Product Information

Magnesium Hydroxide

Magnesium Hydroxide (CAS: 1309-42-8) Supplier in Europe

Magnesium hydroxide is a naturally occurring mineral that possesses several medicinal properties making it a valuable component in healthcare. It is commonly recognized for its ability to neutralize stomach acid, providing relief from indigestion, heartburn, and sour stomach.

This compound appears as a white solid and is only slightly soluble in water, which lends to its effectiveness as an antacid when consumed in appropriate amounts.

Apart from its antacid properties, magnesium hydroxide is also widely used as a laxative. Its mode of action includes drawing water into the intestines, which helps to soften stool and stimulate bowel movements.

This action is particularly helpful in treating occasional constipation, offering a gentle solution for discomfort associated with digestive irregularities.

The importance of magnesium hydroxide in the medical field is underscored by its inclusion in a variety of over-the-counter products, notably those aimed at digestive wellness.

Its utility is enhanced by a profile that is generally well-tolerated by adults and children when used as directed, however, users are advised to be aware of potential side effects and to follow guidelines for safe consumption.

Chemical Properties

The chemical properties of magnesium hydroxide encompass its unique composition, limited solubility in water, and thermal stability, which define its reactivity and applications.

Composition and Structure

Magnesium hydroxide is comprised of a magnesium atom centrally positioned and bonded to two hydroxide groups. Its chemical formula is Mg(OH)_2. This arrangement forms a simple ionic structure, typical of metal hydroxides, with strong ionic bonds between magnesium cations (Mg^2+) and hydroxide anions (OH^−).


Magnesium hydroxide exhibits low water solubility, characterized by a solubility product constant (Ksp) of (5.61 \times 10^{-12}).

When dissolved, it dissociates slightly to release magnesium and hydroxide ions into the solution, but the majority remains as a solid precipitate.

Thermal Stability

It is thermally stable, but upon heating to high temperatures, magnesium hydroxide decomposes into magnesium oxide (MgO) and water. This decomposition is an endothermic reaction, meaning it absorbs heat in the process.


The production of magnesium hydroxide encompasses two main processes: the synthesis of the compound and the subsequent purification to meet industrial standards.


Magnesium hydroxide is synthesized primarily through two methods:

  1. Precipitation: This involves reacting a solution of magnesium salts, like magnesium sulfate (MgSO4), with sodium hydroxide (NaOH). The reaction produces magnesium hydroxide as a precipitate.MgSO4 + 2 NaOH → Mg(OH)2 ↓ + Na2SO4
  2. Extraction from Natural Sources: Magnesium hydroxide can be obtained from brucite, a natural mineral. Another source is seawater or brines where it forms after the addition of lime (calcium hydroxide), leading to the precipitation of magnesium hydroxide.

Purification Methods

Once synthesized or extracted, magnesium hydroxide requires purification, which is carried out through the following steps:

  • Concentration: The raw magnesium hydroxide suspension is concentrated to increase the purity level.
  • Filtration: The concentrated suspension is then subjected to separation of solids from the liquid to remove impurities.
  • Acid-base Reactions: Treatment with acids, such as hydrochloric acid, can be used to convert impurities into soluble salts and then removed from magnesium hydroxide.

Post these purification methods, the result is high-purity magnesium hydroxide suitable for various applications including as an antacid or flame retardant.

Uses and Applications

Magnesium hydroxide is extensively used for its medicinal properties and industrial applications.

Medical Uses

  • Antacid: Magnesium hydroxide is commonly employed as an antacid to neutralize stomach acid and relieve symptoms associated with indigestion and heartburn.
  • Laxative: As a laxative, it works by retaining water in the intestines, which may result in a bowel movement within 30 minutes to 6 hours.

Industrial Uses

  • Fire Retardant: Industrially, magnesium hydroxide is added to plastics and other materials to enhance fire resistance.
  • Wastewater Treatment: It serves as a neutralizing agent in the treatment of wastewater.

