36 SCIENCE PROGRESS 



meta benzoyl derivative of gallic acid instead of the para- 

 benzoyl derivative 



OAc OH 



Bzp( )cOOH > HO<^} COOH 



OAc OBz 



(III) (IV) 



and similarly penta-acetyl-/>-digallic acid on hydrolysis gave 

 m-digallic acid. The penta-acetyl derivatives of m- and p- 

 digallic acids are, however, stable, and from their acid chlorides 

 it has been found possible to synthesise the two corresponding 

 penta-(penta-acetyl digalloyl)-glucoses, and to obtain from these 

 by careful hydrolysis the two penta-(digalloyl)-glucoses. Of these 

 the penta-(m-digalloyl)-/3 glucose is found to be remarkably 

 similar to Chinese tannin and to differ from it only in regard to 

 its specific rotation in aqueous solution ; this difference, how- 

 ever, need not be regarded as serious in view of the fact that 

 the solutions are colloidal and are liable to be considerably 

 influenced by small factors. The same authors have also 

 effected the synthesis of i-galloylglucose of the formula 



C 6 H 2 (OH) 3 • CO • O • CH • (CHOH) 2 • CH • CHOH • CH 2 OH 



I 1 



which is found to be identical in all respects with the natural 

 product glucogallin first isolated from Chinese rhubarb by 

 Gilson in 1903 (Comptes Rend. 136, 385). 



An entirely novel method for isolating the products of the 

 acid hydrolysis of proteins has been devised by Dakin (Biochem. 

 J. 191 8, 12, 290). Caseinogen was hydrolysed by means of 

 sulphuric acid, the excess of acid being removed as barium 

 sulphate. The neutral concentrated solution was then sub- 

 mitted to continuous extraction by means of butyl alcohol, 

 whereby five fractions were obtained. (1) Monoamino acids 

 which, although insoluble in butyl alcohol, are nevertheless 

 extracted and are deposited as a cream-coloured powder in the 

 extraction flask ; their extraction is due to the passage of a 

 certain amount of water into the butyl alcohol since the ex- 

 traction is not satisfactory if the aqueous solution of the amino 

 acids contains an excess of salts, such as calcium chloride. (2) 

 Proline, which is soluble in ethyl alcohol, and is also extracted 



