Sulfur dioxide

Athanor · official

O₂S · 64.07 g/mol

Also called sulfurous anhydride, E220

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

DangerCauses severe skin burns and eye damage · Toxic if inhaled · Causes damage to organs

Names and identifiers

IUPAC name: sulfur dioxide
Synonyms: sulfurous anhydride, E220, sulphur dioxide
+ 36 more
Sulfurous anhydride, Sulfurous oxide, Fermenicide liquid, Sulfurous acid anhydride, Sulfur superoxide, Fermenicide powder, Sulfur oxide (SO2), Schwefeldioxid, Siarki dwutlenek, Sulfur dioxide (SO2), Schwefeldioxyd, FEMA No. 3039, SULFUROXIDE, INS NO.220, DTXSID6029672, INS-220, 0UZA3422Q4, E-220, CHEBI:18422, (oxo-lambda4-sulfanylidene)oxidane, RefChem:6693, DTXCID009672, 231-195-2, dioxidosulfur, Oxosulfane oxide, Surfur dioxide (anhydrous), Sulfur dioxide (NF), SULFUR-DIOXIDE, SO2, UN 1079, Sulfur dioxide (SO2) 10% by volume or more SO2, Sulfur dioxide [NF], Sulfur dioxide, >=99.9%, Sulfurdioxide, Caswell No. 813, Schwefeldioxyd [German]
Molecular formula: O₂S
Empirical formula: O₂S
Molecular weight: 64.07 g/mol
Exact mass: 63.96190
CAS number: 7446-09-5
PubChem CID: 1119
Canonical SMILES: O=S=O
Isomeric SMILES: O=S=O
InChI: InChI=1S/O2S/c1-3-2
InChIKey: RAHZWNYVWXNFOC-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: Colorless gas or liquid[5]
6 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Sulfur dioxide appears as a colorless gas with a choking or suffocating odor. Boiling point -10 °C. Heavier than air. Very toxic by inhalation and may irritate the eyes and mucous membranes. Under prolonged exposure to fire or heat the containers may rupture violently and rocket. Used to manufacture chemicals, in paper pulping, in metal and food processing. Rate of onset: Immediate & Delayed Persistence: Minutes to hours Odor threshold: 1 ppm Source/use/other hazard: Disinfectant and preserving in breweries and food/canning; textile industry; batteries. [1] CAMEO Chemicals
– COLOURLESS GAS OR COMPRESSED LIQUEFIED GAS WITH PUNGENT ODOUR. [2] ILO-WHO International Chemical Safety Cards (ICSCs)
– Colorless gas with a characteristic, irritating, pungent odor. [3] Occupational Safety and Health Administration (OSHA)
– Colorless gas with a characteristic, irritating, pungent odor. [Note: A liquid below 14 °F. Shipped as a liquefied compressed gas.] [4] The National Institute for Occupational Safety and Health (NIOSH)
–shown Colorless gas or liquid [5] Hazardous Substances Data Bank (HSDB)cites Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 1290
– Colorless gas ... [Note: A liquid below 14 degrees F. Shipped as a liquefied compressed gas] [5] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Control & Prevention. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from: https://www.cdc.gov/niosh/npg
Odor: ... Characteristic, irritating, pungent odor ...[5]
Melting point: -75.5 °C[2]
5 values
4 of 5 sources agree on it (most common value).
Value As written Source
−72.7 °C -98.9 °F (EPA, 1998) [1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
−75.5 °Cshown -75.5 °C [2] ILO-WHO International Chemical Safety Cards (ICSCs)
−76 °C -104 °F [3] Occupational Safety and Health Administration (OSHA)
−75.5 °C -75.5 °C [6] PAC Chemical Database, U.S. Department of Energy
−76 °C -104 °F [4] The National Institute for Occupational Safety and Health (NIOSH)
Boiling point: -10.05 °C @760 [mmHg][6]
5 values
5 of 5 sources agree on it (most common value).
Value As written Source
−10 °C 14 °F at 760 mmHg (EPA, 1998) [1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
−10 °C -10 °C [2] ILO-WHO International Chemical Safety Cards (ICSCs)
−10 °C 14 °F [3] Occupational Safety and Health Administration (OSHA)
−10.1 °Cshown -10.05 °C @760 [mm Hg] [6] PAC Chemical Database, U.S. Department of Energy
−10 °C 14 °F [4] The National Institute for Occupational Safety and Health (NIOSH)
Density: Density: 1.434 at 0 °C (liquid)[5]
6 values
4 of 6 sources agree on it (most common value).
Value As written Source
– 1.434 (EPA, 1998) - Denser than water [1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
–shown Density: 1.434 at 0 °C (liquid) [5] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 12th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2012., p. V5: 4106
– Relative density (water = 1): 1.4 (liquid, -10 °C) [2] ILO-WHO International Chemical Safety Cards (ICSCs)
– 1.434 [3] Occupational Safety and Health Administration (OSHA)
– 2.619 @25 °C [6] PAC Chemical Database, U.S. Department of Energy
– 2.26(relative gas density) [4] The National Institute for Occupational Safety and Health (NIOSH)
1 more value was reported but failed the checks (unreadable or out of range), so it is not shown.
Solubility in water: Solubility in water, ml/100ml at 25 °C: 8.5[2]
6 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source
– 10 % (NIOSH, 2024) [1] CAMEO Chemicals
– In water, 1.07X10+5 mg/L at 21 °C [5] Hazardous Substances Data Bank (HSDB)cites Venable CS, Fuwa T; Ind Eng Chem 14: 139-42 (1922)
– Soluble in water ... forms sulfurous acid (H2SO3) [5] Hazardous Substances Data Bank (HSDB)cites Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 1290
– For more Solubility (Complete) data for Sulfur dioxide (7 total), please visit the HSDB record page. [5] Hazardous Substances Data Bank (HSDB)
–shown Solubility in water, ml/100ml at 25 °C: 8.5 [2] ILO-WHO International Chemical Safety Cards (ICSCs)
– 10% [4] The National Institute for Occupational Safety and Health (NIOSH)
Vapor pressure: 2432 mmHg at 20 °C (68 °F, EPA 1998)[1]
3 values
2 of 3 sources agree on it (most common value).
Value As written Source
2432 mmHgshown 2432 mmHg at 68 °F (EPA, 1998) [1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
2500 mmHg Vapor pressure, kPa at 20 °C: 330 [2] ILO-WHO International Chemical Safety Cards (ICSCs)
750 mmHg 750 [mm Hg] @-10.3 °C [6] PAC Chemical Database, U.S. Department of Energy
6 more values were reported but failed the checks (unreadable or out of range), so they are not shown.
Autoignition temperature: Reported, but no value passed the checks.
The value and why
Not flammable (USCG, 1999) (could not be read; source [1])
Viscosity: Gas: 0.0124 mPa.s at 18 °C. Liquid: 0.368 mPa.s at 0 °C.[5]

