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. The mineral form of magnesium hydroxide is known as brucite.

Magnesium hydroxide is common component of antacids and laxatives. Magnesium hydroxide interferes with the absorption of folic acid and iron. The diarrhea caused by magnesium hydroxide carries away much of the body's supply of potassium, and failure to take extra potassium will lead to muscle cramps.

Magnesium hydroxide is very poorly soluble in water, with a Ksp of 1.5x10-11. As it does not completely dissociate and therefore is a weak base.

Preparation
Magnesium hydroxide is commercially available, and there is no need to prepare it in the laboratory. However, it can be precipitated by the metathesis reaction between magnesium salts and Sodium, Potassium, or Ammonium hydroxide:


 * Mg2+ (aq) + 2OH− (aq) → Mg(OH)2 ↓

Uses
Magnesium hydroxide is used as an antacid to neutralize stomach acid. In industries, it is used as a non-hazardous alkali to neutralise acidic wastewaters. In addition, magnesium hydroxide, better known as its common name Milk of Magnesia can be used as a non antiperspirant armpit deodorant. It is also used in bleaching solutions to whiten clothes.