Static properties of solutions. Van der Waals and related models for hydrocarbon mixtures

The van der Waals equation of state, in spite of its oversimplifications, gives useful qualitative information about mixtures over a wide range of temperatures and pressures. When the Brönsted principle of congruence is used to evaluate the parameter a12 for the mixture, a wide range of properties can be predicted: excess functions (including temperature and composition dependence) and phase equilibria (including lower critical solution phenomena at high temperatures), in good qualitative agreement with experimental properties of mixtures of n-alkanes.