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phosphoric acid





Any of a group of acids, the chief forms of which are phosphoric (V) acid, also called orthophosphoric acid, H3PO4), phosphoric (VI) acid, also called metaphosphoric) acid, HPO3, and heptaoxodiphosphoric (V) acid, also called pyrophosphoric acid,H4P2O7. Phosphoric acid was discovered in 1770 by Karl Scheele and J. G. Gahn.

Phosphoric (V) acid is a colorless liquid obtained by the action of sulfuric acid on phosphate rock (calcium phosphate); it is used in fertilizers, soaps and detergents, and dyeing, to flavor food, to clean metals, and to make phosphates.

Phosphoric (VI) acid is obtained by heating phosphoric (V) acid; it is used as a dehydrating agent.

Heptaoxodiphosphoric (V) acid is formed by moderately heating phosphoric (V) acid or by reacting phosphorus (V) oxide (phosphorus pentoxide, P2O5) with water; it is used as a catalyst and in metallurgy.


Properties of phosphoric (v) acid
density relative to water 1.83
melting point 42.3°C


Related category

   • INORGANIC CHEMISTRY