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derived by our research group [ 1 – 7 ] with the main purpose of estimating sublimation vapor pressures of low volatile organic compounds. These estimations can be useful for evaluating vapor pressures when the enthalpy of sublimation is determined using a

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Journal of Thermal Analysis and Calorimetry
Authors: E. Filatov, S. Sysoev, Ludmila Zelenina, Tamara Chusova, V. Logvinenko, P. Semyannikov, and I. Igumenov

Abstract  

Thermal behaviour of a series of lithium β-diketonates: Li(dpm) (dpm=dipivaloylmethanate (2,2,6,6-tetramethylheptane-3,5- dionate)), Li(pta) (pta=pivaloyltrifluoracetonate (2,2-dimethyl-6,6,6-trifluoro-3,5-hexanedionate)), Li(tfa) (tfa=trifluoracetylacetonate (1,1,1-trifluoro-2,4-pentandionate)), Li(hfa) (hfa=hexafluoracetylacetonate (1,1,1,5,5,5-hexafluoro-2,4-pentandionate)) has been investigated. Gas phase composition of these complexes has been established. Temperature dependences of vapor pressure of lithium compounds were obtained by static and dynamic methods, and thermodynamic parameters were calculated. Dependence of compound volatility on ligand structure is shown. For Li(dpm) detailed investigation has been done by differential scanning calorimetry (DSC).

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Journal of Thermal Analysis and Calorimetry
Authors: Kseniya V. Zherikova, Ludmila N. Zelenina, Natalia B. Morozova, and Tamara P. Chusova

these compounds, determination of the fundamental quantitative thermodynamic data is the relevant problems for further efficient development of technological deposition processes. To this moment, vapor pressure data obtained for vaporization of the row

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Abstract  

Radiolabeled morphine and cocaine vapors have been used to determine the approximate binding site densities of immobilized, airdried antibodies toward these substances. Vapor pressures of the radiolabeled substances have also been determined.

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Abstract  

The present study was aimed at determining the kinetics of evaporation and establishing vapor pressure curves for both single and multi-component systems by thermogravimetry (TG) and differential scanning calorimetry (DSC). Essential oils (e.g. lavender oil, orange oil, clove oil and eucalyptus oil, etc.) are typically multi-component systems consisting of various volatile pure components (e.g. linalyl acetate, limonene, cinnamaldehyde, etc.) which resemble single component systems. In this study linalyl acetate was taken as the calibration compound for TG. The vapor pressure curves for the pure substances were plotted using TG and vapor pressure plots for clove oil and eucalyptus oil were constructed using DSC. The thermodynamic and kinetic parameters of the pure compounds were compared to that of the multi-component systems to quantitatively and qualitatively measure the influence of different compounds on each other. The k-value from the vapor pressure data for linalyl acetate was calculated as 112006 Pa kg0.5mol0.5s-1 m-2 K-0.5. The vapor pressure values were used to determine the Antoine constants using the SPSS 10.0 software.

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Abstract  

The heat, equilibrium, and kinetics of adsorption of 1-ethoxy-2-propanol vapours on granulated activated carbon were determined simultaneously by a reaction calorimeter SETARAM C80 D at T=298.15 K at various relative vapour pressures (0.1< p/p s<0.8). The adsorption isotherm was correlated by the Freundlich equation. It was observed that the enthalpies of adsorption decrease slightly with increasing of the relative vapour pressure of the adsorptive. The rate of adsorption were calculated from analysis of the heat flux signals and it was found that the mass-transfer coefficient for 1-ethoxy-2-propanol vapours in granulated activated carbon increased with increasing relative vapour pressure of the adsorptive.

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Polymorphism of paracetamol

Relative stability of the monoclinic and orthorhombic phase revisited by sublimation and solution calorimetry

Journal of Thermal Analysis and Calorimetry
Authors: G. Perlovich, Tatyana Volkova, and Annette Bauer-Brandl

Abstract  

The thermodynamic relationship between crystal modifications of paracetamol was studied by alternative methods. Temperature dependence of saturated vapor pressure for polymorphic modifications of the drug paracetamol (acetaminophen) was mea sured and thermodynamic functions of the sublimation process calculated. Solution calorimetry was carried out for the two modifications in the same solvent. Thermodynamic parameters for sublimation for form I (monoclinic) were found: ΔG sub 298=60.0 kJ mol−1; ΔH sub 298=117.9�0.7 kJ mol−1; ΔS sub 298=190�2 J mol−1 K−1. For the orthorhombic modification (form II), the saturated vapor pressure could only be studied at 391 K. Phase transition enthalpy at 298 K, ΔH tr 298(I→II)=2.0�0.4 kJ mol−1, was derived as the difference between the solution enthalpies of the noted polymorphs in the same solution (methanol). Based on ΔH tr 298 (I→II), differences between temperature dependencies of heat capacities of both modifications and the vapor pressure value of form II at 391 K, the temperature dependence of saturated vapor pressure and thermodynamic sublimation parameters for modification II were also estimated (ΔG sub 298=56.1 kJ mol−1; ΔH sub 298=115.9�0.9 kJ mol−1; ΔS sub 298=200�3 J mol−1 K−1). The results indicate that the modifications are monotropically related, which is in contrast to findings recently reported found by classical thermochemical methods.

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Abstract  

Derivatograph Q-1500D was completed with a partial vapour pressure control unit in order to study the sorption phenomena. The proposed arrangement allows to perform time consuming experiments at ambient atmospheric pressure in the temperature range 10–200°C.

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Journal of Thermal Analysis and Calorimetry
Authors: F. Chehimi-Moumen, P. Llewellyn, F. Rouquerol, G. Vacquier, D. Ben Hassen-Chehimi, M. Ferid, and M. Trabelsi-Ayadi

Summary  

The aim of this work is the optimization of the preparation of anhydrous gadolinium hydrogen phosphate with good fluorescence properties. The products obtained by dehydration of gadolinium hydrogen phosphate trihydrate depend on the conditions chosen for the thermal treatment. For this reason, the dehydration was followed by Constant Rate Thermal Analysis whilst strictly controlling the water vapour pressure above the sample. Intermediate samples, obtained during dehydration were characterised by IR spectroscopy and X-ray diffraction. It has thus been shown that the thermal pathway taken for the dehydration depends on the water vapour pressure above the sample in the region from 10-2to 5 mbar. Under the lowest water vapour pressure (510-3mbar), the elimination of the crystallization water is carried out in a continuous way and produces a quasi-amorphous intermediate. Under higher water vapour pressure (5 mbar), well crystallized intermediate products are obtained. The results obtained suggest that the trihydrate contains zeolitic water which confirms a prior structural study.

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A second generation twin double microcalorimeter

Measurements of sorption isotherms, heats of sorption and sorption kinetics

Journal of Thermal Analysis and Calorimetry
Authors: I. Wadsö and L. Wadsö

Abstract  

A calorimetric method for the study of solid-vapor interactions is described. In one calorimetric chamber a vapor evaporates; in a second calorimetric chamber the vapor is absorbed by a sample. The two chambers are connected by a tube and form part of a double twin microcalorimeter. As vapor is sorbed by the sample the vapor pressure in the sorption chamber will increase from a low value to near saturation. The flow rate of the vapor is governed by diffusion through the tube between the vessels. From the thermal power measured in the vaporization calorimeter it is possible to evaluate the sorption isotherm, and using information from both calorimeters the heat of sorption may be calculated as a function of equilibrium vapor pressure. By conducting experiments with different sized samples it is also possible to study the kinetics of the sorption process. The paper describes some recent improvements of the technique and gives examples of its use.

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