Sodium oxide


Sodium oxide is a chemical compound with the formula Na2O. It is used in ceramics and glasses. The compound is the base anhydride of sodium hydroxide; when water is added to sodium oxide, NaOH is produced.
The alkali metal oxides M2O crystallise in the antifluorite structure. In this motif the positions of the anions and cations are reversed relative to their positions in CaF2, with sodium ions tetrahedrally coordinated to 4 oxide ions and oxide cubically coordinated to 8 sodium ions.

Preparation

Sodium oxide is produced by the reaction of sodium with sodium hydroxide, sodium peroxide, or sodium nitrite:
Most of these reactions rely on the reduction of something by sodium, whether it is hydroxide, peroxide, or nitrite.
Burning sodium in air will produce Na2O and about 20% sodium peroxide Na2O2.
A more accesible way of producing it in the laboratory consists in decomposing the sodium salt of ascorbic acid at temperatures over 209 Celsius degrees.

Applications

Glassmaking

Sodium oxide is a significant component of most glass, although it is added in the form of "soda". Typically, manufactured glass contains around 15% sodium oxide, 70% silica and 9% lime. The sodium carbonate "soda" serves as a flux to lower the temperature at which the silica mixture melts. Soda glass has a much lower melting temperature than pure silica, and has slightly higher elasticity. These changes arise because the silicon dioxide and soda have reacted to form sodium silicates of the general formula Na2x.