Showing papers in "Journal of Thermal Analysis and Calorimetry in 1977"
TL;DR: Rational approximations have been derived for the integral of the Arrhenius function dT which is important in the kinetic analysis of thermogravimetric data and is found to be equivalent to the Gorbachev approximation.
Abstract: Rational approximations have been derived for the integral of the Arrhenius function
$$\int\limits_0^T {\exp ( - E/RT)}$$
dT which is important in the kinetic analysis of thermogravimetric data. The first degree rational approximation is found to be equivalent to the Gorbachev approximation, i.e., RT2
exp (−E/RT)/(E+2RT). The second degree rational approximation is more accurate than the Zsako empirical approximation when E/RT 5. The third and higher degree rational approximations are found to be more accurate than any other previous approximation.
681 citations
TL;DR: In this paper, a DTA was linked to non-dispersive infrared H2O and CO2 analyzers and an SO2 analyzer based on an electrochemical cell, enabling evolution profiles of these three volatiles to be recorded simultaneously with the DTA curve.
Abstract: A DTA apparatus has been linked to non-dispersive infrared H2O and CO2 analyzers and an SO2 analyzer based on an electrochemical cell, enabling evolution profiles of these three volatiles to be recorded simultaneously with the DTA curve. Examples are given of the use of the combined DTA-EGA method in the determination of the quantitative mineralogical composition of potential industrial raw materials.
67 citations
TL;DR: In this article, the exponential integral in non-isothermal kinetic equations for tempering with linear heating was represented in the following analytical form, which is one order inkT/E≪1 more accurate than two other representations recently proposed in this journal.
Abstract: The exponential integral in non-isothermal kinetic equations for tempering with linear heating can be represented in the following analytical form
$$\int\limits_0^T {e^{ - E/kT'} dT'} = \frac{{kT^2 /E}}{{\sqrt {1 + 4kT/E} }}e^{ - E/kT} ,$$
which is one order inkT/E≪1 more accurate than two other representations recently proposed in this journal [1, 2]. A few variants of approximated forms for the exponential integral are compared with regard to the error due to the kind of approximation, which appears when activation energies are evaluated from experimental non-isothermal kinetic curves.
50 citations
TL;DR: In this paper, the influence of residual pressure in the range from 10−5 to 5 torr on the course of thermal analysis was examined and it was shown that the residual pressure is of virtually no use unless the rate of decomposition is also controlled.
Abstract: This paper examines the influence of residual pressures in the range from 10−5 to 5 torr on the course of thermal analysis. With the help of examples concerning in particular the thermolysis of gibbsite, A1(OH)3, it is shown that a) the control of residual pressure is of virtually no use unless the rate of decomposition isalso controlled (otherwise, the TG curves represent a composite phenomenon, which is practically unintelligible); b) the influence of residual pressure may be unexpectedly high both on the shape of the TG curves (and therefore on the apparent kinetic parameters) and on the nature (porosity, structure) of the products.
39 citations
TL;DR: In this article, Brucite and two precipitated Mg(OH)2 samples were analysed in a simultaneous TG-DTG-DSC analyser, and the activation energies deduced by Freeman and Carroll's method are very different from one another.
Abstract: Natural brucite and two precipitated Mg(OH)2 samples were analysed in a simultaneous TG-DTG-DSC analyser. The initial dehydroxylation temperature of natural brucite is lower than those of the precipitated samples, but the maximum and final temperatures of the former are higher than those of the latter. The maximum temperatures of individual samples obtained from DTG and DSC curves are almost the same. Heats of reaction derived from peak areas for the three samples are not exactly the same, as they are influenced by the specific surface area of the individual sample. Activation energies deduced by Freeman and Carroll's method are very different from one another. This is attributed to the difference in pressure when the sample is crimped. A linear relationship is observed between the deduced activation energy and the specific height of the DSC peak.
28 citations
TL;DR: In this paper, isothermal-thermogravimetric analyses were used to obtain kinetic data on the CFx decomposition and time curves were obtained for compounds having stoichiometries CF0,61, CF0.96, CF1.08, and CF 1.12 for several different temperatures over the range 450-650° and in both a nitrogen atmosphere and in vacuum.
