ,,use ,,of ,,oils ,,and ,,fats ,,in ,,currying4 ,the conversion of skin into leather by the agency of oils and fats is probably one of the most primitive methods1 and is used in different ways suited to the skins and fats which are available1 by savage races in all quarters of the globe4 ,in its simplest form1 it consists merely in oiling or greasing the wet skin1 and kneading and stretching it as it slowly loses moisture and absorbs the fat4 ,under these conditions1 the fibres become coated with a greasy layer1 which prevents their adherence after they are once separated by the mechanical treatment4 ,at the same time some chemical change takes place in the fibre itself1 which has a part in its conversion into leather varying in importance according to the method and fat employed1 and of which the chemistry will be best discussed after some slight sketch has been given of the methods themselves4 ,the most complete sort of oil-leather is that produced by 8chamoising10 or oil-dressing with marine oils1 a process applied to the ordinary 8chamois0 or 8wash-leathers0 7now made from the flesh-split or 8lining0 of the sheep-skin71 and to the manufacture of 8buff-leather0 for military purposes4 ,the process varies somewhat according to the character of the leather1 but the manufacture of the common wash-leather may be taken as a type4 ,for this purpose the sheep-splits are freed from the loose and fatty middle layer 7p4 #ea7 by 8frizing0 with a sharp knife on a beam similar to that used for fleshing 7,fig4 #cj1 p4 #adg71 but much more steeply inclined4 ,the process is rather one of scraping than cutting1 and was originally adopted to remove the grain from the deer-skins which were largely used for glove-leathers1 since oil-dressing does not easily penetrate a skin with the grain surface intact4 ,the fleshes are usually delimed by drenching1 but removal of fat is unimportant4 ,after being well drained1 they are 8stocked0 for some time with sawdust till they become partially dry and porous1 the common 8faller0 stocks shown in ,fig4 #bb1 p4 #aaf1 being generally employed4 ,during the stocking1 care must be taken that the goods are not overheated by the friction produced4 ,when the skins have become opaque from the inclusion of air between the fibres1 they are1 according to the ,continental method1 shaken out and oiled on the table1 and after folding into bundles1 are put back in the stocks4 ,in ,england1 the oil is usually added to them during the stocking1 in small quantities1 which become rapidly and evenly distributed by the motion of the skins4 ,in ,england1 cod oil is almost exclusively employed1 but on the ,continent1 a considerable proportion of seal and whale oils is used4 ,as the goods are apt to heat1 not only from friction1 but from the oxidation of the oils employed1 they are removed from the stocks at intervals1 and allowed to cool1 usually hung on hooks exposed to the air4 ,in ,france this exposure to the air is much more considerable than in ,england1 the skins being hung for eight or twelve hours after each stocking4 ,the drying rooms are kept moderately warm1 and a good deal of oxidation of the oil takes place in them1 which materially affects the character of the product1 and especially of the residual oil or dgras1 which is afterwards squeezed out of the skins and used for currying 7p4 #cfh74 ,great care is required to prevent any parts of the skins becoming dry before they are completely saturated by the oil1 which causes hard and transparent patches which the oil will not afterwards penetrate4 ,after each exposure to the air1 the skins are oiled on the table and returned to the stocks4 ,the stocking has to be continued for many hours1 even for wash-leather2 and as it proceeds1 the skins lose the smell of limed skin1 and acquire a peculiar mustard-like odour from the volatile products of oxidation of the oils4 ,when the skins are completely saturated1 they are1 according to the ,english method1 packed in boxes1 and allowed to heat spontaneously by oxidation of the oils1 during which great care is required1 especially at the outset1 that the heat does not rise so high as to destroy the skins4 ,to prevent this1 they are removed at intervals from the boxes and spread on the floor to cool1 and then re-packed1 and this treatment is continued until the oxidation is complete1 and the skins cease to heat4 ,during the heating1 large quantities of volatile and very pungent products are given off1 and especially acrolein 7acrylic aldehyde1 from the dehydration of the glycerine71 which is excessively irritating to the eyes4 ,the ,german method is not unlike the ,english1 but in ,france1 the packing in boxes is omitted1 and the oxidation is completely effected in warm stoves in which the goods are hung on hooks4 ,the heating in this case is much more moderate1 and the oil less thickened1 a result which may be partly due to the different oils employed1 and which leads to differences in the subsequent treatment of the leather4 ,in the ,french process1 the oily skins are dipped in hot water and wrung or hydraulic pressed1 the expressed oil constituting moellon or dgras 7p4 #cfh71 and the skins are afterwards washed in a hot soda or potash solution1 from which a further portion of an inferior dgras is recovered4 ,in the old-fashioned ,english method1 the oil became so thickened that it could not be pressed out1 and the whole was removed by washing with soda or potash solution1 from which it was recovered by the use of acid1 constituting 8sod oil0 7p4 #cfi47 ,now many ,english manufacturers adopt a modified method1 and remove a good deal of their oil by pressure4 ,buff leather1 much used for military accoutrements1 is made in a similar manner to chamois1 from ox or cow hides1 the grain of which is frized off4 ,the bleaching1 both of buff and chamois1 is done by exposing to the sun in a damp condition1 the skins being watered as required with water or fat-liquor1 or the alkaline emulsion of dgras obtained in washing the skins4 ,it may also be bleached by oxidising agents1 such as permanganate of potash or acidified sodium peroxide4 ,if permanganate is used1 the leather is treated in a solution of perhaps #e grm4 per liter till of a deep brown colour1 and then in a solution of sulphurous or oxalic acid till the colour is removed4 ,messrs4 ,j4 and ,e4 ,pullman1 of ,godalming1 make a species of buff leather1 which they style 8,kaspine0 leather1 by treating limed and drenched hides or skins in a drum with a very dilute solution of formaldehyde 78formalin07 rendered alkaline with sodium carbonate 7,eng4 ,pat4 #bhgb1 #ahih74 ,the change to leather takes place very rapidly1 and the leather is afterwards treated with soap solutions of fat-liquors1 to feed and soften it4 ,it is almost indistinguishable from genuine buff leather1 except from the fact that it is white throughout1 and needs no bleaching4 ,it is finding considerable application for military purposes4 ,a type of leathers which bear a close chemical relation to oil-leathers1 is that including 8,crown10 8,helvetia10 and fat-tanned leathers4 ,the first leather of the sort was invented by a ,german cabinet-maker named ,klemm1 by whom the secret was sold to ,preller1 who manufactured it in ,southwark1 under the name of 8,crown0 leather4 ,klemm used flour1 ox-brains1 butter1 milk1 and soft fat1 which was made into a paste with water1 and spread on the limed1 drenched and partially dried skins1 which were rolled into bundles1 and drummed in slightly warmed drums for some hours2 taken out1 again dried slightly1 and coated with the mixture1 and again drummed4 ,for thick hides the process was repeated a third time1 drumming in each operation for about eight hours4 ,the leather was used for laces1 picker-bands1 light belts1 and other purposes where great toughness and flexibility were required4 ,it was found by further experience 7if indeed1 it was not known to ,klemm himself7 that the only really essential ingredients of the mixture were the soft fats and flour2 and even the latter could1 for some sorts of leather1 be dispensed with4 ,it was further ascertained that only the gluten or albuminous part of the flour was absorbed by the leather1 the starch serving mainly to facilitate the emulsification of the fats4 ,the proportions used in the paste are about seven parts of flour1 seven parts of soft fat such as horse grease1 two parts of tallow1 four parts of water1 and a little salt or nitre to act as an antiseptic4 ,other greases1 such as mixtures of tallow and oil1 can be substituted for the horse grease1 and pipe-clay or ochre may to some extent take the place of the flour1 while soap may also be added4 ,the similarity of the mixtures used to the tawing paste in calf- and glove-kid dressing 7pp4 #aia1 #aif7 is obvious1 and ,klemm had an earlier process in which the operation just described was preceded by a slight alum tannage1 and which was almost identical in its detail with the methods now in use for the production of so-called 8raw-hide40 ,on the other hand it is nearly allied to the production of 8,riems10 or raw-hide straps in ,south ,africa1 for which a long thong is cut spirally from a hide1 and wound into a sort of skein which is suspended from a crossbar1 with a heavy weight at its lower end1 and oiled and twisted1 with frequent changes of position1 until the water is dried out1 and the thong is saturated with fat1 forming a very tough and durable leather4 ,a similar material can be made by fulling or otherwise working grease into a raw hide prepared for tanning4 ,eitner examined samples of 8,crown-leather0 chemically1 by removing the gluten of the flour with an alkaline solution1 and found that an imperfectly chamoised leather remained1 which when restuffed with fat1 was much less full1 and carried a much smaller quantity of grease than before4#afh #afh ,gerber1 #ahgh1 p4 #b4 ,various theories have been proposed to explain the reaction which takes place in the production of oil-leathers4 ,knapp supposed that it was merely a case in which the smallest fibrils of the hide were coated with the products of the oxidation of oils1 and so prevented from adhering together1 and protected from the action of water by the sort of waterproof coating which was formed4 ,this explanation is scarcely feasible in the face of the fact that chamois leather can be treated even with hot dilute solutions of the caustic alkalies without destruction1 while cotton fibres waterproofed by treatment with drying oils have their coating entirely removed by treatment with alkalies4 ,lietzmann supposed that the whole of the gelatinous fibres were removed in the liming and subsequent treatment1 and that the finished leather consisted only of the skeleton of yellow or elastic fibre which exists in the skin1 and which is remarkable for its resistance to heat1 acids and alkalis4 ,unfortunately the proportion of these fibres does not exceed about #f per cent4 of the total1 so that they are quite insufficient to account for the production of the leather4 ,we now know1 however1 that aldehydes1 including the acryl-aldehyde1 which is evolved in the oil oxidation of chamoising 7and which is covered by ,messrs4 ,pullman's patent7 are capable in themselves of converting gelatinous substances into a material identical in its properties1 and especially in its power of resisting hot water and alkaline solutions1 with the fibre of chamois leather4 ,in all cases where perfect chamoising is produced1 intense oxidation takes place1 and oxidisable oils are used which will evolve acrylic and other aldehydes4 ,where oils of little drying power are employed1 as in the case of ,crown- and other fat-leathers1 only an imperfect chamoising occurs1 and we are therefore justified in attributing the special qualities of chamois leather to a natural aldehyde tannage4 ,on the other hand1 there is no doubt that the coating of the fibres with oxidised oil-products really occurs1 and is probably a powerful factor in the leathering of ,crown-leather1 and other similar products which are not washed out with alkaline solutions4 ,knapp proved by treating raw pelt which had been dehydrated with alcohol 7p4 #gd7 with a very dilute alcoholic solution of stearic acid1 that a thin coating of stearic acid on the fibres would confer great softness and considerable resistance to water4 ,even where no stearic or other fatty acid is purposely added to alcohol used for dehydrating pelt1 traces are present from the decomposition of the natural fat of the skin1 and there is little doubt that this is the cause why such alcohol-leathers are much more difficult to wet back again to the state of pelt than would a priori be expected2 and why hide-powder dehydrated in this way is unsuitable for use in the hide-powder filter 7p4 #caa7 from its non-absorption of water4 ,illustration3 ,,fig4 #he4--,scouring large ,seal-,skins by ,hand4 ,it is not within the scope of the present volume to describe in detail the processes used in currying1 many of which are purely mechanical1 and of no theoretical interest1 whatever their practical importance2 and with which the writer hopes to deal fully in a future book4 ,the leather is usually scoured with stone1 brush and sleeker to free it from 8bloom0 and loose tan 7,fig4 #he72 or by machines such as ,fig4 #hf2 and is often reduced in thickness by shaving by hand 7,fig4 #hg71 or by machine 7,fig4 #hh74 ,in place of shaving1 hides and skins are frequently split into two or more thicknesses4 ,this is done by various machines1 of which the 8bandknife0 shown in ,fig4 #hi is the most important2 the cutting tool being a thin steel belt stretched like a bandsaw and sharpened on one edge by an emery-wheel4 ,illustration3 ,,fig4 #hf4--,scouring ,machine4 ,illustration3 ,,currying ,,shop1 ,,leather ,,industries ,,department1 ,,yorkshire ,,college4 ,something must be said here about the function of the oils and fats used in currying1 and their general method of application4 ,it is obvious that the possibility of coating the finest fibrils of leather with a fatty layer is not restricted to raw hide1 but is present1 sometimes even in a higher degree1 in tanned or tawed leathers1 in which the fibres are already so far isolated as to make the access of the fat easy4 ,even the possibility of an aldehyde-tannage is not excluded1 where the fibre is not already completely saturated with other tanning agents or where these agents1 from their nature1 have not so firm a hold on the fibre as to be incapable of being displaced by the action of aldehydes4 ,it is therefore obvious that we may apply some of the ideas which we have formed with regard to oil-tannages to the action of fats upon tanned leather4 ,in the first place1 it must be remembered that gelatinous matters are as a rule insoluble in fats2 and vice versa1 that fats are incapable of penetrating dry and solid gelatinous fibres4 ,if the skin becomes dry in the chamoising process1 that part remains raw4 ,it may therefore be concluded that fats and oils have little power in themselves of isolating the fibrils1 and that this must be accomplished by other agencies1 since if they are still adhering together1 the fats cannot penetrate them4 ,hence the necessity of moisture1 which keeps the fibres soft and divisible2 and with raw hide1 the importance of powerful mechanical treatment1 which will work the minute globules of fat between the fibrils4 ,in the case of tanned leathers1 the last condition is less important1 since the fibres are already isolated by the tannage1 and capillarity assists the penetration4 ,even in this case the distribution of the fat is much assisted if it is already in a state of fine division 7emulsification71 and if the surface-tension 7p4 #gf7 between it and water is low1 as is the case with dgras and other partially oxidised oils4 ,on this rather than on any special chemical affinity probably depends the importance of the 8dgras-former0 and other products of oxidation which are present in dgras2 and the difference in penetrating power of different oils4 ,so long as oil remains in an undivided condition1 so long can it be squeezed out1 and the leather will feel and appear greasy2 while1 when it is thoroughly emulsified1 and adherent to the fibre1 it can no longer be expelled by mechanical means4 ,no doubt the different power of different tannages to 8carry grease0 without appearing greasy1 is also related to the degree of isolation of the fibrils1 and their surface tension with regard to fats4 ,we may judge that the more readily an oil can be emulsified1 the more freely and completely it is likely to fix itself on the leather fibre4 ,illustration3 ,,fig4 #hg4--;,hand ,shaving4 ,illustration3 ,,fig4 #hh4--,shaving ,machine4 ,it is a practically invariable rule that the leather-fibre must be wet when it is stuffed4 ,the surface-tension between the water and the fats is less than that of either with regard to air2 and therefore1 as the water dries out of the small interstices of the leather1 the fat follows it in1 and gradually takes its place4 ,generally speaking1 the amount of water should be such that some exsudes in minute drops when the leather is pinched1 that is1 that not only the minutest spaces between the fibrils are filled1 but even the larger ones between the fibre-bundles to a considerable extent4 ,illustration3 ,,fig4 #hi4--;,band-,knife ,splitting ,machine4 ,in 8hand-stuffing10 the leather is now coated on the flesh side1 or occasionally on both sides with 8dubbing10 which is a pasty mixture of fats usually mainly composed of cod-oil and tallow1 which is applied rather thickly with a brush and smoothed down with the fleshy part of the forearm4 ,when such constituents are melted together1 the harder fats dissolve in the oils1 and as the mixture cools1 much of the hard fats again crystallise out4 ,to make a good dubbing1 the cooling fats must be stirred continuously till this has taken place1 as otherwise the mixture separates into little globular masses of crystals with liquid oil between them1 instead of forming a uniform body of salve-like consistency4 ,the proportions of the hard and soft constituents of the dubbing should be adjusted to the season1 and to the temperature at which the drying of the stuffed leather is to take place1 so that on the one hand1 the dubbing will not melt and run off1 and on the other1 that it should not solidify more than is necessary1 as only the liquid solution which remains entangled among the crystals can be absorbed by the leather4 ,the solid crystalline fats remain on the surface1 and are scraped off by the sleeker in finishing1 as 8table-grease10 which is generally re-melted and used over again4 ,it does not answer1 in hand-stuffing1 to carry this re-use too far1 as the table-grease contains only the harder parts of the fat1 with a continually increasing proportion of stearic acid1 so that if a dubbing be made continuously of table-grease and oil1 in the end little but the latter will be absorbed by the leather2 while where fresh tallow is used1 a portion of its softer constituents remains dissolved in the oil4 ,the principal function of the harder fats is the mechanical one of retaining the oil on the surface of the leather2 and to a certain extent they may be replaced by other solids1 such as steatite 78,french chalk071 or perhaps other pulpy materials4 ,the use of a portion of soft fat1 such as bone-fat1 or the better sorts of glue-grease1 is quite practicable1 especially if mixed with the harder table-grease4 ,the drying of hand-stuffed leather should be slow1 to allow time for the absorption of the grease2 and the temperature should be so regulated as to keep the dubbing in a soft but not liquid condition4 ,in winter1 if the temperature of the outer air be raised sufficiently for this1 the drying will be too keen 7cp4 p4 #dbf7 and the water will be dried out before the grease is properly absorbed4 ,it is therefore best1 in cold weather1 to maintain the ventilation mainly by circulating the air in the room1 with little admission from the outside1 and in extreme cases even artificial damping of the air may be advantageous4 ,sometimes the tendency to mildew during slow and warm drying is very troublesome4 ,this may be prevented by the addition of antiseptics to the stuffing grease4 ,carbolic acid and creasote are effective1 but generally objectionable from their smell2 rosin oil has considerable antiseptic power1 and mineral oils also in a less degree4 ,probably -naphthol would prove an efficient remedy1 as it has little odour1 and its antiseptic properties are very strong1 but it has not been tried by the writer4 7,cp4 ,chapter ,v47 ,illustration3 ,,fig4 #ij4--;,haley's ,injector ,stuffing ,drum4 ,in drum-stuffing the conditions differ materially from those of hand-stuffing4 ,the goods1 in a damp condition1 are placed in a drum 7,fig4 #ij71 which has been heated by steam to as high a temperature as the leather will safely stand4 ,cold damp leather may be stuffed in a drum heated to #fj ,c4 and the grease may be run in at the same temperature4 ,the grease should generally be melted and mixed at a somewhat higher temperature4 ,sometimes steam is merely blown into the drum before introducing the leather1 to heat it to the required temperature2 sometimes a steam-coil is placed in the drum itself4 ,a more modern method1 which is now largely used in the ,united ,states1 is to heat by hot air1 which is circulated by a fan over an external steam heater and through the drum4 ,the drum is set in rotation1 and the stuffing grease in a melted condition is run in through the hollow axle1 or if this is not provided1 it is introduced through the door1 and the rotation is maintained for twenty to thirty minutes4 ,during the last few minutes the door is frequently replaced by an open grating or cold air is drawn through the drum by means of the fan1 in order to cool the goods1 which are set out with the sleeker on the table while yet somewhat warm1 and dried under much the same conditions as have been described with regard to hand-stuffed goods4 ,in drum-stuffing1 the hardness of the grease is limited by its melting-point1 which must not be so high as to damage the leather1 but it may be soft as is desired4 ,as the grease is forced by mechanical means into the interior of the leather1 there is no danger of its running off1 but the drying must take place at such a temperature as to keep it at least in a partially soft condition1 as the drumming only forces it into the coarser spaces of the leather1 and does not complete its distribution on the fibre4 ,by the use of exceedingly hard greases1 such as 8stearin0 7p4 #cei7 and oleo-stearin 7p4 #cef71 sometimes with additions of paraffin wax1 it is possible to introduce immense quantities of grease1 and yet to obtain a leather which will board up to a good colour4 ,in ,america1 it is not unusual to reckon #ajj or even #aae lb4 of greases to #ajj lb4 of leather weighed dry after scouring1 or estimated from its wet weight2 and the whole of this is absorbed1 scarcely anything coming off in 8setting40 ,the leather1 as it comes from the drum1 is dark brown1 but when bent sharply in 8boarding0 to form the grain1 after cooling and drying1 the very hard and crystalline fats crumble into white powder1 and the leather takes a light and pretty colour4 ,such leather would of course darken at once if it were held to the fire1 but would again brighten on cooling and breaking up with the 8board40 ,some portion of liquid fats1 such as dgras or fish oil1 should be contained in the stuffing grease1 as the solid fats alone will not penetrate to the heart of the fibres1 but will leave the leather dry and harsh4 ,by drum-stuffing1 it is possible to incorporate solid matter with the leather1 and barytes 7ground heavy-spar or barium sulphate7 was formerly much used for this purpose1 but has now been nearly abandoned4 ,glucose is still used as an adulterant of leather1 but is not introduced in the drum1 but by painting the goods with syrup before stuffing4 ,it not only adds weight1 and gives the leather a lighter colour than an equivalent quantity of grease1 but at the same time lessens its toughness1 and ought to be prohibited in ,england1 as it already is in ,germany4 ,on the detection of adulteration of leather1 see ,l4,i4,l4,b41 p4 #bab4 ,drum-stuffing is in this country mainly applied to shoe-leathers1 but in ,america1 with the hot-air drum1 is coming into increasing use for harness1 and even belting4 ,a method of stuffing is used in ,germany for heavy belting and the like1 which appears at first glance to contradict the axiom that leather must be stuffed wet4 ,it is called ,einbrennen 7to burn in71 and consists in first drying at a high temperature 7#ej ,c471 to ensure the absence of all moisture1 and then either pouring hot melted tallow over the leather on a table1 and holding it over a brazier1 to allow the grease to sink in1 or dipping it completely in a bath of melted tallow4 ,the exception is only apparent1 because1 though the leather is at this stage completely saturated with tallow1 it is only after wetting and drumming that it attains the flexibility due to true stuffing4 ,similar methods are applicable to alumed leathers1 and even to chrome-leather2 and so-called 8waterproof0 or 8anhydrous0 leather is made by immersing thoroughly dried leather in a bath of #b parts of resin and #a of paraffin1 or some similar mixture4 ,if the leather is not first thoroughly dried1 it is scalded and destroyed by the hot grease4 ,the most troublesome defect to which stuffed leathers are liable1 is known as 8spueing10 and is of two kinds1 of which the first and less serious 7perhaps more properly distinguished as 8striking out07 consists of a white efflorescence rather like incipient mould1 which is easily wiped off1 but generally reappears4 ,this is due to the crystallisation of the harder fats1 and especially of the free fatty acids1 on the surface of the leather1 and is almost sure to occur in greater or less degree when the hard fats such as tallow or stearine are combined with a non-drying oil such as neatsfoot1 or when soft fats are present in the leather4 ,it is sometimes combined with actual mildew1 from which it is rather difficult to distinguish1 even under the microscope1 and may even be caused by fungoid plants1 which not only mechanically expel the fats by their growth1 but probably promote their rancidity and the separation of the crystalline fatty acids4 ,it is at most only a defect of appearance1 and does not in any way injure the leather4 ,it is constantly present in calf-kid1 from the neatsfoot oil used in finishing1 and is in this case rather liked by the buyers1 who for some reason regard it as a proof of quality4 ,a very similar appearance may be caused by the use of solutions of barium chloride1 alum or other mineral salts1 for weighting or other purposes2 but is persistent when the leather is held to the fire1 while the crystallised fatty acids at once melt and disappear4 ,the fatty acids are at once removed by a drop of benzene or petroleum spirit2 but unaffected by water1 while with water-soluble salts the reverse occurs4 ,the second form of spueing is of a much more troublesome character1 and makes its first appearance as minute spots or pimples of resinous matter1 raised above the surface of the leather1 which if removed1 generally reappear1 and which may become so bad as to form a sticky resinous coating over the whole surface4 ,the exsuded matter consists of the oxidised products of oxidisable oils1 but the cause of its appearance is not always easy to explain4 ,the currier generally attributes it to adulterated oils1 and it must be admitted that some oils almost invariably produce it1 but it appears occasionally when only the purest and absolutely genuine cod-oil has been used4 ,it can only be produced from drying or semi-drying oils1 which include all the ordinary fish oils and most of the vegetable seed oils1 but can never arise from tallow or stearine1 from mineral oils or vaseline1 or from genuine non-drying oils1 such as tallow1 neatsfoot1 sperm1 or mineral oils1 nor1 probably1 from rosin oil4 ,it is favoured by causes which promote the oxidation of oils1 such as moist heat with limited access of air1 and by the presence of oxygen-carriers1 such as iron-salts in blacks1 and possibly also by the presence of free acids4 ,a large amount of free fatty acid in the oils themselves is suspicious1 not only because the free acids oxidise more freely than the neutral fats1 but because their presence is an evidence of the tendency to rancidity and change in the oil4 ,it is also said to be caused by previous mildewing of the leather1 and certainly often occurs where the grain has been rendered porous by bacterial action in the soaks1 limes1 or bates1 probably from the greater quantity of oil absorbed by these parts4 ,while it is easy to say which oils may possibly spue1 there is no known chemical test which will foretell whether a given sample is likely to do so under ordinary conditions4 ,eitner#afi states that seal oil extracted at a low temperature is very liable to spue1 but that when heated for a considerable time to a temperature of #bej-bij ,c4 it darkens in colour and loses the tendency4 ,this is probably true of many other marine oils2 and may be one cause of the frequent trouble with modern oils1 many of which1 especially the lighter coloured kinds1 are extracted by steam at a temperature below boiling point4 ,it is very probable that one effect of heating to a considerable temperature is to dehydrate and separate albuminous or gelatinous matters which are present in the fresh oils1 and which probably increase their tendency to decomposition4 ,many of these substances separate as 8foots0 from oils during long storing1 and such old oils are said to be less liable to spue than those of recent manufacture4 #afi ,gerber1 #ahhj1 p4 #bdc4 ,if oxidisable oils are used upon leather1 they 8dry0 upon the fibre1 and if a sufficiency of non-drying constituents are not present at the same time1 the leather will ultimately become hard1 and may even crack from hardening of the fibre4 ,mineral oils are not liable in this way to form a hard coating on the fibre1 but as they are slightly volatile1 though of very high boiling point1 they may ultimately evaporate1 and leave the leather insufficiently nourished4 ,from their low surface-tension1 they have great powers of capillary penetration1 as is witnessed by the way that lamp oils 8creep0 over the surface of the lamp1 but they have less affinity for water than the more oxidisable oils1 and probably do not combine so intimately with the leather-fibre4 ,they are probably better used in combination with other greases than alone4 ,the admixture of solid paraffin with stuffing greases has the tendency to make the leather feel less greasy and drier than it otherwise would2 and crude turpentine and rosin are said to have a still greater effect in this direction4 ,the water which is required for satisfactory stuffing may in some cases be introduced into the stuffing grease as well as into the leather4 ,the effect of dgras is largely due to the water with which it is intimately mixed1 and when dgras or sod-oil is deprived of that which it naturally contains1 by heating it to too high a temperature1 either before or after its mixture in a stuffing grease1 its efficacy is greatly lessened4 ,fat-liquoring 7pp4 #bag1 #bci7 may be considered a special case of stuffing1 in which the oil is very perfectly emulsified with a large quantity of water4 ,in this way1 very considerable quantities of oil may be introduced into leather without giving it the least greasy feel4 ,egg-yolk contains about #cj per cent4 of an oil chemically very like olive1 but with a larger proportion of palmitin1 and may be considered as a very perfect natural fat-liquor1 containing also some albumen which serves as 8nourishment0 for the leather4 ,if a means of emulsifying olive1 lard1 or tallow oil 7with the addition of a little palm oil7 with albuminous matter as perfectly as in the egg could be discovered1 the problem of an egg-yolk substitute would in all probability be solved4 ,milk and cream are also natural fat-liquors4 ,,chapter ,,xxv4 ,,dyes ,,and ,,dyeing4 ,before the discovery of artificial organic dyestuffs1 the only colouring materials known to industry were those of mineral and direct organic origin2 and on this account the dyeing of leather was formerly subject to great difficulties and limitations4 ,the discovery of the means of artificially preparing an organic dyestuff 7mauve7 by ,perkin some forty-five years since1 opened up a new field for research1 and since that time1 the list of commercial dyes has so increased that there is now scarcely a tint or shade which cannot be accurately matched and reproduced by the coal-tar colours4 ,these colours are often spoken of as 8aniline dyes0 owing to the fact that many of them1 and especially the earlier ones1 have been derived from aniline1 one of the products of coal-tar2 but more recently1 a considerable number of important colours have been prepared from other constituents of the tar1 and it is therefore more correct to term the whole of the dyes obtained1 either directly or indirectly1 from coal-tar1 the 8coal-tar colours40 ,the coal-tar colours are generally soluble in water1 or mixtures of water and alcohol1 and the majority of them combine with the fibre of the leather without the use of any mordant1 so that in most cases it is only necessary to apply a solution of the dye direct to the leather1 though their suitability for the purpose varies considerably4 ,a few which are only soluble in oils or hydrocarbons1 are not suitable for leather-dyeing1 though they may sometimes be utilised in conjunction with fats in currying2 and there are also certain colours which are not applied to the fibre ready formed1 but are developed on it by subsequent chemical treatment1 and which have only been applied to a limited extent to leather4 ,a number of the coal-tar dyes1 which are produced in the crystalline form1 have a totally different colour when solid to that of their solutions1 and to the colour they produce when dyed4 ,a well-known instance of this is magenta or fuchsine1 which forms glistening green crystals1 while in solution it is a brilliant red dye4 ,the colours of the crystals are usually complementary to those of the solution1 thus several blues have the appearance of metallic copper1 and violets1 such as methyl-violet1 are greenish-yellow1 generally with a pronounced metallic lustre4 ,this peculiarity is the cause of the defect in dyeing known as 8bronzing10 in which the dye1 when applied in too concentrated a form1 takes a surface-shimmer of its complementary colour4 ,the coal-tar colours are mostly either 8acid0 or 8basic40 ,the former are the salts of organic colour-acids with inorganic bases 7generally sodium7 and are usually readily soluble in water1 but frequently do not fix themselves on the fibre till the colour-acid is set free by the addition of some stronger acid to the bath1 and in many cases the free colour-acid is of different colour to its salts4 ,the 8basic0 colours are salts of colour-bases 7organic bases of the nature of very complicated ammonia-derivatives7 with acids 7mostly hydrochloric1 sulphuric or acetic74 ,most of those in commercial use are soluble in water1 though a few require the addition of alcohol4 ,the colour-bases themselves are usually insoluble in water1 and therefore precipitated by alkalies1 and in some cases they are also colourless4 ,the basic dyes have generally greater intensity of colour than the acid dyes1 but large classes of them are very fugitive when exposed to light1 and in strong solution many others are very liable to 8bronze10 a defect which is generally less marked with the acid colours4#agj #agj ,it has recently been shown by ,lamb 7see ,app4 ,d1 p4 #dih7 that many basic colours are much faster to light on leather than on textiles4 ,as it is not obvious at first sight whether a given dye is acid or basic1 a reagent to distinguish them is useful4 ,for this purpose a solution of #a part of tannic acid and #a part of sodium acetate in #aj parts 7by weight7 of water is conveniently employed1 which gives coloured precipitates with basic dyes1 but is not affected by acid ones4 ,the fact that basic dyes are precipitated by tannins influences their use in