Chromatographic separation of colours
Most colours that we see, especially those found in nature, are made up of a mixture of other colours. Today we are going to separate out the colours, which make up a some natural plant colours.
You will need:
- Brightly coloured fruit, flowers or vegetables
- Surgical spirit
- Paper napkins or blotting pape
- Tea cups
- Forks and teaspoons
- Knife
- Pencil
- Drinking straws
- Transparent tape
- Long jars or glasses
And last but not least ... a helping hand from an adult.
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Method
First of all you will need to grind down the different plant materials to extract their colours.
Cut up the fruit, flowers and vegetables and place them into separate cups.
Add some surgical spirit, and grind everything finely.
The surgical spirit ensures that more chemicals and colours can be extracted but you should use as little as possible so that the colours will be deeper.
Next you need to prepare the paper. The thicker the paper the better.
Cut it into two-centimetre-wide strips, with about the same height as the glasses or jars.
Now on each strip of paper draw a line about 2 centimetres from one end.
Do not press hard with the pencil ... you should be barely able to see the line. Place a drinking straw across the opening of each jar or glass, and hang a paper strip from each, taking care that the end with the pencil mark should almost touch the bottom. You can use tape to fix the paper to the straws.
Next dip the knife in the pigments that you got from the different items, and using the back edge of the knife, draw it along the pencil mark. Let it dry and repeat.
You need to repeat this stage more than once so that the pigment is concentrated, without letting it run too much onto the paper.
Now place just less than two centimetres of surgical spirit in every glass or jar, and hang the paper strips. The end of the paper strips should be in the surgical spirit, but the line with the pigment should be above the liquid. It is very important that the paper strips do not touch the sides of the jars and glasses.
The experiment needs a few minutes to give results.