,,synthetic ,,tannins ,,their ,,synthesis1 ,,industrial ,,production ,,and ,,application by ,georg ,crasser1 ,dr4 ,phil41 ,ing4 ,lecturer in ,tanning ,chemistry at the ,german ,technical ,college1 ,brunn ,,author',s ,,preface ,whilst the synthesis of the natural tannins has been successfully outlined by ,emil ,fischer1 it has been left to the ,chemical ,industry1 notably the ,badische ,anilin und ,soda-fabrik in ,ludwigshafen-on-the-,rhine1 to discover the means of making possible the production of the synthetic tannins4 ,the scientific results of ,fischer's researches are to-day common knowledge1 and these1 together with questions arising therefrom1 will only be lightly touched upon in the book herewith presented4 ,even an attempt at enumerating the present synthetic tannins has so far not been published1 and ,i have therefore availed myself of the opportunity of making a brief summary of them4 ,my work at the ,b4,a4,s4,f4 deepened my insight in this new field2 ample opportunity of applying these synthetic products in practice was given me when1 as a result of the war1 ,i was appointed technical consultant to the ,austrian ,hide and ,leather ,commission1 and in this capacity was called upon to act as general adviser to the trade4 ,the ultimate object of my scientific researches was then to investigate the chemistry of this particular field1 and this has led me to present a picture1 complete as far as it goes1 of this branch of chemical technology4 ,the intention of the present volume is to communicate to the reader what has so far been scientifically evolved and practically applied in this field4 ,first of all1 however1 it may illustrate the extreme importance and the universal applicability of the synthetic tannins in the making of leather4 ,the modern leather industry cannot1 to-day1 be without these important products1 but also in those tanneries1 where the synthetic tannins have not so far been regarded as indispensable1 their use is strongly recommended4 ,just as in the case of the coal-tar dyes1 the synthetic tannins will make us independent of foreign supplies1 and thus keep within our own borders the vast sum of money required in former days for the purchase of foreign tanning materials4 ,may this book prove the means of providing an incentive for a still wider application of the synthetic tannins4 ,,grasser4 ,,graz1 ,august #aibj4 ,,translator',s ,,preface ,doctor ,grasser hardly needs an introduction to the leather trade of this country in its scientific aspect1 but if one be sought for1 none could serve the purpose better than a translation of the book herewith presented to the ,british-speaking public4 ,viewed with curiosity from their start1 the synthetic tannins needed--like many other important discoveries--an extreme emergency for the purpose of showing their value4 ,the ,great ,war provided the opportunity of which chemical industry was to avail itself1 and to-day we do not only see synthetic tannins placed upon the market as a veritable triumph of chemical technology and a creditable triumph of manufacturing chemistry2 we also see their immensely practical qualities established as a fact1 and1 as the author aptly remarks1 no modern tanner can to-day dissociate himself from the use of synthetic tannins for the production of leather in the true sense of this word4 ,there is no branch of leather-making where synthetic tannins cannot help and improve processes already established4 ,the immense number of substances patented by ,german manufacturing chemists for the purpose of producing synthetic tanning materials is almost staggering4 ,in view of this fact it is doubly pleasing to see that ,british chemists have found new ways1 and are able to produce equally good and more varied synthetic tannins than has hitherto been deemed possible4 ,the originator of these products and his acolytes must at least share the credit with those who1 in spite of the limitations necessarily set by the former1 have been able to find new and better ways4 ,in his book ,dr4 ,grasser gives a short review of the necessary forerunner of any work upon synthetic tannins3 the investigations and syntheses of the natural tannins4 ,it is certainly to be hoped that we may soon see such works as those of ,fischer's and ,freudenberg's1 recently published1 translated into ,english4 ,for the guidance of the reader it may be noted that a short account of the works of these authors may be found in the ,journal of the ,society of ,leather ,trades' ,chemists1 vol4 v4 7,may issue72 in addition to this some of the matter contained in the chapter on synthesis of tanning matters appeared in the ,january #aiba issue of the ,journal of the ,american ,leather ,chemists' ,association4 ,in addition to these two sections1 the last part of this book deals with the practical applications of synthetic tannins1 and it is hoped that the tanner will find much valuable information in these pages4 ,the main outlines of the synthesis of tanning matters should prove of great value to the chemist engaged in this branch of chemical technology4 ,the translator takes great pleasure in the acknowledging the valuable assistance rendered him by ,mr4 ,robin ,bruce ,croad1 ,a4,r4,t4,c41 ,f4,i4,c41 and by ,mr4 ,arthur ,harvey4 ,f4 ,g4 ,a4 ,,enna ,,contents ,introduction3 ,classification of ,synthetic ,tannins ,,part ,i ,,section ,i ,the ,synthesis of ,vegetable ,tannins #a4 ,tannin #b4 ,digallic ,acid #c4 ,ellagic ,acid #d4 ,depsides ,carbomethoxylation of ,hydroxybenzoic ,acids ,chlorides of ,carbomethoxyhydroxybenzoic ,acids ,preparation of ,didepsides ,preparation of ,tridepsides ,preparation of ,tetradepsides ,tannoid ,substances of the ,tannin ,type ,chart showing the ,decomposition of ,products of ,tannin ,,section ,,ii ,synthesis of ,tanning ,matters #a4 ,aromatic ,sulphonic ,acids #b4 ,condensation of ,phenols ,condensation of ,hydroxybenzene ,condensation of ,dihydroxybenzene ,trihydroxy benzene ,polyhydroxybenzenes ,quinone ,phenolic ,ethers ,nitro ,bodies ,amino ,bodies ,aromatic ,alcohols ,aromatic ,acids #c4 ,condensation of ,naphthalene ,derivatives #d4 ,condensation of the ,anthracene ,group #e4 ,di- and ,triphenylmethane ,groups #f4 ,summary ,table ,,section ,,iii ,tanning ,effects of ,mixtures and ,natural ,products #a4 ,mixture of ,phenolsulphonic ,acid and ,formaldehyde #b4 ,mixture of ,phenolsulphonic ,acid and ,natural ,tannins #c4 ,tanning ,effects of ,different ,natural ,substances ,,section ,,iv ,methods of ,examining ,tanning ,matters ,,part ,,ii ,synthetic ,tannins3 ,their ,industrial ,production and ,application ,a4 ,condensation of ,free ,phenolsulphonic ,acid ,b4 ,condensation of ,partly ,neutralised ,phenolsulphonic ,acid ,c4 ,condensation of ,completely ,neutralised ,phenolsulphonic ,acid ,d4 ,condensation of ,cresolsulphonic ,acid ,e4 ,relative ,behaviour of an ,alkaline ,solution of ,bakelite and ,natural ,tannins ,f4 ,dicresylmethanedisulphonic ,acid 7,neradol ,d7 #a4 ,neradol ,d ,reactions #b4 ,electro-,chemical ,behaviour of ,neradol ,d #c4 ,the ,influence of ,salts and ,acid ,contents on the ,tanning ,effect of ,neradol ,d #d4 ,phlobaphene ,solubilising ,action of ,neradols #e4 ,effect of ,neradol ,d on ,pelt #f4 ,reactions of ,neradol ,d with ,iron and ,alkalies #g4 ,reagents suitable for ,demonstrating the ,various ,stages of ,neradol ,d ,tannage #h4 ,combination ,tannages with ,neradol ,d 7#a7 ,chrome ,neradol ,d ,liquors 7#b7 ,aluminum ,salts and ,neradol 7#c7 ,fat ,neradol ,d ,tannage #i4 ,analysis of ,leather containing ,neradol ,d #aj4 ,properties of ,leather ,tanned with ,neradol ,d #aa4 ,neradol ,d1 ,free from ,sulphuric ,acid #ab4 ,neutral ,neradol ,g4 ,different ,methods of ,condensation as ,applied to ,phenolsulphonic ,acid #a4 ,condensation ,induced by ,heat #b4 ,condensation with ,sulphur ,chloride #c4 ,condensation with ,phosphorus ,compounds #d4 ,condensation with ,aldehydes #e4 ,condensation with ,glycerol ,,register ,,of ,,authors ,,index ,,introduction ,,classification ,,of ,,synthetic ,,tannins ,in laying down a definition of ,synthetic ,tannins1 it is first of all necessary to clearly define the conception of tannin4 ,primarily1 tannins may be considered those substances of vegetable origin which may be found1 as water-soluble bodies1 in many plants1 exhibiting certain chemical behaviour1 possessing astringent properties and being capable of converting animal hide into leather4 ,this latter property of the tannins1 that of converting the easily decomposable protein of animal hide into a permanently conserved substance and imparting to this well-defined and technically valuable properties1 has become the criterion of the practical consideration of a tannin4 ,it appears that different substances certainly show the chemical reactions peculiar to the tannins1 and to a certain extent also exhibit astringent character without1 however1 possessing the important property peculiar to the tannins of converting hide into leather4 ,such substances1 in our present-day terminology1 are termed pseudo-tannins 7e4g41 the tannin contained in coffee-beans74 ,decomposition products of the natural tannins1 to which belong1 for instance1 gallic acid and the dihydroxybenzenes1 exhibit the well-known reactions of the tannins 7coloration with iron salts71 but they cannot be regarded as tannins from either a technical or a physiological standpoint4 ,as regards their chemical constitution1 the natural 7true7 tannins probably belong to different groups of organic compounds1 and with our present-day scant knowledge of their chemistry1 it is impossible to classify them4 ,one is1 however1 justified in assuming that both the natural tannins and the related humic acids are ester-derivatives of hydroxybenzoic acids4 ,footnote3 ,e4 ,fischer1 ,ber41 #aiac1 #df1 #cbec4 ,the production of synthetic tannins employs two quite distinct methods2 one is to synthesise the most simple tannin1 viz41 the tannic acid contained in galls 7tannin71 or to build up substances similar in character to the tannins1 from hydroxybenzoic acids4 ,the other1 entirely new way1 is to produce chemical substances1 which certainly have nothing in common with the constitution of the natural tannins1 but which behave like true tannins in contact with animal pelt1 and in addition1 since they can be manufactured on a commercial scale1 are of practical value4 ,owing to the fact that1 until recently1 the constitution of tannin has remained unknown1 it is easy to comprehend that the efforts to synthesise the latter substance1 or compounds similar to it1 have been mainly attempted on similar lines4 ,the oldest investigation in this direction dates from ,h4 ,schiff1,footnote3 ,liebig's ,ann41 #ahgc1 #dc1 #agj4 who prepared substances similar to tannin by dehydrating hydroxybenzoic acids4 ,by allowing phosphorus oxychloride to interact with phenolsulphonic acid1 he obtained a well-defined substance possessing tanning properties1 which he considered an esterified phenolsulphonic acid anhydride1 the composition of which he determined as ,,ho4,c#f;,h#d4,,so#b4,o4,c#f;,h#d;,,hso #c4 ,it is1 however1 probable that this substance is not homogeneous1 but consists of a mixture of higher condensation products4 ,klepl ,footnote3 ,jour4 pr4 ,chem41 #ahhc1 #bh1 #bjh4 obtained--by simply heating p-hydroxybenzoic acid--a so-called di- and tridepside1 but this simple method is not applicable to many other hydroxybenzoic acids1 since these are decomposed by the high temperature required to induce reaction4 ,amongst other attempts to produce condensation products with characteristics similar to those possessed by the tannins1 those by ,gerhardt ,footnote3 ,liebig's ,ann1 #ahec1 #hg1 #aei4 and ,loewe ,footnote3 ,jahresh4 f4 ,chem41 #ahfh1 #eei4 must be especially noted2 they treated gallic acid with phosphorus oxychloride or arsenic acid1 and thereby obtained amorphous compounds1 exhibiting the reactions characteristic of tanning substances4 ,e4 ,fischer and ,freudenberg1 ,footnote3 ,liebig's ,ann41 #cgb1 #de4 by treating p-hydroxybenzoic acid in the same way1 succeeded in obtaining a didepside1 and during the last years practically only these two investigators have demonstrated the syntheses of these depsides and produced high-molecular polydepsides4 ,at the same time researches were instituted with the object of determining the constitution of tannin1 and ,e4 ,fischer succeeded in demonstrating its probable composition as being that of a glucoside containing #e molecules of digallic acid per #a molecule of glucose4 ,this last-named class of synthetic tannins--which may be properly termed tanning matters in contradistinction to the true tannins--exhibit very distinct tanning character when brought in contact with animal hide1 but from the point of view of chemical constitution have nothing in common with the natural tannins4 ,not only are they of interest to the industry from a practical point of view2 they have also been examined very closely from a chemical standpoint4 ,it is1 however1 necessary to differentiate with great exactitude between the conception of true tanning effect and pickling effect when considering the action of chemical substances on pelt 7i4e41 animal hide1 treated with lime1 depilated1 and the surplus flesh removed74 ,whereas any true tannage is characterised by the complete penetration of the substance and its subsequent fixation by the pelt in such a way that a thorough soaking and washing will not bring about a reconversion 7of the leather7 to the pelt state2 pickling1 on the other hand1 is only characterised by the penetration of the substance in the pelt and fixation to such an extent that a subsequent washing of the pickled pelt will bring back the latter to a state closely approximating that of a true pelt4 ,simple as such a differentiation appears1 there are still a number of cases occupying a position between the two referred to1 and which we may term pseudo-tannage4 ,an example of the latter is formaldehyde tannage2 formaldehyde has for a long time been employed in histological work for the purpose of hardening animal hide1 by which it is readily absorbed from solution whereby it hardens the hide without1 however1 swelling it4 ,a hide which has thus been treated with formaldehyde absorbs the natural tannins with greater ease2 this1 on the one hand1 argues the probability of formaldehyde acting as a pickling agent2 on the other hand1 it is also one of its characteristics that it will either in neutral acid1 ,footnote3 ,r4 ,combret1 ,ger4 ,pat1 #aab1 #ahc4 or1 still better1 in alkaline ,footnote3 ,j4 ,pullman1 ,ger4 ,pat1 #aaa1djh2 ,griffith1 ,lea4 ,tr4 ,rev41 #aijh4 solution1 convert pelt into leather4 ,in a formaldehyde-tanned leather1 however1 no trace of tannin can be detected2 and the yield 7of leather1 based on the pelt employed71 which1 from a practical standpoint1 is so important1 is so very low that it is hardly possible to speak of it as a tannin in the ordinary sense of the word4 ,formaldehyde must1 therefore1 be termed a pseudo-tannin4 ,the tanning effect of formaldehyde is1 according to ,thuau1 ,footnote3 ,collegium1 #aiji1 #cfc1 #baa4 increased by those salts which bring about colloidal polymerisation of the formaldehyde1 the resultant compounds being absorbed by the hide fibre4 ,fahrion considers this to be a true tannage1 and is supported by ,nierenstein ,footnote3 ,ibid41 #aije1 #aeg1 #aei43-- ,r4,,nh#b ,r4,,nh- ,o4,c4,h4 ,,ch#b ,h#b,o ,r4,,nh#b ,r4,,nh- 7,hide47 ,h 7,leather47 ,a peculiar combination between true tannage and pickling is to be found in the tawing process 7tannage with potash1 alum1 and salt71 whereby1 firstly1 the salt and the acid character of the alum produce a pickling effect1 and secondly1 the alum at the same time is hydrolysed1 and its dissociation components partly adsorbed by the hide1 thereby effecting true tannage4 ,this double effect is still more pronounced in the synthetic tannins which contain colloidal bodies of pronounced tanning intensity on the one hand1 inorganic and organic salts on the other1 which then act as described above4 ,their real mode of action can only be explained with the aid of experimental data4 ,the following chapters will deal with the different behaviour of the various groups of synthetic tannins4 ,,part ,i ,,section ,i ,,the ,,synthesis ,,of ,,vegetable ,,tannins #a4 ,,tannin ,the first investigations of gall-tannin date from the year #aggj1 at which time1 however1 no exact differentiation between tannin and gallic acid was made4 ,the first step in this direction was made when ,scheele1,footnote3 ,grell's ,chem4 ,ann41 #aghg1 #c1 ,i4 in #aghg1 discovered gallic acid in fermented gall extract1 and in the same year ,kunzemuller ,footnote3,ibid41 #aghg1c1dac4 separated gallic acid 7or pyrogallol7 as a crystalline body from oak galls4 ,dize ,footnote3 ,jour4 ,chim4 et ,phys41 #agia1 #cii4 continued the investigations1 which were brought to a conclusion with ,deyeux' work ,footnote3 ,ann4 ,chim41 #agic1 #ag1 ,i42 both recognised that the substance isolated was not a single substance1 but was a mixture of gallic acid1 a green colouring matter1 a rosin 7tannin871 and extraneous matter4 ,proust ,footnote3 ,ibid41 #agii1 #be1 #bbe4 was the first to differentiate the crystalline gallic acid from the amorphous1 astringent substance1 which latter he named ,tannin4 ,amongst the numerous subsequent investigations of tannin must be especially noted the one by ,berzelius ,footnote3 ,pogg1,ann41 #ahbg1 #aj1 #beg41 who purified the potash salt and decomposed this with sulphuric acid4 ,pelouze ,footnote3 ,liebig's ,ann41 #ahdc1 #dg1 #ceh41 later on1 observed the formation of the crystalline gallic acid from tannin1 when the latter is boiled with sulphuric acid2 this had already been observed by ,j4 ,liebig4,footnote3 ,ibid4#ahdc1 #ci1 #ajj4 ,both had noticed the absence of nitrogen4 ,in addition to the methods of preparation of tannin then in vogue neutral solvents were mainly employed by subsequent investigators2 ,pelouze ,footnote3 ,jour4 ,prakt4 ,chem41 #ahcd1 #b1 #cja1 and #cbh4 treated powdered galls with ether containing alcohol and water1 and considered the upper layer to be a solution of gallic acid and impurities1 the bottom layer to contain the pure tannin4 ,the ,,empirical ,,formula of tannin has also been the subject of much speculation by the different investigators1 the difficulty here being that of obtaining a pure specimen of the substance free from sugars1 and which could be submitted to elementary analysis4 ,whereas these early purified substances were thought to correspond to the formula of digallic acid 7galloylgallic acid71 ,c#ad;,h#aj,o#i1 ,fischer and ,freudenberg ,footnote3 ,ber41 #aiab1 #iae and #bgji4 were able to show1 with approximate certainty1 that the constitution of tannin is that of a pentadigalloyl glucose4 ,early attempts at hydrolysing tannin gave varying results1 some investigators claiming the presence1 and others the absence of sugars4 ,here1 again1 ,e4 ,fischer and ,freudenberg ,footnote3 ,ibid4 were able to conclusively prove that on hydrolysing tannin with dilute acids1 #g4i per cent4 glucose is dissociated1 and that hence glucose forms part of the tannin molecule4 ,fischer and ,freudenberg also determined the optical activity of pure tannin in water3 ,greek3 a,d was found to lie between #eh and #gj4 ,graham found ,footnote3 ,phil4 ,transact41 #ahfa1 #ahc4 that the tannin molecule is of considerable size1 since its diffusion velocity is #bjj times less than that of common salt4 ,patern ,footnote3 ,zeits4 phys4 ,chem41 #ahij1 iv4 #deg4 was the first to determine the molecular weight of tannin1 employing ,raoult's method2 he found that tannin in aqueous solution behaves like a colloid and that hence ,raoult's method is not applicable4 ,when1 on the other hand1 he dissolved tannin in acetic acid1 results concordant with the formula of ,c#ad;,h#aj,o#i1 corresponding to a molecular weight of #cbb1 were obtained4 ,sabanajew ,footnote3 ,ibid41 #ahij1 v4 #aib4 later determined the molecular weight of tannin in aqueous solution as #aajd1 in acetic acid solution as #aaac-acbb1 ,krafft ,footnote3 ,ber41 #ahii1 #cb1 #afac4 as #aehg-afbf in aqueous solution4 ,walden ,footnote3 ,ibid41 #ahih1 #cafg4 determined the molecular weight of tannin-schuchardt as #acej-aefj1 tannin-merck as #gec-gfc1 digallic acid as #cjg-caf 7calculated #cbb74 ,feist ,footnote3 ,chem4 ,ztg41 #aijh1 #iah4 determined the molecular weight of tannin as #fae and one of his own preparation as #gdf1 ,turkish tannin as #eba and ,chinese tannin as #hii4 ,in this connection it should be noted that the calculated molecular weight of pentagalloyl glucose1 which in ,e4 ,fischer's opinion forms a substantial part of the tannin molecule1 is #idj1 but ,fischer also thinks that this compound possesses a much higher molecular weight4 ,,structure ,,of ,,tannin--,the oldest structural formula of tannin is ,schiff's digallic acid formula3--,footnote #a3 ,ber41 #ahga1 #d1 #bca4 ---------,,co4,o4---------- ,,oh ,,ho ,,oh ,,hooc ,,oh ,v ,v ,,oh ,a drawback to the acceptance of this formula is the absence of an asymmetrical ,c-atom2 the formula1 therefore1 does not explain the optical activity exhibited by tannin4 ,schiff attempted to overcome this difficulty by adopting a diagonal structural formula1 but even when adopting ,clauss' diagonal formula for benzene the optical activity of a number of other compounds depends upon the existence of the asymmetrical ,c-atom4 ,biginelli ,footnote #b3 ,gazz chim4 ,ital41 #aiji1 #ci1 #bfh4 also opposed the digallic acid formula1 and supported his view by referring to the arsenic compounds obtained by him on heating arsenic acid and gallic acid1 instead of obtaining digallic acid4 ,walden1 ,footnote #c3 ,ber41 #ahih1 #ca1 #cafh4 on the other hand1 found1 on analysing the digallic acid thus prepared1 only slight traces of arsenic and1 by the elementary analysis1 obtained figures closely corresponding to those of digallic acid4 ,bottinger ,footnote #d3 ,ibid41 #ahhd1 #ag1 #adgf4 prepared the so-called ,greek3 b-digallic acid by heating ethyl gallate with pyroracemic acid and sulphuric acid and proposed the so-called ketone-tannin formula3-- ,,ho,,oh ,,oh ,,ho--------,,co--------,,oh ,,cooh ,,oh ,schiff completed this formula by a diagonal1 so as to explain the optical activity observed-- ,,ho ,,oh ,,oh ,,ho--------,,co--------,,oh ,,cooh ,,oh ,diagonal bond between ,,ho and ,,cooh on left4 ,the ketone formula was corroborated by ,nierenstein1 ,footnote3 ,ber4 #aije1 #ch1 #cfda4 who distilled tannin with zinc dust and obtained diphenylmethane 7smell of benzene7 and a crystalline product1 ,m4,p4 #g,o-#ga ,c4 7,m4,p4 of diphenyl #ga ,c474 ,knig and ,kostanecki ,footnote3 ,ibid41 #aijf1 #ci1 #djbg4 sought to find the constitution of the tannins in the leuco-compounds of the oxyketones1 to which catechin belongs4 ,nierenstein 7see above71 however1 emphasises that the high molecular weight and the optical activity speak against the digallic acid formula1 but in favour of this are the following points3 7#a7 the decomposition of tannin with the formation of gallic acid2 7#b7 the decomposition of methylotannin with the formation of di- and trimethyl esters of gallic acid2 and 7#c7 the production of diphenylmethane on distillation with zinc dust4 ,the latter reaction especially illustrates the analogous formation of fluorene from compounds of the type-- --,,co4,o ,v ,v ,nierenstein gave the name ,tannophor to the mother-substance of tannin1 phenylbenzoate1 ,c#f;,h#e-;,,coo-,c#f;,h#e4 ,dekker ,footnote3 ,de ,looistoffen1 vol4 ii1 p4 #cj 7#aijh74 was1 however1 unable to detect diphenylmethane on distilling with zinc dust1 and did1 therefore1 not accept ,nierenstein's views4 ,in proposing the formula-- ,o ,,ho ,c ,o ,,oh ,c_/ ,,oh ,,ho ,v _/ ,,oh ,,oh ,,oh ,dekker ,footnote3 ,ber41 #aijf1 #cd1 #bdig4 was enabled to account for most of the details in the behaviour of tannin1 viz43 7#a7 the empirical constitution1 ,c#ad;,h#aj,o#i2 7#b7 the almost complete hydrolysis into gallic acid 7the dotted line indicates the decomposition of the molecule into #b molecules gallic acid by taking up water72 7#c7 the formation of diphenylmethane as a result of distillation with zinc dust2 and 7#d7 the electrical non-conductivity4 ,since tannin on acetylating yields a considerable amount of triacetylgallic acid1 it should1 according to ,dekker1 contain at least six acetylisable hydroxyls4 ,nierenstein ,footnote3 ,chem4 ,ztg41 #aijf1 #ca1 #hhj4 objected to this formula on account of its containing seven hydroxyl groups1 whereas ,dekker found six1 ,nierenstein five1 and ,herzig still fewer hydroxyl groups4 ,the formula would also favour the conception of tinctorial properties which could hardly be ascribed to tannin4 ,lloyd ,footnote3 ,chemical ,news1 #aijh1 #ig1 #acc4 proposed a very intricate formula containing three digallic acid groups joined into one six-ring system1 which would then explain the optical activity2 it would1 on the other hand1 also require an inactive cis-form4 ,iljin ,footnote3 ,jour4 of the ,russian phys4 chem4 ,soc41 #aijh1 #ci1 #dgj4 prepared two phenylhydrazine derivatives of tannin 7,c#gd ,h#eh ,n#h ,o#cj and ,c#ih ,h#hb ,n#ad ,o#if7 and proposed the formula1 ,c#eh ,h#dj ,o#cc1 the constitution of which would be-- ,r#a ,r#a ,c--,o--,o--,c ,r#b ,r#b ,o ,r#a ,r#a ,c--,o--,o--,c ,r#b ,r#b where ,r#a ,,co ,c#f ,h#b 7,,oh7#c and ,r#b ,c#f ,h#b 7,,oh7#b ,nierenstein ,footnote3 ,ber41 #aije1 #ch1 #chda2 #aijg1 #dj1 #iag2 #aijh1 #da1 #gg and #cjae2 #aiji1 #db1 #aabb and #ceeb2 ,chem4 ,ztg41 #aijg1 #ca1 #gb2 #aiji1 #cd1 #ae4 considers tannin to be a mixture of digallic acid and leucotannin1 the latter possessing the formula-- -------,,ch4,,oh--,o---- ,,oh ,,ho ,v ,,oh ,,hooc ,v ,,oh ,,oh ,the optical activity of tannin is expressed in this formula and its probability is corroborated by ,nierenstein1 who was able to resolve the acetylated tannin by fractional precipitation into pentacetyl tannin 7,m4,p4 #bjc-bjh ,c47 and pentacetyl leucotannin 7,m4,p4 #aff ,c474 ,by oxidation1 the former is converted into ellagic acid1 and on hydrolysis with dilute sulphuric acid readily yielded gallic acid4 ,hydrolysis of the pentacetyl leucotannin1 however1 yielded gallic aldehyde1 and oxidation yielded purpurotannin 7a naphthalene derivative7 in addition to ellagic acid4 ,nierenstein ,footnote3 ,ber41 #aiaj1 #dc1 #fbh4 also succeeded in converting tannin into carboethoxytannin1 the latter on saponification yielding crystalline1 inactive digallic acid4 ,on acetylating pentacetyl leucotannin with acetyl chloride a hexacetyl derivative 7,m4,p4 #aei ,c47 is obtained1 the strychnine salt of which is resolved into both of the active components4 ,this proves the presence of digallic acid and leucotannin in tannin lev4 pur4 ,schering investigated by ,nierenstein4 ,the latter author ,footnote3 ,liebig's ,ann41 #aiab1 #chf1 #cah2 #chh1 #bbc4 later considered tannin to be polydigalloylleucodigallic acid anhydride and the simplest tannin to be a digalloylleucodigallic acid anhydride4 ,this view1 however1 would not stand subsequent criticisms1 being in disagreement with the earlier observations of molecular weight and acidic properties of tannin4 ,manning ,footnote3 ,ibid41 #aiab1 #cd1 #iah4 believed to have isolated a pentethylester of the pentagalloyl glucoside from tannin1 but this was shown to be the ethyl ester of gallic acid4 ,feist ,footnote3 ,ber41 #aiab1 #de1 #adic4 had arrived at the conclusion that tannin was a glucose compound1 and maintained that tannin from ,turkish galls was a compound of glucogallic acid combined as an ester with #b molecules gallic acid4 ,but ,fischer and ,strauss ,footnote3 ,ibid41 #aiab1 #de1 #cggc4 synthetically prepared a glucoside of gallic acid exhibiting differences from ,feist's preparation which were so great that the latter no longer could be considered a single glucoside of gallic acid4 ,fischer and ,freudenberg ,footnote3 ,ibid41 #aiab1 #de1 #bgag2 #aiac1 #df1 #aabg4 subsequently elaborated a method of purifying tannin1 and on investigating the purified substance1 arrived at the conclusion that no other hydroxybenzoic acid than gallic acid was present in tannin4 ,on repeating ,strecker's hydrolysis they obtained #g-h per cent1 sugar1 and hence concluded that #a molecule of glucose was combined with about #aj molecules of gallic acid4 ,owing to the difficulty of isolating the intermediary hydrolysis products1 and the subsequent impossibility of drawing any conclusions as to the constitution of tannin1 the latter investigators decided to adopt the methods offered by synthesis4 ,their basic idea was the absence of carboxylic groups in tannin1 and that hence the total gallic acid must be present in ester form4 ,these conditions are fulfilled if one views tannin as being an ester compound of #a molecule of glucose and #e molecules of digallic acid1 of similar construction as1 for example1 pentacetyl glucose4 ,fischer and ,freudenberg succeeded in preparing the former by shaking a mixture of finely powdered glucose1 chloroform1 and quinoline with an excess of tricarbomethoxygalloyl chloride for twenty-four hours and precipitating the resulting product with methyl alcohol2 suitably purified1 a light amorphous colourless substance was obtained which proved to be penta-7tricarbomethoxygalloyl7 glucose4 ,careful saponification with excess alkali in acetone-aqueous solution at room temperature yielded a tannin very closely resembling tannin1 identified as pentagalloyl glucose4 ,it is doubtful1 however1 whether this substance is homogeneous1 and it is probably a mixture of two stereoisomers4 ,fischer and ,freudenberg1 therefore1 further concluded that tannin is mainly an ester compound of glucose and #e molecules m-digallic acid4 ,elucidation on this point offered itself advantageously in ,herzwig's methylotannin1 ,footnote3 ,ber41 #aije1 #ch1 #ihi4 which is obtained by the interaction of diazomethane and tannin4 ,the first step was then to prepare pentamethyl-m-digallic acid ,,ch#c4,o ,,cooh ,,ch#c4,o--,,co4,o-- ,,ch#c4,o ,,ch#c4,o ,o4,,ch#c from trimethylgalloyl chloride and the m-p-dimethyl ether of gallic acid2 the chloride of this substance1 coupled with ,greek3 a- and ,greek3 b-glucose1 yields-- ,,ch4,,or ,,ch4,,or ,h,o4,,ch#c ,r,,co,o4,,ch#c ,o ,,ch4,,or ,h ,o ,h,o4,,ch#c ,,ch ,,co,o4,,ch#c ,h ,o4,,ch#c ,,ch4,,or ,,ch#b4,,or ,illustration3 ,penta-7pentamethyl-m-digalloyl7-glucose 4 ,the ,greek3 a- and ,greek3 b-derivatives thus obtained differ in their behaviour towards polarised light1 and are1 again1 probably mixtures of two stereoisomers1 i4e41 mixtures of derivatives of ,greek3 a- and ,greek3 b-glucose4 ,compared to methylotannin1 these preparations exhibit very close resemblance to the former1 from which it may be concluded that they are closely related to this substance1 and probably possess the same or a very similar structure2 the result of the above experiments has1 therefore1 brought us at least in close proximity to the structure of tannin4 ,it must1 however1 be borne in mind that the analysis and hydrolysis of tannin does not afford an explanation of the question as to whether tannin is a compound of glucose and #aj1 #i1 or #aa molecules of gallic acid2 it is also possible1 though not probable1 that tannin would contain a polysaccharide instead of glucose itself4 ,similarly to sugar1 the true glucosides can be coupled with hydroxybenzoic acids1 which is proved by the preparation of tetra-galloyl-,greek3 a-methyl glucoside2 this substance1 also1 exhibits tannoid character4 #b4 ,,digallic ,,acid ,whereas1 until recently1 tannin had been considered to be gallic acid anhydride1 or digallic acid1 closer investigations have revealed that neither is tannin digallic acid nor is the synthetically prepared digallic acid identical with tannin4 ,schiff ,footnote3 ,ber41 #ahga1 #bca and #ifg4 prepared digallic acid by the interaction of phosphorus oxychloride and gallic acid1 and believed the product obtained to be identical with tannin2 to this latter he first ascribed an ether formula 7,i471 later an ester formula 7,,ii47-- 7,,oh7#b 7,,oh7#b ,c#f;,h#b---j---;,c#f;,h#b ,,cooh ,,cooh 7,i47 7,,oh7#b ,c#f;,h#b7,,oh7#c--;,c--,o4,c#f;,h#b ,o ,,cooh 7,,ii47 ,froda ,footnote3 ,gasz4 chim41 #ahgh1 #i4 held that ,schiff's condensation product contained phosphorus or arsenic acid and ascribed its tanning properties to the latter2 according to this investigator1 digallic acid1 when completely freed from arsenic acid1 does not react with gelatine or quinine4 ,biginelli ,footnote3 ,ibid41 #aiji1 #ci1 ii4 #bfh and #bhc4 did not consider the action of arsenic acid that of a catalyst1 but held that it entered into reaction2 according to his investigations products containing arsenic 7,c#g;,h#g,o#h;,as and ,c#ad;,h#aa,o#ab;,as7 are obtained when gallic acid is heated with arsenic acid4 ,in his preparation of digallic acid1 ,iljin ,footnote3 ,jour4 f4 prakt4 ,chem41 #aiaa1 #hb1 #dea4 could only obtain gallic acid1 and the ethyl ether of gallic acid showing no characteristics of the tannins2 when1 however1 he heated gallic acid with arsenic pentoxide1 he obtained bodies exhibiting the reactions given by tannins4 ,bottinger ,foonote3 ,ber41 #ahhd1 #aejc4 made the first attempt at