Phosphorus. P; at. wt. 30.975; at. no. 15; valence 3-5. Discovered in 1669 by Brandt. Does not occur free in nature; found in form of phosphates in the minerals chlorapatite, fluorapatite, vivianite, wavelite, and "phosphate rock" (S. Carolina, Florida, Tennessee); occurs in small quantities in granite rocks; occurs in all fertile soil; an essential constituent of protoplasm, nervous tissue, and bones. Prepn. Ullmann, Enzyklopädie der Technischen Chemie 8, 362 (1931); DeWitt, Skolnik, J. Am. Chem. Sec. 68, 2305 (1946); Skolnik, Tarbutton, Bergman, ibid. 2310.

Phosphorus exists in three allotropic forms: white, black, and red.

White phosphorus: Colorless or yellowish, transparent, crystalline solid; darkens on exposure to light; m. 44.1° (vapor press. 0.181 mm.); b. 280° d. 1.83; volatile; sublimes in vacuo. at ordinary temperature when exposed to light. When exposed to air in the dark, emits a greenish light and gives off white fumes. Almost insoluble in water (one part in 300,000 parts of water); very slightly soluble in abs. alcohol (1 g./ 400 ml.); slightly sol. in abs. ether (1 g./ 102 ml.); soluble in chloroform (1 g./ 40 ml.); soluble in benzene (1 g./ 35 ml.); very soluble in carbon disulfide (1 g./ O.8 ml.). Solubility in oils: one gram phosphorus dissolves in 80 ml. olive oil, 60 ml. oil of turpentine, about 100 ml. almond oil.

Ignites at about 30° in moist air; the ignition temperature is higher when the air is dry.

Caution: Handle with forceps. Keep under water.

The fumes and the element itself are poisonous. Combines directly with the halogens to form tri- or pentahahdes; combines with sulfur to form sulfides. Reacts with several metals to form phosphides. Yields orthophosphoric acid when treated with nitric acid. Reacts with alkali hydroxides with formation of phosphine and sodium hypophosphite.

Incompat. Sulfur, iodine, oil of turpentine, potassium chlorate.

Use: Mannf. rat poisons; for smoke screens, gas analysis.

Black phosphorus: Crystals; resembles graphite in texture; produced from the white modification under high pressures: Bridgman,. J. Am. Chem. Sec. 36, 1344 (1914); Jacobs, J. Chem. Phys. 5, 945 (1937). d. 2.691. Does not catch fire spontaneously. Insoluble in organic solvents.

Red phosphorus: Red to violet powder; polymorphism: Roth, DeWitt, Smith, J. Am. Chem. Sec. 69, 2881 (1947). Its properties are intermediate between those of the white and black forms. Sublimes at 416°, triple point 589.5° under 43.1 atm. d. 2.34. Insoluble in orgamc solvents. Soluble in phosphorus tribromide. Less active than the white form; reacts only at high temperatures. Yields the white modification when distilled at 290°. Catches fire when heated in air to about 260° and burns with formation of the pentoxide. Burns when heated in an atmosphere of chlorine.

Caution: Avoid contact with KClO₃, KMnO₄, peroxides and other oxidizing agents because with these explosions may result on contact or friction.

Use: (Red phosphorus): Pyrotechnics; manuf. safety matches; in organic synthesis; manuf. phosphoric acid, phosphine, phosphoric anhydride, phosphorus pentachloride, phos phorus trichloride; raanuf. fertilizers, pesticides, incendiary shells, smoke bombs, tracer bullets.

Toxicity: (White phosphorus): Ingestion produces severe G.I. irritation, bloody diarrhea, liver damage, skin eruptions, hematuria, collapse, coma, convulsions. Extern. causes severe burns.