AlOH3

Aluminum hydroxide, commonly written Al(OH)3 and sometimes abbreviated AlOH3, is a poorly soluble, amphoteric hydroxide of aluminum. In solid form it is a gelatinous white precipitate and is often described as hydrated aluminum oxide. The mineral gibbsite is the natural form of Al(OH)3, while related minerals include boehmite (AlO(OH)·H2O) and diaspore (AlO(OH)). In water, Al(OH)3 can react with bases to form the tetrahydroxoaluminate ion [Al(OH)4]−, and with acids it dissolves to form Al3+.

Properties: Al(OH)3 is sparingly soluble in water and is amphoteric, meaning it can dissolve in both acids and bases. It dehydrates upon heating to form alumina (Al2O3) and water; calcination at higher temperatures yields various aluminum oxides.

Production: In industry, aluminum hydroxide precipitates from hot caustic solutions during the Bayer process, a step in refining bauxite to produce alumina. Calcination of Al(OH)3 yields alumina, a precursor to aluminum metal.

Uses: Al(OH)3 is used as an antacid and as a suspending and thickening agent. It serves as an adsorbent in water treatment and as a flame retardant filler in plastics. In vaccines, aluminum hydroxide salts are used as adjuvants to enhance immune response.

Safety: Aluminum hydroxide has relatively low acute toxicity, but inhalation of dust should be avoided. Chronic exposure to aluminum compounds can raise health concerns, so appropriate handling and safeguards are recommended.

Synonyms: aluminum hydroxide, Al(OH)3, aluminum trihydroxide, gibbsite.