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Abstract: A computer code based on a Pitzer model has been developed for the comprehensive prediction of the thermodynamic properties of MgCl2–HCl aqueous solutions over a wide range of conditions from 25 to 120 °C and from 0–350 g L−1 chloride. This code was applied to the calculation of (i) water activities and mean ionic activity coefficients for mixed aqueous solutions of hydrochloric acid and magnesium chloride over a wide range of concentrations and to 100 °C, (ii) solubilities of MgCl2·6H2O in MgCl2–HCl solutions to 80 °C, (iii) partial pressures of HCl(g) and H2O(g) over MgCl2–HCl aqueous solutions at various temperatures and (iv) partial pressures of HCl(g) at the normal boiling point of these mixed electrolyte solutions. The model predictions are in excellent agreement with available experimental data and confirm evidence from the literature that MgCl2(aq) and HCl(aq) mix almost ideally at constant water activity. [Copyright &y& Elsevier]

Abstract: Results of solubility measurements of nickel chloride, manganese chloride, iron(II) chloride, hematite and akaganeite in aqueous solutions of MgCl2 (0.5–3.5 mol L−1) at temperatures of 60 and 90 °C are reported. Solubilities of metal(II) chlorides decrease almost linearly with MgCl2 concentration due to the common ion effect. Nickel chloride and iron(II) chloride solubilities are very similar, while manganese chloride is about 30% more soluble. Hematite is more stable (i.e. less soluble) than akaganeite under all conditions investigated in this study, while ferrihydrite is considerably less stable. In other words, there is no change in the relative stabilities of these phases effected by the presence of high magnesium chloride concentrations. The solubility of all of these phases decreases with temperature and, for each temperature, the solubility constants increase linearly with the MgCl2 concentration. The present results allow the prediction of the iron concentration as a function of the H+ and MgCl2 molality at equilibrium with hematite or akaganeite. The Fe(III)/Fe(II) redox behaviour has been characterized in concentrated aqueous solutions of MgCl2 (1.5–3.5 mol L−1) at a temperature of 25 °C. Standard redox potentials are ca. 100 mV lower than at infinite dilution and change linearly by only 13 mV in the range 2–4 mol L−1 MgCl2. [Copyright &y& Elsevier]

Abstract: Results of density and viscosity measurements for aqueous solutions of MgCl2 (0.5–3.5 mol L−1) and MgCl2 +10% NiCl2 (0.5–3.5 mol L−1) at temperatures of 25, 60 and 90 °C show an almost linear increase in density with total concentration, while low nickel contents and temperature have comparatively small effects. Viscosities of MgCl2 solutions rise sharply at 25 °C but are significantly lower at 90 °C. The viscosity of 3–4 mol kg−1 MgCl2 at 90 °C is similar to water at 25 °C. Nickel has no significant effect on the viscosity of these solutions. Results of heat capacity measurements for aqueous solutions of MgCl2 (0.5–3.5 mol L−1) and MgCl2 +10% NiCl2 (0.5–3.5 mol L−1) at temperatures of 60 and 90 °C show that the heat capacities of these solution decrease significantly with total concentration, while the effects of low nickel contents and temperature are again comparatively small. [Copyright &y& Elsevier]