UREA. 155 



Composition. According to the above formula urea consists 

 of: 



Carbon 2 atoms .... 20'000 



Hydrogen 4 .... 6'666 



Nitrogen 2 .... 46-667 



Oxygen 2 .... 26'667 



lOO'OOO 



Its atomic weight 750*0. Although there have been many 

 discussions regarding the rational constitution of urea, much still 

 remains to be cleared up. Dumas, after his discovery of oxamide, 

 started the hypothesis, that urea is an amide of carbonic acid, since 

 2H 3 N + 2CO 2 - 2HO= C 2 H 4 N 2 O 2 , and the relation of urea towards 

 nitrous acid, and its ready decomposition into carbonic acid and 

 ammonia, seem to support this view. But Berzelius justly points 

 out the analogy, in their combining relations with acids, between 

 the alkaloids and urea, and regards the latter as ammonia conjugated 

 with a nitrogenous body which he names urenoxide, so that the 

 rational formula for urea would be :=H 3 N.C 2 HNO 2 . Independ- 

 ently of the analogy between the salts of urea with those of the 

 alkaloids, the following consideration mainly supports this view : 

 cyanate of ammonia =H 3 N.HO.C 2 NO, is convertible, as we shall 

 presently see, into urea ; the grouping of the atoms in urea must 

 be perfectly different from that in this salt, since urea has lost all 

 the properties of a salt. But we know that free hydrated cyanic 

 acid is spontaneously converted by a transposition of its atoms 

 into the so-called cyame}ide=C t2 HNO 2 ; now, nothing is more 

 obvious than to assume that in the combination with ammonia 

 the cyanic acid becomes incorporated with the water of the am- 

 monia-salt, in the same manner as in the free state, and that this 

 cyamelide, if not identical with, is highly analogous to the urenoxide 

 of Berzelius, and thus forms the adjunct of the ammonia in urea. 

 Probably, also, the existence of the biuret might be made available 

 in the support of this hypothesis, since the most simple view of 

 the biuret is to regard it as consisting of 2 atoms of urenoxide and 

 1 atom of ammonia, for C 4 H 5 N 3 O 4 =H 3 N + 2C 2 HNO 2 . 



Combinations. It is only with some acids that urea has a 

 tendency to combine. Cap and Henry* fancied that they had 

 prepared compounds of urea with sulphuric, lactic, hippuric, and 

 uric acids, but the existence of those compounds is very correctly 



* Journal de Pharra. T. 25, p. 133. 