leather dyeing1 not only as regards their fixation on the leather-fibre by the tannin which it contains1 but as the cause of their precipitation in the dye-bath if great care is not taken to avoid the presence of tannins in a soluble form4 ,the use of the sodium acetate is to combine with the mineral acid of the colour-salt1 which if left free would prevent complete precipitation1 substituting for it acetic acid1 which is much weaker1 especially in presence of excess of sodium acetate 7cp4 p4 #ha74 ,in using the terms 8acid0 and 8basic0 with regard to dyes1 it is not to be understood that the dyestuffs as employed are acid or alkaline in the sense that vinegar is acid1 and soda basic1 but merely that the actual colour-constituent of the salt is in the one case of an acid nature1 and set free by stronger acids1 and in the other case is basic1 and liberated 7and often precipitated7 by stronger alkalies4 ,there are several general theories with regard to the fixation of colours in dyeing organic fibres1 and it is probable that no one of them affords a complete explanation in all cases4 ,one holds that the action of dyeing is mechanical rather than chemical1 the colour adhering to the fibre by surface-attraction2 another1 that an actual chemical compound is formed between the dye and the dyed material or one of its constituents2 and a third1 the 8solid solution0 theory of ,witt1 is in a sense intermediate1 holding that the colouring matter is actually dissolved in the dyed fibre4 ,the idea of a solid solution1 strange at first1 offers little difficulty on consideration4 ,the colouring metallic salts in tinted glasses exist obviously in solution in the melted glass1 and can hardly be said to change their condition in this respect when the glass becomes solid4 ,gelatine1 indiarubber1 and perhaps all other colloid bodies1 absorb water or other liquids without losing their solid form1 and these liquids may fairly be said to be dissolved in the solid4 ,all animal and vegetable fibres are in this respect like gelatine1 and during the process of dyeing are swollen with water4 ,it is quite easy to dye a mass of gelatine throughout with most water-soluble dyestuffs4 7,compare on these points what is said in ,chapter ,,ix4 on the physical chemistry of hide-fibre47 ,the distinctions between solution and molecular surface-attraction on the one hand1 and certain forms of chemical combination on the other1 are not wide ones1 and probably all three theories are true in different cases1 and shade off into each other by imperceptible gradations4 ,the subject of leather-dyeing is1 in fact1 a very complicated one1 since we are not dealing with a fibre of uniform composition1 but with one which has had its structure 7both chemical and physical7 altered by the processes to which it has been subjected during its conversion into leather4 ,although1 strictly speaking1 the constitution of the gelatinous fibre of the skin is unknown1 we are quite justified in stating#aga that1 like the amido-acids which are important proximate products of its decomposition1 it contains both acid and basic groups1 and is therefore capable of attracting both bases and acids4 ,it is well known1 for instance1 that the neutral fibre is capable of withdrawing sulphuric acid from a decinormal solution with such vigour that the residual liquid is neutral to litmus paper2 and it will also absorb caustic alkalies with perhaps equal avidity4#agb #aga ,procter1 ,jour4 ,soc4 ,chem4 ,industry1 #aijj1 p4 #bc4 #agb ,cp4 ,chap4 ,,ix4 ,it is thus readily dyed by colouring matter of either basic or acid character1 and in many cases will even dissociate their salts1 dyeing the characteristic colour of the free dyestuff1 but possibly at the same time fixing the liberated base or acid with which the colouring matter has been combined4 ,many tanning processes consist in a somewhat analogous fixation of weak bases and acids1 and it is1 therefore1 to be anticipated that they will profoundly modify the colour-fixing properties of the original fibre1 as indeed proves to be the case4 ,exactly what the result of a particular tanning process in this respect will be is less easy to foresee4 ,in the ordinary vegetable tanning process1 the tannins1 which are of acid nature1 are freely fixed by the fibre4 ,it is1 therefore1 not surprising that vegetable-tanned leather most readily fixes the basic colours1 especially as these form insoluble compounds with the tannic acids1 so that it is quite probable that the dyeing is mainly effected by the formation of tannin-colour-lakes on the fibre1 rather than by actual fixation of the colour-base in combination with the original matter of the skin4 ,it is noteworthy1 however1 that even fully tanned skin has by no means lost its attractions for acid colouring matters1 many of which will dye it even without the presence of free acid1 though it is possible that the tannic acid performs the function of saturating the alkaline base with which the colour acid has been combined4 ,it should be pointed out that while the substance of animal skin consists practically of gelatinous fibres1 it is covered on the outer surface with a thin membrane of extreme tenuity1 called the hyaline or glassy layer 7p4 #ej7 which1 in the living animal1 separates the true skin from the epidermis4 ,this layer1 the chemistry of which is quite unknown1 reacts to colouring matters differently from the gelatinous fibres1 and probably is less absorbent for basic colours1 and more so for the coloured anhydrides of the tannins1 and perhaps for acid colours generally1 than is the true skin4 ,as a result1 it colours more darkly in tanning1 and less so in dyeing with basic colours1 and as it is extremely liable to damage in the preliminary operations of removing hair and lime by the tanner1 this irregularity of colouring is a serious disadvantage which is most marked with the basic colours4 ,small quantities of lime left in the skin are also probably important causes of irregular dyeing4 ,mordants are chemicals used to enable the fibre to fix dyes for which it would not otherwise have sufficient attraction1 and hence are generally substances which have affinity both for the fibre and the dye4 ,thus cotton1 which does not itself attract the basic colours1 is mordanted for them by a solution of tannin1 which it attracts1 and which1 in its turn1 attracts and fixes the colours4 ,in many cases1 however1 the function of mordants is more complex1 not merely fixing the dyestuff1 but often modifying1 or even producing its colour4 ,thus tannin dyes black on an iron mordant1 though it is itself colourless4 ,such mordants may be applied after the colouring matter1 where it has sufficient attraction for the fibre to be taken up alone1 but does not produce the required colour4 ,this process is often called 8saddening10 as the colour is generally darkened4 ,a familiar instance is the use of iron solutions to darken or blacken tannin or logwood4 ,there is scarcely any distinction in theory between mordants of this class and the constituents of dyes which are successively applied to the leather in order to produce the colouring matter on the fibre4 ,among these may be mentioned several mineral salts which were formerly employed in leather dyeing1 though their use is now nearly obsolete4 ,iron salts are easily fixed by leather1 whether tanned or tawed1 and in the former case produce a dark colour by action of the tannin4 ,on subsequent treatment with a solution of potassium ferrocyanide1 a deep blue is formed 7,prussian blue74 ,if copper acetate or ammoniacal solution of copper sulphate be substituted for the iron salt1 a deep red-brown ferrocyanide is produced4 ,yellows are sometimes dyed by first treating tanned leathers with lead acetate1 which is fixed by the tannin1 and then with potassium bichromate1 by which yellow lead chromate is produced4 ,a more important use of lead is in the so-called 8lead-bleach10 which is really a white pigment-dyeing with lead sulphate4 ,the tanned leather1 after washing1 is first treated with a solution of lead acetate 7usually 8brown sugar of lead0 of about #d grm4 per liter71 and subsequently with a dilute sulphuric acid of about #cj grm4 of concentrated acid per litre1 and then thoroughly washed to free it from acid4 ,the process is often used as a preparation for dyeing pale shades1 as many of the aniline dyes are easily fixed on the bleached leather1 but is subject to the disadvantage attendant on all pigments containing lead1 of becoming rapidly darkened by traces of sulphur or sulphuretted hydrogen1 such as are constantly contained in lighting gas1 or arise from the putrefaction of organic matters4 ,the use of acid is also liable to cause early decay of the leather4 ,a large proportion of the coal-tar colours contain amido-groups 7,,nh groups7 which1 when treated on the fibre with nitrous acid 7or an acidified solution of sodium nitrite71 become 8diazotised0 7converted into --,n 3 ,n-- groups with elimination of ,,oh74 ,on further treating the diazo-compound with solutions of amines or phenols1 combination takes place1 and new azo-colours are formed in or on the fibre1 often remarkably fast to washing or rubbing4 ,since these qualities are less important in leather than in textiles1 and the process is moreover somewhat delicate1 and the nitrous acid is apt to injuriously affect the leather1 these processes have been little used in leather-dyeing1 and are only mentioned here for the sake of completeness4 ,the use of the natural polygenetic colours in dyeing leather of vegetable tannage1 which was once universal1 is gradually disappearing1 except for the production of blacks4 ,leather cannot be very satisfactorily mordanted for these colouring matters2 but they have some natural attraction for the leather itself1 and are generally dyed first1 and their colours afterwards developed by metallic mordants such as iron1 chrome1 tin salts1 and alum1 which act not only on the absorbed dyestuff1 but frequently on the tannin and colouring matters derived from the tanning materials4 ,for black-dyeing1 the use of coal-tar colours1 either alone1 or to deepen the colours produced by iron1 is gradually extending4 ,claus and ,re's 8,autho-black10 the 8,corvolines0 of the ,badische ,co41 and ,casella's 8,naphthylamine ,black10 8,aniline ,grey10 and 8,naphthol ,blue-black0 may be mentioned as useful colours4 ,as coal-tar blacks are mostly dark violets rather than dead blacks1 their colour may be deepened by the admixture of suitable yellows or browns1 and this has already been done in one or two of the colours named4 ,apart from the coal-tar colours1 black dyeing is generally produced by the action of iron 7and chrome71 either on the tannin of the leather itself or on logwood4 ,as the leather is frequently greasy1 and the satisfactory formation of a tannin- or logwood-lake can only take place in presence of a base to absorb the liberated acid of the iron salt1 the skins are either brushed with1 or plunged in1 a logwood infusion1 rendered alkaline with soda or ammonia1 or the tanned leather receives a preliminary treatment with weak soda or ammonia solution4 ,as such solutions act powerfully on tanned leathers1 rendering them harsh and tender1 great care must be taken to avoid excess4 ,the effect of this alkaline treatment is not only to assist the wetting of the greasy surface1 but to prevent too deep penetration of the dye1 by causing rapid precipitation of the colour-lake4 ,in recent times1 however1 leathers are sometimes demanded in which the colour goes right through1 and in this case it might be well to reverse the treatment1 beginning with a weak solution of a ferrous salt1 perhaps with addition of sodium acetate or potassium tartrate1 and finishing with alkaline logwood1 as without alkali the full colour is not developed4 ,the use of iron salts is not very satisfactory in regard to the permanence of the leather2 and in this respect it is of great importance that they should not be used in excess1 and that any strong acids they contain should be saturated with permanent bases1 and if possible washed out4 ,leather-surfaces blacked with iron almost invariably ultimately lose their colour1 becoming brown if tannins1 and red if logwood has been employed1 and at the same time the leather surface usually becomes brittle or friable4 ,this is to a large extent due to the effect of iron oxides as oxygen-carriers4 ,exposed to light1 they become reduced to the ferrous state1 oxidising the organic matters with which they are combined1 and in the dark they re-oxidise1 and the process is repeated4 ,it is therefore of the first importance that excess of the organic colouring matter should be provided1 and that the quantity of the iron should be as small as possible1 and in stable combination4 ,these points are greatly neglected in practice1 especially where blacking is done by the application of iron salts without logwood1 when the evils mentioned are intensified by the actual removal of part of the tannin of the leather1 and perhaps by the combination of ferric oxide with the skin-fibre itself1 forming a brittle iron-leather4 ,treatment with alkaline sumach-1 gambier- or logwood-solutions1 both before and after the application of the iron1 would lessen the evil4 ,iron-logwood blacks are much less permanent1 and fade more rapidly under the influence of light and air than iron-tannin blacks4 ,the use of iron-blacks on curried leathers seems considerably to increase the tendency to 8spueing10 a defect due to oxidation of the oils 7see p4 #cij74 ,copper salts mordant logwood a very dark blue1 which is much more stable than the iron compound1 and hence are often used advantageously in mixture with iron salts4 ,in practice1 iron blacks are generally oiled in finishing1 and this renders them more permanent1 both by protecting the lake from air and by forming iron soaps which are stable4 ,the use of actual soaps in blacking and finishing is not unknown1 and probably deserves more attention4 ,hard soaps of soda and stearic acid1#agc form an excellent finish where a moderate glaze is required1 the soap jelly being applied with a brush very thinly1 allowed to dry thoroughly1 and polished with a flannel or brush1 or glassed4 ,many acid colours are soluble in such soap jellies1 which may thus be employed for staining4 ,similar but harder finishes1 and capable of being glazed to a high polish1 are made by dissolving shellac with dilute borax or ammonia solutions4#agd ,both of these finishes are useful in lessening the tendency of iron blacks to smut or rub off1 a failing which is due to the precipitation of loose iron-lakes on the surface1 instead of in combination with the fibre1 and is particularly obvious where 8inks0 or one-solution blacks are employed1 or where the mordant and the colouring matter solutions are allowed to mix on the surface of the leather4 ,such 8inks0 are generally made with a ferrous salt and logwood or tannin1 together with some aniline black1 and the colour-lake should only be formed on oxidation4 ,chrome is not much employed in blacks with vegetable tannages1 as it only produces blacks with logwood1 the chrome compounds of tannins having no colouring value2 and bichromates used at all freely being very injurious to the leather4 #agc #a of caustic soda in #aj-ae of water1 boiled with #h of stearic acid till clear1 cooled to #be ,c4 and diluted with #djj-hjj water1 with constant stirring1 till the white jelly of suitable consistence is obtained4 ,somewhat similar1 but harder preparations may be made with waxes1 or fatty acids still higher than stearic4 #agd #e parts of shellac digested warm with #ajj water and #c of ammonia fort41 or #a of borax4 ,if the solution is used as a 8seasoning0 for glazing1 the waxy matter which separates on standing should be mixed by shaking before use4 ,as a varnish1 a stronger solution should be used and the wax skimmed off4 ,in dyeing blacks on other than vegetable tannages1 however1 chrome becomes of importance1 as logwood is principally employed1 though sometimes in conjunction with tannin1 and often with addition of quercitron or fustic1 to correct the bluish shade of the logwood-chrome or logwood-iron lake4 ,it must not be overlooked in practice1 that if ferrous salts are mixed with bichromate solutions1 the latter are reduced1 and the iron is oxidised to the ferric state4 ,in alumed leathers the fixing power of the original hide-fibre is much less affected than in vegetable tannages4 ,whatever may be the truth with regard to the latter1 there is little doubt that physical influences are at least as important as chemical ones in the production of mineral tannages4 ,the amount of the tanning agent absorbed is greatly influenced by the concentration of the solutions1 and in ordinary alum tawing much of the alumina may again be removed by free washing4 ,in this case1 the sulphate of potash present takes no part in the operation1 but the alumina salt is absorbed apparently as a normal salt4 ,alum or alumina sulphate alone is incapable of producing any satisfactory tannage without the assistance of common salt1 the quantity absorbed being small1 and the fibre becoming swollen by the action of the acid4 ,in presence of salt the absorption is greater1 and the swelling is prevented4 ,the explanation of this is not to be found in the formation of aluminium chloride1 for though this undoubtedly takes place1 it has been shown that the action of aluminium chloride without salt is not more satisfactory than that of alum4 ,it has long been known that salt prevents the swelling action of acids on skin1 although it does not lessen the absorption of acid2 and the fact is capable of explanation on modern osmotic theories 7cp4 p4 #hi74 ,the skin so treated is found to be converted into leather1 but if the salt be washed out1 the acid is retained by the skin1 which returns to the state of acid-swollen pelt4 ,it is probable1 therefore1 that although the acid and alumina are absorbed in equivalent proportions to each other1 they are really dissociated1 and attached to different groups in the gelatine molecule1 and that the effect of the salt is to allow the absorption of the acid without swelling1 and1 osmotically1 to increase the dissociating power of the pelt4 ,if1 in place of a normal alumina salt1 a basic salt is employed1 such as may be obtained by partial neutralisation of the sulphuric acid with soda1 satisfactory tannage may be accomplished without salt1 a basic compound is absorbed1 and the leather is much less affected by washing4 ,in the analogous case of chrome tannage1 this basic compound may be still further deprived of its residual acid1 by washing the tanned skin with alkaline solutions1 leaving a leather which is extremely resistant even to hot water2 and a somewhat similar result may be obtained with alumina1 though with more difficulty1 as apparently a very small excess of alkali destroys the qualities of the leather4 7,cp4 p4 #ahg47 ,the results on dyeing are almost what might have been foreseen4 ,while ordinary alumed leather absorbs both acid and basic dyes readily1 the basic chrome leather has practically lost its affinity for the latter4 ,both chrome and alumina leathers readily absorb vegetable tannins1 thus supporting the view that the acid-fixing groups of the gelatine molecule are still unsaturated 7tannins are capable of tanning pelt swollen with sulphuric acid and apparently of expelling the acid74 ,in the case of chrome leather the effect of re-tanning with tannins is greatly to lessen its stretch1 and if carried too far1 to destroy its toughness1 but it at once becomes capable of fixing basic dyestuffs4 ,this property is frequently made use of in dyeing1 but the effect on the leather must not be disregarded where softness and stretch are important1 as in the case of glove-leathers4 ,polygenetic dyes are1 of course1 fixed on alum- or chrome-leathers by the alumina- or chrome-mordant1 though apparently the bases are not present in the most favourable condition for fixing colours4 ,thus logwood extracted without alkali dyes tanned leather yellow1 alumed leather violet-blue1 and chrome leather blackish-violet1 and some of the alizarine group dye very well on chrome as its resistance to hot water allows much higher temperatures to be used than with most other leathers4 ,the tannin contained in dyewoods has the effect of lessening the stretch of chrome leathers4 ,something should perhaps be said on the dyeing of oil and aldehyde leathers1 but the subject has as yet been scarcely treated scientifically1 and our practical knowledge of the subject is insufficient to justify theorising4 7,see1 however1 p4 #dif47 ,defects in the colour of the finished leather are due to a variety of causes1 but many are produced by want of cleanliness and system during the dyeing itself4 ,the greatest care is needed in this respect1 and in brush-dyeing a different brush should be used for each different colour1 as it is impossible to thoroughly remove all traces of dye by the ordinary methods of cleansing4 ,irregular and surface dyeing sometimes occurs owing to too rapid fixation of the colours2 while in other cases the affinity of the dye is too small to allow of reasonable exhaustion of the bath4 ,addition of salts of weak acids1 such as potassium hydrogen tartrate 7tartar71 or of those like sodium sulphate1 which form hydric salts1 lessen rapidity of dyeing with acid colours2 while acids generally increase it1 and it is also often increased by addition of common salt1 which lessens the solubility of the dye4 ,weak acids1 such as acetic or formic1 or acid salts1 such as sodium bisulphate1 are generally to be preferred to sulphuric acid as an addition to the dye-bath2 and if the latter is used1 great care is desirable in its complete removal4 ,there is no doubt that the rapid decay of leather bookbindings and upholstery is largely due to the careless use of sulphuric acid in 8clearing0 and dyeing the leather2#age and even if it is fully removed1 it has saturated all bases such as lime1 which are naturally present in leathers in combination with weak acids1 and which would otherwise act as some protection from the sulphuric acid evolved in burning coal gas4 #age ,see ,report of ,committee of ,society of ,arts on ,bookbinding ,leathers1 #aija4 8,bronzing10 the dichroic effect produced by light reflected from the surface of many colouring matters1 complementary to that transmitted by them and reflected by the surface of the dyed material1 is not peculiar to basic colours1 but is generally more marked in them than in acid ones4 ,basic colours1 from their great affinity for tannins1 and consequent rapid dyeing1 are apt to dye irregularly1 and without sufficiently penetrating the leather1 and if the soluble tannin is not wholly washed out of the skins previously to dyeing1 it bleeds in the dye-bath1 and precipitates insoluble tannin-lakes1 which waste colour and adhere to the surface of the leather4 ,the inconvenience of basic colours due to their too rapid fixation may sometimes be lessened by slight acidification of the dye-bath with a weak acid1 such as acetic or lactic4 ,the acid may be still further 8weakened0 if desired1 by the addition of its neutral 7sodium7 salt4 ,the precipitation of tannin-lakes in the bath may be prevented by previous fixation of the tannin with tartar emetic1 titanium potassium oxalate or lactate1 or some other suitable metallic salt4 ,the fading of the colours of dyed goods by exposure to light is a defect which has been much more investigated in the textile industries than in leather manufacture1 though in the latter case1 and especially with regard to bookbinding and furniture leathers1 it is of even greater importance4 ,it is probable that no colours are actually unaffected by strong sunlight1 but in many cases the action is so slight that it may practically be disregarded2 some of the coal-tar colours1 and especially some of the alizarines1 being practically permanent1 while others1 and particularly the aniline colours belonging to the triphenylmethane group1 such as magenta1 are so fugitive as to be practically bleached by a week of strong sunlight4 ,chrysoidine and the eosins are also very bad in this respect4 ,the fastness of colours to light is a good deal influenced by the material on which they are dyed1 and but little has yet been published of the results of direct experiments on leathers1 but ,mr4 ,m4 ,c4 ,lamb has been for some time engaged in a research of this nature1#agf and the subject is now receiving a good deal of attention in other quarters4 ,experiments are easily made by exposing samples to sunlight under glass or in a south window1 a part of the leather being covered with wood or thick brown paper for comparison4 ,the results are often complicated by the tendency of all leathers tanned with tannins of the catechol group1 and especially with turwar bark 7p4 #bih71 mimosa and quebracho1 to darken and redden in sunshine1 or even by exposure to diffused light4 ,pure sumach tannages are nearly free from this defect1 and are also much less easily destroyed by the action of gas fumes 7sulphuric acid71 and the other injurious influences to which books and furniture are often subjected4#agg #agf ,see ,app4 ,d41 p4 #dhh1 #dih1 and ,journ4 ,soc4 ,chem4 ,ind41 #aijb1 pp4 #aef-aeh4 #agg ,cp4 ,report of ,society of ,arts ,committee on ,bookbinding ,leathers1 #aija4 ,want of fastness to friction or rubbing is a defect generally more important in textiles than in leather1 where it is often prevented by glazings or other finishes applied to the surface2 but in some cases1 and1 especially in black leather1 it is apt to be annoying4 ,if suitable colours are used1 the defect is generally due to the precipitation of loose colour on the surface1 either by the too free use of mordants1 or the dyeing of basic colours on leathers which have not been sufficiently freed from loose tannin4 ,it is also often caused by 8flaming0 or the application of colour mixed with the 8seasoning0 used in glazing1 to hide imperfections in the dyeing1 or vary its colour4 ,colour applied in this way is only mechanically fixed on the leather1 and is easily removed by moisture1 staining articles with which it comes in contact4 ,a very similar defect may be caused by incomplete washing of the dyed leather1 which leaves loose dye from the dye-bath in the goods4 ,to avoid it in glove-leathers1 where its occurrence would be particularly annoying1 the natural mordant colours are still largely in use1 which being precipitated on the fibre in an insoluble form by the mordant or 8striker0 7generally a metallic salt7 are little liable to come off4 ,basic colours may be fixed by a subsequent treatment with tannin1 or by topping with certain acid colours such as picric acid4 ,some few colours1 and especially ,martius or 8,manchester0 yellow 7dinitronaphthol7 are volatile at a low temperature1 and therefore liable to 8mark off0 or stain any materials with which the dyed fabric1 even in a dry state1 is placed in contact4 ,illustration3 ,,fig4 #ia4--;,dyeing in the ,tray4 ,the practical dyeing of leathers varies considerably according to whether they are tanned with vegetable materials1 chrome1 alumina salts1 or chamoising4 ,vegetable-tanned leathers are dyed either by hand in the 8dye-tray10 or in the drum or paddle1 the two latter methods being now largely employed4 ,the dye-tray is a shallow vat1 about #aj inches deep1 and large enough for the goods to be laid flat in it4 ,in the ,english method1 one or two dozen skins1 or even more1 are dyed at a time1 being turned over in the tray by hand1 the undermost pair being drawn out and placed on the top 7,fig4 #ia74 ,the method is convenient where only a small number of skins are to be dyed to one particular shade1 which is more easily matched as the goods are always under observation1 and it has the further advantage that1 if desired1 the grain sides only of the skins can be coloured1 by 8pairing0 or 8pleating0 them before dyeing4 ,for this purpose two skins of equal size are laid together flesh to flesh 7pairing71 or each skin is doubled down the back1 flesh side in 7pleating71 and pressed firmly together with a sleeker on the table1 when the skins adhere so closely that if carefully handled1 no colour penetrates between them during the dyeing1 except a little round the edges4 ,this effects considerable economy of dye-stuff1 as the fleshes would absorb a good deal1 and for some purposes1 an undyed flesh is preferred4 ,in dyeing in the paddle or drum1 the skins are merely placed loose in the dye-liquor1 so that the fleshes are dyed equally with the grain sides4 ,paddle-dyeing has the advantage of effecting a considerable saving of labour1 as compared with the dye-tray1 in which constant handling1 which often lasts an hour or more1 is required4 ,it also allows of almost equal facility in examining the colour of the skins1 which is very important when dyeing to shade2 but it is less economical in dye-stuff1 as not only the flesh sides are dyed but a much larger volume of liquor is used1 and as the dye-bath can never be entirely exhausted1 more dye is run away in the used liquor4 ,drum-dyeing is much less expensive in this respect1 as the volume of liquor may be very small1 and from the efficiency of the motion1 the dyeing is very thorough1 and penetrates deeply into or through the skin1 which in many cases is advantageous1 but it is difficult to dye to exact shade1 since the skins can only be examined by stopping and opening the drum4 ,most dyes are more readily fixed at high temperatures1 and in this respect the drum has an advantage over all other methods1 as once heated it retains its heat with very little loss to the end of the operation1 while both in the paddle and the dye-tray the liquor is rapidly cooled1 and special methods of maintaining the temperature complicate the apparatus1 and require great care to avoid overheating4 ,it is usually best to work at the highest temperature which the goods will safely bear1 and this varies to some extent with the class of goods1 chrome tannages and chamois leather being peculiar in standing almost any temperature short of boiling4 ,with vegetable tanned leather #ej ,c4 may be taken as a maximum2 but cold wet skins may safely be introduced rapidly into a liquor heated to #fj1 as they will cool it sufficiently4 ,the ,continental method of dyeing in two trays may be mentioned here1 as it produces very rapid and even dyeing1 with considerable economy of dye-stuff1 and the principle is capable of application to other methods where a large number of skins have to be dyed to the same colour4 ,as generally carried out1 two trays are employed1 each about #d feet long1 #ah inches wide1 and #aj inches or a foot deep1 and these are usually made with a sloping bottom1 or propped up in such a way that the dye-liquor all runs to the further side of the tray4 ,a single pair of skins is usually dyed at once 7in about #f liters 7#e qt47 of liquor for sheep and goat74 ,to begin with1 the first tray is filled with a very weak liquor1 and the second with one of about half strength4 ,the goods are entered in the first tray1 turned a few times1 and passed into the second2 the liquor in the first is run away1 and it is re-filled with one of the full strength1 to which the goods are then transferred1 and dyed to shade4 ,the second tray is much reduced in strength by the skins1 and now serves as the weak liquor for a fresh pair1 which in its turn passes into that from which the goods have been dyed out1 and then into a new liquor2 each pair of goods thus passing through three baths1 of which the last is of full strength1 and which quickly brings up a full and even colour4 ,in the ordinary ,english method1 the goods must1 for the sake of economy of dye-stuff1 be dyed out in a nearly exhausted bath1 which is a tedious operation1 the last stage of dyeing often taking a time far longer than that required to bring the goods nearly up to shade1 and even then failing to produce a good and full colour4 ,this evil may be lessened by adding the dye-stuff in several successive portions1 as the bath becomes exhausted1 but cannot be altogether avoided with a single tray1 if any reasonable exhaustion of the bath is to be attained4 ,at first sight it seems a very slow process to dye the goods in single pairs1 but this is to a great extent compensated by the rapidity with which they take on colour4 ,in the ,continental system1 the dyes1 mostly of the coal-tar series1 are used as strong solutions1 and each new dye-bath is made up by filling the tray with a definite volume of hot water and adding a measured quantity of the dye-solution4 ,the re-use of partially exhausted dye-baths is generally limited to cases where either single dyes1 or mixtures of very equal affinity for the leather are employed1 since where dyes of unequal affinity are employed1 one is more rapidly removed than the other1 and the shade of the dye-bath is altered4 ,many dyes sold as single colours are really mixtures1#agh and alter in shade if successive quantities of leather are dyed in their solutions4 ,basic dyes are also apt to be precipitated by traces of tannin washed out of the goods1 and thus rendered unfit for use a second time4 ,this may be avoided by suitable preparation of the goods 7see p4 #daa74 #agh ,such mixtures may often be detected by putting a drop of their solution on blotting-paper1 when the dyes form differently coloured rings according to their more or less rapid fixation by the paper1 or by dusting the dry dye very thinly on wet blotting-paper1 when each particle produces its separate spot4 ,much of the success of practical leather-dyeing depends on proper selection and preparation of the goods4 ,sound uninjured grain is a matter of first importance2 no satisfactory dyeing can be expected on skins which through carelessness in soaks1 limes1 or bates1 are tainted by what is known as 8weak grain10 caused by destruction or injury of the delicate hyaline layer1 which forms the natural glaze and outer surface of the skin 7p4 #ej74 ,for such goods1 8acid0 are to be preferred to 8basic0 dyes1 the latter having an especial tendency to dye darker and deeper where the grain is imperfect4 ,goods of different tannages and colours should never be dyed together1 as they are certain to produce different shades in the same dye-bath4 ,tanned skins which have been dried1 especially if they have been in stock for some time1 should be thoroughly softened by soaking in tepid water and drumming1 a temperature of between #dj and #de ,c4 being most advantageous4 ,skins1 such as calf of mixed or bark tannage1 must now be freed from all bloom by scouring with brush and if necessary with slate or stone1 but great care is requisite to avoid injury to the grain4 ,a little borax or other weak alkaline solution assists in removing bloom4 ,fresh sumach-tanned skins merely require setting out with a brass sleeker1 but those which have been long dried often dye more evenly and readily if they are re-sumached4 ,dark coloured tannages1 such as ,australian bazils1 and ,east ,india sheep and goat tanned with cassia bark1 are always improved by sumaching1 and if for light colours1 by first stripping a portion of the original tan by drumming for a quarter of an hour with a weak 7 per cent47 solution of soap powder or borax at a temperature of #cj to #ce ,c4 and then passing 7after well washing in warm water1 but with as little exposure as possible to the air7 through a weak sour of sulphuric acid of #a-b per cent4 ,the acid should now be as thoroughly removed as possible by washing in water1 and the goods should be sumached4 ,the process1 and especially the use of sulphuric acid1 is always deleterious to the skins1 and is one of the causes of the early decay of coloured bookbindings and furniture leathers4 ,lactic1 formic1 or acetic acid may be substituted for sulphuric with safety1 and the risk of injury from sulphuric1 which generally is only apparent after the lapse of a considerable time1 is a good deal lessened by adding to the sumach liquor a small quantity of potassium tartrate1 sodium acetate or lactate1 or some other salt of a weak organic acid1 which is thus substituted for the much more dangerous sulphuric4 ,except in cases of absolute necessity for the production of light shades1 the use of sulphuric acid should not be resorted to1 and