ISOPIESTIC MEASUREMENTS AT HIGH-TEMPERATURES .1. AQUEOUS-SOLUTIONS OFLICL, CSCL, AND CACL2 AT 155-DEGREES-C

Isopiestic measurements have been made for LiCl (aq) and CsCl (aq) at a temperature of 155-degrees-C. Equilibrium molalities ranged up to 21 mol-kg-1. MgCl2(aq) was chosen as the reference electrolyte. The appa ratus used for the isopiestic experiments is an enhanced version of th at developed by Grjotheim and co-workers. To test its precision osmoti c coefficients of CaCl2 (aq) have also been determined and compared wi th previously reported vapor pressure measurements at high concentrati ons. The results show a very good coincidence. The data can be describ ed by the ion interaction model of Pitzer. The resulting set of parame ters allows a fit of the experimental osmotic coefficients with a stan dard error of 0.0078 and 0.0114 for LiCl(aq) and CsCl(aq), respectivel y. The osmotic coefficients of LiCl are consistent with data at lower molalities, but there are discrepancies for the CsCl solutions.