Variational Theory of Mixtures

In the past the variational theory of mixtures due to Mansoori and Leland has been applied successfully to the calculation of excess properties of mixtures. In the present work the origin of the variational theory is discussed along with the important applications of the theory to pure fluid and mixture properties. The advances of the theory in performing mixture calculations are reviewed and analyzed. The review includes the area of simple fluid mixtures, for which the intermolecular potential energy function is well known, and the area of real fluid mixtures, where no explicit information about the potential function is available. The role of the reference fluid system and its effect on the predictive capability of the theory is also discussed. The use of the variatjonal theory to obtain least upper and highest lower bounds to thermodynamic properties is described and some recent calculatjons involving infinite dilution thermodynamics are reported. I NTRODUCT I ON In recent years a number of successful theories which deal with the oroblem of mixtures of simple flurds have been formulated. Almost all of these theories were first developed for pure fluids, and then later 0378-3812/87/$03.50