No abstract

The intermolecular free-length is evaluated by making use of thermoacoustical parameters followed by a comparative study. To achieve this objective, thermoacoustical parameters of four ternary and two quaternary liquid mixtures have been computed. These parameters have been utilized to calculate the available volume (V a ), which in turn has been used to compute intermolecular free-length (L f ) for the systems under investigation. The computed values of L f have then been compared with the values estimated from wellestablished thermodynamic and ultrasonic methods. To the best of our knowledge, this investigation is a pioneering attempt in evaluation of intermolecular free-length involving multicomponent liquid mixtures by making use of thermoacoustical parameters.

The densities (ρ) and refractive indices (n) of binary mixtures of 1,4-dioxane with benzene, toluene, o-xylene, m-xylene, p-xylene, and mesitylene, including those of pure liquids, over the entire composition range expressed by mole fraction x 1 of 1,4-dioxane were measured at temperatures (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K under atmospheric pressure. From the experimental data, the excess molar volumes (V m E), deviations in refractive indices (Δn), partial molar volumes (V m,1 °∞ and V m,2 °∞), and excess partial molar volumes (V m,1 °E,∞ and V m,2 °E,∞) of the components at infinite dilution were calculated. The V m E values were negative for 1,4-dioxane + benzene, positive for 1,4-dioxane + o-xylene, + m-xylene, + p-xylene, and + mesitylene mixtures over the entire mole fraction range at all investigated temperatures, and exhibit a sigmoid trend for1,4-dioxane + toluene mixtures wherein V m E changes sign from positive to negative as the mole fraction of 1,4-dioxane in the mixture is increased. The results indicate the presence of weak interactions between 1,4-dioxane and aromatic hydrocarbon molecules. The deviations in V m E values follow the order benzene < toluene < p-xylene < m-xylene < o-xylene < mesitylene. It is observed that V m E values depend on the number and position of the methyl groups in these aromatic hydrocarbons.

When sound waves of high amplitude propagate, several non-linear effects occur. Ultrasonic studies in liquid mixtures provide valuable information about structure and interaction in such systems. The present investigation comprises of theoretical evaluation of the acoustic non-linearity parameter of four binary liquid mixtures using Tong and Dong equation at high pressures and Ì ¿¼¿ ½ K. Thermodynamic method has also been used to calculate the non-linearity parameter after making certain approximations.