Influence of temperature on thermodynamic properties of acid–base liquid mixtures
Ultrasonic velocity, u density, ρ and viscosity, η of mixtures of N,N-dimethyl acetamide with equimolar mixture of ethanol + isopropyl alcohol/isobutyl alcohol/isoamyl alcohol, including those of pure liquids over the entire composition have been measured at T = 308.15, 313.15, and 318.15 K. Using this data, various thermo-acoustic parameters such as deviations in ultrasonic velocity, ∆u, isentropic compressibility, ∆k
 s
 , viscosity, Δη, excess molar volume, $$ V_{\text{m}}^{\text{E}} $$
 and excess Gibb’s free energy of activation for viscous flow, ΔG
 *E have been calculated at different temperatures. The calculated deviation and excess functions have been fitted to the Redlich–Kister type polynomial equation. The influence of temperature on the observed negative and positive values of deviation and excess thermodynamic properties has been explained in terms of molecular interactions present in the investigated acid–base liquid mixtures. The experimental data of ultrasonic velocity have been used to check the applicability of velocity models of Nomoto, Van Dael and Vangeel and Junjie and viscosity data have also been availed to test the applicability of standard viscosity models of Grunberg-Nissan, Hind-Mc Laughlin, and Katti-Chaudhary for all the systems investigated at various temperatures.