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titaniumvanadiumchromium
-

V

Nb
Appearance
blue-silver-grey metal
General properties
Name, symbol, number vanadium, V, 23
Element category transition metal
Group, period, block 54, d
Standard atomic weight 50.9415(1)g·mol−1
Electron configuration [Ar] 3d3 4s2
Electrons per shell 2, 8, 11, 2 (Image)
Physical properties
Phase solid
Density (near r.t.) 6.0 g·cm−3
Liquid density at m.p. 5.5 g·cm−3
Melting point 2183 K, 1910 °C, 3470 °F
Boiling point 3680 K, 3407 °C, 6165 °F
Heat of fusion 21.5 kJ·mol−1
Heat of vaporization 459 kJ·mol−1
Specific heat capacity (25 °C) 24.89 J·mol−1·K−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 2101 2289 2523 2814 3187 3679
Atomic properties
Oxidation states 5, 4, 3, 2, 1, -1
(amphoteric oxide)
Electronegativity 1.63 (Pauling scale)
Ionization energies
(more)
1st: 650.9 kJ·mol−1
2nd: 1414 kJ·mol−1
3rd: 2830 kJ·mol−1
Atomic radius 134 pm
Covalent radius 153±8 pm
Miscellanea
Crystal structure body-centered cubic
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 197 nΩ·m
Thermal conductivity (300 K) 30.7 W·m−1·K−1
Thermal expansion (25 °C) 8.4 µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 4560 m/s
Young's modulus 128 GPa
Shear modulus 47 GPa
Bulk modulus 160 GPa
Poisson ratio 0.37
Mohs hardness 6.7
CAS registry number 7440-62-2
Most stable isotopes
Main article: Isotopes of vanadium
iso NA half-life DM DE (MeV) DP
48V syn 15.9735 d ε+β+ 4.0123 48Ti
49V syn 330 d ε 0.6019 49Ti
50V 0.25% 1.5×1017y ε 2.2083 50Ti
β 1.0369 50Cr
51V 99.75% 51V is stable with 28 neutrons

Vanadium (pronounced /vəˈneɪdiəm/, və-NAY-dee-əm) is the chemical element with the symbol V and atomic number 23. It is a soft, silvery gray, ductile transition metal. The formation of an oxide layer stabilizes the metal against oxidation. Andrés Manuel del Río discovered vanadium in 1801 by analyzing the mineral vanadinite, and named it erythronium. Four years later, however, he was convinced by other scientists that erythronium was identical to chromium. The element was rediscovered in 1831 by Nils Gabriel Sefström, who named it vanadium after the Scandinavian goddess of beauty and fertility, Vanadis (Freya). Both names were attributed to the wide range of colors found in vanadium compounds.

The element occurs naturally in about 65 different minerals and in fossil fuel deposits. It is produced in China and Russia from steel smelter slag; other countries produce it either from the flue dust of heavy oil, or as a byproduct of uranium mining. It is mainly used to produce specialty steel alloys such as high speed tool steels. The compound vanadium pentoxide is used as a catalyst for the production of sulfuric acid. Vanadium is found in many organisms, and is used by some life forms as an active center of enzymes.

Contents

History

Vanadium was originally discovered by Andrés Manuel del Río, a Spanish-born Mexican mineralogist, in 1801. Del Río extracted the element from a sample of Mexican "brown lead" ore, later named vanadinite. He found that its salts exhibit a wide variety of colors, and as a result he named the element panchromium (Greek: παγχρώμιο "all colors"). Later, Del Río renamed the element erythronium (Greek: ερυθρός "red") as most of its salts turned red upon heating. In 1805, the French chemist Hippolyte Victor Collet-Descotils, backed by del Río's friend, Baron Alexander von Humboldt, incorrectly declared that del Río's new element was only an impure sample of chromium. Del Río accepted the Collet-Descotils' statement, and retracted his claim.[1]

