Magnesium chloride serves as precursor to other magnesium compounds, for example by precipitation:
MgCl2(aq) + Ca(OH)2(aq) → Mg(OH)2(s) + CaCl2(aq)
It can be electrolysed to give magnesium metal:
MgCl2(l) → Mg(l) + Cl2(g)
This process is practiced on a substantial scale.
Magnesium chloride is most commonly used for dust control and road stabilisation. Its second-most common use is ice control. In addition to the production of magnesium metal, magnesium chloride also is used for a variety of other applications: fertiliser, mineral supplement for animals, wastewater treatment, wallboard, artificial seawater, feed supplement, textiles, paper, fireproofing agents, cements and refrigeration brine. Mixed with hydrated magnesium oxide, magnesium chloride forms a hard material called Sorel cement.
This compound is also used in fire extinguishers: obtained by the reaction of magnesium hydroxide and hydrochloric acid (HCl) in liquid form along with water in gaseous state.