Potassium sulfite

Potassium sulfite is the inorganic compound with the formula K₂SO₃. It is the salt of potassium cation and sulfite anion. It is a white solid that is highly soluble in water. Potassium sulfite is used for preserving food and beverages.

Potassium sulfite was first obtained by Georg Ernst Stahl in the early 18th century, and was therefore known afterwards as Stahl's sulphureous salt. It became the first discovered sulfite and was first properly studied along with other sulfites by French chemists in the 1790s, and it was called sulphite of potash in the early 19th century. Gilles-François Boulduc also discovered the salt in water of Passy in the 1720s.

Potassium sulfite is produced by the thermal decomposition of potassium metabisulfite at 190 °C:

The structure of solid K₂SO₃, as assessed by X-ray crystallography. The S-O distances are 1.515 Å, and the O-S-O angles are 105.2°