HYDROLYTIC PRECIPITATION OF SOLID-SOLUTIONS OF IRON(III) AND GALLIUM(III) WITH ADMIXTURE OF FLUORIDE IONS

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, K2NaMF6, 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 beta-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.