178 On some Reactions of the Salts of Lime and Magnesia, 
ing ‘154 of sulphate of lime, with some carbonate of lime and a 
trace only of magnesia. 
A solution of five grams of sulphate of magnesia was mingled 
with a portion of solution of bicarbonate of lime, and evaporated 
at 160°-180° F., further portions of the latter, amounting in all 
to 300 c. c. being added as the evaporation went on. There was 
deposited a mixture of carbonate of lime, with crystalline gypsum 
equal to 373 grm. of sulphate of lime to the litre. 
23. It will be remarked, that while the recent solution con- 
taining gypsum and carbonate of magnesia with excess of car- 
bonic acid is neutral to cureuma and ma oiled for some 
minutes before a precipitate of carbonate appears, the liquid 
from which gypsum has n deposited by evaporation is 
it deposits in a few hours, especially if gently warmed, a crystal- 
line precipitate of carbonate of lime, resulting from the decom- 
position of the sulphate of lime by the carbonate of magnesia. 
The hate of magnesia retains the carbonate of magnesia in 
solution in such a manner that the latter is not rendered com- 
pletely insoluble, even when the liquid is evaporated to dryness 
over a water-bath. Hence the deficiency observed in the deter- 
minations of carbonate of magnesia in $17, § 21 and § 22, where 
a large proportion of sulphate was present. The filtrate from 
the carbonate in these cases is still alkaline, and gives wi 
nitrates of silver and copper, precipitates of carbonates. 
24, In the Sse experiments all salts, other than those 
concerned in the reaction, were excluded, but similar results are 
obtained in the presence of sea-salt and chlorid of magnesium. 
Twenty grams of pure chlorid of sodium, and ten grams of sul- 
phate of magnesia, with a portion of carbonate of lime, were 
added to 800 c. c. of water, and the solution saturated with car- 
bonic acid gas. Of this liquid 400 c. ¢. were evaporated at 160°- 
180° F., until sea-salt separated, and gave -045 grm. of sulphate 
of lime, mixed with -291 of carbonate. 
_ Ten grams of chlorid of sodium, and twenty grams of crystal- 
lized chlorid of magnesium were added to 600 c. c. of solution of 
bicarbonate of lime, containing two grams of sulphate of magne- 
sia; 300 ¢.¢. of this solution were now evaporated at 160°- 
180° F., until crystals of sea-salt appeared; there were obtained 
057 grm. of sulphate of lime. 
25. A sai solution of one part of sea-salt and two parts 
ef sulphate of magnesia was exposed to a cold of 82° F., when ® — 
large amount of sulphate of soda separated. The mother liquor, 
containing besides some sea-salt and sulphate of magnesia, ® 