Value	As written	Source
–	Sulfur dioxide appears as a colorless gas with a choking or suffocating odor. Boiling point -10 °C. Heavier than air. Very toxic by inhalation and may irritate the eyes and mucous membranes. Under prolonged exposure to fire or heat the containers may rupture violently and rocket. Used to manufacture chemicals, in paper pulping, in metal and food processing. Rate of onset: Immediate & Delayed Persistence: Minutes to hours Odor threshold: 1 ppm Source/use/other hazard: Disinfectant and preserving in breweries and food/canning; textile industry; batteries.	[1] CAMEO Chemicals
–	COLOURLESS GAS OR COMPRESSED LIQUEFIED GAS WITH PUNGENT ODOUR.	[2] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Colorless gas with a characteristic, irritating, pungent odor.	[3] Occupational Safety and Health Administration (OSHA)
–	Colorless gas with a characteristic, irritating, pungent odor. [Note: A liquid below 14 °F. Shipped as a liquefied compressed gas.]	[4] The National Institute for Occupational Safety and Health (NIOSH)
–shown	Colorless gas or liquid	[5] Hazardous Substances Data Bank (HSDB)cites Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 1290
–	Colorless gas ... [Note: A liquid below 14 degrees F. Shipped as a liquefied compressed gas]	[5] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Control & Prevention. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from: https://www.cdc.gov/niosh/npg

