Molybdenum is achemical element; it hassymbolMo (fromNeo-Latinmolybdaenum) andatomic number 42. The name derived fromAncient GreekΜόλυβδοςmolybdos, meaninglead, since its ores were confused with lead ores.[12] Molybdenum minerals have been known throughout history, but the element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 byCarl Wilhelm Scheele. The metal was first isolated in 1781 byPeter Jacob Hjelm.[13]
Molybdenum does not occur naturally as afree metal on Earth; in its minerals, it is found only inoxidized states. The free element, a silverymetal with a grey cast, has thesixth-highestmelting point of any element. It readily forms hard, stablecarbides inalloys, and for this reason most of the world production of the element (about 80%) is used insteel alloys, including high-strength alloys andsuperalloys.
Most molybdenum compounds have lowsolubility in water. Heating molybdenum-bearing minerals underoxygen and water affordsmolybdate ionMoO2− 4, which forms quite soluble salts. Industrially, molybdenumcompounds (about 14% of world production of the element) are used aspigments andcatalysts.
Molybdenum-bearing enzymes are by far the most common bacterial catalysts for breaking thechemical bond in atmospheric molecularnitrogen in the process of biologicalnitrogen 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. Mostnitrogenases contain an iron–molybdenum cofactorFeMoco, which is believed to contain either Mo(III) or Mo(IV).[14][15] By contrast Mo(VI) and Mo(IV) are complexed withmolybdopterin in all other molybdenum-bearing enzymes.[16] Molybdenum is anessential element for all highereukaryote organisms, including humans. A species ofsponge,Theonella conica, is known for hyperaccumulation of molybdenum.[17]
In its pure form, molybdenum is a silvery-grey metal with aMohs hardness of 5.5 and a standard atomic weight of 95.95 g/mol.[18][19] It has amelting point of 2,623 °C (4,753 °F), sixth highest of the naturally occurring elements; onlytantalum,osmium,rhenium,tungsten, andcarbon have higher melting points.[12] It has one of the lowest coefficients ofthermal expansion among commercially used metals.[20]
Molybdenum is atransition metal with anelectronegativity of 2.16 on thePauling 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 inmolybdenum trioxide. Like many heavier transition metals, molybdenum shows little inclination to form a cation in aqueous solution, although the Mo3+ cation is known to form under carefully controlled conditions.[21]
Gaseous molybdenum consists of the diatomic species Mo2. That molecule is asinglet, with two unpaired electrons in bonding orbitals, in addition to 5 conventional bonds. The result is asextuple bond.[22][23]
There are 39 knownisotopes of molybdenum, ranging inatomic mass from 81 to 119, as well as 13 metastablenuclear 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 is unstable.[10]
Molybdenum-98 is the mostabundant isotope, comprising 24.14% of all molybdenum. Molybdenum-100 has ahalf-life of about 1019y and undergoesdouble beta decay into ruthenium-100. All unstable isotopes of molybdenum decay into isotopes ofniobium,technetium, andruthenium. Of thesynthetic radioisotopes, the most stable is93Mo, with a half-life of 4,839 years.[11]
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 withmetal clusters, and very low oxidation states are typically associated withorganomolybdenum compounds. The chemistry of molybdenum and tungsten show strong similarities. The relative rarity of molybdenum(III), for example, contrasts with the pervasiveness of the chromium(III) compounds. The highest oxidation state is seen inmolybdenum(VI) oxide (MoO3), whereas the normal sulfur compound ismolybdenum disulfide MoS2.[26]
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 the trioxide:[26]
2MoS 2 + 7O 2 → 2MoO 3 + 4SO 2
The trioxide, which is volatile at high temperatures, is the precursor to virtually all other Mo compounds as well as alloys. Molybdenum has severaloxidation states, the most stable being +4 and +6 (bolded in the table at left).
Molybdenum(VI) oxide is soluble in strongalkaline water, forming molybdates (MoO42−). Molybdates are weaker oxidants thanchromates. They tend to form structurally complexoxyanions by condensation at lowerpH values, such as [Mo7O24]6− and [Mo8O26]4−. Polymolybdates can incorporate other ions, formingpolyoxometalates.[30] The dark-bluephosphorus-containing heteropolymolybdate P[Mo12O40]3− is used for thespectroscopic detection of phosphorus.[31]
The broad range ofoxidation states of molybdenum is reflected in various molybdenum chlorides:[26]
Molybdenum(II) chloride MoCl2, which exists as the hexamer Mo6Cl12 and the related dianion [Mo6Cl14]2-.
