The dehydration of copper(II) acetate monohydrate

The thermal dehydration of copper(II) acetate hydrate has been studied between 353 and 406 K, over a range of humidities. The dehydration is controlled by nucleation-and-growth kinetics at low temperatures, with an activation energy of 154 kJ·mol⁻¹, which changes to contracting-disc kinetics at higher temperatures with a lower activation energy of 76 kJ·mol⁻¹. Frequency factors have also been derived; the value for the high temperature process is low (10⁷s⁻¹) and that for the low temperature step is high (10¹⁷s⁻¹). Optical microscopy has been used to clarify the bulk kinetics; there is evidence for a reactive layer at the surface of the decomposing solid. In celebration of the 60^th birthday of Dr Andrew K. Galwey     

Thermal decomposition of copper(II)phthalate monohydrate

The thermal dehydration and decomposition of copper(II) phthalate monohydrate was studied by isothermal and non-isothermal methods. The decomposition process consisted of three steps: two steps of dehydration and the third of decomposition. The kinetics of isothermal dehydration reactions follow (i) a unimolecular law up to the formation of copper(II) phthalate hemihydrate, and (ii) a phase boundary model giving anhydrous copper(II) phthalate, while the kinetics of isothermal decomposition reaction comply with the Erofeev-Avrami equation, [–ln(1–)]^1/n =Kt+C. The energies of activation for the formation of the decomposition products were calculated. The decomposition products were characterized by elemental analysis, photomicrographic observations, infrared and reflectance spectra and X-ray powder diffraction data.

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Zusammenfassung Die thermische Dehydratisierung und Zersetzung von Kupfer(II)Phthalat Monohydrat wurde durch isotherme und nichtisotherme Methoden untersucht. Der Zersetzungsvorgang bestand aus drei Stufen: zwei Stufen der Dehydratisierung und die dritte der Zersetzung. Die Kinetik der isothermen Dehydratisierungsreaktionen folgt (i) einem unimolekularen Gesetz bis zur Bildung von Kupfer(II)Phthalat Hemihydrat und (ii) einem Grenzflächen modell, das wasserfreies Kupfer(II)Phthalat ergibt, während die Kinetik der isothermen Zersetzungsreaktion der Erofeev-Avrami Gleichung, [–ln(1–)]^1/n =Kt+C genügt. Die Aktivierungsenergien für die Bildung der Zersetzungsprodukte wurden berechnet. Die Zersetzungsprodukte wurden durch Elementaranalyse, mikrophotographische Beobachtungen, Infrarot- und Remissionsspektra sowie Röntgen-Pulverdiffraktionsdaten charakterisiert.

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Résumé On a étudié, par des méthodes isothermes et non-isothermes, la déshydratation et la décomposition thermique du phtalate de cuivre(II) monohydraté. Le procèssus de décomposition consiste en trois étapes: deux étapes de déshydratation et la troisième de décomposition. La cinétique des réactions de déshydratation isotherme suit (i) une loi unimoléculaire jusqu'à la formation de phtalate de cuivre(II) hémihydraté, et (ii) un modèle de surfaces limites qui donne du phtalate de cuivre(II) anhydre, tandis que la cinétique de la réaction de décomposition isotherme satisfait l'équation d'Eroféev-Avrami: [–ln(1–)]^1/n =Kt+C. On a calculé les énergies d'activation de la formation des produits de décomposition. On a caractérisé les produits de décomposition par analyse élementaire, par des observations micrographiques, des spectres infrarouges et d'émission ainsi que par des données de diffraction sur poudre des rayons X.

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(II). : . (II) , (II). - : [-In(1-)]^1/n=Kt+. . , , , .

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One of the authors (C. M. K.) is grateful to the University of Jammu, Jammu, for the award of a Fellowship.     

Thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere

The conditions of thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere at heating rates of 10 and 5 deg·min^–1 were studied. At 10 deg · min^–1, the hemimellitate and trimesinate of copper(II) lose crystallization water and then decompose directly to CuO, whereas at 5 deg·min^–1 they decompose to CuO through Cu₂O. The trimellitate of copper(II) heated at various rates decomposes in the same way: it loses 1 water molecule and then decomposes directly to CuO.     

