Hydrothermal synthesis and thermodynamic properties of 2ZnO · 3B2O3 · 3H2O

The important zinc borate of 2ZnO · 3B2O3 · 3H2O 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 · 54.561H2O, of ZnO(s) in the mixture of HCl · 54.561H2O and calculated amount of H3BO3, and of 2ZnO · 3B2O3 · 3H2O(s) in HCl · 54.604H2O 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 · 3B2O3 · 3H2O(s) was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.