1.By the electrolysis of concentrated sodium chloride solution;this process was initially used primarily for the production of sodium hydroxide but the demand for chlorine is now so great that the chlorine is a primary and not a by product.
2.By the electrolysis of fused magnesium chloride or fused sodium chloride.
3.By the oxidation of hydrogen chloride.A mixture of hydrogen chloride with air or oxygen is passed over a catalyst of copper