'Calcium oxalate' is a chemical compound that forms needle-shaped crystals. Large quantities are found in the
poisonous plant
dumb cane. It is also found in
rhubarb leaves, various species of ''
Oxalis'', and
agaves, and (in lower amounts) in
spinach. 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.
Even a small dose of calcium oxalate is enough to cause intense sensations of burning in the mouth and throat, swelling, and choking. In larger 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.
Nonsoluble calcium oxalate crystals are found in plant stems, roots, and leaves. The stalk of the ''
Dieffenbachia'' produces the most severe reactions. These needle-like crystals produce pain and edema when they contact lips, tongue, oral mucosa, conjunctiva, or skin.
Oedema primarily is due to direct trauma from the needle-like crystals and, to a lesser extent, by other plant toxins (e.g.
bradykinins, enzymes).
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.
[2] 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.
References
1. Weast, R.C. 1974. ''Handbook of Chemistry and Physics'', 54th edition. Chemical Rubber Publishing Company.
2. Removing Beerstone
See also
★
Oxalic acid
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