`MgCl_(2).6H_(2)O` on heating gives anhydrous `MgCl_(2)`.

KCl.MgCl_2. 6H_2O is a

MgCl_2.NH_4Cl.6H_2O on heating in air gives as residue

Anhydrous MgCl_(2) is obatined by heating hydrate salt, MgCl_(2).6H_(2)O .

Dow's process of extraction of Mg involves extraction of Mg from sea water. Sea water is concentrated in sun-light and is then treated with slaked lime. Magnesium hydroxide is heated in a stream of HCl to give MgCl_(2) which is electrolysed to discharge Mg. The mixture is in the ratio 35% MgCl_(2)+50% NaCl+15% CaCl_(2) . NaCl and CaCl_(2) are added to lower the fusion temperature and to increases the conductance. Mg^(2+) +Ca(OH)_(2) to Mg(OH)_(2)+Ca^(2+) Mg(OH)_(2)+2HCl to MgCl_(2)+2H_(2)O(l) Electrolysis of fused MgCl_(2) hArr Mg^(2+)+2Cl Mg^(2+)+2e^(-) to Mg ( At Cathode) 2Cl^(-) to Cl_(2)+2e^(-) (At Anode) Mg electrolysed is protected from atmospheric oxidation by a blanket of inert gases. In the hydrated chloride of Mg the value of x is :

When MgCl_(2).6H_(2)O is strongly heated, then if forms :