Aluminium hydroxide

Aluminium hydroxide

Chembox new
Name = Aluminium hydroxide
ImageFile = Gibbsite-crystal-3D-balls.png ImageFile2 = Hydroxid hlinitý.png IUPACName = Aluminium(III) hydroxide
OtherNames = Aluminium hydroxide,
Hydrated alumina
Section1 = Chembox Identifiers
CASNo = 21645-51-2
RTECS =

Section2 = Chembox Properties
Formula = Al(OH)3
MolarMass = 78.00344 g/mol
Appearance = White amorphous powder.
Density = 2.4 g/cm³, solid.
Solubility = Insoluble.
MeltingPt = 300°C
BoilingPt =
pKa =

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.
OtherCpds = Sodium oxide,
aluminium oxide hydroxide.

Aluminium hydroxide, Al(OH)3, is the most stable form of aluminium in 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.

Production

Aluminium hydroxide is an intermediate product in the Bayer process. In this process, bauxite is dissolved in hot sodium hydroxide solution, 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 process in order to produce aluminium.

Chemistry

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 hydrolysis products. It also dissolves in strong alkali, forming Al(OH)4-.

Pharmacology

Pharmacologically, this compound is used as an antacid under 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, heartburn or 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 adjuvant in 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 disease contain 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 dementia that 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.

References

*

External links

* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc03/icsc0373.htm International Chemical Safety Card 0373]


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • aluminium hydroxide — aliuminio hidroksidas statusas T sritis chemija formulė Al(OH)₃ atitikmenys: angl. aluminium hydroxide rus. алюминия гидроксид; алюминия гидроокись …   Chemijos terminų aiškinamasis žodynas

  • aluminium hydroxide — noun white crystalline compound that occurs naturally as the mineral gibbsite • Syn: ↑aluminum hydroxide, ↑hydrated aluminum oxide, ↑hydrated aluminium oxide • Hypernyms: ↑hydroxide, ↑hydrated oxide • Substance Holonyms …   Useful english dictionary

  • aluminium hydroxide — a safe slow acting antacid. It is administered by mouth, alone or in combination with magnesium hydroxide (as co magaldrox), in the treatment of indigestion, gastric and duodenal ulcers, and reflux oesophagitis. Trade names: Alu Cap …   The new mediacal dictionary

  • aluminium hydroxide — noun The hydrated form of alumina, having the formula Al(OH); it reacts with bases to form aluminates. Syn: aluminic acid …   Wiktionary

  • aluminium hydroxide — a safe slow acting antacid. It is administered by mouth, alone or in combination with other antacids, in the treatment of indigestion, gastric and duodenal ulcers, and reflux oesophagitis. Trade names: Alu Cap, Aludrox …   Medical dictionary

  • Aluminium chlorohydrate — is a group of specific aluminium salts having the general formula AlnCl(3n m)(OH)m. It is used in deodorants and antiperspirants and as a coagulant in water purification. In water purification, this compound is preferred in some cases because of… …   Wikipedia

  • Aluminium oxide hydroxide — is found as one of two well defined crystalline phases, which are also known as the minerals boehmite and diaspore. The minerals are important constituents of the aluminium ore, bauxite.List of related compounds and mineralsThe aluminium oxides,… …   Wikipedia

  • Aluminium amalgam — is a solution of aluminium in mercury. Aluminium amalgam may be prepared by either grinding aluminium pellets or wire in mercury, or by allowing aluminium wire to react with a solution of mercury(II) chloride in water.[1][2] This amalgam is used… …   Wikipedia

  • Aluminium acetate — Aluminium acetates are the aluminium salts of acetic acid. Three such salts exist: * neutral aluminium triacetate, Al(C2H3O2)3 * basic Aluminium diacetate, HOAl(C2H3O2)2 * basic Aluminium monoacetate, (HO)2AlC2H3O2ynthesisThe triacetate forms… …   Wikipedia

  • Hydroxide — Lewis structure of the hydroxide ion showing three lone pairs on the oxygen atom …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”