any device in which electrical energy is converted to chemical energy, or vice versa. Such a cell typically consists of two metallic or electronic conductors (electrodes) held apart from each other and in contact with an electrolyte (q.v.), usually a dissolved or fused ionic compound. Connection of the electrodes to a source of direct electric current renders one of them negatively charged and the other positively charged. Positive ions in the electrolyte migrate to the negative electrode (cathode) and there combine with one or more electrons, losing part or all of their charge and becoming new ions having lower charge or neutral atoms or molecules; at the same time, negative ions migrate to the positive electrode (anode) and transfer one or more electrons to it, also becoming new ions or neutral particles. The overall effect of the two processes is the transfer of electrons from the negative ions to the positive ions, a chemical reaction (see oxidation-reduction reaction). An example is the electrolysis of sodium chloride (common salt), forming sodium metal and chlorine gas; the energy required to make the reaction proceed is supplied by the electric current. Other common applications of electrolysis include electrodeposition for refining or plating of metals and the production of caustic soda.
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