The Principle of Corresponding States

The principle of corresponding states in modern form has been applied to the following properties: the critical state, the virial coefficient, the Boyle point, the densities of coexistent phases, the vapor pressure of the liquid, the entropies of evaporation and of fusion, the coefficient of thermal expansion of the liquid, the triple-point temperature and pressure, the heat capacity of the liquid, and the surface tension of the liquid. It has been shown that argon, krypton, xenon, and with less accuracy neon, follow the principle with respect to all these properties. It has further been shown that nitrogen, oxygen, carbon monoxide, and methane follow the principle with fair accuracy as vapors and as liquids, but not as solids. The relations between surface tension, temperature, and densities have been analyzed empirically. For the ``ideal'' substances under consideration Katayama's modification of Eötvos' relation holds good, but McLeod's relation does not; in the relation γ∝ (ρl—ρc)s, the exponent s is not 4 but much more nearly 3⅔.