A Solution-Reaction Calorimeter And Thermodynamic Properties Of Complexes Of Rare Earth

Recent progress in solution-reaction calorimetry has been reviewed. The applications of solution-reaction calorimetry in measuring thermodynamic properties of substances, safety studies of chemical processes, thermodynamics of colloids and surfaces, physical organic chemistry, pharmaceutical research, material research and thermal biosensor were presented.An on-line solution-reaction isoperibol calorimeter has been constructed. The performance of the apparatus was evaluated by measuring the enthalpy of solution of KC1 in water at T = 298.15 K. The uncertainty and the inaccurary of the experimental results were within + 0.3 % compared with the recommended reference data.Using solution-reaction calorimetry, the standard enthalpies of reaction for the following reactions, LaCl3 7H2O (s) + 2C9H7NO (s) + CH3COONa (s) = La(C9H6NO)2(C2H3O2) (s) + NaCl (s) + 2HCl (g) + 7H2O (1) and LnCl3 6H2O (s) + 2C9H7NO (s) + CH3COONa (s) = Ln(C9H6NO)2(C2H3O2) (s) + NaCl (s) + 2HC1 (g) + 6H2O (1) (Ln = Pr, Nd and Sm), were determined at T = 298.15 K, as - (78.3 + 0.6) kJ mol-1, - (97.3 + 0.5) kJ mol-1, - (56.9 + 1.4) kJ mol-1 and - (67.9 + 1.5) kJ mol-1, respectively. From the above standard enthalpies of reaction and other auxiliary thermodynamic quantities, the standard enthalpies of formation of Ln(C9H6NO)2(C2H3O2) (s) (Ln = La, Pr, Nd and Sm), at T = 298.15 K, have been derived to be -(1534.5 + 3.1) kJ mol-1, - (1541.4 + 3.1) kJ mol-1, - (1494.7 + 3.3) kJ mol-1 and - (1501.5 + 3.4) kJ mol"1, respectively. The standard enthalpies of formation of Ln(hq)2Ac (Ln = La, Pr, Nd and Sm) in dependence on the atomic numbers of Ln was discussed.The energy of combustion of crystalline 3, 5-di-tert-butylsalicylic acid in oxygen at T = 298.15 K was determined using combustion calorimetry to be - (8292.57 + 2.51) kJ mol-1. The standard enthalpies of combustion and formation of crystalline 3, 5-di-tert-butylsalicylic acidwere derived, at T= 298.15 K, Hm =-(8302.48 + 2.51) kJ mol-1 and fH =- (744.30 +3.21) kJ mol-1, respectively. The heat capacities of the compound were measured with adiabatic calorimetry over the temperature range from 79 K to 351 K. No indication of any phase transition or thermal anomaly was observed in this temperature range. The fusion and evaporation behavior of 3, 5-di-tert-butylsalicylic acid were examined by thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Theenthalpy and entropy of fusion, fusHm and fusSm, at T - 437.5 K, were determined to be (22.92 + 0.55) kJ mol-1 and (139.4 + 3.3) J mol-1 K-1, respectively; and the enthalpy and entropy of evaporation, vap Hm and vapSm, at T = 477.5 K, were obtained as (83.88 + 2.1) kJ mol-1and (341.7 + 8.4) J mol-1 K-1, respectively.The energy of combustion of crystalline 3, 4, 5-trimethoxybenzoic acid in oxygen at T = 298.15 K was determined to be - (4795.9 + 1.3) kJ mol-1 using combustion calorimetry. Thestandard enthalpy of combustion of crystalline 3, 4, 5-trimethoxybenzoic acid, cHm, at T =298.15 K, was derived, to be - (4797.2 + 1.3) kJ mol-1. The derived standard enthalpies of formation of 3, 4, 5-trimethoxybenzoic acid in crystalline and gaseous states at T - 298.15 K,fHm(cr) and fHm(g), were - (852.9 + 1.9) kJ mol-1 and - (721.7 + 2.0) kJ mol-1, respectively. The results obtained was in good agreement with literature values.