The critical exponent of binary liquid mixtures by Rayleigh and Brillouin scattering measurements: the hexane-methanol system

The Rayleigh and Brillouin scattering has been investigated for the hexane-methanol system at several compositions near their consolute temperatures from one phase to two phases, and some thermodynamical properties such as a ratio of specific heats Cp/Cnu , a concentration-concentration fluctuation Scc(O), and the correlation length xi have been derived. The total scattering intensity and therefore Scc(O) diverge at the spinodal temperature for all samples. However, the critical index depends on the composition. This phenomenon has been analysed in terms of a modified Flory approximation, in which we have assumed that a repulsive term of the interaction varies with temperature. The consolute and spinodal temperatures were estimated. The Brillouin shift and corresponding sound velocity have no anomaly near these consolute temperatures.

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