Sodium hyponitrite, Na₂N₂O₂

The Sodium hyponitrite, Na₂N₂O₂, can be prepared by reducing sodium nitrite with sodium-amalgam and precipitating the solid by addition of alcohol to the solution. The reduction can also be effected by means of sulphur dioxide.

Sodium hyponitrite is readily soluble in water, the concentrated solution being stable in presence of a large proportion of sodium hydroxide. On crystallization the salt is deposited as pentahydrate, this substance losing its water of crystallization in a desiccator or on exposure to air. The anhydrous salt is the more stable form; it melts with decomposition at 300° C. The cryoscopic method gives the double molecular formula, Na₂N₂O₂.