Onset of Rayleigh-Bénard convection in a ternary liquid system and the Onsager law with generalized thermal diffusion

For the ternary system isopropanol-ethanol-water, a model was proposed to estimate the cross diffusion coefficients from measurements of the critical parameters for the onset of Rayleigh-Bénard convection, together with the consideration of the reciprocity laws of Onsager. Among the three forms of the chemical potentials used, not a single chemical potential was found to provide a correlation between the Onsager laws and the experimental data. The present study shows that consideration of a generalized thermal diffusion term taking account of all components is adequate to estimate quantitative values of the cross diffusion coefficients.