synthesising tannin2 he heated gallic acid or its ethyl ester with glyoxylic acid or pyroracemic acid1 and obtained a substance of the composition ,c#ad;,h#aj,o#i4b;,h#b,o1 which certainly showed some of the characteristics exhibited by tannin1 but which by no means was identical with the latter4 ,bottinger's preparation is probably identical with ,greek3 b-digallic acid1 one of two dibasic isomers having the composition-- ,c#f;,h#b7,,oh7#b;,,cooh ,c#f;,h7,,oh7#c;,,cooh the other possible isomer having the composition ,c#f;,h7,,oh7#c;,,cooh ,,co ,c#f;,h#b7,,oh7#c ,fischer ,footnote3 ,ber41 #aijh1 #da1 #bhge4 obtained a digallic acid 7,m4,p4 #bge-bhj ,c7 by coupling tricarbomethoxygalloyl chloride with dicarbomethoxygallic acid4 ,nierenstein ,footnote3 ,ibid41 #aiaj1 #dc1 #fbh4 obtained1 from the carbethoxy compound of tannin1 a crystalline1 optically active digallic acid1 ,m4,p4 #bfh-bgj ,c4 ,the pentacetate of this substance1 obtained by reduction and acetylisation1 yielded hexacetylleucotannin4 ,a pentamethyldigallic acid methyl ester of the composition 77,o4,,ch#c7c7;,c#f;,h#b----;,,coo-----, c#f;,h#b77,,och#c7b7;,,coo4,,ch#c was obtained by ,mauthner ,footnote3 ,jour4 f4 prakt4 ,chem41 #aiaa1 #hd1 #adj4 from the chloride of trimethylgallic acid and the methyl ester of the acid from the glucoside of syringin2 on saponification with caustic potash the former compound yielded trimethylgallic acid and syringic acid4 ,fischer ,footnote3 ,ber41 #aiac1 #df1 #aaaf4 synthesised the so-called m-digallic acid by coupling tricarbomethoxygalloyl chloride with carbonylgallic acid and subsequent splitting off of ,,co#b4 ,the m-digallic acid appears as rather thick1 colourless1 microscopic needles containing about #af per cent4 water of crystallisation1 ,m4,p4 #bga ,c4 ,they are slightly soluble in cold1 soluble in hot water1 and very soluble in methyl and ethyl alcohols4 ,their aqueous solution gives dark blue coloration with ferric chloride1 and precipitates gelatine and quinine4 ,fischer and his students ,footnote #e3 ,ibid41 #aiab1 #de1 #iae1 #bgji2 #aiac1 #df1 #aaaf4 prepared quite a number of digallic acid derivatives1 amongst which are the following3-- ,pentamethyl-m-digallic acid methyl ester1 ,c#bj;,h#bb,o#i4 ,pentacetyl-m-digallic acid1 ,c#bd;,h#bj,o#ad4 ,pentamethyl-m-digallic acid1 ,c#ai;,h#bj,o#i4 ,pentamethyl-m-digalloyl chloride1 ,c#ai;,h#ai,o#h;,cl4 ,pentamethyl-p-digallic acid1 ,c#ai;,h#bj,o#i4 ,pentamethyl-p-digallic acid methyl ester1 ,c#bj;,h#bb,o#i4 ,hydrolysis of digallic acid yields gallic acid2 oxidation1 on the other hand1 ellagic acid and luteic acid 7,luteo ,sure71 which can be separated by shaking with pyridine4 ,the reduction of digallic acid yields1 by different methods1 the same reduction compound1 ,footnote3 ,nierenstein1 ,abderhalden's ,handb4 d4 biochem4 ,arbeitsm41 vi4 #aed4 viz41 the racemic leucodigallic acid1 which differs from digallic acid by being devoid of any tannoid properties2 the latter distinction may be ascribed to the transformation of the tannophor group--,,co4,o--1 to the tannoid-inactive group ,,ch7,,oh7--,o--4 ,the successful resolving of racemic leucodigallic acid into both of its optically active components can only be brought about through the d- or l-hexacarbethoxyleucodigallic acid on introducing the latter into a #a per cent4 pyridine solution and heating to #de-ej ,c41 whereby the d- or l-acid is formed accompanied by a strong evolution of carbon dioxide4 ,hydrolysis of leucogallic acid yields gallic acid and gallic aldehyde2 oxidation by means of hydrogen peroxide yields ellagic acid and luteic acid1 and oxidation with potassium persulphate and sulphuric acid1 in acetic acid solution1 yields purpurotannin 7see below7 ,footnote3 ,liebig's ,ann41 #aiab1 #chf1 #cah44 ,another distinct difference between digallic acid and leucodigallic acid is the fact that the formaldehyde condensation product of the former resembles gallic acid1 whereas that of the latter resembles tannin2 it is therefore probable that the leucodigallic acid part of the tannin molecule imparts this characteristic property to tannin4 ---,,co4,o--- ,,ho ,v ,,oh ,,cooh ,v ,,oh ,,oh ,,oh ,illustration3 ,digallic ,acid becomes444 ---,,co4,o--- ,,oh ,,ho ,v ,,oh ,,cooh ,v ,,oh ,,oh ,,oh ,illustration3 ,luteic ,acid becomes444 ---,,co4,o--- ,,oh ,,ho ,v --,o4,,co-- ,v ,,oh ,,oh ,,oh ,illustration3 ,ellagic ,acid becomes444 ,,cooh ,,cooh ,,ho ,v ---,o--- ,v ,,oh ,,oh ,,oh ,illustration3 ,purpuro ,tannin4 #c4 ,ellagic ,acid ,ellagic acid was discovered in #ahca by ,braconnot1 who named it acide ellagique4 ,its presence in the vegetable kingdom was not quite comprehended for some time1 and ,nierenstein ,footnote3 ,chem4 ,ztg41 #aiji1 #hg4 was the first to prepare this substance from algarobilla1 dividivi1 oak bark1 pomegranate1 myrabolarms1 and valonea4 ,the acid is obtained by precipitating it with water from a hot alcoholic extraction of the plants referred to1 and recrystallising the precipitate from hot alcohol4 ,another method of preparation consists in boiling the disintegrated plants with dilute hydrochloric acid1 washing the residue1 and extracting with hot alcohol1 from which the acid will then crystallise4 ,according to ,lowe1 ,footnote3 ,zeits4 f4 analyt4 ,chem41 #ahge1 #ce4 it may be obtained from dividivi1 an aqueous extract of which is heated to #aaj ,c4 in a tube closed at both ends1 when crystalline ellagic acid is deposited4 ,heinemann ,footnote3 ,ger4 ,pat41 #acg1jcc and #acg1icd4 obtained ellagic acid by simply boiling repeatedly aqueous tannin solutions4 ,lowe ,footnote3 ,jour4 f4 prakt4 ,chem41 #ahfh1 #ajc1 #dfd4 first synthesised ellagic acid by heating gallic acid with arsenic acid or silver oxide4 ,herzig ,footnote3 ,monatshefte fur ,chemie1 #aijh1 #bi1 #bfc4 states that ellagic acid is deposited when air is conducted through a mixture of the ethyl or methyl ester of gallic acid and ammonia4 ,perkin ,footnote3 ,proc4 ,chem4 ,soc41 #aije1 #ba1 #bab4 obtained a substance very similar to ellagic acid by electrolysis of gallic acid in sulphuric acid solution2 on oxidising gallic acid in concentrated sulphuric acid solution1 ,perkin and ,nierenstein ,footnote3 ,ibid41 #aije1 #ba1 #ahe4 obtained flavellagic acid4 ,ellagic acid is also obtained by heating luteic acid in a #aj per cent4 soda solution4 ,ellagic acid thus prepared crystallises with #b molecules of water as yellow micro-crystalline rhombic prisms or prismatic needles4 ,the crystals lose this water when heated to #ajj ,c41 and it is possible that it is water of constitution1 in which case the substance would be hexoxydiphenylcarboxylic acid1 and the substance left after drying at #ajj ,c41 the dilactone4,footnote3 ,arch4 d4 ,pharm41 #aijg1 #bdd1 #ege4 ,ellagic acid is slightly soluble in water1 alcohol1 and ether1 but is easily soluble in caustic potash4 ,with concentrated nitric acid the product assumes a red colour1 which appears to be due to the presence of impurities2 ellagic acid is commercially known as alizarin yellow4 ,the constitution of ellagic acid was uncertain for a long time1 and different structural formulae were proposed which more or less corresponded to its properties4 ,the most satisfactory structural formula was proposed by ,graebe--,footnote3 ,chem4 ,ztg41 #aijc1 #abi4 ---,,co4,o--- -------- ,,oh ,,ho ,v --,o4,,co-- ,v ,,oh ,,oh ,this would represent a tetroxydiphenylmethylolide4 ,the probability of the correctness of this formula is supported by the possibility of the following derivatives3 monomethylellagic acid1 ,c'#ad;,h'#f,o'#g7,o4,,ch'#c72 dimethylellagic acid1 ,c'#ad;,h'#d,o'#f7,o4,,ch'#c7'b2 tetramethylellagic acid1 ,c'#ad;,h'#b,o'#d7,o4,,ch'#c7'd2 phenylhydrazinellagic acid1 ,c'#ad;,h'#f,o'#h4,n'#b;,h'#c;,c'#f;,h'# e4 ,by the electrolytic reduction of ellagic acid1 hexoxydiphenyl1 7,,oh7'#c;,c'#f;,h'#b-;,c'#f;,h'#b7,,oh7 '#c1 is obtained2 the ordinary methods of reduction yield leucoellagic acid1 ,c'#ad;,h'#aj,o'#h1 which crystallises in small sharp needles1 melting with decomposition at #bid-bie ,c4 ,leucoellagic acid is soluble in ethyl and methyl alcohols1 and in glacial acetic acid1 insoluble in chloroform1 benzene1 toluene1 carbon tetrachloride1 and petrol ether2 it gives a bluish-green colour with ferric chloride which quickly turns black4 ,leucoellagic acid is soluble in alkalies1 the solution assuming a deep-red coloration2 it reduces silver nitrate in the cold1 but is not adsorbed by mordanted cotton cloth1 in which respect it differs from ellagic acid4,footnote3 ,liebig's ,ann41 #aiab1 #cid1 #bdi4 ,,ellagitannic ,,acid1 ,c'#bf;,h'#bh',o'#aj-c;,h'#b,o1 is closely related to ellagic acid2 the former consists of faintly yellow needles1 ,m4,p4 #cbi-ccf;,c4 ,it is soluble in water1 precipitates gelatine1 and is adsorbed by hide powder4 ,it occurs with gallic acid1 tannin1 and ellagic acid in dividivi1 myrabolams1 algarobilla1 and chestnut wood extracts4 ,other bodies of this class include3-- ,,metellagic ,,acid1 ,cl#d;,h#f,o#e1 derived from methoxybenzoic acid1 and recrystallised from acetic acid1 forms small crystalline needles1 ,m4,p4 #bgc-bgf ,c41 and yields fluorene on distillation with zinc dust4 ----,,co4,o---- ---------- ,v ---,o4,,co--- ,v ,,oh ,,flavellagic ,,acid1 ,c#ad;,h#f,o#i1 is obtained by the oxidation of gallic acid with concentrated sulphuric acid and potassium persulphate4 ,it crystallises from pyridine in prismatic needles melting above #cfj ,c4 ,distillation with zinc dust yields fluorene 7see above7-- ----,,co4,o---- ---------- ,,oh ,,ho ,v ---,o4,,co--- ,v ,,oh ,,oh ,,oh ,by heating ellagic acid for three-quarters of an hour at #ahe ,c4 with concentrated sulphuric acid1 ceruleo-ellagic acid 7dioxyellagic acid71 ,c#ad;,h#f,o#aj1 is formed as yellowish needles1 ,m4,p4 #cfj ,c41 which are but little soluble in the usual solvents4 ,the acid is slightly soluble in strong caustic soda solution1 the colour of the solution1 on diluting1 changing to green and blue4 ,,luteic ,,acid 7,luteo ,saure1 pentoxybiphenylmethylolide carboxylic acid71,c#ad;,h#h,o#i1 occurs1 in addition to ellagic acid1 in myrabolams-- ,footnote3 ,ber41 #aiji1 #db1 #cec4 ----,,co4,o---- ---------- ,,oh ,,ho ,v ,,oh ,,hooc ,v ,,oh ,,oh ,,oh ,it is obtained by extracting myrabolams for one hour and a half1 under reflux condenser1 with pyridine1 filtering and adding twice the volume of water to the filtrate and boiling till complete solution is obtained4 ,after about thirty hours a reddish powder deposits1 from which ellagic acid may be extracted with pyridine2 the mother-liquor on being concentrated yields luteic acid4 ,it is also obtained by oxidising tannin with hydrogen peroxide1 the other oxidation product being ellagic acid1 and the two may then be separated as indicated above4 ,luteic acid forms reddish needles which are decomposed1 with evolution of gas1 at #cch-cda ,c4 ,heated with #aj per cent4 caustic soda solution it yields ellagic acid4 ,in pyridine solution the carboxyl group maybe eliminated by hydrogen iodide1 whereby pentoxybiphenylmethylolide is formed as long silky needles1 which do not melt below #cjj ,c4 ,the same substance may also be obtained when ellagic acid is boiled with concentrated caustic potash solution4 ,when luteic acid is treated with diazomethane1 it yields the methyl ester of pentamethoxybiphenylmethylolidcarboxylic acid4 #d4 ,,depsides ,the most common decomposition products of the natural tannoids are hydroxybenzoic acids1 notably gallic and proto-catechuic acids2 furthermore1 other aromatic and aliphatic hydroxy compounds frequently occur4 ,so far1 however1 attempts at explaining the constitution of the complex decomposition products obtained by hydrolysing high molecular tannoids have not been successful4 ,on the other hand1 the constitution of the simpler natural tannoids is known to a greater or less extent2 of these1 lecanoric acid 7,lecanorsure7 is the best known1 being an ester anhydride of orsellic acid 7a dihydroxytoluylic acid74 ,it combines with erythrite1 forming another tannoid1 erythrine4 ,the fact that hydroxybenzoic acids are constantly encountered together with the products obtained on hydrolysis of the tannins1 seems to point toward the conclusion that anhydrides of hydroxybenzoic acids are frequent constituents of the natural tannoid molecules4 ,the assumption that1 for instance1 in tannin at least part of the gallic acid radicals are combined with one another is highly probable1 and is supported by the formation of tri- and dimethylgallic acid from methylotannin1 ,footnote3 ,herzig1 ,monatshefte f4 ,chemie1 #aiji1 #cj1 #cdc4 and by the formation of ellagic acid when tannin is oxidised4 ,footnote3 ,nierenstein1 ,ber41 #aijh1 #da1 #cjae4 ,further proof is brought forward by the existence of the pentacetyl-tannin1 ,footnote3 ,schiff1 ,ann4 d4 ,chem41 #ahgc1 #agj1 #gc4 and by the results of hydrolysis which has yielded up to #ajd per cent4 anhydrous gallic acid fiom tannin ,footnote3 ,sisley1 ,bull4 ,soc4 ,chim4 #aiji1 #e1 #gbg4 ,of the three classes of isomeric anhydrides which can be formed from hydroxybenzoic acids1 the chemistry of the natural tannins is only concerned with the class comprising the ester anhydrides4 ,if the carboxyl of the first molecule combines with a hydroxyl of the second molecule 7ester formation71 then a substance possessing character similar to that of a hydroxybenzoic acid is formed1 which is capable of combining up with a further molecule in the same way4 ,it is natural to assume that this ester form is much more prevalent in ,nature than a combination of two carboxyls by the elimination of water4 ,from the point of view of the chemistry of the tannins1 therefore1 the starting-point would naturally be that of synthesising the ester anhydrides of hydroxybenzoic acids4 ,amongst the small number of synthetically prepared ester anhydrides of hydroxybenzoic acids1 a few occur exhibiting the properties of the natural tannoids4 ,in order to simplify the terminology of these substances1 ,fischer ,footnote3 ,liebig's ,ann41 #aiaj1 #cgb1 #ce4 proposed the name ,depsides from ,greek3 depheiv to tan4 ,in analogy with peptides and saccharides1 the names di-1 tri-1 and polydepsides of hydroxybenzoic acids would be suitable for these substances4 ,the principles underlying the synthesis of depsides are the following3--,if the chlorides of carbomethoxy 7or carbethoxy7 hydroxybenzoic acids are coupled with the sodium salts of hydroxybenzoic acids1 esters are formed1 e4g41 ,,ch#c;,,co ,o4,o4,c#f;,h#d4;,,co4,cl ,na,o4,c#f;,h#d4;,,coo4,na ,na,cl ,,ch#c4;,,coo4,o4,c#f;,h#d4;,,co4,o4,c#f ;,h#d4;,,coo4,na ,on gently saponifying the esters1 these are converted into the corresponding hydroxy derivatives-- ,,oh4,c#f;,h#d4;,,co4,o4,c#f;,h#d4;,,coo h ,according to ,fischer and ,freudenberg1 ,footnote3 ,liebig's ,ann41 #aiji1 #cgb1 #cb4 this method possesses the following advantages3-- #a4 ,the synthesis takes place at low temperatures1 so that any intramolecular rearrangements are improbable4 #b4 ,the composition of the substances is controlled by the intermediary compounds1 the carboalkyloxy derivatives4 #c4 ,the synthesis permits of more definite evidence as regards the structure of the resulting compounds4 #d4 ,the substances obtained are easily purified4 ,depsides produced in this manner are by no means new1 and were obtained by ,klepl by simply heating p-hydroxy-benzoic acid 7cf4 ,introduction1 p4 #d74 ,this simple procedure1 however1 is not applicable to most other hydroxybenzoic acids which are decomposed at the high temperature necessary to induce reaction4 ,lowe and ,schiff 7loc4 cit47 have obtained products similar to tannins1 the latter investigator by removing the elements of water from gallic acid1 protocatechuic acid1 salicylic acid1 m-hydroxybenzoic acid1 cresotinic acid1 phloretinic acid1 and pyrogallolcarboxylic acid4 ,these depsides1 however1 are amorphous substances1 and it is hence difficult to substantiate their homogeneity4 ,carbomethoxylation of ,hydroxybenzoic ,acids ,amongst other compounds chlorphydroxybenzoic acid is used in the preparation of the materials employed in the synthesis of depsides2 the free phenolic group1 however1 exerts a disturbing influence when aromatic acids are acted upon by phosphorus chloride1 and another group1 which can subsequently be easily removed1 must therefore be introduced to cover the disturbing influence referred to4 ,for this purpose1 ,fischer ,footnote3 ,ber41 #aijh1 #da1 #bhfj4 chose the carbomethoxy group1 and this investigator succeeded1 by the action of chlorocarbonic alkyl ester and alkali upon hydroxybenzoic acid in cold aqueous solution1 in obtaining substances with the properties required4 ,footnote3 ,ber41 #aijh1 #da1 #bhge4 ,in such substances 7e4g41 salicylic acid7 where the hydroxyl occupies the ortho-position to the carboxyl1 complete carbomethoxylation does not take place1 whereas the m- or p- positions offer no hindrance4 ,in the case of the o-position1 however1 the action of chlorocarbonic alkyl ester is successfully assisted by the presence of dimethylaniline in an inert solvent1 e4g41 benzene4,footnote3 ,u4,s4 ,pat1 #a1fci1agd1 #ab1 xii41 #ahii4 ,the difficulty encountered by the o-position is eliminated when the carboxyl is not directly linked to the benzene nucleus1 e4g41 o-cumaric acid4 ,many hydroxybenzoic acids require an excess of chlorocarbonic methyl ester1 which then also1 to some extent1 attacks the carboxyl group2 but on dissolving the product in acetone and treating it with bicarbonate the carboxyl group as such is again restored without splitting off the carbomethoxy group4,footnote3 ,ber41 #aiac1 #df1 #bdjj4 ,in this way all hydroxybenzoic acids may be carbomethoxylated4 ,footnote3 ,ibid41 #aijh1 #da1 #bhgg1 #bhha1 #bhhb2 #aiji1 #db1 #bbf1 #bah1 #bbc1 #bbe2 ,liebig's ,ann41 #aiab1 #cia1 #ceg1 #cff2 ,ber41 #aiac1 #df1 #aade1 #bcij1 #bdjj4 ,the carbomethoxy group is easily removed by excess of aqueous alkali in the cold1 and is also partially removed when insufficient alkali is present2 the latter fact is of importance in the synthesis of didepsides4 ,chlorides of ,carbomethoxyhydroxybenzoic ,acids ,the chlorides of these compounds are obtained when phosphorus pentachloride is allowed to act upon the acids1 and are as a rule crystalline4 ,for the purpose of synthesis they may be employed as follows3 #a4 ,they readily form esters with alcohols1 which on subsequent saponification with alkali are converted into the esters of the free hydroxybenzoic acids4 #b4 ,the chlorides interact energetically with esters of amino-acids1 and may be coupled with amino-acids in aqueous alkaline solution4 ,on subsequently removing the carbo-methoxy group derivatives of hydroxybenzoic acids are obtained1 e4g41 ,,ch#c4;,,co#b4,o4,c#f;,h#d4;,,co4,cl #b,,nh#b;,,ch#b4;,,co4,c#b;,h#e ,,nh#b4;,,ch#b4;,,co#b4;,c#b;,h#e ,h,cl ,,ch#c4;,,co#b4,o4,c#f;,h#d ,,co4,,nh4,,ch#b;,,co#b;,c#b;,h#e4 ,,ch#c4;,,co#b4,o4,c#f;,h#d4;,,co4,,nh4, ,ch#b4;,,co#b4;,c#b;,h#e #c,na,o,h ,na#b;,,co#c ,c#b;,h#e,,oh ,,ch#c,,oh ,,ho4,c#f;,h#d4;,,co4,,nh4,,ch#b4;,c,o,o ,na4 #c4 ,in the presence of ,al,cl#c the chlorides easily combine with benzene1 and on removing the carbomethoxy group unsymmetrical hydroxy derivatives of benzophenone are formed3-- ,,ch#c4;,,co#b4,o4,c#f;,h#d4;,,co4,cl ,c#f;,h#f ,,ch#c4;,,co#b4,o4,c#f;,h#d4;,,co4,c#f;, h#e ,h,cl ,,ch#c4;,,co#b4,o4,c#f;,h#d4;,,co4,c#f;, h#e #c,na,o,h ,na,o4,c#f;,h#d4;,,co4,c#f;,h#e ,na#c;,,co#c ,,ch#c,,oh ,h#b,o #d4 ,the chlorides may be coupled with free hydroxybenzoic acids1 and on removing the carbomethoxy group didepsides are obtained4 ,repetition of these operations yields tri- and tetradepsides4 ,preparation of ,didepsides ,a simple application of these syntheses is offered by p-hydroxybenzoic acid4 ,when the chloride of its carbomethoxy derivative is allowed to interact with p-hydroxybenzoic acid in aqueous alkaline solution1 in the cold1 the alkali salt of carbomethoxy-p-hydroxybenzoic acid is formed3--,footnote #a3 ,ber41 #aiji1 #db1 #baf4 ,,ch#c4;,,co#b4,o4,c#f;,h#d4;,,co4,cl ,na,o4,c#f;,h#d4;,c,o,o,na ,,ch#c4;,,co#b4,o4,c#f;,h#d4;,,co#b4;,c# f;,h#d4;,,co#b4,na ,na,cl4 ,being sparingly soluble1 the salt in this case is readily deposited as crystals1 but is readily converted into the free acid by hydrochloric acid4 ,in most other cases1 however1 the alkali salts are easily soluble and the aqueous solution is then directly acidified with a mineral acid4 ,the chlorides1 being for the most part solids1 the mode of procedure is as follows3--the hydroxybenzoic acid required for coupling is dissolved in normal or double-normal alkali 7the volume calculated per molecule acid71 a little acetone added1 and the mixture well cooled2 a further molecule of #b,n caustic soda and the chloride 7,i molecule7 dissolved in dry acetone are added in small portions1 whilst stirring1 to the mixture4 ,in spite of the low temperature the coupling proceeds quickly and the sparingly soluble product can in most cases be precipitated from the solution by acidifying and diluting with water4 ,in case of more easily soluble coupling products the acetone is driven off under reduced pressure or the liquid acidified and diluted1 and the substance extracted with ether4 ,instead of alkali1 dimethylaniline may be employed1 with the exclusion of water as a solvent for the purpose of coupling4 ,another suitable method of obtaining o-didepsides is that of treating o-hydroxybenzoic acids with phosphorus trichloride and dimethylaniline 7e4g41 synthesis of disalicylic acid1 ,boehringer ,sons74,footnote3 ,ger4 ,pat41 #baa1djc4 ,the carbomethoxy derivatives of the depsides are as a rule crystalline substances of distinct acidic character1 and decompose alkaline carbonates4 ,the elimination of the carbomethoxy group may be brought about by dilute alkaline solutions in the cold1 or by aqueous ammonia4 ,if the depside formed is so stable as to resist the action of alkali for several hours1 the use of the latter is very convenient for the purpose required4 ,the substance is dissolved directly in sufficient normal alkali to neutralise the carboxyl group and a further #b molecules of caustic soda for each carbomethoxy group to be eliminated are added4 ,the temperature should be about #bj ,c41 when the reaction as a rule is completed after one-half to three-quarters of an hour4 ,it is usual1 however1 to use an aqueous ammonia solution in considerable excess1 whereby the temperature should again be about #bj ,c41 and the solution of ammonia normal or half normal4 ,the didepsides so far investigated are crystalline bodies1 sparingly soluble in cold water2 they--as a rule--decompose when fused1 possess acid reaction1 and are dissolved by bicarbonates4 ,on account of the presence of a free phenolic group they give a coloration with ferric chloride2 if the phenolic group occupies the o-position to carboxyl1 the coloration with ferric chloride is red or bluish-violet ,excess of dilute alkali resolved all didepsides into their components at ordinary temperatures4 ,the didepsides of gallic1 proto-catechuic1 gentisinic1 and ,greek3 b-resorcylic acids precipitate gelatine and quinine acetate1 and in this respect approach the natural tannins4 ,the following summary gives an account of depsides which have been prepared synthetically or which occur naturally3--,footnote #a3 ,ber41 #aijh1 #da1 #bhhh2 #aiji1 #db1 #bag2 #aiac1 #de1 #bgah2 #aiac1 #df1 #aacj1 #bcif1 #aada1 #aadc2 ,liebig's ,ann41 #chd1 #bcj1 #bcc1 #bch2 #cia1 #cef1 #cfb4 ,di-p-hydroxybenzoic acid4 ,di-m-hydroxybenzoic acid4 ,disalicylic acid4 ,diprotocatechuic acid4 ,digentisinic acid4 ,di-,greek3 b-resorcylic acid4 p-,diorsellic acid4 o-,diorsellic acid4 m-,digallic acid4 ,disyringic acid4 ,di-o-cumaric acid4 ,diferulic acid4 ,di-,greek3 b-hydroxynaphthoic acid4 p-,hydroxybenzoyl-m-hydroxybenzoic acid4 m-,hydroxybenzoyl-p-hydroxybenzoic acid4 ,salicyl-p-hydroxybenzoic acid1 ,vanilloyl-p-hydroxybenzoic acid4 ,feruloyl-p-hydroxybenzoic acid4 ,greek3 a-,hydroxynaphthoyl-p-hydroxybenzoic acid4 ,orsellinoyl-p-hydroxybenzoic acid4 ,protocatechuyl-p-hydroxybenzoic acid4 ,galloyl-p-hydroxybenzoic acid4 ,pyrogallolcarboy p-hydroxybenzoic acid4 ,syringoyl-p-hydroxybenzoic acid4 p-,hydroxybenzoyl-syringic acid4 ,pentamethyl-m-digallic acid4 ,pentamethyl-p-digallic acid4 ,vanilloyl vanillin4 ,preparation of ,tridepsides ,monohydroxybenzoic acids allow theoretically of tri-depsides of the type ,,ho4,c#f;,h#d;,,coo4,c#f;,h#d4;,,coo4,c #f;,h#d4;,,cooh only2 if1 on the other hand1 di- or trihydroxybenzoic acids are dealt with1 two formulae are possible1 viz43-- ,,ho4,c#f;,h#d4;,,coo ,c#f;,h#c4;,,cooh ,,ho4,c#f;,h#d4;,,coo ,of the former type1 two compounds are known1 i4e41 di-p-hydroxybenzoyl-p-hydroxybenzoic acid and vanilloyl-p-hydroxybenzoyl-p-hydroxybenz oic acid-- ,,ho ,c#f;,h#c4;,,coo4,c#f;,h#d4;,,coo4,c#f;, h#d4;,,cooh ,,ch#c,o ,the first named of these two compounds was obtained by ,klepl1 in addition to the didepside1 by heating p-hydroxybenzoic acid4 ,fischer and ,freudenberg obtained a beautifully crystalline form in the following way3 carbethoxyhydroxy-benzoyl chloride was coupled with p-hydroxybenzoyl-p-hydroxybenzoic acid in alkaline solution1 the compound dissolved in a mixture of pyridine and acetone1 and ammonia added for the purpose of removing the carbethoxy group4 ,the tridepside was then obtained as long needles by re-dissolving in acetone4 ,both tridepsides melt well above #bjj ,c41 are practically insoluble in water1 and are but sparingly soluble in practically all organic solvents4 ,in alcoholic solution they give colour reaction with ferric chloride similar to those given by p-hydroxybenzoic acids4 ,preparation of ,tetradepsides ,footnote3 ,fischer and ,freudenberg1 ,liebig's ,ann41 #aiaj1 #cgb1 #cb4 ,here1 again1 two forms are known1 e4g41 tri-p-hydroxybenzoyl-p-hydroxybenzoic acid-- ,,ho4,c#e;,h#d4;,,coo4,c#f;,h#d4;,,coo4, c#f;,h#d;,,coo4,c#f;,h#d ,,cooh and vanilloyl-di-p-hydroxybenzoyl-p-hydroxyb enzoic acid-- ,,ho ,c#f;,h#c4;,,coo4,c#f;,h#d4;,,coo4,c#f;, h#d4;,,coo4,c#f;,h#d4;,,cooh ,,ch#c,o ,the former has been prepared from carbethoxyhydroxy-benzoyl-p-hydroxybenzo yl chloride and p-hydroxybenzoyl-p-hydroxybenzoic acid in alkaline solution2 the second tetradepside was prepared from carbomethoxyvanilloyl-p-hydroxybenzoyl chloride and p-hydroxybenzoyl-p-hydroxy-benzoic acid4 ,the preparation of these compounds is rendered difficult by the slight solubility of the substances and their slight affinities for entering into reaction4 ,both tetradepsides were obtained in crystalline form1 and are but very little soluble in most organic solvents4 ,they decompose on being fused4 ,tannoid ,substances of the ,tannin ,type ,the preparation of pentagalloyl glucose has proved this compound to be nearly identical with tannin obtained from galls 7tannin72 a few other natural tannins belong to this type which ,fischer terms acyl compounds of sugar with hydroxybenzoic acids4 ,the method of preparation employed in the synthesis of pentagalloyl glucose may be easily applied to other hydroxybenzoic acids1 e4g4 pentap-hydroxybenzoyl glucose ,footnote3 ,fischer and ,freudenberg1 ,ber41 #aiab1 #de1 #icc4 was prepared in this way4 ,similar characteristics are exhibited by pentasalicylo glucose4 ,mention must also be made of the corresponding derivative of pyruvic acid and the compound with pyrogallolcarboxylic acid1 penta-pyrogallolcarboylglucose4 ,footnote3 ,fischer and ,rapoport1 ,ber41 #aiac1 #df1 #bcig4 ,the latter is isomeric with pentagalloyl glucose and possesses similar properties2 there is1 however1 a vast difference in the solubility of the two4 ,whereas the galloyl compound is easily soluble in cold water1 its isomer is hardly soluble in hot1 and completely insoluble in cold water4 ,considering the very similar structure of these two tannins1 such differences appear surprising1 but an analogy may be readily found in the existence of colloidal solutions of tannin and the 7nearly7 identical pentagalloyl glucose4 ,these properties clearly show how dependent is the colloidal state on small differences in the structure of two substances4 ,on the other hand1 the formation of hydrosols is of the greatest importance relatively to the part played by these substances in ,nature as well as relating to their chemical characteristics2 thus it is extremely difficult to make a solution of penta-pyrogallolcarboyl-glucose1 at the same time ascertaining its astringent taste and its property of precipitating gelatine4 ,the experience gained by the methyl glucosides makes it exceedingly probable that the simpler polyhydric alcohols also are suitable substances to employ in these syntheses2 as a matter of fact1 glycerol has been condensed with gallic acid4 ,footnote3 ,fischer and ,freudenberg1 ,ber41 #aiab1 #de1 #ice4 ,one of the chief characteristics of synthetic tannins is their high molecular weight2 for instance1 the molecular weight of penta-tricarbomethoxygalloyl-glucose is #a1haj1 that of penta-pentamethyl-m-digalloyl-glucose #b1jea4 ,employing gallic acid derivatives1 especially the tribenzoyl compounds1 coupled with glucose1 e4g41 mannite1 yielded a neutral ester of molecular weight #b1ifg4 ,the determination of the elementary composition of compounds of high molecular weight is greatly facilitated by employing their halogen derivatives2 so1 for instance1 is p iodophenyl maltosazone very suitable4 ,coupling the latter with tribenzoylgalloyl chloride yielded hepta-tribenzoyl-galloyl-p-iodophenyl maltosazone1 the structure of which is represented by-- ,,ch3,n#b;,h4,c#f;,h#d;,i ,c3,n#b;,h4,c#f;,h#d;,i ,,ch4,o4,r ,r ,,co4,c#f;,h#b7,o4,,co4,c#f;,h#f7b ,,ch4,o4,r ,,ch4,o4,r ,r ,r ,r ,r ,o ,o ,o ,o ,,ch#b4,o4,,ch4,,ch4,,ch4,,ch4,,ch4,,ch# b ---,o--- ,the molecular weight of this substance is #d1jba1 and probably represents the highest molecular organic body obtained in any chemical synthesis4 ,from a physiological standpoint the recognition of tannins as esters of glucose and hydroxybenzoic acids1 possessing characteristics similar to those of tannin1 is of great importance4 ,especially interesting appears the fact of plants utilising sugars for the esterification of acids1 just as glycerol or monohydric alcohols may be employed for the same purpose4 ,free acids1 as a rule1 are only tolerated in certain parts of the organism1 the latter usually striving to neutralise acidic groups which may be brought about by salt formation2 formation of amino compounds 7proteins7 or esterification 7fats72 and1 lastly1 esterformation by means of sugars4 ,why ,nature should always build up substances of very complex constitution can only be explained by biochemical investigations1 but it may1 at any rate1 be assumed that by this means any substance poisonous to the living organism is rendered inactive4 ,the function of the tannins present in plants may thus be explained2 if1 for instance1 phenols are formed by the oxidation of corresponding sugars1 ,footnote3 ,mielke1 ,ueber die ,stellung der ,gerbstoffe im ,stoffwechsel der ,pflanzen 7,hamburg1 #ahic74 the poisonous character of the former would be lessened by the introduction of the carbonic acid esters and subsequent coupling of the substances 7depside formation74 ,the depsides thus formed would serve as vehicle of the sugars and transport the migrating tannins1 ,footnote3 ,kraus1 ,grundlinien zu einer ,physiologie der ,gerbstoffe 7#ahhi74 and1 after subsequent deposition of the sugars1 would then be eliminated from the plant organism1 either by oxidation into ellagic acid and phlobaphenes or by condensation with the formation of cork4 ,diagrammatically1 the following would represent the physiology of the tannins3--,footnote3 ,nierenstein1 ,chemie der ,gerbstoffe 7,stuttgart1 #aiaj74 ,sugar--,phenol--,hydroxybenzoic ,acid--,depside-- ,phlobaphene --,migrating ,depside--,glucoside--,free ,depside---,ellagic ,acid ,cork4 ,illustration3 ,chart ,showing the ,decomposition of ,products of ,tannin4 ,,section ,,ii ,,synthesis ,,of ,,tanning ,,matters #a4 ,,aromatic ,,sulphonic ,,acids ,in organic chemistry distinction is made between sulphonic acids of the aliphatic and the aromatic series1 the characteristic group of these acids being the so-called sulphonic acid group1 ,,hso#c4 ,when sulphides or mercaptans in glacial acetic acid solution are heated with permanganate1 the resulting sulphonic acid compounds exhibit great similarity to compounds containing free carboxyl groups4 ,the sulphonic acid group may also be directly introduced either by concentrated1 or by fuming sulphuric acid1 or by elimination of halogen by the action of sodium or silver sulphite on the halogen derivatives of the aliphatic compounds4 ,saturated hydrocarbons do not react with sulphur trioxide1 but unsaturated hydrocarbons are readily attacked by ,,so#c4 ,similarly1 halogenated compounds and alcohols react with concentrated or fuming sulphuric acid forming sulphonic and hydrosulphonic acids respectively4 ,the aromatic compounds form1 as a rule1 sulphonic acids with much greater facility4 ,benzene1 for instance1 is easily converted into the m-disulphonic acid by gently heating with fuming sulphuric acid2 stronger heating converts the m- into the p-disulphonic acid1 and at #aij ,c4 the trisulphonic acid is formed4 ,toluene treated with fuming