then only for goods which are not expected to possess great permanence4 ,for light shades for bookbinding and upholstery1 good sumach-tanned leathers and organic acids only should be employed4 ,alkaline treatment also demands great caution1 as excess of strong alkalies is very injurious to the leather4 ,another objectionable method for the preparation of leather for very light shades1 is the use of the lead-bleach described on p4 #cii4 ,the sumaching is best done in a drum1 at a temperature of about #dj4 ,lamb advises that #a to #b lb4 of sumach per dozen is sufficient for calf1 and recommends running in this liquor for two or three hours4 ,the skins are then rinsed in water to free them from adhering sumach1 and set out on a table with a brass sleeker1 and are now ready for dyeing with 8acid0 dye-stuffs4 ,if 8basic0 dyes are used1 thorough washing in several tepid waters is necessary to free them from the loose tannin2 and if deep colours are to be dyed1 it is better1 instead of too much washing1 to fix the tannin1 which then serves as a mordant for the colour4 ,for blues1 blue-greens1 or violets1 this is done with a solution of 8tartar emetic0 7antimony potassium tartrate1 of #e to #bj grm4 per liter according to the amount of tannin to be fixed1 often with addition of some common salt71 which produces no alteration in the colour4 ,for browns1 yellows1 deep reds1 or yellow-greens1 it is advantageous to use titanium-potassium lactate or oxalate 7#b grm4 per liter71 which in combination with the tannin produces a very permanent yellow coloration on which the basic colours dye freely4 ,in many cases the titanium salt is best applied after dying with one of the dyewoods 7,dreher74 ,the basic colours usually require simple solution in hot water before adding to the dye-bath1 and are used in quantities of #je to #be grm4 per liter of dye-bath1 according to their colouring power1 which varies a good deal1 and to the depth of shade required4 ,the solutions should not be boiled1 and some colours are injured by too high a temperature4 ,some colours dissolve incompletely1 and require filtration through a cotton cloth4 ,as basic colours are precipitated by calcium carbonate1 it is important that 8temporary0 hard waters should be neutralised with acetic or lactic acid till they faintly redden litmus2 and in the case of colours which1 from their attraction for the leather fibre1 dye too rapidly1 and consequently unevenly1 better dyeing is often obtained by the use of a small excess of acetic acid1 which also increases the solubility of the colour4 ,too much acid1 however1 will prevent the proper exhaustion of the bath4 ,some few colours1 now little used1 require to be dissolved in the first instance in a little methylated spirit2 and the addition of spirit will often assist dyeing and staining where the leather is slightly greasy1 though considerations of cost generally prevent its use4 ,sodium sulphate is not unfrequently added to dyeing baths to improve equality of dyeing2 and with some of the cotton dyes common salt is used to lessen their solubility and facilitate the exhaustion of the dye-bath4 8,acid0 colours usually dye better if acid is added to the bath1 to liberate their colour-acids1 and for this purpose sulphuric acid is generally used in weight about equal to that of the colour used4 ,its use is1 however1 objectionable1 in this case1 for the same reasons as in bleaching1 since it is impossible by mere washing to remove it entirely from the leather1 which it ultimately rots when concentrated by exposure to a dry atmosphere or high temperature2 and it is better to use formic or acetic acid to the extent of two or three times the weight of the dye-stuff4 ,sodium acid sulphate may also be used1 but is probably more objectionable than an organic acid4 ,many acid colours1 however1 dye quite satisfactorily from a neutral bath4 ,the acid colours are used in somewhat similar quantities to the basic1 but are generally inferior in colouring power1 though they dye more evenly1 especially on defective grain1 and are often more permanent to light4 ,mention has already been made of the polygenetic or mordant dye-stuffs1 which are still used to some extent for dyeing glove-leathers1 and of which logwood is important in dyeing blacks4 ,fustic and ,brazil-wood 7peach-wood7 are not quite gone out of use among old-fashioned dyers1 even for dyeing moroccos and other coloured leathers of vegetable tannage4 ,peach-wood1 with a tin mordant 7generally a so-called 8tin spirits0 made by dissolving tin in mixtures of hydrochloric and nitric acid7 was formerly much used in dyeing cheap crimsons1 but is now quite displaced by the azo-scarlets4 ,the acid tin-solutions were frequently very injurious to the leather4 ,the wood-infusion1 rendered slightly alkaline with soda1 ammonia or1 formerly1 with stale urine1 is usually dyed first on the leather1 and followed by the mordant 8striker02 ferrous or ferric solutions1 and potassium bichromate being used for dark colours1 and tin salts1 or sometimes alum1 for the brighter ones4 ,the mordant is sometimes added to the dye-bath towards the end of the operation1 but is better used as a separate bath1 as it is apt to produce a precipitate of colour-lake on the surface of the skin1 which rubs off on friction4 ,in some cases1 and especially in black dyeing1 the strong infusion of dye-wood1 and the necessary 8striker0 are successively applied by brushing instead of in the dye-tray4 ,logwood and ,brazil wood are both ,csalpinias closely allied to divi-divi4 ,logwood is ,csalpinia 7see p4 #bhg7 ,campechianum4 ,its colouring matter is hmatoxylin1 a substance nearly allied to tannins1 and almost colourless2 which on oxidation gives hmatin1 which dyes a yellow-brown1 only developing other colours by the aid of mordants4 ,logwood chips are extracted by boiling or heating under pressure for some time with water2 and as hmatin gives dark purplish-red compounds with alkalies1 soda or stale urine is frequently added under the mistaken belief that it produces a better extraction1 but really leads to waste of colouring matter by oxidation4 ,it is best to extract with water alone1 and add any necessary alkali to the infusion before use4 #a-b lb4 of wood per gallon is frequently employed in making the infusion1 and as this proportion of water is quite insufficient to properly extract the wood1 the residue should be boiled with one or more further quantities1 which are employed in turn for extracting fresh portions of wood4 ,logwood dyes best at high temperatures1 and especially in the case of chrome leather with which a temperature of #hj ,c4 may be safely used4 ,the presence of a trace of a salt of lime is advantageous1 and with very soft waters a little lime water or chalk may be added to the logwood liquor4 ,in blacking skins1 the strong infusion is rendered slightly alkaline with sodium carbonate or ammonia1 and brushed undiluted on the leather4 ,if employed as a bath1 a somewhat weaker infusion is used1 and the leather is frequently treated first in an alkaline bath1 to which a small quantity of potassium bichromate is often added4 ,the object of the alkali is not only to assist in the formation of the colour-lake1 by saturating the acid set free from the iron-salt used as a striker1 and thus to prevent the colour from penetrating the leather too deeply1 but1 at the same time1 to overcome the resistance to wetting caused by grease or oil which the leather may contain4 ,it must thus be used more freely when stuffed leather is to be blacked1 but excess should be carefully avoided1 as it easily renders the leather tender and brittle4 ,the potassium bichromate oxidises the hmatoxylin1 or the ferrous salt subsequently applied1 and forms a nearly black chrome-logwood lake4 ,the iron solution is generally either of ferrous sulphate of perhaps #e per cent4 strength1 or commercial 8iron-liquor10 which is a 8pyrolignite0 or crude acetate of iron1 containing catechol-derivatives and other organic products from the distillation of wood1 which act advantageously1 both as antiseptics1 and in preventing the rapid oxidation which occurs when pure ferrous acetate is used4 ,iron-liquor is generally to be preferred to ferrous sulphate 78green vitriol071 as the sulphuric acid of the latter1 unless completely neutralised by the alkali employed in preparation1 acts in the end disastrously on the leather4 ,commercial iron-liquor is often adulterated with ferrous sulphate1 which may be detected by its giving a precipitate with barium chloride4 ,great care should be taken not to use iron in excess of the logwood or tannin present1 as it otherwise takes tannin from the leather itself1 making it hard and liable to crack1 while any uncombined iron acts as a carrier of oxygen1 giving up its oxygen to the colouring matter or tannin with which it is in contact1 and again oxidising from the air1 and so causing 8spueing0 or oil-oxidation1 and other evils4 ,good blacks which are more permanent than those with logwood1 may be obtained by merely treating leather containing an excess of oak-bark tannin or sumach1 first with an alkaline solution 7not at the most stronger than #b per cent4 of liquid ammonia1 or #e per cent4 of soda crystals71 and then with iron-liquor4 ,if it is not certain that the leather contains excess of a suitable tannin1 a tannin-solution must be employed like the logwood infusion1 or the leather must be sumached4 ,the addition of some sumach to logwood liquor is often advantageous1 and a blacker 7i4e4 less blue7 black1 especially on alumed leathers1 is obtained by using a proportion of fustic4 ,solutions made by boiling #aj per cent4 of cutch with #e per cent4 of sodium carbonate give good blacks with iron-liquor1 and do not make the leather tender1 and they can be used in mixture with logwood4 ,many commercial logwood extracts contain chestnut-wood extract as an adulterant4 ,instead of dyeing in the bath1 it is very common1 especially for the cheaper leathers such as linings1 and coloured leathers of the commoner sort1 to apply the colour by brushing 7commonly called 8staining074 ,many colours1 however1 which dye well with time and warmth1 are inapplicable in this way1 and only those should be used which have a strong attraction for the leather1 and hence go on well in the cold4 ,if 8acid0 colours are employed1 it is essential to select those which can be used in neutral solution1 or at most with addition of some mild organic acid such as formic or acetic1 since1 as the leather is not washed after staining1 the sulphuric acid would remain in it1 and would ultimately destroy it4 ,where leathers have a hard and repellent surface1 the addition of a little methylated spirit to the dye is often very useful4 ,the colours are used in solutions of from to #a per cent41 which should be quite clear and free from sediment4 ,difficultly soluble colours must be used in weak solution1 or the dye kept warm while in use4 ,dye-solutions will not generally keep for any great length of time without change4 ,before staining1 the leather must be carefully 8set out10 or otherwise made as smooth as possible1 and the staining is generally done after most of the other operations of currying or dressing have been completed4 ,staining is best begun with the leather in a slightly damp or 8sammied0 condition1 and the colour is applied evenly with a softish brush in two or three coats1 the leather being slightly dried after each4 ,as a rule the more coats are applied1 the more even is the work2 but to save cost of labour it is common on cheap goods to be content with two1 of which the first is given1 preferably with a weaker solution1 to the dry leather4 ,where the leather is 8weak-grained0 it is sometimes advantageous to size it first with a weak solution of gelatine1 gum tragacanth1 or linseed mucilage1 and similar solutions are often used to fix the colour and give a higher gloss4 ,the stearine-glaze mentioned on p4 #dja may also be used for this purpose1 and a weak solution of it is sometimes employed as a vehicle for the acid colours4 ,acid yellows and browns may also be dissolved in the undiluted glaze where only a pale colour is required1 or to heighten the colour of leather already stained4 ,a list of suitable colours for staining is given in the ,appendix1 p4 #dhf4 ,it rarely happens in leather dyeing that the required colour can be given by the application of a single dye1 most of the shades now required being produced by mixtures4 ,it is1 therefore1 necessary to say a few words on the theory of colour combinations4 ,white light is of course composed of a mixture of all the spectrum-colours1 and can be separated into them by the prism4 ,it is probable1 however1 that the eye is only capable of three distinct colour-sensations1 and that all the colours we perceive are represented by the excitement of these in different proportions1 the actual colour-sensations being red1 blue-green1 and violet4#agi ,if we interpose a piece of yellow glass between the eye and white light1 the violet and blue are absorbed1 and the remaining red and green rays combine to produce the sensation of yellow4 ,if pure blue glass is used1 the red is absorbed1 and we have blue as the result of the remaining mixture of green and violet4 ,red glass absorbs the whole of the green1 and greenish-blue1 allowing red and much of the violet to pass4 ,thus1 if we combine blue and yellow glass1 only the green is allowed to pass1 and similarly with red and blue glass1 green and blue is cut out1 and only the violet remains4 ,thus red1 yellow1 and blue are frequently called the primary colours1 and by combining all three in equal proportions all colours are cut out1 and black or grey results4 ,the blue and violet which are stopped by yellow glass are those colours which would produce the sensation of violet-blue1 and hence the latter is called the 8complementary colour0 of yellow1 and so on with the rest4 ,it will be noted that all the colours of coloured objects are produced by absorption of a part of the light1 and therefore coloured bodies are always darker than white ones1 and where a colour is mixed with its complementary in suitable proportion1 all colours are absorbed and black or grey is produced4 #agi ,the subject of colour is too complicated to be adequately treated here2 and for fuller information1 readers are referred to ,abney's #8,colour ,measurement and ,mixture1' ,s4,p4,c4,k41 ,london1 #ahia4 ,it may1 however1 be pointed out that1 while the true primary colour-sensations are unquestionably red1 blue-green and violet1 and by mixture of light of these colours1 all other colours1 including white1 can be produced2 the primary pigments or dyes are red1 yellow1 and blue2 the effect being produced in the former case by the addition of colours1 and in the latter by their subtraction4 ,colours which are made by mixing two primary colours are generally called 8secondary02 while the duller tints made by the addition to these of black1 or of a complementary colour which produces black1 are called 8tertiary40 ,any primary colour is complementary to the secondary colour produced by mixing the other two primaries and vice versa4 ,the following tabular arrangement shows at once the effect of colour mixing4 ,,primary4 ,,secondary4 ,,tertiary4 ,red ,orange with ,black4 ,brown4 ,yellow ,green ,olive1 ,sage4 ,blue ,purple 7,violet74 ,puce1 ,maroon4 ,red ,theoretically1 any colour may be obtained by mixture of the primaries1 and that this is possible to a great extent is shown in the success of modern 8three colour0 printing1 by which pictures are obtained in natural colours by the use of three primaries only2 but in practice few colours are quite pure1 and if two very different colours are mixed1 it is difficult to avoid the production of tertiaries4 ,the most brilliant colours are generally produced by dyeing with the nearest colour which can be obtained to that required1 and shading with another which is near1 but on the other side of the desired tint4 ,thus if we want to produce bright shades in dyeing1 we must avoid the introduction of complementary colours4 ,a bluish red mixed with a reddish blue will produce a bright shade of violet1 but if we mix an orange-red with a greenish-blue1 we introduce yellow into the mixture1 and obtain a dull maroon or puce according to the proportion of the other colours4 ,in a similar way1 the introduction of a blue dye will dull a bright orange to a brown1 and a little of a yellow dye will dull a bright purple to a maroon4 ,this fact is frequently used in producing the quiet shades of colour often required from the most brilliant dyes4 ,if to a bright orange we add black1 or a blue dye which as its complementary produces black1 we convert it into a brown4 ,if instead of blue we use green for dulling1 we give the brown a yellower shade1 since the green produces black at the expense of the red of the orange4 ,violet similarly used gives a redder brown1 since it produces black by combination with the yellow4 ,this shading1 if small in amount1 is frequently done by direct mixture of a suitable dye1 but if considerable1 it is generally better to top one colour with another4 ,thus a blue1 topped with a powerful orange1 will produce a ,havanna brown4 ,for dark colours1 it is frequently convenient to produce a dark ground with some cheap dye1 such as logwood and iron or chrome1 and to top it with a bright shade of the colour required4 ,in this way cheap dark blues and greens can be easily produced4 ,for reds and browns1 mixtures of logwood and ,brazil-wood1 or ,brazil-wood and fustic may be used1 topped with coal-tar colours4 ,tanning materials1 such as quebracho and mangrove extracts1 which give browns with bichromate1 are also employed on cheap goods4 ,it is also frequently wise to dye with a basic colour and top with an acid one1 or vice versa2 as in many cases the one fixes and combines with the other1 and an increase of fastness is obtained4 ,morocco and many other coloured leathers are finished by damping the surface of the dried leather with a very dilute 8seasoning0 of water1 milk1 and blood or albumen1 allowing the leather to become quite or nearly dry1 and polishing by friction under a cylinder of agate1 glass1 or wood in the glazing machine4 ,many leathers are also grained by printing from engraved or electrotype rollers1 or by 8boarding10 or a combination of the two4 8,boarding0 consists in pushing forward a fold in the leather on a table with a flat board roughed underneath1 or lined with cork1 in a way which is difficult to describe1 but which in skilful hands wrinkles or 8grains0 the skin in a regular pattern4 ,the colour of a dyed skin is much altered by finishing and especially by glazing1 which always darkens and enriches the colour4 ,in dyeing to pattern1 it is useful to glaze a little bit of the rapidly dried skin by friction with a smooth piece of hard wood for comparison1 and a portion of the pattern may also be wetted for comparison with the wet skin4 ,colours which look full and even in the dye-bath1 often go down in a most disappointing manner on drying1 though to some extent they regain intensity on finishing4 ,in comparing the dyeing value of colours1 the most practical way is to make actual dyeing trials with equal or known quantities of the colours and of water4 ,such trials may be made1 either by 8turning0 the samples in photographic porcelain trays1 kept warm in a water-bath 7a 8dripping tin0 may be used for the purpose1 the trays being supported a little above the bottom on tin supports soldered to the tin71 or the leather may be hung from glass rods1 by hooks of copper wire1 in glass vessels 7square battery jars71 also placed in a water-bath4 ,the leather samples should be of equal surface in every case2 for suspension1 pieces of 8skiver0 7sheep-grain7 of #h by #d in4 or #bj by #aj cm4 are very convenient4 ,these may either be 8pleated0 or suspended by the two ends grain side out1 with a short glass rod to weight the fold1 and keep them flat4 ,the weight of colour used for a sample #h in4 by #d in4 multiplied by #ed times the area of a single skin in feet1 will give approximately the weight of colour needed per dozen2 which is1 however1 a good deal influenced by the mode of dyeing1 and the quantity of water used4 ,in dyeing on the large scale1 iron1 zinc and even copper are to be avoided1 the latter acting very injuriously on many colours1 and on the whole wooden vessels are to be preferred4 ,though these become deeply dyed1 they become very hard1 and if well washed with hot water1 and occasionally with dilute acid1 they may be cleansed so as to give up no colour in subsequent dyeing operations1 though of course it is not desirable1 if it can be avoided1 to use the same vessel for very different colours4 ,zinc rapidly bleaches many colours1 especially while wet and slightly acid1 and discharge-patterns may often be produced by pressing the wet leather on perforated zinc plates4 ,,chapter ,,xxvi4 ,,evaporation1 ,,heating ,,and ,,drying4 ,questions of evaporation1 whether for raising steam1 or for the concentration of tanning extracts and other solutions are of considerable importance in the tanning industry1 and as the same natural laws which apply to these equally govern the drying of leather1 it is convenient to study the theory of the whole subject in one chapter1 rather than to divide it1 and place each part in a different portion of the book4 ,the modern conception of evaporation and vapour pressures has been described on page #ge1 but it will be necessary to recapitulate a little4 ,it is a well-known fact that most liquids1 if left exposed in an open vessel1 gradually disappear by evaporation into the air1 even at ordinary temperatures4 ,if the vessel is heated sufficiently1 the liquid 8boils02 that is1 bubbles of vapour are formed in it1 and escape1 and the evaporation is therefore much more rapid4 ,to avoid complication1 let us first imagine a liquid sealed in a glass flask1 which contains no air1 but which is only partially filled by the liquid4 ,it has been pointed out that the motion of heat by which the molecules of the liquid are agitated1 enables some of them to break away from the attraction by which liquid particles are held together1 and pass into the form of gas or vapour1 which will fill the empty part of the flask4 ,this evaporation will1 however1 soon reach a limit1 since the vapour cannot escape from the flask4 ,the flying molecules of vapour produce pressure by striking the walls of the flask1 while a proportion of them will strike the surface of the liquid1 and again be caught and retained by its attraction2 and as the pressure rises1 the number of these necessarily increases till a point is reached when as many fall back and are retained 7or 8condensed071 as those which evaporate1 and the pressure will then remain constant4 ,the amount of the pressure will vary with the nature of the liquid1 and will be the greater the more volatile it is1 or1 in other words1 the less the power of its internal attraction4 ,it will also increase with rising temperature1 which1 by increasing the velocity of motion of the molecules1 renders their escape from the liquid easier1 and their recapture more difficult4 ,it will not be at all affected by the volume of vapour or the size of the flask1 but so long as any liquid is present1 it will depend merely upon the nature of the liquid1 and the temperature4 ,if the flask is large1 more of the liquid will evaporate till the same pressure is reached4 ,if at the outset the flask is not empty1 but filled with air1 it will make no difference to the pressure or quantity of the vapour in it1 which will be added to that of the air1 whatever that may be4 ,if the sealing of the flask is broken so that it is open to the atmosphere1 air and vapour will escape1 or air will pass in1 till the total pressure is equal to the atmospheric pressure outside1 7about #ae lb4 per square inch74 ,as1 however1 the vapour in the flask is always renewed by evaporation1 so that the full vapour-pressure of the liquid is maintained1 the 8partial0 pressure 7as it is called7 of the air in the flask will be less than that of the outer atmosphere by the amount of the vapour-pressure1 which makes up the difference4 ,once this balance is attained1 evaporation will go on very slowly in the flask1 as it can only replace the small quantity of vapour which escapes4 ,if1 however1 the vapour is removed by blowing fresh air into the flask1 it will rapidly be replaced in the old proportion by fresh evaporation4 ,thus goods in a close room will dry only very slowly1 even if the temperature is high1 unless the moistened air is replaced by dryer air from the outside by some effective system of ventilation4 ,in absence of this1 evaporation only becomes rapid when the temperature of the liquid is raised to its 8boiling point10 that is1 when the vapour-pressure becomes slightly in excess of that of the atmosphere1 so that the freshly formed vapour can push out that already in the flask or chamber into the outer air1 and at the same time1 bubbles can be formed in the interior of the liquid by the escaping vapour4 ,as the vapour-pressure of a liquid rises continuously with increasing temperature1 and its boiling point is defined as that temperature at which it is equal in pressure to the air 7or vapour7 in contact with it1 it is evident that the boiling point must entirely depend on the pressure4 ,thus the boiling point of water in a boiler at a pressure of #ee lb4 per square inch above the atmosphere is #aej;,c41 and in a partial vacuum equal to #eh inches of barometric pressure1 is only #fj ,c41 a fact which is made use of in the concentration of extracts and other liquids at a low temperature in the vacuum-pan4 7,atmospheric pressure is taken at #cj inches or #gfj millimeters of the barometer or #adg lb4 per inch1 or #ajcc kilos per square centimeter47 ,if a piece of iron is placed over a powerful gas-burner1 it will go on getting hotter till its temperature is nearly or quite equal to that of the gas-flame4 ,on the other hand1 a pan of water1 in the same condition1 once it has reached its boiling point1 becomes no hotter till all the water is evaporated4 ,it is evident that the whole available heat or energy of the gas-flame is consumed in converting the water into steam4 ,we might convert a proportion of this energy into mechanical work1 by using the steam in a steam engine2 but even without this1 work is actually being done by the escaping steam in raising the weight of the atmosphere1 and in overcoming the attractive force which holds the particles of water together in the liquid form4 ,it is of course known to everyone1 that energy may change its form1 as from heat to work1 but that it cannot be destroyed1 diminished or increased2 and therefore the whole of the work performed in converting the water into steam is again recovered as heat when the steam is condensed4 ,in this connection a clear distinction must be made between quantity of heat1 and temperature1 which in popular language are often confused4 ,it is for instance obvious that if we mix a pound of water at boiling temperature with another pound at freezing point1 the temperature is altered to #ej ,c41 but the total quantity of heat is unchanged4 ,it is equally clear that no change in quantity of heat takes place when #a lb4 of mercury at #ajj is mixed with #a lb4 of water at #j1 though in this case1 owing to the small capacity of mercury for heat1 the common temperature would only be raised to about #c4 ,we must therefore have some measure of heat apart from the mere direct indications of the thermometer1 and that most generally used is the quantity of heat required to raise #a kilo of water #a ,c4 7kilogram-calorie74#ahj ,in ,england the heat required to raise #a lb4 of water #a ,f4 is also in use as a unit4 ,the k4-calorie is equal to #cig 7very approximately #d7 lb4 ,f4 units4 ,for our purpose it may be taken that #ajj k4-calories of heat are required to raise #a kilo or liter of water from freezing to boiling temperature4 ,if1 however1 the water is actually frozen1 we require #hj k-calories merely to melt the kilogram of ice without perceptibly raising its temperature1 and when the water is raised to #ajj1 #ecf calories of heat are still necessary merely to convert it into steam at the same temperature4 ,to melt #a lb4 of ice requires #add lb4 ,f4 units1 to raise it to boiling point #ahj more1 and to evaporate it #ife additional4 ,the quantity of heat required for actual evaporation varies a little at different temperatures1 being somewhat larger at lower temperatures1 but the total heat required to raise water from the freezing point1 and convert it into steam at any pressure is nearly constant1 being #fce calories at atmospheric pressure1 and only about #fej calories1 or #aahj lb4 ,f4 units at #ej lb4 per sq4 inch4 ,the quantity of heat evolved by the combustion of #a lb4 of good coal is #ac1jjj to #ae1jjj lb4 ,f4 units2 or of #a kilo1 #gbjj to #hcjj k-calories1 but in raising steam in a good boiler coal will only evaporate #aj times its weight of water at #ajj 7#ecfj calories or #ifej lb4 ,f4 units71 the remaining heat being lost4 #a horse-power 7#cc1jjj foot-pounds per minute7#aha in the best engines requires about #a lb4 of coal or #ae lb4 of steam per hour1 but in those of worse construction may run up to many times that amount4 ,as1 even theoretically1 not #bj per cent4 of the total heat can be converted into mechanical work in a 8perfect0 engine working at #ge lb4 pressure1 it is often economical to use waste steam for heating or evaporation1 and where this can be done profitably1 the additional cost of the mechanical power is very small4 #ahj ,a gram-calorie of one-thousandth part of the above is also in use for some scientific purposes1 but the kilogram-calorie only is used in the following pages4 #aha ,this is equal to #gfjd kilogrammeters per sec41 but the metrical horse-power is only taken at #ge kilogrammeters in ,france and ,germany4 ,in evaporating liquids in the open pan #ecf calories is required to evaporate #a kilo of water already raised to boiling temperature1 and a larger amount for salt-solutions1 and it makes comparatively little difference whether this is done at #ajj or at a lower temperature4 ,where1 however1 evaporation is done in vacuo1 considerable economy can be effected by what are known as multiple 8effects10 in which the steam from one vacuum-pan is employed to boil a second under a reduced pressure1 and consequently boiling at a lower temperature4 ,this principle can be practically applied to as many as five or six successive 8effects10 the weaker liquor being usually evaporated at the highest temperature and lowest vacuum in the first 8effect10 by the exhaust steam of the engine used for the vacuum pumps1 while the steam from the first effect heats that of the next higher concentration1 and so on4 ,in the ,yaryan evaporator 7p4 #cci71 the boiling liquid is sprayed through coil-tubes1 thus exposing an enormous surface to evaporation1 and the whole concentration of any given portion of liquid takes place as it passes through the apparatus1 which does not1 even in multiple effects1 occupy more than #d or #e minutes2 and without the temperature of the liquid ever rising above #fj or #gj ,c4 ,in the case of liquids1 like sugar- and tannin-solutions which are liable to chemical change from continued heating1 the shortness of the time is a very great advantage4 ,the number of effects which it is desirable to use depends greatly on the cost of fuel as compared to the largely increased cost of the apparatus4 #a lb4 of coal employed in raising steam will evaporate #h lb4 in a single-effect ,yaryan1 #af lb4 in a double-effect1 #bc lb4 in a triple1 #cj lb4 in a quadruple1 and #cg lb4 in a quintuple-effect apparatus4 ,where liquids are evaporated in the open air at temperatures below boiling1 it is advisable by some means to spread the liquid in a thin film1 so as to expose a large surface1 which must be continuously removed by agitation1 so as to prevent the formation of a skin4 ,a good apparatus for this purpose is the ,chenalier evaporator 7,fig4 #ib71 which consists of steam-heated copper discs rotating in a trough containing the liquid1 which is taken up by buckets attached to the rims of the discs1 and poured over their heated surfaces4 ,in other forms1 the liquid is allowed to trickle over steam-heated pipes or corrugated plates4 ,such evaporators should be placed in a current of air so as to rapidly carry off the vapour formed4 ,their use is very objectionable for liquids1 like tannin-liquors1 which are injured by oxidation1 and they are not nearly so economical as vacuum-pans4 ,the drying of leather depends on the same laws as the evaporation of liquids1 but demands special consideration from its very different conditions of temperature and supply of heat4 ,it is important to remember that evaporation cannot go on unless the vapour-pressure of the liquid to be evaporated is higher than that of the vapour in contact with it1 and that air-pressure does not prevent evaporation1 so that if we sweep away the stagnant vapour with dry air1 evaporation will go on as quickly as in vacuo1 except that the liquid cannot boil4 ,we must also bear in mind that evaporation consumes quite as much heat at low temperatures as in a steam boiler1 and that this heat must generally come from the surrounding air1 the temperature of which it reduces4 ,illustration3 ,,fig4 #ib4--;,chenalier ,evaporator and ,glue ,coolers4 ,the rapidity of evaporation1 and the quantity of moisture which can be taken up by a given volume of air depends on the vapour-pressure1 which increases with temperature4 ,the relation between the two1 and the weight of water in grams per cubic meter which can be dissolved in dry air is given in the following table4 7,grams per cubic meter is practically equivalent to ounces per #ajjj cubic feet4 ,vapour-pressure is given in millimeters of mercury of the barometer1 p4 #dbb47 ,,vapour ,,pressure ,,of ,,water4 ---------------------------------------- --------------- ,temperature1 ,c -#aj- #e #j #e #aj #ae #bj #be #cj #ce #dj ,f #ad #bc #cb #da #ej #ei #fh #gg #hf #ie #ajd ,pressure1 mm4 #bbcbdffeiaabgagdbcecaedaiedi ,grams per cb4 m4#bdcddifhicabhagbbbhcjacib 44 ---------------------------------------- --------------- ,air is practically never dry1 and in damp weather is frequently saturated with moisture to the full extent corresponding to its temperature4 ,in ,england the average quantity of moisture contained in the air throughout the year is #hb per cent4 of the total possible1 and even in the driest summer weather it is never less than #eh per cent4 ,so long as the water is in the form of vapour1 the air remains quite clear and does not feel damp2 in fogs1 the air is not only saturated with moisture1 but contains small liquid particles floating in it4 ,of course when the air is really saturated with moisture1 it has no drying power whatever4 ,as is evident from the table1 the amount of water which can be dissolved in a given volume of air rapidly increases with temperature4 ,air at #j ,c4 is only capable of containing #di grams per cubic meter1 or not much more than #bj per cent4 of what it can contain at #be ,c4 ,it hence rapidly increases in drying power as it is warmed1 and consequently the air in a warm well-ventilated drying room in winter is generally much drier1 and has greater capacity for absorbing moisture than the open air in the driest summer weather4 ,this is the principal cause of the tendency to harsh and irregular drying by the use of artificial heat2 and may be remedied by a proper circulation of the air by a fan without too frequent change with the colder air outside4 ,on the other hand the use of a little artificial heat in damp summer weather1 when the air is saturated with moisture1 may be quite as necessary as in winter4 ,the amount of moisture in the air is most easily ascertained by a device known as the 8wet and dry bulb thermometers40 ,this consists of two thermometers mounted on a board2 one of which has the bulb covered with muslin1 and kept moist by a lamp-wick attached to it1 and dipping in a vessel of water4 ,the temperature of the wet bulb is lowered by the heat consumed in evaporation1 and the difference of its temperature from that of the dry bulb is proportionate to the drying