In 1831, the Swedish chemist, Nils Gabriel Sefström, rediscovered the element in a new oxide he found while working with iron ores. Later that same year, Friedrich Wöhler confirmed del Río's earlier work.[2] Sefström chose a name beginning with V, which had not been assigned to any element yet. He called the element vanadium after Vanadis (another name for Freya, the Norse goddess of beauty and fertility), because of the many beautifully colored chemical compounds it produces.[2] In 1831, the geologist George William Featherstonhaugh suggested that vanadium should be renamed "rionium" after del Río, but this suggestion was not followed.[3]

1910 Model T

The isolation of vanadium metal proved difficult. In 1831, Berzelius reported the production of the metal, but Henry Enfield Roscoe showed that Berzelius had in fact produced the nitride, vanadium nitride (VN). Roscoe eventually produced the metal in 1867 by reduction of vanadium(III) chloride, VCl3, with hydrogen.[4] In 1927, pure vanadium was produced by reducing vanadium pentoxide with calcium.[5] The first large scale industrial use of vanadium in steels was found in the chassis of the Ford Model T, inspired by French race cars. Vanadium steel allowed for reduced weight while simultaneously increasing tensile strength.[6]

Characteristics

Vanadium is a soft, ductile, silver-gray metal. It has good resistance to corrosion and it is stable against alkalis, sulfuric and hydrochloric acids.[7] It is oxidized in air at about 933 K (660 °C, 1220 °F), although an oxide layer forms even at room temperature.

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Isotopes

Naturally occurring vanadium is composed of one stable isotope 51V and one radioactive isotope 50V. The latter has a half-life of 1.5×1017 years and a natural abundance 0.25%. 51V has a nuclear spin of 7/2 which is useful for NMR spectroscopy.[8] A number of 24 artificial radioisotopes have been characterized, ranging in mass number from 40 to 65. The most stable of these isotopes are 49V with a half-life of 330 days, and 48V with a half-life of 15.9735 days. All of the remaining radioactive isotopes have half-lives shorter than an hour, most of which are below 10 seconds. At least 4 isotopes have metastable excited states.[8] Electron capture is the main decay mode for isotopes lighter than the 51V. For the heavier ones, the most common mode is beta decay. The electron capture reactions lead to the formation of element 22 (titanium) isotopes, while for beta decay, it leads to element 24 (chromium) isotopes.

Chemistry and compounds

Vanadium(V) oxide is a catalyst in the Contact process for producing sulfuric acid

The chemistry of vanadium is noteworthy for the accessibility of four adjacent oxidation states. The common oxidation states of vanadium are +2 (lilac), +3 (green), +4 (blue) and +5 (yellow). Vanadium(II) compounds are reducing agents, and vanadium(V) compounds are oxidizing agents. Vanadium(IV) compounds often exist as vanadyl derivatives which contain the VO2+ center.[7]

Metavanadate chains

Ammonium vanadate(V) (NH4VO3) can be successively reduced with elemental zinc to obtain the different colors of vanadium in these four oxidation states. Lower oxidation states occur in compounds such as V(CO)6, [V(CO)6] and substituted derivatives.[7]

The vanadium redox battery utilizes these oxidation states; conversion of these oxidation states is illustrated by the reduction of a strongly acidic solution of a vanadium(V) compound with zinc dust. The initial yellow color characteristic of the vanadate ion, VO 3−4, is replaced by the blue color of [VO(H2O)5]2+, followed by the green color of [V(H2O)6]3+ and then violet, due to [V(H2O)6]2+.[7]

The most commercially important compound is vanadium pentoxide, which is used as a catalyst for the production of sulfuric acid.[7] This compound oxidizes sulfur dioxide (SO2) to the trioxide (SO3). In this redox reaction, sulfur is oxidized from +4 to +6, and vanadium is reduced from +5 to +3:

V2O5 + 2 SO2 → V2O3 + 2 SO3

The catalyst is regenerated by oxidation with air:

V2O3 + O2 → V2O5

Oxy and oxo compounds

The Pourbaix diagram for vanadium in water.[9]

