Phosphorus:chemical element that has the symbol P

Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalentnonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks. Elemental phosphorus exists in two major forms—white phosphorus and red phosphorus—but due to its high reactivity, phosphorus is never found as a free element on Earth.Sony VAIO VGN-AR83S Battery

The first form of elemental phosphorus to be produced (white phosphorus, in 1669) emits a faint glow upon exposure to oxygen– hence its name given from Greek mythology, ???????? meaning "light-bearer" (Latin Lucifer), referring to the "Morning Star", the planet Venus. Sony VAIO VGN-AR83US Battery

Although the term "phosphorescence", meaning glow after illumination, derives from this property of phosphorus, the glow of phosphorus originates from oxidation of the white (but not red) phosphorus and should be called chemiluminescence.

The vast majority of phosphorus compounds are consumed as fertilizers. Other applications include the role of organophosphorus compounds in detergents, pesticides and nerve agents, and matches.Sony VAIO VGN-AR84S Battery

Phosphorus is essential for life. As phosphate, it is a component of DNA, RNA, ATP, and also the phospholipids that form all cell membranes. Demonstrating the link between phosphorus and life, elemental phosphorus was historically first isolated from human urine, and bone ash was an important early phosphate source. Phosphate minerals are fossils. Sony VAIO VGN-AR84US Battery

Low phosphate levels are an important limit to growth in some aquatic systems. Today, the most important commercial use of phosphorus-based chemicals is the production of fertilizers, to replace the phosphorus that plants remove from the soil.

Phosphorus exists as several forms (allotropes) that exhibit strikingly different properties.Sony VAIO VGN-AR85S Battery

The two most common allotropes are white phosphorus and red phosphorus. Another form, scarlet phosphorus, is obtained by allowing a solution of white phosphorus in carbon disulfide to evaporate in sunlight. Black phosphorus is obtained by heating white phosphorus under high pressures (about 12,000 standard atmospheres or 1.2 gigapascals). Sony VAIO VGN-AR85US Battery

In appearance, properties, and structure, it resembles graphite, being black and flaky, a conductor of electricity, and has puckered sheets of linked atoms. Another allotrope isdiphosphorus; it contains a phosphorus dimer as a structural unit and is highly reactive.Sony VAIO VGN-AR870EA Battery

White phosphorus and related molecular forms

The most important form of elemental phosphorus from the perspective of applications and chemical literature is white phosphorus. It consists of tetrahedral P4 molecules, in which each atom is bound to the other three atoms by a single bond. Sony VAIO VGN-AR890U Battery

This P4 tetrahedron is also present in liquid and gaseous phosphorus up to the temperature of 800 °C when it starts decomposing to P2 molecules. Solid white exists in two forms. At low-temperatures, the ? form is stable. At high-temperatures ? form is predominant. These forms differ in terms of the relative orientations of the constituent P4 tetrahedra.Sony VAIO VGN-AR93S Battery

White phosphorus is the least stable, the most reactive, more volatile, less dense, and more toxic than the other allotropes. White phosphorus gradually changes to red phosphorus. This transformation, which is accelerated by light and heat, and samples of white phosphorus almost always contain some red phosphorus and therefore appear yellow. Sony VAIO VGN-AR93US Battery

For this reason, it is also called yellow phosphorus. It glows in the dark (when exposed to oxygen) with a very faint tint of green and blue, is highly flammable and pyrophoric (self-igniting) upon contact with air as well as toxic (causing severe liver damage on ingestion). Because of pyrophoricity, white phosphorus is used as an additive in napalm. Sony VAIO VGN-AR94S Battery

The odour of combustion of this form has a characteristic garlic smell, and samples are commonly coated with white "(di)phosphorus pentoxide", which consists of P4O10 tetrahedra with oxygen inserted between the phosphorus atoms and at their vertices. White phosphorus is insoluble in water but soluble in carbon disulfide.Sony VAIO VGN-AR94US Battery

Thermolysis (cracking) of P4 at 1100 kelvin) gives diphosphorus, P2. This species not stable as a solid or liquid. The dimeric unit contains a triple bond and is analogous to N2. It can also be generated as a transient intermediate in solution by thermolysis of organophosphorus precursor reagents.[9] At still higher temperatures, P2 dissociates into atomic P.Sony VAIO VGN-AR95S Battery

Although the term phosphorescence is derived from phosphorus, the reaction that gives phosphorus its glow is properly calledchemiluminescence (glowing due to a cold chemical reaction), not phosphorescence (re-emitting light that previously fell onto a substance and excited it).Sony VAIO VGN-AR95US Battery

Red phosphorus

Red phosphorus is polymeric in structure. It can be viewed as a derivative of P4 wherein one P-P bond is broken, and one additional bond is formed between the neighbouring tetrahedron resulting in a chain-like structure. Red phosphorus may be formed by heating white phosphorus to 250 °C (482 °F) or by exposing white phosphorus to sunlight.Sony VAIO VGN-AW110J/H Battery

Phosphorus after this treatment is amorphous. Upon further heating, this material crystallises. In this sense, red phosphorus is not an allotrope, but rather an intermediate phase between the white and violet phosphorus, and most of its properties have a range of values. Sony VAIO VGN-AW11M/H Battery

For example, freshly prepared, bright red phosphorus is highly reactive and ignites at about 300 °C,[11] though it is still more stable than white phosphorus, which ignites at about 30 °C.[12] After prolonged heating or storage, the color darkens (see infobox images); the resulting product is more stable and does not spontaneously ignite in air.Sony VAIO VGN-AW11S/B Battery

Violet phosphorus

Violet phosphorus is a form of phosphorus that can be produced by day-long annealing of red phosphorus above 550 °C. In 1865, Hittorf discovered that when phosphorus was recrystallized from molten lead, a red/purple form is obtained. Therefore this form is sometimes known as "Hittorf's phosphorus" (or violet or ?-metallic phosphorus).Sony VAIO VGN-AW11XU/Q Battery

Black phosphorus

Black phosphorus is the least reactive allotrope and the thermodynamically stable form below 550 °C. It is also known as ?-metallic phosphorus and has a structure somewhat resembling that of graphite. High pressures are usually required to produce black phosphorus, but it can also be produced at ambient conditions using metal salts as catalysts.Sony VAIO VGN-AW11Z/B Battery

Twenty-three isotopes of phosphorus are known, including all possibilities from 24P up to 46P). Only 31P is stable and is therefore present at 100% abundance. The half-integer nuclear spin and high abundance of 31P make phosphorus-31 NMR spectroscopy a very useful analytical tool in studies of phosphorus-containing samples.Sony VAIO VGN-AW120J/H Battery

Two radioactive isotopes of phosphorus have half-lives that make them useful for scientific experiments. 32P has a half-life of 14.262 days and 33P has a half-life of 25.34 days. Biomolecules can be "tagged" with a radioisotope to allow for the study of very dilute samples.Sony VAIO VGN-AW150Y/H Battery

Radioactive isotopes of phosphorus include

• 32P, a beta-emitter (1.71 MeV) with a half-life of 14.3 days, which is used routinely in life-science laboratories, primarily to produce radiolabeled DNA and RNAprobes, e.g. for use in Northern blots or Southern blots. Sony VAIO VGN-AW160J/Q Battery
• Because the high energy beta particles produced penetrate skin and corneas, and because any 32Pingested, inhaled, or absorbed is readily incorporated into bone and nucleic acids, Occupational Safety and Health Administration in the United States, and similar institutions in other developed countries require that a lab coat, Sony VAIO VGN-AW170Y/Q Battery
• disposable gloves and safety glasses or goggles be worn when working with 32P, and that working directly over an open container be avoided in order to protect the eyes. Monitoring personal, clothing, and surface contamination is also required. In addition, due to the high energy of the beta particles,Sony VAIO VGN-AW180Y/Q Battery
• shielding this radiation with the normally used dense materials (e.g. lead), gives rise to secondary emission of X-rays via Bremsstrahlung (braking radiation). Therefore shielding must be accomplished with low density materials, e.g. Plexiglas (Lucite), other plastics, water, or (when transparency is not required), even wood.Sony VAIO VGN-AW190JAH Battery
• 33P, a beta-emitter (0.25 MeV) with a half-life of 25.4 days. It is used in life-science laboratories in applications in which lower energy beta emissions are advantageous such as DNA sequencing.

