magnesium hydroxide

chemical compound

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Last updated

June 30, 2026

Quick Summary

Magnesium hydroxide is a crystalline compound with the chemical formula Mg(OH)₂. It is a slightly alkaline substance primarily recognized for its use as a laxative and gastric antacid.1

This compound is produced in large quantities from seawater by adding calcium hydroxide. Magnesium hydroxide is a key raw material in the production of magnesium metal and also serves as a fire-retardant additive. When suspended in water, it forms "milk of magnesia," a well-known remedy for indigestion and constipation.2

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magnesium processing
Electrolysis
An insoluble magnesium hydroxide precipitates to the bottom of a settling tank, whence it is pumped as a slurry, filtered, converted to magnesium chloride by reaction with hydrochloric acid, and dried in a series of evaporation steps to 25 percent water content. Final dehydration takes place during…
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An insoluble magnesium hydroxide precipitates to the bottom of a settling tank, whence it is pumped as a slurry, filtered, converted to magnesium chloride by reaction with hydrochloric acid, and dried in a series of evaporation steps to 25 percent water content. Final dehydration takes place during…
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magnesium
Principal compounds
Magnesium hydroxide, Mg(OH)₂, is a white powder produced in large quantities from seawater by the addition of milk of lime (calcium hydroxide). It is the primary raw material in the production of magnesium metal and has been used as a fire-retardant additive. In water it…
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Magnesium hydroxide, Mg(OH)₂, is a white powder produced in large quantities from seawater by the addition of milk of lime (calcium hydroxide). It is the primary raw material in the production of magnesium metal and has been used as a fire-retardant additive. In water it…
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laxative
…are magnesium sulfate (Epsom salts), magnesium hydroxide (milk of magnesia), sodium sulfate (Glauber salt), and potassium sodium tartrate (Rochelle salt or Seidlitz powder).
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…are magnesium sulfate (Epsom salts), magnesium hydroxide (milk of magnesia), sodium sulfate (Glauber salt), and potassium sodium tartrate (Rochelle salt or Seidlitz powder).
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