Molybdenum 19052 221521967 2008-06-24T21:39:21Z DOI bot 6652755 Citation maintenance. Formatted: pages. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. {{Elementbox_header | number=42 | symbol=Mo | name=molybdenum | left=[[niobium]] | right=[[technetium]] | above=[[chromium|Cr]] | below=[[tungsten|W]] | color1=#ffc0c0 | color2=black }} {{Elementbox_series | [[transition metal]]s }} {{Elementbox_groupperiodblock | group=6 | period=5 | block=d }} {{Elementbox_appearance_img | Mo,42| gray metallic }} {{Elementbox_atomicmass_gpm | [[1 E-25 kg|95.94]][[List of elements by atomic mass|(2)]] }} {{Elementbox_econfig | &#91;[[krypton|Kr]]&#93; 4d<sup>5</sup> 5s<sup>1</sup> }} {{Elementbox_epershell | 2, 8, 18, 13, 1 }} {{Elementbox_section_physicalprop | color1=#ffc0c0 | color2=black }} {{Elementbox_phase | [[solid]] }} {{Elementbox_density_gpcm3nrt | 10.28 }} {{Elementbox_densityliq_gpcm3mp | 9.33 }} {{Elementbox_meltingpoint | k=2896 | c=2623 | f=4753 }} {{Elementbox_boilingpoint | k=4912 | c=4639 | f=8382 }} {{Elementbox_heatfusion_kjpmol | 37.48 }} {{Elementbox_heatvaporiz_kjpmol | 617 }} {{Elementbox_heatcapacity_jpmolkat25 | 24.06 }} {{Elementbox_vaporpressure_katpa | 2742 | 2994 | 3312 | 3707 | 4212 | 4879 | comment= }} {{Elementbox_section_atomicprop | color1=#ffc0c0 | color2=black }} {{Elementbox_crystalstruct | cubic body centered }} {{Elementbox_oxistates | '''6''', 5, 4, 3, 2, 1<ref>{{cite web|url=http://openmopac.net/data_normal/molybdenum(i)%20fluoride_jmol.html|title=Molybdenum: molybdenum(I) fluoride compound data|accessdate=2007-12-10|publisher=OpenMOPAC.net}}</ref><br />(strongly [[acid]]ic oxide) }} {{Elementbox_electroneg_pauling | 2.16 }} {{Elementbox_ionizationenergies4 | 684.3 | 1560 | 2618 }} {{Elementbox_atomicradius_pm | [[1 E-10 m|145]] }} {{Elementbox_atomicradiuscalc_pm | [[1 E-10 m|190]] }} {{Elementbox_covalentradius_pm | [[1 E-10 m|145]] }} {{Elementbox_section_miscellaneous | color1=#ffc0c0 | color2=black }} {{Elementbox_magnetic | no data }} {{Elementbox_eresist_ohmmat20 | 53.4 n}} {{Elementbox_thermalcond_wpmkat300k | 138 }} {{Elementbox_thermalexpansion_umpmkat25 | 4.8 }} {{Elementbox_speedofsound_rodmpsatrt | 5400 }} {{Elementbox_youngsmodulus_gpa | 329 }} {{Elementbox_shearmodulus_gpa | 126 }} {{Elementbox_bulkmodulus_gpa | 230 }} {{Elementbox_poissonratio | 0.31 }} {{Elementbox_mohshardness | 5.5 }} {{Elementbox_vickershardness_mpa | 1530 }} {{Elementbox_brinellhardness_mpa | 1500 }} {{Elementbox_cas_number | 7439-98-7 }} {{Elementbox_isotopes_begin | color1=#ffc0c0 | color2=black }} {{Elementbox_isotopes_stable | mn=92 | sym=Mo | na=14.84% | n=50 }} {{Elementbox_isotopes_decay | mn=93 | sym=Mo | na=[[synthetic radioisotope|syn]] | hl=4&times;10<sup>3</sup> [[year|y]] | dm=[[electron capture|ε]] | de=- | pn=93 | ps=[[niobium|Nb]] }} {{Elementbox_isotopes_stable | mn=94 | sym=Mo | na=9.25% | n=52 }} {{Elementbox_isotopes_stable | mn=95 | sym=Mo | na=15.92% | n=53 }} {{Elementbox_isotopes_stable | mn=96 | sym=Mo | na=16.68% | n=54 }} {{Elementbox_isotopes_stable | mn=97 | sym=Mo | na=9.55% | n=55 }} {{Elementbox_isotopes_stable | mn=98 | sym=Mo | na=24.13% | n=56 }} {{Elementbox_isotopes_decay2 | mn=99 | sym=Mo | na=[[synthetic radioisotope|syn]] | hl=65.94 [[hour|h]] | dm1=[[beta emission|β<sup>-</sup>]] | de1=0.436, 1.214 | pn1=99 | ps1=[[technetium|Tc]] | dm2=[[gamma ray|γ]] | de2=0.74, 0.36,<br />0.14| pn2= | ps2=- }} {{Elementbox_isotopes_decay | mn=100 | sym=Mo | na=9.63% | hl=7.8&times;10<sup>18</sup> [[year|y]] | dm=[[double beta decay|β<sup>-</sup>β<sup>-</sup>]] | de=3.04 | pn=100 | ps=[[ruthenium|Ru]] }} {{Elementbox_isotopes_end}} {{Elementbox_footer | color1=#ffc0c0 | color2=black }} '''Molybdenum''' ({{pronEng|məˈlɪbdənəm}}, from the [[Greek language|Greek]] meaning "[[lead]]-like"), is a [[Group 6 element|Group 6]] [[chemical element]] with the symbol '''Mo''' and [[atomic number]] 42. It has the sixth-highest melting point of any element, and for this reason it is often used in high-strength steel alloys. Molybdenum is found in trace amounts in plants and animals, although excess molybdenum can be toxic in some animals. Molybdenum was discovered in 1778 by [[Carl Wilhelm Scheele]] and first isolated in 1781 by [[Peter Jacob Hjelm]]. == Characteristics == Molybdenum is a [[transition metal]] with an [[electronegativity]] of 1.8 on the Pauling scale and an atomic mass of 95.9&nbsp;g/mole.<ref>{{cite web | title = Properties of Molybdenum | work = Integral Scientist Periodic Table | publisher = Qivx, Inc. | date= 2003 | url = http://www.qivx.com/ispt/elements/ptw_042.php | accessdate = 2007-06-10 }}</ref> It does not react with oxygen or water at room temperature. At elevated temperatures, molybdenum trioxide is formed in the reaction 2Mo + 3O<sub>2</sub> → 2MoO<sub>3</sub>.<ref>{{cite web| last = Winter| first = Mark| title = Chemistry| work = Molybdenum| publisher = The University of Sheffield| url = http://www.webelements.com/webelements/elements/text/Mo/chem.html| accessdate = 2007-06-10 }}</ref> In its pure metal form, molybdenum is silvery white with a [[Mohs_scale_of_mineral_hardness|Mohs hardness]] of 5.5, though it is somewhat more [[ductile]] than tungsten. It has a [[melting point]] of 2623°C, and only [[tantalum]], [[osmium]], [[rhenium]], and [[tungsten]] have higher melting points.<ref name="CRCdescription" /> Molybdenum burns only at temperatures above 600°C.<ref name="Nostrand">{{Citation |contribution = Molybdenum |year = 2005| title = Van Nostrand's Encyclopedia of Chemistry| editor-last = Considine| editor-first = Glenn D.| pages = 1038–1040| place= New York| publisher = Wylie-Interscience| id = 0-471-61525-0 }}</ref> It also has the lowest heating expansion of any commercially used metal.<ref name="nbb" /> Molybdenum has a value of approximately $65,000 per [[tonne]] as of 4 May 2007. It maintained a price at or near $10,000 per tonne from 1997 through 2002, and reached a high of $103,000 per tonne in June 2005.<ref>{{cite web| title = Dynamic Prices and Charts for Molybdenum | publisher = InfoMine Inc. | date= 2007 | url = http://www.infomine.com/investment/metalschart.asp?c=molybdenum&u=mt&submit1=Display+Chart&x=usd&r=15y | accessdate = 2007-05-07 }}</ref> == Isotopes == {{Main|Isotopes of molybdenum}} There are 35 known [[isotopes]] of molybdenum ranging in [[atomic mass]] from 83 to 117, as well as four metastable [[nuclear isomer]]s. Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and 100. Of these naturally occurring isotopes, five are stable, with atomic masses from 94 to 98. All unstable isotopes of molybdenum decay into isotopes of [[niobium]], [[technetium]], and [[ruthenium]].<ref name="CRCisotopes">{{Citation |year = 2006 |title = CRC Handbook of Chemistry and Physics |editor-last = Lide |editor-first = David R. |volume = 11 |pages = 87–88 |publisher = CRC |id = 0-8493-0487-3 }}</ref> Molybdenum-92 and molybdenum-100 are the only naturally occurring isotopes that are not stable. Molybdenum-100 has a [[half-life]] of approximately 1×10<sup>19</sup>&nbsp;[[year|y]] and undergoes [[double beta decay]] into [[ruthenium]]-100. Molybdenum-98 is the most common isotope, comprising 24.14% of all molybdenum. Molybdenum isotopes with mass numbers from 111 to 117 all have half-lives of approximately .15&nbsp;μs.