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51-478: There are many lakes within the district, and wetlands account for 30% of the district's territory. Natural resources include molybdenum , iron ore , quartzite , copper , and peat . Within the framework of administrative divisions , Kalevalsky District is one of the fifteen in the Republic of Karelia and has administrative jurisdiction over one urban-type settlement ( Kalevala ) and eight rural localities . As

102-642: A froth flotation process to recover molybdenite from ores; flotation remains the primary isolation process. During World War I , demand for molybdenum spiked; it was used both in armor plating and as a substitute for tungsten in high-speed steels . Some British tanks were protected by 75 mm (3 in) manganese steel plating, but this proved to be ineffective. The manganese steel plates were replaced with much lighter 25 mm (1.0 in) molybdenum steel plates allowing for higher speed, greater maneuverability, and better protection. The Germans also used molybdenum-doped steel for heavy artillery, like in

153-429: A municipal division , the district is incorporated as Kalevalsky Municipal District . The urban-type settlement of Kalevala and one rural locality (the settlement of Kuusiniemi ) are incorporated into an urban settlement, while the remaining seven rural localities are incorporated into three rural settlements within the municipal district. The urban-type settlement of Kalevala serves as the administrative center of both

204-429: A pterin -based molybdenum cofactor (Moco) in their active site: sulfite oxidase , xanthine oxidoreductase , aldehyde oxidase , and mitochondrial amidoxime reductase . People severely deficient in molybdenum have poorly functioning sulfite oxidase and are prone to toxic reactions to sulfites in foods. The human body contains about 0.07 mg of molybdenum per kilogram of body weight, with higher concentrations in

255-649: A cation in aqueous solution, although the Mo cation is known to form under carefully controlled conditions. Gaseous molybdenum consists of the diatomic species Mo 2 . That molecule is a singlet , with two unpaired electrons in bonding orbitals, in addition to 5 conventional bonds. The result is a sextuple bond . There are 39 known isotopes of molybdenum, ranging in atomic mass from 81 to 119, as well as 13 metastable nuclear isomers . Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and 100. Of these naturally occurring isotopes, only molybdenum-100

306-648: A commodity. The Knaben mine in southern Norway, opened in 1885, was the first dedicated molybdenum mine. Closed in 1973 but reopened in 2007, it now produces 100,000 kilograms (98 long tons; 110 short tons) of molybdenum disulfide per year. Large mines in Colorado (such as the Henderson mine and the Climax mine ) and in British Columbia yield molybdenite as their primary product, while many porphyry copper deposits such as

357-447: A flame-resistant coating for other metals. Although its melting point is 2,623 °C (4,753 °F), molybdenum rapidly oxidizes at temperatures above 760 °C (1,400 °F) making it better-suited for use in vacuum environments. TZM (Mo (~99%), Ti (~0.5%), Zr (~0.08%) and some C) is a corrosion-resisting molybdenum superalloy that resists molten fluoride salts at temperatures above 1,300 °C (2,370 °F). It has about twice

408-524: A greater supply of molybdenum in the soil, people living in those areas have about 16 times greater risk for esophageal squamous cell carcinoma . Molybdenum deficiency has also been reported as a consequence of non-molybdenum supplemented total parenteral nutrition (complete intravenous feeding) for long periods of time. It results in high blood levels of sulfite and urate , in much the same way as molybdenum cofactor deficiency . Since pure molybdenum deficiency from this cause occurs primarily in adults,

459-565: A hardness on the Mohs scale. However, hardness can make it difficult to determine if the substance is a mixture of other substances or if it may be misleading or meaningless. For example, some sources have assigned a Mohs hardness of 6 or 7 to granite but it is a rock made of several minerals, each with its own Mohs hardness (e.g. topaz-rich granite contains: topaz — Mohs 8, quartz — Mohs 7, orthoclase — Mohs 6, plagioclase — Mohs 6–6.5, mica — Mohs 2–4). Despite its lack of precision,

510-413: A process of purine catabolism , is catalyzed by xanthine oxidase , a molybdenum-containing enzyme. The activity of xanthine oxidase is directly proportional to the amount of molybdenum in the body. An extremely high concentration of molybdenum reverses the trend and can inhibit purine catabolism and other processes. Molybdenum concentration also affects protein synthesis , metabolism , and growth. Mo

