Phosphorus

Description

Phosphorus (chemical symbol P) is a mineral discovered by the German alchemist Henig Brand in 1699. It plays an essential part in multiple biochemical reactions for both plants and animals and is essential to all life. Phosphorus is found in living things, in soil and rock, mostly as chemical compounds known as phosphates. Rock and soil phosphorus are mined extensively throughout the world, but especially in the Peoples' Republic of China and the United States.

Phosphorus extracted from rock is classified as either white, red or black. White (also called yellow or common) phosphorus is a wax-like substance created by heating phosphate rock until it vaporizes and the condensation solidifies. One of this form's characteristics has given the English language the adjective phosphorescent, from white phosphorus's capacity to glow in the dark when exposed to air.

White phosphorus is highly toxic, causes burns if it comes in contact with skin, and is so combustible that it has to be stored underwater for safety. Red phosphorus is a rust-colored powder created by heating white phosphorus and exposing it to sunlight. It is not as combustible as the white form. Black phosphorus is made by heating white phosphorus under extremely high pressure until it resembles graphite.

In plants, phosphorus is necessary for photosynthesis to take place. In the human body, phosphorus works in tandem with another element, calcium , in much the same way that two other electrolyte components, sodium and potassium , do. Though phosphorus is found in every cell of the human body and accounts for 1% of the body's total weight, its primary function is working in conjunction with calcium to form teeth and bones.

Eighty-five percent of the phosphorus found in the body is located in these structures. In a delicately balanced chemical reaction, substances known as PTH (parathyroid hormone), Calcitonin, and 25-Dihydroxy vitamin D regulate the absorption of both calcium and phosphorus from the intestinal tract, thus making it available for the production of bones and teeth. If an excessive amount of phosphorus is absorbed, this will result in the phosphorus combining with all available calcium and preventing the calcium's efficient use in making and maintaining bones and teeth.

PTH balances the proportions of calcium and phosphorus in the body by increasing the release of calcium and phosphate from bone and the loss of phosphorus via the kidneys while limiting the excretion of calcium. PTH also increases the activity of the 25-Dihydroxy v25-Dihydroxy vitamin D , which, in contrast, increases the absorption of both phosphorus and calcium from the intestinal tract.

General use

White phosphorus is a component of fertilizers, detergents and water softeners. It is also used in the manufacture of steel, plastics, insecticides, medical drugs, and animal feeds. Both white and red phosphorus are used in the making of safety matches and pesticides, including rat poison.

But the 15% of this element found in the blood stream and in other soft tissue also has a highly significant part to play in a variety of other body functions. Working with Vitamin B, phosphorus is involved in the metabolism of fats and carbohydrates, in both the repair of damaged cells and tissues and the routine maintenance of healthy ones. Phosphorus is necessary for the regularity of the heartbeat, and aids in the contraction of all other muscles throughout the body. Phosphorus is needed for the functioning of the kidneys and plays a part in the conduction of impulses along the network that makes up the nervous system.

Preparations

According to the American Dietetic Association, phosphorus intake in the United States is generally above what is needed, and in recent years has actually increased. Therefore, under normal circumstances with normal food intake, there is seldom if ever a need to supplement intake of phosphorus. Persons suffering from eating disorders such as anorexia and bulimia can be deficient in phosphorus intake as well as other nutrients. As the best source of phosphorus is in protein foods such as meat, eggs and milk products, some vegetarians may also need to evaluate their intake of this element. Excess consumption of processed foods, and inadequate intake of whole foods, plus fertilizers and pesticides are some of the causes for excess phosphorus.

Beside high-protein foods, phosphorus is also found in decreasing quantities in whole grain breads and cereals, especially unprocessed ones, and in minute amounts in fruits and vegetables. The phosphorus present in whole grain breads and cereals, however, exists as a substance called phytin. Phytin combines with calcium to create a salt that the human body is incapable of absorbing, thus making unprocessed, unenriched grains a negligible source of phosphorus. But both commercially prepared cereals and breads may provide this element as they are frequently enriched with it. Phosphates can also be taken by mouth as a tablet.

Precautions

White phosphorus is poisonous. Red phosphorus is not. As noted, white phosphorus is a highly toxic, flammable substance capable of burning the skin if it makes contact, and of igniting at room temperature. It should be handled with extreme care. Accidental phosphorus poisoning can happen from both fertilizers and pesticides. Phosphates sometimes are leached into water systems through sewage and can drastically alter the chemical makeup of lakes and rivers. In sufficient quantities, they can lead to the death of nearly all forms of aquatic life.

A normal blood serum level of phosphorus is 2.4-4.1 mg per deciliter of blood. An abnormal serum phosphorus level should be evaluated by a physician.

