SURFACE-TENSION OF NONELECTROLYTE SOLUTIONS

The composition dependence of the surface tension of highly nonideal organic-organic and aqueous-organic nonelectrolyte solutions is described, based on the assumption that the surface layer can be treated as a separate phase located between the vapor and bulk liquid phases. The Wilson, NRTL, and UNIQUAC equations are used for activity coefficients of surface and bulk phases, and two methods for calculating molar surface areas are tested. Comparisons of the calculated surface tensions with experimental data yield mean absolute errors of less than 2.5% for the systems studied, all of which exhibit highly nonideal behavior. Excess surface tension-composition curves are employed to correlate nonideality of aqueous-organic solutions and offer insight into the surface-orientation effects at work. © 1993 Academic Press, Inc.