Paper Chromatography: An Experiment

Developers:

Linda Schweizer
Upper Dublin HS
Ft. Washington, PA

Michael Gavaghan
Dr. Peter Yarnell
Rohm and Haas Company
Spring House, PA

Grade Levels:

Grades 8 through 12

Purpose:

To separate a mixture of dyes in water soluble ink

Materials:

Two pieces of 11-cm filter paper

One petri dish

Several water soluble markers (washable transparency pens work very well)

Procedures:

First piece of filter paper:

1. Mark your name or intitials near the edge of the paper IN PENCIL.
2. Tear a small round hole (smaller than a dime) in the center of the paper.
3. Use a marker or several markers to place small dots of ink in a ring close to the torn hole.
4. This paper will become your chromatogram.

Second piece of filter paper:

1. Fold the paper in half then in fourths lengthwise.
2. Tear along folds, and discard outer sections.
3. The two longer strips can be made into wicks.
4. To make a wick, roll one of the longer strips, starting at the shorter end, much like you would roll a stick of gum.
5. Insert this rolled wick into the round hole in your chromatogram.

The petri dish:

1. Fill the bottom half (the deeper one) half full of tap water.
2. Lay the chromatogram over the dish so that it rests on the rim with the wick extending down into the water
3. Watch the water enter the wick and travel out across your chromatogram, carrying the ink as it travels.
4. Note how some of the inks begin to separate into differently colored dyes.
5. When the water nearly reaches the edge of your chromatogram, remove it and place it somewhere clean and safe to dry.
6. Discard the wick into the waste basket.
7. Dry the petri dish and return it to its designated location.

Analysis:

Observe your chromatograms and note which inks display more than one color.

Record the colors you see, beginning with the ones closest to the hole and ending with the ones which traveled farthest from the hole.

Which pigment travels the farthest on the paper?

Conclusion:

Which color of inks contain a mixture of pigments and which contain only one pigment? Which pigment is least soluble in water and which pigment is most soluble in water.