Aluminium oxide as an amphoteric acid. Footage of aluminium (III) oxide (Al2O3) being added to an alkali, with the results monitored using a pH probe. The probe is in the beaker, with the pH reading displayed at right. An amphoteric chemical is one that can react with and neutralise both acids and bases. Here, the aluminium oxide is reacting with an alkali, acting as an acid to neutralise it. As the reaction progresses, the pH has changed from alkaline (above 7) to neutral (7) by the end of the clip.