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This paper, devoted to cadmium(II) carbonate, is the first in a series dedicated to the solubility of compounds relevant to mobility of metals in the environment. Here, we present compilations and critical evaluation of the experimental solubility data for cadmium(II) carbonate, otavite, in aqueous ternary and higher-order systems. The solubility of cadmium(II) carbonate depends on temperature, carbon dioxide partial pressure, pH, the presence of complexing ions, and ionic strength of the solution. Papers referring to solubility of cadmium(II) carbonate have been published since 1901; the thorough search of the literature in this field covered the period from 1901 through 2009. The compilation of the available experimental data is introduced with a critical evaluation. The evaluation of the experimental data considers the possible correlation between the data obtained under similar experimental conditions of temperature, carbon dioxide partial pressure, electrolyte, and ionic strength. Those experiments where the solid phase was well identified and the interactions between the electrolyte and the dissolved cadmium(II) ion were considered practically negligible were used to determine the thermodynamic properties of the solid cadmium(II) carbonate. Recommended values for the thermodynamic quantities are lg*Kps0° = 6.11 ± 0.10, ΔfG°(CdCO3, cr, 298.15 K) = -(674.3 ± 0.6) kJ mol-1, ΔfH°(CdCO3, cr, 298.15 K) = -(752.2 ± 0.8) kJ mol-1, S°(CdCO3, cr, 298.15 K) = (103.9 ± 0.2) J K-1 mol-1. [ABSTRACT FROM AUTHOR]

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]