.org20 Separation of felt-tip pen colours 1 (thin-layer chromatography)..

Material
Black felt-tip pen STABILO point 88 fine 0.4,  plastic strip coated with silicagel, 5-ml ampoule (wide mouth), dropper bottle with methylated spirit.
Experiment
1. Cut a plastic strip that fits to the mouth of the bottle.
2. Make two dots  on the silicagel with the pen: side by side and 5 mm above the lower end of the strip (Fig. 1).
3. Transfer 10 drops of methylated spirit into the bottle.
4. Carefully place the strip into the liquid (Fig. 2 ).

Observations
a) The blue colour is separated into yellow, violet and blue dyes by the ascending spirit (Fig. 2 und 3).
b) The strip was dried (Fig. 4). (The silicagel with the yellow, violet and blue colours can be removed separately.)
Explanations
The black colour of the pen was attracted by the silicagel. The spirit was lifted upwards through the silicagel by capillary forces (similar to ink in a blotting paper). The black colour proved to be a mixture of three different dyes. Each of them is bonded  by the silicagel with in a specific force and each of them is dissolved differently by the spirit while it moves upwards through the silicagel. So the three dyes moved upwards with different speeds resulting in their separation.

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Separation of felt-tip pen colours 2 (paper chromatography)..

1. Make a wick by coiling up a half piece of toilet paper.
2. Cut a small hole into the middle of a filter paper (or a piece of coffee filter).
3. Photo 1: Draw half circles around the hole using a black and a brown STABILO point 88 fine felttipped pen.
4. Photo 2: Drill the wick into the hole of the filter paper,
                  Transfer the wick into a Liquemin ampoule with water.
5. Photo 2 and 3: Observe what happens to the water and to the black and brown colours. DESCRIBE  your observations.
ERPLANATIONS:
The black and the brown colours of the pens are soluble in water.
The water does not only climb up in the wick but also flows from the center of the filter papers to their rims.
The colours of the two pens are no pure substances but mixtures of blue, yellow, pink and brown colours.
These colours have a different solubility in the water passing through the the half circles (pink and brown dissolve best).