HIPPURIC ACID. 189 



Heated with hydrate of lime or caustic potash, hippuric acid 

 yields benzine and ammonia, while the residue consists solely of 

 carbonate of [lime or] potash, without a trace of cyanide of [calcium 

 or] potassium. In fermenting and putrefying fluids this acid 

 becomes decomposed into benzoic acid and other yet unknown 

 products. 



Shortly after Liebig's discovery of hippuric acid, while preparing 

 it in large quantities from the urine of horses, I obtained one iso- 

 lated crystal of hippuric acid half an inch in length, in which the 

 vertical rhombic prism of the elementary form <x> P was combined 

 with 2 microdiagonal horizontal prisms, whereby the combining 

 corners were truncated by the brachydiagonal horizontal prism. 

 I have never again succeeded in obtaining crystals of such size and 

 thickness. 



Composition. According to the above formula hippuric acid 

 consists of : 



Carbon 18 atoms .... 60-335 



Hydrogen .... 8 .... 4'469 



Nitrogen 1 .... 782l 



Oxygen 5 .... 22'347 



Water 1 .... 5-028 



100-000 



The atomic weight of the hypothetical anhydrous acid=2125'0; 

 and its saturating capacity =4*706. 



From the various modes in which hippuric acid may be disin- 

 tegrated, corresponding views have been taken of its constitution ; 

 all, however, agree in the opinion that in hippuric acid there must be 

 concealed the radical benzoyl, C 14 H 5 , which is common to benzoic 

 acid, volatile oil of bitter almonds, and benzamide. From the 

 behaviour of hippuric acid with peroxide of manganese and sul- 

 phuric acid, and from the composition of formobenzoic acid, which, as 

 may be shown, consists of formic acid and oil of bitter almonds, 

 (hydride of benzoyl,) Pelouze* concluded that hippuric acid was a 

 kind of formobenzoic acid, which had assimilated hydrocyanic acid, 

 so that it consisted of 1 equivalent of hydrocyanic acid, 1 equivalent 

 of hydride of benzoyl, and 1 equivalent of formic acid, and 

 =H.C 2 N + H.C 14 H 5 + C 2 HO 3 .HO. 



This view of the composition of hippuric acid also finds some 

 support in the circumstance that amygdalic acid, according to the 

 recent investigations of W6hler,t seems most probably to be formic 



* Ann. de Chim. et de Pharm. T. 26, pp. 60-68. 

 t Ann. d. Ch. u. Pharm. Bd. 66, S. 238-242. 



