| |
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 | |
PubChem CID | |
UNII |
|
CompTox Dashboard (EPA) | |
| |
| |
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 for CaC2O4 [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 | |
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). |
Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula CaC2O4 or Ca(COO)2. 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. Cultural groups with diets that depend highly on fruits and vegetables high in calcium oxalate, such as those 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.
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 nutrient calcium carbonate. [9]
The poisonous plant dumb cane ( Dieffenbachia ) contains the substance and on ingestion can prevent speech and be suffocating. It is also found in sorrel, rhubarb (in large quantities in the leaves), cinnamon, turmeric and in species of Oxalis , Araceae, Arum italicum , taro, kiwifruit, tea leaves, agaves, Virginia creeper ( Parthenocissus quinquefolia ), and Alocasia and in spinach in varying amounts. Plants of the genus Philodendron 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 in idioblasts. Vanilla plants exude calcium oxalates upon harvest of the orchid seed pods and may cause contact dermatitis.
Calcium oxalate crystals are commonly found in lichens, 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 called pruina and within the internal structures of the lichen thallus. 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 as sulfur dioxide. The formation of these crystals is linked to the lichen's ability to dissolve calcium from rocky substrates 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 or even ruin the flavour 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.
Calcium oxalate is a combination of calcium ions and the conjugate base of oxalic 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 of sodium oxalate, due to its lower solubility in water. Solid calcium oxalate hydrate has been characterized by X-ray crystallography. It is a coordination polymer featuring planar oxalate anions linked to calcium, which also has water ligands. [1]
Calcium oxalate can produce sores and numbing on ingestion and may even be fatal.
The monohydrate and dihydrate can be distinguished by the shape of the respective crystals.
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.
In one study of modulators of calcium oxalate crystallization in urine, magnesium-alkali citrate was shown to inhibit CaOx (calcium oxalate) crystallization, “probably via actions of the citrate, but not the Mg.” This was in comparison to magnesium, citrate, and magnesium citrate. Currently the preparation of magnesium-potassium citrate that was used in one positive study is not available in the United States. [17]
Calcium oxalate is used in the manufacture of ceramic glazes. [18]
Kidney stone disease, also known as renal calculus disease, nephrolithiasis or urolithiasis, is a crystallopathy where a solid piece of material develops in the urinary tract. Renal calculi typically form in the kidney and leave the body in the urine stream. A small calculus may pass without causing symptoms. If a stone grows to more than 5 millimeters, it can cause blockage of the ureter, resulting in sharp and severe pain in the lower back that often radiates downward to the groin. A calculus may also result in blood in the urine, vomiting, or painful urination. About half of people who have had a renal calculus are likely to have another within ten years.
A bladder stone is a stone found in the urinary bladder.
Oxalic acid is an organic acid with the systematic name ethanedioic acid and chemical formula HO−C(=O)−C(=O)−OH, also written as (COOH)2 or (CO2H)2 or H2C2O4. It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name comes from the fact that early investigators isolated oxalic acid from flowering plants of the genus Oxalis, commonly known as wood-sorrels. It occurs naturally in many foods. Excessive ingestion of oxalic acid or prolonged skin contact can be dangerous.
Oxalate is an anion with the chemical formula C2O2−4. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate, and several esters such as dimethyl oxalate. It is a conjugate base of oxalic acid. At neutral pH in aqueous solution, oxalic acid converts completely to oxalate.
The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are white solids of nutritional value and are found in many living organisms, e.g., bone mineral and tooth enamel. In milk, it exists in a colloidal form in micelles bound to casein protein with magnesium, zinc, and citrate–collectively referred to as colloidal calcium phosphate (CCP). Various calcium phosphate minerals, which often are not white owing to impurities, are used in the production of phosphoric acid and fertilizers. Overuse of certain forms of calcium phosphate can lead to nutrient-containing surface runoff and subsequent adverse effects upon receiving waters such as algal blooms and eutrophication (over-enrichment with nutrients and minerals).
Barium chloride is an inorganic compound with the formula BaCl2. It is one of the most common water-soluble salts of barium. Like most other water-soluble barium salts, it is a white powder, highly toxic, and imparts a yellow-green coloration to a flame. It is also hygroscopic, converting to the dihydrate BaCl2·2H2O, which are colourless crystals with a bitter salty taste. It has limited use in the laboratory and industry.
