Carbon monoxide
Preferred IUPAC name Carbon monoxide
Other names	Carbon monooxide Carbonous oxide Carbon(II) oxide Carbonyl Flue gas Monoxide
Identifiers
CAS number	630-08-0
PubChem	281
EC number	211-128-3
KEGG	D09706
MeSH	Carbon+monoxide
ChEBI	CHEBI:17245
RTECS number	FG3500000
SMILES	[C-]#[O+]
InChI InChI=1/CO/c1-2
Beilstein Reference	3587264
Gmelin Reference	421
Properties
Molecular formula	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, 68 K, -337 °F
Boiling point
Solubility in water	27.6 mg/L (25 °C)
Solubility	soluble in chloroform, acetic acid, ethyl acetate, ethanol, ammonium hydroxide, benzene
kH	1.04 atm·m3/mol
Magnetic susceptibility (χ)	−9.8·10−6 cm3/mol
Refractive index (nD)	1.0003364
Dipole moment	0.122 D
Thermochemistry
Std enthalpy of formation ΔfHo298	−110.5 kJ/mol
Std enthalpy of combustion ΔcHo298	−283.4 kJ/mol
Standard molar entropy So298	197.7 J/(mol·K)
Specific heat capacity, C	29.1 J/(K·mol)
Hazards
EU classification	F+ T+
NFPA 704	4 3 0
R-phrases	R61 R12 R26 R48/23
S-phrases	S53 S45
Explosive limits	12.5–74.2%
U.S. Permissible exposure limit (PEL)	TWA 50 ppm (55 mg/m3)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. It consists of one carbon atom covalently bonded to one oxygen atom. It is made when carbon compounds burn and there is not enough oxygen. It is a good fuel and burns in air with a blue flame, making carbon dioxide. It is very toxic, but it is useful for modern technology as well.