The enthalpy of formation of zinc acetate dihydrate (Zn(CH3COO)(2)center dot 2H(2)O) was measured with respect to crystalline zinc oxide (ZnO), glacial acetic acid (CH3COOH) and liquid water by room temperature solution calorimetry. The enthalpy of formation was verified by utilizing two independent thermodynamic cycles, using enthalpy of solution measurements in 5 mol.L-1 sodium hydroxide (NaOH) and in 5 mol.L-1 hydrochloric acid (HCl) solutions. The enthalpy of the reaction ZnO (cr) + 2CH(3)COOH (I) + H2O (I) to form Zn(CH3COO)(2)center dot 2H(2)O (Cr) is -(65.78 +/- 0.36) kJ mol(-1) for measurements in 5 mol.L-1 NaOH and -(66.25 +/- 0.17) kJ mol(-1) for measurements in 5 mol.L-1 HCl. The standard enthalpy of formation of Zn(CH3COO)(2)center dot 2H(2)O from the elements is -(1669.35 +/- 1.30) kJ.mol(-1). This work provides the first calorimetric measurement of the enthalpy of formation of Zn(CH3COO)(2)center dot 2H(2)O. (c) 2011 Elsevier Ltd. All rights reserved.