Strontium phosphate

Strontium phosphate is the phosphate salt of strontium, with the molecular formula Sr₃(PO₄)₂. It is a white solid insoluble in water.^[5]

Strontium phosphate

Identifiers
CAS Number	7446-28-8 N
3D model (JSmol)	Interactive image
ChemSpider	140450
ECHA InfoCard	100.028.369
EC Number	231-206-0
PubChem CID	159737
UNII	B7CF3BD0TT
CompTox Dashboard (EPA)	DTXSID20889576
InChI InChI=1S/2H3O4P.3Sr/c2*1-5(2,3)4;;;/h2*(H3,1,2,3,4);;;/q;;3*+2/p-6 Key: JOPDZQBPOWAEHC-UHFFFAOYSA-H
SMILES [O-]P(=O)([O-])[O-].[O-]P(=O)([O-])[O-].[Sr+2].[Sr+2].[Sr+2]
Properties
Chemical formula	Sr3(PO4)2
Molar mass	452.8 g/mol
Appearance	White solid
Density	4.53 g/cm3
Melting point	1,620 °C (2,950 °F; 1,890 K)[1]
Solubility in water	Insoluble[2][3]
Structure[4]
Crystal structure	Rhombohedral
Space group	R3m
Lattice constant	a = 5.39 Å, c = 19.78 Å
Lattice volume (V)	497.8 Å3
Related compounds
Other anions	Strontium sulfate
Other cations	Tricalcium phosphate Barium phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation and properties

Strontium phosphate is commonly produced by the reaction of soluble strontium compounds, such as strontium nitrate, and a phosphate source, such as phosphoric acid or tripotassium phosphate, in water, resulting in a white precipitate of the tetrahydrate:^[6][7]

3 Sr(NO₃)₂ + 2 K₃PO₄ + 4 H₂O → Sr₃(PO₄)₂·4H₂O↓ + 6 KNO₃

Under water, the tetrahydrate slowly hydrolyses to strontium hydroxyapatite (Sr₁₀(PO₄)₆(OH)₂). The tetrahydrate decomposes to the anhydrous form when heated to 900 °C.^[6][7]

The anhydrous form can be produced without the presence of water, to avoid hydrolysis, by the heating of ammonium dihydrogen phosphate and strontium carbonate at 1030 °C and 30 MPa of pressure.^[4][8]