Sulfur trioxide - SO₃

Sulfur trioxide is an anhydride to sulfur acid and in pure form it is a fluid. Gaseous sulfur trioxide is highly irritating to the eyes, throat and respiratory tract.

It reacts with water and water vapour. Without water it’s not particularly reactive to metals.

Properties

Molecular weight   80.066 g/mol

Solid phase   Melting point: 16.9 °C

Liquid phase   Boiling point: 45 °C