Dehydration of CuSO4 · 5H2O studied by conventional and advanced thermal analysis techniques

With the aim of determining the exact dehydration (decomposition) temperatures for hydrated copper sulphate, measurements have been performed using two techniques: STA (simultaneous DTA and TG) using dynamic heating at various heating rates and SIA (stepwise isothermal analysis). In accordance with literature data, the dynamic heating measurements showed that the dehydration takes place in three steps: loss of two water molecules at 65°C, loss of two more at 90°C and loss of the final water molecule at 220°C. A better resolution was obtained with the SIA technique, however, which showed the following five steps: loss of one water molecule at 58 and 65°C, respectively, loss of 112 molecules at 75°C, loss of half a molecule at 85°C and finally loss of the last molecule at 215°C. The decomposition temperatures obtained by this technique are believed to be the most accurate data so far determined for this compound.