Ion Activity Products of AIPO4, 2H2O and FePO4, 2H2O in Acid Soils Part I. Single Extraction of Soils with Neutral Salt Solutions of Different Ionic Strengths.

Presidency College, Calcutta.-12 Manuscript received 30 September 1969; revised 6 August 1974; accepted 14 August 1974 Ionic activity products of variscite, AIPO4.2H2O and strengite, FePO4, 2H2O have been com­puted in some Indian acid soils on the basis of the general formula M(OH)2 H2PO4, where M stands for Fe3+ or Ar3+ by extracting the soils with KCl, (NH4)2SO4 and CaCl2 solutions of two ionic strengths 0.02 and 0.04. Satisfactory results have been obtained for the pKsp. [—log (solu­bility product)] values of these phosphates in different soils at different pH ranges. The variation of pKSP. values with pH observed has been explained