Thermal dehydration of cobalt and zinc formate dihydrates by controlled-rate thermogravimetry (CRTG) and simultaneous X-ray diffractometry differential scanning calorimetry (XRD-DSC)

The thermal dehydration study of the similar hydrated salts, cobalt and zin c formate dihydrates, have been carried out successfully by means of X-ray diffractometry-differential scanning calorimetry (XRD-DSC) and controlled-r ate thermogravimetry (CRTG). X-ray diffraction analysis recorded simultaneo usly indicates that the resulting anhydrous product Zn(HCO2)(2), was crysta lline, while Co(HCO2)(2) was amorphous. The XRD-DSC data are proven to be invaluable in verifying the interpretatio n of overlapping processes in thermal events. In addition, these difference s in the resulting anhydrous products can be explained from kinetic analysi s results based on the CRTG data. The kinetic mechanism governing the dehyd ration of zinc formate dihydrate is a nucleation and growth process, while in the case of cobalt formate dihydrate a phase boundary controlled reactio n is the governing mechanism. (C) 1999 Elsevier Science B.V. All rights res erved.