Sodium peroxide

Properties

Sodium peroxide crystallizes with hexagonal symmetry. Upon heating, the hexagonal form undergoes a transition into a phase of unknown symmetry at 512 °C. With further heating above the 675 °C melting point, the compound decomposes to Na₂O, releasing O₂, before reaching a boiling point.

2 Na₂O₂ → 2 Na₂O + O₂

Preparation

Sodium peroxide can be prepared on a large scale by the reaction of metallic sodium with oxygen at 130–200 °C, a process that generates sodium oxide, which in a separate stage absorbs oxygen:

4 Na + O₂ → 2 Na₂O2 Na₂O + O₂ → 2 Na₂O₂

It may also be produced by passing ozone gas over solid sodium iodide inside a platinum or palladium tube. The ozone oxidizes the sodium to form sodium peroxide. The iodine is freed into iodine crystals, which can be sublimed by mild heating. The platinum or palladium catalyzes the reaction and is not attacked by the sodium peroxide.

Uses

On contact with water sodium peroxide is hydrolyzed to give sodium hydroxide and hydrogen peroxide according to the reaction:

Na₂O₂ + 2 H₂O → 2 NaOH + H₂O₂

Sodium peroxide was used to bleach wood pulp for the production of paper and textiles. Presently it is mainly used for specialized laboratory operations, e.g., the extraction of minerals from various ores. Sodium peroxide may go by the commercial names of Solozone and Flocool. In chemistry preparations, sodium peroxide is used as an oxidizing agent. It is also used as an oxygen source by reacting it with carbon dioxide to produce oxygen and sodium carbonate; it is thus particularly useful in scuba gear, submarines, etc. Lithium peroxide has similar uses.

2Na₂O₂ + 2CO₂ → 2Na₂CO₃ + O₂