561-500: A surface or as a solid lubricant. Even when molybdena was distinguishable from graphite, it was still confused with the common lead ore PbS (now called galena ); the name comes from Ancient Greek Μόλυβδος molybdos , meaning lead . (The Greek word itself has been proposed as a loanword from Anatolian Luvian and Lydian languages). Although (reportedly) molybdenum was deliberately alloyed with steel in one 14th-century Japanese sword (mfd. c.  1330 ), that art

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612-853: Is a fission product . It is a parent radioisotope to the short-lived gamma-emitting daughter radioisotope technetium-99m , a nuclear isomer used in various imaging applications in medicine. In 2008, the Delft University of Technology applied for a patent on the molybdenum-98-based production of molybdenum-99. Molybdenum forms chemical compounds in oxidation states −4 and from −2 to +6. Higher oxidation states are more relevant to its terrestrial occurrence and its biological roles, mid-level oxidation states are often associated with metal clusters , and very low oxidation states are typically associated with organomolybdenum compounds . The chemistry of molybdenum and tungsten show strong similarities. The relative rarity of molybdenum(III), for example, contrasts with

663-488: Is a component in most nitrogenases . Among molybdoenzymes, nitrogenases are unique in lacking the molybdopterin. Nitrogenases catalyze the production of ammonia from atmospheric nitrogen: The biosynthesis of the FeMoco active site is highly complex. Molybdate is transported in the body as MoO 4 . Molybdenum is an essential trace dietary element . Four mammalian Mo-dependent enzymes are known, all of them harboring

714-399: Is also used in steel alloys for its high corrosion resistance and weldability . Molybdenum contributes corrosion resistance to type-300 stainless steels (specifically type-316) and especially so in the so-called superaustenitic stainless steels (such as alloy AL-6XN , 254SMO and 1925hMo). Molybdenum increases lattice strain, thus increasing the energy required to dissolve iron atoms from

765-526: Is an essential element for all higher eukaryote organisms, including humans. A species of sponge , Theonella conica , is known for hyperaccumulation of molybdenum. In its pure form, molybdenum is a silvery-grey metal with a Mohs hardness of 5.5 and a standard atomic weight of 95.95 g/mol. It has a melting point of 2,623 °C (4,753 °F), sixth highest of the naturally occurring elements; only tantalum , osmium , rhenium , tungsten , and carbon have higher melting points. It has one of

816-490: Is an ordinal scale . For example, corundum (9) is twice as hard as topaz (8), but diamond (10) is four times as hard as corundum. The table below shows the comparison with the absolute hardness measured by a sclerometer , with images of the reference minerals in the rightmost column. Below is a table of more materials by Mohs scale. Some of them have a hardness between two of the Mohs scale reference minerals. Some solid substances that are not minerals have been assigned

867-495: Is an essential element in most organisms; a 2008 research paper speculated that a scarcity of molybdenum in the Earth's early oceans may have strongly influenced the evolution of eukaryotic life (which includes all plants and animals). At least 50 molybdenum-containing enzymes have been identified, mostly in bacteria. Those enzymes include aldehyde oxidase , sulfite oxidase and xanthine oxidase . With one exception, Mo in proteins

918-433: Is bound by molybdopterin to give the molybdenum cofactor. The only known exception is nitrogenase , which uses the FeMoco cofactor, which has the formula Fe 7 MoS 9 C. In terms of function, molybdoenzymes catalyze the oxidation and sometimes reduction of certain small molecules in the process of regulating nitrogen , sulfur , and carbon . In some animals, and in humans, the oxidation of xanthine to uric acid ,

969-458: Is of great antiquity, having been mentioned by Theophrastus in his treatise On Stones , c.  300 BC , followed by Pliny the Elder in his Naturalis Historia , c.  AD 77 . The Mohs scale is useful for identification of minerals in the field , but is not an accurate predictor of how well materials endure in an industrial setting. The Mohs scale of mineral hardness is based on

1020-557: Is reduced by the aluminothermic reaction with addition of iron to produce ferromolybdenum . A common form of ferromolybdenum contains 60% molybdenum. Molybdenum had a value of approximately $ 30,000 per tonne as of August 2009. It maintained a price at or near $ 10,000 per tonne from 1997 through 2003, and reached a peak of $ 103,000 per tonne in June 2005. In 2008, the London Metal Exchange announced that molybdenum would be traded as

