Developers:
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Linda Schweizer
Upper Dublin HS
Ft. Washington, PA
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Michael Gavaghan
Dr. Peter Yarnell
Rohm and Haas Company
Spring House, PA
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Grade
Levels:
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Grades 8 through 12
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Purpose:
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To separate a mixture of dyes in water
soluble ink
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Materials:
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Two pieces of 11-cm filter
paper
One petri dish
Several water soluble markers
(washable transparency pens work very well)
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Procedures:
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First piece of filter paper:
- Mark your name or intitials near the edge of the
paper IN PENCIL.
- Tear a small round hole (smaller than a dime) in the
center of the paper.
- Use a marker or several markers to place small dots
of ink in a ring close to the torn hole.
- This paper will become your chromatogram.
Second piece of filter paper:
- Fold the paper in half then in fourths lengthwise.
- Tear along folds, and discard outer sections.
- The two longer strips can be made into wicks.
- To make a wick, roll one of the longer strips,
starting at the shorter end, much like you would roll a
stick of gum.
- Insert this rolled wick into the round hole in your
chromatogram.
The petri dish:
- Fill the bottom half (the deeper one) half full of
tap water.
- Lay the chromatogram over the dish so that it rests
on the rim with the wick extending down into the water
- Watch the water enter the wick and travel out across
your chromatogram, carrying the ink as it travels.
- Note how some of the inks begin to separate into
differently colored dyes.
- When the water nearly reaches the edge of your
chromatogram, remove it and place it somewhere clean and
safe to dry.
- Discard the wick into the waste basket.
- Dry the petri dish and return it to its designated
location.
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Analysis:
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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?
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Conclusion:
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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.
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