Carbon monoxide
6136
225961746
2008-07-16T05:49:30Z
Vaughan Pratt
1068018
/* Industrial uses */ - fixed minor English errors
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{{Chembox new
| Name = Carbon monoxide
| ImageFileL1 = Carbon monoxide 2D.svg
| ImageSizeL1 = 100px
| ImageNameL1 = Structure of the carbon monoxide molecule
| ImageFileR1 = Carbon-monoxide-3D-vdW.png
| ImageSizeR1 = 120px
| ImageNameR1 = Space-filling model of the carbon monoxide molecule
| IUPACName = Carbon monoxide
| OtherNames = Carbonic oxide,<br />Coal gas,<br />Exhaust Fumes
| Section1 = {{Chembox Identifiers
| CASNo = 630-08-0
| RTECS = FG3500000
}}
| Section2 = {{Chembox Properties
| Formula = CO
| MolarMass = 28.0101 g/mol
| Appearance = Colourless, odorless gas
| Density = 0.789 g/cm³, liquid<br />1.250 g/L at 0°C, 1 atm.<br />1.145 g/L at 25°C, 1 atm.<br />([[lighter than air]])
| Solubility = 0.0026 g/100 mL (20 °C)
| MeltingPt = -205 °C (68 K)
| BoilingPt = -192 °C (81 K)
| Dipole = 0.112 [[Debye|D]] (3.74×10<sup>−31</sup> C·m)
}}
| Section7 = {{Chembox Hazards
| FlashPt = Flammable gas
| EUClass = Highly flammable ('''F+''')<br />Repr. Cat. 1<br />Toxic ('''T''')
| NFPA-H = 4
| NFPA-F = 4
| NFPA-R =
| RPhrases = {{R12}}, {{R23}}, {{R33}}, {{R48}}, {{R61}}
| SPhrases = {{S9}}, {{S16}}, {{S33}}, {{S45}}, {{S53}}
}}
| Section8 = {{Chembox Related
| Function = oxides
| OtherFunctn = [[carbon dioxide]]; [[carbon suboxide]]; [[dicarbon monoxide]]; [[carbon trioxide]]
}}
}}
'''Carbon monoxide''', with the chemical formula CO, is a colorless, odorless, and tasteless [[gas]]. It consists of one [[carbon]] atom [[covalent bond|covalently bonded]] to one [[oxygen]] atom. There are two covalent bonds and a [[coordinate covalent bond]] between the oxygen and carbon atoms.
Carbon monoxide is produced from the partial [[combustion]] of [[carbon]]-containing compounds, notably in [[internal-combustion engine]]s. Carbon monoxide forms in preference to the more usual carbon dioxide when there is a reduced availability of oxygen present during the combustion process. Carbon monoxide has significant fuel value, burning in air with a characteristic blue flame, producing [[carbon dioxide]]. Despite its serious [[toxicity]], CO plays a highly useful role in modern technology, being a precursor to myriad products.
==Production==
Carbon monoxide is so fundamentally important that many methods have been developed for its production.<ref>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 200. ISBN 0-12-352651-5.</ref>
'''[[Producer gas]]''' is formed by combustion of carbon in oxygen at high temperatures when there is an excess of carbon. In an oven, air is passed through a bed of [[coke (fuel)|coke]]. The initially produced CO<sub>2</sub> equilibrates with the remaining hot carbon to give CO. The reaction of O<sub>2</sub> with carbon to give CO is described as the Boudouard equilibrium. Above 800 °C, CO is the predominant product:
:O<sub>2</sub> + 2 C → 2 CO
:ΔH = -221 kJ/mol
The downside of this method is if done with air it leaves a mixture that is mostly nitrogen.
'''[[Syngas|Synthesis gas]]''' or '''[[Water gas]]''' is produced via the endothermic reaction of [[steam]] and carbon:
:H<sub>2</sub>O + C → H<sub>2</sub> + CO
:ΔH = 131 kJ/mol
CO also is a byproduct of the reduction of metal oxide ores with carbon, shown in a simplified form as follows:
:MO + C → M + CO
:ΔH = 131 kJ/mol
Since CO is a gas, the reduction process can be driven by heating, exploiting the positive (favorable) [[entropy]] of reaction. The [[Ellingham diagram]] shows that CO formation is favored over CO<sub>2</sub> in high temperatures.
