Sulfur trioxide (SO₃)

Sulfur trioxide (SO₃)

One of the oxides of sulfur, forms sulfuric acid with water.



sulfur trioxide, molecule, sulphuric acid, sulphuric acid production, molecular shape, volcanic gases, oleum, disulphuric acid, inorganic chemistry, chemistry

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Sulfur trioxide SO₃


Molar mass: 80.06 g/mol

Molecular shape: triangle

Bond angle: 120°

Melting point: 16.8 °C (62.24 °F)

Boiling point: 45 °C (113 °F)

Density: 1.93 g/cm³ (0.0697 lb/in³)


Sulfur trioxide is one of the oxides of sulfur, a thick, colorless liquid at room temperature. When stored for a longer period of time, it is converted into a crystalline variant. It reacts intensely with water, while forming sulfuric acid. It dissolves well in concentrated sulfuric acid and forms oleum. It is a strong oxidant; it carbonizes carbohydrates and other organic compounds. It causes serious burns on the skin.

Occurrence and production

Sulfur trioxide is produced during the catalytic oxidation of sulfur dioxide. It occurs naturally in volcanic gases.


It is used in industrial quantities in the production of sulfuric acid.

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Sulfur dioxide (SO₂)

Sulfur dioxide emission is the main cause of acid rains. It is an intermediate product in the production of sulfuric acid.

Copper sulfate (CuSO₄)

A compound of sulfur often used as a pesticide.

Hydrogen sulfide (H₂S)

A colorless, toxic gas with the characteristic odor of rotten eggs. It occurs in certain mineral waters and spring waters.

Sulfate ion (SO₄²⁻)

A compound ion produced when sulfuric acid releases a proton.

Sulfur (S₈)

An odorless, yellow, solid substance, the 16th most common in the Earth´s crust. One of the best known sulfur compounds is pyrite, also known as ´fool´s gold´.

Sulfuric acid (H₂SO₄)

A colorless, viscous liquid, a highly corrosive, strong acid used in several industrial processes.

Sulfurous acid (H₂SO₃)

Colorless, moderate acid, only known in aqueous solution.

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