Tonic water added is known as bitter lemon or bitter lime, respectively. The quinine in tonic water will fluoresce under ultraviolet light. In fact, the sensitivity of quinine to ultraviolet light is such that it will appear visibly fluorescent in direct sunlight. Tonic water Tonic water (or Indian tonic water) is a carbonated soft drink in which quinine is dissolved. Originally used as a prophylactic against malaria, tonic water usually now has a significantly lower quinine content and is consumed for its distinctive bitter flavor. It is often used in mixed drinks, particularly in gin and tonic. Quinine was added to the
Tonic (music) so on. In western European tonal music (key-based music) of the 18th and 19th centuries, the tonic center was the most important of all the different tone centers which a composer used in a piece of music, with most pieces beginning and ending on the tonic, usually modulating to the dominant (the fifth above the tonic, or the fourth note down from the tonic) in between. Two parallel keys have the same tonic. For example, in both C major and C minor, the tonic is C. However, relative keys (two different scales that share a key signature) have different tonics.