Complex sentence: While solid cryolite is denser than solid aluminium at room temperature, the liquid aluminium product is denser than the molten cryolite at temperatures around, and the aluminium sinks to the bottom of the electrolytic cell, where it is periodically collected.
Split into simpler sentences: While solid cryolite is denser than solid aluminium at room temperature, liquid aluminium is denser than molten cryolite at temperatures around. The aluminium sinks to the bottom of the electrolytic cell, where it is periodically collected.