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1.
The thermal decomposition of CdCO3 has been studied by DTA on samples of different origins. A classical experimental device enables work at different pressures up to 12 bar for any gas used. Evaluation of the data measured by the author and their comparison with those given by others show that the carbonates obtained by the chemical method are different from those prepared by hydrothermal crystallization. As the latter exhibit higher thermal stability, they may permit a further, real thermodynamic study on the decomposition of cadmium carbonate.  相似文献   

2.
Résumé On a étudié la réaction à l'état solide et fondu entre l'oxyde de chrome trivalent et les nitrates alcalins par analyse thermogravimétrique et analyse thermique différentielle. Les conditions optimales pour l'oxydation complète du chrome(III) en chrome(VI) ont été déterminées. De plus, on a établi le rendement de la réaction. La spectrophotométrie d'absorption infrarouge a permis d'identifier les phases formées aux divers stades de la réaction.
The reaction between trivalent chromium and alkali nitrates in the solid and molten phase was studied by thermogravimetry and differential thermal analysis. The optimum conditions for the oxidation Cr(III) Cr(IV) as well as the yield were determined. The phases existing at various reaction stages were identified by infrared spectroscopy.

Zusammenfassung Die Reaktion in fester sowie in geschmolzener Phase zwischen dreiwertigem Chrom und Alkalinitraten wurde thermogravimetrisch und differential-thermoanalytisch geprüft. Die optimalen Umstände der Oxydation Cr(III) Cr(VI) sowie die Reaktionsausbeute wurden bestimmt. Durch infrarote Spektroskopie wurden die in verschiedenen Reaktionszeitpunkten vorliegenden Phasen identifiziert.

() () . Cr(III) Cr(IV) . .
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3.
Résumé On dose, à l'état solide, des mélanges chromate-bichromate de potassium, à côté d'oxyde de chrome(III), par spectrophotométrie d'absorption infrarouge et par analyse thermique différentielle. Certains aspects de la dissociation du bichromate de potassium ont été mis en évidence.
Mixtures of chromate and dichromate were determined in the presence of chromium(III) by infrared spectroscopy and differential thermal analysis. Questions connected with the dissociation of potassium dichromate were also treated.

Zusammenfassung Es wurde über die Bestimmung von Chromat-Bichromat Gemischen in fester Phase durch infrarote Spektroskopie und Differentialthermoanalyse in Gegenwart von Chrom(III) berichtet. Fragen der Dissoziation von Kaliumbichromat wurden ebenfalls erörtert.

() (III). .
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4.
Résumé On a étudié le comportement thermique sous oxygène des acides humiques et de leurs sels de sodium. On prépare les humates de sodium, soit par neutralisation des acides humiques, soit par dialyse de leurs pseudo-solutions dans la soude. L'examen des spectres infrarouges et de diffraction X des prélèvements effectués entre les étapes de dissociation (suivie par ATD-TG -TGD) suggère un double mécanisme. Au-dessous de 500°, il s'est formé du carbonate de sodium et du carbone. Dès 600°, débute la dissociation du carbonate. Le carbone restant s'oxyde brutalement à 770°. L'importance de la réaction varie avec la teneur initiale en sodium.
The thermal behaviour of humic acids and their sodium salts in oxygen has been studied. The sodium humates were prepared by neutralization of humic acids or by dialysis of their pseudosolutions in sodium hydroxide. Infrared and X-ray diffraction spectra of samples taken between the dissociation steps obtained from the DTA-TG-DTG curves suggest a double mechanism. Below 500°, sodium carbonate and carbon are formed. At 600°, the dissociation of carbonate starts. The residual carbon burns at once at 770°. The extent of reaction changes with the amount of sodium initially present.

Zusammenfassung Es wird über die Untersuchung der thermischen Eigenschaften von Huminsäuren und ihren Natriumsalzen unter Sauerstoff berichtet Letztere wurden entweder durch Neutralisation der entsprechenden Huminsäuren oder durch Dialyse ihrer Pseudolösungen in Natriumhydroxyd erzeugt. Die infrarotspektroskopische und röntgenanalytische Prüfung von zwischen zwei (durch DTA, TG und DTG verfolgte) Dissoziationen entnommenen Proben zeigt zwei Vorgänge. Unter 500° werden Natriumkarbonat und Kohle gebildet. Bei 600° beginnt die Dissoziation des Karbonats. Die zurückbleibende Kohle wird bei 770° plötzlich oxidiert.

Na- . . - , ( — ), . 500° . 600° . 770°. .