sulphuric acid first yields o- and p-sulphonic acids1 finally o- and p-disulphonic acids1 ethylbenzene at the boiling point p-ethylbenzene-sulphonic acid4 ,of the three isomeric xylenes o- and m-xylene dissolve in concentrated1 p-xylene in fuming sulphuric acid only4 ,the action of sulphuric acid on naphthalene is stronger even than on benzene4 ,equal parts of naphthalene and sulphuric acid heated to #ajj ,c4 yield #hj per cent4 ,greek3 a and #bj per cent4 ,greek3 b-monosulphonic acid4 ,at #afj-agj;,c4 #be per cent ,greek3 a- and #ge per cent4 ,greek3 b-sulphonic acid is formed1 and at higher temperatures ,greek3 b-monosulphonic acid only4 ,if1 on the other hand1 #h parts of naphthalene are heated with #c parts of concentrated sulphuric acid to #ahj ,c41 two different naphthyldisulphonic acids are obtained4 ,complete solution of the substance in sulphuric acid is1 generally speaking1 a criterion of complete sulphonation4 ,a completely sulphonated compound should remain clear on dilution with water1 or1 in case precipitation occurs1 the precipitate should be completely soluble in alkali or ammonia4 ,it is necessary to submit the product to this test1 since many organic substances are soluble in concentrated sulphuric acid without undergoing any alteration in composition4 ,phosphoruspentoxide or potassium sulphate considerably increase the sulphonating property exhibited by fuming sulphuric acid4 ,the separation of the sulphonic acids from sulphuric acid is effected by salting out the former with common salt1 or by removing the sulphuric acid with calcium1 barium1 or lead salts1 provided that the sulphonic acid salts of these metals are soluble in water4 ,the sulphonic acid1 in its chemically pure state1 is best obtained from its crystalline barium salts1 which are decomposed with the equivalent of sulphuric acid2 another way is to decompose the calcium salts of the sulphonic acids with oxalic acid4 ,the sulphonic acids are frequently hygroscopic and are easily soluble in water2 the majority of their barium and lead salts are also soluble in water4 ,the sulphonic acids are insoluble in ether4 ,the halogens do not easily react with sulphonic acids1 but when they do they usually replace the sulphonic acid group4 ,in order to prepare the halogen substitution products1 therefore1 use is made of sulphonic chlorides4 ,the latter are obtained by the action of chlorosulphonic acid on aromatic hydrocarbons2 a simpler method1 however1 is to treat the dry alkali sulphonates with phosphorus pentachloride-- ,c#f;,h#e,,so#c,na ,p,cl#e ,c#f;,h#e,,so#b4;,cl ,na,cl ,p,o,cl#c ,derivatives of sulphonic chlorides are sulphonamides1 which are easily prepared from the former by grinding with ammonium carbonate-- ,c#f;,h#e,,so#b4;,cl 7,,nh#d7b;,,co#c ,c#f;,h#e4,,so#b4,,nh#b ,,nh#d;,cl ,,co#b ,h#b,o ,sulphonic chlorides react with alkaline sulphides to form thiosulphonic acids-- ,c#f;,h#e,,so#b4;,cl ,k#b,s ,c#f;,h#e,,so#b4,,sk ,k,cl ,sulphonic chlorides1 dissolved in ether1 yield sulphinic acids on reduction with zinc dust or metallic sodium-- ,c#f;,h#e,,so#b4;,cl ,h#b ,c#f;,h#e,,so#b4;,h ,h,cl ,in the sulphonic acid compounds it is assumed that the sulphur is hexavalent1 and it is hence possible to consider the sulphones to be esters of sulphinic acid4 ,o ,r--,s,o --,h ,the sulphones are mostly solid bodies1 which soften prior to melting when heated4 ,they are very stable towards chemical reagents2 for instance1 saponification of a mono-sulphone very rarely yields sulphinic acid4 ,if a hydroxyl is substituted for a hydrogen atom in the aromatic hydrocarbons1 the action of sulphuric acid is greatly facilitated2 thus1 by merely mixing phenol with sulphuric acid1 the sulphonic acid is at once formed1 whereby1 in the cold1 o-phenolsulphonic acid prevails which on heating for some time to #ajj-aaj ,c4 is completely converted into p-phenolsulphonic acid4 ,in the absence of free sulphuric acid the conversion of o- into p-phenolsulphonic acid is brought about by heating the aqueous solution4 ,phenol-#b1d-;disulphonic acid is prepared from o- or p-phenolsulphonic acid1 whereas phenol-#b1d1f-trisulphonic acid is prepared directly from phenol by heating with concentrated sulphuric acid in presence of phosphorus pentoxide4 ,phenolsulphonic acids are also obtained by fusing benzenedisulphonic acid with alkali4 ,cresol is not so easily sulphonated as is phenol2 o-cresol when heated eight to ten hours at #ij ,c4 with one and one-half times its weight of concentrated sulphuric acid1 yields o-cresol-p-sulphonic acid4 ,the phenolsulphonic acids are strong1 rather stable acids2 their alcoholic hydroxyl-hydrogen atom may1 similarly to that of the phenols1 be substituted by a metal or an alkyl radical4 ,from ,greek3 a- and ,greek3 b-naphthol a number of sulphonic acids may easily be prepared2 viz41 mono-1 di-1 and trisulphonic acids4 ,nearly all these acids are important as basic materials in the dyestuff industry1 especially #b1f-;,greek3 b-naphtholmonosulphonic acid 7,s-acid71 #b1c1f-;,greek3 b-naphtholdisulphonic acid 7,r-acid7 and #b1f1h-;,greek3 b-naphtholdisulphonic acid 7,g-acid74 #b4 ,condensation of ,phenols ,phenolsulphonic acids exhibit pronounced tendencies to condensation1 for which purpose ,a4 v4 ,baeyer 7#ahgb7 employed aldehydes4 ,the reaction is rather violent1 and yields1 in addition to well-defined crystalline substances1 amorphous bodies resembling rosins4 ,in addition to formaldehyde1 paraformaldehyde1 trioxymethylene1 methylal1 hexamethylene-tetramine1 and other substances containing a reactive methylene group1 as well as acetaldehyde1 benzaldehyde and other aldehydes may be employed to induce reaction4 ,a number of these condensation products are derivatives of diphenylamine or hydroxybenzyl alcohols4 ,when the latter are heated1 either by themselves or in presence of acids1 anhydrides and polymerisation products are formed producing hard1 brittle1 fusible substances1 insoluble in water but fairly soluble in organic solvents4 ,the same substances are formed when phenols are condensed with formaldehyde1 especially in the presence of acid contact substances and excess of phenol by sufficiently long heating at certain temperatures4 ,the substances referred to are termed ,novolak3 similar to these are the so-called ,resols1 insoluble and non-fusible substances1 very resistant to chemical and physical action4 ,another member of the series is the so-called ,bakelite or ,resitol1 which does not fuse but softens when heated and swells in organic solvents4 ,the ultimate product of this class of substances is ,resit which is obtained when concentrated hydrochloric acid is allowed to act upon a mixture of phenol and formaldehyde2 the temperature rises spontaneously1 and a hard1 porous1 insoluble mass of great resistance is obtained4 ,by heating resols1 resitols are formed which1 on further heating1 are finally converted into resits4 ,footnote3 ,ber41 #ahib1 #be1 #cbac4 ,of all these products1 bakelite 7resitol7 has found the greatest industrial application2 in its purest form1 this substance is a nearly colourless or light yellow body of sp4 gr4 #a4be and1 being a poor conductor of heat and electricity1 constitutes an excellent insulating material2 it is exceedingly resistant towards most chemical reagents even in concentrated forms of the latter4 ,its pronounced refractivity1 and the ease with which it may be worked1 makes bakelite a favourite substitute for amber 7,ger4 ,pat1 #bhf1 #efh74 ,similarly1 the resols which can be easily moulded are used either as such or mixed with sand1 pulverised cork1 asbestos or wood1 and the moulded substances then converted into the more highly resistant bakelite by heating4 ,the constitution of these bodies no doubt depends largely on their method of preparation2 ,baekeland ,footnote3 ,chem4 ,ztg41 #aiac1 #gc1 #gcc4 considers resit a polymerised hydroxybenzylmethylene glycol anhydride2 ,raschig1 a diphenylmethane derivative 7e4g41 dihydroxydiphenylmethane alcohol72 ,wohl ,footnote3 ,ber41 #aiab1 #de1 #bjdf4 considers them polymerisation products of methylene derivatives of tautomeric phenol4 ,,ch,,ch ,h#b;,c3,c ,,co ,,ch,,ch ,note3 ,lower ,right ,,ch has double bond to ,,co ,this group possesses the characteristic property of being capable of converting animal hide into leather when suitably dissolved4 ,the author has dissolved a number of these water-insoluble condensation products in alkali and alcohol and was able to demonstrate their tanning effects on pelt2 bakelite is easily soluble in alkali2 a faintly alkaline solution partially precipitates gelatine1 and completely so when the alkali is neutralised4 ,this latter solution gives a dirty brown precipitate with iron salts4 ,these condensation products gained extraordinary importance for the tanning trade when ,stiasny ,footnote3 ,ger4 ,pat1 #bfb1eeh2 ,austr4 ,pat1 #eh1dje4 succeeded in preparing them in water-soluble form when they are enabled to directly exert their tannoid properties4 ,this may be done by acting upon two molecules of concentrated phenolsulphonic acid with one molecule of formaldehyde1 the temperature thereby not exceeding #ce;,c4 ,by condensation1 however1 considerable heat is liberated1 and hence the rise in temperature can only be limited by adding the diluted formaldehyde drop by drop1 whilst stirring and cooling1 to the phenolsulphonic acid4 ,the original letters patent is worded as follows3 #aj kilos each of crude phenol and sulphuric acid 7#ff ,b47 are heated with stirring for two hours at #aje-ajf;,c41 cooled to about #ce;,c41 and #dfc kilos #cj per cent4 formaldehyde added during three hours1 the temperature thereby not exceeding #ce;,c42 the stirring is continued for a couple of hours after the final addition of formaldehyde4 ,this yields about #bd kilos of the crude condensation product4 ,on a commercial scale1 however1 cresol 7cresylic acid7 is substituted for phenol4 ,there are three isomers of cresol1 viz41 o-1 m-1 and p-cresol1 and it was naturally of interest to investigate whether one or the other of the isomers exerted any particular influence on the properties of the final product4 ,it was found1 however1 that condensation products from the three isomers were distinguishable from one another neither in physical nor in tannoid properties4 ,it is hence possible to employ crude cresol1 which contains varying quantities of the o-1 m-1 and p-compounds1 in the manufacture of these tanning matters4 ,footnote3 ,gen ,pat1 #bia1deg4 ,the tar obtained from the ,rochling coal-gas generator contains considerable quantities of phenols 7,b4,p4#bjj-bej;,c471 and the author has protected the use of these for the production of synthetic tannins by ,ger4 ,pat1 #bfb1eeh4 ,a deep brown viscous mass is obtained which1 when partly neutralised1 yields similar results to those given by the product above referred to4 ,it may be anticipated that by analogy from the chemical reactions taking place in the condensation of phenols on the one hand and cresolsulphonic acid on the other1 that all other homologues of phenol1 its polyvalent derivatives1 substitution products and acids1 would yield similar condensation products4 ,the particular position occupied by the aromatic hydroxy compounds in the chemistry of substance possessing tannoid character is not only evidenced by the natural classification of the tannins1 tannin derivatives1 and decomposition products so far isolated and investigated1 but also by other chemical behaviour shown by these substances4 ,meunier and ,seyewetz ,footnote3,collegium1 #aijh1 #cae1 #aie41 for example1 were able to show that phenol1 p-aminophenol1 chlorophenol1 trinitrophenol1 catechol1 resorcinol1 hydroquinone1 monochlorohydroquinone1 orcinol1 pyrogallol1 and gallotannic acid precipitate gelatine from its aqueous solution1 that is1 to a certain extent possess tanning properties4 ,the author has extended this series somewhat and obtained the following results3-- ,relative ,behaviour ,towards ,substances ,gelatine4 ,hide ,powder4 ,pelt4 ,tribromophenol ,slight ppte4 ,tans ,surface tannage ,footnote3 ,in alcoholic solution o-,nitrophenol ,no ppte4 ,br-o-,nitrophenol ,slight ppte4 ,tribromopyrogallic ,ppte4 acid ,bromophloroglucinol ,no tannage ,galloflavine ,slight ppte4 ,bromosalicylic acid ,bromo-,greek3 b ,tans -naphthol ,footnote3 ,in alcoholic solution ,rosolic acid ,footnote3 ,in alcoholic solution ,gallic acid ,no ppte4 ,no tannage ,no tannage ,by the condensation of their sulphonic acids1 it may be demonstrated experimentally how the tannoid properties of nearly every member of the series are intensified4 ,investigattion in this direction1 however1 has not been systematically undertaken1 for which reason the author determined to examine this subject2 but the enormous number of samples required1 obtainable only with great difficulty during the war1 made it impossible to conclude completely the researches in this field4 ,what little has so far been done relatively to this subject should1 when collected1 indicate the way to be pursued in this wide field of investigation4 ,what follows will hence comprise the conversion of a few of the most important members of this series of substances into their methylene-condensation products with a brief discussion of the qualitative and tannoid reactions of the latter4 ,the didepside of phenolsulphonic acid is obtained by condensing carbomethoxyphenolsulphonic chloride with sodium phenolsulphonate in the presence of the calculated amount of caustic soda4 ,a product of the composition ,,ch#c4j4;,,coo4,c#f;,h#d,,so#b4j4;,c#f; ,h#d4,,so#c,na is first obtained1 which on saponification with soda yields the pure didepside-- ,,ho4,c#f;,h#d4,,so#b4;,c#f;,h#d4,,so#c4 ,na ,by acidifying the concentrated solution the didepside is obtained as a white crystalline substance2 a solution of which precipitates gelatine without1 however1 exhibiting any tanning effect upon animal hide4 ,if1 on the other hand1 the above ester is converted into the chloride ,,ch#c,o4,,coo4,c#d;,h#d,,so#b4,o4,c#f;, h#d4,,so#b;,cl by treatment with ,p,cl#e1 and the chloride thus obtained further condensed with sodium phenolsulphonate1 saponified1 and the solution acidified1 the pure tridepside ,,ho4,c#f;,h#d4,,so#b4,o4,c#f;,h#d4,,so# b4,o4,c#f;,h#d4,,so#c,na is precipitated as white crystalline needles which not only precipitate gelatine1 but are capable of converting animal hide into leather4,footnote3 ,chem4 ,ztg41 #aiai1 #dc1 #cah4 ,of the class of hydroxy-cymenes thymol1 ,c#f;,h#c4;,,ch#c4;,c#c;,h#g,,oh1 was converted into the water-soluble sulphonic acid by warming with concentrated sulphuric acid at #ej ,c41 the sulphonic acid being subsequently easily condensed with formaldehyde by slightly heating the mixture4 ,the condensation product thus obtained is a viscous brown mass which is easily soluble in water1 precipitates gelatine completely1 gives a bluish-black coloration with iron salts1 and gives a precipitate with aniline hydrochloride4 ,to investigate its tannoid properties1 the mixture was brought to the acidity #a gm #aj c4c4 ,n_/#aj ,na,o,h and a piece of bated calf skin was then introduced into a solution measuring about #b ,b4 ,after eighteen hours the pelt was nearly tanned through1 and a further twenty-four hours completed the tanning process1 after which a light fat-liquor was given4 ,the dried leather was brownish-grey in colour1 possessed soft and full feel and good tensile strength4 ,on account of their importance1 the three dihydroxybenzenes were examined with a view to test their suitability for conversion into tannoid substances4 o-,dihydroxybenzene1 catechol1 yields a sulphonic acid easily soluble in water1 which on the careful addition of formaldehyde assumes a blue colour4 ,the compound thus obtained may be heated to #ajj ,c41 without depositing insolubles4 ,a further addition of formaldehyde1 however1 results in the formation of a considerable quantity of insolubles whilst the liquid assumes a brown coloration4 ,if1 on the other hand1 the sulphonic acid is diluted with twice its volume of water1 formaldehyde added and the mixture heated on the water bath1 the liquid immediately turns brown1 the formaldehyde is completely fixed1 and a condensation product soluble in water results4 ,the latter gives a brownish-black coloration with ferric chloride1 completely precipitates gelatine1 but gives no opalescence with aniline hydrochloride4 ,tanning experiments with the partly neutralised 7#a gm4 #aj c4c4 ,n_/#aj ,na,o,h7 substance resulted in both grain and flesh being tanned with a black colour1 whereas the interior of the pelt was pickled 7white colour74 ,after a further forty-eight hours1 however1 the black colour penetrated the pelt1 and tannage was complete4 ,the washed and lightly fat-liquored leather was soft1 of full feel and good tensile strength1 and was greyish coloured throughout4 ,with regard to the black colour possessed by leathers tanned with synthetic tannins the following should be noted4 ,when sulphonating and especially when condensing substances1 black dyestuffs or very finely divided carbon in the colloidal state are often formed4 ,such a substance does not deposit the black particles1 even when filtered through kaolin1 and hence convert pelt into leather possessing black colour on the surface4 ,the hide in this case acts as a perfect filtration medium1 whereby the surface layers retaining the coloured particles assume their colour2 thus only the pure tanning matter enters into the interior1 which then1 according to the composition of the former1 imparts a colour varying from white to light brown to the inner layers4 m-,dihydroxybenzene1 resorcinol1 is also easily sulphonated by concentrated sulphuric acid1 the brownish-coloured sulphonic acid being easily soluble in water4 ,if the sulphonic acid is diluted with three times its volume of water1 cooled down1 a few drops of formaldehyde added and the mixture heated on the water bath to completely fix the formaldehyde1 and this process repeated till no more formaldehyde is taken up1 a brown water-soluble condensation product results1 the aqueous solution of which precipitates gelatine completely1 aniline hydrochloride only partly and which gives a deep blue colour with ferric chloride4 ,a piece of calf skin immersed in a solution of the partly neutralised 7as above7 product was tanned through in twenty-four hours2 when lightly fat-liquored1 the resulting leather possessed a yellowish-green colour and good tensile strength1 and was soft and full4 p-,dihydroxybenzene1 hydroquinone1 was converted into the water-soluble sulphonic acid by heating it with concentrated sulphuric acid at #ajj ,c42 the sulphonic acid1 mixed with formaldehyde at ordinary temperature1 immediately solidifies to a white mass1 which is soluble in water and which had completely fixed the formaldehyde4 ,if1 however1 this mass is heated for some time to #ajj;,c1 it assumes a light brown coloration and its solubility in water is diminished4 ,a slight excess of formaldehyde and the application of heat result in dark violet insoluble condensation products4 ,the aqueous solution precipitates gelatine1 gives a deep blue colour with ferric chloride1 but gives no precipitate with aniline hydrochloride2 on the other hand1 addition of potassium nitrite produces the yellow colour characteristic of hydroquinone4 ,the product effects a slower tannage 7seven days7 than the former product1 when a brown1 soft1 but rather empty leather of good tensile strength is obtained4 ,of the trihydroxybenzenes pyrogallol and phloroglucinol only were included in these investigations4 ,when pyrogallol is sulphonated with concentrated sulphuric acid a violet-coloured sulphonic acid1 soluble in water1 is obtained1 which1 when treated with formaldehyde first in the cold and then when heated1 yields a solid deep red-coloured mass1 which precipitates gelatine but not aniline hydrochloride1 and gives a blackish-brown colour with ferric chloride4 ,the partly neutralised substance in aqueous solution tans pelt in twenty-four hours with black colour on the surface only1 the intermediary layer being pickled 7white colour7 only1 but the black-coloured tanning matter ultimately penetrates the pelt1 which tanned through in seven days4 ,the resultant leather is coloured black throughout1 is full1 soft1 and possesses good tensile strength4 ,sulphonation of phloroglucinol succeeds at higher temperatures only1 the sulphonic acid being a solid which is scarcely soluble in water1 the latter then assuming a wine-red colour4 ,the condensation product--prepared as described for resorcinol1 but requiring higher temperature--is a brick-red powder1 insoluble in water4 ,the same end-product also seems to be obtained by simply heating the sulphonic acid at a higher temperature2 this also induces condensation with the formation of a reddish-brown mass insoluble in water4 ,it is1 of course1 impossible to attempt any tanning experiments with this product in aqueous solution2 attempts at dissolving the condensation product in alcohol proved barren of result1 since only traces of impurities accompanying the substance dissolved1 imparting a light reddish-brown colour to the solution4 ,in highly concentrated alcohol1 however1 the condensation product is somewhat soluble1 yielding a reddish-brown solution4 ,a piece of pelt introduced into the alcoholic solution was surface tanned only after forty-eight hours1 leaving the remainder of the pelt pickled2 extending the experiment over a further four days produced no change in the pelt4 ,the latter was therefore rinsed with water1 lightly fat-liquored and dried1 when a soft but empty leather of grey colour and good tensile strength was obtained4 ,it appears1 therefore1 to be a case of pseudo-tannage1 where an infinitesimal amount of synthetic tannin produces a tanning effect without1 however1 a true tannage being effected4 ,the ,elberfelder ,farbenfabriken have protected the use of the condensation products of di- and polyhydroxybenzenes by ,ger4 ,pat41 #bhb1cac2 owing to the high cost of the latter substances1 however1 it is doubtful whether synthetic tannins prepared from these materials would not be too expensive for any other than pharmaceutical purposes4 ,before leaving the phenols1 mention must be made of the quinones1 the use of which for tanning purposes was first protected by ,ger4 ,pat41 #bjf1ieg 7#cjth ,april #aijg74 ,according to this patent1 only #djj gm4 of quinone are required for the conversion into leather of #djj kilos pelt1 drum tannage being preferable4 ,during the process the leather first assumes a reddish colour1 changing through violet to brown2 its resistance to water1 acids1 and alkalies is said to be considerably greater than that exhibited by all other kinds of leather4 ,the chemistry of the quinone tannage has been investigated1 and an explanation given by ,thuau ,footnote3 ,collegium1 #aiji1 #cfc1 #baa4 assumes a reaction between the quinone and the amino groups of the hide protein with the formation of hydroquinone-- -,o ,,oh #b,r4,,nh#b #b;,c#h;,h#d ,c#f;,h#d ,c#f;,h#d7,o4,,nh4,r7#b -,o ,,oh 7,pelt47 7,leather47 ,fahrion has shown that1 during the tanning process1 the quinone loses its active oxygen1 and this can only be brought about by the amino group of the hide protein1 the amino group only being capable of effecting reduction of the quinone4 ,an analogy is here offered by dianilinoquinone4 ,a spent quinone liquor contains considerable amounts of hydroquinone4 ,the tannage may also be effected by exposing pelt saturated with hydroquinone to oxidation by the air4 ,the pelt1 which is unaltered by the hydroquinone bath1 on being removed from the latter1 and in the presence of alkali1 assumes a red colour at first1 which changes into violet1 blue1 and finally brown1 the pelt being thereby converted into a quinone-tanned leather4 ,it may be noted that quinone only effects pseudo-tannage2 quinone mixed with water deposits1 in time1 a black amorphous substance practically insoluble in water4 ,this substance is easily adsorbed by hide powder1 but is not capable of converting the latter into that insoluble form into which it is converted by the natural tannins4 ,amongst polyhydric alcohols1 the behaviour of the methyl ester of catechol1 guaiacol was investigated4 ,the sulphonic acid was prepared by heating guaiacol with concentrated sulphuric acid1 the resulting water-soluble product possessing a light1 brownish-green colour4 ,on condensing the sulphonic acid with formaldehyde1 the same precautions were observed as in the case of resorcinol1 but complete fixation of the formaldehyde could only be obtained by finally heating the product for a short time over a free flame1 at about #aje ,c4 ,condensation was indicated by the brownish appearance of the liquid4 ,no insoluble products were formed4 ,the condensation product easily dissolves in water1 the solution assuming a rich brown colour and exhibiting the following reactions3 gelatine is completely precipitated1 aniline hydrochloride produces opalescence1 and ferric chloride a deep brown coloration4 ,tannage1 with the partly neutralised product1 was rapid1 the pelt being nearly tanned through in twenty-four hours1 excepting a small white streak in the middle2 after a further twenty-four hours this streak had vanished1 and the completely tanned1 dark grey-coloured leather1 after washing1 fat-liquoring1 and drying1 was soft1 full1 and of good tensile strength1 very similar to the leather yielded by the catechol-condensation product4 ,of the nitro-compounds1 trinitrophenol1 ,c#f;,h#b7,,no#b7c,,oh 7picric acid71 was investigated4 ,if a concentrated solution of picric acid is brought into contact with pelt it will penetrate the latter completely in a few days2 it is1 however1 difficult to fat-liquor the resultant leather1 since the fat is absorbed only with difficulty4 ,if a pelt treated in this way be dried1 a soft but rather flat leather results1 the colour of which easily rubs off1 the leather also tasting intensely bitter4 ,these disagreeable qualities prevent a general use of this material for tanning purposes2 in spite of them1 however1 picric acid1 in admixture with boracic acid1 salicylic acid1 and glycerol1 is used in the production of the so-called transparent leather4 ,the latter is very flexible and possesses great tensile strength1 but loses the latter quality when exposed to heat1 and1 when stored1 also loses its flexibility4 ,by simply washing with water1 the leather is reconverted into pelt4 ,when picric acid is treated with hot sulphuric acid and formaldehyde gradually added1 a dark coloured water-soluble condensation product is formed which strongly precipitates gelatine4 ,exposed to the action of bromine1 the condensation product yields a mass which is insoluble in water4 ,experience has taught that the amino bodies--the basic ,n-derivatives of the phenols--do not yield substances possessing tannoid properties on condensation4 ,on account of their importance1 however1 a few have been included in this series of investigations4 ,aminobenzene1 ,c#f;,h#e,,nh#b1 aniline1 treated with sulphuric acid1 yields the water-soluble aniline sulphate1 which1 on cautious addition of formaldehyde1 yields a reddish-coloured gel1 insoluble in water1 in addition to a small volume of a reddish-yellow liquid4 ,the latter precipitates gelatine1 but is not capable of converting pelt into leather4 ,the insoluble gel is likewise insoluble in alcohol1 so that tanning experiments with this substance are excluded4 ,dimethylaniline1 ,c#f;,h#e,n7,,ch#c7b1 when treated with sulphuric acid1 yields a product soluble in water which neither reacts with nor fixes formaldehyde4 ,hence the substance does not precipitate gelatine4 ,if1 on the other hand1 nitrosodimethylaniline1 ,,no ,c#f;,h#d 7,,ch#c7b is sulphonated1 and the water-soluble sulphonation product heated with formaldehyde for some time1 the product remains soluble in water and precipitates gelatine4 ,no tanning effect could1 however1 be detected4 ,arylsulphaminoarylsulphonic acids and arylsulphoxyarylsulphonic acids precipitate gelatine but are devoid of tannoid character4 ,the latter is acquired by compounds belonging to this class containing two or more sulphamino groups1 or when they1 in addition to one sulphamino group1 contain a sulphoxy group and another sulphonic group4 ,according to ,ger4 ,pat41 #big1ahg 7,society oc ,chemical ,industry1 ,basle71 such compounds are obtained when1 for instance1 sodium sulphanilide in alkaline solution acts upon nitrotoluenesulphochloride1 and the resulting nitrotoluenesulphamino compound is subsequently reduced with acetic acid and iron4 ,the resulting aminotoluenesulphaminobenzenesulphonic acid is finally treated with p-toluenesulphonic chloride till the latter disappears4 ,a compound of the composition -----,,nh-----,,so#b----- ---,,nh--- ,v ,v ,v ,,so#b,na ,,ch#b is thereby obtained1 which1 when acidified1 is readily capable of being used for tanning purposes4 ,the intermediary product of the aminotoluenesulphaminobenzenesulphonic acid obtained by this process may again be employed for the purpose of reacting with one-half molecule soda and #a molecule nitrotoluenesulphonic chloride4 ,the following compound is obtained-- ---,,nh---,,so#b--- ---,,nh---,,so#b--- ,,ch#c v v ---,,nh---,,so#b--- v v ,,so#c,na ,,ch#c ,,ch#c ,if p-toluenesulphaminobenzenesulphonic chloride is condensed with sodium sulphanilide1 a compound1 ---,,so#b---,,nh--- ,na,s,o#c v v ---,,so#b---,,nh--- v ,,so#c,na is obtained which1 when acidified1 exhibits tannoid properties4 ,on condensing sodium phenolsulphonate with nitrotoluenesulphonic chloride1 reducing the condensation product and condensing the latter with p-toluenesulphonic chloride1 a compound similar to the above is obtained-- ---,o---,,so#b--- ,,ch#c v v ---,,nh---,,so#b--- v ,na,s,o#c ,,ch#c ,again1 a similar product is obtained when p-toluenesulphaminobenzenesulphonic chloride or its homologues or isomers are condensed with sodium-o-cresylsulphonate-- ---,,so#b---,,nh--- ,,so#c,na ,,ch#c v v ---,,so#b---,o--- v ,,ch#c ,the chloride of this compound may again be condensed1 for instance1 with sodium aminotoluenesulphaminobenzene-sulphonate 1 and yields the compound-- ---,,nh---,,so#b--- ---,,nh---,,so#b--- v v ---,,nh---,,so#b--- v v ,,ch ,na,s,o#c ,,ch#c ,the three latter compounds1 when dissolved in water and the solution acidified1 exert tanning action4 ,it is also possible to employ mixtures of arylsulphaminobenzylsulphonic acids in acidified aqueous solution for tanning purposes4 ,according to ,ger4 ,pat41 #big1ahh1 such mixtures are obtained by nitrating benzylchloride and heating with an equimolecular amount of sodium sulphite2 the sodium nitrobenzylsulphonate thus obtained is reduced to aminobenzylsulphonic acid with iron and acetic acid1 and finally condensed with the calculated amount of p-toluenesulphonic chloride4 ,a mixture o- and p-toluenesulphaminobenzylsulphonic acid ,footnote #a3 ,cf4 also ,ger4 ,pat1 #cai1gac and #cbj1fac4 thus results4 ,amongst aromatic alcohols the dihydric alcohols show characteristic behaviour2 the latter combine with sulphonic acids with the elimination of water1 condensation taking place without formaldehyde1 and the resulting products being soluble in water and possessing tannoid properties4 ,footnote #b3 ,ger4 ,pat41 #cjj1efg1 of #bjth ,september #aiag4 ,in addition to phenolic mono- and disulphonic acids 7and higher sulphonation compounds71 the homologues1 cresols1 xylenols1 and naphthols enter into reaction4 ,the two components condense with great ease1 liberating heat2 dilute solutions 7of the components7 are heated to about #ajj ,c41 the process being complete in a few minutes4 ,the products obtained are exceedingly pure and are easily crystallisable4 ,employing #a1 respectively #b1 molecules of sulphonic acid1 the reactions take place according to3-- ,,oh ,,ch#b4,,oh ,,oh ,,oh ,c#f;,h#d ,,ho4,c#f;,h#c ,h#b,o ,c#f;,h#c-;,,ch#b-;,c#f;,h#c ,,hso#c ,,ch#b4,,oh ,,hso#c ,,ch#b4,,oh ,,oh ,,oh ,,ch#b4,,oh ,,ch#b4;,c#f;,h#c ,c#f;,h#d ,,ho4,c#f;,h#c #b7;,h#b,o7 ,,ho4,c#f;,h#c ,,hso#c ,,hso#c ,,ch#b4,,oh ,,oh ,,ch#b4;,c#f;,h#c ,,hso#c ,,oh ,,ch#b4,,oh ,,oh ,,oh ,c#f;,h#c4;,,ch#c ,,ho4,c#f;,h#c ,h#b,o ,c#f;,h#b4;,,ch#c4;,,ch#b4;,c#f;,h#c ,,hso#c ,,ch#b4,,oh ,,hso#c ,,ch#b4,,oh ,,oh ,,oh ,,ch#b4,,oh ,,ch#b4;,c#f;,h#b4;,,ch#c ,c#f;,h#c4;,,ch#c ,,ho4,c#f;,h#c #b7;,h#b,o7 ,,ho4,c#f;,h#c ,,hso#c ,,hso#c ,,ch#b4,,oh ,,oh ,,ch#b4;,c#f;,h#b4;,,ch#c ,,hso#c ,,oh ,,ch#b4,,oh ,,oh ,,oh 7,c#aj7;,h#f ,,ho4,c#f;,h#c ,h#b,o 7,c#aj7;,h#e4;,,ch#b4;,c#f;,h#c ,,hso#c ,,ch#b4,,oh ,,hso#c ,,ch#b4,,oh ,,oh ,,oh ,,ch#b4,,oh ,,ch#b47;,c#aj7;,h#e 7,c#aj7;,h#f ,,ho4,c#f;,h#c #b7;,h#b,o7 ,,ho4,c#f;,h#c ,,hso#c ,,hso#c ,,ch#b4,,oh ,,oh ,,ch#b47;,c#aj7;,h#e ,,hso#c ,the condensation products above enumerated were tested with regard to their tanning power1 both non-neutralised and partly neutralised 7#a3aj1 #a3bj1 and #a3cj c4c4 ,n_/#aj ,na,o,h7 samples being examined4 ,in all cases rapid tannage was observed yielding firm and soft leathers of light brown colour and varying degrees of swollenness4 ,relatively to their reactions1 all the products strongly precipitate gelatine1 whereas only the condensation products of phenol1 cresol1 and