Magnesium carbonate, MgCO
3, is a white
solidMatter is generally found in three different forms: solid, liquid, and gas . The solid state of matter is characterized by a distinct structural rigidity and resistance to deformation . Most solids have high values both of Young's modulus and of the shear modulus of elasticity...
that occurs in nature as a
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
. Several hydrated and
basicIn chemistry, a base is most commonly thought of as an aqueous substance that can accept hydrogen ions. Bases are also the oxides or hydroxides of metals. A soluble base is also often referred to as an alkali if hydroxide ions are involved. This refers to the Brønsted-Lowry theory of acids and bases...
forms of magnesium carbonate also exist as
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
s. In addition, MgCO
3 has a variety of uses.
Forms
The most common magnesium carbonate forms are the
anhydrousAs a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another.-Solvents:...
salt called
magnesiteMagnesite is magnesium carbonate, MgCO
3. Iron substitutes for magnesium with a complete solution series with siderite, FeCO
3. Calcium, manganese, cobalt, and nickel may also occur in small amounts...
(MgCO
3) and the di, tri, and pentahydrates known as
barringtonite (MgCO
3·2H
2O),
nesquehonite (MgCO
3·3H
2O), and
lansfordite (MgCO
3·5H
2O), respectively. Some basic forms such as
artinite (MgCO
3·Mg(OH)
2·3H
2O),
hydromagnestite (4MgCO
3·Mg(OH)
2·4H
2O), and
dypingite (4MgCO
3· Mg(OH)
2·5H
2O) also occur as minerals. Magnesite consists of white trigonal crystals. The
anhydrousAs a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another.-Solvents:...
salt is practically insoluble in
waterWater is an ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life.In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71%...
,
acetoneAcetone is the organic compound with the formula OC2. This colorless, mobile, flammable liquid is the simplest example of the ketones. Owing to the fact that acetone is miscible with water it serves as an important solvent in its own right, typically as the solvent of choice for...
, and
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
. All forms of magnesium carbonate react in acids. Magnesium carbonate crystallizes in the
calciteCalcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 470°C, and vaterite is even less stable....
structure where in
Mg2+Magnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the earth's crust by mass, although ninth in the Universe as a whole...
is surrounded by six
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
atoms. The dihydrate one has a triclinic structure, while the trihydrate has a monoclinic structure.
References to 'light' and 'heavy' magnesium carbonates actually refer to the magnesium hydroxy carbonates
hydromagnesiteHydromagnesite is a hydrated magnesium carbonate mineral with the formula: Mg542.4H2O....
and dypingite (respectively).
Reactions
Although magnesium carbonate is ordinarily obtained by mining the mineral magnesite, the trihydrate salt, MgCO
3·3H
2O, can be prepared by mixing solutions of
magnesiumMagnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the earth's crust by mass, although ninth in the Universe as a whole...
and
carbonateIn chemistry, a carbonate is a salt or ester of carbonic acid, characterized by the presence of the carbonate ion, or a carbonate functional group O=C2....
ions under an atmosphere of
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
. Magnesium carbonate can also be synthesized by exposing a
magnesium hydroxideMagnesium hydroxide is an inorganic compound with the chemical formula Mg2. As a suspension in water, it is often called milk of magnesia because of its milk-like appearance. The solid mineral form of magnesium hydroxide is known as brucite.Magnesium hydroxide is common component of...
slurry to
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
under
pressurePressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
(3.5 to 5 atm) below 50 °C, which gives soluble magnesium bicarbonate:
-
- Mg(OH)2 + 2 CO2 → Mg(HCO3)2
Following the filtration of the solution, the filtrate is dried under vacuum to produce magnesium carbonate as a hydrated salt:
-
- Mg2+ + 2 HCO3- → MgCO3 + CO2 + H2O
When dissolved with
acidAn acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water, i.e. a pH less than 7.0...