The oxyanion chemistry of vanadium(V) is complex. The vanadate ion, VO 3−4, is present in dilute solutions at high pH. On acidification, HVO 2−4 and H2VO 4 are formed, analogous to HPO 2−4 and H2PO 4. The acid dissociation constants for the vanadium and phosphorus series are remarkably similar. In more concentrated solutions many polyvanadates are formed. Chains, rings and clusters involving tetrahedral vanadium, analogous to the polyphosphates, are known. In addition, clusters such as the decavanadates V10O 4−28 and HV10O 3−28, which predominate at pH 4-6, are formed in which compound is octahedral about vanadium.[7]

The correspondence between vanadate and phosphate chemistry can be attributed to the similarity in size and charge of phosphorus(V) and vanadium(V). Orthovanadate VO 3−4 is used in protein crystallography[10] to study the biochemistry of phosphate.[11]

Halide compounds

Several halides are known for oxidation states +2, +3 and +4. VCl4 is the most important commercially. This liquid is mainly used as a catalyst for polymerization of dienes.

Coordination compounds

A ball-and-stick model of VO(acac)2

Vanadium's early position in the transition metal series lead to three rather unusual features of the coordination chemistry of vanadium. Firstly, metallic vanadium has the electronic configuration [Ar]4s23d3, so compounds of vanadium are relatively electron-poor. Consequently, most binary compounds are Lewis acids (electron pair acceptors); examples are all the halides forming octahedral adducts with the formula VXnL6−n (X = halide; L = other ligand). Secondly, the vanadium ion is rather large and can achieve coordination numbers higher than 6, as is the case in [V(CN)7]4−. Thirdly, the vanadyl ion, VO2+, is featured in many complexes of vanadium(IV) such as vanadyl acetylacetonate (V(=O)(acac)2). In this complex, the vanadium is 5-coordinate, square pyramidal, meaning that a sixth ligand, such as pyridine, may be attached, though the association constant of this process is small. Many 5-coordinate vanadyl complexes have a trigonal bypyramidal geometry, such as VOCl2(NMe3)2.[12]

Organometallic compounds

Organometallic chemistry of vanadium is well developed, but organometallic compounds are of minor commercial significance. Vanadocene dichloride is a versatile starting reagent and even finds minor applications in organic chemistry.[13] Vanadium carbonyl, V(CO)6, is a rare example of a metal carbonyl containing an unpaired electron, but which exists without dimerization. The addition of an electron yields V(CO) 6 (isoelectronic with Cr(CO)6), which may be further reduced with sodium in liquid ammonia to yield V(CO) 3−6 (isoelectronic with Fe(CO)5).[14][15]

Occurrence

Vanadinite

Metallic vanadium is not found in nature, but is known to exist in about 65 different minerals. Economically significant examples include patronite (VS4),[16] vanadinite (Pb5(VO4)3Cl), and carnotite (K2(UO2)2(VO 4)2·3H2O). Much of the world's vanadium production is sourced from vanadium-bearing magnetite found in ultramafic gabbro bodies. Vanadium is mined mostly in South Africa, north-western China, and eastern Russia. In 2007 these three countries mined more than 95 % of the 58,600 tonnes of produced vanadium.[17]

Vanadium is also present in bauxite and in fossil fuel deposits such as crude oil, coal, oil shale and tar sands. In crude oil, concentrations up to 1200 ppm have been reported. When such oil products are burned, the traces of vanadium may initiate corrosion in motors and boilers.[18] An estimated 110,000 tonnes of vanadium per year are released into the atmosphere by burning fossil fuels.[19] Vanadium has also been detected spectroscopically in light from the Sun and some other stars.[20]

Production

Ferrovanadium chunks

Most vanadium is used as ferrovanadium as an additive to improve steels. Ferrovanadium is produced directly by reducing a mixture of vanadium oxide, iron oxides and iron in an electric furnace. Vanadium-bearing magnetite iron ore is the main source for the production of vanadium.[21] The vanadium ends up in pig iron produced from vanadium bearing magnetite. During steel production, oxygen is blown into the pig iron, oxidizing the carbon and most of the other impurities, forming slag. Depending on the used ore, the slag contains up to 25% of vanadium.[21]

