Sentence:  Liter quantities of Mallinckrodt , low sulfur , reagent grade <WSD>carbon</WSD> tetrachloride were saturated with * * f and * * f and illuminated for about 50 hours with a 1000 watt tungsten lamp at a distance of a few inches . 
Meaning of the word marked with <WSD> tags:  a colorless nonflammable liquid used as a solvent for fats and oils; because of its toxicity its use as a cleaning fluid or fire extinguisher has declined