Abstract: Isothermal-thermogravimetric analyses were used to obtain kinetic data on the CFx decomposition. Weight of samplevs. time curves were obtained for compounds having stoichiometries CF0,61, CF0.96, CF1.08, and CF1.12 for several different temperatures over the range 450–650° and in both a nitrogen atmosphere and in vacuum. A small percentage of fluorine in the atmosphere was shown to strongly inhibit thermal decomposition.
28 citations
TL;DR: In this paper, a derivatograph of sunflower and rapeseed oils using both dynamic and static temperature programs was used to find the optimum experimental conditions for studying the oxidative stability of edible oils, in order to determine their storability.
Abstract: The thermooxidative behaviour of sunflower and rapeseed oils has been investigated by means of a derivatograph, using both dynamic and static (isothermal) temperature programs. The aim was to find the optimum experimental conditions for studying the oxidative stability of edible oils, in order to determine their storability. A novel method has been developed for the rapid indication of stability by modelling the oxidative changes under isothermal conditions.
25 citations
TL;DR: The environment can influence the thermal decomposition of an oxysalt by causing a change in the course of chemical decomposition or causing an alteration in the physical nature of the solid product or solid intermediates as mentioned in this paper.
Abstract: The environment can influence the thermal decomposition of an oxysalt by;
(a)
causing a change in the course of chemical decomposition or
(b)
causing an alteration in the physical nature of the solid product or solid intermediates.
25 citations
TL;DR: In this paper, non-isothermal thermogravimetric analysis was used for determination of the kinetics of aluminium hydroxide dehydration in an air atmosphere and for processing of the experimental results by the method due to Chatterjee.
Abstract: Non-isothermal thermogravimetric analysis was used for determination of the kinetics of aluminium hydroxide dehydration in an air atmosphere and for processing of the experimental results by the method due to Chatterjee.
23 citations
TL;DR: In this article, the authors studied the oxidative behavior of synthetic millerite (Ni0.994S) in a dynamic oxygen atmosphere (0.2 l min−1) over the temperature range 20-1000° (heating rate 10° min− 1).
Abstract: The oxidative behaviour of synthetic millerite (Ni0.994S) has been studied by TG and DTA in a dynamic oxygen atmosphere (0.2 l min−1) over the temperature range 20–1000° (heating rate 10° min−1). EGA was carried out by a coupled mass spectrometer. The reaction products at various intermediate temperatures were characterized by X-ray powder diffractometry. A reaction sequence has been deduced, in which in the temperature range 550–700° complete oxidation of Ni0.994S had occurred with the formation of NiSO4, Ni3S2, NiO and possiblyα-Ni7S6. Between 700–800°, NiSO4 continued to be formed, whilst Ni3S2 andα-Ni7S6 were oxidised. Above 800°, NiSO4 decomposed to NiO, the latter being the only species evident above 800°.
21 citations
TL;DR: In this paper, a derivatographic study was made of the influence of the slow heat transport between the sample and its surroundings upon the courses of exothermic transformations, and it was found that if the sample was placed in a thin film layer on the multiplate sample holder and the quasi-isothermal heating technique was applied, then the rate of the decomposition could already be regulated at will, up to a certain limit.
Abstract: A derivatographic study was made of the influence of the slow heat transport between the sample and its surroundings upon the courses of exothermic transformations. It was found that if the sample was placed in a thin film layer on the multiplate sample holder and the quasi-isothermal heating technique was applied, then the rate of the decomposition could already be regulated at will, up to a certain limit. Under the conventional thermoanalytical conditions the same sample decomposed in an explosion-like way. The examinations were supplemented with thermo-gas-titrimetric (TGT) measurements.
TL;DR: In this article, the authors investigated the first-order kinetics of bulk crystallization of Se61.5Ge15 4Sb23.1 glasses from their thermal behavior.
Abstract: The kinetics of bulk crystallization of Se61.5Ge15 4Sb23.1 glasses was investigated from their thermal behaviour. In the thermal characterization of a glass the recrystallization temperature is highly dependent on both the rate of heating and the thermal history of the glass. Vitreous samples were prepared by quenching. From ratedependent curves it was found that the recrystallization process obeys first-order kinetics with an apparent activation enthalpy of 48±5 kcal/mole. Further analysis allows determination of both the activation enthalpy,H=90±4 kcal/mole, and the kinetic exponent of the Avrami equation,n=1.9±0.3.
TL;DR: In this article, the melting and crystallization of sorbitol were investigated with the DSC method and thermal microscopy, and two crystalline modifications with different melting points were confirmed by X-ray diffraction.
