Sentence:  Liter quantities of Mallinckrodt , low <WSD>sulfur</WSD> , reagent grade carbon 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:  an abundant tasteless odorless multivalent nonmetallic element; best known in yellow crystals; occurs in many sulphide and sulphate minerals and even in native form (especially in volcanic regions)