CO is the [[anhydride]] of [[formic acid]]. As such it is conveniently produced by the dehydration of formic acid, for example with [[sulfuric acid]]. Another laboratory preparation for carbon monoxide entails heating an intimate mixture of powdered [[zinc]] metal and [[calcium carbonate]].
:Zn + CaCO<sub>3</sub> → [[zinc oxide|ZnO]] + [[calcium oxide|CaO]] + CO
Another lab style of generate CO is reacting Sucrose and Sodium Hydroxide in a closed system.
==Structure==
The CO molecule is characterized by a [[chemical bond|bond]] length of 0.1128 [[nanometre|nm]].<ref name=gilliam>{{cite journal | author = O. R. Gilliam, C. M. Johnson and W. Gordy | title = Microwave Spectroscopy in the Region from Two to Three Millimeters | year = 1950 | journal = [[Physical Review]] | volume = 78 | issue = 2 | pages = 140 | doi = 10.1103/PhysRev.78.140}}</ref> [[Formal charge]] and [[electronegativity]] difference cancel each other out. The result is a small dipole moment with its negative end on the carbon atom<ref>{{cite book | author = W. Kutzelnigg | title = Einführung in die Theoretische Chemie | publisher = Wiley-VCH | isbn = 3-527-30609-9}}</ref>. The reason for this, despite oxygen's greater electronegativity, is that the highest occupied molecular orbital has an energy much closer to that of carbon's p orbitals, meaning that greater electron density is found near the carbon. In addition, carbon's lower electronegativity creates a much more diffuse electron cloud, enhancing the dipole moment. This is also the reason that almost all chemistry involving carbon monoxide occurs through the carbon atom, and not the oxygen.
The molecule's bond length is consistent with a partial triple bond. The molecule has a small [[Bond dipole moment|dipole moment]] and can be represented by three resonance structures:
:[[Image:Carbon Monoxide(png).svg|300px]]
The leftmost resonance form is the most important.<ref name=gilliam/> This is illustrated by the reactivity of carbon monoxide: it reacts with [[carbocation]]s.
[[Dinitrogen]] is isoelectronic to carbon monoxide, which means that these molecules have the same number of electrons and similar bonding. The physical properties of N<sub>2</sub> and CO are similar, although CO is more reactive.
==Principal chemical reactions==
===Industrial uses===
Carbon monoxide is a major [[industrial gas]] that has many applications in bulk chemicals manufacturing.<ref>Elschenbroich, C.;Salzer, A. ”Organometallics : A Concise Introduction” (2nd Ed) Wiley-VCH: Weinheim, 2006. ISBN 3-527-28165-7</ref>
High volume [[aldehydes]] are produced by the [[hydroformylation]] reaction of [[alkene]]s, CO, and H<sub>2</sub>. In one of many applications of this technology, hydroformylation is coupled to the [[Shell Higher Olefin Process]] to give precursors to [[detergent]]s.
[[Methanol]] is produced by the [[hydrogenation]] of CO. In a related reaction, the hydrogenation of CO is coupled to C-C bond formation, as in the [[Fischer-Tropsch process]] where CO is hydrogenated to liquid hydrocarbon fuels. This technology allows [[coal]] to be converted to petrol.
In the [[Monsanto process]], carbon monoxide and [[methanol]] react in the presence of a homogeneous [[rhodium]] [[catalyst]] and HI to give [[acetic acid]]. This process is responsible for most of the industrial production of [[acetic acid]].
Carbon monoxide is a principle component of [[syngas]], which is often used for industrial power.
Carbon monoxide(CO) is also used in industrial scale operations for purifying [[Nickel]]. It is a precursor for a corrosion process called [[Mond process|Mond Process]].
