Surface tension and density of mixtures of m-xylene + n-alkane at 293.15 K: Analysis under the extended Langmuir and Shereshefsky models

Surface tension (σ) and density (ρ) for {m-xylene + n-pentane, hexane, heptane and octane} at the temperature 293.15 K and pressure 1.013 bar have been determined as a function of mole fraction. In order to analyze the surface tension behavior, the extended Langmuir (EL) and Shereshefsky models were used and parameters of the models were obtained for these mixtures. The standard Gibbs energy of adsorption (-ΔG∘) was calculated using both models. The free energy change of replacing one mole of solute with one mole of solvent in surface region (ΔGS) and the excess number of molecular layers of solute in the surface region were calculated using Shereshefsky model. The magnitude of ΔGS and (-ΔG∘) was discussed in terms of nature and type of intermolecular interactions in binary mixtures. The Redlich-Kister polynomial equation was fitted to each of the experimental surface tension deviation (δσ) and excess molar volume (vE) results. Using the resulting polynomial equations, the surface tension deviations and the excess molar volumes (δσ, vE) were calculated over the entire composition range.