17: The Apothecary's Cocktail

Have you ever wondered how the weird coloured liquids are created in science fiction films? You may have seen them bubbling away in round bottomed flasks and retorts.

These coloured solutions are a legacy of the apothecaries of the 18th century who were the equivalents of our modern day pharmacists. The apothecary’s shop always had a large coloured bottle in the window.

Have a go at making your own cocktails. Ask your teacher to hunt around in the glassware store and find weird shaped vessels to store your concoctions.

What you will need

1dm3 measuring cylinder
500cm3 conical flask and bung
500cm3 measuring cylinder
filter paper
filter funnel
eye protection 		potassium carbonate
copper sulphate
ethanol
paraffin oil
dimethylbenzene (xylene) - dyed with Sudan III
Note: An intermediate stage of this experiment needs to be left for several hours

What you do

  1. Eye ProtectionHighly Flammable
    Pour equal volumes of ethanol and distilled water into the conical flask.
  2. Keep adding solid potassium carbonate, with shaking, until no more will dissolve.
    This is a saturated solution.
  3. Put in the bung and leave the flask to stand. Two layers will form.
  4. Harmful
    Add a few crystals of copper sulphate and stir well. Replace the bung and leave for several hours.
  5. Pour off the top layer of liquid (the supernatant).
    Filter the remaining solution and pour it into the measuring cylinder.
  6. Harmful
    Add a few cm3 of the dyed dimethylbenzene (xylene). A deep red layer forms at the top. Next is a colourless layer of ethanol. At the bottom the blue aqueous (watery) layer contains dissolved copper sulphate.
  7. Seal the top with a paraffin layer and put in a bung. This will remain stable for several years.
Eye Protection
eye protection must be worn

Highly Flammable
HIGHLY FLAMMABLE
ethanol

Harmful
HARMFUL
dimethylbenzene (xylene)
copper sulphate crystals

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