Recherches sur la thermodiffusion en phase liquide. (3e communication) l'effet soret élémentaire

The author has studied the Soret effect by an optical method which is described. The experiments have been carried out with the following organic solutions: cyclohexane-carbon tetrachloride, benzene-chlorobenzene, carbon tetrachloride-chlorobenzene, carbon tetrachloride-bromobenzene, benzene-cyclohexane, tetrachlorethane-tetrabromethane, benzene-methanol. The Soret coefficients are given as a function of the mole fraction for the systems presenting a sufficient separation. The sign reversal of thermodiffusion coefficient (D′) was recorded in the case of the benzenemethyl alcohol systems for an alcoholic mole fraction of 0.16. The phenomenological theory is discussed in relation to the boundary singularities which, according to Tanner, appear during the initial stages of the phenomenon. It is shown that De Groot's approximation, for the determination of the isothermal coefficient of diffusion, cannot lead to correct results. The results, obtained by Soret- and thermogravitational methods show a good agreement. Both corroborate the kinetic scheme developed by I. Prigogine in a previous paper. © 1951.SCOPUS: ar.j