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Description

This experiment shows how ink can be separated into its component dyes by chromatography.

Resources

Coffee filter (use a brand which is fairly thick, such as the Molinex or the Kafilta cone filter), plastic cups, water, rubbing alcohol, one each of several brands of black felt tip pen or marker (use no more than one brand of "permanent" marker, the rest should be the non-permanent type)

Instructions

Put a small amount of water in a plastic cup, so as to barely cover the bottom of the cup.
Assign a number to each pen.
Cut the coffee filter into long strips (about 3 - 4 cm wide and 10 cm long). Cut it in such a way that the grain of the filter paper runs parallel to the 10 cm dimension of the strip. Fold each strip along the 10 cm dimension so as to make a crease along the middle of the strip. Identify each strip near one end of the filter paper along the 10 cm dimension. For convenience, this end will be called the top of the paper. Use the same numbering system as used with the pens.
Take a black pen and a strip. The two should have the same identification number. Make two small marks with the pen about 2 cm from the bottom of the strip, one on each side of the crease. (It is important to keep the size of the marks small). Repeat with another pen and another numbered strip until all the different pens have been used.
Take a marked strip and stand it in the cup so that the bottom of the strip is touching the water. Make sure that the pen mark stays above the water level.
Observe the separation of the ink into different colors as water rises up the coffee filter. Remove the paper from the cup when the water (not the colors) has risen to about 2 - 3 cm from the top.
Repeat the above with all the marked strips. Observe the color patterns produced with different pens.
Repeat the above using rubbing alcohol in the cup instead of water. Compare the color patterns produced in this case with those produced with the corresponding pens using water.

Tags

• chromotograpthy
• colour
• experiment
• paper
• science
• water

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