Source : Webster's Revised Unabridged Dictionary (1913)

Chlorination \Chlo`ri*na"tion\, n.
   The act or process of subjecting anything to the action of
   chlorine; especially, a process for the extraction of gold by
   exposure of the auriferous material to chlorine gas.

Source : WordNet®

chlorination
     n 1: the addition or substitution of chlorine in organic
          compounds
     2: disinfection of water by the addition of small amounts of
        chlorine or a chlorine compound