Vanadium metal is obtained via a multistep process that begins with the roasting of crushed ore with NaCl or Na2CO3 at about 850 °C to give sodium metavanadate (NaVO3). An aqueous extract of this solid is acidified to give "red cake", a polyvanadate salt, which is reduced with calcium metal. As an alternative for small scale production, vanadium pentoxide is reduced with hydrogen or magnesium. Many other methods are also in use, in all of which vanadium is produced as a byproduct of other processes.[21] Purification of vanadium is possible by the crystal bar process developed by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925. It involves the formation of the metal iodide, in this example vanadium(III) iodide, and the subsequent decomposition to yield pure metal.[22]

2 V + 3 I2 is in equilibrium with 2 VI3

Applications

Tool made from vanadium steel
Vanadium

Alloys

Approximately 85% of vanadium produced is used as ferrovanadium or as a steel additive.[21] The considerable increase of strength in steel containing small amounts of vanadium was discovered in the beginning of the 20th century. Vanadium forms stable nitrides and carbides, resulting in a significant increase in the strength of the steel.[23] From that time on vanadium steel was used for applications in axles, bicycle frames, crankshafts, gears, and other critical components. There are two groups of vanadium containing steel alloy groups. Vanadium high-carbon steel alloys containing 0.15 to 0.25% vanadium and high speed tool steels (HSS) with a vanadium content ranges from 1 % to 5 %. For high speed tool steels, a hardness above HRC 60 can be achieved. HSS steel is used in surgical instruments and tools.[24]

Vanadium stabilizes the beta form of titanium and increases the strength and temperature stability of titanium. Mixed with aluminium in titanium alloys it is used in jet engines and high-speed airframes. One of the common alloys is Titanium 6AL-4V, a titanium alloy with 6% aluminium and 4% vanadium.[25]

Other uses

Vanadium is compatible with iron and titanium, therefore vanadium foil is used in cladding titanium to steel.[26] The moderate thermal neutron-capture cross-section and the short half-life of the isotopes produced by neutron capture makes vanadium a suitable material for the inner structure of a fusion reactor.[27][28] Several vanadium alloys show superconducting behavior. The first A15 phase superconductor was a vanadium compound, V3Si, which was discovered in 1952.[29] Vanadium-gallium tape is used in superconducting magnets (17.5 teslas or 175,000 gauss). The structure of the superconducting A15 phase of V3Ga is similar to that of the more common Nb3Sn and Nb3Ti.[30]

The most common oxide of vanadium, vanadium pentoxide V2O5, is used as a catalyst in manufacturing sulfuric acid by the contact process[31] and as an oxidizer in maleic anhydride production.[32] Vanadium pentoxide is also used in making ceramics.[33] Another oxide of vanadium, vanadium dioxide VO2, is used in the production of glass coatings, which blocks infrared radiation (and not visible light) at a specific temperature.[34] Vanadium oxide can be used to induce color centers in corundum to create simulated alexandrite jewelry, although alexandrite in nature is a chrysoberyl.[35] The possibility to use vanadium redox couples in both half-cells, thereby eliminating the problem of cross contamination by diffusion of ions across the membrane is the advantage of vanadium redox rechargeable batteries.[36] Vanadate can be used for protecting steel against rust and corrosion by electrochemical conversion coating.[37] Lithium vanadium oxide has been proposed for use as a high energy density anode for lithium ion batteries, at 745 Wh/L when paired with a lithium cobalt oxide cathode.[38] It has been proposed by some researchers that a small amount, 40 to 270 ppm, of vanadium in Wootz steel and Damascus steel, significantly improves the strength of the material, although it is unclear what the source of the vanadium was.[39]

Biological role

Ascidiacea contain vanadium.
Amanita muscaria contains amavadin.

