A method of making alumina (Al2O3) from aluminium ore or bauxite. It involves crushing the bauxite and separating it from the oxides of iron, silica, and titanium that are also contained in the ore. It is then mixed with caustic soda and heated (p. 29) under pressure. The alumina dissolves in the caustic soda forming a solution of sodium aluminate. After filtration, crystals of aluminium hydroxide are added to the solution. The alumina precipitates out as crystals and are collected by filtration. The crystals are then dried by heating to around 1,200°C to leave a fine white powder. It was invented in 1887 by Austrian chemist Karl Josef Bayer (1847–1904).