Molybdenum(III) chloride MoCl3, a dark red solid, which converts to the anion trianionic complex [MoCl6]3-.
Molybdenum(VI) chloride MoCl6 is a black solid, which is monomeric and slowly decomposes to MoCl5 and Cl2 at room temperature.[32]
The accessibility of these oxidation states depends quite strongly on the halide counterion: althoughmolybdenum(VI) fluoride is stable, molybdenum does not form a stable hexachloride, pentabromide, or tetraiodide.[33]
Likechromium and some other transition metals, molybdenum formsquadruple bonds, such as in Mo2(CH3COO)4 and [Mo2Cl8]4−.[26][34] TheLewis acid properties of the butyrate and perfluorobutyrate dimers,Mo2(O2CR)4 and Rh2(O2CR)4, have been reported.[35]
The oxidation state 0 and lower are possible with carbon monoxide as ligand, such as inmolybdenum hexacarbonyl, Mo(CO)6.[26][28]
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 weregraphite. Like graphite, molybdenite can be used to blacken a surface or as a solid lubricant.[36] Even when molybdena was distinguishable from graphite, it was still confused with the commonlead ore PbS (now calledgalena); the name comes fromAncient GreekΜόλυβδοςmolybdos, meaninglead.[20] (The Greek word itself has been proposed as aloanword fromAnatolianLuvian andLydian languages).[37]
By 1778Swedish chemistCarl Wilhelm Scheele stated firmly that molybdena was (indeed) neither galena nor graphite.[41][42] Instead, Scheele correctly proposed that molybdena was an ore of a distinct new element, namedmolybdenum for the mineral in which it resided, and from which it might be isolated.Peter Jacob Hjelm successfully isolated molybdenum usingcarbon andlinseed oil in 1781.[20][43]
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.[44][45][46] Early molybdenum steel alloys showed great promise of increased hardness, but efforts to manufacture 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 molybdenumductile, 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.[47] In 1913,Frank E. Elmore developed afroth flotation process to recovermolybdenite from ores; flotation remains the primary isolation process.[48]
DuringWorld War I, demand for molybdenum spiked; it was used both inarmor plating and as a substitute for tungsten inhigh-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.[20] The Germans also used molybdenum-dopedsteel for heavy artillery, like in the super-heavy howitzerBig Bertha,[49] because traditional steel melts at the temperatures produced by the propellant of theone ton shell.[50] After the war, demand plummeted until metallurgical advances allowed extensive development of peacetime applications. InWorld War II, molybdenum again saw strategic importance as a substitute for tungsten in steel alloys.[51]
Molybdenum is the54th most abundant element in 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.[20][52] The SovietLuna 24 mission discovered a molybdenum-bearing grain (1 × 0.6 μm) in apyroxene fragment taken fromMare Crisium on theMoon.[53] The comparative rarity of molybdenum in 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 suchminerals aswulfenite (PbMoO4) andpowellite (CaMoO4), the main commercial source ismolybdenite (MoS2). Molybdenum is mined as a principal ore and is also recovered as a byproduct of copper and tungsten mining.[12]
The world's production of molybdenum 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 the rest of Asia (mostly Armenia, Russia, Iran and Mongolia) produce the remainder.[54]
World production trend
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 themolybdenum(VI) oxide:[26]
The resulting oxide is then usually extracted with aqueous ammonia to give ammonium molybdate:
Copper, an impurity in molybdenite, is separated at this stage by treatment withhydrogen sulfide.[26] Ammonium molybdate converts toammonium dimolybdate, which is isolated as a solid. Heating this solid gives molybdenum trioxide:[55]
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 is reduced by thealuminothermic reaction with addition of iron to produceferromolybdenum. A common form of ferromolybdenum contains 60% molybdenum.[26][56]
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.[57] In 2008, theLondon Metal Exchange announced that molybdenum would be traded as a commodity.[58]
TheKnaben mine in southern Norway, opened in 1885, was the first dedicated molybdenum mine. Closed in 1973 but reopened in 2007,[59] it now produces 100,000 kilograms (98 long tons; 110 short tons) of molybdenum disulfide per year. Large mines in Colorado (such as theHenderson mine and theClimax mine)[60] and in British Columbia yield molybdenite as their primary product, while manyporphyry copper deposits such as theBingham Canyon Mine in Utah and theChuquicamata mine in northern Chile produce molybdenum as a byproduct of copper-mining.
