Theories of solubilities of non-electrolytes

A brief history of solubility theory is outlined, and the distinguishing features of modern solubility theory are discussed. It is shown how the perturba— tion theory—based terms in the expression for the Henrys law constant provide microscopic information on covitation and solvation. Results are given both for atomic and molecular systems. In the case of atomic systems, where no adjustable parameters are used, excellent agreement with experiment is found. In these systems we also probe in a fundamental way for the role of quantum effects and non— additive three—body forces on solubility. For molecular systems, in which the required pair potentials are generally unknown, a somewhat different approach is perhaps most useful. In particular we show how a molecular liquid state perturba— tion theory can be used to probe for the role of dipoles and quadrupoles on the thermodynamics on non—electrolyte solubilities in water. Finally, some of the difficulties that lie ahead in the field of solubility theory are mentioned.