Castner process

At that time (prior to the introduction in the same year of the Hall-Héroult process) the primary use for sodium metal was as a reducing agent to produce aluminium from its purified ores.

[1] This in turn reduced the cost of producing aluminium, although the reduction-by-sodium method still could not compete with Hall-Héroult.

The temperature is cooler at the bottom and hotter at the top so that the sodium hydroxide is solid in the neck (B) and liquid in the body of the vessel.

Wire gauze (G) confines the sodium metal to accumulating at the top of the collection device (P).

[4] This water diffuses throughout the electrolyte and results in the reverse reaction taking place on the electrolyzed sodium metal: with the hydrogen gas also accumulating at (P).