Calcium oxalate

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Calcium oxalate
IUPAC name	calcium ethanedioate
Identifiers
CAS number	25454-23-3,(anhydrous) 5794-28-5 (monohydrate)
PubChem	16212978
Properties
Molecular formula	CaC2O4
Molar mass	128.097 g/mol, anhydrous 146.112 g/mol, monohydrate
Appearance	white solid
Density	2.2 g/cm³, anhydrous 2.2 g/cm³, monohydrate
Melting point	200°C, decomposes (monohydrate)
Solubility in water	0.00067 g/100 ml (20 °C)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Calcium oxalate is a chemical compound that forms needle-shaped crystals. Its chemical formula is CaC₂O₄ or Ca(COO)₂.

Occurrence

Large quantities of calcium oxalate are found in the poisonous plant dumb cane (Dieffenbachia). It is also found in rhubarb (especially in the leaves), various species of Oxalis, Araceae, taro, kiwifruit, and agaves, and (in smaller amounts) spinach. Insoluble calcium oxalate crystals are found in plant stems, roots, and leaves.

Urine microscopy showing calcium oxalate crystals in the urine

Calcium oxalate also forms a major component of beerstone, a brownish precipitate that tends to accumulate within vats, barrels and other containers used in the brewing of beer.^[1] Beerstone is composed of calcium and magnesium salts and various organic compounds left over from the brewing process; it promotes the growth of unwanted microorganisms that can adversely affect or even ruin the flavor of a batch of beer.

Calcium oxalate crystals in the urine are the most common constituent of human kidney stones, and calcium oxalate crystal formation is also one of the toxic effects of ethylene glycol poisoning.

Natural occurrence is connected with three minerals: whewellite (monohydrate, known from some coal beds), weddellite (dihydrate) and a very rare trihydrate called caoxite.

Effects of ingestion

Even a small dose of calcium oxalate is enough to cause intense sensations of burning in the mouth and throat, swelling, and choking. In greater doses, however, calcium oxalate causes severe digestive upset, breathing difficulties and—if enough is consumed—convulsions, coma, and death. Recovery from severe oxalate poisoning is possible, but permanent liver and kidney damage may have occurred.

The stalk of the Dieffenbachia produces the most severe reactions. These needle-like crystals produce pain and swelling when they contact lips, tongue, oral mucosa, conjunctiva, or skin. Edema primarily is due to direct trauma from the needle-like crystals and, to a lesser extent, by other plant toxins (e.g., bradykinins, enzymes).

Treatment

Immediately seek advice from a physician. Depending on the plant ingested, mild (Elephant Ear Colocasia esculenta) to more severe (Jack in the Pulpit Arisaema) can cause compromised airways. One bite on the Arisaema seed pod will result in immediate swelling and burning. It will take over 12 hours for the swelling to subside. Medication administered at the ER may include Benadryl, epinephrine, or Pepcid, all intravenously. Although this most likely will be a localized reaction, it will be treated by the ER as an anaphylactic reaction.

References

1. ^ Johnson, Dana (23 March 1998). "Removing Beerstone". Modern Brewery Age. Birko Corporation R&D. http://birkocorp.com/brewing/beerstone.asp. Retrieved 2007-08-06. 

See also

• Oxalic acid