En l'honneur du 70e anniversaire du Professeur Clément Duval. Etude entreprise dans le cadre des travaux de l'Equipe de Recherche Associée du C. N. R. S. n 220 (Pédologie des Pays Atlantiques).  相似文献   

5.
Résumé On a modifié la méthode différentielle pour le calcul des paramètres cinétiques des réactions de décomposition thermique du type: A(s) B(s) + C(g), en utilisant les données de l'analyse thermodifférentielle. En effectuant le calcul des paramètres cinétiques des réactions de déshydratation de l'oxalate de calcium monohydraté et de décomposition du carbonate de calcium on obtient des résultats qui concordent d'une manière satisfaisante avec ceux obtenus par d'autres méthodes.
A modification of the differential method is presented in order to evaluate the kinetic parameters of thermal decomposition reactions of the type A s B s + +Cg, using differential thermal analysis (DTA) data. The kinetic parameters calculated for the dehydration and decomposition of calcium oxalate and carbonate agree satisfactorily with those mentioned in the literature.

Zusammenfassung Es wird über eine Abänderung der Differentialmethode zur Errechnung der kinetischen Parameter von thermischen Zersetzungsreaktionen des Typs A(s) B(s) + C(g) mit Hilfe von differentialthermoanalytischen Daten berichtet. Die am Beispiel der Dehydratation des Calciumoxalat-Monohydrats und der Zersetzung des Calciumcarbonats erhaltenen Ergebnisse der auf angegebene Weise durchgeführten kinetischen Berechnungen stimmen gut mit den nach anderen Methoden erhaltenen Resultaten überein.

A(s) (s) + C(g), (). , , , .
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6.
The study of a new spherically symmetrical apparatus to measure heat conductivity of particular liquids under transient heat transfer conditions is proposed. Three experimental investigations on paraffin oil, cyclohexanon, and macromolecular solution are presented.  相似文献   

7.
A method is described where the simultaneous measurement of a thermal flow (by means of Tian-Calvet type calorimetry) and of a gas flow (by means of constant decomposition rate thermal analysis) allows the knowledge at any time of the instantaneous enthalpy of thermal dissociation. The method is used to study the thermal decomposition of an industrial Al(OH)3 gibbsite sample.  相似文献   

8.
Cd(NO3)2 undergoes a phase transition at 160°C. The high temperature form is cubic and isomorphic with M(NO3)2 (M = Ba, Ca, Sr, Pb). The crystal structure of the low temperature phase has been solved by X-ray diffraction at 20°C, using 774 independent reflections collected with a 4-circle diffractometer. The dimensions of the orthorhombic unit cell are: a ? c = 7.5073 (14) Å, b = 15.3692 (35) Å, Z = 8, space group Pca21. The structure has been refined to the final weighted R = 0.044. The cadmium atoms are nearly in a face-centered arrangement. Each cadmium is octahedrally surrounded by six oxygen, the CdO distances varying from 2.34 to 2.46 Å. Each nitrate group belongs through its three oxygens to three different octahedra. The structural change cubic Cd(NO3)2 → orthorhombic Cd(NO3)2 is characterized by a small rotation of NO3 groups in their plane; the face-centered array of cadmium atoms is only slightly modified. The coordination of cadmium atoms changes from 12 to 6, and the approximate doubling of parameter (b) as well as the difference of symmetry can be explained by two different directions of rotation of the NO3 groups situated in the same plane.  相似文献   

9.
Thermogravimetry and differential thermal analysis were used to study hydrated sodium peroxide and the so-called anhydrous commercial product. Prolonged dehydration of the octahydrate under vacuum led to the partial formation of Na2O2-H2O2 compounds as well as the dihydrate and monohydrate The DTA curves for commercial sodium peroxide heated in air or other gases, showed the partial formation of Na2O2·2H2O2·nH2O and of NaHCO4·H2O by the action of the gases on the NaO2 contained in the Na2O2.  相似文献   

10.
The thermal behaviour of PbSnF4 has been studied by means of a differential scanning calorimeter over the range 298–700 K. Five allotropic forms of PbSnF4 have been found and the associated enthalpies of transition have been measured. The crystallographic data have been determined for the allotropes by single cristal studies.
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11.
To obtain more information on the reactions during the pyrolysis of polyacrylonitrile at 290° in air, we studied the thermal degradation of its trimers, tetramers and pentamers having the general formula: R  CH(CN)  CH2  CH(CN)n?1  R where R = H or CH3 and n = 3,4,5. Study by gas chromatography of the volatile compounds produced during pyrolysis at 290° and 770° showed that the first step of the degradation is homolytic scission of the chain. There are then intra and intermolecular polymerisations of the nitrile groups and formation of a ladder polymer. This reaction is clearly exothermic only for pentamers. This increase of the reactivity with DP is borne out by a kinetic study by EPR of the pyrolysis in air at 290°, oxidation of the ladder polymer giving a paramagnetic solid. Its EPR characteristics (band width and number of spins per g) are very dependent of the DP and nature of the end-groups, H or CH3, of the pyrolysed oligomer.  相似文献   