About 86% of molybdenum produced is used inmetallurgy, 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%, andsuperalloys 5%.[61]
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 inlight bulbs.[20][62]
Most high-strength steelalloys (for example,41xx steels) contain 0.25% to 8% molybdenum.[12] Even in these small portions, more than 43,000 tonnes of molybdenum are used each year instainless steels,tool steels, cast irons, and high-temperaturesuperalloys.[52]
Molybdenum is also used in steel alloys for its highcorrosion resistance andweldability.[52][54] Molybdenum contributes corrosion resistance to type-300 stainless steels (specifically type-316) and especially so in the so-calledsuperaustenitic stainless steels (such as alloyAL-6XN, 254SMO and 1925hMo). Molybdenum increases lattice strain, thus increasing the energy required to dissolve iron atoms from the surface.[contradictory] Molybdenum is also used to enhance the corrosion resistance of ferritic (for example grade 444)[63] and martensitic (for example 1.4122 and 1.4418) stainless steels.[citation needed]
Because of its lower density and more stable price, molybdenum is sometimes used in place of tungsten.[52] 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 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.[62]
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 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 inmolten salt reactors for 1100 hours with so little corrosion that it was difficult to measure.[64][65] Due to its excellent mechanical properties under high temperature and high pressure, TZM alloys are extensively applied in the military industry.[66] It is used as the valve body oftorpedo engines,rocket nozzles and gas pipelines, where it can withstand extreme thermal and mechanical stresses.[67][68] It is also used asradiation shields in nuclear applications.[69]
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.[70]
Molybdenum powder is used as a fertilizer for some plants, such ascauliflower.[52]
Elemental molybdenum is used in NO, NO2, NOx analyzers in power plants for pollution controls. At 350 °C (662 °F), the element acts as a catalyst for NO2/NOx to form NO molecules for detection by infrared light.[71]
Molybdenum anodes replace tungsten in certain low voltage X-ray sources for specialized uses such asmammography.[72]
The radioactive isotopemolybdenum-99 is used to generatetechnetium-99m, used for medical imaging[73] The isotope is handled and stored as the molybdate.[74]
Molybdenum disulfide (MoS2) is used as a solidlubricant and a high-pressure high-temperature (HPHT) anti-wear agent. It forms strong films on metallic surfaces and is a common additive to HPHT greases — in the event of a catastrophic grease failure, a thin layer of molybdenum prevents contact of the lubricated parts.[75]
When combined with small amounts of cobalt, MoS2 is also used as a catalyst in thehydrodesulfurization (HDS) of petroleum. In the presence of hydrogen, this catalyst facilitates the removal of nitrogen and especially sulfur from the feedstock, which otherwise would poison downstream catalysts. HDS is one of the largest scale applications of catalysis in industry.[76]
Molybdenum oxides are important catalysts for selective oxidation of organic compounds. The production of the commodity chemicalsacrylonitrile andformaldehyde relies on MoOx-based catalysts.[55]
Lead molybdate (wulfenite) co-precipitated with lead chromate and lead sulfate is a bright-orange pigment used with ceramics and plastics.[78]
The molybdenum-based mixed oxides are versatile catalysts in the chemical industry. Some examples are the catalysts for the oxidation of carbon monoxide, propylene toacrolein and acrylic acid, theammoxidation of propylene to acrylonitrile.[79][80]
Molybdenum carbides, nitride and phosphides can be used for hydrotreatment of rapeseed oil.[81]
Molybdenum, despite its low concentration in the environment, is a critically important element for Earth'sbiosphere due to its presence in the most commonnitrogenases. Without molybdenum,nitrogen fixation would be greatly reduced, and a large part ofbiosynthesis as we know it would not occur. Molybdenum is also essential to many individual organisms as a component of enzymes, particularly as part of themolybdopterin class ofcofactors.
