Sulfur trioxide

contains stabilizer, ≥99%

Sulfuric anhydride
Linear Formula:
CAS Number:
Molecular Weight:
EC Number:
MDL number:
PubChem Substance ID:

vapor density

2.8 (vs air)

vapor pressure

280 mmHg ( 25 °C)







reaction suitability

reagent type: oxidant


low-melting solid polymer (the formation of which is unavoidable)


44.7 °C (lit.)


16.8 °C (lit.)


1.97 g/mL at 25 °C (lit.)

SMILES string




InChI key


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General description

Sulfur trioxide is an oxide of sulfur that is released during the combustion of sulfur bearing fuels. It can be prepared by the oxidation of sulfur dioxide in the presence of vanadia catalyst.


Sulfur trioxide may be used in the synthesis of methane sulfonic acid (MSA) by sulfonating methane. it may also be used in the synthesis of fluorinated β-sultones by reacting with fluoroolefins.

Certificate of Analysis

Certificate of Origin

  1. Which document(s) contains shelf-life or expiration date information for a given product?

    If available for a given product, the recommended re-test date or the expiration date can be found on the Certificate of Analysis.

  2. How do I get lot-specific information or a Certificate of Analysis?

    The lot specific COA document can be found by entering the lot number above under the "Documents" section.

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  4. Is Product 227692, Sulfur trioxide, OK to use if it contains solids?

    This product may contain low-melting solid polymer, which is unavoidable. If the material is not completely liquid, place the bottle in a glass beaker or metal pail and warm under heat lamp or in an oven at 35°C. DO NOT OVERHEAT! This product boils at 44.7°C. Melting may take up to one week. When the material is liquid, it is ready for use.

  5. What is the stabilizer used in Product 227692, Sulfur trioxide?

    The manufacturer considers the identity of the stabilizer to be proprietary information.

  6. Why does Product 227692, Sulfur trioxide, contain a stabilizer?

    The stabilizer is present to facilitate melting, not to prevent polymerization.

  7. How is Product 227692, Sulfur trioxide, packaged?

    This product is packaged in a screw-capped glass bottle.

  8. What is the Department of Transportation shipping information for this product?

    Transportation information can be found in Section 14 of the product's (M)SDS.To access the shipping information for this material, use the link on the product detail page for the product. 

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Emissions of sulfur trioxide from coal-fired power plants.
Srivastava RK, et al.
Journal of the Air & Waste Management Association (1995), 54(6), 750-762 (2004)
Emilia Ivanova et al.
Journal of hazardous materials, 167(1-3), 306-312 (2009-02-10)
Various ion exchange forms of preliminary partly decationised zeolite (hydrogen forms) were obtained by indirect modification with metal salt solutions, as well as by direct treatment of natural clinoptilolite taken from Bulgarian deposits. Direct modification leads to a higher extent...
Ri-sheng Yao et al.
Bioresource technology, 102(10), 6340-6343 (2011-03-12)
In this paper, a sulfur trioxide collaborative dilutes alkali method has been developed to pre-treat rice straw and it has been studied that the pre-treated rice straw structure affected the saccharification of the rice straw hydrolyzed by cellulose enzymatic hydrolysis....
Direct sulfonation of methane to methanesulfonic acid by sulfur trioxide catalyzed by cerium (IV) sulfate in the presence of molecular oxygen.
Mukhopadhyay S and Bell AT
Advanced Synthesis & Catalysis, 346(8), 913-916 (2004)
Fluorinated ?-Sultones.
Knunyants IL & Sokolski GA
Angewandte Chemie (International Edition in English), 11(7), 583-595 null

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