H. L. Callendar and the Theory of the Liquid State

Abstract

In 1902, H. L. Callendar¹ suggested that the variation of specific heat of water with temperature could be explained by assuming that a volume of liquid in equilibrium with its vapour contained dissolved in it a number of molecules of its own vapour. The number of molecules assumed to be dissolved was such that, as a vapour, they would occupy the same volume as the liquid, so that the concentration of dissolved molecules in the liquid was the same as that of ordinary molecules in the vapour.