COMPOUNDS Or PHOSPHORUS. P110S111101115 forms at least three different compounds with hydrogen: viz, a solid hydrogen phosphate, a liquid phosphide, P,H.,; and a gaseous phosphide, PH„, called phosphine. The last-named compound, analogous to ammonia (NIL), is usually pre pared by heating phosphorus with a strong solu tion of caustic potash. When thus prepared, how ever, it contains some vapor of the liquid phos phide, P,IL. and as the latter takes fire spontane ously in the air, the impure phosphide, too, is in flammable. But under the influence of light, or by the action of strong hydrochloric or sulphuric acid, and certain other substances, the vapor of the liquid phosphide is decomposed; and if pure phosphide is prepared, say, by passing the hn pure gas through concentrated hydrochloric acid, it is found not to take fire in the air. The odor of phosphide resembles that of garlic and of rot ten fish. The oxides of phosphorus include phos phorus trioxide, P.O., and phosphorus pentoxide. The latter, usually termed 'phosphoric' anhydride, is formed when common phosphorus burns in the air. It forms a white, exceedingly
hygroscopic powder, taking up water with great energy to form phosphoric acid. With the halo gens phosphorus forms a triehloride, PCI,; a pen tachloride, PC1,; a tribromide. I'Br,; a penta bromide, and a tri-iodide, PI,. All these compounds are formed by the direct union of the elements. A tri-thioride, PE,, and a penis fluoride, are also known.
Phosphorus is a constituent of many tissues, especially the nerve-centres, and its physiological action is that of a tonic. It is chiefly used in medicine in nerve exhaustion, myelitis, neuralgia, ostsomalacia, and rickets. it has been used with success in lupus, acne, and psoriasis. It may he given in pill or in solution, the hitter being pref erable. It may lie exhibited dissolved in oil or in chloroform. Phosphide of zinc has been used as a substitute for phosphorus. See ANTIDOTES.