14 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



Anhydrides of Aspartic Acid. Schaal, in 1871, heated asparagine 

 hydrochloride in a current of carbonic acid for three days at 180 C. ; 

 he obtained a hard white mass, the greater portion of which was in- 

 soluble in water and the remainder soluble only with difficulty. The 

 insoluble body was formed by the loss of fifteen molecules of water from 

 eight molecules of aspartic acid, and the other body by the loss of seven 

 molecules of water from four molecules of aspartic acid : 



CH 14 N 4 9 = 4 C 4 H 7 N0 4 - 7 H a O 

 C M H W N 8 17 = 8C 4 H 7 N0 4 - I 5 H,O 



Both compounds were converted into aspartic acid by hydrolysis 

 with baryta water. 



J. Guareschi, in 1876, further investigated these substances by 

 determining the amount of silver in the silver salts, but their nature 

 was only demonstrated in 1897-1899 by Schiff. He obtained them by 

 heating aspartic acid, prepared from asparagine and dried at iioC., 

 for twenty hours at 190-200 C., the yield amounting to 72-75 per cent. 

 Not only were the anhydrides, octaspartide and tetraspartide, as Schiff 

 called these compounds, formed in the process, but also the tetraspartic 

 and octaspartic acids. These acids he also prepared from the anhy- 

 drides by hydrolysis with the calculated quantity of cold dilute alkali. 

 From the analysis of their salts, as also their anilides and phenyl- 

 hydrazides, and from the fact that they gave the biuret reaction which 

 was not observed by Schaal, but pointed out by Grimaux in 1882, he 

 gave these acids the following formulae : 



Tetraspartic acid 



CO CO CO CO CO CO CO COOH 

 H.C.NH, C.NH, C.NH, C.NH, C.NH, C.NH,C. NH, C.NH, 

 CH, CH, CH, CH, CH, CH, CH, CH, 



COOH COOH COOH COOH COOH COOH COOH COOH 



Octaspartic acid 



and their anhydrides : 



NH - v / NH - 1 v 



H \ CO C . CH, . CO/ 4 OH H \CO-C . CH, . CO/ S OH 



Tetraspartide Octaspartide 



The octaspartic acid was an octobasic acid, its ninth carboxyl 

 group being neutralised by the adjacent NH a group. 



