A method and system for treating liquid chlorine to remove inert gases therefrom. Liquid chlorine is treated by passing it through a molecular sieve having a molecular pore diameter greater than the molecular diameter of the inert gases and smaller than the molecular diameter of chlorine so that the inert gases are adsorbed by the sieve while the liquid chlorine passes therethrough. The sieve may be regenerated by heating the sieve and evacuating by vacuum, followed by a purging with a gas and then a further vacuum evacuation.