Barium peroxide

Barium peroxide is a chemical compound. Its chemical formula is BaO2. It contains barium and peroxide ions.
Properties.
Barium peroxide is a gray-white solid. It reacts with water to make oxygen gas. When it is heated very hot, it releases oxygen and turns into barium oxide. 
Preparation.
It is made by heating barium oxide. This process used to be used to get oxygen from the air. Barium oxide was heated to around 300°C, absorbing oxygen and making barium peroxide. The barium peroxide was heated above 500°C, releasing the oxygen. Then it could be reused.
Uses.
Barium peroxide can be used to make hydrogen peroxide by reaction with sulfuric acid. This also makes the solid barium sulfate.