280 URINE 



Hippuric acid, benzoylamino-acetic acid, C 9 H 9 NO 3 , or C 6 H 5 .CO. 

 NH.CH 2 .COOH. This substance is found (to the amount of about 2 per 

 cent) in the urine of horses, cattle and many herbivora ; it is also pre- 

 sent in human urine (usually about 0'5 per cent), and, during starva- 

 tion, in that of carnivora. 



Hippuric acid readily decomposes (under hydrolysis), giving ben- 

 zoic acid and amino-acetic acid (glycocoll) 



C 6 H 5 CO.NH.CH 2 .COOH + H 2 O = C 6 H 5 .COOH + CH 2 (NH 2 ).COOH. 



It is probably from the phenyl derivatives present in hay, grass 

 and many fruits and berries that hippuric acid is formed in the animal. 

 Moreover, the hydrolysis of proteids yields certain phenyl derivatives, 

 e.g., phenylalanine, which may produce benzoic acid and thus hippuric 

 acid on oxidation. 



Other derivatives of benzene occur in the urine, especially of her- 

 bivora ; thus, phenyl sulphuric acid, C 6 H 5 .O.SO 2 .OH, occurs as potas- 

 sium salt. Cresyl sulphuric acid, C 6 H 4 (CH 3 ).O.SO 2 .OH, and pyro- 

 catechin sulphuric acid, C 6 H 4 (OH).O.SO 2 .OH, also occur in the urine 

 of horses. Indoxyl sulphuric acid, C 8 H 6 N.O.S0 2 .OH, or indican, is 

 also found in urine, especially of herbivora. By warming with acids, 

 its potash salt yields indoxyl and potassium acid sulphate : 



C 8 H 6 N.O.SO 2 .OK + H 2 O = C 8 H 6 N(OH) + KHSO 4 . 

 On oxidation, e.g., by bleaching powder, indoxyl yields indigo : 

 2C 8 H 6 N.OH+0 2 = C 16 H 10 N 2 2 + 2H 2 0. 



