| Abstract |
Mixing processes at constant volume (i.e. subject to a given volumetric constraint) associated with molecular theories of liquid mixtures are analysed phenomenologically. Included are the Scatchard mixing at constant ideal volume, the Guggenheim mixing at constant packing fraction and mixing at constant reduced number density and at constant number density. For binary mixtures, a convenient path variable to describe these isothermal mixing processes is the rate of change of the molar volume with respect to the mole fraction. By using this rate of change and the temperature as independent variables for defining appropriate partial molar properties, a single formalism capable of describing that set of different constant volume binary mixtures is developed. Exact expressions for thermodynamic potentials and higher-order mixing quantities of the corresponding ideal mixtures are obtained in terms of experimentally determinable quantities for the pure components. The formalism presented permits calculation of differences between excess functions at any of the different volumetric constraints and excess functions at constant pressure. Finally, it is shown that the ideal Scatchard mixture is the conventional isobaric ideal mixture at the pressure before mixing. |
