Thermodynamics of Aqueous Mixtures of Magnesium Chloride with Sodium Chloride from 298.15 to 573.15 K. New Measurements of the Enthalpies of Mixing and of Dilution

Abstract

Heats of mixing of NaCl(aq) with MgCl2(aq) at 373.15, 423.15, 473.15, 523.15, and 573.15 K for ionic strengths 0.5−3.8 mol·kg-1 and heats of dilution of MgCl2(aq) at 523.15 and 573.15 K for ionic strengths 0.3−4.6 mol·kg-1 have been measured at a constant pressure of 20.5 MPa. These experimental data are combined with published heat of mixing data at 298 and 373 K to provide a comprehensive Pitzer ion-interaction treatment for the thermodynamic properties of the NaCl + MgCl2 + H2O system to 573 K. The treatment includes a general equation valid to 523 K, incorporating the published equations for NaCl(aq) and MgCl2(aq), and new equations for MgCl2(aq) and the mixed system at 573 K.