power of the air4 ,this may be approximately calculated in grams per cubic meter by multiplying the difference by #jfd for ,centigrade or #jce for ,fahrenheit degrees2 and if deducted from the total capacity for moisture corresponding to the temperature of the wet bulb as given in table1 p4 #dbf1 will give the actual moisture in grams contained in a cubic meter of air2 but for practical purposes1 all that is necessary is to find by experience the temperature and difference between the wet and dry bulbs1 which gives the best result for the drying required1 and to maintain it as nearly as possible by regulation of the heating and ventilation4 ,cheap forms of the instrument are made for use in cotton-mills1 where it is necessary to maintain a certain degree of moisture2 or it may be improvised from two chemical thermometers which agree well together4 ,distilled 7rain or steam7 water should be used to moisten the bulb1 or it will quickly become coated with lime salts1 and it should be placed in a draught1 or its indications will not be accurate4 ,it is of course obvious that not only the wet thermometer1 but the wet hides or skins are cooled by evaporation1 and they1 in their turn1 cool the air with which they are in contact1 which not only becomes moistened1 but is lessened in its capacity for moisture by cooling1 and thus rapidly reaches a condition when it can absorb no more moisture4 ,it is thus necessary to maintain its temperature by artificial heat1 or to replace it constantly by fresh air from the outside1 and which of these expedients is most economical will depend on the temperature of the air outside as compared with that which it is required to maintain4 ,if the outside air is sufficiently warm1 and not saturated with moisture1 it is generally best to use it in large quantities without artificial heat1 wind usually supplying the necessary motive power for its circulation4 ,wet goods from the pits may thus be dried to a 8sammed0 condition by any air which is not saturated1 and above freezing point2 though the drying will often be slow4 ,for drying 8off10 artificial heat is generally necessary1 since the attraction of the fibre for the last traces of moisture is very considerable1 and to remove it the drying power of the air must be considerably higher than that required for the evaporation of free water4#ahb ,in drying stuffed leather a temperature must generally be maintained sufficient to keep the fats employed in partial fusion1 and so permit their absorption by the leather1 while at the same time the drying must be gradual1 or the water may be dried out before the fats have time to take its place4 ,this is generally best attained by the use of artificial heat1 and ventilation by circulating the air by a fan without its too frequent renewal1 especially in cold weather4 ,frequently air which has been heated and used for drying off finished goods1 and so partially saturated with moisture1 may be used with advantage for wet goods1 or for other purposes where a more gentle drying is required4 ,if the temperature is low outside1 the amount of heat consumed in heating cold air to the temperature required may be very considerable4 ,the weight of a cubic meter of air at #j ,c4 and atmospheric pressure is #abic kilos1 and its specific heat at constant pressure is #jbcge of that of water4 ,therefore to heat a cubic meter of air at ordinary pressure and temperature #a ,c4 will require the same amount of heat as that used to heat #jc kilo of water to the same extent1 or in other words #jc of a k4-calorie4 ,if steam-heating is used1 #a kilo of good coal burnt under the boiler should heat about #ahjj cubic meters #aj ,c41 or #a lb4 should heat #eb1jjj cubic feet #aj ,f41 assuming that the condensed water is not cooled below #ajj ,c4 ,these seem large volumes1 but if we reflect that a #dh-;inch ,blackman fan may move #cj1jjj cubic feet per minute1 we shall realise that the cost of coal in heating air is not inconsiderable4 #ahb ,commercially-dry leather generally1 if unstuffed1 contains about #ae per cent4 of residual moisture1 which varies in amount with the weather1 and can be more or less completely removed by drying at high temperatures4 ,if leather has been over-dried1 it only slowly regains its weight on exposure to cold air4 ,commercial disputes not unfrequently arise on the dryness of leather4 ,in the opinion of the writer1 a customer can only claim that the leather should be sufficiently dry not to lose weight when exposed to dry air at the ordinary temperature and degree of dryness of a warehouse or factory1 and claims based on re-drying in hot drying rooms are distinctly fraudulent4 ,we must now consider the heat consumed by the actual evaporation of the water in the leather4 ,the actual evaporation of water already raised to #ajj ,c4 consumes #ecf k4-calories1 but the evaporation of water which has not previously been heated so far consumes more heat1 and we may take that required at ordinary temperatures as in round numbers #fjj k4-calories per kilo1 or #ajhj lb4 ,f4 units per lb4 ,disregarding small fractions1 this is equivalent to the cooling to the same temperature of an equal weight of steam in the heating pipes1 and this1 as we have seen1 demands about of its weight of coal for its production from water already heated to #ajj ,c4 ,the cooling takes place1 in the first instance1 in the leather1 the temperature of which is reduced like that of the wet-bulb thermometer2 and this in its turn cools the air in contact with it4 ,thus in air-drying without artificial heat1 the whole heat must be supplied by the air and the loss reduces its capacity for moisture1 greatly increasing the volume required4 ,this is not of much consequence in open-air drying1 since even a light wind will supply air in enormous volume4 ,a moderate breeze of ten miles an hour moves about #ae feet or #d meters per second4 ,when1 however1 the air must be moved by fans1 the power required becomes important4 ,the evaporation of #a kilo of water at summer temperature will cool about #bjjj cubic meters1 and that of #a lb4 #cb1jjj cubic feet of air #a ,c4 ,in calculating the ventilating and heating power required in fitting up drying rooms1 it is usually necessary to ascertain that required under the most unfavourable circumstances1 and then add a liberal margin to cover errors and accidents4 ,as the calculations are1 in consequence of the many varying conditions1 somewhat complex1 it may be convenient to give as examples the quantities of air and heat required to evaporate #a kilo 7#bbje lb47 of water under different ordinary conditions1 and these may serve as a basis of calculation of the drying power which must be provided for different tanneries4 #a4 ,indifferent ,open-,air ,drying4--,air at #aj ,c4 7#ej ,f471 wet-bulb thermometer #g ,c4 7#ddc ,f471 indicating a total capacity for moisture of about #b grm4 per cubic meter2 air not to be cooled beyond #gge ,c4 7#df ,f471 leaving a residual capacity for moisture of #je grm4 per cubic meter4 ,each cubic meter will therefore take up #ae grm4 of moisture1 and as #a kilo contains #ajjj grm4 we have #ajjj ---- #ae #fff cubic meters per kilo required to absorb moisture2 and #fjj ----------- #bbe #jc #hhh cubic meters reduced #bbe to furnish the #fjj cal4 required for evaporation4 ,total air used #aeed cubic meters or #ed1ijj cubic feet4 #b4 ,drying with ,heat4--,outside-air at #aj saturated with moisture1 heated to #bj ,c4 7#fh ,f47 acquires a capacity for #gi grm4 per cubic meter4 ,if we assume that a drying capacity of #b grm4 per meter is required to complete the drying1 we have an effective capacity of #ei grm4 #ajjj ---- #ei #agj cubic meters or #fjjj cubic feet1 and to heat this #aj ,c4 will require #eaj cal4 ,evaporation of #a kilo will consume #fjj cal4 ,total heat #aaaj cal4 #c4 ,drying with ,heat4--,outside-air at #aj as above1 heated to #be ,c41 giving an effective capacity for moisture of #ace - #bj #aae grm4 per cubic meter4 #ajjj ---- #aae #hg cubic meters or #cjgj cubic feet4 ,to warm this #ae requires #cia cal42 and #fjj cal4 added for evaporation gives a total of #iia cal4 ,comparing #b and #c we see that the higher temperature is more economical1 where it can be allowed1 than the lower1 both in air and heat1 though this is partly compensated by the greater loss of heat by cooling of the building1 etc41 which it entails4 #d4 ,air at #j ,c4 heated to #bj requires about #ig cubic meters1 or #cdcj cubic feet of air1 and a total of #aahj cal4 #e4 ,air at #j ,c4 and heated to #be ,c4 requires #fc cubic meters or #bbcj cubic feet1 and a total of #ajge cal4 #f4 ,air at -#ae ,c4 7#e ,f47 requires #de cal4 per cubic meter to raise it to #j ,c41 and acquires a capacity for drying of about #b grm4 per meter4 ,we will apply these figures to a drying room arranged with a screw-fan with a central division1 or two floors1 so that the air can be either circulated or replaced with fresh air from the outside at will 7see ,fig4 #id1 p4 #dce74 ,such a room with #ajj feet of length clear of space required for fans1 air passages1 and heating pipes1 and #bj feet #h feet in section1 should hang about #hjj medium butts1 weighing say #ab kilo 7#bg lb47 each1 and when wet from the yard1 containing the same weight of water4 ,a #dh-;inch ,blackman fan1 under these conditions would probably move say #bj1jjj cubic feet 7#efe cubic meters7 of air per minute1 at the cost of #b or #b horse-power4 ,this1 in a room of the section named1 would give an average velocity of #abe feet per minute or rather under #a miles an hour2 not at all too much to keep the air freely circulating among closely hung leather4 ,if we assume that these butts are to be dried in a week 7practically #aj1jjj minutes7 under the conditions of ,no4 #b1 the #aj1jjj kilos of water they contain will require #a1gjj1jjj cubic meters of air1 or about #agj cubic meters per minute1 or about of the air must be fresh every time it passes through the fan4 #a kilo of water requiring #aaaj cal4 must be evaporated per minute4 ,under the conditions of ,no4 #d1 only #ig cubic meters of air per minute would be required1 or about might be circulated without change1 but the total heat required would be about the same1 #aahj cal4 ,under the conditions of ,nos4 #d and #f some #afbj cal4 per minute would be employed4 ,it is hardly necessary to provide for the full amount of heat required by ,no4 #f1 since in this country such conditions occur but seldom1 and never for more than a few days at a time1 and during such a period1 much less heat would suffice to carry on the drying at a slower rate1 and keep out the frost4 ,beside the heat required for actual drying1 it is necessary to provide for that lost by the building during cold weather1 and this is much more difficult to calculate4 ,if1 by arranging the outlet for moist air on the pressure side of the fan1 the internal pressure of the building be kept a little lower than the outside1 there can be no loss by escape of hot air1 any leakage being inwards1 and supplying a part of the change of air which1 we have seen1 is necessary4 ,in a brick building with glass windows1 the loss of heat is far less than in the old-fashioned wooden louvre-boarded structure1 and where fan-drying is in constant use1 the brick structure is much to be preferred4 ,frequent windows1 with casements horizontally pivoted at the centre1 will supply enough air for favourable conditions of air-drying1 and when the weather is bad1 resort is had to the fan4 ,most modern drying rooms in the ,leeds district are built upon this plan4 ,where louvre-boarded structures must be used for fan-drying1 the sides should be made as tight as possible in winter by sheets of canvas or sail-cloth nailed on1 for which purpose old sails can be bought in seaport towns at reasonable rates1 a few louvre-boards only being kept open for the admission of air in suitable positions4 ,box1 in his #8,practical ,treatise on ,heat'#ahc puts the loss through walls in brick buildings for a difference of #cj ,f4 7#aff ,c47 between inside and outside temperatures1 at the approximate amounts shown in the following table4 #ahc ,e4 ,f4 ,n4 ,spon1 ,ltd41 ,london4 ,,loss ,,of ,,heat ,,through ,,walls4 ---------------------------------------- ---------------------------- ,thickness ,k4-calories -- of ,wall per ,sq4 ,foot in ,inches4 per ,hour4 ---------------------------------------- ---------------------------- #de #agf ,stone walls must be about one-half thicker1 to #i #add afford equal warmth with brick ones4 #ad #abj ,the loss from glass windows amounts to #c or #d #ah #ajf k4-calories per square foot per hour4 ---------------------------------------- ---------------------------- ,if the building is of several stories1 the loss to the roof in the intermediate ones need hardly be taken into account1 but if the ceiling is not tight1 and open to the roof1 the loss may be great1 but difficult to estimate4 ,if we consider the drying room already described1 the total area of the walls and ceiling is about #djjj feet1 and to maintain its temperature #cj ,f4 above the atmosphere at #ab cal4 per sq4 foot would require #dhjj cal4 per hour or #hj cal4 per minute1 a very small amount compared to that consumed in drying4 ,the following table calculated from data given by ,box will give some idea of the amount of steam or hot-water piping required for heating4 ,the sizes given are for the internal diameter of the pipe1 allowance being made for the increased heating surface of pipes of ordinary thickness4 ,small pipes are considerably more effective in proportion to their surface than large ones1 and for high-pressure heating #a or #b-;inch wrought-iron pipes are to be recommended as in many ways preferable to cast iron4 ,the gilled or ribbed pipes now often used are also advantageous as giving a greatly increased heating surface4 ,,heat ,,given ,,by ,,steam-,,pipes4 ---------------------------------------- --------- ,steam ,temperature ,k4-calories per ,pressure1 of hour per foot run lb4 per ,pipe4 of ,pipe4 sq4 in4 ---------------------------------------- ------- ,f4 #b in4#c in4#d in4 #eb #cjj #ajb #acg #afi #ce #bhj #ib #aba #adh #ba #bfj #ha #ajf #acj #aj #bdj #fh #ib #aac #be #bbj #ei #ha #ig #baj #ed #gb #hi #bjj #di #ff #ha #aij #de #fj #gd #ahj #dj #ed #fg #agj #cf #di #fj ---------------------------------------- ------- ,the temperature of the air to be heated is understood to be #fj ,f42 at lower temperatures the quantity of heat given off by the pipes would be greater1 and at higher temperatures less2 the amount being approximately proportional to the difference of temperature between the air and the hot pipes4 ,it is also important to note that the table refers to steam-pipes in still air1 and that if placed in a powerful draught1 7as immediately before or behind the fan71 their heating effect may be at least doubled4 ,this has not been considered in the following calculations4 ,applying these figures to the estimate of #aaaj calories per minute required for drying in our building1 and assuming #hj calories per minute for the loss of heat through the walls1 we have a total of about #ga1djj calories per hour1 and to obtain this would require #gcf feet of #d-;inch pipe at #bbj ,f4 7heated by exhaust steam7 or #gjj feet of #b-;inch pipe heated to #cjj ,f4 by steam at #eb lb4 pressure4 ,if we adopt the estimate of #afbj calories of ,no4 #e and #f1 we shall require #ajej and #ajjj feet of the two pipes respectively1 and this covers approximately the worst conditions4 ,we must1 however1 remember that these estimates are made for continuous drying during the twenty-four hours1 and that if the fan and steam are only applied during a portion of this time1 the supply both of air and steam must be proportionately increased1 or the time of drying correspondingly lengthened4 ,it is very desirable1 however1 that the fan should be driven by a small separate engine1 the steam for which will only form a small proportion of that required for heating1 and of which the whole of the heat will be recovered1 since even that utilised in driving the fan will again be converted into heat by the friction of the air1 and will therefore cost nothing4 ,this arrangement will enable the drying to proceed so long as the necessary steam is maintained1 which in bad weather can easily be done by the night watchman4 ,it may also be pointed out that1 during a great part of the year1 the goods can be dried to a 8sammied0 condition without heat1 or in the open air1 or in the case of dressing leather1 a considerable part of the water can be removed by pressing or squeezing1 effecting a further economy4 ,illustration3 ,,fig4 #ic4--;,blackman ,fan4 ,it must be left to the reader to apply the same calculation to other sorts of leather than sole1 but it may be pointed out that the essential point1 as regards heating and ventilation1 is the weight of water to be evaporated in a given time1 and that the actual size and shape of the drying room is unimportant1 so long as adequate heating and circulation of the air between the leather is secured2 and these remarks also apply to the particular form of fan or other ventilation employed1 and to the means of heating4 ,as the quantity of heat consumed is very considerable1 it is well to look out for sources of waste heat which can be employed1 or for means by which the heat of the fuel can be more directly and completely utilised than it is in raising steam4 ,thus a large amount of heat can sometimes be obtained by passing air through pipes or 8economisers0 fitted in a chimney-flue2#ahd or gilled stoves or 8calorifers0 may be used in a separate chamber to directly heat the air which is drawn in by the fan4 #ahd ,these pipes should be provided with scrapers to remove soot as in ,green's economiser1 or their efficiency will be much diminished4 ,illustration3 ,,fig4 #id4--,section of ,drying ,rooms with ,fan4 ,figs4 #ic and #id1 furnished by the ,james ,keith and ,blackman ,co41 ,ltd41 give a good idea of the construction of screw fans1 and the general principle of arrangement of fan drying rooms1 the air in this case being circulated in opposite directions on two floors1 and the amount of change being regulated by the shutters at ,a1 etc4 ,the grouping of pipes at the ends of the two floors which it shows is in general a good arrangement1 but the length between them should not be too great1 or the drying will be unequal in different parts of the room4 ,sometimes this is convenient2 thus if most of the heat be supplied to the air coming fresh from the inlet on the upper floor1 the damper and colder air of the lower room can be continuously used for drying wet goods from the yard1 and the upper reserved for drying off the finished leather4 ,a disadvantage of this plan is that open air drying can seldom be utilised except in an elevated building2 and even when it is adopted1 means should be provided for heating the lower room in cold weather4 ,in place of two floors1 it is obvious that a single floor may be divided into two compartments by a longitudinal partition4 ,whatever pipes are grouped at the ends of the building1 it is advisable to arrange sufficient to prevent frost1 against the walls1 or in the old-fashioned way on the floors beneath the leather1 but not too close to it1 and protected by a wooden lattice on which the workmen can stand1 which removes the risk of accident from wet leather falling on the hot pipes4 ,the latticed space should be open at the end facing the air current1 so as to receive a portion of the draught1 which will become heated and ascend1 its place being taken by damp and cold air from the leather1 to be re-warmed4 ,water-vapour in itself is lighter than air1 but the contraction produced by the cooling of evaporation more than compensates this1 and the damp air is therefore heavier than the dry4 ,the arrangement of hot pipes near the ceiling of a drying room1 which has been borrowed from some ,american tanneries1 is wrong in principle1 unless the air is forced in at the upper part of the room1 or the upper floor is latticed1 and only acts in other cases when the air is thoroughly mixed and circulated by mechanical ventilators2 while pipes near the floor will continue to produce a certain amount of circulation of the air1 even when the fan is not running4 ,in protecting pipes by lattices care should be taken not to confine them too closely1 or their heating effect will be seriously diminished4 ,in fan-drying1 leather should be hung edgeways to the current of air1 so as to allow of its free and uniform passage between4 ,in the case of sole leather the butts or bends are conveniently suspended by ,s-hooks of brass or iron wire1 to hooks or nails fixed in the joists4 ,if gangways between the leather must be left in the direction of the draught1 they should be closed at intervals in the length of the room by curtains or shutters1 so as to deflect the air-current into the leather4 ,screw fans like the ,blackman can be used either to suck or to blow the air1 though the former is preferable where it can be arranged1 because it produces a more uniform current in the room4 ,on the blowing side the air issues with considerable velocity in a sort of cone1 but little coming through the centre of the fan1 while that near the edges spreads rapidly from its centrifugal motion4 ,this is rather advantageous where the fan blows into an open room1 but involves waste of power where it discharges into narrow and square air-ways4 ,the ends of the vanes of the ,blackman are turned in at the rim of the fan to prevent this tangential discharge1 but it is probable that where a fan is to blow into a room1 it would be more advantageous to put it on the inner side of the wall1 and without curved ends to the vanes1 so as to distribute the air as widely as possible4 ,a somewhat similar result would be attained with a ,blackman1 by placing it in a position the reverse of that for which it is intended1 and running it also the reverse way2 but its 8efficiency0 might possibly be lessened4 ,screw-fans are good for moving large volumes of air at comparatively low velocities1 and against little or no resistance1 but they are quite unsuitable for forcing air against high resistance1 or through narrow channels1 and for this purpose centrifugal fans like the ,capel 7,fig4 #ie7 are much more suitable1 and mechanically more efficient4 ,in any case there is much loss of power in forcing air through narrow airways1 and if a screw fan must be employed for the purpose1 the channel should be as large in section as the area of the fan1 and all sharp angles in its course should be avoided4 ,there is great loss of power where a current of air or water has to pass suddenly either from a wider to a narrower channel1 or the reverse1 and in both cases the resistance is diminished by making the enlargement or contraction gradual or 8bell-mouthed40 ,thus a pipe conveying water at a given head into or out of a cistern will discharge a much larger quantity1 if the ends are bell-mouthed1 than if it terminates abruptly4 ,for the same reasons1 air suffers considerable resistance if it has to pass suddenly into1 or out of a larger space1 such as a drying room2 and unnecessary partitions1 and other abrupt changes of dimension in the current should be avoided4 ,curves should also take the place of angles as much as possible4 ,illustration3 ,,fig4 #ie4--;,capel ,centrifugal ,fan4 ,systems in which air is drawn or forced over systems of heating pipes by a centrifugal fan1 and then distributed through comparatively small airways among the leather which is to be dried are in some cases convenient and advantageous4 ,among these may be mentioned the ,sturtevant and the ,seagrave-,bevington4 ,there can be no valid patent on the general principle of heating by distributing air in this way1 but only on the particular arrangement or appliances used in the special case4 ,centrifugal fans should be considerably larger in diameter than in axial length1 those with long vanes of small radius being wasteful in power from the insufficient supply of air to the centre4 ,there is also no reason why1 in some cases1 centrifugal fans should not be substituted for screw-fans in drying on the system which ,i first described1 especially in cases where the air has to encounter considerable resistance1 as for instance in traversing a filter to remove dust4 ,one of the best filters for this purpose is a table of wire-gauze covered to a depth of #c or #d inches with loose wool4 ,hair or cheaper fibrous materials may be substituted for the wool1 but are less efficient4 ,the air must of course be sucked downwards through the gauze4 ,when the wool becomes dirty1 it may be washed1 if possible in a wool- or hair-washing machine1 and again spread on the table in a damp condition1 as it will quickly be dried by the current of air4 ,flannel is also useful where the wool-filter is impracticable1 but requires frequent washing4 ,apart from wind1 natural ventilation is seldom to be relied on for drying on any considerable scale4 ,heated air is1 of course1 lighter than cold1 and this is the cause of chimney-draught1 but to get a good circulation in this way1 a high shaft1 and high temperature is required4 ,nevertheless1 in one of its best forms1 the method has been a good deal used in ,america1 in the so-called 8turret-dryer10 a building of seven or eight stories in height1 constructed of wood with latticed floors1 and heated by steam-piping at the bottom1 where the air is admitted4 ,the method is not likely to be much used in this country1 as apart from the questions of cost of building1 fire-risk1 and trouble of raising and lowering the leather1 a good draught will only be obtained when the outer temperature is low in comparison to that inside1 and in our milder and moister climate the conditions are not nearly so favourable as in the ,united ,states4 ,as the air is rendered heavier by the cooling of evaporation to a larger extent than it is lightened by the water vapour1 there is a tendency in drying by upward ventilation for the warm air to form local upward currents1 while the cold and damp air falls back2 and from this irregularity of flow1 it is difficult to saturate the air equally4 ,this may be avoided by downward ventilation1 in which the warm air is admitted at the top of the drying room and the cold and damp air allowed to escape at the bottom4 ,this fact suggests that in using systems of drying such as the ,sturtevant1 it would be better to place the distributing pipes at the top rather than the bottom of the room1 but in this case care would have to be taken that there were no openings left by which the air could escape at the top of the room without descending through the leather4 ,if this be avoided1 the warm air will float on the top of the colder and damper1 and press it uniformly down and out4 ,i believe the merit of first having applied the principle of downward ventilation to leather-drying is due to ,edward ,wilson of ,exeter4 ,it is necessary that the hot air should be forced in at the top1 or the cold air sucked out from the bottom2 and the mere placing of hot pipes near the top of the room 7p4 #dcf7 will not cause the required circulation4 ,wilson placed his heating pipes in a partitioned space at the side of the room1 at the bottom of which cold air was admitted from the outside1 which escaped into the room at the top4 ,as the temperature of this side chamber was high and the air consequently light1 an upward current was produced in it1 though probably somewhat inefficiently1 as the height of the column of heated air could only be small4 ,assisted by a fan1 and circulating a part of the air1 the method should give good results1 especially over two 7latticed7 floors4 ,as the air could not be satisfactorily heated in its downward course1 the method would not be suited for more than about two floors1 and the drying in the lower room would be cool and gentle4 ,one or two points in the practical arrangement of steam-pipes may be mentioned1 as they are often overlooked even by professional engineers4 ,the steam must always be admitted at the highest point in the system1 and there must be a steady descent1 without hollow places where condensed water can accumulate1 to the steam-trap by which it is removed4 ,in horizontal pipes1 about #a inch descent in #ajj is sufficient4 ,if water accumulates1 there is not merely serious danger in case of frost1 but during use1 by the sudden condensation of the steam1 a vacuum is frequently formed1 into which the water is shot like the liquid in a 8water hammer10 producing violent and noisy concussions1 and in some cases even fracture of the pipes1 or loosening of their joints4 ,if high-pressure steam is used1 a very small supply-pipe will feed a considerable system of heating pipes or radiators1 but with exhaust steam1 great pains should be taken to have pipes of ample size1 to avoid back-pressure on the engines4 ,in both cases it is often convenient to arrange the pipes1 not as a continuous line1 in which drainage is generally difficult1 but in parallels like the bars of a gridiron4 ,with high-pressure steam1 there need be no fear1 if the pipes are kept clear of air by allowing a little escape through small air-taps1 of the steam failing to find its way to all parts of the pipe1 as a vacuum is produced by condensation in proportion to the heat given off4 ,with exhaust-steam1 no steam-trap is desirable1 but any steam not condensed should escape freely into the open air or a chimney 7after separating condensed water71 and it is well to render the resistance in all the pipes of a gridiron approximately equal1 which may be done by admitting steam at one corner1 and allowing it to escape at the opposite 7diagonal7 one4 ,in the arrangement of steam-pipes in parallels1 the practicability of repair to one pipe or joint without interfering with the others must always be considered4 ,if screwed wrought-iron pipes are used1 each parallel must be provided with a bolted flange1 or 8running socket10 to permit of unscrewing4 ,the difficulty of accurately adjusting the lengths of the several parallels must be considered1 especially with flanged metal pipes1 and also their motion by expansion when hot1 which amounts to #a or #b parts per #ajjj of length according to the temperatures of steam and air4 ,expansion-joints with stuffing boxes are costly and troublesome1 and apt to leak1 and may in many cases be avoided by suitable arrangement of the pipes4 ,thus instead of having the pipes rigidly fixed at both ends1 one end of the system may be left free to move1 each pipe being separately returned to an exit pipe at the same end but lower in level than the supply2 or a single exit pipe may be thus returned1 its expansion and contraction being practically the same as that of the heating pipes4 ,in moderate lengths of wrought-iron pipe1 sufficient relief may often be obtained from the flexure of the pipe1 if in some part of its course it is carried at right angles to its general direction1 which is often necessary for other reasons4 ,if pipes are laid in long lengths1 the loose end should be supported on rollers or short pieces of pipe1 so as to avoid moving the supports or straining the pipe in expansion4 ,it is useless to attempt to regulate the temperature of low pressure steam-pipes by turning down the steam1 since1 so long as the pipe is supplied with sufficient steam to fill it1 its temperature cannot be less than #ajj1 and even with high-pressure pipes1 the power of regulation by altering the steam-pressure is very limited4 ,it is far better to arrange the pipes or radiators in groups1 from some of which the steam can be turned off entirely when less heat is needed4 ,it must not be forgotten that if these discharge into a common steam-trap1 it will be necessary to turn off their exits as well as their steam supply1 or steam will come back into them from the other pipes1 and probably prevent the escape of condensed water4 ,in some cases it is more convenient to give the several sections independent exits or steam-traps4 ,many good steam-traps are now on the market1 depending either on the expansion and contraction of metals1 or on floats in a closed box1 which open a valve as the water accumulates4 ,traps of the latter class with closed copper balls are to be avoided1 as the ball is sure eventually to become filled with water4 ,several traps have been devised in which an open vessel is used as a float1 which is always kept empty by the discharge of the water through a pipe dipping into it4 ,the condensed water from steam-pipes is rarely suitable for use in the tannery1 from the dissolved and suspended iron-oxide which it contains1 from which it can only be freed by boiling and filtering1 or treatment with precipitants 7p4 #ie74 ,its most appropriate use is generally return to the boiler4 ,systems were formerly in vogue by which it was allowed to run back to the boiler as it condensed1 but these could only answer when the pressure in the pipes was equal to that in the boiler1 which is rarely the case4 ,it must generally be forced in by the feed-pump or injector4 ,hot water has often been advocated in preference to steam for heating1 but is more costly1 as it requires a separate boiler1 and much larger pipe-surface for the same effect4 ,its only important advantage is that the pipes maintain their heat for some time1 even when the fire has gone down1 while steam-pipes cool at once if steam is allowed to go down in the boiler4 ,in any considerable tannery1 however1 this will seldom or never be the case1 since if a good pressure of steam is up at night1 when the fires are banked up1 the boiler will in itself contain a large reserve of heat1 and1 of course1 working pressure will be required before the engines can start in the morning4 ,hot water systems require careful planning to obtain reliable and uniform circulation4 ,,chapter ,,xxvii4 ,,construction ,,and ,,maintenance ,,of ,,tanneries4 ,as few architects have specially studied the construction of tanneries1 and in most cases much of the arrangement depends on the knowledge of the tanner himself1 a short chapter on the subject will not be out of place4 ,in the selection of a site1 a clay or loamy soil is to be preferred to a gravelly or sandy one1 as lessening the liability to leakage1 and waste of liquor4 ,perhaps1 however1 the first consideration of all is the possibility of drainage and disposal of effluent waste liquors and washing waters1 since it is now rarely possible to run these1 without previous treatment1 into a river or stream4 ,some information is given in ,chapter ,,xxviii4 on the methods of partial purification which are available to the tanner1 but these are always costly and troublesome1 and the possibility of running direct into a sewerage system1 or a tidal river is of great advantage4 ,under the ,public ,health ,act1 authorities are bound to receive manufacturing effluents into their sewers if the latter are of sufficient capacity1 and the effluents not such as either to damage the sewers1 or interfere with the processes of purification adopted by the authority4 ,this act is in many districts practically superseded by special legislation1 but tanners' effluents are generally received into sewers if freed from solid matter4 ,when mixed with other sewage1 they do not interfere with irrigation or bacterial treatment4 ,in selecting a site within a sewered district1 regard must be had to the possibility of causing a nuisance to the neighbourhood by foul smells4 ,really injurious smells should not be caused by a properly conducted tannery1 but it is difficult to avoid odour1 and a single badly disposed neighbour may cause infinite trouble and expense4 ,another important consideration is the water supply1 since for the large quantities used in a tannery1 town water is generally very expensive4 ,with regard to quality and impurities of water information may be found in ,chapter ,x42 but1 as a general rule1 the softer and purer the supply the better4 ,it is also of great advantage when the source is at such a level that the water can flow into the tan-yard1 or at least into the beam-house1 without pumping4 ,filtration too1 when needed1 is much facilitated by a sufficient head of water4 ,commercial facilities1 such as nearness to markets and sources of supply of raw materials1 and the availability of rail and water carriage are of an