Dicalcium phosphate

Dicalcium phosphate

Names
IUPAC name Calcium hydrogen phosphate dihydrate
Other names Calcium Hydrogen Phosphate Phosphoric acid, calcium salt (1:1)
Identifiers
CAS Number	7757-93-9 Y 7789-77-7 (dihydrate) N
3D model (Jmol)	Interactive image
ChemSpider	94606 N
ECHA InfoCard	100.028.933
PubChem CID	104805
UNII	L11K75P92J Y
InChI InChI=1S/Ca.H3O4P.2H2O/c;1-5(2,3)4;;/h;(H3,1,2,3,4);2*1H2/q+2;;;/p-2 N Key: XAAHAAMILDNBPS-UHFFFAOYSA-L N InChI=1/Ca.H3O4P.2H2O/c;1-5(2,3)4;;/h;(H3,1,2,3,4);2*1H2/q+2;;;/p-2 Key: XAAHAAMILDNBPS-NUQVWONBAM
SMILES O.O.OP(=O)([O-])[O-].[Ca+2]
Properties
Chemical formula	CaHPO4
Molar mass	136.06 g/mol (anhydrous) 172.09 (dihydrate)
Appearance	white powder
Odor	odorless
Density	2.929 g/cm3 (anhydrous) 2.31 g/cm3 (dihydrate)
Melting point	decomposes
Solubility in water	0.02 g/100 mL (anhydrous) 0.02 g/100 mL (dihydrate)
Structure
Crystal structure	triclinic
Hazards
NFPA 704	0 1 0
Flash point	Non-flammable
Related compounds
Other anions	Calcium pyrophosphate
Other cations	Magnesium phosphate Monocalcium phosphate Tricalcium phosphate Strontium phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

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 HPO₄^2– 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.

Dibasic calcium phosphate is produced by the neutralization of calcium hydroxide with phosphoric acid, which precipitates the dihydrate as a solid. At 60 °C the anhydrous form is precipitated:

To prevent degradation that would form hydroxyapatite, 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) calcium phosphate cements is:

Three forms of dicalcium phosphate are known:

The structure of the anhydrous and dihydrated forms have been determined by X-ray crystallography. The dihydrate (shown in table above) adopts a layered structure.