Volumetric, Optical, Acoustical and Viscometric Study of Molecular Association in Binary Mixtures of Butylamine with 1-Butanol and Tert-Butanol

Density (ρ), refractive index (n), ultrasonic velocity (u), and viscosity (η) were measured for the binary mixtures formed by butylamine with 1-butanol and tert-butanol at temperatures 293, 303, and 313 K over the entire composition range. Excess molar volume V E m , molar refraction deviation ∆Rm, deviation in ultrasonic velocity ∆u, viscosity deviation ∆η, and excess Gibb’s free energy of activation for viscous flow ∆G∗E were derived from the experimental data and the computed results were fitted to the Redlich–Kister polynomial equation. The values of V E m , ∆Rm, ∆u, ∆η, and ∆G∗E were plotted against the mole fraction of butylamine. The observed positive and negative values of excess parameters for both the mixtures were explained on the basis of intermolecular interactions present in these mixtures. The higher negative values of V E m and ∆Rm and positive values of ∆u, ∆η, and ∆G∗E for butylamine + 1-butanol mixture suggest that specific interactions are taking place in butylamine + 1-butanol mixture, while weak dipole-dipole induced forces and dispersive forces seem to be responsible for butylamine + tert-butanol mixture. Furthermore, different empirical relations were used to correlate the binary refractive indices. An excellent agreement was found between experimental and theoretical values.