Effects of heating rate (1–300° h −1) on the non-isothermal thermogravimetry of CuSO 4 · 5 H 2O

Abstract

The course of the reaction CuSO 4 · 5 H 2O − CuSO 4 · H 2O + 4 H 2O was studied by non-isothermal thermogravimetry with various heating rates ranging from 1 to 300° h −. The measurements were made either in static air, in a dry nitrogen stream, or in water vapor at a reduced pressure (9 mm Hg). In static air, the shape of the TG curve changed drastically at a heating rate of 13 to 15° h −, and this change was explained by considering the nature of the plateaus and inflections present. In a dry nitrogen stream, the dehydration is made much easier at slow heating rates and occurs almost in one step at 2° h −; in water vapor at 9 mm Hg, on the other hand, a very distinct two-step curve is obtained at 1° h −. This can reasonably be compared with the phase diagram of copper sulfate.