A Novel Reaction of HCrO4- with PH2O2-, Induced by Molecular Oxygen, Forming Peroxodiphosphate Ions in an Aqueous Solution

Article abstract of DOI:10.1246/bcsj.70.2699

The chromate (VI) ion HCrO₄^- at pH 2-4 was not appreciably reduced by the phosphinate ion PH₂O₂^- in the absence of molecular oxygen (O₂), but was reduced in the presence of O₂, forming peroxodiphosphate ions (denoted by PDP and meaning all forms of P₂O₈^4-, HP₂O₈^3- etc.) in much higher concentrations than those of the added chromate(VI). Both the rates of the chromate decay and the PDP formation increased with decreasing pH. When the chromate(VI) ion disappeared completely, PDP formation stopped and its concentration remained constant. However, such PDP once formed in the presence of O₂ began to decompose after the solution was saturated with N₂ gas; its decomposition ceased again when the solution was again saturated with air. Such behaviors are discussed while presenting the reaction mechanisms.