| Identification | More | [Name]
Phosphorus | [CAS]
7723-14-0 | [Synonyms]
PHOSPHOROUS ICP STANDARD
PHOSPHOROUS RED
PHOSPHORUS
PHOSPHORUS, AAS STANDARD SOLUTION
PHOSPHORUS ATOMIC ABSORPTION STANDARD
PHOSPHORUS ATOMIC ABSORPTION STANDARD SOLUTION
PHOSPHORUS ICP/DCP STANDARD
PHOSPHORUS ICP STANDARD
PHOSPHORUS, OIL BASED STANDARD SOLUTION
PHOSPHORUS, ORGANIC AAS STANDARD SOLUTION
PHOSPHORUS PLASMA EMISSION SPECTROSCOPY STANDARD
PHOSPHORUS PLASMA EMISSION STANDARD
PHOSPHORUS, PLASMA STANDARD SOLUTION
PHOSPHORUS, RED
PHOSPHORUS SINGLE ELEMENT STANDARD
PHOSPHORUS STANDARD
PHOSPHORUS STANDARD, (AS PHOSPHATE)
PHOSPHORUS STANDARD SOLUTION
Phosphorus white
PHOSPHORUS, YELLOW | [EINECS(EC#)]
231-768-7 | [Molecular Formula]
H3P | [MDL Number]
MFCD00133771 | [Molecular Weight]
34 | [MOL File]
7723-14-0.mol |
| Chemical Properties | Back Directory | [Description]
White or yellow white phosphorus is a yellow waxy or colourless, transparent, volatile crystalline
solid, waxy appearance with a garlic-like odour. On exposure to light, it darkens and
ignites in air. It is also called yellow phosphorus colour because of impurities. White phosphorus
does not occur naturally but is manufactured from phosphate rocks. It is insoluble
in water, slightly soluble in benzene, ethanol, and chloroform, and is soluble in carbon disulphide. White phosphorus reacts rapidly with oxygen, easily catching fire at temperatures
10°C–15°C above room temperature. White phosphorus is used by the military in various
types of ammunition and to produce smoke for concealing troop movements and identifying
targets. It is also used by industry to produce phosphoric acid and other chemicals for use
in fertilisers, food additives, and cleaning compounds. Small amounts of white phosphorus
were used in the past in pesticides and fireworks.White phosphorus is used mainly for producing phosphoric acid and other chemicals.
These chemicals are used to make fertilisers, additives in foods and drinks, cleaning compounds,
and other products. In the military, white phosphorus is used in ammunitions such
as mortar and artillery shells, and grenades. | [Appearance]
reddish-brown powder | [Melting point ]
280 °C (white)(lit.)
| [Boiling point ]
280℃ | [density ]
2.34 g/mL at 25 °C(lit.)
| [vapor density ]
0.02 (vs air)
| [vapor pressure ]
0.03 mm Hg ( 21 °C)
| [Fp ]
30°C | [storage temp. ]
2-8°C | [solubility ]
insoluble | [form ]
powder (red)
| [color ]
Red-brown | [Specific Gravity]
2.34 | [Odor]
Acrid fumes when exposed to air | [PH]
3 at 37℃ and 500-10000mg/L | [Stability:]
Stable. Highly flammable. Incompatible with strong oxidizing agents, strong bases. Light and heat sensitive. | [Resistivity]
10 μΩ-cm, 20°C | [Water Solubility ]
insoluble | [Merck ]
13,7433 | [Dielectric constant]
4.1（34℃） | [Exposure limits]
ACGIH: TWA 2 ppm; STEL 4 ppm
OSHA: TWA 2 ppm(5 mg/m3)
NIOSH: IDLH 25 ppm; TWA 2 ppm(5 mg/m3); STEL 4 ppm(10 mg/m3) | [History]
Discovered in 1669 by Brand, who prepared it from urine.
