Metaphosphoric acid is obtained as a polymeric glassy solid by prolonged heating of phosphoric acid. Either phosphoric acid, H3PO4, or pyrophosphoric acid, H4P2O7, when heated above 300°C, on cooling yields the transparent glassy mass of composition (HPO3)n.
Metaphosphoric acid also is obtained from partial hydration of phosphorus pentoxide by dissolving it in cold water.
Glass-like colorless solid; soft and transparent; deliquesces; sublimes at red heat; dissolves slowly in cold water, decomposing to phosphoric acid; soluble in alcohol.
In dentistry for making zinc oxyphosphate cement; as reagent in chemical analysis.
An inorganic reagent used for research purposes