PROPERTIES OF LIQUIDS AT THE BOILING-POINT - EQUATION OF STATE, INTERNAL-PRESSURE AND VAPORIZATION ENTROPY

Liquids at their respective boiling points are considered in the frame work of factorization of density and temperature dependencies in the a ttraction term of the liquid equation of state. The factorization func tions psi(eta) and a(T) are expressed through the vaporization enthalp y and the liquid packing density eta. The latter is computed from the compressibility of the liquid with correcting for dipole-dipole intera ctions in the framework of the mean-spherical approximation. On the ba sis of the functional dependencies of psi(eta) and a(T), derived from experimental data for a number of liquids, the applicability of equati ons of state to dense liquids at the boiling point can be analyzed. Th e function of eta determined in this way relates the internal pressure to the cohesive energy. Upon decomposing the entropy of vaporization into the contributions from repulsions and attractions, the famous Tro uton constant is shown to be largely determined by the unpacking of mo lecular hard spheres.