In an earlier paper Hoffman et al.( 1 ) discussed a method for predicting the vaporization equilibrium ratios, defined as y/x, for the components of a multicomponent mixture through use of standard state liquid fugacities, standard state vapor fugacities, liquid phase activity coefficients, and vapor phase activity coefficients. As used here and throughout this paper, standard state fugacity means the fugacity of a pure component at the temperature and pressure of the system. The relationship among these variables has been shown to be