Excess thermodynamic quantities in binary systems of non electrolytes.: Different ways of calculating excess compressibilities.

Abstract

Recent work involved the evaluation of ideal and excess quantities for a wide-ranging set of thermodynamic variables. A literature search revealed that unjustifiable assumptions are frequently made in establishing the expressions of ideal mixing laws, giving rise to erroneous values of corresponding quantities. A large number of such approximate laws have been proposed to estimate “excess” isothermal and isentropic compressibility. The knowledge of rigorous ideal mixing laws allows the difference between pseudo-excess and exact excess compressibility to be evaluated. This provides us with an excellent tool for recalculating exact excess quantities from erroneous data likely to be found in the literature. The amplitude of the various differences has been illustrated using examples taken from among the properties of the water—acetonitrile system.