Thermodynamics of Arsenates, Selenites, and Sulphates in the Oxidation Zone of Sulfide Ores. XVI. Solubility of the Synthetic Analogue of Mandarinoite at 25°C

This study aims to synthesize two iron(III) selenites—Fe2(SeO3)3·5H2O (analogous to the mineral mandarinoite) and Fe2(SeO3)3·3H2O—and to investigate their solubility. The obtained samples were identified by powder X-ray diffraction and energy-dispersive X-ray microanalysis. Solubility was determined through the method of isothermal saturation at 25°C. To suppress the hydrolysis of Fe3+ ions and prevent the precipitation of iron hydroxide, the experiments were conducted in nitric- or sulfuric-acid solutions. The compositions of the saturated solutions were used to calculate the solubility product using a Geochemist’s Workbench (GMB 9.0, SpecE8 program). The calculated values of the solubility product are log Ksp(Fe2(SeO3)3·5H2O) = –38.6 ± 0.5 and log Ksp(Fe2(SeO3)3·3H2O) = –39.0 ± 0.2.