(i) Absorption spectra

Absorption curves were obtained using a Perkin Elmer Model 137 ultra-violet and visible spectrophotometer. The ultraviolet and visible regions are covered on separate quarto size charts, 190 to 390 and 350 to 750 millimicrons. Each range represents one drum revolution, and turning from one range to the other automatically switches the hydrogen and tungsten lamp sources.

(ii) Rf values

Rf. values for all the pigments were calculated and compared with those of known pigments.

The main criterion for identification was the value obtained for the absorption curves, as it is difficult to reproduce Rf. values exactly from one run to another in chromatography. No great reliance therefore was praced on the Rf. values obtained.