Molybdenum 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 ofeukaryotic life (which includes all plants and animals).[85]
In terms of function, molybdoenzymes catalyze the oxidation and sometimes reduction of certain small molecules in the process of regulatingnitrogen,sulfur, andcarbon.[89] In some animals, and in humans, the oxidation ofxanthine touric acid, a process ofpurinecatabolism, is catalyzed byxanthine 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 affectsprotein synthesis,metabolism, and growth.[90]
Mo is a component in mostnitrogenases. Among molybdoenzymes, nitrogenases are unique in lacking the molybdopterin.[91][92] Nitrogenases catalyze the production of ammonia from atmospheric nitrogen:
Structure of theFeMoco active site ofnitrogenaseThe molybdenum cofactor (pictured) is composed of a molybdenum-free organic complex calledmolybdopterin, which has bound an oxidized molybdenum(VI) atom through adjacent sulfur (or occasionally selenium) atoms. Except for the ancient nitrogenases, all known Mo-using enzymes use this cofactor.
Molybdate is transported in the body as MoO42−.[90]
Molybdenum is an essential tracedietary element.[94] Four mammalian Mo-dependent enzymes are known, all of them harboring apterin-basedmolybdenum cofactor (Moco) in their active site:sulfite oxidase,xanthine oxidoreductase,aldehyde oxidase, andmitochondrial amidoxime reductase.[95] People severely deficient in molybdenum have poorly functioning sulfite oxidase and are prone to toxic reactions to sulfites in foods.[96][97] The human body contains about 0.07 mg of molybdenum per kilogram of body weight,[98] with higher concentrations in the liver and kidneys and lower in the vertebrae.[52] Molybdenum is also present within humantooth enamel and may help prevent its decay.[99]
Acute toxicity has not been seen in humans, and the toxicity depends strongly on the chemical state. Studies on rats show amedian lethal dose (LD50) as low as 180 mg/kg for some Mo compounds.[100] 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, andgout; it can also affect the lungs, kidneys, and liver.[101][102]Sodium tungstate is acompetitive inhibitor of molybdenum. Dietary tungsten reduces the concentration of molybdenum in tissues.[52]
Low soil concentration of molybdenum in a geographical band from northern China to Iran results in a general dietarymolybdenum deficiency and is associated with increased rates ofesophageal cancer.[103][104][105] Compared to the United States, which has a greater supply of molybdenum in the soil, people living in those areas have about 16 times greater risk foresophagealsquamous cell carcinoma.[106]
Molybdenum deficiency has also been reported as a consequence of non-molybdenum supplementedtotal parenteral nutrition (complete intravenous feeding) for long periods of time. It results in high blood levels ofsulfite andurate, in much the same way asmolybdenum cofactor deficiency. Since pure molybdenum deficiency from this cause occurs primarily in adults, the neurological consequences are not as marked as in cases of congenital cofactor deficiency.[107]
A congenitalmolybdenum cofactor deficiency disease, seen in infants, is an inability to synthesizemolybdenum cofactor, the heterocyclic molecule discussed above that binds molybdenum at the active site in all known human enzymes that use molybdenum. The resulting deficiency results in high levels ofsulfite andurate, and neurological damage.[108][109]
Most molybdenum is excreted from the human body as molybdate in the urine. Furthermore, urinary excretion of molybdenum increases as dietary molybdenum intake increases. Small amounts of molybdenum are excreted from the body in the feces by way of the bile; small amounts also can be lost in sweat and in hair.[110][111]
High levels of molybdenum can interfere with the body's uptake ofcopper, producingcopper deficiency. Molybdenum prevents plasma proteins from binding to copper, and it also increases the amount of copper that is excreted inurine.Ruminants that consume high levels of molybdenum suffer fromdiarrhea, stunted growth,anemia, andachromotrichia (loss of fur pigment). These symptoms can be alleviated by copper supplements, either dietary and injection.[112] The effective copper deficiency can be aggravated by excesssulfur.[52][113]
Copper reduction or deficiency can also be deliberately induced for therapeutic purposes by the compoundammonium tetrathiomolybdate, in which the bright red aniontetrathiomolybdate is the copper-chelating agent. Tetrathiomolybdate was first used therapeutically in the treatment ofcopper toxicosis in animals. It was then introduced as a treatment inWilson's disease, a hereditary copper metabolism disorder in humans; it acts both by competing with copper absorption in the bowel and by increasing excretion. It has also been found to have an inhibitory effect onangiogenesis, potentially by inhibiting the membrane translocation process that is dependent on copper ions.[114] This is a promising avenue for investigation of treatments forcancer,age-related macular degeneration, and other diseases that involve a pathologic proliferation of blood vessels.[115][116]
In some grazing livestock, most strongly in cattle, molybdenum excess in the soil of pasturage can produce scours (diarrhea) if the pH of the soil is neutral to alkaline; seeteartness.
