582 
THE CHEMISTR Y OF THE URINE. 
Its relations to ammonium carbonate and carbamate are very im- 
portant from a physiological standpoint. 
,NH, /ONH 4 /ONH 4 
/' 
+ H.,0 = C0< 
C0< +H 9 = C0< 
X NH 2 X NH 2 x ONH 4 
(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 x ) ; 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 urcce is the best 
known of these ; but other organisms are found in decomposing urine 
1 Virchows Archiv, 1885, Bd. c. S. 552. 
