The important zinc borate of 2ZnO center dot 3B(2)O(3) center dot 3H(2)O has been synthesized and characterized by means of chemical analysis, XRD, FT-IR, and DTA-TG techniques. The molar enthalpies of solution of H3BO3(s) in HCl center dot 54.561H(2)O, of ZnO(s) in the mixture of HCl center dot 54.561H(2)O and calculated amount of H3BO3, and of 2ZnO center dot 3B(2)O(3) center dot 3H(2)O(s) in HCl center dot 54.604H(2)O were measured, respectively. With the use of the standard molar enthalpies of formation for ZnO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of -(5561.7 +/- 4.9) kJ.mol(-1) for 2ZnO center dot 3B(2)O(3) center dot 3H(2)O(s) was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method. (C) 2008 Elsevier Ltd. All rights reserved.