The document discusses the production of caustic soda and chlorine through the electrolysis of salt water. There are three main electrolytic cell types used: mercury cell, diaphragm cell, and membrane cell. In the electrolysis process, salt water is purified and passed through the cells, where an electric current decomposes the brine into chlorine gas at the anode and sodium at the cathode. The sodium and chlorine then undergo further reactions to produce caustic soda and chlorine. The membrane cell process produces high quality caustic soda without contamination from salt, and operates at low voltage and energy efficiency.