Chemical formula:

Also known as milk of magnesia, magnesium hydrate, and brucite (mineral form).

Magnesium hydroxide is a naturally occurring chemical which has a number of medicinal and industrial uses. Industrially, it is an environmentally friendly and relatively safe-to-handle alkali (most alkalis are very caustic) used to control pH levels in wastewater treatment (having a pH of 9.5-10.5 as an aqueous solution). It can also be found in a number of consumer products as a flame retardant, fuel-oil additive, drying agent in food, clarifier in sugar refining, and an additive in toothpaste.

Medically it is most often used as an over the counter laxative or an antacid. As an antacid, its medical and industrial purposes are similar. As a laxative, it works by drawing water into the bowel from surrounding body tissue, softening and moisturizing waste to help it pass through the system.

Magnesium hydroxide should be stored in a tightly closed container away from direct light, heat, and moisture (not in a bathroom). Typical adult dosages as an antacid are 5-15ml or 650mg. As a laxitive: 2.4-4.8g or 30-60ml daily. Do not use any laxative for extended periods of time, as laxative dependancy may develop. To overdose requires very large amounts and is unlikely to be serious except in the most extreme cases. Check for possible drug interactions or conflicts with existing health problems before using.

In its pure form, magnesium hydroxide is a white solid or powder with a melting point of 350°C (662°F, 623K) and a density of 2.4x103kg/m3. As a medicine is it usually mixed with other ingredients to create a pill or a liquid suspension (shake well before using, it doesn't dissolve well).

A materials safety data sheet for magnesium hydroxide is available at:


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