Sentence:  The mixture was then extracted with alkali and with water following which the carbon tetrachloride was distilled on a Vigreux <WSD>column</WSD> , a 25 % center cut being retained which was then degassed under vacuum in the presence of * * f . 
Meaning of the word marked with <WSD> tags:  a vertical glass tube used in column chromatography; a mixture is poured in the top and washed through a stationary substance where components of the mixture are adsorbed selectively to form colored bands