Magnesium hydroxide
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2008-06-25T19:11:29Z
Iridescent
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Cleanup/[[WP:AWB/T|typo fixing]], typos fixed: and and → and using [[Project:AutoWikiBrowser|AWB]]
{{Chembox new
| ImageFile =
| ImageSize =
| IUPACName =
| OtherNames = Milk of Magnesia
| Section1 = {{Chembox Identifiers
| CASNo = 1309-42-8
| PubChem =
| SMILES =
}}
| Section2 = {{Chembox Properties
| Formula = Mg(OH)<sub>2</sub>
| MolarMass = 58.33 g/mol
| Appearance = White solid
| Density = 2.4 g/cm<sup>3</sup>
| MeltingPt = 350 °C, dec.
| BoilingPt =
| Solubility = 1.2 mg/100 mL
}}
| Section3 = {{Chembox Hazards
| ExternalMSDS = [http://ptcl.chem.ox.ac.uk/MSDS/MA/magnesium_hydroxide.html External MSDS]
| MainHazards =
| FlashPt =
| Autoignition = }}
| Section4 = {{Chembox Thermochemistry
| DeltaHf = -925 kJ/mol
| DeltaHc =
| Entropy = 63 J/mol/K
| HeatCapacity = }}
}}
'''Magnesium hydroxide''' is an inorganic compound with the chemical formula Mg(OH)<sub>2</sub>. As a suspension in water, it may be referred to as [[Milk of Magnesia]]. The mineral form of magnesium hydroxide is known as [[brucite]]. It has a pH of 10.2
Magnesium hydroxide is common component of [[antacid]]s and [[laxative]]s. Magnesium hydroxide interferes with the absorption of [[folic acid]] and [[iron]].
Magnesium hydroxide is not very soluble in water, with a [[solubility product|K<sub>sp</sub>]] of 1.5x10<sup>-11</sup>. While the solubility of magnesium hydroxide is low, all of the magnesium hydroxide that does dissolve in the water does dissociate. Since the dissociation of this small amount of dissolved magnesium hydroxide is complete, magnesium hydroxide is considered a strong base.
==Preparation==
Magnesium hydroxide is commercially available, and there is no need to prepare it in the laboratory. It can be precipitated by the [[metathesis reaction]] between [[magnesium]] salts and [[sodium hydroxide|sodium]], [[potassium hydroxide|potassium]], or [[ammonium hydroxide]]:
: Mg<sup>2+</sup> (aq) + 2OH<sup>−</sup> (aq) → Mg(OH)<sub>2</sub> (s)
==Uses==
Magnesium hydroxide, in the form of Milk of Magnesia, is used as an [[antacid]] to neutralize stomach [[acid]], and a [[laxative]]. The [[diarrhea]] caused by magnesium hydroxide carries away much of the body's supply of [[potassium]], and failure to take extra [[potassium]] may lead to [[muscle cramps]].<ref>[http://www.revolutionhealth.com/articles/magnesium-hydroxide/hn-drug_magnesium_hydroxide Magnesium Hydroxide - Revolution Health<!-- Bot generated title -->]</ref> In addition it can be used as a non antiperspirant armpit deodorant.<ref>[http://www.peoplespharmacy.com/archives/pharmacy_qa/milk_of_magnesia_makes_good_antiperspirant.asp Milk of Magnesia Makes Good Antiperspirant<!-- Bot generated title -->]</ref> It is also used in [[bleach]]ing solutions to whiten clothes.<ref>http://www.sandonoakhill.com/documents/Grooming_Tips.pdf</ref>
Magnesium hydroxide is used industrially as a non-hazardous alkali to neutralise acidic wastewaters.{{Fact|date=April 2008}}
Magnesium hydroxide is also used for growing new reefs called [[Seacrete]] or [[Biorock]]
Magnesium hydroxide also has smoke suppressing and fire retarding properties. This is due to the [[Thermal decomposition|endothermic decomposition]] it undergoes at 332°C (630°F) :
:Mg(OH)<sub>2</sub> → [[Magnesium oxide|MgO]] + [[Water (molecule)|H<sub>2</sub>O]]
The heat absorbed by the reaction acts as a retardant by delaying ignition of the associated substance. The water released dilutes any combustible gases and inhibits oxygen from aiding the combustion. Common uses of Magnesium hydroxide as a fire retardant include plastics, roofing, and coatings.
==References==
{{Refimprove|date=May 2008}}
<references/>
{{Urologicals}}
[[Category:Magnesium compounds]]
[[Category:Hydroxides]]
[[Category:Bases]]
{{inorganic-compound-stub}}
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