Used in human and animal diet, food seasoning and food preservation; used to prepare sodium hydroxide, soda ash, caustic soda, hydrochloric acid, chlorine, metallic sodium; used in ceramic glazes; metallurgy, curing of hides; mineral waters; soap manufacturing; home water softeners; highway de-icing; photography; in scientific equipment for optical parts. Single crystals used for spectroscopy, ultraviolet and infrared transmission.