It is not possible to obtain absolute alcohol by simple fractional distillation, because a mixture containing at least 95.4% alcohol and 5.6% water becomes a constant boiling mixture (an azeotropic mixture). To obtain 100% pure alcohol a small quantity of benzene is added to rectified spirit and the mixture is then distilled. Absolute alcohol is obtained in third fraction that distills over at 351.3 ºK (78.2 ºC).
There is also an absolute alcohol production process by dehydration using glycerine.
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