py·ro·phos·pho·ric acid noun
\-fäs-ˌfȯr-ik-, -ˌfär-; -ˌfäs-f(ə-)rik-\
: a crystalline acid H4P2O7 that is formed when orthophosphoric acid is heated or that is prepared in the form of salts by heating acid salts of orthophosphoric acid
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