In the previous experiment a redish material could
be seen around some of the numbers written on the fabrics by a black CD-R
Pen. Experiment
1. Use a pencil lead to draw
a circle in the middle of the filter paper and then trace it with
the CD-R PEN (Fig. 1).
2. Make a hole in the middle
of the paper.
3. Twist a wick with a half
piece of toilet paper, of water and placed in a stopper as stand (Fig.
2).
5. Wait until the water moved
up in the wick, reached the black circle (Fig. 3) and finally the
rim of the paper circle (Fig. 4).
Observations
1. Water moves upwards in
the wick and horizontally in the filter paper.
2. A reddish substance leaves
the black ring, while the front of the water passed through the filter paper.
Explanation
1. The cellulose fibres of
filter paper leave space between each other like the fibres in the fabrics.
Capillary forces move the water in the
papers of the wick and the filter.
2. The separation of the
reddish substance is due to its limited solubility in cold water, the
movement of the water by capillarity and the limited
adsorption to the paper. In this process
called paper chromatography the cellulose fibres are the stationary phase
and the water is the
mobile phase.