As soon as the law of definite chemical combination was firmly
established, the circumstance that changes of temperature accompanied
most chemical combinations was noticed, and chemists were not long in
suspecting that the amount of heat developed or absorbed by chemical
reaction should be as much a property of the substances entering into
combination as their atomic weights. Solid ground for this expectation
lies in the dynamic theory of heat. A body of water at a given height
is competent by its fall to produce a definite and invariable quantity
of heat or work, and in the same way two substances falling together
in chemical union acquire a definite amount of kinetic energy, which,
if not expended in the work of molecular changes, may also by suitable
arrangements be made to manifest a definite and invariable quantity of
heat.
At the end of last century Lavoisier and Laplace, and after them, down
to our own time, Dulong, Desprez, Favre and Silbermann, Andrews,
Berthelot, Thomson, and others, devoted much time and labor to the
experimental determination of the heat of combustion and the laws
which governed its development. Messrs. Favre and Silbermann, in
particular, between the years 1845 and 1852, carried out a splendid
series of experiments by means of the apparatus partly represented in
Fig. 1 (opposite), which is a drawing one-third the natural size of
the calorimeter employed.
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