Pyranine is a hydrophilic, pH-sensitive fluorescent dye from the group of chemicals known as arylsulfonates.[2][3] Pyranine is soluble in water and is used as a coloring agent, biological stain, optical detecting reagent, and pH indicator.[4][5] Pyranine is also used in yellow highlighters to provide their characteristic fluorescence and bright yellow-green colour. It is also found in some types of soap.[6]
Synthesis
Pyranine is synthesized from pyrenetetrasulfonic acid and a solution of sodium hydroxide in water under reflux.[7] The trisodium salt crystallizes as yellow needles when adding an aqueous solution of sodium chloride.
^Tietze, Ernst; Bayer, Otto (1939). "Die Sulfosäuren des Pyrens und ihre Abkömmlinge". Justus Liebig's Annalen der Chemie. 540 (1): 189–210. doi:10.1002/jlac.19395400113. ISSN0075-4617.