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VANADIUM

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Originally appearing in Volume V27, Page 879 of the 1911 Encyclopedia Britannica.
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VANADIUM [See also:

symbol, V; atomic See also:weight, 51.2 (0=16)1, a metallic chemical See also:element. It was first mentioned in 18or by M. del Rio (Gill). See also:Ann., 1801, 71, p. 7), but subsequently thought by him to be an impure See also:chromium. Later, it was examined by N. G. Sefstrem, who found it in the slags of the Taberg See also:iron ores (Pogg. Ann., 1830, 21, p. 48), by J. J. See also:Berzelius (ibid., 1831, 22, p. I), and finally by See also:Sir H.

See also:

Roscoe (Trans. See also:Roy. See also:Soc., 1868—187o), who showed that the supposed vanadium obtained by previous investigators was chiefly the nitride or an See also:oxide of the element. In his researches, Roscoe showed that the atomic weight of the See also:metal as determined by Berzelius and the formulae given to the oxides were incorrect, and pointed out that the element falls into its natural See also:place in See also:group V of the periodic See also:classification along with See also:phosphorus and See also:arsenic, and not in the chromium group where it had originally been placed. In small quantities, vanadium is found widely distributed, the See also:chief See also:sources being vanadite, mottramite, See also:descloizite, roscoelite, dechenite and pucherite, whilst it is also found as a constituent of various See also:clays, iron-ores and pitchblendes. Vanadium salts may be obtained from mottramite by digesting the See also:mineral with concentrated hydrochloric See also:acid, the liquid being run off and the See also: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 See also:water into which See also:ammonia is passed, when ammonium metavanadate is again formed and may be purified by re-See also:crystallization. The pure metal may be obtained by reducing vanadium dichloride in See also:hydrogen, the operation being exceedingly difficult (for details, see Roscoe's See also:original papers). In a somewhat impure See also:condition it may be obtained by the reduction of vanadium pentoxide with a mixture of the rare See also:earth metals which are obtained by reduction of the See also:waste oxides formed in the manufacture of thoria (See also:Weiss and Aichel, Ann., 1904, 337, p. 380); from the oxide by See also:Goldschmidt's thermite method (Koppel and See also:Kaufmann, Zeit. anorg. Chem., 1905, 45, p. 352); by See also:electrolysis in a See also:bath of fused fluorspar containing a See also:steel See also:cathode and an anode composed of See also:carbon and vanadium pentoxide (M.

See also:

Gin, L'Electricien, 1903, 25, p. 5); and by the electrolysis of vanadium trioxide when heated in an evacuated See also:glass See also:tube (W. v. See also:Bolton, Zeit. f. Elekirochem., 1905, 11, p. 45). H. See also:Moissan (Comples rendus, 1896, 122, p. 1297) obtained a vanadium containing from to to 16% of carbon by fusing vanadic anhydride with carbon in the electric See also:furnace. For other methods of obtaining vanadium and its compounds, see See also:Cowper Cowles, En gin. and See also:Mining Journ. 67, p. 744; Herrenschmidt, Comples rendus, 1904, 139, p. 635; M.

Gin, Elektrochem. Zeit., 19(36, 13, p. 119; W. Prandtl and B. Bleyer, Zeit. anorg. Chem., 1909, 64, p. 217. Vanadium is a See also:

light-coloured metal of specific gravity 5.5• It is not volatilized even when heated to redness in a current of hydrogen, and it See also:burns readily to the pentoxide when heated in See also:oxygen. It dissolves slowly in hydrofluoric acid and in nitric acid, the See also:solution turning See also:blue; it is insoluble in hydrochloric acid. When fused with See also:caustic soda, hydrogen is liberated and a vanadate is formed. It precipitates See also:platinum, See also:gold and See also:silver from solutions of their salts, and also reduces mercuric, cupric and ferric salts. It absorbs See also:nitrogen when heated in a current of that See also: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 See also:

time becoming See also:lavender blue in See also:colour; or if See also:zinc be used as a reducing See also:agent, the solution becomes at first See also:green and ultimately blue. Five oxides of vanadium are known (cf. NITROGEN), the mono-, di- and trioxides being basic in See also:character, the tetra- and pentoxides being acidic and also feebly basic. The monoxide, V20, is formed when the metal is oxidized slowly in See also:air. In a hydrated See also:form it is obtained by the reduction of vanadyl monochloride, VOC1, with See also:sodium See also:amalgam, being precipitated from the liquid by the addition of ammonia (See also:Locke and See also:Edwards, Zeit. anorg. Chem., 1899, 19, p. 378). The dioxide, V202, is formed in the reduction of vanadyl trichloride by hydrogen (Roscoe). It is a See also:grey See also:powder which is insoluble in water, but dissolves in acids to give a lavender-blue solution which possesses strong reducing properties. The addition of ammonia to this solution precipitates a See also:brown hydrated oxide. The dioxide when heated in oxygen burns, forming the pentoxide. The trioxide, V,O3, is formed when the pentoxide is reduced at a red See also:heat in a current of hydrogen, or by the See also:action of oxalic acid on ammonium metavanadate.

It forms a See also:

black amorphous powder or a dark green crystalline See also: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 tri- and pentoxide is warmed in the See also:absence of air, or when the pentoxide is reduced by See also:sulphur dioxide. It is an amorphous or crystalline mass of See also: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, Io1, p. 698) it exists in three forms: 879 1 a red amorphous soluble form which results when ammonium metavanadate is heated in a closed See also: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 in-soluble 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, See also:magnesium, &c.), with carbon and with oxalic acid. On See also:fusion with the caustic alkalis and alkaline See also:carbonates it yields vanadates. It forms numerous compounds with See also:potassium fluoride. Many complex derivatives are known, such, for example, as phosphor-vanaclates, arsenio-vanadates, tungsto-vanadates, molybdovanadates, &c.

For the use of this oxide in the electrolytic oxidation and reduction of organic compounds, see See also:

German See also:Patents 172654 (1903) and 183022 (1905). Many salts of oxy-acids of vanadium are known, but of the more See also:common oxy-acids, metavanadic acid, HVO3, and pyrovanadic acid, H4V207, alone appear to have been isolated. Metavanadic acid is obtained in the form of yellow scales by boiling See also: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 ortho- and pyro-acids are the least See also:stable, the orthovanadates being obtained on fusion of vanadium pentoxide with an alkaline carbonate. The metavanadates are usually yellowish or colour-less 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 See also:dyeing with See also:aniline black. Tetra- and hexavanadates have also been de-scribed (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 See also:

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 (Comples rendus, 1906, 143, 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 See also:composition 2V204.3S02.10H2O can be isolated) is then boiled with water, when sulphur dioxide is liberated and a See also: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, VC13, is a deliquescent solid formed when the tetra-chloride is heated in a See also:retort as See also:long as See also:chlorine is given off (Roscoe), or by See also:heating vanadium trisulphide in a current of chlorine and fractionally distilling the resulting product at 15o° C. in a current of carbon dioxide (See also:Halberstadt, Ber., 1882, 15, p. 1619). The tetrachloride, VCI4, is formed by the See also:direct See also: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 See also:

benzene and in acetic acid; it dissolves in water to form a deep blue solution. Several oxychlorides have also been described. Vanadium See also:carbide, VC, was prepared by H, Moissan (Comptes rendus, 1896, 1'22, p. 1297) by heating vanadium pentoxide and carbon for a few minutes in the electric furnace. It is a volatile See also: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.

End of Article: VANADIUM

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