To expand the range of applicability of the group contribution equation of state PSRK, 10 new main groups for the gases SO 2, NO, N 2O, He, Ne, Kr, Xe, HCl, HBr and SF 6 have been added to the already existing 59 main groups (50 main groups from original UNIFAC plus 9 groups for the gases NH 3, CO 2, CH 4, O 2, Ar, N 2, H 2S, H 2 and CO). The group interaction parameters for the new and already existing main groups have been determined for 128 group pairs with the help of experimental VLE data for low boiling substances. Typical results for gas solubilities and VLE using the PSRK model are presented. Using the idea of effective van der Waals volumes and surface areas for the subgroups CH 3, CH 2, CH and C, reliable results are also obtained for highly asymmetric systems over a large temperature and pressure range.