importance at least equal to the points already considered1 but hardly come within the scope of this work4 ,the site chosen1 the next question is the arrangement of the buildings4 ,it is very doubtful1 where ground is not inordinately expensive1 whether it is wise to erect drying-sheds over the pits4 ,in case of fire1 very serious damage is done to liquor and leather by the heat and burning timber4 ,if the turret form of drier be decided on1 strong foundations are required1 and the ground-floor or basement is occupied with heating apparatus2 if fan-drying1 no lofty buildings are needed1 and the drying rooms are conveniently placed over the finishing and currying shops2 and1 on the other hand1 the tan-house may be easily and cheaply covered with slated roofs1 with nearly vertical sections of glass1 to the north if possible1 like a weaving-shed1 through which sufficient light for convenient work and cleanliness is admitted4 ,the direct rays of the sun should be avoided1 but in the writer's opinion the balance of advantage is largely in favour of a liberal supply of light4 ,iron roofs are unsuitable1 since the moisture condenses on1 and rusts them2 and particles of oxide fall into the liquors1 and cause iron-stains4 ,good ventilation along the ridge of the roof should be provided1 wherever there is any steam or hot liquor used2 or the condensed moisture soon leads to decay4 ,in arranging the general plan of the buildings1 much depends on local circumstances2 but as far as possible1 they must be so arranged that the hides and leather work straight forward from one department to another with as little wheeling or carrying as possible2 that the buildings where power is used be near to the engine so as to avoid long transmissions1 which are very wasteful of power2 and that the different buildings be so isolated as to diminish the risk of the whole being destroyed in case of fire4 ,a chapter on the construction and maintenance of tanneries and leather works would be incomplete if it did not refer to the very important question of ,fire ,insurance4#ahe ,to an extent this may be regarded as a fixed charge against any business1 very much in the same way as local and imperial rates4 ,it is not1 however1 to be lost sight of1 that to some considerable extent the amount of insurance premium is regulated by the insured himself4 ,if a man conducts his business in unsuitable and badly constructed buildings2 if attention is not paid to some of the elementary hazards connected with a fire outbreak2 he must not blame the insurance companies for the demand of what he considers an excessive premium4 ,if this faulty construction and imperfect equipment of buildings pertain to any considerable extent throughout a given trade where the process is more or less hazardous1 it is futile to appeal to insurance companies1 which1 after all1 are merely commercial and not charitable institutions1 for a reduction in the rates4 ,the only standard to guide the company is the loss-ratio1 and given a high loss-ratio1 there must be a corresponding premium paid4 #ahe ,with regard to fire insurance1 ,i am much indebted to ,mr4 ,a4 ,w4 ,bain1 of ,leeds for valuable information4 ,there is1 however--thanks to modern science--a method available whereby the great bulk of fires may be checked in their inception2 an appliance1 automatic in its operation1 and of proved efficiency4 ,this appliance is known as the sprinkler4 ,a system of water-pipes is fixed under the ceilings of the building to be protected1 to which are attached sprinkling jets at suitable intervals1 each of which is closed by a valve held in place by a joint of fusible metal1 which gives way if the temperature rises beyond a given point4 ,there are two or three recognised patterns approved by the ,fire ,offices ,committee after patient investigation and practical test4 ,these appliances have now been at work for something like fifteen years in this country4 ,one of the first trades to recognise their utility was that of the cotton-spinner4 ,at one time serious fires in the cotton trade were of frequent occurrence4 ,now--owing to the efficient fire appliances--while fires may be as frequent in their inception as formerly1 they are stopped at such a stage as to prevent any considerable loss4 ,the consequence has been that the cotton-spinner1 at one time the owner of a highly-rated risk1 and one which few companies cared to insure1 is now in the position of having his business eagerly sought after1 and large discounts offered him off the charges he was once called upon to pay4 ,more important still is the consideration to him that his business is not so liable to be interfered with or stopped as the result of fire4 ,there are1 it is estimated1 at the present moment1 no less a proportion than #ij per cent of the cotton-spinners whose premises are protected by sprinkler installations4 ,other hazardous risks such as corn-millers'1 woollen and worsted manufacturers'1 saw-millers'1 engineers'1 are adopting these appliances freely1 and it is a matter of surprise that so very few tanneries or currying shops--so far as ,i have been able to learn1 not more than twelve--have done the same4 ,the consequence is that the loss-ratio in tannery risks still retains its unenviable notoriety3 the rates for fire insurance have risen considerably1 and as a result the tanners' profits are correspondingly less4 ,considering the extent and importance of many of the tannery risks throughout ,great ,britain1 one can only express surprise that these appliances have been so little adopted4 ,the construction of a new tannery demands serious attention from an insurance standpoint4 ,the boiler-house should be a detached building2 the grinding of bark and myrobalans should be conducted in buildings isolated from the general works2 in fact no better advice could be given to a tanner1 either in the construction of new premises1 or the rearrangement and remodelling of old1 than to consult an experienced insurance man1 whether official or broker1 as to the best means of constructing and arranging to secure the most favourable terms4 ,another point which should be provided for1 and which is often overlooked1 is the feasibility of future extension without serious changes of arrangement4 ,it may be taken as a probability of the future1 even if it be not already a fact1 that small tanneries cannot be made to pay1 and that if a business succeeds1 its extension will prove desirable2 and in an ill-planned yard this may involve either entire reconstruction of a very expensive and inconvenient sort1 or the separation of new departments1 so as to involve serious increase of carrying4 ,a good arrangement is that of a long front building serving to connect the whole1 behind which the various departments are erected at right angles leaving room for extension backwards as required4 ,as regards the first of these conditions1 if the various soaks1 limes1 bates1 and handlers are well arranged1 it is hardly necessary to do more than draw the goods from one pit into the next throughout the whole of the process4 ,to1 and from the layers1 the goods must generally be carried or wheeled4 ,in the sheds1 if it be a sole-leather tannery1 the butts should first come into turrets or open sheds for the rough drying2 then into a room sheltered from draughts to temper for striking4 ,the striking machines or beams should be in an adjoining room1 or immediately below2 then a small shed-space for drying before rolling2 next the roller room2 and then the warm stove for drying off4 ,if two of the latter can be provided to be used alternately1 it will allow the goods to be aired off without taking down1 and they may then be immediately handed or lowered into the warehouse1 without fear of over-drying1 which is sometimes difficult to avoid where leather must be taken direct out of the hot drying-room4 ,the same principles are easily applied in yards for lighter leathers4 ,to lessen loss of power in transmission1 the engine should be near the centre of the main range of buildings1 with perhaps the grinding machinery on one side1 and the leather finishing on the other2 but this would be rather liable to increase the fire-risk4 ,a very good plan would be to have the engine-house in the centre as suggested1 but separated from the buildings on each side by brick gables2 and with the boiler-house behind it1 and under a separate roof1 say of corrugated iron4 ,if it be impossible to have the engine near its work1 it is in most cases better to employ a separate high-pressure engine1 which may be within a glass partition1 and will work all day with scarcely any attention4 ,the loss of power in carrying steam for moderate distances through sufficiently large and well-clothed pipes is much smaller than that of long lines of shafting4 ,the writer has known cases where fully half the indicated power of the engine was consumed in friction of the engine1 shafting and belts4 ,high-pressure engines are as a rule to be preferred to condensing for tannery use1 since the waste steam can generally be employed for heating1 and both the first cost and that of maintenance are smaller4 ,where much fuel is used1 it is quite worth while to have the cylinders indicated occasionally1 both running light1 and driving the machinery2 much information is gained in this way as to the power spent on the various machines1 and very frequently large economy is effected by proper adjustment of the valves4 ,to work economically1 an engine should be of ample power for all it has to do2 and adjusted to its work1 not by lowering the pressure of steam1 or by checking it at the throttle-valve1 but by setting the slide-valves to cut off as early in the stroke as may be4 ,as to how early this is possible1 an indicator-diagram will at once give information4 ,if the whole of the waste steam can be used profitably for heating purposes1 economy in the working of the engine is of little consequence1 but1 otherwise1 it is very injudicious1 for the sake of a little saving in first cost1 to put in an old or inferior engine1 which has to be dearly paid for in waste of fuel4 ,in the choice of an engine1 the advice of an expert engineer is desirable1 since many engines which are mechanically well made1 are uneconomical through the faults of a rule-of-thumb design4 ,in this respect the ,english engine-builder is frequently inferior to his better trained continental competitor4 ,in place of using small steam engines to distribute power1 electric driving deserves consideration4 ,for long drives the loss of power is much less than that of shafting1 and by concentrating the whole production of the power in one large and well-constructed engine1 the cost per horse-power can be much reduced4 ,while large and well-constructed engines may develop #a horse-power at a cost in coal of #a lb4 per hour1 it is not uncommon to use #ab lb4 for the same output4 ,in tanneries1 however1 the power used bears a much less proportion to total expenses than it does in the textile and many other trades4 ,the first cost of electric driving is somewhat high4 ,motors of the 8armoured0 or iron-cased type must be used in all positions where they are subject to wet or dust4 ,it must be borne in mind that an electric motor will not start against a heavy load1 as it only develops its full power at a high speed1 and if it receive the full pressure of the current before this is attained1 its coils will probably be burnt out1 unless saved by the melting of its safety-fuse4 ,a similar danger is incurred1 if the motor is brought up by overloading while the current is on4 ,it is therefore generally necessary to connect a motor with its work by a belt which is only brought on to the working pulley when its full speed is attained4 ,in some cases the use of gas-engines is convenient and economical2 for though gas from town-supplies is an expensive fuel1 the best gas engines give a higher mechanical efficiency than steam-engines1 and they work with very little attention4 ,in arranging shafting1 moderate speeds1 say #ajj-aej revolutions per minute1 should be chosen for main lines1 and when higher speeds are necessary1 they should be got by light and well balanced counter-shafts1 with wrought iron or wooden pulleys4 7,cp4 p4 #deb47 ,in calculating speeds1 it must be remembered that they vary inversely as the size of the pulleys4 ,thus a #c-;feet pulley running at #ajj revolutions will drive a #b-;foot pulley at #aej revolutions1 and a #ab-;inch one at #cjj4 ,of course the higher its speed1 the more power any shaft will transmit1 but increased friction and wear and tear soon limit this advantage4 ,the velocity of a belt in feet per minute is obtained by multiplying the number of revolutions per minute by the girth of the pulley in feet or by its diameter multiplied by #c1 or more accurately1 #cadaf4 ,pulleys should always be of ample breadth for the power they have to transmit2 and it is more economical1 both in power and cost1 to use broad single belting than the same strength in double4 ,if the pulley will not take a belt broad enough for the work it has to do1 a second belt may be made to run on the top of the first1 as suggested by ,mr4 ,j4 ,tullis1 and will do its share of the work4 ,belts should be washed occasionally with soap and tepid water1 and oiled with castor or neatsfoot oil2 but if of sufficient breadth1 should not require the use of rosin1 or adhesive materials1 to make them grip the pulley4 ,chrome-leather belts should be kept thoroughly oiled4 ,they have a much greater adhesion than vegetable tannages1 and this is increased by oiling4 ,good chrome belting is much stronger than bark-tanned2 and is unaffected by damp or steam1 but generally stretches somewhat more4 ,makers of machines often err in constructing their driving pulleys too small both in breadth and diameter4 ,the horse-power which a belt is capable of transmitting obviously varies extremely with circumstances1 but may be approximately calculated by the formula a 4 v ---------1 #ffjjj where a is the area of contact of the belt with the smallest pulley1 and v its velocity in feet per minute4 ,another rule is1 that at a velocity of #ajjj feet per minute1 each inch of breadth of belt should transmit #b horse-power on metal pulleys1 or #e on wooden ones1 on which the adhesion is greater4 ,adhesion may also be increased by covering the pulleys with leather or indiarubber4 ,both rules assume that the belt is of ample strength4 ,one horse-power would be transmitted by a belt running #ajjj feet per minute with a pull of #cc lb4 ,a good single belt should not break with a much less stress than #ajjj lb4 per inch of breadth1 and should stand about as much as a working stress4 ,the following table gives the experimental breaking stresses and extensions of some leathers4 ,it may be noted that #a square inch sectional area is equal to a belt #d inches wide inch thick2 and that kilos per cm #adbb lb4 per inch4 ,,breaking ,,stresses ,,of ,,leather4#ahf ---------------------------------------- ------------------- -- ,kilo per sq4 ,lb4 per ,stretch centimetre4sq4 inch4per cent4 ---------------------------------------- ------------------- ,belting leather1 layer system #bhc #d1jcj #bed ,durio system #bih #d1bdj #ba ,well-tanned chrome leather #gdj #aj1ejj #cbe ,over-tanned chrome leather #bcd #c1ccj #bc ,stuffed alumed leather #hce #aa1ijj #chc ,alumed 8rawhide0 #iba #ac1ajj #cad ---------------------------------------- ------------------- #ahf #8,gerber1' #aijj1 p4 #gc4 ,good ,english tanned belting leather breaks at from #dejj to #eejj lb4 per sq4 inch sectional area4 ,over-tanned leathers are less tough1 whether of vegetable or mineral tannage1 than those somewhat lightly tanned1 and the tensile strength of leather varies considerably with the part of the hide from which it is taken1 that from approximately over the kidneys being the strongest4 ,even thick and tough leather is easily torn if a cut or nick is once started1 and all holes used in jointing belts should be carefully rounded4 ,glucose1 and the use of acid in bleaching both lessen the toughness of belts1 and they may also be rendered tender by the heat evolved in slipping on a pulley4 ,countershafting and high-speed machinery1 such as disintegrators1 striking machines of the ,priestman type1 etc41 should run without material jar or vibration4 ,if this occurs1 it is generally a sign that the running part is not equally balanced4 ,in this case the shaft or spindle must be taken out of its bearings1 and supported on two exactly horizontal straight-edges1 on which it will roll till the heaviest part is downwards2 and weight must then be taken off or added till it will lie in any position4 ,in this way the writer has had to add fully #b lb4 of iron to balance the drum of a striking machine before equilibrium was secured1 and a most troublesome vibration prevented4 ,of course all machinery should be supported as solidly as possible2 and if circumstances permit1 most machines are better on a ground floor4 ,in placing bark mills1 however1 it is frequently convenient to fix them at a higher level1 so that the ground material may be sent down shoots by its own weight to the required places4 ,an alternative plan is to set the mill on the ground over a pit1 and to raise the ground material with a bucket-elevator4 ,this may be done successfully by letting the material fall directly from the mill into the buckets2 but otherwise it must be thrown in with a shovel1 as buckets will not pick up ground bark1 even from a hopper2 and in any case such elevators are apt to be troublesome4 ,in a grinding plant designed by the writer1 the unground material was filled on the basement floor into an iron barrow1 which was wheeled into an iron sling working between upright guide-rails like a hoist4 ,on pulling a brake line1 the barrow was raised to the top of the building1 and its contents were tipped into a large hopper1 after which the barrow righted itself1 and descended for another load4 ,in the bottom of the hopper was a sliding shover1 which forced the material on to vibrating screens1 by which it was guided either into a disintegrator1 or crusher-rolls1 at pleasure4 ,both these discharged through iron spouts into large hoppers on the outside of a brick gable1 from which powdery materials like myrobalans and valonia could be run direct into barrows or trucks4 ,it is very desirable that such hoppers should be separated from the main building by a fireproof partition4 ,fires may occur from hard substances getting into disintegrators along with the bark1 etc4 and if this occur with a dry and dusty tanning material1 it is not unlikely that it may result in an explosion such as sometimes happens in flour mills1 in which the fire is rapidly conveyed along spouts1 and into chambers filled with dusty air4 ,insurance companies generally charge an extra rate for disintegrators1 and it is very desirable to keep the mill-house structurally apart from other buildings1 either by actual separation or by the introduction of brick gables dividing the roofs4 ,on the whole1 however1 mills of the coffee-mill type are probably quite as dangerous as disintegrators2 since if they become partially choked1 the heat caused by friction is very great4 ,in ,america1 the fire-risk from mills is often lessened or prevented by the introduction of a jet of steam into the chamber or spout by which the mill discharges1 but this is only permissible if the tanning material is conveyed at once to the leaches or yard4 ,the use of chain-conveyors for handling tanning material both wet and dry is practically universal in ,america1 though comparatively rare in ,england4 ,various forms are used1 the most common consisting of a chain of square links of malleable cast iron which hook into each other1 so that a broken link can be immediately replaced 7see p4 #cbe74 ,at intervals special links are inserted1 which can be had of various patterns1 for the attachment of scrapers or buckets4 ,the endless chain runs in a trough of rectangular or ,v-shaped section1 and is driven by a toothed wheel1 over which it runs like a belt4 ,in some cases the returning half of the chain can be utilised to bring back the spent tan on its way to the boiler house4 ,for dry materials1 cotton or leather belts with short wooden cross-laths attached1 may often be used satisfactorily in place of the chain4 ,for lubricating purposes1 mineral oils of high density are not more dangerous than animal or vegetable1 but rather the reverse2 as1 though they are possibly more inflammable1 and make more smoke1 their mixture with cotton-waste and other porous materials is not spontaneously combustible1 as those of vegetable and animal oils occasionally are4 ,the danger of spontaneous combustion is very considerable when heaps of leather shavings or cuttings containing fish-oils are allowed to accumulate in warm workshops1 and1 especially near steam-pipes4 ,heavy mineral oils should always be used as cylinder-oils in high-pressure engines1 in preference to other oils or tallow1 since they are not decomposed by steam1 and do no harm if blown into the feed-water1 but serve to loosen and prevent scale and deposit4 ,ordinary oils and tallow1 on the other hand1 when submitted to the action of high-pressure steam1 are separated into glycerin and fatty acids 7see p4 #cea71 and the latter corrode the valve faces and seatings1 and are liable with 8temporary hard0 waters to form a very dangerous porous deposit in the boilers1 which often leads to overheating of the tubes4 ,next to the machinery1 the pits demand special consideration4 ,the chapter on the subject in the late ,mr4 ,jackson ,schultz's book on #8,leather ,manufacture1' is well worth attentive study as giving ,american practice on the subject4 ,the old-fashioned method of sinking pits is to make them of wood1 and carefully puddle them round with clay1 which should be well worked up before use4 ,it is of no use to throw it in in lumps and attempt to puddle it between the pits1 which will not be made tight1 but probably displaced by the pressure4 ,such pits1 if made of good pine and kept in constant use1 are very durable1 some of the original pits at ,lowlights ,tannery1 constructed in #agfe1 having been in use till #ahhi4 ,loam mixed with water to the consistence of thin mortar may also be employed1 the pits being filled up with water1 to keep them steady1 at the same rate as the loam is run in4 ,probably the best materials for pit-sides are the large ,yorkshire flagstones4 ,where these are not attainable1 very durable pits may be made of brick1 either built with ,lias lime1 and pointed with ,portland cement1 or built entirely with the latter4 ,common lime cannot be used1 as it spoils both liquors and leather2 and even cements with too large a percentage of lime are unsatisfactory4 ,brick and common mortar are1 however1 suitable for lime-pits1 and for these ,mr4 ,c4 ,e4 ,parker's plan of constructing the bottom of cement1 the ends and sloping hearth of brick1 and the sides of #c-;inch planks bolted together is also very satisfactory 7,fig4 #if74 ,the writer has constructed wooden pits in two ways4 ,in the one case1 after making the excavation1 beams were laid in a well-puddled bed of clay2 on these a floor of strong tongued and grooved deals was laid1 and on this the pits were constructed of similar wood to the floor1 and puddled round with clay4 ,in the second case the pits were built like large boxes above ground1 and when finished1 lowered on to a bed of clay prepared for them1 and then puddled both around and between4 ,it may have been due to defective workmanship in the first case1 but those made on the last-named plan1 which is that adopted from very early times1 certainly proved the tightest and most satisfactory4 ,mr4 ,schultz describes a plan as the ,buffalo method1 in which a floor is laid as just described1 and grooves cut with a plane for the reception of the sides1 which are formed of perpendicular planks1 each end and side being finally tightened up by the insertion of a 8wedge plank40 ,owing to the perpendicular position of the side-planks such pits would be difficult to repair in the common case of decay at the top4 ,illustration3 ,,fig4 #if4--,mr4 ,c4 ,e4 ,parker's construction of ,lime-,pits4 ,if bricks be used1 great care must be taken that the cement is not merely laid so as to fill the joints towards the two surfaces of the wall1 as is the habit of modern bricklayers1 but actually floated into all the joints so as to make the wall a solid mass2 or leaks can hardly be avoided4 ,hard pressed bricks are best1 and should be tested as to whether they discolour liquor4 ,cement-pits are very good1 and1 though not particularly cheap in material1 which must be of the best1 are readily made by intelligent labourers under good supervision4 ,the first step is to lay a level floor of good concrete1 in which glazed pipes for emptying the pits may be embedded2 care being also taken that all joints in these are thoroughly tight1 since future repairs are impossible4 ,the next step is to make frames1 the exact length and breadth of the pits required1 and perhaps #ae inches deep4 ,these are arranged on the floor where the pits are to be1 and the intervening spaces are filled with concrete of perhaps #a of cement to #c or #d of crushed stone or brick4 ,rough stones and bricks may also be bedded in the concrete as the work goes on1 to help to fill up4 ,after the first layer has set1 the frames may be raised and a second added1 and so on4 ,the work is generally finished by floating over it1 while still damp1 a little pure cement1 to give a smooth surface4 ,before using1 the cement should be tried on a small scale1 to be sure that it does not discolour leather or liquors1 and the pits should always be seasoned with old or cheap liquor before actual use4 ,illustration3 ,,fig4 #ig4--;,cleaning ,rod ,joint4 ,if possible1 both leaches and handler-pits should be provided with plugs and underground pipes1 communicating with a liquor-well some feet below their levels4 ,glazed fire-clay is very suitable both for pipes and plug-holes1 which should be in the pit corners4 ,if fire-clay blocks for plug-holes cannot be obtained1 they may be cast in good cement1 the wooden mould being soaked with hot paraffin wax to prevent adhesion4 ,means must be provided for the ready clearing of the pipes when choked with tanning materials4 ,a good plan is to let each line of pipes end in a liquor-well large enough for a man to go down4 ,as it is almost impossible to make plugs fit without occasional leakage1 it is not well to run pits with very different strengths of liquors to one well1 but the layers1 handlers1 and different sets of leaches should each have their own1 so as to avoid mixture4 ,a good means of clearing pipes consists in a series of iron rods #c-d feet long1 connected by hooks fitting into double eyes1 as shown in ,fig4 #ig4 ,it is obvious that in a narrow pipe or drain1 these cannot become disconnected4 ,pipes may often be forced out by fitting a strong delivery-hose of a steam-pump into one of the plug-holes4 ,it is1 as ,schultz points out1 of questionable advantage to lay wooden troughs under the alleys for supplying liquor to each pit1 since it is almost impossible to preserve them from decay2 but the same objection would not apply to glazed pipes1 jointed with pitch or cemented4 ,a good and cheap plan in practice1 is to let the liquor-pump1 or a raised liquor-cistern1 discharge into a large and quite horizontal trough raised #f or #g feet above the level of the yard1 and provided with plug-holes at intervals1 from which the liquor can be run into the various pits by short spouts or sailcloth hose4 ,in place of plugs in the raised trough1 a simple and convenient valve devised by the writer may be advantageously employed4 ,a lead weight is made by casting in a hemispherical tin basin of about #e inches diameter and #b inches deep in the centre1 a loop of strong brass wire with turned up lower ends1 being suspended in the middle1 so as to become fixed in the lead4 ,to prevent adhesion1 the tin must be previously burned off1 and the basin well blackleaded4 ,this weight forms the valve1 which rests in use on a #f-;inch washer of good indiarubber with a #d-;inch hole1 which is held by a wood block against the bottom of the trough1 through which a #e-;inch hole is cut4 ,the valve is raised by a lever or cord1 and is absolutely water-tight in use4 ,it is shown in section in ,fig4 #gi1 p4 #ccc4 ,it is very advantageous in practice1 instead of pumping direct into the pits1 to have one or more tanks1 into which liquor can be delivered by the pump1 and which are sufficiently raised to allow it to be run from them into the horizontal distributing troughs which have been mentioned4 ,this is specially important with regard to liquors for leaches and suspenders which are worked on a circulating system1 since they do not run very quickly1 and much time is lost in pumping out pits1 if the speed of the pump has to be regulated by the rate at which the liquor will circulate4 ,it also enables liquors to be run through suspender- and rocker-pits during the night or at meal-times while the machinery is standing2 and it is often useful on beginning work in the morning1 to have an empty tank into which the first liquor can be pumped4 ,direct-acting steam-pumps without fly-wheels are very unsatisfactory for tan-yards1 since they are usually uncertain in their action1 difficult to run slowly1 and apt to 8hammer02 and they are also costly in steam1 which cannot be used expansively4 ,steam-pumps with fly-wheels1 operating the steam-valve by an eccentric1 are free from these defects1 and though more costly at the outset1 soon save the difference in lessened repairs and consumption of steam4 ,pumps with a capacity of #hjjj gallons per hour are very suitable1 and can be used with a #c-;inch hose pipe2 smaller sizes are decidedly more liable to choke with tanning material4 ,rubber mitre-valves work satisfactorily1 and do not choke frequently1 but are costly1 and easily damaged by hot liquors4 ,on the whole brass clack-valves are the most satisfactory1 but the hinge-pins1 instead of fitting neatly in circular sockets1 should be held in slots1 allowing the back of the valve to rise half an inch1 when it will clear itself of small hard myrobalan stones and suchlike things1 which getting under a more tight-fitting hinge would prevent the valve closing1 and so stop the pump4 ,whatever valves are employed1 means should be provided for easy access without unscrewing too many bolts4 ,if the several valve-chambers of the pump are closed by a single cover with an indiarubber washer1 the spaces between them which make the joint should be faced with brass or gun-metal1 as1 if the least leakage takes place over an iron surface1 the friction and solvent power of the liquors soon eat away the metal and render a good joint impossible4 ,where colour is of first importance1 it is well to have the whole pump of gun-metal1 but in any case the working cylinder should be brass-lined1 and the piston and rod1 and the valves and seatings should be of brass or gun-metal4 ,spring-rings are far better than pump-leather and are unaffected by hot liquors2 chrome leather1 however1 will stand a good deal of heat4 ,double-acting force-pumps have practically superseded the older single-acting double or triple pumps4 ,instead of direct driving with a steam cylinder1 it is sometimes advantageous to drive by belt1 but at least one steam pump should be provided1 so that pumping can be done when the main engine is not running1 and the speed of the pump can be regulated to the work1 which is impossible in a belt-driven pump4 ,steam pumps are sometimes very useful as fire engines4 ,centrifugal pumps are very suitable for tannery work1 where the liquor is drawn from a well1 but are not well adapted for use with suction-pipes4 ,if the form with vertical spindle is adopted1 which is sunk below the liquor in the well1 the pump fills itself1 and needs no foot-valve1 but unless the well is very large1 or some convenient means is devised of withdrawing the pump1 repair or cleaning is difficult4 ,if the horizontal pattern is used1 which is above the ground1 repair1 cleaning1 and driving is much easier1 but a foot-valve is necessary1 which may itself give trouble1 and some convenient means1 such as a pipe from a raised tank1 should be provided for filling the pump with liquor1 as1 unlike suction pumps1 centrifugals will not start unless full1 although they raise very large quantities when running1 and from their steady flow1 will deliver much more through a given pipe than an ordinary reciprocating pump with the same power4 ,in selecting the pump1 care should be taken that the pattern allows ready access1 not only to the foot-valve1 but to the body of the pump4 ,it is seldom satisfactory to use windbores or strainers to prevent tanning material getting into a pump1 as they speedily become choked2 and it will be found better1 after taking such precautions as are possible1 to have the pump and valve of ample size and suitable construction to pass what comes with the liquor4 ,the writer has known a mop-head pumped and delivered through a #c-;inch hose without stoppage1 by a ,tangye fly-wheel steam-pump with brass clack-valves such as have been alluded to4 ,pulsometers have not1 in the experience of the writer1 proved satisfactory in tanneries1 warming and diluting the liquor1 consuming much more steam than a pump of the same power1 and becoming easily choked4 ,for the same reasons1 steam-jet water-raisers are not to be recommended except where raising is to be combined with heating1 as in some leaching devices 7p4 #ccd74 ,,chapter ,,xxviii4 ,,waste ,,products ,,and ,,their ,,disposal4 ,the products which are of no direct value to the tanner and currier in the manufacture of leather1 and which are nevertheless obtained in fairly large quantities1 are of very varying characters4 ,in the present chapter1 the most important of them will be described1 and some of their uses mentioned4 ,hair is removed from the skin of the animal in the process of depilation 7p4 #adc7 in the form of a wet sodden mass1 containing a considerable amount of lime when the skin has been through the lime-pits4 ,as white hair is the more valuable1 care should be taken in the unhairing to keep it separate from the coloured4 ,it is washed first in plain water to get rid of as much of the lime as possible1 and then in water containing a little acid4 ,hydrochloric acid is often used for this purpose1 but sulphurous acid 7p4 #be7 is preferable as it has a slight bleaching action on the hair4 ,the acid neutralises and renders soluble the lime which still remains in the hair1 so that it can be easily removed by washing with water4 ,in many tanneries1 hair-washing machines are used4 ,the washed hair is dried by laying it out on frames2 or preferably1 the greater part of the water is first removed by a centrifugal drier1 or by pressing1 and the drying is completed in a drying room1 the temperature of which is a few degrees higher than that of the outside air1 and which is provided with a fan or some other appliance for mechanical ventilation4 ,tables of wire gauze on which the hair is spread1 and through which the warm air of the room is drawn by a centrifugal fan1 are the most effective4 ,coloured hair is sometimes washed and treated like the white hair1 but is usually sold direct to plasterers1 in which case there is no necessity to remove all the lime and other impurities which the hair contains4 ,a considerable amount of hair is also sold to iron founders1 who use it in preparing cores and in loam-casting4 ,the loose lime may be effectively beaten from dried hair by passing it through a disintegrator with one of the grates removed4 ,fleshings and ,glue-stuff4--,the various scraps of fat and flesh1 more or less free from actual hide substance1 are usually worked up for glue1 though if they cannot be sold for a fair price it will pay to boil them in order to recover the fat they contain4 ,if this is to be done1 the fatty portions may be thrown out at the beam and not mixed with the fleshings as in the ordinary way4 ,before boiling1 the fat is treated with sulphurous1 sulphuric or hydrochloric acid1 sufficient to neutralise the lime present4 ,the boiling should be carried on very gently1 so as to allow the fat to