Phosphorus exists in four or more allotropic forms: white
(or yellow), red, and black (or violet). White phosphorus has
two modifications: α and β with a transition temperature at
–3.8°C. Never found free in nature, it is widely distributed
in combination with minerals. Twenty-one isotopes of phosphorus
are recognized. Phosphate rock, which contains the
mineral apatite, an impure tricalcium phosphate, is an important
source of the element. Large deposits are found in
the Russia, China, Morocco, and in Florida, Tennessee, Utah,
Idaho, and elsewhere. Phosphorus in an essential ingredient
of all cell protoplasm, nervous tissue, and bones. Ordinary
phosphorus is a waxy white solid; when pure it is colorless
and transparent. It is insoluble in water, but soluble in carbon
disulfide. It takes fire spontaneously in air, burning to
the pentoxide. It is very poisonous, 50 mg constituting an approximate
fatal dose. Exposure to white phosphorus should
not exceed 0.1 mg/m3 (8-hour time-weighted average — 40-
hour work week). White phosphorus should be kept under
water, as it is dangerously reactive in air, and it should be handled
with forceps, as contact with the skin may cause severe
burns. When exposed to sunlight or when heated in its own
vapor to 250°C, it is converted to the red variety, which does
not phosphoresce in air as does the white variety. This form
does not ignite spontaneously and it is not as dangerous as
white phosphorus. It should, however, be handled with care
as it does convert to the white form at some temperatures and
it emits highly toxic fumes of the oxides of phosphorus when
heated. The red modification is fairly stable, sublimes with a
vapor pressure of 1 atm at 417°C, and is used in the manufacture
of safety matches, pyrotechnics, pesticides, incendiary
shells, smoke bombs, tracer bullets, etc. White phosphorus
may be made by several methods. By one process, tricalcium
phosphate, the essential ingredient of phosphate rock,
is heated in the presence of carbon and silica in an electric
furnace or fuel-fired furnace. Elementary phosphorus is liberated
as vapor and may be collected under water. If desired,
the phosphorus vapor and carbon monoxide produced by the
reaction can be oxidized at once in the presence of moisture
to produce phosphoric acid, an important compound in making
super-phosphate fertilizers. In recent years, concentrated
phosphoric acids, which may contain as much as 70 to 75%
P2O5 content, have become of great importance to agriculture
and farm production. World-wide demand for fertilizers has
caused record phosphate production. Phosphates are used
in the production of special glasses, such as those used for
sodium lamps. Bone-ash, calcium phosphate, is also used to
produce fine chinaware and to produce monocalcium phosphate
used in baking powder. Phosphorus is also important
in the production of steels, phosphor bronze, and many other
products. Trisodium phosphate is important as a cleaning
agent, as a water softener, and for preventing boiler scale and
corrosion of pipes and boiler tubes. Organic compounds of
phosphorus are important. Amorphous (red) phosphorus
costs about $70/kg (99%). | [CAS DataBase Reference]
7723-14-0(CAS DataBase Reference) | [NIST Chemistry Reference]
Phosphorus atom(7723-14-0) | [EPA Substance Registry System]
7723-14-0(EPA Substance) |
| Safety Data | Back Directory | [Hazard Codes ]
F,N,C,T+ | [Risk Statements ]
R11:Highly Flammable.
R16:Explosive when mixed with oxidizing substances.
R52/53:Harmful to aquatic organisms, may cause long-term adverse effects in the aquatic environment .
R50:Very Toxic to aquatic organisms.
R35:Causes severe burns.
R26/28:Very Toxic by inhalation and if swallowed .
R17:Spontaneously flammable in air. | [Safety Statements ]
S7:Keep container tightly closed .
S43:In case of fire, use ... (indicate in the space the precise type of fire-fighting equipment. If water increases the risk add-Never use water) .
S61:Avoid release to the environment. Refer to special instructions safety data sheet .
S45:In case of accident or if you feel unwell, seek medical advice immediately (show label where possible) .
S38:In case of insufficient ventilation, wear suitable respiratory equipment .
S26:In case of contact with eyes, rinse immediately with plenty of water and seek medical advice .
S5:Keep contents under ... (appropriate liquid to be specified by the manufacturer) .
S27:Take off immediately all contaminated clothing .
