232 MR HENRY HOW ON CERTAIN SALTS AND 
The crystals contain in addition eight atoms of water. 
{ 14-380 grains air-dry salt lost at 250° 
2°775 ... water, and 
11-665 grains air-dry substance lost at 250° 
2°180 ... water. 
the mean of these numbers, when calculated on 100 parts, 
Ti + II. Mean. 
19-29 18-77 19:03 
agrees perfectly with that,—18°88,—corresponding to the formula 
2 BaO, C,, H, O,, 2 HO +8 aq. 
The crystallized salt when boiled in water is converted into a basic com- 
pound, which loses no water at a temperature of 250°. A portion, which had been 
so dried, gave on analysis 54°5 per cent. of baryta; this is considerably more than 
would correspond with a normal neutral salt entirely free from water. 
Salts of Magnesia with Comenie Acid. 
Acid Comenate of Magnesia.—This salt is much more soluble than the corre- 
sponding salts of lime and baryta; it crystallizes out after some time, in perfect 
small rhombs, when strong cold solutions of bicomenate of ammonia and sulphate 
of magnesia are mixed. When obtained from dilute solutions, by spontaneous or 
very slow artificial evaporation, these crystals are of very large size, and when 
possessing the yellow colour so apt to adhere to salts of comenic acid, they very 
much resemble regular crystals of ferrocyanide of potassium. They are readily 
soluble in hot water, and react strongly acid. The following is the analysis, the 
magnesia being estimated as sulphate, by ignition with sulphuric acid :— 



" 7-426 grains dried at 240° Fahr. gave 
10-517... carbonic acid, and 
1:988 ... water. 
5-613 grains dried at 240° Fahr. gave 
1:863 ... sulphate of magnesia. 
Experiment. Calculation. 
3a4c.0£20©0eT—=€=sS=e 
Carbon, . : 38°62 38°77 Cio 72 
Hydrogen, : 2-97 2-69 H, 
Oxygen, . ? Jan 47-41 0,, 88 
Magnesia, ; 11-10 11:13 MgO 20-67 
100-00 100:00 185-67 
from which it appears that two atoms of water are retained in combination at 
the temperature of 240° Fahr.; the composition of the so-dried salt being ex- 
pressed by the formula 
MgO, Ho, C,, H, O,+2 HO. 

