Direct Observations of Nonintegral Hydrous Ferric Oxide Solubility Products: Ksubso/subsup*/sup=[Fesup3+/sup][Hsup+/sup]sup-2.86/sup

Robert H Byrne, Yu-Ran Luo

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Abstract

Previous studies have indicated that hydrous ferric oxide precipitates, formed and aged at low temperatures, exhibit solubility products of the form K S0 = [Fe 3+ ][H + ] −m , where m < 3 ([ ] free ion concentration). Although previous observations have either been obtained over a very narrow pH range or have involved phase separations and solution chemical modeling, the present work involves direct potentiometric observations of log [Fe 3+ ] and log [H + ] over a wide range of Fe 3+ concentrations and pH. Our observations obtained at 25°C in 0.7 molar NaClO 4 provide substantial evidence for log [Fe 3+ ] vs. pH relationships with slopes (m) smaller than three but larger than those obtained in previous works (m = 2.70 and m = 2.35). Over a four unit range in pH and a nearly 12 order of magnitude range in [Fe 3+ ] the observed relationship between pH and log [Fe 3+ ] in this work is log [Fe 3+ ] = 4.28 ± 0.05 − (2.86 ± 0.009) pH. This solubility behavior has substantial implications for the behavior of Fe III in natural waters.

Original languageAmerican English
JournalGeochimica et Cosmochimica Acta
Volume64
DOIs
StatePublished - Jan 1 2000

Disciplines

  • Life Sciences

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