1071-400: Is separated at this stage by treatment with hydrogen sulfide . Ammonium molybdate converts to ammonium dimolybdate , which is isolated as a solid. Heating this solid gives molybdenum trioxide: Crude trioxide can be further purified by sublimation at 1,100 °C (2,010 °F). Metallic molybdenum is produced by reduction of the oxide with hydrogen: The molybdenum for steel production

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1122-482: Is unstable. Molybdenum-98 is the most abundant isotope, comprising 24.14% of all molybdenum. Molybdenum-100 has a half-life of about 10   y and undergoes double beta decay into ruthenium-100. All unstable isotopes of molybdenum decay into isotopes of niobium , technetium , and ruthenium . Of the synthetic radioisotopes , the most stable is Mo, with a half-life of 4,839 years. The most common isotopic molybdenum application involves molybdenum-99 , which

1173-527: Is used as the valve body of torpedo engines, rocket nozzles and gas pipelines, where it can withstand extreme thermal and mechanical stresses. It is also used as radiation shields in nuclear applications. Other molybdenum-based alloys that do not contain iron have only limited applications. For example, because of its resistance to molten zinc, both pure molybdenum and molybdenum- tungsten alloys (70%/30%) are used for piping, stirrers and pump impellers that come into contact with molten zinc. Molybdenum

1224-561: Is used for the spectroscopic detection of phosphorus. The broad range of oxidation states of molybdenum is reflected in various molybdenum chlorides: The accessibility of these oxidation states depends quite strongly on the halide counterion: although molybdenum(VI) fluoride is stable, molybdenum does not form a stable hexachloride, pentabromide, or tetraiodide. Like chromium and some other transition metals, molybdenum forms quadruple bonds , such as in Mo 2 (CH 3 COO) 4 and [Mo 2 Cl 8 ] . The Lewis acid properties of

1275-1147: The Bingham Canyon Mine in Utah and the Chuquicamata mine in northern Chile produce molybdenum as a byproduct of copper-mining. About 86% of molybdenum produced is used in metallurgy , with the rest used in chemical applications. The estimated global use is structural steel 35%, stainless steel 25%, chemicals 14%, tool & high-speed steels 9%, cast iron 6%, molybdenum elemental metal 6%, and superalloys 5%. Molybdenum can withstand extreme temperatures without significantly expanding or softening, making it useful in environments of intense heat, including military armor, aircraft parts, electrical contacts, industrial motors, and supports for filaments in light bulbs . Most high-strength steel alloys (for example, 41xx steels ) contain 0.25% to 8% molybdenum. Even in these small portions, more than 43,000 tonnes of molybdenum are used each year in stainless steels , tool steels , cast irons, and high-temperature superalloys . Molybdenum

1326-500: The Earth's crust with an average of 1.5 parts per million and the 25th most abundant element in the oceans, with an average of 10 parts per billion; it is the 42nd most abundant element in the Universe. The Soviet Luna 24 mission discovered a molybdenum-bearing grain (1 × 0.6 μm) in a pyroxene fragment taken from Mare Crisium on the Moon . The comparative rarity of molybdenum in

1377-478: The Earth's crust is offset by its concentration in a number of water-insoluble ores, often combined with sulfur in the same way as copper, with which it is often found. Though molybdenum is found in such minerals as wulfenite (PbMoO 4 ) and powellite (CaMoO 4 ), the main commercial source is molybdenite (Mo S 2 ). Molybdenum is mined as a principal ore and is also recovered as a byproduct of copper and tungsten mining. The world's production of molybdenum

1428-524: The German geologist and mineralogist Friedrich Mohs , in his book Versuch einer Elementar-Methode zur naturhistorischen Bestimmung und Erkennung der Fossilien (English: Attempt at an elementary method for the natural-historical determination and recognition of fossils); it is one of several definitions of hardness in materials science , some of which are more quantitative. The method of comparing hardness by observing which minerals can scratch others

1479-464: The Mohs scale can create microscopic, non-elastic dislocations on materials that have a higher Mohs number. While these microscopic dislocations are permanent and sometimes detrimental to the harder material's structural integrity, they are not considered "scratches" for the determination of a Mohs scale number. Each of the ten hardness values in the Mohs scale is represented by a reference mineral , most of which are widespread in rocks. The Mohs scale

1530-406: The Mohs scale is relevant for field geologists, who use it to roughly identify minerals using scratch kits. The Mohs scale hardness of minerals can be commonly found in reference sheets. Mohs hardness is useful in milling . It allows the assessment of which type of mill and grinding medium will best reduce a given product whose hardness is known. Electronic manufacturers use the scale for testing

