Hydrolytic precipitation of solid solutions of iron(III) and gallium(III) with admixture of fluoride ions

Abstract

Investigations were carried out on the formation of solid solutions of iron(III) and gallium(III) compounds crystallizing from fluoride-containing solutions. Out of a range of many possible solids, the elpasolite type and oxide hydroxides were chosen. The hexafluoride complexes, K 2NaMF 6, form a complete series of solid solutions. There is also a complete solubility series for the oxide hydroxides. Crystallization from a pure solution of iron(III) salt leads to the formation of β-FeOOH(F), in which up to 50 mol.% of iron(III) can be substituted by gallium(III). Higher proportions of gallium result in oxide hydroxides with a diaspore structure. The high fluoride content in these compounds is thought to be due to substitution of hydroxide ions by fluoride.