The term “Magnesium Dioxide” (\(\text{MgO}_2\)) often leads to confusion because it is generally unstable or refers specifically to magnesium peroxide. The widely recognized, stable, and commercially used compound is actually Magnesium Oxide (\(\text{MgO}\)), also known by its mineral name, periclase. This white, odorless solid is the primary magnesium compound referenced in medicine, environmental science, and materials engineering.
Chemical Identity and Structure of Magnesium Oxide
Magnesium Oxide (\(\text{MgO}\)) is an inorganic compound characterized by a simple 1:1 chemical formula, consisting of one magnesium ion (\(\text{Mg}^{2+}\)) and one oxide ion (\(\text{O}^{2-}\)). These ions are held together by a strong ionic bond, forming a stable crystal lattice structure similar to common table salt. This structure gives Magnesium Oxide an extremely high melting point of approximately 2,852 °C. The compound is classified as an alkaline earth metal oxide and appears as a fine, white powder. Although its solubility in water is very low, it slowly reacts with water to form magnesium hydroxide.
Magnesium oxide is primarily manufactured through calcination, which involves heating natural minerals like magnesium carbonate (magnesite) or magnesium hydroxide (brucite). This thermal decomposition removes carbon dioxide or water, leaving behind the purified Magnesium Oxide powder. The specific temperature used during calcination determines the final product’s density and reactivity, leading to different grades like light-burned or dead-burned magnesia.
Applications in Dietary Supplements and Digestive Health
Magnesium Oxide is a common component in both dietary supplements and over-the-counter digestive aids, serving two distinct purposes. As a supplement, it is used to address low magnesium levels. While it contains a high percentage of elemental magnesium—up to 60%—it is classified as an inorganic compound with low bioavailability, meaning only a small fraction is absorbed by the body. Its poor absorption rate makes it less effective for raising systemic magnesium levels compared to more bioavailable forms like magnesium glycinate or citrate.
This characteristic of low absorption is precisely what makes it effective for digestive uses, such as an antacid and a saline laxative. As an antacid, Magnesium Oxide is alkaline and reacts with the hydrochloric acid (\(\text{HCl}\)) in the stomach to produce magnesium chloride and water. This neutralization reaction quickly reduces stomach acidity, providing relief from heartburn and indigestion.
Magnesium Oxide’s function as a saline laxative is also a direct result of its low absorption. The unabsorbed magnesium ions remain in the intestinal lumen, increasing the osmotic pressure of the contents. This osmotic effect draws water into the intestines, which softens the stool and stimulates muscle contractions (peristalsis) to promote a bowel movement.
Industrial and Environmental Uses
Beyond its applications in health, Magnesium Oxide is a foundational material in heavy industry and environmental management, largely due to its remarkable heat resistance and chemical stability. Its extremely high melting point makes it the material of choice for refractory applications, which involve materials that are physically and chemically stable at high temperatures. Magnesium Oxide is used to manufacture refractory bricks and linings for furnaces, kilns, and steelmaking vessels, protecting the equipment from intense heat and corrosive molten materials.
In the construction sector, Magnesium Oxide is used in the production of magnesia cement, sometimes called Sorel cement, which is valued for its high strength and fire resistance. It is also incorporated into structural boards and insulation to create fireproof and moisture-resistant building materials. The compound’s alkaline nature also makes it useful in environmental applications, where it acts as a neutralizing agent. This includes treating acidic wastewater, cleaning up contaminated soil, and removing sulfur dioxide from power plant emissions in a process called flue gas desulfurization.