Two strontium hydrated borates, SrB2O4 center dot 2.5H(2)O and SrB6O10 center dot 5H(2)O, have been synthesized and characterized by XRD, FT-IR, DTA-TG and chemical analysis. The molar enthalpies of solution of SrB2O4 center dot 2.5H(2)O and SrB(6)O(10 center dot)5H(2)O 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 center dot)8H(2)O in (HCl+H3BO3)(aq) and the standard molar enthalpies of formation of Sr(OH)AH(2)O(s), H3BO3(S) and H2O), the standard molar enthalpies of formation of SrB2O4 center dot 2.5H(2)O and SrB6O10].5H(2)O were calculated to be -(2827.2 +/- 1.7) and -(6177.6 +/- 4.9) kJ mol(-1), respectively. (C) 2007 Elsevier B.V. All rights reserved.