Magnesium oxalate

Magnesium oxalate is an inorganic compound comprising a magnesium cation with a 2+ charge bonded to an oxalate anion. It has the chemical formula MgC2O4. Magnesium oxalate is a white solid that comes in two forms: an anhydrous form and a dihydrate form where two water molecules are complexed with the structure. Both forms are practically insoluble in water and are insoluble in organic solutions.

Magnesium oxalate
Names
IUPAC name
magnesium oxalate
Systematic IUPAC name
magnesium oxalate
Other names
  • magnesium ethanedioate
  • ethanedioic acid, magnesium salt (1:1)
  • (Dihydrate)
  • magnesium oxalate-2-hydrate
  • magnesium oxalate dihydrate
  • oxalic acid magnesium salt dihydrate
[1]
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.008.121
EC Number
UNII
UN number 2811 [4]
Properties
  • MgC2O4
  • MgC2O4•2H2O (Dihydrate)
Molar mass
  • 112.324 g/mol
  • 148.354 g/mol (Dihydrate)
[2]
Appearance white solid [2]
Density 2.45 g/cm3[5]
Melting point between 420 and 620 °C (788 and 1,148 °F; 693 and 893 K)
150 °C (302 °F; 423 K) (dihydrate) both decompose[7]
Boiling point Not Applicable
0.038g/100g H2O (anhydrous and dihydrate)[2]
Solubility insoluble in organics
Vapor pressure 2.51×10−6 mmHg[3]
Thermochemistry
-1269.0 kJ mol−1[2]
Hazards
Main hazards Irritant
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
1
0
Flash point Not Applicable
Not Applicable
Related compounds
Related compounds
 Magnesium Oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Natural occurrence

Magnesium oxalate has been found naturally near Mill of Johnston, which is located close to Insch in northeast Scotland. This naturally occurring magnesium oxalate is called glushinskite and occurs at the lichen/rock interface on serpentinite as a creamy white layer mixed in with the hyphae of the lichen fungus. A scanning electron micrograph of samples taken showed that the crystals had a pyramidal structure with both curved and striated faces. The size of these crystals ranged from 2 to 5 μm.[8]

Synthesis and reactions

Magnesium oxalate can by synthesized by combining a magnesium salt or ion with an oxalate.

Mg2+ + C2O42− → MgC2O4

A specific example of a synthesis would be mixing Mg(NO3)2 and KOH and then adding that solution to dimethyl oxalate, (COOCH3)2.[9]

When heated, magnesium oxalate will decompose. First, the dihydrate will decompose at 150 °C into the anhydrous form.

MgC2O4•2H2O → MgC2O4 + 2 H2O

With additional heating the anhydrous form will decompose further into magnesium oxide and carbon oxides between 420 °C and 620 °C. First, carbon monoxide and magnesium carbonate form. The carbon monoxide then oxidizes to carbon dioxide, and the magnesium carbonate decomposes further to magnesium oxide and carbon dioxide.[7]

MgC2O4 → MgCO3 + CO
CO + 1/2 O2 → CO2
MgCO3 → MgO + CO2

Magnesium oxalate dihydrate has also been used in the synthesis of nano sized particles of magnesium oxide, which have larger surface are to volume ratio than conventionally synthesized particles and are optimal for various applications, such as in catalysis. By using a sol-gel synthesis, which involves combining a magnesium salt, in this case magnesium oxalate, with a gelating agent, nano sized particles of magnesium oxide can be produced.[10]

Health and safety

Magnesium oxalate is a skin and eye irritant. If inhaled, it will irritate the lungs and mucous membranes. Magnesium oxalate has no known chronic effects nor any carcinogenic effects. Magnesium oxalate is non-flammable and stable, but in fire conditions it will give off toxic fumes. According to OSHA, magnesium oxalate is considered to be hazardous.[4][11]

References
  1. "Oxalates-Compound Summary". Retrieved 16 November 2012.
  2. CRC Handbook of Chemistry and Physics (93 ed.). 2012–2013.
  3. "Magnesium Oxalate Chemical Formula, Chemical CAS 547-66-0". Retrieved 16 November 2012.
  4. "Magnesium Oxalate". Archived from the original on 20 February 2014. Retrieved 16 November 2012.
  5. "Magnesium Oxalate". Retrieved 16 November 2012.
  6. "Magnesium Oxalate". Retrieved 16 November 2012.
  7. Gadala, Ahmed (1984). "Kinetics of the Decomposition of Hydrated Oxalates of Calcium and Magnesium in Air". Thermochimica Acta. 74: 255–272. doi:10.1016/0040-6031(84)80027-1.
  8. Wilson, M; D. Jones; D.J. Russell (1980). "Glushinskite, a naturally occurring magnesium oxalate". Mineralogical Magazine. 43: 837–840. doi:10.1180/minmag.1980.043.331.02.
  9. Masuda, Yoshio (1987). "Kinetics of the Thermal Dehydration of Magnesium Oxalate Dihydrate in a Flowing Atmosphere of Dry Nitrogen". J. Phys. Chem. 91: 6543–6547. doi:10.1021/j100310a024.
  10. Mastuli, Mohd; Roshidah Rusdi; Annie Mahat; Norazira Saat; Norlida Kamarulzaman (2012). "Sol-Gel Synthesis of Highly Stable Nano Sized MgO from Magnesium Oxalate Dihydrate". Advanced Materials Research. 545: 137–142. doi:10.4028/www.scientific.net/amr.545.137.
  11. "Material Safety Data Sheet Magnesium Oxalate". Retrieved 16 November 2012.

See also
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