Magnesium hydroxide - Mg(OH)2

What is Magnesium hydroxide?

Magnesium Hydroxide is an inorganic compound which has a low solubility in water. It is also called Milk of magnesia or magnesium(2+) hydroxide. Naturally, it occurs in the form of a mineral brucite and is a common compound found in antacids. The chemical formula of Magnesium hydroxide is Mg(OH)2.

History of Magnesium hydroxide

In the year 1872, Charles Henry Phillips was the first to use the term milk of magnesia. It was used for the suspension of magnesium hydroxide Mg(OH)2 formulated at about 8%w/v.

Properties of Magnesium hydroxide – Mg(OH)2

Magnesium hydroxide


Molecular Weight of Magnesium hydroxide

58.3197 g/mol

Density of of Magnesium hydroxide

2.3446 g/cm3

Melting Point of Magnesium hydroxide

350 °C

Monoisotopic Mass

57.991 g/mol

Structure of Magnesium hydroxide (Mg(OH)2)

Structure of Magnesium hydroxide

Uses of Magnesium hydroxide (Mg(OH)2)

  • Magnesium hydroxide is an excellent thermal conductor and poor electrical conductor.
  • It is used in suspensions as a laxative or antacid.
  • Used as a food additive.
  • It is widely used in waste-water treatment.
  • Used as a fire retardant.
  • It is used in wet plate collodion process as a photographic fixer.
  • It is used in gold mining.
  • Used in warehouses.

Preparation of Magnesium hydroxide

When a solution of magnesium salts is combined with alkaline water it instigates precipitation of solid magnesium hydroxide. The reaction is as follows:

Mg2+ + 2 OH → Mg(OH)2

Commercially it is produced by treating lime and sea water. Approximately one ton of magnesium hydroxide is obtained from 600 m3 of seawater. Calcium hydroxide is more soluble in magnesium hydroxide therefore Mg(OH)2 precipitates as a solid. The reaction is as follows:

MgO + H2O → Mg(OH)2

Effects on Health

Flushing or drowsiness are side effects of magnesium hydroxide. Consuming this compound on a daily basis can result in electrolyte disturbances. Excessive use can result in nausea, diarrhea, and abdominal cramping. Symptoms include watery diarrhea or gastrointestinal irritation may occur. Poisoning causes hypermagnesemia which includes symptoms such as: vomiting, hypotension, confusion, muscle weakness, cardiac arrhythmias, Cardiac arrest, nausea, flushing, thirst, drowsiness, loss of tendon reflexes, respiratory depression, and coma.

Learn more about the physical and chemical properties of Magnesium hydroxide (Mg(OH)2) from the experts at BYJU’S.

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