12.
The thermodynamic study of the different compounds of the system MgCl2, H2O, HCl allows to draw the stability diagram of the 8 solid phases into a three-dimensional space (temperature, total pressure and ratio of HCl and H2O partial pressures). The evolution of the composition of solid and gaseous phases during an isobaric heating is described. The conclusions of this study are in good agreement with the experimental results obtained in laboratory and with the industrial requirements set for the different steps of the dehydration of MgCl2.  相似文献   

13.
The study of nickel and iron ex-carbonyl powders, using various thermal analysis techniques permitted clarification of the initial mechanism of sintering. Solid-gas reactions prior to “bridging” of grains were determined: water desorption, reduction of oxygen and carbon-monoxide surface groups, decomposition of carbides. Initiation of sintering (bridging) can be explained by the prominent part played by impurities and particularly carbon.  相似文献   

14.
Résumé Une méthode d'analyse débitmétrique à laquelle peut Être associée ATD est présentée. Elle s'applique à l'étude de réactions de la forme solide 1 solide 2+gaz dans des domaines de températures et de pressions jusqu'à 900 et 150 bar.On décrit le principe de la mesure et les conditions de fonctionnement d'un dispositif expérimental plus particulièrement mis au point pour l'étude de la décomposition thermique de CdCO3 en atmosphère de CO2.Cette méthode sensible et précise permet d'obtenir des résultats quantitatifs.
An experimental device based on the measurement of gas flow rate is described, to which a DTA apparatus can be attached. The method is suited to the investigation of reactions of the type Solid1Solid2+gas, in the temperature interval up to 900C and at pressures up to 150 bar. The principle of the measurements is given, as well as the working conditions of an experimental device constructed specially to study the thermal decomposition of CdCO3 in a CO2 atmosphere.This sensitive and accurate method enables quantitative results to be obtained.

Zusammenfassung Es wird eine Methode der Strömungsmessungs-Analyse beschrieben, an die DTA angeschlossen werden kann. Sie eignet sich zum Studium von Reaktionen des Typs: Festkörper 1 Festkörper 2 + Gas im Temperatur- und Druckbereich bis zu 900, bzw. 150 bar.Das Meßprinzip wird beschrieben, sowie die Betriebsbedingungen einer besonders zum Studium der thermischen Zersetzung von CdCO3 in CO2-Atmosphäre entwickelten Versuchsvorrichtung.Diese empfindliche und genaue Methode ermöglicht quantitative Ergebnisse.

, , . = + 900 150 . , CdCO3 2. , , .
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15.
16.
Journal of Thermal Analysis and Calorimetry - Les difficultés de l'étude des résidus d'évaporation de solutions mixtes de Ca(HCO3)2 et de Mg(HCO3)2, par les...  相似文献   

17.
Thermogravimetric and differential thermal methods as well as chemical analysis show that sodium peroxide attacks beryllium oxide to form beryllate, apparently in the molecular ratio 1 Na2O:1 BeO. An unidentified peroxy compound of beryllium is formed at about 165° by the action of the NaO2 present in the Na2O2 sample; it decomposes between 280 and 310°. IR absorption spectroscopy indicates the presence of Be-O bonds in the sodium beryllate which are different from those in the oxide used.  相似文献   

18.
Résumé Les paramètres cinétiques de la décomposition du complexe CdPy2Br2 ont été déterminés à l'aide de plusieurs méthodes nonisothermes à l'aide des données fournies par la thermogravimétrie et l'ATD. Les valeurs obtenues concordent de faÇon satisfaisante.
Six nonisothermal thermogravimetric and DTA methods have been applied for determining the kinetic parameters of the decomposition of CdPy2Br2. The values obtained are in satisfactory agreement.

Zusammenfassung Die kinetischen Parameter der Zersetzung des Komplexes CdPy2Br2 wurden durch verschiedene nicht-isotherme Methoden, durch Thermogravimetrie und Differentialthermoanalyse bestimmt. Die Resultate stimmten gut überein.

6 CdPy2Br2. .
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19.
Radiactive decay chains, composed of two radionuclides have been classified into six different categories. Equations expressing the total activity of the chain were systematically applied to 41 radioisotopes. Conditions necessary to the observation of a maximum activity were determined for every chain. The case of the99Mo was studies experimentally, and a maximum of activity was observed with a good concordance with calculated values.   相似文献   

20.
Journal of Thermal Analysis and Calorimetry - L'adsorption de vapeur d'eau sur montmorillonite lithique en provenance de Marnia et Camp Berteaux a été analysée après...  相似文献   

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