Difference between revisions of "Magnesium hydroxide"

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| PIN =
 
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| SystematicName = Magnesium hydroxide
 
| SystematicName = Magnesium hydroxide
−
| OtherNames = Brucite<br>Milk of magnesia
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| OtherNames = Brucite<br>Magensium dihydroxide<br>Milk of magnesia
 
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| ImageFile = Magnesium hydroxide.jpg
 
| ImageFile = Magnesium hydroxide.jpg
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| OtherFunction =  
 
| OtherFunction =  
 
| OtherFunction_label =  
 
| OtherFunction_label =  
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| OtherCompounds = [[Calcium hydroxide]]
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| OtherCompounds = [[Calcium hydroxide]]<br>[[Strontium hydroxide]]<br>[[Barium hydroxide]]
 
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Magnesium hydroxide reacts with acids, forming the magnesium salt of said acid and water.
 
Magnesium hydroxide reacts with acids, forming the magnesium salt of said acid and water.
  
−
:Mg(OH)<sup>2</sup> + 2 HCl → MgCl<sub>2</sub> + 2 H<sub>2</sub>O
+
: Mg(OH)<sub>2</sub> + 2 HCl → MgCl<sub>2</sub> + 2 H<sub>2</sub>O
  
 
Magnesium hydroxide decomposes when heated at high temperatures.
 
Magnesium hydroxide decomposes when heated at high temperatures.
  
−
:Mg(OH)<sup>2</sup> → MgO + H<sub>2</sub>O
+
: Mg(OH)<sub>2</sub> → MgO + H<sub>2</sub>O
  
 
===Physical===
 
===Physical===
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Magnesium hydroxide is composed of magnesium ions and hydroxide ions and it will precipitate whenever the two are present together - ie, combine in a metathesis reaction. The reaction is as follows:
 
Magnesium hydroxide is composed of magnesium ions and hydroxide ions and it will precipitate whenever the two are present together - ie, combine in a metathesis reaction. The reaction is as follows:
  
−
:Mg<sup>2+</sup> (aq) + 2 OH<sup>−</sup> (aq) → Mg(OH)<sub>2</sub> (s)
+
: Mg<sup>2+</sup> (aq) + 2 OH<sup>−</sup> (aq) → Mg(OH)<sub>2</sub> (s)
  
−
It can be easily prepared by mixing [[sodium hydroxide]] (or [[potassium hydroxide]]) with [[magnesium sulfate]]. Note that it is extremely hard to filter milk of magnesia: magnesium hydroxide forms a slime-like gel that clogs most filters, and even strong vacuum does not help much.
+
It can be easily prepared by mixing [[sodium hydroxide]] or [[potassium hydroxide]] with [[magnesium sulfate]].
 +
 
 +
: 2 NaOH + MgSO<sub>4</sub> → Mg(OH)<sub>2</sub> + Na<sub>2</sub>SO<sub>4</sub>
 +
: 2 KOH + MgSO<sub>4</sub> → Mg(OH)<sub>2</sub> + K<sub>2</sub>SO<sub>4</sub>
 +
 
 +
Note that it is extremely hard to filter milk of magnesia: magnesium hydroxide forms a slime-like gel that clogs most filters, and even strong vacuum does not help much.
 +
 
 +
Very pure magnesium hydroxide can be obtained by reacting [[magnesium]] metal with water, which works much better with hot water than cold water.
 +
 
 +
: Mg + 2 H<sub>2</sub>O → Mg(OH)<sub>2</sub> + H<sub>2</sub>
 +
 
 +
Magnesium metal does not react with alkali hydroxides, thus the hydroxide cannot be produced this way.
  
 
==Availability==
 
==Availability==
−
Magnesium hydroxide can be bought from companies like http://magnesiaspecialties.com
+
Magnesium hydroxide is sold by chemical suppliers and can be bought cheaply online.
 +
 
 +
Some companies, like [http://magnesiaspecialties.com Martin Marietta Magnesia Specialties], deal in high purity products.
  
 
It's also available in some drugstores as an antacid.
 
