Sulfur dioxide

Sulfur dioxide (also sulphur dioxide) is the chemical compound with the formula SO₂. It is a gas. It smells like burnt matches or rotten eggs. It can also cause suffocation. Sulfur dioxide is produced by volcanoes and in various industrial processes. It is also used to protect wine from oxygen and bacteria. It can be produced by burning sulfur. It dissolves in water to produce sulfurous acid. It can be oxidized to trioxide, which is dissolved in sulfuric acid to make more sulfuric acid. It is used to make sulfites.

Sulfur dioxide
File:Sulfur-dioxide-2D.svg
File:Sulfur-dioxide-3D-vdW.png
IUPAC name	Sulfur dioxide
Other names	Sulfurous anhydride Sulfur(IV) oxide
Identifiers
CAS number	7446-09-5
PubChem	1119
EC number	231-195-2
KEGG	D05961
MeSH	Sulfur+dioxide
ChEBI	CHEBI:18422
RTECS number	WS4550000
SMILES	O=S=O
InChI InChI=1/O2S/c1-3-2
Beilstein Reference	3535237
Gmelin Reference	1443
Properties
Molecular formula	SO2
Molar mass	64.066 g mol−1
Appearance	Colorless gas
Odor	Pungent; similar to a just-struck match
Density	2.6288 kg m−3
Melting point	-72 °C, 201 K, -98 °F
Boiling point
Solubility in water	94 g/L forms sulfurous acid
Vapor pressure	237.2 kPa
Acidity (pKa)	1.81
Basicity (pKb)	12.19
Magnetic susceptibility (χ)	−18.2·10−6 cm3/mol
Viscosity	0.403 cP (at 0 °C)
Structure
Point group	C2v
Coordination geometry	Digonal
Molecular shape	Dihedral
Dipole moment	1.62 D
Thermochemistry
Std enthalpy of formation ΔfHo298	−296.81 kJ mol−1
Standard molar entropy So298	248.223 J K−1 mol−1
Hazards
NFPA 704	75px 0 3 0
U.S. Permissible exposure limit (PEL)	TWA 5 ppm (13 mg/m3)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Sulfur Dioxide Media

• 

  Two resonance structures of sulfur dioxide

• The blue auroral glows of Io's upper atmosphere are caused by volcanic sulfur dioxide.

• An experiment showing burning of sulfur in oxygen. A flow-chamber joined to a gas washing bottle (filled with a solution of methyl orange) is being used. The product is sulfur dioxide (SO2) with some traces of sulfur trioxide (SO3). The "smoke" that exits the gas washing bottle is, in fact, a sulfuric acid fog generated in the reaction.

• Cheletropic reaction of butadiene with SO2

• Preparationofmtrifluoromethylbenzenesulfonylchloride

• US Geological Survey volunteer tests for sulfur dioxide after the 2018 lower Puna eruption.

• The effect of major volcanic eruptions on sulfate aerosol concentrations and chemical reactions in the atmosphere

• Acid rain-damaged forest in Europe's Black Triangle

• Early 2010s estimates of past and future anthropogenic global sulfur dioxide emissions, including the Representative Concentration Pathways. While no climate change scenario may reach Maximum Feasible Reductions (MFRs), all assume steep declines from today's levels. By 2019, sulfate emission reductions were confirmed to proceed at a very fast rate.

• The extent to which physical factors in the atmosphere or on land affect climate change, including the cooling provided by sulfate aerosols and the dimming they cause. The large error bar shows that there are still substantial unresolved uncertainties.