The properties of dilute mixtures play an important role in many applications. For example, in supercritical extraction, knowledge of the critical point of the system of solvent and extracted material is very useful, in order to determine the conditions at which the solubility change is the maximum. Gualtieri et al. (1982) proposed a general framework for calculating the critical properties of dilute mixtures. They proposed a procedure that used the van der Waals (vdW) equation of state to obtain an analytical expression for the critical properties. Morrison and Kincaid (1984) pointed out that the agreement between the theoretical results of Gualtieri et al. (1982) (dilute-vdW) and the experimental results was only qualitative. Anselme and Teja (199)) used the framework of Gualtieri et al. (1982) with the Soave-Redlich-Kwong (SRK) equation of state to obtain the expression of the critical properties of dilute mixtures. The results of Anselme and Teja (1990) are better than those obtained by the dilute-vdW method. However, the method of Anselme and Teja (1990) cannot predict properties: it needs some binary interaction parameters that are regressed from the experimental results. According to Reid et al. (1987), the dependence of the critical pressure of the mixture Pc on mole fraction is often nonlinear. The estimation of Pc is often unreliable compared with that of the critical temperature Tc and the critical volume Vc of the mixture. In this work, a simple method is proposed to predict the critical pressure of a dilute mixture. The method uses only properties of pure components in the mixture. The method is much simpler than other methods proposed in the literature and the results of this work are better.; A simple method is proposed for predicting the critical pressure of a dilute multicomponent mixtures from the properties of the pure components. The method inverts the formula of Chen that was proposed to calculate the heat of vaporization of a liquid at its normal boiling temperature to calculate the critical pressure of dilute multicomponent mixtures. The method employs only the properties of pure components that are required such as boiling temperature, critical temperature, critical pressure, and critical volume. The absolute relative error of the proposed method was 3% based on the tested 47 mixtures, which was smaller than those of the existing methods.
