Tricalcium phosphate

Tricalcium phosphate is a compound with formula Ca₃(PO₄)₂. It is also known as calcium orthophosphate, tertiary calcium phosphate, tribasic calcium phosphate, or "bone ash" (calcium phosphate being one of the main combustion products of bone).

It has an alpha and a beta crystal form, the alpha state being formed at high temperatures. As rock, it is found in Whitlockite.

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General case

In minerals, "calcium phosphate" refers to minerals containing calcium ions (Ca²⁺) together with orthophosphates (PO₄^3-), metaphosphates or pyrophosphates (P₂O₇^4-) and occasionally hydrogen or hydroxide ions.

Especially, the common mineral apatite has formula Ca₅(PO₄)₃X, where X is F, Cl, OH, or a mixture; it is hydroxyapatite if the extra ion is mainly hydroxide. Much of the "tricalcium phosphate" on the market is actually powdered hydroxyapatite.

Natural occurrence

It is found in nature as a rock in Morocco, Israel, Philippines, Egypt, and Kola (Russia) and in smaller quantities in some other countries. The natural form is not completely pure, and there are some other components like sand and lime which can change the composition. In terms of P₂O₅, most calcium phosphate rocks have a content of 30% to 40% P₂O₅ in weight.

The skeletons and teeth of vertebrate animals are composed of calcium phosphate, mainly hydroxylapatite.

Uses

Tricalcium phosphate is used in powdered spices as an anti-caking agent.

Calcium phosphate is an important raw material for the production of phosphoric acid and fertilizers, for example in the Odda process.

Calcium phosphate is also a raising agent (food additives) E341. Is a mineral salt found in rocks and bones, it is used in cheese products.

It is also used as a nutritional supplement. There is some debate about the different bioavailabilities of the different calcium salts.

It is commonly used in porcelain and dental powders, and medically as an antacid or calcium supplement, although calcium carbonate is more common in this regard.

Another practical application of the compound is its use in gene transfection. The calcium ions can make a cell competent (a euphemism for "rip holes in its membrane") to allow exogenous genes to enter the cell by diffusion. A heat shock afterwards then invokes the cell to repair itself. This is a quick and easy method for transfection, albeit a rather inefficient one.