Vanadium plays a very limited role in biology. A vanadium-containing nitrogenase is used by some nitrogen-fixing micro-organisms. Vanadium is essential to ascidians or sea squirts 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.[40] Vanadium is a relatively controversial dietary supplement, primarily for increasing insulin sensitivity[41] 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.[42] Vanadyl sulfate may improve glucose control in people with type 2 diabetes.[43][44][45][46][47]. In addition, decavanadate and oxovanadates are species that potentially have many biological activities and that have been successfully used as tools in the comprehension of several biochemical processes.[48]

Ten percent of the blood cell pigment of the sea cucumber is vanadium. Just as the horseshoe crab has blue blood due to copper in hemocyanin, and land animals have red blood from the iron in hemoglobin, the blood of the sea cucumber is yellow because of the vanadium in the vanabin pigment.[49] Nonetheless, there is no evidence that vanabins carry oxygen, in contrast to hemoglobin and hemocyanin.[50] Several species of macrofungi, namely Amanita muscaria and related species, accumulate vanadium (up to 500 mg/kg in dry weight). Vanadium is present in the coordination complex, amavadin,[51] in fungal fruit-bodies. However, the biological importance of the accumulation process is unknown.[52][53]

Safety

All vanadium compounds should be considered to be toxic. Tetravalent VOSO4 has been reported to be over 5 times more toxic than trivalent V2O3.[54] 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.[55] 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.[55]

Vanadium compounds are poorly absorbed through the gastrointestinal system. Inhalation exposures to vanadium and vanadium compounds result primarily in adverse effects on the respiratory system.[56][57][58] Quantitative data are, however, insufficient to derive a subchronic or chronic inhalation reference dose. Other effects have been reported after oral or inhalation exposures on blood parameters,[59][60] on liver,[61] on neurological development in rats,[62] and other organs.[63]

There is little evidence that vanadium or vanadium compounds are reproductive toxins or teratogens. Vanadium pentoxide was reported to be carcinogenic in male rats and male and female mice by inhalation in an NTP study,[57] although the interpretation of the results has recently been disputed.[64] Vanadium has not been classified as to carcinogenicity by the United States Environmental Protection Agency.[65]

Vanadium traces in diesel fuels present a corrosion hazard; it is the main fuel component influencing high temperature corrosion. During combustion, it oxidizes and reacts with sodium and sulfur, yielding vanadate compounds with melting points down to 530 °C, which attack the passivation layer on steel, rendering it susceptible to corrosion. The solid vanadium compounds also cause abrasion of engine components.

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External links


1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

VANADIUM [[[symbol]], V; atomic weight, 51.2 (0= 16)], a metallic chemical element. It was first mentioned in 1801 by M. del Rio (Gilb. Ann., 1801, 71, p. 7), but subsequently thought by him to be an impure chromium. Later, it was examined by N. G. Sefstri m, who found it in the slags of the Taberg iron ores (Pogg. Ann., 1830, 21, p. 48), by J. J. Berzelius (ibid., 1831, 22, p. 1), and finally by Sir H. Roscoe (Trans. Roy. Soc., 1868-1870), who showed that the supposed vanadium obtained by previous investigators was chiefly the nitride or an oxide of the element. In his researches, Roscoe showed that the atomic weight of the metal as determined by Berzelius and the formulae given to the oxides were incorrect, and pointed out that the element falls into its natural place in group V of the periodic classification along with phosphorus and arsenic, and not in the chromium group where it had originally been placed.