Abstract: The melting and crystallization of sorbitol were investigated with the DSC method and thermal microscopy. Sorbitol was found to have two crystalline modifications (confirmed by X-ray diffraction) with different melting points, while rapid cooling of molten sorbitol resulted in an amorphous form.
TL;DR: In this article, the thermal properties of metal acrylates were investigated and it was found that metal carbonates or oxides make up the major proportion of the residue obtained after the decomposition of the metal acylates.
Abstract: The thermal behaviours of Na, Ca, Mg and Zn acrylates were investigated by TG and DTA. It was found that the anhydrous acrylates were subject to thermal polymerization processes, which preceded the main decomposition. The presence of oxygen influences the decomposition of the organic part of the molecule very strongly, but it does not markedly affect the extent of polymerization or the type of the resulting solid products. Metal carbonates or oxides make up the major proportion of the residue obtained after the decomposition of the metal acrylates, similarly as in the case of other low molecular monocarboxylic acid salts.
TL;DR: In this article, the eutectic bisulphate systems, ammonium-potassium bisulate and sodium-pot potassium bisulate, appear to be excellent molten solvents in view of their low melting points, long liquid ranges and prolonged thermal stability at 200°.
Abstract: Lithium, sodium, potassium and ammonium bisulphate have been shown by detailed TG/DTA studies to have limited application as molten solvents. By contrast, the eutectic bisulphate systems, ammonium-potassium bisulphate and sodium-potassium bisulphate, appear to be excellent molten solvents in view of their low melting points, long liquid ranges and prolonged thermal stability at 200°. In contrast to previous studies, potassium pyrosulphate has been found to be an excellent molten solvent, provided rigorous preliminary drying procedures have been applied.
TL;DR: Les propionates monohydrates de calcium, strontium and baryum ont ete etudies par radiocristallographie (sur monocristal et sur poudre) and par TG and ATD (a l'air and en milieu inerte).
Abstract: Les propionates monohydrates de calcium, strontium et baryum ont ete etudies par radiocristallographie (sur monocristal et sur poudre) et par TG et ATD (a l'air et en milieu inerte). Ils cristallisent dans les systemes monoclinique (Ca) ou orthorhombique (Sr, Ba). Ils perdent leur eau en une fois (Ca, Sr) ou deux fois (Ba) avec formation d'un hemihydrate intermediaire. Tous les sels anhydres, d'abord amorphes aux rayons X, cristallisent vers 200°. Le propionate de baryum anhydre cristallise subit une transformation polymorphique a 240°. Apres 300° a l'air et 350° sous atmosphere inerte, la fusion et la decomposition se produisent simultanement: il y a degagement de diethylcetone et le residu solide est du carbonate metallique bien cristallise.
TL;DR: In this paper, the influence of factors caused by different experimental conditions on the stoichiometry of thermal decomposition of the complex Ni(NCS)2(β-picoline)4 was studied.
Abstract: The influence of factors caused by different experimental conditions on the stoichiometry of thermal decomposition of the complex Ni(NCS)2(β-picoline)4 was studied. By means of TG it was found that the release ofβ-picoline was shown by the derivatograph (air atmosphere, sample of 50–500 mg, rate of temperature increase 1–6°/min, crucible with a hole in the bottom) in three steps (−2, −1, −1), by the micro-balance (sample of 2.59 mg) in two steps (−2, −2), and by the vacuum thermobalance in one step (−4). Under quasi-isothermal and quasi isobaric conditions in a special crucibleβ-picoline was released in three steps (−1, −2, −1). An analogous result was obtained with the derivatograph using a crucible with a lid. The reasons for these differences are discussed.RésuméOn a étudié l'influence des facteurs en relation avec des conditions d'expérience différentes, sur la stoechiométrie de la décomposition thermique du complexe Ni(SCN)2 (β-picoline)4. On a établi que le dégagement de laβ-picoline s'effectue en trois étapes (−2, −1, −1) si l'expérience TG est réalisée à l'aide d'un Derivatograph (atmosphère d'air, échantillon de 50–500 mg, vitesse d'échauffement 1–6 °C/min, creuset avec fond percé d'un trou), en deux étapes (−2, −2) avec une microbalance (prélèvement de 2.59 mg) et en une étape (−4) si l'expérience TG est réalisée sous vide. En