Mr. Graham on the Heat disengaged in Combinations. 33'7 
soluble salts were pounded fine and sifted; the solution took 
place with stirring within one minute. 
Of the anhydrous salt, 49°84 grains, the equivalent quantity, 
were dissolved in 1000 grains of water, with a rise in two ex- 
periments of 3°72 and 3°74. Hence the results for the 
anhydrous salt are,— 
Rise on solution of CuO, SO; . . . . 3%73 
Fall on solution of CuO, SO, + 5HO . 0°67 
Whole heat disengaged by CuO, SO,. . 4°40 
The protohydrate was prepared by drying the crystallized 
salt by a nitre-bath; it retained to 100 sulphate of copper 
11°83 water, instead of | 1-29 water, the single equivalent. The 
equivalent quantity, 55°72 grains, was dissolved in 1000 grains 
of water, with a rise in two experiments of 2°15 and 2°13. 
The result is 3°73 — 2:14 = 1°59 for the combined water. 
This hydrate contained 13, H O. 
After being dried still further on an oil-bath at S70: 4,it 
consisted of 100 sulphate of copper and 11°44 water, or was 
1,'; HO; the salt was now almost white, the green tint bein 
barely perceptible. The equivalent quantity of the last salt, 
55°54 grains, was dissolved in 1000 grains of water, but some- 
what more slowly and with greater difficulty than the prece- 
ding salt. The heat evolved in two experiments was 2°09 and 
2°:07, which instead of exceeding falls short of the preceding 
results. The deficiency of heat in the last experiments is re- 
markable, and is in some measure, but I believe not fully, 
accounted for by the slowness of the solution. Giving a pre- 
ference to the first results, and deducting ,,nd part for the 
excess of water above one atom already combined with the 
salt, there remains 1°-47 for the heat due to the combination of 
the first atom of water. The result for the protohydrate is,;— 
Rise on solution of CuO, S O; HO . . 2%96 
Fall on solution of CuO,SO,+5HO . 0%67 
Whole heat disengaged by CuO, SO, HO 2°93 
One-third of 4°-40, the whole heat evolved in the hydration 
of sulphate of copper, is 1°-466, which is as nearly as possible 
the result obtained above for the first atom of water. The 
ratio is the same as in the sulphate of zinc, while in the hy- 
dration of the sulphate of magnesia the heat evolved by the 
first atom of water was one-fourth of that evolved by the 
whole. It may be inferred from the experiments on oil of 
vitriol, that it approaches more closely to the former salts 
than to sulphate of magnesia in this character, although a 
rigid comparison cannot be made, as we are unacquainted 
