The Soret Effect: A Review of Recent Experimental Results

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.