xylenol derivatives give a characteristic coloration with iron salts4 ,the tannin contents of the non-neutralised condensation products lie between #gb-hj per cent4--figures which clearly indicate the purity and efficiency of these substances4 ,notable amongst aromatic acids is salicylic acid1 ,c#f;,h#d4,,oh4,,cooh1 which at higher temperatures is easily sulphonated with concentrated sulphuric acid2 the sulphonation product represents a white solid1 which easily dissolves in water forming a clear liquid4 ,the sulphonic acid1 when mixed with about one-third of its weight of water and heated to about #abj ,c41 is easily condensed with formaldehyde4 ,towards the end of the reaction1 considerable frothing sets in1 but in spite of the high temperature required by this reaction no insoluble bakelites are formed4 ,a reddish-brown fluid is obtained easily soluble in water1 to which it imparts a brown colour4 ,an aqueous solution of the product completely precipitates gelatine1 gives a strong opalescence with aniline hydrochloride and a deep violet coloration with ferric chloride4 ,neutralised as usual1 the product1 in a #c ,b solution1 converts pelt within three days into a white1 full leather of good tensile strength4 ,this process has been patented by the ,deutsch-,koloniale ,gerb und ,farbstoff ,gesellschaft 7,german-,colonial ,tanning and ,colour ,extracts ,ltd47 in ,karlsruhe1 the letters patent also including the ring homologues of salicylic acid4 ,similar results are obtained when cresotinic acid 7hydroxy-toluic acid71 ,,oh4,c#f;,h#c4;,,ch#c4;,,cooh1 is employed as base4 ,if the phenyl ester of salicylic acid1 ,salol1 ,,ho4,c#f;,h#d4;,,co4,o4,c#f;,h#e is sulphonated1 a product is obtained which is easily soluble in water1 but which is identified as a mixture of the sulphonation products of salicylic acid and phenol1 the salol being dissociated on sulphonation4 ,the temperature must not exceed #hj ,c4 by condensation with formaldehyde1 or insoluble bakelite will be formed from the phenol2 the aldehyde must also be added gradually4 ,an aqueous solution of the partly neutralised condensation product has a pronounced tanning effect on pelt1 and converts the latter into leather in one to two days2 the leather being very similar to that produced by the salicylic acid condensation product4 ,the qualitative reactions of the product in aqueous solution are the same as those given by the salicylic acid condensation product4 ,salicylic acid may1 however1 also be condensed with formaldehyde without first being sulphonated2 in this case1 a little hydrochloric acid should be present4 ,a product slightly soluble in water is obtained1 which may be looked upon as being methylenedisalicylic acid4 ,in alkaline solution it is easily soluble1 ,footnote #a3 ,its solubility in alcohol and alkalies renders this product an effective and cheap substitute for shellac4--,transl4 the liquid possessing an intensely bitter taste4 ,the sodium salt gives a deep violet coloration with ferric chloride1 a slight precipitate with gelatine1 and slight opalescence with aniline hydrochloride4 ,in contact with pelt1 however1 it exhibits no tanning effect1 but when dissolved in alcohol1 a pickling effect may be observed4 ,footnote #b3 ,a similar reaction is observable in the case of the sodium salts of ,,methylenedisalicylic acid brommated or iodised1 which form a clear solution varying from red to reddish-brown4 ,the attempt at preparing a condensation product from sodium-m-hydroxybenzoate by means of formaldehyde and bisulphite is worthy of attention4 ,a dark brown1 viscous liquid is obtained which is perfectly soluble in water1 and the aqueous solution of which gives opalescence with gelatine1 a precipitate with aniline hydrochloride1 and a bluish-black coloration with ferric chloride4 ,its behaviour towards pelt is very similar to that of phenolsulphonic acid1 and it yields a similar leather4 ,a very similar condensation product was obtained by condensing sodium-p-hydroxybenzoate with formaldehyde and subsequent sulphonation with sulphuric acid4 ,from a practical standpoint1 however1 these substances cannot be employed1 since their tanning action is only effective in acid solutions of such concentration of acid as would gelatinise the pelt4#c ,if1 on the other hand1 non-condensed methane derivatives of phenol1 e4g41 hydroxyphenylmethanesulphonic acid1 are partly neutralised and a solution of the product thus obtained used for tanning experiments1 no tanning action is observable4 ,the acidified solution does not precipitate gelatine1 and gives a dark brown coloration only with ferric chloride4 ,,gallic ,,acid1 ,c#f;,h#b7,,oh7#c;,,cooh1 when heated with sulphuric acid1 is easily converted into the insoluble rufigallic acid1 which is also insoluble in alcohol4 ,if1 however1 gallic acid is heated with an excess of sulphuric acid1 the product cooled and treated with formaldehyde1 a deep brown condensation product is obtained which is soluble in alcohol1 and in this state is capable of converting pelt into a substance similar to leather which1 though rather hard1 possesses good tensile strength4 ,this water-insoluble condensation product is also soluble in alkalies1 the solution exhibiting properties similar to that described above4 ,gallic acid1 therefore1 is not a suitable base for the production of synthetic tannins soluble in water4 ,phthalic acid also is difficult to sulphonate3 the sulphonated compound treated with formaldehyde gives only water-insoluble condensation products4 #c4 ,condensation ,of ,naphthalene ,derivatives ,the simplest method of condensing ,greek3 b-naphthalene-sulphonic acid is to heat it at #ace ,c4 at a pressure of #bj mm4 for several hours4,footnote3 ,austr4 ,pat41 #fa1jfa1 of #ajth ,september #aiac4 ,the resulting product is a cheesy mass which reacts strongly acid4 ,by reducing the acidity of the substance to #a gm4 #aj c4c4 ,n_/#a,o ,na,o,h1 a grey1 cheesy mass results1 which easily dissolves in water1 the solution being coloured a light yellow-brown and precipitating gelatine aniline hydrochloride2 no coloration1 however1 appears on adding ferric chloride4 ,the condensation of ,greek3 b-naphthalenesulphonic acid1 however1 proceeds with much greater energy in the presence of formaldehyde4 ,in practice1 for instance1 #aj kilos of naphthalene is heated with the same weight of concentrated sulphuric acid 7#ff ,b71 when the mixture is converted into ,greek3 b-naphthalenesulphonic acid by heating for several hours at #aej-afj ,c2 the sulphonation completed1 the sulphonic acid is cooled to about #he ,c41 and #d kilos of formaldehyde 7#cj per cent1 by weight7 slowly added2 finally1 the product is stirred at the temperature mentioned till all formaldehyde has combined4,footnote3 ,austr4 ,pat41 #fi1aid1 of #beth ,june #aiae2 ,ger4 ,pat1 #bij1ife4 ,tanning experiments with this product yielded1 in a short time1 a nearly white coloured leather 7see later74 ,in addition to formaldehyde1 there are other substances which induce condensation of naphthalenesulphonic acid2 if1 for instance1 sulphur chloride is allowed to act upon ,greek3 b-naphthalenesulphonic acid1 a light brown solid of pronounced acidic character is obtained2 if the latter is partly neutralised with caustic soda1 a greyish-brown solid results1 which dissolves in water with a light brown colour1 the solution precipitating gelatine and aniline hydrochloride1 but giving no coloration with ferric chloride4,footnote3 ,austr4 ,pat41 #if1aid4 ,tanning experiments with this product in aqueous solution gave a light brown1 rather soft leather1 and this1 in addition to the qualitative reactions of the substance1 prove that this method of condensation hardly alters the character of the product from a tanning point of view4 ,the brown coloration imparted to the leather tanned with this condensation product owes its existence to coloured intermediary products4 ,attempts at condensing chloronaphthalenesulphonic acid and nitronaphthalenesulphonic acid resulted in soluble condensation products which gave some of the reactions given by the tannins 7precipitation of gelatine and aniline hydrochloride71 but which were incapable of tanning pelt1 a light tannage being effected on the surface only4 ,greek3 a-,naphthol dissolved in hot concentrated sulphuric acid and heated for some time on the water bath1 yields the light brown1 water-soluble ,greek3 a-naphtholsulphonic acid4 ,a dilute solution of the latter1 when treated with formaldehyde in the cold1 undergoes no change2 on heating the mixture on the water bath a brown precipitate is thrown down4 ,if gelatine solution is added to the opaque liquid1 a yellow flocculent precipitate separates4 ,if caustic soda is added to the opaque liquid containing the condensation product described above1 a clear solution results from which no deposit separates on the addition of acetic acid4 ,gelatine is precipitated by this solution4 ,the concentrated hot a-naphtholsulphonic acid1 upon addition of sufficient formaldehyde1 effervesces strongly and yields a dark brown condensation product insoluble in water1 but soluble in caustic soda4 ,if acetic acid is added in excess to the alkaline solution1 the resultant solution strongly precipitates gelatine4 ,a suspension in water of the insoluble condensation product does not precipitate gelatine4 b-,naphthol1 dissolved in hot concentrated sulphuric acid and heated for some time1 yields the light brown1 viscous b-naphtholsulphonic acid4 ,a dilute solution of the latter1 mixed with formaldehyde1 remains clear2 when heated on the water bath1 however1 it assumes a dark1 reddish-yellow colour1 and remains soluble in water and precipitates gelatine strongly4 ,this condensation product1 on adding excess of caustic soda1 assumes a deep blue coloration1 the alkaline solution giving no precipitate with gelatine2 on adding acetic acid the solution turns brown1 remains clear1 and now precipitates gelatine4 ,the concentrated b-naphtholsulphonic acid heated with formaldehyde on the water bath yields as condensation product a dark1 reddish-yellow mass1 soluble in water1 which precipitates gelatine4 ,a dilute solution1 when allowed to act upon pelt1 gave in a few days a light brown leather1 the properties of which are very similar to those possessed by vegetable tanned leathers4 ,the use of naphtholsulphonic and aminonaphtholsulphonic acids for the manufacture of synthetic tannins is protected by ,ger4 ,pats41 #bic1fdj1 #bic1fic1 #bic1jdb1 and #cjc1fdj4 ,footnote3 ,cf4 ,austr4 ,pat41 #gj1afb4 ,it is a remarkable fact that non-condensed methane derivatives of naphthol1 e4g41 b-naphthol-a-methanesulphonic acid1 dissolved in water and partly neutralised1 are devoid of tanning character when allowed to act upon pelt4 ,neither does this substance precipitate gelatine1 but it does give a deep blue coloration with ferric chloride4 ,the condensation product of b-naphthol above referred to precipitates gelatine and aniline hydrochloride and gives a brown coloration with ferric chloride4 ,thionaphtholsulphonic acid1 when acted upon by formaldehyde1 yields a condensation product of the following constitution3-- ,,hso#d ,,sh ,,sh ,,hso#d ,,ch#b v v v v ,this is a light yellow powder which1 dissolved in water1 yields an opaque solution2 the latter only exhibits any tanning properties when it is not neutralised and even slightly acidified and then precipitates gelatine1 aniline hydrochloride and barium chloride2 dissolved in alkali1 it forms a clear1 yellow solution devoid of tannoid properties4 ,leather tanned with the acidified solution is very similar to those tanned with the phenolsulphonic acid condensation products2 its colour1 however1 is more pronouncedly yellow4 b-,naphthol condensed with hydrochloric acid and formaldehyde yields a methylenedinaphthol1 which is insoluble in water2 the sodium salt1 however1 easily dissolves4 ,the same condensation1 however1 takes place in alkaline solution with direct formation of the sodium salt4 ,the condensation product gives a slight precipitate with gelatine1 and a bluish-grey precipitate with ferric chloride2 acids re-precipitate the insoluble methylene compound4 ,towards pelt it exhibits tanning properties1 whereby the insoluble product referred to above is deposited1 and soft1 full1 and white leather is obtained1 possessing1 however1 but little tensile strength4 #d4 ,condensation of the ,anthracene ,group ,anthracene heated with excess sulphuric acid yields the water-soluble anthracenesulphonic acid2 the latter1 when heated with formaldehyde1 yields water-soluble1 reddish-brown condensation products1 which remain soluble on prolonged heating with formaldehyde4 ,the aqueous solution of the condensation product shows no particular reactions2 it gives a flocculent precipitate with gelatine and a green precipitate with copper sulphate1 soluble with blue colour in excess of the reagent4 ,the partly neutralised solution tans pelt--to which it imparts a brown colour--in eight days1 but on the surface only2 the inner layers are merely pseudo-tanned 7white colour74 ,when dried1 pelt thus treated yields a full and soft leather with brown grain and flesh possessing but little tensile strength4 ,hence1 this condensation product exerts a pickling rather than a tanning effect4 ,anthraquinone heated with sulphuric acid and treated with formaldehyde in the usual manner1 yields a substance which1 when mixed with water1 forms an opaque1 milky solution4 ,this is not altered by excess of caustic soda4 ,the aqueous solution precipitates gelatine and aniline hydrochloride2 all other tannin reagents give no reaction4 ,the partly neutralised solution of the condensation product exerts1 in the main1 a pickling action on pelt2 only the surface of which is tanned1 with brown colour1 the remainder being merely pickled 7white colour74 ,during tannage1 bakelite is formed in the liquid1 and practically all solubles originally present are deposited4 ,the tannage completed1 a light brown1 fairly soft and full leather1 possessing little tensile strength1 results2 this leather can be washed only with great difficulty and approaches more the character of a pickled pelt4 #a-;,hydroxyanthraquinone1 #a1e-;dichloroanthraquinone1 l1#e-;diaminoanthraquinone1 #a-methylaminoanthraquinone1 #a-;benzoylamino1 #f-;chloranthraquinone1 #a-m-toluidoanthraquinone1 when treated with sulphuric acid and formaldehyde1 all yield condensation products which are but little soluble in water1 and which do not at all precipitate gelatine4 ,tanning experiments with these condensation products in alcoholic solution yielded empty leathers of pronounced pickle character4 ,if1 however1 #a-methylamino-#d-;bromanthraquinone is condensed with sulphuric acid and formaldehyde1 a condensation product is obtained which is but slightly soluble in water1 but which precipitates gelatine4 ,when phenanthrequinone is heated with excess of sulphuric acid for some time1 a water-soluble1 reddish-yellow coloured condensation product results4 ,the latter1 when treated with formaldehyde in the cold and then finally heated1 gradually fixes the formaldehyde and forms a substance soluble in water4 ,if the heating1 however1 is prolonged1 insoluble bakelites are formed1 which are neither soluble in alkali nor in alcohol4 ,an aqueous solution of these condensation products gives no reactions with the usual tannin reagents1 though it completely precipitates gelatine4 ,when acting upon pelt1 the partly neutralised dilute solution of the condensation product pickles the former1 and after a few days the pelt is converted into a light brown1 full1 and rather soft leather possessing good tensile strength4 ,when the condensation product is acted upon by bromine in hot aqueous solution1 an additive compound is formed and the resulting product is soluble in water4 ,the aqueous solution of the brominated product gives no special reactions with the usual tannin reagents1 but precipitates gelatine completely4 ,its tanning action upon pelt is much slower than that of the original condensation product2 the surface of the pelt only is tanned with brown colour1 the inner pelt being only pickled 7light brown colour74 ,when dried1 a hard and empty leather of good tensile strength is obtained1 possessing mainly the properties of a pickled pelt4 ,,co ,,oh ,,quinizarene1 1 treated with sulphuric acid v v v ,,co ,,oh and formaldehyde1 yields a condensation product which is but little soluble in water and which does not precipitate gelatine4 ,,quinoline1 when sulphonated and condensed with formaldehyde1 yields a dark coloured condensation product1 completely soluble in water2 the solution does not precipitate gelatine4 ,,oxyquinoline exhibits similar behaviour4 ,on the other hand1 the use of retene 7methylisopropylphenanthrene71 ,,ch#c ,,ch3,,ch ,c#c;,h#g v v for the production of synthetic tannins1 is protected by ,ger4 ,pat41 #bij1ife ,footnote #a3 ,cf ,austr4 ,pat41 #fi1aid #e4 ,di- and ,triphenylmethane ,groups ,if ,,diphenylmethane1 7,c#f;,h#e7b;,,ch#b1 is heated with excess sulphuric acid1 a dark blue mass1 easily soluble in water1 is obtained4 ,the product gently heated with formaldehyde yields a brown1 water-soluble condensation product2 once condensation is complete1 the product will stand stronger heat4 ,if1 on the other hand1 more formaldehyde is added1 brown1 water-insoluble bakelites are formed4 ,the water-soluble condensation product precipitates gelatine1 but not aniline hydrochloride4 ,dissolved in water1 it possesses tannoid properties3 the pelt is1 however1 tanned on the surface only1 the intermediary layers being merely pickled2 after four days in the solution1 the pelt after drying was found to be converted into a greyish-brown1 badly coloured leather1 which was empty1 hard1 and possessed but little tensile strength4 ,,carbazole 7dibenzopyrrole71 v v v ,n#c on the other hand1 was found a suitable base for the commercial production of synthetic tannins2 its use is protected by ,ger4 ,pat1 #bij1ife4 ,,triphenylmethane1 7,c#f;,h#e7c;,,ch1 heated with excess sulphuric acid1 yields a nearly black mass which1 when condensed with formaldehyde in the cold1 and subsequently heated1 yields a mass which is soluble in water4 ,with gelatine and aniline hydrochloride it exhibits reactions similar to those given by the diphenylmethane condensation products2 its tanning properties also are similar to those of the latter4 ,the resultant leather is black1 but is soft and full and possesses good tensile strength4 ,baeyer's observation1 ,footnote3 ,ber41 #ahgb1 #e1 #bhj1 #ajif4 that pyrogallol on condensation with formaldehyde yields an amorphous body soluble in water1 which precipitates gelatine and is very similar to tannin1 was confirmed by ,caro ,footnote3 ,ibid41 #ahib1 #be1 #idg4 and ,kahl4 ,footnote3 ,ibid41 #ahih1 #ca1 #aad4 ,these investigators found that by the condensation of phenols and hydroxybenzoic acids with formaldehyde1 diphenylmethane derivatives were formed2 pyrogallol yields hexahydroxydiphenylmethane-- ,c#f;,h#b7,,oh7#c ,,ch#b ,c#f;,h#b7,,oh7#c ,nierenstein ,footnote3 ,collegium1 #aije1 #bba4 repeated these experiments1 and found that in addition to the insoluble diphenylmethanes1 water-soluble bodies were formed1 which latter precipitate gelatine4 ,the condensation product yielded by gallic acid was identified as hexahydroxyaurinecarboxylic acid-- ,c#f;,h7,,oh7#c;,,cooh ,c-,c#f;,h7,,oh7#c;,,cooh ,c#f;,h7,,oh7#b;,,cooh ,o which is formed in addition to hexahydroxydiphenylmethane-dicarboxylic acid-- ,c#f;,h7,,oh7#c;,,cooh ,,ch#b ,c#f;,h7,,oh7#c;,,cooh ,baeyer's experiment with pyrogallol probaly also yields1 according to ,nierenstein1 another compound of the following constitution-- ,c#f;,h#b7,,oh7#c ,c-,c#f;,h#b7,,oh7#c ,c#f;,h#b7,,oh7#b ,o ,nierenstein considers these bodies confirmation of his hypothesis of the existence of a tannophor1--,,co--1 in the tannins4 ,this supposition was adopted by ,stiasny ,footnote3 ,gerber1 #aije1 #bcc4 and ,kauschke ,footnote3 ,collegium1 #aijf1 #cfb4 and the latter points out that these easily soluable substances exhibit tanning properties4 ,nierenstein ,footnote3 ,ibid41 #aijf #dbd4 was further able to show that by all processes of condensation between phenols 7or hydroxybenzoic acids7 and formaldehyde1 compounds of the character of hydroxyaurine 7or hydroxyaurinecarboxylic acid7 were formed in addition to the insoluble hydroxydiphenylmethanes 7or hydroxydiphenylmethanecarboxylic acids71 the former possessing the characteristic tannophor group and hence precipitating gelatine1 i4e41 exerting tanning action4 ,if the formation of leather is viewed in the light of ,schiff's base1 ,footnote3 ,ibid41 #aije1 #aei4 one may consider the constitution of a hexahydroxyaurinecarboxylic acid leather as follows3-- ,c#f;,h#b7,,oh7#c4;,,cooh ,c-,c#f;,h#b7,,oh7#c4;,,cooh ,c#f;,h#b7,,oh7#b4;,,cooh ,r-,n ,in the preparation of these and similar condensation products1 ,nierenstein and ,webster ,footnote3 ,ber41 #aijh1 #da1 #hj4 observed a peculiar steric effect of the carboxyl group4 ,each #b4e gm4 of the phenol or the acid in question were dissolved in #cj c4c4 of water1 the solution brought to boil and #e c4c4 formaldehyde 7#bj per cent47 and #b4e c4c4 hydrochloric acid added drop by drop2 the precipitate formed was filtered off after twenty-four hours1 dried at #aaj ,c4 to constant weight1 extracted 7in a ,gooch crucible7 freely with water1 and the residue again dried at #aaj ,c4 till constant4 ,the following values were obtained3-- ,total ,insol4 ,aq4 ,sol4 ,aq4 ,oxy- ,precipitate ,diphenylmethane aurinecarboxylic in ,grammes4 ,derivatives ,acid4 ,per ,cent4 ,per ,cent4 ,phloroglucinol #b4djjb #ajj 444 ,hydroquinone #b4cgaf #ajj 444 #b4jedb #ajj 444 ,pyrogallol #b4eaej #ajj 444 #b4gidj #ajj 444 ,pyrocatechol #b4ihje #ajj 444 #b4iegd #ajj 444 ,resorcinol #b4iied #ajj 444 #b4igbe #ajj 444 ,gallic acid #b4jgjf #gh4hd #ba4af #a4bbdj #hc4ah #af4hb #a4adje #ei4id #da4jf ,greek3 b-,resorcylic acid #b4ajdj #ea4jh #dh4ib #b4bjjh #dg4ab #eb4hh ,protocatechuic acid 444 444 444 444 444 444 ,vanillic acid 444 444 444 ,tannin #b4jeii 444 ,nearly all sol4 ,digallic acid #b4ajdb #hj4af #ai4hd ,leucodigallic acid #b4jjda #a4id #ih4jf ,with the introduction of the carboxylic group the tendency of condensation to diphenylmethane derivatives is lessened2 by protocatechuic acid the tendency is nil4 ,nierenstein considers this reaction analogous to the formation of cork1 to the genetic relation of which with the diphenylmethane formation ,drabble and ,nierenstein have referred in an earlier publication4 ,footnote3 ,biochemical ,jour441 #aijg1 #b1 #if4 ,it is hence possible that the plants may employ formaldehyde as a methylation medium1 and produce these insoluble condensation products for the purpose of ridding themselves of the poisonous phenols and aromatic hydroxy acids 7and tannins71 in addition to oxidising processes whereby phlobaphenes1 ellagic acid1 etc41 are formed4 ,the reaction between phenols and aldehydes has been further studied by ,michael1 ,footnote3 ,amer4,jour41 #e1 #cch2 #i1 #acj4 who prepared a condensation product from phenol and resorcinol with benzaldehyde1 and ,russanow1 ,footnote3 ,ber4#i #ahhi1 #bb1 #aidd4 who also employed benzaldehyde and phenol4 ,lipp ,footnote3 ,diss41 ,bern41 #aije4 investigated the action of benzaldehyde and piperonal on phenols1 anisoles1 cresols1 cresylic ether1 resorcinol1 and the ether of the latter and phenol1 and showed that when free phenols are condensed with benzaldehyde the hydroxyls occupy the same position as by the interaction between benzaldehyde and the corresponding phenolic ethers4 ,the resulting dihydroxytriphenylmethane derivatives form beautiful crystals1 which on oxidation are converted into benzaurines1 the constitution of the latter probably being-- ,o ,,oh v v v ,c ,c#f;,h#e ,in alkalies1 the hydroxylated triphenylmethanes dissolve without imparting any colour to the solution2 by concentrated sulphuric acid they are taken up with intense coloration4 ,if the hydroxyls occupy the ortho-position to methyl1 they may form xanthenes by splitting off water-- ,o ,,ch#c v v v ,,ch#c ,,ch ,c#f;,h#e ,in the benzene series this reaction is difficult to establish1 and has to be induced by distilling the particular dihydroxy-diphenylmethane at ordinary pressure4 ,in the naphthalene series1 on the other hand1 the ring closes up by1 for instance1 the condensation of ,greek3 b-naphthol with benzaldehyde or paraldehyde1 and yields the following compounds3-- ,c#aj;,h#f ,c#aj;,h#f ,c#f;,h#e-;,,ch ,o ,,ch#c-;,,ch ,o ,c#aj;,h#f ,c#aj;,h#f ,these xanthenes are white1 silk-glossy needles1 which are soluble in water and in alkalies4 ,in concentrated sulphuric acid1 they are taken up with beautiful fluorescence4 #f4 ,summary ,from the qualitative reactions of the different condensation products described it may be seen that their tannoid properties are not dependent on whether they precipitate gelatine or are adsorbed by hide powder or not4 ,hydroxynaphthylmethanesulphonic acid1 for instance1 precipitates gelatine but does convert pelt into leather2 on the other hand1 sodium dicresylmethanesulphonate does not precipitate gelatine1 and neither does it tan pelt2 nevertheless it is adsorbed by hide powder as tanning matter4 ,the author discovered that o-nitrophenol does not precipitate gelatine1 but has some tanning action on both hide powder and pelt4 ,relatively to the possibilities of forming condensation products possessing tannoid properties1 the following may be stated3-- ,all mono- and polyhydric phenols may be converted into true tanning matters by either condensing them as such1 or after their conversion into the corresponding sulphonic acids1 by substances capable of eliminating the elements of water4 ,it makes no difference to the final product whether the condensation is the first step followed by sulphonation and consequent solubilisation of the intermediary insoluble product1 or whether1 vice versa1 the sulphonic acid is subjected to condensation4 ,alkaline solution of phenols may also be condensed1 the reaction products1 when condensed1 constituting tanning matters soluble in water4 ,among the substitution products of the phenols1 the thio-1 chloro-1 bromo-1 nitro-1 and aminophenols as a rule yield tanning matters similar in character4 ,the quinones are as such--i4e41 without being condensed--substances possessing tannoid properties4 ,the aromatic dihydric alcohols are easily condensed with the different sulphonic acids and yield valuable tanning matters4 ,of aromatic acids all those which yield water-soluble sulphonation products seem suitable for the industrial production of tanning matters4 ,if the acids themselves do not yield water-soluble sulphonation products1 the alkali salts of the latter may be condensed with formaldehyde1 and the resulting products then constitute tanning matters provided their solutions can be neutralised or faintly acidified without the solute being thrown out of solution in insoluble form4 ,the diphenyl derivatives of the above groups often possess tannoid properties4 ,the same holds good of those compounds with condensed nuclei 7naphthalene1 anthracene1 etc471 and all their derivatives which satisfy the above conditions4 ,the choice of condensing agent is1 as a rule1 of little significance4 ,elimination of the elements of water by the mere application of heat succeeds in few cases only1 since the high temperature required to induce reaction in many cases causes decomposition of the substances4 ,this difficulty is overcome by heating in vacuo4 ,condensation with formaldehyde always succeeds1 with acetaldehyde and benzaldehyde only partly4 ,the action on hide powder1 pelt1 and gelatine by these characteristic substances is tabulated below3-- ,relative ,behaviour towards ,substance4 ,gelatine4 ,hide ,powder ,pelt ,formaldehyde 444 444 ,tanning ,phenol ,ppte4 444 444 ,chlorophenol 444 444 ,surface ,tribromophenol ,slight ppte ,tanning tanning o ,nitrophenol ,no ppte ,bromonitrophenol ,slight ppte ,trinitrophenol ,ppte ,tanning ,bromotrinitrophenol ,slight ppte p ,aminophenol ,ppte 444 444 m ,dihydroxybenzene 444 444 ,orcinol 444 444 p ,dihydroxybenzene ,tanning ,tanning ,monochloro p dihydroxybenzene 444 444 o ,dihydroxybenzene 444 444 ,pyrogallic acid 444 444 ,surface ,tribromopyrogallic acid ,tanning ,tanning ,gallic acid ,no ppte ,not tanning ,not tanning ,bromophloroglucinol ,ppte ,tanning ,gallotannic acid ,tanning ,galloflavine ,slight ppte ,not tanning ,quinone ,tanning ,bromosalicylic acid ,not tanning ,dinaphthylmethanedisulphonic acid ,ppte ,tanning ,diphenylmethanedisulphonic acid ,dicresylmethanedisulphonic acid ,sodium dicresylmethanedisulphonate acid ,no ppte ,not tanning ,dixylylmethanedisulphonic acid ,ppte ,tanning ,naphtholdisulphonic acid ,not tanning ,not tanning ,methylenedinaphthol ,tanning ,tanning ,hydroxyphenylmethanesulphonic acid ,not tanning ,hydroxynaphthylmethanesulphonic ,slight ppte acid ,diaminonaphthylmethanedisulphonic ,ppte ,tanning ,not tanning acid ,dihydroxynaphthylmethanedisulphonic acid ,dichloronaphthylmethanedisulphonic acid ,surface tanning ,dinitronaphthylmethanedisulphonic acid ,dithionaphthylmethanedisulphonic acid ,tanning ,bromo ,greek3 b naphthol #a ,slight ppte ,rosolic acid #a ,ppte ,footnote #a3 ,in alcoholic solution4 ,,section ,,iii ,,tanning ,,effects ,,of ,,mixtures ,,and ,,natural ,,products #a4 ,mixture of ,phenolsulphonic ,acid and ,formaldehyde ,the most important invention relatively to the search for new tanning materials was that of ,weinschenk1,footnote3 ,ger4 ,pat41 #ahd1ddi4 who first showed that pelt may be converted into leather by the action upon it of mixtures of naphthols and formaldehyde4 ,this process consists of two steps3 the pelt is first immersed in a #j4be-j4ej per cent1 formaldehyde solution1 and secondly in an aqueous solution of -,greek3 a or -,greek3 b naphthol2 this order may be reversed4 ,if1 on the other hand1 a pasty mixture is made of formaldehyde and naphthol1 and this is allowed to act upon the pelt1 the latter is rapidly converted into leather1 but the mixture must be administered very gradually or otherwise the insoluble methylenedinaphthol is formed outside the pelt and hinders any tanning effect4 ,leather obtained through the action of ,greek3 a-naphthol is1 when freshly tanned1 pure white and sufficiently soft and firm1 but quickly assumes a brown colour on storing2 if1 however1 ,greek3 b-naphthol is employed1 a cream-coloured leather results1 the colour of which turns only slightly more yellowish even when exposed to the direct rays of the sun4 ,a similar process has recently 7#be1 xii41 #aiae7 been protected by ,ger4 ,pat1 #cje1eaf1 granted to the ,deutsch-,koloniale ,gerb--und ,farbstofif ,gesellschaft1 in ,karlsruhe4 ,according to this patent1 pelt is treated in separate solutions1 one of which is formaldehyde1 the other being that of such aromatic compounds or their salts which yield water-soluble condensation products with formaldehyde2 for example1 pelt is immersed in #b-e per cent1 solution of formaldehyde for a few days1 and is subsequently treated with #a-b per cent neutral or faintly acidified solutions of ,greek3 a-naphthylamine hydrochloride1 resorcinol or sodium phenate or cresylate1 for several days4 ,the resultant leather is claimed to be soft and full and to possess good tensile strength4 ,the tanning properties of mixtures of phenolsulphonic acid and formaldehyde have been examined by the author with the following results3-- ,i4 ,,ii4 ,,iii4 ,grammes formaldehyde #aj #bj #dj phenolsulphonic acid #bj #ej #ajj caustic soda 7sol1 #dj per cent47 #aj #bj #dj water #ejj #ejj #ejj ,the above solutions were made up and allowed to act upon pelt pieces weighing #ae gm42 whereas ,solution ,i4 remained clear throughout the experiment1 ,solution ,,ii4 became somewhat clouded1 and ,solution ,,iii4 assumed a milky appearance4 ,the pelts were tanned through in seven days and yielded leathers which1 after drying and finishing1 possessed yellow colour1 long fibre1 and good tensile strength1 but a rather empty feel4 ,to prevent separation of insoluble matter during tannage1 another experiment was carried out1 in which the pelts were first submitted to the action of formaldehyde 7#aj1 #bj1 and #dj gm4 in #ejj c4c4 water7 for three days1 being subsequently removed to fresh solutions of partly neutralised phenolsulphonic acid 7cf4 above74 ,similar results were obtained1 but the leather felt even more empty than those obtained by the former experiment4 ,attempts at converting pelt into leather by first immersing the pelt in a partly neutralised solution of phenolsulphonic acid1 and subsequently transferring it to fresh solutions of formaldehyde1 gave merely negative results2 the phenolsulphonic acid effected pickling action upon the pelt1 but was subsequently quickly replaced by the formaldehyde1 before the latter had penetrated the pelt in sufficient quantity to induce condensation1 thereby exerting tanning action4 ,to explain the tanning effects of these mixtures1 the author analysed the leathers resulting from the effects of the latter1 and was able to show1 that in these cases also1 condensation of phenolsulphonic acid and formaldehyde takes place inside the pelt1 