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Fractional distillation is used to separate mixtures of volatile liquids. The round-bottomed distillation flask is underneath the fractionating column, which bears a stillhead and a thermometer adaptor. The stillhead leads to the water condenser (Liebig condenser) which is connected to the receiver by a vented delivery bend.

The fractionating column can be filled with almost anything that gives it a large surface area - glass beads or spirals, bits of broken glass tubing, ceramic rings. Alternatively it can be made with glass spikes sticking inwards (Vigreux column), or contain a spiral that forces the vapour around a helter-skelter pathway (Dufton column).

If a mixture of liquids forms an azeotrope, then that mixture cannot be completely separated by fractional distillation. This is covered further in the pages on Raoult's Law.

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Chemistry Contents     Simple distillation    Reflux   Gas preparation    Drawing introduction

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