Aluminium Hydroxide

Aluminum hydroxide, white solid, is a typical amphoteric hydroxide that is insoluble in water but soluble in acid or alkali. It can be transformed into alumina after heated in the air for dehydration, which is important for alumina production. Aluminum hydroxide is a widely used chemical product, and it is mainly used as plastic and polymer fillers, blanket flame retardant and binder, epoxy resin filler, toothpaste fillers, glass ingredients as well as paper color fillers and coatings. It can b
Aluminum hydroxide, insoluble in water, soluble in dilute mineral acids and alkali hydroxides (4 % suspension in water), white, amorphous powder. For other relevant properties and production, see→Aluminum Oxide, Chap. 1.1. Available as Al(OH)3·nH2O (algedrate) and algedrate hexitol complex.
Aluminum hydroxide adjuvant is a white hydrogel that sediments slowly and forms a clear supernatant.
aluminium hydroxide: A white crystalline compound, Al(OH)3; r.d. 2.42-2.52. The compound occurs naturally as the mineral gibbsite (monoclinic). In the laboratory it can be prepared by precipitation from solutions of aluminium salts. Such solutions contain the hexaquoaluminium( III) ion with six water molecules coordinated, [Al(H2O)6]3+. In neutral solution this ionizes:[Al(H2O)6]3+→H++ [Al(H2O)5OH]2+The presence of a weak base such as S2-or CO32-(by bubbling hydrogen sulphide or carbon dioxide through the solution) causes further ionization with precipitation of aluminium hydroxide[Al(H2O)6]3+(aq)→ Al(H2O)3(OH)3(s)+ 3H+(aq)The substance contains coordinated water molecules and is more correctly termed hydrated aluminium hydroxide. In addition, the precipitate has water molecules trapped in it and has a characteristic gelatinous form. The substance is amphoteric. In strong bases the aluminate ion is produced by loss of a further proton:Al(H2O)3(OH)3(s)+ OH-(aq)→[Al(H2O)2(OH)4]-(aq)+ H2O(l)On heating, the hydroxide transforms to a mixed oxide hydroxide, AlO.OH (rhombic; r.d. 3.01). This substance occurs naturally as diaspore and boehmite. Above 450℃ it transforms to γ-alumina.In practice various substances can be produced that are mixed crystalline forms of Al(OH)3, AlO.OH, and aluminium oxide (Al2O3) with water molecules. These are known as hydrated alumina. Heating the hydrated hydroxide causes loss of water, and produces various activated aluminas, which differ in porosity, number of remaining -OH groups, and particle size. These are used as catalysts (particularly for organic dehydration reactions), as catalyst supports, and in chromatography. Gelatinous freshly precipitated aluminium hydroxide was formerly widely used as a mordant for dyeing and calico printing because of its ability to form insoluble coloured lakes with vegetable dyes.
Poison by intraperitoneal route. Human systemic effects by ingestion: fever, osteomalacia, and gastrointestinal effects. When coprecipitated with bismuth hydroxide and reduced by H2, it is violently flammable in air. Incompatible with chlorinated rubber.