Occurrence

In terms of stellar nucleosynthesis, stable forms of phosphorus are produced in large (greater than 3 solar masses) stars by fusing two oxygen atoms together. This requires temperatures above 1,000 megakelvins.Sony VAIO VGN-AW190NAB Battery

Phosphorus is not found free in nature, but it is widely distributed in many minerals, mainly phosphates. Phosphate rock, which is partially made of apatite (an impure tri-calcium phosphate mineral), is an important commercial source of this element. About 50 percent of the global phosphorus reserves are in the Arab nations.Sony VAIO VGN-AW190NBB Battery

Large deposits of apatite are located in China, Russia, Morocco, Florida, Idaho, Tennessee, Utah, and elsewhere. Albright and Wilson in the United Kingdom and their Niagara Falls plant, for instance, were using phosphate rock in the 1890s and 1900s from Connetable, Tennessee and Florida; by 1950 they were using phosphate rock mainly from Tennessee and North Africa.Sony VAIO VGN-AW190NCB Battery

In the early 1990s Albright and Wilson's purified wet phosphoric acid business was being adversely affected by phosphate rock sales by China and the entry of their long-standing Moroccan phosphate suppliers into the purified wet phosphoric acid business.Sony VAIO VGN-AW190YAB Battery

Scarcity

Recent reports suggest that production of phosphorus may have peaked, leading to the possibility of global shortages by 2040.In 2007, at the rate of consumption, the supply of phosphorus was estimated to run out in 345 years. However, scientists are now claiming that a "Peak Phosphorus" will occur in 30 years and that "At current rates, reserves will be depleted in the next 50 to 100 years."Sony VAIO VGN-AW190YBB Battery

Production

The majority of phosphorus-containing compounds are produced for use as fertilisers. For this purpose, phosphate-containing minerals are converted to phosphoric acid. Two distinct routes are employed, the main one being treatment of phosphate minerals with sulfuric acid.Sony VAIO VGN-AW190YCB Battery

The other process utilises white phosphorus, which may be produced by reaction and distillation from very low grade phosphate sources. The white phosphorus is then oxidised to phosphoric acid and subsequently neutralised with base to give phosphate salts.Sony VAIO VGN-AW190YDB Battery

Phosphoric acid obtained via white phosphorus is relatively pure and is the main source of phosphates used in detergents and other non-fertiliser applications.

Elemental phosphorus

About 1,000,000 short tons (910,000 t) of elemental phosphorus is produced annually. Sony VAIO VGN-AW220J/B Battery

Calcium phosphate (phosphate rock), mostly mined in Florida and North Africa, can be heated to 1,200–1,500 °C with sand, which is mostly SiO2, and coke (impure carbon) to produce vaporized P4. The product is subsequently condensed into a white powder under water to prevent oxidation by air. Sony VAIO VGN-AW230J/H Battery

Even under water, white phosphorus is slowly converted to the more stable red phosphorus allotrope. The chemical equation for this process when starting with fluoroapatite, a common phosphate mineral, is:

4 Ca5(PO4)3F + 18 SiO2 + 30 C ? 3 P4 + 30 CO + 18 CaSiO3 + 2 CaF2 Sony VAIO VGN-AW235J/B Battery

Side products from this production include ferrophosphorus, a crude form of Fe2P, resulting from iron impurities in the mineral precursors. The silicate slag is a useful construction material. The fluoride is sometimes recovered for use in water fluoridation.Sony VAIO VGN-AW290JFQ Battery

More problematic is a "mud" containing significant amounts of white phosphorus. Production of white phosphorus is conducted in large facilities in part because it is energy intensive. The white phosphorus is transported in molten form. Some major accidents have occurred during transportation, train derailments at Brownston, Nebraska and Miamisburg, Ohio led to large fires. Sony VAIO VGN-AW41JF Battery

The worst incident in recent times was an environmental one in 1968 when the sea became contaminated due to spillages and/or inadequately treated sewage from a white phosphorus plant at Placentia Bay, Newfoundland.

Thermphos International is Europe's only producer of elemental phosphorus.Sony VAIO VGN-AW41JF/H Battery

About 6,500 short tons (5,900 t) of red phosphorus were produced in 1988. It is produced by heating white phosphorus near 270 °C. The product is treated to remove traces of white phosphorus. Red phosphorus is a component of fire retardants and striking surfaces for matches (see Applications below).Sony VAIO VGN-AW41MF Battery

Oxyacids of phosphorus

Phosphorous oxyacids are extensive, often commercially important, and sometimes structurally complicated. They all have acidic protons bound to oxygen atoms and some have nonacidic protons that are bonded directly to phosphorus.Sony VAIO VGN-AW41MF/H Battery

Although many oxyacids of phosphorus are formed, only six are important, and three of them,hypophosphorous acid, phosphorous acid and phosphoric acid are particularly important ones.

Oxides

The most prevalent compounds of phosphorus are derivatives of phosphate (PO43-), a tetrahedral anion.Sony VAIO VGN-AW41XH Battery

Phosphate is the conjugate base of phosphoric acid, which is produced on a massive scale for use in fertilizers. Being triprotic, phosphoric acid converts stepwise to three conjugate bases:

H3PO4 + H2O H3O+ + H2PO4? Ka1= 7.25×10?3

H2PO4? + H2O H3O+ + HPO42? Ka2= 6.31×10?8

HPO42? + H2O H3O+ + PO43? Ka3= 3.98×10?13

Phosphate exhibits the tendency to form chains and rings with P-O-P bonds.Sony VAIO VGN-AW41XH/Q Battery

Many polyphosphates are known, including ATP. Polyphosphates arise by dehydration of hydrogen phosphates such as HPO42- and H2PO4-. For example, the industrially important trisodium triphosphate (also known as sodium tripolyphosphate, STPP) is produced industrially on a megatonne scale via this condensation reaction:Sony VAIO VGN-AW41ZF Battery

2 Na2[(HO)PO3] + Na[(HO)2PO2] ? Na5[O3P-O-P(O)2-O-PO3] + 2 H2O

Phosphorus pentoxide (P4O10) is the acid anhydride of phosphoric acid, but several intermediates are known between the two. This waxy white solid reacts vigorously with water.Sony VAIO VGN-AW41ZF/B Battery

With metal cations, phosphate forms a variety of salts. These solids are polymeric, featuring P-O-M linkages. When the metal cation has a charge of 2+ or 3+, the salts are generally insoluble, hence they exist as common minerals. Many phosphate salts are derived from hydrogen phosphate (HPO42-).Sony VAIO VGN-AW50DB/H Battery

PCl5 and PF5 are common compounds. Both are volatile and pale or colourless. The other two halides, PBr5 and PI5PI5 are unstable. The pentachloride and pentafluoride adopt trigonal bipyramid molecular geometry and are Lewis acids. With fluoride, PF5 forms PF6–, an anion that is isoelectronic with SF6. Sony VAIO VGN-AW51JGB Battery

The most important oxyhalide is phosphorus oxychloride (POCl3), which is tetrahedral.

Before extensive computer calculations were feasible, it was proposed that bonding in phosphorus(V) compounds involved dorbitals. It is now accepted that the bonding can be better explained by molecular orbital theory and involves only s- and p-orbitals on phosphorus.Sony VAIO VGN-AW52JGB Battery

Nitrides

Compounds of the formula (PNCl2)n exist mainly as rings such as the trimer hexachlorophosphazene. The phosphazenes arise by treatment of phosphorus pentachloride with ammonium chloride: PCl5 + NH4Cl ? 1/n (NPCl2)n + 4 HCl The chloride groups can be replaced by alkoxide (RO-) to give rise to a family of polymers with potentially useful properties.Sony VAIO VGN-AW53FB Battery

Sulfides

Phosphorus forms a wide range of sulfides, where phosphorus can be P(V), P(III) or other oxidation states. Most famous is the three-fold symmetric P4S3 used in strike-anywhere matches. P4S10 and P4O10 have analogous structures.Sony VAIO VGN-AW70B/Q Battery

Phosphorus(III) compounds

Phosphine (PH3) and its organic derivatives (PR3) are structural analogues with ammonia (NH3) but the angles at phosphorus are closer to 90° for phosphine and its organic derivatives. It is an ill-smelling, toxic compound. Phosphine is produced by hydrolysis of calcium phosphide, Ca3P2. Sony VAIO VGN-AW71JB Battery

Unlike ammonia, phosphine is oxidised by air. Phosphine is also far less basic than ammonia.

All four symmetrical trihalides are well known: gaseous PF3, the yellowish liquids PCl3 and PBr3, and the solid PI3. These materials are moisture sensitive, hydrolysing to give phosphorus acid. Sony VAIO VGN-AW72JB Battery

The trichloride, a common reagent, is produced by chlorination of white phosphorus:

P4 + 6 Cl2 ? 4 PCl3

The trifluoride is produced by from the trichloride by halide exchange. PF3 is toxic because it binds to haemoglobin.Sony VAIO VGN-AW73FB Battery

Phosphorus(III) oxide, P4O6 (also called tetraphosphorus hexoxide) is the anhydride of P(OH)3, the minor tautomer of phosphorous acid. The structure of P4O6 is like that of P4O10 less the terminal oxide groups.