rise without emulsifying with the gelatinous matter4 ,for boiling1 open steam may be used1 but in this case the size formed will have little value2 on the other hand1 if sulphurous acid has been used and a wooden vat with a copper steam-coil be employed1 really good glue may be obtained1 and the slight trace of bisulphite which it may contain will prevent its putrefaction4 ,except under special conditions it will not pay to make glue on a small scale in ,england1 as its value depends much on its appearance1 and the necessary plant is somewhat expensive4 ,in some places1 however1 size can be sold to advantage4 ,fig4 #ih shows a glue-boiling plant4 ,after separation of the fat by skimming1 the clear size is run off from the residual matter into wooden cooling troughs about #e feet long by #i inches deep and #ae inches wide1 in which it is allowed to set 7,fig4 #ib1 p4 #dbe74 ,great care is required that both size and coolers are quite sweet and free from putrefaction1 the coolers being frequently washed with sulphurous acid solution or fresh milk of lime4 ,the jelly is cut out in blocks1 and sliced into cakes of appropriate thickness by means of a series of frames like slate-frames which fit over the block of glue1 and between which a wire or thin blade stretched on a saw-frame is inserted to cut the glue into sheets4 ,in some factories a machine is used1 with a series of parallel blades against which the glue-block is pushed4 ,the sheets are afterwards separated by girls and laid to dry on nets1 on which they are frequently turned4 ,when dry1 the cakes may be washed with warm water to remove any adhering dirt1 but this causes some loss of weight1 and in many cases it pays better to dry in a stove until quite hard1 then grind in a disintegrator and sell as 8size-powder10 in which appearance counts for little if the colour and strength of the size are good4 ,illustration3 ,,fig4 #ih4--;,glue ,boiling4 ,fat4--,the fat1 whether obtained in the manufacture of glue1 or by boiling the fleshings and shavings for its recovery alone1 is skimmed from the surface of the heated liquor1 and should afterwards be freed from gelatinous matter by washing it with hot water in a tub and running off the upper layer after allowing the water to settle out4 ,the fat thus obtained is a light-coloured grease of buttery consistence4 ,there are various other sources of waste fats which may be considered here4 ,if glue is made from dried glue-stuff without previous treatment with acid1 the fat skimmed off the pans1 though dark in colour1 will be neutral or alkaline1 and a considerable additional quantity of fat and free fatty acids may be obtained by reboiling the 8scutch0 or refuse with open steam in lead pans with the addition of water and enough sulphuric acid to render the contents of the pan distinctly acid4 ,this grease will be dark and of unpleasant smell from volatile fatty acids1 but its odour may be to a considerable extent improved by blowing air and steam through it1 and washing with water1 or by heating to a temperature somewhat above the boiling-point of water for a considerable time4 ,the same sort of treatment may be applied to the fat pressed out of sheepskins1 and to that obtained by boiling currier's shavings with water and a little acid4 ,recovered fats may be separated into a tolerably firm grease suitable for use instead of tallow in currying1 and an oil not unlike neatsfoot oil1 by melting1 allowing to cool slowly to a soupy consistency to promote the crystallisation of the harder fats1 and forcing the mixture through flannel cloths in a filter press4 ,the temperature at which the filtration should take place is generally #bj-be ,c4 ,the oil is1 of course1 8tender10 or liable to solidify in cold weather2 and the more so the higher the temperature at which filtration takes place4 ,the tallow is obtained in cakes4 ,if from fresh fleshings1 it will be white and with little odour1 but that from dried glue-stuff is usually brown and of unpleasant smell1 while recovered grease from curriers' shavings or 8moisings0 is always dark in colour4 ,if the fleshings are to be sold wet1 they should be preserved in a sweet lime liquor2 if to be dried1 they are washed carefully in a fresh lime1 spread on frames1 and frequently turned over so that they may dry evenly and rapidly4 ,heat1 if employed at all1 is in most cases only used at the end of the drying operation1 but some tanners dry from the first in a room the temperature of which is a few degrees higher than the normal1 and which is provided with good ventilation4 ,for the purposes of the glue manufacturer1 the roundings and larger pieces are more valuable than the fleshings1 and should be treated with correspondingly greater care by the beamsman and his assistants4 ,bate-,shavings are very valuable as sizing materials4 ,they should be well washed in water1 or with a very dilute solution of sulphurous acid1 and are then laid out in thin layers to dry4 ,they may also be partially dried by pressing between latticed boards in a screw or hydraulic press1 and are then best finished as cakes4 ,on the manufacture of sulphurous acid compare p4 #be4 ,horns are usually kept until the 8slough10 8pith10 or internal bone can be knocked out1 having become loosened through drying and putrefaction4 ,if kept dry1 practically no longer time is required1 and the smell and other annoyances incidental to storing in a damp place are avoided4 ,the sloughs may be removed by steaming1 but the horns are somewhat damaged by this treatment4 ,the sloughs are principally ground for 8bone-meal10 but some are boiled for glue1 either without preparation1 or after decalcifying with dilute hydrochloric acid4 ,the actual horn itself1 which is quite incapable of making glue1 is used chiefly in the manufacture of combs1 buttons1 and similar articles4 ,the value of horns is to a considerable extent dependent on their size1 small horns being unprofitable to work up for the articles above mentioned4 ,spent ,tan4--,the tan as it is obtained from the leaches after extraction has1 naturally1 no value for the tanner except as a fuel4 ,spent tan cannot be profitably sold as manure1 as its worth in this respect is extremely small4 ,in those places where white lead is still made by the ,dutch process1 oak-bark is used to cover up the earthen pots1 and commands a good price4 ,it is1 however1 essential that oak-bark only should be used1 as many other tanning materials give off products which injure the colour of the white lead4 ,the quantities of tan used for hot-beds1 and for deadening the noise of traffic in the streets1 are so small that they are of no practical account in the disposal of this product4 ,spent tan is not nearly so good as wood for the manufacture of paper1 and an attempt to distil it and thereby obtain pyroligneous acid and wood-spirit did not result in any commercial success4 ,on the ,continent1 fine-ground tan is usually pressed into briquettes for use as domestic fuel1 but it would be hard to obtain a market for these in ,england4 ,on the whole1 in spite of its low heating value1 spent tan is best utilised as a fuel4 ,for this purpose specially constructed furnaces are necessary on account of the dampness of the tan1 and its low calorific value1 which varies1 however1 with the particular materials3 thus while oak-bark and valonia are only poor fuels1 hemlock and myrobalans are much better on account of the resin and lignine they contain4 ,the first successful furnaces for raising steam with wet tan were introduced in the ,united ,states1 and consisted of large arched combustion chamber with abundant grate-area1 and with four or six feed-holes in the fire-brick top which formed a floor on which the spent tan was laid1 and where to some extent it was dried by the waste heat4 ,the flames and furnace gases were conducted under the boilers1 the flue being very large and deep so as to collect the light ash which was drawn in great quantities from the furnace1 and the gases then returned through the tubes of the boiler1 afterwards passing down the sides and going to the chimney4 ,the wet fuel was fed in through the firing holes alternately1 so that only a part of the grate-space was covered at once with wet fuel2 which was speedily ignited by the heat from other parts of the furnace1 and especially from the vaulted arch4#ahg ,the large grate-area was a necessity not only on this account1 but because of the light weight of the fuel and its low calorific power1 which involved the need of burning a large volume4 ,fig4 #ii represents a furnace of similar principle constructed by ,messrs4 ,huxham and ,browns4 ,furnaces of this type are1 the author believes1 still largely in use in the ,united ,states1 but in ,germany 8step-grates0 sloping from the furnace-doors towards the back1 are now preferred4 ,in these the combustible material rests upon the flat surfaces of the grate1 while the air enters by the spaces between the steps without the fuel being able to fall through4 ,fig4 #ajj represents the furnace on this principle constructed by the ,moenus ,co4 of ,frankfort4 #ahg ,detailed drawings and particulars are given in ,jackson ,schultz's #8,leather ,manufacture in the ,united ,states1' ,new ,york1 #ahgf4 ,illustration3 ,,fig4 #ii4--;,huxham and ,browns' ,furnace4 ,the essential conditions which are to be observed in the proper burning of the tan are a sufficiently large grate-area1 a correct and sufficient supply of air1 and a combustion-chamber of very high temperature4 ,it is consequently not possible to burn tan very successfully in an ordinary ,lancashire or ,cornish boiler1 since not only the grate-space is too limited1 but the water of the boiler prevents the upper part of the furnace from attaining a high temperature2 and it is therefore difficult to get the damp tan rapidly into vigorous combustion4 ,the difficulty may to some extent be overcome by mixing the tan with a proportion of coal1 and by closing the ash-pit and employing a forced draught unless the chimney is a very powerful one4 ,in this way large quantities of tan may be burnt1 but without effecting any great saving of coal4 ,the heating power of the tan is improved by the partial removal of its water by pressing1 and this is almost essential where a special furnace is not employed4 ,illustration3 ,,fig4 #ajj4--,moenus ,step-grate ,furnace4 ,the answer to the question as to whether tan should be used as fuel in the wet state in which it is obtained from the leaches1 or whether it should be previously pressed1 depends upon the nature and quantity of the tan4 ,where abundant quantities of a fairly good material such as hemlock bark are to be disposed of1 the cost of pressing is an unnecessary expenditure2 but if it is desirable to obtain the highest value from the fuel1 or if the furnaces are not well constructed for burning very wet fuels1 it will be profitable to press the tan4 ,hydraulic presses have been used for this purpose1 but those now commonly employed consist of powerful rollers arranged in the same way as those of the valonia-crusher 7p4 #cbb74 ,the pressure is given by levers loaded with weights or fitted with powerful springs4 ,the liquid which runs from these presses is of little value1 as it contains such large quantities of finely divided material that it is almost impossible to filter it1 and if run upon the leaches it chokes them and prevents their proper circulation4 ,much of the cost of pressing is caused by the labour of feeding it to the press1 and this may be greatly reduced by the use of mechanical conveyors 7p4 #cbe7 from the leaches4 ,a tan press is shown in ,fig4 #aja4 ,illustration3 ,,fig4 #aja4--,tan ,press4 ,sewage and other ,waste ,liquids4--,the waste liquors from the different liming1 bateing1 puering1 tanning1 washing and other soaking processes are1 without any doubt1 the most troublesome of any of the side-products which are obtained in the manufacture of leather4 ,in former times they were simply run into the nearest stream1 but nowaday the various sanitary authorities and other similar bodies will only permit comparatively pure waters to be turned into a public stream or watercourse4 ,various methods of effecting the necessary purification of the waste liquors from tanneries have been proposed at different times1 and have been used with varying degrees of success4 ,these methods may be divided into three heads3 precipitation1 followed by filtration or sedimentation land-treatment2 and bacterial purification4 ,the first of these depends on the power of certain substances1 such as alumina and oxide of iron1 to carry down organic matter with them if precipitated in solutions containing it4 ,the method usually consists in adding a sufficient quantity of lime to render the waste liquid slightly alkaline1 and then treating it with some crude salt of aluminium or of iron4 ,by this means a precipitate of aluminium or iron hydrate is formed1 which encloses within itself a considerable proportion of the organic matter of the liquid1 and after settling to the bottom of the precipitation-tank is drawn off as 8sludge40 ,various chemicals are sold under fancy names1 such as 8alumino-ferric10 8ferrozone10 etc41 and have a composition not very dissimilar to that of crude sulphate of iron or alumina4 ,in some cases by-products1 such as the acid liquors used in preparing iron articles for 8galvanizing10 can be used with advantage4 ,in the case of the waste liquors from a tannery1 the use of these chemicals may often be avoided if sufficient care be taken in regulating the proportion of the various liquids which are to be mixed together and run into the settling tank4 ,as tanning matter combines with lime and dissolved hide-substance to form a heavy brown insoluble precipitate1 it is clear that if care be taken to have rather more waste lime-liquor mixed with the waste tan-liquors than is necessary to throw all the tan out of solution1 a very considerable amount of purification of the effluent will have taken place without any cost whatever to the tanner4 ,hence1 if the proportion of waste lime is small in comparison to that of the tanning liquors1 an extra addition of lime may be necessary in order to precipitate the tannin4 ,the precipitation- or settling-tanks are usually square or rectangular vessels or pits1 the size of which varies with the quantity of liquid to be treated1 but the depth of which rarely exceeds six feet4 ,they may be divided into two classes--the 8intermittent10 and the 8continuous40 ,in the former class the tank is filled with the mixed waste liquids1 taking care that such a sufficiency of lime is present that the mixture is faintly alkaline to phenolphthalein paper1 and is then allowed to rest until the suspended matter has settled down to the bottom of the tank1 when the clear1 or almost clear upper liquid is drawn off1 the remainder being the 8sludge02 some means must also be employed to prevent the passage of scum and floating matters4 ,in the case of the intermittent process it is advisable to have two tanks1 one of which is being filled while the other one is settling or being emptied4 ,with the continuous process the liquids are run into the tank in the proportions calculated to give a maximum amount of purification1 as described above1 but as they enter very slowly the undissolved matter soon settles1 and consequently the liquid may be continuously run out at the further end of the tank4 ,this plan1 though it does not yield such good results in the hands of unskilled workmen1 is yet useful in many cases1 as only one tank is absolutely necessary4 ,it is desirable that in running off the tanks1 the effluent should be taken as near the surface as possible1 by means of a hinged pipe attached to a float1 or some equivalent device2 and care is required1 as the tank gets low1 to avoid the escape of any of the sludge4 ,for continuous settling the tanks are usually long and somewhat shallow rectangular ponds1 into which the previously well-mixed precipitating liquid flows through a wooden trough fixed across one end and as long as the breadth of the tank1 and perforated with holes to allow the uniform and quiet influx of the liquid1 which finally escapes by a similar trough crossing the opposite end of the tank4 ,in front of the exit-trough a 8scum board0 must be placed1 which is a simple plank dipping slightly below the surface of the liquid1 so as to prevent any oil1 scum or other floating matter from passing out of the tank along with the clear effluent4 ,whether the intermittent or continuous system is employed1 the effluent should in most cases be afterwards passed through a bacterial filter-bed1 or treated by land filtration before it is allowed to flow into a stream or river4 ,tannery effluents are usually received into sewers without further treatment than mixing and settling to remove solid matter1 and many authorities are satisfied with the removal of merely such coarse suspended matters as might choke the sewers4 ,where continuous precipitation-tanks are used1 they must be emptied at frequent intervals1 and the sludge run on to cinder-filters1 to part with most of its water4 ,these filters are conveniently placed at a lower level than the settling tanks1 and it is generally necessary to return the effluent from them for further precipitation and settling4 ,several types of continuous settling tank with upward flow have been devised by ,mr4 ,candy and others1 which are very suitable for use where space is limited2 but otherwise less costly constructions are often sufficient4 ,apart from the question of obtaining an effluent sufficiently good to satisfy the sanitary authority1 the treatment of the sludge is one of the greatest difficulties in the purification of effluents4 ,it is usually very bulky1 easily putrescible1 and therefore difficult to dry2 it is of little value for manure2 and if allowed to remain long wet1 its smell is very offensive4 ,it has been mentioned that in most cases the liquid1 and in every case the sludge1 must be freed from solid undissolved matter by filtration4 ,this may take place through open filters or through filter-presses4 ,the open filters generally consist of a pit with an exit at the bottom for the filtered liquid4 ,this pit is filled with either stones and sand1 with clinker1 ashes or coke4 ,most tanners use clinker and ashes1 as they do not cost anything2 and the material should be so arranged that while the lowest layers are very coarse1 the surface of the filter-bed should be of the finest material4 ,as soon as this has become covered with so thick a layer of solid matter that the filtration proceeds too slowly1 the top surface of the filter may be removed with a rake 7taking care to remove as little of the ashes or sand as possible71 and burnt1 or dried and used as manure4 ,in some cases1 filter-presses are used which are composed of grooved or perforated plates with cloths between them through which the liquid is forced by pressure4 ,the solid matter remains behind in the form of a comparatively dry 8cake40 ,the filter-cake1 dried if desired1 is sold as manure1 for which it is in many ways very suitable4 ,although they work much more rapidly than do the open filters1 the cloths so soon become rotten and have to be replaced1 that the open ash-filter is on the whole the most convenient for the tanner's use4 ,it will be readily understood that apparatus of this kind1 though very efficient on a small scale1 is quite out of the question when many thousand gallons of liquid have to be filtered daily1 and so can only be effectively applied to 8sludge40 ,no system of chemical precipitation has as yet proved entirely satisfactory4 ,undoubtedly a great deal of purification is effected by this means1 but in most cases the 8purified0 liquid is still too impure to be turned into a stream1 though for various reasons this is often permitted by the authorities4 ,a great advance was made in the purification of effluents when manufacturers were compelled by law to allow the effluent from the precipitation-tank to filter through land set apart for that purpose4 ,in this case certain hardy cereals were sown on the land1 which was watered as often as possible with the effluent4 ,this latter1 after soaking through the land1 was drained off into the nearest stream4 ,although in many ways this treatment was satisfactory1 it had the disadvantage of being very expensive1 especially in the neighbourhood of large towns where the price of land is high1 and1 in addition to this1 the conditions necessary for success were far from being correctly understood1 so that the land often became 8sewage-sick0 or waterlogged1 and ceased to purify the effluent4 ,it was not until the researches of bacteriologists proved that the purification by land-filtration was mainly due to the bacteria in the soil1 that any really satisfactory solution of the problem could be found1 but the question has now been to a considerable extent simplified by the introduction of 8bacterial treatment40 ,bacteria1 considered from the point of view of their action on organic matter1 are often classified as 8anaerobic0 and 8aerobic10 though many species are capable of existing under both conditions 7,cp4 ,l4,i4,l4,b41 ,section ,,xxiv474 ,the anaerobic bacteria thrive only in the absence of air1 and their chemical action consists in breaking down the organic matter on which they feed into simpler1 and generally more soluble forms1 by processes which do not involve oxidation4 ,the aerobic bacteria1 on the other hand1 require air or oxygen for their existence1 and produce changes which are generally of a less complex character1 but result in the complete oxidation and conversion of the organic matter to simple compounds1 such as nitrates and carbonic acid1 which are perfectly harmless and inoffensive4 ,the two classes therefore are to a large extent complementary to each other1 the anaerobic bacteria converting the animal or vegetable substances into more soluble and simple compounds which are adapted to the needs of the aerobic1 which complete the destruction of the organic matter4 ,in harmony with what has just been said1 bacterial treatment of sewage is of two kinds1 each of which may be used alone1 or in conjunction with a preliminary precipitation-process1 but which are generally best used successively4 ,the oldest form of bacterial purification depends mainly on the action of anaerobic bacteria1 and is known as the 8septic tank40 ,this originally consisted of a tank sometimes filled with small pieces of coke1 but generally containing the liquid only1 and which was tightly closed to prevent access of air and escape of foul gases4 ,it has1 however1 been found that if deep tanks 7#f to #aj feet7 are employed1 they soon become in continuous use so covered with scum and floating matter as effectually to prevent access of air and light1 or any serious escape of smell4 ,the liquid to be purified is allowed to flow very slowly through a tank or series of tanks of this description1 entering about a foot below the surface through a distributing trough at one end1 and flowing out similarly at the other1 at such a rate as to change the contents of the tank about once in twenty-four hours2 and when the tank is in working order1 the liquid is much purified by the process1 and most of the solid organic matter has become liquefied and disappears4 ,it not unfrequently happens1 especially where the septic tank treatment is not very prolonged1 that the liquid which escapes has a stronger and more offensive odour than it had on entering the tank4 ,it is nevertheless really purer than before1 the increased smell being due to the volatile products of the partially decomposed organic matter2 and1 by passing the liquid through an open coke-filter1 the smell will be effectually removed4 ,in all cases it must be borne in mind that as septic tanks and bacterial filters depend for their efficiency on the organisms they contain1 time must be allowed for these to develop and accumulate before good results are obtained2 and for this about six weeks' use is generally necessary1 after which they will continue to act for an indefinite period until they become choked by sand and inorganic matter4 ,it must not be supposed that the action in the septic tank is wholly anaerobic2 and with weak sewage1 most of the organic matter may under favourable circumstances be converted into nitrates and carbonic acid by this means only2 but generally a much more complete purification is effected by the subsequent use of 8bacterial filters40 ,these in their simplest form consist of tanks of about #d feet deep1 filled with coke1 broken bricks1 or clinkers1 and fitted with drain pipes at the bottom1 by which they can be easily emptied4 ,these tanks1 often known as 8contact-beds10 are filled with the sewage or septic tank effluent1 which is allowed to remain on them two hours1 and the tank is then emptied1 and allowed a rest of six hours for oxidation and aeration4 ,in most cases the sewage requires two such treatments1 the last often through a bed with finer coke1 in order to be completely freed from putrescible matter4 ,in place of the intermittent process1 as applied on the contact-beds1 continuous aerobic filtration is often employed1 the bed being so constructed as to allow of free admission of air at the bottom and sides1 and the liquid to be purified being distributed on the surface by a sprinkler1 or some similar device1 and allowed to trickle through the bed4 ,the continuous process seems likely to supersede the intermittent one1 as the beds are not only capable of treating a much larger quantity of sewage in proportion to their area1 but are also less liable to choke4 ,about six weeks is required1 with either contact-beds or continuous filters1 before the material they contain becomes coated with the necessary bacterial layer and they get into full working order4 ,the results as regards the effluent are perfectly satisfactory1 and the great difficulty and cost consists in the slow but inevitable choking of the beds1 which involves the replacement of the porous material4 ,this is considerably delayed by the use of a settled or precipitated sewage1 and in this respect1 beside its bacteriological function1 the septic tank serves a useful purpose in settling insoluble matter1 which is much more cheaply removed from it than from the filter-beds4 ,it will be obvious that ordinary settling-tanks1 if deep1 fulfil many of the functions of the septic-tank1 and both lead to the production of a much more uniform liquid from the different effluents which the tanner produces1 which is important in the subsequent bacterial purification4 ,a good deal of interesting information on these subjects will be found in a paper by ,mr4 ,w4 ,h4 ,harrison on the #8,bacteriological ,treatment of ,sewage4'#ahh #ahh ,journ4 ,soc4 ,chem4 ,ind41 #aijj1 p4 #eaa4 ,there are a good many patents in connection with the various methods of sewage purification1 and some caution is necessary to avoid their infringement1 though of course the general principles of settling and filtration1 and the destruction of organic matter by bacterial action1 are open to all4 ,as a general rule the waste-liquors from a tan-yard or leather dye-works are exceedingly impure4 ,they contain the organic matter 7in a state of great putrefaction7 from the soaks1 bates and puers2 other organic matter1 also more or less putrefied1 from the tan-pits2 the lime liquors1 with their large proportion of lime and of dissolved hide-substance1 and in addition the various dyes and other chemicals which may have been used in the conversion of the raw hide into the finished leather2 and hence their efficient purification has presented difficulties which do not occur in most other trades4 ,the different waste liquids are best run into a capacious tank1 and1 after being thoroughly mixed up together1 are allowed to settle for some hours4 ,by this means the greater part of the tanning matter will combine with the lime also present to form a heavy1 brown insoluble substance2 some of the dye and other organic matter will become entangled in this1 and thus be removed from the liquid4 ,the clear liquid is next run off into a bacterial filter 7preferably a septic tank1 followed by an open coke filter71 and then into the nearest stream4 ,if the tannery is near to a town1 and the corporation sewers can be utilised1 it is probable that a filter made of spent tan may be substituted1 as this material will not only remove all excess of lime from the liquid but will also fix much of the colouring matter as well 7,koenig74 ,the tan1 after being used for this purpose1 contains so much lime in its pores that it is said to be useful as manure4 ,in tanneries where large quantities of disinfectants such as mercuric chloride1 carbolic acid1 etc41 are used1 it is necessary that the mixed liquids shall contain so much lime as to make them distinctly alkaline4 ,in this way most of the disinfectants will be either precipitated or rendered inactive4 ,where arsenic is used in the limes it may be advisable to add a little ferrous sulphate 7green vitriol or copperas71 in order that the arsenic may form an insoluble compound with the iron1 and so be removed along with the sludge4 ,the ink produced by the action of the iron salt on the tan liquors will be completely removed by the bacterial filter4 ,,appendices4 ,,appendix ,a4 ,,method ,,of ,,the ,,international ,,association ,,of ,,leather ,,trades ,,chemists ,,for ,,the ,,analysis ,,of ,,tanning ,,materials4 ,,including ,,alterations ,,adopted ,,at ,,the ,,leeds ,,conference ,,in #aijb4 ,,section ,i4--,,sampling ,,from ,,bulk4#ahi #ahi ,see ,london ,report1 pp4 #bb-bi and #abd4 #a4 ,liquid ,extracts4--,in drawing samples1 at least #e per cent4 of the casks must be taken1 the numbers being selected as far apart as possible4 ,the heads must be removed1 and the contents mixed thoroughly by means of a suitable plunger1 care being taken that any sediment adhering to sides or bottom shall be thoroughly stirred in4 ,all samples must be drawn in the presence of a responsible person4 #b4 ,gambier and ,pasty ,extracts4--,gambier and pasty extracts should be sampled from not less than #e per cent4 of blocks1 by a tubular sampling tool1 which shall be passed completely through the block in seven places4 ,solid extracts shall be broken1 and a sufficient number of portions drawn both from the inner and outer parts of the blocks to fairly represent the bulk4 ,in both cases samples shall be rapidly mixed and enclosed at once in an air-tight bottle or box1 sealed and labelled4 #c4 ,valonia1 ,algarobilla1 ,divi-divi1 and ,general ,tanning ,materials4 ,valonia1 algarobilla1 and all other tanning materials containing dust or fibre1 shall be sampled1 if possible1 by spreading at least #e per cent4 of the bags in layers one above another on a smooth floor1 and taking several samples vertically down to the floor4 ,where this cannot be done1 the samples must be drawn from the centre of a sufficient number of bags4 ,while valonia and most materials may be sent to the chemist ground1 it is preferable that divi-divi1 algarobilla1 and other fibrous materials shall be unground4 ,bark in long rind1 and other materials in bundles1 shall be sampled by cutting a small section from the middle of #c per cent4 of the bundles with a saw4 #d4 ,samples for more than one ,chemist4--,samples to be submitted to more than one chemist must be drawn as one sample1 and well mixed2 then divided into the requisite number of portions1 not less than three1 and at once enclosed in suitable packages1 sealed and labelled4 ,,section ,,ii4--,,preparation ,,for ,,analysis4#aij #aij ,see ,london ,report1 p4 #dj et seq4 #a4 ,liquid ,extracts4--,liquid extracts shall be thoroughly stirred and mixed immediately before weighing1 which shall be rapidly done to avoid loss of moisture4 ,thick extracts1 which cannot be otherwise mixed1 may be heated to #ej ,c41 then stirred and rapidly cooled before weighing1 but the fact that this has been done must be noted in the ,report4 #b4 ,solid ,extracts4--,solid extracts shall be coarsely powdered and well mixed4 ,pasty extracts shall be rapidly mixed in a mortar1 and the requisite quantity weighed out with as little exposure as possible1 to avoid loss of moisture4 ,where extracts are partly dry and partly pasty1 so that neither of these methods is applicable1 the entire sample shall be weighed and allowed to dry at the ordinary temperature sufficiently to be pulverised1 and shall then be weighed1 and the loss of weight taken into calculation as moisture4 ,in such cases as gambier1 in which it is not possible to grind1 or by other mechanical means to thoroughly mix the constituents of the sample1 it is permissible to dissolve the whole1 or a large portion of the sample1 in a small quantity of hot water1 and immediately after thorough mixing to weigh out a portion of the strong solution for analysis4 #c4 ,barks1 and other ,solid ,tanning ,materials4--,the whole sample1 or not less than #bej grms41 shall be ground in a mill until it will pass through a sieve of #e wires per centimetre4 ,where materials such as barks and divi-divi contain fibrous materials which cannot be ground to powder1 the ground sample shall be sieved1 and the respective parts which do and do not pass through the sieve shall be weighed separately1 and the sample for analysis shall be weighed so as to contain like proportions4 ,,section ,,iii4--,,preparation ,,of ,,infusion4 #a4 ,strength of ,solution4--,the tannin solution employed shall contain from #jce to #jde grms4 per #ajj c4c4 of tanning matters absorbed by hide4 7,paris #aijj47 #b4 ,solution of ,liquid ,extracts4--,a sufficient quantity shall be weighed into a covered basin or beaker1 from which it shall be washed into a liter flask with boiling water and well shaken1 and the flask shall be filled to the mark with boiling water4 ,the neck being covered with a small beaker1 the flask shall be placed under a cold water tap or otherwise rapidly cooled to a temperature between #ae and #bj ,c41 and made up accurately to the mark1 after which it shall be thoroughly mixed1 and the filtration at once proceeded with4 ,note4--,tannin infusions may be kept from fermenting by the addition of #c to #e drops of essential oil of mustard per liter4 7,f4 ,kathreiner47 #c4 ,filtration4--,the filtration of the solution for analysis may take place through any paper which may be considered most suitable for the particular case1 and with or without the use of kaolin1 absorption of tanning matter1 if any1 being corrected for by an amount determined by a similar filtration of a clear solution4 ,perfectly clear solutions need not be filtered4 ,to determine the correction1 about #ejj c4c4 of the tanning solution of the strength prescribed for analysis is obtained perfectly clear1 preferably by the method of filtration which is to be corrected for4 ,after thorough mixing1 #ej c4c4 is evaporated to determine 8total soluble ,no4 #a40 ,a portion of the remainder is then filtered in the manner for which correction is to be made1 and #ej c4c4 of the filtrate is evaporated for 8total soluble ,no4 #b40 ,deducting ,no4 #b from ,no4 #a the difference is the correction required1 which must be added to the total soluble found by analysis4 ,it is generally advisable1 both in analysis and in the second filtration for correction1 to filter first #aej c4c4 7which in analysis may be used for the determination of non-tannins71 and then to employ the next #ej c4c4 for evaporation1 keeping the filter full during the operation2 but whatever procedure is adopted must be rigidly adhered to in all analyses to which the correction is applied4 ,where kaolin is employed1 a constant weighed quantity 7#a or #b grm47 must be used1 which is first washed with #ge c4c4 of the liquor by decantation1 and then washed on to the filter with a further quantity of liquor1 of which #bjj c4c4 is filtered as above4#aia #aia ,it is obvious that in the first instance it will be necessary to determine the correction for each particular material employed1 but it will soon be found that the correction is practically constant for large groups of tanning materials1 so long as the same method of filtration is rigidly adhered to4 #d4 ,solid ,extracts4--,solid extracts shall be dissolved by stirring in a beaker with boiling water1 the undissolved portions being allowed to