Magnesium sulfite

Magnesium sulfite is the magnesium salt of sulfurous acid with the formula MgSO3. Its most common hydrated form has 6 water molecules making it a hexahydrate, MgSO3·6H2O. When heated above 40 °C (104 °F), it is dehydrated to magnesium sulfite trihydrate, or MgSO3·3H2O. The anhydrous form is hygroscopic, meaning that it readily absorbs water from the air. Magnesium sulfite is the magnesium salt of sulfurous acid with the formula MgSO3. Its most common hydrated form has 6 water molecules making it a hexahydrate, MgSO3·6H2O. When heated above 40 °C (104 °F), it is dehydrated to magnesium sulfite trihydrate, or MgSO3·3H2O. The anhydrous form is hygroscopic, meaning that it readily absorbs water from the air.