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A glacial or syrupy viscous liquid, H4P2O7, used as a catalyst and in organic chemical manufacture.
(Elements & Compounds) a crystalline soluble solid acid formed by the reaction between one molecule of phosphorus pentoxide and two water molecules. Formula: H4P2O7. See also polyphosphoric acid
py′ro•phos•phor′ic ac′id(ˈpaɪ roʊ fɒsˈfɔr ɪk, -ˈfɒr-, ˌpaɪ-)
a crystalline, water-soluble powder, H4P2O7, used as a catalyst.