You know that metals can be separated from molten compounds of metals by electrolysis.

Find out how metals like Na, Ca and Mg are extracted

Metals of high reactivity such as sodium, calcium, magnesium, aluminium, etc. are extracted from their ores by electrolytic reduction. Electrolytic Reduction is the process where electric current is passed through the molten state of metal ores. Metal being positively charged is deposited over the cathode.

i. Sodium

Sodium is usually mined from the ore called rock salt, which is made up of sodium chloride (NaCl). This ore is dissolved and filtrated to remove impurities. Solution of sodium chloride will be left behind from which sodium chloride is crystallized out. This is melted and then mixed with calcium chloride which reduces the melting point of NaCl. Electrolysis of molten NaCl is carried out in Down’s cell. sodium chloride dissociates into sodium cations and chloride anions. Sodium is obtained at cathode and chlorine at anode.

ii. Calcium

Calcium occurs in combined form like slaked lime, calcium chloride, calcium carbonate etc. on industrial scale calcium can be obtained by the electrolysis of molten calcium chloride. A mixture of molten calcium chloride with 16% calcium fluoride is melted in an iron tank lined from inside with graphite which acts as anode. The cathode is a water-cooled iron tube which just touches the electrolyte. When the current is passed through the electrolyte, calcium is deposited at the cathode.

iii. Magnesium

Electrochemical processes are used to extract the metal from dolomite and magnesite ore. Then dolomite is crushed, roasted and mixed with seawater in large tanks, magnesium hydroxide settles to the bottom. Heating, mixing in coke, and reacting with chlorine, produces molten magnesium chloride. This can be electrolyzed, releasing magnesium, which floats to the surface.

Pidgeon process is a popular commercial technique to produce magnesium. In this process, closed-end, nickel-chromium-steel alloy retorts are filled with a mixture of calcined dolomite ore and ferrosilicon, which are heated until magnesium crowns form.