Chromatography is a method for analyzing complex mixtures (such as ink) by separating them into the chemicals from which they are made. Chromatography is used to separate and identify all sorts of substances in police work. Drugs from narcotics to aspirin can be identified in urine and blood samples, often with the aid of chromatography.
You Will Need:
Coffee filter (or filter paper)
Water soluble food colors
Water-soluble marking pens,
Clear glasses or other containers
1. Cut several coffee filters into long strips, one strip per pen.
2. Fold the end of each strip over then staple it to form a loop.
3. Place a dot of ink near the bottom of each strip. Use a pencil to identify which strip belongs to which pen.
4. Poke a pencil through one of the loops you just made. Use the pencil to suspend the strip in a small glass or container.
5. Carefully add water to the glass until it reaches the bottom of the paper strip just below the ink dot. Be sure the ink stays above the water and the paper stays in the water.
6. Allow the water to soak up the strip and watch what happens to the ink drop.
7. If the ink you are testing does not spread out, re-test it using rubbing alcohol.
8. Repeat this process for each strip and compare your results.
9. Let the strips dry and tape them on a sheet of paper as a record of the different pen types.
SCIENCE BEHIND THE EXPERIMENT
Because molecules in ink and other mixtures have different characteristics (such as size and solubility), they travel at different speeds when pulled along a piece of paper by a solvent (in this case, water). For example, black ink contains several colours. When the water flows through a word written in black, the molecules of each one of the colours behave differently, resulting in a sort of “rainbow” effect.
Many common inks are water soluble and spread apart into the component dyes using water as a solvent. If the ink you are testing does not spread out using water, it may be “permanent” ink. In such cases, you will have to use a different solvent such as rubbing alcohol.