Solubility Criteria for the Existence of Variscite in Soils

Abstract

Abstract The pK sp value of a highly purified synthetic variscite, Al(OH) 2 H 2 PO 4 , was found to be 30.5 at 25° C. The equilibrium between variscite and its constituent ions in solution was attained only very slowly. The solubility criteria obtained in this study would indicate that the immediate reaction products of applied phosphate in acid soils are much more soluble than variscite but, upon ageing, these intermediate reaction products are slowly transformed into variscite which may coexist with gibbsite as stable solid phases.