COMPARISON OF 2 HARD-SPHERE REFERENCE SYSTEMS FOR PERTURBATION THEORIES FOR MIXTURES

The Carnahan-Starling equation of state for hard spheres can be extended to mixtures using either a one-fluid theory, or the generalization of scaled-particle (or Percus-Yevick theory) proposed by T. Boublik and by G. A. Mansoori and coworkers. The two reference systems are combined with a perturbation term of the van der Waals form; they are then used to correlate the phase behavior of binary mixtures of nonpolar molecules differing significantly in molecular size. In each case, one adjustable binary parameter ( alpha //1//2) is used to correlate vapor-liquid equilibria over the entire composition range. Predicted Henry's constants and liquid densities for the saturated mixture are compared with experiment. The Boublik-Mansoori hard-sphere-mixture equation is superior to the Carnahan-Starling One-Fluid theory, especially in the dilute region.