Thermal diffusion in (LiCl, $RH2O$⁠)

By means of an accurate investigation of the hydrodynamical behavior of the studied liquid, we have been able to perform interdiffusion and pure Soret effect measurements in (LiCl, $RH2O)$ with R ranging from 6 to 100 and temperature from −60 to 0 °C. The interdiffusion coefficient corrected by a thermodynamic factor shows a characteristic evolution with concentration, which is a straightforward consequence of the role of the ions in this direct transport phenomenon. The Soret coefficient has revealed itself to be strongly negative, to increase with temperature, and to exhibit a sharp minimum with concentration. By comparison with measurements in other aqueous alkali chlorides, these results have contradicted the existing theory: negative Soret coefficients do not seem to be associated with poorly organized water. Furthermore, the extremum in the medium concentration range is likely to be related to the polarizing influence of the alkali ions on the outer hydration shells.