SOLUTION OP CARBONATE OP MAGNESIA. 
325 
gas escaped, or was expelled, and a salt was deposited in the 
form of minute prismatic crystals. 
This separation of magnesia in a solid form, on the disen- 
gagement of the excess of carbonic acid, was no more than 
might have been expected from the known nature of the com- 
pound, and the artificial manner in which it is formed by the 
condensation of the gaseous acid ; and must be considered as 
quite incompatible with the declaration of its " fluid state" in 
the stomach and bowels, and sufficient ground to call in ques- 
tion the propriety of placing confidence in the preparation, as 
a medicine, in preference to common carbonate of magnesia 
or calcined magnesia, than either of which it is so much more 
costly an article. 
The prismatic salt deposited on the escape of the excess of 
carbonic acid, has been examined by several chemists; resting 
chiefly on the results of the experiments of Berzelius, and the 
late Dr. Henry, it has been considered as a hydrated carbonate 
of magnesia, composed as follows, viz. 
29.61 Magnesia. 
32.23 Carbonic acid. 
10.27 Water expelled at 212° F. 
27.90 " " by a higher temperature, as by ignition. 
100.00 
or of one proportion and half of magnesia, and carbonic acid, 
one of water expelled at 212°, and three proportions of water 
expelled by a higher temperature. Compared with the com- 
mon carbonate of magnesia, from results which I have obtained 
operating on the latter, this appears to differ chiefly from the 
former in possessing a half proportion more of magnesia, and 
one proportion less of water, being composed of 
41.52 Magnesia. 
33.31 Carbonic acid. 
17.47 Water expelled at 212°. 
7.70 " " at a higher temperature. 
100.00 
