Reactions of Alumina in Aqueous Solutions

Alumina is amphoteric, which means that it dissolves in acidic and basic solutions, but not in neutral aqueous solutions. The solubility of alumina in solutions of pH from about 4-9 is low; at 25°C it is less than 10-7 mol l-1 at pH 6 [1]. Alternatively, alumina dissolves readily in strong acids (HCl, HNO3, H2SO4) and strong bases (NaOH, KOH) at temperatures well above ambient (e. g., 90°C).