The electrolytic process is typically used to refine substances such as metals or to extract materials from a solution. There are three main components that are required for any electrolytic process, which are electricity, a substance that contains free ions, and two objects to act as electrodes. The presence of an electrical current flowing through the electrolyte can cause a chemical reaction that would not otherwise occur spontaneously. In the refining of metals, atoms from an impure substance are caused to transfer to a pure cathode due to the flow of electricity. The electrolytic process can also be used to extract substances, such as refining hydrogen from water.
In order to use electrolysis to refine metal, both electrodes will typically be made of that material. An impure ore or alloy can be used for the anode, and the cathode is made from the pure form. The electrolyte will also contain the same metal in the form of free ions that are held in solution. When an electrical current is applied to the electrodes, it can flow between them through the electrolyte. This will tend to cause ions from the solution to attach to the corresponding electrode, depending on whether they are positively or negatively charged, resulting in pure metal atoms gathering on the cathode.
The electrolytic process can also be used to plate one metal with another or for decorative etching. These uses of the process are very similar to the refining method, though coating one metal with another is referred to as electroplating. The use of the electrolytic process for etching typically uses acrylics and other substances to coat the metal, and is sometimes referred to as electroetching.
Gases, such as hydrogen, can also be refined using the electrolytic process. Water is chemically composed of hydrogen and oxygen, and an electrical current can be used to split it into these components. The anode and cathode are each made of the same substance, typically stainless steel or another inert metal.
When current is applied to electrodes submerged in water, it will tend to decay into oxygen near the anode and hydrogen at the cathode. By placing collection vessels at the appropriate electrode, pure oxygen or hydrogen can be gathered. Since pure water tends to undergo a limited amount of self-ionization, the presence of free ions can be low and the process tends to progress slowly. Due to this, hydrogen is not often collected with the electrolytic process on an industrial scale.