Sodium: Fused Caustic Soda Electrolysed in a Castner Cell

Metallic sodium by Castner's process, as Thorpe's Dictionary (1913) describes it: molten caustic soda is electrolysed in an iron pot. Sodium, lighter than the melt, rises inside a wire-gauze collector over the cathode and is skimmed off with a perforated iron spoon. The melt must stay within 20 °C of its melting point, no hotter than 330 °C; 1000–1200 amperes at 4–5 volts is usual. Water formed in the cell limits the yield to about 40 %. Sodium burns and reacts violently with water: face shield, dry tools. The picture: our diagram.