AMMONIA WITH CARBONIC ACID. 119 



^H"*, which ought here to be formed^ does not seem to exist in a 

 soHd state of itself, as has ah'eady been remarked. On this 

 account, at the beginning of the heating, ammonia is disengaged, 

 and this escapes, in common, mth so much water as would be ne- 

 cessary to convert it into the oxide of ammonium, whilst the ses- 

 quicarbonate of ammonia is formed. From 3 atoms of carbonate 

 of oxide of ammonium, which ought to evolve from the mixture 

 when heated, 1 atom of carbonate of ammonia is formed, and 1 atom 

 of hydrous bicarbonate, which two form the double salt, and it 

 disengages 1 atom of ammonia and 1 of water. 3 C + 3 NH^ + 

 3 H = (C + NH3) + (2 C + NH4 + H) + NH^ + H . ~If the 

 products of this operation are received in the order in which 

 they are produced, over mercury, pure ammoniacal gas is first 

 obtained, which is wholly absorbed by muriatic acid ; and af- 

 terwards come the products, which appear during the sublima- 

 tion of the common sesquicarbonate, of which we shall speak 

 further on. As the sesquicarbonate can be evaporated only 

 with the disengagement of carbonic acid gas, this gas is found 

 amongst the products of the sublimation ; there is, however a de- 

 finite interval between the disengagement of the ammoniacal gas 

 and of the carbonic acid gas. The latterfirst begins to escape when 

 the evolution of the ammonia has entirely ceased, and when the 

 glass cylinder, in which the gaseous px*oducts are received, begins 

 to be covered with a thin incrustation of the carbonate of am- 

 monia, and at the same time water passes over. When all the 

 gaseous products are received together in one glass cylinder, over 

 mercury, the ammoniacal gas which first goes over gradually 

 combines with the carbonic acid gas which subsequently passes 

 over. 



IV. Sesquicarbonate of Ammonia with a larger proportion of 



Water. 

 If the common sesquicarbonate is exposed for some time to a 

 very gentle heat, in a retort, the neck of which is connected with a 

 long glass tube, the following appearances occur : at the veiy 

 beginning carbonic acid gas is disengaged, and then the hydrous 

 neutral carbonate of ammonia sublimes, which, as the most 

 volatile of the solid products of sublimation, consolidates in that 

 part of the glass tube furthest from the retort. The nearer to the 

 retort the sublimate adheres, the more the solution is precipitated 



