Thermodynamics of binary n-alkane mixtures : partial molar volumes and free energies

Excess partial molar free energies and excess volumes of n-alkane/n-alkane mixtures were investigated, with special emphasis placed on the low concentration regions. Using a vibrating tube densitometer, the excess volumes of the following systems are reported; n-C₈ + n-C₉ and n-C₈ + n-C₁₀ at 288.15 K, and n-C₈ + n-C₉, n-C₈ + n-C₁₀ at 298.15 K across the entire concentration range; and n-C₈ + n-C₁₀, n-C₉ + n-C₁₁ and n-C₉ + n-C₁₃ at 298. 15 K at low concentrations (characterized by a particularly high density of data points). The excess partial molar free energies were measured with a continuous dilution vapor pressure apparatus. Limiting activity coefficients are reported for n-C₆ + n-C₇ + n-C₈ at 303.15 K and n-C₆ + n-C₅, n-C₇ + n-C₆, n-C₈, n-C₇, n-C₉ + n-C₈ and n-C₉ + n-C₇ at 323.15 K. Activity coefficients are also reported for the benzene-cyclohexane and benzene-cyclohexane-water test systems.

Correlations between the excess properties and carbon number are given. The data are interpreted and the observations are compared with the predictions of the various theories of binary n-alkane mixtures.