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| Magnesium carbonate | |
|---|---|
| General | |
| Other names | Magnesite dihydrate: Barringtonite trihydrate: Nesequehonite pentahydrate: Lansfordite |
| Molecular formula | MgCO3 |
| Molar mass | 84.32 g/mol |
| Appearance | white solid |
| CAS number | * |
| Properties | |
| Density and phase | 2.958 g/cm3, solid |
| Solubility in water | 10.6 mg/100 ml |
| Melting point | 662 °C decomp. |
| Structure | |
| Coordination geometry | ? |
| Crystal structure | Trigonal |
| Thermodynamic data | |
| Standard enthalpy of | formation]] ΔfH°solid
-1111.69 kJ/mol |
| Standard molar entropy S°solid | 65.84 J.K−1.mol−1 |
| Safety data | |
| EU classification | not listed |
| Flash point | non flammable |
| RTECS number | OM2470000 |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other cations | Calcium carbonate Strontium carbonate Barium carbonate |
| Related compounds | Artinite Hydromagnesite Dypingite |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Chemical infobox | |
Magnesium carbonate, MgCO3, is a white solid that occurs in nature as a mineral. Several hydrated and basic forms of magnesium carbonate also exist as minerals. In addition, MgCO3 has a variety of applications.
Properties
The most common magnesium carbonate forms are the anhydrous salt called magnesite (MgCO3) and the di, tri, and pentahydrates known as barringtonite (MgCO3·2H2O), nesquehonite (MgCO3·3H2O), and lansfordite (MgCO3·5H2O), respectively. Some basic forms such as artinite(MgCO3·Mg(OH)2·3H2O), hydromagnestite (4MgCO3·Mg(OH)2·4H2O), and dypingite (4MgCO3· Mg(OH)2·5H2O) also occur as minerals. Magnesite consists of white trigonal crystals. The anhydrous salt is practically insoluble in water, acetone, and ammonia. All forms of magnesium carbonate dissolve in acids. Magnesium carbonate crystallizes in the calcite structure wherein Mg2+ is surrounded by six oxygen atoms. The dihydrate has a triclinic structure, while the trihydrate has a monoclinic strucure. The pentahydrate is a white crystalline solid with monoclinic crystals.
Reactions
Although magnesium carbonate is ordinarily obtained by mining the mineral magnesite, the trihydrate salt, MgCO3·3H2O, can be prepared by mixing solutions of magnesium and carbonate ions under an atmosphere of carbon dioxide. Magnesium carbonate can also be synthesized by exposing a magnesium hydroxide slurry to carbon dioxide under pressure (3.5 to 5 atm) below 50 °C, which gives soluble magnesium bicarbonate:
- Mg(OH)2 + 2CO2 → Mg(HCO3)2
- Mg(OH)2 + 2CO2 → Mg(HCO3)2
Following the filtration of the solution, the filtrate is dried under vacuum to produce magnesium carbonate as a hydrated salt:
- Mg2+ + 2HCO3- → MgCO3 + CO2 + H2O
- Mg2+ + 2HCO3- → MgCO3 + CO2 + H2O
When dissolved with acid, magnesium carbonate decomposes with release of carbon dioxide:
- MgCO3 + HCl → MgCl2 + CO2 + H2O
- MgCO3 + H2SO4 → MgSO4 + CO2 + H2O
- MgCO3 + HCl → MgCl2 + CO2 + H2O
At high temperatures, MgCO3 can be decomposes to magnesium oxide and carbon dioxide, this process is called calcining:
- MgCO3 → MgO + CO2
- MgCO3 → MgO + CO2
Uses
Magnesite and dolomite minerals are used to produce magnesium metal and basic refractory bricks. MgCO3 is also used in flooring, fireproofing, fire extinguishing compositions, cosmetics, dusting powder, and toothepaste. Other applications are as filler material, smoke suppressant in plastics, a reinforcing agent in neoprene rubber, a drying agent, and color retention in floods. In addition, high purity magnesium carbonate is used as antacid and as an additive in table salt to keep it free flowing.
Magnesium carbonate, most often referred to as 'chalk', is used as a drying agent for hands in rock climbing and weight lifting.
References
External links
Magnesium compounds | Carbonates
Uhličitan hořečnatý | Magnesiumcarbonat | Magnesiumcarbonat | Węglan magnezu | Magnezit | Магнезијум карбонат
"Magnesium carbonate"