Volumetric Properties of Mixed Electrolyte Aqueous Solutions at Elevated Temperatures and Pressures. The Systems CaCl2–NaCl–H2O and MgCl2–NaCl–H2O to 523.15 K, 70 MPa, and Ionic Strength from (0.1 to 18) mol·kg–1

Abstract

The densities of aqueous solutions in the systems CaCl2–NaCl–H2O and MgCl2–NaCl–H2O were determined experimentally at temperatures from (298.15 to 523.15) K, pressures up to 70 MPa and over a range of composition at ionic strengths from (0.1 to 18) mol·kg–1. The vibrating-tube densimeters used for the experimental measurements have an accuracy on density better than 9.9·10–5 g·cm–3. The mean apparent molar volumes of the mixtures calculated from the experimental data permitted a parametrization of the Pitzer equation for mixed electrolyte solutions within the entire range of temperatures, pressures, and compositions covered by this study. The parametrization of the Pitzer model for the pure binary salt aqueous solutions CaCl2–H2O and MgCl2–H2O was also refined based on new experimental and literature data. These models were used to evaluate the partial molar volumes and limiting partial molar volumes of components in aqueous mixtures of electrolytes. Using the refined models for the binary systems, Young’...