since on the one hand the analyses left no doubt but that true tannage had been effected1 and on the other hand an ammoniacal extract of the leathers gave the typical reaction for condensation products of phenolsulphonic acid1 with aniline hydrochloride4 ,footnote3 ,collegium #aiac1 #eaf1 #adb4 ,the leather analyses gave the following figures3-- ,moisture - - - #ah4cj per cent4 ,fats - - - - #j4dg ,ash - - - - #j4ih ,leather ,tannin - - - #bf4cg substance ,hide substance - - #ec4hh ,a characteristic feature is the low value of tannin1 which is considerably higher ,footnote3 ,ibid41 #aiac1 #eba1 #dgh4 where condensation products of phenolsulphonic acids are used as tanning agents2 the action effected by the separate constituents1 therefore1 is more that of pickling4 #b4 ,mixture of ,phenolsulphonic ,acid and ,natural ,tannins ,a piece of pelt was immersed in a half-neutralised solution1 measuring #f ,b41 of phenolsulphonic acid1 and left sixteen hours in the solution1 which completely penetrated the pelt during this time2 it was then transferred to a #ab ,b4 solution of a mixture of quebracho and chestnut1 which in two days converted the pelt into a light coloured leather possessing good tensile strength4 ,by using a bath composed of half-neutralised phenolsulphonic acid and quebracho extract in #g ,b4 solution1 another piece of pelt was completely tanned in two days4 ,the same result was obtained by first half neutralising the phenolsulphonic acid and then adding sulphited quebracho extract till a #e ,b4 solution was obtained4 ,a piece of pelt received a #b ,b4 liquor composed of #c parts of phenolsulphonic acid and #a part of formaldehyde for sixteen hours1 and was then completely penetrated2 it was subsequently transferred to a #aj ,b4 liquor composed of chestnut and quebracho1 being completely tanned in two days4 ,the same result was obtained on adding sufficient sodium sulphate to the above mixture of phenolsulphonic acid and formaldehyde to raise the density from #b-c ,b4 ,sixty grammes of phenolsulphonic acid were partly neutralised with #ajj c4c4 of a #aj per cent solution of caustic soda1 and #aj c4c4 formaldehyde added to #djj c4c4 of the mixture 7#b ,b473 a piece of pelt was completely penetrated by the solution in sixteen hours1 and was subsequently tanned in two days1 using an extract of #aj ,b4 ,similarly1 by treating a pelt with #djj c4c4 of a half-neutralised solution of phenolsulphonic acid 7#c ,b47 plus #h c4c4 formaldehyde1 and adding after eighteen hours sulphited quebracho extract to the same bath1 strengthening the latter to #f ,b41 the pelt was converted into leather in two days2 in this case1 however1 much of the tannin was precipitated by the formaldehyde present in the solution4 ,if1 on the other hand1 a mixture of #hj gm4 dilute phenolsulphonic acid 7#a3a aq7 and #ad gm4 of formaldehyde were cooled for several hours and subsequently strengthened with sulphited quebracho extract to #g ,b41 no tannin was precipitated in the liquor1 and a piece of pelt immersed in the latter was completely tanned in sixteen hours4 ,to prevent the precipitation of tannin caused by the formaldehyde1 sulphite cellulose extract 7wood pulp7 was substituted for sulphited quebracho extract1 and the following experiments carried out3-- ,to #bjj c4c4 of a #f ,b4 sulphite cellulose extract plus #bjj c4c4 of half-neutralised phenolsulphonic acid solution was added #ae c4c4 formaldehyde1 and this solution tanned pelt in four days2 the resultant leather was light brown1 firm1 and possessed good tensile strength and long fibre4 ,another piece of pelt was immersed in a solution of #djj c4c4 phenolsulphonic acid of #c;,b4 plus #ae c4c4 formaldehyde for eighteen hours1 and was then tanned in a #f ,b4 solution of sulphite cellulose extract4 ,the resultant leather was extremely light coloured1 and possessed qualities similar to those described in the former experiment4 ,finally1 pelt was immersed in a #f ,b4 solution composed of #adj gm4 of a #ae ,b4 sulphite cellulose extract1 #aj gm4 of formaldehyde1 #djj gm4 water1 #ae gm4 phenolsulphonic acid1 and #cj gm4 of a #aj per cent caustic soda solution1 and was tanned in four days4 ,this leather also was coloured light brown1 of good tensile strength1 and rather firm4 ,these experiments prove that when pelt is treated with formaldehyde1 phenolsulphonic acid1 and vegetable tannins1 the two former components effect1 more or less1 actual tannage2 it is admittedly a matter of some difficulty to establish whether the effect is one of pickling or pseudo-tannage1 or whether the tannage may be considered a true one4 ,the final effect1 however1 is nearly always that of a true tannage1 i4e41 by varying the composition of the tanning solutions leather is obtained with properties identical with those tanned with true tannins of vegetable origin4 ,the only difficulty encountered in these combinations is the property of formaldehyde1 of precipitating the natural tannins1 and it is hence essential1 for practical purposes1 to so arrange the combination that their value is not reduced by the property referred to4 ,the fact that not only compounds already existing may convert pelt into leather1 but that a similar effect is obtained inside the pelt1 by their components1 is indeed of theoretical interest4 #c4 ,tanning ,effects of ,different ,natural ,substances ,in addition to the vegetable tannins1 ,nature has also provided other substances of vegetable origin1 which1 admittedly1 do not effect tannage in their original state1 but which may1 by suitable treatment1 acquire this property4 ,the oldest information on this point is supplied by ,resch1 ,footnote3 ,scherer's ,jour41 #ahja1 #f1 #die4 who carried out tanning experiments1 using three parts of peat and one part of oak bark4 ,by the action of nitric acid on substances of vegetable and animal origin1 ,hatchett1 ,footnote3 ,gehlen's ,jour41 #ahje1 #a1 #ede4 ,chevreul1 ,footnote3 ,ann4 ,chim41 #ahaj1 #gc1 #cf4 and ,vogel ,footnote3 ,jour4 ,chem4 ,phys41 #ahab1 #f1 #aja4 claim to have obtained tanning materials1 whilst later1 ,buff ,footnote3 ,ibid41 #ahbg1 #ea1 #ch4 obtained a material suitable for tanning purposes from indigo4 ,by subsequent treatment with lime and soot1 or tar1 ,ashmore ,footnote3 ,dingier's ,jour41 #ahcc1 #dh1 #fg4 claims to have converted pelt into leather4 ,by treating peat with nitric acid1 ,jennings ,footnote3 ,jahresber4 d4 ,chem41 #aheh1 #fff4 and ,payne ,footnote3 ,chem4 ,centralbl41 #aijh1 ii4 #eed2 ,ger4 ,pat41 #bjj1 #eci4 have produced artificial tanning materials4 ,skey ,footnote3 ,chem4 ,news1 #ahff1 #bjf2 ,zeits4 f4 ,chem41 #ahff1 #gec4 obtained a dark brown extract1 soluble in water and precipitating gelatine1 by treating bituminous coal or lignite with nitric acid2 by extracting coal with alkalies1 ,reinsch ,footnote3 ,pharm4 ,centralh41 #ahhg1 #ada4 isolated a substance 7pyrofuscine7 which1 when partly neutralised with carbon dioxide1 was capable of converting pelt into leather4 ,in addition to these tanning materials the recovery of a substance possessing tanning properties from the so-called acid rosins has been made the subject of a patent2 ,footnote3 ,ger4 ,pat41 #cf1jai4 this rosin is formed when crude oil is treated with concentrated sulphuric acid in the oil refineries4 ,the greasy substance is partly neutralised with alkali and is claimed to produce a very springy leather4 ,the waste liquors obtained in the manufacture of cellulose1 the so-called sulphite and sodium cellulose waste1 have1 however1 been the subject of numerous investigations1 and several hundred publications have appeared and a great number of patents ,footnote3 ,literatur beri,sulfitablauge #aiaj-ac4 7,reprint from ,woche,wochenbl,papie,papierfabrikation7 taken out1 the first one being that of ,mitscherlich ,footnote3 ,jahresber4 d4 ,chem41 #ahic1 #hij2 ,ger4 ,pat41 #gb1afa4 and ,hnig ,footnote3 ,chem4 ,centralbl41 #aijb1 ii4 #agd2 ,ger4 ,pat41 #acb1bbd4 ,the waste liquors contain large quantities of acids and lime1 and in order to utilise the liquors for tanning purposes1 the excessive sulphuric and sulphurous acids as well as the lime must be removed4 ,the active tannin is no doubt the ligninsulphonic acid1 and those cellulose extracts containing the largest amounts of free ligninsulphonic acid may also be considered the most efficient4 ,according to the author1,footnote3 ,technikum1 #aiab1 #bj1 #aef4 such sulphitecellulose extracts precipitate gelatine1 aniline hydrochloride1 ammoniacal zinc acetate1 and basic coal-tar dyes1 and give a greenish-black coloration with ferric chloride4 ,these reactions indicate the presence of tanning matters in cellulose extracts4 ,the official shake method of analysis gives the following results3--,footnote3 ,ibid4 ,tanning matters #bc4j per cent4 ,non-tannins #cj4c ,insoluble matters #j4g ,water #df4j --------------- #ajj4j per cent4 ,ash #d4c ,sulphurous acid #j4f ,many other substances have been used for tanning experiments1 a number of them precipitating gelatine4 ,zacharias ,footnote3 ,zeits4 f4 ,ang4 ,chem41 #aijg1 #afde4 obtained leather by the action of many coal-tar dyes on pelt1 similarly ,herzog and ,adler1 by using ,prussian blue1 ,neufuchsin1 patent blue ,v1 crystal violet1 and colloidal gold4 ,most inorganic substances possess tanning properties when in the colloidal state1 e4g41 sulphur1 halogens1 chromium salts1 iron salts1 silver oxide1 and the salts of mercury1 copper1 bismuth1 zinc1 lead1 platinum1 cesium1 vanadium1 and the rare earths 7salts of cerium1 lanthanum1 didymium1 neodymium1 thorium1 and zerconium74 ,for practical purposes1 however1 only sulphur1 chrome1 and alum salts are used1 the latter two being of the greatest importance4 ,,section ,,iv ,,methods ,,of ,,examining ,,tanning ,,matters ,whereas the evaluation of vegetable tanning matters necessitates determinations of their practical applicability in addition to qualitative and quantitative analyses1 the latter two determinations are of practically no value when dealing with synthetic tannins4 ,the way in which tanning matters obtained by chemical means exert their action1 in addition to the intensity with which they convert pelt into leather1 is the only criterion of their quality for practical 7tanning7 purposes2 both may be demonstrated by experimental tests4 ,when dealing with the natural tanning materials it is desirable to know their contents of actual tanning matter1 from which their special qualities as tanning agents may be deduced4 ,where the vegetable tanning materials have already been converted into extracts1 it is essential to establish the identity of the original material used by the qualitative reactions of the extract in addition to the quantitative estimation of actual tannin contents4 ,it is frequently necessary to examine whether the extract in question has been actually prepared from the material giving the extract its name1 or whether the extract has suffered the addition of other extracts of tanning materials of but low quality4 ,such determinations may be undertaken by microscopical observations and by means of qualitative and quantitative reactions2 for this purpose many colour reactions and precipitation methods are available in addition to the determination of the molybdenum figure 7,lauffmann71,footnote3 ,collegium1 #aiac1 #aj4 the alcohol and ethyl acetate figures and microscopical examination 7,grasser74,footnote3 ,ibid41 #aiaa1 #cdi4 ,of other adulterants tending to reduce the quality of extracts may be mentioned sugars1 mineral salts1 and coal-tar dyes2 ,footnote3 ,grasser1 ,collegium1 #aiaj1 #cgi4 for the determination of these1 the special literature should be consulted4 ,footnote3 ,grasser1 ,handbuch f4 gerbereichem4 ,laboratorien 7,leipzig1 #aiad72 ,procter-,paessler1 ,gerbereichem4 ,untersuchungen 7,berlin1 #aija74 ,two methods are devised for the purpose of quantitatively determining the tannin contents1 both of which employ hide powder1 and which are known as the shake method and the filter bell method respectively3 the former is adopted as the official method of the ,international ,association of ,leather ,trades' ,chemists 7,i4,a4,l4,t4,c474 ,footnote3 ,and also by the ,society of ,leather ,trades' ,chemists4-,transl4 ,the original method1 ,footnote3 ,leather ,manufacturer1 #ahid1 ,no4 #i ,j4,s4,c4,i41#ahid1 #did4 worked out in the laboratory of the ,yorkshire ,college 7now the ,university of ,leeds71 essentially consists in introducing #f-i gm4 of hide powder in a shaker1 washing it at least twice with distilled water and carefully squeezing out the powder in a linen cloth between each washing4 #ajj c4c4 of the solution to be examined1 which may not contain more than #a per cent1 total solids1 are introduced into the shaking bottle which is then weighed4 ,about one-third of the washed hide powder is then added1 and the bottle shaken ten to fifteen minutes2 another third is then added and1 after shaking1 the third portion4 ,the bottle plus contents is now weighed1 and the amount of hide powder introduced ascertained by difference of the two weighings4 ,the liquid is then filtered through filter paper1 #ej c4c4 of the clear filtrate evaporated in a basin1 dried and weighed4 ,the residue in the original solution is then obtained by multiplying the former by #ajj 7plus weight of water added with hide powder71 and dividing by #ajj4 ,this method was closely investigated by a large number of leather trades' chemists1 was considerably improved1 and in its final form presented a method of the highest degree of accuracy2 the method was therefore adopted as ,the ,official ,method of ,tanning ,analysis by the ,i4,a4,l4,t4,c41 which body1 at the same time1 gave precise instructions as to the details of the method4 ,the latest instructions1 which are reprinted below1 permit of any method of analysis which observes the following conditions3-- #a4 ,the solution for analysis must contain between #c4e and #d4e gm4 of tanning matter per litre1 and solid materials must be extracted so that the greater part of the tannin is removed at a temperature not exceeding #ej ,c4 #b4 ,the total solubles must be determined by the evaporation of a measured quantity of the solution previously filtered till optically clear1 both by reflected and transmitted light4 ,this is obtained when a bright object such as an electric light filament is distinctly visible through at least #e cm thickness1 and a layer of #a cm4 deep in a beaker placed on a black glass or black glazed paper appears dark and free from opalescence when viewed from above4 ,any necessary mode of filtration may be employed1 but if such filtration causes appreciable loss when applied to a clear solution1 a correction must be determined and applied as described in paragraph #f4 ,filtration shall take place between the temperatures of #ae ,c4 and #bj ,c4 ,evaporation to dryness shall take place between #ih4e ,c4 and #ajj ,c4 in shallow1 flat-bottomed basins1 which shall afterwards be dried until constant at the same temperature1 and cooled before weighing for not less than twenty minutes in air-tight desiccators over dry calcium chloride4 #c4 ,the total solids must be determined by drying a weighed portion of the material1 or a measured portion of its uniform turbid solution1 at a temperature between #ih4e ,c4 and #ajj ,c4 in shallow1 flat-bottomed basins1 which shall afterwards be dried until constant weight at the same temperature1 and cooled before weighing for not less than twenty minutes in air-tight desiccators over dry calcium chloride4 ,moisture is the difference between #ajj and the percentage of total solids1 and insoluble the difference between total solids and total solubles4 #d4 ,non-,tannins4--,the solution must be detannised by shaking with chromed hide powder till no turbidity or opalescence can be produced in the clear solution by salt-gelatine solution4 ,the chromed powder must be added in one quantity equal to #f4j-f4e gm4 of dry hide powder per #ajj c4c4 of the tanning solution1 and must contain not less than #j4b per cent4 and not more than #a per cent4 of chromium calculated on the dry weight1 and must be so washed that in a blank experiment with distilled water1 not more than #e mg4 of solid residue shall be left on evaporation of #ajj c4c4 ,all water contained in the powder should be determined and allowed for as water of dilution4 #e4 ,preparation of ,infusion4--,such a quantity of material shall be employed as to give a solution containing as nearly as possible #d gm4 of tanning matter per litre1 and not less than #c4e or more than #d4e gm4 ,liquid extracts shall be weighed in a basin or beaker and washed with boiling water into a litre flask1 filled up to the mark with boiling water1 and well mixed and rapidly cooled to a temperature of #ag4e ,c41 after which it shall be accurately made up to the mark1 again well mixed1 and filtration at once proceeded with4 ,sumac and myrabolam extracts should be dissolved at a lower temperature4 ,solid extracts shall be dissolved by stirring in a beaker with successive quantities of boiling water1 the dissolved portions being poured into a litre flask1 and the undissolved being allowed to settle and treated with further portions of boiling water4 ,after the whole of the soluble matter is dissolved1 the solution is treated similarly to that of a liquid extract4 ,solid tanning materials1 previously ground till they will pass through a sieve of sixteen meshes per square centimetre1 are extracted in ,koch's or ,procter's extractor with #ejj c4c4 of water at a temperature not exceeding #ej ,c42 the extraction is then continued with boiling water till the filtrate amounts to #a litre4 ,it is desirable to allow the material to soak for some hours before commencing the percolation1 which should occupy not less than three hours1 so as to extract the maximum of tannin4 ,any remaining solubles in the material must be neglected or reported separately as difficultly soluble substances4 ,the volume of liquid in the flask must1 after cooling1 be accurately made up to #a litre4 #f4 ,filtration4--,the infusion shall be filtered till optically clear 7vide #b74 ,no correction for absorption is needed for the ,berkefeld candle1 or for ,s4 and ,s4 #eij paper ,footnote3 ,schleicher and ,schll1 ,dren 7,rheinland71 ,germany4 if a sufficient quantity 7#bej-cjj c4c47 is rejected before measuring the quantity for evaporation1 and the solution may be passed through repeatedly to obtain a clear filtrate4 ,if other methods of filtration are employed1 the average correction necessary must be determined in the following manner3--,about #ejj c4c4 of the same or a similar tanning solution is filtered perfectly clear1 and after thorough mixing #ej c4c4 is evaporated to determine ,total ,soluble ,a4 ,a further portion is now filtered in the exact method for which the correction is required 7time of contact and volume rejected being kept as constant as possible71 and #ej c4c4 is evaporated to determine ,total ,soluble ,b4 ,the difference between ,a and ,b is the correction sought1 which must be added to the weight of the total solubles found in analysis4 ,an alternative method of determining correction1 which is equally accurate and often more convenient1 is to filter a portion of the tanning solution through the ,berkefeld candle till optically clear1 which can be generally accomplished by rejecting #cjj or #djj c4c41 and returning the remaining filtrate repeatedly2 and at the same time to evaporate #ej c4c4 of the clear filtrate obtained by the method for which correction is required1 when the difference between the residues will be the correction sought4 ,an average correction must be obtained from at least five determinations4 ,it will be found that this is approximately constant for all materials1 and amounts in the case of ,s4 and ,s4 #fje1 #aej c4c4 being rejected1 to about #j4jje gm41 and where #b gm4 of kaolin are employed in addition to #j4jjge gm4 ,the kaolin must be previously washed with #ge c4c4 of the same liquor1 which is allowed to stand fifteen minutes and then poured off4 ,paper #fje has a special absorption for a yellow colouring matter often contained in sulphited extracts4 #g4 ,hide powder shall be of a woolly texture1 thoroughly delimed1 preferably with hydrochloric acid4 ,it shall not require more than #e c4c4 or less than #b4e c4c4 of decinormal ,na,o,h or ,,koh to produce a permanent pink colour with phenolphthalein on #f4e gm4 of the dry powder suspended in water4 ,if the acidity does not fall within these limits it must be corrected by soaking the powder before chroming for twenty minutes in ten to twelve times its weight of water1 to which the requisite calculated quantity of standard alkali or acid has been added4 ,the hide powder must not swell in chroming to such an extent as to render difficult the necessary squeezing to #gj-ge per cent4 of water1 and must be sufficiently free from soluble organic matter to render it possible in the ordinary washing to reduce the total solubles in a blank experiment with distilled water below #j4jje gm per #ajj c4c4 ,the powder1 when sent out from the maker1 shall not contain more than #ab per cent4 of moisture1 and shall be sent out in air-tight tins4 ,the detannisation shall be carried out in the following manner3-- ,the moisture in the air-dried powder is determined1 and the quantity equal to #f4e gm4 actual dry powder is calculated1 which will be practically constant if the powder be kept in an air-tight vessel4 ,any multiple of this quantity is taken according to the number of analyses to be made1 and wet back with approximately ten times its weight of distilled water4 ,two grammes per #ajj of dry powder of crystallised chromic chloride1 ,cr,cl#c4f;aq41 is now dissolved in water and made basic with #j4f gm4 of ,na#b;,,co#c by the gradual addition of #aa4be c4c4 of normal ,na#b;,,co#c1 thus making the salt correspond to the formula ,cr#b;,cl#c7,,oh7#c4 ,in laboratories where analyses are continually being made1 it is more convenient to employ a #aj per cent stock solution1 made by dissolving #ajj gm4 of ,cr#b;,cl#f4f;aq4 in a little distilled water in a litre flask and very slowly adding a solution containing #cj gm4 of anhydrous sodium carbonate1 with constant stirring1 finally making up to the mark with distilled water and well mixing4 ,of this solution #bj c4c4 per #ajj gm41 or #a4c c4c4 per #f4e gm4 of dry powder1 should be used4 ,this solution is added to the powder1 and the whole churned for one hour4 ,at the end of the one hour the powder is squeezed in linen to free it as far as possible from the residual liquor1 and washed and squeezed repeatedly with distilled water1 until1 on adding to #ej c4c4 of the filtrate one drop of #aj per cent4 ,k#b;,cr,o#d and four drops of decinormal silver nitrate1 a brick-red colour appears4 ,four or five squeezings are usually sufficient4 ,such a filtrate cannot contain more than #j4jja gm4 of ,na,cl in #ej c4c4 ,the powder is then squeezed to contain #gj-ge per cent1 of water1 and the whole weighed4 ,the quantity ,q containing #f4e gm4 dry hide is thus found1 weighed out1 and added immediately to #ajj c4c4 of the unfiltered tannin infusion along with 7#bf4e-,q7 of distilled water4 ,the whole is corked up and agitated for fifteen minutes in a rotating bottle at not less than #fj revs4 per minute4 ,it is then squeezed through linen1 the fitrate stirred and filtered through a folded filter of sufficient size to hold the entire filtrate1 returning till clear4 ,sixty c4c4 of the filtrate is then evaporated and calculated as #ej c4c41 or the residue of #ej c4c4 multiplied by #f_/e4 ,the non-tannin filtrate must give no turbidity with a drop of a solution of #a per cent1 gelatine and #aj per cent1 common salt4 ,footnote3 ,it is convenient for technical purposes to employ the commercially obtainable chromed hide powder as prepared1 for instance1 by the ,german ,experimental ,station at ,freiberg1 ,saxony4 ,one gramme of kaolin1 freed from all soluble matter1 may be added to the filtrate1 or it may be used by mixing it with the hide powder in the shaking bottle4 ,the analysis of used liquors and spent tans shall be made by the same methods as are employed for fresh tanning materials2 the liquors being diluted1 are concentrated by boiling in vacuo1 or in a vessel so closed as to restrict access of air1 until the tanning matter is if possible between #c4e and #d4e gm4 per litre1 but in no case beyond a concentration of #aj gm4 per litre of total solids1 and the weight of hide powder used shall not be varied from #f4e gm4 ,the results shall be reported as shown by the direct estimation1 but it is desirable that in addition efforts shall be made1 by determination of acids in the original solution and in the non-tannin residue1 to ascertain the amount of lactic and other non-volatile acids absorbed by the hide powder1 and hence returned as tanning matters4 ,in the case of tanning materials it must be clearly stated in the report whether the calculation is on the sample with moisture as received1 or upon some arbitrarily assumed percentage of water2 and in that of liquors whether the percentage given refers to weight or to grammes per #ajj c4c41 and in both cases the specific gravity shall be reported4 ,all analyses reported must be the average result of duplicate determinations1 which must agree in the case of liquid extracts within #j4f per cent1 and of solid extracts within #a4e per cent1 or the analysis shall be repeated until such agreement is obtained4 ,all reports shall be marked3 ,analysed in accordance with the rules of the ,s4,l4,t4,c4 7,i4,a4,l4,t4,c47--when the analyses have been carried out according to the method described above4 ,as has been repeatedly emphasised in this treatise1 the synthetic tannins form a special class of substances1 and the results obtained by either of the two hide-powder methods do not give figures which are always comparable to those of the natural tannins4 ,an example of the inapplicability of the methods where synthetic tannins are concerned is illustrated by the behaviour towards hide powder of them when partly neutralised to varying degrees3 commercial ,neradol ,d of acidity #a gm4 #aj c4c4 ,n_/#aj ,na,o,h contains #cc per cent4 tanning matters1 completely neutralised ,neradol ,d1 which exerts no true tanning action on pelt1 still contains #bj per cent tanning matter when analysed according to the ,official ,method2 a difference hence exists regarding the adsorption by hide powder of a tannin and the adsorption of the latter by hide4 ,as1 however1 we are unable to make a distinction between these two different properties by using hide powder only1 we are also unable to draw the factor into account4 ,another source of error is the swelling influence on hide powder by acids2 for instance1 an acid extract of vegetable tannins would show higher tannin contents in the analysis than would the same extract when less acid4 ,the free sulphonic acid1 however1 is the active principle in synthetic tannins1 and since the latter always contain other acids 7of organic and inorganic origin7 devoid of tannoid character1 a source of error is thus introduced1 which we cannot eliminate by the present method of analysis4 ,of other methods of estimating the quality of a tanning material or tanning extract the determination of solubility1 ash1 colour1 and weight-giving properties in addition to the firmness imparted to the leather by the particular material are of importance4 ,as regards the synthetic tannins they are as a rule very soluble and it will generally be found sufficient to subject them to the ordinary qualitative examination4 ,the ash determination in synthetic tannins1 on the other hand1 is not of such value as in the case of natural tanning extracts4 ,from their composition we know that synthetic tannins contain considerable quantities of mineral salts1 the presence of some of which on the one hand emphasises their pickling effect1 and that on the other hand the property of dissolving phlobaphenes exhibited by the synthetic tannins is closely connected with their salt contents4 ,a colour determination of synthetic tannins is not of much importance1 since synthetic tannins nearly always impart a white or light brown colour to the hide4 ,in those cases only where coloured decomposition products appear as a result of intermediary reactions1 may the former impart greyish or dirty colorations of little beauty to the hide4 ,this is easily ascertained by lightly tanning a pelt4 ,the determination of the weight and solidity-giving properties is important both for leathers tanned with vegetable tanning extracts and for those treated with synthetic tannins1 but the results obtained when using animalised cotton are not directly convertible into figures required for practical purposes4 ,comparative figures are better obtained by actually tanning pieces of pelt on as practical a scale as is possible1 and testing the weights and tensile strengths of the pieces as against those of the original pelts1 whereby in the former case the yield 7pelt -- leather7 is obtained4 ,its capability as a tanning agent may be ascertained by submitting the synthetic tannin to an actual test tannage4 ,the latter is carried out by introducing the dilute extract into open glass jars1 holding about #djj c4c4 at a width of about #h cm4 ,footnote3 ,accumulator jars are excellent for the purpose4--,transl4 ,the concentration of the solution is chosen according to acidity and salt contents of the synthetic tannin1 the most suitable being #a4e-b4e ,b4 ,a piece of bated pelt is suspended in the liquor in such a way that the pelt is completely surrounded by liquor1 without1 however1 being creased or touching the bottom4 ,if the pelt were creased during tannage1 the wrinkles would become fixed and would show in the finished leather4 ,thus an unfair judgment of the extract would be delivered1 since similar results are produced by liquors which are either too concentrated or are not properly composed1 and naturally this property of an extract would be greatly to its disadvantage4 ,the various stages of tannage may be judged from various standpoints when examining the pelt as tannage proceeds4 ,on the one hand1 the surface of the but slightly porous pelt is altered so as to present a more porous appearance1 which is now rendered more capable of absorbing liquids4 ,on the other hand1 a similar alteration takes place within the pelt1 to the extent to which the tanning matter has penetrated it4 ,how far the penetration has proceeded is easily determined by utilising the different adsorption of coal-tar dyes by untanned and tanned pelt 7see p4 #aba74 ,an indicator for those synthetic tannins1 which are derived from the phenols1 is ferric chloride1 which only colours those parts of the pelt which have been penetrated by the synthetic tannins2 clearer and better results are1 however1 obtained when the dyestuffs referred to above are employed4 ,as soon as the tanning matter has completely penetrated the pelt1 the total time of tannage is noted1 and the velocity with which the tanning matter converts the pelt into leather at that particular concentration is thus obtained4 ,the tannage completed1 the leather must be well washed in running water to remove excess of synthetic tannin and then dried4 ,on examining the dry leathers1 the colour may then be observed1 and a cut will give an idea of the tensile strength and the length of fibre of the leather4 ,the tensile strength is1 however1 not of much value in such a barely tanned leather and cannot be compared with that obtained in leathers tanned on a practical scale4 ,the length of fibre is1 however1 of some importance1 since a special feature of finished leathers tanned with synthetic tannins is the beautifully long fibre--a property which manifests itself when the leather is torn and in which an expression of the quality of the synthetic tannin may be found4 ,similarly1 tanning experiments combining synthetic and natural tannins may be carried out1 the most interesting features of these being the different proportions in which the two products are mixed4 ,such experiments may be done1 for instance1 by preparing #b ,b4 solutions of each extract and then mixing them in proportions of1 say1 #aj3ij1 #bj3hj1 #cj3gj1 etc4 ,here it is again possible to infer the tanning intensity of the synthetic tannin from the concentration and the time used for tannage4 ,a further determination of the quality of a synthetic tannin is the capability of the latter of dissolving or precipitating the natural tannins4 ,as is well known1 synthetic tannins frequently possess the practically important property of rendering natural tannins easily soluble in water4 ,in some cases1 however1 synthetic tannins appear to solubilise natural tannins in concentrated solutions2 when1 however1 the latter are diluted1 the natural tannin is precipitated with varying completeness1 the reason of which is often the presence of excessive acid or the presence of such salts as have no phlobaphene-solubilising properties4 ,for practical purposes this determination may be carried out by mixing1 in different proportions1 concentrated tannin solutions and the synthetic tannin2 heating the mixture on the water