The simple and predictive method for describing vapour liquid equilibr
ia at high pressure and temperature developed previously by the author
s and applied to different kinds of binary mixture is extended to the
description of ternary mixtures and to a multicomponent reactive syste
m. The method is based on the use of the UNIFAC-VIRIAL method for gene
rating vapour-liquid equilibrium data of binary systems at moderate pr
essures (3-4 atm) and temperatures. The data were then reproduced by t
he Redlich-Kwong Soave equation of state and the quadratic mixing rule
s. The best fit of the data was obtained by regression analysis of the
binary interaction parameters. We observed that these parameters can
be used directly at higher pressures and temperatures to describe sati
sfactorily the vapour-liquid equilibria of binary and multicomponent m
ixtures.