on Magnesia and its Carbonate . 307 
Magnesia, therefore, requires 36000 of water at SI 2 for its 
solution. 
To prove still farther that magnesia is more soluble in cold 
than in warm water, six ounces of its solution, made at a natu- 
ral temperature, were heated very gradually in a long-necked 
flask, so as to prevent as much as possible the evaporation of 
the fluid. During the application of the heat, the liquid be- 
came slightly turbid ; the moment, however, that it began to 
boil, a flocculent matter was precipitated, which, after being 
well washed, was dissolved by muriatic acid ; and, from its so- 
lution, on the addition of carbonate of ammonia and phosphate 
of soda, a white precipitate was thrown down. During the 
heating, the fluid lost only 160 grains by evaporation, and 
afforded phosphate of magnesia and ammonia, on the addi- 
tion of the alkaline salts. 
These different experiments then prove satisfactorily the re- 
markable fact that magnesia is much more soluble in cold than 
in warm water. The same I have found is also the case with 
the carbonate of this earth. The carbonate of magnesia em- 
ployed in the following experiments, was prepared in the usual 
way, washing it after its precipitation, till the whole of the sub- 
stances in solution was removed. 
Exp. 1. The powder thrown down by the addition of carbo- 
nate of ammonia and phosphate of soda to 5760 grains of a 
cold solution of carbonate of magnesia, was treated in the same 
way as that from the solution of the pure earth, after which it 
weighed 2.5 grains, which are equivalent to 1.0 of magnesia. 
Exp. 2. 5760 of a warm solution of the carbonate, prepared 
in the same way as that of the pure earth, yielded, when cold, 
0.7 of the magnesian phosphate, which are equivalent to 0.28 
of magnesia. 
The carbonate of magnesia which I employed in these expe- 
riments, lost by exposure to a strong heat 56.75 per cent ., leav- 
ing 43.25 for the magnesia. If this be the constitution of car- 
bonate of magnesia, 1 of pure earth is equivalent to 2.31, and 
0.28 to 0.64 of carbonate ; 
and, as 2.31 : 5760 : : 1 : 2493. 
Again, as 0.64 : 5760 : : 1 : 9000 ; 
so that carbonate of magnesia is soluble in 2493 of cold water*, 
