Fractional Distillation of Water & Ethanol

Written by andrew youngker
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Fractional Distillation of Water & Ethanol
Graduated cylinders make the best collection containers. (cylinder image by Hubert from

Fractional distillation is a purification technique commonly done in chemical laboratories and is achieved by the addition of a fractionated column on a simple distillation apparatus. Fractional distillation works by separating miscible liquids by their boiling points by a process of vaporising and condensing. Miscible liquids are those that are soluble together to form a homogeneous mixture. The first component to pass through the distillation apparatus will be ethanol, followed by water.

Skill level:

Things you need

  • Mantle
  • Power regulator
  • Round bottom flask
  • Fractionated column
  • Bent adaptor
  • Condenser with rubber connections
  • Water supply
  • 3 collecting containers
  • Distillation head
  • Thermometer
  • Neoprene cover with one hole
  • Ring stands with clamps
  • Rubber bands
  • Boiling chips

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  1. 1

    Set up the apparatus by securing the mantle on the bottom of the ring stand. Since most mantles have only an on and off switch, plug the mantle into the power regulator, then regulator to power source.

  2. 2

    Clamp the round bottom flask in the mantle followed by the fractionated column and bent adaptor.

  3. 3

    Push the thermometer through the neoprene cover and attach to the upward portion of the bent adaptor. The bulb should be just below the bent arm.

  4. 4

    Attach the condenser to the horizontal portion of the bent adaptor. Clamp in place with another ring stand. Water hoses should be attached so that the water flows into the lower portion and out through the upper hose.

  5. 5

    Attach distillation head to end of condenser, which should rest just inside of the collecting container.

  6. 6

    Secure all glassware, using rubber bands connected to the glass hooks located on the ends of each piece of glassware, to ensure a tight seal.

  1. 1

    Fill round bottom flask with water and ethanol mixture along with boiling chips. Check apparatus for visible loss of connections.

  2. 2

    Turn on mantle heat source to medium heat. Turn on the cool water for condenser on low.

  3. 3

    Watch thermometer for temperature to stop moving once distillation is under way. Adjust the heat so that only about one to two drops are distilled every few seconds.

  4. 4

    Change out the collecting container with a fresh one once the temperature starts to rise. This is a mixture of both ethanol and water.

  5. 5

    Change the collecting container again a few seconds after temperature is stabilised. This is now the water portion of the mixture.

  6. 6

    Turn off the mantle while there are a few drops still present in the reaction flask. Explosions may occur when heating glassware until dry.

Tips and warnings

  • Distilling at a slow, steady rate will make the final result more pure.
  • Distillation temperatures may differ from ideal due to atmospheric pressure on that day at that location.
  • Do not use open flame sources to heat the round bottom flask.
  • Completely closed systems may explode glassware. Be sure there is a space between the end of the apparatus and the collecting container.

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