Mixed oxyhalides and oxyhydrides of phosphorus(III) are almost unknown.Sony VAIO VGN-AW80NS Battery

Organophosphorus compounds

Compounds with P-C and P-O-C bonds are often classified as organophosphorus compounds. They are widely used commercially. The PCl3 serves as a source of P3+ in routes to organophosphorus(III) compounds. For example it is the precursor to triphenylphosphine:Sony VAIO VGN-AW80S Battery

PCl3 + 6 Na + 3 C6H5Cl ? P(C6H5)3 + 6 NaCl

Treatment of phosphorus trihalides with alcohols and phenols gives phosphites, e.g. triphenylphosphite:

PCl3 + 3 C6H5OH ? P(OC6H5)3 + 3 HCl

Similar reactions occur for phosphorus oxychloride, affording triphenylphosphate:

OPCl3 + 3 C6H5OH ? OP(OC6H5)3 + 3 HCl Sony VAIO VGN-AW80US Battery

Phosphorus(I) and phosphorus(II) compounds

These compounds generally feature P-P bonds.[8] Examples include catenated derivatives of phosphine and organophosphines. The highly flammable gas diphosphine (P2H4) is the first of a series of derivatives of this type. Diphosphine is an analogue of hydrazine. Compounds containing P=P double bonds have also been observed, although they are rare.Sony VAIO VGN-AW81DS Battery

Phosphides

The phosphide ion is P3-. Phosphides arise by reaction of metals with red phosphorus. Salts of P3- do not exist in solution and these derivatives are refractory, reflecting their high lattice energy. Illustrated by the behaviour calcium phosphide, many metal phosphides hydrolyse in water with release of phosphine:Sony VAIO VGN-AW81JS Battery

Ca3P2 + 6 H2O ? 2 PH3 + 3 Ca(OH)2

Schreibersite is a naturally occurring phosphide found in meteorites. Many polyphosphides are known such as derivatives of OsP2. These can be structurally complex ranging from Na3P7 and derivatives of P264-. Often these species adopt cage-like structures that resemble fragments of violet phosphorus.Sony VAIO VGN-AW81YS Battery

Spelling and etymology

The name Phosphorus in Ancient Greece was the name for the planet Venus and is derived from the Greek words (??? = light, ???? = carry), which roughly translates as light-bringer or light carrier. (In Greek mythology and tradition,Sony VAIO VGN-AW82DS Battery

Augerinus (????????? = morning star, in use until today), Hesperus or Hesperinus (???????? or ????????? or ??????????? = evening star, in use until today) and Eosphorus (???????? = dawnbearer, not in use for the planet after Christianity) are close homologues, and also associated with Phosphorus-the-planet).Sony VAIO VGN-AW82JS Battery

According to the Oxford English Dictionary, the correct spelling of the element is phosphorus. The word phosphorous is the adjectival form of the P3+ valence: so, just as sulfur forms sulfurous and sulfuric compounds, phosphorus forms phosphorouscompounds (e.g., phosphorous acid) and P5+ valence phosphoric compounds (e.g.,phosphoric acids and phosphates).Sony VAIO VGN-AW82YS Battery

History and discovery

The discovery of phosphorus is credited to the German alchemist Hennig Brand in 1669, although other chemists might have discovered phosphorus around the same time. Brand experimented with urine, which contains considerable quantities of dissolved phosphates from normal metabolism.Sony VAIO VGN-AW83FS Battery

Working in Hamburg, Brand attempted to create the fabled philosopher's stone through the distillation of some salts by evaporating urine, and in the process produced a white material that glowed in the dark and burned brilliantly. It was named phosphorus mirabilis ("miraculous bearer of light").Sony VAIO VGN-AW83GS Battery

His process originally involved letting urine stand for days until it gave off a terrible smell. Then he boiled it down to a paste, heated this paste to a high temperature, and led the vapours through water, where he hoped they would condense to gold. Instead, he obtained a white, waxy substance that glowed in the dark. Sony VAIO VGN-AW83HS Battery

Brand had discovered phosphorus, the first element discovered since antiquity. We now know that Brand produced ammonium sodium hydrogen phosphate, (NH4)NaHPO4. While the quantities were essentially correct (it took about 1,100 L of urine to make about 60 g of phosphorus), it was unnecessary to allow the urine to rot.Sony VAIO VGN-AW90NS Battery

Later scientists would discover that fresh urine yielded the same amount of phosphorus.

It was known from early times that the glow would persist for a time in a stoppered jar but then cease. Robert Boyle in the 1680s ascribed it to "debilitation" of the air; in fact, it is oxygen being consumed. By the 18th century, it was known that in pure oxygen, phosphorus does not glow at all;there is only a range ofpartial pressure at which it does.Sony VAIO VGN-AW90S Battery

Heat can be applied to drive the reaction at higher pressures.

In 1974, the glow was explained by R. J. van Zee and A. U. Khan. A reaction with oxygen takes place at the surface of the solid (or liquid) phosphorus, forming the short-lived molecules HPO and P2O2 that both emit visible light. Sony VAIO VGN-AW90US Battery

The reaction is slow and only very little of the intermediates are required to produce the luminescence, hence the extended time the glow continues in a stoppered jar.

Since that time, phosphors and phosphorescence were used loosely to describe substances that shine in the dark without burning.Sony VAIO VGN-AW91CDS Battery

However, as mentioned above, even though the term phosphorescence was originally coined as a term by analogy with the glow from oxidation of elemental phosphorus, is now reserved for another fundamentally different process—re-emission of light after illumination.Sony VAIO VGN-AW91CJS Battery

Brand at first tried to keep the method secret, but later sold the recipe for 200 thalers to D Krafft from Dresden, who could now make it as well, and toured much of Europe with it, including England, where he met with Robert Boyle. The secret that it was made from urine leaked out and first Johann Kunckel (1630–1703) in Sweden (1678) and later Boyle in London (1680) also managed to make phosphorus. Sony VAIO VGN-AW91CYS Battery

Boyle states that Krafft gave him no information as to the preparation of phosphorus other than that it was derived from "somewhat that belonged to the body of man". This gave Boyle a valuable clue, however, so that he, too, managed to make phosphorus, and published the method of its manufacture.Sony VAIO VGN-AW91DS Battery

Later he improved Brand's process by using sand in the reaction (still using urine as base material),

4 NaPO3 + 2 SiO2 + 10 C ? 2 Na2SiO3 + 10 CO + P4

Robert Boyle was the first to use phosphorus to ignite sulfur-tipped wooden splints, forerunners of our modern matches, in 1680.Sony VAIO VGN-AW91JS Battery

In 1769 Johan Gottlieb Gahn and Carl Wilhelm Scheele showed that calcium phosphate (Ca3(PO4)2) is found in bones, and they obtained phosphorus from bone ash. Antoine Lavoisier recognized phosphorus as an element in 1777. Bone ash was the major source of phosphorus until the 1840s. Sony VAIO VGN-AW91YS Battery

Phosphate rock, a mineral containing calcium phosphate, was first used in 1850 and following the introduction of the electric arc furnace in 1890, this became the only source of phosphorus. Phosphorus, phosphates and phosphoric acid are still obtained from phosphate rock. Phosphate rock is a major feedstock in the fertilizer industry.Sony VAIO VGN-AW92CDS Battery

White phosphorus was first made commercially, for the match industry in the 19th century, by distilling off phosphorus vapour from precipitated phosphates, mixed with ground coal or charcoal, which was heated in an iron pot, in retort. The precipitated phosphates were made from ground-up bones that had been de-greased and treated with strong acids. Sony VAIO VGN-AW92CJS Battery

Carbon monoxide and other flammable gases produced during the reduction process were burnt off in a flare stack. This process became obsolete when the submerged-arc furnace for phosphorus production was introduced to reduce phosphate rock. The electric furnace method allowed production to increase to the point where phosphorus could be used in weapons of war.Sony VAIO VGN-AW92CYS Battery

In World War I it was used in incendiaries, smoke screens and tracer bullets. A special incendiary bullet was developed to shoot at hydrogen-filled Zeppelins over Britain (hydrogen being highly flammable if it can be ignited). During World War II, Molotov cocktails of benzene and phosphorus were distributed in Britain to specially selected civilians within the British resistance operation, for defence;Sony VAIO VGN-AW92DS Battery

and phosphorus incendiary bombs were used in war on a large scale. Burning phosphorus is difficult to extinguish and if it splashes onto human skin it has horrific effects.

Early matches used white phosphorus in their composition, which was dangerous due to its toxicity. Sony VAIO VGN-AW92JS Battery

Murders, suicides and accidental poisonings resulted from its use. (An apocryphal tale tells of a woman attempting to murder her husband with white phosphorus in his food, which was detected by the stew giving off luminous steam). In addition, exposure to the vapours gave match workers a severe necrosis of the bones of the jaw, the infamous "phossy jaw". Sony VAIO VGN-AW92YS Battery

When a safe process for manufacturing red phosphorus was discovered, with its far lower flammability and toxicity, laws were enacted, under the Berne Convention (1906), requiring its adoption as a safer alternative for match manufacture.The toxicity of white phosphorus led to discontinuation of it use in matches.Sony VAIO VGN-AW93FS Battery

Ironically, the Allies used phosphorus incendiary bombs in World War II to destroy Hamburg, the place where the "miraculous bearer of light" was first discovered.

Fertiliser

The dominant application of phosphorus is in fertilisers, which provides phosphate as required for all life and is often a limiting nutrient for crops. Sony VAIO VGN-AW93GS Battery

Phosphorus, being an essential plant nutrient, finds its major use as a constituent of fertilizers for agriculture and farm production in the form of concentrated phosphoric acids, which can consist of 70% to 75% P2O5. Global demand for fertilisers led to large increase in phosphate (PO43–) production in the second half of the 20th century. Sony VAIO VGN-AW93HS Battery

Due to the essential nature of phosphorus to living organisms, the low solubility of natural phosphorus-containing compounds, and the slow natural cycle of phosphorus, the agricultural industry is heavily reliant on fertilisers that contain phosphate, mostly in the form of superphosphate of lime. Sony VAIO VGN-AW93ZFS Battery

Superphosphate of lime is a mixture of two phosphate salts, calcium dihydrogen phosphate Ca(H2PO4)2 and calcium sulfate dihydrate CaSO4·2H2O produced by the reaction of sulfuric acid and water with calcium phosphate.

Organophosphorus compounds

White phosphorus is widely used to make organophosphorus compounds, through the intermediates phosphorus chlorides and two phosphorus sulfides, phosphorus pentasulfide, and phosphorus sesquisulfide.Sony VAIO VGN-AW93ZGS Battery

Organophosphorus compounds have many applications, including in plasticizers, flame retardants, pesticides,extraction agents, and water treatment. in particular the herbicide glyphosate sold under the brand name Roundup.

