Dicalcium phosphate is the

calcium phosphate 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 ...

with the formula CaHPO₄ and its dihydrate. The "di" prefix in the common name arises because the formation of the HPO₄^2– anion involves the removal of two protons from

phosphoric acid Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, ...

, H₃PO₄. It is also known as dibasic calcium phosphate or calcium monohydrogen phosphate. Dicalcium phosphate is used as a

food additive Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives, such as vinegar ( pickling), salt ( salting), smoke ( smoking) and sugar ( crystallization), have been used f ...

, and it is found in some

toothpaste Toothpaste is a paste or gel dentifrice that is used with a toothbrush to clean and maintain the aesthetics of Human tooth, teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from th ...

s as a

polishing Polishing is the process of creating a smooth and shiny surface by rubbing it or by applying a chemical treatment, leaving a clean surface with a significant specular reflection (still limited by the index of refraction of the material accordi ...

agent and

biomaterial A biomaterial is a substance that has been Biological engineering, engineered to interact with biological systems for a medical purpose – either a therapeutic (treat, augment, repair, or replace a tissue function of the body) or a Medical diag ...

Preparation

Dibasic calcium phosphate is produced by neutralizing

calcium hydroxide Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime ( calcium oxide) is mixed with water. Annually, approxim ...

with

, precipitating the dihydrate as a solid. At 60 °C the anhydrous form is precipitated: To prevent degradation that would form

hydroxyapatite Hydroxyapatite (International Mineralogical Association, IMA name: hydroxylapatite) (Hap, HAp, or HA) is a naturally occurring mineral form of calcium apatite with the Chemical formula, formula , often written to denote that the Crystal struc ...

, sodium pyrophosphate or trimagnesium phosphate octahydrate are added when, for example, dibasic calcium phosphate dihydrate is to be used as a polishing agent in toothpaste. In a continuous process CaCl₂ can be treated with (NH₄)₂HPO₄ to form the dihydrate: A slurry of the dihydrate is then heated to around 65–70 °C to form anhydrous CaHPO₄ as a crystalline precipitate, typically as flat diamondoid crystals, which are suitable for further processing. Dibasic calcium phosphate dihydrate is formed in "brushite" calcium phosphate cements (CPC's), which have medical applications. An example of the overall setting reaction in the formation of "β-TCP/MCPM" (β- tricalcium phosphate/

monocalcium phosphate Monocalcium phosphate is an inorganic compound with the chemical formula Ca(H2PO4)2 ("AMCP" or "CMP-A" for anhydrous monocalcium phosphate). It is commonly found as the monohydrate ("MCP" or "MCP-M"), Ca(H2PO4)2·H2O. Both salts are colourless so ...

) calcium phosphate cements is:

Structure

Three forms of dicalcium phosphate are known: *

dihydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

, CaHPO₄•2H₂O ('DCPD'), the mineral

brushite Brushite is a phosphate mineral with the chemical formula . Crystals of the pure compound belong to the monoclinic space group C2/c and are colorless.monohydrate, CaHPO₄•H₂O ('DCPM') *

anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...

CaHPO₄ ('DCPA'), the mineral monetite. Below pH 4.8, the dihydrate and anhydrous forms of dicalcium phosphate are the most stable (insoluble) calcium phosphates. The structure of the anhydrous and dihydrated forms has been determined by

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

, and the structure of the monohydrate was determined by electron crystallography. The dihydrate (shown in table above) as well as the monohydrate, adopt layered structures.

Uses and occurrence

Dibasic calcium phosphate is mainly used as a

dietary supplement A dietary supplement is a manufactured product intended to supplement a person's diet by taking a pill (pharmacy), pill, capsule (pharmacy), capsule, tablet (pharmacy), tablet, powder, or liquid. A supplement can provide nutrients eithe ...

in prepared breakfast cereals, dog treats, enriched flour, and noodle products. It is also used as a tableting agent in some pharmaceutical preparations, including some products meant to eliminate

body odor Body odor or body odour (BO) is present in all animals and its intensity can be influenced by many factors (behavioral patterns, survival strategies). Body odor has a strong genetic basis, but can also be strongly influenced by various factors, ...

. Dibasic calcium phosphate is also found in some dietary calcium supplements (e.g., Bonexcin). It is used in poultry feed. It is also used in some toothpastes as a tartar control agent. Heating dicalcium phosphate gives dicalcium diphosphate, a useful polishing agent: In the dihydrate (brushite) form, it is found in some

kidney stone Kidney stone disease (known as nephrolithiasis, renal calculus disease, or urolithiasis) is a crystallopathy and occurs when there are too many minerals in the urine and not enough liquid or hydration. This imbalance causes tiny pieces of cr ...

s and dental calculi.

References

{{DEFAULTSORT:Dicalcium Phosphate Acid salts Calcium compounds Food additives Phosphates E-number additives

Preparation

Structure

Uses and occurrence

See also

References