Densities, apparent and partial molar volumes of aqueous KBr solutions at high temperatures and high pressures

Abstract

Density of four (0.2378, 0.4645, 0.9440, and 2.2310) mol kg −1 binary aqueous KBr solutions have been measured with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made at pressures up to 30 MPa. The range of temperature was from 298 to 629 K. The total uncertainty of density, pressure, temperature, and composition measurements were estimated to be less than 0.06%, 0.05%, 15 mK, and 0.02%, respectively. Apparent molar volumes ϕ V were derived using measured values of density for the solutions and for pure water calculated with IAPWS formulation. The apparent molar volumes were analytically extrapolated to zero concentration to yield partial molar volumes at infinite dilution V ¯ 2 ∞ . The temperature, pressure, and concentration dependence of apparent and partial molar volumes were studied. The derived apparent molar volumes have been interpreted in terms of the Debye–Hückel theory (limiting law) of electrolyte solutions to accurate calculates the values of partial molar volume at infinite dilution V ¯ 2 ∞ and limiting slope A V as a function of temperature and pressure. All experimental and derived properties (apparent and partial molar volumes) are compared with the experimental values and correlations reported in the literature. The maximum of the apparent and partial molar volumes at temperature around 340–363 K depending on concentration and pressure was found.