Hall–Héroult electrochemical smelting process

The electrolyte a molten salts called Cryolite (Na₃AlF₆) used in the Hall–Héroult electrochemical smelting process to dissolve alumina [aluminum oxide (Al₂O₃)]. 

"The Carbon anodes are immersed into the electrolyte (usually referred as the "bath") carrying electrical current which then flows into the molten cryolite containing dissolved alumina. As a result, the chemical bond between aluminum and oxygen in the alumina is broken, the aluminum is deposited in the bottom of the cell, where a molten aluminum deposit is found, while the oxygen reacts with the carbon of the anodes producing carbon dioxide (CO₂) bubbles."