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 40 C, it is dehydrated to magnesium sulfite trihydrate, or ·3. The anhydrous form is hygroscopic, meaning that it readily absorbs water from the air.