Metallurgical aspects

Phosphorus is also an important component in steel production, in the making of phosphor bronze, and in many other related products. Sony VAIO VGN-AW93ZHS Battery

Phosphorus is added to metallic copper during its smelting process to react with oxygen present as an impurity in copper and to produce oxygen-free copper or phosphorus-containing copper (CuOFP) alloys with a higher thermal and electrical conductivity than normal copper.Sony VAIO VGN-BZ11EN Battery

Matches

Phosphorus-contained matches were first produced in 1830s and contained a mixture of white phosphorus, an oxygen-releasing compound (potassium chlorate, lead dioxide or some nitrate) and a binder in their heads. They were rather sensitive to storage conitions, toxic and unsafe, as they could be lit by striking on any rough surface. Sony VAIO VGN-BZ11MN Battery

Therefore, their production was gradually banned between 1872 and 1925 in different countries.The international Berne Convention, adopted in 1906, prohibited the use of white phosphorus in matches. As a consequence, the 'strike-anywhere' matches were gradually replaced by 'safety matches' where white phosphorus was substituted by phosphorus sesquisulfide (P4S3),Sony VAIO VGN-BZ11XN Battery

sulfur or antimony sulfide. Such matches are hard to ignite on an arbitrary surface and require a special strip. The strip contains red phosphorus which heats up upon striking, reacts with the oxygen-releasing compound in the head and ignites the flammable material of the head.Sony VAIO VGN-BZ12VN Battery

Water softening

Sodium tripolyphosphate made from phosphoric acid is used in laundry detergents in some countries, but banned for this use in others. It is useful for softening water to enhance the performance of the detergents and to prevent pipe/boiler tubecorrosion.Sony VAIO VGN-BZ12XN Battery

Niche applications

• Phosphates are utilized in the making of special glasses that are used for sodium lamps.
• Bone-ash, calcium phosphate, is used in the production of fine china. Sony VAIO VGN-BZ31VT Battery
• Phosphoric acid made from elemental phosphorus is used in food applications such as some soda beverages. The acid is also a starting point to make food grade phosphates. These include mono-calcium phosphate that is employed in baking powder and sodium tripolyphosphate and other sodium phosphates.Sony VAIO VGN-BZ31XT Battery
• Among other uses these are used to improve the characteristics of processed meat and cheese. Others are used in toothpaste.
• White phosphorus, called "WP" (slang term "Willie Peter") is used in military applications as incendiary bombs, for smoke-screening as smoke pots and smoke bombs, and in tracer ammunition. Sony VAIO VGN-BZ560 Battery
• It is also a part of an obsolete M34 White Phosphorus US hand grenade. This multipurpose grenade was mostly used for signalling, smoke screens and inflammation; it could also cause severe burns and had a psychological impact on the enemy.Sony VAIO VGN-BZ560N24 Battery
• In trace amounts, phosphorus is used as a dopant for n-type semiconductors.
• 32P and 33P are used as radioactive tracers in biochemical laboratories.
• Phosphate is a strong complexing agent for the hexavalent uranyl (UO22+) species and this is the reason why apatite and other natural phosphates can often be very rich in uranium.Sony VAIO VGN-BZ560N30 Battery
• Tributylphosphate is an organophosphate soluble in kerosene and used to extract uranium in the Purex process applied in the reprocessing of spent nuclear fuel.

Biological role

Inorganic phosphorus in the form of the phosphate PO43– is required for all known forms of life, playing a major role in biological molecules such as DNA and RNA where it forms part of the structural framework of these molecules.Sony VAIO VGN-BZ560P Battery

Living cells also use phosphate to transport cellular energy in the form of adenosine triphosphate (ATP). Nearly every cellular process that uses energy obtains it in the form of ATP. ATP is also important for phosphorylation, a key regulatory event in cells. Phospholipids are the main structural components of all cellular membranes. Calcium phosphate salts assist in stiffening bones.Sony VAIO VGN-BZ560P20 Battery

Living cells are defined by a membrane that separates it from its surroundings. Biological membranes are made from a phospholipid matrix and proteins, typically in the form of a bilayer. Phospholipids are derived from glycerol, such that two of the glycerol hydroxyl (OH) protons have been replaced with fatty acids as an ester, and the third hydroxyl proton has been replaced with phosphate bonded to another alcohol.Sony VAIO VGN-BZ560P22 Battery

An average adult human contains about 0.7 kg of phosphorus, about 85–90% of which is present in bones and teeth in the form of apatite, and the remainder in soft tissues and extracellular fluids (~1%). The phosphorus content increases from about 0.5 weight% in infancy to 0.65–1.1 weight% in adults. Sony VAIO VGN-BZ560P28 Battery

Average phosphorus concentration in the blood is about 0.4 g/L, about 70% of that is organic and 30% inorganic phosphates.A well-fed adult in the industrialized world consumes and excretes about 1–3 g of phosphorus per day, with consumption in the form of inorganic phosphate and phosphorus-containing biomolecules such as nucleic acids and phospholipids;Sony VAIO VGN-BZ560P30 Battery

and excretion almost exclusively in the form of phosphate ions such as H2PO4- and HPO42-. Only about 0.1% of body phosphate circulates in the blood, and this amount reflects the amount of phosphate available to soft tissue cells.

Bone and teeth enamel

The main component of bone is hydroxyapatite as well as amorphous forms of calcium phosphate, possibly including carbonate.Sony VAIO VGN-BZ560P34 Battery

Hydroxyapatite is the main component of tooth enamel. Water fluoridation enhances the resistance of teeth to decay by the partial conversion of this mineral to the still harder material called fluoroapatite:

Ca5(PO4)3OH + F- ? Ca5(PO4)3F + OH- Sony VAIO VGN-BZ561 Battery

Phosphorus deficiency

In medicine, low-phosphate syndromes are caused by malnutrition, by failure to absorb phosphate, and by metabolic syndromes that draw phosphate from the blood (such as re-feeding after malnutrition) or pass too much of it into the urine.Sony VAIO VGN-BZ561N20 Battery

All are characterized by hypophosphatemia, which is a condition of low levels of soluble phosphate levels in the blood serum, and therefore inside cells. Symptoms of hypophosphatemia include muscle and neurological dysfunction, and disruption of muscle and blood cells due to lack of ATP. Sony VAIO VGN-BZ561P20 Battery

Too much phosphate can lead to diarrhoea and calcification (hardening) of organs and soft tissue, and can interfere with the body's ability to use iron, calcium, magnesium, and zinc.

Phosphorus is an essential macromineral for plants, which is studied extensively in edaphology in order to understand plant uptake from soil systems.Sony VAIO VGN-BZ562P Battery

In ecologicalterms, phosphorus is often a limiting factor in many environments; i.e. the availability of phosphorus governs the rate of growth of many organisms. In ecosystems an excess of phosphorus can be problematic, especially in aquatic systems, resulting in eutrophication which sometimes lead to algal blooms.Sony VAIO VGN-BZ563P Battery

Food sources

The main food sources of phosphorus are kinds of food containing protein, for example, milk and meat. As a rule, if one holds a meal plan providing sufficient amount of protein and calcium then amount of phosphorus is also sufficient.Sony VAIO VGN-BZAAFS Battery

Precautions

Organic compounds of phosphorus form a wide class of materials, many are required for life, but some are extremely toxic. Fluorophosphate esters are among the most potent neurotoxins known. A wide range of organophosphorus compounds are used for their toxicity to certain organisms as pesticides(herbicides, insecticides, fungicides, etc.) and weaponised as nerve agents.Sony VAIO VGN-BZAAHS Battery

Most inorganic phosphates are relatively nontoxic and essential nutrients.

The white phosphorus allotrope presents a significant hazard because it ignites in air and produces phosphoric acid residue. Chronic white phosphorus poisoning leads to necrosis of the jaw called "phossy jaw". Sony VAIO VGN-BZAANS Battery

Ingestion of white phosphorus may cause a medical condition known as "Smoking Stool Syndrome".

Upon exposure to elemental phosphorus, in the past it was suggested to wash the affected area with 2% copper sulfate solution to form harmless compounds that can be washed away. Sony VAIO VGN-BZAAPS Battery

According to the recent US Navy's Treatment of Chemical Agent Casualties and Conventional Military Chemical Injuries: FM8-285: Part 2 Conventional Military Chemical Injuries, "Cupric (copper(II)) sulfate has been used by U.S. personnel in the past and is still being used by some nations. Sony VAIO VGN-CR11H/B Battery

However, copper sulfate is toxic and its use will be discontinued. Copper sulfate may produce kidney and cerebral toxicity as well as intravascular hemolysis."

The manual suggests instead "a bicarbonate solution to neutralize phosphoric acid, which will then allow removal of visible white phosphorus. Sony VAIO VGN-CR11S/L Battery

Particles often can be located by their emission of smoke when air strikes them, or by their phosphorescence in the dark. In dark surroundings, fragments are seen as luminescent spots. Promptly debride the burn if the patient's condition will permit removal of bits of WP (white phosphorus) that might be absorbed later and possibly produce systemic poisoning.Sony VAIO VGN-CR11S/P Battery

DO NOT apply oily-based ointments until it is certain that all WP has been removed. Following complete removal of the particles, treat the lesions as thermal burns."[note 1] As white phosphorus readily mixes with oils, any oily substances or ointments are not recommended until the area is thoroughly cleaned and all white phosphorus removed.Sony VAIO VGN-CR11S/W Battery

US DEA List I status

Phosphorus can reduce elemental iodine to hydroiodic acid, which is a reagent effective for reducing ephedrine or pseudoephedrine to methamphetamine. For this reason, red and white phosphorus were designated by the United States Drug Enforcement Administration as List I precursor chemicals under 21 CFR 1310.02 effective on November 17, 2001.Sony VAIO VGN-CR11Z/R Battery

As a result, in the United States, handlers of red or white phosphorus are subject to stringent regulatory controls.

