Hydrated potassium monoborate(KBO 2 ·4/3H 2 O)was obtained from an aqueous solutio n in a mole ratio of K 2 O∶B 2 O 3 =2∶1and characterized by powder X-ray diffraction(XRD),infrared spectroscopy(FT-IR)and Raman spectroscopy.The enthalpy of solut ion of hydrated potassium monoborate,KBO 2 ·4/3H 2 O,in approximately1mol·dm -3 aqueous hydrochloric acid was determined.Together with the previously determined enthalpies of so-lution of H 3 BO 3 in approximately 1mol·dm -3 HCl (aq),and of KCl in aqueous(hydrochloric acid +boric acid),the standard molar enthalpy of forma tion of -(1411.11±0.84)kJ·mol -1 for KBO 2 ·4/3H 2 O was obtained from the standard molar enthalpies of formation of KCl (s),H 3 BO 3 (s),and H 2 O(l).The standard molar entropy of formation of -422.94J ·K -1 ·mol -1 and standard molar entropy of 163.47J·K -1 ·mol -1 for KBO 2 ·4/3H 2 O were calculated from the thermodynamic relations.A group contribution method is applicable to KBO 2 ·4/3H 2 O.
