Chromatography

What you need:

• Coffee filters and paper towels
• Water
• Various colors of water-soluble markers
• Various brands of black water-soluble markers
• Pipettes and medicine droppers
• Plastic cups

What to do:

1. On a coffee filter or paper towel, draw a circle with the black marker of your choice.
2. Place your paper on top of an empty plastic cup.
3. Using the pipette, drop water, by droplets, onto your paper in the center of the circle you drew with black marker.
4. Slowly add drops of water until the water starts to ‘bleed’ through the black circle. What appears to be happening?
5. Repeat this with the other brands of black markers. Are there any differences?
6. Repeat steps 1-4 again using the colored markers. With which colors do you see multiple color bands appearing in the water run? With which colors do you see no other color bands? Can you use this method to blend colors?

What’s the Science?

Chromatography comes from chroma, the Greek word for color. It is a method of separating mixtures using a solid support plus a liquid solvent. In every kind of chromatography, a mixture separates because some of its components stick better to the solid so they ‘stay behind’. These components have a strong affinity or attraction for the solid. Other parts of the mixture dissolve in the solution that wicks into or across the solid. Often you see bands of color that separate out in the experiment.