118 HEINRICH ROSE ON THE COMBINATIONS OF 



also be separated from the bicarbonate, not only by water, but 

 also by being preserved in vessels from which the air is not en- 

 tirely excluded. The more volatile carbonate gradually disap- 

 pears entirely, and the less volatile bicarbonate is left quite free 

 from the carbonate. This succeeds especially well if the sesqui- 

 carbonate is employed pulverized in the way above mentioned, 

 and if the atmosphere in which the vessel is situated be not too 

 moist. The remaining bicarbonate of the oxide of ammonium 

 contains 1 atom of water ; the volatile carbonate of ammonia is 

 consequently anhydrous, and contains no oxide of ammonium, on 

 which account, as remarked above, the latter can hardly be con- 

 sidered to exist in the common sesquicarbonate. 



The double salts, which the carbonate of ammonia forms with 

 the bicarbonate, are, however, in so far of an uncommon kind, that 

 whereas in general the simple salts which form the constituents 

 in other double salts are of one and the same degree of satura- 

 tion, this is not the case here. We must, however, certainly 

 distinguish two kinds of double salts. In the double salts of one 

 kind, which form the majority, the simple salts are of the same 

 degree of saturation ; in them, generally half, or another defi- 

 nite portion of one base is replaced by an equivalent of another 

 base, and the one salt consequently cannot act in them the part 

 of an acid or a base towards the other, which was formerly the 

 view taken with regard to the composition of these combinations. 

 In the second kind of the double salts, on the contrary, both the 

 combinations of which they consist are not of the same degree 

 of saturation ; in these double combinations one constituent part 

 may be considered as the acid, the other as the base. Certain 

 combinations of carbonic acid, of silicic acid, and of other weak 

 acids with bases, belong to this class ; and also the propei'ty 

 of boracic acid to dissolve, when melted, all substances of acid 

 and basic properties, depends on the tendency to form double 

 salts of this second class. 



In the combinations of the carbonate and of the bicarbonate 

 of ammonia, which also belong to this class of double combina- 

 tions, the carbonate is naturally the base, and the bicarbonate the 

 part which replaces the acid. The tendency which the carbonate 

 has to form a double salt with the bicarbonate, when sal-ammo- 

 niac or sulphate of ammonia is subjected with the carbonate of 

 1 me or a dry carbonated alkali to distillation, rests in part on this 

 circumstance; that the carbonate of the oxide of ammonium, C + 



