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Encyclopedia :
V :
VA :
VAN :
Vanadium |
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Vanadium
Vanadium is a chemical element in the periodic table that has the symbol V and atomic number 23. A rare, soft and ductile element, vanadium is found combined in certain minerals and is used mainly to produce certain alloys. Notable characteristicsVanadium is a soft and ductile, bright white metal. It has good resistance to corrosion by alkalis, sulfuric and hydrochloric acid. It oxidizes readily at about 933 K. Vanadium has good structural strength and a low fission neutron cross section, making it useful in nuclear applications. Although definitely a metal, it shares with Chromium and Manganese the property of having valency oxides with acid properties. Common oxidation states of vanadium include +2, +3, +4 and +5. A popular experiment with ammonium vanadate (NH4VO3), reducing the compound with zinc metal, can demonstrate colorimetrically all four of these vanadium oxidation states. A +1 oxidation state is also rarely seen. ApplicationsApproximately 80% of vanadium produced is used as ferrovanadium or as a steel additive. Other uses; HistoryVanadium (Scandinavian goddess, Vanadis) was originally discovered by Andrés Manuel del Río (a Spanish mineralogist) at Mexico City in 1801, who called it "brown lead" (now named vanadinite). Through experimentation, he saw that the colors it exhibited were reminiscent of chromium, so he named the element panchromium. He later renamed this compound erythronium, since most of the salts turned red when heated. 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 statement of the French chemist. In 1831, Sefström of Sweden rediscovered vanadium in a new oxide he found while working with some iron ores and later that same year Friedrich Wöhler confirmed del Rio's earlier work. Metallic vanadium was isolated by Henry Enfield Roscoe in 1867, who reduced the vanadium chloride (VCl3) with hydrogen. The name vanadium comes from Vanadis, a goddess in Scandinavian mythology, because the element has beautiful multicolored chemical compounds. Biological roleIn biology, a vanadium atom is an essential component of some enzymes, particularly the vanadium nitrogenase used by some nitrogen-fixing microorganisms. Vanadium is essential to ascidianss or sea squirtss in Vanadium Chromagen Proteins. The concentration of vanadium in their blood is more than 100 times higher than the concentration of vanadium in the seawater 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. OccurrenceVanadium is never found unbound in nature but it does occur in about 65 different minerals among which are patronite (VS4), vanadinite ]Pb5(VO4)3Cl[], and carnotite K2(UOO2)2(VO4)2.3H2O. Vanadium is also present in bauxite, and in carbon containing deposits such as crude oil, coal, oil shale and tar sands. The spectra of vanadium has also been detected in light from the sun and some other stars. Much of the vanadium metal being produced is now made by calcium reduction of V2O5 in a pressure vessel. Vanadium is usually recovered as a by-product or co-product, and so world resources of the element are not really indicative of available supply. CompoundsVanadium pentoxide (V2O5) is used as a catalyst, dye and color-fixer. It is extremely toxic if inhaled, and dangerous for the environment. Vanadyl sulfate (VOSO4), also called vanadium (IV) sulfate oxide hydrate, is used as a relatively controversial dietary supplement, primarily for increasing insulin levels and body-building. Whether it works for the latter purpose has not been proven, and there is some evidence that athletes who take it are merely experiencing a placebo effect. It is toxic in high doses. IsotopesNaturally occurring vanadium is composed of 1 stable isotope; V-51. 15 radioisotopes have been characterized with the most stable being V-50 with a half-life of 1.4E17 years, V-49 with a half-life of 330 days, and V-48 with a half-life of 15.9735 days. All of the remaining radioactive isotopes have half-lifes that are less than 1 hour and the majority of these have half lifes that are less than 10 seconds. This element also has 1 meta state. The isotopes of vanadium range in atomic weight from 43.981 amu (V-43) to 59.959 amu (V-59). The primary decay mode before the most abundant stable isotope, V-51, is electron capture and the primary mode after is beta decay. The primary decay products before V-51 are element 22 (titanium) isotopes and the primary products after are element 24 (chromium) isotopes. PrecautionsPowdered metallic vanadium is a fire hazard, and unless known otherwise, all vanadium compounds should be considered highly toxic. Generally, the higher the oxidation state of vanadium, the more toxic the compound is. The most dangerous one is vanadium pentoxide. Vanadium compounds may cause lung cancer if inhaled. The Occupational Safety and Health Administration (OSHA) has set an exposure limit of 0.05 mg/m3 for vanadium pentoxide dust and 0.1 mg/m3 for vanadium pentoxide fumes in workplace air for an 8-hour workday, 40-hour work week. The National Institute for Occupational Safety and Health (NIOSH) has recommended that 35 mg/m3 of vanadium be considered immediately dangerous to life and health. This is the exposure level of a chemical that is likely to cause permanent health problems or death. ReferencesExternal links
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