Ask A Scientist: Shine On You Crazy DiamondPosted: April 5, 2012
Question: “Why does tonic water glow under ultraviolet light?” -Thomas H, New Brunswick, NJ
Answer: If you’re been anywhere near The Shore, Miami or parts of Chico State on or near spring break, at some point you’ve probably seen a drink so dazzling, so magical that it nearly glows right in its own glass! Is it magic? Demonic posession? An epicly bad decision?
Well, aside from some few ill advised frat house adventures, the glowing drinks that you’re seeing are not suffering from black magic. What you’re seeing is a drink that contains quinine, one of the few naturally glowing food additives. (Poor taste and regret just happen to be the distillate.)
Quinine, a crystalline alkaloid found in chinchona bark, is the bitter component of modern day tonic water as well as one of the first effective antimaliarial drugs. In the early 19th century, many British officers in the Indian Army found their vile daily doses of quinine went down much smoother at the cocktail hour when combined with carbonated water, sugar and just a touch of gin. Since then, the gin and tonic has remained England’s iconic drink.
….An iconic drink that has a fluorescent quantum yield, that is.
The reason why tonic water glows under blacklight is simply a lesson in how fluorescence works. When a fluorescent material, such as our tonic water, absorbs light photons, it also releases shorter versions of light photons simultaneously. The light photons that have been absorbed are on the ultraviolet spectrum and thus emit more of the same, giving the tonic water a creepy bluish glow when they’re near a blacklight. It doesn’t take much quinine to create an eerie glow- most tonic waters have 83 parts per million (PPM) of quinine, much less than the theraputic dosage starting at 167 PPM.
So the next time you’re stoked on that hottie from the Alpha Epsillon house whilst kicking it Sandy Hook style, you may want to get intense on a lesson on luminescence. (Hotties love luminescence.) You’re welcome, brah.