settle1 and treated with further quantities of boiling water1 and the solution poured into a liter flask4 ,after the whole of the soluble matter is dissolved1 the solution is treated similarly to that of a liquid extract4 #e4 ,extraction of ,solid ,materials4--,such quantities shall be weighed as will give an infusion of the strength already prescribed4 7,preparation of ,infusion1 ,resolution #a47 ,not less than #ejj c4c4 of the infusion shall be extracted at a temperature not exceeding #ej ,c41 after which the temperature shall be gradually raised to #ajj ,c41#aib and the extraction continued till the percolate is free from tannin and the whole made up to one liter1 the weaker portions of the solution being first concentrated if necessary by evaporation in a flask1 in the neck of which a funnel is placed4 #aib ,in substances which1 like canaigre1 contain a large quantity of starch1 the extraction should be completed at a temperature of #ej ,c4--,h4 ,r4 ,p4 ,,section ,,iv4--,,determination ,,of ,,tanning ,,matters ,,and ,,non-,,tannins2 ,,etc4 #a4 ,total ,soluble ,matter4--#ajj c4c4#aic of the clear filtered tanning solution1 or a smaller quantity if the balance employed is of sufficient delicacy1 shall be evaporated in an open weighed basin of platinum1 hard glass1 porcelain1 or nickel1 on the water-bath1 and the basin shall afterwards be dried till constant in an air-oven1 at a temperature of #ajj to #aje ,c41 or at a temperature not exceeding #ajj ,c4 in vacuo till constant1 care being taken that no loss occurs by splintering of the residue4 ,the use of the vacuum-oven for drying the residues is recommended when possible4 #aic #ej c4c4 is sufficient1 and is the quantity now generally employed4 #b4 ,determination of ,non-,tannins4--,that the filter method shall remain the official method until the next ,conference1 but that members be permitted to employ the chromed hide-powder method of the ,american ,association of ,official ,agricultural ,chemists of #aija 7,appendix ,c7 where it is desired1 the fact being clearly stated on the report that the ,a4,o4,a4,c4 method has been employed1 and not that of the ,i4,a4,l4,t4,c4 7,leeds1 #aijb1 see note1 p4 #dhj47 ,that the 8bell form0#aid of filter1 as described by ,professor ,procter1 shall be employed2 not less than #e grms4 of hide-powder be used2 the hide-powder should be so packed in the tube that the detannised liquor shall come over at a rate of about one drop in two seconds2 and the filtrate be rejected so long as it gives a turbidity with a clear tanning solution4 ,the filtrate may be used for the determination of non-tannin so long as it gives no reaction with salted gelatine solution4#aie ,the first #cj to #ce c4c4 should be thrown away1 and the next #ej c4c4 of detannised solution1 or an aliquot part of it1 evaporated in a weighed basin on a water bath1 and then dried till constant in an air-oven at a temperature of #ajj to #aje ,c41 or1 in vacuo1 not exceeding #ajj ,c4 #aid ,it is obvious that the exact form and dimensions of the filter must be adapted to the character of the hide-powder available1 as considerable differences exist in the absorptive power of different samples4 #aie #h to #i grams of good gelatine are dissolved in #ejj c4c4 of hot water1 #ajj grams of salt added1 and the whole cooled and filtered4 #c4 ,hide-,powder4--,that the hide-powder must be sufficiently absorbent for use in the filter1 and that in a blank experiment conducted with distilled water in the same way as an analysis1 the residue from the evaporation of #ej c4c4 should not exceed #e milligrams4 ,the ,freiberg ,hide-,powder1 made by ,mehner and ,stransky1 containing between #aj and #bj per cent4 of cellulose 7as suggested by ,cerych71 is recommended by the ,conference 7,lige1 #aija7 and is very suitable for the filter method2 but the powder1 when analysed by the ,kjeldahl method and calculated to #ah per cent4 of moisture1 must not contain less than #aae per cent4 of nitrogen 7,leeds1 #aijb74 #d4 ,determination of ,moisture and 8,total ,dry ,matter40--,that the moisture in the sample be determined by drying a small portion at the temperature adopted in the determination of the 8total soluble40 ,in extracts yielding turbid solutions which can be thoroughly mixed1 it is generally preferable after mixing the solution and before filtration1 to measure off and evaporate #ej c4c4 for the determination of total dry matter 7and moisture7 in the same manner as the 8total soluble40 #e4 ,statement of ,results4--,it is recommended1 when full analysis is given1 that the ,statement should be made in the following manner3-- 7#a7 ,tanning ,matters ,absorbed by ,hide4--,obtained by deducting the 8soluble non-tanning matters0 found by evaporating the hide-powder filtrate from the 8total soluble40 7#b7 ,soluble ,non-,tanning ,matters4--,found by evaporation of filtrate from hide-powder filter4 7#c7 ,insoluble4--,by deducting 8total soluble matter0 from the 8total dry matter40 7#d7 ,moisture4--,determined by drying a portion at the temperature adopted in the determination of 8total soluble40 ,if other determinations are given they shall form a separate additional statement4 ,density4--,the statement of densities of extracts1 etc41 should be given as specific gravity in preference to arbitrary degrees1 such as ,baum1 ,twaddell1 etc4 ,,section ,v4--,,colour ,,measurement4 ,colour ,measurement4--,it is recommended that the method used by ,english chemists1 namely1 measuring with ,lovibond's ,tintometer 7as described by ,professor ,procter and ,dr4 ,parker1 ,journ4 ,soc4 ,chem4 ,ind41 #ahie1 #abe71 shall be used1 and the results stated in units of red1 yellow and black4 ,the measurement may be made on the solution used for analysis1 but must be calculated to one containing #je per cent4 of tanning matter1 in a centimetre cell4 ,,analysis ,,of ,,used ,,liquors4 ,it was decided at ,lige1 #aija1 and ,leeds1 #aijb1aif that the 8,shake ,method0 with chromed hide-powder1 of the ,american ,association of ,official ,agricultural ,chemists1 #aija 7,a4,o4,a4,c471 should be employed in the detannisation of used tanning liquors1 as with these the filter method is apt to give too high results owing to the amount of non-volatile acids which they contain4 ,the method of the ,a4,o4,a4,c4 is given in ,appendix ,c4 #aif ,procter and ,blockey quoted experiments at the ,leeds ,conference1 proving that gallic acid and some other non-tanning substances were largely absorbed by the hide-powder filter1 though probably not permanently retained by leather2 while the error1 though still considerable1 was much less when the chromed hide-power shake method was employed4 ,where only gallotannic and gallic acids are present1 as in the case of sumach and commercial gallotannic acids1 the most accurate quantitative estimation is probably that by the ,lwenthal method carried out as described ,l4,i4,l4,b41 p4 #abc1 but considerable skill is required in its execution4 ,,analysis ,,of ,,spent ,,tans4 ,it was decided at ,leeds1 #aijb1 that spent tans must be analysed like fresh tanning materials2 but where the prescribed strength of solution cannot otherwise be obtained it is permissible to concentrate the entire solution by evaporation4 ,it is advisable1 where suitable apparatus is available1 to concentrate in vacuo2 but failing this1 an ordinary flask may be used1 in the neck of which a funnel is placed4 ,,appendix ,b4--,,the ,,decimal ,,system4 ,the metrical system of weights and measures1 and the ,centigrade thermometer scale have been generally used throughout the book1 as more international and scientific than the complicated systems still unfortunately in use in this country4 ,they have been fully explained in the ,author's #8,laboratory ,book1' p4 #b2 but as this is not always at hand1 a short sketch may be permitted here4 ,the basis of the metrical system is the 8meter10 which is approximately 11 of the distance from the earth's pole to the equator1 and is equal to #cicgjh ,english inches1 and for many practical purposes may be roughly reckoned as #dj inches4 ,the meter is divided into #aj parts or 8decimeters10 #ajj parts or 8centimeters10 and #ajjj parts or 8millimeters40 ,the standard of capacity is a cube of #a decimeter1 or about #d inches1 and consequently contains #ajjj cubic centimeters1 and is denominated a 8liter40 ,the standard of weight is #a cubic centimeter of water 7at #d ,c471 which is called a 8gram40 ,hence #a liter of water weighs #a 8kilogram10 or #ajjj grams4 #a cubic meter of water contains #ajjj liters1 and weighs #ajjj kilograms1 or #a metrical ton 7#bbjj lb4 ,english74 ,for purposes of reduction1 the following figures may be given3-- #a gram #aedca grains4 #a lb4 av4 #decf grams4 #a liter #jbb gallon4 #a gallon #dedc litres4 ,actual reduction is1 however1 generally unnecessary if the question be treated as one of proportion4 ,thus a solution of #a gram per liter is of the same strength as one of #a lb4 per #ajj gallons 7#ajjj lb471 and very approximately1 as one of #a oz4 avoirdupois per cubic foot4 ,in the case of pits1 it is often simplest to measure them directly with a meter rule2 length1 breadth and depth1 measured in decimeters and multiplied together1 giving the contents in liters1 and1 in the case of water1 the weight in kilograms4 ,the ,centigrade or ,celsius thermometer divides the difference between the freezing and the boiling points of water into #ajj4 ,the following table gives the points at which its scale agrees without fractions with that of ,fahrenheit3 ,,comparison ,,of ,,centigrade ,,and ,,fahrenheit ,,degrees4 ,c4 ,f4 -#bj -#d -#ae #e -#aj #ad -#e #bc #j #cb #e #da #aj #ej #ae #ei #bj #fh #be #gg #cj #hf #ce #ie #dj #ajd #de #aac #ej #abb #ee #aca #fj #adj #fe #adi #gj #aeh #ge #afg #hj #agf #he #ahe #ij #aid #ie #bjc #ajj #bab #aje #bba #aaj #bcj #aae #bci ,,appendix ,c4 ,,official ,,method ,,for ,,analysis ,,of ,,tanning ,,materials1 ,,adopted ,,at ,,the ,,eighteenth ,,convention ,,of ,,the ,,american ,,association ,,of ,,official ,,agricultural ,,chemists1 #aija4 ,i4 ,,preparation ,,of ,,sample4 ,barks1 woods1 leaves1 dry extracts1 and similar tanning materials should be ground to such a degree of fineness that they can be thoroughly extracted4 ,fluid extracts must be heated to #ej ,c41 well shaken1 and allowed to cool to room-temperature4 ,,ii4 ,,quantity ,,of ,,material4 ,in the case of bark and similar material1 use such quantity as will give about #jce to #jde gram tannins per #ajj c4c4 of solution1 extract in ,soxhlet or similar apparatus at steam-heat for non-starchy materials4 ,for canaigre and substances containing like amounts of starch use temperature of #ej to #ee ,c41 until near complete extraction1 finishing the operation at steam-heat4 ,in case of extract1 weigh such quantity as will give #jce to #jde gram tannins per #ajj c4c4 of solution1 dissolve in #ijj c4c4 of water at #hj ,c41 let stand twelve hours1 and make up to #ajjj c4c4 ,,iii4 ,,moisture4 7a7 ,place #b grams1 if it be an extract1 in a flat-bottom dish1 not less than #f cm4 in diameter1 add #be c4c4 of water1 warm slowly till dissolved1 continue evaporation and dry4 7b7 ,all dryings called for1 after evaporation to dryness on water-bath1 or others1 shall be done by one of the following methods1 the soluble solids and non-tannins being dried under similar1 and so far as possible identical conditions3 #a4 ,for eight hours at the temperature of boiling water in a steam bath4 #b4 ,for six hours at #ajj ,c41 in an air bath4 #c4 ,to constant weight in vacuo at #gj ,c4 ,,iv4 ,,total ,,solids4 ,shake the solution1 and without filtering immediately measure out #ajj c4c4 with a pipette1 evaporate in a weighed dish1 and dry to constant weight1 at the temperature of boiling water4 ,dishes should be flat-bottomed1 and not less than #f cm4 in diameter4 ,v4 ,,soluble ,,solids4 ,double-pleated filter paper 7,s4 and ,s41 ,no4 #eij1 #ae cm47 shall be used4 ,to #b grams of kaolin add #ge c4c4 of the tanning solution1 stir1 let stand fifteen minutes1 and decant as much as possible4 ,add #ge c4c4 more of the solution1 pour on filter1 keep filter full1 reject the first #aej c4c4 of filtrate1 evaporate the next #ajj c4c4 and dry4 ,evaporation during filtration must be guarded against4 ,,vi4 ,,non-,,tannins4 ,prepare #bj grams of hide-powder by digesting twenty-four hours with #ejj c4c4 of water1 and adding #jf gram chrome alum in solution1 this solution to be added as follows4 ,one-half at the beginning and the other half at least six hours before the end of the digestion4 ,wash by squeezing through linen1 continue the washing until the wash-water does not give a precipitate with barium chloride4 ,squeeze thoroughly by hand1 and remove as much water as possible by means of a press1 weigh the pressed hide1 and take approximately one-fourth of it for moisture determination4 ,weigh this fourth carefully and dry to constant weight4 ,weigh the remaining three-fourths carefully and add them to #bjj c4c4 of the original solution2 shake ten minutes1 throw on funnel with cotton plug in stem1 return until clear1 evaporate #ajj c4c4 and dry4 ,the weight of this residue must be corrected for the dilution caused by the water contained in the pressed hide-powder4#aig ,the shaking must be done in some form of mechanical shaker4 ,the simple machine used by druggists1 and known as the milk-shake1 is recommended4 #aig ,for method of correction1 see p4 #cac4 ,,provisional ,,method4--,to #ad grams of dry chromed hide-powder in a shaker glass add #bjj c4c4 of the tannin solution1 let stand two hours1 stirring frequently1 shake fifteen minutes1 throw on funnel with a cotton plug in the stem1 let drain1 tamp down the hide-powder in the funnel1 return the filtrate until clear and evaporate #ajj c4c4 ,,vii4 ,,tannins4 ,the amount of these is shown by the difference between the soluble solids and the corrected non-tannins4 ,,viii4 ,,testing ,,hide-,,powder4 7a7 ,shake #aj grms4 of hide-powder with #bej c4c4 of water for five minutes1 strain through linen1 squeeze the magma thoroughly by hand2 repeat this operation three times1 pass the last filtrate through paper 7,s4 and ,s4 ,no4 #eij1 #ae cm47 till clear1 evaporate #ajj c4c4 and dry4 ,if this residue amounts to more than #aj mg4 the hide must be rejected4 7b7 ,prepare a solution of pure gallo-tannin by dissolving #f grams in #ajjj c4c4 of water4 ,determine the total solids by evaporating #ajj c4c4 of this solution and drying to constant weight4 ,treat #bjj c4c4 of the solution with hide-powder exactly as described in paragraph #f4 ,the hide-powder must absorb at least #ie per cent4 of the total solids present4 ,the gallo-tannin used must be completely soluble in water1 alcohol1 acetone and acetic ether1 and should not contain more than #a per cent4 of substances not removed by digesting with excess of yellow mercuric oxide on steam-bath for two hours4 ,,ix4 ,,testing ,,non-,,tannin ,,filtrate4 7a7 ,for ,tannin4--,test a small portion of the clear non-tannin filtrate with a few drops of a #a per cent4 solution of ,nelson's gelatin4 ,a cloudiness indicates the presence of tannin1 in which case repeat the process described under ,,vi41 using #ce instead of #bj grams of hide-powder4 7b7 ,for ,soluble ,hide4--,to a small portion of the clear non-tannin filtrate add a few drops of the filtered tannin solution4 ,a cloudiness indicates the presence of soluble hide1 in which case repeat the process described under ,,vi41 giving the hide-powder a more thorough washing4 ,the temperature of solutions shall be between #af and #bj when measured or filtered4 ,all dryings should be made in flat-bottomed dishes of at least #f cm4 diameter1 ,s4 and ,s4 ,no4 #eij1 #ae cm4 filter paper should be used in all filtrations4 ,,appendix ,d4 ,the following ,lists of ,colours have been furnished by ,mr4 ,m4 ,c4 ,lamb1 ,director of the ,leather ,dyeing ,department of ,herold's ,institute1 ,london1 who has devoted much time to testing the various dyes with regard to their permanence and suitability for leather4 ,many of the colours have also been tested and found satisfactory in the ,leather ,department of the ,yorkshire ,college4 ,the following abbreviations of makers' names are used in the lists3-- ,b4 ,,basler ,,chemische ,,fabrik1 ,a4 ,g4 ,basle1 ,switzerland4 ,b4,a4,s4,f4 ,,badische ,,anilin ,,und ,,soda ,,fabrik4 ,ludwigshafen a4 ,rhine1 ,germany4 ,ber4 ,,berlin ,,aniline ,,co4 ,berlin ,s4,o41 ,germany4 ,b4,s4 ,spl4 ,,brooke1 ,,simpson ,,spiller4 ,atlas ,dye ,works1 ,hackney ,wick1 ,london1 ,n4,e4 ,by4 ,,farben-,,fabriken1 late ,,bayer ,,co4 ,elberfeld1 ,germany4 ,c4 ,l4 ,,cassella ,,co4 ,frankfort a4 ,main1 ,germany4 ,c4,a4 ,,french ,,aniline ,,colour ,,works4 ,vieux-,conde 7,norde71 ,france4 ,c4 ,r4 ,,claus ,r,e4 ,clayton1 near ,manchester4 ,d4 ,,dahl ,,co4 ,barmen1 ,germany4 ,d4 ,h4 ,,durand1 ,,huguenin ,,co4 ,basle1 ,switzerland4 ,g4 ,r4 ,,geigy ,,co4 ,basle1 ,switzerland4 ,ger4 ,,gerber ,,co4 ,basle1 ,switzerland4 ,k4 ,,kalle ,,co4 ,bierbrich a4 ,rhine1 ,germany4 ,leon4 ,a4 ,,leonhardt ,,co4 ,muhlheim a4 ,main1 ,germany4 ,leitch ,j4 ,w4 ,,leitch4 ,milnsbridge ,chemical ,works1 ,huddersfield4 ,lev4 ,,levinstein ,,ltd4 #ba ,minshull ,street1 ,manchester4 ,m4,l4,b4 ,,meister1 ,,lucius ,,bruning4 ,hoechst a4 ,main1 ,germany4 ,mo4 ,,gilliard1 ,p4 ,,monnet ,,gartier4 ,lyons1 ,france4 ,n4 ,,noetzel1 ,,istel ,,co4 ,griesheim a4 ,main1 ,germany4 ,o4 ,k4 ,,oehler ,,co4 ,offenbach a4 ,main1 ,germany4 ,p4 ,,st4 ,,denis ,,dyestuff ,,co41 late ,,pourier4 ,st4 ,denis1 near ,paris4 ,r4 ,,soci,,te ,,chimique ,,des ,,usines ,,du ,,rhone4 ,lyons1 ,france4 ,r4 ,h4 ,s4 ,,read1 ,,holliday ,,sons4 ,huddersfield4 ,s4,c4,ind4 ,,society ,,of ,,chemical ,,industry4 ,basle1 ,switzerland4 ,uer4 ,,chemische ,,fabriken4 ,uerdingen a4 ,rhein1 ,germany4 ,w4 ,bros4 ,,williams ,,bros4 ,,co4 ,hounslow1 ,middlesex4 ,,staining4 ,,single ,,acid ,,dyes ,,suitable ,,for ,,staining ,,vegetable ,,tanned ,,leather4 ,browns4 ,solid brown4 7,m4,l4,b47 ,acid brown4 7,w4 ,bros47 ,brown ,a#b4 7,b4,s4 ,spl47 ,brown ,a#a4 7,b4,s4 ,spl47 ,mikado brown ,b4 7,leon47 ,new acid brown4 7,b4,s4 ,spl47 ,bronze acid brown4 7,by47 ,golden brown ,y4 7,c471 7,by47 ,acid anthracene brown ,r4 7,by47 ,fast brown ,n4 7,b4,a4,s4,f47 ,nut brown ,a4 7,c47 ,fast brown4 7,by47 ,fast brown ,g4 7,ber47 ,resorcin brown4 7,ber47 ,resorcin brown4 7,d47 ,acid brown4 7,ber47 ,dark nut brown4 7,w4 ,bros47 ,acid brown ,r4 7,c47 ,acid brown ,r4 7,uer47 ,acid brown ,r4 7,r4 ,h4 ,s47 ,new golden brown ,a#a4 7,c47 ,dark brown4 7,c47 ,acid brown ,l4 7,b4,a4,s4,f47 ,acid brown ,d4 7,c47 ,yellows4 ,azo yellow4 7,uer47 ,phosphine subst4 7,b4,s4 ,spl47 ,chrysoine4 7,w4 ,bros47 ,azo-acid-yellow4 7,ber47 ,new phosphine ,g4 7,c47 ,cuba yellow #bjgb4 7,s4,c4 ,ind47 ,cuba yellow 7,w4 ,bros47 ,azo-flavine ,,rs4 7,c47 and 7,b4,a4,s4,f47 ,azo-flavine #c,r4 7,b4,a4,s4,f47 ,indian yellow ,r4 7,by47 ,turmeric yellow4 7,g47 ,solid yellow ,g4 7,leon47 ,solid yellow ,b4 7,leon47 ,indian yellow ,r4 7,c47 ,cuba yellow4 7,c47 ,napthol yellow ,s4 7,by471 7,c471 7,b4,a4,s4,f47 ,turmeric yellow4 7,c471 7,g47 ,fast acid yellow4 7,c4,a47 ,reds and ,oranges4 ,scarlet ,r4 7,by47 ,crocein scarlet #c;,,bn4 7,by47 ,orange #b4 7,m4,l4,b471 7,s4,c4 ,ind471 7,c47 and 7,b4,a4,s4,f47 ,orange #b;,b4 7,by47 ,mandarin ,g extra4 7,ber47 ,brill4 crocein ,m4,o4,o4 7,c47 ,bordeaux ,g4 7,by47 ,atlas orange4 7,b4,s4 ,spl47 ,bordeaux cov4 7,ber47 ,fast red #baebh4 7,by47 ,fast red ,a4 7,leon471 7,by471 7,ber471 and 7,b4,a4,s4,f47 ,bordeaux ,b4 7,m4,l4,b47 ,greens4 ,acid green extra conc4 7,c47 ,guinea green ,b4 7,ber47 ,guinea green ,g4 7,ber47 ,acid green ,,gg4 7,by47 ,acid green ,,bb4 7,by47 ,acid green ,b4 7,by47 ,acid green ,g4 7,by47 ,acid green #jjj4 7,leon47 ,acid green extra4 7,by47 ,acid green 7,uer47 ,acid green 7,r4 ,h4 ,s47 ,light green ,,sf4 7,b4,a4,s4,f47 ,erioglaucine4 7,g47 ,violets4 ,acid violet #d,,rs4 7,ber47 ,acid violet #g;,b4 7,ber47 ,acid violet #f;,b4 7,by47 ,formyl violet ,s#d;,b4 7,c47 ,blues4 ,bavarian blue ,d4,b4 7,ber47 ,marine blue o4 7,k47 ,solid blue4 7,m4,l4,b47 ,blue #a4 7,lev47 ,blue #b4 7,lev47 ,blue #c4 7,lev47 ,,single ,,basic ,,dyes ,,suitable ,,for ,,staining ,,vegetable ,,tanned ,,leather4 ,browns4 ,bismark brown ,,gg4 7,c47 ,chrysoidine ,,ag4 7,o47 ,bismark brown #b;,b4 7,k47 ,bismark brown 7,by47 ,bismark brown ,r4,c4,e4 7,lev47 ,bismark brown ,m4 7,by47 ,vesuvine conc4 7,m4,l4,b47 ,vesuvine conc4 7,b4,a4,s4,f47 ,bismark brown ,c extra4 7,leon47 ,bismark brown ,,rs4 7,b4,s4 ,spl47 ,bismark brown #cgfb4 7,w4 ,bros47 ,rheonine ,a4 7,b4,a4,s4,f47 ,rheonine ,n4 7,b4,a4,s4,f47 ,brown ,r4 7,g47 ,brown ,g4 7,g47 ,manchester brown4 7,c47 ,yellows4 ,acridine yellow ,,nc4 7,leon47 ,phosphine ,n4 7,ber47 ,patent phosphine ,r4 7,s4,c4 ,ind47 ,leather yellow #fgcj4 7,c4,a47 ,auramine #b4 7,by47 ,chrysoidine cryst4 7,b4,s4 ,spl47 and 7,by47 ,chrysoidine diamond cryst4 7,w4 ,bros47 ,leather yellow o4 7,m4,l4,b47 ,chrysoidine4 7,r4 ,h4 ,s47 ,leather yellow ,g4 7,m4,l4,b47 ,leather yellow #fgcj4 7,c4,a47 ,patent phosphine ,g4 7,s4,c4 ,ind47 ,leather yellow ,,drr4 7,ber47 ,xanthine4 7,o47 ,cannella ,g4 7,w4 ,bros47 ,pure phosphine4 7,c47 ,new phosphine ,g4 7,c47 ,cori-phosphine o4 7,by47 ,para-phosphine ,r4 7,c47 ,para-phosphine ,g4 7,c47 ,leather yellow #cgd4 7,d47 ,leather yellow #cge4 7,d47 ,homo-phosphine ,g4 7,leon47 ,phosphine ,,abn4 7,leon47 ,auramine #b patent4 7,s4,c4 ,ind47 ,greens4 ,methyl green cryst4 7,ber47 ,methylene green4 7,m4,l4,b47 ,solid green4 7,leon47 ,malachite green4 7,ber471 7,m4,l4,b471 7,p471 7,c4,a471 7,s4,c4 ,ind471 7,r4 ,h4 ,s471 7,lev471 7,c471 7,b4,s4 ,spl47 and 7,k47 ,reds4 ,safranine4 7,m4,l4,b471 7,b4,a4,s4,f471 7,s4,c4 ,ind47 and 7,k471 7,ber471 7,by471 7,c4,a471 7,leon471 7,uer47 ,russian ,red4 7,by47 and 7,ber47 ,violets4 ,methyl violets4 7,ber471 7,by471 7,m4,l4,b471 7,r4 ,h4 ,s471 7,b4,s4 ,spl471 7,c47 7,s4,c4 ,ind471 7,p47 and 7,d474 ,blacks4 ,corvoline ,b4 7,b4,a4,s4,f47 ,corvoline ,g4 7,b4,a4,s4,f47 ,,dyeing4 ,,single ,,acid ,,colours ,,suitable ,,for ,,dyeing ,,vegetable ,,tanned ,,leathers4#aih #aih ,for explanation of ,roman numerals see end of ,appendix ,d4 ,yellows4 ,,ii4 ,napthol yellow ,s4 7,ber471 7,b4,a4,s4,f471 7,by47 and 7,c474 ,,vii4 ,quinoline yellow4 7,ber471 7,by47 and 7,b4,a4,s4,f474 ,,ii4 ,citronine4 7,leon47 ,,iv4 ,solid yellow ,g4 7,leon47 ,,iv4 ,solid yellow ,b4 7,leon47 ,v4 ,indian yellow ,s4 ,v4 ,azo-acid yellow4 ,,iv4 ,indian yellow ,t4 7,c47 ,,vii4 ,indian yellow ,r4 7,by47 and 7,c474 ,,iv4 ,indian yellow ,g4 7,by47 and 7,c474 ,,iv4 ,cuba yellow4 7,c471 7,w4 ,bros47 and 7,s4,c4,ind474 ,v4 ,azo-flavine ,,rs4 7,b4,a4,s4,f47 and 7,c474 ,v4 ,azo-flavine #c,r4 7,b4,a4,s4,f47 and 7,c474 ,,vi4 ,circumein extra4 7,ber47 ,,vii4 ,tartrazine4 7,b4,a4,s4,f47 ,oranges4 ,v4 ,orange #b4 7,b4,a4,s4,f471 7,c471 7,m4,l4,b471 7,s4,c4 ,ind471 7,p47 7,w4 ,bros47 and 7,by474 ,v4 ,mandarin ,g extra4 7,ber47 ,v4 ,crocein orange4 7,k47 and 7,by474 ,,vi4 ,ponceaux #aj,,rb1 #d,r1 ,bo1 #d,,rb1 #f,,rb4 7,ber471 7,by47 and 7,d474 ,bordeaux4 ,,vii4 ,azo bordeaux4 7,by47 ,,iv4 ,bordeaux ,b extra4 7,by47 ,,vi4 ,bordeaux ,g4 7,by47 ,v4 ,bordeaux ,y4 7,w4 ,bros47 ,v4 ,acid maroon4 7,m4,l4,b47 and 7,b4,s4 ,spl474 ,,viii4 ,chromatrop #f;,b4 7,m4,l4,b47 ,reds4 ,v4 ,fast red ,a4 7,ber471 7,by471 7,b4,a4,s4,f471 7,b4,s4 ,spl47 and 7,leon47 ,,viii4 ,fast red ,s4 7,m4,l4,b47 ,,vi4 ,fast red #baebh4 7,by47 ,scarlets4 ,v4 ,crocein scarlet ,r4 7,by47 and 7,k474 ,v4 ,crocein scarlet #b,r4 7,by47 ,,vii4 ,fast scarlet ,b4 7,b4,a4,s4,f471 7,w4 ,bros47 and 7,k47 ,browns4 ,,iv4 ,acid brown ,r4 7,c47 ,v4 ,acid brown ,l4 7,b4,a4,s4,f47 ,v4 ,acid brown ,y4 7,s4,c4 ,ind47 ,,iv4 ,acid brown ,d4 7,c471 7,b4,a4,s4,f47 ,,iv4 ,acid brown 7,r4,h4 ,s47 ,,iv4 ,acid brown #dfja4 7,b4,s4 ,spl47 ,v4 ,acid brown ,d4 7,c47 ,,vii4 ,resorcin brown4 7,ber47 ,v4 ,acid brown4 7,uer47 ,,iv4 ,acid brown ,r4 7,ber47 ,,viii4 ,acid brown ,y4 7,m4,l4,b474 ,,vi4 ,solid brown o4 7,m4,l4,b47 ,v4 ,fast brown4 7,by47 ,v4 ,fast brown4 ,g4 7,ber47 ,v4 ,fast brown4 ,n4 7,b4,a4,s4,f47 ,,iv4 ,fast brown4 #c;,b4 7,ber47 ,v4 ,bronze acid brown4 7,by47 ,,viii4 ,acid anthracine brown ,r4 7,by47 ,v4 ,new acid brown4 7,b4,s4 ,spl47 ,,vi4 ,dark nut brown4 7,uer47 ,,iv4 ,new golden brown ,a#a4 7,c47 ,blacks4 ,,iv4 ,napthol blue black4 7,c47 ,v4 ,napthylamine black #d;,b4 7,c47 ,v4 ,napthylamine black #f;,b4 7,c47 ,,vii4 ,phenol black ,s4 7,by47 ,,iv4 ,phenylamine black #d;,b4 7,by47 ,,vii4 ,victoria black ,b4 7,by47 ,blues4 ,,viii4 ,fast blue ,r4 7,ber47 ,,viii4 ,bavarian blue ,,db4 7,ber47 ,v4 ,erioglaucine4 7,g47 ,,iv4 ,cyanole ext4 7,c47 ,,iv4 ,marine blue4 7,k47 ,,vii4 ,water blue ,n4 7,b4,a4,s4,f47 ,,viii4 ,water blue #d ,b4 7,ber47 ,,vii4 ,cotton blue ,,ii4 7,by474 ,,vii4 ,toluidine blue4 7,b4,a4,s4,f47 and 7,by474 ,,vii4 ,water blue ,r4 7,leon47 ,,vii4 ,water blue #c,r4 7,leon47 ,,vii4 ,water blue ,,btr4 7,b4,a4,s4,f47 ,violets4 ,acid violets 7,lev471 7,b4,a4,s4,f47 and 7,by47 ,,ix4 ,acid violets #d,r4 7,b4,a4,s4,f47 ,v4 ,acid violets ,r4 7,c47 ,v4 ,acid violets ,r4 7,b4,a4,s4,f47 ,,vi4 ,acid violets #c;,,ba4 7,m4,l4,b47 ,,iv4 ,acid violets #c;,,bn4 7,lev47 ,,ii4 ,acid violets #f;,b4 7,by47 and 7,c474 ,,iii4 ,formyl violet ,s#d;,b4 7,c47 ,greens4 ,,iv4 ,acid green extra conc4 7,c47 ,,iv4 ,guinea green ,b and ,g4 7,ber47 ,,iv4 ,acid green ext4 7,by47 ,,iv4 ,acid green ,,gg ext4 7,by47 ,,iv4 ,acid green #bbe4 7,by47 ,,iv4 ,acid green ,,bb4 ext4 7,by47 ,,iv4 ,acid green o4 7,m4,l4,b47 ,,iv4 ,acid green #efgg4 7,b4,s4 ,spl47 ,v4 ,capri green #b;,g4 7,lev47 ,,single ,,basic ,,dyes ,,suitable ,,for ,,dyeing ,,vegetable ,,tanned ,,leathers4 ,browns4 ,,iv4 ,vesuvine ooo ext4 7,b4,a4,s4,f47 ,,ii4 ,vesuvine ,b4 7,b4,a4,s4,f47 ,,ii4 ,vesuvine 7,c47 ,,iii4 ,vesuvine conc4 7,m4,l4,b47 ,,iii4 ,bismark brown ext4 7,ber47 and 7,b4,s4 ,spl474 ,,iii4 ,bismark brown ext4 ,m4 7,by47 ,,iii4 ,bismark brown ,f4 7,by47 ,,iv4 ,bismark brown ,,ys4 7,b4,s4 ,spl47 ,,iii4 ,bismark brown ,,ps4 7,c47 ,,iii4 ,bismark brown ,,gg4 7,c47 ,,iii4 ,bismark brown ,o4 7,l47 ,,iii4 ,bismark brown ,g4 7,o47 ,,iii4 ,bismark brown 7,s4,c4 ,ind47 ,,iii4 ,bismark brown ,,nyy4 7,w4 ,bros47 ,,iii4 ,bismark brown o4 7,m4,l4,b47 ,,ii4 ,cannella4 7,b4,s4 ,spl47 ,,ii4 ,cannella4 7,b4,a4,s4,f47 ,,ii4 ,cannella4 7,c47 ,v4 ,cannella4 7,s4,c4 ,ind47 ,,ii4 ,cannella ,s4 7,ber47 ,,iii4 ,cannella ,p4 7,w47 ,,iv4 ,nanking4 7,b4,a4,s4,f47 ,,iv4 ,nanking4 7,r4,h4 ,s47 ,,iv4 ,nanking4 7,s4,c4 ,ind47 ,,iii4 ,lavilliere's #abb4 7,by47 ,,ii4 ,rheonine4 7,b4,a4,s4,f47 ,,iv4 ,xanthine4 7,o47 ,yellowish ,oranges4 ,,iii4 ,chrysoidines1 7,leitch72 ,r1 7,r4,h4 ,s47 ,,iv4 ,chrysoidines ext4 7,w474 ,,ii4 ,chrysoidines 7,s4,c4,ind472 ,,gg17,c47 ,,iii4 ,chrysoidines ,g4 7,leon47 ,,ii4 ,chrysoidines ,,re4 7,lev47 ,,iii4 ,chrysoidines ,,yy4 7,c47 ,,iii4 ,chrysoidines cryst4 7,b4,s4 ,spl47 ,,iii4 ,chrysoidines ,g4 7,by47 ,v4 ,chrysoidines cryst4 7,c4,a47 ,yellows4 ,,iii4 ,auramine #b4 7,b4,a4,s4,f47 ,,iii4 ,auramine4 7,s4,c4 ,ind47 ,,iii4 ,auramine4 7,g47 ,,iii4 ,auramine4 7,ber47 ,,iii4 ,auramine4 7,by47 ,,iii4 ,auramine4 7,l47 ,,iii4 ,auramine4 7,w47 ,,iii4 ,auramine4 7,c47 ,,iii4 ,auramine4 7,w47 ,v4 ,auramine conc4 7,m4,l4,b474 ,,iv4 ,phosphine ,e4 7,b4,a4,s4,f47 ,,iv4 ,phosphine ,l4 7,b4,a4,s4,f47 ,,iv4 ,phosphine ,g4 7,ber47 ,,iv4 ,phosphine4 7,o47 ,,iv4 ,phosphine4 7,c47 ,,iv4 ,phosphine ,ext4 7,m4,l4,b47 ,,iv4 ,phosphine ,b ext4 7,s4,c4 ,ind47 ,,iii4 ,phosphine ,,iii41 ,,ii41 ,i4 7,leon47 ,,iii4 ,phosphine ,n4 7,ber474 ,v4 ,cori-phosphine4 7,by47 ,v4 ,homo-phosphine4 7,leon47 ,v4 ,para-phosphine4 7,c47 ,greens4 ,,iii4 ,methyl green cryst4 7,by47 ,d4 ,v4 ,methylene green o4 7,m4,l4,b47 ,,ii4 ,diamond green ,b and ,g4 7,b4,a4,s4,f47 ,,ii4 ,benzal green4 7,o47 ,,ii4 ,brillt4 green cryst4 7,m4,l4,b47 ,,ii4 ,brillt4 green cryst4 7,by47 ,,ii4 ,brillt4 green cryst4 7,o47 ,,ii4 ,brillt4 green cryst4 7,l47 ,,ii4 ,brillt4 green cryst4 7,lev47 ,,ii4 ,brillt4 green cryst4 7,uer47 ,,ii4 ,brillt4 green cryst4 7,s4,c4 ,ind47 ,,ii4 ,malachite green4 7,b4,s4 ,spl47 ,,ii4 ,malachite green4 7,ber47 ,,ii4 ,malachite green4 7,c4,a47 ,,ii4 ,malachite green4 7,k47 ,,ii4 ,malachite green4 7,m4,l4,b47 ,,ii4 ,malachite green4 7,lev47 ,,ii4 ,malachite green4 7,g47 ,,ii4 ,malachite green4 7,o47 ,blues4 ,,vii4 ,methylene blue ,b1 #b;,b and ,r4 7,ber47 ,,vii4 ,methylene blue4 7,b4,a4,s4,f47 ,,vii4 ,methylene blue4 7,m4,l4,b47 ,,vii4 ,methylene blue4 7,lev47 ,,vii4 ,methylene blue4 7,c47 ,,vii4 ,methylene blue4 7,c4 ,r47 ,,viii4 ,new methylene blue4 ,,gg4 7,c47 ,,viii4 ,new methylene blue4 ,,bb4 7,c47 ,,iv4 ,new blue ,r4 7,ber47 ,v4 ,new blue ,r4 7,by47 ,,vi4 ,new patent blue #d;,b4 7,by47 ,violets4 ,,iv4 ,methyl ,violet #d;,b4 7,b4,a4,s4,f47 ,,iv4 ,methyl ,violet #d,r4 7,k47 ,,iv4 ,methyl ,violet #d,r4 7,c47 ,,iv4 ,methyl ,violet #c;,b4 7,by47 ,,iv4 ,methyl ,violet #c;,b4 7,ber47 ,,iv4 ,methyl ,violet #b;,b4 7,m4,l4,b47 ,,iv4 ,methyl ,violet 7,d47 ,,iv4 ,methyl ,violet #f;,b4 7,leon47 ,,iv4 ,neutral violet ext4 7,c47 ,bordeaux4 ,,iv4 ,magenta ,,wb4 7,leon47 ,,iv4 ,magenta #c;,b4 7,ber47 ,,iv4 ,magenta ,,re4 7,leon47 ,,iv4 ,magenta ,,wbg4 7,leon47 ,,iv4 ,magenta4 7,m4,l4,b47 ,,iv4 ,magenta4 7,k47 ,,iv4 ,magenta4 7,b4,a4,s4,f47 ,,iv4 ,magenta #dabh4 7,b4,s4 ,spl47 ,reds4 ,,viii4 ,rhodamine ,b extra4 7,ber47 ,,viii4 ,rhodamine ,b4 7,b4,a4,s4,f47 ,,viii4 ,rhodamine ,b4 7,by47 ,,viii4 ,rhodamine 7,s4,c4 ,ind47 ,,viii4 ,rhodamine 7,m4,l4,b47 ,,vii4 ,safranine4 7,b4,a4,s4,f47 ,,iv4 ,russian red ,g4 7,b4,a4,s4,f474 ,,iv4 ,russian red ,b4 7,c47 ,,iv4 ,russian red 7,ber47 ,,iv4 ,russian red 7,uer47 ,,iv4 ,russian red ,b4 7,b4,a4,s4,f47 ,,iv4 ,russian red ,g4 7,c47 ,,iv4 ,russian red 7,ber47 ,,iv4 ,russian red ,r4 7,by47 ,,iv4 ,cardinal #d;,b4 7,by47 ,,viii4 ,rhoduline red4 7,by47 ,v4 ,safranine ,g ext4 7,c47 ,,vii4 ,safranine ,,bs4 7,by47 ,safranine ,g ext4 7,ber47 ,,acid ,,mixtures ,,suitable ,,for ,,dyeing ,,and ,,staining ,,vegetable ,,tanned ,,leathers4 ,orange #b4 7,m4,l4,b47 ,azo-yellow o4 7,m4,l4,b47 ,patent blue ,v4 7,m4,l4,b47 ,resorcin brown4 7,ber47 ,circumein ext4 7,ber47 ,nigrosine #aje4 7,ber47 ,acid brown ,r4 7,c47 ,indian yellow ,g4 7,c47 ,pure soluble blue4 7,c47 ,new acid brown4 7,b4,s4 ,spl47 ,phosphine subst4 7,b4,s4 ,spl47 ,induline4 7,b4,s4 ,spl47 ,acid brown ,r4 7,c47 ,azo-flavine ,r4,s4 7,c47 ,naphtol blue black4 7,c47 ,resorcin brown1 7,ber47 ,fast brown ,g4 7,ber47 ,napthylamine black ,d4 7,c47 ,fast brown ,g4 7,ber47 ,circumine ext4 7,ber47 ,nigrosine #aje4 7,ber47 ,fast brown4 7,by47 ,indian yellow ,r4 7,by47 ,fast green blue shade4 7,by47 ,acid anthracene brown4 7,by47 ,indian yellow ,r4 7,by47 ,fast green blue shade4 7,by47 ,fast brown ,n4 7,b4,a4,s4,f47 ,azo-flavine ,,rs4 7,b4,a4,s4,f47 ,light green ,s4,f4 7,b4,a4,s4,f47 ,dark nut brown4 7,uer47 ,azo-yellow4 7,uer47 ,acid green4 7,uer47 ,acid brown4 7,d47 ,crocein orange4 7,d47 ,cotton blue #c,r4 7,d47 ,resorcin brown4 7,d47 ,cotton blue #c,r4 7,d47 ,acid brown ,b4 7,s4,c4 ,ind47 ,cuba yellow #bjgb4 7,s4,c4 ,ind47 ,acid green4 7,s4,c4 ,ind47 ,resorcin brown4 7,w4 ,bros47 ,cuba yellow4 7,w4 ,bros47 ,acid green4 7,w4 ,bros47 ,napthol brown4 7,leon47 ,citronine ,a4 7,leon47 ,acid green #jjj4 7,leon47 ,acid brown ,r4 7,r4,h4 ,s47 ,acid yellow4 7,r4,h4 ,s47 ,nigrosine cryst4 7,r4,h4 ,s47 ,orange #b4 7,p47 ,yellow o,s4 7,p47 ,acid green ,j#c;,e4 7,p47 ,acid brown4 7,c4,a47 ,acid yellow ,s4 7,c4,a47 ,pure blue cryst4 7,c4,a47 ,resorcin brown4 7,ber47 ,azo-acid-yellow or ,circumine ext4 7,ber47 ,bavarian blue ,,db1 or ,guinea green ,g4 7,ber47 ,indian yellow ,r4 7,c47 ,acid brown ,r4 7,c47 ,pure soluble blue4 7,c47 ,azo-acid-yellow conc4 7,m4,l4,b47 ,solid brown o4 7,m4,l4,b47 ,fast blue o sol4 7,m4,l4,b47 ,bronze acid brown4 7,by47 ,indian yellow ,r4 7,by47 ,fast green blue shade4 7,by47 ,acid anthracene brown4 7,by47 ,indian yellow ,r4 7,by47 ,fast green blue shade4 7,by47 ,orange #aa4 7,b4,a4,s4,f47 ,scarlet ,,gl4 7,b4,a4,s4,f47 ,light green ,,sfys4 7,b4,a4,s4,f47 ,azo-flavine ,,rs4 7,b4,a4,s4,f47 ,acid brown ,l4 7,b4,a4,s4,f47 ,light green ,,sfys4 7,b4,a4,s4,f47 ,chocolate4 7,uer47 ,tartrazine1 7,b4,a4,s4,f472 or ,azo-yellow1 7,uer47 ,,basic ,,mixtures ,,suitable ,,for ,,dyeing ,,and ,,staining ,,vegetable ,,tanned ,,leathers4 ,bismark brown ,m4 7,by47 ,auramine #b4 7,by47 ,methylene blue ,,bb4 7,by47 ,rheonine ,a4 7,b4,a4,s4,f47 ,vesuvine ,b#b4 7,b4,a4,s4,f47 ,diamond green ,g4 7,b4,a4,s4,f47 ,bismark brown ,o4 7,leon47 ,auramine #b4 7,leon47 ,solid green ,p4 7,leon7 ,bismarck ,brown ext4 7,ber47 ,philadelphia yellow ,r4 7,ber47 ,malachite green cryst4 7,ber47 ,new phosphine ,g4 7,c47 ,chrysoidine4 7,c47 ,new blue ,b4 7,c47 ,phosphine ext4 7,f47 ,chrysoidine diamond cryst4 7,f47 ,bright green cryst4 ext4 7,f47 ,bismark brown ,,gg4 7,o47 ,aniline yellow ext4 7,o47 ,neutral violet ext4 7,o47 ,dark brown ,b4 7,by47 ,auramine #b4 7,by47 ,emerald green cryst4 7,by47 ,phosphine #c,,rb4 7,ber47 ,philadelphia yellow ,r4 7,ber47 ,russian green #cfghd4 7,ber47 ,bismark ,brown ,,rs4 7,b4,s4 ,spl47 ,cannella4 7,b4,s4 ,spl47 ,malachite green4 7,b4,s4 ,spl47 ,vesuvine conc4 7,m4,l4,b47 ,auramine conc4 7,m4,l4,b47 ,methylene green4 7,m4,l4,b47 ,cutch brown4 7,leitch47 ,lemon yellow ,g4 7,leitch47 ,russian green #c ,b4 7,leitch47 ,bismark brown #b ,b4 7,k47 ,yellow for leather ext4 7,k47 ,malachite green cryst4 7,k47 ,auramine4 7,g47 ,brown ,r4 7,g47 ,malachite green4 7,g47 ,auramine o4 7,lev47 ,bismark brown ,r4,c4,e4 7,lev47 ,brill4 green4 7,lev47 ,bismark brown ,y#dj4 7,r4,h4 ,s47 ,canary #b4 7,r4,h4 ,s47 ,green cryst4 ,y4 7,r4,h4 ,s474 ,leather brown ,a4 7,s4,c4 ,ind47 ,auramine #b4 7,s4,c4 ,ind47 ,leather black #a4 7,s4,c4 ,ind47 ,leather black ,r4 7,uer474 ,yellow #dhjc4 7,uer47 ,blue black ,s4 7,uer47 ,bismark brown ,,nyy4 7,w4 ,bros47 ,cannella ,g4 7,w4 ,bros47 ,brown for leather #cge4 7,d47 ,fast yellow #afh4 7,d47 ,methyl green ,g ext4 fine4 7,d47 ,brown ,n4 7,d47 ,leather brown ,p4 7,d47 ,paris violet o4 7,d47 ,,chrome ,,leather4 ,the following dye-stuffs are suitable for dyeing chrome leather4 ,the leather after tanning1 is boraxed in the usual manner and then mordanted by drumming or paddling in a tannin solution2 for dark shades #c per cent4 gambier and #c per cent4 fustic extract 7the weight being calculated on the leather struck out after boraxing7 is suitable2 for light shades #a per cent4 gambier is to be recommended4 ,the leather1 after mordanting1 is fat-liquored and dyed1 adding a weight of sodium or potassium bisulphate equal to that of the dye-stuff1 to the dye-bath4 ,the following is not by any means a complete list of the dyes which will dye chrome leather well1 but merely representative4 ,after the goods are dyed1 they should be well washed in tepid water to which has been added a little common salt2 one pound to every three dozen skins being a suitable amount to use4 ,when the goods have been washed1 they are struck out by machine and are then ready for shaving1 if the operation has not been performed previous to dyeing4 ,the skins are afterwards nailed out flat1 grain-side up1 on boards1 and a mixture of glycerine and water--#c lb4 of glycerine dissolved in one gallon of water being a suitable strength--is well sponged on the grain-side2 the goods are now lightly oiled 7using a good sperm1 neat's-foot or mineral oil71 before being taken to the drying room4 ,when thoroughly dry they are taken off the boards1 and placed with layers of damp sawdust between each skin1 for a few hours in order to allow the goods to become suitably damp for staking4 ,the skins should now be well staked by machine1 the ,haley 7,england71 ,slocomb or ,vaughn 7,america7 being good machines for this purpose 7p4 #aib74 ,after staking1 the goods are 8soft-boarded10 and a thin coat of a weak linseed mucilage is applied to the skins1 which are afterwards dried out and seasoned with the following mixture3-- 8,soak #aj to #ae oz4 of dry egg albumen for four hours in #a gallon of cold water1 with occasional stirring1 strain off any insoluble matter and add #a gallon of milk4 ,a little carbolic acid 7phenol7 may be added to the above if it is desired to keep the finish for more than two or three days--#a oz4 of phenol previously dissolved in a little water1 added to each gallon of the finish1 being a suitable amount40 ,a little dye should be added to the mixture4 ,after seasoning1 the skins are dried out in the stove1 glazed twice round and re-seasoned with the above mixture diluted with its own volume of water4 ,the goods are dried out and again glazed1 perched lightly1 