Elemental phosphorus can exist in several allotropes; the most common of which are white and red solids. Solid violet and black allotropes are also known. Gaseous phosphorus exists as diphosphorus and atomic phosphorus.Sony VAIO VGN-CR120E/L Battery

White phosphorus, or yellow phosphorus, or simply tetraphosphorus (P4) exists as molecules made up of four atoms. Thetetrahedral arrangement results in ring strain and instability. The molecule is described as consisting of six single P–P bonds. Two different crystalline forms are known. Sony VAIO VGN-CR120E/P Battery

The ? form, which is stable under standard conditions, has a body-centered cubic crystal structure. It transforms reversibly into the ? form at 195.2 K. The ? form is believed to have a hexagonal crystal structure.

White phosphorus is a transparent waxy solid that quickly becomes yellow when exposed to light.Sony VAIO VGN-CR120E/R Battery

For this reason it is also called yellow phosphorus. It glows greenish in the dark (when exposed to oxygen), is highly flammable and pyrophoric (self-igniting) upon contact with air as well as toxic (causing severe liver damage on ingestion and phossy jaw from chronic ingestion or inhalation). Sony VAIO VGN-CR120E/W Battery

The odour of combustion of this form has a characteristic garlic smell, and samples are commonly coated with white "(di)phosphorus pentoxide", which consists of P4O10 tetrahedra with oxygen inserted between the phosphorus atoms and at their vertices. White phosphorus is only slightly soluble in water and, indeed, it can be stored under water. Sony VAIO VGN-CR125E/B Battery

It is, however, soluble in benzene, oils,carbon disulfide, and disulfur dichloride.

Production and applications

The white allotrope can be produced using several different methods. In one process, calcium phosphate, which is derived from phosphate rock, is heated in an electric or fuel-fired furnace in the presence of carbon and silica. Sony VAIO VGN-CR13/B Battery

Elemental phosphorus is then liberated as a vapour and can be collected under phosphoric acid.

White phosphorus has an appreciable vapour pressure at ordinary temperatures. The vapour density indicates that the vapour is composed of P4 molecules up to about 800 °C. Above that temperature, dissociation into P2 molecules occurs.Sony VAIO VGN-CR13/L Battery

It ignites spontaneously in air at about 50 °C, and at much lower temperatures if finely divided. This combustion gives phosphorus (V) oxide:

P4 + 5 O2 ? P4O10

Because of this property, white phosphorus is used as a weapon.Sony VAIO VGN-CR13/P Battery

Non-existence of cubic-P8

Although white phosphorus converts to thermodynamically more stable red allotrope, the formation of the cubic P8 is not observed in the condensed phase. Derivatives of this hypothetical molecule have, however, been prepared from phosphaalkynes.Sony VAIO VGN-CR13/R Battery

Red phosphorus

Red phosphorus may be formed by heating white phosphorus to 250 °C (482 °F) or by exposing white phosphorus to sunlight. Red phosphorus exists as an amorphous network. Upon further heating, the amorphous red phosphorus crystallizes. Sony VAIO VGN-CR13/W Battery

Red phosphorus does not ignite in air at temperatures below 240 °C, whereas white phosphorus ignites at about 30 °C. Red phosphorus can be converted to white phosphorus upon heating to 260 °C, as can be seen when one strikes a match.

It is a controlled substance (precursor) in Russia and much of the rest of the former Soviet Union, due to its use in illicit amphetamine production.Sony VAIO VGN-CR131E/L Battery

Hittorf's violet phosphorus

Monoclinic phosphorus, or violet phosphorus, is also known as Hittorf's Metallic Phosphorus.In 1865, Hittorf heated red phosphorus in a sealed tube at 530 °C. The upper part of the tube was kept at 444 °C. Brilliant opaque monoclinic, or rhombohedral, crystals sublime.Sony VAIO VGN-CR13G Battery

Violet phosphorus can also be prepared by dissolving white phosphorus in molten lead in a sealed tube at 500 °C for 18 hours. Upon slow cooling, Hittorf's allotrope crystallises out. The crystals can be revealed by dissolving the lead in dilutenitric acid followed by boiling in concentrated hydrochloric acid.Sony VAIO VGN-CR13G/B Battery

In 1865 Johann Wilhelm Hittorfdiscovered that when phosphorus was recrystallized from molten lead, a red/purple form is obtained. This purple form is sometimes known as Hittorf's phosphorus. In addition, a fibrous form exists with similar phosphorus cages. Below is shown a chain of phosphorus atoms which exhibits both the purple and fibrous forms.Sony VAIO VGN-CR13G/L Battery

Reactions of violet phosphorus

It does not ignite in air until heated to 300 °C, and it is insoluble in all solvents. It is not attacked by alkali and only slowly reacts with halogens. It can be oxidised by nitric acid to phosphoric acid.Sony VAIO VGN-CR13G/P Battery

If it is heated in an atmosphere of inert gas, for example nitrogen or carbon dioxide, it sublimes and the vapour condenses as white phosphorus. If, however, it is heated in a vacuum and the vapour condensed rapidly, violet phosphorus is obtained. It would appear that violet phosphorus is a polymer of high relative molecular mass, which on heating breaks down into P2 molecules.Sony VAIO VGN-CR13G/R Battery

On cooling, these would normally dimerize to give P4 molecules (i.e. white phosphorus) but, in vacuo, they link up again to form the polymeric violet allotrope.

Black phosphorus

Black phosphorus is the thermodynamically stable form of phosphorus at room temperature and pressure. Sony VAIO VGN-CR13G/W Battery

It is obtained by heating white phosphorus under high pressures (12,000 atmospheres). In appearance, properties and structure it is very like graphite, being black and flaky, a conductor of electricity, and having puckered sheets of linked atoms.

Black phosphorus has an orthorhombic structure and is the least reactive allotrope: a result of its lattice of interlinked six-membered rings. Sony VAIO VGN-CR13T/L Battery

Each atom is bonded to three other atoms. A recent synthesis of black phosphorus using metal salts as catalysts has been reported.

One of the forms of red/black phosphorus is a cubic solid.Sony VAIO VGN-CR13T/P Battery

Diphosphorus

The diphosphorus allotrope (P2) can be obtained normally only under extreme conditions (for example, from P4 at 1100 kelvin). Nevertheless, some advancements were obtained in generating the diatomic molecule in homogenous solution, under normal conditions with the use by some transition metal complexes (based on for example tungsten and niobium).Sony VAIO VGN-CR13T/R Battery

Diphosphorus is the gaseous form of phosphorus, and the thermodynamically stable form above 1200 °C and until 2000 °C. The dissociation of tetraphosphorus (P4) begins at lower temperature: the percentage of P2 at 800 °C is ? 1%. At temperatures about 2000 °C, the diphosphorus molecule begins to dissociate into atomic phosphorus.Sony VAIO VGN-CR13T/W Battery

Phosphorus nanorods

Phosphorus nanorods were synthesized as P?12 polymers in two modifications.

The red-brown phase differs from red phosphorus and is also stable in air for weeks. Electron microscope showed the red-brown form as having long, parallel nanorods with a diameter between 0.34 nm and 0.47 nm.Sony VAIO VGN-CR15/B Battery

Although phosphorus (P) has 24 isotopes from 24P to 47P, only one of these isotopes is stable 31P; as such, it is considered a monoisotopic element. The longest-lived radioactive isotopes are 33P with a half-life of 25.34 days and 32P with a half-life of 14.263 days. Sony VAIO VGN-CR150E/B Battery

All other have half-lives under 2.5 minutes, most under a second. The least stable is 25P with a half-life shorter than 30 nanoseconds—the half-life of 24P is unknown.

Standard atomic mass: 30.973762(2) u

Radioactive isotopes of phosphorus include: Sony VAIO VGN-CR190 Battery

• 32P; a beta-emitter (1.71 MeV) with a half-life of 14.3 days which is used routinely in life-science laboratories, primarily to produce radiolabeled DNA and RNAprobe, e.g. for use in Northern blots or Southern blots. Because the high energy beta particles produced penetrate skin and corneas,Sony VAIO VGN-CR190E/L Battery
• and because any 32P ingested, inhaled, or absorbed is readily incorporated into bone and nucleic acids, OSHA requires that a lab coat, disposable gloves, and safety glasses or goggles be worn when working with 32P, and that working directly over an open container be avoided in order to protect the eyes.Sony VAIO VGN-CR190E/P Battery
• Monitoring personal, clothing, and surface contamination is also required. In addition, due to the high energy of the beta particles, shielding this radiation with the normally used dense materials (e.g. lead), gives rise to secondary emission of X-rays via a process known as Bremsstrahlung, meaning braking radiation.Sony VAIO VGN-CR190E/R Battery
• Therefore shielding must be accomplished with low density materials, e.g. Plexiglas, Lucite, plastic, wood, or water.
• 33P; a beta-emitter (0.25 MeV) with a half-life of 25.4 days. It is used in life-science laboratories in applications in which lower energy beta emissions are advantageous such as DNA sequencing. Phosphorus-33 can be used to label nucleotides. Sony VAIO VGN-CR190E/W Battery
• It is less energetic than 32P, giving a better resolution. A disadvantage is its higher cost compared to 32P, as most of the bombarded 31P will have acquired only one neutron, while only some will have acquired two or more. Its maximum specific activity is 5118 Ci/mol.Sony VAIO VGN-CR19VN/B Battery

Phosphoric acid, also known as orthophosphoric acid or phosphoric(V) acid, is a mineral (inorganic) acid having thechemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way.Sony VAIO VGN-CR19XN/B Battery

The term phosphoric acid can also refer to a chemical orreagent consisting of phosphoric acids, usually orthophosphoric acid.

