Monolayer properties of fatty acids : III. Thermodynamics of mixing

The thermodynamic properties of mixed fatty acids have been studied in the region of the surface vapor pressure. Using myristic acid as a common component various saturated and unsaturated fatty acid mixtures have been compared with regard to their tendency to be miscible or immiscible. Deviations from expected ideal behavior have allowed estimation of activity coefficients. Measurement of surface heats of vaporization has led to the determination of solubility parameters for each fatty acid. Applying regular solution theory or using activity coefficients allows independent estimation of , the partial molar enthalpy of mixing, and the two approaches are in good agreement. Therefore, it is possible to predict mixing tendencies for any combination of fatty acids used in this study.