Chemical Properties
White or almost white powder.
Uses
Used in Pharmaceutical units as a Magnesium Salt, Heat Insulator and Refractor, Antacid. Also used in Cosmetics, inks, glass, drying agent, color retention agent and etc.
General Description
White, yellowish, grayish-white or brown crystalline solid or crystalline powder. Density: 3-3.1 g cm-3. An important ore for magnesium. Used in the manufacture of materials capable of withstanding very high temperatures. Sometimes used to produce carbon dioxide.
Reactivity Profile
MAGNESITE has generally low chemical reactivity. Non-flammable and non-combustible. Reacts with acids and acidic salts to generate gaseous carbon dioxide with effervescence (bubbling). The reaction may be rapid and exothermic with concentrated solutions of acids. The efferversence can create foaming. Incompatible with formaldehyde.
Hazard
A nuisance particulate.
Physical properties
This material is available in a very light, fluffy grade which absorbs well. The before-mentioned qualities are why magnesium carbonate is often used to absorb perfume before incorporation into face powders.
Production Methods
Depending upon the manufacturing process used, the composition
of the magnesium carbonate obtained may vary from normal
hydrated magnesium carbonate to basic hydrated magnesium
carbonate.
Light magnesium carbonate may be manufactured by saturating
an aqueous suspension of dolomite, CaMg(CO3)2, with carbon
dioxide under pressure. On increase of the temperature, calcium
carbonate precipitates almost entirely. The filtered solution is then
heated to boiling; the magnesium bicarbonate in the solution loses precipitates.
Heavy magnesium carbonate may be manufactured by mixing a
hot concentrated solution of magnesium chloride or magnesium
sulfate with a solution of sodium carbonate. The heavy magnesium
carbonate may be either precipitated to produce a granular material
or spray-dried. Varying the temperature of the reaction solutions
produces heavy magnesium carbonate with differing physical
properties: e.g. material with a higher specific surface area is
produced at a lower reaction temperature. Low processing
temperature provided the largest surface area, which produced
optimum granules or spray-dried powder.If dilute magnesium
chloride or magnesium sulfate solutions are used for the reaction, a
less dense material is produced.
Magnesium carbonates in varying states of hydration are also
found as minerals in nature.
Health Hazard
Magnesite is considered to be a
nuisance dust.
Flammability and Explosibility
Nonflammable
Agricultural Uses
Hydromagnesite is a magnesium ore which occurs as a carbonate. Magnesium carbonate occurs in a mixed salt dolomite (CaCO3.MgCO3) and as basic magnesium carbonate in two minerals, namely, artinite (MgCO3.Mg(OH)2.3H2O) and hydromagnesite (3MgCO3.Mg(OH)2.3H2O).
Agricultural Uses
Magnesium carbonate is a white compound occurring in
anhydrous and hydrated forms. It is used as a fertilizer
and also for making magnesium oxide.
The anhydrous material is found naturally in mineral
magnesite. There is also a trihydrate, MgC03·3H2O
(rhombic) that occurs naturally as nesquehonite, and a
pentahydrate, MgCO3.5H2O (monoclinic) that occurs as
lansfordite.
Magnesium carbonate also occurs in a mixed salt
dolomite (CaCO3·MgCO3) and as basic magnesium
carbonate in two minerals, namely, artinite
[MgCO3·Mg(OH)2.3H2O] and hydromagnesite
[3MgC03·Mg(OH)2.3H2O]. Heating magnesium oxide
in a stream of carbon dioxide leads to the formation of the
anhydrous salt.
Above 350°C, the reverse reaction predominates and
the carbonate decomposes to give back MgO.
Agricultural Uses
Nesquehonite is the natural form of magnesium
carbonate trihydrate (MgCO3.3H2O).
Pharmaceutical Applications
As an excipient, magnesium carbonate is mainly used as a directly
compressible tablet diluent in concentrations up to 45% w/w.
Heavy magnesium carbonate produces tablets with high crushing
strength, low friability, and good disintegration properties.
However, magnesium carbonate can have varying effects on
dissolution and stability.Magnesium
carbonate has been incorporated in microsphere formulations for
the purpose of stabilizing encapsulated proteins. It has also been
coencapsulated in poly(lactide-co-glycolide) microsphere formulations
to neutralize acidity and enhance the immunogenicity of a
contraceptive peptide vaccine. Magnesium carbonate is also used
to absorb liquids, such as flavors, in tableting processes.
Magnesium carbonate is additionally used as a food additive and
therapeutically as an antacid.
Safety
Magnesium carbonate is used as an excipient in oral solid-dosage
pharmaceutical formulations and is generally regarded as an
essentially nontoxic and nonirritant material. However, the use of
magnesium salts, such as magnesium carbonate, is contraindicated
in patients with renal impairment. In certain studies, magnesium
carbonate has been shown to be an effective phosphate binder in
short-term use for patients with chronic kidney disease, but the
effects of long-term use require further study.The probable oral
lethal dose in humans has been estimated at 0.5–5.0g/kg bodyweight.
On contact with gastric acid, magnesium carbonate reacts in the
stomach to form soluble magnesium chloride and carbon dioxide.
Magnesium carbonate should therefore not be used as an antacid by
those individuals whose stomachs cannot tolerate the evolution of
carbon dioxide. Some magnesium is absorbed but is usually
excreted in the urine. As with other magnesium salts, magnesium
carbonate has a laxative effect and may cause diarrhea.
Therapeutically, the usual dose of magnesium carbonate as an
antacid is 250–500mg, and 2.0–5.0g as a laxative.
storage
Magnesium carbonate is stable in dry air and on exposure to light.
The bulk material should be stored in a well-closed container in a
cool, dry place.
Incompatibilities
Incompatible with phenobarbital sodium,diazepam solution at
a pH≥5, some binary powder mixtures, lansoprazole,
and formaldehyde. Acids will dissolve magnesium carbonate,
with the liberation of carbon dioxide. Slight alkalinity is imparted to
water. Magnesium carbonate was also found to increase the
dissolution of acetazolamide formulations at a pH of 1.12; however,
dissolution was retarded at a pH of 7.4.
Regulatory Status
GRAS listed. Accepted as a food additive in Europe. Included in the
FDA Inactive Ingredients Database (oral capsules and tablets).
Included in nonparenteral medicines licensed in the UK.
