Xiao-Zheng Lan

Calorimetric study and thermal analysis of [ErY(Ala)4(H2O)8](ClO4)6 (Ala=ALANINE)

A solid complex of rare-earth compounds with alanine, [ErY(Ala)4(H2O)8](ClO4)6 (Ala=alanine), was synthesized, and a calorimetric study and thermal analysis for it was performed through adiabatic calorimetry and thermogravimetry. The low-temperature heat capacity of [ErY(Ala)4(H2O)8](ClO4)6 was measured with an automated adiabatic precision calorimeter over the temperature range from 78 to 377 K. A solid-solid phase transition was found between 99 and 121 K with a peak temperature at 115.78 k. The enthalpy and entropy of the phase transition was determined to be 1.957 Kj mol-1, 16.90 j mol-1 k-1, respectively. Thermal decomposition of the complex was investigated in the temperature range of 40~550°C by use of the thermogravimetric and differential thermogravimetric (TG/DTG) analysis techniques. The TG/DTG curves showed that the decomposition started from 120 and ended at 430°C, completed in three steps. A possible mechanism of the thermal decomposition was elucidated.

Calorimetric study and thermal analysis of berberine sulphate

The heat capacities of berberine sulphate [(C20H18NO4)2SO4·3H2O] were measured from 80 to 390 K by means of an automated adiabatic calorimeter. Smoothed heat capacities, HT-H298.15 and ST-S298.15 were calculated. The loss of crystalline water started at about 339.3±0.2 K, and its peak temperature was 365.8±0.6 K. The peak temperature of decomposition for berberine sulphate was at about 391.4±0.4 K by DSC curve. TG-DTG analysis of this material was carried out in temperature range from 310 to 970 K. TG and DSC curves show that there is no melting in the whole heating process.

Low-temperature heat capacity and thermodynamic properties of [Re2(Ile)4(H2O)8](ClO4)6 (Re=Nd, Er, Ile=isoleucine)

AbstractThe heat capacities of two kinds of rare-earth element solid complexes with isoleucine [Re 2 (Ile) 4 (H 2 O) 8 ](ClO 4 ) 6 (whereRe = Nd, Er, and Ile = isoleucine) have been measured by an automatic adiabatic calorimeter in the temperature rangefrom 80 to 370K. Two solid–solid phase transitions were found from the C p curve of Nd formed complex in the rangeof 165–175K with a peak temperature of 167.88K and in the range of 195–210K with a peak temperature of 202.13K.The corresponding molar enthalpies of these phase transitions were determined to be 404.61Jmol −1 and 2.955kJmol ,respectively. One solid–solid phase transition was found for the Er formed complex in the range of 190–205K with a peaktemperature of 193.42K. The corresponding molar enthalpy of this transition was 14.11kJmol −1 . Smooth heat capacities andthermodynamic functions relative to the standard state (298.15K), H T − H 298 . 15 , S T − S 298 . 15 and −[ G T − G 298 . 15 ], of thetwo compounds, were calculated on basis of experimental heat capacity data. Possible mechanisms of thermal decompositionsfor the pair of compounds were suggested according to the thermogravimetric (TG) analysis.© 2002 Elsevier Science B.V. All rights reserved.

Thermodynamic investigation of crystalline K2Cr2O7 and aqueous K2Cr2O7 solution

The molar heat capacities (c-p,c-m) of crystalline potassium dichromate (k2cr2o7 (cr)) and aqueous k2cr2o7 solution (0.1699 mol(.)kg(-1)) were measured in the temperature range from 100 to 390 k and from 80 to 370 k by an automatic adiabatic calorimeter equipped with a small cell of internal volume of 6 cm(3), respectively. no phase transition took place in the temperature range from 100 to 390 k for k2cr2o7 (cr). the relationships of c-p,c-m of k2cr2o7 (cr) with respect to t were established to be c-p,c-m = 177.53 + 161.92x - 138.14x(2) - 209.67x(3) + 160.35x(4) + 137.44x(5) - 41.291x(6) and c-p,c-m = 177.52 + 171.66x - 149.59x(2) - 246.17x(3) + 194.79x(4) + 167.30x(5) - 64.368x(6) (x = (t - 245.00)/145.00) for series i and series 2 experiments, respectively. no phase transition took place for the solution from 80 to 270 k. the function of c-p,c-m of the solution with respect to t was established to be c-p,c-m = 0.137t + 2.5068 [j(.)k(-1.)mol(-1)]. a fusion transition at t-fus = 272.19 k was found from the c-p,c-m-t curve of the solution. the molar enthalpy and entropy of the phase transition were calculated to be 6.115 kj(.)mol(-1) and 22.47 j(.)k(-1.)mol(-1), respectively. the molar heat capacities of the solution are about a constant in the temperature range from 275 k to 370 k, c-p,c-m =76.75 +/- 1.12 [j(.)k(-1.)mol(-1)]. the thermodynamic data of k2cr2o7 (cr) and the solution were derived from the heat capacity data and the relationship of thermodynamic functions. (c) 2003 editions scientifiques et medicales elsevier sas. all rights reserved.