Magnesium hydroxide
[CAS# 1309-42-8]

Identification

• Classification: API >> Digestive system medication >> Acid and gastric mucosal protective drugs
• Name: Magnesium hydroxide
• Molecular Formula: Mg(OH)₂
• Molecular Weight: 58.32
• CAS Registry Number: 1309-42-8
• EC Number: 215-170-3
• SMILES: [OH-].[OH-].[Mg+2]

Properties

• Density: 2.36 g/mL
• Melting point: 350 ºC
• Water solubility: 0.9 mg/100 mL (18 ºC)

Safety Data

• Hazard Symbols: GHS05;GHS07 Danger
• Hazard Statements: H302-H315-H317-H318-H319-H332-H335
• Precautionary Statements: P261-P264-P264+P265-P270-P271-P272-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P305+P354+P338-P317-P319-P321-P330-P332+P317-P333+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H302
Serious eye damage	Eye Dam.	1	H318
Skin sensitization	Skin Sens.	1	H317
Specific target organ toxicity - repeated exposure	STOT RE	1	H372

Discovory and Applicatios

Magnesium hydroxide, with the chemical formula Mg(OH)₂, is a white solid inorganic compound. It is slightly soluble in water and is often referred to as "milk of magnesia" when suspended. This compound is of great importance in various fields, including medicine, environmental science, and industrial applications.

Magnesium hydroxide was first isolated in the early 19th century. It occurs naturally in the form of the mineral brucite, named after the American mineralogist Archibald Bruce, who described it in 1824. Brucite can be found in metamorphic rocks, often associated with serpentine.

Magnesium hydroxide can be prepared by the reaction of a magnesium salt, such as magnesium chloride, with an alkaline substance, such as sodium hydroxide. This method is often used for laboratory preparation. The compound is characterized by its low solubility in water, which makes it a weak base. After dissolution, it partially dissociates to form magnesium ions and hydroxide ions.

One of the most famous applications of magnesium hydroxide is in the medical field as an antacid and laxative. It is sold in the form of "milk of magnesia" and neutralizes stomach acid by reacting with hydrochloric acid in the stomach to form magnesium chloride and water. This reaction relieves indigestion, heartburn, and acid reflux. As a laxative, magnesium hydroxide draws water into the intestines, promoting bowel movements and relieving constipation.

Magnesium hydroxide plays a vital role in environmental management, especially in water treatment. It is used to neutralize acidic wastewater, stabilize heavy metals, and remove impurities through precipitation. Its buffering capacity helps maintain optimal pH levels in various industrial processes. In addition, it is used as a flocculant, which helps to aggregate and remove suspended particles from water.

In the industrial sector, magnesium hydroxide is used as a flame retardant. When exposed to high temperatures, it breaks down into magnesium oxide and water, absorbing heat and releasing water vapor, which helps to extinguish fires. This property makes it valuable in the production of flame-retardant materials such as plastics, textiles, and coatings.

Another important application is in the manufacture of magnesium-based refractory materials, which can withstand high temperatures. Magnesium hydroxide is also used in the pulp and paper industry to produce chlorine-free bleach, as well as in the production of ceramics, rubber, and fertilizers.

Magnesium hydroxide is generally considered safe for use in food, pharmaceutical, and industrial applications. However, it should be handled with care to avoid inhaling dust, which can cause respiratory irritation. Ingestion of large amounts can lead to hypermagnesemia, a condition characterized by elevated levels of magnesium in the blood that can have adverse health effects.