Phosphorus [Monograph #7503, Merck Index, Ed. 12.1]

CAS Registry number:

[7723-14-0]

Literature references:

P; at. wt 30.97376; at. no. 15; valences 3, 5. One naturally occurring isotope: 31P; artificial, radioactive isotopes: 28-30; 32-34. Abundance in earth's crust: about 0.12%. Does not occur free in nature; found in the form of phosphates in the minerals chlorapatite [3Ca₂(PO₄)₂·CaCl₂], fluorapatite [3Ca(PO₄)₂·CaF₂], vivianite, wavellite and "phosphate rock" or phosphorite; occurs in small quantities in granite rocks; occurs in all fertile soil; an essential constituent of protoplasm, nervous tissue and bones. Discovered in 1669 by Brandt. Prepn: Ullmann, Enzyklopdie der Technischen Chemie 8, 362 (1931); DeWitt, Skolnik, J. Am. Chem. Soc. 68, 2305 (1946); Skolnik et al., J. Am. Chem. Soc. 68, 2310 (1946). Lab prepn and purification: Klement in Handbook of Preparative Inorganic Chemistry vol. 1, pp 518-525, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963). Reviews: J. R. Van Waser, Phosphorus and Its Compounds, 2 vols. (Interscience, New York, 1958, 1961) 2046 pp; Corbridge, "The Structural Chemistry of Phosphorus Compounds" in Topics in Phosphorus Chemistry, Vol. 3, E. J. Griffith, M. Grayson, Eds. (Interscience, New York, 1966) pp 57-394; Toy, "Phosphorus" in Comprehensive Inorganic Chemistry, Vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 389-545; J. R. Van Wazer in Kirk-Othmer Encyclopedia of Chemical Technology vol. 17 (Wiley-Interscience, New York, 3rd ed., 1982) pp 473-490.

Properties:

Phosphorus exists in three main allotropic forms: white, black, and red. The same liquid is obtained on melting. Caution: Avoid contact with KClO₃, KMnO₄, peroxides and other oxidizing agents; explosions may result on contact or friction. Phosphorus atoms exist as symmetrical, tetrahedral P₄ molecules in the liquid phase and in the vapor phase below 800°C; molecules dissociate to P₂ above 800°C.

Caution:

Ingestion of even small amounts of white phosphorus may produce severe G.I. irritation, bloody diarrhea, liver damage, skin eruptions, oliguria, circulatory collapse, coma, convulsions, death. The approx fatal dose is 50 to 100 mg. External contact may cause severe burns. Chronic poisoning (from ingestion or inhalation) is characterized by boney necrosis, especially of the mandible, spontaneous fractures, anemia, weight loss. Red phosphorus is relatively nontoxic unless it contains the white form as an impurity: Clinical Toxicology of Commercial Products, M. N. Gleason et al., Eds. (Williams Wilkins, Baltimore, 1969) Section III, pp 192-195.

Derivative:

White phosphorus

Properties:

Colorless or white, transparent, cryst solid; waxy appearance; darkens on exposure to light. Sometimes called yellow phosphorus; color due to impurities. Two allotropic modifications: α-form exists at room temp; cubic crystals containing P₄ molecules; d 1.83. β-Form prepd by conversion of α-form at -79.6°C; hexagonal crystals. Volatile; sublimes in vacuo at ordinary temp when exposed to light. When exposed to air in the dark, emits a greenish light and gives off white fumes. Solubilities in water: 1g/300 L water; in EtOH(abs): 1 g/400 mL; in abs ether: 1 g/102 mL; in CHCl₃: 1 g/40 mL; in benzene: 1 g/35 mL; in CS₂: 1 g/0.8 mL. Solubilityy in oils: one gram phosphorus dissolves in 80 ml olive oil, 60 ml oil of turpentine, =100 ml almond oil. Ignites at about 30°C in moist air; the ignition temp 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 pentahalides; 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.

Melting point:

44.1°C (vap. press. 0.181 mmHg)

Boiling point:

280°C

Density:

1.83 (α); 1.88 (β)

Derivative:

Black Phosphorus

Properties:

Polymorphic. Orthorhombic crystalline form: stable in air; resembles graphite in texture; produced from the white modification under high pressures: Bridgman, J. Am. Chem. Soc. 36, 1344 (1914); Jacobs, J. Chem. Phys. 5, 945 (1937); Krebs, Inorg. Syn. 7, 60 (1963). Does not catch fire spontaneously. Insol in organic solvents. Amorphous form prepd at lower pressures: Jacobs, J. Chem. Phys. 5, 945 (1937). At higher pressure the orthorhombic form undergoes reversible transition to a rhombohedral structure, and a cubic structure: Jamieson, Science 139, 1291 (1963).

Density:

2.691 (orthorhombic); 3.56 (rhombohedral); 3.83 (cubic)

Derivative:

Red phosphorus

Properties:

Red to violet powder. The properties of red phosphorus are intermediate between those of the white and black forms. Sublimes at 416°C, triple point 589.5°C under 43.1 atm. Insol in organic solvents. Sol in phosphorus tribromide. Less active than the white form; reacts only at high temp. Yields the white modification when distilled at 290°C. Catches fire when heated in air to about 260°C and burns with formation of the pentoxide. Burns when heated in an atmosphere of chlorine.

Density:

2.34