Molybdenum targets are used in mammography because they produce X-rays in the energy range of 17-20 keV, which is optimal for imaging soft tissues like the breast.[117][118] The characteristic X-rays emitted from molybdenum provide high contrast between different types of tissues, allowing for the effective visualization of microcalcifications and other subtle abnormalities in breast tissue.[119] This energy range also minimizes radiation dose while maximizing image quality, making molybdenum targets particularly suitable for breast cancer screening.[120]
In 2000, the then U.S. Institute of Medicine (now theNational Academy of Medicine, NAM) updated its Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for molybdenum. If there is not sufficient information to establish EARs and RDAs, an estimate designatedAdequate Intake (AI) is used instead.
An AI of 2 micrograms (μg) of molybdenum per day was established for infants up to 6 months of age, and 3 μg/day from 7 to 12 months of age, both for males and females. For older children and adults, the following daily RDAs have been established for molybdenum: 17 μg from 1 to 3 years of age, 22 μg from 4 to 8 years, 34 μg from 9 to 13 years, 43 μg from 14 to 18 years, and 45 μg for persons 19 years old and older. All these RDAs are valid for both sexes.Pregnant orlactating females from 14 to 50 years of age have a higher daily RDA of 50 μg of molybdenum.
As for safety, the NAM setstolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of molybdenum, the UL is 2000 μg/day. Collectively the EARs, RDAs, AIs and ULs are referred to asDietary Reference Intakes (DRIs).[121]
TheEuropean Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL are defined the same as in the United States. For women and men ages 15 and older, the AI is set at 65 μg/day. Pregnant and lactating women have the same AI. For children aged 1–14 years, the AIs increase with age from 15 to 45 μg/day. The adult AIs are higher than the U.S. RDAs,[122] but on the other hand, the European Food Safety Authority reviewed the same safety question and set its UL at 600 μg/day, which is much lower than the U.S. value.[123]
For U.S. food and dietary supplement labeling purposes, the amount in a serving is expressed as a percent of Daily Value (%DV). For molybdenum labeling purposes, 100% of the Daily Value was 75 μg, but as of May 27, 2016 it was revised to 45 μg.[124][125] A table of the old and new adult daily values is provided atReference Daily Intake.
Average daily intake varies between 120 and 240 μg/day, which is higher than dietary recommendations.[101] Pork, lamb, and beefliver each have approximately 1.5 parts per million of molybdenum. Other significant dietary sources include green beans, eggs, sunflower seeds, wheat flour, lentils, cucumbers, and cereal grain.[20]
Molybdenum dusts and fumes, generated by mining or metalworking, can be toxic, especially if ingested (including dust trapped in thesinuses and later swallowed).[100] Low levels of prolonged exposure can cause irritation to the eyes and skin. Direct inhalation or ingestion of molybdenum and its oxides should be avoided.[126][127]OSHA regulations specify the maximum permissible molybdenum exposure in an 8-hour day as 5 mg/m3. Chronic exposure to 60 to 600 mg/m3 can cause symptoms including fatigue, headaches and joint pains.[128] At levels of 5000 mg/m3, molybdenum isimmediately dangerous to life and health.[129]
^abcArblaster, John W. (2018).Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International.ISBN978-1-62708-155-9.
^Mo(–4) occurs inNa4Mo(CO)4; seeJohn E. Ellis (2003). "Metal Carbonyl Anions: from [Fe(CO)4]2− to [Hf(CO)6]2− and Beyond†".Organometallics.22 (17):3322–3338.doi:10.1021/om030105l.
^Mo(0) occurs inmolybdenum hexacarbonyl; seeJohn E. Ellis (2003). "Metal Carbonyl Anions: from [Fe(CO)4]2− to [Hf(CO)6]2− and Beyond†".Organometallics.22 (17):3322–3338.doi:10.1021/om030105l.
