GALLOTANNIC ACID 215 



infusion of gall nuts to undergo fermentation, obtained gallic 

 acid. Within recent years this change has been studied anew 

 by Fernbach,* who isolated a tannin splitting enzyme, tannase, 

 from Penicillium, and also by Pottevin.f who isolated a similar 

 enzyme from the mould Aspergillus. 



This change, which may be represented by the equation 



Ci 4 H 10 9 + H a o = 2 C 7 H 6 B 



may be effected more rapidly by boiling gallotannic acid with 

 dilute sulphuric acid. 



When, therefore, it was found by Schiff J that gallic acid 

 could be converted back into the anhydride by means of phos- 

 phorus oxychloride it was assumed that this substance, which 

 was called digallic acid, was identical with "tannin". This 

 view came to be generally accepted, although objections were 

 raised from time to time on the ground that the physical con- 

 stants, such as electrical conductivity and absorption of light, 

 of natural tannin and synthetic digallic acid were different. 



The formula which Schiff in 1 87 1 assigned to his synthetic 

 product was as follows : 



-CO. i 



XX 



vOH 



OH 



but it was not until Dekker |j pointed out that natural tannic 

 acid was optically active, that real doubt was cast on this 

 formula. Dekker accordingly proposed an alternative formula 

 containing an asymmetric carbon atom as follows : 



OH 



HO 1 



OH 

 Other suggestions were offered by Iljin U and by Nierenstein ** 



* Fernbach : " Compt. rend.," 1900, 131, 1214. 

 t Pottevin : " Compt. rend.," 1900, 131, 1215. 

 JSchiff: " Ber. deut. chem. Gesells.," 1871, 4, 232. 

 Walden: "Ber. deut. chem. Gesells.," 1897, 30, 3151; 1898, 31, 3167. 

 || Dekker: "Ber. deut. chem. Gesells.," 1906, 39, 2497. 

 IT Iljin : "Journ. Prakt. Chem.," 1900, (2), 82, 422. 



** Nierenstein: " Ber. deut. chem. Gesells.," 1908, 41, 77; 1909, 42, 1122; 

 1910, 43, 628. 



