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 tempe rature from 260 to 0 degrees 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 di rect transport phenomenon. The Soret coefficient has revealed itself to be strongly negative, to increase with temperature, and to exhibit a sharp min imum with concentration. By comparison with measurements in other aqueous a lkali chlorides, these results have contradicted the existing theory: negat ive Soret coefficients do not seem to be associated with poorly organized w ater. 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. (C) 1999 American Institute of Physics. [S0021-9606(99)50 817-9].