Value	As written	Source
−72.7 °C	-98.9 °F (EPA, 1998)	[1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
−75.5 °Cshown	-75.5 °C	[2] ILO-WHO International Chemical Safety Cards (ICSCs)
−76 °C	-104 °F	[3] Occupational Safety and Health Administration (OSHA)
−75.5 °C	-75.5 °C	[6] PAC Chemical Database, U.S. Department of Energy
−76 °C	-104 °F	[4] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
−10 °C	14 °F at 760 mmHg (EPA, 1998)	[1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
−10 °C	-10 °C	[2] ILO-WHO International Chemical Safety Cards (ICSCs)
−10 °C	14 °F	[3] Occupational Safety and Health Administration (OSHA)
−10.1 °Cshown	-10.05 °C @760 [mm Hg]	[6] PAC Chemical Database, U.S. Department of Energy
−10 °C	14 °F	[4] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	1.434 (EPA, 1998) - Denser than water	[1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
–shown	Density: 1.434 at 0 °C (liquid)	[5] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 12th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2012., p. V5: 4106
–	Relative density (water = 1): 1.4 (liquid, -10 °C)	[2] ILO-WHO International Chemical Safety Cards (ICSCs)
–	1.434	[3] Occupational Safety and Health Administration (OSHA)
–	2.619 @25 °C	[6] PAC Chemical Database, U.S. Department of Energy
–	2.26(relative gas density)	[4] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	10 % (NIOSH, 2024)	[1] CAMEO Chemicals
–	In water, 1.07X10+5 mg/L at 21 °C	[5] Hazardous Substances Data Bank (HSDB)cites Venable CS, Fuwa T; Ind Eng Chem 14: 139-42 (1922)
–	Soluble in water ... forms sulfurous acid (H2SO3)	[5] Hazardous Substances Data Bank (HSDB)cites Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 1290
–	For more Solubility (Complete) data for Sulfur dioxide (7 total), please visit the HSDB record page.	[5] Hazardous Substances Data Bank (HSDB)
–shown	Solubility in water, ml/100ml at 25 °C: 8.5	[2] ILO-WHO International Chemical Safety Cards (ICSCs)
–	10%	[4] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
2432 mmHgshown	2432 mmHg at 68 °F (EPA, 1998)	[1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
2500 mmHg	Vapor pressure, kPa at 20 °C: 330	[2] ILO-WHO International Chemical Safety Cards (ICSCs)
750 mmHg	750 [mm Hg] @-10.3 °C	[6] PAC Chemical Database, U.S. Department of Energy

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 3
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 0
H-bond acceptors: 2 computed here · PubChem 3
Rotatable bonds: 0
TPSA (Å²): 34.1 computed here · PubChem 35.1
Formal charge: 0
XLogP3: 0.1 PubChem
Complexity: 18 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C2v of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

O49.95%
S50.05%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: -0.67 Crippen (Wildman and Crippen 1999)
log S (water solubility): 0.19 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 4.17 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 64.06
log P ≤ 5 (Crippen): -0.67
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 2

Passes all four rules.

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Harmonized EU classification (CLP Annex VI). Source [7].

Compressed gas
Corrosive
Acute toxicity
Health hazard

NFPA 704[5]

H314Causes severe skin burns and eye damage
H331Toxic if inhaled
H370Causes damage to organs

Precautionary statements: P260, P261, P264, P270, P271, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P308+P316, P316, P321, P363, P403+P233, P405, P501

View all classifications (4)

[7] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH314, H331, H370
[8] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 16.2% (425 of 2617) of reports.
[8] European Chemicals Agency (ECHA) · 2,617 reports · DangerH280, H314, H331
[5] Hazardous Substances Data Bank (HSDB) · DangerH314, H318, H331

