Aqueous solutions of the alkaline-earth metal chlorides at elevated temperatures. Isopiestic molalities and thermodynamic properties

Abstract

Isopiestic results for SrCl 2(aq) and BaCl 2(aq) were obtained at T= 498 K and T= 523 K. As a check on previously reported results for MgCl 2(aq) (from T= 383 K to T= 473 K), new isopiestic measurements were made over the temperature range from 383 K to 523 K. The new measurements are slightly different from our previous results. Here, NaCl(aq) was used as the reference electrolyte for computation of osmotic and activity coefficients. Our published model for the thermodynamic properties of CaCl 2(aq) was used in global least-squares treatment of the present results in combination with published results to provide comprehensive equations for the properties of these three electrolyte solutions. At elevated temperature, the available results consist primarily of excess Gibbs free energies (our isopiestic results), particularly for SrCl 2(aq) and BaCl 2(aq). Void regions in the temperature and pressure ranges of acceptable experimental results were estimated by reference to the properties of CaCl- (aq). Trends in the thermodynamic properties of aqueous solutions of the alkaline-earth metal chlorides were uniform at all temperatures and pressures used in the present work.