Magnesium oxide: properties, production, application
Magnesium oxide is often called still burntmagnesia or simply magnesium oxide. This substance is a light and fine crystalline white powder. In nature, magnesium oxide is found in the form of a periclase mineral. In the food industry, this substance is known as a food additive under the code E530.
Properties of magnesium oxide
The chemical formula of this substance is MgO. This compound is practically odorless, it dissolves well in ammonia and acid, in water its solubility at 30 ° C is only 0,0086 g / 100 ml, and in alcohol it does not dissolve at all. The molar mass of MgO is 40.3044 g / mol. At 20 ° C, its density is 3.58 g / cm³, the boiling point is 3600 ° C, and the melting point is 2852 ° C. The fine-grained magnesium oxide is chemically quite active. It is able to absorb carbon dioxide to form the corresponding carbonate:
- MgO + CO2= MgCO3;
although slowly, but still reacts with water, forming an insoluble weak base:
- H2O + MgO = Mg (OH)2;
reacts with acids:
- 2HCl + MgO = MgCl2+ H2O
The calcined magnesium oxide loses its chemical activity. It should also be added that this powder is hygroscopic.
Preparation of magnesium oxide
In industry, this compound is mainlyare obtained by roasting. Minerals such as dolomite (MgCO3.CaCO3) or magnesite (MgCO3) are used as raw materials. In addition, burnt magnesia is produced by calcination of bischofite (MgCl2x 6H2O) in water vapor, calcination of Mg (OH) 2 and other temperature-unstable compounds Mg. In laboratory conditions MgO can be obtained by the interaction of its constituent components:
- 2Mg + O2= 2MgO;
or by thermal decomposition of some salts or hydroxide:
- MgCO3= MgO + CO2.
Depending on the method of obtaining magnesium oxideit is common to distinguish two main types of this compound: light and heavy magnesia. The first is a colorless powder that readily reacts with dilute acids quite easily, resulting in the formation of Mg salts. The second consists of large crystals of natural or artificial periclase and is water resistant and more inert.
Application of magnesium oxide
In industry, this compound is used forproduction of cements, refractories, as a filler in the production of rubber and for the cleaning of petroleum products. Ultra-light magnesium oxide is used as a very fine abrasive, which cleans the surface. In particular, it is used in the electronics industry. In addition, burnt magnesia is widely used in medicine. Here, MgO is used when the level of acidity of gastric juice that occurs due to an excess of hydrochloric acid is violated. Magnesium oxide is also used to neutralize the active substances accidentally trapped in the stomach. In the food industry, MgO is used as a food additive (code E530), which prevents clumping and caking. Burnt magnesia is also used in gymnastics. Here, this powder is applied to the hands of athletes in order to make contact with the gymnastic apparatus more reliable. We also add that magnesium oxide is an absolute reflector. The reflection coefficient of this substance in the extended spectral band is equal to unity and therefore it can be used as a standard for white color.