Opalescence and concentration fluctuations in binary liquid mixtures near the critical mixing point - I. Experimental

Abstract

This investigation deals with the measurement of the coherent scattering of light in binary liquid mixtures near the critical mixing point, usually called ‘critical opalescence’, which is due to fluctuations of concentration produced by the thermal molecular movement. The apparent extinction of the incident light beam and the angular distribution of the scattered light intensity was measured by a photo-electric method over a wide range of wave-lengths in the visible and ultra-violet region and a range of temperatures above the critical point for nine suitably selected liquid mixtures. It was found that they could be grouped into two classes, each of which is characterized by a specific law of temperature and wave-length dependence of the transmitted and transversely scattered light intensity and a specific shape of the angular distribution of scattered light.