Physical Properties of the Ternary System Toluene + n-Hexane + Cyclohexane at 298.15 K: Experimental and Modeling Study

This work reports experimental densities ρ, sound speeds u, and refractive indices n for the ternary system (toluene + n-hexane + cyclohexane) and related binary subsystems at 298.15 K and ambient pressure. Experimental data were used to derive excess molar volumes (VmE), excess isentropic compressibilities (κSE), and refractive index deviations (Δn). Redlich–Kister and Cibulka's equations correlated the binary and ternary excess and deviation data, respectively, with standard deviations below the estimated uncertainties of the corresponding properties. The excess and deviation properties helped probe the interactions between mixture components. Furthermore, the Perturbed Chain Statistical Associating Fluid Theory Equation of State modeled the density of binary and ternary mixtures. Schaaff’s collision factor theory and Nomoto’s relation were compared for their capability to predict the sound speed of the studied mixtures. Mixing rules by Lorentz-Lorenz, Gladstone-Dale, Laplace, and Eykman modeled the mixtures' refractive indices. The average absolute percentage deviation between experimental and calculated values measured the models' predicting capabilities. The modeled densities are reasonably concordant with experimental data with deviations of 0.25%, 0.32%, 0.74%, and 0.31% for the binary n-hexane + cyclohexane, toluene + cyclohexane, and toluene + n-hexane, and ternary toluene + n-hexane + cyclohexane mixture, respectively. Nomoto’s relation was better for predicting binary (overall deviation of 0.46%) and ternary (deviation of 0.62%) sound speeds. Lorentz–Lorenz mixing rule was the best option for predicting binary (overall deviation of 0.08%) and ternary (deviation of 0.14%) refractive indices.