===Coordination chemistry===
{{main|metal carbonyl}}
[[Image:Carbon-monoxide-HOMO-phase-3D-balls.png|thumb|right|150px|The [[HOMO/LUMO|HOMO]] of CO is a σ [[molecular orbital|MO]]]]
[[Image:Carbon-monoxide-LUMO-phase-3D-balls.png|thumb|right|150px|The [[HOMO/LUMO|LUMO]] of CO is a π* [[antibonding]] [[molecular orbital|MO]]]]
Most metals form [[coordination complex]]es containing covalently attached carbon monoxide. Only those in lower oxidation states will complex with carbon monoxide [[ligands]]. This is because there must be sufficient electron density to facilitate back donation from the metal d<sub>xz</sub>-orbital, to the π* [[molecular orbital]] from CO. The lone pair on the carbon atom in CO, also donates electron density to the d<sub>x²−y²</sub> on the metal to form a [[sigma bond]]. In [[nickel carbonyl]], Ni(CO)<sub>4</sub> forms by the direct combination of carbon monoxide and [[nickel]] metal at room temperature. For this reason, nickel in any tubing or part must not come into prolonged contact with carbon monoxide (corrosion). [[Nickel carbonyl]] decomposes readily back to Ni and CO upon contact with hot surfaces, and this method was once used for the industrial purification of [[nickel]] in the [[Mond process]].<ref>{{cite journal | author= Mond L, Langer K, Quincke F| title= Action of carbon monoxide on nickel| journal=Journal of the Chemical Society | year=1890| pages=749–753 | doi = 10.1039/CT8905700749| volume= 57}}</ref>
In nickel carbonyl and other carbonyls, the electron pair on the carbon interacts with the metal; the carbon monoxide donates the electron pair to the metal. In these situations, carbon monoxide is called the '''carbonyl''' [[ligand]]. One of the most important metal carbonyls is [[iron pentacarbonyl]], Fe(CO)<sub>5</sub>:
[[Image:IronPentacarbonylStructure.png|150px|Structure of iron pentacarbonyl]]
[[Image:Iron-pentacarbonyl-3D-balls.png|120px|Iron pentacarbonyl]]
<!-- Deleted image removed: [[Image:Chp co ligand.jpg|250px||Bonding in CO]] -->
Many metal-CO complexes are prepared by decarbonylation of organic solvents, not from CO. For instance, [[iridium(III) chloride|iridium trichloride]] and [[triphenylphosphine]] react in boiling [[methoxyethanol]] or [[dimethylformamide|DMF]]) to afford [[Vaska's complex|IrCl(CO)(PPh<SUB>3</SUB>)<SUB>2</SUB>]].
===Organic and main group chemistry===
In the presence of strong acids and water, carbon monoxide reacts with [[olefins]] to form [[carboxylic acids]] in a process known as the Koch-Haaf reaction.<ref>Koch, H.; Haaf, W. "1-Adamantanecarboxylic Acid" Organic Syntheses, Collected Volume 5, p.20 (1973).</ref> In the [[Gattermann-Koch reaction]], [[Aromatic hydrocarbon|arenes]] are converted to [[benzaldehyde]] derivatives in the presence of [[aluminium chloride|AlCl<sub>3</sub>]] and [[hydrogen chloride|HCl]].<ref>Coleman, G. H.; Craig, D. "''p''-Tolualdehyde" Organic Syntheses, Collected Volume 2, p.583 (1943).</ref> Organolithium compounds, e.g. [[butyl lithium]] react with CO, but this reaction enjoys little use.
Although CO reacts with [[carbocation]]s and [[carbanion]]s, it is relatively unreactive toward organic compounds without the intervention of metal catalysts.<ref>Chatani, N.; Murai, S. "Carbon Monoxide" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. {{doi|10.1002/047084289}}</ref>
With main group reagents, CO undergoes several noteworthy reactions. [[Chlorination]] of CO is the industrial route to the important compound [[phosgene]]. With [[borane]] CO forms an adduct, H<sub>3</sub>BCO, which is isoelectronic with the [[acylium]] cation [H<sub>3</sub>CCO]<sup>+</sup>. CO reacts with [[sodium]] to give products resulting from C-C coupling such as Na<sub>2</sub>C<sub>2</sub>O<sub>2</sub> (sodium acetylenediolate), and [[potassium]] to give K<sub>2</sub>C<sub>2</sub>O<sub>2</sub> (potassium acetylenediolate) and K<sub>2</sub>C<sub>6</sub>O<sub>6</sub> (potassium rhodizonate).
==Carbon monoxide in the atmosphere==
[[Image:Mopitt first year carbon monoxide.jpg|thumb|240px|[[MOPITT]] 2000 global carbon monoxide ]]
Carbon monoxide, though thought of as a pollutant today, has always been present in the atmosphere, chiefly as a product of [[volcano|volcanic activity]]. It occurs dissolved in molten volcanic rock at high [[pressure]]s in the earth's [[mantle (geology)|mantle]]. Carbon monoxide contents of volcanic gases vary from less than 0.01% to as much as 2% depending on the volcano. It also occurs naturally in [[bushfire]]s. Because natural sources of carbon monoxide are so variable from year to year, it is extremely difficult to accurately measure natural emissions of the gas.
