Contribution de l'analyse thermique a l'etude des acides humiques et de leurs sels de sodium

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.

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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.

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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.

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

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En l'honneur du 70^e 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).     

Contribution a l'etude de la conductivite thermique de liquides et solutions

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.     

Analyse par activation non destructive: Contribution a l'etude des conditions d'analyses exactes

In non destructive activation analysis, either relative measurements or parametric counting techniques are used. However, in so complex media as biological or geological samples, where a lot of radionuclides are produced, an accurate determination of an element, must take into account, the “background shape and height effect” due to the other radionuclides. To achieve accuracy in such determinations, a new method is developed.     

Contribution a l'etude des echangeurs inorganiques: Echangeurs a base de plomb(II)

Sorption properties of Pb²⁺ compounds (fluoride, ferrocyanide, oxyde) have been investigated by tracers methods and batch equilibrium study. The fluoride exibits high selectivity and capacity values for REE and the ferrocyanide, high selectivity for Cs and transition ions. The great solubility of the oxyde in acidic ambients limits its analytical value. Adsorption on lead fluoride seems to be governed by the formation of a low solubility product while on ferrocyanide ion exchange phenomenons are predominant.      

Contribution a l'etude du systeme PbO-PbSO4

Résumé Les auteurs étudient le système PbO-PbSO₄ entre 400 et 900°. Trois sulfates basiques sont mis en évidence et caractérisés par leur spectre de diffraction X: PbO, PbSO₄; 2PbO, PbSO₄ et 4PbO, PbSO₄.L'analyse thermique différentielle effectuée sur le sulfate dibasique Pb₃SO₆ montre que la forme de basse température se transforme à 450° en une forme. Cette variété instable à cette température se décompose progressivement en sulfates mono et tétrabasique. Ces derniers se recombinent vers 620° pour redonner le sulfate dibasique.La forme est monoclinique (a=7.814 Å, b=5.803 Å, c=8.035 Å,=102.64°, Z=2, groupe de symétrie P 2₂ ou P 2₁). L'analyse radiocristallographique à haute température a permis de caractériser la forme.

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The behaviour of the system PbO-PbSO₄ was studied between 400 and 900°. Three basic sulphates could be identified by X-ray diffractometry namely: PbO · ·PbSO₄; 2 PbO·PbSO₄ and 4 PbO·PbSO₄.Differential thermal analysis of the dibasic sulphate Pb₃SO₆ has shown that the-modification which is stable at lower temperatures, transforms into a-form at 450°. The latter is an unstable modification which gradually decomposes to form mono- and tetrabasic sulphates. These compounds form dibasic sulphate again at about 620°.The-modification is monoclinic (a=7.814 Å,b=5.803 Å,c=8.035 Å,=102.64°, Z=2, symmetry groups P2₁ or P2₁/m). The-form could be characterized at a higher temperature by radiocrystallographic analysis.

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Zusammenfassung Es wurde das Verhalten des Systems PbO-PbSO₄ zwischen 400 und 900° untersucht. Drei basische Sulfate konnten durch Röntgen-Diffraktion identifiziert werden: PbO, PbSO₄; 2PbO, PbSO₄ und 4PbO, PbSO₄.Die Differentialthermoanalyse des zweibasischen Sulfats Pb₃SO₆ zeigte, daß die bei niedriger Temperatur stabile -Modifikation bei 450° in eine -Form übergeht. Diese ist eine unstabile Modifikation, die sich sukzessiv in mono- und tetrabasische Sulfate zersetzt. Letztere bilden gegen 620° erneut das dibasische Sulfat.Die-Modifikation ist monoklin (a=7.814 Å. b=5.803 Å, c=8.035 Å,=102.64°, Z=2, Symmetriegruppe P 2₁ oder P 2₁/m). Durch radiokristallographische Analyse konnte auch die-Form bei hoher Temperatur charakterisiert werden.

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PbO-PbSO₄ 400– 900° . Pb. PbSO₄, 2 b. PbSO₄ 4b. PbSO₄. () Pb₃SO₆. , - , , 450° -. - , . 620°.- (a=7.814 Å, b=5 803 Å, c=8.035 Å, =102.64°).- .

     

Contribution a l'etude du systeme ternaire aluminium-zinc-etain

This work is a study of theL?S andS?S equilibria in the ternary system Al-Zn-Sn. The diagram has been established by an isopleth cutting method using coupled direct and differential thermal analysis and an electron probe microanalyser. This study has permitted:

confirmation of the existence of invariant ternary reactions suggested in the literature;

demonstration of the existence, shape and limits of the SSα′ solid solution presenting tin retrograde solubility;

determination of the critical point temperature of the monovariant liquid curve conjugated toSSα andSSα′ solids (446?) rich in aluminium,

     

Contribution a l'etude de la fluorescence x induite par des particules chargees de moyennes energies

The apparatus mounted beside the Saclay variable-energy cyclotron to develop this new analytical technique is described. Photon emission yield measurements were carried out on copper, selenium and gold bombarded with 5 to 20 MeV protons and 10 to 28 MeV α-particles; the results obtained are given. The method is applied to the analysis of dusts collected on atmospheric sampling filters. These tests show that optimum experimental conditions are obtained by the use of 2 to 3 MeV protons or 8 to 12 MeV α-particles; it is established moreover that intrinsically the latter give the best results.     

