Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The densities of aqueous solutions in the systems Na2SO4 H2O and Na2SO4 NaCl H2O were determined experimentally at temperatures from (298.15 to 523.15) K and pressures up to 70 MPa, and over a wide range of salt concentrations (up to 5 mol*kg 1 of NaCl and up to 1.2 mol*kg 1 of Na2SO4). The measurements were conducted in vibrating-tube densimeters permitting density determinations with an accuracy varying from (2.8*10 5 to 1.0*10 4) g*cm 3 depending on temperature. The Pitzer equation for the apparent molar volume was parametrized on the basis of the newly obtained experimental data and data from literature. The resulting model for binary Na2SO4 H2O and ternary Na2SO4 NaCl H2O solutions can be applied across the entire range of temperatures, pressures, and compositions covered by this study. Most importantly, it is the first model capable of calculating the mean apparent molar volume of the mixed solutes and, consequently, the density of solution in aqueous system Na2SO4 NaCl H2O at elevated temperatures and pressures. The volumetric properties derived from the parametrized model for mixed electrolyte solutions (i.e., partial molar volume, limiting partial molar volume, and excess molar volume of components) provide an access to quantitative evaluation of the effect of pressure on the activity coefficients of electrolytes in multicomponent aqueous solutions. Calculation of the pressure dependence of a chemical equilibrium is thus much facilitated by the presented models, which can assist in modeling of aqueous systems at elevated temperatures and pressures.