TRANSACTIONS OF SECTION B. 813 



J. T. Wood aud others have succeeded in isolating over twenty different kinds of 

 bacteria ii-oin the puer and bate referred to, and in culturing the bacteria. 

 Within the last few weeks tubes coutainiug cultures of the bacteria which are 

 suitable for bateing and puering purposes have, I believe, been put upon the 

 market in Germany. This is a form of applying the excrement bate that makes it 

 far less objectionable than heretofore. 



Mr. Wood has also applied bacteriological investigation to the bran drench, 

 and he has shown that for some leathers acetic and lactic acids may be substituted 

 for the fermenting bran. 



The rush alter quick tanning processes is somewhat reactionary. No great 

 success has been achieved by the various drum processes, and no leather has been 

 made by any of them that will serve other than second-class work. Leather pro- 

 duced by the so-called electric process is'being worked successfully in Sweden, and 

 the leather which is tanned in ifrom eight to twelve weeks is to all appearance 

 satisfactory; it has not been commercially tried in England. There is most pro- 

 bably what may be regarded as a rational limit of time for the conversion of hide 

 into leather, and it is doubtful whether the time that up to now has been regarded 

 as proper in such conversion will ever be very greatly reduced, as there is in 

 tanning more than simple cbemical combination of tannin with hide substance. 



In the extraction of tanning materials in the tanyard, English tanners are far 

 behind those of America and the Continent. A large amount of available 

 tannin is often wasted by cold extraction. Most of the large tanyards on the Con- 

 tinent extract with warm water in closed vats, some even extracting under pressure. 

 Analyses of over 300 samples of waste spent tan from over forty tanyards in Great 

 Britain have shown an average of over 9 per cent, of available tannic acid. 

 Supposing with valonia, costing 1:*/. per ton, and containing 36 per cent, of tannin, 

 5 per cent, to be thus wasted, a loss is incurred of 1/. 13s. Ad. per ton ; and valonia 

 is only one of the materials used in this country. 



Investigation in the case of oak bark shows Gl per cent, of tannin extracted 

 with cold water, and 95 per cent, with water at 60° C. Valonia extracted cold 

 gives over 70 per cent, of tannin ; at 00° C. gives off the whole of it. Even with 

 hemlock, containing only about 16 per cent, of tannin, the Americans find warm 

 extraction pay, and the Germans years ago adopted the method. The fear of 

 darker colour in leather arising from the use of warm extracts is much 

 exaggerated. 



Chrome leather tannage has emanated from the chemist's laboratory, and 

 leather is chromo-tanned by a two-bath process and by a one-bath process. The 

 leather tanned by either method, for it is leather, has many advantages over 

 vegetable-tanned leather. It is more elastic, more waterproof, and lighter and 

 softer for foot-wear, except as to soles, for which its water-resisting quality makes 

 it too slippery. Millions of dozens of skins are chromed weekly in America. 



Owing to the labours of the late Professor von Scbroeder, it is possible now to 

 determine at any period during the tanning process what amount of tannin a hide 

 has absorbed, and to Professor Proctor, of Leeds, we owe our present system of 

 analysis. As to the future, a great advance in our knowledge may be expected 

 from the several tanning schools and research laboratories that have come into 

 existence, but there is still a marked need of more research and of specially trained 

 chemists with a thorough knowledge of tanning. 



2. Diamidated Aromatic Amidines, a Neio Class of Colouring Matters, 

 By E. NoELTiNG, Professor of Chemistry, College of Chemistry, Mul- 

 house. 



The benzenyl-di-phenyl-amidine, 



C = N-C„H, 



