
Magnesium sulfite

Magnesium sulfite is the magnesium salt of sulfurous acid with the formula . Its most common hydrated form has 6 water molecules making it a hexahydrate, ·6. When heated above , it is dehydrated to magnesium sulfite trihydrate, or ·3. The anhydrous form is hygroscopic, meaning that it readily absorbs water from the air.
References.
solubility tables of MgSO3 hydrates PDF