Tonic Water

Tonic water is a mainstay behind any bar. One thing you might not know about tonic water is that it is strongly fluorescent under UV light, glowing bright blue. The active fluorescent molecule within tonic water is called quinine. This organic compound is extracted from the bark of the Cinchona tree and is responsible for the bitter taste of tonic water, as well as the liquid's anti-malarial properties. The brightness of light emitted by quinine is so reliable and stable that it is used as a fluorescence intensity standard, against which levels of fluorescence are measured and experimental equipment calibrated.