Correlating the Density and Refractive Index of Ternary Liquid Mixtures

Abstract

Some physical properties of ideal solutions, e.g. the molar volume and the molar refraction, vary linearly with composition. Others can be expressed, either as ratios or as products of two other properties which vary with composition in this way. It is postulated that the non-ideal behaviour of real solutions can be adequately modelled by substituting these linear functions with higher order Scheffé polynomials. A suite of such models is presented for which the parameters are fully determined by knowledge of pure component properties and binary behaviour. Their binary data representation ability, and capacity to predict ternary properties, was tested using density and refractive index data for the acetic acid–ethanol-water ternary system as well as fourteen additional ternary data sets. Model performance was ranked on the basis of the Akaike Information criterion. With respect to predicting ternary density and refractive index behaviour from knowledge of binary data, it was found that lower-order models outperformed higher order models.