Sulfur trioxide
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For other uses, see SO3 (disambiguation).
Sulfur trioxide (alternative spelling sulphur trioxide, also known as nisso sulfan) is the chemical compound with the formula SO3. It has been described as "unquestionably the most [economically] important sulfur oxide".[1] It is prepared on an industrial scale as a precursor to sulfuric acid.
Quick Facts Names, Identifiers ...
Names | |
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Preferred IUPAC name
Sulfur trioxide | |
Systematic IUPAC name
Sulfonylideneoxidane | |
Other names
Sulfuric anhydride, Sulfur(VI) oxide | |
Identifiers | |
3D model (JSmol) |
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ChEBI | |
ChemSpider |
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ECHA InfoCard | 100.028.361 |
EC Number |
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1448 | |
PubChem CID |
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RTECS number |
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UNII | |
UN number | UN 1829 |
CompTox Dashboard (EPA) |
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Properties | |
SO3 | |
Molar mass | 80.066 g/mol |
Appearance | Colorless to white crystalline solid which will fume in air.[2] Colorless liquid and gas.[3] |
Odor | Varies. Vapor is pungent; like sulfur dioxide.[4] Mist is odorless.[3] |
Density | 1.92 g/cm3, liquid |
Melting point | 16.9 °C (62.4 °F; 290.0 K) |
Boiling point | 45 °C (113 °F; 318 K) |
Reacts to give sulfuric acid | |
Thermochemistry | |
Std molar entropy (S⦵298) |
256.77 JK−1mol−1 |
Std enthalpy of formation (ΔfH⦵298) |
−395.7 kJ/mol |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards |
Highly corrosive, extremely strong dehydrating agent |
GHS labelling: | |
Danger | |
H314, H335 | |
P261, P280, P305+P351+P338, P310[5] | |
NFPA 704 (fire diamond) | |
Flash point | Non-flammable |
Lethal dose or concentration (LD, LC): | |
LC50 (median concentration) |
rat, 4 hr 375 mg/m3[citation needed] |
Safety data sheet (SDS) | ICSC 1202 |
Related compounds | |
Other cations |
Selenium trioxide Tellurium trioxide Polonium trioxide |
Sulfur monoxide Sulfur dioxide | |
Related compounds |
Sulfuric acid |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Close
Sulfur trioxide exists in several forms - gaseous monomer, crystalline trimer, and solid polymer. Sulfur trioxide is a solid at just below room temperature with a relatively narrow liquid range. Gaseous SO3 is the primary precursor to acid rain.[6]