AMMONIA WITH CARBONIC ACID. 



105 



Since the salt undergoes no change in its composition by sub- 

 limation, and volatilizes at a low temperature, it was easy to de- 

 termine the specific gravity of its vapour. This was performed 

 according to the well-known method of Dumas*. Two expe- 

 riments gave the following results : 



But one vol. carbonic acid = 1 '5 2400 

 Two vols, ammonia. . = 1 "18240 



2-70640 



The calculated specific gravity of a volume of the vapour of 

 the neutral carbonate of ammonia is consequently 0-902 13, which 

 coincides particularly well with the result of the first experiment, 

 which was performed with great accm-acy, and it agrees also pretty 

 fairly with the second. 



The gaseous constituents in the vapour of the carbonate of 

 ammonia are consequently combined without condensation. 



For the first experiment a salt was taken, as it had been ob- 

 tained by the method above mentioned. For the second expe- 

 riment, on the contrary, a sublimed salt was employed. It is 

 hence evident, that, as already proved by the analysis of the sub- 

 limed salt, its composition does not undergo any change by 

 being sublimed once or even twice. 



These experiments, however, disagree with those of M. Bi- 

 neauf, who alleges that he had observed that the gaseous product 

 obtained by exposing the salt to heat retains its gaseous property 

 at a temperature which is lower than that at which it is formed. 

 But his statement of the specific gravity of the vapour coincides 

 with the results obtained by me, although he determined it in an 



* The calculation was made according to Poggendorff's formula {Annalen, 

 vol. -xli. p. 419), having regard to the circumstance, that the gas of carbonic acid 

 gas i.s lighter tlian the atniosiihcric air, the /' of the formula, consequently the 

 entire last member (p. 153) was taken negatively. 



t Annaks ik C'kimie at de Physique, vol. Ixvii. p. 210. 