S6:Keep under ... (inert gas to be specified by the manufacturer) . | [RIDADR ]
UN 1338 4.1/PG 3
| [WGK Germany ]
2
| [RTECS ]
TH3495000
| [F ]
10-21 | [Autoignition Temperature]
White phosphorus: 29 °C
Red phosphorus: 260 °C | [TSCA ]
Yes | [HazardClass ]
4.1 | [PackingGroup ]
III | [HS Code ]
28047000 | [Safety Profile]
Human poison by ingestion. Experimental poison by ingestion and subcutaneous routes. Experimental reproductive effects. Human systemic effects by ingestion: cardiomyopathy, cyanosis, nausea or vomiting, sweating. Toxic quantities have an acute effect on the liver and can cause severe eye damage. Inhalation can cause photophobia with myosis, dilation of the pupils, retinal hemorrhage, congestion of the blood vessels, and, rarely, an optic neuritis. Chronic exposure by inhalation or ingestion can cause anemia, gastrointestinal effects, and brittleness of the long bones, leading to spontaneous fractures. The most common symptom, however, of chronic phosphorus poisoning is necrosis of the jaw (phossyjaw). More reactive than red phosphorus. Dangerous fire hazard when exposed to heat, flame, or by chemical reaction with oxidtzers. Igmtes spontaneously in air. Very reactive. If combustion occurs in a confined space, it will remove the oxygen and cause asphyxiation. Dangerous explosion hazard by chemical reaction with: alkaline hydroxides, NH4NO3, SbF5, Ba(BrO3)2, Be, Bl3, Ca(BrO3)2, Mg(BrO3)2, K(BrO3), NaBrO3, Zn(BrO3)2, Br2, halogens, BrF3, BrN3, (chlorates of Ba, Ca, Mg, K, Na, Zn), (iodates of Ba, Ca, Mg, K, Na, Zn), Ce, Cs,CsHC2, CS3N, (charcoal + air), ClO2, (Ch + heptane), Cl0, ClF3, ClO3, chlorosulfonic acid, Cr03, Cr(OCl)2, Cu, NCl, IBr, ICl, IFj, Fe, La, PbO2, Li, LizC2, Li6CS, Mg(ClO4)z, Mn, HgO, HgNO3, Nd, Ni, nitrates, NBr, N02, NBr3, NCh, NOF, FN02, O2, performic acid, Pt, K, KOH, K3N, I(Mn04, K2O2, Rb, RbHC2, Se2Cl2, SeOCl2, SeOF2, SeF4, AgNO3, Ag20, Na, Na2C2, NaClO2, NaOH, Na2O2, S, so3, H2SO4, Th, VOCl2, Zr, peroxyformic acid, chloro sulfuric acid, halogen azides, hexalithum dtshcide. Can react vigorously with oxidtzing materials. To fight fire, use water. Used in fertilizers, tracer bullets, incendiaries manufacturing, rat poison, and gas analysis. When heated to decomposition it emits highly toxic fumes of POx. See also PHOSPHORUS (red). | [Hazardous Substances Data]
7723-14-0(Hazardous Substances Data) | [Toxicity]
LD50 oral (rat) 3 mg/kg
PEL (OSHA) 0.1 mg/m3
TLV-TWA (ACGIH) 0.02 ppm (0.1 mg/m3) | [IDLA]
5 mg/m3 |
| Hazard Information | Back Directory | [General Description]
A white or yellow colored semi-liquid. Transported at high temperatures. Insoluble in water and denser than water. Contact may cause burns to skin, eyes, and mucous membranes. May be toxic by ingestion, inhalation and skin absorption. May ignite upon exposure to air. Used to make other chemicals. | [Reactivity Profile]
WHITE PHOSPHORUS reacts with air (fire, acidic solution); sulfur and oxidants (fire, explosion). Bromine trifluoride reacts similarly with arsenic, boron, bromine, iodine, phosphorus, and sulfur [Mellor 2:113. 1946-47]. Bromoazide explodes on contact with antimony, arsenic, phosphorus, silver foil, or sodium. Red phosphorus reacts in the cold with selenium oxychloride evolving light and heat; white phosphorus reacts explosively [Mellor 10:906. 1946-47]. When thorium is heated with phosphorus, they unite with incandescence [Svenska Akad. 1829. p. 1]. | [Air & Water Reactions]
When exposed to air emits a green light and gives off white fumes. Ignites at 30°C in moist air, higher temperatures are required for ignition in dry air [Merck 11th ed. 1989]. The reactivity of phosphorus with oxygen or air depends on the allotrope of phosphorus involved and the conditions of contact, white (yellow) phosphorus being by far more reactive. White phosphorus readily ignites in air if warmed, finely divided, or under conditions where the slow oxidative isotherm cannot be dissipated. Contact with finely divided charcoal or lampblack promotes ignition, probably by the absorbed oxygen. Contact with amalgamated aluminum also promotes ignition [Mellor 1940 and 1971]. | [Health Hazard]
