Reactions of Triammonium Pyrophosphate with Soils and Soil Minerals

Abstract

Abstract Whole soils of several genetic groups promoted hydrolysis of pyrophosphate to orthophosphate in dilute solutions, but the catalytic action was largely biological. Clay minerals and hydrous oxides, particularly iron oxide, showed some catalytic activity which might be significant in sterile, dilute pyrophosphate solutions. The microorganisms were inactive in solutions more concentrated than 0.2 M in pyrophosphate. Autoclaved specimens of kaolinite, montmorillonite, and goethite suspended in sterile 0.5 or 2.0 M solutions of (NH 4 ) 3 ‐HP 2 O 7 for 15 weeks were practically inert, but gibbsite dissolved slowly in both solutions and Al(NH 4 ) 2 P 2 O 7 OH · 2H 2 O began to crystallize from the 0.5 M solution after 5 weeks. Less than 6% of the pyrophosphate in these solutions, with or without suspended mineral, was hydrolyzed in 15 weeks; only goethite increased the hydrolysis, and that barely significantly. Pyrophosphate was adsorbed more strongly on clays and soils than was orthophosphate.