Carbon monoxide has an indirect radiative forcing effect by elevating concentrations of [[methane]] and [[troposphere|tropospheric]] [[ozone]] through chemical reactions with other atmospheric constituents (e.g., the [[hydroxyl]] [[Radical (chemistry)|radical]], OH<sup>'''.'''</sup>) that would otherwise destroy them. Through natural processes in the atmosphere, it is eventually oxidized to [[carbon dioxide]]. Carbon monoxide concentrations are both short-lived in the atmosphere and spatially variable.
Anthropogenic CO from automobile and industrial emissions may contribute to the [[greenhouse effect]] and global warming. In urban areas carbon monoxide, along with [[aldehydes]], reacts photochemically to produce [[peroxy]] radicals. Peroxy radicals react with [[nitrogen oxide]] to increase the ratio of NO<sub>2</sub> to NO, which reduces the quantity of NO that is available to react with [[ozone]]. Carbon monoxide is also a constituent of tobacco smoke.
==Role in physiology and food==
Carbon monoxide is used in [[modified atmosphere]] packaging systems in the US, mainly with fresh meat products such as beef and pork. The CO combines with [[myoglobin]] to form carboxymyoglobin, a bright cherry red pigment. Carboxymyoglobin is more stable than the oxygenated form of myoglobin, oxymyoglobin, which can become oxidized to the brown pigment, metmyoglobin. This stable red colour can persist much longer than in normally packaged meat, giving the appearance of freshness.<ref name="Meatsci1999_SORHEIM">{{cite journal | author=Sorheim, S, Nissena, H, Nesbakken, T | title=The storage life of beef and pork packaged in an atmosphere with low carbon monoxide and high carbon dioxide | journal=Journal of Meat Science | year=1999 | pages=157–64 | volume=52 | issue=2 | doi = 10.1016/S0309-1740(98)00163-6}}</ref> Typical levels of CO used are 0.4% to 0.5%.
The technology was first given [[generally recognized as safe]] status by the [[FDA]] in 2002 for use as a secondary packaging system. In 2004 the FDA approved CO as primary packaging method, declaring that CO does not mask spoilage odour.<ref name="Meatsci2005_eilert">{{cite journal | author=Eilert EJ | title=New packaging technologies for the 21st century | journal=Journal of Meat Science | year=2005 | pages=122–27 | volume=71 | issue=1 | doi = 10.1016/j.meatsci.2005.04.003}}</ref> Despite this ruling, the technology remains controversial in the US for fears that it is deceptive and masks spoilage.<ref>{{cite news | url = http://www.foodsafetymagazine.com/article.asp?id=644&sub=sub1 | title = Low-Oxygen Packaging with CO: A Study in Food Politics That Warrants Peer Review| accessdate = 2007-04-18}}</ref>
One reaction in the body produces CO. Carbon monoxide is produced naturally as a breakdown of [[heme]] (which is one of [[hemoglobin]] moieties), a substrate for the enzyme [[heme oxygenase]]. The enzymatic reaction results in breakdown of heme to CO, biliverdin and Fe<sup>3+</sup> radical. The endogenously produced CO may have important physiological roles in the body (eg as a [[neurotransmitter]] or a blood vessels relaxant). In addition CO regulates inflammatory reactions in a manner that prevents the development of several diseases such as atherosclerosis or severe malaria.
CO is a nutrient for [[methanogen]]ic bacteria,<ref>{{cite journal | author = R. K. Thauer | title = Biochemistry of methanogenesis: a tribute to Marjory Stephenson. 1998 Marjory Stephenson Prize Lecture | year = 1998 | journal = [[Microbiology]] | volume = 144 | issue = 9 | pages = 2377–2406 | url = http://mic.sgmjournals.org/cgi/reprint/144/9/2377 | format = Free}}</ref> a building block for acetyl[[coenzyme A]]. This theme is the subject for the emerging field of [[bioorganometallic chemistry]]. In bacteria, CO is produced via the reduction of carbon dioxide via the enzyme carbon monoxide dehydrogenase, an Fe-Ni-S-containing protein.<ref>{{cite book | title = Bioorganometallics: Biomolecules, Labeling, Medicine | author = Jaouen, G., Ed. | publisher = Wiley-VCH | location = Weinheim | year = 2006 | isbn = 3-527-30990-X}}</ref>
A haeme-based CO-sensor protein, CooA, is known.<ref>{{cite journal | author = Roberts, G. P.; Youn, H.; Kerby, R. L. | title = CO-Sensing Mechanisms | journal = Microbiology and Molecular Biology Reviews | year = 2004 | volume = 68 | pages = 453–473 | doi = 10.1128/MMBR.68.3.453-473.2004 | pmid = 15353565}}</ref> The scope of its biological role is still unclear, it is apparently part of a signaling pathway in bacteria and archaea, but its occurrence in mammals is not established.
