An apparatus for measuring the quantity of heat evolved or produced by
or under different conditions. Dulong’s water calorimeter consists of a
water jacket, and by the increase of temperature of the water and
enclosing vessels the amount of heat produced by anything in the inner
vessels is determined. The amount of ice a heated body will melt is
sometimes made the basis of a calorimeter. The expansion of a fluid, as
water, may be used. In the calorimeter shown in the cut the heat
produced in a conductor by the passage of an electric current is caused
to heat water whose temperature is shown by a thermometer immersed
therein. The increase of temperature and the weight of the water give
the basis for a determination of the heat produced by the current.
Knowing the resistance of the conductor immersed, the watts can be
calculated. This gives the bases for the determination of the
heat-equivalent of electric energy. This is but an imperfect
calorimeter, as it constantly would lose heat by the surrounding
atmosphere, and would cease to operate as a calorimeter when the water
was as hot as the wire normally would be, for then it would not absorb
all the heat.