Solubility Criteria for the Existence of Calcium and Aluminum Phosphates in Soils
1955
Clark, J. S. | Peech, Michael
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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