Sentence:  In addition to the method described in the section above , <WSD>chlorine</WSD> and radiochlorine were prepared by the electrolysis of a * * f eutectic on the vacuum line , and by exchange of * * f with molten * * f . 
Meaning of the word marked with <WSD> tags:  a common nonmetallic element belonging to the halogens; best known as a heavy yellow irritating toxic gas; used to purify water and as a bleaching agent and disinfectant; occurs naturally only as a salt (as in sea water)