IIG HEINRICH ROSE ON THE COMBINATIONS OF 



We find that there is sometimes in commerce a salt that con- 

 tains about 31 per cent, ammonia, 51 percent, carbonic acid. 

 This is I of carbonate of ammonia. 



The composition of the sesquicarbonate of ammonia is such 

 that it may be conceived as a combination of anhydrous neutral 

 salt, and hydrous bicarbonate of the oxide of ammonium (C + 

 NH^) + (2 C + NH'* + H) ; or if it is thought that the anhy- 

 di'ous neutral salt cannot exist in combination with hydrous 

 salts of the oxide of ammonium, we might consider the for- 

 mula (C + NH'*) + (2 C 4- N'H^) to be the more correct. 

 Perhaps the preference might be given to the first formula, 

 partly because the bicarbonate of the oxide of ammonium can- 

 not be prepared alone, but is mixed with water, and at least 

 with 1 atom of water ; and partly because, as will be shown here- 

 after, anhydrous neutral carbonate of ammonia is volatilized 

 when exposed to the air from the sesquicarbonate, and leaves 

 behind hydrous bicarbonate of the oxide of ammonium. 



This view is, in a great measure, confirmed by some recent 

 experiments of Scanlan, and some earlier ones of Dalton*. They 

 found that if the sesquicarbonate of ammonia is treated at the 

 usual temperature for several times with less water than is ne- 

 cessary to dissolve it completely, the first saturated solutions 

 had a greater specific weight than the last. In the same degree 

 that the specific gravity of the solutions decreased, they lost their 

 ammoniacal odour ; the last solution gave crystals of the bicar- 

 bonate. They hence concluded, that either the sesquicarbonate 

 is a mixture of two salts, or that the water exerts an action upon 

 the salt similar to that it is usually imagined to have on some 

 salts of bismuth, and that it decomposes it into two salts of two 

 dissimilar degrees of saturation. Should, however, the last action 

 take place, the salt of more difficult solution woidd remain in the 

 form of a powder, which is not the case, for it is left as a skeleton. 



The crystalhne structure of the salt CAndently shows that it is 

 not a mere mixture, but is composed according to fixed propor- 

 tions, which is also confirmed by analysis. But the experiments 

 above mentioned prove that it is a double salt composed of 1 atom 

 of neutral, and 1 atom of the bicarbonate of ammonia, both which 

 constituents may be separated by water, according to their solu- 

 bility in it. This separation, from the two salts being perfectly 



* The Athenaeum, 1838, No. 5G5, p. 59C. 



