Studies on fluorescein-VI Absorbance of the various prototropic forms of yellow fluorescein in aqueous solution.

The absorbance of yellow fluorescein in water, at ionic strength 0.10, as a function of pH at 437, 455, 464, 475 and 490 nm has been resolved into four components, the absorbances of the individual prototropic forms of fluorescein in water. The molar absorptivity of each species at each of the five wavelengths is reported. A novel type of isosbestic point is described.