Science Questions

How do glowsticks work?

Sun, 6th Nov 2005

Part of the show Fireworks, Explosions and Chemistry

Question

Catherine in Ashwell asked:

When you snap a glowstick, what makes it glow?

Answer

It's luminol, or a dye like it, that you're activating.

This is a chemical that can absorb chemical energy and thenGlowstick Diagram release it as visible light.

In a glowstick, the chemical reaction that energises the luminol is usually the oxidation of an ester, called phenyl oxalate, by hydrogen peroxide (H2O2) in the presence of a strong alkali, like sodium hydroxide (NaOH).

If all of these chemicals were present in the same tube when the glowstick was manufactured, they would begin reacting immediately and, by the time you needed it, the glowstick would be exhausted.

Instead,the chemicals are kept apart by putting the luminol and the ester and the alkali in one tube and the peroxide into a separate tube, usually made of thin Breaking Glowstickglass, which is floating inside the tube containing the luminol. 

This means that the reaction will only begin when you break the glass by bending the glowstick and allowing the chemicals to mix.

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