Equilibria in Non-electrolyte Solutions in Relation to the Vapor Pressures and Densities of the Components.

Abstract

The method to be outlined is an-outgrowth of the treatment of gaseous systems used in the laboratory of the Massachusetts Institute of Technology. It may be regarded also as a quantitative development of the treatment of Hildebrand, although it disagrees with his ideas in some important details, or as a method of freeing the van Laar treatment from the inadequacies of the van der Waals equation. I n this paper is presented the simplest first approximation. Though its success is not astounding, it is hoped that the presentation will show some of the reasons for the limitations of so simple a theory, as well as indicate some of the possibilities of improvement. It will also serve as a comparative review of the different theories.The general method is to make all variations of composition1 and temperature a t such low pressures that the perfect gas laws are applicable, and to make the pressure variations a t constant temperature and composition (1). There is no obvious method of extending to liquids the treatment of free energy itself, but progress may be made through the energy. We may express the energy of a mole of liquid as Ul = Ua -u. Uo is the molal energy of the gas a t zero pressure, and we need not consider it further for it is a function only of the temperature, independent of the pressure, the state of aggregation, and of the composition unless there is a chemical change which persists a t zero pressure.

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“…and where I have separated the surface energy into 6) where f h (h) and f φ (φ) depend only on h and φ respectively, and f φ,h (φ, h) contains any cross terms. This separation of the energy into parts simply makes it easier to write a compact form of the model, the convenience mainly being in Eq.…”

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