How do glowsticks work?

06 November 2005

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Question

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 then 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 glass, 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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