Aluminium hydroxide
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| Aluminium hydroxide | |
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| General | |
| Systematic name | Aluminium(III) hydroxide |
| Other names | Aluminium hydroxide, Hydrated alumina |
| Molecular formula | Al(OH)3 |
| Molar mass | 78.00344 g/mol |
| Appearance | White amorphous powder. |
| CAS number | [[21645-51-2] [1]] |
| Properties | |
| Density and phase | 2.4 g/cm³, solid. |
| Solubility in water | Insoluble. |
| Melting point | ?°C |
| Boiling point | ?°C |
| Acidity (pKa) | N/A |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Irritant (I) |
| NFPA 704 | N/A |
| R-phrases | R36, R37, R38 |
| S-phrases | S26, S36 |
| Flash point | Non-flammable. |
| RTECS number | N/A |
| Supplementary data page | |
| Structure & properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | None. |
| Related compounds | Sodium oxide, aluminium oxide hydroxide. |
| Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references |
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Aluminium hydroxide, Al(OH)3, is the most stable form of aluminium in normal conditions. As found in nature it is known as the mineral gibbsite. Closely related are aluminium oxide hydroxide, AlO(OH), and aluminium oxide, Al2O3, differing only by loss of water. These compounds together are the major components of the aluminium ore, bauxite.
The character of 'aluminium hydroxide' has been controversial. It is safe to say that a simple scheme of Al3+ ions and OH- ions is oversimplified. More and less hydrated forms are very common. Some people write Al2O3.xH2O instead.
Aluminium hydroxide is amphoteric. In strongly acid conditions, Al(OH)2+ is formed; in strongly basic conditions, Al(OH)4- is formed. These are the main ions in dilute solutions; in concentrated solutions, polymeric ions are formed which can be quite complex.
Salts of the anion Al(OH)4- (or similar, such as AlO2-) are sometimes called aluminates.
Al(OH)3 has a molar mass of 78.01.
When used, aluminum hydroxide neutralizes the excess acid. For example, Al(OH)3 + 3HCl yields AlCl3 + 3H2O.
[edit] Pharmacology
Pharmacologically this compound, also known as Alu-Cap or Aludrox, is used as an antacid. It binds with the excess acid in the stomach, thus reducing its acidity. This decrease of acidity of the contents of the stomach may in turn help to relieve the symptoms of ulcers, heartburn or dyspepsia. It can also cause constipation and is therefore often used with magnesium carbonate. This compound is also used to control phosphate levels in the blood for people suffering from kidney failure. However, there are unverified claims that excessive consumption of aluminium is a cause of Alzheimer's disease.
[edit] References
Galbraith, A; Bullock, S; Manias, E. Hunt, B. & Richards, A. (1999). Fundamentals of pharmacology: a text for nurses and health professionals. Harlow: Pearson Education Ltd. p482.
[edit] External links
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