Brillouin Scattering Evidence of Nonideal Mixing in Methanol/CCl4 Mixtures

A Brillouin scattering experiment has been performed on the methanol/CCl4 mixture as a function of the concentration to test the hypothesis, recently suggested by Raman spectroscopy experiments, of some clustering effects. The obtained concentration dependence of the adiabatic compressibility diverges from that expected for an ideal mixture. The observed result is interpreted as due to polarization effects induced by methanol on the (originally) isotropic CCl4 molecule that induces some coordination with carbon tetrachloride. The occurrence of a maximum in the adiabatic compressibility, near the equimolar concentration, suggests the existence of different regimes in the system and is consistently compared with literature for the solution enthalpy and mixing entropy.