<ref name="CRCisotopes"/> == Occurrence == [[Image:2005molybdenum (mined).PNG|thumb|left|Molybdenum output in 2005]] The world's largest producers of molybdenum materials are the United States, Canada, Chile, Russia, and China.<ref>{{Citation |year = 2006 |title = CRC Handbook of Chemistry and Physics |editor-last = Lide |editor-first = David R. |volume = 4 |pages = 22–23 |publisher = Chemical Rubber Publishing Company |id = 0-8493-0487-3 }}</ref><ref name="nbb">{{cite book| last = Emsley| first = John| title = Nature's Building Blocks| publisher = Oxford University Press| date= 2001| location = Oxford| pages = 262-266| id = 0-19-850341-5 }}</ref> Though molybdenum is found in such [[mineral]]s as [[wulfenite]] ([[lead|Pb]]Mo[[oxygen|O]]<sub>4</sub>) and [[powellite]] ([[calcium|Ca]]Mo[[oxygen|O]]<sub>4</sub>), the main commercial source of molybdenum is [[molybdenite]] (Mo[[sulfur|S]]<sub>2</sub>). Molybdenum is mined as a principal ore, and is also recovered as a byproduct of copper and tungsten mining.<ref name="CRCdescription" /> Large mines in [[Colorado]] ([[Climax, Colorado|Climax]]) and in [[British Columbia]] yield [[molybdenite]], while many [[porphyry copper]] deposits such as the [[Chuquicamata]] mine in northern [[Chile]] produce molybdenum as a byproduct of copper mining. The Knaben mine in southern Norway was opened in 1885, making it the first molybdenum mine. It remained open until 1973. Molybdenum is the 42nd-most-abundant element in the universe, and the 25th-most-abundant element in Earth's oceans, with an average of 10.8&nbsp;mt/km³.<ref name="Nostrand" /> The Russian [[Luna 24]] mission discovered a single molybdenum-bearing grain (1 &times; 0.6&nbsp;µm) in a [[pyroxene]] fragment taken from [[Mare Crisium]] on the [[Moon]].<ref>{{cite web | url=http://www.minsocam.org/msa/AmMin/TOC/Abstracts/2002_Abstracts/Jan02_Abstracts/Jambor_p181_02.pdf | title=American Mineralogist, Volume 87, pages 181-184, 2002 | accessdate=2007-04-09}}</ref> A side product of molybdenum mining is [[rhenium]]. As it is always present in small varying quantities in molybdenite, the only commercial source for rhenium is molybdenum mines. ==Compounds== {{seealso|Category:Molybdenum compounds}} {{Expand|date=December 2007}} Molybdenum has several common [[oxidation state]]s, +2 +3 +4 +5 and +6. The highest oxidation state is common in the [[molybdenum(VI) oxide]] MoO<sub>3</sub> while the normal sulfur compound is [[molybdenum disulfide]] MoS<sub>2</sub>. The broad range of oxidation states shows up in the chlorides of molybdenum: *[[Molybdenum(II) chloride]] MoCl<sub>2</sub> (yellow solid), *[[Molybdenum(III) chloride]] MoCl<sub>3</sub> (dark red solid), *[[Molybdenum(V) chloride]] MoCl<sub>5</sub> (dark green solid), *[[Molybdenum(VI) chloride]] MoCl<sub>6</sub> (brown solid), Like [[chromium]] and some other transition metals molybdenum is able to form [[quadruple bond]]s == Biological role == The most important use of the molybdenum atom in living organisms is as a metal hetero-atom at the active site in certain enzymes. In [[nitrogen fixation]] in certain bacteria, the [[nitrogenase]] enzyme which is involved in the terminal step of reducing molecular nitrogen, usually contains molybdenum in the active site (though replacement of Mo with iron or vanadium is known). In March 2008, researchers reported that they had found strong evidence for the hypothesis that a scarcity of molybdenum in the earth's early oceans was a limiting factor in the further evolution of [[eukaryote|eukaryotic life]] (which includes all plants and animals) as eukaryotes cannot fix nitrogen and must acquire it from prokaryotic bacteria. [http://www.eurekalert.org/pub_releases/2008-03/asu-ito032508.php] [http://www.eurekalert.org/pub_releases/2008-03/nu-sut032508.php] The scarcity of molybdenum resulted from the relative lack of oxygen in the early ocean. Oxygen dissolved in seawater is the primary mechanism for dissolving molybdenum from minerals on the sea bottom. Though molybdenum forms compounds with various [[organic molecule]]s, including [[carbohydrate]]s and [[amino acid]]s, it is transported throughout the human body as MoO<sub>4</sub><sup>2-</sup>.