A Study of Some Excess Thermodynamic Properties in Binary Mixtures of Non-Aqueous Solvents at Variable Temperatures

Excess thermodynamic properties such as viscosity deviation (ln ∆ƞ), excess isentropic compressibility (KsE), excess molar volume (VmE), excess intermolecular free length (LfE), excess free volume (VfE), excess acoustic impedance (ZE) and excess internal pressure (ΠiE) were evaluated from the experimentally measured values of density (ρ), ultrasonic velocity (u) and viscosity (ƞ) for the binary mixtures of acetonitrile (AN) with dimethyl sulfoxide (DMSO) and with N, N-dimethylacetamide (DMA) as a function of mole fraction at temperatures- 298 K, 308 K, 318 K and 328 K. The excess values were further fitted to Redlich-Kister polynomial equation to ascertain the fitting parameters and standard deviations. The variations of excess parameters with composition and with temperature were further discussed with regard to the nature and extent of molecular interactions among the dissimilar component molecules of the investigated solvent systems. Overall positive deviation in ZE values and negative deviations in the values of LfE, VfE and KsE over the entire solvent composition range suggested the existence of strong molecular interactions between unlike molecules of the components. AN-DMA solvent system was found to exhibit a deviation more towards a stronger interaction mode as compared to AN-DMSO solvent system.