The calcium oxalate It is an organic compound formed by the elements carbon (C), oxygen (O) and calcium (Ca). Its chemical formula is CaCtwoOR4. It is generally found in its three hydrated forms: mono-, di- and trihydrate. That is, with one, two or three molecules of water respectively in its crystalline structure..
Calcium oxalate is found in minerals, plants, fungi and other living beings such as mammals and even in humans as a consequence of the metabolism of some proteins. It can be found in the urine of humans and some animals.
Some foods such as spinach, rhubarb, soy, and chocolate contain a lot of oxalates, and when sensitive people eat them, calcium oxalate stones can form in their kidneys..
CaC stones can be preventedtwoOR4 in the kidneys if you ingest a lot of fluids, especially water, avoiding foods high in oxalates and consuming those rich in calcium and magnesium.
Calcium oxalate forms undesirable scale in pipes and tanks in processes such as pulp and paper manufacturing, and also in breweries.
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Calcium oxalate is formed by the calcium ion Catwo+ and the oxalate ion CtwoOR4two-. The oxalate anion is made up of two carbon atoms and four oxygen atoms. The negative charges of the oxalate anion are found on the oxygen atoms.
Colorless, white, yellow or brown crystalline solid that can be in three different hydrated forms.
128.1 g / mol
Calcium oxalate monohydrate decomposes at 200 ° C.
Monohydrate CaCtwoOR4•HtwoO = 2.22 g / cm3
Dihydrate CaCtwoOR4•2HtwoO = 1.94 g / cm3
Trihydrate CaCtwoOR4•3HtwoO = 1.87 g / cm3
Almost insoluble in water: 0.00061 g / 100 g of water at 20 ° C. Monohydrate dissolves in dilute acid.
Aqueous calcium oxalate solutions are weakly basic.
Calcium oxalate is the calcium salt of oxalic acid. This is a natural by-product of metabolism, so it is very abundant in the human body, and is part of many foods.
Oxalic acid and its conjugate base, oxalate, are highly oxidized organic compounds, with powerful chelating activity, that is, they can easily combine with positive ions with charges of +2 or +3.
Its aqueous solutions are weakly basic because the oxalate ion tends to take up H protons.+ from water, which releases OH ions-. After taking two protons H+ the oxalate ion becomes oxalic acid HtwoCtwoOR4:
CtwoOR4two- + HtwoO → HCtwoOR4- + Oh-
HCtwoOR4- + HtwoO → HtwoCtwoOR4 + Oh-
Calcium oxalate is the most common oxalate and comes in the form of the minerals whewellite, weddellite, and caoxite..
Whewellite is the monohydrate CaCtwoOR4•HtwoOr and is the most stable of the forms of this compound.
Weddellite is the dihydrate CaCtwoOR4•2HtwoO and is less stable than monohydrate.
Caoxite is calcium oxalate trihydrate CaCtwoOR4•3HtwoOR.
Calcium oxalate is associated with dry soils and leaves, also with pathogenic fungi, free, in symbiosis or associated with plants. In the latter, crystals are formed by the precipitation of calcium in the form of its oxalate.
CaC formationtwoOR4 by fungi has an important influence on the biological and geochemical processes of soils, since it constitutes a reserve of calcium for the ecosystem.
Oxalate originates in the liver, in red blood cells or erythrocytes, and to a lesser extent in the kidney. It is formed from the metabolism of amino acids (such as phenylalanine and tryptophan) and by oxidation of glyoxal dialdehyde,.
Also vitamin C can be converted into oxalate when performing its antioxidant function.
Calcium oxalate is found in stones that form in the kidneys of people or animals with kidney disease..
Calcium oxalate calculi or stones are formed by the crystallization or aggregation of CaCtwoOR4 in urine supersaturated with calcium and oxalate. This means that the urine contains so much calcium and oxalate that it is not possible for this compound to remain dissolved, but rather it precipitates or passes to the solid state in the form of crystals.
The formation of grit or stones in the kidneys is a disease called nephrolithiasis; attacks approximately 10% of the population and about 75% of these stones are composed of calcium oxalate CaCtwoOR4.
The formation and growth of calcium oxalate crystals in the kidney occur because in some people the urine is supersaturated with this salt. Calcium oxalate develops in acidic urine at pH less than 6.0.
Supersaturation occurs when the excretion or elimination of this salt (which is very poorly soluble in water) in the urine occurs in a small volume of water..
Among the factors that favor the formation of calcium oxalate grit are excess calcium in the urine or hypercalciuria, excess oxalate in the urine or hyperoxaluria, elements derived from diet and the absence of inhibitors.
Excess oxalate can occur when high amounts of spinach, rhubarb, soy, nuts and chocolate are ingested, among other foods.
However, there are substances that inhibit or prevent stone formation from occurring. Compounds that prevent stone formation include small molecules such as citrate and pyrophosphate, and large molecules such as glycoproteins and proteoglycans..
A good strategy to prevent the recurrence of grit or calcium oxalate stones includes increasing your fluid intake, increasing your intake of calcium-rich foods (such as dairy), and restricting table salt (NaCl), animal protein and foods rich in oxalate.
Since the beginning of the year 2000, an increase in calcium oxalate stones has been observed in the urinary system of cats and dogs. It seems that this depends on the type of diet that these animals eat and has to do with the acidity of the urine and magnesium (Mg) deficiency.
There is evidence that both humans and animals respond to excess oxalate by increasing the number of bacteria that can break down oxalate..
Some of these bacteria are Oxalobacter formigenes, Bifidobacterium sp., Porphyromonas gingivalis Y Bacillus sp., among others, and are naturally present in the intestine.
According to sources consulted, calcium oxalate is used in ceramic coating.
It has been used to coat limestone sculptures and other artistic elements, and has been found to improve the hardness of the material, decrease its porosity, and increase its resistance to acids and alkalis..
In the pulp and paper industry, calcium oxalate can form scale which causes many problems in the process..
To prevent its formation in the ducts or pipes of industrial processes, the enzymatic degradation of oxalic acid has been proposed, by means of enzymes such as oxalate oxidase..
It also tends to accumulate like stone in the containers where beer is made, from where it must be removed to avoid the formation of microorganisms that can give the drink an unpleasant taste..
In high concentrations, oxalate can cause death in animals and occasionally in humans, mainly due to its corrosive effects..
Buildup of oxalate and its conjugated acid, oxalic acid, can cause disorders such as heart malfunction, calcium oxalate stones, kidney failure, and even death from toxicity..
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