Thames & Kosmos Glowing Chemistry handleiding

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Invisible Light

EXPERIMENT 2

Blue clouds from

chestnut tree bark

UV-fluorescent materials can also be found in

nature. There’s a particularly pretty fluorescent

substance to be found in the bark of the horse-

chestnut tree and buckeye trees.

YOU WILL NEED

› UV lamp

› Large measuring cup

› Small measuring cup

› Bark from a horse-

chestnut tree or buckeye tree*

› Fine paintbrush

› Colored paper

HERE’S HOW

1. Peel a small piece of bark off a freshly-cut

chestnut twig (young growth). Fill the large

measuring cup with cold water.

2. Go inside a dark room, shine the UV lamp on

the measuring cup from the side, and float

the piece of chestnut bark on the water. Right

away, you will see magnificent light blue

clouds spread out through the water.

3. Switch on the room light and turn off the UV

lamp. The clouds will disappear. After a little

while, the water will turn brown.

WHAT’S HAPPENING

Aesculus tree bark contain a material

called aesculin (pronounced ess-cue-

lin), which converts UV light into

visible, light blue light.

Twig

Bark

BONUS EXPERIMENT:

Secret messages

You can use your aesculin solution to make invisible

ink. Swirl a little rind in a small amount of water in the

measuring cup for a few minutes, but pull it out before the

water turns brown. You can use this as an invisible ink to

write secret messages with a paintbrush, which will be visible

under UV light after the ink dries. Use colored paper without

any brighteners, and be sure it’s not a kind of paper that turns

slightly brown when you paint on it.

*Horse-chestnuts and buckeye trees (genus

Aesculus) can be found across North America

and Europe. If you search the web for Aesculus,

you can find the common names for the species

that grow in your area.

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