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Facts About Phosphorus

phosphorus
Credit: Greg Robson/Creative Commons, Andrei Marincas | Shutterstock
Atomic Number: 15
Atomic Symbol: P
Atomic Weight: 30.973762
Melting Point: 111.5 F (44.15 C)
Boiling Point: 536.9 F (280.5 C)

Word origin: Phosphorus comes from the Greek word phosphoros (light bearing). It is an ancient name for the planet Venus when appearing before sunrise.

Discovery:  Phosphorous was recognized as a distinct substance by Hennig Brand in 1669 when he prepared it in a pure form from urine.

Properties of phosphorus

Phosphorus is a nonmetal and part of Group 15, the pnictogens, or nitrogen family. [See Periodic Table of the Elements]

It exists in multiple allotropic forms: white or yellow, red, and black or violet. Standard phosphorus is a waxy white solid substance, but when it is pure it is colorless and transparent. White phosphorus has two modifications: alpha and beta. The transition temperature to produce these modifications is at25.16 F (minus 3.8 C).

Phosphorous is insoluble in water but soluble in carbon disulfide. It can catch fire spontaneously in air.

Phosphorus is a highly poisonous element. A fatal dose is approximately 50 milligrams (0.0017 ounces), and exposure to white phosphorus should not exceed 0.1 mg/m3 per eight-hour shift of a 40-hour work week. White phosphorus is dangerously reactive when exposed to air and should be kept underwater and handled with forceps, as contact with skin may cause severe burns.

matches, phosphorus
Phosphorus is used in the red tips of ordinary kitchen matches.
Credit: suvijakra | Shutterstock

When white phosphorus is exposed to sunlight or heated by its own vapor to 250 C (482 F), it converts to red phosphorus. Red phosphorus does not ignite spontaneously and is not as dangerous as white. It is fairly stable and is used to manufacture safety machines, pyrotechnics, pesticides, incendiary shells, smoke bombs, tracer bullets and more. It must still be handled with care, however, lest it convert back to the white form in the wrong temperature. It also emits highly toxic fumes when heated.

Sources of phosphorus

Phosphorus is never found free in nature; it is found in combination with a wide variety of minerals. Phosphate rock, which contains the mineral apatite, is an impure tri-calcium phosphate and an important source of phosphorus. Large deposits of phosphate rock are found in Russia, Morocco, Florida, Tennessee, Utah, Idaho and other places.

White phosphorus can be made through several methods. A common process is heating tri-calcium phosphate, the essential ingredient of phosphate rock, in the presence of carbon and silica in an electric furnace or fired furnace. Elementary phosphorus is then released as a vapor and can be collected under phosphoric acid. It is an important compound in making super-phosphate fertilizers.

Uses of phosphorus

Phosphorus is an important component in the production of steel, phosphor bronze and many other products. Trisodium phosphate is valuable as a cleaning agent, a water softener, and for preventing boiler scale and corrosion of pipes and boiler tubes.

Phosphates are used in the production of special glasses, such as those used for sodium lamps (street lights). Phosphorus is a key ingredient in the red tip of ordinary kitchen matches.

In recent years, concentrated phosphoric acids have become a critical part of agriculture and farm production. Phosphoric acids may contain as much as 75 percent phosphorus pentoxide (P2O5) content and are used as fertilizers. Large agricultural businesses around the world have increased demand for fertilizer resulting in record phosphate production.

Phosphoric acid is also used in soft drinks. Calcium phosphate — also known as bone-ash — is used in creating chinaware and to produce mono-calcium phosphate that is used in baking powder.

Phosphorus is not only useful in inorganic products, though; it is an essential ingredient of all cell protoplasm, nerve tissue and bones.

(Source: Los Alamos National Laboratory)

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