Vanadium
|
 |
Atomic Number: |
23 |
|
Melting
Point: |
1910 ºC |
| Atomic Symbol: |
V |
|
Boiling
Point: |
3407 ºC |
| Atomic Weight: |
50.9414
amu |
|
Density: |
6110
kg/m 3
|
| Atomic
Radius: |
132.1 pm
|
|
Oxidation States: |
5, 4, 3, 2 |
| Covalent Radius: |
125
pm |
|
Electron
Configuration: |
[Ar]4s23d3 |
| van der Waals
Radius: |
-- |
|
State of Matter: |
solid |
History
(Scandinavian goddess, Vanadis) Vanadium was first discovered by del Rio in
1801. Unfortunately, a French chemist incorrectly declared that del Rio's new
element was only impure
chromium. Del Rio
thought himself to be mistaken and accepted the French chemists' statement.
The element was rediscovered in 1830 by Sefstrom, who named the element in
honor of the Scandinavian goddess, Vanadis, because of its beautiful
multicolored compounds. It was isolated in nearly pure form by Roscoe, who in
1867 reduced the chloride with
hydrogen.
Vanadium of 99.3 to 99.8% purity was not produced until 1922.
Properties
Pure vanadium is a bright white metal, and is soft and ductile. It has good
corrosion resistance to alkalis, sulfuric and hydrochloric acid, and salt water,
but the metal oxidizes readily above 660oC.
It is intermediate between the metals and the non-metals, having both basic and
acid properties.
The metal has good structural strength and a low fission neutron cross
section, making it useful in nuclear applications.
Sources
Vanadium is never found unbound in nature. It is however, found in
about 65 different minerals among which are carnotite, roscoelite, vanadinite,
and patronite, important sources of the metal. Vanadium is also found in
phosphate rock and certain iron ores, and is present in some crude oils in the
form of organic complexes. It is also found in small percentages in meteorites.
Commercial production from petroleum ash holds promise as an important source
of the element. High-purity ductile vanadium can be obtained by reduction of
vanadium trichloride with
magnesium or with
magnesium-sodium mixtures.
Much of the vanadium metal being produced is now made by
calcium reduction
of V2O5
in a pressure vessel, an adaption of a process developed by McKechnie and
Seybair.
Uses
Vanadium is used in producing rust resistant and high speed tool steels.
Alloys of vanadium include special stainless steel used in surgical instruments
and tools. When mixed with aluminum in titanium alloys, vanadium is used in jet
engines and high-speed airframes. Vanadium steel alloys are used in axles,
crankshafts, gears, and other critical componenets. It is an important carbide
stabilizer in making steels.
About 80% of the vanadium now produced is used as ferrovanadium or as a steel
additive. Vanadium foil is used as a bonding agent in cladding titanium to
steel.
Vanadium also finds use in nuclear applications because of its low fission
neutron cross section.
In biology, a vanadium atom is an essential component of some
enzymes, particularly the vanadium nitrogenase used by some
nitrogen-fixing microorganisms. Vanadium is essential for
electron transfer chain of ascidians, or sea squirts. The
concentration of vanadium in their bodies is one million times
higher than the concentration of vanadium in the water around
them. Rats and chickens are also known to require vanadium in
very small amounts and deficiencies result in reduced growth and
impaired reproduction.
Administration of oxovanadium compounds
has been shown to alleviate diabetes mellitus symptoms in
certain animal models and humans. Much like the chromium effect
on sugar metabolism, the mechanism of this effect is unknown.
Vanadium compounds are used as catalysts in producing maleic anhydride and
sulfuric acid. Vanadium pentoxide (V2O5) is used as a
catalyst, dye and color-fixer. It is also used to produce a superconductive
magnet with a field of 175,000 gauss. Glass coated with vanadium dioxide (VO2)
can block infrared radiation (and not visible light) at some specific
temperature.
Isotopes
Natural vanadium is a mixture of two isotopes, 50V (0.24%) and
51V (99.76%). 50V is slightly radioactive, having a
half-life of > 3.9 x 1017
years. Nine other unstable isotopes are recognized. 15 radioisotopes have been
characterized with the most stable being V-50 with a half-life of 1.4E17 years.
Vanadium does include 1 meta state.
Hazards
Vanadium and its compounds are toxic and should be handled with care.
Vanadium compounds act chiefly as an irritant to the conjunctiva and respiratory
tract. Acute and chronic exposure can give rise to conjunctivitis, rhinitis,
reversible irritant of the respiratory tract, and to bronchitis, broncho spasms,
and asthma-like diseases in more severe cases. The maximum allowable
concentration of V2O5
dust in air is about 0.05 (8-hour time-weighted average - 40-hour week).