Densities, Ultrasonic Speeds, Viscosities, Refractive Indices, and Excess Properties of 1-Butyl-3-methylimidazolium Tetrafluoroborate plus N-Methylacetamide Binary Mixtures at Different Temperatures

The thermophysical properties, viz., densities, rho, ultrasonic speeds, u, viscosities, eta, and refractive indices, n(D), were measured for the binary liquid mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim] [BF4] with N-methylacetamide [NMA] over the whole concentration range, including those of pure liquids, at temperatures T/K = 293.15-318.15 and at pressure p = 101 kPa. Experimental data were used to determine the excess molar volume, V-m(E) excess isentropic compressibility, K-s(E), excess speed of sound, u(E), excess molar isentropic compressibility, K-s,m(E) deviations in viscosity Delta eta, and deviations in refractive index, Delta(phi)n(D). These parameters were fitted to the Redlich-Kister type polynomial equation. The partial molar volumes and partial molar compressibilities and excess partial excess partial molar compressibilities over the entire range of mole fraction and at infinite dilution were also determined. The observed negative values of V-m(E), K-s(E), K-s,m(E) and Delta eta and positive values u(E) and Delta(phi)n(D) indicate the strong interactions between the component molecules of these mixtures.