<ref name="IMOAoverview">{{cite web| last = Mitchell| first = Phillip C. H.| title = Overview of Environment Database| publisher = International Molybdenum Association| date= 2003| url = http://www.hse.imoa.info/Default.asp?page=110| accessdate = 2007-05-05 }}</ref> Molybdenum is present in approximately 20 enzymes in animals, including [[aldehyde oxidase]], [[sulfite oxidase]], [[xanthine oxidase]].<ref name="nbb" /> In some animals, the oxidation of [[xanthine]] to [[uric acid]], 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. However, an extremely high concentration of molybdenum reverses the trend, and can act as an inhibitor in both purine catabolism and other processes. Molybdenum concentrations also affect [[protein synthesis]], [[metabolism]], and growth.<ref name="IMOAoverview" /> These enzymes in plants and animals catalyse the reaction of [[oxygen]] in small molecules, as part of the regulation of [[Nitrogen_cycle|nitrogen-]], [[Sulfur_cycle|sulfur-]] and [[Carbon_cycle|carbon cycle]]s. In a 70&nbsp;kg human body, there is approximately 9.3&nbsp;mg molybdenum, comprising .00001% of the total body mass.<ref>{{Citation |year = 2006 |title = CRC Handbook of Chemistry and Physics |editor-last = Lide |editor-first = David R. |volume = 7 |pages = 18 |publisher = Chemical Rubber Publishing Company |id = 0-8493-0487-3 }}</ref> It occurs in higher concentrations in the liver and kidneys, and in lower concentrations in the vertebrae.<ref name="Nostrand" /> Molybdenum is also present within human [[tooth enamel]] and may help prevent the decaying thereof.<ref>{{cite web| last = Ismail| first = Mumtaz| title = Dental Problems and Diet| work = Health and Nutrition| publisher = Bawarchi| url = http://www.bawarchi.com/health/dental.html| accessdate = 2007-05-19 }}</ref> Pork, lamb, and beef liver each have approximately 1.5 parts molybdenum per million. Other significant dietary sources include green beans, eggs, sunflower seeds, wheat flour, lentils, and cereal grain.<ref name="nbb" /> The average daily intake of molybdenum is .3&nbsp;mg. Acute toxicity hasn't been seen in humans, and the toxicity depends strongly on the chemical state. Rats show LD<sub>50</sub> as low as 180 mg/kg for some Mo compounds.<ref>{{cite web| url = http://rais.ornl.gov/tox/profiles/molybdenum_f_V1.shtml | publisher=Oak Ridge National Laboratory | title=Risk Assessment Information System: Toxicity Summary for Molybdenum| access-date=2008-04-23}}</ref> Molybdenum deficiency is not usually seen in healthy people.<ref>{{cite web| title = Nutrient Reference Values for Australia| publisher = National Medical and Health Research Council (Australia)| url = http://www.nrv.gov.au/Nutrients.aspx?code=71128006 | accessdate = 2008-04-23 }}</ref> [[Sodium tungstate]] is a [[competitive inhibition|competitive inhibitor]] of molybdenum. Dietary [[tungsten]] reduces the concentration of molybdenum in tissues.<ref name="Nostrand" /> === Copper-molybdenum antagonism === High amounts of molybdenum can interfere with the body's uptake of [[copper]], both by preventing plasma proteins from binding the copper and by increasing the amount of copper that is excreted in [[urine]]. [[Ruminant]]s that consume high amounts of molybdenum develop symptoms including [[diarrhea]], stunted growth, [[anemia]], and [[achromotrichia]]. These symptoms can be alleviated by the administration of more copper into the system, both in dietary form and by injection.