Magnesium sulfide reacts with oxygen to form the corresponding sulfate, magnesium sulfate. MgS reacts with water to give hydrogen sulfide and magnesium hydroxide. In the BOS steelmaking process, sulfur is the first element to be removed. Sulfur is removed from the impure blast furnace iron by the addition of several hundred kilograms of magnesium powder by a lance. Magnesium sulfide is formed, which then floats on the molten iron and is removed. MgS is a wide band-gap direct semiconductor of interest as a blue-green emitter, a property that has been known since the early 1900s. The wide-band gap property also allows the
Magnesium oxychloride It can be prepared by calcination of magnesium hydroxycarbonate ·4 at about 600 °C. (Higher temperatures increase particle size leading to lower reaction rate.) It is believed that, during the reaction, the magnesium oxide is continuously hydrated and dissolved, helped by the slightly acidic character of the magnesium chloride solution. The acidity is attributed to hydrolysis of the magnesium hexahydrate cations: The protons (which are actually hydrated, e.g. as ) make the solution acidic; the pH varies from 6.5 to 4.7 as the concentration of increases from 30% to 70% (weight basis). The protons then react with and dissolve the