CHEMICAL BASIS OF THE ANIMAL BODY. 



897 



The crystals may be heated to 120 C. without being decomposed; at a higher tem- 

 perature they are first liquefied and then decomposed, leaving no residue. Heated 

 with strong acids or alkalies, decomposition ensues, the final products being car- 

 bonic anhydride and ammonia. The same decomposition may also occur as the 

 result of the action of a specific ferment on urea in an aqueous solution. l Nitrous 

 acid at once decomposes it into carbonic anhydride and free nitrogen. It readily 

 forms compounds with acids and bases ; of these the following are of importance : 



Nitrate of Urea. (NH 2 ) 2 CO.HN0 3 . 



Crystallizes in six-sided or rhombic tables [Fig. 237]. Insoluble in ether and 

 nitric acid, soluble in water, slightly soluble in alcohol. 



[FIG. 237. 



Crystals of Nitrate of Urea. (Krukenberg, after Kiihne.}] 



Oxalate of Urea. [(NH 2 ) 2 CO] 2 ,H 2 CA+H 2 0. 



Often crystallizes in long thin prisms [Fig. 238], but under the microscope is 

 obtained in a form closely resembling the nitrate ; it is slightly soluble in water, 

 less so in alcohol. 



. 238. 



Crystals of Oxalate of Urea. (Krukenberg, after Kiihne.)] 



With mercuric nitrate urea yields three salts, containing respectively, four, 

 three, and two equivalents of mercuric oxide to one of urea. The first is the pre- 



nsfii 

 (,lool), 



' pflti S er ' s Archiv, Bd. xii. (1876), S. 214. Jaksch, Zeitsch. f. physiol. Chem., Bd. v. 



57 