Orthophosphoric acid chemistry

Pure anhydrous phosphoric acid is a white solid that melts at 42.35 °C to form a colorless, viscous liquid.Sony VAIO VGN-CR20 Battery

Most people and even chemists refer to orthophosphoric acid as phosphoric acid, which is the IUPAC name for this compound. The prefix ortho is used to distinguish the acid from other phosphoric acids, called polyphosphoric acids two(ii). Orthophosphoric acid is a non-toxic, inorganic, rather weak triprotic acid, which, when pure, is a solid at room temperatureand pressure.Sony VAIO VGN-CR21/B Battery

The chemical structure of orthophosphoric acid is shown above in the data table. Orthophosphoric acid is a verypolar molecule; therefore it is highly soluble in water. The oxidation state of phosphorus (P) in ortho- and other phosphoric acids is +5; the oxidation state of all the oxygen atoms (O) is ?2 and all the hydrogen atoms (H) is +1. Sony VAIO VGN-CR21E/L Battery

Triprotic means that an orthophosphoric acid molecule can dissociate up to three times, giving up an H+ each time, which typically combines with awater molecule, H2O, as shown in these reactions:

H3PO4(s) + H2O(l) H3O+(aq) + H2PO4?(aq) Ka1= 7.25×10?3

H2PO4?(aq)+ H2O(l) H3O+(aq) + HPO42?(aq) Ka2= 6.31×10?8

HPO42?(aq)+ H2O(l) H3O+(aq) + PO43?(aq) Ka3= 3.98×10?13

The anion after the first dissociation, H2PO4?, is the dihydrogen phosphate anion. Sony VAIO VGN-CR21E/P Battery

The anion after the second dissociation, HPO42?, is the hydrogen phosphate anion. The anion after the third dissociation, PO43?, is the phosphate or orthophosphateanion. For each of the dissociation reactions shown above, there is a separate acid dissociation constant, called Ka1, Ka2, and Ka3 given at 25 °C.Sony VAIO VGN-CR21E/W Battery

Associated with these three dissociation constants are corresponding pKa1=2.12 , pKa2=7.21 , and pKa3=12.67 values at 25 °C. Even though all three hydrogen (H) atoms are equivalent on an orthophosphoric acid molecule, the successive Ka values differ since it is energetically less favorable to lose another H+ if one (or more) has already been lost and the molecule/ion is more negatively-charged.Sony VAIO VGN-CR21S/L Battery

Because the triprotic dissociation of orthophosphoric acid, the fact that its conjugate bases (the phosphates mentioned above) cover a wide pH range, and, because phosphoric acid/phosphate solutions are, in general, non-toxic, mixtures of these types of phosphates are often used as buffering agents or to make buffer solutions, where the desired pH depends on the proportions of the phosphates in the mixtures.Sony VAIO VGN-CR21S/P Battery

Similarly, the non-toxic, anion salts of triprotic organic citric acid are also often used to make buffers. Phosphates are found pervasively in biology, especially in the compounds derived from phosphorylated sugars, such as DNA, RNA, and adenosine triphosphate (ATP). There is a separate article on phosphate as an anion or its salts.Sony VAIO VGN-CR21S/W Battery

Upon heating orthophosphoric acid, condensation of the phosphoric units can be induced by driving off the water formed from condensation. When one molecule of water has been removed for each two molecules of phosphoric acid, the result ispyrophosphoric acid (H4P2O7). Sony VAIO VGN-CR21Z/N Battery

When an average of one molecule of water per phosphoric unit has been driven off, the resulting substance is a glassy solid having an empirical formula of HPO3 and is called metaphosphoric acid. Metaphosphoric acid is a singly anhydrous version of orthophosphoic acid and is sometimes used as a water- or moisture-absorbing reagent.Sony VAIO VGN-CR21Z/R Battery

Furtherdehydrating is very difficult, and can be accomplished only by means of an extremely strong desiccant (and not by heating alone). It produces phosphoric anhydride, which has an empirical formula P2O5, although an actual molecule has a chemical formula of P4O10. Phosphoric anhydride is a solid, which is very strongly moisture-absorbing and is used as a desiccant.Sony VAIO VGN-CR220E/R Battery

Composition and pH of a phosphoric acid aqueous solution

For a given total acid concentration [A] = [H3PO4] + [H2PO4?] + [HPO42?] + [PO43?] ([A] is the total number of moles of pure H3PO4which have been used to prepare 1 liter of solution), the composition of an aqueous solution of phosphoric acid can be calculated using the equilibrium equations associated with the three reactions described above together with the [H+][OH?] = 10?14 relation and the electrical neutrality equation. Sony VAIO VGN-CR23/B Battery

Possible concentrations of polyphosphoric molecules and ions is neglected. The system may be reduced to a fifth degree equation for [H+] which can be solved numerically, yielding:

[A] (mol/L)	pH	[H3PO4]/[A] (%)	[H2PO4?]/[A] (%)	[HPO42?]/[A] (%)	[PO43?]/[A] (%)
1	1.08	91.7	8.29	6.20×10?6	1.60×10?17
10?1	1.62	76.1	23.9	6.20×10?5	5.55×10?16
10?2	2.25	43.1	56.9	6.20×10?4	2.33×10?14
10?3	3.05	10.6	89.3	6.20×10?3	1.48×10?12
10?4	4.01	1.30	98.6	6.19×10?2	1.34×10?10
10?5	5.00	0.133	99.3	0.612	1.30×10?8
10?6	5.97	1.34×10?2	94.5	5.50	1.11×10?6
10?7	6.74	1.80×10?3	74.5	25.5	3.02×10?5
10?10	7.00	8.24×10?4	61.7	38.3	8.18×10?5

For large acid concentrations, the solution is mainly composed of H3PO4. For [A] = 10?2, the pH is close to pKa1, giving an equimolar mixture of H3PO4 and H2PO4?.Sony VAIO VGN-CR23/L Battery

For [A] below 10?3, the solution is mainly composed of H2PO4? with [HPO42?] becoming non negligible for very dilute solutions. [PO43?] is always negligible. Note that the above analysis does not take into account ion activity coefficients; as such, the pH and molarity of a real phosphoric acid solution may deviate substantially from the above values.Sony VAIO VGN-CR23/N Battery

Chemical reagent

Pure 75–85% aqueous solutions (the most common) are clear, colourless, odourless, non-volatile, rather viscous, syrupy liquids, but still pourable. Phosphoric acid is very commonly used as an aqueous solution of 85% phosphoric acid or H3PO4.Sony VAIO VGN-CR23/P Battery

Because it is a concentrated acid, an 85% solution can be corrosive, although nontoxic when diluted. Because of the high percentage of phosphoric acid in this reagent, at least some of the orthophosphoric acid is condensed into polyphosphoric acids in a temperature-dependent equilibrium, but, for the sake of labeling and simplicity, Sony VAIO VGN-CR23/R Battery

the 85% represents H3PO4 as if it were all orthophosphoric acid. Other percentages are possible too, even above 100%, where the phosphoric acids and water would be in an unspecified equilibrium, but the overall elemental mole content would be considered specified. Sony VAIO VGN-CR23/W Battery

When aqueous solutions of phosphoric acid and/or phosphate are dilute, they are in or will reach an equilibrium after a while where practically all the phosphoric/phosphate units are in the ortho- form.

