Thermal dehydration and decomposition of cobalt chloride hydrate (CoCl2·xH2O)

Abstract

Dehydration and decomposition of an undried and a partly dried sample of hydrated CoCl2 have been investigated by using both isothermal and non-isothermal weight loss methods. The intermediate products of dehydration and decomposition at different temperatures have been characterized by chemical analysis, X-ray diffraction, microscopy, infrared and diffuse reflectance spectroscopy. Though XRD failed to identify clearly the formation of basic salt, infrared spectra reveal the occurrence of hydrogen bonded OH groups in the samples heated at even 500°–600°C. This is further supported from the diffuse reflectance spectra of “dehydrated” samples which indicate tetragonally distorted co-ordination structures due to the presence of H2O. Thermodynamic functions for different steps of dehydration have been calculated and discussed in the light of structural changes taking place in the dehydrated salts.