^Lindemann, A.; Blumm, J. (2009).Measurement of the Thermophysical Properties of Pure Molybdenum. Vol. 3. 17thPlansee Seminar.
^abcdLide, David R., ed. (1994). "Molybdenum".CRC Handbook of Chemistry and Physics. Vol. 4. Chemical Rubber Publishing Company. p. 18.ISBN978-0-8493-0474-3.
^abcdefghHolleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985).Lehrbuch der Anorganischen Chemie (91–100 ed.). Walter de Gruyter. pp. 1096–1104.ISBN978-3-11-007511-3.
^Ellis, J. E. (2003). "Metal Carbonyl Anions: from [Fe(CO)4]2− to [Hf(CO)6]2− and Beyond".Organometallics.22 (17):3322–3338.doi:10.1021/om030105l.
^Pope, Michael T.; Müller, Achim (1997). "Polyoxometalate Chemistry: An Old Field with New Dimensions in Several Disciplines".Angewandte Chemie International Edition.30:34–48.doi:10.1002/anie.199100341.
^Tamadon, Farhad; Seppelt, Konrad (2013-01-07). "The Elusive Halides VCl 5, MoCl 6, and ReCl 6".Angewandte Chemie International Edition.52 (2):767–769.doi:10.1002/anie.201207552.PMID23172658.
^Walton, Richard A.; Fanwick, Phillip E.; Girolami, Gregory S.; Murillo, Carlos A.; Johnstone, Erik V. (2014). Girolami, Gregory S.; Sattelberger, Alfred P. (eds.).Inorganic Syntheses: Volume 36. John Wiley & Sons. pp. 78–81.doi:10.1002/9781118744994.ch16.ISBN978-1118744994.
^Drago, Russell S.; Long, John R.; Cosmano, Richard (1982-06-01). "Comparison of the coordination chemistry and inductive transfer through the metal-metal bond in adducts of dirhodium and dimolybdenum carboxylates".Inorganic Chemistry.21 (6):2196–2202.doi:10.1021/ic00136a013.ISSN0020-1669.
^Lansdown, A. R. (1999).Molybdenum disulphide lubrication. Tribology and Interface Engineering. Vol. 35. Elsevier.ISBN978-0-444-50032-8.
^Hoyt, Samuel Leslie (1921).Metallography. Vol. 2. McGraw-Hill.
^Krupp, Alfred; Wildberger, Andreas (1888).The metallic alloys: A practical guide for the manufacture of all kinds of alloys, amalgams, and solders, used by metal-workers ... with an appendix on the coloring of alloys. H.C. Baird & Co. p. 60.
^Gupta, C. K. (1992).Extractive Metallurgy of Molybdenum. CRC Press.ISBN978-0-8493-4758-0.
^Kean, Sam (2011-06-06).The Disappearing Spoon: And Other True Tales of Madness, Love, and the History of the World from the Periodic Table of the Elements (Illustrated ed.). Back Bay Books. pp. 88–89.ISBN978-0-316-05163-7.
^abcdefghConsidine, Glenn D., ed. (2005). "Molybdenum".Van Nostrand's Encyclopedia of Chemistry. New York: Wiley-Interscience. pp. 1038–1040.ISBN978-0-471-61525-5.
^Jambor, J.L.; et al. (2002)."New mineral names"(PDF).American Mineralogist.87: 181.Archived(PDF) from the original on 2007-07-10. Retrieved2007-04-09.
^abSebenik, Roger F.; Burkin, A. Richard; Dorfler, Robert R.; Laferty, John M.; Leichtfried, Gerhard; Meyer-Grünow, Hartmut; Mitchell, Philip C. H.; Vukasovich, Mark S.; Church, Douglas A.; Van Riper, Gary G.; Gilliland, James C.; Thielke, Stanley A. (2000). "Molybdenum and Molybdenum Compounds".Ullmann's Encyclopedia of Industrial Chemistry.doi:10.1002/14356007.a16_655.ISBN3527306730.S2CID98762721.
^Gupta, C. K. (1992).Extractive Metallurgy of Molybdenum. CRC Press. pp. 1–2.ISBN978-0-8493-4758-0.
