Fractional Distillation Essay

1062 WordsDec 19, 20115 Pages
Fractional distillation [edit] Laboratory setup Fractional distillation in a laboratory makes use of common laboratory glassware and apparatuses, typically including a Bunsen burner, a round-bottomed flask and a condenser, as well as the single-purpose fractionating column. [edit] Apparatus Fractional distillation apparatus using a Liebig condenser. A conical flask is used as a receiving flask. Here the distillation head and fractionating column are combined in one piece.[1] * heat source, such as a hot plate with a bath, and ideally with a magnetic stirrer. * distilling flask, typically a round-bottom flask * receiving flask, often also a round-bottom flask * fractionating column * distillation head * thermometer and adapter if needed * condenser, such as a Liebig condenser, Graham condenser or Allihn condenser * vacuum adapter (not used in image to the right) * boiling chips, also known as anti-bumping granules * Standard laboratory glassware with ground glass joints, e.g. quickfit apparatus. [edit] Discussion As an example, consider the distillation of a mixture of water and ethanol. Ethanol boils at 78.4 °C while water boils at 100 °C. So, by heating the mixture, the most volatile component will concentrate to a greater degree in the vapor leaving the liquid. Some mixtures form azeotropes, where the mixture boils at a lower temperature than either component. In this example, a mixture of 96% ethanol and 4% water boils at 78.2 °C, being more volatile than pure ethanol. For this reason, ethanol cannot be completely purified by direct fractional distillation of ethanol-water mixtures. The apparatus is assembled as in the diagram. (The diagram represents a batch apparatus, as opposed to a continuous apparatus.) The mixture is put into the round bottomed flask along with a few anti-bumping granules (or a Teflon coated
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