- Aluminium hydroxide
Name = Aluminium hydroxide
ImageFile = Gibbsite-crystal-3D-balls.png
ImageFile2 = Hydroxid hlinitý.png
IUPACName = Aluminium(III) hydroxide
OtherNames = Aluminium hydroxide,
Section1 = Chembox Identifiers
CASNo = 21645-51-2
Section2 = Chembox Properties
Formula = Al(OH)3
MolarMass = 78.00344 g/mol
Appearance = White
Density = 2.4 g/cm³, solid.
Solubility = Insoluble.
MeltingPt = 300°C
Section7 = Chembox Hazards
EUClass = Irritant (I)
RPhrases = R36, R37, R38
SPhrases = S26, S36
FlashPt = Non-flammable.
ExternalMSDS = [http://physchem.ox.ac.uk/MSDS/AL/aluminium_hydroxide.html External MSDS]
Section8 = Chembox Related
OtherAnions = None.
Sodium oxide, aluminium oxide hydroxide.
Aluminium hydroxide, Al(OH)3, is the most stable form of
aluminiumin normal conditions. It is found in nature as the mineral gibbsite(also known as hydrargillite) and its three, much more rare, polymorphs: bayerite, doyleite and nordstrandite. 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. Freshly precipitated aluminium hydroxide forms gels, which is the basis for application of aluminium salts as flocculants in water purification. This gel crystallizes with time. Aluminium hydroxide gels can be dehydrated (e.g., with the utility of water-miscible non-aqueous solvents like ethanol) to form an amorphous aluminium hydroxide powder, which is readily soluble in acids. Heat-dried aluminium hydroxide powder is known as activated alumina and is used in gas purification, as a catalyst support and an abrasive.
Aluminium hydroxide is an intermediate product in the
Bayer process. In this process, bauxiteis dissolved in hot sodium hydroxidesolution, and insoluble are filtered off. On cooling, aluminium hydroxide precipitates. The aluminium hydroxide is further calcined to give alumina, which may be smelted in the Hall-Héroult processin order to produce aluminium.
Gibbsite has a typical metal hydroxide structure with
hydrogen bonds. It is built up of double layers of hydroxyl groups with aluminium ions occupying two-thirds of the octahedral holes between the two layers. [A. F. Wells, "Structural Inorganic Chemistry", 4th. edition 1975, Oxford University Press.]
Aluminium hydroxide is
amphoteric. It dissolves in acid, forming Al(H2O)63+ or its hydrolysisproducts. It also dissolves in strong alkali, forming Al(OH)4-.
Pharmacologically, this compound is used as an
antacidunder names such as Alu-Cap, Aludrox or Pepsamar. The hydroxide reacts with excess acid in the stomach, reducing its acidity. This decrease of acidity of the contents of the stomach may in turn help to relieve the symptoms of ulcers, heartburnor dyspepsia. It can also cause constipation and is therefore often used with magnesium carbonate, which has counterbalancing laxative effects. This compound is also used to control phosphate (phosphorus) levels in the blood of people suffering from kidney failure.
Aluminium hydroxide is included as an
adjuvantin some vaccines (e.g., " Alhydrogel"), since it contributes to induction of a good antibody(Th2) response. However, it has little capacity to stimulate cellular (Th1) immune responses, important for protection against many pathogens. [cite journal | author = Petrovsky N, Aguilar JC. | title = Vaccine adjuvants: current state and future trends | journal = Immunol Cell Biol.| year = 2004 | volume = 82 | issue = 5 | pages = 488–96 | doi = 10.1111/j.0818-9641.2004.01272.x]
Because the brain lesions found in
Alzheimer's diseasecontain aluminium, there is concern that consumption of excess aluminium compounds may cause or contribute to the development of this and other neurodegenerative diseases. [cite journal |author=Perl DP, Moalem S |title=Aluminum and Alzheimer's disease, a personal perspective after 25 years |journal=J. Alzheimers Dis. |volume=9 |issue=3 Suppl |pages=291–300 |year=2006 |pmid=17004365 |doi= |url=http://iospress.metapress.com/openurl.asp?genre=article&issn=1387-2877&volume=9&issue=3&spage=291] [cite journal |author=Kawahara M |title=Effects of aluminum on the nervous system and its possible link with neurodegenerative diseases |journal=J. Alzheimers Dis. |volume=8 |issue=2 |pages=171–82; discussion 209–15 |year=2005 |month=November |pmid=16308486 |doi= |url=http://iospress.metapress.com/openurl.asp?genre=article&issn=1387-2877&volume=8&issue=2&spage=171] In addition, elevated aluminium levels in blood, resulting from kidney dialysis with well water containing high aluminium, result in dementiathat is similar to but probably different from that of Alzheimer's disease. [cite journal |author=Carpenter DO |title=Effects of metals on the nervous system of humans and animals |journal=Int J Occup Med Environ Health |volume=14 |issue=3 |pages=209–18 |year=2001 |pmid=11764847 |doi= |url=] However, this hypothesis is controversial.
* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc03/icsc0373.htm International Chemical Safety Card 0373]
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