What Is Aluminum Hydroxide?

In nature, the element aluminum combines with other elements to form compounds. Aluminum hydroxide is a compound which is closely related to aluminum oxide and aluminum oxide hydroxide, the primary difference between the three being the loss of water. All three compounds are found in bauxite, the ore used for creating pure aluminum. While pure aluminum is a metal, aluminum hydroxide is a crystal.

Description and Actions

In pure form, aluminum hydroxide is a whitish powder or granulate which is insoluble in water, but dissolves in strong acids or bases. It acts as a neutralizing agent for both acids and bases, binding with elements to form new compounds. For instance, when exposed to hydrochloric acid it forms aluminum chloride. It is used in both industry and medicine, often in a gel which forms naturally when it is precipitated (mixed in a solution to form a solid).

Properties of Aluminum Hydroxide

Like other aluminum compounds, aluminum hydroxide binds with other elements and can be used in purification processes. As with aluminum oxide, it reacts with impurities to create a sediment which can be easily filtered from water and other liquids. It is stable and combines well with inks and vegetable dyes as a mordant. It can also be used as a fixative during the development of photography. It is not a conductor of electricity and it has a melting point of 300 degrees Celsius.

Toxicity in Humans

In most individuals, aluminum hydrate does not irritate skin or cause rashes. It is non toxic in topical form and is not acutely toxic if inhaled, ingested or injected. There is concern in the medical community of long term exposure to aluminum compounds because aluminum accumulates during repeated exposure and cannot be flushed from the body. There is some indication of a correlation between Alzheimer's disease and long term exposure to aluminum compounds.

Environmental Concerns

While not toxic to humans, aluminum and alumina compounds are highly toxic to fish and aquatic life. These compounds are not known to be harmful to plants and some are used to alter the soil ph in gardens and agriculture to encourage plant growth. The primary concern in using and disposing of alumina compounds is to avoid their runoff into waterways and lakes where they can alter eco-systems. They are used in man-made ponds to discourage the growth of algae.

Long Term Effects

While there is no evidence that low levels of aluminum hydroxide have any long term effects on healthy individuals, there have been medical reports showing that therapeutic amounts of aluminum hydroxide, in patients undergoing dialysis, may cause metabolic and nervous system changes. There is also some concern over the compound's use in certain vaccines such as tetanus, hepatitis A and hepatitis B, although the long term effects are seen in a very small number of people.

Aluminum hydroxide is a commonly occurring natural chemical compound which has many uses in industry and in medical science. It is used in many products from cosmetics to cement as a mordant, a purifying agent and a fixative. There is no evidence that normal exposure to aluminum hydroxide presents any risk to humans.