<ref name="suttle">{{cite journal| last = Suttle| first = N. F.| title = Recent studies of the copper-molybdenum antagonism| journal = Proceedings of the Nutrition Society| volume = 33| issue = 3| pages = 299–305| publisher = CABI Publishing| date= December 1974| url = http://www.ingentaconnect.com/content/cabi/pns/1974/00000033/00000003/art00020| doi = 10.1079/PNS19740053| accessdate = 2007-05-11 }}</ref> The condition can be aggravated by excess [[sulfur]].<ref name="Nostrand" /> == Applications == The ability of molybdenum to withstand extreme temperatures without significantly expanding or softening makes it useful in applications that involve intense heat, including the manufacture of aircraft parts, electrical contacts, industrial motors, and filaments.<ref name="azom" /><ref name="nbb"/> Molybdenum is also used in [[alloy]]s for its high [[corrosion]] resistance and [[weldability]].<ref name="Nostrand" /><ref name="USGS">{{cite web| title = Molybdenum Statistics and Information| publisher = U.S. Geological Survey| date= 2007-05-10| url = http://minerals.usgs.gov/minerals/pubs/commodity/molybdenum/| accessdate = 2007-05-10 }}</ref> Most high-strength steel alloys are .25% to 8% molybdenum.<ref name="CRCdescription" /> Despite being used in such small portions, more than 43 million kg of molybdenum is used as an alloying agent each year in [[stainless steel]]s, [[tool steel]]s, [[cast iron]]s, and high-temperature [[superalloy]]s.<ref name="Nostrand" /> Because of its lower density and more stable price, molybdenum is implemented in the place of tungsten.<ref name="Nostrand" /> Molybdenum can be implemented both as an alloying agent and as a flame-resistant coating for other metals. Although its melting point is 2623 °C, molybdenum rapidly oxidizes at temperatures above 760 °C, making it better-suited for use in vacuum environments.<ref name="azom">{{cite web| title = Molybdenum| publisher = AZoM.com Pty. Limited| date= 2007| url = http://www.azom.com/details.asp?ArticleID=616| accessdate = 2007-05-06 }}</ref> Molybdenum 99 is used as a parent radioisotope to the radioisotope Technetium 99, which is used in many medical procedures [[Molybdenum disulfide]] (MoS<sub>2</sub>) is used as a lubricant and an agent. It forms strong films on metallic surfaces, and is highly resistant to both extreme temperatures and high pressure, and for this reason, it is a common additive to engine motor oil; in case of a catastrophic failure, the thin layer of molybdenum prevents metal-on-metal contact. Lead molybdate co-precipitated with lead chromate and lead sulfate is a bright-orange pigment used with ceramics and plastics.<ref> International Molybdenum Association, www.moly.imoa.info </ref> [[Molybdenum trioxide]] (MoO<sub>3</sub>) is used as an adhesive between [[enamel]]s and metals.<ref name="elemental" /> Molybdenum powder is used as a fertilizer for some plants, such as cauliflower.<ref name="Nostrand" /> Also used in NO, NO2, NOx analyzers in power plants for pollution controls. At 350 °C the element acts as a catalyst for NO2/NOx to form only NO molecules for consistent readings by infrared light. == History == Molybdenite (from the Greek Μόλυβδος ''molybdos'', meaning ''lead''),<ref name="CRCdescription">{{Citation| contribution = Molybdenum| year = 1994| title = CRC Handbook of Chemistry and Physics| editor-last = Lide| editor-first = David R.