A complex of praseodymium perchlorate with L-α-glutamic acid, [Pr₂(Glu)₂(ClO₄)₄(H₂O)₇]- (ClO₄)₃•4H₂O, was synthesized. By chemical analysis, elemental analysis, FTIR, TG/DTG, and comparison with relevant literatures, its chemical composition and structure were established. The purity was found to be＞99.0%, without melting point. Low-temperature heat capacities were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 370 K. An obvious endothermic peak in the heat capacity curve was observed over the temperature region of 285～306 K, which was ascribed to a solid-to-solid phase transition according to the results of TG/DTG analysis and melting point measurement. The temperature T_tr, the enthalpy D_trH_m and the entropy D_trS_m of the phase transition for the compound were determined to be: (297.158±0.280) K, (12.338±0.016) kJ•mol^－1 and (41.520±0.156) J•K^－1•mol^－1, respectively through three repeated heat capacity measurements in the phase transition region with different amounts of the sample. Two polynomial equations of heat capacities as a function of the temperature in the regions of 78～285 K and 306～370 K were fitted by the least square method, respectively. Based on the two fitted polynomials, the smoothed heat capacities and thermodynamic functions of the complex relative to the standard reference temperature 273.15 K were calculated with the interval of 5 K. The mechanism about thermal decomposition of the complex was deduced on the basis of the TG/DTG analysis. In accordance with Hess law the standard molar enthalpy of formation for the complex was determined as Δ_fH_m⁰＝(－7223.1±2.4) kJ•mol^－1, by application of an isoperibol solution-reaction calorimeter and choice of 1 mol•L^－1 HCl as calorimetric solvent.

Key words: rare earth perchlorate salt, L-α-glutamic acid, adiabatic calorimetry, low-temperature heat capacity, isoperibol solution-reaction calorimetry, standard molar enthalpy of formation