conditions quasi-isothermes et quasi-isobares, dans un creuset de forme spéciale, laβ-picoline se dégage en trois étapes (−1, −2, −1). On parvient à un résultat analogue avec un Derivatograph en utilisant un creuset muni d'un couvercle. On discute les causes de ces différences.ZusammenfassungDer Einfluß verschiedener Versuchsbedingungen auf die Stöchiometrie der thermischen Zersetzung des Komplexes Ni(NCS)2(β-Pikolin)4 wurde untersucht. Mittels TG wurde festgestellt, daß der Derivatograph (Luft-Atmosphäre, 50–500 mg Probe, Geschwindigkeit des Temperaturanstiegs 1 bis 6 °C/min., Tiegel mit Loch im Boden) die Freisetzung desβ-Pikolins in drei Stufen (−2, −1, −1), die Mikrowaage (Probe von 2.59 mg) in zwei Stufen (−2, −2) und die Vakuumthermowaage in einer Stufe (−4) angibt. Bei quasi-isothermen und quasi-isobaren Bedingungen in einem besonderen Tiegel wurdeß-Pikolin in drei Stufen (−1, −2, − 1) freigesetzt. Ein ähnliches Ergebnis wurde mit dem Derivatograph en bei Verwendung eines Tiegels mit Deckel erhalten. Die Ursachen dieser Unterschiede werden erörtert.РезюмеБыло изучено влияние факторов, обусловлен ных различными эксперим ентальными условиями, на стехиом етрию термического р азложения комплекса Ni(NCS)2 (βпиколи н)4. С помощью ТГ было найд ено, что дериватограф (воздушная атмосфера, вес образца 50–500 мг, скорост ь повышения температ уры 1–6 °С/мин, тигель с углубл енным дном) показал выделен ие пиколина в три стад ии (−2, −1, −1), микровесовой (вес обр азца 2.59 мг) — в две стадии (−2, −2) и вакуумно-термовесов ой — в одну стадию (−4). При квази-изобарных усло виях в специальном ти гле выделениеβ-пиколина происходило в три стадии (−1, −2, −1). Аналогич ный результат был пол учен на дериватографе, испол ьзуя тигель с крышкой. Обсу ждены причины этих ра зличий.
TL;DR: A thermal analytical study of Li, Na, K, Rb, Cs, NH4, Mg, Ca, Sr, Ba and Zn dithionates is reported in this article.
Abstract: A thermal analytical study of Li, Na, K, Rb, Cs, NH4, Mg, Ca, Sr, Ba and Zn dithionates is reported. The decomposition of the dithionate ion is endothermic in the case of the Na, K, Rb, Cs and NH4 salts, but exothermic with Li, Mg, Sr, Ba and Zn. Kinetic parameters have been derived from the TG curves by means of the Coats-Redfern method. The validity of a linear kinetic compensation law is reported for the loss of crystal water and separately for the decomposition of the dithionate ion.
TL;DR: Differential scanning calorimetry was used to determine the decomposition heat of decomposition of 1,3,5,7-tetranitro-1, 3, 5, 7tetraazacyclooctane(DADN), 1,5-endomethylene-3, 7-dinitroso-1
Abstract: Differential scanning calorimetry was used to determine the heats of decomposition of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane(HMX), 1,5-diacetyl-3,7-dinitro-1,3, 5,7-tetraazacyclooctane(DADN), 1,5-endomethylene-3,7-dinitro-1,3,5,7-tetraazacyclooctane(DPT), 1,3,5-trinitro-1,3,5-triazacyclohexane(RDX), 1,3,5-trinitroso-1,3,5-triazacyclohexane (R-salt), and 1,5-endomethylene-3,7-dinitroso-1,3,5,7-tetraazacyclooctane(DNPT). The value of the decomposition heat of unit mass of sample was found to increase inHMX, DADN andRDX with decreasing degree of filling of the reaction volume. In the R-salt and inDNPT, however, the trend of this dependence was found to be the reverse and more pronounced. No analogous dependence was found to exist forDPT under the given experimental conditions.
Abstract: Previous studies of fibrous keratins have enabled assignments to be proposed for the endothermic processes identified in the relatively complex DTA curve. From this base, the influence of well defined chemical modifications to keratin on their observed DTA curves has been discussed. Wools are specifically treated commercially to improve shrink resistance and machine washability. To achieve these desired characteristics wools are treated, (a) by special oxidative processes, (b) with specific polymers, and (c) by combinations of (a) and (b). The DTA curves of wool samples which have been subjected to each of the three different treatments were reproducibly recorded. The significance of differences between these curves and that for the untreated fibre are discussed. Although characteristic differences in the DTA curves of wools after specific treatments can be distinguished, differential thermal analysis cannot be regarded as a general tool for such treatment characterisation. It is considered that thermogravimetry should offer a greater potential for this purpose.
