Abstract: The current work was done for the study of the absorption and photostability of fluores-cein in gelatin films. Some interesting phenomina were observed. The films with high dye concentration showed the absorption maxima at about 503 nm under proper base concentration, but the absorption maxima would be changed into 490 nm or even lower with the decrease of the absorbance at the same time after illumination or dilution. The dye films with absorption maxima at about 503 nm had little fluorescence but would be induced to have fluorescence by intense light. From the natures and reported results in literatures, the state was thought most likely to be the dimer of the fluorescein dianions.

Key words: dye, fluorescein, absorption, fluorescence, photostability