and finally boarded up from neck to tail in order to raise the popular straight-grain4 ,should the glaze be too bright the albumen solution may be reduced to half-strength4 ,when the goods have been glazed they are rubbed over on the grain side with a flannel cloth which is slightly damp with linseed oil1 trimmed up1 and are ready for sale4 ,,dyes ,,suitable ,,for ,,dyeing ,,chrome-,,tanned ,,leather4 ,browns4 ,resorcin brown4 7,ber47 ,chocolate4 7,uer47 ,fast brown4 7,,by47 ,fast brown4 7,ber47 ,new golden brown ,a4#a4 7,c47 ,fast brown4 7,b4,a4,s4,f47 ,acid brown ,y4 7,s4,c4 ,ind47 ,acid brown ,b4 7,s4,c4 ,ind47 ,golden brown4 7,leitch47 ,bronze acid brown4 7,by47 ,light nut brown4 7,uer47 ,resorcin brown4 7,w4 ,bros47 ,acid brown #ebaj4 7,w4 ,bros47 ,new acid brown4 7,b4,s4 ,spl47 ,light nut brown4 7,r47 ,brown #b,y4 7,r47 ,azo-phosphine4 7,uer47 ,golden brown ,y4 7,w4 ,bros47 ,yellowish ,browns and ,yellows4 ,citronine4 7,leon47 ,azo-flavine ,,rs4 7,b4,a4,s4,f47 ,cuba yellow #bjgb4 7,s4,c4 ,ind47 ,phosphine substitute4 7,b4,s4 ,spl47 ,azo-yellow conc4 7,m4,l4,b47 ,azo-flavine4 7,r47 ,golden orange ,r4 7,leitch47 ,circumein ext4 7,ber47 ,indian yellow ,g4 7,by47 ,turmeric substitute 7,w4 ,bros474 ,azo-yellow ,r4 7,m4,l4,b474 ,chrysophenin ,g4 7,leon47 ,indian yellow ,t4 7,c47 ,quinoline yellow4 7,ber47 ,cuba yellow4 7,c47 and 7,w4 ,bros47 ,indian yellow4 ,g4 7,c47 ,chrysoine ext4 7,w4 ,bros47 ,azo-flavine4 7,b4,s4 ,spl47 ,turmeric yellow ,b4 7,leitch47 ,azo-yellow ,,fy4 7,r4,h4 ,s47 ,orange #d4 7,r4,h4 ,s47 ,naphtol yellow ,s4 7,b4,a4,s4,f47 ,turmeric yellow ,y4 7,leitch47 ,azo-flavine #gjcb4 7,s4,c4 ,ind47 ,turmeric yellow4 7,g47 ,solid yellow ,y4 7,leon47 ,solid yellow ,b4 7,leon47 ,milling brown ,g4 7,leon47 ,napthamine yellow #c ,g4 7,k47 ,orange ,,gg4 7,c47 ,resorcin yellow4 7,ber47 ,greens4 ,acid green conc4 7,m4,l4,b47 ,acid green ooo4 7,leon47 ,guinea greens ,g and ,b4 7,ber47 ,acid green ext4 conc4 7,c47 ,fast acid green ,,bn4 7,c474 ,erioglaucine4 7,g47 ,acid green #efgg4 7,w4 ,bros47 ,acid green 7,uer47 ,light green ,,sf4 7,b4,a4,s4,f47 ,acid green ext4 ,,gg4 7,by47 ,violets and ,blues4 ,bavarian blue ,,db4 7,ber47 ,blue ,r4 7,lev47 ,water blue ,,tr4 7,b4,a4,s4,f47 ,fast blue ,o4 7,m4,l4,b47 ,water blue #d;,b4 7,leon47 ,cyanole extra4 7,c47 ,acid blue4 7,c4,a47 ,acid violets #c;,,bn and #f;,,bn4 7,lev47 ,oranges4 ,orange #b1 7,s4,c4 ,ind472 ,c1 7,m4,l4,b472 ,b1 7,by47 and 7,b4,a4,s4,f474 ,orange ,a4 7,leon47 ,orange ,g4 7,r4,h4 ,s47 ,ponceaus4 7,ber47 and 7,by47 ,crocein oranges4 7,k47 and 7,by47 ,mandarine ,g ext4 7,ber47 ,atlas oranges4 7,b4,s4 ,spl47 ,scarlets and ,reds4 ,most acid scarlets and reds dye chrome leather well on the mordant1 particulars of which are given above4 ,blacks4 ,these are dyed direct without any mordanting4 ,leather black ,v4 7,by47 ,leather black #a4 7,s4,c4,ind47 ,naphthylamine blacks #d;,b and #f;,b4 7,c47 ,french black4 7,uer47 ,chrome leather black4 7,c4 ,r47 ,coomassie black #d;,,bs4 7,lev47 ,phenylamine black #d;,b4 7,by47 ,titanium salts 7potassium titanium oxalate and tanno-titanium oxalate7 may be employed in conjunction with the coal-tar colours for dyeing chrome leather1 with many advantages over the ordinary mordants1 the colour produced being faster to light1 rubbing1 fuller in shade1 and with much less tendency to 8grinning40 ,when employing titanium mordants1 the leather should be first lightly mordanted with some tannin solution and afterwards dyed with the titanium and dye-stuff in the same bath1 in which case only 8acid0 dyestuffs may be employed4 ,if desired the goods may be mordanted with the tannin mordant1 afterwards treated with the titanium salts1 washed and dyed2 in this case the dyeing and application of the titanium mordant being carried out separately1 the leather may be dyed with either the acid or basic dye stuffs4 ,the titanium and tannin mordants may also be applied in the same bath4 ,,dyeing ,,chamois ,,leather4 ,the following colours dye chamois leather well1 after washing the leather in a weak soda solution1 mordanting with #c per cent4 basic chrome alum solution1 and transferring to the dye-bath without washing4 ,equal weight of bisulphate of soda to that of the dyestuff is added to the dye-bath4 ,,basic ,,coal-,,tar ,,colours4 ,bismark brown extra4 7,ber47 ,philadelphia yellow ,r4 7,ber47 ,pure phosphine4 7,c47 ,leather blue ,v4 7,g47 ,leather brown ,y4 7,s4,c4 ,ind47 ,leather brown ,a4 7,s4,c4 ,ind47 ,philadelphia brown4 7,ber47 ,,acid ,,coal-,,tar ,,colours4 ,circumine extra4 7,ber47 ,resorcin brown4 7,ber47 ,induline ,,nn4 7,b4,a4,s4,f47 ,orange #b4 7,m4,l4,b47 ,golden brown4 7,leitch47 ,fast brown4 7,by47 ,azo-yellow ,r4 7,m4,l4,b47 ,napthylamine black #d;,b4 7,c47 ,chocolate4 7,uer47 ,azo-flavine ,,rs4 7,c47 ,azo-phosphine4 7,uer47 ,acid anthracene brown ,r4 7,by47 ,acid green conc4 7,m4,l4,b47 ,acid brown ,y4 7,s4,c4 ,ind47 ,acid brown ,b4 7,s4,c4 ,ind47 ,napthylamine black #d;,b4 7,o47 ,jet black cryst4 7,c47 ,anthracene brown ,r4 7,by47 ,anthracene brown ,,gg4 7,by47 ,anthracene brown ,w4 7,by47 ,dark nut brown4 7,uer47 ,orange #b4 7,m4,l4,b47 ,,natural ,,dyestuffs4 ,peachwood extract4 ,sapan ext4 ,logwood ext4 ,fustic ext4 ,turmeric ext4 ,a variety of shades may be obtained on chamois leather by mordanting in a #a per cent4 solution of the titanium salts above mentioned and then transferring without washing to the dye-liquor1 which is best used in the drum4 ,the colours which are most suitable are the ,alizarin colours1 ,janus colours and the natural dyestuffs4 ,alizarin ,colours4 ,alizarin black produces light slate4 ,alizarin orange bright orange4 ,alizarin blue blue4 ,azo-alizarin black brownish maroon4 ,azo-alizarin brown reddish violet4 ,alizarin red bright scarlet red4 ,azo-alizarin blue slate blue4 ,coerulein yellowish green4 ,azo-alizarin yellow bright yellow4 ,anthracene brown fawn brown4 ,acid anthracene brown ,g brownish orange4 ,acid anthracene brown ,r dull chocolate brown4 ,anthracene blue pale blue4 ,mordant yellow lemon yellow4 ,janus ,colours4 ,janus yellow ,g4 produces bright orange4 ,janus yellow ,r4 reddish orange4 ,janus red dark maroon4 ,janus claret red bluish maroon4 ,janus brown ,r4 dark reddish chocolate4 ,janus blue ,b4 bluish black4 ,natural ,dyestuffs4 ,barwood produces salmon pink4 ,logwood dull reddish brown4 ,fustic bright yellow4 ,turmeric yellow4 ,brazil wood reddish brown4 ,sapan wood light nut brown4 ,sumach buff yellow4 ,persian berries light orange yellow4 ,madder red4 ,quercitron bark light orange yellow4 ,cutch fawn brown4 ,campeche canary yellow4 ,peach wood pale reddish tint4 ,divi-,divi buff yellow4 ,the leather is run in the dyestuff solution at a temperature of about #de to #ej ,c4 for about half an hour1 and then lightly fat-liquored1 if desired1 and afterwards dried4 ,in addition to the dyestuffs mentioned above many basic colours may be employed after the treatment with titanium1 some of these producing a colour lake with the titanium mordants4 ,as regards the permanency of the various colours to light1 the reader is referred to an important paper by ,mr4 ,lamb1#aii but in many cases the probable permanency is indicated by a number prefixed to the name of the colour in ,roman figures1 ,i4 corresponding to the lowest1 and ,x4 to the highest permanency4 ,in the research referred to1 about #aejj samples of leathers dyed with coal-tar dyes were exposed to light for a series of 8periods10 each equal in actinic power to nine days of the brightest summer sunshine4 ,the most fugitive colours faded completely1 even in the first 8period10 and the most permanent before the end of the tenth4 ,the prefixed numerals indicate to which of these 8periods0 the colour survived4 #aii ,journal of ,society of ,chemical ,industry1 #aijb1 p4 #aef4 ,,index4 ,abies1 #bdf ,acacia1 #bhh -- arabica1 #afe ,acetic acid1 #aed1 #bba1 #daj ,acid1 acetic1 #aed1 #bba1 #daj -- amido-acetic1 #fa -- -- -caproic1 #fa -- -- -propionic1 #fa -- -- -succinic1 #fa -- arsenious1 #bf -- aspartic1 #fa -- benzoic1 #bi -- boric1 #aee1 #afb1 #bba1 #bbi -- butyric1 #fa -- carbolic1 #bf1 #bie -- carbonic1 #ii1 #aje1 #afa -- chromic1 #bjj -- cresotinic1 #bi1 #afb -- digallic1 #bie -- ellagic1 #bca1 #bif -- ellagitannic1 #bca1 #big -- formic1 #aed1 #aei1 #daj -- gallotannic1 #bie -- hydrochloric1 #aed1 #aeg -- lactic1 #aed1 #aeh1 #bba -- linolenic1 #cee -- oleic1 #bdj1 #ced1 #cfj -- oxalic1 #aee1 #bba -- oxynaphthoic1 #cj1 #afc -- perchromic1 #bjj -- protocatechuic1 #bie -- pyroligneous1 #aed -- salicylic1 #bh1 #bie -- stearic1 #cea -- sulphuric1 #aad1 #aed1 #aeg1 #daj -- sulphurous1 #bc1 #aad1 #cch -- xanthoproteic1 #fg ,acids1 action on hide1 #hd -- amido-1 #fa1 #ff -- in tanning liquors1 #bj -- mineral1 #bc -- use in softening1 #aad ,acrilene bating acid1 #afc ,adipose tissue1 #ec thalium septicum1 #aj ,african oak1 #beg ,ageing1 #ahh ,ailantus1 #bgb ,air1 capacity for moisture1 #dbf -- cost of heating1 #dbh -- -filters1 #dci -- -passages1 #dcg -- weight of1 #dbh ,alanine1 #fa ,albumin of hide1 #fe ,albumins1 #ef1 #ff ,alcohol1 action on hide1 #hc ,alcoholic fermentation1 #ac1 #af ,alder1 #bej ,allen1 #cff ,aleppo pine1 #bdh ,algarobilla1 #bhf1 #bic ,alizarine colours1 #djc ,alkalies1 action on gelatine1 #hi -- -- on hide1 #hd ,alkaline carbonates1 #ach ,alnus1 #bej ,alsop1 #cac ,alum1 #aei1 #cci1 #ahe ,alumed leathers1 #b1 #d1 #i -- -- dyeing1 #djb ,alumina1 #ahe -- in water1 #ajc -- soap1 #ceb ,aluminium1 #ahe ,amido-acetic acid1 #fa -- -acids1 #fa1 #ff -- -caproic acid1 #fa -- -propionic acid1 #fa -- -succinic acid1 #fa ,amines1 #agc ,amba1 #aj ,ammonium chloride1 #aeg1 #aei -- sulphate1 #aei1 #ahd ,analysis of tanning materials1 #cjj1 #dge1 #dhb ,anacardiace1 #bfi ,andreasch1 #bgb ,angicabark1 #bic ,anhydrides of tannins1 #big ,aniline dyes1 #cid ,anion1 #hj ,anogeissus1 #bic ,anticalcium1 #bi1 #aeg ,antiseptics1 #ba ,a4,o4,a4,c4 method1 #cjj1 #cab1 #dhb ,apocynace1 #bgi ,apples of ,sodom1 #bfa ,arata1 #bfi ,arbutus1 #bgi ,archbutt and ,deeley1 #ie ,arctostaphylos1 #bgi ,arsenic1 #bf -- cures1 #ci1 #db -- -limes1 #aid -- sulphide1 #aci1 #adb ,arsenious acid1 #bf ,aspartic acid1 #fa ,aspidospermum1 #bgi ,association of ,official ,agric4 ,chem41 #cjj1 #cab1 #dhb ,atmospheric pressure1 #dbb ,attractions of molecules1 #gd ,avidity of acids1 #ha ,azo-colours1 #cii ,bablah1 #bhi ,babool1 #afe1 #bbh1 #bhh ,babul--see ,babool ,bacillus erodiens1 #age ,bacteria1 #ad1 #ae -- aerobic and anaerobic1 #dga ,bacterial filters1 #dfi1 #dgb -- products1 #ah1 #ai ,bacterium furfuris1 #aff ,badamier bark1 #bhb ,bag-tannage1 #bce ,bakau bark1 #bhc ,balance1 analytical1 #caj ,balaustines1 #bhe ,bali-babilan1 #bhh ,balsamocarpon1 #bhf ,band-knife splitting machine1 #chd1 #chg ,banksia1 #bfh ,barbed wire scratches1 #dc ,barium chloride1 #cia -- sulphydrate1 #adb ,bark1 #bdc1 #bdd ,bark mills1 #caf1 #deb ,barytes1 #cij ,basic chrome liquors1 #baa1 #bda -- salts1 #ahg1 #aii ,bast1 #bdc ,bastin1 #bdd ,bate-shavings1 #dfc -- -stains1 #agf ,bating1 #h1 #ai1 #aeb1 #agj1 #bcc -- effect of water on1 #ajg ,baudouin's test1 #cfe ,bearberry1 #bgi ,becker1 #agb1 #agd ,bedda nuts1 #bhb ,beeswax1 #cga ,beetle attacking hides1 #db 8,bell0-mills1 #cag ,belting1 #dej ,benzene1 #bie ,benzoic acid1 #bi ,bernardin1 #bdb ,betel nut1 #bdh ,betula1 #bej ,betulace1 #bej ,bichromate of potash1 #bja ,biernacki1 #ba ,bilberry1 #bhj ,birch1 #bej -- -tar oil1 #cb ,bistort1 #bff ,bisulphites1 #be1 #cch ,biuret reaction1 #fg ,black-dyeing1 #cih1 #cii1 #dac ,bleunard1 #eg ,blood-albumen1 #ccg ,bloom1 #bca1 #big ,bluebacking1 #bag ,boarding1 #bcc ,boiler incrustations1 #ii1 #aja ,boiling point1 #ge1 #dba ,bone-oil1 #fb ,book-binding leathers1 #bcd ,boral1 #aee ,borax1 #aef1 #baf ,borgman1 #aha ,boric or boracic acid1 #aef ,bottle-tannage1 #bce ,bourgois1 #eg ,brabium1 #bfh ,bran-drench1 #aff1 #aie ,brands1 #dc ,brazil-wood1 #bhg1 #dac ,breaking stress of leathers1 #dea ,breed1 effect on skin1 #de ,brick pits1 #dee ,brining hides1 #ch ,briquettes of tan1 #dfd ,bronzing1 #cie1 #djd ,brunton1 #fa ,brusca1 #bgb1 #bhj ,brushing machine1 #bbf ,buff-leather1 #cgh 8,buffalo0 method1 #abi ,burns and ,hull1 #afc ,butea1 #bhe ,butyric acid1 #fa ,byrsonima1 #bfi ,c4 ,t4 bate1 #afc ,calcium sulphydrate1 #adj ,calculation of tannin analysis1 #cad ,calf-kid1 #ahi ,calorie1 #dbb ,cambium1 #bdc ,camphor1 #ca ,canaigre1 #bfd -- root1 extraction1 #cdh ,carbolic acid1 #bf1 #bie ,carbolineum1 #bh ,carbon disulphide1 #cj ,carbonic acid1 #ii1 #aje1 #afa ,carboxyl1 #bie ,carr's disintegrator1 #cai ,carter's disintegrator1 #cai ,cascalote1 #bhf ,casein1 #fh ,cassia1 #bce1 #bhg1 #bii ,castanea1 #bea ,casuarina1 #bdi ,catechins1 #bih ,catechol1 #bie -- tannages1 #bcd1 #bie ,catechu1 #bgg1 #bhi ,caustic alkalies1 #bb -- soda1 #aad1 #acf ,cavallin1 #bjb ,cavallo1 #bhe ,cebil1 #bic ,cells1 #aj ,cellulose1 #ab ,centigrade thermometer1 #dha ,centrifugal pumps1 #deh ,ceriops1 #bhc ,chain-conveyors1 #cbe1 #dec ,chamois leather1 #i1 #cgh -- -- dyeing1 #dif ,chamoising1 #cfi1 #cgh ,chemical deliming1 #aec ,chenailier evaporator1 #dbd ,chestnut1 #bea -- -oak1 #bed1 #bfc -- -wood extract1 #bbb1 #bca ,chlorides in water1 #ajd ,chondrin1 #fc ,chromalin1 #bab ,chrome-alum1 #bja -- -blacks1 #djb -- combination tannages1 #bae -- -iron ore1 #bjj -- leather1 #d1 #i -- -- dyes for1 #did -- tannages1 #bjj ,chromic acid1 #bjj ,chromium1 #ahe1 #bjj ,churco bark1 #bhj ,clark1 #ie ,cleistanthus1 #bic ,coal-tar or ,c4 ,t4 bate1 #bi1 #afc -- -- dyes1 #cid ,coccoloba1 #bfg ,cocos1 #bdi ,cockle1 #de ,csalpinia1 #bhe ,coffee-mill1 #cag ,cohn's solution1 #agg ,colloids1 #gg1 #cif ,colour1 theory of1 #daf -- -measurement1 #dgi ,colouring matters1 #bii ,colours1 primary1 #daf -- secondary1 #daf -- tertiary1 #daf ,combination-tannages1 #d1 #bcf ,combretace1 #bhj1 #bic ,concentration of extracts1 #cci ,concrete pits1 #dee ,cone-mill1 #cag ,conifer1 #bdf ,connective tissue1 #ej ,conocarpus1 #bhc ,contact-beds1 #dgb ,conveyors1 #cbe1 #cbg1 #dec ,copper in water1 #ajd -- sulphate1 #bf ,coriariace1 #bgg ,coriaria1 #bgb1 #bgg ,corium1 #df ,coriin1 #fd ,cork1 #bdd ,cork-cambium1 #bdc ,cork oak1 #beg ,corrosive sublimate1 #be ,cortegia rossa1 #bdh ,couperus1 #bgg ,creasote1 #bh ,creolin1 #bh ,cresotinic acid1 #bi1 #afb ,crown leather1 #cha ,crystallisation1 #gg ,crystalloids1 #gg ,cupulifer1 #bea ,curtidor bark1 #bhj ,curupy bark1 #bic ,cutch1 #bhi ,cuticle1 #df ,cutis1 #df ,cylinder-oils1 #ajj ,danish glove-leather1 #bcf1 #bch ,daphne1 #bfg ,daphnoid1 #bfg ,decoloration of extracts1 #ccg ,degrees of hardness1 #id1 #aje ,dgras1 #cfh1 #chj 8,dgras-former10 #cgj1 #che ,deliming by acids1 #aed -- by washing1 #aed1 #afj ,de ,lof1 #bdb ,denaturised salt1 #bc ,dennis1 #afc1 #baa ,depickling1 #ia ,depilation1 #g1 #ed1 #aai ,depletion by puers and bates1 #ia ,derma1 #df ,dermestes vulpinus1 #db 8,devil disintegrator10 #cah ,dextrose1 #af ,diazo-compounds1 #cii ,digallic acid1 #bie ,diffusion1 #gh ,dippel's oil1 #fb ,disc-mill1 #cag ,disinfectants1 #ba1 #dgd ,disintegrators1 #cah ,dissociation1 #he ,distilled grease1 #cei ,divi-divi1 #bhe ,djaft1 #bfc ,docks1 #bfd ,dog-dung1 #agd1 #agi1 #aha 8,dogskin10 #aig ,dongola1 #aig -- imitations1 #bda -- leather1 #bcf1 #bci ,doornbosch1 #bic ,drench fermentation1 #ai ,drenching1 #h1 #bj1 #aeb1 #aff1 #aie1 #bcc ,drepanocarpus1 #bhe ,dressing-leather tannage1 #bcb -- leathers1 #h ,driers for oils1 #cfc ,drum-stuffing1 #chh ,drumming1 #bcd ,drums1 #aag ,dry hides1 #aaj ,drying1 effect on skin1 #aab -- hides1 #da -- leather1 #dbd -- oven1 #cjh -- rooms1 #dca -- of sole leather1 #bcb ,dry-salted hides1 #aaj -- -salting1 #ch ,dschigh dschighe1 #bhf ,dubbing1 #chf ,dust-prevention1 #cbe ,dye-testing1 #dai ,dyeing alumed leathers1 #djb -- chrome leather1 #djc1 #dic -- ,continental method1 #djh -- defects in1 #djd -- in drum1 #djh -- in paddle1 #djg -- in tray1 #djf1 #djh -- kid1 #aif -- oil-leathers1 #djd -- selection of goods1 #dji -- theories of1 #cif ,dyes1 acid1 #cie1 #dab -- basic1 #cie1 #daa -- lists of1 for leather1 #dhf1 et seq4 -- list of manufacturers1 #dhe -- mixtures for leather1 #dia -- -woods1 #dab ,earp1 ,w4 ,r41 #adc ,east ,india skins1 #bce1 #bch1 #bda ,eberle1 #bab ,edge-stones1 #caf ,effluents1 #dfg ,egg-albumin1 #fg -- -yolk1 #fh1 #cic ,eglinton ,tanning 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centrifugal1 #dcg1 #dci -- drying by1 #dcc -- screw1 #dcj1 #dcd1 #dcg ,fat1 #dfa1 #dfb -- -cells1 #eb -- -glands1 #dh -- -liquoring1 #bag1 #bcg1 #bci1 #cic -- -liquors1 #ajj -- -tanned leathers1 #a1 #d ,fats and oils1 #cej -- solvents of1 #cec ,fatty acids1 liquid1 #ced -- -- saturated1 #ced -- -- unsaturated1 #cee ,fellmongering1 #cd ,fermentation1 #ac1 #ae ,ferric chloride1 #hf -- salts1 #aih ,ferrocyanides1 #cci ,ferrous salts1 #aih ,fibre-bundles1 #ej ,fibres1 elastic1 #ec ,fibrils1 #ej ,filao bark1 #bdi ,filter method1 #caa1 #dgh ,filtration for analysis1 #cjg1 #dgg1 #dhc -- of sludge1 #dgj 8,fine-hairing10 #ahj ,finishes for leather1 #dja ,fire insurance1 #cbe ,fish-tallow1 #cfh ,flaying1 #db ,fleshing1 #h1 #adf -- machines1 #adg ,fleshings1 #dfa ,flckiger and ,hanbury1 #bgg ,fluorides1 #bf 8,foots10 #cef ,formaldehyde1 #cj1 #chj ,formalin1 #ca1 #chj ,formic acid1 #aed1 #aei1 #daj ,frizing1 #cgh ,fuchsia1 #bhd ,fuchsine1 #cie ,fungi1 #ae ,fusanus1 #bfg ,gall oak1 #bfa ,gallotannic acid1 #bie ,galls1 #bfa1 #bhj ,gambier1 #bbb1 #bca1 #bgg -- extraction1 #cdi ,garcinia1 #bic ,gas-engine1 #ddi -- -lime1 #ada ,gaseous state of matter1 #gd ,gaultheria1 #bea1 #cgc ,gelatin1 #ef1 #eh -- action of bacteria on1 #fa -- analyses1 #eg -- chemical constitution1 #eg -- decompositions1 #fj -- determination1 #ei1 #fj -- properties of1 #eh -- reactions1 #fb -- swelling of1 #hb ,glaeser mill1 #cah ,glassy layer1 #ej1 #cih ,glazing1 #dah ,globulin1 #fg ,globig1 #ag ,glove-kid1 #aid ,glucose1 #ac1 #af1 #agg1 #cij ,glue1 #dfa ,gluestuff1 #dfa ,glutin1 #ef1 #eh ,glycerin1 #cea 8,golden spoon10 #bfi -- tan bark1 #bdh ,gonagra1 #bfd ,grain1 #bcc -- 8drawn10 #bbh -- -layer1 #ea -- microscopic examination1 #eb1 #ee -- pattern of1 #eb ,grains of various skins1 #eb ,granatace1 #bhe ,grease1 recovery1 #dfb -- refining1 #dfc ,greases1 #ceg 8,green leather10 #aig1 #bci ,grevillia1 #bfh ,griffith1 #bca ,grinding machinery1 #deb -- samples1 #cjc1 #dgf ,grounding1 #ahi ,guano1 #agg ,gum tree1 #bhd ,gumming1 #bj ,guttifer1 #bic ,gunnera1 #bhd ,gunnerace1 #bhd ,glycocine1 #fa ,glycocoll1 #fa ,hmatoxylon1 #bhf ,hair1 #fh1 #dfj -- -bulb1 #di -- -cuticle1 #dh1 #di -- -muscle1 #ej -- -papilla1 #di -- structure and growth1 #dg ,hand-stuffing1 #chf ,handlers1 #bba ,hardness determination1 #id -- effect on dyeing1 #ajj -- effects on tanning1 #ih1 #aje -- of water1 #ic ,harrison1 #bgc1 #dgc ,hauff1 #aeg1 #afb1 #afc ,heal1 #bjc ,heat1 capacity for1 #dbb -- consumed in evaporation1 #dbc1 #dbh -- -- in melting ice1 #dbc -- given by pipes1 #dcb -- loss through walls1 #dca -- measure of quantity1 #dbb -- of combustion of coal1 #dbc ,heating by hot water1 #ddb -- by steam1 #dcb1 #dcf1 #ddj ,heath honeysuckle1 #bfh ,heaths1 #bgi ,hehner1 #id ,heinzerling1 #bjc ,helvetia leather1 #cha ,hemicollin1 #fj ,hemlock-bark1 #bbb ,hen-dung1 #agi1 #aha ,henry1 #ie 8,hickory0 bark1 #bia ,hide-fibre1 analysis1 #eg -- -markets1 #cc -- -mill1 #aag -- powder1 #caj1 #cab1 #dgi1 #dhd -- -- filter1 #caa1 #dgh -- -- chromed1 #cac1 #dhc ,high-speed machinery1 #dea ,hofmeister1 #ef1 #eg1 #fj ,holbrook system1 #cca ,holden fat1 #cei ,horns1 #dfd ,horn-sloughs1 #dfd ,horny structures1 #ej ,horse-fat1 #ceg -- -flesh1 #agg -- -power1 #dbc ,hruschau1 #bad ,hull1 #afc1 #afe ,hummel1 #bjc1 #bej1 #bhe ,hunt1 #ahh ,hyaline layer1 #ej1 #agf1 #cih ,hydrochloric acid1 #hf1 #aed1 #aeg ,hydronaphthol1 #cj ,hypoderma bovis1 #dc ,hyposulphite of soda1 #bjd ,hyph1 #ad ,i4,a4,l4,t4,c4 method1 #cjj1 #caa1 #dge ,ice1 heat to melt1 #dbc ,ilex1 #bef ,immiscible liquid1 #gf ,inga1 #bic ,inks1 #djb 8,inoffensive10 #adc ,international ,association of ,leather ,trade ,chemists1 #cjj1 #caa1 #dge ,internal pressure of liquids1 #gf ,invertase1 #af ,iodine-value1 #cec ,ionisation-pressure1 #ha ,ions1 #hj ,iron-alum1 #aii -- -bark tree1 #bhd -- -blacks1 #cih1 #dac -- in water1 #ajb -- stains1 #bb1 #ch -- tannages1 #aih ,izal1 #bh ,jamrosa bark1 #bhb ,japans1 #cee ,jeye's fluid1 #bh ,jellies1 #gg ,jensen1 #bda ,jones fleshing machine1 #adh ,juniper1 #bdh ,kaspine leather1 #chj ,kath1 #bhi ,kathreiner1 #cja ,kation1 #hj ,kent1 #bcf ,keratin1 #ad1 #ef1 #fh ,kermes oak1 #beh ,kid-leather1 #i ,kilogram1 #dha ,kips1 soaking1 #aac ,kjeldahl's method1 #gj1 #agi ,klemm1 #cha ,knapp1 #gd1 #ahh1 #aii1 #bjb1 #baj1 #chb ,knoppern1 #bfb ,knotted tree1 #bfh ,koch1 #bea ,koerner1 #hb1 #ia1 #bhc ,krameria1 #bfi ,lace-,leathers1 #aig ,lactic acid1 #aed1 #aeh1 #bba1 #daj -- fermentation1 #ah ,lamb1 #bah1 #bgc1 #dje1 #dhe ,land filtration1 #dgj ,lanoline1 #cei ,lanosoap1 #bah ,larch1 #bdg ,larix1 #bdg ,laurace1 #bfg ,layers1 #bbb1 #bca ,leach-bottom1 #cbi ,leaching1 #cbh ,lead-bleach1 #cii -- in water1 #ajd ,leather ,industries ,laboratory ,book1 #e ,leguminos1 #bhh ,leidgen unhairing machine1 #ade ,lentisque1 #bfi ,leucadendron1 #bfh ,leucine1 #fa ,leucospermum1 #bfh ,levulose1 #af ,lewkowitsch1 #cff ,lietzmann1 #chb ,l4,i4,l4,b41 #e ,liliace1 #bdh ,lime1 #ba1 #abj -- action on hide1 #abe -- analyses1 #abd -- 8available10 #abe -- -burning1 #aba -- -liquors1 analysis1 #adc -- pits1 #abg1 #dee -- quantity used1 #abi -- solubility in water1 #abc -- -water1 #abc ,limes1 age of1 #acj -- bacterial action in1 #acd -- plumping1 #acc ,liming1 #abf -- loss of hide-substance1 #acb -- ,pullman's method1 #acg -- sheep-skins1 #cd -- temperature1 #abi ,linolenic acid1 #cee ,lipowitz1 #ei ,liquor-pipes1 #def ,liquid state of matter1 #gd ,liquor tanks1 #ccb1 #deg -- -troughs1 #ccc1 #deg ,liter1 #dha ,logwood1 #bhf1 #dac1 #cih1 #dja ,loxopteryngium1 #bfi ,lubrication1 #dec ,lufkin1 ,prof41 #adb ,lymph corpuscules1 #aj ,lysol1 #bh ,mc,fadyen1 #fa ,madder1 #bci1 #bgg ,maiden1 #bij ,magenta1 #cie ,magnesia1 #ie ,malpighia1 #bfi ,malpighiace1 #bfi ,manganese1 #ahe ,mangifera1 #bgg ,mangle1 #bhc ,mango1 #bgg ,mangosteen1 #bic ,mangrove1 #bhc -- bark1 extraction1 #cdh ,mangrutta1 #bfi ,market-hides1 #cc1 #ajh 8,marking off10 #djf -- weight of hides1 #cc ,marsh ,rosemary1 #bfh ,mather and ,platt1 #ig ,mauve1 #cid ,maynard1 #aad 8,mellowing0 of liquors1 #hb ,mellowness of liquors1 #bbi ,mercuric chloride1 #be -- iodide1 #bf ,metabisulphite of soda1 #be1 #aad1 #afj ,meter1 #dha ,metrical system1 #dha ,milk-shaker1 #cac ,millon's reagent1 #fg ,mill for samples1 #cjc ,mills1 arrangement of1 #deb -- construction1 #caf ,mimosa1 #bca1 #bij -- extraction1 #cdf ,mimose1 #bhh ,mineral acids1 #bc ,moellon1 #cfh1 #chj ,moisture in tanning materials1 #cad1 #cae1 #dgi1 #dhb ,molecules1 #gd ,mordant colouring matters1 #bch ,mordants1 #cih ,moulds1 #ad1 #ae1 #bj ,mountain ash1 #bhe ,mucous layer1 #dg ,mud1 #ajb ,muir1 ,john1 #ada ,multiple effect1 #cdb1 #dbc ,munkwitz1 #ade ,muscle1 voluntary1 #ec ,mycoderma1 #ad1 #bj ,myrica1 #bej ,myricace1 #bej ,myrobalans1 #bca1 #bhj1 #bic -- crusher1 #cbb -- extraction1 #cde ,myrtace1 #bhd ,myrtus1 #bhd ,nancite1 #bfi ,naphthalene sulphonic acid1 #bi ,naphthols1 #bi ,nauclea1 #bgg ,neb-neb1 #bhi ,nesbitt's bating process1 #afa 8,neutralising0 chrome leathers1 #baf ,nihoul1 #ajd ,nitrates and nitrites in water1 #ajd ,nitrogen estimation1 #gj 8,non-tannins10 #caj1 #dgh1 #dhc ,nucleolus1 #aa ,nucleus1 #aa ,oak-,bark1 #bbb1 #bec -- - -- extraction1 #cdd -- -twigs1 #bdd ,oakwood1 #bed -- extract1 #bbb1 #bca1 #bef ,oaks1 #beb nothera1 #bhd ,oil1 ,arctic sperm1 #cga -- birch1 #cgb -- black birch1 #cgc -- boiled linseed1 #cfc -- bottlenose1 #cga -- castor1 #cec1 #cee1 #cfj -- cod-liver1 #cfe -- cottonseed1 #cfd -- egg-yolk1 #cic -- from fats1 #dfc -- herring1 #cfh -- ,japanese1 #cfh -- linseed1 #cfb -- menhaden1 #cfg -- neatsfoot1 #ceh -- olive1 #cei -- porgie1 #cfg -- ,russia1 #cgb -- sandalwood1 #cgc -- sardine1 #cfh -- sassafras1 #cgc -- seal1 #cfg -- sesam1 #cfd -- shark-liver1 #cff -- sod1 #cfh1 #chj -- sperm1 #cec1 #cga -- ,straits1 #cfg -- ,three-crown1 #cfg -- ,turkey-red1 #cfa -- vaseline1 #cge -- whale1 #cfg -- wintergreen1 #cgc ,oils and fats in currying1 #chd -- blown1 #cee1 #cfa -- drying1 #cec -- essential1 #cej1 #cgb -- fixed1 #cej -- lubricating1 #dec -- mineral1 #cgd -- non-drying1 #cec -- resin1 #cgf -- volatile1 #cgb ,oleic acid1 #bdj1 #ced1 #cfj ,oleine1 #cei ,oleostearine1 #cef1 #cei ,onagrace1 #bhd ,one-bath chrome process1 #baa ,organised ferments1 #ae ,origin of leather manufacture1 #a ,osmotic pressure1 #gh ,osyris1 #bfg ,ovum1 development of1 #df ,oxalates1 #aei ,oxalic acid1 #aee1 #bba ,oxalide1 #bhj ,oxalis1 #bhj ,oxynaphthoic acid1 #cj1 #afc ,ozokerit1 #cgf ,paal1 #eg1 #fb1 #ff ,paessler1 #ef ,pairing1 #djg ,palmer1 ,a4 ,n41 #afg ,palmer1 ,t41 #agf ,palmetto1 #bde ,palm1 #bdh ,pancreatin1 #agb ,panniculus adiposus1 #ec ,papilionace1 #bhe ,paraffin1 #cge ,paraform1 #ca ,parapeptones1 #ff ,parenchym1 #bdc ,parker1 ,j4 ,g41 #afb ,parker1 ,c4 ,e41 #dee ,pars papillaris1 #ea 8,partial0 pressure1 #gf ,paypay1 #bic ,payne and ,pullman1 #acg ,peaty waters1 #ajf ,penicillium1 #ad ,pepsin1 #aga ,peptones1 #fj1 #fa1 #fb ,perching1 #ahh ,perchromic acid1 #bjj ,perkin1 #bej1 #cid -- and ,allen1 #bgf -- and ,gunnell1 #bfi ,permanent hardness1 #ajj ,persea1 #bfg 8,persians10 #bce1 #bhg1 #bii1 #cfe ,phenol1 #bf -- for deliming1 #afb ,phenols1 #bie ,phenolphthalein1 #aee ,phloem1 #bdc ,phlobaphenes1 #bca ,phloroglucol1 #bie1 #big ,phosphates1 #aei ,phyllanthus1 #bic ,phyllocladus1 #bdh ,pickling1 #bc1 #hi1 #ahg ,pigeon-dung1 #agh ,pilang1 #bij ,pinus1 #bdf ,pipes1 arrangement of1 #dcf1 #ddj -- heat from1 #dcb ,piptadenia1 #bic ,pistacia1 #bfi1 #bgb ,pits1 construction of1 #ded ,plaster-cure of ,indian kips1 #ci ,pleating1 #djg ,plumbagin1 #bfh ,podocarpus1 #bdh ,poison ivy1 #bgd ,polygalace1 #bfi ,polygenetic colours1 #cii1 #djc ,polygonace1 #bfd ,polygonum1 #bff ,polysulphides1 #afe1 #baa 8,polysulphin10 #aci ,pomegranate1 #bhe ,poplars1 #bfd ,popp1 #agb1 #agd ,porcelain1 to mark1 #cjd ,porter-,clark1 #ih ,potassium dichromate1 #bja -- hydrate1 #acf ,potentilla1 #bhe ,precipitation tanks1 #dfh ,preller1 #cha ,press-leaches1 #ccj 8,pricking10 #afi ,primitive leather manufacture1 #a1 #gc ,printing1 #dah ,protace1 #bfh ,procter1 #bjc ,procter's extractor1 #cjf ,prosopis1 #bhf ,protea1 #bfh ,protocatechuic acid1 #bie ,protoplasm1 #aj ,pseudopodia1 #aa ,pterocarpus1 #bhe ,puering1 #h1 #ai1 #aeb1 #agj1 #bcc ,pulleys1 #dej 8pulling down10 #aeg ,pullman1 #chj ,pullman's liming method1 #acg ,pulsometers1 #dei ,pumps1 #deg ,punica1 #bhe ,putrefaction1 #ae1 #ai ,putrid soak1 #aac1 #acg ,putz1 ,dr41 #fi ,pyrogallol1 #bie -- tannages1 #bcd -- tannins1 #bie ,pyroligneous acid1 #aed ,pyrrol1 #fb ,pyrus1 #bhe ,quebracho1 #bca1 #bfi1 #bgg -- wood1 extraction1 #cdg ,quercetin1 #bfc ,quercus1 #beb ,quicklime1 #abb ,rabinowitsch1 #ag ,raw hide leather1 #cha ,realgar1 #adb ,reddening of leather by light1 #dje 8,reds10 #bca1 #big1 #cci ,reimer1 #eh1 #fd ,resin1 #cgf ,rete malpighi1 #dg ,rhatany1 #bfi ,rhizophorace1 #bhc ,rhus1 #bgj ,riems1 #cha ,roans1 #bce ,rollet1 #fd ,rolling machines1 #bbd ,roman leathers1 #b ,rosace1 #bhe ,rosin1 #cgf ,rounding1 #aea ,rove1 #bfa ,rubiace1 #bgg ,rumex1 #bfd ,rusma1 #aci 8,russia0 leather1 #bea ,sabal1 #bdh ,saccharomyces1 #ad1 #bj ,saccharomycetes1 #ae ,saddening1 #cih ,salicace1 #bfc ,salicylic acid1 #bh1 #bie ,saliva-corpuscles1 #aj ,salix arenaria1 #bch1 #bfc -- caprea1 #bci1 #bfd ,salomon1 #agh ,salt1 #bb -- and acids1 action on gelatine1 #hh -- -stains1 #bb1 #ch ,salts1 action on hide1 #hd1 #ib ,salted hides1 #aji ,salting1 #ce ,sampling tanning materials1 #cja1 #dge -- tool1 #cja ,santalace1 #bfg ,saponification1 #cea ,sappan-wood1 #bhg ,saturated solutions1 #gg ,saxifragace1 #bhj ,schilling1 #fb ,schinia1 #bgb ,schinus1 #bgj ,schmeija mill1 #cah ,schulze1 #agh ,schultz1 ,a41 #bjc1 #bjd -- ,jackson ,s41 #aab1 #ded1 #def ,schutzenberger1 #eg ,scilla1 #bdh ,scorza rossa1 #bdh ,scouring1 #chd -- machine1 #chd ,screening tanning materials1 #cbc ,scudding1 #ahj ,sea lavender1 #bfh ,seagrave-,bevington dryer1 #dch ,seaside grape1 #bfg ,seasonings1 #dah ,sebaceous glands1 #dh ,semiglutin1 #fj ,semipermeable membranes1 #gh ,senna1 #bhh ,septa1 #ad ,septic tank1 #dgb ,settling tanks1 #dfh ,sewage1 #dfg -- purification1 #dfh ,shafting1 #ddh1 #dej ,shake-method1 #cab1 #dhc ,shaving1 #chd -- machine1 #chd1 #chf -- mill1 #cbc ,sheep-skins1 #cd ,shellac glaze1 #dja ,silent boiling jets1 #ccd1 #cdc ,silicic acid in water1 #ajd ,silver fir1 #bdf ,skens1 #bgb ,skin1 structure1 #df ,skivers1 alumed1 #aig ,skutch1 #dfb ,slaking of lime1 #abb ,slocomb staking machine1 #aib ,sludge1 #dgj ,smoked leathers1 #b ,snakeweed1 #bff ,snoubar bark1 #bdh ,soaking and washing1 #g -- of hides1 #ajh -- with caustic soda1 #aad ,soaps1 #cea -- cold process1 #ceb ,soap test1 #id ,society of ,arts1 #bcd ,soda in water1 #ajc ,sodium bisulphate1 #aee -- carbonate1 #aci -- hydrate1 #acf -- silicate1 #baf -- sulphate1 #bc1 #da -- sulphide1 #aad1 #aci -- thiosulphate1 #bjd1 #bac1 #baf ,sole-leather tanning1 #bbj ,solid solution1 #hc1 #cif -- state of matter1 #gd ,solubility of liquids1 #gf ,solution-pressure1 #gf1 #gh ,soluble phenyl1 #bh ,sorbus1 #bhe ,souring1 #daj ,spent tan1 #cbi1 #dfd -- tans1 analysis1 #dhj ,spermaceti1 #cga ,splitting1 #chd ,sprinkler1 #ddf -- -leach1 #ccf ,spruce fir1 #bdf ,spueing1 #bj1 #cec1 #cee1 #cij ,squill1 #bdh ,staining1 #dae -- dyes suitable for1 #dhf1 #dia ,stains caused by hard water1 #ii -- on sole-leather1 #bbg ,staking1 #ahh -- machines1 #aib ,staling1 #cd ,stanhope1 #ih ,statice1 #bfh ,steam-engine1 #dbc1 #dcc1 #ddh -- - -- indicator1 #ddi -- -pumps1 #deg -- -traps1 #ddb ,stearic acid1 #cea ,stearin1 #cea1 #cei ,stearine glaze1 #dja1 #dae ,stenhouse1 #bif ,sterilisation1 #ah ,stinco1 #bgb ,stippen1 #aji ,stocking1 #ahj ,stocks1 #aaf -- for unhairing1 #ade ,stone-cells1 #bde -- pits1 #ded ,striking1 #bbc -- machine1 #bbc ,stringy bark tree1 #bhd ,structure of skin1 #df ,stuffing1 #chf -- drum1 #chh ,sturtevant dryer1 #dch ,sudoriferous glands1 #di ,sugar-bush1 #bfh ,sulphate of soda1 #bc ,sulphates in water1 #ajd ,sulphide of sodium1 #cd1 #acb1 #aci1 #afe ,sulphides1 #aci ,sulphur dioxide1 #bc -- in chrome-leather1 #baf ,sulphonated oils1 #cfa ,sulphuric acid1 #aad1 #aed1 #aeg1 #daj ,sulphurous acid1 #bc1 #aad1 #cch ,sumach1 #bcd -- ,cape1 #bfg -- extraction1 #cdg -- ,french1 #bgg -- ,sicilian1 #bgj -- ,venetian1 #bgf ,sumachs1 ,american1 #bgc ,sumaching1 #daj1 #daa ,supersaturated solutions1 #gg ,surface-tension1 #gf ,suspenders1 #bba1 #bbg1 #bcb ,suspension lime-pit1 #abh ,swan1 #bjb ,sweat-glands1 #di -- -pit1 #aai ,sweating1 #a1 #ai1 #cd1 #aai ,swedish glove-leather1 #bcf1 #bch ,swelling1 #hb1 #hd ,tallow1 #cef -- fish1 #cfh ,tamarix1 #bgb1 #bhj ,tamariscini1 #bhj ,tamwood1 #bfi ,tan as fuel1 #dfd -- -burning furnaces1 #dfd -- -press1 #dfg ,tanekahi bark1 #bdh ,tanghadi bark1 #bhg ,tank-waste1 #ada ,tannery1 construction1 #dde -- extension1 #ddg -- fire risks1 #ddf1 #deb -- selection of site1 #ddd ,tannin colour-lakes1 #cig -- materials1 extraction1 #cje -- -- sampling1 #cjb 8,tanning matters10 #caa1 #dgh1 #dhc ,tannins1 #bdb1 #bid1 #cig -- pathological1 #bih -- physiological1 #bih ,tari pods1 #bhf ,tartar emetic1 #daa ,tawing1 #aia1 #aif ,temperature1 #dbb -- in leaching1 #cdc ,temporary hardness1 #id1 #aed1 #daa ,tengah bark1 #bhc ,teri pods1 #bhf ,terminalia1 #bhj ,terra japonica1 #bgg ,thann tree1 #bhb ,thermophilic bacteria1 #ag ,tinian pine1 #bdi ,tintometer1 #cae1 #dgi ,titanium1 #ahe1 #bah1 #daa1 #die ,tjamara laut1 #bdi ,topping1 #djf ,tormentilla1 #bhe ,torula1 #ad 8,total soluble0 matter1 #cjg1 #dgg1 #dgh ,treacle1 #agg ,tri-formol1 #ca ,trimble1 #bfc ,trioxymethylene1 #ca ,trypsin1 #aga1 #agb ,tsuga1 #bdf ,tub-leaches1 #cca ,tugwar1 #bic ,turkey oak1 #bee1 #bef -- -red oil1 #bag1 #bdj ,turwar bark1 #bce1 #bhg ,turret-dryer1 #dci ,two-bath chrome process1 #bjd1 #bac1 #baf ,tyrosin1 #ff ,unhairing1 #g1 #ed1 #adc -- machines1 #add ,unorganised ferments1 #ae1 #af ,used liquors1 analysis1 #dhj ,vaccini1 #bhj ,vaccinium1 #bhj ,vacuoles1 #ac ,vacuum-oven1 #cjh -- pans1 #cdb ,valdivia leather1 #bfg ,valonia1 #bbb1 #bca1 #beh -- extraction1 #cde1 #cdf ,valve1 #deg -- for liquor troughs1 #ccc ,van ,tieghem1 #bdc ,vapour-pressure1 #ge1 #dba ,vaseline1 #cge ,vaughn fleshing machine1 #ade1 #adh ,vegetable-tanned leathers1 #b1 #c ,velocity of gaseous molecules1 #ge ,ventilation and heating1 #dbi -- downward1 #ddj ,verbeek and ,peckholdt1 #caj ,vibration1 #deb ,vitellin1 #fg ,vitis1 #bgb ,von ,hhnel1 #bdb -- ,schroeder1 #ef1 #abi1 #acd ,wagner1 #bih ,warbles1 #dc ,ward1 ,h4 ,marshall1 #bdc ,wash-wheel1 #ajh1 #aah1 #ahj -- -- for unhairing1 #ade ,washing of hides1 #ajh1 #aaa ,waste liquids1 #dfg ,water1 condensed1 #ddb -- hardness1 #ic -- impurities1 #ic -- oven1 #cjh -- raisers1 #dei -- softening1 #ie1 #aja ,wattles1 #bij ,wax1 bees-1 #cga -- ,brazilian1 #cgb -- carnauba1 #cgb -- ,japan1 #cgb -- mineral1 #cgd -- paraffin1 #cge ,waxes1 #cej1 #cec1 #cgj -- liquid1 #cej1 #cec1 #cga ,weak grain1 #ajh ,weighing for analysis1 #cjd ,weimannia1 #bhj ,weiske1 #fc 8,wet and dry bulb0 thermometer1 #dbf 8,white bark10 #bic -- leathers1 #aig -- or gelatinous fibres1 #ej -- spruce1 #bdg ,wichellow and ,tebbutt1 #bda ,wild almond1 #bfh ,williams' patent crusher1 #cbj ,willow-bark1 #bch ,willows1 #bfc ,wilson1 #bbc1 #bbd1 #ddj ,wind1 #dbg1 #dci ,windbores1 #dei ,wood1 ,j4 ,t41 #aff1 #aga ,woolfat1 #ceh ,woolly butt tree1 #bhd 8,working10 #ahj ,xanthoproteic acid1 #fg ,yaryan evaporator1 #cci1 #dbd ,yeast1 #ab ,yeasts1 #ae ,yellow fibres1 #ec1 #fi ,yolk of egg1 #fh ,yorkshire grease1 #cei ,youl1 #bca ,young hair1 #add ,zinc chloride1 #bf -- sulphate1 #bf1 #aei ,zollickoffer1 #afj ,zymases1 #ae1 #af1 #ag1 #fa1 #bif ,,london3 ,,printed ,,by ,,william ,,clowes ,,and ,,sons1 ,,limited1 ,,great ,,windmill ,,street1 ,w41 ,,and ,,duke ,,street1 ,,stamford ,,street1 ,s4,e4 ,transcriber's ,notes ,inconsistent and unusual spelling1 hyphenation1 etc4 7including in names and non-,english words7 have been retained1 except as mentioned below4 ,the original work does not have a ,fig4 #ag4 ,page #aii1 7,it must be distinctly understood 4443 the closing bracket is missing in the source document4 ,page #bbc3 444 tool of triangular section shown in ,fig4 #bi3 the reference should possibly be to ,fig4 #bg 7or #cj74 ,page #bfg1 kruppelboom3 should possibly read kreupelboom4 ,changes made3 ,footnotes1 illustrations1 and tables have been moved outside text paragraphs4 ,the following phrases have been standardised3 ,c4 ,t4 bate and ,c4,t4 bate to ,c4,t4 bate 7cole-tar72 c4c4 and cc4 to c4c4 7cubic centimetre72 ,lige and ,lige to ,lige4 ,pullman and ,pullmans to ,pullman2 ,huxham and ,brown and ,huxham and ,browns to ,huxham and ,browns2 ,kjehldahl and ,kjeldahl to ,kjeldahl2 ,krner and ,koerner to ,koerner4 ,where useful for clarity's sake1 ,ibid4 in literature references has been replaced with the actual 7abbreviated7 title4 ,some obvious minor typographical errors have been corrected silently2 accents in ,french and ,german words have not been corrected or added4 ,page #dj3 ,in the re-renewal 444 changed to ,in the renewal 444 ,page #fd3 ,chrondrin changed to ,chondrin ,page #gd3 ,die ,natur und ,wesen 444 changed to ,natur und ,wesen 444 ,page #aci3 ,na,s1#i,,oh changed to ,na,s#i,,oh ,page #bdh3 footnote anchor removed from after 444 by cork lamell 7there is no footnote in the original work74 ,page #beb3 444 and the more colouring matter is contained 444 changed to 444 the more colouring matter is contained 444 ,page #bec3 444 and the better the bark changed to 444 the better the bark ,page #bgb3 ,ailantus gladulosa changed to ,ailantus glandulosa ,page #caj3 ,verbeck changed to ,verbeek ,page #cbi3 444 is shown in ,fig4 #hf changed to 444 is shown in ,fig4 #gg ,page #cfa3 ,benedict changed to ,benedikt ,page #djj3 ,claus and ,ree changed to ,claus and ,re ,page #dbi3 #ddc ,f4 changed to #ddc ,f4 ,page #dea3 kilos per cm #adbb lb4 per inch changed to kilos per cm #adbb lb4 per inch ,page #dhf3 ,acid green ,b4,b4 changed to ,acid green ,,bb4 ,page #eja3 ,blue-backing changed to ,bluebacking ,page #ejg3 ,oxalic acid1 page number #aee corrected ,page #ejh3 ,pay-pay changed to ,paypay2 ,phylocladus changed to ,phyllocladus2 ,protac changed to ,protace ,page #eji3 ,schutzenberger changed to ,schtzenberger ,page #eab1 ,zymases3 page numbers #ag1 #fa1 #bif inserted ,index3 some entries moved to their proper place4