1581-424: The ability of one natural sample of mineral to visibly scratch another mineral. Minerals are chemically pure solids found in nature. Rocks are mixtures of one or more minerals. Diamond was the hardest known naturally occurring mineral when the scale was designed, and defines the top of the scale, arbitrarily set at 10. The hardness of a material is measured against the scale by finding the hardest material that

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1632-451: The administrative and municipal district. As of the 2002 Census , the district's ethnic composition was as follows: Molybdenum Molybdenum is a chemical element ; it has symbol Mo (from Neo-Latin molybdaenum ) and atomic number 42. The name derived from Ancient Greek Μόλυβδος molybdos , meaning lead , since its ores were confused with lead ores. Molybdenum minerals have been known throughout history, but

1683-471: The alloys on a large scale were hampered with inconsistent results, a tendency toward brittleness, and recrystallization. In 1906, William D. Coolidge filed a patent for rendering molybdenum ductile , leading to applications as a heating element for high-temperature furnaces and as a support for tungsten-filament light bulbs; oxide formation and degradation require that molybdenum be physically sealed or held in an inert gas. In 1913, Frank E. Elmore developed

1734-484: The butyrate and perfluorobutyrate dimers, Mo 2 (O 2 CR) 4 and Rh 2 (O 2 CR) 4 , have been reported. The oxidation state 0 and lower are possible with carbon monoxide as ligand, such as in molybdenum hexacarbonyl , Mo(CO) 6 . Molybdenite —the principal ore from which molybdenum is now extracted—was previously known as molybdena. Molybdena was confused with and often utilized as though it were graphite . Like graphite, molybdenite can be used to blacken

1785-529: The element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by Carl Wilhelm Scheele . The metal was first isolated in 1781 by Peter Jacob Hjelm . Molybdenum does not occur naturally as a free metal on Earth; in its minerals, it is found only in oxidized states . The free element, a silvery metal with a grey cast, has the sixth-highest melting point of any element. It readily forms hard, stable carbides in alloys , and for this reason most of

1836-411: The given material can scratch, or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite , its hardness on the Mohs scale would be between 4 and 5. Technically, "scratching" a material for the purposes of the Mohs scale means creating non- elastic dislocations visible to the naked eye. Frequently, materials that are lower on

1887-585: The liver and kidneys and lower in the vertebrae. Molybdenum is also present within human tooth enamel and may help prevent its decay. Acute toxicity has not been seen in humans, and the toxicity depends strongly on the chemical state. Studies on rats show a median lethal dose (LD 50 ) as low as 180 mg/kg for some Mo compounds. Although human toxicity data is unavailable, animal studies have shown that chronic ingestion of more than 10 mg/day of molybdenum can cause diarrhea, growth retardation, infertility , low birth weight, and gout ; it can also affect

1938-583: The lowest coefficients of thermal expansion among commercially used metals. Molybdenum is a transition metal with an electronegativity of 2.16 on the Pauling scale. It does not visibly react with oxygen or water at room temperature, but is attacked by halogens and hydrogen peroxide. Weak oxidation of molybdenum starts at 300 °C (572 °F); bulk oxidation occurs at temperatures above 600 °C, resulting in molybdenum trioxide . Like many heavier transition metals, molybdenum shows little inclination to form

1989-471: The lungs, kidneys, and liver. Sodium tungstate is a competitive inhibitor of molybdenum. Dietary tungsten reduces the concentration of molybdenum in tissues. Low soil concentration of molybdenum in a geographical band from northern China to Iran results in a general dietary molybdenum deficiency and is associated with increased rates of esophageal cancer . Compared to the United States, which has

2040-453: The mineral in which it resided, and from which it might be isolated. Peter Jacob Hjelm successfully isolated molybdenum using carbon and linseed oil in 1781. For the next century, molybdenum had no industrial use. It was relatively scarce, the pure metal was difficult to extract, and the necessary techniques of metallurgy were immature. Early molybdenum steel alloys showed great promise of increased hardness, but efforts to manufacture

2091-560: The most common bacterial catalysts for breaking the chemical bond in atmospheric molecular nitrogen in the process of biological nitrogen fixation . At least 50 molybdenum enzymes are now known in bacteria, plants, and animals, although only bacterial and cyanobacterial enzymes are involved in nitrogen fixation. Most nitrogenases contain an iron–molybdenum cofactor FeMoco , which is believed to contain either Mo(III) or Mo(IV). By contrast Mo(VI) and Mo(IV) are complexed with molybdopterin in all other molybdenum-bearing enzymes. Molybdenum

