 | |
 | |
| Names | |
|---|---|
| Preferred IUPAC name Calcium oxalate | |
| Systematic IUPAC name Calcium ethanedioate | |
| Other names Oxalate of lime | |
| Identifiers | |
| |
3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
|
| ECHA InfoCard | 100.008.419 |
| EC Number |
|
| KEGG | |
| UNII |
|
| |
| |
| 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] | |
Solubility product (Ksp) | 2.7 × 10−9 forCaC2O4[3] |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Harmful, Irritant |
| GHS labelling: | |
 | |
| Warning | |
| H302,H312 | |
| P280 | |
| NFPA 704 (fire diamond) | |
| Safety data sheet (SDS) | External SDS |
| Related compounds | |
Otheranions | Calcium carbonate Calcium acetate Calcium formate |
Othercations | 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 theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Calcium oxalate (in archaic terminology,oxalate of lime) is acalciumsalt ofoxalic acid with the chemical formulaCaC2O4 orCa(COO)2. It forms hydratesCaC2O4·nH2O, wheren varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydrateCaC2O4·H2O occurs naturally as the mineralwhewellite, forming envelope-shaped crystals, known in plants asraphides. The two rarer hydrates are dihydrateCaC2O4·2H2O, which occurs naturally as the mineralweddellite, and trihydrateCaC2O4·3H2O, which occurs naturally as the mineralcaoxite, are also recognized. Some foods have high quantities of calcium oxalates and can produce sores and numbing on ingestion and may even be fatal. Cultural groups with diets that depend highly on fruits and vegetables high in calcium oxalate, such as those inMicronesia, reduce the level of it by boiling and cooking them.[4][5] They are a constituent in 76% of humankidney stones.[6] Calcium oxalate is also found in beerstone, a scale that forms on containers used inbreweries.
Many plants accumulate calcium oxalate as it has been reported in more than 1000 different genera of plants.[7] The calcium oxalate accumulation is linked to the detoxification of calcium (Ca2+) in the plant.[8] Upon decomposition, the calcium oxalate is oxidised by bacteria, fungi, or wildfire to produce the soil nutrientcalcium carbonate.[9]
Thepoisonous plant dumb cane (Dieffenbachia) contains the substance and on ingestion can prevent speech and be suffocating. It is also found insorrel,rhubarb (in large quantities in the leaves),cinnamon,turmeric and in species ofOxalis,Araceae,Arum italicum,taro,kiwifruit, tea leaves,agaves, Virginia creeper (Parthenocissus quinquefolia), andAlocasia and inspinach in varying amounts. Plants of the genusPhilodendron contain enough calcium oxalate that consumption of parts of the plant can result in uncomfortable symptoms. Insoluble calcium oxalate crystals are found in plant stems, roots, and leaves and produced inidioblasts.Vanilla plants exude calcium oxalates upon harvest of the orchid seed pods and may causecontact dermatitis.
Calcium oxalate crystals are commonly found inlichens, where they occur in two mineral forms: weddellite (CaC2O4·(2+x)H2O) and whewellite (CaC2O4·H2O). These crystals can form both on the surface of the lichen as a powdery coating calledpruina and within the internal structures of the lichenthallus. The type and distribution of these crystals often correlates with environmental conditions: weddellite typically forms in dry environments and can serve as a water source for the lichen, while whewellite is more common in moist habitats. In addition to water regulation, calcium oxalate crystals in lichens serve several protective functions, including shielding against excessive sunlight and potentially helping to neutralize pollutants such assulfur dioxide. The formation of these crystals is linked to the lichen's ability to dissolve calcium from rockysubstrates through the production of oxalic acid, with the amount of calcium oxalate often correlating with the calcium content of the substrate on which the lichen grows.[10]
Calcium oxalate, as‘beerstone’, is a brownish precipitate that tends to accumulate within vats, barrels, and other containers used in the brewing of beer. If not removed in a cleaning process, beerstone will leave an unsanitary surface that can harbour microorganisms.[11] 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 a batch of beer.
Calcium oxalate crystals in the urine are the most common constituent of humankidney stones, and calcium oxalate crystal formation is also one of the toxic effects ofethylene glycol poisoning.
Calcium oxalate is a combination of calcium ions and the conjugate base ofoxalic acid, the oxalate anion. Its aqueous solutions are slightly basic because of the basicity of the oxalate ion. The basicity of calcium oxalate is weaker than that ofsodium oxalate, due to its lower solubility in water. Solid calcium oxalate hydrate has been characterized byX-ray crystallography. It is acoordination polymer featuring planar oxalate anions linked to calcium, which also has waterligands.[1]
Calcium oxalate can produce sores and numbing on ingestion and may even be fatal.[citation needed]
The monohydrate and dihydrate can be distinguished by the shape of the respective crystals.
_-_kalsiyum_oksalat_kristalleri_(idrar)_-_01.png)
_-_kalsiyum_oksalat_kristalleri_(idrar)_-_02.png)
![Histopathology of calcium oxalate crystals in a benign breast cyst, H&E stain. In the breast, they can be seen on mammography and are usually benign, but can be associated with lobular carcinoma in situ.[13]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aHistopathology_of_a_breast_cyst_with_calcium_oxalate_crystals%2c_annotated.jpg)
About 76% of kidney stones are partially or entirely of the calcium oxalate type.[6] They form when urine is persistently saturated with calcium and oxalate. Between 1% and 15% of people globally are affected by kidney stones at some point.[14][15] In 2015, they caused about 16,000 deaths worldwide.[16]
Some of the oxalate in urine is produced by the body. Calcium and oxalate in the diet play a part but are not the only factors that affect the formation of calcium oxalate stones. Dietary oxalate is an organic ion found in many vegetables, fruits, and nuts. Calcium from bone may also play a role in kidney stone formation.
Calcium oxalate is used in the manufacture ofceramic glazes.[17]
| International | |
|---|---|
| National | |
| Other | |
