Magnesium hydroxide

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Magnesium hydroxide

Magnesium hydroxide is an inorganic compound with the chemical formula Mg(OH)₂. As a suspension in water, it may be referred to as Milk of Magnesia

Milk of Magnesia

Milk of Magnesia is an aqueous suspension of magnesium hydroxide, magnesium2 in water. Milk of Magnesia is a salt osmosis laxative. The name derives from the suspension's milky white appearance and the magnesium in its composition....
. The solid mineral form of magnesium hydroxide is known as brucite

Brucite

Brucite is the mineral form of magnesium hydroxide, with the chemical formula Magnesium2. It is pearly white or pale green in colour, translucent, with perfect cleavage, and tabular crystals or massive....
.

Magnesium hydroxide is common component of antacid

Antacid

An antacid is any substance, generally a Base or basic salt, which counteracts gastric acid. In other words, antacids are stomach acid neutralization ....
s and laxative

Laxative

Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the Colon for rectum and bowel examinations, and may be supplemented by enemas in that circumstance....
s. Magnesium hydroxide interferes with the absorption of folic acid

Folic acid

Folic acid and Folate are forms of the water-soluble B vitamins. Vitamin B9 is essential to numerous bodily functions ranging from nucleotide synthesis to the remethylation of homocysteine....
and iron

Iron

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Encyclopedia

Magnesium hydroxide is an inorganic compound with the chemical formula Mg(OH)₂. As a suspension in water, it may be referred to as Milk of Magnesia

Milk of Magnesia

Brucite

Antacid

An antacid is any substance, generally a Base or basic salt, which counteracts gastric acid. In other words, antacids are stomach acid neutralization ....
s and laxative

Laxative

Folic acid

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
.

Magnesium hydroxide is not very soluble in water, with a K_sp of 1.5x10^-11. 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

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, atomic weight 24.3050 and common oxidation number +2.Magnesium, an alkaline earth metal, is the ninth most abundance of the chemical elements in the universe by mass....
salts and sodium

Sodium hydroxide

Sodium hydroxide , also known as lye, caustic soda and sodium hydrate, is a caustic metallic Base . Sodium hydroxide forms a strong alkaline solution when dissolved in a solvent such as water, however, only the hydroxide ion is basic....
, potassium

Potassium hydroxide

Potassium hydroxide is the inorganic compound with the formula potassiumhydroxide. Along with sodium hydroxide, this colourless solid is a prototypical "strong base"....
, or ammonium hydroxide

Ammonium hydroxide

Ammonium hydroxide, also known as ammonia water, ammonical liquor, ammonia liquor, aqua ammonia, or aqueous ammonia, is a solution of ammonia in water....
:

Mg²⁺ (aq) + 2OH^- (aq) ? Mg(OH)₂ (s)

Uses

Magnesium hydroxide has a variety of uses.

Magnesium hydroxide, in the form of Milk of Magnesia, is used as an antacid

Antacid

An antacid is any substance, generally a Base or basic salt, which counteracts gastric acid. In other words, antacids are stomach acid neutralization ....
to neutralize stomach acid

Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
, and a laxative

Laxative

Diarrhea

In medicine, diarrhea, also spelled diarrhoea , is characterized by frequent loose or liquid bowel movements. The spelling of "diarrhea" is an appropriation of the Greek "diarrhoia" meaning "a flowing through." ....
caused by magnesium hydroxide carries away much of the body's supply of potassium

Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
, and failure to take extra potassium

Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
may lead to muscle cramps. In addition it can be used as a non antiperspirant underarm (armpit) deodorant. It is also used in bleach

Bleach

A bleach is a chemical that removes colors or whitens, often via oxidation. Common chemical bleaches include household "chlorine bleach", a solution of approximately 3?6% sodium hypochlorite , and "oxygen bleach", which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate, sodium percarbonate, sodium persulfat...
ing solutions to whiten clothes.

Magnesium hydroxide is used industrially as a non-hazardous alkali to neutralise acidic wastewaters.

Magnesium hydroxide takes part in the Biorock

Biorock

The Biorock Process for mineral accretion is used to grow structures and marine ecosystems, specifically for mariculture of corals, oysters, clams, lobsters and fish, in salt water....
method of building artificial reef

Artificial reef

An artificial reef is a man-made, underwater structure, typically built for the purpose of promoting Marine biology#Reefs in areas of generally featureless bottom....
s.

Magnesium hydroxide also has smoke suppressing and fire retarding properties. This is due to the endothermic decomposition

Thermal decomposition

Thermal decomposition, also called thermolysis, is defined as a chemical reaction when a chemical substance breaks up into at least two chemical substances when heated....
it undergoes at 332°C (630°F) :

Mg(OH)₂ ? MgO

Magnesium oxide

Magnesium oxide, or magnesia, is a white solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of ....
+ H₂O

Water (molecule)

File:Blue-water-pool.jpgWater is the most abundant molecule on Earth's surface, constituting about 70% of the Earth's surface in liquid, solid, and gaseous states....

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.