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This article in SSSAJ

  1. Vol. 29 No. 2, p. 151-153
    Received: July 20, 1964
    Accepted: Sept 29, 1964

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The Effect of Salts on the Dissolution of Monocalcium Phosphate1

  1. A. W. Taylor and
  2. E. L. Gurney2



Additions of KCl, NH4NO3, or K2SO4 to Ca(H2PO4)2·H2O so complicate the dissolution processes that the final distribution of the phosphate cannot be interpreted in terms of the simple system CaO-P2O5-H2O as can the dissolution of Ca(H2PO4)2·H2O alone. In KCl and NH4NO3 mixtures, formation of Ca2KH7(PO4)4·2H2O and Ca2(NH4)H7(PO4)4·2H2O lowers the pH of the initial solutions to < 1 and decreases the initial phosphate concentrations; in the later stages both salts hydrolyze to CaHPO4·2H2O, but the amounts of phosphate remaining as this salt are less than that remaining from pure Ca(H2PO4)2·H2O. In mixtures containing K2SO4, Ca(H2PO4)2·H2O is rapidly decomposed with formation of syngenite, CaK2(SO4)2·H2O, and the phosphate is dissolved as KH2PO4. Sulfate decreases markedly the amount of residual phosphate.

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