Abstract
The effect of pressure on the thermal dehydration process of CuSO4, 5H2O has been investigated using thermobalance and DTA apparatus under nitrogen pressure in the range between 1 and 40 atm.
On the dehydration of four moles of coordination water, two peaks appeared at 1 atm and only one peak appeared above 4 atm on the DTG curves and three endothermic peaks appeared on DTA curves. The peak positions of DTG curves and one of three peaks of DTA curves shifted to higher temperature with the increase of pressure. This shift of peaks was observed at similar temperature both DTG and DAT curves, and the tempature was approximately the boiling point of water under each pressure applied. No peaks were observed on DTG curve that corresponded to the two unshifted peaks on DTA curves.
From examinations of these results, two unshifted peaks on DTA curves were attributed to the dissociation of coordination water and the shifted peaks on DTG and DTA curves to the evaporation of liquid water dissociated from the heated sample. The activation energies of these reactions were calculated by Kissinger's method.
