Pyranine fluoresces green in neutral conditions and blue in acidic conditions.

Pyranine is a yellow arylsulfonate dye, commonly found in highlighters, that exhibits strong fluorescence.


The fluorescence of depends on the pH of the solution, which makes it a fluorescent pH indicator. At low pH levels, the color of its fluorescence changes from green to blue. It also acts as a regular pH indicator, and turns from yellow to colorless at the same low pH levels.

Pyranine is highly soluble in water.


Relatively pure pyranine can be found in highlighters and used as a pH indicator.


  • "Radioactive" color-changing baking soda volcano
  • Lava lamp

See alsoEdit

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