REDUCTION OF ERYTHROSIN AT DROPPING MERCURY ELECTRODE

The polarographic reduction of erythrosin, the disodium salt of 2′,4′,5′,7′-tetraiodofluorescein, was examined at pH 4·7. Three reduction steps were found. The first step involves two electrons and the reduction of the quinone group as in fluorescein. The second step results from the removal of the 4′,5′-iodo groups and the last step from the removal of the 2′,7′-iodo groups; each of these steps involves four electrons. This sequence was elucidated by the identification of the products of the controlled potential electrolysis of erythrosin. The value for the diffusion coefficient of erythrosin was found to be 6·45 × 10-6 cm2/s at 25°C. © 1968.