Abstract
Thermal decomposition of magnesium sulfate heptahydrate was studied by TG-DTG-DTA under various sealed atmospheres (open, quasi-sealed, and completely sealed). In the case of open system, stable hexahydrate was obtained, and in the case of quasi-sealed system (29.8μm∅ and 130μm∅ tungsten wires), stable tri-, di-, and mono-hydrate were obtained. However in the case of completely sealed system, mono-hydrate was only obtained. Concerning the condition of completely sealed system, there is some relation between the results of MgSO4·7H2O and CaSO4·2H2O. In the case of CaSO4·2H2O, the hemihydrate was obtained under completely sealed system. The results explain directly that self-generated atmosphere plays an important role of dehydration reaction. The intermediate stages of dehydration were easily obtained by this method.
