Magnesium oxalate

Magnesium Oxalate
IUPAC name magnesium oxalate
Systematic 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
CAS number	[2] 547-66-0[2],  6150-88-5 (Dihydrate) [2]
PubChem	[1] 68353 [1]
ChemSpider	[1].html 61648 [1]
EC number	[3] 208-932-1[3]
UN number	2811 [4]
Jmol-3D images	{{#if:C(=O)(C(=O)[O-])[O-].[Mg+2]|Image 1
SMILES C(=O)(C(=O)[O-])[O-].[Mg+2]
InChI InChI= 1S/C2H2O4.Mg/c3-1(4)2(5)6;/h(H,3,4)(H,5,6);/q;+2/p-2 1S/C2H2O4.Mg.2H2O/c3-1(4)2(5)6;;;/h(H,3,4)(H,5,6);;2*1H2/q;+2;;/p-2 (Dihydrate) [5] [6]
Properties
Molecular formula	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 420-620°C 150 °C (Dihydrate) (both decompose[7])
Boiling point	Not Applicable
Solubility in water	0.038g/100g H2O (anhydrous and dihydrate) [2]
Solubility	insoluble in organics
Vapor pressure	2.51*10-6 mm Hg [3]
Thermochemistry
Std enthalpy of formation ΔfHo298	-1269.0 kJ mol-1 [2]
Hazards
Main hazards	Irritant
NFPA 704	0 1 0
Flash point	Not Applicable
Autoignition temperature	Not Applicable
Related compounds
Related compounds	Magnesium Oxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

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.

Natural occurrence

Some oxalates can be found in nature and the most known naturally occuring oxalates are whewellite and weddellite, which are calcium oxalates. Magnesium oxalate has been found naturally near Mill of Johnston which is located close to Insch in northeast Scotland. The naturally occuring magnesium oxalate is called glushinskite. The magnesium oxalate was found at the lichen and rock interface on serpentinite. It was found in a creamy white layer which was mixed in with 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.

Mg⁺²+C₂O₄^-2 → MgC₂O₄

A specific example of a synthesis would be mixing Mg(NO₃)₂ and KOH and then adding that solution to (COOCH₃)₂.^[9] Magnesium oxalate when heated will decompose. First, the dihydrate will decompose at 150 °C into the anhydrous form.

MgC₂O₄•2H₂O → MgC₂O₄ + 2H₂O

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 + 1/2O₂ → CO₂

MgCO₃ → MgO + CO₂

Magnesium oxalate dihydrate has also been used in the synthesis of nano sized magnesium oxide. Magnesium oxide is important because it is used as a catalyst, refractory materials, adsorbents, superconductors, and ferroelectric materials. Nano sized particles of magnesium oxide are optimal for some of these uses because of the larger surface area to volume ratio as compared with larger particles. Most common syntheses of magnesium oxide produce fairly large particles, however, the sol-gel synthesis using magnesium oxalate produces highly stable nano sized particles of magnesium oxide. The sol-gel synthesis involves combining a magnesium salt, or in this case magnesium oxalate, with a gelating agent. This process effectively produces nano sized particles of magnesium oxide.^[10]

Health and safety

Magnesium oxalate is a skin and eye irritant. If inhaled, it will irritate the lungs and mucus membrane. Magnesium oxalate has no known chronic effects nor any carcinogenic effects. If magnesium oxalate does come in contact with skin or eyes, flush with water for at least 15 minutes and call a physician if irritation occurs. If inhaled, go to fresh air and call a physician. If swallowed, call a physician immediately. If a spill occurs wash with water and make sure that no dust is released into the air. Dispose of the wash water accordingly. Whenever working with magnesium oxalate, safety goggles, boots, and a lab apron should be worn. If there is dust in the air, a respirator should be worn also. 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

See also

• oxalic acid