Molecular orientation in binary liquid mixtures from excess Cotton-Mouton constant

Abstract

We show the results of magnetically induced birefringence measurements performed in binary mixtures of simple molecular liquids. New excess function was introduced based on experimentally determined values of Cotton-Mouton constant - a quantity directly related to the induced orientation of anisotropic molecules. Concentration dependencies of excess molar Cotton-Mouton constant were compared with analogous characteristics of excess molar volume. Both excess functions are well reproduced using Redlich-Kister polynomial expansion. The results suggest that in the examined mixtures binary pairs of unlike molecules are formed in which molecular planes are oriented parallel to each other with simultaneous rotation along the axis perpendicular to benzene plane. Such preferred angular arrangement is independent on the average intermolecular distance within a pair-aggregate.