A detailed thermodynamic study of the systems LnSe2–LnSe1.5 (Ln = La, Nd) was performed by static method of vapour pressure measurement using quartz membrane-gauge manometers within the
temperature range 713–1,395 K. The pSe–T–x dependences obtained in this study have shown that the phase regions in composition intervals studied consist of discrete
phases: LnSe1.95LnSe1.90, LnSe1.85, LnSe1.80 (Ln = La, Nd). The enthalpies and the entropies for the stepwise dissociation process were calculated from the experimental data.
The standard enthalpies of formation and the absolute entropies were estimated for the compounds investigated using literature
Authors:St. Perisanu, Iulia Contineanu, Ana Neacsu, and Speranta Tanasescu
The energies of combustion of creatine (anhydrous and monohydrate), creatinine, and arginine were measured in a static bomb
adiabatic calorimeter, in pure oxygen at 3,040 kPa. The derived standard enthalpies of formation in solid state of the above-mentioned
compounds are, respectively, −520.4 ± 4.3, −809.7 ± 1.3, −204.2 ± 7.0, and −634.8 ± 2.3 kJ mol−1. The data of enthalpy of formation are compared with literature values and with estimated values by means of group additivity. The dehydration of creatine monohydrate and the processes occurring in the three guanidine derivatives at temperatures exceeding
200 °C were investigated by means of DSC.
The enthalpy of formation for LiMyMn2–yO4 (M=Co, Cr, Li, Mg, Ni) was measured by a Tian-Calvet type high temperature isothermal microcalorimeter. The standard enthalpy of formation for LiMn2O4 at 876 K was evaluated to be
Hf0=–1404.2±6.4 kJ mol–1. The partial substitution of Co and Ni for Mn decreased the absolute
Hf0 value, while that of Cr and Mg for Mn increased the absolute
Hf0 value. In the case of the partial substitution of Li for Mn, no marked change in
Hf0 could be observed.
Authors:T. Kimura, T. Ozaki, Y. Nakai, K. Takeda, and S. Takagi
The molar excess enthalpies of 1,2- and 1,3-propanediamine+1,2- and 1,3-propanediol have been determined at 298.15 K by using
a twin-microcalorimeter which requires each component liquid 1 to 1.5 cm3 for a series of runs over the whole range of mole fraction. All excess enthalpies are exothermic and large. An equilibrium
constant K1 expressed in terms of mole fractions and standard enthalpy of formation of 1:1 complex have been evaluated by ideal mixtures
of momomeric molecules and their associated complexes.
The heat capacities of selected inorganic binary and ternary alkali metal compounds are determined using differential scanning calorimetry (DSC). As part of an ongoing research program at Battelle Memorial Institute since 1983, the heat capacities of cesium and rubidium chalcogenides, aluminates, silicates and uranates in the temperature range 310 to 800 K have been added to the series of compounds. The measured data is to be combined with the standard enthalpies of formation and low temperature heat capacities to obtain reliable thermodynamic data on the alkali metal compounds to high temperatures.
With the use of various calculation methods, unknown thermodynamic properties (TP) of Bi2O5 and BiO2, as well as the temperature dependencies of reduced Gibbs energy (TDRGE) were determined. With the help of thermodynamic
simulation (TS) methods at 300–1500 K, common P=105 Pa the thermal decompositions of condensed Bi2O5, BiO2, Bi2O3 and BiO have been investigated in initial atmosphere of O2 and Ar. Every condensed substance was presented as the individual phase.
It was found that BixOyoxides have temperature stability fields and also districts of possible mixture formation. During equilibrium heating of BixOy oxides the various types of phase transformations were observed. The characteristics of some transformations were estimated.
Authors:Z. Zhang, L. Sun, Z. Tan, F. Xu, X. Lv, J. Zeng, and Y. Sawada
The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF4) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity
on temperature is given as a function of the reduced temperature X by polynomial equations, Cp,m [J K−1 mol−1]=181.43+51.297X −4.7816X2−1.9734X3+8.1048X4+11.108X5 [X=(T−135)/55] for the solid phase (80–190 K), Cp,m [J K−1 mol−1]= 349.96+25.106X+9.1320X2+19.368X3+2.23X4−8.8201X5 [X=(T−225)/27] for the glass state (198–252 K), and Cp,m[J K−1 mol−1]= 402.40+21.982X−3.0304X2+3.6514X3+3.4585X4 [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship,
the values of thermodynamic function of the BPBF4 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition
of BPBF4 was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔHg=2.157 kJ mol−1 and ΔSg=11.12 J K−1 mol−1, respectively. The result showed that the melting point of the BPBF4 is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔHm = 8.453 kJ mol−1 and ΔSm=30.21 J K−1 mol−1. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF4 was determined to be ΔcHm0 = −5451±3 kJ mol−1. The standard molar enthalpy of formation of BPBF4 was evaluated to be ΔfHm0 = −1356.3±0.8 kJ mol−1 at T=298.150±0.001 K.
Authors:San-Ping Chen, Na Li, Qing Wei, and Sheng-Li Gao
A novel complex [Ni(H2O)4(TO)2](NO3)2·2H2O (TO = 1,2,4-triazole-5-one) was synthesized and structurally characterized by X-ray crystal diffraction analysis. The decomposition
reaction kinetic of the complex was studied using TG-DTG. A multiple heating rate method was utilized to determine the apparent
activation energy (Ea) and pre-exponential constant (A) of the former two decomposition stages, and the values are 109.2 kJ mol−1, 1013.80 s−1; 108.0 kJ mol−1, 1023.23 s−1, respectively. The critical temperature of thermal explosion, the entropy of activation (ΔS≠), enthalpy of activation (ΔH≠) and the free energy of activation (ΔG≠) of the initial two decomposition stages of the complex were also calculated. The standard enthalpy of formation of the new
complex was determined as being −1464.55 ± 1.70 kJ mol−1 by a rotating-bomb calorimeter.
Authors:Vera Freitas, José Gomes, and Maria Ribeiro da Silva
The present work reports an experimental thermochemical study supported by state of the art calculations of two heterocyclic
compounds containing oxygen in the ring: xanthone and tetrahydro-γ-pyrone. The standard (pº = 0.1 MPa) molar enthalpies of formation in the condensed phase, at T = 298.15 K, were derived from the measurements of the standard molar energies of combustion in oxygen atmosphere, using a
static bomb calorimeter. The standard molar enthalpies of sublimation or vaporization, at T = 298.15 K, of the title compounds were obtained from Calvet microcalorimetry measurements. These values were used to derive
the standard enthalpies of formation of the compounds in the gas-phase at the same temperature, which were compared with estimated
data from G3(MP2)//B3LYP computations.