Differential chemoreductive dissolution of iron oxides in a Brazilian Oxisol

R. B. Bryant, J. Macedo

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Stabilities of naturally occurring hematite and goethite in the Bol horizon of a well-drained Brazilian Oxisol, and their rate of reductive dissolution by sodium dithionite, were investigated. The soil has codominant hematitic and goethitic Fe oxide mineralogy and a reddish hue (2.5YR). There was no apparent foreign-ion substitution in the hematite, but the goethite contained 34 mole percent of AlOOH substituting for FeOOH. Results of limited additions of sodium dithionite and measured redox-potential (Eh) development during the reaction showed that hematite and Al goethite were metastable at Eh = 98 mV, pH = 7.3, and 25°C. Aluminum goethite was metastable at Eh = -2 mV, pH = 7.3, and 25°C. Hematite dissolution at low Eh occurred readily at 25°C. Aluminum-goethite dissolution at low Eh was imperceptible at 25°C, but occurred readily at 75°C. -Authors

Original languageEnglish (US)
Pages (from-to)819-821
Number of pages3
JournalSoil Science Society of America Journal
Issue number3
StatePublished - Jan 1 1990

All Science Journal Classification (ASJC) codes

  • Soil Science


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