Equation of state for mixtures of non-polar molecular fluids

We present a new analytical equation of state for mixtures of non-polar fluids by a generalization of the Ihm-Song-Mason corresponding-states equation for non-polar fluids. It has a sound statistical-mechanical basis and is both simple and accurate enough to describe the thermodynamic properties of mixtures at all fluid densities, temperatures, and compositions. The temperature-dependent parameters in the equation are fundamentally related to the intermolecular forces, but can be calculated with reasonable accuracy for most practical purposes just from experimental second virial coefficients. The remaining constant parameters are best found empirically from p-ν-T data on pure dense fluids (one constant parameter for each pure fluid). No ‘mixing rules’ are needed. We test the equation of state on three systems with quite different available input information -Ar + Kr, CH4 + CF4, and CO2 + C2H6. Agreement with experiment is good for all three systems.