Zinc pyrophosphate

Zinc pyrophosphate (Zn₂P₂O₇) is an ionic inorganic chemical compound composed of Zn²⁺ cations and pyrophosphate anions.

Zinc pyrophosphate^[1]

Zinc pyrophosphate
Names
Other names Dizinc diphosphate
Identifiers
CAS Number	7446-26-6 Y
3D model (JSmol)	Interactive image
ChemSpider	56393 Y
ECHA InfoCard	100.028.367
PubChem CID	62641
UNII	6ERT96A621 Y
CompTox Dashboard (EPA)	DTXSID0064705
InChI InChI=1S/H4O7P2.2Zn/c1-8(2,3)7-9(4,5)6;;/h(H2,1,2,3)(H2,4,5,6);;/q;2*+2/p-4 Y Key: OMSYGYSPFZQFFP-UHFFFAOYSA-J Y InChI=1/H4O7P2.2Zn/c1-8(2,3)7-9(4,5)6;;/h(H2,1,2,3)(H2,4,5,6);;/q;2*+2/p-4 Key: OMSYGYSPFZQFFP-XBHQNQODAA
SMILES [Zn+2].[Zn+2].[O-]P([O-])(=O)OP([O-])([O-])=O
Properties
Chemical formula	Zn2P2O7
Molar mass	304.72 g/mol
Appearance	White crystalline powder
Density	3.75 g/cm3
Solubility in water	Insoluble
Solubility	Soluble in dilute acids
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Preparation

Zinc pyrophosphate can be obtained from the thermal decomposition of zinc ammonium phosphate.^[2]

2 ZnNH₄PO₄ → Zn₂P₂O₇ + 2 NH₃ + H₂O

It can also be obtained from the reaction between sodium carbonate, zinc oxide, and ammonium dihydrogen phosphate.^[3]

Na₂CO₃ + 2 ZnO + 2 (NH₄)H₂PO₄ → Zn₂P₂O₇ + 2 NaOH + 2 NH₃ + 2 H₂O + CO₂

It is also produced when a strongly acidic solution of zinc sulfate is heated with sodium pyrophosphate.^[4]

2 ZnSO₄ + Na₄P₂O₇ → Zn₂P₂O₇ + 2 Na₂SO₄

Another method is precipitating zinc as a phosphate, then heating over 1123 K.^{[citation needed]}

Properties

Zinc pyrophosphate is a white crystalline solid that is insoluble in water.^[5] On heating in water, it decomposes to form Zn₃(PO₄)₂ and ZnHPO₄. It crystallizes in the monoclinic system. The α-form crystallizes at low temperatures and the β-form crystallizes at high temperatures.^[2][3]

Uses

Zinc pyrophosphate is used as a pigment.^[5] It is useful in gravimetric analysis of zinc.^[6]