Phosphorus




Phosphorus

MELTING POINT: 44.1°C
BOILING POINT: 280°C
DENSITY : 1.82 g/cm
3
MOST COMMON IONS : PH 4 + , P 3− , H 2 PO 3 , PO 4 3−

The element phosphorus is essential to living organisms. It is part of the backbone of DNA (deoxyribonucleic acid), the carrier and transmitter of genetic information in cells. The element and its compounds have many commercial applications.

Phosphorus was first isolated by the alchemist Hennig Brand of Hamburg around 1670. He prepared white phosphorus, one of two common forms (allotropes) of the element, by evaporating human urine and strongly heating the residual solids. White phosphorus distilled and was collected under water.

The two common forms of phosphorus are white, which is made up of P 4 molecules, containing four atoms of phosphorus arranged in a regular tetrahedral formation, and red, which is a noncrystalline polymer. White phosphorus glows in the dark and bursts into flame in air. Red phosphorus does not react rapidly with air.

Phosphorus makes up about 0.12 percent of Earth's crust. It is extracted from minerals that contain phosphate (PO 4 3− ) groups. Large deposits of such minerals, of which the most important is fluorapatite, Ca 5 F(PO 4 ) 3 , are found in the United States, Morocco, Russia, and Tunisia. At the present rate of extraction, the known deposits of phosphate rock would be sufficient to supply the world's demand for phosphorus for the next 1,000 years.

More than 90 percent of commercial phosphorus production is in the form of calcium salts of phosphoric acid, H 3 PO 4 , used as fertilizers. Other significant uses of phosphorus compounds are in the manufacture of matches (phosphorus sulfides), food products and beverages (purified phosphoric acid and its salts), detergents (sodium polyphosphates), plasticizers for polymers ( esters of phosphoric acid), and pesticides (derivatives of phosphoric acid). Related to the phosphorus pesticides are nerve gases, poisonous compounds that rapidly attack the central nervous system, initially developed during World War II.

SEE ALSO Deoxyribonucleic Acid (DNA) ; Fertilizer ; Pesticides .

Harold Goldwhite

Bibliography

Greenwood, Norman N., and Earnshaw, A. (1984). Chemistry of the Elements. New York: Pergamon Press.

Weeks, Mary Elvira, and Leicester, Henry M. (1968). Discovery of the Elements, 7th edition. Easton, PA: Journal of Chemical Education.



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