Fire will produce irritating, corrosive and/or toxic gases. TOXIC; ingestion of substance or inhalation of decomposition products will cause severe injury or death. Contact with substance may cause severe burns to skin and eyes. Some effects may be experienced due to skin absorption. Runoff from fire control may be corrosive and/or toxic and cause pollution. | [Fire Hazard]
Extremely flammable; will ignite itself if exposed to air. Burns rapidly, releasing dense, white, irritating fumes. Substance may be transported in a molten form. May re-ignite after fire is extinguished. Corrosive substances in contact with metals may produce flammable hydrogen gas. Containers may explode when heated. | [Chemical Properties]
reddish-brown powder | [Chemical Properties]
Yellow or white
phosphorus ignites spontaneously in air at 34 °C. It should
be stored under water. Under this condition, however, it
may form phosphoric acid. Stainless steel containers
should be used to hold the corrosive material. White
phosphorus fires can be controlled by using water or sand
or by excluding air. | [Isotopes]
There are a 23 isotopes of phosphorus, ranging from P-24 to P-46, with halflivesthat range from a few nanoseconds to about two and half minutes. The one stableisotope is phosphorus-31, which accounts for 100% of the natural phosphorus on Earth. | [Origin of Name]
Its name is derived from the Greek word phosphoros, which means
“bringer of light” or “light bearing.” | [Occurrence]
Phosphorus is the 12th most abundant element. It makes up about 0.1% of the Earth’s crust.Phosphorous occurs in nature in several forms, mostly as phosphates. The most commonsource is phosphate rock [Ca3(PO4)2] and a mineral called “apatite.” Phosphorus is found inall animal bones and teeth and in most living tissue. Phosphorous nodules are found on theocean floor along with manganese nodules.Most commercial phosphorus is produced in electric furnaces where the phosphate-richminerals are heated to drive off the phosphorus as a gas, which is then condensed under water.Another process uses sulfuric acid to remove the phosphorus. | [Characteristics]
White phosphorus occurs in nature in phosphate rock. It is insoluble in water and alcoholand will ignite spontaneously in air. It exhibits what is known as phosphorescence; that is, itglows in the dark at room temperature. White phosphorus is poisonous and must be storedunder water.
Red phosphorus is less reactive than the white variety. It is not poisonous, but largeamounts can explode. It is used in fireworks and matches.
Black phosphorus is the only one of the three that will conduct electricity; white and redare poor conductors. Black phosphorus has no significant commercial uses. | [Uses]
Phosphorus is an essential constituent of plants and animals, being present in deoxyribonucleic acid (DNA), bones, teeth and other components of high biological importance. Phosphorus does not occur in its elemental state in nature, as it readily oxidises and therefore is deposited as phosphate rock. The remaining elements of group 15 are mostly obtained from minerals, but can also be found in their elemental form in the earth’s crust.
| [Uses]
It is used to make safety matches, incendiary shells,andsmokebombs;inpyrotechnics;and in the manufacture of fertilizers, pesticides, phosphoric acid, and phosphorus halides. | [Uses]
The allotropes and compounds of phosphorus have many important uses and are anessential commercial commodity. Phosphorus is essential to all living tissue, both plant andanimal. It is the main element in the compound adenosine triphosphate (ATP), the mainenergy source for living things.
Red phosphors are formed either by heating white phosphorus or by exposing white phosphorusto sunlight. It is quite different from the explosive white phosphorus. For instance,when scratched on a surface, the heads of safety matches made of red phosphorus convert backto white phosphorus and ignite due to the heat of the slight friction of the match on a roughsurface. Red phosphorus is also used in fireworks, smoke bombs, and pesticides and to makephosphoric acid, electroluminescent paints, and fertilizers.
Most elemental phosphorus is used to manufacture phosphoric acid, a solid that is usedto produce triple-phosphate fertilizers. Some soils require large amounts of phosphorus toproduce a viable crop.
