With water it gives sulphur, sulphuretted hydrogen, hydrobromic, phosphorous and phosphoric acids, the sulphur and phosphorous acid being produced by the interaction of the previously formed sulphuretted hydrogen and phosphoric acid.
Phosphorous acid, P(OH) 3, discovered by Davy in 1812, may be ' obtained by dissolving its anhydride, P 4 0 61 in cold water; by immersing sticks of phosphorus in a solution of copper sulphate contained in a well-closed flask, filtering from the copper sulphide and precipitating the sulphuric acid simultaneously formed by baryta water, and concentrating the solution in vacuo; or by passing chlorine into melted phosphorus covered with water, the first formed phosphorus trichloride being decomposed by the water into phosphorous and hydrochloric acids.
It is probable, however, that pure phosphorous oxide vapour is odourless, and the odour of phosphorus as ordinarily perceived is that of a mixture of the oxide with ozone.
It slowly reacts with cold water to form phosphorous acid; but with hot water it is energetically decomposed, giving much red phosphorus or the suboxide being formed with an explosive evolution of spontaneously inflammable phosphoretted hydrogen; phosphoric acid is also formed.
Both phosphoric and phosphorous acids became known, although imperfectly, towards the end of the 18th century; phosphorous acid was first obtained pure by Davy in 1812, while pure phosphorous oxide, the anhydride of phosphorous acid, remained unknown until T.
Oxyacids.-Phosphorus forms several oxyacids: hypophosphorous acid, H 3 P0 2, and hypophosphoric acid, H 4 P 2 0 6 or H2P03, of which the anhydrides are unknown; phosphorous acid, H 3 P0 3, derived from P 4 0 5; monoperphosphoric acid, H 3 P0 5; perphosphoric acid, H4P208; and meta-, pyro-, and ortho-phosphoric acids, derived from P4010, for which see Phosphates.
Soc. chim., 99 (3), 21, p. 926; Matignon, Comptes rendus, 1900, 130, p. 1391); and by the reduction of phosphorous acid with nascent hydrogen.
Phosphorus trichloride or phosphorous chloride, PC13, discovered by Gay-Lussac and Thenard in 1808, is obtained by passing a slow current of chlorine over heated red phosphorus or through a solution of ordinary phosphorus in carbon disulphide (purifying in the latter case by fractional distillation).
The haloid esters of the paraffin alcohols formed by heating the alcohols with the halogen acids are the monohaloid derivatives of the paraffins, and are more conveniently prepared by the action of the phosphorous haloid on the alcohol.