magnesium carbonate

The most common magnesium carbonate forms are the anhydrous salt called magnesite ({{chem2|MgCO3}}), and the di, tri, and pentahydrates known as barringtonite ({{chem2|MgCO3*2H2O}}), nesquehonite ({{chem2|MgCO3*3H2O}}), and lansfordite ({{chem2|MgCO3*5H2O}}), respectively. Some basic forms such as artinite ({{chem2|Mg2CO3(OH)2*3H2O}}), hydromagnesite ({{chem2|Mg5(CO3)4(OH)2*4H2O}}), and dypingite ({{chem2|Mg5(CO3)4(OH)2*5H2O}}) also occur as minerals. All of those minerals are colourless or white.

Magnesite consists of colourless or white trigonal crystals. The anhydrous salt is practically insoluble in water, acetone, and ammonia. All forms of magnesium carbonate react with acids. Magnesite crystallizes in the calcite structure wherein magnesium is surrounded by six oxygen atoms.{{ cite journal | title = The equation of state and high-pressure behavior of magnesite | first1 = Nancy L. | last1 = Ross | journal = Am. Mineral. | year = 1997 | volume = 82 | issue = 7–8 | pages = 682–688 | doi = 10.2138/am-1997-7-805 | bibcode = 1997AmMin..82..682R | s2cid = 43668770 }}

The dihydrate 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 hydromagnesite and dypingite, respectively.{{cite journal|doi=10.1016/S0304-386X(01)00197-9|title=Preparation of a magnesium hydroxy carbonate from magnesium hydroxide | year=2001 | last1=Botha | first1=A. | last2=Strydom | first2=C.A. | journal=Hydrometallurgy | volume=62 | issue=3 | pages=175|bibcode=2001HydMe..62..175B }} The "light" form is precipitated from magnesium solutions using alkali carbonate at "normal temperatures" while the "heavy" may be produced from boiling concentrated solutions followed by precipitation to dryness, washing of the precipitate, and drying at 100 C. {{cite book|title=General and inorganic chemistry, 2nd ed. | year=1951 | author= J.R. Partington}}

Magnesium carbonate is ordinarily obtained by mining the mineral magnesite. Seventy percent of the world's supply is mined and prepared in China.{{cite web |title=The Hidden Environmental Cost of Climbing Chalk |url=https://www.climbing.com/gear/the-hidden-environmental-cost-of-climbing-chalk/ |last=Allf |first=Bradley |date=2018-05-21 |website=Climbing Magazine |publisher=Cruz Bay Publishing |access-date=2018-05-22 |quote=In fact, China produces 70 percent of the world’s magnesite. Most of that production—both mining and processing—is concentrated in a small corner of Liaoning, a hilly industrial province in northeast China between Beijing and North Korea.}}

Magnesium carbonate can be prepared in laboratory by reaction between any soluble magnesium salt and sodium bicarbonate:

:{{awrap|MgCl₂(aq) + 2 NaHCO₃(aq) →}} {{awrap|MgCO₃(s) + 2 NaCl(aq) + H₂O(l) + CO₂(g)}}

If magnesium chloride (or sulfate) is treated with aqueous sodium carbonate, a precipitate of basic magnesium carbonate – a hydrated complex of magnesium carbonate and magnesium hydroxide – rather than magnesium carbonate itself is formed:

:{{awrap|5 MgCl₂(aq) + 5 Na₂CO₃(aq) + 5 H₂O(l) →}} {{awrap|Mg₄(CO₃)₃(OH)₂·3H₂O(s) + Mg(HCO₃)₂(aq) + 10 NaCl(aq)}}

High purity industrial routes include a path through magnesium bicarbonate, which can be formed by combining a slurry of magnesium hydroxide and carbon dioxide at high pressure and moderate temperature.{{Ullmann | title = Magnesium Compounds | author1 = Margarete Seeger | author2 = Walter Otto | author3 = Wilhelm Flick | author4 = Friedrich Bickelhaupt | author5 = Otto S. Akkerman | doi = 10.1002/14356007.a15_595.pub2}} The bicarbonate is then vacuum dried, causing it to lose carbon dioxide and a molecule of water:

:{{chem2|Mg(OH)2 + 2 CO2 → Mg(HCO3)2}}

:{{chem2|Mg(HCO3)2 → MgCO3 + CO2 + H2O}}

Like many common group 2 metal carbonates, magnesium carbonate reacts with aqueous acids to release carbon dioxide and water:

:{{chem2|MgCO3 + 2 HCl → MgCl2 + CO2 + H2O}}

:{{chem2|MgCO3 + H2SO4 → MgSO4 + CO2 + H2O}}

At high temperatures MgCO₃ decomposes to magnesium oxide and carbon dioxide. This process is important in the production of magnesium oxide. This process is called calcining:

:{{chem2|MgCO3 → MgO + CO2}} (ΔH = +118 kJ/mol)

The decomposition temperature is given as 350 °C (662 °F).{{cite web|url=http://avogadro.chem.iastate.edu/MSDS/MgCO3_anhydrous.htm|title=IAState MSDS}}{{cite book |author= Weast, Robert C.|title=CRC Handbook of Chemistry and Physics |url= https://archive.org/details/crchandbookofche00clev|url-access= registration|edition=59th |year=1978 |publisher=CRC Press |location=West Palm Beach, FL |id={{Listed Invalid ISBN|0-8493-0549-8}}|page=B-133 |display-authors=etal}}

However, calcination to the oxide is generally not considered complete below 900 °C due to interfering readsorption of liberated carbon dioxide.

