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Calcium oxalate

Calcium salt of oxalic acid / From Wikipedia, the free encyclopedia

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Calcium oxalate
Calcium oxalate
structure of calcium oxalate dihydrate
Names
IUPAC name
Calcium oxalate
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.008.419 Edit this at Wikidata
EC Number
  • 209-260-1
KEGG
UNII
  • InChI=1S/C2H2O4.Ca/c3-1(4)2(5)6;/h(H,3,4)(H,5,6);/q;+2/p-2 checkY
    Key: QXDMQSPYEZFLGF-UHFFFAOYSA-L checkY
  • InChI=1/C2H2O4.Ca/c3-1(4)2(5)6;/h(H,3,4)(H,5,6);/q;+2/p-2
    Key: QXDMQSPYEZFLGF-NUQVWONBAM
  • C(=O)(C(=O)[O-])[O-].[Ca+2]
Properties
CaC2O4
Molar mass 128.096 g·mol−1
Appearance colourless or white crystals (anhydrous and hydrated forms)
Density 2.20 g/cm3, monohydrate[1]
Melting point 200 °C (392 °F; 473 K) decomposes (monohydrate)
0.61 mg/100 g H2O (20 °C)[2]
2.7 × 10−9 for CaC2O4[3]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Harmful, Irritant
GHS labelling:
GHS07: Exclamation mark GHS06: Toxic
Warning
H302, H312
P280
NFPA 704 (fire diamond)
2
1
0
Related compounds
Other anions
 Calcium carbonate
Calcium acetate
Calcium formate
Other cations
 Sodium oxalate
Beryllium oxalate
Magnesium oxalate
Strontium oxalate
Barium oxalate
Radium oxalate
Iron(II) oxalate
Iron(III) oxalate
Related compounds
 Oxalic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Surface_of_a_kidney_stone.jpg
Scanning electron micrograph of the surface of a kidney stone showing tetragonal crystals of Weddellite (calcium oxalate dihydrate) emerging from the amorphous central part of the stone (the horizontal length of the picture represents 0.5 mm of the figured original)

Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula CaC2O4. It forms hydrates CaC2O4·nH2O, where n varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydrate CaC2O4·H2O occurs naturally as the mineral whewellite, forming envelope-shaped crystals, known in plants as raphides. The two rarer hydrates are dihydrate CaC2O4·2H2O, which occurs naturally as the mineral weddellite, and trihydrate CaC2O4·3H2O, which occurs naturally as the mineral caoxite, are also recognized. Some foods have high quantities of calcium oxalates and can produce sores and numbing on ingestion and may even be fatal. Tribes with diets that depend highly on fruits and vegetables high in calcium oxalate, such as in Micronesia, reduce the level of it by boiling and cooking them.[4][5] They are a constituent in 76% of human kidney stones.[6] Calcium oxalate is also found in beerstone, a scale that forms on containers used in breweries.