Sodium tripolyphosphate is the main phosphate found in detergents. It acts as a watersoftener and counteracts the elements that are responsible for “hard water” while at the sametime making the detergent a more effective cleaner. | [Definition]
phosphorus: Symbol P. A nonmetallicelement belonging togroup 15 (formerly VB) of the periodictable; a.n. 15; r.a.m. 30.9738; r.d.1.82 (white), 2.34 (red); m.p. 44.1°C(α-white); b.p. 280°C (α-white). It occursin various phosphate rocks,from which it is extracted by heatingwith carbon (coke) and silicon(IV)oxide in an electric furnace (1500°C).Calcium silicate and carbon monoxideare also produced. Phosphorushas a number of allotropic forms.The α-white form consists of P4 tetrahedra(there is also a β-white formstable below –77°C). If α-white phosphorusis dissolved in lead andheated at 500°C a violet form is obtained.Red phosphorus, which is acombination of violet and whitephosphorus, is obtained by heatingα-white phosphorus at 250°C with airexcluded. There is also a black allotrope,which has a graphite-likestructure, made by heating whitephosphorus at 300°C with a mercurycatalyst. The element is highly reactive.It forms metal phosphides andcovalently bonded phosphorus(III)and phosphorus(V) compounds. Phosphorusis an essential element forliving organisms. It is an importantconstituent of tissues (especiallybones and teeth) and of cells, beingrequired for the formation of nucleic acids and energy-carrying molecules(e.g. ATP) and also involved in variousmetabolic reactions. The elementwas discovered by Hennig Brand(c. 1630–92) in 1669. | [Production Methods]
Elemental phosphorous is produced as a by-product or
intermediate in the production of phosphate fertilizer. Environmental
contamination with phosphorus results from its
manufacture into phosphorus compounds and during the
transport and use of these compounds. In the manufacturing
process, phosphate rock containing the mineral apatite (tricalcium
phosphate) is heated, and elementary phosphorus is
liberated as a vapor. Phosphorus is used to manufacture
explosives, incendiaries, smoke bombs, chemicals, rodenticides,
phosphor bronze, and fertilizer. The use of phosphate
fertilizers results in increased level of nutrients in fresh water and is a major source of environmental pollution
problem.
Phosphorus exists in several allotropic forms: white (or
yellow), red, and black (or violet). The last is of no industrial
importance. Elemental yellow phosphorus extracted from
bone was used to make “strike anywhere” matches. In 1845,
the occupational disease “phossy jaw,” a jaw bone necrosis,
was recognized in workers who manufactured such matches.
A prohibitive tax imposed in 1912 on matches made from
yellow phosphorus led to the use of less toxic materials, red
phosphorus and phosphorus sesquisulfide. The United States
appears to have lagged behind European countries in that
signatories of the Berne Convention of 1906 agreed not to
manufacture or import matches made with yellow phosphorus.
Occasional injuries continued to result from using
yellow phosphorus to manufacture fireworks until 1926,
when an agreement was reached to discontinue using yellow
phosphorus for this purpose.
The world production of elemental phosphorus exceeds
1,000,000 metric ton. It is manufactured either in electric or
blast furnaces. Both depend on silica as a flux for the
calcium present in the phosphate rock. Almost all of the
phosphorus produced is converted into phosphoric acid or
other phosphorus compounds.
Red phosphorus does not ignite spontaneously but
may be ignited by friction, static electricity, heating, or
oxidizing agents. Handling it in an aqueous solution helps
prevent fires. | [Hazard]
Many of the compounds of phosphorus are extremely dangerous, both as fire hazardsand as deadly poisons to the nervous system of humans and animals. Some of the poisonouscompounds (PClx) can be absorbed by the skin as well as inhaled or ingested. Flushing withwater is the only way to stop the burning of white phosphorus on the skin, but water doesnot affect the combustion of some phosphorus compounds. Although red phosphorus is notas dangerous or poisonous as white phosphorus, merely applying some frictional heating willinduce the red allotrope to change back to the explosive white allotrope (the striking of a safetymatch is an example).
Some of the main types of poisonous gases used in warfare have a phosphorus base. Manycountries stockpile these gases, but, by agreement, the supplies are being reduced. | [Flammability and Explosibility]
White phosphorus ignites spontaneously upon contact with air, producing an
irritating, dense white smoke of phosphorus oxides. Use water to extinguish
phosphorus fires.
Red phosphorus is a flammable solid but does not ignite spontaneously on exposure
to air. At high temperatures (-300 °C), red phosphorus is converted to the white form. | [Agricultural Uses]
Phosphorus (P) is an important nutrient for plants. It
is a non-metallic element having an atomic number
15. It belongs to Group 15 of the Periodic Table
. The use of phosphorus is as high as one tenth
of nitrogen.
