Surface tension of binary mixtures of (1,4-dioxane or DMF + n-alkyl acetate) were measured experimentally using the ring method and the results compared with those predicted by using the Sprow and Prausnitz method. The σ values decreased with an increase of the n-alkyl acetate mole fraction for its binary mixtures with 1,4-dioxane or DMF. Bulk mole fractions, surface molar area, and surface tension of pure components are necessary inputs for this equation. Also, the UNIFAC group contribution method is applied to account for the nonideality of the bulk liquid as well as that of the surface layer. The mean relative standard deviation values for six binary mixtures are less than 1 %. Surface mole fractions and surface excess concentration values show that the surface is enriched with n-alkyl acetate molecules relative to bulk composition.
