Irreversible Photobleaching of the Solution of Fluorescent Dyes. III. Photoreaction of Eosine in the Aqueous Alcoholic Solutions under Evacuated State

The photoreaction of eosine has been studied in ethanol-water mixture in vacuo. Irradiated solution showed a gradual spectral shift towards shorter wavelengths. Analyzing the spectra and applying the chemical method, it was found that the spectral shift is due to the production of uranine. The rate of disappearance of eosine increases with rising concentration of ethanol until 20 vol. per cent, at which it reaches its maximum and constant value, which is the same as that in pure ethanol. The primary processes of the aerobic photo-bleaching of eosine in aqueous solution were discussed and it was concluded that the process must be D^t+O_2→D···O_22O···prod. (iii)