Statistical surface thermodynamics of simple liquid mixtures

The surface properties of nonpolar liquid mixtures are derived from the application of the grand partition function to a cell model of the vapor‐liquid interface. The surface tension and surface composition are expressed in terms of the activity coefficients in the bulk liquid and pure‐component properties. The results are in excellent agreement with existing data for the surface tension of mixtures. This treatment provides a sound theoretical basis for the prediction of surface properties of other liquid systems and is especially applicable to cryogenic mixtures.