 Aluminium hydroxide Al(OH)3 is amphoteric and dissolves in alkaline solution.In the Bayer process for the production of pure aluminium oxide from bauxite minerals this equilibrium is manipulated by careful control of temperature and alkali concentration.In the first phase, aluminium dissolves in hot alkaline solution as , but other hydroxides usually present in the mineral, such as iron hydroxides, do not dissolve because they are not amphoteric.