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Soil Science Society of America Journal Abstract -

The Dissolution of Complex Ferric Phosphates Under Controlled Eh and pH Conditions1


This article in SSSAJ

  1. Vol. 37 No. 1, p. 33-36
    Received: Nov 15, 1971
    Accepted: Oct 20, 1972

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  1. B. G. Williams and
  2. W. H. Patrick Jr.2



The dissolution of complex ferric phosphates, CaFe2H4(PO4)4 · 8H2O and KFe3H14(PO4)8 · 4H2O, was studied in a reduced chemical system. Both salts dissolved incongruently to release calcium and phosphorus in a molar ratio of 1:2 and solid FePO4. Below an Eh of — 200 mV further P was released due to FePO4 dissolution. Potassium ferric phosphate crystals dissolved rapidly with complete release of K, whereas dissolution of calcium ferric phosphate was retarded probably due to interference by precipitated FePO4. The solubility of precipitated FePO4 differed slightly from that observed with crystalline strengite and at pH 6 and 7, ferric hydroxides apparently entered into the reaction.

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