View source for Aluminium hydroxide

{{chembox
| verifiedrevid = 322319835
|   Name = Aluminium hydroxide
|   ImageFile = Gibbsite-crystal-3D-balls.png
|   ImageFile2 = Hydroxid hlinitý.PNG
|   IUPACName = Aluminium hydroxide
|   OtherNames = Aluminium(III) hydroxide,<br />Hydrated alumina
| Section1 = {{Chembox Identifiers
|   ChemSpiderID = 8351587
| InChI = 1/Al.3H2O/h;3*1H2/q+3;;;/p-3
| SMILES = [Al+3].[OH-].[OH-].[OH-]
| InChIKey = WNROFYMDJYEPJX-DFZHHIFOAJ
| CASNo = 21645-51-2
|   CASNo_Ref = {{cascite}}
|   RTECS = BD0940000
  }}
| Section2 = {{Chembox Properties
|   Formula = Al(OH)<sub>3</sub>
|   MolarMass = 78.00 g/mol
|   Appearance = White [[amorphous]] powder
|   Density = 2.42 g/cm³, solid
|   Solubility = 0.0001 g/100 mL (20 °C)
|   SolubleOther = soluble in [[acid]]s, [[alkali]]s, [[hydrochloric acid|HCl]], [[sulfuric acid|H<sub>2</sub>SO<sub>4</sub>]]
|   MeltingPtC = 300
|   BoilingPt = 
|   pKa = >7 
  }}
| Section7 = {{Chembox Hazards
|   EUClass = Irritant ('''I''') Xi
|   RPhrases = {{R36}} {{R37}} {{R38}}
|   SPhrases = {{S26}} {{S36}}
|   FlashPt = Non-flammable
|   NFPA-H = 1 | NFPA-F = 0 | NFPA-R = 0
|   ExternalMSDS = [http://physchem.ox.ac.uk/MSDS/AL/aluminium_hydroxide.html External MSDS]  }}
| Section8 = {{Chembox Related
|   OtherAnions = None
|   OtherCpds = [[Sodium oxide]],<br />[[aluminium oxide hydroxide]]
  }}
}}

'''Aluminium hydroxide''', Al(OH)<sub>3</sub>, ATH, sometimes erroneously called Hydrate of alumina, is found in nature as the mineral [[gibbsite]] (also known as hydrargillite) and its three, much more rare forms, polymorphs: bayerite, doyleite and nordstrandite. Closely related are [[aluminium oxide hydroxide]], AlO(OH), and [[aluminium oxide]], Al<sub>2</sub>O<sub>3</sub>, differing only by loss of water. These compounds together are the major components of the aluminium [[ore]] [[bauxite]].  Freshly precipitated aluminium hydroxide forms [[gel]]s, which is the basis for application of aluminium salts as [[flocculation|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. Aluminium hydroxide powder which has been heated to an elevated temperature under carefully controlled conditions is known as activated alumina and is used as a desiccant, an adsorbent, in gas purification, as a Claus catalyst support, water purification, and an adsorbent for the catalyst during the manufacture of polyethylene by the Sclairtech process.

==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.<ref>A. F. Wells, ''Structural Inorganic Chemistry'', 4th. edition 1975, Oxford University Press.</ref>

Aluminium hydroxide is [[amphoteric]]. It dissolves in [[acid]], forming Al(H<sub>2</sub>O)<sub>6</sub><sup>3+</sup> (hexaaquaaluminate) or its [[hydrolysis]] products. It also dissolves in strong [[alkali]], forming Al(OH)<sub>4</sub><sup>-</sup> (tetrahydroxoaluminate).

==Production==
Virtually all the aluminium hydroxide used commercially is manufactured by the [[Bayer process]] which involves dissolving bauxite in sodium hydroxide as the first step.  It is marketed as Alu-Tabs.

==Uses==
Annual production is some 100 million tonnes, over 90% of which is converted to aluminium oxide (alumina) which is used in the manufacture of aluminium metal.

The major other uses of aluminium hydroxide is as a feedstock for the manufacture of other aluminium compounds: specialty calcined aluminas, aluminium sulfate, polyaluminium chloride, aluminium chloride, zeolites, sodium aluminate, activated alumina, aluminium nitrate.

==Use as a fire retardant==
Aluminium hydroxide also finds use as a fire retardant filler for polymer applications in a similar way to [[magnesium hydroxide]] and [[hydromagnesite]]. It decomposes at about 180 °C, absorbing a considerable amount of heat in the process and giving off water vapour. In addition to behaving as a fire retardant, it is very effective as a smoke suppressant in a wide range of polymers, most especially in polyesters, acrylics, ethylene vinyl acetate, epoxies, PVC, rubber.

