Volumetric and ultrasonic studies of molecular interactions in binary mixtures of dimethyl sulfoxide with some aromatic hydrocarbons at different temperatures

The densities (rho) and ultrasonic speeds (u) of pure dimethyl sulfoxide (DMSO), benzene, toluene, o-xylene, m-xylene, p-xylene, and mesitylene, and those of their binary mixtures, with DMSO as the common component, over the whole composition range have been measured at 298.15, 303.15, 308.15, 313.15, and 318.15 K. The excess molar volume (V-E), deviation in isentropic compressibility (Delta k(s)), apparent molar volume (V-phi,V-2), apparent molar compressibility (K-phi,K-2), partial molar volume ((V) over bar (o)(phi,2)), and partial molar compressibility ((K) over bar (o)(phi,2)) of aromatic hydrocarbons in DMSO at infinite dilution have been calculated from the experimental data. The variation of these parameters with the composition and temperature of the mixtures indicates that the interaction (DMSO-aromatic hydrocarbons) follows the order: benzene > toluene > p-xylene > m-xylene > o-xylene > mesitylene. The effect of the number and position of the methyl groups in these aromatic hydrocarbons on molecular interactions in these mixtures is also discussed. The V-E values have also been calculated theoretically by using Flory's statistical theory and the Prigogine-Flory-Patterson theory. The calculated V-E values were found to be in good agreement with the experimental V-E values for most of the mixtures.