PARADOX

        Tonic water (or Indian tonic water) is a fizzy soft drink flavoured with quinine. The drink gains its name from the medicinal effects of this slightly bitter flavouring.
The quinine was added to the drink as a prophylactic against malaria, since it was originally intended for consumption in tropical areas of India and Africa where that disease is endemic.
Tonic water originally contained only carbonated water and quinine, and it contained a large amount of the latter. However, most tonic water today contains a medically insignificant amount of quinine, and is thus used for its flavor only. It is consequently less bitter, and is also usually sweetened. Some manufacturers also produce diet tonic water.
Tonic water is often used as a mixer for alcoholic spirits, especially gin (the mixture commonly known as a gin and tonic).
Tonic water with lemon or lime flavor added is known as bitter lemon or bitter lime, respectively. Such soft drinks are more popular in Europe than in the United States.
Tonic water will glow under ultraviolet light, due to the quinine in it.