Exposure limits

PEL-TWA (8-Hour Time Weighted Average): 5 ppm (13 mg/m³)[3]
PEL: TWA 5 ppm (13 mg/m3) See Appendix G[4]
REL-TWA (Time Weighted Average): 2 ppm (5 mg/m³)[3]
REL: TWA 2 ppm (5 mg/m3) ST 5 ppm (13 mg/m3)[4]
TLV: 0.25 ppm as STEL; A4 (not classifiable as a human carcinogen).[2]
TLV-STEL (Short Term Exposure Limit): 0.25 ppm [2008][3]

First aid

Note: Persons with asthma, subnormal pulmonary function, or cardiovascular disease are at greater risk. Signs and Symptoms of Acute Sulfur Dioxide Exposure: Sulfur dioxide may irritate the eyes and respiratory tract. Signs and symptoms of acute exposure to sulfur dioxide may be severe and include coughing, choking, dyspnea (shortness of breath), sneezing, wheezing, and chest discomfort. Upper airway edema (swelling) or obstruction, bronchoconstriction, pneumonia, pulmonary edema, and respiratory paralysis may occur. Fatigue may be noted.[1]
General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped…[9]
(General first aid procedures) Eye: Frostbite - If eye tissue is frozen, seek medical attention immediately; if tissue is not frozen, immediately and thoroughly flush the eyes with large amounts of water for at least 15 minutes, occasionally lifting the lower and upper eyelids. If irritation, pain, swelling, lacrimation, or photophobia persist, get medical attention as soon as possible. Skin: Frostbite - Compressed gases may create low temperatures when they expand rapidly. Leaks and uses that allow rapid expansion may cause a frostbite hazard.[4]
Fresh air, rest. Artificial respiration may be needed. Refer for medical attention.[2]

Storage

Ventilation along the floor. Dry.[2]
Storage temp: Less than 54 °C (130 °F)[5]
Compressed gas cylinders containing sulfur dioxide should be stored in accordance with 29 CFR 1910.101.[5]
Store in a cool, dry, well-ventilated location. Outside or detached storage is preferred. Isolate from oxidizing materials and alkalies. (sulfur dioxide, liquefied)[5]

Incompatibilities

Will react with water or steam to produce toxic and corrosive fumes.[5]
Monocesium or monopotassium acetylides, and the ammoniate of monolithium acetylide, all ignite and incandesce in unheated sulfur dioxide. The dimetal derivatives including sodium acetylide appear to be less reactive, needing heat before ignition occurs.[5]
Cesium monoxide, iron(II) oxide, tin oxide, and lead(IV) oxide all ignite and incandesce on heating in (sulfur dioxide) gas. Finely divided (pyrophoric) chromium incandesces in sulfur dioxide, while pyrophoric manganese burns ... On heating in gas. Molten sodium reacts violently with dry gas or liquid, while moist gas reacts as vigorously as water with cold sodium.[5]
Heated oxide (barium peroxide) attains incandescence in a rapid stream of ... Sulfur dioxide.[5]

Safety data sheets on the supplier’s page: BenchChem, Sigma-Aldrich, SynQuest Laboratories.

Always read the supplier’s safety data sheet before working with it.

Spectra

NMRNMRShiftDB
GC-MSNIST Mass Spectrometry Data Center · NIST Mass Spectrometry Data Center · SpectraBase (CH7)

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]CAMEO Chemicals · Public domain (NOAA) · via PubChem · retrieved 2026-10-14
[2]ILO-WHO International Chemical Safety Cards (ICSCs) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[3]Occupational Safety and Health Administration (OSHA) · Public domain (US DOL) · via PubChem · retrieved 2026-10-14
[4]The National Institute for Occupational Safety and Health (NIOSH) · Public domain (US CDC) · via PubChem · retrieved 2026-10-14
[5]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[6]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[7]Regulation (EC) No 1272/2008 of the European Parliament and of the Council · EU reuse policy, CC BY 4.0 · via PubChem · retrieved 2026-10-14
[8]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[9]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
[10]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
[11]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[12]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.