Preparation of hydrogen halides

Phosphoric acid reacts with halides to form the corresponding hydrogen halide gas (steamy fumes are observed on warming the reaction mixture). This is a common practice for the laboratory preparation of hydrogen halides.Sony VAIO VGN-CR240E/B Battery

NaCl(s)	+ H3PO4(l) ? NaH2PO4(s)	+ HCl(g)
NaBr(s)	+ H3PO4(l) ? NaH2PO4(s)	+ HBr(g)
NaI(s)	+ H3PO4(l) ? NaH2PO4(s)	+ HI(g)

Rust removal

Phosphoric acid may be used as a "rust converter", by direct application to rusted iron, steel tools, or surfaces. The phosphoric acid converts reddish-browniron(III) oxide, Fe2O3 (rust) to black ferric phosphate, FePO4.Sony VAIO VGN-CR240N/B Battery

"Rust converter" is sometimes a greenish liquid suitable for dipping (in the same sort of acid bath as is used for pickling metal), but it is more often formulated as a gel, commonly called naval jelly. It is sometimes sold under other names, such as "rust remover" or "rust killer". As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces.Sony VAIO VGN-CR25G/N Battery

After treatment, the black ferric-phosphate coating can be scrubbed off, leaving a fresh metal surface. Multiple applications of phosphoric acid may be required to remove all rust. The black phosphate coating can also be left in place, where it will provide moderate further corrosion resistance (such protection is also provided by the superficially similar Parkerizing and blued electrochemical conversion coating processes).Sony VAIO VGN-CR290EAL Battery

Processed food use

Food-grade phosphoric acid (additive E338) is used to acidify foods and beverages such as various colas, but not without controversy regarding its health effects. It provides a tangy or sour taste and, being a mass-produced chemical, is available cheaply and in large quantities.Sony VAIO VGN-CR290EAN Battery

The low cost and bulk availability is unlike more expensive seasonings that give comparable flavors, such as citric acid which is obtainable from lemons and limes. However, most citric acid in the food industry is not extracted from citrus fruit, but fermented by Aspergillus niger mold from scrap molasses, waste starch hydrolysates and phosphoric acid.Sony VAIO VGN-CR290EAP Battery

Biological effects on bone calcium and kidney health

Phosphoric acid, used in many soft drinks (primarily cola), has been linked to lower bone density in epidemiological studies. For example, a study[2] using dual-energy X-ray absorptiometry rather than a questionnaire about breakage, provides reasonable evidence to support the theory that drinking cola results in lower bone density. Sony VAIO VGN-CR290EAR Battery

This study was published in the American Journal of Clinical Nutrition. A total of 1672 women and 1148 men were studied between 1996 and 2001. Dietary information was collected using a food frequency questionnaire that had specific questions about the number of servings of cola and other carbonated beverages and that also made a differentiation between regular, Sony VAIO VGN-CR290EAW Battery

caffeine-free, and diet drinks. The paper cites significant statistical evidence to show that women who consume cola daily have lower bone density. Total phosphorus intake was not significantly higher in daily cola consumers than in nonconsumers; however, the calcium-to-phosphorus ratios were lower.Sony VAIO VGN-CR29XN/B Battery

On the other hand, another study suggests that insufficient intake of phosphorus leads to lower bone density. The study does not examine the effect of phosphoric acid, which binds with magnesium and calcium in the digestive tract to form salts that are not absorbed, but rather studies general phosphorus intake.Sony VAIO VGN-CR305E/RC Battery

A clinical study by Heaney and Rafferty using calcium-balance methods found no impact of carbonated soft drinks containing phosphoric acid on calcium excretion. The study compared the impact of water, milk, and various soft drinks (two with caffeine and two without; Sony VAIO VGN-CR31S/D Battery

two with phosphoric acid and two with citric acid) on the calcium balance of 20- to 40-year-old women who customarily consumed ~3 or more cups (680 mL) of a carbonated soft drink per day. They found that, relative to water, only milk and the two caffeine-containing soft drinks increased urinary calcium, Sony VAIO VGN-CR323/W Battery

and that the calcium loss associated with the caffeinated soft drink consumption was about equal to that previously found for caffeine alone. Phosphoric acid without caffeine had no impact on urine calcium, nor did it augment the urinary calcium loss related to caffeine. Sony VAIO VGN-CR33 Battery

Because studies have shown that the effect of caffeine is compensated for by reduced calcium losses later in the day, Heaney and Rafferty concluded that the net effect of carbonated beverages—including those with caffeine and phosphoric acid—is negligible, and that the skeletal effects of carbonated soft drink consumption are likely due primarily to milk displacement.Sony VAIO VGN-CR382 Battery

Other chemicals such as caffeine (also a significant component of popular common cola drinks) were also suspected as possible contributors to low bone density, due to the known effect of caffeine on calciuria. One other study, involving 30 women over the course of a week, suggests that phosphoric acid in colas has no such effect, and postulates that caffeine has only a temporary effect, which is later reversed. Sony VAIO VGN-CR490EBL Battery

The authors of this study conclude that the skeletal effects of carbonated beverage consumption are likely due primarily to milk displacement (another possible confounding factor may be an association between high soft drink consumption and sedentary lifestyle).Sony VAIO VGN-CR490EBN Battery

Cola consumption has also been associated with chronic kidney disease and kidney stones through medical research. The preliminary results suggest that cola consumption may increase the risk of chronic kidney disease.Sony VAIO VGN-CR490EBP Battery

Medical use

Phosphoric acid is used in dentistry and orthodontics as an etching solution, to clean and roughen the surfaces of teeth where dental appliances or fillings will be placed. Phosphoric acid is also an ingredient in over-the-counter anti-nausea medications that also contain high levels of sugar (glucose and fructose). Sony VAIO VGN-CR490EBR Battery

This acid is also used in many teeth whiteners to eliminate plaque that may be on the teeth before application.

Preparation

Phosphoric acid can be prepared by three routes – the thermal process, the wet process and the dry kiln process.Sony VAIO VGN-CR490EBT Battery

Thermal phosphoric acid

This very pure phosphoric acid is obtained by burning elemental phosphorus to produce phosphorus pentoxide and dissolving the product in dilute phosphoric acid. This produces a very pure phosphoric acid, since most impurities present in the rock have been removed when extracting phosphorus from the rock in a furnace. Sony VAIO VGN-CR490EBW Battery

The end result is food-grade, thermal phosphoric acid; however, for critical applications, additional processing to remove arsenic compounds may be needed.

Elemental phosphorus is produced by an electric furnace. At a high temperature, a mixture of phosphate ore, silica and carbonaceous material (coke, coal etc...) produces calcium silicate, phosphorus gas and carbon monoxide. Sony VAIO VGN-CR50B/W Battery

The P and CO off-gases from this reaction are cooled under water to isolate solid phosphorus. Alternatively, the P and CO off-gases can be burned with air to produce phosphorus pentoxide and carbon dioxide.

Wet phosphoric acid

Wet process phosphoric acid is prepared by adding sulfuric acid to tricalcium phosphate rock, typically found in nature as apatite.

The reaction is: Sony VAIO VGN-CR51B/W Battery

Ca5(PO4)3X + 5 H2SO4 + 10 H2O ? 3 H3PO4 + 5 CaSO4·2H2O + HX

where X may include OH, F, Cl, and Br

The initial phosphoric acid solution may contain 23–33% P2O5, but can be concentrated by the evaporation of water to produce commercial- or merchant-gradephosphoric acid, which contains about 54% P2O5. Sony VAIO VGN-CR520E/J Battery

Further evaporation of water yields superphosphoric acid with a P2O5 concentration above 70%.

Digestion of the phosphate ore using sulfuric acid yields the insoluble calcium sulfate (gypsum), which is filtered and removed as phosphogypsum. Wet-process acid can be further purified by removing fluorine to produce animal-grade phosphoric acid, or by solvent extraction and arsenic removal to produce food-grade phosphoric acid.Sony VAIO VGN-CR52B/W Battery

Other applications

• Phosphoric acid is used as an external standard for phosphorus-31 Nuclear magnetic resonance (NMR).
• Phosphoric acid is used for high-performance liquid chromatography.
• Phosphoric acid is used as a chemical oxidizing agent for activated carbon production, as used in the Wentworth Process.Sony VAIO VGN-CR590EBL Battery

• Phosphoric acid is used as the electrolyte in phosphoric acid fuel cells.
• Phosphoric acid is used with distilled water (2–3 drops per gallon) as an electrolyte in oxyhydrogen (HHO) generators.
• Phosphoric acid is used as an electrolyte in copper electropolishing for burr removal and circuit board planarization.Sony VAIO VGN-CR590EBN Battery

• Phosphoric acid is used as a flux by hobbyists (such as model railroaders) as an aid to soldering.
• In compound semiconductor processing, phosphoric acid is a common wet etching agent: for example, in combination with hydrogen peroxide and water it is used to etch InGaAs selective to InP.Sony VAIO VGN-CR590EBP Battery
• Hot phosphoric acid is used in microfabrication to etch silicon nitride (Si3N4). It is highly selective in etching Si3N4 instead of SiO2, silicon dioxide.
• Phosphoric acid is used as a cleaner by construction trades to remove mineral deposits, cementitious smears, and hard water stains.Sony VAIO VGN-CR590EBR Battery
• Phosphoric acid is also used as a chelant in some household cleaners aimed at similar cleaning tasks.

