phosphoric acid

phosphoric acid
any of three acids, orthophosphoric acid, H3PO4, metaphosphoric acid, HPO3, or pyrophosphoric acid, H4P2O7, derived from phosphorus pentoxide, P2O5, and various amounts of water.

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also called  orthophosphoric acid,  

      (H3PO4), the most important oxygen acid of phosphorus, used to make phosphate salts for fertilizers. It is also used in dental cements, in the preparation of albumin derivatives, and in the sugar and textile industries. It serves as an acidic, fruitlike flavouring in food products.

      Pure phosphoric acid is a crystalline solid (melting point 42.35° C, or 108.2° F); in less concentrated form it is a colourless syrupy liquid. The crude acid is prepared from phosphate rock, while acid of higher purity is made from white phosphorus.

      Phosphoric acid forms three classes of salts corresponding to replacement of one, two, or three hydrogen atoms. Among the important phosphate salts are: sodium dihydrogen phosphate (NaH2PO4), used for control of hydrogen ion concentration (acidity) of solutions; disodium hydrogen phosphate (Na2HPO4), used in water treatment as a precipitant for highly charged metal cations; trisodium phosphate (Na3PO4), used in soaps and detergents; calcium dihydrogen phosphate or calcium superphosphate (Ca[H2PO4]2), a major fertilizer ingredient; calcium monohydrogen phosphate (CaHPO4), used as a conditioning agent for salts and sugars.

      Phosphoric acid molecules interact under suitable conditions, often at high temperatures, to form larger molecules (usually with loss of water). Thus, diphosphoric, or pyrophosphoric, acid (H4P2O7) is formed from two molecules of phosphoric acid, less one molecule of water. It is the simplest of a homologous series of long chain molecules called polyphosphoric acids, with the general formula H(HPO3)nOH, in which n = 2, 3, 4, . . . . Metaphosphoric acids, (HPO3)n, in which n = 3, 4, 5, . . . , are another class of polymeric phosphoric acids. The known metaphosphoric acids are characterized by cyclic molecular structures. The term metaphosphoric acid is used also to refer to a viscous, sticky substance that is a mixture of both long chain and ring forms of (HPO3)n. The various polymeric forms of phosphoric acid are also prepared by hydration of phosphorus oxides.

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Universalium. 2010.

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Look at other dictionaries:

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  • phosphoric acid — noun an acid used in fertilizers and soaps: H3PO4 • Syn: ↑orthophosphoric acid • Hypernyms: ↑oxyacid, ↑oxygen acid * * * phosphoric acid f17 [phosphoric acid] [fɒsˌfɒrɪk ˈæsɪd] …   Useful english dictionary

  • phosphoric acid — [[t]fɒsfɒ̱rɪk æ̱sɪd, AM fɔ͟ːr [/t]] N UNCOUNT Phosphoric acid is a type of acid which contains phosphorus. [TECHNICAL] …   English dictionary

  • phosphoric acid — ortofosfato rūgštis statusas T sritis chemija formulė H₃PO₄ atitikmenys: angl. orthophosphoric acid; phosphoric acid rus. ортофосфорная кислота; фосфорная кислота ryšiai: sinonimas – vandenilio tetraoksofosfatas (3–) sinonimas – fosforo rūgštis …   Chemijos terminų aiškinamasis žodynas

  • Phosphoric acid fuel cell — Phosphoric acid fuel cells (PAFC) are a type of fuel cell that uses liquid phosphoric acid as an electrolyte. The electrodes are made of carbon paper coated with a finely dispersed platinum catalyst, which make them expensive to manufacture. They …   Wikipedia

  • phosphoric acid diluted — [NF] a preparation of phosphoric acid in purified water, containing 9.5–10.5 g phosphoric acid per mL; it is used as a solvent in pharmaceutical preparations and orally as a gastric acidifier …   Medical dictionary

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