The Thermal Analysis of the Decomposition of Magnesium Chloride Hexahydrate under Pressure

Abstract

The thermal decomposition of MgCl2 H₂0 has been studied by thermogravimetry (TG) and differential thermal analysis (DTA) in the pressure range from one to 30 atm, and by the thermal analytical technique based on electrical conductivity (EC) at atmospheric pressure.
Although the TG curves of the decomposition under one and 3 atm indicated the presence of four step reactions, the TG curves of decomposition above 10 atm showed two step reactions apparently. Six endothermic peaks appeared on the DTA curve at one atm. The temperature of 1 st peak (at 117° C) was unshifted but the other 5 peaks shifted to higher temperature with the increase of pressure. The 1 st peak on the DTG curves corresponded to the 3 rd peak on the DTA curve, and the initial and final positions of EC peak corresponded to the 1 st and 3 rd peak on the DTA curve, respectively.
From examination of these results, the 1 st peak on DTA curves was attributed to the dissociation of two moles of water and 2 nd and 3 rd peaks on DTA curves were interpreted as due to the evaporation of MgCl2 solution.