The hydrates of the salts lose water at different temperatures during decomposition.{{cite web|url=http://core.kmi.open.ac.uk/download/pdf/10883918.pdf|title=Conventional and Controlled Rate Thermal analysis of nesquehonite Mg(HCO₃)(OH)·2(H₂O)}} For example, in the trihydrate {{chem2|MgCO3*3H2O}}, which molecular formula may be written as {{chem2|Mg(HCO3)(OH)*2H2O}}, the dehydration steps occur at 157 °C and 179 °C as follows:

:{{chem2|Mg(HCO3)(OH)*2(H2O) → Mg(HCO3)(OH)*(H2O) + H2O}} at 157 °C

:{{chem2|Mg(HCO3)(OH)*(H2O) → Mg(HCO3)(OH) + H2O}} at 179 °C

The primary use of magnesium carbonate is the production of magnesium oxide by calcining. Magnesite and dolomite minerals are used to produce refractory bricks. {{chem2|MgCO3}} 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 neoprene rubber, a drying agent, and colour retention in foods.

Because of its low solubility in water and hygroscopic properties, {{chem2|MgCO3}} was first added to table salt ({{chem2|NaCl}}) in 1911 to make it flow more freely. The Morton Salt company adopted the slogan "When it rains it pours", highlighting that its salt, which contained {{chem2|MgCO3}}, would not stick together in humid weather.{{cite web |title=Her Debut - Morton Salt |url=http://www.mortonsalt.com/heritage-era/her-first-appearance/ |access-date = 2017-12-27 }}

File:Hojer jan 0429.JPG blows surplus chalk from his hand. Boulder World Cup 2015]]

Powdered magnesium carbonate, known as climbing chalk or gym chalk is also used as a drying agent on athletes' hands in rock climbing, gymnastics, powerlifting, weightlifting and other sports in which a firm grip is necessary. A variant is liquid chalk.

As a food additive, magnesium carbonate is known as E504. Its only known side effect is that it may work as a laxative in high concentrations.{{cite web|title=Food-Info.net : E-numbers : E504: Magnesium carbonates|url=http://www.food-info.net/uk/e/e504.htm}} 080419 food-info.net

Magnesium carbonate is used in taxidermy for whitening skulls. It can be mixed with hydrogen peroxide to create a paste, which is spread on the skull to give it a white finish.

Magnesium carbonate is used as a matte white coating for projection screens.{{Cite book|title = Certified Technology Specialist-Installation|last = Noronha|first = Shonan|publisher = McGraw Hill Education|year = 2015|isbn = 978-0071835657|pages = 256}}

It is a laxative to loosen the bowels.

In addition, high purity magnesium carbonate is used as an antacid and as an additive in table salt to keep it free flowing. Magnesium carbonate can do this because it does not dissolve in water, only in acid, where it will effervesce (bubble).{{Cite web|url=https://sciencing.com/magnesium-carbonate-5626269.html|title=What Is Magnesium Carbonate?|website=Sciencing|date=24 April 2017 |language=en|access-date=2018-04-15}}

Magnesium carbonate is non-toxic and non-flammable.

• British Pharmacopoeia{{cite web

|last=British Pharmacopoeia Commission Secretariat

|title=Index, BP 2009

|year=2009

|url=http://www.pharmacopoeia.co.uk/pdf/2009_index.pdf

|access-date=31 January 2010

|url-status=dead

|archive-url=https://web.archive.org/web/20090411071437/http://www.pharmacopoeia.co.uk/pdf/2009_index.pdf

|archive-date=11 April 2009

}}

• Japanese Pharmacopoeia{{cite web

|title=Japanese Pharmacopoeia, Fifteenth Edition

|year=2006

|url=http://jpdb.nihs.go.jp/jp15e/JP15.pdf

|access-date=31 January 2010

|url-status=dead

|archive-url=https://web.archive.org/web/20110722105441/http://jpdb.nihs.go.jp/jp15e/JP15.pdf

|archive-date=22 July 2011

}}

• Calcium acetate/magnesium carbonate
• Upsalite, a reported amorphous form of magnesium carbonate

{{reflist}}

{{commons category|Magnesium carbonate}}

• [http://www.inchem.org/documents/icsc/icsc/eics0969.htm International Chemical Safety Card 0969]
• [http://webbook.nist.gov/chemistry/ NIST Standard Reference Database]

{{Carbonates}}

{{Magnesium compounds}}

{{Antacids}}

{{Laxatives}}

{{Authority control}}

{{DEFAULTSORT:Magnesium Carbonate}}

Category:Magnesium compounds

Category:Carbonates

Category:Antacids