Most plants contain phosphorus in concentrations
varying from 0.1 to 0.4%, which are considerably lower
than for potassium and nitrogen in plants. Phosphorus is
an essential part of nucleoproteins in cell nuclei which
control the cell division and the DNA molecules, the
latter transmitting heredity to living organisms.
Phosphorus also plays an important role in (a) stimulating
early root growth, (b) hastening plant maturity, (c)
transforming energy within the cells, and (d) developing
and ripening the fruit and the seed. Phosphorus is rightly
called the key to life, as it is directly involved in most life
processes.
Relations between phosphorus and N, Cu, Fe, Mn
and Zn are well known. Ratios of 3: 1 of N to P and 200: 1
of P to Zn are considered critical for addressing nutrient
deficiency in plants. The ratio of nitrogen to phosphorus
(N:P) serves as a Diagnosis and Recommendation
Integrated System (DRIS) norm for interpreting results
of plant analysis.
Soils have low total phosphate content and hence such
soils provide low supplies of available phosphate (400 to
2000 kg/ha) to plants because mineral phosphate forms
are not readily soluble. Plants absorb phosphorus as
H2PO4-; and HPO42- ions. On average, a soil solution
contains about 0.05 ppm phosphorus which varies from
soil to soil. This amount of phosphorus is adequate for
plants, as its concentration varies from 0.003 to 0.3 ppm
depending on the crop. For instance, maximum corn
yields are obtained at 0.01 ppm of the solutionphosphorus,
while the incorporation of solution
phosphorus in the case of wheat is only marginally more.
Soil phosphorus occurs in both organic and inorganic
forms. Plants differ in their ability to compete for soil
phosphorus at the growth stage when they need it most.
Young plants rapidly absorb phosphorus and accumulate
75 % of their requirement when the crop produces 25 % of
its dry weight. Winter wheat absorbs about 70% of
phosphorus between tillering and flowering. For corn,
the peak phosphorus demand is during the initial three
weeks of the growing season. | [storage]
Work with
white phosphorus should be conducted in a fume hood to prevent exposure by
inhalation, and splash goggles and impermeable gloves should be worn at all times
to prevent eye and skin contact. Phosphorus should be stored under water in
secondary containers in areas separate from oxidizing agents and other incompatible
substances. | [Purification Methods]
Purify white phosphorus by melting it under dilute H2SO4—dichromate (possible carcinogen) mixture and allow to stand for several days in the dark at room temperature. It remains liquid, and the initial milky appearance due to insoluble, oxidisable material gradually disappears. The phosphorus can then be distilled under vacuum in the dark [Holmes Trans Faraday Soc 58 1916 1962]. It sublimes in vacuo. Other methods of purification include extraction with dry CS2 followed by evaporation of the solvent, or washing with 6M HNO3, then H2O, and drying under vacuum. It ignites in air at ~50o, or by friction if dry. Store and cut it under H2O . POISONOUS. | [Toxicity evaluation]
Phosphorus is an oxidizing agent that, when exposed to air, may
burn spontaneously. Thus, direct contact may result in both
thermal and chemical burns. Second- and third-degree burns
can be seen at the point of contact. When absorbed, phosphorus
acts as a cellular poison by uncoupling oxidative phosphorylation.
Red phosphorus is not considered to be potentially toxic
as it is insoluble, nonvolatile, and unabsorbable. | [Incompatibilities]
White phosphorus reacts with a number of substances to form explosive mixtures.
For example, dangerous explosion hazards are produced upon reaction of
phosphorus with many oxidizing agents, including chlorates, bromates, and many
nitrates, with chlorine, bromine, peracids, organic peroxides, chromium trioxide, and
potassium permanganate, with alkaline metal hydroxides (phosphine gas is
liberated), and with sulfur, sulfuric acid, and many metals, including the alkali
metals, copper, and iron.
Red phosphorus is much less reactive than the white allotrope but may ignite or react
explosively with strong oxidizing agents. | [Waste Disposal]
Excess phosphorus and waste material containing this substance should be placed in
an appropriate container, clearly labeled, and handled according to your institution's
waste disposal guidelines. |
| Questions And Answer | Back Directory | [Outline]
Elemental phosphorus was discovered in 1669 by Hennig Brand. About two hundred years later James Readman developed a process for phosphorus recovery from phosphatic rocks using an electric furnace.