Weddellite (CaC2O4·2H2O) is a mineral form of calcium oxalate named for occurrences of millimeter-sized crystals found in bottom sediments of the Weddell Sea, off Antarctica. Occasionally, weddellite partially dehydrates to whewellite, forming excellent pseudomorphs of grainy whewellite after weddellite's short tetragonal dipyramids. It was first described in 1936 but only named in 1942.
Whewellite is a mineral, hydrated calcium oxalate, formula Ca C2O4·H2O. Because of its organic content it is thought to have an indirect biological origin; this hypothesis is supported by its presence in coal and sedimentary nodules. However, it has also been found in hydrothermal deposits where a biological source appears improbable. For this reason, it may be classed as a true mineral.
Dicalcium phosphate is the calcium phosphate with the formula CaHPO4 and its dihydrate. The "di" prefix in the common name arises because the formation of the HPO42– anion involves the removal of two protons from phosphoric acid, H3PO4. It is also known as dibasic calcium phosphate or calcium monohydrogen phosphate. Dicalcium phosphate is used as a food additive, it is found in some toothpastes as a polishing agent and is a biomaterial.
Bladder stones or uroliths are a common occurrence in animals, especially in domestic animals such as dogs and cats. Occurrence in other species, including tortoises, has been reported as well. The stones form in the urinary bladder in varying size and numbers secondary to infection, dietary influences, and genetics. Stones can form in any part of the urinary tract in dogs and cats, but unlike in humans, stones of the kidney are less common and do not often cause significant disease, although they can contribute to pyelonephritis and chronic kidney disease. Types of stones include struvite, calcium oxalate, urate, cystine, calcium phosphate, and silicate. Struvite and calcium oxalate stones are by far the most common. Bladder stones are not the same as bladder crystals but if the crystals coalesce unchecked in the bladder they can become stones.
Ammonium oxalate is a chemical compound with the chemical formula [NH4]2C2O4. Its formula is often written as (NH4)2C2O4 or (COONH4)2. It is an ammonium salt of oxalic acid. It consists of ammonium cations ([NH4]+) and oxalate anions (C2O2−4). The structure of ammonium oxalate is ([NH4]+)2[C2O4]2−. Ammonium oxalate sometimes comes as a monohydrate ([NH4]2C2O4·H2O). It is a colorless or white salt under standard conditions and is odorless and non-volatile. It occurs in many plants and vegetables.
Renal stone formation and passage during space flight can potentially pose a severe risk to crew member health and safety and could affect mission outcome. Although renal stones are routinely and successfully treated on Earth, the occurrence of these during space flight can prove to be problematic.
Lead(II) oxalate is an organic compound with the formula PbC2O4. It is naturally found as a heavy white solid.
Magnesium oxalate is an organic 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.
Sodium hydrogenoxalate or sodium hydrogen oxalate is a chemical compound with the chemical formula NaHC2O4. It is an ionic compound. It is a sodium salt of oxalic acid H2C2O4. It is an acidic salt, because it consists of sodium cations Na+ and hydrogen oxalate anions HC2O−4 or HO−C(=O)−CO−2, in which only one acidic hydrogen atom in oxalic acid is replaced by sodium atom. The hydrogen oxalate anion can be described as the result of removing one hydrogen ion H+ from oxalic acid, or adding one to the oxalate anion C2O2−4.
Crystallopathy is a harmful state or disease associated with the formation and aggregation of crystals in tissues or cavities, or in other words, a heterogeneous group of diseases caused by intrinsic or environmental microparticles or crystals, promoting tissue inflammation and scarring.
Copper(II) oxalate are inorganic compounds with the chemical formula CuC2O4(H2O)x. The value of x can be 0, 0.44, and 1. Two of these species are found as secondary minerals, whewellite (monohydrate) and moolooite. The anhydrous compound has been characterized by X-ray crystallography. Many transition metal oxalate complexes are known.
Yttrium oxalate is an inorganic compound, a salt of yttrium and oxalic acid with the chemical formula Y2(C2O4)3. The compound does not dissolve in water and forms crystalline hydrates—colorless crystals.
Alkali citrate is an inhibitor of kidney stones. It is used to increase urine citrate levels - this prevents calcium oxalate stones by binding to calcium and inhibiting its binding to oxalate. It is also used to increase urine pH - this prevents uric acid stones and cystine stones.
Rubidium oxalate is a chemical compound with the chemical formula Rb2C2O4. It is a rubidium salt of oxalic acid. It consists of rubidium cations Rb+ and oxalate anions C2O2−4. Rubidium oxalate forms a monohydrate Rb2C2O4·H2O.