Abstract
The method for preparing anhydrous MgSO3 from MgS03·6H2O was examined. Thermogravimetry and differential thermal analysis of MgSO3 in an argon stream were carried out. The decomposition products of MgSO3 at various temperatures were examined in detail by chemical analysis and X-ray diffractometry. The decomposition of MgS2O3, formed during the decomposition process of MgSO3, on heating was also examined.
MgSO3 decomposes above about 80°C with the evolution of gaseous SO2. The products obtained in the heating zone were MgO at 80-250°C, MgO, β-MgSO4, and MgS2O3 at 300-500°C, and MgO and β-MgSO4 at 525-550°C. Sulfur was also obtained outside the heating zone above 400°C. MgS2O3 decomposes as early as 300°C to form MgSO3 and sulfur.
From these results, the thermal decomposition process of MgSO3 can be represented as follows : The decomposition of MgSO3 proceeds above about 80°C according to the reaction, MgSO3→MgO+SO2.Above about 300°C, the reaction, 4MgSO3→2MgSO4+MgS2O3+MgO, occurs in addition to the above reaction. Subsequently, the decomposition of MgS2O3 formed, MgS2O3→MgSO3+S, occurs.
