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Join
the American Chemical Society at the Illinois State Fair, August 12-21, 2005, Springfield,
Illinois |
Magic Skin Writing
| Materials: |
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| Note: | Handle the ingredients with care. Adult supervision is required. |
| The reaction: |
C6H8O6 + I2 → C6H606 + 2I - + 2H + ascorbic acid + iodine → dehydroascorbic acid + iodide + hydrogen ions |
Procedure:
- Using a cotton swab, wipe some tincture of iodine on your arm.
- Gently spray starch over the same area and it will turn black. This is the classic iodine and starch reaction.
- Using a vitamin C tablet (ascorbic acid) and wipe designs into the black area and the color disappears.
- When done wipe the area with a moist paper towel to remove the ingredients from your arm. Vitamin C is an antioxidant. Iodine will react with vitamin C and be converted to a form that won't turn blue in the presence of the starch.
Topics that can be discussed include the formation of a starch-iodine complex, and the reduction of the iodine to the iodide anion by the vitamin C.
----Contributed
by Frank Salter, Mark Twain Section