• Phosphoric acid is also used in hydroponics pH solutions to lower the pH of nutrient solutions. While other types of acids can be used, phosphorus is a nutrient used by plants, especially during flowering, making phosphoric acid particularly desirable.
• Phosphoric acid is used as a pH adjuster in cosmetics and skin-care products.Sony VAIO VGN-CR590EBT Battery
• Phosphoric acid can be used as a dispersing agent in detergents and leather treatment.
• Phosphoric acid can be used as an additive to stabilize acidic aqueous solutions within a wanted and specified pH range
• Phosphoric acid is the ingredient that provides acidity to Coca-Cola and Pepsi sodas.Sony VAIO VGN-CR590EBW Battery

Organophosphorus compounds are degradable organic compounds containing carbon–phosphorus bonds (thus excluding from phosphate and phosphite esters, which lack such kind of bonding), used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Sony VAIO VGN-CR60B/L Battery

Organophosphorus chemistry is the corresponding science of the properties and reactivity of organophosphorus compounds. Phosphorus shares group 5 in the periodic table with nitrogen and phosphorus compounds and nitrogen compounds are somewhat related.Sony VAIO VGN-CR60B/P Battery

The definition of organophosphorus compounds is variable, which can lead to confusion. In industrial and environmental chemistry, an organophosphorus compound need contain only an organic substituent, but need not have a direct P-C bond. Thus most pesticides, e.g., malathion, are often included in this class of compounds.Sony VAIO VGN-CR60B/R Battery

Phosphorus can adopt a variety of oxidation states, and it is general to classify organophosphorus compounds based on their being derivatives of phosphorus(V) vs phosphorus(III), which are the predominant classes of compounds. In a descriptive but only intermittently used nomenclature, phosphorus compounds are identified by their coordination number ? and their valency ?. In this system, a phosphine is a ?3?3 compound.Sony VAIO VGN-CR61B/L Battery

Phosphate esters have the general structure P(=O)(OR)3 feature P(V). Such species are of technological importance as flame retardant agents, and plasticizers. Lacking a P?C bond, these compounds are in the technical sense not organophosphorus compounds but esters of phosphoric acid. Sony VAIO VGN-CR61B/N Battery

Many derivatives are found in nature, such as phosphatidylcholine. Phosphate ester are synthesized by alcoholysis of phosphorus oxychloride. A variety of mixed amido-alkoxo derivatives are known, one medically significant example being the anti-cancer drug cyclophosphamide. Sony VAIO VGN-CR61B/P Battery

Also derivatives containing the thiophosphoryl group (P=S) include the pesticidemalathion. The organophosphates prepared on the largest scale are the zinc dithiophosphates, as additives for motor oil. Several million kilograms of thiscoordination complex are produced annually by the reaction of phosphorus pentasulfide with alcohols.Sony VAIO VGN-CR61B/R Battery

Phosphonates are esters of phosphonic acid and have the general formula RP(=O)(OR')2. Phosphonates have many technical applications, a well-known member beingGlyphosate, better known as Roundup. With the formula (HO)2P(O)CH2NHCH2CO2H, this derivative of glycine is one of the most widely used herbicides. Sony VAIO VGN-CR62B/L Battery

Bisphosphonatesare a class of drugs to treat osteoporosis. The nerve gas agent Sarin, containing both C–P and F–P bonds, is a phosphonate.

Phosphinates feature two P–C bonds, with the general formula R2P(=O)(OR'). A commercially significant member is the herbicide Glufosinate. Similar to Glyphosate mentioned above, it has the structure CH3P(O)(OH)CH2CH2CH(NH2)CO2H.Sony VAIO VGN-CR62B/N Battery

The Michaelis–Arbuzov reaction is the main method for the synthesis of these compounds. For example, dimethylmethylphosphonate (see figure above) arises from the rearrangement of trimethylphosphite, which is catalyzed by methyl iodide. Sony VAIO VGN-CR62B/P Battery

In the Horner–Wadsworth–Emmons reaction and the Seyferth–Gilbert homologation, phosphonates are used in reactions with carbonyl compounds. The Kabachnik–Fields reaction is a method for the preparation of aminophosphonates. These compounds contain a very inert bond between phosphorus and carbon. Sony VAIO VGN-CR62B/R Battery

Consequently, they hydrolyze to give phosphonic and phosphinic acid derivatives, but not phosphate.

Phosphine oxides, imides, and chalcogenides

Phosphine oxides (designation ?3?3) have the general structure R3P=O with formal oxidation state V. Phosphine oxides form hydrogen bonds and some are therefore soluble in water. Sony VAIO VGN-CR70B/W Battery

The P=O bond is very polar with a dipole moment of 4.51 D for triphenylphosphine oxide.

Compounds related to phosphine oxides are the imides (R3PNR') and related chalcogenides (R3PE, where E = S, Se, Te). These compounds are some of the most thermally stable organophosphorus compounds, but few are useful in significant amounts.Sony VAIO VGN-CR71B/W Battery

Phosphonium salts and phosphoranes

Compounds with the formula [PR4+]X- comprise the phosphonium salts. These species are tetrahedral phosphorus(V) compounds. From the commercial perspective, the most important member is tetrakis(hydroxymethyl)phosphonium chloride, [P(CH2OH)4]Cl, which is used as a fire retardant in textiles.Sony VAIO VGN-CR72B/W Battery

Approximately 2M kg are produced annually of the chloride and the related sulfate.[4] They are generated by the reaction of phosphine with formaldehyde in the presence of the mineral acid:

PH3 + HX + 4 CH2O ? [P(CH2OH)4+]X-

A variety of phosphonium salts can be prepared by alkylation and arylation of organophosphines:Sony VAIO VGN-CR90HS Battery

PR3 + R'X ? [PR3R'+]X-

The methylation of triphenylphosphine is the first step in the preparation of the Wittig reagent.

The parent phosphorane (?5?5) is PH5, which is unknown. Related compounds containing both halide and organic substituents on phosphorus are fairly common. Those with five organic substituents are rare, although P(C6H5)5 is known, being derived from P(C6H5)4+ by reaction with phenyllithium.Sony VAIO VGN-CR90NS Battery

Phosphorus ylides are unsaturated phosphoranes, known as Wittig reagents, e.g. CH2P(C6H5)3. These compounds feature tetrahedral phosphorus(V) and are considered relatives of phosphine oxides. They also are derived from phosphonium salts, but by deprotonation not alkylation.Sony VAIO VGN-CR90S Battery

Comparison of phosphines and amines

The phosphorus atom in phosphines has a formal oxidation state ?3 (?3?3) and are the phosphorus analogues of amines. Like amines, phosphines have a trigonal pyramidal molecular geometry although often with smaller C-E-C angles (E = N, P), at least in the absence of steric effects.Sony VAIO VGN-CR92HS Battery

The C-P-C bond angle is 98.6° for trimethylphosphine increasing to 109.7° when the methyl groups are replaced by tert-butyl groups. When used as ligands, the steric bulk of tertiary phosphines is evaluated by their cone angle. The barrier to inversion is also much higher than in amines for a process like nitrogen inversion to occur, Sony VAIO VGN-CR92NS Battery

and therefore phosphines with three different substituents can be resolved into thermally stable optical isomers. Phosphines are often less basic than corresponding amines, for instance the phosphonium ion itself has a pKa of ?14 compared to 9.21 for the ammonium ion; trimethylphosphonium has a pKa of 8.65 compared to 9.76 for trimethylamine. Sony VAIO VGN-CR92S Battery

However, triphenylphosphine (pKa 2.73) is more basic than triphenylamine (pKa ?5), mainly because the lone pair of the nitrogen in NPh3 is partially delocalized into the three phenyl rings. Whereas the lone pair on nitrogen is delocalized in pyrrole, the lone pair on phosphorus atom in the phosphorus equivalent of pyrrole (phosphole) is not. Sony VAIO VGN-CS118E/Q Battery

The reactivity of phosphines matches that of amines with regard to nucleophilicity in the formation of phosphonium salts with the general structure PR4+X?. This property is used in the Appel reaction for converting alcohols to alkyl halides. Phosphines are easily oxidized to the corresponding phosphine oxides, whereas amine oxides are less readily generated.Sony VAIO VGN-CS118E/R Battery

In part for this reason, phosphines are very rarely encountered in nature.

Synthetic routes

From the commercial perspective, the most important phosphine is triphenylphosphine, several million kilograms being produced annually. It is prepared from the reaction of chlorobenzene, PCl3, and sodium.Sony VAIO VGN-CS118E/W Battery

Phosphines of a more specialized nature are usually prepared by other routes. Phosphorus halides undergo Nucleophilic displacement by organometallic reagents such as Grignard reagents. Conversely, some syntheses entail nucleophilic displacement of phosphide anion equivalents ("R2P-") by aryl- and alkyl halides.Sony VAIO VGN-CS11S/P Battery

Primary (RPH2) and secondary phosphines (RRPH and R2PH) add to alkenes in presence of a strong base (e.g., KOH in DMSO).Markovnikov's rules apply. Similar reactions occur involving alkynes.[6] Base is not required for electron-deficient alkenes (e.g., derivatives of acrylonitrile) and alkynes.Sony VAIO VGN-CS11S/Q Battery

Under free-radical conditions the P-H bonds of primary and secondary phosphines add across alkenes. Such reactions proceed with anti-Markovnikov regiochemistry. AIBNor organic peroxides are used as initiators. Tertiary phosphine oxides and sulfides can be reduced with chlorosilanes and other reagents.Sony VAIO VGN-CS11S/W Battery

Reactions

The main reaction types of phosphines are as nucleophiles and bases. Their nucleophilicity is evidence by their reactions with alkyl halides to phosphonium salts. Phosphines are nucleophilic catalysts in the dimerization of enones in various reactions in organic synthesis, e.g. the Rauhut–Currier reaction.Sony VAIO VGN-CS11Z/R Battery

Phosphines are reducing agents, as illustrated in the Staudinger reduction converting azides to amines and in the Mitsunobu reaction for converting alcohols into esters. In these processes, the phosphine is oxidized to the phosphine oxide.Sony VAIO VGN-CS120J/P Battery

Phosphines have also been found to reduce activated carbonyl groups for instance the reduction of an ?-keto ester to an ?-hydroxy ester in scheme 2.In the proposed reaction mechanism, the first proton is on loan from the methyl group in trimethylphosphine (triphenylphosphine does not react).Sony VAIO VGN-CS120J/Q Battery,Sony VAIO VGN-CS120J/R Battery,Sony VAIO VGN-CS190JTB Battery,Sony VAIO VGN-CS190JTP Battery,Sony VAIO VGN-CS190JTQ Battery,Sony VAIO VGN-CS190JTR Battery