Optical evidence for molecular clustering in fluids

6. Summary

It is pointed out that the presence of molecular clusters in fluids of size comparable with the wave-length of light should be capable of detection by two optical methods, one based on the asymmetry of scattering, and the second based on the anomalous depolarisation of scattered light. In this investigation the second method is developed. Ordinary liquids did not give any positive evidence for the existence of large molecular aggregates at room temperatures. A mixture of carbon disulphide and methyl alcohol when examined gave definite evidence for the formation of molecular clusters in the mixture by the observation of the anomalous depolarisation. This method is so delicate that it has made it possible to detect the pressence of molecular clusters in the mixtures even at temperatures considerably removed from the critical solution temperature.