, magnesium carbonate decomposes with release of
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
:
-
- MgCO3 + 2 HCl → MgCl2 + CO2 + H2O
- MgCO3 + H2SO4 → MgSO4 + CO2 + H2O
At high temperatures (800C-1000C), MgCO
3 decomposes to
magnesium oxideMagnesium oxide, or magnesia, is a white solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of . It is formed by an ionic bond between one magnesium and one oxygen atom. Magnesium oxide is hygroscopic in nature and care must be taken to...
and
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
with reaction
enthalpyIn thermodynamics and molecular chemistry, the enthalpy is a thermodynamic property of a thermodynamic system. It can be used to calculate the heat transfer during a quasistatic process taking place in a closed thermodynamic system under constant pressure...
118 kJ / mole, this process is called calcining:
-
- MgCO3 → MgO + CO2
Uses
Magnesite and
dolomiteDolomite is the name of a sedimentary carbonate rock and a mineral, both composed of calcium magnesium carbonate CaMg
2 found in crystals....
minerals are used to produce
magnesiumMagnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the earth's crust by mass, although ninth in the Universe as a whole...
metal and basic refractory bricks. MgCO
3 is also used in flooring, fireproofing, fire extinguishing compositions, cosmetics, dusting powder, and toothpaste. Other applications are as filler material, smoke suppressant in plastics, a reinforcing agent in
neopreneNeoprene or polychloroprene is a family of synthetic rubbers that are produced by polymerization of chloroprene. It is used in a wide variety of applications, such as in wetsuits, laptop sleeves, orthopedic braces , electrical insulation, liquid and sheet applied elastomeric membranes or...
rubber, a drying agent, a laxative to loosen the bowels, and color retention in foods. In addition, high purity magnesium carbonate is used as
antacidAn antacid is any substance, generally a base or basic salt, which counteracts stomach acidity. In other words, antacids are stomach acid neutralizers.-Action mechanism:...
and as an additive in table salt to keep it free flowing.
Because of its water-insoluble,
hygroscopicHygroscopy is the ability of a substance to attract water molecules from the surrounding environment through either absorption or adsorption.Hygroscopic substances include sugar, honey, glycerol, ethanol, methanol, sulfuric acid, methamphetamine, iodine, many chloride and hydroxide salts, and a...
properties MgCO
3 was first added to salt in 1911 to make the salt flow more freely. The
Morton SaltMorton Salt is a United States company producing salt for food, water conditioning, industrial, agricultural, and road/highway use. Based in Chicago, the business is North America's leading producer and marketer of salt.-History:...
company adopted the slogan "When it rains it pours" in reference to the fact that its MgCO
3-containing salt would not stick together in wet weather.
Magnesium carbonate, most often referred to as 'chalk', is used as a drying agent for hands in
rock climbingRock climbing is a sport in which participants climb up or across natural rock formations or man-made rock walls. The goal is to reach the summit of a formation or the endpoint of a pre-defined route...
,
gymnasticsGymnastics is a sport involving performance of exercises requiring physical strength, flexibility, agility, coordination, balance and grace. Artistic gymnastics is the best known and most popular of the gymnastics sports governed by the Fédération Internationale de Gymnastique...
,
weight liftingWeight training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the force of gravity to oppose the force generated by muscle through concentric or eccentric contraction...
and
powerliftingPowerlifting is a strength sport, consisting of three events: the squat, the bench press, and the deadlift.Powerlifting resembles the sport of olympic weightlifting, as both disciplines involve lifting weights in three attempts. It evolved from a sport known as 'odd lifts' which followed the same 3...
.
Magnesium carbonate is also used in taxidermy for whitening skulls. It can be mixed with hydrogen peroxide to create a paste, which is then spread on the skull to give it a white finish.
Magnesium Carbonate Hydroxide is used as a clay in face masks, it has mild astringent properties and helps to smooth and soften skin. Recommended for use on normal to dry skins.
Food additive
As a food additive magnesium carbonate is known as E504, for which the only known side effect is that it may work as a
laxativeLaxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and bowel examinations, and may be supplemented by enemas in that...
in high concentrations.
External links