7757-88-2

White, crystalline powder. Slightly soluble in water; insoluble in alcohol.

Magnesium Sulfite can be prepared by the reaction of a magnesium hydroxide slurry and SO2 gas:
Mg(OH)2＋ SO2(gas) ＋H2O→MgSO3·6H2O
If the solution temperature is kept below 40°C, the hexahydrate results. Above 40°C, the trihydrate, MgSO3·3H2O, is the usual product. Magnesium sulfite may also be prepared by adding a solution of sodium sulfite to a solution of magnesium chloride. The mix is kept at 25°C for 1–2 h and the solid phase which forms is separated and washed with isopropanol and dried at 60°C. Again, the hexahydrate results.