In small quantities, vanadium is found widely distributed, the chief sources being vanadite, mottramite, descloizite, roscoelite, dechenite and pucherite, whilst it is also found as a constituent of various clays, iron-ores and pitchblendes. Vanadium salts may be obtained from mottramite by digesting the mineral with concentrated hydrochloric acid, the liquid being run off and the residue well washed; the acid liquid and the washings are then evaporated with ammonium chloride, when ammonium metavanadate separates. This is recrystallized and roasted to vanadium pentoxide, which is then suspended in water into which ammonia is passed, when ammonium metavanadate is again formed and may be purified by recrystallization. The pure metal may be obtained by reducing vanadium dichloride in hydrogen, the operation being exceedingly difficult (for details, see Roscoe's original papers). In a somewhat impure condition it may be obtained by the reduction of vanadium pentoxide with a mixture of the rare earth metals which are obtained by reduction of the waste oxides formed in the manufacture of thoria (Weiss and Aichel, Ann., 1904, 337, p.. 380); from the oxide by Goldschmidt's thermite method (Koppel and Kaufmann, Zeit. anorg. Chem., 1905, 45, p. 35 2); by electrolysis in a bath of fused fluorspar containing a steel cathode and an anode composed of carbon and vanadium pentoxide (M. Gin, L'Electricien, 1903, 2 5, p. 5); and by the electrolysis of vanadium trioxide when heated in an evacuated glass tube (W. v. Bolton, Zeit. f. Elektrochem., 1905, II, p. 45). H. Moissan (Comptes rendus, 1896, 122, p. 1297) obtained a vanadium containing from Io to 16% of carbon by fusing vanadic anhydride with carbon in the electric furnace. For other methods of obtaining vanadium and its compounds, see Cowper Cowles, Engin. and Mining Journ. 67, p. 744; Herrenschmidt, Comptes rendus, 1904, 1 39, p. 635; M. Gin, Elektrochem. Zeit., 1906, 13, p. 119; W. Prandtl and B. Bleyer, Zeit. anorg. Chem., 1909, 64, p. 217.

Vanadium is a light-coloured metal of specific gravity 5.5. It is not volatilized even when heated to redness in a current of hydrogen, and it burns readily to the pentoxide when heated in oxygen. It dissolves slowly in hydrofluoric acid and in nitric acid, the solution turning blue; it is insoluble in hydrochloric acid. When fused with caustic soda, hydrogen is liberated and a vanadate is formed. It precipitates platinum, gold and silver from solutions of their salts, and also reduces mercuric, cupric and ferric salts. It absorbs nitrogen when heated in a current of that gas, forming a nitride. Vanadium may be detected by converting it into the pentoxide, which on passing sulphuretted hydrogen through its acid solution becomes reduced to the dioxide, the solution at the same time becoming lavender blue in colour; or if zinc be used as a reducing agent, the solution becomes at first green and ultimately blue.

Five oxides of vanadium are known (cf. Nitrogen), the mono-, diand trioxides being basic in character, the tetraand pentoxides being acidic and also feebly basic. The monoxide, V 2 0, is formed when the metal is oxidized slowly in air. In a hydrated form it is obtained by the reduction of vanadyl monochloride, Voci, with sodium amalgam, being precipitated from the liquid by the addition of ammonia (Locke and Edwards, Zeit. anorg. Chem., 18 99, 19, p. 37 8). The dioxide, V 2 0 2, is formed in the reduction of vanadyl trichloride by hydrogen (Roscoe). It is a grey powder which is insoluble in water, but dissolves in acids to give a lavenderblue solution which possesses strong reducing properties. The addition of ammonia to this solution precipitates a brown hydrated oxide. The dioxide when heated in oxygen burns, forming the pentoxide. The trioxide, V 2 0 3, is formed when the pentoxide is reduced at a red heat in a current of hydrogen, or by the action of oxalic acid on ammonium metavanadate. It forms a black amorphous powder or a dark green crystalline mass, and is insoluble in water and in most acids. The tetroxide, V204, results when the pentoxide is heated with dry oxalic acid and the resulting mixture of the triand pentoxide is warmed in the absence of air, or when the pentoxide is reduced by sulphur dioxide. It is an amorphous or crystalline mass of indigo-blue or steel-grey colour, which is insoluble in water and is also infusible. It oxidizes slowly in moist air, and dissolves easily in acids with the formation of blue solutions. The pentoxide, V205, is obtained when ammonium metavanadate is strongly heated, on calcining the sulphide, or by the decomposition of vanadyl trichloride with water. According to Ditte (Comptes rendus, 101, p. 698) it exists in three forms: a red amorphous soluble form which results when ammonium metavanadate is heated in a closed vessel and the residue oxidized with nitric acid and again heated; a yellow amorphous insoluble form which is obtained when the vanadate is heated in a current of air at 440° C.; and a red crystalline form which is almost insoluble in water. It is soluble in hot concentrated sulphuric acid and in concentrated hydrochloric acid. It is an energetic oxidizing agent and is consequently readily reduced when heated with various metals (zinc, magnesium, &c.), with carbon and with oxalic acid. On fusion with the caustic alkalis and alkaline carbonates it yields vanadates. It forms numerous compounds with potassium fluoride. Many complex derivatives are known, such, for example, as phosphor-vanadates, arsenio-vanadates, tungsto-vanadates, molybdovanadates, &c. For the use of this oxide in the electrolytic oxidation and reduction of organic compounds, see German Patents 172654 (1903) and 183022 (1905).

