What is "hypophosphoric acid"

Hypophosphoric \Hy`po*phos*phor"ic\, a. [Pref. hypo- + phosphoric.] (Chem.) Pertaining to, or derived from, or containing, phosphorus in a lower state of oxidation than in phosphoric compounds; as, hypophosphoric acid.

Hypophosphoric acid (Chem.), an acid, P2H4O6, produced by the slow oxidation of moist phosphorus, and isolated only as a solution in water. It is regarded as a condensation product of one molecule of phosphoric acid with one of phosphorous acid, by partial dehydration.

n. (context inorganic chemistry English) The oxyacid of phosphorus H₄P₂O₆

n. a crystalline tetrabasic acid (H4P2O6)

Hypophosphoric acid is a mineral acid with the formula HPO, with phosphorus in a formal oxidation state of +4. In the solid state it is present as the dihydrate, HPO·2HO. In hypophosphoric acid the P atoms are identical and joined directly with a P-P bond. There is an isomeric form isohypophosphoric acid which has a different structure with non-identical P atoms, one of which has a directly bonded H atom and an oxidation state of +3, which is joined by a P-O-P bridge to the second P atom which has an oxidation state of +5.