Magnesium Oxide

Products

Magnesium oxide is found in medicines and in dietary supplements, for example in the form of capsules.

Structure and properties

Magnesium oxide (MgO, Mr = 40.3 g/mol) is the metal oxide of magnesium. It consists of magnesium ions (Mg2+) and oxide ions (O2-). The pharmacopoeia differentiates depending on the filling volume achieved:

  • Light magnesium oxide: Magnesii oxidum leve
  • Heavy magnesium oxide: Magnesii oxidum ponderosum

Magnesium oxide exists as a fine, white and almost odorless powder and is practically insoluble in water. It dissolves in dilute acids with at most weak gas evolution. Aqueous solutions are basic. Magnesium oxide has a very high melting point of over 2800°C. The water-soluble magnesium chloride is formed with gastric acid:

  • MgO (magnesium oxide) + 2 HCl (hydrochloric acid) MgCl2 (magnesium chloride) + H2O (water)

With water, magnesium hydroxide is formed, which is also contained in various medicines:

  • MgO (magnesium oxide) + H2O (water) Mg(OH)2 (magnesium hydroxide)

Magnesium oxide is formed, for example, during the combustion of elemental magnesium. The reaction requires activation energy:

  • 2 Mg (elemental magnesium) + O2 (oxygen) 2 MgO (magnesium oxide).

See also under redox reactions.

Effects

Magnesium oxide has acid neutralizing and laxative properties. Inorganic magnesium salts are considered less bioavailable than organic ones. However, this statement is controversial; see under the article Organic Magnesium. According to the literature, magnesium oxide is absorbed at about 22%.

Areas of application