582 



THE CHEMISTR Y OF THE URINE. 



Its relations to ammonium carbonate and carbamate are very im- 

 portant from a physiological standpoint. 



CO 



+H0 



C0 



+ H0 - CO; 



(urea) 



(ammonium carbamate) 



(ammonium carbonate) 



The two molecules of water necessary to form carbonate of ammonia 

 are very readily taken up. Even at a temperature of 60 C., an aqueous 

 solution of urea slowly develops ammonia (Leube 1 ); while a boiling 

 solution decomposes with considerable rapidity. Heated with water 



FIG. 49. Upper half, urea nitrate crystals. Lower half, urea oxalate 

 crystals. 



under pressure, at 180, the conversion into ammonium carbonate is 

 quickly complete. A solution of pure urea may be evaporated at tem- 

 peratures from 60 to 75, without serious loss, but in the urine it is less 

 stable. Quite appreciable proportions of its nitrogen are lost as ammonia 

 when urine is evaporated, even at low temperatures. In the presence 

 of free acids and bases, the hydrolysis occurs with still greater readiness, 

 the ammonium carbonate formed being further decomposed by the 

 reagent. Thus, on boiling urea solutions with acids, carbonic acid is 

 given off; on boiling them with alkalies, free ammonia is evolved. 



The hydrolysis is also induced by micro-organisms, as in the 

 ammoniacal fermentation of urine. The Micrococcus urece is the best 

 known of these ; but other organisms are found in decomposing urine 

 1 Virchow's Arckiv, 1885, Bd. c. S. 552. 