Application des methodes thermoanalytiques a l'etude des solides divises

Résumé L'application des méthodes thermoanalytiques à l'étude des solides finement divisés s'avère dans certains cas plus efficace que celle de la diffraction des rayons X. A propos d'oxydes constitués de cristallites de quelques dizaines d'angströms, nous montrons comment la TG et l'ATD ont permis une caractérisation de phases. Celles-ci, qualifiées généralement et hâtivement «d'amorphes» n'avaient pu, pour la plupart, être mises en évidence jusque là.

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The application of thermoanalytical methods to study finely-divided solids is found more efficient in some cases than X-ray diffraction. For oxides whose crystallite size is in the range of a few ten angströms, it is shown how TG and DTA have allowed phase identifications. The majority of these phases, called generally and prematurely amorphous had not previously been yet reported.

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Zusammenfassung Der Einsatz thermoanalytischer Methoden zur Untersuchung fein verteilter Feststoffe erweist sich in gewissen Fällen als wirksamer als die Anwendung der Röntgendiffraktion. An Hand von Oxiden, welche aus Kristalliten der Grössenordnung einiger zehn Angström bestehen, wird gezeigt, in welcher Weise die Thermogravimetrie und die Differentialthermoanalyse eine Charakterisierung der Phasen gestatten. Die im allgemeinen voreilig als amorph bezeichneten Phasen konnten größtenteils bis jetzt nicht nachgewiesen werden.

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, - , , , . , ** , , . , , .

     

Contribution a l'etude du maximum d'activite globale de chaines radioactives

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.      

Contribution a l'etude du maximum d'activite globale de chaines radioactives

The total activity of a radioactive decay chain presents a maximum in many cases, but the maximum can seldom be observed. General equations are developed, which take into account branching ratios, emissions, formation and counting yields. This mathematical model is applicable by analogy to other systems with same kinetics.      

Contribution a l'etude de l'oxyde de cadmium en milieu alcalin

Résumé L'étude de la réaction de NaOH sur CdO ou Cd(OH)₂ a nécessité de reprendre celle des courbes ATG et ATD de NaOH à différents stades de pureté. Ceci a permis, en particulier, de préciser l'existence de l'eutectique ternaire NaOH-Na₂O-Na₂CO₃ dans les mélanges réactionnels traités, d'exclure la possibilité de la présence de peroxyde. Le produit de la réaction, obtenu avant 130°, est plus stable à la chaleur que NaOH. Son spectre IR est compatible avec l'existence d'un hydroxocadmiate de sodium.

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The investigation of the reaction of sodium hydroxide with CdO or Cd(OH)₂ made necessary some studies on the DTA and TG curves of sodium hydroxide samples of different purities. These studies have evidenced the formation of a ternary eutectic NaOH-Na₂O-Na₂CO₃ in the heat-treated reaction mixtures, and have also shown that no peroxide is present. The product of reaction obtained below 130° had a greater thermal stability than NaOH. On the basis of the infrared spectrum the existence of a sodium hydroxocadmiat can be assumed.

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Zusammenfassung Die Untersuchung der Reaktion von Natriumhydroxyd mit CdO oder Cd(OH)₂ erforderte eine neue Untersuchung der DTA und TG Kurven des NaOH von verschiedenem Reinheitsgrad. Dies bewies das Vorhandensein eines ternären Eutektikums NaOH-Na₂O-Na₂CO₃ in den behandelten Reaktionsgemischen, weiterhin, daß kein Peroxyd gegenwärtig ist. Das vor 130° erhaltene Reaktionsprodukt besitzt höhere thermische Stabilität als NaOH. Aufgrund der infraroten Spektren darf die Existenz eines Natriumhydroxocadmiats angenommen werden.

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NaOH CdO Cd(OH)₂ . NaOH-Na₂O-Na₂CO₃ . , 130°, , NaOH. - .

     

Application des methodes d'analyse thermique a l'etude du frittage des poudres metalliques

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.     

Le developement de l'etude de la diffusion de la lumiere et des neutrons par les polymeres a strasbourg

In this paper one recalls the history of the development of scattering studies after the first world war in Strasbourg. Tremendous progress has been made and some examples of this progress are discussed     

Contribution a l'etude de la decomposition thermique du carbonate de cadmium

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.     