Isokinetic relationships at the thermal decomposition of tetranuclear copper(II)-complexes

A dependence of the activation energy upon the extent of conversion has been discovered for the thermal decomposition of Cu₄OCl₆L₄ with piperidine (1), morpholine (2), and triphenylphosphine oxide (3) as the ligand (L). Within the interval of conversions 0–0.3 the process shows a decrease in the activation energy (230–130 (1), 130–50 (2), and 200–100 (3) kJ mol^?1). The processes considered show an isokinetic relationship with T_iso = 255 ± 15 K which corresponds to a vibrational frequency of v_iso = 177 ± 10 cm^?1. This value accords well with IR absorption bands assigned to the stretching vibration in the trigonal CuCl₃ chromophore as predicted by theory. Based on this, an assumption about the CuCl₃-group as a central site of the reaction can be made. The IR- and X-ray data are presented to support the assumption made. © 1995 John Wiley & Sons, Inc.     

Study of thermal decomposition of silver acetate

Thermal decomposition of silver acetate was studied (TG, DSC, mass-spectrometry, X-ray analysis, electron microscopy). Non-isothermal thermogravimetric data (obtained at two different rates of linear heating) were used for kinetic studies. Kinetic parameters were calculated only for the chosen decomposition step.     

Ferromagnetic long range ordering in copper(II) maleate monohydrate

Summary The magnetic properties of copper(II) maleate monohydrate, Cu(C₄H₂O₄)·H₂O, have been measured in the 1.8–66 K range. Magnetic susceptibility and isothermal magnetization measurements on powdered samples reveal a transition to a ferromagnetic state in this layered compound. The transition to the ordered state occurs at T_c=4.0 K. The positive value of 8.0 K for the Weiss constant in the paramagnetic region confirms the ferromagnetic nature of the interactions. The magnetic susceptibility data above 3T_c may be fitted with a Heisenberg quadratic layer expression with the best-fit parameters J=+4.3 cm^–1, g=2.0, and zJ=+0.42 cm^–1. The e.p.r. spectrum at room temperature indicates orthorhombic symmetry. A complex containing the isomeric form of the ligand, copper(II) fumarate dihydrate, has also been prepared and its magnetic properties determined in the 80–300 K range. The data may be accomodated by two-dimensional theory with J=+1.05 cm^–1, g=2.09, and zJ=+0.10 cm^–1.     

Thermal decomposition of copper(II) benzenedicarboxylates

The conditions and products of thermal decomposition of copper(II) benzenedicarboxylates in air atmosphere were studied at heating rates of 10 and 5 deg · min^–1. At a heating rate of 10 deg · min^–1, the o- and p-phthalate of copper(II) lose the crystallization water in two steps and the anhydrous complexes then decompose directly to CuO. Copper(II) m-phthalate loses crystallization water in one step to give the dihydrate, which then decomposes directly to CuO. When heated at 5 deg · min^–1 the m- and p-phthalates of copper(II) decompose in the same way, whereas the anhydrous o-phthalate decomposes to CuO through Cu₂O.

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Zusammenfassung Die Umstände und Produkte der thermischen Zersetzung von Kupfer(II)-benzoldicarboxylaten wurden in Luftatmosphäre bei einer Aufheizgeschwindigkeit von 10 bzw. 5 grd/min untersucht. Bei einer Aufheizgeschwindigkeit von 10 grd/min geben Kupfer(II)-o- und pphthalat ihr Kristallwasser in zwei Stufen ab, die wasserfreien Komplexe zerfallen anschliessend unmittelbar zu CuO. Kupfer(II)-m-phthalate geben Kristallwasser in einem Schritt ab und bilden dabei ein Dihydrat, was anschliessend direkt zu CuO zerfällt. Bei einer Aufheizgeschwindigkeit von 5 grd/min zeigt das m- und p-Phthalat des Kupfers(II) die gleichen Zersetzungserscheinungen, wogegen wasserfreies o-Phthalat sich zu CuO über die Zwischenstufe Cu₂O zersetzt.

