Molecular clustering in binary liquid mixtures

Abstract

This paper deals with a comparative study of the intensity and depolarisation of the light scattered transversely by mixtures of phenol and water in different proportions and at different temperatures. The lowest values for the depolarisationsρu,ρv andρh are obtained with the critical composition mixture (in this case 34% phenol mixture) at the critical solution temperature, whereρu,ρv andρh are the depolarisations of the light scattered transversely when the incident light is (1) unpolarised, (2) polarised with electric vector vertical, and (3) polarised with electric vector horizontal respectively. The photoelectric method was employed for the comparison of intensities of scattering by these mixtures at various temperatures above the critical solution temperature. The intensity of scattering is found to increase considerably for the 34% phenol mixture as the critical solution temperature is approached. It is found that the tendency for the formation of clusters and the size of the clusters formed depend on the temperature and composition of the mixture. These phenomena are found to be most pronounced for the critical composition mixture at the critical solution temperature. The bearing of these results on the anomalies of viscosity, magnetic birefringence, etc., noticed in the vicinity of the critical conditions is also pointed out.