SECTION V. SYNTHETIC TANNING 

 MATERIALS 



IN spite of much valuable work on the constitution of the 

 vegetable tannins and the compounds usually associated 

 with them, such as that of B. Fischer, K. Freudenberg and 

 their collaborators on gallo-tannic acid, and that of A. G. 

 Perkin on ellagic acid and catechin, we are still in the dark 

 with respect to the constitution of the tannins which are of 

 commercial importance, and any synthetic production of 

 these materials is thus out of the question as yet. Attempts, 

 however, have been made to produce artificially substances 

 which possess similar properties to the tannins and which 

 may be used for converting pelt into leather. Into this 

 category fall some of the earlier attempts to synthesize 

 gallo-tannic acid by heating gallic acid with condensing 

 reagents. 



The first commercial success in this direction was attained 

 by Stiasny, who produced condensation products of the phenol- 

 sulphonic acids, to which products he gave the general name 

 of " syntans " (synthetic tannins). The Badische Co. 

 placed one of these products on the market as " Neradol D," 

 and later took out subsidiary patents for the manufacture 

 of similar products by slightly differing methods of pro- 

 ductions. Since the outbreak of the European War such 

 patent rights have been suspended, and several British 

 firms have been manufacturing synthetic tanning materials 

 by similar methods, but doubtless with developments and 

 improvements of their own discovery. These products (e.g. 

 Cresyntan, Maxyntan, Paradol, Syntan, etc.) are now in 

 use in many factories, and assist rather than substitute the 

 vegetable tannins in producing leather of the desired colour 

 and quality. 



These synthetic tanning materials resemble the vegetable 

 tannins in the following respects. They are organic acids 



