350 
MISCELLANY. 
composition, including always the same proportions of carbonic acid and 
waters : this he calls the carbonate, the other the subcarbonate. Dr. 
Dalton, in a letter dated the 3d of March last, refers me to this printed 
paper, in which there is no mention of the action of water, noticed above 
by me ; but he gives me, in his letter, some additional facts from his notes 
in 1813, from which it appears he had observed precisely the same thing 
I did. He says, »* I took abundance of salt — that is, what is commonly 
called carbonate of ammonia — first poured (the same as you do) a small 
quantity of water on the salt, then tried its specific gravity, which was 
1.114; a second solution was 1. 106, a third, 1.093, and, each diminishing, 
the last (seventh) was 1.043, when it was all dissloved. A like sample, 
dissolved altogether, had sp. gr. 1.086." Dr. Dalton then goes on to 
say, "It was evident from this, you will see, that there was a mixture of 
two salts. I take it, there is no sesquicarbonate, nor other sesqui at all." 
It would appear, then, from the facts observed by Dalton, and moreiately 
by myself, without any knowledge, of his experiments, that the com- 
mercial carbonate of ammonia is not a homogeneous salt, a true sesqui- 
carbonate, as Mr. Phillips looks upon it to be, but a mechanical mixture 
of carbonate and bicarbonate — for, as I have already observed, the water 
must act in one or two ways — either it simply separates the carbonate, 
being the more soluble, from the bicarbonate, which is the less soluble 
salt, or it decomposes the sesquicarbonate (if such it be) in the same way 
that a crystal of nitrate of bismuth is decomposed by water. Now, if 
this latter were the case, the masses of the commercial salt, operated upon 
as I have described, would have been disintegrated — they must have 
been broken down to powder. But, upon experiment, this is found not to 
be the case. The irregular masses of salt still retain, almost exactly, 
their original form and dimensions — they are, in point of fact, skeletons 
of the original mass, but consisting solely of a congeries of crystals of 
bicarbonate of ammonia, from the interstices of which carbonate of am- 
monia has been removed by the solvent power of the water, if we do not 
proceed so far as to dissolve all. What takes place here may be likened, 
in some measure, to bone from which the gelatine is removed by water, 
leaving the phosphate of lime. Independently of showing the true nature 
of the salt, this is of some importance, as it affords us a very ready mode 
of preparing hicarbonate of ammonia without waste, such as occurs by 
exposure of the commercial salt in powder of air, or without the trouble 
of transmitting a current of carbonic acid gas through its solution, as 
directed by the Dublin Pharmacopoeia: indeed, the latter method is both 
troublesome and wasteful, for it is difficult to evaporate a solution of 
bicarbonate of ammonia without decomposition. I have found that water 
at 90° or 100° decomposes bicarbonate of ammonia, setting carbonic acid 
at liberty. 
Athenaeum — Transactions of the British Association, 