Construction d'un enthalpimetre adapte a l'etude des equilibres solide-liquide multiconstitues

In order to study solid-liquid equilibria in multicomponent systems, an enthalpimeter has been built and perfected. Measurements can be carried out between —100 and +150°. During the thermal analysis, samples are continually stirred and heated, or cooled, at constant flow rate.In these conditions, reproducible and accurate results are obtained and very closed temperature phenomena may be separated. As an illustration, the ternary system waterstrontium choride-barium chloride has been studied at low temperature and the polythermic diagram is described up to 100°.

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Zusammenfassung Für die Untersuchung von fest-flüssig-Gleichgewichten in Multikom-ponentensystemen wurde ein Enthalpiemeter gebaut und verbessert. Darin können Messungen zwischen –100 und + 150°C durchgeführt werden. Während der Thermoanalyse werden die Proben bei konstanter Duchsatzgeschwindigkeit ständig gerührt und erhitzt oder gekühlt. Unter diesen Bedingungen werden reproduzierbare und sehr genaue Ergebnisse erzielt und sehr eng beieinanderliegende Temperatur-phänomene können getrennt werden. Als Beispiel wurde das ternäre System Wasser-Strontiumchlorid-Bariumchlorid bei niederen Temperaturen untersucht und ein polythermisches Diagramm bis 100°C erstellt.

     

Contributions a l'etude cinetique des decompositions endothermiques dans des systemes solide-gaz,a l'aide des donnees thermogravimetriques

Résumé On a déterminé les paramètres cinétiques des réactions de décomposition de quelques combinaisons complexes des halogénures et pseudohalogénures de cobalt, nickel, manganèse, cuivre et cadmium, avec l'ammoniaque, la pyridine et des pyridines substituées. Pour les réactions d'ordre zéro, les valeurs des facteurs préexponentiels, calculées en considérant comme étape limitante la diffusion du composant volatil à travers la couche de la substance décomposée, concordent de façon satisfaisante avec celles déterminées expérimentalement.

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Kinetic parameters were determined for the decomposition reactions of some com plexes of cobalt, nickel, manganese, copper and cadmium halides and pseudohalides with ammonia, pyridine and substituted pyridines. For the zero order reactions, the values of the pre-exponential factors calculated assuming as limiting step the diffusion of the volatile component through the layer of the decomposed substance, are in satisfactory agreement with the experimental values.

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Zusammenfassung Es wurden die kinetischen Parameter der Zersetzungsreaktionen einiger Komplexe der Halogenide und Pseudohalogenide von Kobalt, Nickel, Mangan, Kupfer und Kadmium mit Ammoniak, Pyridin und substituiertem Pyridin bestimmt. Bei den Reaktionen von Null-Ordnung zeigten die preexponentiellen Koeffizienten, berechnet, indem für die limitierende Stufe die Diffusion des flüchtigen Bestandteils durch die Schicht der zersetzten Substanz betrachtet wurde, gute Übereinstimmung mit den experimentellen Werten.

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Application de la calorimetrie AC a l'etude des transitions a l'etat solide des cristaux plastiques

In this work we give the specific heat values of different plastic crystals, determined by AC calorimetry are presented. The heat capacity evolution during different types of solid transitions in these molecular crystals is compared. The influence of the kinetic of the transformation on the shape of this evolution can be seen.     

Contribution a l'etude des systemes Ca3(PO4)2-MSO4 (M=Sr,Ba)

In the systems Ca₃(PO₄)₂-MSO₄ (M = Sr, Ba), the series of single phase Ca_21?3xM_2xI(PO₄)_14?2x(SO₄)_2x with 0<x<0.15 forM=Sr and 0<x<0.1 forM = Ba have been prepared. These solid solutions, respectively strontium phosphosulfate and barium phosphosulfate, are isostructural with anhydrous tricalcium orthophosphate. They have been characterized by their infrared spectra and their crystallographic unit cell parameters.     

Sur un dilatometre-conductimetre pour l'etude des transformations en phase solide a haute temperature

The apparatus described produces the change of both thermal expansion and electrical conductivity as a function of temperature, simultaneously, in the temperature range between 20°–1550°. Two examples are given:i) study of the monoclinicquadratic transformation of a zirconia sample [comp. (ZrO₂)_0.95(CaO)_0.05],ii) study of an order-desorder transformation on a sample composed of (HfO₂)_0.84(Y₂O₃)_0.16.     

Contribution a l'etude de la determination du fluor a la surface des metaux par detection des photons gamma prompts de la reaction19F(p, αγ)16O

The 837 keV resonance is used for the rapid and non-destructive determination of the gradient of fluorine on the surface of metallic samples. The precise yield curve of this resonance for thick target and the experimental sensitivity of the method have been determined. With this method less than 5·10^?4 μg·cm^?2 fluorine content can be measured. The resolution is of the order of 1000 Å in aluminium and the concentration profiles can be measured to the depth of 1 μm. The time requirement of a surface analysis is 15–30 min, and 2–3 hrs of a gradient measurement. In addition, this method is simpler and more sensitive than the detection of the 1350 keV alpha-particles from the¹⁹F(p, α_o)¹⁶O reaction.