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.
[1785-95]

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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.

Look at other dictionaries:

  • Phosphoric acid — Phosphoric Phos*phor ic, a. [Cf. F. phosphorique.] 1. (Chem.) Of or pertaining to phosphorus; resembling, or containing, from us; specifically, designating those compounds in which phosphorus has a higher valence as contrasted with the… …   The Collaborative International Dictionary of English

  • phosphoric acid — n. any of several oxygen acids of phosphorus: see ORTHOPHOSPHORIC ACID, METAPHOSPHORIC ACID, and PYROPHOSPHORIC ACID …   English World dictionary

  • phosphoric acid — ► NOUN Chemistry ▪ a crystalline acid obtained by treating phosphates with sulphuric acid …   English terms dictionary

  • Phosphoric acid — This article is about orthophosphoric acid. For other acids commonly called phosphoric acid , see Phosphoric acids and phosphates. Phosphoric acid …   Wikipedia

  • phosphoric acid — Orthophosphoric acid; a strong acid of industrial importance; m.p. 42.35°C; dilute solutions have been used as urinary acidifiers and as dressings to remove necrotic debris. In dentistry, it constitutes about 60% of the liquid used in zinc… …   Medical dictionary

  • 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 — noun Date: 1784 1. a syrupy or deliquescent tribasic acid H3PO4 used especially in preparing phosphates (as for fertilizers), in rust proofing metals, and especially formerly as a flavoring in soft drinks called also orthophosphoric acid 2. a… …   New Collegiate Dictionary

  • phosphoric acid — phosphor′ic ac′id n. chem. any of three acids, orthophosphoric acid, H3PO4, metaphosphoric acid, HPO3, or pyrophosphoric acid, H4P2O7, derived from phosphorus pentoxide, P2O5, and various amounts of water …   From formal English to slang


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