THE SOLUBILITY OF PHOSPHATE IN A CALCAREOUS SOIL

The concept of chemical potentials was used to study the solubility of phosphate in a calcareous soil when equilibrium was approached by precipitation. By comparison with results obtained by dissolution of soil phosphate it was demonstrated that precipitation resulted in a considerably greater solubility than did dissolution. The relationship between the monocalcium phosphate potential and lime potential could be reconciled with the presence of hydroxyapatite in the soil. Ion activity products near to those of pure hydroxyapatite in the presence of calcium carbonate were also obtained.