Thermodynamic properties of binary systems containing hexafluorobenzene. Part 3.—Excess Gibbs free energy of the system hexafluorobenzene + cyclohexane

The vapour pressure of the system hexafluorobenzene + cyclohexane has been measured over the complete composition range at 30, 40, 50, 60 and 70° using a static method. The excess Gibbs free energy has been calculated as a function of temperature and composition. The experimental results have been analyzed using regular solution theory and the Prigogine average potential theory of liquid mixtures. Both analysis lead to the conclusion that, in this mixture, the energy of the unlike interactions is some 5 % weaker than the value predicted by the usual combining rule.