Aluminum hydroxide

Aluminum Hydroxide is a chemical compound with the formula Al(OH)3. It is found in nature as the mineral gibbsite (also known as hydrargillite) and its three, much rarer polymorphs: bayerite, doyleite, and nordstrandite. Aluminum hydroxide is amphoteric in nature, i.e., it has both basic and acidic properties. Closely related are aluminum oxide hydroxide, AlO(OH), and aluminum oxide, Al2O3, differing only by loss of water. These compounds together are the major components of the aluminum ore bauxite.

Chemistry

Aluminum hydroxide is a typical metal hydroxide, being weakly acidic. It reacts with acids, forming a aluminum salt and water. With strong bases, it forms aluminates. It also acts as a Lewis acid, accepting electron pairs from other molecules, a property exploited in many of its uses.

Uses

Aluminum hydroxide is used widely in pharmaceutical and industrial applications. In pharmaceuticals, it's used as an antacid under names such as Alu-Cap, Aludrox, or Pepsamar. It acts on the stomach acid by neutralizing it and preventing damage to the stomach lining. It's also used as an adjuvant in vaccines, improving the immune response.

In industry, it's used as a fire retardant, a clarifying agent in water treatment, and as a raw material in the production of aluminum metal, glass, and ceramics.

Health and Safety

While generally considered safe for use in pharmaceuticals, excessive consumption of aluminum hydroxide can lead to complications such as hypophosphatemia, osteomalacia, and, in severe cases, aluminum toxicity.

See Also

• Aluminum
• Hydroxide
• Bauxite
• Antacid
• Vaccine