Zinc pyrophosphate (Zn2P2O7) is an ionic inorganic chemical compound composed of Zn2+ cations and pyrophosphate anions. Preparation Zinc pyrophosphate can be obtained from the thermal decomposition of zinc ammonium phosphate. 2 ZnNH4PO4 → Zn2P2O7 + 2 NH3 + H2O It can also be obtained from the reaction between sodium carbonate, zinc oxide, and ammonium dihydrogen phosphate. 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. 2 ZnSO4 + Na4P2O7 → Zn2P2O7 + 2 Na2SO4 Another method is precipitating zinc as a phosphate, then heating over 1123 K. Properties Zinc pyrophosphate is a white crystalline solid that is insoluble in water. 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. Uses Zinc pyrophosphate is used as a pigment. It is useful in gravimetric analysis of zinc. References Pyrophosphates pyrophosphate