^Langedal, M. (1997). "Dispersion of tailings in the Knabena—Kvina drainage basin, Norway, 1: Evaluation of overbank sediments as sampling medium for regional geochemical mapping".Journal of Geochemical Exploration.58 (2–3):157–172.Bibcode:1997JCExp..58..157L.doi:10.1016/S0375-6742(96)00069-6.
^Coffman, Paul B. (1937). "The Rise of a New Metal: The Growth and Success of the Climax Molybdenum Company".The Journal of Business of the University of Chicago.10: 30.doi:10.1086/232443.
^Smallwood, Robert E. (1984)."TZM Moly Alloy".ASTM special technical publication 849: Refractory metals and their industrial applications: a symposium. ASTM International. p. 9.ISBN978-0803102033.
^Yang, Zhi; Hu, Ke (2018). "Diffusion bonding between TZM alloy and WRe alloy by spark plasma sintering".Journal of Alloys and Compounds.764:582–590.doi:10.1016/j.jallcom.2018.06.111.
^Everett, M.M.; Miller, W.A. (1974). "The role of phosphotungstic and phosphomolybdic acids in connective tissue staining I. Histochemical studies".The Histochemical Journal.6 (1):25–34.doi:10.1007/BF01011535.PMID4130630.
^Enemark, John H.; Cooney, J. Jon A.; Wang, Jun-Jieh; Holm, R. H. (2004). "Synthetic Analogues and Reaction Systems Relevant to the Molybdenum and Tungsten Oxotransferases".Chem. Rev.104 (2):1175–1200.doi:10.1021/cr020609d.PMID14871153.
^Mendel, Ralf R.; Bittner, Florian (2006). "Cell biology of molybdenum".Biochimica et Biophysica Acta (BBA) - Molecular Cell Research.1763 (7):621–635.doi:10.1016/j.bbamcr.2006.03.013.PMID16784786.
^Chi Chung, Lee; Markus W., Ribbe; Yilin, Hu (2014). "Biochemistry of Methyl-Coenzyme M Reductase: The Nickel Metalloenzyme that Catalyzes the Final Step in Synthesis and the First Step in Anaerobic Oxidation of the Greenhouse Gas Methane". In Peter M.H. Kroneck; Martha E. Sosa Torres (eds.).The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment. Metal Ions in Life Sciences. Vol. 14. Springer. pp. 147–174.doi:10.1007/978-94-017-9269-1_6.ISBN978-94-017-9268-4.PMID25416393.
^Schwarz, Guenter; Belaidi, Abdel A. (2013). "Molybdenum in Human Health and Disease". In Astrid Sigel; Helmut Sigel; Roland K. O. Sigel (eds.).Interrelations between Essential Metal Ions and Human Diseases. Metal Ions in Life Sciences. Vol. 13. Springer. pp. 415–450.doi:10.1007/978-94-007-7500-8_13.ISBN978-94-007-7499-5.PMID24470099.
^Curzon, M. E. J.; Kubota, J.; Bibby, B. G. (1971). "Environmental Effects of Molybdenum on Caries".Journal of Dental Research.50 (1):74–77.doi:10.1177/00220345710500013401.S2CID72386871.
^Reiss, J. (2000). "Genetics of molybdenum cofactor deficiency".Human Genetics.106 (2):157–63.doi:10.1007/s004390051023 (inactive 1 November 2024).PMID10746556.{{cite journal}}: CS1 maint: DOI inactive as of November 2024 (link)
^Brewer GJ; Hedera, P.; Kluin, K. J.; Carlson, M.; Askari, F.; Dick, R. B.; Sitterly, J.; Fink, J. K. (2003). "Treatment of Wilson disease with ammonium tetrathiomolybdate: III. Initial therapy in a total of 55 neurologically affected patients and follow-up with zinc therapy".Arch Neurol.60 (3):379–85.doi:10.1001/archneur.60.3.379.PMID12633149.
^Brewer, G. J.; Dick, R. D.; Grover, D. K.; Leclaire, V.; Tseng, M.; Wicha, M.; Pienta, K.; Redman, B. G.; Jahan, T.; Sondak, V. K.; Strawderman, M.; LeCarpentier, G.; Merajver, S. D. (2000). "Treatment of metastatic cancer with tetrathiomolybdate, an anticopper, antiangiogenic agent: Phase I study".Clinical Cancer Research.6 (1):1–10.PMID10656425.
_NIST_ASD_emission_spectrum.png)
