Sentence:  The fraction of exchange was determined as the ratio of the counts / minute observed in the carbon tetrachloride to the counts / minute calculated for the carbon tetrachloride fractions for equilibrium distribution of the activity between the <WSD>chlorine</WSD> and carbon tetrachloride , empirically determined correction being made for the difference in counting efficiency of * * f in * * f and * * 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)