Aluminum Oxide

Aluminum Oxide

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Aluminum oxide occurs as a white crystalline powder. Aluminum oxide occurs as two crystalline forms: a-aluminum oxide is composed of colorless hexagonal crystals, and g-aluminum oxide is composed of minute colorless cubic crystals that are transformed to the a-form at high temperatures.

Synonyms

Activated alumina; activated aluminum oxide; alpha aluminum oxide; alumina; alumina, calcined; alumina, tabular; aluminum oxide alumite; alum inum trioxide; gamma aluminum oxide.

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Aluminum Oxide

Chemical Name and CAS Registry Number: Aluminum oxide [1344-28-1]

Empirical Formula and Molecular Weight: Al2O3 101.96

Structural Formula

Aluminum oxide occurs naturally as the minerals bauxite, bayerite, boehmite, corundum, diaspore, and gibbsite.

Functional Category: Adsorbent; dispersing agent.

Applications in Pharmaceutical Formulation or Technology

Aluminum oxide is used mainly in tablet formulations. It is used for decoloring powders and is particularly widely used in antibiotic formulations. It is also used in suppositories, pessaries, and urethral inserts. Hydrated aluminum oxide is used in mordant dyeing to make lake pigments, in cosmetics, and therapeutically as an antacid.

Typical Properties

Boiling point 29778°CDensity (bulk) 0.9_1.1 g/cm3Flammability Nonflammable.Hardness (Mohs) 8.8Hygroscopicity: Very hygroscopicMelting point 20508°CSolubility: Slowly soluble in aqueous alkaline solutions with the formation of hydroxides; practically insoluble in nonpolar organic solvents, diethyl ether, ethanol (95%), and water.Specific gravity: 2.8 (becomes 4.0 at 8008°C)Vapor pressure: 133.3 Pa at 21588°C

Method of Manufacture

Most of the aluminum oxide produced commercially is obtained by the calcination of aluminum hydroxide.

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