Many salts of oxy-acids of vanadium are known, but of the more common oxy-acids, metavanadic acid, HV03, and pyrovanadic acid, H 4 V 2 0 7, alone appear to have been isolated. Metavanadic acid is obtained in the form of yellow scales by boiling copper vanadate with an aqueous solution of sulphur dioxide. It is only very slightly soluble in water. Pyrovanadic acid is deposited as a dark brown unstable powder when an acid vanadate is decomposed by nitric acid. Of the salts of these acids, those of the orthoand pyro-acids are the least stable, the orthovanadates being obtained on fusion of vanadium pentoxide with an alkaline carbonate. The metavanadates are usually yellowish or colourless solids. Ammonium metavanadate is obtained when the hydrated vanadium pentoxide is dissolved in excess of ammonia and the solution concentrated. It has been used in dyeing with aniline black. Tetraand hexavanadates have also been described (see Ditte, Comptes rendus, 104, pp. 902, 1061; 102, p. 918; Manasse, Ann. 240, p. 23). The hypovanadates are insoluble in water, except those of the alkali metals, which are obtained by the addition of caustic alkalis to concentrated solutions of the chloride or sulphate of the tetroxide. They are brown in colour and easily oxidize. Pure hypovanadic acid has been obtained by G. Gain (Comptes rendus, 1906, 1 43, p. 823) by calcining ammonium metavanadate and saturating a solution of the resulting oxides with sulphur dioxide; the resulting blue solution (from which a sulphate of composition 2V 2 0 4.3S0 2.10H 2 O can be isolated) is then boiled with water, when sulphur dioxide is liberated and a pale red crystalline powder of hypovanadic acid, H4V205, is precipitated.

Vanadium dichloride, VC12, is a green crystalline solid obtained when the tetrachloride is reduced with hydrogen at a dull red heat. It is very deliquescent and readily soluble in water. The trichloride, VC1 31 is a deliquescent solid formed when the tetrachloride is heated in a retort as long as chlorine is given off (Roscoe), or by heating vanadium trisulphide in a current of chlorine and fractionally distilling the resulting product at 150° C. in a current of carbon dioxide (Halberstadt, Ber., 1882, 15, p. 1619). The tetrachloride, VC14, is formed by the direct union of vanadium and chlorine or by the action of sulphur chloride on vanadium pentoxide (Matignon, Comptes rendus, 1904, 138, p. 631). It is a fuming liquid, which is soluble in benzene and in acetic acid; it dissolves in water to form a deep blue solution. Several oxychlorides have also been described. Vanadium carbide, VC, was prepared by H. Moissan (Coniptes rendus, 1896, 122, p. 1297) by heating vanadium pentoxide and carbon for a few minutes in the electric furnace. It is a volatile compound which burns when heated in oxygen and which is unacted upon by sulphuric and hydrochloric acids.

For vanadium steels, see Iron And Steel Manufacture.


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Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also vanadium

German

Chemical element
V Previous: Titan (Ti)
Next: Chrom (Cr)

Noun

Vanadium n.

  1. vanadium (a metallic chemical element with an atomic number of 23).

Simple English

[[File:|thumb|right|Vanadium]] Vanadium is chemical element 23 on the periodic table. Its symbol is V.

Vanadium is a metal and is part of the group known as the transition metals. It is mostly used in steel where it helps strengthen the steel metal.

The human body may require a little bit of vanadium, even though scientists are not really sure. There is a little bit of vanadium in vitamins just to make sure that we do not get sick (in case our body does need vanadium).

Vanadium can react with a variety of other elements, and the chemical compounds it forms often have beautiful colors.


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