OCCURRENCE AND DETERMINATION OF LEPIDOCROCITE IN CANADIAN SOILS

Abstract
Lepidocrocite occurred in B and C horizons of several poorly drained, acid soils; it was determined by X-ray diffraction, electron optical, and chemical dissolution methods. A comparison of X-ray diffraction results obtained by diffractometer, Debye-Scherrer and Guinier-de Wolff methods showed the latter method to be superior in providing the more distinct and complete evidence of lepidocrocite in soil clays. Dithionite-soluble aggregates commonly had a dumbbell-like shape characteristic of lepidocrocite but their electron diffraction patterns were similar to those of maghemite. This suggested the topotactic dehydroxylation of lepidocrocite in the electron microscope. Amounts of lepidocrocite estimated from X-ray diffraction intensities agreed fairly well (within 2.5%) with amounts calculated from iron dissolved by dithionite and oxalate treatments. Lepidocrocite concentrations in soil clays of 1–2% gave distinct X-ray diffraction evidence.

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