Sentence:  Liter quantities of Mallinckrodt , low sulfur , reagent grade carbon tetrachloride were saturated with * * f and * * f and illuminated for about 50 hours with a 1000 watt <WSD>tungsten</WSD> lamp at a distance of a few inches . 
Meaning of the word marked with <WSD> tags:  a heavy grey-white metallic element; the pure form is used mainly in electrical applications; it is found in several ores including wolframite and scheelite