308 Dr Fyfe on the Action of Water on Magnesia. 
while it requires 9000 of the fluid at a boiling heat for its solu- 
tion. Other statements have been given of the composition of 
carbonate of magnesia, which will, of course, make the quantity 
of this substance dissolved by water to be different. The above 
experiments, however, prove, that it is soluble in this fluid when 
cold, and when warm, in the ratio of 2.31 to 0.6*4. 
The more sparing solubility of carbonate of magnesia in 
warm than in cold water, was also proved, by heating gradually 
six ounces of its solution made at a natural heat, during 
which the fluid became very slightly turbid. At the instant 
that it began to boil, a minute quantity of a flocculent matter ap- 
peared, which, when dissolved in muriatic acid, became tur- 
bid, on the addition of carbonate of ammonia and phosphate of 
soda. During the heating, the fluid lost 190 grains by evapo- 
ration, and yielded ammoniaco-magnesian phosphate, when the 
alkaline salts were added. 
In the paper of Mr Phillips above alluded to, it is suppos- 
ed that the crystallization of lime occasioned by the heat, is the 
cause of this substance being less soluble in warm than in cold 
water. In the case of magnesia and its carbonate, I do not 
know if the same cause can be assigned for the difference in the 
solubility of these substances in water at different temperatures, 
as both of them are separated from the fluid during the heating, 
in the form of a light flocculent matter, which floats in the li- 
quid, — an appearance very different from that presented by lime ; 
this earth, in the experiments which I have performed, being de- 
posited on the sides of the vessel, to which it adhered with con- 
siderable force. 
I may here remark, that I have reason to believe, that other 
bodies are also more soluble in cold than in warm water. The 
experiments, however, which I have performed, are not suf- 
ficiently conclusive, to warrant my making at present any defi- 
nite remarks on the subject. 
Edinburgh, July 4. 1821. 
