Modified wilson equation for vapor-liquid and liquid-liquid equilibria

Abstract

A new equation is derived explicitly based on an excess energy equation with Wilson's local volume fractions and the Gibbs-Helmholtz correlation. The equation is expressed as the combination of the Wilson equation and a volume ratio term which has been introduced as a result of the derivation. The new equation (modified Wilson equation) contains only two parameters for a binary system, and is applicable to both miscible and partially miscible systems. The equation is readily generalized to multicomponent systems without any additional parameters. The wide applicability of the new equation is shown in representing vapor-liquid and liquid-liquid equilibria for binary and ternary systems. It is also shown that the original Wilson equation is obtained without obscurity by the same derivation as for the new equation. © 1975, The Society of Chemical Engineers, Japan. All rights reserved.