Phosphorus is one of the most widely distributed elements on earth. It is found as phosphate salts in nearly all igneous rocks and in sedimentary deposits and sea beds. Phosphorus occurs in more than three hundred minerals, usually associated with Ca, Mg, Fe, Sr, Al, Na, and several other metals, and with anions such as silicates, sulfates, oxides, hydroxides, and halides. Phosphorus is an essential element present in all living matter and is vital in biological and ecological processes. It occurs in DNA and other nucleic acids, and in bones.
Phosphorus is used in pyrotechnics, smoke bombs, incendiary shells, and safety matches. It also is used in organic syntheses, manufacture of phosphoric acid, phosphorus trichloride, phosphine, and other compounds.
| [Physical Properties]
Elemental phosphorus in solid phase exists in three major allotropic forms: (1)white or yellow phosphorus that may occur in alpha or beta modification, (2) red phosphorus, and (3) black phosphorus.
White phosphorus is a white, soft, wax-like transparent mass which often acquires a yellow appearance due to impurities, especially traces of red phosphorus. It has a garlic-like odor. It is made up of cubic crystals, has a density 1.82 g/cm3, and melts at 44.1°C to a colorless or yellowish liquid. X-ray diffraction studies and 31P-NMR analysis indicate tetrahedral P4 molecules with an interatomic distance of 2.21Å , and the molecules are able to rotate freely in the crystals. When cooled below –76.9°C, the cubic alpha form converts to a hexagonal beta modification with a density 1.88 g/cm3. The beta form, unlike the alpha form, does not rotate freely in the crystal but has a fixed orientation of P4 molecules in the lattice.
Red phosphorus is obtained from white phosphorus by heating at 230 to 240°C, allowing complete conversion to occur in about 48 hours. Conversion is catalyzed by sulfur, iodine, and selenium. The red allotrope also slowly deposits from liquid phosphorus or from a solution of white phosphorus, the rate and yield depending on catalysts, temperature, light, and other factors. Red phosphorus exhibits various modifications. Three important ones are an amorphous form at ordinary temperatures and two crystalline modifications which include a triclinic form and a hexagonal or a tetragonal form that may prevail at higher temperatures. There also are a few more modifications, all of which may coexist, accounting for variability in physical properties of red phosphorus. The triclinic variety of red phosphorus is the most stable of all allotropes of phosphorus at ordinary temperatures. Red phosphorus possesses a density of 2.0 to 2.31 g/cm3 and melts at 590°C.
Black phosphorus is the third major allotropic form of phosphorus. It occurs in two forms, one is an amorphous modification having a laminar structure similar to graphite and the other is an orthorhombic crystalline form. The density of black phosphorus may vary between 2.20 to 2.69 g/cm3. Black phosphorus is obtained from white phosphorus by heating the latter at 220°C under an extremely high pressure of about 10,000 atm.
When solid phosphorus of any form—white, red, or black—is melted, it forms the same liquid phosphorus. This liquid has a density of 1.74 g/cm3 and viscosity 1.69 centipoise at 50°C. Liquid phosphorus boils at 280.5°C. Upon cooling, liquid phosphorus solidifies to only white phosphorus. Liquid phosphorus and its vapors consist of tetrahedral P4 molecules. The vapors, on rapid condensation, convert to white phosphorus.
While white and red phosphorus have high electrical resistivity, the black variety has a low resistivity of 0.71 ohm-cm at 0°C. Solubility also varies widely. White phosphorus is soluble in a number of organic solvents. It is very highly soluble in carbon disulfide, about 400 g/100 g solvent at 0°C and moderately soluble in benzene (~3.59 g/100g at 25°C) and exhibits lower solubility in ether (~1.5g/100g at 25°C). Red and black phosphorus are insoluble in organic solvents. White phosphorus is a flammable solid, igniting spontaneously in air at 35°C. Red and black phosphorus are nonflammable. The latter is difficult to ignite.
| [Production]
White phosphorus usually is obtained by heating some form of calcium phosphate with quartz and coke, usually in an electric furnace. The reactions may be written in two steps as follows:
Ca3(PO4)2 + 3SiO2 → 3CaSiO3 + P2O5
P2O5 + 5C → 2P + 5 CO
In commercial scale, white phosphorus is manufactured mostly from the mineral fluorapatite by heating with silica and coke in an electric-arc or blast furnace at a temperature of 1,200 to 1,500°C. An overall reaction may be represented in the following equation.
