Electrolysis is a process by which electric current is passed through a substance to effect a chemical change. The process is carried out in an electrolytic cell, which consists of positive and negative electrodes held apart and dipped into a solution containing positively and negatively charged ions. The substance to be transformed may form the electrode, may constitute the solution, or may be dissolved in the solution. The products of electrolysis depend on the standard electrode potentials of the different oxidizing and reducing agents that are present in the electrolytic cell.
Key components required to achieve electrolysis include an electrolyte, electrodes, and an external power source. Electrolysis is usually done in a vessel named an "electrolytic cell" containing two electrodes (cathode and anode), connected to a direct current source and an electrolyte which is an ionic compound undergoing decomposition, in either molten form or in a dissolved state in a suitable solvent. Electrodes that are made from metal, graphite, and semiconductor materials are commonly used.
The products of electrolysis depend on the substance being transformed and the type of electrolyte used. For example, the electrolysis of aqueous solutions is easier and safer for students to do for themselves, but the presence of water complicates what students may decide are the products formed at the electrodes.
Electrolysis is used extensively in metallurgical processes, such as in extraction (electrowinning) or purification (electrorefining) of metals from ores or compounds and in deposition of metals from solution (electroplating). It is also used to separate components of ionic compounds.