| volume = 4| pages = 18| publisher = Chemical Rubber Publishing Company| id = 0-8493-0474-1 }}</ref> the principal ore from which molybdenum is now extracted, was previously known as molybdena. Molybdena was confused with and often implemented as though it were [[graphite]]. Even when the two ores were distinguishable, molybdena was thought to be a [[lead]] ore.<ref name="nbb" /> In 1754, [[Bengt Qvist]] examined the mineral and determined that it did not contain lead.<ref name="vanderkroft">{{cite web| last = Van der Krogt| first = Peter| title = Molybdenum| work = Elementymology & Elements Multidict| date= 2006-01-10| url = http://www.vanderkroft.net/elements/elem/mo.html| accessdate = 2007-05-20 }}</ref> It was not until 1778 that [[Sweden|Swedish]] chemist [[Carl Wilhelm Scheele]] realized molybdena was neither graphite nor lead.<ref name="elemental">{{cite web| last = Gagnon| first = Steve| title = Molybdenum| publisher = Jefferson Science Associates, LLC| url = http://education.jlab.org/itselemental/ele042.html| accessdate = 2007-05-06 }}</ref><ref>{{cite journal | author = C. W. K. Scheele | title = Versuche mit Wasserbley;Molybdaena | journal = svenska vetensk. Academ. Handlingar | pages = 238 | year = 1779 | volume = 40 | issue = | url = http://dz1.gdz-cms.de/no_cache/dms/load/img/?IDDOC=120058 | format = {{dead link|date=June 2008}} &ndash; <sup>[http://scholar.google.co.uk/scholar?hl=en&lr=&q=author%3A+intitle%3AVersuche+mit+Wasserbley%3BMolybdaena&as_publication=svenska+vetensk.+Academ.+Handlingar&as_ylo=1779&as_yhi=1779&btnG=Search Scholar search]</sup>}}</ref> He and other chemists then correctly assumed that it was the ore of a distinct new element, named ''molybdenum'' for the mineral in which it was discovered. [[Peter Jacob Hjelm]] successfully isolated molybdenum using [[carbon]] and [[linseed oil]] in 1781.<ref name="nbb" /><ref>{{cite journal | author = P. J. Hjelm | title = Versuche mit Molybdäna, und Reduction der selben Erde | journal = svenska vetensk. Academ. Handlingar | pages = 268 | year = 1788 | volume = 49 | issue = | url = http://dz1.gdz-cms.de/no_cache/dms/load/img/?IDDOC=168136 | format = {{dead link|date=June 2008}} &ndash; <sup>[http://scholar.google.co.uk/scholar?hl=en&lr=&q=author%3A+intitle%3AVersuche+mit+Molybd%C3%A4na%2C+und+Reduction+der+selben+Erde&as_publication=svenska+vetensk.+Academ.+Handlingar&as_ylo=1788&as_yhi=1788&btnG=Search Scholar search]</sup>}} </ref> For a long time there was no industrial use for molybdenum. The French [[Schneider SA|Schneider Electrics]] company produced the first steel molybdenum alloy armor plates in 1894. Until [[World War I]] most other armor factories also used molybdenum alloys. In [[World War I]], some British tanks were protected by 75&nbsp;mm [[manganese]] plating, but this proved to be ineffective. The manganese plates were then replaced with 25&nbsp;mm molybdenum plating. These allowed for higher speed, greater maneuverability, and, despite being thinner, better protection.<ref name="nbb" /> The high demand of molybdenum in [[World War I]] and [[World War II]] and the steep decrease after the wars had a great influence on prices and production of molybdenum. == Precautions == Molybdenum dusts and fumes, as can be generated by mining or metalworking, are not toxic. There are no long-term effects associated with exposure to molybdenum; however, prolonged exposure can cause irritation to the eyes and skin. The direct inhalation or ingestion of molybdenum should also be avoided.<ref>{{cite web| title = Material Safety Data Sheet - Molybdenum| publisher = The REMBAR Company, Inc.