Enthalpies of Dilution of Aqueous Solutions of LiCl, KCl, and CsCl at 300, 325, and 350°C

Dilution enthalpies, measured using isothermal flow calorimetry, are reported for aqueous solutions of LiCl, KCl, and CsCl at 300°C and 11.0 MPa, 325°C and 14.8 MPa, and 350°C and 17.6 MPa. The concentration range of the chloride solutions was 0.5 to 0.02 m. Parameters for the Pitzer excess Gibbs ion-interaction equation were determined from the fits of the experimental heat data. Equilibrium constants, enthalpy changes, entropy changes, and heat capacity changes for ion association of the chloride salts were estimated from the heat data. For all systems, the enthalpy and entropy changes were positive and had accelerating increases with temperature. The resulting equilibrium constants show significant, but smaller, increases with temperature.