==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.<ref>{{cite book | author = Galbraith, A; Bullock, S; Manias, E. Hunt, B. & Richards, A. | year = 1999 | title =  Fundamentals of pharmacology: a text for nurses and health professionals | location = Harlow | publisher = Pearson | pages = 482}}</ref> This decrease of acidity of the contents of the stomach may in turn help to relieve the symptoms of [[peptic ulcer|ulcers]], [[heartburn]] or [[dyspepsia]]. It can also cause constipation and is therefore often used with [[magnesium hydroxide]] or [[magnesium carbonate]], which have 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 [[vaccine]]s (e.g., ''[[Alhydrogel]]'', [[Anthrax Vaccine]]), since it appears to contribute to induction of a good [[antibody]] (Th2) response. Its pharmacological action is not known. However, it has little capacity to stimulate cellular (Th1) immune responses, important for protection against many pathogens.<ref>{{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 | pmid = 15479434}}</ref>

Because the brain lesions found in [[Alzheimer's disease]] sometimes contain traces of aluminium, there is concern that consumption of excess aluminium compounds may cause or contribute to the development of this and other [[neurodegenerative disease]]s.<ref>{{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}}</ref><ref>{{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}}</ref> However, multiple epidemiological studies have found no connection between exposure to aluminium and neurological disorders.<ref>{{cite journal
|author=Rondeau V
|title=A review of epidemiologic studies on aluminum and silica in relation to Alzheimer's disease and associated disorders
|journal=Rev Environ Health
|volume=17
|issue=2
|pages=107–21
|year=2002
|pmid=12222737
}}</ref><ref>{{cite journal
|author=Martyn CN, Coggon DN, Inskip H, Lacey RF, Young WF
|title=Aluminum concentrations in drinking water and risk of Alzheimer's disease
|journal=Epidemiology
|volume=8
|issue=3
|pages=281–6
|year=1997
|month=May
|pmid=9115023
|doi=10.1097/00001648-199705000-00009
}}</ref><ref>{{cite journal
|author=Graves AB, Rosner D, Echeverria D, Mortimer JA, Larson EB
|title=Occupational exposures to solvents and aluminium and estimated risk of Alzheimer's disease
|journal=Occup Environ Med
|volume=55
|issue=9
|pages=627–33
|year=1998
|month=September
|pmid=9861186
|pmc=1757634
|doi=10.1136/oem.55.9.627
}}</ref>

In addition, elevated aluminium levels in blood, resulting from kidney dialysis with well water containing high aluminium, may result in [[dementia]] that is similar to but probably different from that of Alzheimer's disease.<ref>{{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=}}</ref>. However, this hypothesis is controversial.

In 2007, tests with mice of the [[anthrax vaccine]] using aluminium hydroxide adjuvant were reported as resulting in adverse neuropathy symptoms.<ref>{{cite journal | author=Petrik MS, Wong MC, Tabata RC, Garry RF, Shaw CA. | title=Aluminum adjuvant linked to Gulf War illness induces motor neuron death in mice. | journal=Neuromolecular Med. | year=2007 | issue=9 | pages=83–100 |pmid= |doi= 10.1385/NMM:9:1:83|url= | volume=9 }}</ref>

==References==
<references/>

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

{{Aluminium compounds}}
{{Antacids}}

[[Category:Hydroxides]]
[[Category:Aluminium compounds]]
[[Category:Inorganic compounds]]
[[Category:Phosphate binders]]
[[Category:Antacids]]
[[Category:World Health Organization essential medicines]]

[[ar:هيدروكسيد الألومنيوم]]
[[ca:Hidròxid d'alumini]]
[[cs:Hydroxid hlinitý]]
[[de:Aluminiumhydroxid]]
[[es:Hidróxido de aluminio]]
[[fa:آلومینیم هیدروکسید]]
[[fr:Hydroxyde d'aluminium]]
[[gl:Hidróxido de aluminio]]
[[it:Idrossido di alluminio]]
[[lv:Alumīnija hidroksīdi]]
[[hu:Alumínium-hidroxid]]
[[nl:Aluminiumhydroxide]]
[[ja:水酸化アルミニウム]]
[[pl:Wodorotlenek glinu]]
[[pt:Hidróxido de alumínio]]
[[ro:Hidroxid de aluminiu]]
[[ru:Гидроксид алюминия]]
[[sk:Hydroxid hlinitý]]
[[sr:Алуминијум хидроксид]]
[[fi:Alumiinihydroksidi]]
[[sv:Aluminiumhydroxid]]
[[th:อะลูมิเนียมไฮดรอกไซด์]]
[[uk:Гідроксид алюмінію]]
[[zh:氢氧化铝]]
[[Category:2Fix]]