What is the structure of orthophosphoric acid

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Orthophosphoric acid,, is one of the most important and longest known phosphorus compounds.

Presentation: The technical production of phosphoric acid takes place predominantly from the naturally occurring apatites, (F, OH, Cl), by wet or dry digestion (Phosphoric acid digestion or. thermal phosphoric acid): When displaying on the wet route, the digestion of calcium phosphate with sulfuric acid takes place at 80-95:

Depending on the process, as plaster of paris, or hemihydrate, CaSO4 · ½ H2The calcium sulphate obtained is filtered off and the remaining 30-50% phosphoric acid is concentrated to up to 70%. The raw acid can be purified by precipitation of interfering ions and extraction with solvents such as methanol, butanol or similar, if necessary up to food quality (component of lemonades, cola, malt beer).

Thermal phosphoric acid arises from the combustion of white phosphorus obtained from apatites with excess air to form phosphorus pentoxide, and its conversion with water or dilute phosphoric acid. By continuously adding water, an approximately 85%, relatively clean phosphoric acid is obtained. About 90% of the white phosphorus produced is processed into thermal phosphoric acid in this way.

Orthophosphoric acid forms colorless, water-clear, odorless crystals that are easily soluble in water (melting point: 42). Melted material has ionic conductivity, which is due to self-dissociation:

The commercially available 85% acid is very syrupy. The high viscosity can be explained by the formation of intermolecular hydrogen bridges between the oxygen atoms of the molecules.

is a medium-strength, tri-basic acid and accordingly forms three series of salts:

  • primary phosphates (dihydrogen phosphates),
  • secondary phosphates (hydrogen phosphates),
  • tertiary phosphates (phosphates),