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.
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.
The vaporization enthalpies of two acetanilide pesticides, alachlor
(2’,6’-diethyl-N-(methoxymethyl)-2-chloroacetanilide) and metolachlor
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 (Tvap=470±2
K and Tvap=479±2
K) and enthalpies (ΔvapH°(436
K)=85±1 kJ mol–1 and ΔvapH°(436 K)=70±1 kJ mol–1)
for alachlor and metolachlor, were selected, respectively.
Authors:M. Ribeiro da Silva, C. Santos, M. Monte, and C. Sousa
MPa) molar enthalpies of formation, ΔfHm0, 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, ΔcrgHm0, 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)
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.
Authors:S. Kurkov, G. Perlovich, and W. Zielenkiewicz
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.
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.
Authors:Y. Shin, I. Kim, H. Shin, S. Ro, and H. Park
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.
Authors:E. Ukraintseva, V. Logvinenko, D. Soldatov, and T. Chingina
The thermal dissociation processes of clathrates [CuPy4(NO3)2]·2G (G=tetrahydrofuran, chloroform) were studied. Thermodynamic parameters (
G2980) 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.
The present work is part of a broader research program on the energetics of formation of heterocycles, aiming the study of
the enthalpic effects of the introduction of different substituents into heterocycles. In this work we present the results
of the thermochemical research on sulphur heterocycles of the type substituted thiophenes with different kind of substituents,
mainly alkyl, ester, acetyl, carboxamide, acetamide, carbonitrile and carboxaldehyde.
The standard (po=0.1 MPa) molar enthalpies of formation, in the condensed phase, at T=298.15 K, of a large number of substituted thiophenes, were derived from their standard massic energies of combustion, measured
by rotating-bomb combustion calorimetry, while the standard molar enthalpies of vaporization or sublimation of those compounds
were obtained either by high temperature Calvet Microcalorimetry, or by the temperature dependence of their vapour pressures
determined by the Knudsen effusion technique. The standard molar enthalpies of formation, of the studied sulphur heterocycles
in the gaseous phase, were then derived. The results are interpreted in terms of structural contributions to the energetics
of the substituted thiophenes, the internal consistency of the results is discussed and, whenever appropriate and possible,
empirical correlations are suggested for the estimation of standard molar enthalpies of formation, at T=298.15 K, of substituted thiophenes. A Table of enthalpic increments for different group substituents in positions 2 or 3
of the thiophene ring has been established.
Room temperature ionic liquids are a new class of solvents of potential interest for liquid chromatography. Ionic liquids possess a combination of physical and solvation properties that are complementary to conventional organic solvents. Applications in liquid chromatography are currently limited by their unfavorable viscosity and low-wavelength absorption in the ultraviolet (UV) region. In addition, for planar chromatography, the absence of a vapor pressure does not allow evaporation of ionic liquid solvents after development. The room temperature ionic liquids are good solvents for nonionic compounds with a different blend of intermolecular interactions compared with conventional organic solvents as indicated by solvatochromic measurements and the system constants of the solvation parameter model. Current applications in column and planar chromatography are reviewed to demonstrate the potential of room temperature ionic liquids as mobile phases or mobile phase additives in separation science. A real breakthrough in their use, however, requires the identification of new room temperature ionic liquids with viscosity closer to those of conventional organic solvents as well as addressing other minor issues described in the text.