The critical properties of tertiary systems containing n-paraffins, and pseudo-binary systems containing carbon dioxide and several n-paraffins treated as a continuous component, are calculated by making use of White's recursive procedure based on renormalization group (RG) theory and a classical Redlich-Kwong-Soave (SRK) equation of state. Both the multi-component method and the continuous thermodynamic method are used to calculate the critical temperature, pressure and volume. The latter costs much less computer time than the former traditional approach. Generally, the calculated results from the RG recursive procedure with an SRK equation provide better agreement with experimental data than those from the classical equation of state alone. (c) 2005 Elsevier B.V. All rights reserved.