X-Radiolysis of Aqueous Erythrosin

X-Radiolysis of aqueous erythrosin (2′,4′,5′,7′-tetraiodofluorescein) under reducing conditions (complete removal of OH radicals) has given rise to dye-bleaching and formation of leucoerythrosin, due to reactions of erythrosin with ${\rm e}_{(aq)}^{-}$ and H atoms. The reaction rate constant between erythrosin and H atoms was found to be $4.4\times 10^{9}\ M^{-1}\ {\rm sec}^{-1}$. Scavenging of OH radicals with formate, and subsequent reactions of erythrosin with the formate radical ion, ${\rm CO}_{2}^{\overline{\cdot}}$, give rise to both semireduced dye (1,2) and dehalogenation of the dye in an approximate ratio of 1:2. Radiolysis of erythrosin under oxidizing conditions gives rise to products whose absorption spectra overlap strongly with the absorption spectra of erythrosin. Under these conditions the true dye-bleaching cannot be determined. The apparent dye-bleaching is very low. Apparent and true values of dye-bleaching under various conditions are being discussed.