SYNTHESIS OF GREEN RUST II(FeIII1-FeII2) AND ITS SPONTANEOUS TRANSFORMATION INTO Fe3O4.

Abstract

Conditions for the synthesis of a pure green rust II with a definite chemical composition and its transformation reaction to Fe//3O//4 under a nitrogen atmosphere were studied. A pure green rust II with the composition of (Fe**3** plus )//1(Fe**2** plus )//2(SO//4**2** minus )(OH** minus )//5// minus //2//n(O//2** minus )//n was obtained by the air oxidation of an aqueous solution containing (0. 05 mol dm** minus **3) Fe**I**I and (0. 3 mol dm** minus **3) SO//4**2** minus ions at pH 6. 8 and 25 degree C. This iron composition differs from those estimated previously; therefore, the green rust II synthesized here is designated as green rust II(Fe**I**I**I//1-Fe**I**I//2). This green rust II is spontaneously transformed into Fe//3O//4 under a nitrogen atmosphere at 50-75 degree C. It has been accepted that green rust II is transformed to Fe//3O//4 by oxidation. The evidence suggests that the green rust II can be transformed into Fe//3O//4 not only by oxidation but also spontaneously without oxidants.