THE CHEMICAL CONSTITUTION OF THE UNITS 83 



mined in 1 846 by Mulder and by Laurent, and in that year, after Des- 

 saignes had pointed out the unsuitability of the name given to it of 

 sugar of gelatin, as there were other substances like it with a sweet 

 taste and which were not fermentable, its name of glycocoll (V\VKV<;, 

 sweet, tc6\\a, glue) originated with, and was first used by, Horsford, 

 who made an extensive study of it and its derivatives, whilst working 

 in Liebig's laboratory where much of the early work on proteins was 

 carried out. 



Laurent regarded glycocoll as belonging to the ammonia type of or- 

 ganic compounds ; it was supposedly Cahours to be a derivative of acetic 

 acid, which supposition was only proved by its synthesis from brom- 

 acetic acid and ammonia by Perkin and Duppa, and from chloracetic 

 acid and ammonia by Cahours, both in 1858 : 



CH 2 C1 . COOH + NH 3 = HC1 + CH 2 . NH a . COOH. 



About this time the terms glycocine and glycine were used for 

 glycocoll, as this was then recognised as a homologue of alanine and 

 leucine. The whole of this series of compounds was named the 

 glycines. 



A very interesting synthesis of glycine was described by Emmerling, 

 in 1873, by the action of hydriodic acid upon cyanogen; here the 

 hydriodic acid acts both as a reducing agent and as a hydrolysing 

 agent : 



CN CH 2 . NH a 



| + sHI + 2H 2 = I + NH 4 I + 2 I 3 , 



CN COOH 



and, in 1877, Wallach obtained it by the reduction of cyanoformic ester 

 with zinc : 



COOC 2 H 6 COOC 2 H. 



+ 4 H= I 

 CN CH 2 .NH a 



Lubavin, in 1882, stated that glycine was formed by the action of 

 ammonium cyanide upon glyoxal, which probably first breaks down 

 into formaldehyde and then, by the cyanhydrin reaction, yields glycine : 



P TJ , rrpvr I TVJW r u ^ r> tr 

 rtUIN -JNtt s = L, H -U H 



NH, |\ NH , 



:N COOH 



The direct synthesis of glycine from formaldehyde was only carried 

 out in 1894 by Eschweiler. This method, as well as the method from 

 chloracetic acid and ammonia, by which Nencki and also Mauthner 



and Suida, by slight modifications in technique, attempted to obtain 



6* 



