118 CHEMISTRY OF THE PROTEIDS^ CHAP. 



cyanic acid and trichloracetic acid give no precipitate. From watery 

 solutions the base crystallises in feebly anisotropous platelets, which 

 begin to change at 218 and decompose at 270, becoming black, 

 without melting however. 



Curtius 1 with the help of Wiistenf eld 2 has also prepared the 

 following benzoyl-amino-acid compounds : 



benzoyl-amino-acetic acid (hippuric acid). Melting point 187. 

 C 6 H 5 CO.NHCH 2 .COOH. 



benzoyl-glycyl-amino-acetic acid. Melting point 206*5. 



C 6 H 5 CO . NHCH 2 CO . - NHCH 2 . COOH. 

 benzoyl-bis-glycyl-amino-acetic acid. Melting point 2 1 5-2 1 6. 



C 6 H 5 CO . (NHCH 2 C0) 2 - NHCH 2 . COOH. 

 benzoyl-tri-glycyl-amino-acetic acid. Melting point 235. 



C 6 H 5 CO . (NHCH 2 C0) 3 - NHCH 2 . COOH. 

 benzoyl-tetra-glycyl-amino-acetic acid. Mel ting point 24 6-2 5 2. 



C 6 H 5 CO . (NHCH 2 C0) 4 - NHCH 2 . COOH. 



benzoyl-penta-glycyl-amino-aceticacid (y-acid). Melting point about 268. 



C 6 H 5 CO . (NHCH 2 C0) 5 - NHCH 2 . COOH. 



The benzoyl-bis- to the benzoyl-penta-compounds and all their 

 derivatives give a violet colour with Fehling's solution. On boiling 

 the above acids with concentrated HC1 they dissociate into benzoic 

 acid and the respective number of glycocoll-molecules. There is no 

 tendency to ring-formation or to dissociation. The acids are slightly 

 soluble in cold water, more so in hot water, giving a marked acid 

 reaction ; less soluble with alcohol ; with alkaline metals they form 

 readily soluble salts and are precipitated from such solutions by the 

 addition of acids; their esters, hydrazides, and azides are readily 

 prepared. 2 



With the view of introducing acyl-groups 3 into glycocoll, Curtius 4 

 has further employed acid-anhydrides instead of acid chlorides, thus : 



(CH 3 . C0) 2 + NH 2 . CH 2 . COOH = CH 3 CO . NHCH 2 . COOH 



Acetic acid anhydride + glycocoll aceturic acid. 



1 Th. Curtius, Journ.f. prakt. Ohem. [2] 70. 57 (1904). 



2 Curtius and Wustenfeld, ibid. N.F. 70. 75 (1904). 



3 Acyl is a collective term which Liebermann introduced for the acid radical of fatty 

 acids, thus in acetic acid, CH 3 . COOH, acyl means the acetyl -remainder : CH 3 . CO 

 while the analogous acid radicals of the homologous fatty acids are formyl : H . CO ; 

 propionyl : CH 3 . CH 2 . CO ; butyryl : CH 3 . CH 2 . CH 2 . CO. 



4 Th. Curtius, Ber. d. deutsch. chem. Gesell. 17. 1662 (1884). 