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10 5 . 10 - - , . - , , . 5 - - , - .

     

Thermal decomposition of basic copper sulphate monohydrate

The thermal decomposition of copper sulphate hydroxide hydrate, (CuO·CuSO₄). 2Cu(OH)₂·H₂O, to copper oxysulphate and CuO was investigated by X-ray phase analysis, IR spectroscopy, complex thermal analysis and electron microscopy. The effect of water vapour and time of treatment on the formation of decomposition products with a large surface area is studied. The strong decrease in specific surface area of the precipitate (from 80 m²/g to 20 m²/g) thermally treated at a temperature above 250°C is associated with the elimination of water having a coordination bond with the Cu²⁺ ion. During this process, the interplanar distances of the crystal lattice of copper sulphate hydroxide hydrate decrease. The time of decomposition of this compound essentially affects the decrease of the specific surface area. When the decomposition proceeds in an atmosphere containing water vapour sintering processes are predominating and the phase obtained has a considerably smaller specific surface area than in cases of decomposition under dry air.     

Combined derivatographic and thermo-gas-titrimetric examination of the thermal decomposition of copper tetra-ammine sulphate monohydrate

The thermal decomposition of copper tetra-ammine sulphate monohydrate has been investigated by a combined derivatographic and thermo-gas-titrimetric method. It has been found that decomposition starts with splitting off of the water of crystallization and only after part of this water has departed does stepwise release of ammonia begin. First two moles, then one and finally again one mole of ammania (per mole of compound) are released. It has been established that a small amount of sulphur trioxide splits off during the last decomposition step, and that about 20 % of the last ammonia to be released is thermally decomposed.     

Thermal decomposition of bis-(DL-valinato)copper(II) and bis-(DL-methioninato)copper(II)

A kinetic study of the thermal decomposition of the complexes bis-(DL-valinato)copper(II) and bis-(DL-methioninato)copper(II) was carried out using thermogravimetry in a dynamic regime, following the theoretical model of Satava and including the equation used by Johnson and Gallagher:1/1––1=kt. Kinetic parameters were calculated and are compared with those obtained previously for the complex bis-(L-tryptophanato)copper(II). The sequence of thermal stability found is: Cu(DL-Val)₂22.

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Zusammenfassung Die thermische Zersetzung der Komplexe Bis-(DL-valinato)kupfer(II) und Bis-(DL-methioninato)kupfer(II) wurde thermogravimetrisch im dynamischen Regime untersucht, indem von dem theoretischen Modell von atava Gebrauch gemacht und die von Johnson und Gallagher benutzte Gleichung 1/1-–1=kt einbezogen wurde. Kinetische Parameter wurden berechnet und mit den kürzlich für den Komplex Bis-(L-tryptophanato)kupfer(II) erhaltenen parametern verglichen. Die Stabilität der Komplexe nimmt in folgender Reihenfolge zu: Cu(DL-Val)₂22.

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-(-)- -(L-) (II) , -: 1/1– –1=kt. -(L-) (II). Cu(DL-Val)₂22.

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Presented at the 1985 World Conference on Thermal Analysis, Bad Hofgastein, Austria.     

Effect of atmosphericwater vapor on the kinetics of thermal decomposition of copper(II) carbonate hydroxide

The effect of atmospheric water vapor on the kinetic rate behavior of the thermal decomposition of copper(II) carbonate hydroxide, Cu₂CO₃(OH)₂, was investigated by means of TG-DTA coupled with a programmable humidity controller. With increasing water vapor pressure p(H₂O) from 0.8 to 10.6 kPa, a systematic reduction of the reaction temperature of the thermal decomposition was observed as the continuous trend from the previous works at the lower p(H₂O). Through a comparative kinetic analysis of the reaction at different p(H₂O), a catalytic action of the atmospheric water vapor on the nucleation process at the first half of the reaction was identified as the possible origin of the reduction of the reaction temperature.