Phosphorus levels higher than normal can indicate a diet that includes an excessive phosphorus intake, inadequate intake of calcium, or lack of PTH (parathyroid hormone) in the system. It can be related to bone metastasis associated with cancer , liver or kidney disease, or sarcoidosis.

Serum phosphorus levels that are below normal can be related to insufficient phosphorus or vitamin D in one's diet leading to rickets in children and osteomalacia in adults. Disorders of the parathyroid gland, causing it to secrete excessive quantities of PTH, or of the pancreas, causing it to secrete too much insulin, also affect blood levels of phosphorus. Diabetic ketoacidosis or too much calcium are other possible causes. Multiple endocrine neoplasia (MEN) is yet another condition that often is associated with lower than normal levels of phosphorus.

Side effects

Phosphorus preparations taken to supplement low phosphorus levels in the body can cause diarrhea .

Interactions

Antacids can decrease the absorption of phosphorus. Laxatives and enemas that contain the chemical compound sodium phosphate and excessive intake of vitamin D can increase phosphorus levels in the body. Administration of intravenous glucose solutions will cause phosphorus to combine with the glucose that is being absorbed by the cells.

Resources

BOOKS

Busch, Marianna A., Ph.D. Phosphorus, World Book. Chicago, IL: World Book, Inc., 1999.

Clayman, Charles B., MD. The American Medical Association Home Medical Encyclopedia. New York: Random House, 1989.

PERIODICALS

Affenito, Sandra G., pH, RD, and Jane Kerstetter, pH, RD. "Position of the American Dietetic Association and Dietitians of Canada: Women's Health and Nutrition." Journal of the American Dietetic Association 1999.

OTHER

"Phosphorus in the Diet." http//www.Healthcentral.com. (June 2000).

"Serum Phosphorus." http//www.Healthcentral.com. (June 2000).

"Vitamin D." http//www.Healthcentral.com. (June 2000).

Joan Schonbeck

phosphorus [Gr.,=light-bearing], nonmetallic chemical element; symbol P; at. no. 15; at. wt. 30.97376; m.p. 44.1°C; b.p. about 280°C; sp. gr. 1.82 at 20°C; valence -3, +3, or +5. Solid phosphorus has a tetratomic molecule (P ₄ ) with molecular weight 123.8952 atomic mass units (amu). Phosphorus was discovered c.1674 by Hennig Brand of Hamburg, an alchemist, who prepared it from urine. Phosphoric acid was discovered in 1770 by K. W. Scheele and J. G. Gahn in bone ash (see ash ); Scheele later isolated phosphorus from bone ash (1774) and produced phosphoric acid by the action of nitric acid on phosphorus (1777).

Forms

Phosphorus exhibits allotropy (i.e., it has multiple forms in the same physical state); the physical constants given above are for the common white phosphorus. White phosphorus is an extremely poisonous, yellow to white, waxy, solid substance, nearly insoluble in water but very soluble in carbon disulfide. When exposed to air it ignites spontaneously, burning to form white fumes of phosphorus pentoxide, P ₂ O ₅ . Because of its toxicity and pyrophoric nature, phosphorus is stored underwater. Contact with the skin may cause burns. White phosphorus is phosphorescent (i.e., glows without emitting heat).

When white phosphorus is heated to about 250°C in the absence of air, it changes into the more stable red phosphorus. This form appears as dull, reddish-brown cubic crystals or amorphous powder. Its specific gravity is 2.34. The red form is less dangerous than the white form, but should be handled with caution. It is insoluble in carbon disulfide and most other solvents. It does not ignite unless heated to about 200°C, does not phosphoresce, and is not poisonous. Another form of phosphorus is black phosphorus, a crystalline electrically conductive material similar to graphite in appearance. It was first prepared by P. W. Bridgman by heating white phosphorus to 200°C under a pressure of 12,000 atmospheres. Its specific gravity is 2.70.

Natural Occurrence and Commercial Preparation

Because of its chemical activity phosphorus does not occur uncombined in nature but is widely distributed in many minerals. A major source is apatite , an impure calcium phosphate mineral found in phosphate rocks. In the United States major deposits are found in Florida, Tennessee, Montana, and Idaho. White phosphorus is prepared commercially from phosphate rock in an electric furnace or blast furnace. The principal use of phosphorus is in compounds; for this reason, most of the phosphorus produced in furnaces is burned to make phosphorus pentoxide, a white powdery substance. While the pentoxide is used as a drying agent and chemical reagent, it is chiefly converted to phosphoric acid , H ₃ PO ₄ , also called orthophosphoric acid, by reaction with water. Another important source of phosphoric acid is from phosphate rocks by treatment with sulfuric acid; this is the so-called wet-acid process.

