MISCELLANY. 
Observations on the Constitution of the Commercial Carbonate of Ammonia, 
by M. Scanlan. — Having occasion (said Mr. S.) some months ago to 
make a quantity of the " Solution of Sesquicarbonate of Ammonia," of 
the London Pharmacopoeia, instead of adding, at once, the entire quantity 
of water necessary for the solution of the salt, I took a large jar of the 
commercial carbonate of ammonia, just as it is furnished by the manufac- 
turers, in lumps, and poured upon it barely as much cold distilled water 
as was sufficient to cover the salt, expecting, of course, to obtain thus a 
saturated solution. When the solution was completely a saturated 
one, (specific gravity 1.150,) it was decanted, and the undissolved salt 
covered with fresh distilled water. This, also, was suffered to stand 
until it ceased to increase in specific gravity; but I was surprised to find 
the gravity much less than that of the first solution. Successive portions 
of distilled water were added, as before, till the solution of the whole of 
the salt was effected ; and it was found, that solutions constantly decreas- 
ing in gravity, and smelling less of ammonia in proportion as the specific 
gravity decreased, were obtained. I satisfied myself that each solution 
was a saturated one, by decanting it, taking its specific gravity and re- 
turning- it upon the undissolved salt, until it ceased to acquire additional 
specific gravity, allowing for temperature. It was obvious from this, that 
the commercial salt operated upon, either originally consisted of two 
distinct salts, separable from one another by virtue of their different rates 
of solubility, or that the water decomposed and resolved it into two 
distinct carbonates of ammonia. My last solutions had scarcely any 
smell of ammonia, and afforded, on reduction of temperature, regular 
crystals of bicarbonate of ammonia. The first solution of sp. gr. 1.150, 
also afforded crystals on reduction of temperature, which, when dried on 
bibulous paper, smell powerfully of ammonia, and are, no doubt, the 
carbonate: these effloresce readily; the bicarbonate does not. I was not, 
aware, until apprised by Mr. Richard Phillips, that Dalton had noticed 
this action of water on the commercial carbonate of ammonia long ago. 
In vol. 3 of the Manchester Memoirs, will be found a paper by Dalton, 
put into my hands by Mr. R. Phillips, in which he notices the loss of 
weight and smell of the commercial carbonate of ammonia by exposure to 
air ; and he proves there, that the salt which remains is constant in its 
VOL. IV, — NO, IV. 44 
