Excess properties for binary liquid mixtures of propionic acid with aniline derivatives

Abstract

Excess viscosities, excess volumes, and excess free energies of activation for flow of the binary mixtures containing propionic acid with aniline, o-toluidine, o-anisidine, and o-chloroaniline were determined at five different temperatures from density and viscosity measurements. Based on the Regular Solutions Theory, the empirical parameter θ was calculated; this parameter is related to the viscosity, and also denotes the extent of the non-ideality of the system. The results obtained suggest the existence of acid–base interactions, as well as the formation of 1:2 complexes for the three first mixtures, and 2:1 complexes for o-chloro-aniline + propionic acid. The extent of the specific interaction decreases with an increase in the strength of the base, and increases with an increase in the dipole moments. The equatioin [Formula: see text] is proposed for predicting the mole volume of the mixtures, V, at any composition, Xi, as a function of the mole volumes of the pure components, Vi. Key words: binary mixture, excess properties, predicting mole volumes, propionic acid.