bath for a short time1 cooling and finally diluting #aj1 #bj1 and #cj gm4 of the mixture to #ajj c4c41 which are then left in measuring cylinders for twelve to twenty-four hours2 the amount deposited will then be an indication of the solubilising or precipitating effect exhibited by the synthetic tannin4 ,other properties of the synthetic tannins connected with their practical application will be discussed in ,part ,,ii4 of this treatise4 ,,part ,,ii ,,synthetic ,,tannins3 ,,their ,,industrial ,,production ,,and ,,application ,with regard to their industrial production1 but few synthetic tannins are1 to-day1 of practical and commercial interest4 ,in addition to simplicity in the method of manufacture a certain degree of purity of the raw materials constitutes the criterion of their suitability4 ,the methods of manufacture1 of which nearly all are the property of the ,b4,a4,s4,f41 have been so worked out that the production of synthetic tannins presents no difficulties on a practical scale4 ,cresols1 naphthalenes1 and higher hydrocarbons are used as starting materials in the production of synthetic tannins2 the former substances or their oxidation products are sulphonated by means of concentrated sulphuric acid1 and the tanning matter produced by condensing the sulphonic acids with formaldehyde4 ,the crude synthetic tannin thus obtained has yet to be diluted and partly neutralised before it can be applied in practice1 and this is carried out by mixing the crude product with strong caustic lye4 ,by these means the high acidity is reduced to a suitable degree learned from experience on the one hand2 on the other hand1 the salts of the sulphonic acids form valuable components of the commercial synthetic tannins4 ,the first product placed on the market was named ,neradol ,d2 this represents the condensation product of cresolsulphonic acid4 ,the second synthetic tannin was ,neradol ,n1 which represents the condensation product of naphthalenesulphonic acid2 when diluted and neutralised to the same extent as is done in the case of ,neradol ,d1 the product is named ,neradol ,n ,d4 ,the latest synthetic tannin has been called ,ordoval ,g1 the starting material of which is a still higher hydrocarbon4 ,the tannoid-chemical properties of these synthetic tannins have been exhaustively determined by the author1 who employed ,neradol ,d1 which is most suitable for such a purpose1 and the investigations relating to it will now be treated fully in the following chapters4 ,the two other synthetic tannins exhibit very similar properties1 but their few characteristics shall be shortly dealt with4 ,the condensation product obtained by the method described on p4 #ee forms a viscous1 dark coloured mass1 the analysis of which by the shake method gives the following figures3- ,tanning matters #fb4f per cent4 ,non tannins #f4d ,insolubles #j4j ,water #ca4j --------------- #ajj4j per cent4 ,acidity3 #a gm4 #dj c4c4 ,n_/#aj ,na,o,h4 ,according to its chemical constitution1 this product may be considered to be dinaphthylmethanedisulphonic acid4 ,samples of this crude1 strongly acid material were partly neutralised1 and the following figures obtained on analysis3-- ,acidity4 ,tanning ,soluble ,water4 ,matters4 ,non-tans4 ,per ,cent4 ,per ,cent4 ,per ,cent4 #a gm4 #ce c4c4 ,n_/#aj ,na,o,h #fa4h #g4j #ca4b #a #cj #eh4i #g4a #cd4j #a #be #ej4a #g4i #db4j #a #bj #db4b #h4i #dh4i #a #ae #cg4d #aj4d #eb4b #a #aj #ca4f #ac4f #ed4h #a #e #bf4c #af4f #eg4a ,experimental tanning tests which were carried out with the various partly neutralised samples yielded leathers which1 on an average1 were nearly white1 but which in comparison with a leather tanned with ,neradol ,d appeared rather more greyish and were much harder4 ,a solution of the half-neutralised substance 7#a;gm4 #bj c4c4 ,n_/#aj ,na,o,h7 gives the following reactions3--- ,gelatine--,precipitate1 partly soluble in excess tannin solution4 ,ferric chloride-----,no coloration4 ,barium chloride-----,precipitate1 insoluble ,,hno#c4 ,bromine water-----,no reaction4 ,silver nitrate-----,no reaction4 ,aniline hydrochloride----,precipitate1 dissolves when solution is heated4 ,this condensation product is very soluble in water1 but insoluble in most solvents1 excepting methyl and ethyl alcohols4 ,the above reactions show the similarity of this dinaphthyl derivative to the dicresyl derivative1 and the absence in the former of characteristic reactions with iron salts is mainly accounted for by its lack of phenolic groups4 ,the absence of this reaction does not1 of course1 influence the tannoid character of dinaphthylmethanedisulphonic acid in the least1 and is of no importance in practice1 since the various stages of tannage may be demonstrated by means of a solution of indigotine4 ,from a technical point of view the absence of this reaction is advantageous to this extent1 that it eliminates the exceedingly great care to avoid the contact of tan liquors and tanned pelt with iron particles which has to be observed when tannins of phenolic character are employed4 ,in a chemical and technological evaluation of this tanning matter1 all those details apply which will be described when discussing ,neradol ,d4 ,the most important advantage possessed by this tanning matter1 from a commercial point of view1 is the lower price which it owes to the greater ease with which naphthalene may be obtained4 ,by treating the non-condensed crude product with barium chloride1 a product completely devoid of sulphuric acid is easily obtained2 the contents of sulphuric acid calculated as ,ba,s,o#d is about #i4e per cent4 ,this value is higher than that found by ,neradol ,d1 and may be explained by the fact that a slight excess of sulphuric acid is necessary for the preparation of ,greek3 b-naphthalenesulphonic acid4 ,comparative tanning tests using products containing sulphuric acid and products free from sulphuric acid 7neutralised to the same degree of acidity7 yielded leathers which were very similar2 the liquor containing no sulphates yielded slightly softer leather than that obtained from a liquor containing sulphates4 ,an experiment was also carried out1 using a liquor containing the tannin completely neutralised with caustic soda and subsequently acidified with acetic acid till the acidity of #a gm4 #aj c4c ,n_/#aj ,na,o,h2 here1 again1 no essential difference could be detected in the leather as compared with that from a liquor containing sulphates4 ,one of the most striking properties of this tanning matter is its solubilising effect on natural tannins and the phlobaphenes2 this property may mainly be compared to the similar one of other condensed sulphonic acids in their behaviour towards natural tannins4 ,if1 therefore1 natural tannins are mixed with this product and the solution used for tanning purposes1 the resultant leather will possess a dark colour owing to the presence of solubilised phlobaphenes2 if1 on the other hand1 a dark coloured leather1 which has been tanned with natural tannins1 is washed over with a #e ,b solution of this synthetic tannin1 or immersed for some time in the solution1 the leather assumes a lighter colour owing to the phlobaphenes being dissolved and removed from the leather by the synthetic tannin4 ,the presence of ,neradol ,,nd in leathers is detected by methods to be described under ,neradol ,d 7cf4 p4 #ajh74 ,the oxyazo reaction only succeeds when the solution has been boiled with a few drops of hypochlorite solution1 quickly cooled and excess of ammonia added4 ,when applying the indophenol reaction1 the solution must be treated as follows3 #c-d drops of hypochlorite solution is added1 and the solution heated for a short time2 or #e-f drops hypochlorite solution may be added1 and the solution left for some time1 in which case the heating may be omitted4 ,the solution is then made distinctly ammoniacal1 #a-b drops of dimethyl-p-phenylenediamine solution and a layer of alcohol poured on the top4 ,in most cases a blue coloration will appear2 the addition of #a-b drops of potassium ferricyanide solution with formation of a blue coloration indicates the presence of ,neradol ,,nd without fail4 ,the fact that a product possessing tanning properties may be obtained by condensing ,greek3 b-naphthalenesulphonic acid makes it interesting to investigate the behaviour of a non-condensed ,greek3 b-naphthalenesulphonic acid towards pelt4 ,the following solutions were allowed to act upon pelt for twelve days3-- 7#a7 ,concentrated solution of ,greek3 a-naphthalenesulphonic acid 7#aj ,b74 7#b7 ,greek3 b- 7#f ,be47 7#c7 #b1g- 7#ah ,b474 ,solution #a swells the pelt to a considerable extent without1 however1 solubilising it4 ,solution #b produces a similar effect4 ,solution #c dissolves the pelt appreciably on the first day2 after six days1 solubilisation is complete4 ,the reason of this different behaviour of the mono- and disulphonic acids is mainly to be sought in their difference of solubility2 the monosulphonic acids are not very soluble1 and are only capable of giving solutions measuring #aj and #f ,b1 respectively1 whereas the disulphonic acid yields an #ah ,b solution1 in addition to which the much higher acidity of the latter quickly gelatinises the pelt4 ,as regards the capability of the naphthalenesulphonic acids of dissolving phlobaphenes1 the following results were obtained3--solid ,argentine quebracho extract was mixed with-- #e percent1 ,greek3 a-naphthalenesulphonic acid3 opaque sol41 large quantity of insolubles4 #aj lesser #bj no insolubles4 #cj #e ,greek3 b-naphthalenesulphonic acid3 opaque sol41 lesser quantity of insolubles4 #aj #bj clear solution1 no insolubles #cj #e #b1g-naphthalenedisulphonic acid3 opaque sol41 large quantity of insolubles4 #aj #b1g as above4 #bj #b1g slightly opaque1 some insolubles4 #cj #b1g nearly clear solution1 no insolubles4 ,it is hence clear that the ,greek3 b-sulphonic acid possesses phlobaphene-solubilising qualities greater than those of the ,greek3 a-sulphonic acid or the disulphonic acid2 the ,greek3 b-sulphonic acid was therefore made the subject of ,ger4 ,pat41 #aha1bhh 7#hth ,february #aiag74 ,the synthetic tannin1 ,ordoval ,g1 is the formaldehyde condensation product of higher hydrocarbons 7mainly retenes71 and is a partly neutralised product containing no sulphuric acid4 ,the author's analysis gave the following figures3-- ,tanning matters #aj4g per cent4 ,soluble non-tannins #af4d ,insolubles #j4j ,water #gc4j ,acidity3 #a gm4 #d c4c4 ,n_/#aj ,na,o,h4 ,density3 #bc ,be4 ,ordoval ,g is completely soluble in water and glacial acetic acid4 ,only its organic constituents are soluble in alcohol1 ethyl acetate1 and acetone1 whereby a dark coloured crystalline mass separates4 ,ordoval ,g is insoluble in benzene4 ,the aqueous solution of ,ordoval ,g gives the following reactions3-- ,gelatine ,moderate flocculent precipitate4 ,ferric chloride ,darkish coloration4 ,potassium dichromate ,no reaction4 ,aniline hydrochloride ,dark brown precipitate4 ,formaldehyde hydrochloric acid ,no precipitate4 ,bromine water ,no reaction4 ,zinc acetate ,very slight opalescence4 ,barium chloride ,slight opalescence4 ,its capability of solubilising and consequent saving of natural tannins is shown by the fact that #ajj kilos of vegetable tanning material may be substituted by #dj kilos of ,ordoval ,g and the material in question in order to obtain the entire tanning intensity of the latter4 ,in one respect--that of its salts--,ordoval ,g differs from the ,neradols2 whereas the chromium and aluminium salts of the latter possess no such tannoid properties as will make the resultant leather exhibit any of the characteristics of either tannage1 it is possible to carry out combined tannage with a mixture of ,ordoval ,g and metallic salts4 ,tanning experiments carried out with the chromium1 iron1 aluminium1 and calcium salts of ,ordoval ,g yielded leathers which possessed proportionate characteristics of either kind of tannage to the extent to which either material was present4 ,this combination tannage seems to be assured of a great future2 especially may a combination tannage of iron salts and ,ordoval ,g eventually entirely replace chrome tannage4 ,the detection of ,ordoval ,g in leather is carried out as follows3 #aj gm4 of leather are boiled with #aej c4c4 of acetic acid1 a solution of #be gm4 of ,cr,o#h in #be c4c4 of a #ej per cent1 solution of acetic acid gradually added1 and the mixture boiled for three hours1 till the leather is decomposed and the solution has assumed a brown instead of the original light yellow colour4 ,the solution is then evaporated1 the residue dissolved in #fjj c4c4 hot water1 and the chromium precipitated with a #dj ,b4 solution of caustic soda4 ,the solution is filtered and cooled1 and a little hydrosulphite is added to #bj c4c4 of the cold alkaline filtrate2 in the presence of ,ordoval ,g1 a red colour will appear 7oxanthranolsulphonic acid74 ,brief mention must be made of the so-called ,corinal ,footnote3 ,swiss ,pat1 #gh1bhb1 #gh1gig1 #gi1ci4 a synthetic tannin placed upon the market by ,chem4 ,fabrik ,worms ,a4-,g41 in ,worms-on-the-,rhine4 ,it is a viscous1 brown fluid1 containing the aluminium salts of the tannoid acids4 ,the latter are formaldehyde-condensation products of sulphonated tar oils1 or the hydroxylated derivatives of the latter4 ,the density being #cc ,b1 it contains #bh4a per cent4 tanning matters1 #ac per cent4 soluble non-tannins1 and #aj4h per cent4 inorganic matter 7#c4b per cent4 ,al#b,o#c and #g4f per cent4 ,na#b,,so#d4 ,a similar product1 containing chrome salts as base1 is the so-called ,,esco-,,extract1 ,footnote3 ,schorlemmer1 ,collegium1 #aiag1 #abd manufactured by the ,chem4 ,fabrik ,jucker ,co4 in ,haltingen 7,baden74 ,this product is a dark1 reddish-brown fluid1 possessing acid reaction1 which strongly precipitates gelatine4 ,analysed by the filter method it contains #ab-ae per cent4 tanning matters1 #ag-bj per cent4 soluble non-tannins1 and #ah per cent4 ash1 of which #c per cent4 is ,cr#b,o#c4 ,this synthetic tannin may be employed alone or in conjunction with other tannins1 and yields a leather similar to that obtained by chrome tannage4 ,a4 ,condensation of ,free ,phenolsulphonic ,acid ,in practice1 the results of condensing phenolsulphonic acid with formaldehyde are manifold1 according to whether these materials are used in their concentrated or dilute state2 whether they interact in the cold or when heated2 or whether their interaction is gradual or rapid4 #a4 ,if a moderately dilute solution of phenolsulphonic acid 7#a3a7 is mixed with one-sixth of its volume of a dilute formaldehyde solution 7#a part #cj per cent4 ,,hcho solution plus #c parts of water7 in the cold1 with continuous stirring1 the solution remains clear and assumes a brown colour4 ,when left several hours1 a light1 white flocculent precipitate deposits1 which increases in quantity on diluting with water4 ,the solution precipitates gelatine2 the flocculent precipitate is easily soluble in hot caustic soda solution1 and1 when subsequently neutralised with acetic acid1 precipitates gelatine4 ,if equal parts of dilute phenolsulphonic acid and dilute formaldehyde 7concentrations as above7 are gradually mixed in the cold1 whilst stirring1 the mixture soon becomes opalescent1 and a flocculent deposit separates after eighteen to twenty-four hours4 ,these experiments carried out on the water bath immediately yield opalescent liquids1 from which an insoluble1 brown1 gluey1 and very sticky mass separates after twenty-four hours2 the latter is sparingly soluble in alkalies1 partly so in organic solvents4 #b4 ,if a moderately dilute solution of phenolsulphonic acid 7#a3a7 is gradually mixed with one-sixth of its volume of a concentrated 7#cj per cent47 formaldehyde solution in the cold1 whilst stirring1 slight opalescence immediately results1 and a flocculent deposit separates after about twenty minutes1 which gradually increases in quantity during the next few hours4 ,if the volume of formaldehyde is increased to the same as that of phenolsulphonic acid solution1 the flocculent deposit immediately separates1 and after twenty-four hours a brown1 gluey1 and very sticky mass--of the same solubility as that described in the previous experiment--is to be found at the bottom of the vessel used4 ,it should be noted that in both these experiments with concentrated formaldehyde solution a slight increase in temperature occurs concurrently with the process of condensation4 ,if the experiments are carried out on the water bath1 a gelatinous mass is instantly formed1 which assumes the colours of grey1 dirty light violet and dark violet1 in the order named1 and which1 whilst left several hours--or when heated on the water bath--is suddenly converted into the insoluble1 brown1 gluey mass above referred to4 #c4 ,if1 for the purpose of condensation1 phenolsulphonic acid to which #aj per cent1 of water has been added1 is employed1 the reaction proceeds very quickly and energetically4 ,if one-sixth of its volume of formaldehyde 7#a3c of the #cj per cent4 solution7 is added drop by drop to a cold solution of phenolsulphonic acid1 a reddish1 milky solution results1 which assumes a slightly lighter colour on addition of more formaldehyde and deposits an insoluble flocculent precipitate4 ,if the solution is kept below #de ,c41 by artificial cooling1 the light colour is maintained1 but a gelatinous precipitate is soon formed1 the viscosity of which increases on stirring1 and finally is converted into an insoluble1 tough1 gummy mass4 ,if1 on the other hand1 the mass is heated at the beginning of the reaction1 or if the amount of formaldehyde is increased and the mass cooled during reaction1 effervescence occurs1 and a cheesy1 dirty-coloured mass results1 which1 on cooling1 rapidly becomes solid and yields a very firm1 elastic1 rubbery mass1 which is absolutely insoluble in water4 #d4 ,the condensation proceeds exceedingly violently when concentrated phenolsulphonic acid is acted upon by one-sixth of its volume of formaldehyde4 ,if the latter is firstly added drop by drop to the phenolsulphonic acid1 a gel immediately results1 the temperature of which quickly increases on further addition of formaldehyde and suddenly boils over1 yielding a reaction product which1 when cooled1 forms a dirty violet1 firm1 elastic1 and rubbery mass1 insoluble in alkalies and hardly affected by organic solvents4 ,finally1 if the amounts of concentrated phenolsulphonic acid and formaldehyde stated above are mixed1 strong effervescence occurs and heat is evolved1 and a dirty blackish-violet mass is instantly formed which1 on cooling1 yields a rather brittle1 hard product insoluble in water4 #e4 ,totally different end-products are1 however1 obtained when the addition of formaldehyde 7#cj per cent47 in the proportion of one-sixth of the volume of dilute phenolsulphonic acid 7#a plus #i aq47 to the latter is extended over several hours4 ,in this case a slightly opalescent liquid is obtained which1 when left twelve hours1 is transformed into a brown mass soluble in water1 which strongly precipitates gelatine and possesses tanning properties4 ,hence direct tannoid substances are obtained by this method of condensation4 ,whereas no direct tanning experiment can be carried out with the insoluble compact mass obtained in the preparations described above on account of their absolute insolubility1 it is still possible to carry out tanning experiments with opalescent colloidal solutions in the following ways3-- 7a7 ,if a bated pelt is immersed in a liquid containing a condensation product obtained by gradually mixing a moderately dilute solution of phenolsulphonic acid and a dilute solution of formaldehyde1 the pelt is rapidly tanned on the surface4 ,complete penetration of the substance does not occur even after several days1 since the strong acidity of the solution causes a strong swelling of the pelt4 7b7 ,if a pelt is shaken for six hours in a shaking apparatus containing the liquid mentioned under 7a71 tannage again only takes place on the surface1 penetration being impeded by the strong swelling effect of the liquid4 ,repetition of the latter two experiments1 with the addition of #ae per cent1 common salt1 increases the tanning effect to some extent2 the pelt1 however1 is not tanned through1 but the non-tanned layers may be clearly seen to be pickled4 ,the tanning effects described above are only exhibited when the colloidal tan-liquor is present in great excess over the pelt1 since the former obviously only contains small amounts of tanning matter1 and even the presence of common salt does not bring about complete tannage of the pelt4 ,in order to prove the presence of tanning matters in the liquid described above1 several freshly prepared samples of the latter were analysed by the shake method of analysis without being first filtered and the following figures obtained3-- #a4 #b4 #c4 #d4 ,per ,cent4 ,per ,cent4 ,per ,cent4 ,per ,cent4 ,tanning matters #f4d #g4g #h4b #i4a ,soluble non-tannins #ae4b #ag4d #ad4e #aa4h ,these condensation products suspended in water all precipitate gelatine strongly and leave behind a perfectly clear liquid4 ,in all cases1 an intense blue colour was obtained on adding ferric chloride1 a slight precipitate only was obtained with aniline hydrochloride1 and bromine was rapidly absorbed with the separation of an insoluble white deposit4 ,the condensation products obtained by the interaction of dilute solutions of phenolsulphonic acid and formaldehyde at moderately high temperature1 which form slimy masses and are insoluble in water1 are soluble in alcohol4 ,an alcoholic solution of such a product was used in a tanning experiment1 and a piece of pelt immersed in the solution was tanned through in a few days2 the resultant leather being rather firm1 springy1 and slightly hard1 and the colour was a light brownish-grey4 ,all those condensation products which are easily or partly soluble in alcohol dissolve in caustic soda1 sodium carbonate1 in some cases also in borax and sodium sulphite4 ,they are rendered soluble with greater ease when the freshly prepared solution is heated on the water bath with the alkali2 the alkaline solution1 neutralised as far as is possible with acetic acid1 yields light brown coloured solutions1 the tanning effects of which have proved very satisfactory4 ,leathers tanned in such solutions1 however1 are rather empty and hard1 possess but little resilience and an uneven1 dirty greyish-brown colour4 ,a sample of such a product1 as nearly as possible neutralised with acetic acid1 contained #ad4h per cent4 tanning matters1 by the shake method of analysis4 ,b4 ,condensation of ,partly ,neutralised ,phenolsulphonic ,acid ,attempts were made at condensing partly neutralised phenolsulphonic acid2 the latter was obtained by mixing equal quantities of phenolsulphonic acid and sodium phenolsulphonate 7prepared by exactly neutralising phenolsulphonic acid with a concentrated solution of caustic soda74 ,the consequent dilution and decrease in acidity1 however1 considerably diminished the velocity of the reaction4 ,hence1 if the half-neutralised ,solution ,a#a 7cf4 p4 #ih7 is diluted with water1 taking equal volumes1 and one-sixth of the volume of dilute formaldehyde 7#a3c7 gradually added in the cold1 condensation is not induced4 ,when heated several hours an opalescent liquid results from which1 however1 no flocculent deposits separate when left for some time4 ,using a concentrated solution of formaldehyde 7,experiment ,a#b1 p4 #ih7 in the cold produces no reaction1 but after heating for a time an opalescent liquid is obtained4 ,both liquids give only slight precipitates with gelatine4 ,excess formaldehyde does not influence the reaction4 ,a repetition of ,experiment ,a#c 7cf4 p4 #ii71 using the above half-neutralised phenolsulphonic acid1 similarly required heat to induce condensation1 when a milky liquid of light reddish colour resulted4 ,whereas the addition of formaldehyde to non-neutralised concentrated phenolsulphonic acid caused violent reaction1 this proceeded very slowly in the case of half-neutralised phenolsulphonic acid1 resulting in the formation of a semi-solid mass1 which on heating became more viscous1 and finally1 when left twenty-four hours1 became a solid1 compact1 insoluble mass possessing a dirty light violet colour4 ,tanning experiments with these opalescent solutions proved them to exert a rapid penetration on the surface1 complete tannage1 however1 taking place after eight days only1 when a flat1 greyish-coloured and rather hard leather resulted4 ,c4 ,condensation of ,completely ,neutralised ,phenolsulphonic ,acid ,if concentrated phenolsulphonic acid is gradually neutralised with concentrated caustic soda solution till the former is faintly alkaline1 the sodium salt thus obtained is not so easily condensed with formaldehyde as is the case with the free acid4 #a4 ,if formaldehyde is gradually added to the neutralised phenolsulphonic acid in the cold1 opalescence immediately results2 on addition of water1 the liquid assumes a milky appearance4 ,on adding gelatine to this liquid1 a slimy precipitate is thrown down1 leaving a slightly opalescent liquid4 #b4 ,if formaldehyde is added to neutralised phenolsulphonic acid whilst it is heated on the water bath1 a slimy mass instantly separates1 which on cooling solidifies and forms a greyish-blue brittle mass1 insoluble in water and but sparingly soluble in alcohol2 the alcoholic solution is capable of converting pelt into leather4 ,the filtrate from the solidified mass strongly precipitates gelatine1 whereas the insoluble condensation product is soluble in caustic soda2 this alkaline solution also precipitates gelatine and the addition of acetic acid transforms the mixture into the gel state4 ,if the insoluble condensation product is dissolved in warm concentrated sulphuric acid1 the solution remains clear upon the addition of water1 but does not precipitate gelatine4 ,if1 finally1 this solution is neutralised with caustic soda1 the solution remains clear and precipitates gelatine strongly4 ,d4 ,condensation of ,cresolsulphonic ,acid ,experiments were carried out with the object of condensing o-1 m-1 and p-cresolsulphonic acids with formaldehyde in various ways2 no essential differences could be detected as regards the mode of reaction or the properties of the intermediary and end-products as compared to those of phenolsulphonic acid4 ,similarly1 condensation of different samples of crude cresol containing varying quantities of o-1 m-1 and p-cresol did not yield end-products sufficiently different to justify describing them in detail4 ,e4 ,relative ,behaviour of an ,alkaline ,solution of ,bakelite and ,natural ,tannins ,phenolsulphonic acid was condensed with a little formaldehyde1 and the reddish pasty condensation product dissolved in caustic soda4 ,this alkaline solution of bakelite was exactly neutralised with acetic acid and mixed with strong solutions of an untreated quebracho extract4 ,it was observed that the solubility of the quebracho extract was not increased by this treatment1 but the faintly acidic character of the natural tannin caused the bakelite to be thrown down as an insoluble precipitate4 ,crude phenolsulphonic acid1 when added to a solution of the quebracho extract referred to1 does not increase the solubility of the latter1 which even deposits considerable amounts of insoluble tannin particles4 ,quite different properties are exhibited by sodium phenolsulphonate1 which completely converts quebracho tannin into a water-soluble substance1 the aqueous solution of which deposits no insolubles4 ,the partly neutralised condensation product of phenolsulphonic acid and formaldehyde exhibits similar properties ,footnote3 ,grasser1 ,collegium1 #aiac1 #eba1 #dgh4 7see later74 ,f4 ,dicresylmethanedisulphonic ,acid 7,neradol ,d7 ,footnote3 ,ger1 ,pat41 #bia1 #deg2 ,austr4 ,pat41 #fa1 #jeg4 ,neradol ,d is a viscous liquid1 measuring about #cc ,b41 which is similar to extracts of natural tannins4 ,one of its characteristics is its phenolic odour2 it is completely soluble in water1 forming a clear1 semi-colloidal solution1 but is insoluble in all organic solvents with the exception of alcohol1 glacial acetic acid and ethyl acetate1 which dissolve all but its inorganic constituents4 ,the latter owe their presence to the neutralisation of the crude ,neradol with caustic soda1 and are composed of sodium salts of the sulphonic acid in addition to ,glauber salts4 ,the aqueous solution of ,neradol ,d shows properties similar to those exhibited by solutions of natural tannins and reacts as follows3--,footnote3 ,grasser1 ,collegium1 #aiac1 #ebj1 #dac4 ,methyl orange ,acid reaction4 ,barium chloride ,white precipitate1 insoluble in ,,hno#c4 ,ferric chloride ,deep blue coloration4 ,silver nitrate ,slight opalescence4 ,bromine water ,no precipitate4 ,formaldehyde hydrochloric acid ,no precipitate4 ,gelatine ,complete precipitation4 ,aniline hydrochloride ,strong precipitate4 ,the reactions with ferric chloride and gelatine should be especially noted1 since they are analogous to those given by natural tannins4 ,on the other hand1 the reactions with ,ba,cl#b1 bromine water and formaldehyde hydrochloric ,footnote3 ,stiasny carries out the reaction with formaldehyde-hydrochloric acid as follows3--#ej c4c4 of the tannin solution1 plus #e c4c4 concentrated hydrochloric acid and #aj c4c4 formaldehyde 7#dj per cent47 are heated under reflux condenser for ten minutes2 most natural tannins are completely precipitated 7,collegium1 #aijf1 #dce2 #aijg1 #eb et #ahh74 acid prove the different chemical composition of ,neradol ,d as compared to that of the natural tannins4 ,the fact that a positive reaction is given with aniline hydrochloride ,footnote3 ,this reaction is carried out as follows3--#e c4c4 of the tannin solution to be examined 7about #d gm4 tanning matter per litre7 are shaken violently in a test tube with #j4e c4c4 aniline and #b c4c4 concentrated ,h,cl added4 ,all natural tannins are unaffected by this treatment1 ligninsulphonic and other sulphonic acids cause opalescence4 ,note4--,employing formic acid in lieu of hydrochloric acid 7,knowles7 renders the reaction no more reliable4--,transl4 is very puzzling2 none of the natural tannins are precipitated by this reagent1 but only sulphite cellulose on account of its content of ligninsulphonic acid4 ,one is justified in assuming that there is at least some connection between the constitution of ligninsulphonic acid and that of dicresylmethanedisulphonic acid4 ,stiasny ,footnote3 ,collegium1 #aiac1 #eaf1 #adb4 recommends the following reaction for the detection of and differentiation between ,neradol ,d and wood pulp extract3--#aj c4c4 of a #e per cent4 solution of the extract to be analysed are violently shaken with #a-b drops of a #a per cent4 alum solution and about #e gm4 of ammonium acetate4 ,if only ,neradol ,d is present no precipitate separates even after twenty-four hours1 but if wood pulp be present1 a precipitate is thrown down in a quantity corresponding to the amount of wood pulp present4 ,the official analysis gives the following figures3 ,footnote3 ,grasser1 loc4 cit4 ,tanning matters #cb4e per cent4 ,soluble non-tannins #cc4j ,insolubles #j4j ,water #cd4e ------------- #ajj4j per cent4 ,ash #ag4j ,acidity3 #a gm4 #aj c4c4 ,n_/#aj ,na,o,h4 ,density3 #cc ,b4 ,a comparison of its quantitative analysis to that of a natural tanning extract is illustrated by the following figures of a chestnut and a quebracho extract of same density 7#bf ,b73-- ,chestnut ,quebracho ,per ,cent4 ,per ,cent4 ,tanning matters #cb4j #cd4j ,soluble non-tannins #ab4j #h4j ,insolubles #a4e #b4j ,water #ed4e #ef4j ----- ----- #ajj4j #ajj4j ,ash #j4d #b4j ,this comparison shows that extracts of natural tannins firstly contain certain amounts of insolubles1 whereas ,neradol is completely soluble in water1 forming a clear solution2 secondly1 natural tanning extracts contain smaller quantities of soluble non-tannins1 consisting of colouring matter and sugars1 in addition to small quantities of mineral matters 7ash74 ,neradol ,d contains considerable amounts of soluble non-tannins1 derived from salts of sulphonic and sulphuric acids1 again offering a satisfactory explanation of the high ash4 ,if1 therefore1 a mixture of ,neradol ,d and a natural tanning extract was submitted to a quantitative analysis1 the higher non-tannins and the high ash would indicate the presence of ,neradol ,d1 provided that wood pulp or a highly sulphited extract were not components of the mixture4 ,the chemical reactions taking place in the preparation of ,neradol ,d may be expressed thus3- ,,oh ,,oh ,,oh ,,oh ,h ,h,o,h ,h ,h ,h,,ch#b;,h ,h ,h#b,o ,,ch#b ,h v ,,ch#c ,,ch#c v ,h v ,,ch#c ,,ch#c v ,h ,,hso#c ,,hso#c ,,hso#c ,,hso#c #a4 ,neradol ,d ,reactions #a4 ,the quantitative determination of phenols introduced by ,bader1 ,footnote3 ,bull4 soc4 scient41 ,bucarexi1 #ahii1 #h1 #ea4 which consists in precipitating them as oxyazo compounds1 has been modified by ,appelius and ,schmidt ,foot,note3 ,collegium1 #aiad1 #eig4 for the purpose of detecting ,neradol ,d3--,to #ej c4c4 of the tannin solution 7analytical strength7 #ae c4c4 of diazo solution are added1 the