The spectra of the two tautomeric isomers V and VI have been studied in the range 200–350 mμ, using n-hexane, dioxane, acetonitrile and water as solvents. Both molecules possess a shoulder at about 45,000 cm −1 which is assigned to a n → π* transition. The recorded spectra give evidence for a strong absorption band slightly above 50,000 cm −l, which should be assigned to a π → π* transition. These results are regarded as an indication that the lowest energy levels of the two tautomeric forms have a rather similar pattern, the main difference being in their transition moments, and, hence, in the intensity of the corresponding bands.