It's also available in some drugstores as an antacid.
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*Make magnesium salts
 
*Make magnesium salts
 
*Make magnesium oxide
 
*Make magnesium oxide
 +
*Antiacid
  
 
==Handling==
 
==Handling==
 
===Safety===
 
===Safety===
−
Magnesium hydroxide has low to none toxicity, though if too much is ingested it may cause digestion issues and hypermagnesemia. It's non-flamable and non-explosive.
+
Magnesium hydroxide has low to no toxicity, though if too much is ingested it may cause digestion issues and hypermagnesemia. It's non-flammable and non-explosive.
  
 
===Storage===
 
===Storage===

Latest revision as of 17:13, 13 March 2024

Magnesium hydroxide
Magnesium hydroxide.jpg
Names
IUPAC name
Magnesium hydroxide
Systematic IUPAC name
Magnesium hydroxide
Other names
Brucite
Magensium dihydroxide
Milk of magnesia
Identifiers
Jmol-3D images Image
Properties
Mg(OH)2
Molar mass 58.3197 g/mol
Appearance White solid
Odor Odorless
Density 2.3446 g/cm3
Melting point 350 °C (662 °F; 623 K) decomposes
Boiling point Decomposes
0.00064 g/100 ml (25 °C)
0.004 g/100 ml (100 °C)
Solubility Reacts with acids
Vapor pressure ~ 0 mmHg
Thermochemistry
64 J·mol−1·K−1
−924.7 kJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Related compounds
Related compounds
 Calcium hydroxide
Strontium hydroxide
Barium hydroxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Magnesium hydroxide is inorganic compound with formula Mg(OH)2. It is often known as milk of magnesia, because of its milk-like appearance as a suspension. The solid mineral form of magnesium hydroxide is known as brucite. Suspensions of magnesium hydroxide in water are used as an antacid to neutralize stomach acid, and as 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. Magnesium hydroxide is also used as an antiperspirant underarm deodorant.

Properties

Chemical

Magnesium hydroxide reacts with acids, forming the magnesium salt of said acid and water.

Mg(OH)2 + 2 HCl → MgCl2 + 2 H2O

Magnesium hydroxide decomposes when heated at high temperatures.

Mg(OH)2 → MgO + H2O

Physical

Magnesium hydroxide is an inorganic compound with the chemical formula of hydrated Mg(OH)2. While magnesium hydroxide has a low solubility in water, with a Ksp of 1.5×10−11, it is large enough that it will partially dissolve to produce ions in the solution, forming the suspension. A relatively high concentration of magnesium or hydroxide ions would be required to revert the suspension to the solid precipitate by reversing the equilibrium.

In this suspended form, magnesium hydroxide is a common component of antacids and laxatives; it interferes with the absorption of folic acid and iron. The antacid properties come from the hydroxide ions which are responsible for neutralizing the acid.

Preparation

Magnesium hydroxide is composed of magnesium ions and hydroxide ions and it will precipitate whenever the two are present together - ie, combine in a metathesis reaction. The reaction is as follows:

Mg2+ (aq) + 2 OH− (aq) → Mg(OH)2 (s)

It can be easily prepared by mixing sodium hydroxide or potassium hydroxide with magnesium sulfate.

2 NaOH + MgSO4 → Mg(OH)2 + Na2SO4
2 KOH + MgSO4 → Mg(OH)2 + K2SO4

Note that it is extremely hard to filter milk of magnesia: magnesium hydroxide forms a slime-like gel that clogs most filters, and even strong vacuum does not help much.

Very pure magnesium hydroxide can be obtained by reacting magnesium metal with water, which works much better with hot water than cold water.

Mg + 2 H2O → Mg(OH)2 + H2

Magnesium metal does not react with alkali hydroxides, thus the hydroxide cannot be produced this way.

Availability

Magnesium hydroxide is sold by chemical suppliers and can be bought cheaply online.

Some companies, like Martin Marietta Magnesia Specialties, deal in high purity products.

It's also available in some drugstores as an antacid.

Projects

  • Make magnesium salts
  • Make magnesium oxide
  • Antiacid

Handling

Safety

Magnesium hydroxide has low to no toxicity, though if too much is ingested it may cause digestion issues and hypermagnesemia. It's non-flammable and non-explosive.

Storage

Magnesium hydroxide should be stored in closed bottles, away from open air to prevent it from absorbing carbon dioxide or sulfur dioxide from air.

Disposal

Magnesium hydroxide can be safely thrown out with your normal garbage or dumped in plant-less soil.

References

Relevant Sciencemadness threads

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