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Art. X.— On the Action of' Water on Magnesia and its Carbo- 
nate. By Andrew Fyfe, M. D. Lecturer on Chemistry. 
Communicated by the Author. 
"V*" arious statements have been given by different authors of 
the action of water on Magnesia. According to Dr Henry, water, 
when kept on this earth, does not dissolve more than a 2000th 
part of it. Kirwan states, that magnesia is soluble in about 7900 
of water; while Dalton asserts, that it requires no less than 
16,000 of this fluid for its solution. Sir Humphry Davy, on the 
contrary, states, that magnesia is scarcely soluble ; and, according 
to Mr Brande, it is almost infusible and insoluble in water ; while 
Dr Thomson considers it as quite insoluble in this fluid. The 
same diversity of opinion prevails with respect to the action be- 
tween water and carbonate of magnesia. Thus, according to 
Mr Brande, it is a white, insipid, insoluble substance ; while Dr 
Murray asserts that water takes up about a 2000th part of it. 
Several years ago, when I first became acquainted with the 
fact stated by Dalton, that lime is more soluble in cold than in 
boiling water, it occurred to me, that magnesia might be acted 
on in a similar way by this fluid. By making solutions of the 
earth in cold and in boiling water, I found that the former re- 
quired a larger quantity of diluted acid for neutralisation than 
the latter, using litmus paper as a test of the point of saturation. 
Accordingly, I concluded, that magnesia in its action with this 
substance was similar to lime, being more soluble in at its na- 
tural than at its boiling temperature. I did not, however, as- 
certain the quantities of the earth dissolved by water in these 
different states. 
Since reading the paper of Mr Phillips on the solubility and 
crystallisation of lime, my attention has been again drawn to 
this subject. The experiments which I have performed, have 
enabled me not only to confirm the conclusion which I had pre- 
viously made, but also to ascertain, I think, with precision, the 
quantity of magnesia dissolved by water, at a natural and at a 
boiling heat. The magnesia which I employed in the follow- 
ing experiments, was prepared by precipitating it from its sul- 
phate, by means of an alkaline subcarbonate, and exposing it to 
