Thermodynamics of the System MgCl2–NaCl–H2O to 573 K: New Measurements of Heat of Mixing and Heat 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 of 0.5 to 3.8 mol·kg−1, and heats of dilution of MgCl2(aq) at 523.15 and 573.15 K for ionic strengths of 0.3 to 4.6 mol·kg−1, have been measured at 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 \({\text{NaCl}}{\kern 1pt} {\kern 1pt} - {\text{MgCl}}_{\text{2}} {\kern 1pt} ---{\kern 1pt} {\text{H}}_{\text{2}} {\text{O}}\) 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 equations for MgCl2(aq) and the mixed system valid at 573 K.