Equation of state of aqueous NaCl solutions over a wide range of temperatures, pressures and concentrations

Abstract

This work describes an equation of state for calculating the density of aqueous, liquid-phase NaCl solutions, based on an analytical equation for a mixture of hard-sphere ions and dipoles in the mean spherical approximation. The equation gives reasonable accuracy at temperatures from 273 to 973 K, pressures from 0.1 to 1000 MPa, concentrations from 0 to 50 wt.%, and densities higher than 650 kg m −3. The observed data of Hilbert (1979), Rogers and Pitzer (1982) and Urusova (1975) are fitted with only 10 empirically adjusted parameters plus the two water molecule parameters (diameter and dipole moment) which were determined from the density and dielectric properties of water. A comparison of the calculated and observed density data is presented. Errors in the calculated values vary from 0.5 to 1.5% over the whole range of temperature, pressure and concentration. A table of densities at temperatures from 273 to 973 K, pressures from 0.1 to 1000 MPa and concentrations from 0 to 50 wt.% is presented.