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The product,Pr(C7H5O3)2·(C9H6NO),which was formed by praseodymium nitrate hexahydrate,salicylic acid (C7H6O3) and 8-hydroxyquinoline (C9H7NO),was synthesized and characterized by elemental analysis,UV spectra,IR spectra,molar conductance and thermogravimatric analysis.During the process of coordination,C7H5O3 - was bidentate-coordinated with Pr3+ in the carboxyl form; the hydroxyl oxygen atom and heterocyclic nitrogen atom of C9H6NO- formed a chelate ring with Pr3+ for coordination.In a optimalizing calorimetric solvent,the dissolution enthalpies of [Pr(NO3)3·6H2O(s)],[2 C7H6O3(s)+C9H7NO(s)],[Pr(C7H5O3)2·(C9H6NO)(s)]and[solution D(aq)]were measured to be,by means of an solution-reaction isoperibol microcalorimeter,ΔsHθm[Pr(NO3)3·6H2O(s),298.15K]=-(20.66±0.29)kJ·mol-1,ΔsHθm[2C7H6O3(s)+C9H7NO(s),298.15K]=(42.27±0.31)kJ·mol-1,ΔsHθm[solution D(aq),298.15K]=-(89.15±0.43kJ·mol-1)and ΔsHθm[Pr(C7H5O3)2(C9H6NO)(s),298.15K]=-(41.04±0.33)kJ·mol-1,respectively.The enthalpy change of the designed coordination reaction was calculated to be ΔrHθm=(213.18±0.69)kJ·mol-1 in accordance with a thermochemical cycle and the experimental results..From the enthalpies of dissolution and other auxiliary thermochemical data,the standard molar enthalpy of the formation of the complex Pr(C7H5O3)2(C9H6NO)(s) wasdetermined as ΔfHθm[Pr(C7H5O3)2(c9H6NO)(s),298.15K]=-(1875.4±3.1)kJ·mol-1.