Aluminium is the most abundant metal on Earth. It is extracted from its ore, bauxite, by electrolysis. The process involves dissolving the bauxite in hot caustic soda and then passing an electric current through it. This causes the aluminium to be deposited as a thin layer on the anode and oxygen to be released at the cathode. The aluminium is then removed from the anode and purified by a process called fractional distillation.