Health and Safety

The “Health and Safety” section examines the risks associated with magnesium hydroxide, provides guidelines for its proper handling and storage, and outlines the regulatory context governing its use.


Magnesium hydroxide is generally considered safe when used as directed. However, toxicity can occur if it’s consumed in excessive amounts.

Symptoms of magnesium hydroxide toxicity include:

  • Severe nausea
  • Vomiting
  • Diarrhea

Long-term overuse may lead to more serious health issues, such as electrolyte imbalances and renal impairment.

Handling and Storage

Proper handling and storage of magnesium hydroxide are critical to maintain safety:

  • It should be stored in a cool, dry place away from incompatible substances.
  • Containers of magnesium hydroxide should be sealed to prevent contamination.
  • Use appropriate personal protective equipment (PPE) to prevent skin and eye contact or inhalation.

Regulatory Information

Magnesium hydroxide is regulated by various agencies to ensure its safe use:

  • In the United States, the Food and Drug Administration (FDA) includes magnesium hydroxide in the list of Generally Recognized as Safe (GRAS) substances when used according to prescribed amounts.
  • The maximum tolerable intake level for magnesium for adults is set at 350 mg/day to prevent overdose.
  • It is important to follow all labeling requirements and any occupational safety guidelines for handling, such as those outlined by the Occupational Safety and Health Administration (OSHA).

Physical Properties

Magnesium hydroxide is known for specific physical characteristics that define its applications and handling. This section discusses its appearance, density, and melting point, which are critical to understanding this compound’s physical behavior.


Magnesium hydroxide typically appears as a white, crystalline solid. Its fine powder form is commonly recognized and used in various commercial products.


The density of magnesium hydroxide is about 2.34 grams per cubic centimeter, which influences its usage in scenarios where weight is a concern.

Melting Point

Magnesium hydroxide has a melting point of approximately 350 degrees Celsius. However, it often decomposes into magnesium oxide (MgO) and water (H2O) before reaching this temperature.

Environmental Impact

Magnesium hydroxide plays a crucial role in environmental applications, and its impact is evident in biodegradability and interactions with water.


Magnesium hydroxide is a naturally occurring compound that does not degrade but instead persists in the environment. It is non-toxic and stable, which means it poses minimal risk from a biodegradability standpoint.

Water Interaction

In water treatment processes, magnesium hydroxide is highly efficient due to its large specific area which facilitates active reactions with pollutants. It acts by neutralizing acids and adsorbing heavy metals, thereby improving water quality without degrading itself, which confirms its role in sustainable environmental management practices.

Frequently Asked Questions

This section addresses some of the common inquiries surrounding magnesium hydroxide, a compound widely used for its medicinal properties.

What are the common uses of magnesium hydroxide in medicine?

Magnesium hydroxide is primarily used to treat occasional constipation and, due to its alkaline properties, it is also an ingredient in antacid formulas to relieve heartburn and indigestion.

What is the chemical formula of magnesium hydroxide?

The chemical formula of magnesium hydroxide is Mg(OH)₂.

Can magnesium hydroxide have adverse effects on the skin?

In general, magnesium hydroxide is not known to adversely affect the skin. However, if used inappropriately, it may cause irritation or other undesired reactions.

How is magnesium hydroxide administered in tablet form?

When administered in tablet form, magnesium hydroxide is typically taken orally with a glass of water. It’s crucial to follow the dosing instructions provided on the package or by a healthcare professional.

What are the potential health benefits associated with magnesium hydroxide?

Aside from its laxative effect, magnesium hydroxide can help to neutralize stomach acid and is therefore beneficial for treating indigestion and heartburn.

How does magnesium hydroxide help with constipation?

Magnesium hydroxide acts as an osmotic laxative. It draws water into the intestines, which helps to soften stool and stimulates bowel movements. This usually happens within 30 minutes to 6 hours after intake.