EQUATION OF STATE FOR COMPLEX LIQUID-MIXTURES

The present work shows a successful extension of previous studies to molecular liquids for which the second virial coefficients are not known. Recent advances in statistical-mechanical theory of equilibrium fluids can be used to obtain an equation of state for compressed liquids. The average contact pair distribution function (G), which is at the heart of the equation of state, has the very simple form of a single curve in lambdab*rho* (any substance). The effect of many-body forces may still be included in G. The temperature-dependent parameters in the equation can be calculated with reasonable accuracy for most practical purposes just from the experimental heat of vaporization and triple-point density. Thus, thermodynamic consistency is achieved by the use of two scaling parameters (DELTAH(nu), rho(t)). In terms of these parameters, the reduced second virial coefficient (B2*(T)) obeys a single law of corresponding states in which alpha*(T) and b*(T) are only slightly modified. The correlations embrace the temperature range T(t) less-than-or-equal-to T < T(c) and can be used in a predictive mode. The remaining constant parameters are best found empirically from rho(t) data for pure dense fluids. We tested the equation of state on several liquid mixtures. The results indicate that the density of liquid mixtures can be predicted within about 5% at any pressure and temperature.