Sulfurous acid

Athanor · official

H₂O₃S · 82.08 g/mol

Also called sulfur dioxide solution

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

DangerCauses severe skin burns and eye damage · Causes serious eye damage · Harmful if inhaled

Names and identifiers

IUPAC name: sulfurous acid
Synonyms: sulfur dioxide solution, Sulphurous acid, Schweflige saure
+ 36 more
H2SO3, EINECS 231-973-1, acide sulfureux, acido sulfuroso, schweflige Saeure, trioxosulfuric acid, dihydroxidooxidosulfur, UNII-J1P7893F4J, CHEBI:48854, SULFUROUS ACID (H2SO3), J1P7893F4J, SULPHUROSUM ACIDUM, DTXSID7042435, S(O)(OH)2, SULFUROUS ACID (II), SULFUROUS ACID [II], (SO(OH)2), [SO(OH)2], RefChem:6277, DTXCID5022435, 231-973-1, MFCD00011335, Schweflige saure [German], UN1833, H2O3S, Trioxosulphate(IV), Trioxosulphate(2-), dihydrogen trioxosulfate, SCHEMBL3181, SULFUROUS ACID [MI], Sulfur dioxide 6 % solution, CHEMBL1161699, SCHEMBL11330940, SULPHUROSUM ACIDUM [HPUS], BDBM50147623, Sulfurous acid [UN1833] [Corrosive]
Molecular formula: H₂O₃S
Empirical formula: H₂O₃S
Molecular weight: 82.08 g/mol
Exact mass: 81.97247
CAS number: 7782-99-2
PubChem CID: 1100
Canonical SMILES: OS(=O)O
Isomeric SMILES: OS(=O)O
InChI: InChI=1S/H2O3S/c1-4(2)3/h(H2,1,2,3)
InChIKey: LSNNMFCWUKXFEE-UHFFFAOYSA-N
Molfile

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

Physical properties

TemperaturePressureDensity

Appearance: Sulfurous acid appears as a colorless liquid with a pungent burning sulfur odor. Corrosive to metals and tissue.[1]
2 values
From CAMEO Chemicals, the most authoritative source here.
Value As written Source
–shown Sulfurous acid appears as a colorless liquid with a pungent burning sulfur odor. Corrosive to metals and tissue. [1] CAMEO Chemicals
– Liquid [2] EPA Chemical Data Reporting (CDR)
Density: 1.03 @25 °C[3]

Value	As written	Source
–shown	Sulfurous acid appears as a colorless liquid with a pungent burning sulfur odor. Corrosive to metals and tissue.	[1] CAMEO Chemicals
–	Liquid	[2] EPA Chemical Data Reporting (CDR)

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: 4
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 2
H-bond acceptors: 1 computed here · PubChem 4
Rotatable bonds: 0
TPSA (Å²): 57.5 computed here · PubChem 76.7
Formal charge: 0
XLogP3: -0.5 PubChem
Complexity: 26 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

H2.46%
O58.48%
S39.07%

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: -0.32 Crippen (Wildman and Crippen 1999)
log S (water solubility): -0.15 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 3.14 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 82.08
log P ≤ 5 (Crippen): -0.32
H-bond donors ≤ 5: 2
H-bond acceptors ≤ 10: 1

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

Most widely reported: 130 company reports to ECHA. Source [4].

Corrosive
Harmful or irritant

H314Causes severe skin burns and eye damage (95.4% of reports)
H318Causes serious eye damage (81.5% of reports)
H332Harmful if inhaled (99.2% of reports)

Precautionary statements: P260, P261, P264, P264+P265, P271, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P317, P321, P363, P405, P501

View all classifications (2)

[4] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 0.8% (1 of 130) of reports.
[4] European Chemicals Agency (ECHA) · 130 reports · DangerH314, H318, H332

First aid

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]: Refer to the "General First Aid" section. Specific First Aid: For corrosives, in case of contact, immediately flush skin or eyes with running water for at least 30 minutes. Additional flushing may be required. (ERG, 2024)[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…[5]

Safety data sheets on the supplier’s page: VladaChem, AA BLOCKS, 10X CHEM.

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

Spectra

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]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[3]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[4]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[5]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
[6]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[7]MassBank of North America (MoNA) · CC BY 4.0 · 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.