Rayleigh light scattering ratios obtained using a laser light source, combined with molar volume and refractive index measurements, were used to evaluate the excess Gibbs potentials of mixing in binary liquid mixtures. When these quantities are measured as functions of temperature, as well as composition, the excess enthalpy and entropy of the binary mixtures can be obtained. This contribution presents the pertinent experimental techniques and data analyses necessary to extract excess Gibbs potentials from light scattering measurements. Data is presented for one representative system consisting of toluene and propan-2-ol mixtures.