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Soil Science Society of America Journal Abstract -

Solubility Criteria for the Existence of Calcium and Aluminum Phosphates in Soils1


This article in SSSAJ

  1. Vol. 19 No. 2, p. 171-174

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  1. J. S. Clark and
  2. Michael Peech



The solubilities of calcium phosphates may be represented on a single solubility diagram in which functions of the chemical potentials of Ca(OH)2 and Ca(H2PO4)2 are used as co-ordinates. In the presence of solid phase CaCO3, the chemical potential of lime (the value of pH - ½pCa) depends upon the partial pressure of CO2 in the atmosphere. Solubility determinations showed that neither dicalcium phosphate nor hydroxyapatite was present in the soil or clay systems studied.

A similar solubility diagram may be constructed for the aluminum phosphates using functions of the chemical potentials of Al(OH)3 and Al(H2PO4)3 as co-ordinates. In the absence of reliable solubility data, the existence of the aluminum phosphates in the soils studied could not be established.

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