Solid State Oscillatory Reaction. I. Thermal Decomposition Studies of [Co(NH3)6]Br3 and CoBr2·2H2O

Thermogravimetric analysis, TGA, of cobalt(II)bromide, [Co(NH3)6]Br3 –henceforth referred to by the shortname HCBR– was carried out using a wide diameter short one and a narrow diameter long sample cups. In the former type of cup the TGA trace was similar to that reported one. However, when the latter cup was used, the TGA showed oscillations in the % weight-loss. Cobalt(II)bromide, CoBr2, is formed as an intermediate product in the thermal decomposition of HCBR. The oscillatory nature of weight-loss curve was studied for both HCBR and CoBr2. The oscillatory behavior in the present system has been confirmed on the basis of the following experiments: (a) Dynamic TGA and differential thermal analysis, DTA, of HCBR and CoBr2·2H2O. (b) Isothermal TGA by weight-loss method for HCBR and CoBr2. (c) Thermal decomposition studies, in closed system, of (i) CoBr2 and of (ii) CoO in a mixture of O2 and Br2 gases, and of a mixture of (iii) Co3O4 and CoBr2 in dry nitrogen. The oscillations in the composition of the sol...