Potassium sulfite

Potassium sulfite is a chemical compound. Its chemical formula is K2SO3. It contains potassium and sulfite ions. 
Properties.
It is a white crystalline solid. It is a reducing agent. It can react with oxidizing agents to make potassium sulfate. 
Preparation.
It is made by reacting sulfur dioxide with potassium hydroxide.
Uses.
It is used to preserve food. Sulfites can cause allergies in some people, though.