Information about thermodynamic properties such as distribution coefficients for each component of a mixture between the coexisting Liquid and vapor phases is required for the design of separation plants. When a nonideal liquid mixture is described by an equation of state with its mixing and combining rules, the quality of the model is usually appraised by the accuracy obtained in correlating experimental VLE data. We propose another method here that provides a rapid test of the flexibility and applicability of such equation of state models.