CO is also currently being studied in several research laboratories throughout the world for its anti-inflammatory and cytoprotective properties that can be used therapeutically to prevent the development of a series of pathologic conditions such as ischemia reperfusion injury, transplant rejection, atherosclerosis, sepsis, severe malaria or autoimmunity. There are yet no clinical applications of CO in humans.
==History==
Carbon monoxide was first prepared by the [[France|French]] [[chemist]] de Lassone in 1776 by heating [[zinc oxide]] with [[Coke (fuel)|coke]]. He mistakenly concluded that the gaseous product was [[hydrogen]] as it burned with a blue flame. The gas was identified as a compound containing [[carbon]] and [[oxygen]] by the English chemist [[William Cumberland Cruikshank]] in the year 1800.
The toxic properties of CO were first thoroughly investigated by the French physiologist [[Claude Bernard]] around 1846. He poisoned dogs with the gas, and noticed that their blood was more ''rutilant'' in all the vessels. 'Rutilant' is a French word, but also has an entry in English dictionaries, meaning ruddy, shimmering, or golden. However, it was translated at the time as crimson, scarlet, and now is famously known as 'cherry pink'.
During [[World War II]], carbon monoxide was used to keep [[motor vehicle]]s running in parts of the world where [[gasoline]] was scarce. External charcoal or wood [[Wood gas generator|burners]] were fitted, and the carbon monoxide produced by [[gasification]] was piped to the [[carburetor]]. The CO in this case is known as "[[wood gas]]". Carbon monoxide was also reportedly used on a small scale during [[the Holocaust]] at some [[Extermination camps in the Holocaust|Nazi extermination camp]]s, and in the [[Action T4]] "[[euthanasia]]" program.
==Source concentrations==
* 0.1 ppm - natural background atmosphere level ([[MOPITT]])
* 0.5 to 5 ppm - average background level in homes<ref name="EPA_CO">{{cite web
| title = Basic Information : Carbon Monoxide
| url=http://www.epa.gov/iaq/co.html
| accessdate = 2007-12-01 }}</ref>
* 5 to 15 ppm - levels near properly adjusted gas stoves in homes<ref name="EPA_CO"/>
* 100-200 ppm - Mexico City central area from autos etc.<ref name="Fred_1">{{cite book
| last = Singer
| first = Siegfried Fred
| title = The Changing Global Environment
| pages = pp. 90
| month = March
| date = 1975
| url = http://books.google.com/books?id=Ww3DnCF_KZcC&pg=PA90&lpg=PA90&dq=%22carbon+monoxide%22+ppm+concentration+traffic+%22mexico+city%22&source=web&ots=SzIyYgUxWh&sig=ZM4p8whF1mtj1kE3XSx1YUx70zw#PPA90,M1
| isbn = 9789027704023 }}</ref>
* 5,000 ppm - chimney of a home wood fire <ref name=Alaska_CO>
{{cite web
| last = Gosink
| first = Tom
| title = What Do Carbon Monoxide Levels Mean?
| work = Alaska Science Forum
| publisher = Geophysical Institute, University of Alaska Fairbanks
| date = 1983-01-28
| url = http://www.gi.alaska.edu/ScienceForum/ASF5/588.html
| format = HTML
| accessdate = 2007-12-01 }}
</ref>
* 7,000 ppm - undiluted warm car exhaust - without catalytic converter<ref name=Alaska_CO/>
* 30,000 ppm - undiluted cigarette smoke<ref name=Alaska_CO/>
==Toxicity==
{{main|Carbon monoxide poisoning}}
Carbon monoxide is a significantly toxic gas and has no odor or color. It is the most common type of fatal poisoning in many countries.<ref name="Toxicology2002-omaye">{{cite journal | author=Omaye ST. | title=Metabolic modulation of carbon monoxide toxicity | journal=Toxicology | year=2002 | pages=139–50 | volume=180 | issue=2 | doi = 10.1016/S0300-483X(02)00387-6}}</ref> Exposures can lead to significant toxicity of the [[central nervous system]] and [[heart]]. Following poisoning, long-term [[sequela]]e often occur. Carbon monoxide can also have severe effects on the [[baby]] of a pregnant woman. Symptoms of mild poisoning include headaches and dizziness at concentrations less than 100 ppm. Concentrations as low as 667 ppm can cause up to 50% of the body's haemoglobin to be converted to [[Carboxyhaemoglobin|carboxy-haemoglobin (HbCO)]]. Carboxy-haemoglobin is quite stable but this change is reversible. Carboxy-haemoglobin is ineffective for delivering oxygen, resulting in some body parts not receiving oxygen needed. As a result, exposures of this level can be life-threatening. In the United States, [[Occupational Safety and Health Administration|OSHA]] limits long-term workplace exposure levels to 50 ppm.
