J.C. Rainwater
Accepted for publication in the Int. J. Thermophysics
A model with nonclassical exponents is developed for phase equilibria of a Type 2 mixture with vapor-liquid equilibrium (VLE) and liquid-liquid equilibrium (LLE). Starting with a Leung-Griffiths model for a Type 1 mixture with only VLE, the model adds a Schofield parametric construction to describe LLE and a three-phase locus. Care is taken to suppress a spurious and artificial phase boundary. The model is applied to VLE data of carbon dioxide + methane. It is conjectured that this mixture upon cooling would undergo liquid-liquid separation, but is freezes before such "virtual LLE" can be observed. Experimental bubble curves and the LLE structure from a classical equation of state are accurately modeled.