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Fractional distillation is used as a purification technique to separate liquids. A "fractionating
column," which is packed with some kind of inert material (such as metal turnings, glass
beads or even paper clips), is placed above the distillation flask. As the vapors rise
through the packing material, they condense, revaporize and condense again (called reflux).
This is like having several tiny simple distillations, one after another, so as the vapors rise,
thay are very much enriched in A by the time they reach the top and are collected. In this
way, we can distill off and collect pure A. By recording the temperature as a distillation
proceeds, we can observe the efficiency of a fractional distillation. In a simple distillation,
the temperature should steadily increase as a mixture of two liquids distills. In a successful
fractional distillation, the initial temperature should be the boiling point of the more volatile
component and should remain steady as the pure liquid distills. When all of this component
is gone, the temperature should rapidly climb to the boiling point of the less volatile
liquid as that liquid finally starts to distill.