COMPARISON OF 2 FREE-ENERGY EXPRESSIONS AND THEIR IMPLICATIONS IN SURFACE ENRICHMENT

We compare two free-energy expressions, developed by Cohen and Multhuk umar [J. Chem. Phys. 90, 5749 (1989)] and by Jerry and Nauman [J. Coll oid interface Sci. 154, 122 (1992)], in terms of their predictions con cerning surface enrichment. We show that a term must be added to the f ormer expression so that it may predict the correct dependence of the surface composition on the bulk. The latter expression does predict th e correct dependence. We have also derived the quadratic surface-energ y contribution from a finite (nonzero) range interaction model.