Sentence:  These estimates indicated that the quantum yield for the exchange of <WSD>chlorine</WSD> with liquid carbon tetrachloride at 65 ` is of the order of magnitude of unity . 
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)