mixture filtered1 if necessary1 and the filtrate made alkaline with caustic soda2 in the presence of ,neradol ,d in sufficient quantity1 a blood-red coloration results4 ,if but little ,neradol ,d be present1 the procedure is altered as follows3--,the tannin solution1 to which the diazo solution has been added1 is filtered1 and the filtrate poured on a piece of filter paper which is then dried2 a solution of caustic soda is spotted on the paper1 when1 if ,neradol ,d be present1 a red-edged spot will appear4 ,according to ,tschirch and ,edner1 ,footnote3 ,archiv4 d4 ,pharm41 #aijg1 #aej4 the diazo solution is prepared as follows3--#e gm4p-nitraniline are introduced into a #ejj c4c4 measuring flask1 #be c4c4 of water and #f c4c4 concentrated sulphuric acid added1 the mixture shaken and a solution of #c gm4 of sodium nitrite in #be c4c4 of water plus #ajj c4c4 of water added1 and the whole then filled up to #ejj c4c4 ,the solution should be stocked in the dark4 #b4 ,a less sensitive reaction for ,neradol and wood pulp extract constitutes that of ,appelius and ,schmidt employing cinchonine1 ,footnote3 ,collegium #aiad1 #eig4 while the presence of the substances in question yields characteristic precipitates4 #c4 ,seel and ,sander ,footnote3 ,zeits4 f4 ang4 ,chem41 #aiaf1 #ccc4 recommend the following method of detecting ,neradol ,d3-- 7a7 ,oxyazo ,reaction4--,about #e c4c4 of the tannin solution are rendered alkaline with caustic soda2 after cooling with ice1 about half the volume of alcohol is added4 #c-d drops of diazo solution are then added4 ,frequently1 this results in the solution assuming a blue coloration4 ,if not1 the solution is acidified with hydrochloric acid1 ether added1 and the mixture well shaken4 ,the water is now separated from the mixture1 fresh water added1 together with some caustic soda solution1 when1 if ,neradol ,d be present1 the salt of the colour acid formed dissolves in the water with a beautiful green or bluish-green colour4 ,at the place of contact of the water and the ether a bluish-green ring appears4 ,the diazo solution is prepared by dissolving p-aminophenol or its hydrochloric in a little dilute hydrochloric acid1 cooling in ice and carefully diazotising in the cold till a slight excess of nitrous acid is present4 ,it is essential that this solution should be tested before use1 and this is carried out by coupling it with an alkaline phenol solution2 if a dark blue oxyazo colour is formed1 the solution may be used4 ,it must be kept cool by surrounding it with ice4 7b7 ,indophenol ,reaction4--,to #e c4c4 of the solution to be tested1 a drop of a solution of dimethyl-p-phenylenediamine is added1 the solution rendered alkaline with caustic soda and #a-b drops of a #e per cent4 solution of potassium ferricyanide added4 ,if ,neradol ,d be present1 a blue colour appears1 either immediately or after some time4 ,the reaction is rendered more sensitive if alcohol is carefully poured on the solution after it has been rendered alkaline1 and potassium ferricyanide is then added4 ,at the place of contact a blue layer is formed1 which ultimately diffuses into the alcohol4 ,according to ,lauffmann ,footnote3 ,collegium1 #aiag1 #bcc4 the presence of natural tannins as well as that of wood pulp diminishes the sensitiveness of the reactions described above2 ,footnote3 ,zeits4 f4 ang4 ,chem41 #aiaf1 #ccc4 this investigator recommends a modification of these reactions4 #b4 ,electro-,chemical ,behaviour of ,neradol ,d ,the author's investigations of the electro-osmosis of an aqueous solution of ,neradol ,d ,footnote3 ,collegium1 #aibj1 #eig1 #bd4 proved that dicresylmethanedisulphonic acid exhibits anodic migration2 hence this product possesses negative charge and acidic character4 ,the impurities accompanying the synthetic tannin1 i4e41 salts1 free sulphuric acid1 and some phenols1 migrated anodic and cathodic respectively1 according to their charges4 ,a ,neradol ,d purified by electro-osmosis finally yielded a pure solution of dicresylmethanedisulphonic acid1 which precipitated gelatine and exhibited pronounced tanning effects1 but gave a greenish-black coloration with iron salts4 ,this conclusively proves that the blue coloration given by ,neradol ,d with iron salts is no characteristic feature of the pure synthetic tannin1 but is caused by the phenolic impurities accompanying the latter4 ,especially the first stage of the electro-osmosis produces a cathodic migration of the phenols1 which may then be detected at a cathode by means of the iron and bromine reactions4 ,it is characteristic of a dicresylmethanedisulphonic acid purified by electro-osmosis that it does not precipitate aniline hydrochloride4 ,it appears1 therefore1 that this reaction--which is characteristic of most synthetic tannins--is again caused by the presence of impurities4 #c4 ,the ,influence of ,salts and ,acid ,contents on the ,tanning ,effect of ,neradol ,d ,chemical analysis of crude ,neradol revealed a natural dicresylmethanedisulphonic acid 7the tanning agent7 contents of about #fh per cent1 which agrees fairly well with the calculated amount4 ,like other strong and weak acids this sulphonic acid exercises a strongly swelling influence on pelt4 ,whereas the effect of acid present in solutions of ,neradol ,d of medium concentration and its tanning effect both influence the pelt and are fairly well balanced1 this is not the case as regards highly concentrated and very dilute solutions4 ,if1 for instance1 a very dilute solution of crude ,neradol 7about #j4be ,b47 is used1 the tanning effect of this solution is exceedingly small and does not show itself till after several hours4 ,the relatively high dissociation of the acids at this high degree of dilution causes an extremely rapid and strong swelling of the pelt1 which has therefore absorbed its maximum amount of water 7maximum swelling7 before the tanning effect of the sulphonic acid comes into play and by fixing the surface of the pelt is enabled to prevent the excessive swelling effect of the acids4 ,the addition of neutral salts to the tan liquor diminishes the effect of the acids on pelt 7dehydrates the pelt7 and prevents drawing of the grain4 ,if1 for instance1 common salt be added to a solution of crude ,neradol1 the original quantity of sulphonic acid present would remain constant1 but the presence of salt would diminish the degree of dissociation and consequently the swelling4 ,this effect is still more pronounced when the absolute amount of free sulphonic acid is diminished4 ,hence1 if crude ,neradol is treated with increasing amounts of caustic soda1 a series of products containing increasing quantities of salt and decreasing concentrations of sulphonic acid is obtained4 ,the acidity of the ,neradols may be determined by titration with ,n_/#aj caustic soda2 this procedure hence establishes a means of determining the 7unknown7 acidities which may be expressed in terms of c4c4 ,n_/#aj ,na,o,h4 ,the acidity of crude ,neradol was found to be-- #a gm4 #ej c4c4 ,n_/#aj ,na,o,h i4e41 #a gm4 of crude ,neradol requires #ej c4c4 ,n_/#aj ,na,o,h for complete neutralisation2 the decrease in acidity causes a decrease in contents of tanning matters and the quantities of salts increase4 ,the following table gives the figures obtained by differently neutralised neradols3-- ,acidity4 ,tanning ,matters4 ,na#b,,so#d4 ,per ,cent4 ,per ,cent4 #a gm4 #ej c4c4 #fh 444 #a gm4 #dj c4c4 #ei #d #a gm4 #cj c4c4 #ej #h #a gm4 #bj c4c4 #da #ab #a gm4 #aj c4c4 #cc #ag #a gm4 #e c4c4 #bh #bj #a gm4 #j c4c4 #bj 444 ,tanning experiments with these different neradols 7employing solutions of #a ,b4 strength7 demonstrated that neradols of acidity #ej1 #dj1 and #cj exerted strong swelling and gave comparatively hard leathers2 neradols of acidity #bj1 #aj1 and #e exert no swelling1 yield quick tannage and soft leather4 ,the swelling 7hardening7 effect of the acid and the dehydrating 7softening7 effect of the salts in this case1 therefore1 are well balanced1 and this fact affords an explanation of the rapid change from hardening to softening effects exhibited by partly neutralised ,neradol where less acid and a greater quantity of salts respectively are present4 ,it may finally be noted that the acidity of ,neradol ,d1 #a gm4 #aj c4c4 ,n_/#aj ,na,o,h1 has been found to be the most suitable one for practical purposes4 ,the author has1 however1 successfully employed some neradols of considerably higher acidities4 ,the acidity above mentioned is possessed by a ,neradol ,d containing #ag per cent4 ash and #cj per cent4 sodium sulphonates and ,glauber's salts crystals respectively4 ,this large quantity of salts present on the one hand effects the rapid pickle and tanning effect exhibited by ,neradol ,d1 on the other hand it also effects the softness in the leather resulting from its use either alone or in admixture with natural tannins4 #d4 ,phlobaphene ,solubilising ,action of ,neradols ,a special feature of ,neradol ,d is its property of solubilising phlobaphenes1 which may be ascribed to its contents of sulphonic acids or their salts4 ,in order to demonstrate whether the sulphonic acids and their salts are capable of solubilising the insoluble or sparingly soluble anhydrides of the tannins 7the phlobaphenes7 before and after condensation1 the following experiments were carried out3-- ,crude ,argentine solid quebracho extract was converted into a highly viscous liquid by treating it for several hours with water at #ajj ,c41 and the anhydrides rendered insoluble by diluting the liquid with a large volume of cold water4 ,the precipitate formed1 consisting of quebracho phlobaphenes1 was separated from the liquid by decantation1 and purified by washing it several times with water4 ,each #aj gm4 of this moist paste were treated in the cold with 7a7 free phenolsulphonic acid2 7b7 sodium phenolsulphonate2 7c7 crude ,neradol and 7d7 ,neradol ,d1 #bj c4c4 of water at #de ,c4 added1 and the mixture allowed to cool slowly2 the following solutions resulted3-- 7a7 ,opalescent solution1 much deposit1 7b7 ,clear solution1 no deposit4 7c7 ,nearly clear solution1 very little deposit4 7d7 ,clear solution1 no deposit4 ,this clearly proves that free and condensed phenolsulphonic acids as such are not capable of completely solubilising phlobaphenes1 whereas the sodium salts of free and condensed phenolsulphonic acids possess this property4 ,the salt contents of ,neradol ,d1 therefore1 constitute an advantage in this respect1 that not only may ,neradol ,d be mixed with solutions of any natural tannin without insolubles being thereby deposited1 but it may also be added in large quantities to a tannin solution with the result that the sparingly soluble and wholly insoluble constituents 7phlobaphenes7 are completely brought into solution4 ,the practical importance of the solubilising effect of ,neradol ,d relating to solid ,argentine quebracho extract is demonstrated in the following series of investigations carried out by the author3-- ,footnote3 ,collegium1 #aiac1 #dgh2 ,austr4 ,pat41 #fh1 #gif4 ,solid ,neradol ,matters ,tanning ,abs4 ,increase ,argentine ,d4 ,calc4 of ,mixture ,increase per ,quebracho ,found4 in ,tanning #ajj gms4 ,extract4 ,matters4 ,extract4 ,gm4 ,gm4 ,per ,cent4 ,per ,cent4 #ajj #j #ff4j #ff4j 444 444 #j #ajj #cb4e #cb4e 444 444 #ij #aj #fb4g #fd4g #b4j #b4b #hj #bj #ef4a #eh4g #b4f #c4c #fj #dj #eb4f #ef4i #d4c #g4a #ej #ej #di4c #ee4b #e4i #aa4h #cj #gj #db4f #dg4c #d4g #ae4f #bj #hj #ci4b #db4c #c4a #ae4e ,the maximum solubilising effect is exhibited in the mixture of #gj parts of ,neradol and #cj parts of quebracho1 with an additional percentage of tanning matters in the mixture of #ae4f per cent4--a figure which is very nearly identical with that of the insolubles present in the original ,argentine quebracho extract4 ,the phlobaphene-solubilising property of ,neradol ,d is closely connected with the influence of the latter on the colour of leathers tanned with natural tannins4 ,if1 on the one hand1 a pelt is tanned with natural 7i4e41 non-treated7 quebracho extract1 a rather light coloured leather results1 the fleshy colour of which is characteristic of quebracho4 ,the dark coloured phlobaphenes present1 on account of their insolubility1 will have no influence on the colour of the leather4 ,if1 now1 the quebracho extract be treated with sulphite and bisulphite in the usual way1 the phlobaphenes are solubilised1 but the reducing effect of the bisulphite tends to brighten the colour of the otherwise dark coloured phlobaphenes as well as that of the soluble tannins1 and a reddish-yellow coloured extract results1 imparting its own colour to the pelt4 ,when1 on the other hand1 the quebracho extract is solubilised by means of ,neradol ,d1 the phlobaphenes are brought into solution without reduction taking place1 and a dark brownish-red extract results1 which imparts a similar colour to the finished leather4 ,this darkening effect of ,neradol ,d is most conspicuous in the case of mangrove1 maletto1 and chestnut1 but is absent in the case of algarobilla1 dividivi1 gambir1 sumac1 and valonea4 ,the varying phlobaphene contents of the tannins easily afford an explanation of the different properties above alluded to3 the mangrove phlobaphenes are dark coloured bodies1 those of mimosa1 maletto1 and chestnut are of lighter colour1 and the last-named tanning materials enumerated above are either devoid of phlobaphenes or possess them only as very light coloured bodies4 ,algarobilla1 sumac1 gambir1 dividivi1 and valonea1 on the other hand1 are associated with large amounts of sparingly soluble ellagic acid1 known as bloom or mud which imparts a light colour to the finished leather1 and conveniently covers the dark colour imparted to the leather by other tanning materials2 for this reason the former are often used in the lay-aways or in the finishing processes4 ,similar effects to those of ,neradol ,d are exhibited by other salts of sulphonic acids1 e4g41 sodium benzylsulphanilate 7,solvenol ,b4,a4,s4,f41 or solution salt 7,solutionsalz7 ,hoechst72 the author prepared mixtures of such salts and untreated quebracho extract in order to determine their solubilising effects1 and arrived at the following results3-- #cj parts ,solvenol plus #gj parts quebracho extract3 clear solution1 no deposit4 #be parts ,solvenol plus #be parts quebracho extract3 clear solution1 very little deposit #bj parts ,solvenol plus #hj parts quebracho extract3 nearly clear solution1 very little deposit4 #ae parts ,solvenol plus #he parts quebracho extract3 slightly opaque solution some deposit4 ,leathers tanned with these mixtures were more or less dark coloured according to the amounts used of solvenol and the consequent solubilisation of the phlobaphenes4 ,a similar effect1 though of opposite nature from a tanning standpoint1 is exhibited by sulphonates on certain colloidal dark coloured substances4 ,a phenolsulphonic acid1 which had been overheated during sulphonation and subsequently condensed 7crude ,neradol71 imparted a conspicuous greyish-brown colour to the leather2 samples of this crude product were then partly neutralised with varying amounts of alkali1 and these samples 7containing increasing quantities of salts7 tested for tannin and colour effects4 ,it was found that the more highly neutralised samples imparted a darker colour to the solutions1 but these dark products did not deposit the dark impurities on the pelt4 ,one may therefore assume that tannoid substances are colloidally suspended1 and when converted into true solutions are incapable of being fixed in insoluble form by the pelt4 ,just as1 by adding ,neradol ,d to a tanning extract1 the phlobaphenes are solubilised and a dark coloured extract results1 it is also possible to remove the mechanically deposited phlobaphenes and oxidised tannins from the finished leather1 and1 as a consequence1 lighten the colour of the leather4 ,for practical purposes1 bleaching with ,neradol ,d is carried out by brushing over the darkly coloured leather with a #b-c ,b4 solution of ,neradol ,d1 and then rinsing well with water1 in order to remove the solubilised tannin4 ,a lighter colour may also be obtained by immersing the leather in a liquor of the strength mentioned above for several hours1 and then rinsing with water1 but by this procedure not only the surface tannin is removed1 but also tannin from the leather substance itself2 this method is therefore not suitable for heavy leathers which are sold by weight4 ,the advantage of employing ,neradol ,d as a bleach in this way is to be found in the fact that1 on the one hand1 the bleaching sulphonic acid attacks the leather to a much slighter extent than is the case with inorganic acids usually employed for this purpose2 on the other hand1 the method of brushing the sulphonic acid on the leather only introduces small amounts of sulphonic acid in the leather1 thus lessening the harmful effects of acids upon leather4 ,furthermore1 the common methods of using alkalies as tannin-solubilising agents with the consequent running off and waste of alkaline tan liquors are here substituted by a method leaving liquors rich in tannin and ,neradol1 and which may be used in the ordinary procedure of tannage4 ,since ,neradol ,d contains neutral sodium sulphate 7about #c per cent471 and the latter1 by precipitating colouring matters present in tan liquors1 may slightly bleach these1 it was of interest to determine whether the sodium sulphate plays any part in the bleaching effected by ,neradol4 ,mixtures of chestnut and quebracho extracts were prepared1 to which were added3-- 7#a7 #e per cent4 ,neradol ,d4 7#b7 #e per cent4 ,neradol ,d4 free from ,na#b,,so#d4 7#c7 #ae ,per cent4 sodium sulphate 7corresponding to above ,neradol ,d74 ,these mixtures were allowed to act upon pelt alongside of comparison tests using quebracho and chestnut extracts only1 the strength of the liquors in all cases being #a4e ,b2 the pelt was left in the solution till tanned through4 ,the following results were obtained3-- 7#a7 ,quebracho tanned leather was darker2 no difference in colour by chestnut extract4 7#b7 ,similar to 7,i74 7#c7 ,same colour as given by the original extracts4 ,this experiment demonstrates that absence of sodium sulphate in the mixture is without influence on the colour of the resulting leather1 and that an addition of sodium sulphate to natural extracts does not affect the colour imparted by them to pelt #e4 ,effect of ,neradol ,d on ,pelt ,being a sulphonic acid derivative1 the chemical constitution of ,neradol is obviously considerably different from that of the natural tannins1 and the question has been asked3 ,will ,neradol ,d1 in its concentrated form1 attack the hide substance8,footnote #a3 ,collegium1 #aiac1 #eba1 #dhg4 ,bearing in mind that concentrated extracts of vegetable tannins in some circumstances effect a dead tannage 7cf4 case-hardening7 and hence reduce their practical value1 and that for this reason it is impossible to allow either concentrated extracts or concentrated ,neradol ,d to act upon pelt1 the author still decided to carry out some experiments in this direction4 ,concentrated ,neradol ,d 7#cc ,b47 and strong aqueous solutions of this material in strengths of-- #cj #be #bj #ae #aj #e #c #a ,b4 were therefore allowed to remain in contact with pelt for a period of ten days1 when the pelts were taken out and washed in running water for twenty-four hours1 and then dried4 ,the resultant leathers possessed the following properties3-- #cc ,b4 solution3 completely gelatinised4,footnote #b #cj ,footnote #b #be two-thirds gelatinised2 surface tanned4 #bj one third gelatinised2 surface dead tanned4 #ae pelt was glassy throughout4 #aj rather cracky leather1 but well tanned4 #e normal tannage4 #c #a ,footnote #b3 ,impossible to subject the pieces to a proper washing out4 ,the interiors of the leathers obtained from the #be and #bj ,b4 solutions were completely gelatinised2 this may be accounted for by assuming that the surface was dead tanned1 and that hence the free dissociated sulphonic acid diffused into the leather1 towards which it exhibited hydrolysing rather than a tannoid effect with the consequent result described above4 ,above #aj ,b4 the effect is more that of an acid with concentrations below #aj ,b4--the only ones of technical importance--however1 no ill-effects may be observed4 ,for tanning purposes1 ,neradol ,d solutions of #b ,b4 are quite satisfactory1 and it has been found ,footnote #a3 ,technikum1 #aiac1 #hj1 #cbd4 that solutions of this strength do not dissolve out any protein of the hide4 ,footnote #b3 ,the translator cannot agree with the author on this point4 ,he has1 for instance1 found that solutions of analytical strength dissolve considerable amounts of hide substance1 and his practical experience confirms results arrived at in the laboratory4 ,a purely ,neradol ,d tanned leather may be produced by immersing a bated pelt1 free from lime1 in a #b ,b4 ,neradol ,d liquor for about four days2 the resultant leather being nearly white and otherwise very similar to a leather tanned with vegetable tanning materials4 ,the main application of ,neradol ,d is in admixture with vegetable tanning materials2 especially in the early stages of tannage is this substance of value1 since by its use not only a light coloured leather surface is obtained1 but its presence prevents a subsequent dead tannage when strong vegetable tan liquors are applied1 and it also imparts strength to the grain layer4 ,it is thus possible to shorten the time consumed by the tanning process by employing ,neradol ,d in the manner described4 ,a further explanation as to why the tanning process is considerably hastened by using ,neradol ,d1 either alone or in conjunction with natural tannins1 is afforded by the fact that though ,neradol ,d quickly penetrates the grain1 it is but loosely fixed by the latter1 i4e41 it is not deposited to such an extent that it would prevent penetration of the vegetable tannins4 ,in the case of a mixture of ,neradol ,d and vegetable tannins1 the former quickly diffuses into the pelt and fixes the fibres1 thus facilitating penetration of the vegetable tannins4 ,this assumption is justified in view of the speed with which ,neradol ,d completely penetrates and tans the pelt1 since ,neradol ,d containing acids and salts exhibits effects similar to those of a pickle4 #f4 ,reactions of ,neradol ,d with ,iron and ,alkalies ,a special characteristic of ,neradol ,d tannage is the sensitiveness of the latter to the action of iron and alkalies4 ,the active principle of ,neradol ,d being free dicresylmethanedisul-phonic acid1 which is easily neutralised by lime1 ammonia1 and amino-acids and hence rendered inactive for tanning purposes1 it is essential that the pelt prior to tannage with ,neradol ,d should be completely delimed1 bated1 and freed from all constituents possessing alkaline reaction4 ,it is1 however1 possible to regenerate ,neradol ,d liquors contaminated with alkali or partly neutralised by the addition of small quantities of organic 7formic1 acetic1 lactic1 and butyric7 or inorganic 7hydrochloric or sulphuric7 acids1i4e41 the dicresyl-methanedisulphonic acid is again partly liberated1 and this procedure is always preferred where the tanning process does not allow of a complete deliming of the pelt prior to introducing the latter into a ,neradol ,d liquor4 ,if1 on the other hand1 such liquors are kept properly1 and the addition of acid referred to kept up1 they will remain active for weeks and need only strengthening up with the requisite quantity of ,neradol prior to introducing fresh pack4 ,the sensitiveness to alkalies of ,neradol ,d is considerably greater than in the case of natural tannins1 and it appears that a vegetable tan liquor neutralised with lime will not even surface-tan when acting upon pelt and will neither impart a dark colour to the leather nor remove from it any appreciable amount of protein4 ,similarly1 a ,neradol ,d liquor neutralised with lime exerts no tanning action1 but in contradistinction to the vegetable tan liquor similarly treated1 will impart a blue or blackish-blue colour to the pelt1 from which it removes larger quantities of protein4 ,the author examined two such liquors relating to their contents of tanning matters and protein and obtained the following results3-- ,reaction4 ,bark4 ,tans4 ,non-,tans ,insol4 ,proteins ,per ,per ,per ,per ,cent4 ,cent4 ,cent4 ,cent4 ,vegetable ,slightly #ab #j #b4ic #j4ce #j4ja tan alkaline liquor ,neradol #aj #j #d4dc #j4ag #j4ag ,these figures do not only show the higher protein contents of the ,neradol ,d liquor1 but do also show higher contents in soluble non-tannins1 which consist mainly of lime 7#b4ab per cent47 and sodium salts 7#a4h per cent471 thus establishing the fact of the sensitiveness of ,neradol ,d to alkalies in addition to its lime-solubilising effects4 ,the sensitiveness towards alkalies is also noticeable on a large scale where the tanpits have been built of cement2 though the pelt may be quite free from lime1 the ,neradol ,d is quickly neutralised by the cement1 with results similar to those enumerated above4 ,the blue coloured soluble compound of ,neradol ,d and iron salts1 to which frequent reference has been made1 is very important from a practical standpoint4 ,whereas the catechol tannins 7i4e41 fir1 gambir1 hemlock1 cutch1 mangrove1 and quebracho7 are coloured black1 those of the pyrogallol class 7i4e41 algarobilla1 dividivi1 valonea1 gallotannic acid1 myrabolams1 and sumac7 bluish-black1 and the mixed tannins 7i4e41 canaigre1 oak1 and mimosa bark7 bluish-purple by iron alum1 ,neradol ,d is coloured a pure blue4 ,how sensitive this reaction is1 the following comparative analyses illustrate3 to each litre of tan liquor containing #d gm4 tanning matter prepared from 7a7 quebracho extract and 7b7 ,neradol ,d1 #aj c4c4 of a #aj per cent4 iron alum solution were added1 the solutions heated to #ajj ,c41 cooled and filtered1 and the colour of the filtrates and the weight of the precipitates determined3-- 7a7 ,quebracho solution3 light reddish-brown filtrate1 #c4bb gm4 precipitate4 7b7 ,neradol solution3 deep blue filtrate1 #j4jb gm4 precipitate4 ,hence1 on adding a soluble iron salt to a solution of a natural tannin1 most of the tanning matter is precipitated2 the colour of the filtrate1 however1 is much the same as that of the original solution4 ,a ,neradol ,d liquor similarly treated gives no precipitate1 but is coloured blue throughout4 ,the filtrates from the above solutions were allowed to act upon pelt1 and the following observations were made3-- 7a7 ,the light reddish-brown filtrate from the quebracho liquor exhibited no well-defined tanning effect on pelt1 to which it imparted a light brown colour4 7b7 ,on the other hand1 the deep blue filtrate from the ,neradol ,d liquor exhibited well-defined tanning effects1 and imparted a deep blue colour to the pelt4 ,for practical purposes1 the sensitiveness of ,neradol ,d to iron is not only remarkable because any contact with iron particles will colour the liquor 7and hence the pelt7 blue1 but also because the slight amount of iron always present in cement renders the use of cement pits prohibitive where ,neradol ,d liquors are used4 ,this intense blue coloration might have made possible a colorimetric estimation of ,neradol ,d4 ,the author has investigated this possibility1 using different concentrations of ,neradol ,d liquors to which a solution of iron ammonium alum was added1 and found that when1 at certain concentrations1 the maximum blue colour had been obtained1 it was still possible to increase the quantity of ,neradol without the intensity of the colour being affected4 ,addition of a little alkali tends at first to darken the blue colour1 more alkali changes the blue colour to brown and yellow1 successive additions of a weak organic acid 7e4g41 acetic acid7 rapidly lighten the blue colour4 ,since industrially used ,neradol ,d liquors always contain varying quantities of acid and may be neutral or even slightly alkaline1 it must be considered impossible to make any use of such a colorimetric estimation for practical purposes4 #g4 ,reagents ,suitable for ,demonstrating the ,various ,stages of ,neradol ,d ,tannage ,the extent to which tannage with ,neradol ,d proceeds on the surface and within the pelt may be judged from the feel of the skin1 but such a method is totally unsuited to any but a practical tanner4 ,a suitable and reliable reagent is indigotine 7,b4,a4,s4,f471 which clearly distinguishes tanned and untanned layers of the pelt4 ,if1 for instance1 a #a-b per cent1 solution of indigotine is brought into contact with a fresh cut on a pelt1 and the latter subsequently washed with warm water1 the indigotine is only retained by the untanned parts2 a leather tanned with ,neradol ,d is therefore only coloured by indigotine to the extent to which it has combined with the ,neradol4 ,footnote3 ,according to ,seel and ,sander 7,zeits4 f4 ang4 ,chem41 #aiaf1 #ccc71 basic dyestuffs are also very suitable for demonstrating tanned parts of the pelt4 ,another reagent is constituted by iron ammonium sulphate2 the extent of the penetration of ,neradol ,d1 which gives an intense blue coloration with iron salts1 into the leather may be determined by washing the pelt treated with ,neradol ,d1 making a cut1 again washing and treating the cut with a few drops of a weak solution of iron ammonium sulphate4 ,those parts of the pelt which have been converted into leather then appear deep blue2 on the other hand1 those which have been in contact with ,neradol ,d1 but have not yet been converted into leather1 are light blue4 ,those parts which have not yet been in contact with ,neradol ,d appear pure white2 the results of this reaction are therefore opposite to those obtained by the use of indigotine4 #h4 ,combination ,tannages with ,neradol ,d ,whereas mixtures of ,neradol ,d and vegetable tannins impart properties to the leather consistent with the proportions in which these materials are present1 it is not possible to combine ,neradol ,d with mineral tanning agents or fats 7e4g41 fish oils1 etc47 in such a way that a leather characterised by the properties of either material is obtained4 ,experiments were carried out using 7#a7 chrome salts plus ,neradol ,d2 7#b7 aluminium salts plus ,neradol ,d2 and 7#c7 oils plus ,neradol ,d1 and the following conclusions were arrived at3-- #a4 ,,chrome-,,neradol ,d liquors1 containing comparatively larger amounts of ,neradol ,d1 act too rapidly on the pelt and draw the grain2 smaller amounts of ,neradol ,d seem without influence on the finished leather1 which possesses pronounced characteristics of chrome leather4 ,another disagreeable factor is the following3 the chrome salts must possess a certain degree of basicity in order to produce good leather2 the ,neradol ,d must1 on the other hand1 possess a certain acidity to produce the optimum results1 and it is hence impossible to balance practically the basicity of the chrome salts and the acidity of the ,neradol in order to justify the presence of both4 ,if one of the two is used separately before the other1 a leather always results possessing the characteristics of the material first employed1 provided the time of action has been sufficiently extended4 ,if insufficient time has been allowed1 the characteristics imparted by the main tanning agent are not altered4 #b4 ,,aluminium ,,salts ,,and ,,neradol require practically the same basicity and acidity respectively1 and when combined always yield a leather possessing mainly the properties of one of the components4 ,in addition to this fact1 leathers tanned with aluminium salts possess great softness and stretch1 those tanned with ,neradol ,d greater firmness and less stretch1 and these opposing qualities completely compensate one another and render nil the value of such mixtures4 ,in addition to this1 the presence of aluminium salts produces no better fixation on the leather fibre of basic coal-tar dyes1 so that in this respect also a combination of aluminium salts and ,neradol ,d is of no value4 #c4 ,,fat ,,neradol ,d ,,tannage3 ,just as aluminium salts impart special characteristics to leather1 this property is exhibited by fatty matters1 especially so as regards stretchiness and softness4 ,both of the latter are not apparent to the same extent in an oil tannage into which ,neradol ,d and oil enter as constituents4 ,it is1 however1 not excluded that1 in view of the fact that the combination of oils and ,neradol ,d appear to produce the most promising results of the three from a technical point of view1 such combination would yield products possessing less stretch and greater softness which1 by occupying an intermediary position1 might possess certain advantages and be useful for certain technical purposes4 #i4 ,analysis of ,leather ,containing ,neradol ,d ,chemical examination of leathers tanned with ,neradol ,d or with mixtures of natural tannins and ,neradol ,d often involve a determination of the materials employed in tannage4 ,in most leathers exclusively tanned with vegetable tanning materials1 it is usually possible to determine at least the nature of the main tanning agent1 whereas the attempts at determining those tannins