Reactions of Ammonium Hydrogen Fluoride with Oxides of Iron in Solid State

Abstract

The reactions of ammonium hydrogen fluoride with three oxides of iron, viz., a-Fe₂O₃, Fe₃O₄ (magnetite) and γ-Fe₂O₃ (maghemite) in the solid state at room temperature and at slightly higher than the ambient have been studied. The products were characterised by powder XRD, TG/DTA, chemical analysis and Mössbauer techniques. In all the cases, the product of reaction was [NH₄]₃FeF₆.1.5H₂O. This shows that although magnetite contains both ferrous and ferric species, reaction with ammonium hydrogen fluoride in the solid state brought about by mere physical mixing at room temperature in air results in oxidation of Fe(II) to Fe(III).