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|Atomic Number:||15||Atomic Symbol:||P|
|Atomic Weight:||30.97376||Electron Configuration:||2-8-5|
|Melting Point:||44.1oC||Boiling Point:||280oC|
|Uses:||In matches, fertilizers etc.|
History(Gr. phosphoros, light bearing; ancient name for the planet
Venus when apearing before sunrise). Hennig Brand of Germany discovered
phosphorus in 1669 by preparing it from urine.
PropertiesPhosphorus exists in four or more allotropic forms: white (or
yellow), red, and black (or violet). Ordinary phosphorus is a waxy white solid;
when pure it is colorless and transparent. White phosphorus has two
modifications: alpha and beta with a transition temperature at -3.8C.
It is insoluble in water, but soluble in carbon disulfide. It takes fire
spontaneously in air, burning to the pentoxide.
SourcesNever found free in nature, it is widely distributed in
combination with minerals. Phosphate rock, which contains the mineral apatite,
an impure tri-calcium phosphate, is an important source of the element. Large
deposits are found in Russia, in Morocco, and in Florida, Tennessee, Utah,
Idaho, and elsewhere.
HandlingIt is very poisonous, 50 mg constituting an approximate fatal
dose. Exposure to white phosphorus should not exceed 0.1 mg/m^3 (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 250C, 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 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 17C, and is used in the manufacture
of safety matches, pyrotechnics, pesticides, incendiary shells, smoke bombs,
tracer bullets, etc.
ProductionWhite phosphorus may be made by several methods. By one
process, tri-calcium 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
phosphoric acid, an important compound in making super-phosphate fertilizers.
UsesIn 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 used to create fine chinaware and to produce
mono-calcium 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
Phosphorus is also an essential ingredient of all cell protoplasm, nervous
tissue, and bones.