| date= 2000-09-19| url = http://www.rembar.com/MSDSmo.htm| accessdate = 2007-05-13 }}</ref> [[Occupational Safety and Health Administration|OSHA]] regulations specify the maximum permissible molybdenum exposure in an 8-hour day to be 5 mg/m³. Chronic exposure to 60 to 600 mg Mo/m³ can cause symptoms including fatigue, headaches, and joint pains.<ref>{{cite web| title = NIOSH Documentation for ILDHs Molybdenum| publisher = National Institute for Occupational Safety and Health| date= 1996-08-16| url = http://www.cdc.gov/niosh/idlh/moly-mo.html| accessdate = 2007-05-31 }}</ref> == Supply and demand == Although current molybdenum production meets demand, refiners, or roasters, are expected to run into a shortfall between 2009 and 2015, depending on demand. A roaster processes the moly into a fine powder, pellets, or other forms. Total world moly roaster capacity is currently 320 million pounds per year, barely enough to meet demand. There is not much excess roasting capacity, and no one is actively permitting for the production of any new roasters in the United States. Global roaster capacity also looks limited, and a future roaster shortage is predicted. The data above are based on the assumption that mines will be able to increase output. Western demand is projected to increase by around 3 percent annually, while China and the CIS demand is projected to increase by around 10 percent annually, increasing overall global demand by around 4.5 percent annually. Increasing demand can be attributed to two main factors. Hydroprocessing catalysts are becoming essential for crude oil. The other contributing factor is the increase in nuclear reactor construction. There are 48 nuclear reactors to be built by 2013, and approximately 100 are to be built by 2020. The International Molybdenum Association (IMOA) says that an average reactor contains about 520,000 feet of stainless steel alloy. Some larger reactors contain over 1 million feet of stainless steel alloy. Unless moly mine production picks up at a rapid pace, shortfalls of the metal are expected to arrive around 2009. <ref>Nick Jones. [http://www.whiskeyandgunpowder.com/archives/2008/20080228.html By Any Other Name]. ''Whiskey and Gunpowder''. February 28, 2008</ref> ==References== {{reflist}} == External links == {{Commons|Molybdenum}} {{wiktionary|molybdenum}} *[http://www.webelements.com/molybdenum/ WebElements.com] &mdash; Molybdenum *[http://www.imoa.info/index.html International Molybdenum Association] &mdash; Main page {{clear}} {{compact periodic table}} [[Category:Chemical elements]] [[Category:Dietary minerals]] [[Category:Molybdenum|*]] [[Category:Transition metals]] [[Category:Refractory materials]] [[af:Molibdeen]] [[ar:موليبدنوم]] [[az:Molibden]] [[bn:মলিবডেনাম]] [[be:Малібдэн]] [[bs:Molibden]] [[bg:Молибден]] [[ca:Molibdè]] [[cv:Молибден]] [[cs:Molybden]] [[co:Molibdenu]] [[da:Molybdæn]] [[de:Molybdän]] [[et:Molübdeen]] [[el:Μολυβδαίνιο]] [[es:Molibdeno]] [[eo:Molibdeno]] [[eu:Molibdeno]] [[fa:مولیبدن]] [[fr:Molybdène]] [[fur:Molibden]] [[gv:Molybdenum]] [[ko:몰리브데넘]] [[hy:Մոլիբդեն]] [[hi:मोलिब्डेनम]] [[hr:Molibden]] [[io:Molibdeno]] [[id:Molibdenum]] [[is:Mólýbden]] [[it:Molibdeno]] [[he:מוליבדן]] [[jv:Molibden]] [[sw:Molibdeni]] [[ku:Molîbdên]] [[la:Molybdenum]] [[lv:Molibdēns]] [[lb:Molybdän]] [[lt:Molibdenas]] [[jbo:mlibdena]] [[hu:Molibdén]] [[ml:മൊളിബ്ഡിനം]] [[mr:मॉलिब्डेनम]] [[nl:Molybdeen]] [[ja:モリブデン]] [[no:Molybden]] [[nn:Molybden]] [[oc:Molibdèn]] [[uz:Molibden]] [[pl:Molibden]] [[pt:Molibdênio]] [[ro:Molibden]] [[ru:Молибден]] [[scn:Molibdenu]] [[simple:Molybdenum]] [[sk:Molybdén]] [[sl:Molibden]] [[sr:Молибден]] [[sh:Molibden]] [[fi:Molybdeeni]] [[sv:Molybden]] [[ta:மாலிப்டினம்]] [[th:โมลิบดีนัม]] [[vi:Mô lip đen]] [[tr:Molibden]] [[uk:Молібден]] [[zh:钼]]