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 phosphate and silicate cements; solutions in varying concentrations are used for etching enamel and dentin surfaces prior to applications of various types of resins.

- cyclic p. 1. in general, a linear polymer of p. residues in pyrophosphate linkage in which the α and ω residues are similarly linked to make one endless loop or cyclic compound; 2. specifically, a generic term applied to compounds in which one p. residue is esterified to two hydroxyl groups of a single carbon chain, as in adenosine 3′,5′-p., adenosine 2′,3′-p., etc.

- dilute p. a solvent containing 10% H₃PO₄.

- glacial p. an anhydride of p. used as a reagent and in the manufacture of zinc oxyphosphate cement for dentistry. SYN: metaphosphoric acid.

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phosphoric acid n

1) a syrupy or deliquescent tribasic acid H₃PO₄ used esp. in preparing phosphates (as for fertilizers), in rust-proofing metals, and esp. formerly as a flavoring in soft drinks called also orthophosphoric acid

2) a compound (as pyrophosphoric acid or metaphosphoric acid) consisting of phosphate groups linked directly to each other by oxygen

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phos·phor·ic ac·id (fos-forґik) 1. orthophosphoric acid, the monomeric form H₃PO₄. 2. a general term encompassing the monomeric (orthophosphoric acid), dimeric (pyrophosphoric acid), and polymeric (metaphosphoric acid) forms of the acid. Phosphoric acid is an important metabolite; see phosphate and specific acids and salts.