TL;DR: In this paper, the authors examined the thermal behavior of ammonium nitrate (AN) and found that phase IV had been transformed to metastable phase III, as a consequence of which the III→II transformation at 86° also became possible.
Abstract: The reason for the special thermal behaviour of ammonium nitrate (AN) has been examined. Under certain experimental conditions more transition temperatures were obtained than hitherto found (37–42°, 50° and 86°). With Du Pont DSC curves several exothermic peaks or exothermic oscillations were shown after the endothermic peak at 51°, indicating that phase IV had been transformed to metastable phase III, as a consequence of which the III→II transformation at 86° also became possible. On repeated cycling the exothermic peak decreased or disappeared if the III→II transformation had developed to a greater extent. A successful IV→III transformation was induced by inoculation of AN with phase III, an unusual procedure in investigating the phase transformation of AN. The use of the method is obvious with regard to the fact that all transformations are controlled by the rate of nucleation.
TL;DR: In this article, the experimental conditions influencing thermoanalytical results are summarized and subdivided into three groups: sample properties, experimental parameters, apparative parameters, and special care is given to particle size, the atmosphere as part of the reacting system and as experimental parameter.
Abstract: The experimental conditions influencing thermoanalytical results are summarized and subdivided into three groups: sample properties, experimental parameters, apparative parameters. By means of selected examples, some experimental conditions are discussed, mainly for TG and DTA. Special care is given to particle size, the atmosphere as part of the reacting system and as experimental parameter, the buoyancy problem, dynamic re-impact phenomena of molecules, heat transfer and supercooling problems in melting, and DTA under different isobaric conditions. In quantitative thermal analysis, experimental conditions need careful control. Standard reference materials as well as automatic data collection and processing techniques help in achieving better thermoanalytical results.
TL;DR: In this paper, the temperature dependence of the preexponential factor in the Arrhenius expression for the rate constant has been investigated for both thermogravimetric and derivative data.
Abstract: The well-known methods of Coats-Redfern, Freeman-Carroll, and Achar et al. are modified to include the temperature dependence of the pre-exponential factor in the Arrhenius expression for the rate constant. These modifications serve to cast these methods into their most general Arrhenius form. Suggestions are given regarding various numerical methods for extracting the temperature dependence of the preexponential factor from thermogravimetric and derivative thermogravimetric data.
TL;DR: A simplified deconvolution procedure which can be used to remove the distortion, due to thermal lags, from calorimetric data is described and tested.
Abstract: A simplified deconvolution procedure which can be used to remove the distortion, due to thermal lags, from calorimetric data is described and tested. The procedure is based on the state function theory. Noise in the deconvoluted data can be abated by smoothing the experimental data and by a careful choice of the data-sampling frequency. The method is adaptable to on-line processing by means of a microprocessor.
TL;DR: In this paper, the authors investigated the solid-state reactions in MgO-Cr2O3 and ZnO-cr2O 3 systems under atmospheres of oxygen, air and nitrogen using DTA and isothermal kinetic techniques.
Abstract: The solid-state reactions in MgO-Cr2O3 and ZnO-Cr2O3 systems under atmospheres of oxygen, air and nitrogen were investigated by means of DTA and isothermal kinetic techniques. It was shown that the application of DTA to the solid-state reactions affords useful information with respect to the initial reaction stage: oxidation of Cr2O3 to CrO3 in the presence of MgO or ZnO, followed by the formation of a thin layer of spinel, which consisted of an imperfect lattice, on the surface of the MgO or ZnO grains.
TL;DR: In this article, the double cyanides of nickel and platinum form structures capable of enclosing also phenol, for example, as guest molecule, and different thermal stabilities of their clathrate compounds could be achieved by alteration of the constituents of the cage structure and also of the guest molecules.
