Synthesis, characterization and thermodynamic properties of NaCs[B4O5(OH)4]·4H2O

Abstract The crystalline form of a new tetraborate, NaCs[B 4 O 5 (OH) 4 ]·4H 2 O was synthesized and characterized. The enthalpies of solution of NaCs[B 4 O 5 (OH) 4 ]·4H 2 O in approximately 1 mol dm −3 HCl(aq) and of CsCl in aqueous (HCl + H 3 BO 3  + NaCl) were determined. From these results and the enthalpy of solution of H 3 BO 3 in approximately 1 mol dm −3 HCl(aq), the enthalpy of solution of NaCl(s) in aqueous (HCl + H 3 BO 3 ) and the standard molar enthalpies of formation of NaCl(s), CsCl(s), H 3 BO 3 (s) and H 2 O(l), the standard molar enthalpy of formation for NaCs[B 4 O 5 (OH) 4 ]·4H 2 O as being −(5140.55 ± 1.94) kJ mol −1 . The standard molar entropy of formation of NaCs[B 4 O 5 (OH) 4 ]·4H 2 O was calculated from the thermodynamic relation with the standard molar Gibbs free energy of formation of NaCs[B 4 O 5 (OH) 4 ]·4H 2 O computed from a group contribution method.