4Ca5F(PO4)3 + 18SiO2 + 30C → 18CaO • SiO2 • 2CaF2 + 30CO↑ + 3P4↑
(slag) White phosphorus also can be produced by a wet process using phosphoric acid, a process that was practiced historically in commercial production. In this method the starting material, phosphoric acid, usually is prepared in large vats by reacting phosphate rock with sulfuric acid:
Ca5F(PO4)3 + 5H2SO4 + 10H2O → 3H3PO4 + 5CaSO4 • 10H2O + HF
Phosphoric acid is filtered out of the mixture. It is then mixed with coke, charcoal or sawdust; dried; charred; and finally heated to white heat in a fireclay retort:
H3PO4 + 16C → P4 + 6H2 + 16CO
The vapor is condensed to obtain white phosphorus.
As stated earlier, all other forms of phosphorus can be made from white phosphorus. Thus, heating white phosphorus first at 260°C for a few hours and then at 350°C gives red phosphorus. The conversion is exothermic and can become explosive in the presence of iodine as a catalyst. When a solution of white phosphorus in carbon disulfide or phosphorus tribromide is irradiated the scarlet red variety is obtained.
Black phosphorus allotrope is produced by heating white phosphorus at 220°C under 12,000 atm pressure. The conversion is initially slow, but can became fast and explosive after an induction period.
White phosphorus is stored under water as it ignites in air. It may be cut into appropriate sizes only under water.
| [Reactions]
Reactivity of white phosphorus is much greater than red or black phosphorus. Black phosphorus is the least reactive of all phosphorus allotropes. White phosphorus ignites in air spontaneously. When placed on a paper, the paper catches fire after a short delay. It catches fire at about 35°C. At room temperature white phosphorus glows in the dark on exposure to air emitting faint green light. Such chemiluminescence is attributed to the oxidation of P4 molecules in the vapor phase in contact with the surface of solid phosphorus:
P4(g) + 5O2(g) → P4O10(s) + light
The mechanism involves a complicated oxidative process that occurs only at certain partial pressures of oxygen and not in pure oxygen at atmospheric pressure, nor in vacuum.
Red phosphorus ignites when struck with a hammer blow or when heated at 260°C. Black phosphorus ignites in contact with flame. White phosphorus reacts spontaneously with halogens at ordinary temperatures forming phosphorus trihalides. However, in excess halogen the product is phosphorus pentahalide:
P4(s) + 6Cl2(g) → 4PCl3 (l)
P4 (s) + 10Cl2 (g) → 4PCl5 (s)
White phosphorus reacts with sulfur on warming forming phosphorus trisulfide:
P4(s) + 6S(s) → 2P2S3 (s)
White phosphorus reacts with strong aqueous alkali solution forming hypophosphite with evolution of phosphine, PH3:
P4 + 3KOH + 3H2O → 3KH2PO2 + PH3 ↑
P4(s) + 6Cl2(g) → 4PCl3 (l)
P4 (s) + 10Cl2 (g) → 4PCl5 (s)
White phosphorus reacts with sulfur on warming forming phosphorus trisulfide:
P4(s) + 6S(s) → 2P2S3 (s)
White phosphorus reacts with strong aqueous alkali solution forming hypophosphite with evolution of phosphine, PH3:
P4 + 3KOH + 3H2O → 3KH2PO2 + PH3 ↑
P4 + 6Ca → 2Ca3P2
Reactions with alkali metals occur under warm conditions producing the corresponding metal phosphides:
P4 + 12Na → 4Na3P
| [Hazards]
White phosphorus is a highly toxic substance, both an acute and chronic toxicant. Chronic exposure to it’s vapors can cause “phossy jaw;” necrosis of the jaw. Other symptoms are bronchopneumonia, bone changes, anemia and weight loss, Ingestion can cause nausea, vomiting, abdominal pain, diarrhea and coma. Skin contact can cause severe burns. In the eye it damages vision. Red phosphorus is much less toxic than its white allotrope. Its fumes, when burned, are highly irritating. White phosphorus is a flammable solid, igniting spontaneously when exposed to air.
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