Sentence:  The mixture was then extracted with <WSD>alkali</WSD> and with water following which the carbon tetrachloride was distilled on a Vigreux column , 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:  any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water