CAPABILITIES AND LIMITATIONS OF THE WONG-SANDLER MIXING RULES

An analysis of the mixing rules proposed by Wong and Sandler (1992) fo r the attractive and covolume parameter of a cubic equation of state i s presented. This set of mixing rules (WS MR) reproduces the correct q uadratic composition dependence of the second virial coefficient and, in addition, retains the ability to predict directly high pressure-hig h temperature phase equilibria from existing low-pressure GE models. I t is demonstrated that the proposed mixing rules are valid for symmetr ic systems, but not for asymmetric ones, where the basic assumptions b ehind them do not hold anymore.