ABSTRACT
The solid matter of the earth’s crust is made up of nearly a hundred elements, the most abundant of which are oxygen, silicon, and then aluminium. Commercial ores are grouped under the generic term ‘bauxite’, derived from the medieval village of Les Baux in Southern France, where high concentrations of hydrated aluminium oxide are found, and where early mining of the ore took place. The reduction of bauxite to metal involves two main operations. The bauxite is treated chemically to remove impurities and obtain aluminium oxide, alumina. The basic process discovered by Hall and Heroult is the one used today, although refinements in the techniques used have resulted in much more power-efficient operations. The process involves a bath of fused cryolite containing dissolved alumina which is electrolysed by the passage of a high amperage, low voltage current between carbon anodes and the carbon lining of the cell, which forms the cathode.
