Oxidation-reduction potentials of different chlorophylls in methanol

It was found that the reversible decolorisation of some chlorophylls upon the subsequent addition of ferric and ferrous salts, as originally measured by Rabinowtich and Weiss for chlorophyll a, proceeded at a reproducible oxidation-reduction potential. A marked difference was found to occur between the redox potentials of the bacterial pigments and those of the green plant pigments. Apart from these measurements in organic solvents, reversible bleaching could also be demonstrated in aqueous extracts from photosynthetic bacteria. The possible significance of these data is discussed