The group contribution equation of state PSRK (predictive Soave-Redlich-Kwong) as suggested by Holderbaum and Gmehling (1991) combines the UNIFAC model (Hansen et al., 1991) with the SRK equation of state. In this work the range of applicability of the PSRK method was extended by the introduction of additional gases and the determination of the missing interaction parameters between the following gases: CH₄, CO₂, CO, Ar, NH₃, H₂S, H₂, O₂, N₂ and the original UNIFAC structural groups. The VLE results of the PSRK model have been compared with other predictive equations of state (MHV2 (Dahl and Michelsen (1990)), Lermite and Vidal (1992), LCVM (Boukouvalas et al. (1994)), Wong et al. (1992), UVIWALLS (Gupte et al. (1986)), GCEOS (Skjold-Jørgensen (1984), Tochigi et al. (1990)). Furthermore a comparison between experi-mental and predicted VLE and Henry coefficients is presented.

The PSRK mixing rule can also be used to introduce other G^E models into the SRK equation of state. The results show, that for any G^E model the parameters derived from VLE can be used to enable reliable predictions of phase equilibria, whereby usually excellent results are obtained for a large temperature range.

The thermodynamic analysis of G^E mixing rules enables a reduction of all approaches to one general A^E mixing rule. From this formalism the derivation of the PSRK, and other, G^E mixing rules can be easier understood.