THE 
LONDON, EDINBURGH anv DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[THIRD SERIES.] 
MAY 1843. 
LVII. Experiments on the Heat disengaged in Combinations, 
By Tuomas Grauam, Esq., F.R.S., §c.* 
(THE observations, of which an account shall be given in 
the present paper, are exclusively confined to the heat 
disengaged in combinations formed in the humid way. The 
heat disengaged in such combinations is in general easily col- 
lected and measured, as it is immediately communicated to a 
mass of fluid, of which the temperature may be observed with 
accuracy. ‘The elevation of temperature in an experiment 
may often, however, be greatly affected by incidental circum- 
stances; such as the liquefaction of the product of the com- 
bination, arising from its solution in the water, or other men- 
struum employed; or the hydration of the compound formed, 
which so generally occurs with a salt formed by uniting an 
acid and base; and can rarely, therefore, be taken as the ex- 
pression of the heat disengaged from the combination without 
considerable correction. 
Thus in a few preliminary experiments to ascertain whether, 
as has been anticipated, different bases of the same class 
evolve equal quantities of heat on combining with the same 
acid, it was found that equivalents of oxides of copper and 
zinc, and the equivalent of magnesia on dissolving in highly 
diluted sulphuric acid, evolved respectively 4°°20, 5°18, and 
11°70. But the sulphates formed are all hydrated salts, and 
a large portion of the heat was found to be due to the com- 
bination of this water, naniely 3°-49 in the sulphate of copper, 
$°-90 in the sulphate of zinc, and 4°12 in the sulphate of 
magnesia. Again, the salts are obtained in solution; now 
the liquefaction or solution of salts is attended with the ab- 
* Communicated by the Chemical Society ; having been read Novem- 
ber 1, 1842. 
Phil. Mag. 8. 3. Vol. 22. No. 146, May 1843. Z 