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2142-415: The neurological consequences are not as marked as in cases of congenital cofactor deficiency. Mohs scale of mineral hardness The Mohs scale ( / m oʊ z / MOHZ ) of mineral hardness is a qualitative ordinal scale , from 1 to 10, characterizing scratch resistance of minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by

2193-414: The pervasiveness of the chromium(III) compounds. The highest oxidation state is seen in molybdenum(VI) oxide (MoO 3 ), whereas the normal sulfur compound is molybdenum disulfide MoS 2 . From the perspective of commerce, the most important compounds are molybdenum disulfide ( MoS 2 ) and molybdenum trioxide ( MoO 3 ). The black disulfide is the main mineral. It is roasted in air to give

2244-403: The rest of Asia (mostly Armenia, Russia, Iran and Mongolia) produce the remainder. In molybdenite processing, the ore is first roasted in air at a temperature of 700 °C (1,292 °F). The process gives gaseous sulfur dioxide and the molybdenum(VI) oxide : The resulting oxide is then usually extracted with aqueous ammonia to give ammonium molybdate: Copper, an impurity in molybdenite,

2295-409: The strength of pure Mo, and is more ductile and more weldable, yet in tests it resisted corrosion of a standard eutectic salt ( FLiBe ) and salt vapors used in molten salt reactors for 1100 hours with so little corrosion that it was difficult to measure. Due to its excellent mechanical properties under high temperature and high pressure, TZM alloys are extensively applied in the military industry. It

2346-420: The super-heavy howitzer Big Bertha , because traditional steel melts at the temperatures produced by the propellant of the one ton shell. After the war, demand plummeted until metallurgical advances allowed extensive development of peacetime applications. In World War II , molybdenum again saw strategic importance as a substitute for tungsten in steel alloys. Molybdenum is the 54th most abundant element in

2397-453: The surface. Molybdenum is also used to enhance the corrosion resistance of ferritic (for example grade 444) and martensitic (for example 1.4122 and 1.4418) stainless steels. Because of its lower density and more stable price, molybdenum is sometimes used in place of tungsten. An example is the 'M' series of high-speed steels such as M2, M4 and M42 as substitution for the 'T' steel series, which contain tungsten. Molybdenum can also be used as

2448-678: The trioxide: The trioxide, which is volatile at high temperatures, is the precursor to virtually all other Mo compounds as well as alloys. Molybdenum has several oxidation states , the most stable being +4 and +6 (bolded in the table at left). Molybdenum(VI) oxide is soluble in strong alkaline water, forming molybdates (MoO 4 ). Molybdates are weaker oxidants than chromates . They tend to form structurally complex oxyanions by condensation at lower pH values, such as [Mo 7 O 24 ] and [Mo 8 O 26 ] . Polymolybdates can incorporate other ions, forming polyoxometalates . The dark-blue phosphorus -containing heteropolymolybdate P[Mo 12 O 40 ]

2499-485: The world production of the element (about 80%) is used in steel alloys, including high-strength alloys and superalloys . Most molybdenum compounds have low solubility in water. Heating molybdenum-bearing minerals under oxygen and water affords molybdate ion MoO 4 , which forms quite soluble salts. Industrially, molybdenum compounds (about 14% of world production of the element) are used as pigments and catalysts . Molybdenum-bearing enzymes are by far

2550-629: Was 250,000 tonnes in 2011, the largest producers being China (94,000 t), the United States (64,000 t), Chile (38,000 t), Peru (18,000 t) and Mexico (12,000 t). The total reserves are estimated at 10 million tonnes, and are mostly concentrated in China (4.3 Mt), the US (2.7 Mt) and Chile (1.2 Mt). By continent, 93% of world molybdenum production is about evenly shared between North America, South America (mainly in Chile), and China. Europe and

2601-478: Was never employed widely and was later lost. In the West in 1754, Bengt Andersson Qvist examined a sample of molybdenite and determined that it did not contain lead and thus was not galena. By 1778 Swedish chemist Carl Wilhelm Scheele stated firmly that molybdena was (indeed) neither galena nor graphite. Instead, Scheele correctly proposed that molybdena was an ore of a distinct new element, named molybdenum for

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