1885.] Limited Hydration of Ammonium Carbamate. 387 



presence of sodium hydroxide, yields one-half of its nitrogen in the 

 free state, the other half remaining in the form of sodium carbamate — 



20O(NH a )(ONH 4 )+3Na01O-+2NaOH=2CO(NH 8 )(ONa) + 3N'aCl 



+ 50H 2 + N 2 . 



Sodium hypobromite at once decomposes sodium carbamate, evolving 

 its nitrogen in the free state — 



2CO(NH 2 ) (ONa) + 3NaBrO + 2NaOH =2CO(Wa) 2 + 3NaBr 

 + 3H 3 + N 2 . 



This, in fact, may be claimed as a specific reaction for carbamates — 

 no other substance yet investigated will yield nitrogen when treated 

 with a hypobromite after the completed action of a hypochlorite. 

 Urea evolves but half its nitrogen with a hypochlorite, in presence of 

 caustic alkali, but the other half remains as a cyanate, which is not 

 acted upon by a hypobromite.* 



Based upon this reaction, then, we have a direct and simple method 

 of determining the amount of carbamate existing in a solution at any 

 given time. 



Since, under the action of a hypochlorite, ammonium carbamate 

 yields one-half of its nitrogen (i.e., that present as ammonium), it is 

 evident that any excess over and above this half which is evolved 

 from its solution, is a measure of the water which has been assimilated 

 converting the carbamate into carbonate. 



For the sake of convenience we may express the hydration which 

 occurs in terms of the ratio of the number of molecules of water 

 assimilated to that of the molecules of ammonium carbamate taken. 

 Let V = the total volume of nitrogen contained in the ammonium 

 carbamate taken, and V 1 = that evolved by the action of a hypochlo- 

 rite on its solution. Then the above ratio evidently = ^ 



(since one atom of nitrogen evolved in excess of the half total corre- 

 sponds to one molecule of water assimilated, and two atoms of nitrogen 

 originally present represent one molecule of ammonium carbamate 

 taken). 



The ammonium carbamate used in these experiments was prepared 

 by the direct union of carefully dried ammonia and carbon dioxide. 

 The apparatus employed in the estimation of the evolved nitrogen 

 was similar to that described in a former paper on the action of 

 Hypochlorites in Urea.* 



Experiments were undertaken with a view of investigating to what 

 extent the action is influenced by (1) time, (2) mass, (3) tempera- 

 ture, and (4) to study the reverse action, namely, the dehydration of 

 normal ammonium carbonate into ammonium carbamate. 



* " Chem. Soc. Jour.," 33, 300. 



