Text: The splitting up of molecules into ions. Ionization may apply either to a chemical compound or to a gas. When an electric current is passed through an electrolyte the constituents of the electrolyte which are liberated or deposited at the electrodes are called ions and this process is called ionization. Gases at or near atmospheric pressure are normally good insulators. They are said to undergo ionization when they are made conductive, that is when they allow the flow of electricity. A gas may be made conductive by passing X-rays through it, by the action of ultra-violet light, by subjecting it to radium rays, by passing it close to a flame or hot piece of metal or by forming in it a brush discharge or corona. Gases which have been made conductive carry current because of their dissociation into ions, which carry positive or negative charges of electricity.

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