Aluminum Hydroxide (Al(OH)₃) A white powder prepared as a colorless gelatinous precipitate by adding ammonia solution or a small amount of sodium hydroxide solution to a solution of an aluminum salt. It is an amphoteric hydroxide and is used as a foaming agent in fire extinguishers and as a mordant in dyeing. Its amphoteric nature causes it to dissolve in excess sodium hydroxide solution to form the aluminate ion (systematic name tetrahydroxoaluminate(III)):
Al(OH)₃ + OH⁻ → Al(OH)₄⁻ + H₂O
When precipitating from solution, aluminum hydroxide readily absorbs colored matter from dyes to form lakes.
Molecular mass for aluminium hydroxide 78.00 g/mol, density 2.42 g/cm3 , melting point 300 °C.