Explanation

Highly reactive metals such as sodium, potassium and aluminium cannot be reduced by ordinary chemical reducing agents, so they are extracted by the electrolysis of their molten compounds — e.g., sodium by the electrolysis of molten sodium chloride (Downs process). Copper, gold and tin are less reactive and are extracted by chemical reduction, roasting or smelting. The Downs process electrolyses a molten mixture of sodium chloride and calcium chloride.