Thermodynamic investigation of N, N-dimethylformamide/toluene binary mixtures in the temperature range from 278.15 to 293.15 K

Abstract

Densities ( ρ), surface tensions ( σ), and absolute viscosities ( η) of binary mixtures of N, N-dimethylformamide (DMF) with toluene have been measured over the entire composition range at the temperatures (278.15, 283.15, and 293.15) K. The excess molar volumes ( V E), the excess surface tensions ( σ E), the deviations in viscosity (Δ η), and the excess free energies of activation of the viscous flow (Δ G ∗E) have been calculated. The excess thermodynamic properties V E, σ E, Δ η, and Δ G ∗E were fitted to the Redlich–Kister polynomial equation, and the A k coefficients as well as the standard deviations between the calculated and experimental values have been derived. The surface tension values have been further used to calculate the surface entropy ( S S) and surface enthalpy ( H S) per unit surface area. The lyophobicity ( β) and the surface mole fraction ( x 2 S ) of the surfactant toluene have been also derived using the extended Langmuir model. The results obtained are discussed from the viewpoint of the existence of interactions between the components in the bulk and the surface.