Abstract
ABSTRACT It was found by X-ray analysis that lepidocrocite (FeOOH) or limonite (FeOOH) in the presence of organic matter (humus, amylum, citric acid, oxalic acid, etc.), are converted to Fe2O3 = maghemite when heated in the air. The Fe2O3 (with an unit cell of 8.39 A) obtained from natural epidocrocite or limonite concretions, which commonly contain small amounts of sodium or managanese in their natural state, can withstand heating for 2 hours at about 600° C. Furthermore, stabilized Fe2O3, having a unit cell of 8.48 A, was obtained by heating ferric citrate containing sodium as an impurity. In nature Fe2O3 is formed by slow reduction and afterwards oxidation of lepidocrocite (FeOOH) or limonite (FeOOH) particles (concretions) rich in organic matter. Thus F2O3 may be a common mineral in sediments (soils) rich in iron and organic matter, such as the brown-red colored peaty soils of the provinces of Groningen and Drenthe in the Netherlands. The reduction--oxidation process may be accelerated which happens when these peats are set on fire by accident or with the purpose to obtain better crops.
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