Is Aluminium Oxide Acidic Or Basic?

What are the best resources for finding information on whether aluminium oxide is acidic or basic?

Aluminium oxide is amphoteric, meaning that it reacts as an acid with certain acids (such as hydrofluoric) but also reacts as a base with other bases (such as sodium hydroxide). This makes it difficult to categorize it. The simplest way to describe its reaction with bases is that it neutralises them, producing salt and water.

It is a common compound that is found in nature. The most well-known crystalline form is corundum, which is used to make gemstones including rubies and sapphires. These gems get their distinctive colours from trace impurities such as chromium and iron. It is also widely used in industrial ceramics, as abrasives and in electrical insulators such as wire guides.

One of its major commercial uses is as a catalyst support for industrial reactions such as the Claus process for converting hydrogen sulfide waste gases to elemental sulfur in refineries, and for dehydration of alcohols to alkenes. It is also used to make refractories, which are ceramic materials employed in furnaces and kilns.

Acute exposure to the inhalation of aluminium oxide particles produces a constriction of the lungs which can cause respiratory distress. Chronic exposure is less harmful, although it can still produce health issues. The particle size of the alumina produced by anodising is about 0.4um. Inhalation of this particle size for 30 minutes by guinea pigs produced time-dependent bronchoconstriction.