Calcium pyrophosphate has the molecular formula of
Ca2P2O7 and the molecular weight of 254.1378 g/mol. It
has the CAS number of 7790-76-3. It may be prepared by
the solid-state reaction of the dibasic orthophosphate, or
alternately by the precipitation of a soluble Ca salt with
aqueous pyrophosphoric acid:
2CaHPO4 + heat ? Ca2P2O7 +H2O
CaCl2 (aq) +H4P2O7 (aq) ? Ca2P2O7 (solid) + 2HCl (aq)
The solid-state reaction produces an amorphous crystal
at 240–500°C. b-Ca2P2O7 forms >750°C and a-Ca2P2O7
forms in the temperature range of 1140 to 1350°C. The
free energy of formation, △Gf=-3132 kcal/mol.
The product of the aqueous method is the dihydrate,
Ca2P2O7·2H2O. It is a white powder and has the CAS
number of 7790-76-3. It is insoluble in water but soluble
in dilute acids. The anhydrate decomposes at 1353°C to
form a metaphosphate:
Ca2P2O7 + heat ? Ca(PO3)2 + CaO
Calcium pyrophosphate is dimorphic. The phase
transformation and sintering behaviors of Ca2P2O7 with
different phase composition has been investigated by
using X-ray powder diffraction (XRD), dilatometery and
SEM techniques. It was found that although α-Ca2P2O7
(high-temperature form) could be maintained during its
cooling process, it was metastable and retransformed
into β-Ca2P2O7 (low-temperature form) at about 950 °C
during its reheating process.
Calcium phosphate is used in the production of phosphoric acid and fertilizers. It is used in baking as the acid in a leavening agent. It is also used in cheese products. This compound has also been used in gene transfection of cells. It is also being used in the development of contrast agents.
Calcium Pyrophosphate is a nutrient and dietary supplement that
exists as a white odorless powder, insoluble in water. it is used in
dental impression materials and as a buffer.
ChEBI: Calcium diphosphate is a calcium phosphate. It contains a diphosphate(4-).
Flammability and Explosibility
Non flammable