Biological Importance and Applications

Phosphorus is present in plants and animals. There is over 1 lb (454 grams) of phosphorus in the human body. It is a component of adenosine triphosphate (ATP), a fundamental energy source in living things. It is found in complex organic compounds in the blood, muscles, and nerves, and in calcium phosphate, the principal material in bones and teeth. Phosphorus compounds are essential in the diet. Organic phosphates, ferric phosphate, and tricalcium phosphate are added to foods. Dicalcium phosphate is added to animal feeds.

White phosphorus is used as a deoxidizing agent in the preparation of steel and phosphor bronze. It is also used in rat poisons and to make smoke screens (by burning) for warfare. Red phosphorus is used in making matches. The major use of phosphorus compounds is in fertilizers, especially in a mixture called superphosphate, obtained from phosphate minerals by sulfuric acid treatment; and in nitrophosphates. Phosphorus compounds are also used commercially in detergents, water softeners, pharmaceuticals, dentifrices, and in many other less important uses. Toxic nerve gases such as sarin contain phosphorus.

Phosphoric acid is primarily used in the production of phosphate compounds. It is also used in pickling metals, in sugar refining, and in soft drinks. Phosphorus forms a number of compounds with the halogens, e.g., the trichloride, PCl ₃ , and the pentachloride, PCl ₅ , both used as reagents. It also forms an oxychloride, POCl ₃ . It reacts with sulfur to form a pentasulfide, P ₂ S ₅ , and a thiochloride, PSCl ₃ , used in insecticides and oil additives. Phosphine, PH ₃ , is a poisonous gas. Besides the pentoxide, phosphorus forms several other oxides; there are several acids other than the orthophosphoric acid noted above. Phosphorus also combines with various other nonmetals and with some metals.

Phosphorus

melting point: 44.1°C
boiling point: 280°C
density: 1.82 g/cm ³
most common ions: PH ₄⁺, P ³⁻, H ₂PO ₃⁻, PO ₄³⁻

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 P₄ 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 (PO₄³⁻) groups. Large deposits of such minerals, of which the most important is fluorapatite, Ca₅F(PO₄)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, H₃PO₄, 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.

phosphorus An essential element, occurring in tissues and foods as phosphate (salts of phosphoric acid), phospholipids, and phosphoproteins. In the body most (80%) is present in the skeleton and teeth as calcium phosphate (hydroxyapatite); the remainder is in the phospholipids of cell membranes, in nucleic acids, and in a variety of metabolic intermediates, including ATP. The parathyroid hormone controls the concentration of phosphate in the blood, mainly by modifying its excretion in the urine.

Adult needs (about 1.3 g per day) are always met. The calcium to phosphate ratio of infant foods is, however, important. Phosphate deficiency is common in livestock and gives rise to osteomalacia (also known as sweeny or creeping sickness).

phosphorus (P) An element that is required by plants in the oxidized form, as orthophosphate (PO₄²⁺). The special chemical properties of orthophosphate are utilized in reactions in which energy is transferred, often involving ATP. It is also a good buffer, helping to maintain a neutral pH. The leaves of plants deficient in phosphate become dark green or blue-green and a reddish pigment may develop. Growth is generally reduced.

phos·pho·rus / ˈfäsfərəs/ • n. the chemical element of atomic number 15, a poisonous, combustible nonmetal that exists in two common allotropic forms, white phosphorus, a yellowish waxy solid that ignites spontaneously in air and glows in the dark, and red phosphorus, a less reactive form used in making matches. (Symbol: P)

phosphorus †morning star; phosphorescent substance; highly inflammable non-metallic element luminous in the dark. XVII. — L. phōsphorus — Gr. phōsphóros light-bringing, sb. morning star, f. phôs light + -phóros -PHORE.
So phosphoric (- F.), phosphorous XVIII. Hence phosphoresce, phosphorescence, phosphorescent XVIII.

phosphorus Symbol P. A nonmetallic element that is a major essential element for living organisms. It is an important constituent of tissues (especially bones and teeth) and of cells, being required for the formation of nucleic acids and energy-carrying molecules (e.g. ATP) and also involved in various metabolic reactions.

phosphorus(P) An element that is an essential nutrient for all living organisms. Plants require it in the oxidized form, as orthophosphate (PO²⁺₄). The growth of phosphorus-deficient plants is usually reduced and their leaves become dark green or blue-green and a reddish pigment may develop.

phosphorus (fos-fer-us) n. a nonmetallic element that is toxic in its pure state. Phosphorus compounds are major constituents in the tissues of both plants and animals. In humans, phosphorus is mostly concentrated in bone. Symbol: P.

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