In the first part of the paper, we recall what the Soret effect is, together with its applications in science and industry. We emphasize the need to have a reliable data base for the Soret coefficient. Next we review the different techniques to measure the Soret coefficient (elementary Soret cell, beam deflection technique, thermal diffusion forced Rayleigh scattering technique, convective coupling and, in particular, the onset of convection in horizontal layers and the thermogravitational method). Results are provided for several systems, with both negative and positive Soret coefficients, and comparison between several laboratories are made for the same systems. We end with “benchmark” values of the Soret coefficient for some organic liquid mixtures of interest in the oil industry and to which all future new techniques should refer before gaining confidence. We conclude that correct values of the Soret coefficient can be obtained in earth conditions and we deny the need to go to microgravity.

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This paper presents a study of the convection in acetone due jointly to the thermocapillary (Marangoni) and thermogravitational effects. The liquid (acetone) is submitted to a horizontal temperature difference. Experiments and numerical simulations both show the existence of three different states: monocellular steady states, multicellular steady states and spatio-temporal structures. The results are discussed and compared with the linear stability analysis of Smith & Davis (1983).

In this paper, we report Soret coefficients obtained by two independent methods and for two different systems-(water-ethanol containing respectively 60.88 and 50 wt % of water). The Soret coefficient is defined by S T ) D T /D where D T is the thermal diffusion coefficient, and D is the isothermal diffusion coefficient. In the first method, D T is determined by a 5-point sampling process in a thermogravitational column and D by the well-known OEC technique (open-ended capillary). The ratio of the experimental values of D T and D gives the expected value of S T . A totally new method consists of velocity measurements of a transient natural convective state: indeed, the Soret effect induces modifications of density gradients and therefore of the buoyancy responsible for free or natural convection. The modifications of the convective amplitudes are thus an indirect way to have access to the Soret coefficient. The velocity measurements were obtained by LDV. The comparison between the two techniques shows a deviation of the order of 4%, which is quite satisfactory. The agreement with the literature is also excellent.