VANADIUM PENTOXIDE (VANADIC ANHYDRIDE)

Vanadium a soft, ductile, silver-grey metallic transition element in the member of group Vb of the periodic table; symbol V; Atomic number 23; atomic mass; 50.9415; melting point ca 1,890 C; boiling point ca 3,380 C; specific gravity about 6 at 20 C; valence +2, +3, +4, and maximum +5; electronic config [Ar]3d34s2; resembles chromium in properties; found in several minerals such as carnotite, patronite, roscoelite, and vanadinite with good structural strength. Vanadium has two natural isotopes, 50_v and 51_v, and several radioactive isotopes (^46-49V, ^52-54V) have been obtained artificially. It dissolves in water to form acidic solutions and dissolves in acids. It reacts with bases to form vanadates. Vanadium trioxide (V₂O₃) is basic in solution and dissolves in acids to give the green hexa-aquo ion (V(H₂O)₆)³⁺. In solution, V³⁺ is a strong reducing agent and slowly attacks water with the production of hydrogen. Vanadium is usually found bound to oxygen as a negatively charged polymeric oxyanion that tends to complex to polarizable ligands, such as phosphorus and sulfur. Vanadium can be obtained by the extraction from ores, extraction from fossil fuels and extraction from slag . It has good resistance to corrosion by hydrochloric and sulfuric acids, saltwater, or alkalies at room temperature but oxidizes readily above 660 C. Vanadium has good structural strength and a low fission neutron cross section, making it useful in nuclear applications. It is intermediate between the metals and the non-metals, having either an electronegative or an electropositive metal results in numerous chemical compounds including vanadates and complex organic compounds. The principal use of vanadium is in alloys, where almost three quarters of all vanadium produced is used as additive in making special steels. It is a powerful alloying agent; a small amount adds strength, toughness and heat resistance. It is added to steel in the form of either ferrovanadium (vanadium-iron alloy) or vanadium carbide. Vanadium is also a major alloying element in titanium alloys for high-strength. Non-ferrous metals alloys are used in the atomic energy industry, aircraft and space technology due to its low fission neutron cross section. Vanadium disilicide is used in the production of high-temperature refractory products. Vanadium-aluminum-titanium alloys are used in high-speed airframes and jet engines. Vanadium chemical compounds such as vanadium oxides and various vanadates are used as catalysts for the synthesis of sulfuric acid (the oxidation of SO₂ to SO₃) and maleic and phthalic anhydride, the oxidation reaction of organic compounds including ethanol to acetaldehyde and petroleum cracking. They are used in the manufacture of polyamides (nylon), sugar to oxalic acid and anthracene to anthraquinone. They are used as catalytic converters for the exhaust gases of internal combustion engines. They also have applications in producing glass and enamels, organic ion exchangers, luminescent compounds, synthetic rubbers, thermistors and switching elements as well as in producing paints, as developers, sdepolarizers, and colouring agents in photography and cinematography. They are used in inhibiting UV light transmission in glass. Vanadium compounds are used as mordants in the dyeing and printing of fabrics, particularly for fixing aniline black on silk (in form of ammonium vanadate) and cathode-ray tubes. Europium-activated yttrium vanadate is used in colour television tubes. Vanadium hydride can be used as a neutron moderator in atomic reactors. Soluble salts of arsenous-vanadous acid have been used as fungicides and insecticides. Vanadium slags are used in casting shops as a moulding material to improve the quality of the casting surface and to facilitate cleaning.