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PHOSPHORUS

(Gr. phosphoros, light-bearing (ancient name for the planet Venus when appearing before sunrise)

P  at. wt. 30.9738
   at. no. 15
   m.p. (white) 44.1°C
   b.p. (white) 280°C 
   sp. gr. (white) 1.82
   sp. gr. (red) 2.20
   sp. gr. (black) 2.25 to 2.69
   valence 3 or 5.
Electronic configuration
 SHELL  K L M N O P Q
 SUB  SHELL He Neon Argon Krypton Xenon Radon Eka-radon
1s 2s 2p 3s 3p 3d 4s 4p 4d 5s 5p 4f 5d 6s 6p 5f 6d 7s 7p
Phosphorus 1s22s22p63s23p3        
Symbol 4P3/2
Phorphorus was discovered in 1669 by Brand, who prepared it from urine. Phosphorus exists in four or more allotropic forms: white (or yellow), red, and black (or violet). White phosphorus has two modifications: a and p with a transition temperature at - 3.80C. Never found free in nature, it is widely distributed in combination with minerals. Phosphate rock, which contains the mineral apatite-an impure tri-calcium phosphate-is an important source of the element. Large deposits are found in the U.S.S.R., in Morocco, and in Florida, Tennessee, Utah, Idaho, and else- where. Phosphorus is an essential ingredient of all cell prot~ plasm, nervous tissue, and bones. Ordinary phosphorus is a waxy white solid; when pure it is colorless and transparent. It is insoluble in water, but soluble in carbon disulfide. It takes fire spontaneously in air, burning to the pentoxide. It is very poisonous-SO mg constituting an approximate fatal dose. The maximum recommended allowable con- centration in air is 0.1 mg/cubic meter. White phosphorus should be kept under water as it is dangerously reactive in air, and it should be handled with forceps, as contact with the skin may cause severe burns. When exposed to sunlight or when heated in its own vapor to 2500C, it is converted to the red Variety, which does not phosphoresce in air as does the white variety. This form does not ignite spontaneously and it is not as dangerous as white phosphorus. It should, however, be handled with care as it does convert to the white form at some temperatures and it emits highly toxic fumes of the oxides of phosphorus when heated. The red modifica- tion is fairly stable, sublimes with a vapor pressure of 1 atm. at 41 70C, and is used in the manufacture of safety matches, pyrotechnics, pesticides, incendiary shells, smoke bombs, tracer bullets, etc. White phosphorus may be made by several methods. By one process, tri-calcium phosphate, the essential ingredient or phosphate rock, is heated in the presence of carbon and silica in an electric furnace or fuel-fired blast furnace. Elementary phosphorus is liberated as vapor and may be collected under water. If desired, the phosphorus vapor and carbon monoxide producedby the reaction can be oxidized at once in the presence of moisture or water to produce phosphoric acid-an important compound in making super-phosphate fertilizers. In recent years, con- centrated phosphoric acids, which may contain as much as 70 to 75 % P205 content, have become of great importance to agriculture and farm production. World-wide demand for fertilizers has caused record phosphate production in recent years. Phosphates are used in the production of special glasses, such as those used for sodium lamps. Bone-ash, calcium phosphate, is also used to produce fine china-ware and to produce monocalcium phosphate used in baking powder. Phosphorus is also important in the production of steels, phosphor bronze, and many other products. Tn- sodium phosphate is impQrtant as a cleaning agent, as a THE ELEMEN'1W4Continilwd) water-softener, and for preventing boiler scale and corrosion of pipes and boiler tubes. Organic compounds of phosphorus are important.

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