Two new forms of apparatus for determining the heat of evaporation of liquids of high boiling point are described, and their relative merits briefly discussed.
In the one the determination is made by a measurement of the amount of liquid vapourised for a given energy supply (radiation loss being eliminated by means of a constant temperature jacket) and in the other, the energy given up on condensing is estimated by means of a continuous flow calorimeter. The latter is thus a modification of the well-known apparatus of Berthelot, but particular attention has been paid to the avoidance of defects inherent in earlier types of apparatus.
The apparatus have been tested by determining with them the heats of evaporation of such liquids as alcohol, water, and aniline, whose heats of evaporation are well known.
A brief survey of the earlier work is included, and a number of references given.