Thermoacoustic, volumetric, and viscometric investigations in the binary mixtures of 1,4-dioxane with n-hexane or n-heptane or n-octane

Ultrasonic velocity, u, density, \( \rho \), and viscosity, \( \eta \), have been measured in the binary liquid mixture of 1,4-dioxane with n-hexane or n-heptane or n-octane at 308.15, 313.15, and 318.15 K over the entire composition range. Properties such as molar volume, V m, intermolecular free length, L f, acoustic impedance, Z, internal pressure, π i, enthalpy, ΔH, Gibb’s free energy of activation of viscous flow, \( \Delta G^{*} \), and their excess/deviation properties such as deviations in ultrasonic speed, ∆u, viscosity, \( \Delta \eta \), excess molar volume, \( V_{\text{m}}^{\text{E}} \), excess intermolecular free length, \( L_{\text{f}}^{\text{E}} \), excess acoustic impedance, Z E, excess internal pressure, \( \pi_{\text{i}}^{\text{E}} \), excess enthalpy, \( \Delta H^{\text{E}} \), and excess Gibb’s free energy of activation of viscous flow, \( \Delta G^{{*{\text{E}}}} \), have been calculated from the experimental data. The calculated deviation/excess properties have been fitted to the Redlich–Kister-type polynomial equation. Partial molar volumes, (\( \bar{V}_{\text{m,1}} \), \( \bar{V}_{\text{m,2}} \)), and excess partial molar volumes, (\( \bar{V}_{\text{m,1}}^{\text{E}} \), \( \bar{V}_{\text{m,2}}^{\text{E}} \)), have also been evaluated. The observed positive and negative values of the relevant deviation/excess properties are attributed to the dominance of weak interactions (physical interactions) between the unlike molecules in the mixtures, and the strength of weak interactions follows the order: (1,4-dioxane + n-octane) > (1,4-dioxane + n-heptane) > (1,4-dioxane + n-hexane). The prevailing physical interactions are found to increase with the increase in temperature. The experimental data of ultrasonic velocity and viscosity have been used to check the applicability of various velocity and viscosity theory models at all temperatures under investigation.