Abstract
The dehydration and decomposition characteristics of an undried and a partly dried sample of NiCl2·xH2O have been investigated by isothermal and non-isothermal (TG and DTA) methods in static air as well as flowing nitrogen environment. While the isothermal weight loss method fails to distinguish between different steps of reaction, TG curves upto 800°C reveal as many as five steps in static air and four steps in nitrogen atmosphere. However, both methods indicate that NiCl2 is stable upto 400°C above which dehydrochlorination takes place in presence of water vapour. The intermediate products of dehydration and decomposition at different temperatures have been characterized by chemical analysis, X-ray diffraction, infrared and diffuse reflectance spectroscopy. All these methods reveal the presence of water in samples calcined at even 400°–600°C. Thermodynamic functions for different steps of dehydration have been calculated and discussed in the light of the possible structural changes occurring in the partially dehydrated products.
Zusammenfassung
Mittels isothermen und nichtisothermen (TG und DTA) Methoden wurden die Dehydratations- und die Zersetzungseigenschaften von ungetrockneten und teilweise getrockneten Proben von NiCl2·xH2O sowohl in statischer Luftatmosphäre als auch in dynamischer Stickstoffatmosphäre untersucht. Während die isothermen Massenverlustsmethoden für die Unterscheidung der verschiedenen Reaktionsschritte ungeeignet sind, zeigen TG-Kurven bis 800°C nicht weniger als 5 Schritte in statischer Luftatmosphäre und vier Schritte in Stickstoffatmosphäre. Beide Methoden zeigen, daß NiCl2 bis 400°C stabil ist, darüber findet in Gegenwart von Wasserdampf eine Dehydrochlorierung statt. Mittels Elementaranalyse, Röntgendiffraktion, IR- und Remissionsspektroskopie wurden die Zwischenprodukte von Dehydratation und Zersetzung bei verschiedenen Temperaturen charakterisiert. All dieser Methoden zeigen die Gegenwart von Wasser in den bei 400°–600°C kalzinierten Proben. Im Hinblick auf die möglichen strukturellen Veränderungen in den teilweise dehydratierten Produkten wurden thermodynamische Funktionen für verschiedene Schritte der Dehydratation berechnet und diskutiert.
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The authors wish to express their sincere thanks to Mr. D. N. Dey, Head, Pyrometallurgy Division for his keen interest and constant support during the course of investigation. Thanks are also due to Director, Regional Research Laboratory, Bhubaneswar for his kind permission to publish this paper. One of the authors (S. K. M.) is thankful to the Council of Scientific and Industrial Research, New Delhi for awarding a Junior Research Fellowship.
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Mishra, S.K., Kanungo, S.B. Thermal dehydration and decomposition of nickel chloride hydrate (NiCl2·xH2O). Journal of Thermal Analysis 38, 2417–2436 (1992). https://doi.org/10.1007/BF01974621
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DOI: https://doi.org/10.1007/BF01974621