Using MgSO4 and NaOH solutions as starting materials, the whisker of 5Mg(OH)2·MgSO4·2H2O has been prepared by hydrothermal method at 160℃ for different time. The whisker was separated, washed by water, ethanol and ether,and characterized by chemical analysis, XRD, IR and microphotography. The growth time of whisker would affect its morphology.
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.
