Synthesis and thermochemistry of SrB2O4·2.5H2O and SrB6O10·5H2O

Two strontium hydrated borates, SrB2O4·2.5H2O and SrB6O10·5H2O, have been synthesized and characterized by XRD, FT-IR, DTA-TG and chemical analysis. The molar enthalpies of solution of SrB2O4·2.5H2O and SrB6O10·5H2O in 1 mol dm−3 HCl(aq) were measured to be −(7.02 ± 0.21) and 51.92 ± 0.29 kJ mol−1, respectively. With the incorporation of the enthalpy of solution of H3BO3 in 1 mol dm−3 HCl(aq), the enthalpy of solution of Sr(OH)2·8H2O in (HCl + H3BO3)(aq) and the standard molar enthalpies of formation of Sr(OH)2·8H2O(s), H3BO3(s) and H2O(l), the standard molar enthalpies of formation of SrB2O4·2.5H2O and SrB6O10·5H2O were calculated to be −(2827.2 ± 1.7) and −(6177.6 ± 4.9) kJ mol−1, respectively.