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Journal of Thermal Analysis and Calorimetry
Authors: Xian'e Cia, Daichun Du, Youming Jin, and Yixiang Qian

Abstract  

N(C5F11)3 (Fluorint FC-70) has been chosen as the test material to compare the chemicophysical data obtained by static-sample and DSC methods. The normal boiling point, the molar enthalpy of vaporization, and the constants of the Antoine equation of fluorint FC-70 are reported. DSC can be developed into a simple and rapid routine instrument to determine the enthalpy of vaporization as well as the boiling point of liquid, particularly at relative high temperature.

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A CO2-laser cw system and a photoacoustic detection apparatus, based on a nonresonant gas cell, was constructed and built. Coincidences of D2O absorption with several laser lines were observed. The strongest absorption was observed with the line at 9.26 m, which was used in the experiments. Samples of deuterated water in the range from 10 to 100% deuterium were used to examine the behaviour of the photoacoustic signal under conditions of varying deuterium content and total vapour pressure. A principal calibration procedure with respect to this is proposed. The behaviour of the system on buffer gas introduction was examined with hydrogen and dry air. Self-buffering of water vapour is also discussed on the basis of the results.

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Recent experiments are reviewed which used on-line isothermal gas chromatography techniques for studying chemical properties of transactinide elements. In these experiments the volatilities of chloride and bromide molecules in quartz columns were investigated. Measured chromatograms obtained with single molecules are shown to be correlated with the vapor pressure of the corresponding macroamounts. All existing data reveal that element 104 (rutherfordium) chloride has a volatility resembling very much those of the chlorides from the homologous elements hafnium and zirconium. For element 105 (hahnium) a surprisingly low volatility of the bromide compound, is found if compared to those of the corresponding bromides from the homologous elements tantalum and niobium. This latter experimental observation contrasts relativistic theoretical calculations which would predict a higher volatility for hahnium bromide if compared to those of tantalum and niobium bromides.

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Abstract  

The comprehensive analysis of volatile β-diketonate compound—ruthenium(III) trifruoroacetylacetonate (Ru(tfac)3)—was carried out. By means of flow method in quasi-equilibrium conditions and static method the temperature dependencies of saturated vapor pressure have been measured over solid and liquid cis- and trans-modifications of Ru(tfac)3 and isomer mixture. The thermodynamic characteristics of sublimation, evaporation, melting, and phase conversion have been calculated for structural isomers. Also by differential-scanning calorimetry the temperature meanings and the thermodynamic characteristics of melting have been determined for individual isomers of Ru(tfac)3 and their mixtures. By XRD the structures for cis- and trans-modifications have been determined. Both structures consist of neutral molecules arranged in pseudo layers.

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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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Volatility rate by thermogravimetry

An ASTM interlaboratory study for ASTM international E2008

Journal of Thermal Analysis and Calorimetry
Authors: Q Kwok and R Seyler

Abstract  

ASTM Committee E37 on Thermal Measurements published a new test method 'Standard Test Method for Volatility Rate by Thermogravimetry' in June 1999 with the designation E 2008. This approach to assessing volatility utilizes an extension of the pinhole technology previously employed by E37 for vapor pressure determinations using differential scanning calorimetry (ASTM E 1782). After publication of the test method E 2008, an Interlaboratory Study was undertaken to develop a 'Precision and Bias' statement to be assigned with the test method. This paper provides some background data that supports the claim that E 2008 is generally insensitive to experimental conditions other than temperature. The Interlaboratory Study showing the statistical review is also 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  

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  

A differential microcalorimeter (E. Calvet) was used to study the processes of adsorption of five aliphatic alcohols (C1-C5) on α-Al2O3 at 25, 50, 100, 150 and 200°C. In particular, the importance of the thermokinetic study of the chemisorption of such alcohols at different experimental temperatures was demonstrated, with regard to the variations in the thermokinetic parameters (tmax, t1/2 and t0) and the evolution of the alcohol vapor pressure on the adsorbent during the adsorption process. It was concluded that: a)  all the heat emission peaks of alcohol adsorption have the same rounded shape at 25°C; b)  on passing from methanol to 1-pentanol, the area of the adsorption peaks increases as the chain length or molecular weight increases; c)  on passing from 25 to 200°C, the shape of the adsorption peaks becomes more pointed.

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Abstract  

The present article describes the synthesis, spectral, coordination and thermal aspects of N,N′-polymethylene bis(1-phenyl-3-methyl-4-trifluoroacetylimino-2-pyrazoline-5-ol)oxovanadium(IV) or copper(II) Schiff base complexes with alkyl backbones ranging from two to four carbons have been characterized on the basis of elemental analysis, magnetic moments, molar conductivity measurements, spectra (FTIR, ESR, UV-Visible, MS), VPO and thermal studies. The vapour pressure osmometry (VPO) and mass spectral studies indicate that the complexes are monomeric. An ESR study of all these complexes of VO(IV) and Cu(II) are consistent with the square pyramidal and square planar geometries of these metal ions, respectively. In addition, the kinetics and thermodynamic parameters for the different thermal decomposition steps of the complexes have been studied employing Horowitz-Metzger and Freemen-Carroll methods.

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