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Names | |||
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IUPAC name
Sulfur dioxide
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Other names
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Identifiers | |||
3D model (JSmol)
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3535237 | |||
ChEBI | |||
ChEMBL | |||
ChemSpider | |||
ECHA InfoCard | 100.028.359 | ||
EC Number |
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E number | E220 (preservatives) | ||
1443 | |||
KEGG | |||
MeSH | Sulfur+dioxide | ||
PubChem CID
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RTECS number |
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UNII | |||
UN number | 1079, 2037 | ||
CompTox Dashboard (EPA)
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Properties | |||
SO 2 | |||
Molar mass | 64.066 g/mol | ||
Appearance | Colorless and pungent gas | ||
Odor | Pungent; similar to a just-struck match[1] | ||
Density | 2.619 kg m−3[2] | ||
Melting point | −72 °C; −98 °F; 201 K | ||
Boiling point | −10 °C (14 °F; 263 K) | ||
94 g/L[3] forms sulfurous acid | |||
Vapor pressure | 230 kPa at 10 °C; 330 kPa at 20 °C; 462 kPa at 30 °C; 630 kPa at 40 °C[4] | ||
Acidity (pKa) | ~1.81 | ||
Basicity (pKb) | ~12.19 | ||
−18.2·10−6 cm3/mol | |||
Viscosity | 12.82 μPa·s[5] | ||
Structure | |||
C2v | |||
Digonal | |||
Dihedral | |||
1.62 D | |||
Thermochemistry | |||
Std molar
entropy (S⦵298) |
248.223 J K−1 mol−1 | ||
Std enthalpy of
formation (ΔfH⦵298) |
−296.81 kJ mol−1 | ||
Hazards | |||
GHS labelling: | |||
Danger | |||
H314, H331[6] | |||
NFPA 704 (fire diamond) | |||
Lethal dose or concentration (LD, LC): | |||
LC50 (median concentration)
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3000 ppm (mouse, 30 min) 2520 ppm (rat, 1 hr)[8] | ||
LCLo (lowest published)
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993 ppm (rat, 20 min) 611 ppm (rat, 5 hr) 764 ppm (mouse, 20 min) 1000 ppm (human, 10 min) 3000 ppm (human, 5 min)[8] | ||
NIOSH (US health exposure limits): | |||
PEL (Permissible)
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TWA 5 ppm (13 mg/m3)[7] | ||
REL (Recommended)
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TWA 2 ppm (5 mg/m3) ST 5 ppm (13 mg/m3)[7] | ||
IDLH (Immediate danger)
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100 ppm[7] | ||
Related compounds | |||
Sulfur monoxide Sulfur trioxide Disulfur monoxide | |||
Related compounds
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Ozone | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula SO
2. It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is released naturally by volcanic activity and is produced as a by-product of copper extraction and the burning of sulfur-bearing fossil fuels.[9]
Sulfur dioxide is somewhat toxic to humans, although only when inhaled in relatively large quantities for a period of several minutes or more. It was known to medieval alchemists as "volatile spirit of sulfur".[10]
Greenwood
was invoked but never defined (see the help page).