Preferential Solvation in Ternary Solutions Containing Methylbenzoate. A Kirkwood−Buff Fluctuation Theory Study

Density, dynamic viscosity, and refractive index of the hexane/cyclohexane/methylbenzoate ternary solvent and its binary constituents were measured at 298.15 K over the whole composition range. From the experimental measurements, excess and mixing properties were evaluated and correlated with composition using different models. The structure and interactions in the ternary solvent were analyzed starting from the experimental properties by application of the Kirkwood−Buff fluctuation theory of solutions along with the UNIFAC group contribution method for predicting activity coefficients. The local composition and excess (or deficit) number of molecules aggregated around a central one were determined using the Kirkwood−Buff integrals. The properties of the ternary system were used to test the predictive ability of several models. The volumetric properties of the binary and ternary systems were correlated and predicted with the cubic equations of state by Soave and Peng−Robinson combined with two simple mixi...