P 5766 (OTTO) Pyrene, 98%, Cas 129-00-0 - used commercially to make dyes and dye precursors, for example pyranine and naphthalene-1,4,5,8-tetracarboxylic acid. P 5766 (OTTO) Pyrene, 98%, Cas 129-00-0 - used as a probe to determine solvent environments and fluorescence spectroscopy.