A metaphosphate ion is an oxyanion that has the empirical formula PO−
3. The structure of a metaphosphate ion can be described as being made up of PO4 structural units in which each unit shares two corners with another unit. This can come about in two ways.
- Formation of a ring, as in trimetaphosphate, illustrated.
- Formation of an infinite chain, with the same structure as in ammonium metavanadate
Metaphosphates can be considered as salts of the corresponding metaphosphoric acids (HnPnO3n) although none of these acids has been isolated. The metaphosphoric acids can be formulated as H2O·P2O5. In comparison, phosphoric acid, H3PO4 can be formulated as 3H2O·P2O5 and pyrophosphoric acid, H4P2O7, as 2H2O·P2O5.
- Averbuch-Pouchot, M.T; Durif, A. (1996). Topics in Phosphate Chemistry. World Scientific Pub Co Inc. ISBN 981-02-2634-9.
- Corbridge, D. (1995). "Chapter 3: Phosphates". Studies in inorganic Chemistry vol. 20. Elsevier Science B.V. pp. 169–305. ISBN 0-444-89307-5. Retrieved January 30, 2015. – via ScienceDirect (Subscription may be required or content may be available in libraries.)