which are only present in minor quantities rarely succeed4 ,since ,neradol ,d usually is employed in comparatively small quantities1 it has been imperative to find a method which also permits of the detection of smaller quantities of ,neradol ,d4 ,provided the presence of not less than #e per cent4 7on the weight of the leather7 of ,neradol ,d1 the following method yields reliable results3--#bj-cj gm4 of the leather are ground or sliced as finely as possible and the powder 7or the slices7 treated in the cold with a sufficient volume of dilute ammonia solution 7#e c4c4 ammonia plus #ie c4c4 of water7 for eight to twelve hours4 ,the object of this is to dissolve the tannins1 but no protein should go into solution4 ,the solution is filtered and the filtrate evaporated on the water bath till it occupies a volume of about #cj c4c4 ,a few c4c4 of aniline hydrochloride are now cautiously added1 when it should be carefully noted if a precipitate is thrown down which might be either completely or only partly soluble in excess of aniline hydrochloride4 ,a precipitate is always thrown down when ,neradol ,d or wood pulp is present2 only the ,neradol ,d precipitate is soluble in excess of aniline hydrochloride4 ,partial solubility of the precipitate therefore indicates the presence of both wood pulp and ,neradol ,d4 ,the quantitative determination of sulphuric acid--the detection and estimation of which in leather is important--is considerably influenced by the presence of ,neradol ,d4 ,practically all methods in vogue dealing with its determination were based on the estimation of the sulphur introduced into leather by sulphuric acid4 ,the presence of ,neradol ,d1 the main constituent of which is dicresylmethanedisulphonic acid1 renders it impossible by such methods to determine whether the combined sulphur owes its origin to sulphuric or sulphonic acid4 ,it remains yet to be determined whether the sulphonic acid influences the leather substance to the extent that sulphuric acid does2 it must1 however1 be borne in mind that ,neradol ,d in addition to free sulphonic acid also contains sulphonates and sulphates1 which may enter into the leather and thus increase the sulphur contents of the latter4 ,a method must hence be devised which estimates the free acid only and provides the means of distinguishing this from all other acids of organic and inorganic acids4 ,paessler1 ,footnote3 ,collegium1 #aiad1 #ebg1 #abf2 #eca1 #eji2 #ecb1 #efg4 by extracting the leather and dialysing the filtrate1 has effected a separation of the acids and the tanning and colouring matters and quantitatively estimated the sulphuric acid in the dialysate4 ,immerheiser ,footnote #a3;,collegium1 #aiah1 #ehb1 #bic4 devised a method1 based upon the property of sulphuric acid of combining with ether1 for the purpose of determining free sulphuric acid in leathers3--#aj gm4 of the leather1 cut into small pieces1 are extracted three times with #bjj c4c4 distilled water at room temperature1 the time of each extraction being ten to twelve hours1 and the combined extracts evaporated to dryness on the water bath1 #e gm4 of quart sand being added4 ,the dry residue is now powdered1 introduced into an ,erlenmeyer flask provided with a glass stopper1 and #bjj c4c4 of anhydrous ether ,footnote #b3 ,to be tested for water by shaking with anhydrous copper sulphate4 added4 ,after about two hours1 during which the flask is occasionally shaken1 the ether is poured through a filter1 the residue washed with a little ether1 and the operation repeated twice with each #dj c4c4 anhydrous ether1 using the same filter4 ,to the combined ether extracts 7about #bjj c4c47 ,h,cl and ,greek3 ba,cl#b are added1 the ether distilled off and the residue evaporated on the water bath1 in order to decompose the ether-sulphuric acid compound4 #ej c4c1 of hot water acidified with ,h,cl are now added1 the precipitate allowed to settle1 filtered1 washed1 dried1 and weighed4 ,the sulphuric acid thus estimated was present in the leather as free sulphuric acid4 ,that present as sulphates soluble in water is estimated in the residue on the filter3 the residue is extracted with hot water1 the sand filtered off1 the filtrate acidified with ,h,cl1 boiled for one quarter hour and filtered if necessary4 ,the clear filtrate1 which may be coloured1 is brought to boil and ,greek3 ba,cl#b is added4 ,the barium sulphate indicates the sulphuric acid present in the leather as water-soluble sulphates4 ,whether the latter be sulphates or bisulphates may be indicated by the aqueous extract of the above residue1 since neutral reaction would indicate the absence of bisulphates1 acid reaction their presence in addition to possible normal sulphates2 the quantitative estimation of the metals would decide this point definitely4 #aj4 ,properties of ,leathers ,tanned with ,neradol ,d ,whereas the colour of leathers tanned with ,neradol ,d only is nearly a pure white1 those tanned with mixtures of ,neradol ,d and vegetable tanning materials are more or less light coloured according to the quantity of ,neradol ,d present1 as has been explained when discussing the phlobaphene-solubilising action of ,neradol ,d4 ,in any case1 all leathers tanned with ,neradol ,d possess fibre of remarkable length1 which explains their increased tensile strength and elasticity4 ,the tensile strength of a leather tanned with a mixture of ,neradol ,d and vegetable tannins was #c4g per cent1 as compared to #c per cent when no ,neradol was used2 the extension was #ef per cent1 when tanning with ,neradol ,d as against #cf per cent1 without the latter4 ,the sensitiveness to light of leathers tanned with ,neradol ,d may be mentioned4 ,exposed to direct sunlight1 the surface of the leather assumes a yellowish colour after two days' exposure1 and assumes a pure yellow colour after a further three days4 ,a further fifteen days' exposure only darkens the leather slightly1 the final colour being very little different from the one obtaining after five days' exposure4 ,in passing1 it may be remarked that this yellow colour is observed on the surface only1 the grain otherwise possessing that pure white colour characteristic of ,neradol ,d tanned leather4 ,further1 it may be noted that leathers tanned--with ,neradol ,d fix basic coal-tar dyes excellently1 whereas acid and substantive dyestuffs are fixed with other than their natural shades4 ,the author has analysed a leather exclusively tanned with ,neradol ,d1 and has obtained the following results3--,footnote3 ,collegium1 #aiac1 #eba1 #dgh4 ,moisture - - - - - #ae4ec per cent4 ,ash - - - - - - #j4ic per cent4 ,fats- - - - - - #a4bf per cent4 ,extraneous matters - - - #j4jj per cent4 ,leather ,substance ,tanning matters- #cf4ib per cent4 ,leather ,substance ,hide substance - #de4cf per cent4 --------------- #ajj4jj per cent4 ,footnote3 ,sp4 gr41 #j4fdb4 ,from these figures1 those of degree of tannage and yield 7pelt--leather7 are calculated as #ha4d and #bbj respectively4 ,these figures correspond closely to those obtained by the analysis of leathers tanned with vegetable tanning materials1 and this proves the similarity between the ,neradol ,d tannage and a vegetable tannage in their chemical aspects4 #aa4 ,neradol ,d ,free ,from ,sulphuric ,acid ,in order to prepare phenol and cresulphonic acids1 such quantities of technical sulphuric acid are used as do not allow of the assumption of complete utilisation of the sulphuric acid2 hence it was of theoretical interest to remove eventual traces of free sulphuric acid from the product4 ,for this purpose1 the author diluted crude ,neradol to #bj ,b4 and gradually added small quantities of milk of lime2 the precipitates were freed from the liquid by suction and washing1 and a ,neradol free from sulphuric acid resulted1 which was then brought to the acidity of ,neradol ,d with the calculated amount of alkali4 ,from the calcium sulphate precipitate1 the amount of sulphuric acid originally present was calculated1 and was found to be only #d per cent4 ,the acid-free sample of ,neradol was tested with regard to its suitability as a tanning agent2 leather tanned with this sample differed from one tanned with an untreated sample 7,neradol ,d7 by being harder and possessing a pronouncedly greyish colour4 ,this difference1 however1 may not be due to the absence of sulphuric acid but to the presence of the slightly soluble calcium sulphate in the sample treated with milk of lime4 ,to prove this point1 another way of preparing ,neradol ,d free from sulphuric acid was looked out for4 ,sodium acetate was added to a solution of crude ,neradol until the latter was no longer acid to congo-red2 at this point no free sulphuric acid can be present in the solution4 ,the product1 partly neutralised till the acidity of ,neradol ,d was reached 7part of the acidity then being due to liberated acetic acid71 yielded a leather which neither in colour nor in feel differed from the usual ,neradol ,d tanned leather4 ,this proves that the grey colour and the hardness of the leather described in the former experiment is due to the presence of calcium sulphate4 ,if the crude ,neradol treated with sodium acetate is not partly neutralised1 the analysis gives the following figures3-- ,tanning matters #fg4c per cent4 ,soluble non-tannins #h4f ,insolubles #j4j ,water #bd4a --------- #ajj4j per cent4 ,acidity3 #a gm4 #df c4c4 ,n_/#aj ,na,o,h4 ,compared to the analysis of crude ,neradol containing sulphuric acid1 the figures show that1 on the one hand1 the presence of the comparatively small quantity of sodium acetate but slightly influences the contents of non-tannins and water1 but1 on the other hand1 reduces the contents of tannins and also the acidity4 ,the tanning intensity of this product1 however1 is considerably increased1 and using a #a ,b4 solution a leather is obtained in a very short time very similar to that yielded by ordinary ,neradol ,d1 but considerably harder2 the latter property is due to higher acidity and almost complete absence of salts in the product treated with sodium acetate4 ,the author finally attempted to partly neutralise crude ,neradol with various hydroxides and carried out tanning tests with samples containing the different metals4 ,hardly any difference in the finished leathers could be observed as regards colour or quality2 the tannage could by no means be described as that of a combination of ,neradol ,d and the respective metals4 #ab4 ,neutral ,neradol ,crude ,neradol1 completely neutralised with caustic soda1 yields a product of the following composition3-- ,tanning matters #ai4h per cent4 ,soluble non-tannins #cg4i ,insolubles #j4j ,water #db4c ------------ #ajj4j per cent4 ,the qualitative reactions of this product differ from those of non-neutralised ,neradol to the extent that gelatine is not precipitated and iron salts are not coloured blue1 but dirty brown1 by the aqueous solution of this product4 ,the completely neutralised product1 diluted to various concentrations 7of #a1 #b1 #c1 and #e ,b47 and tested as to tanning properties1 revealed the surprising fact that the pelts were not even surface tanned1 and were coloured evenly blue throughout by indigotine4 ,it might have been anticipated that sodium dicresylmethanedisulphonate would be as devoid of tanning powers as is a neutralised vegetable tannin1 but it is difficult to explain the fact of the sodium salt being adsorbed by hide powder as tanning matters in the ,official ,method of ,analysis4 ,brought to a logical conclusion1 the figure #ai4h per cent1 should be deducted from #cb4e per cent1 obtained in the analysis of a partly neutralised ,neradol ,d1 which comparatively large quantities of the sodium sulphonate also adsorbed by hide powder1 leaving the tanning matters of ,neradol ,d at #ac4e per cent4 ,this diminished figure1 however1 does in no way reduce the value as a tanning agent of ,neradol ,d2 it merely shows how inadequate is the hide powder method of analysis when applied to substances of the composition of ,neradol ,d4 ,this is further confirmed by the ,loewenthal permanganate method1 which yields the following figures3-- ,tanning matters #g4b per cent4 ,soluble non-tannins #ei4a ,footnote3 ,collegium1 #aiac1 #eba1dhg4 ,if1 on the other hand1 completely neutralised ,neradol is acidified with an organic acid1 such as acetic acid1 till the acidity1 7#a gm4 #aj c4c4 ,n_/#aj ,na,o,h7 is reached1 the resulting product is in all respects similar to ,neradol ,d and yields a corresponding leather4 ,it is permissible to assume that the irregularity exhibited by ,neradol ,d as regards the analytical estimation of its tannin contents is connected with the low molecular weight of the tanning principle4 ,whereas all tannins so far isolated from the natural tanning materials possess rather high molecular weights1 that of ,neradol ,d deviates considerably from this rule1 as is shown by the following table3-- ,neradol ,d tannin ,cl#e;,h#af,s#b,o#h #ceh ,mangrove ,c#bd;,h#dj,o#bl #fgj ,oak bark ,c#bh;,h#bh,o#bc #hdj ,myrabolam ,c#ed;,h#dh,o#ce #abef ,dividivi ,c#ed;,h#df,o#ce #abgj ,malletto 7,c#dl,h#ej,o#bj7b #agbd ,this low molecular weight may mainly account for the figures obtained by the incorrect oxymetric estimation with permanganate2 the apparent tannoid property of the tannoid-inactive neutral salt of dicresylmethanedisulphonic acid may be explained by assuming that though it is1 probably1 in the colloidal state1 and as such adsorbed by hide powder1 it is still devoid of astringent properties4 ,g4 ,different ,methods of ,condensation as ,applied to ,phenolsulphonic ,acid ,in addition to formaldehyde1 many other substances may1 theoretically1 induce condensation of phenolsulphonic acid2 condensation takes place either with the elimination of water or1 in addition to this1 with the introduction of methane group4 ,so far1 the following condensing agents have been investigated3-- 7#a7 ,heating in vacuo4 7#b7 ,sulphur chloride4 7#c7 ,phosphorus compounds4 7#d7 ,aldehydes4 7#e7 ,glycerol4 #a4 ,condensation ,induced by ,heat ,if phenolsulphonic acid is heated in vacuo at #acj ,c4 for twenty hours1 condensation takes place ,footnote3 ,austr4 ,pat41 #fd1dgi4 without the addition of any condensing agent1 and an anhydride of the ,o v v ,,hso#c ,,hso#c composition is formed4 ,this product is a viscous liquid1 possessing a very corrosive action4 ,added to a solution of gelatine1 a light1 fine flocculent precipitate is thrown down4 ,analysed by the shake method of analysis1 the tannin content of the product equals about #df per cent4 ,its strongly acidic and hence swelling character does not express qualities consistent with the conception of suitability for tanning purposes3 a sample of the product was therefore partly neutralised to the acidity of ,neradol ,d1 when the shake method of analysis yielded the following figures3-- ,tanning matters #ba4e per cent4 ,soluble non-tannins #dh4c ,water #cj4b -------------- #ajj4j per cent4 ,this partly neutralised sulphonic acid represents a white1 pasty mass1 which is not particularly easily soluble in water1 yielding a solution of milky appearance4 ,treated with the usual tannin reagents1 it exhibits the following characteristics3-- ,gelatine ,light ,flocculent precipitate4 ,bromine water ,compete fixation4 ,ferric chloride ,cherry-red coloration4 ,lead acetate ,very slight ,percipitate1 insoluble ,,hno#c4 ,aniline hydrochlonde ,slight percipitate4 ,solutions of this product in concentrations from #a-h ,b4 exerted no tanning action whatever1 whereas more concentrated solutions 7#ae ,b47 converted pelt in eight days into a leather very similar to a ,neradol ,d leather in colour and feel1 but considerably harder4 ,in order to determine its phlobaphene-solubilising effects1 samplesof the product were mixed with concentrated quebracho extract in the proportions #e1aj1 #bj1 and #cj per cent4 on the weight of extract1 and the following observations made3--#e and #aj per cent4 were without effect1 #bj and #cj per cent4 showed some solubilising tendency1 but on diluting the mixture with water the quebracho was completely thrown out of solution4 ,apparently this anhydride is1 in this respect also1 quite different from the partly neutralised diphenylmethanedisulphonic acid4 #b4 ,condensation with ,sulphur ,chloride ,when sulphur chloride is allowed to act upon phenolsulphonic acid whilst heat is applied1 a yellowish-grey mass results1 which dissolves in water1 forming a reddish-yellow solution4 ,neutralised to acidity #aj1 it exhibits the following reactions3-- ,gelatine----------------,precipitate4 ,ferric chloride---------,deep blue coloration4 ,lead acetate------------,white precipitate1 insoluble ,,hno#c4 ,aniline hydrochloride---,precipitate4 ,bromine water-----------,no reaction4 ,the partly neutralised #b ,b4 solution of this product yielded a reddish-grey coloured leather1 the qualities of which were very similar to that yielded by ,neradol ,d4 #c4 ,condensation with ,phosphorus ,compounds ,schiff's well-known synthesis1 ,footnote3 ,liebig's ,ann41 #agh1 #agc4 in which phosphorus oxychloride interacts with phenolsulphonic acid1 yields a product which exhibits some tannin reactions1 but which1 when acting on pelt1 converts the latter into a leather which1 when dried1 is very cracky4 ,if1 on the other hand1 cresolsulphonic acid is condensed with phosphorus oxychloride by heating the two together1 products eminently suitable for tanning purposes result4 ,these products are non-crystalline bodies easily soluble in water1 and are coloured bluish-violet by ferric chloride and precipitate gelatine4 ,solutions of the free acids and acidified solutions of the salts convert pelt into firm and white leathers possessing great softness and pliability4,footnote3 ,austr4 ,pat1 #ff1hie4 #d4 ,condensation with ,aldehydes ,by treating phenolsulphonic acid with acetaldehyde in the usual way1 a viscous brown mass is obtained1 which is very soluble in water1 the solution being of a brown colour4 ,when brought to acidity #aj1 the following reactions are exhibited by the product3-- ,gelatine - - - ,precipitate4 ,ferric chloride - - ,deep blue coloration4 ,aqueous ammonia - - ,cherry-red coloration4 ,lead acetate - - - ,yellowish precipitate1 insoluble ,,hno#c4 ,aniline hydrochloride - - ,yellow precipitate1 soluble excess aniline4 ,bromine water- - - ,no reaction4 ,tanning experiments with this substance yielded1 even after extended tannage1 an undertanned leather1 the surfaces being coloured brown1 the inner layers1 however1 white4 ,further neutralisation reduces the tanning intensity of the product2 the addition of sodium sulphate to the original partly neutralised product hastened tannage1 the leather1 however1 possessing dark colour and being undertanned4 ,the following constitution may be ascribed to this product3-- ,,oh ,,oh ---,,ch#b---;,,ch#b--- v v ,,hso#c ,,hso#c ,if benzaldehyde is used in lieu of acetaldehyde for condensing phenolsulphonic acid1 a water-soluble product results1 exhibiting reactions similar to those of the acetaldehyde-condensation product4 ,the former product is more suitable as a tanning agent and yields a reddish-brown rather firm and hard leather2 it possesses the constitution-- ,h ,,oh ,,oh ,c v v ,,hso#c v ,,hso#c ,for the purpose of condensing phenol with formaldehyde1 it is not essential to first convert the phenol into the water-soluble phenolsulphonic acid1 since it is possible to convert the condensation products of phenol and its derivatives1 which are soluble in alkali1 into water-soluble form by either heating the condensation products with concentrated solutions of formaldehyde and neutral sulphites1 or by dissolving the condensation products in alkali and inducing reaction by means of formaldehyde bisulphite4 ,footnote3 ,collegium1 #aiac1 #eah1 #cbd4 ,highly concentrated solutions result1 which may be concentrated either as such or after the alkali present has been neutralised4 ,the sulphurous acid formed prevents oxidation of the product on evaporation4 ,a special advantage of this method of preparation is the fact that sulphuric acid1 which is but difficultly removed from the end-product1 is not employed at all4 ,the product thus obtained is a yellowish-white crumbly mass1 which is very soluble in water1 forming a clear solution4 ,the latter exhibits the following reactions3-- ,gelatine---------------,precipitate4 ,ferric chloride--------,deep blue coloration4 ,aqueous ammonia--------,cherry-red coloration4 ,lead acetate-----------,white precipitate1 insoluble in ,,hno#c4 ,aniline hydrochloride--,precipitate4 ,bromine water----------,no reaction4 ,the product brought to acidity #aj1 yielded on analysis the following figures3-- ,tanning matters------------------ #be4b per cent4 ,soluble non-tannins-------------- #ef4c ,insolubles----------------------- #j4j ,water---------------------------- #ah4c ------------- #ajj4j per cent4 ,tanning experiments with this substance yielded white and soft leathers1 which were indistinguishable from those tanned with ,neradol ,d4 ,a characteristic feature of this synthetic tannin is its behaviour in concentrated form towards pelt1 which is not attacked by it1 but is readily tanned even at such high concentrations4 ,an explanation of this is to be found in the large quantity of salts present in the product4 ,a disadvantage of this synthetic tannin is its complete incapability of dissolving phlobaphenes1 which is even so far extended as to precipitate otherwise easily soluble tannins when adding it to solutions of the latter in comparatively large proportions2 here1 again1 the salts are responsible for this behaviour1 their large quantities effecting a salting out of the natural tannins4 ,the class of aldehyde condensations also comprises that of inducing condensation by means of sugars2 if phenolsulphonic acid is heated with glucose1 a reddish-brown liquid results1 which is soluble in water4 ,the solution exhibits reactions similar to those of ,neradol ,d4 ,it is1 however1 not possible1 by this method of condensation1 to prepare as highly concentrated products as is possible in the case of ,neradol ,d1 since employing sugars as condensation agents means liberation of a large volume of water4 ,analysis of this product1 using the shake method1 gives a tannin content of #af4b per cent2 tanning experiments demonstrated that the time of tannage1 using a #b ,b4 solution1 was the same as that required by ,neradol ,d1 and yielded a leather1 the surface of which was reddish-grey1 the inner layers being white1 but which is otherwise very similar to ,neradol ,d tanned leather4 ,footnote3 ,austr4 ,pat1 #fi1cge1 #fi1cgf1 #fi1cgg4 ,relatively to its capability of solubilising phlobaphenes1 this product exhibits similar properties to that obtained by merely heating phenolsulphonic acid1 to a slight extent only solubilising quebracho extract1 which1 on diluting the mixture1 is completely thrown out of solution4 #e4 ,condensation with ,glycerol ,phenolsulphonic acid1 when heated with glycerol1 undergoes the process of condensation1 and forms a brown fluid1 which1 when brought to acidity #aj1 exhibits the following reactions3-- ,gelatine-----------------,precipitate4 ,ferric chloride----------,brown-black coloration4 ,lead acetate-------------,white precipitate1 insoluble in ,,hno#c4 ,aniline hydrochloride----,slight precipitate4 ,tanning experiments with this partly neutralised product resulted in a very gradual conversion of the pelt into a greenish-grey coloured leather2 the colour1 however1 does not penetrate the pelt and is hence caused by colloidally suspended impurities4 ,if the solution is filtered through a filter candle1 a somewhat clearer solution results1 but the latter also tans very slowly and yields a brown coloured leather4 ,analysis of the partly neutralised product reveals a tannin content of #ag4f per cent4 ,a #b ,b4 solution of the non-neutralised product showed a rapid tanning effect at first1 when brought into contact with pelt1 on which it had a strong swelling effect1 and to which it imparted a greenish colour2 the tanning effect1 however1 slowed down considerably1 after a few days1 and the solution penetrated the pelt only very gradually2 this is probably due to the presence of large quantities of colloidally suspended impurities1 which1 when the substance is partly neutralised with the formation of salts of the sulphonic acids1 are brought into true solution and hence penetrate the pelt with greater rapidity4 ,,index ,,of ,,authors ,adler ,appelius ,ashmore ,bader ,badische ,anilin u47,german abbreviation for und7 ,soda-,fabrik ,baekeland ,baeyer ,berzelius ,biginelli ,boehringer ,sons ,bottinger ,braconnot ,buff ,caro ,chem4 ,fabrik ,jucker ,co4 ,chevreul ,dekker ,deutsch-,koloniale ,gerb u4 ,farbstoff ,gesellschaft ,deyeux ,diz ,drabble ,edner ,elberfelder ,farbenfabriken ,fahrion ,feist ,fischer1 ,e4 ,freudenberg ,froda ,gerhardt ,gesellschaft f47,german abbreviation for fr7 ,chem4 ,industrie1 ,basle ,graebe ,graham ,grasser ,hatchett ,heinemann ,herzig ,herzog ,hnig ,iljin ,immerheiser ,jennings ,kahl ,kauschke ,klepl ,knig ,kostanecki ,krafft ,krauss ,kunzemller ,lauffmann ,liebig ,lipp ,lloyd ,lwe ,manning ,mauthner ,meunier ,michael ,mielke ,mitscherlich ,nierenstein ,paessler ,patern ,payne ,pelouze ,perkin ,proust ,rapoport ,raschig ,reinsch ,resch ,russanow ,sabanajew ,sander ,scheele ,schiff ,schmidt ,schorlemmer ,seel ,seyewetz ,sisley ,skey ,stiasny ,strauss ,thuau ,tschirch ,vogel ,walden ,webster ,weinschenk ,wohl ,zacharias ,a ,alcohol figure ,algarobilla ,alizarin ,alizarin yellow1 in paste ,alkalies1 reaction of1 to ,neradol ,d ,alum-neradol tannage ,alum tannage ,aminobenzene ,aminophenol1 p- ,aniline dyes ,anthracene ,anthraquinone ,arylsulphaminoarylsulphonic acids ,arylsulphoxyarylsulpho acids ,b ,bakelite ,bakelite solution ,benzoylamino #f-;chloranthraquinone ,benzylsulphanilate sodium ,bismuth salts ,bleaching method for leather with ,neradol ,d ,bloom ,bromo-,greek3 b-naphthol ,bromonitrophenol ,bromophloroglucinol ,bromosalicylic acid ,bromotrinitrophenol ,c ,carbazole ,carbomethoxyhydroxybenzoic acid1 ,carbomethoxyhydroxybenzoic acid chloride1 ,catechine ,catechol ,cerium salts ,ceruleoellagic acid ,cesium salts ,chestnut wood extract ,chloronaphthalenesulphonic acid ,chlorophenol ,chrome-,neradol ,d tannage ,chrome salts ,chrome tannage ,coal1 bituminous ,coffee tannin ,combination tannage with ,ordoval ,combination tannage with ,neradol ,d ,condensation by heat ,condensation methods ,condensation with aldehydes ,condensation with glycerol ,condensation with phosphorus compounds ,condensation with sulphur chloride ,copper salts ,corinal ,cresol ,cresol-p-sulphonic acid1 o- ,cresolsulphonic acid ,cresotinic acid ,d ,depsides ,detannisation with hide powder ,diaminoanthraquinone ,diaminonaphthylmethanedisulphonic acid ,dianilinoquinone ,dibenzopyrrol ,di-,greek3 b-oxynaphthoic ,di-,greek3 b-resorcylic acid ,dichloranthraquinone ,dichloronaphthylmethanedisulphonic acid ,dicresylmethanedisulphonic acid ,dicresylmethanedisulphonic acid purified electro-osmotically ,dicresylmethane sulphonate sodium ,didepsides ,didymium salts ,diferulic acid ,digallic acid ,digallic acid1 ,greek3 b- ,digallic acid1 inactive ,digallic acid1 m- ,digalloylleucodigallic acid anhydride ,digentisinic acid ,dihydric alcohols1 aromatic ,dihydroxybenzene1 m- ,dihydroxybenzene1 o- ,dihydroxybenzene1 p- ,dihydroxybenzenes ,dimethylaniline ,dimethylellagic acid ,di-m-oxybenzoic acid ,dinaphthylmethanedisulphonic acid ,dinitronaphthylmethanedisulphonic acid ,di-o-cumaric acid ,diorsellic acid1 o- ,diorsellic acid1 p- ,dioxyellagic acid ,dioxynaphthylmethanedisulphonic acid ,dioxytoluic acid ,diphenylmethane ,diphenylmethanedisulphonic acid ,di-p-hydroxybenzoic acid ,diprotocatechuic acid ,disalicylic acid ,disyringic acid ,dithionaphthylmethanedisulphonic acid ,dividivi ,dividivi tannin ,dixylylmethanedisulphonic acid ,e ,electro-chemical behaviour of ,neradol ,d ,electro-osmosis of ,neradol ,d ,ellagic acid ,ellagitannic acid ,empirical formula of tannin ,erythrine ,esco-extract ,ester formula of tannin ,ethyl acetate figure ,f ,fat-,neradol ,d tannage ,feruloyl-p-oxybenzoic acid ,flavellagic acid ,fluorene ,formaldehyde ,formaldehyde tannage ,g ,g-acid ,gallate ethyl ,gallic acid ,galloflavine ,galloyl-p-hydroxybenzoic acid ,galls1 oak ,gall tannin ,generator tar ,guaiacol ,h ,halogens ,hepta-tribenzoyl-galloyl-p-iodophenylma ltosazone ,hexahydroxyaurinecarboxylic acid ,hexoxyanthraquinone ,hexoxydiphenyl ,hexoxydiphenyldicarboxylic acid ,hexoxydiphenylmethanedicarboxylic acid ,humic acid ,hydrolysis of tannins ,hydroquinone ,hydroxybenzoate sodium1 m- ,hydroxybenzoate sodium1 p- ,hydroxybenzoic acid1 p- ,hydroxybenzoic acid ,hydroxy-cymenes ,i ,indophenol reaction ,iron1 reaction of1 to ,neradol ,d ,iron salts ,k ,ketone formula of tannin ,l ,lanthanum salts ,lead salts ,leather analysis in presence of ,neradol ,d ,lecanoric acid ,leucodigallic acid ,leucoellagic acid ,leucotannin ,lignite ,luteic acid ,m ,malletto tannin ,mangrove tannin ,melangallic acid ,mercury salts ,metellagic acid ,methylamino-#d-;bromanthraquinone ,methylenedinaphthol ,methylenedisalicylic acid ,methylenedisalicylic acid1 brominated ,methylenedisalicylic acid1 iodised ,methylisopropylphenanthrene ,methylotannin ,molybdenum figure ,monochloro-p-dihydroxybenzene ,mud ,myrabolams ,myrabolams1 tannin ,n ,naphthalenesulphonic acid1 ,greek3 b- ,naphthol1 ,greek3 a- ,naphthol1 ,greek3 b- ,naphthol-,greek3 a-methanesulphonic acid ,naphtholdisulphonic acid ,naphtholmonosulphonic acid ,naphtholsulphonic acid1 ,greek3 a- ,naphtholsulphonic acid1 ,greek3 b- ,neodymium salts ,neradol ,d ,neradol ,d tannin ,neradol ,n ,neradol ,,nd ,neradol ,,nd1 neutral ,nitronaphthalenesulphonic acid ,nitrophenol1 o- ,nitrosodimethylaniline ,non-tannins ,novolak ,o ,oak bark ,oak bark tannin ,official method of tannin analysis ,orcinol ,ordoval ,g ,orsellic acid ,orsellinoyl-p-oxybenzoic acid ,oxyanthraquinone ,oxyazo reaction ,oxybenzoyl-m-hydroxybenzoic acid ,oxybenzoyl-p-hydroxybenzoic acid1 m- ,oxybenzoylsyringic acid ,oxynaphthoyl-p-hydroxybenzoic acid1 a- ,oxynaphthylmethanesulphonic acid ,oxyphenylmethanesulphonic acid ,oxyquinoline ,p ,,patents-- ,austrian #eh1dje2 #fa1jeg2 #fa1jfa2 #fd1dgi2 #ff1hie2 #fh1gif2 #fi1aid2 #fi1cge2 #fi1cgf2 #fi1cgg2 #gj1afb ,german #gb1afa2 #aaa1djh2 #aab1ahc2 #acb1bbd2 #aha1bhh2 #ahd1ddi2 #bjj1eci2 #bjf1ieg2 #baa1djc2 #bfb1eeh2 #bhb1cac2 #bhf1efh2 #bij1ife2 #bia1deg2 #bic1jdb2 #bic1fdj2 #bic1fic2 #big1ahg2 #big1ahh2 #cjj1efg2 #cjc1fdj2 #cje1eaf2 #cai1gac2 #cbj1fac ,swiss #gh1bhb2 #gh1gig2 #gi1aci ,u4,s4,a4 #a1fci1agd ,peat ,pelts ,pelts1 action on1 of ,neradol ,d ,penta-p-hydroxybenzoyl glucose1 ,penta-p-methyl-m-digalloyl-glucose ,penta-pyrogalloylcarboyl-glucose ,pentacetylleucotannin ,pentacetyl-m-digallic acid ,pentacetyl tannin ,pentadigalloylglucose ,pentagalloylglucose ,pentagalloylglucoside ,pentamethyldigallic acid1 methyl ester ,pentamethyl-m-digalloyl chloride1 ,pentamethyl-m-digallic acid ,pentamethyl-m-digallic acid methyl ester ,pentamethyl-p-digallic acid ,pentamethyl-p-digallic acid methyl ester ,pentamethoxybiphenylmethylolide carboxylic acid methyl ester ,pentoxybiphenylmethylolide ,pentoxybiphenylmethylolide carboxylic acid ,phenanthraquinone ,phenolsulphonate sodium ,phenolsulphonic acid ,phenolsulphonic acid anhydride ,phenol1 tautomeric ,phenylcarboxylic acid ,phenylhydrazine derivatives of tannin ,phenylhydrazine ellagic acid ,phlobaphene ,phlobaphene-solubilising action of neradols ,phloroglucinol ,phthalic acid ,pickling ,picric acid ,platinum salts ,polydepsides ,polydigalloylleucodigallic acid anhydride ,polyhydroxybenzenes ,pomegranate ,preparation of tannin infusion ,properties of leather tanned with ,neradol ,protocatechuic acid ,protocatechuyl-p-hydroxybemoic acid ,pseudo-tannage ,purpuro tannin ,pyrogallol ,pyrogallic acid ,pyrogalloylcarboyl-p-oxybenzoic acid ,pyruvic acid ,q ,quinazarene ,quinoline ,quinone ,r ,r-acid ,reaction1 ,procter-,hirst ,reagents for ,neradol ,d tannage ,resites ,resitol ,resols ,resorcinol ,resorcylic acid1 ,greek3 b- ,retene ,rosins1 acid ,rosolic acid ,rufigallic acid ,s ,s-acid ,salicylic acid ,salicylic acid phenyl ester ,salicyl-p-hydroxybenzoic acid ,salol ,silver oxide ,solution salt ,solvenol ,structure of tannin ,sulphinic acid ,sulphite cellulose extract ,sulphite lye ,sulphonamide ,sulphonic acids1 aromatic ,sulphonic chloride ,sulphur ,sulphur tannage ,sulphuric acid-free ,neradol ,d ,sulphuric acid in leather ,syringoyl-p-hydroxybenzoic acid ,t ,tannin ,tannin action1 real ,tannin analysis ,tanning matters ,tannin molecule ,tannin1 pure ,tannophor ,test tannage ,tetradepsides ,tetragalloyl-,greek3 a-methylglucoside ,tetramethylellagic acid ,tetroxydiphenyldimethylolide ,thionaphtholsulphonic acid ,thiosulphonic acid ,thorium salts ,thymol ,toluidoanthraquinone1 l-m- ,total solids ,total solubles ,tribromophenol ,tribromopyrogallic acid ,tricarbomethoxygalloyl chloride ,tridepside ,trihydroxybenzenes ,trinitrophenol ,triphenylmethane ,v ,valonea ,vanadium salts ,vanillic acid ,vanilloyl-di-p-oxybenzoyl-p-hydroxybenz oic acid ,vanilloyl-p-hydroxybenzoic acid ,vanilloyl vanillin ,x ,xanthenes ,z ,zinc salts ,zirconium salts