Aluminium fluoride (AlF3) is usually added to the electrolyte. The ratio NaF/AlF3 is called the cryolite ratio and it is 3 in pure cryolite. In industrial production, AlF3 is added so that the cryolite ratio is 2–3 to further reduce the melting point, so that the electrolysis can happen at temperatures between 940 and 980 °C (1700 to 1800°F). The density of liquid aluminum is 2.3 g/ml at temperatures between 950 and 1000 °C (1750° to 1830°F). The density of the electrolyte should be less than 2.1 g/ml, so that the molten aluminum separates from the electrolyte and settles properly to the bottom of the electrolysis cell. In addition to AlF3, other additives like lithium fluoride may be added to alter different properties (melting point, density, conductivity etc.) of the electrolyte.
Aluminium fluoride (AlF3) is usually added to the electrolyte The ratio NaF/AlF3 is called the cryolite ratio and it is 3 in pure cryolite In industrial production AlF3 is added so that the cryolite ratio is 2–3 to further reduce the melting point so that the electrolysis can happen at temperatures between 940 and 980 °C (1700 to 1800°F) The density of liquid aluminum is 23 g/ml at temperatures between 950 and 1000 °C (1750° to 1830°F) The density of the electrolyte should be less than 21 g/ml so that the molten aluminum separates from the electrolyte and settles properly to the bottom of the electrolysis cell In addition to AlF3 other additives like lithium fluoride may be added to alter different properties (melting point density conductivity etc) of the electrolyte