Synthesis and thermochemistry of 2CaO·B2O3·H2O

A pure calcium borate 2CaO·B2O3·H2O has been synthesized under hydrothermal condition and characterized by XRD, FT-IR and TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·B2O3·H2O in HCl·54.579H2O was determined. From a combination of this result with measured enthalpies of solution of H3BO3 in HCl·54.561H2O and of CaO in HCl+H3BO3 solution, together with the standard molar enthalpies of formation of CaO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(3041.8±2.5) kJ mol−1 of 2CaO·B2O3·H2O was obtained.