Abstract: The double cyanides of nickel and platinum form structures capable of enclosing also phenol, for example, as guest molecule. Such clathrates are Ni(NH3)2Pt(CN)4 2 C6H5OH and Ni(en)2Pt(CN)4 · 0.14 C6H5OH. In the case of the tetracyano complexes, different thermal stabilities of their clathrate compounds could be achieved by alteration of the constituents of the cage structure and also of the guest molecules. According to the thermal behaviour, the clathrates may be divided into two groups: those which release the guest molecules in the first step of thermal decomposition (Ni(NH3)2Pt(CN)4· 2 C6H5OH), and those which lose the guest component only after partial destruction of the host cage (Ni(en)2Pt(CN)4 · 0.14 C6H5OH). The temperature ranges of loss of the guest component may determine the interval for their use in sorptive experiments. The temperature range for release of phenol from Ni(NH3)2Pt(CN)4 · · 2 C6H5OH is 55–244°, and from Ni(en)2Pt(CN)4 · 0.14 C6H5OH is 139–284°. The model host molecules NiPt(CN)4 · 6 H2O and Ni(en)3Pt(CN)4 · 3 H2O were also studied by thermal analysis.
TL;DR: In this article, a double cristallisation of l'huile de palme and preciser les differentes formes polymorphiques of cette huile is described. But this is not the case in this paper.
Abstract: L'utilisation complementaire de l'analyse calorimetrique differentielle a compensation de puissance et de la diffraction des rayons X avec porte echantillon a temperature contrOlee nous a permis de mettre en evidence la double cristallisation de l'huile de palme et de preciser les differentes formes polymorphiques de cette huile.
TL;DR: Les chaleurs differentielles d'adsorption de l'anhydride carbonique par la mordenite sodique and differents tamis moleculaires (NaX, NaY, HZ, Na0.25Ca0.375A) ont ete mesurees par calorimetrie as discussed by the authors.
Abstract: Les chaleurs differentielles d'adsorption de l'anhydride carbonique par la mordenite sodique et differents tamis moleculaires (NaX, NaY, HZ, Na0.25Ca0.375A) ont ete mesurees par calorimetrie.
TL;DR: In this article, the influence of different degrees of distortion of the coordination polyhedra in some Cu(II) complexes on the courses of their thermal destruction was studied, and it was found that differences in the thermal stability and stoichiometry of thermal decomposition may be satisfactorily explained by the different degree of distortion.
Abstract: The influence of different degrees of distortion of the coordination polyhedra in some Cu(II) complexes on the courses of their thermal destruction was studied. It was found that differences in the thermal stability and stoichiometry of thermal decomposition may be satisfactorily explained by the different degrees of distortion of the coordination polyhedra in the Cu(II) complexes under discussion. This fact appears to be significant with respect to the chemical reactivities of these complexes, though the influence of other factors cannot be excluded.
TL;DR: In this paper, a formulation theorique des loisg(x) is proposed for le regime non-isotherme, se basant sur les deux hypotheses suivantes: a) l'equation de vitesse en regime isotherme est the forme limite de l'Equation de Vitesse de chauffe en regime dynamique, b) the variation de temperature en regime dynamicique affecte the frequence d'apparition des germes de la nouvelle phase.
Abstract: Dans la premiere partie de ce travail, les auteurs mettent en evidence que la vitesse d'une reaction en regime non isotherme depend d'un facteur supplementaire: le regime de montee en temperature. Cette assertion est basee sur le fait que le taux de reactionx est une fonction de trois variables: temperatureT, tempst, et vitesse de chauffeT′, variable qui n'avait pas ete prise en consideration jusqu'ici par les autres auteurs travaillant sur ce probleme. Puis, se basant sur les deux hypotheses suivantes: a) l'equation de vitesse en regime isotherme est la forme limite de l'equation de vitesse en regime dynamique, b) la variation de temperature en regime dynamique affecte la frequence d'apparition des germes de la nouvelle phase, une formulation theorique des loisg(x) est proposee pour le regime non-isotherme. Cette formulation est explicitee en fonction de l'ecart, a une temperature donnee, entre les valeurs de Lnk
i (isotherme) et Lnk
d (dynamique) dans le diagramme Lnk = f(1/T). L'etude, par thermogravimetrie, de la decomposition du gypse, du sulfate de calcium semihydrate, et de l'oxalate de calcium monohydrate, realisee en montee lineaire de temperature, permet de verifier experimentalement la formulation theorique proposee. Pour obtenir une bonne interpretation cinetique d'une reaction chimique en regime dynamique, la vitesse de chauffe ne doit pas exceder 20°/heure.