The mechanisms by which carbon monoxide produces toxic effects are not yet fully understood, but [[haemoglobin]], [[myoglobin]], and mitochondrial [[cytochrome oxidase]] are thought to be compromised. Treatment largely consists of administering 100% [[oxygen]] or [[hyperbaric oxygen]] therapy, although the optimum treatment remains controversial.<ref name="ToxicolRev2005-buckley">{{cite journal | author=Buckley NA, Isbister GK, Stokes B, Juurlink DN. | title=Hyperbaric oxygen for carbon monoxide poisoning : a systematic review and critical analysis of the evidence | journal=Toxicol Rev | year=2005 | pages=75–92 | volume=24 | issue=2 | pmid = 16180928 | url=http://toxicology.adisonline.com/pt/re/tox/abstract.00139709-200524020-00002.htm | format = Abstract}}</ref> Domestic carbon monoxide poisoning can be prevented by the use of household [[carbon monoxide detector]]s.
==See also==
* [[Carbon monoxide (data page)]]
*[[Boudouard reaction]]
* [[Carbon monoxide poisoning]]
* [[Criteria air contaminants]]
* [[Undersea and Hyperbaric Medical Society]] Hyperbaric Treatment for CO Poisoning
* [[Rubicon Foundation]] research articles on CO Poisoning
==References==
{{reflist|2}}
==External links==
*[http://www.infowars.com]
* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc00/icsc0023.htm International Chemical Safety Card 0023]
* [http://www.npi.gov.au/database/substance-info/profiles/19.html National Pollutant Inventory - Carbon Monoxide]
* [http://www.cdc.gov/niosh/npg/npgd0105.html NIOSH Pocket Guide to Chemical Hazards]
* {{PubChemLink|281}}
* [http://www.epa.gov/ebtpages/airairpocarbonmonoxide.html United States Environmental Protection Agency Carbon Monoxide page]
* [http://physchem.ox.ac.uk/MSDS/CA/carbon_monoxide.html External MSDS data sheet]
* [http://www.carbonmonoxidekills.com Carbon Monoxide Kills Awareness Campaign Site]
* [http://www.rccostello.com/copure.html Carbon Monoxide Purification Process]
* [http://zenstoves.net/COHazard.htm Carbon Monoxide Hazards with Backpacking Stoves]
* [http://seafood.ucdavis.edu/Guidelines/fdabulletin16b.htm USFDA IMPORT BULLETIN 16B-95, May 1999]
* [http://www.cfsan.fda.gov/~rdb/opa-g083.html FDA Agency Response Letter GRAS Notice No. GRN 000083]
* [http://www.co-meat.com/background.html Carbon Monoxide in Fresh Meat site]
* [http://www.carbonmonoxide.net Carbon Monoxide Network & Forum]
* [http://mattson.creighton.edu/CO/index.html Microscale Gas Chemistry Experiments with Carbon Monoxide]
* Research on the therapeutic effects of CO [http://www.igc.gulbenkian.pt/research/unit/43 (Gulbenkian Science Institute)]
*[http://www.rsc.org/Publishing/Journals/cb/Volume/2007/11/Dont_blame_the_messenger.asp Instant insight] outlining the physiology of carbon monoxide from the [[Royal Society of Chemistry]]
*[http://www.floridarealtors.org/NewsAndEvents/n3-072507.cfm] Article about Sen. Chris mandating CO detectors in new homes & hotels in Florida as of 2008.
{{Oxides of carbon}}
[[Category:Oxides]]
[[Category:Inorganic carbon compounds]]
[[Category:Inorganic compounds]]
[[Category:Hazardous air pollutants]]
[[Category:Smog]]
[[Category:Toxicology]]
[[Category:Gases]]
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[[es:Óxido de carbono (II)]]
[[eo:Karbona monooksido]]
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[[pt:Monóxido de carbono]]
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