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Abstract  

The vaporization enthalpies of two acetanilide pesticides, alachlor (2’,6’-diethyl-N-(methoxymethyl)-2-chloroacetanilide) and metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy-1-methylethyl] acetamide), were determined by processing non-isothermal thermogravimetry data according to the Clausius-Clapeyron equation. The reliability of the procedure proposed was tested carrying out some experiments at different heating rates using acetanilide as a reference compound. A good agreement is found among the vaporization enthalpies derived from all the multi-heating rate experiments as well as with the one predicted from the vapor pressure data taken from literature. The vaporization temperatures (T vap=470±2 K and T vap=479±2 K) and enthalpies (Δvap H°(436 K)=85±1 kJ mol–1 and Δvap H°(436 K)=70±1 kJ mol–1) for alachlor and metolachlor, were selected, respectively.

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Abstract  

Temperature dependences of solubility, saturated vapour pressure and crystal heat capacity of [4-(Benzyloxy)phenyl]acetic acid were determined. The solubility of this compound was investigated in n-hexane, buffered water solutions with pH 2.0 and 7.4 and n-octanol. The enthalpy of sublimation and vaporization as well as the fusion temperature were determined. Solvation and solubility processes have been analyzed. The thermodynamics of transfer processes from one buffer to another (protonation process), from buffers to 1-octanol (partitioning process), and from n-hexane to the applied solvents (specific interaction) have been calculated and compared to those of other NSAIDs. The relevant shares of specific and non-specific interactions in the process of solvation have been investigated and discussed.

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Abstract  

The standard (p 0=0.1 MPa) molar enthalpies of formation, Δf H m 0, for crystalline phthalimides: phthalimide, N-ethylphthalimide and N-propylphthalimide were derived from the standard molar enthalpies of combustion, in oxygen, at the temperature 298.15 K, measured by static bomb-combustion calorimetry, as, respectively, – (318.01.7), – (350.12.7) and – (377.32.2) kJ mol–1. The standard molar enthalpies of sublimation, Δcr g H m 0, at T=298.15 K were derived by the Clausius-Clapeyron equation, from the temperature dependence of the vapour pressures for phthalimide, as (106.91.2) kJ mol–1 and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide as, respectively, (106.31.3), (91.01.2) and (98.21.4) kJ mol–1. The derived standard molar enthalpies of formation, in the gaseous state, are analysed in terms of enthalpic increments and interpreted in terms of molecular structure.

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Abstract  

In order to determine the operating condition of an uranium chlorination process with U3O8-C-Cl2 system, the experimental conditions have been evaluated preliminarily by the thermochemical analysis and experimentally confirmed in this study. The dry-type chlorination of U3O8 occurs as irreversible and exothermic reaction and produces many kinds of chloride compounds such as UCl3, UCl4, UCl5 and UCl6 in the air and humidity controlled argon environment. Taking account of Gibbs free energy and vapor pressure for various chloride compounds, the proper temperature range of chlorination appears to be 863 to 953 K in aspects of increasing reaction rate and the yield of nonvolatile product. In the course of the experimental confirmation the powder of U3O8 is perfectly converted into uranium chlorides within 4 hours above 863K, and then the maximum fraction of uranium chloride remaining in the reactor is about 30% of total conversion mass.

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Abstract  

The effect of atmospheric water vapor on the kinetic rate behavior of the thermal decomposition of copper(II) carbonate hydroxide, Cu2CO3(OH)2, was investigated by means of TG-DTA coupled with a programmable humidity controller. With increasing water vapor pressure p(H2O) from 0.8 to 10.6 kPa, a systematic reduction of the reaction temperature of the thermal decomposition was observed as the continuous trend from the previous works at the lower p(H2O). Through a comparative kinetic analysis of the reaction at different p(H2O), a catalytic action of the atmospheric water vapor on the nucleation process at the first half of the reaction was identified as the possible origin of the reduction of the reaction temperature.

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Abstract  

A thermobalance for studies of the high-temperature sulfidation of metals and alloys is described. This apparatus permits the determination of mass changes in a sulfidized sample as a function of temperature and sulfur vapour pressure. The main parts of this apparatus are the container with liquid sulfur and the reaction chamber with the quartz space and quartz spiral. All parts of the apparatus are equipped with thermostating furnaces. The temperature within the apparatus is controlled with an accuracy of 0.5 K. The quartz spiral (diameter 0.2 mm), consisting of 50 coils (diameter 30 mm), permits the recording of mass changes in the sample (about 200 mg) with an accuracy of 10-5 g. Besides heterogeneous kinetics measurements, it has been shown that the self- and chemical diffusion coefficients or the deviation from stoichiometry of the metal sulfides can also be studied as functions of temperature and sulfur pressure by means of equilibration measurements.

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Abstract  

Hydroxy benzoic acids were subjected to rising temperature thermogravimetric analysis. After optimizing the procedural variables, the kinetics of decomposition was determined and methyl paraben was taken as the calibration compound to characterize the evaporation patterns for the ortho and meta derivatives. The E act values for ortho, meta and para derivatives were 64.8, 78.2, and 119.1 kJ mol–1, respectively. The Antoine and Langmuir equations were utilized to determine the coefficient of evaporation k, which was 1245250.8, units being in the SI system. The vapor pressure plots were generated for the ortho and meta derivatives; ΔH vap for these two compounds were obtained as 66.7 and 80.4 kJ mol–1, respectively.

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Abstract  

The thermal dissociation processes of clathrates [CuPy4(NO3)2]·2G (G=tetrahydrofuran, chloroform) were studied. Thermodynamic parameters ( H AV 0, S 298 0 and G 298 0) of the processes, producing solid host complex [CuPy4(NO3)2] and gaseous guest (G), were determined from the strain measurements. These data are compared with previous data for clathrates of the host complex with benzene and pyridine. Quasi-equilibrium thermogravimetry was used to investigate the step-by-step character of the dissociation processes. Kinetic studies were carried out for clathrate [CuPy4(NO3)2]·2THF.

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Abstract  

The use of modulated temperature differential scanning calorimetry (TMDSC) and differential scanning calorimetry (DSC) in the measurement of the glass transition temperature (T g) in polymer-water systems presents several important problems. These include the presence of water evaporation endotherms, partial water evaporation during scanning, changes in pan integrity due to vapour pressure developing in the pan headspace during analysis, and possible interaction between water and polymer at high temperatures. As a result, in most of the cases, only apparent T g values can be obtained. In this study, TMDSC and DSC were used to determinate the thermal behaviour of methylmethacrylate copolymer-water systems. The samples were previously equilibrated at different relative humidities (RH) from 0 to 97% RH. Three different pan arrangements were used. In addition, thermogravimetric analysis (TG) was carried out to determine the initial amount of water in the sample. None of the pan arrangements was entirely suitable for the study of these systems. When sealed pans were used, the plastification effect of water was observed. Some evidence of degradation was also observed in which water and methylmethacrylate appeared to play roles.

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A new tin dithiocarbamate containing sulphur bridges, di-μ-sulphidobis [bis(N,N-diethyldithiocarbamato)tin(IV)], has been isolated from the thermal decomposition of tetrakis(N,N-diethyldithiocarbamato)tin(IV). A dimeric structure is proposed on the basis of results from mass spectrometry, infrared spectroscopy, thermal analysis and vapour pressure osmometry.

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