Aluminium oxide is an amphoteric substance, meaning it can react with both acids and bases, such as hydrofluoric acid and sodium hydroxide, acting as an acid with a base and a base with an acid, neutralising the other and producing a salt.
A 7484 (OTTO) Aluminium oxide pieces, 1-3 mm, 99.99% Cas 1344-28-1 - used as a dopant to produce optical fiber amplifiers and high-power fiber lasers.