A colorless, odorless, highly poisonous gas formed by the incomplete combustion of carbon.
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| Names | |||
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| Preferred IUPAC name
Carbon monoxide | |||
| Other names
Carbon monooxide
Carbonous oxide Carbon(II) oxide Carbonyl Flue gas Monoxide | |||
| Identifiers | |||
3D model (JSmol)
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| 3587264 | |||
| ChEBI | |||
| ChemSpider | |||
| ECHA InfoCard | 100.010.118 | ||
| EC Number | 211-128-3 | ||
| 421 | |||
| KEGG | |||
| MeSH | Carbon+monoxide | ||
PubChem CID
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| RTECS number | FG3500000 | ||
| UNII | |||
| UN number | 1016 | ||
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| Properties | |||
| CO | |||
| Molar mass | 28.010 g/mol | ||
| Appearance | colorless gas | ||
| Odor | odorless | ||
| Density | 789 kg/m3, liquid 1.250 kg/m3 at 0 °C, 1 atm 1.145 kg/m3 at 25 °C, 1 atm | ||
| Melting point | −205.02 °C (−337.04 °F; 68.13 K) | ||
| Boiling point | −191.5 °C (−312.7 °F; 81.6 K) | ||
| 27.6 mg/L (25 °C) | |||
| Solubility | soluble in chloroform, acetic acid, ethyl acetate, ethanol, ammonium hydroxide, benzene | ||
Henry's law
constant (kH) |
1.04 atm·m3/mol | ||
| −9.8·10−6 cm3/mol | |||
Refractive index (nD)
|
1.0003364 | ||
| 0.122 D | |||
| Thermochemistry | |||
| 29.1 J/(K·mol) | |||
Std molar
entropy (S |
197.7 J/(mol·K) | ||
Std enthalpy of
formation (ΔfH |
−110.5 kJ/mol | ||
Std enthalpy of
combustion (ΔcH |
−283.4 kJ/mol | ||
| Hazards | |||
| Safety data sheet | See: data page ICSC 0023 | ||
EU classification (DSD) (outdated)
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 F  T+
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| R-phrases (outdated) | R61 R12 R26 R48/23 | ||
| S-phrases (outdated) | S53 S45 | ||
| NFPA 704 | |||
| Flash point | −191 °C (−311.8 °F; 82.1 K) | ||
| 609 °C (1,128 °F; 882 K) | |||
| Explosive limits | 12.5–74.2% | ||
| Lethal dose or concentration (LD, LC): | |||
LC50 (median concentration)
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8636 ppm (rat, 15 min) 5207 ppm (rat, 30 min) 1784 ppm (rat, 4 h) 2414 ppm (mouse, 4 h) 5647 ppm (guinea pig, 4 h) | ||
LCLo (lowest published)
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4000 ppm (human, 30 min) 5000 ppm (human, 5 min) | ||
| US health exposure limits (NIOSH): | |||
PEL (Permissible)
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TWA 50 ppm (55 mg/m3) | ||
REL (Recommended)
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TWA 35 ppm (40 mg/m3) C 200 ppm (229 mg/m3) | ||
IDLH (Immediate danger)
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1200 ppm | ||
| Related compounds | |||
Related carbon oxides
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Carbon dioxide Carbon suboxide Oxocarbons | ||
| Supplementary data page | |||
| Refractive index (n), Dielectric constant (εr), etc. | |||
Thermodynamic
data |
Phase behaviour solid–liquid–gas | ||
| UV, IR, NMR, MS | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
 verify (what is   ?)
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| Infobox references | |||
Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is slightly less dense than air. It is toxic to hemoglobic animals (both invertebrate and vertebrate, including humans) when encountered in concentrations above about 35 ppm, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal biological functions. In the atmosphere, it is spatially variable and short lived, having a role in the formation of ground-level ozone.
Carbon monoxide consists of one carbon atom and one oxygen atom, connected by a triple bond that consists of two covalent bonds as well as one dative covalent bond. It is the simplest oxocarbon and is isoelectronic with other triply-bonded diatomic molecules having ten valence electrons, including the cyanide anion, the nitrosonium cation and molecular nitrogen. In coordination complexes the carbon monoxide ligand is called carbonyl.