SYNTHETIC TANNINS AUTHORS PREFACE WHILST the synthesis of the natural tannins has been suc cessfully outlined by Emil Fischer, it has been left to the Chemical Industry, notably the Badische Anilin und Soda fabrik in Ludwigshafen-on-the-Rhine, to discover the means of making possible the production of the synthetic tannins. The scientific results of Fischers researches are to-day common knowledge, and these, together with questions arising therefrom, will only be lightly touched upon in the book herewith presented. Even an attempt at enumerating the present synthetic tannins has so far not been published, and I have therefore availed myself of the opportunity of making a brief summary of them. My work at the B. A. S. F. deepened my insight in this new field ample opportunity of applying these synthetic products in practice was given me wfyen, as a result of the war, I was appointed technical consultant to the Austrian Hide and Leather Commission, and in this capacity was called upon to act as general adviser to the trade. The ultimate object of my scientific researches was then to investigate the chemistry of this particular field, and this has led me to present a picture, complete as far as it goes, of this branch of chemical technology. The intention of the present volume is to communicate to the reader what has so far been scientifically evolved and practically applied in this field. First of all, however, it may illustrate the extreme importance and the universal applicability of the synthetic tannins in the making of vi AUTHORS PREFACE leather. The modern leather industry cannot, to-day, be without these important products but also in those tan neries, where the synthetic tanninshave not so far been regarded as indispensable, their use is strongly recom mended. Just as in the case of the coal-tar dyes, the synthetic tannins will make us independent of foreign supplies, and thus keep within our own borders the vast sum of money required in former days for the purchase of foreign tanning materials. May this book prove the means of providing an incentive for a still wider application of the synthetic tannins. CRASSER. GRAZ, August 1920. TRANSLATORS PREFACE DOCTOR CRASSER hardly needs an introduction to the leather trade of this country in its scientific aspect, but if one be sought for, none could serve the purpose better than a translation of the book herewith presented to the British speaking public. Viewed with curiosity from their start, the synthetic tannins needed like many other important discoveries an extreme emergency for the purpose of showing their value. The Great War provided the opportunity of which chemical industry was to avail itself, 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 chemistry we also see their immensely practical qualities established as a fact, and, as the author aptly remarks, no modern tanner can to-day dissociate him self from the use of synthetic tannins for the production of leather in the true sense of this word. There is no branch of leather-making where synthetic tannins cannot help and improve processes already established. The immense number of substances patented by German manufacturing chemists for the purpose of producing synthetic tanning materials is almost staggering. In view of this fact it is doublypleasing to see that British chemists have found new ways, and are able to produce equally good and more varied synthetic tannins than has hitherto been deemed possible. The originator of these products and his acolytes viii TRANSLATORS PREFACE must at least share the credit with those who, in spite of the limitations necessarily set by the former, have been able to find new and better ways. In his book Dr Crasser gives a short review o f the necessary forerunner of any work upon synthetic tannins the investigations and syntheses of the natural tannins...