58 FLUORESCENCE SPECTROPHOTOMETRY 



been redetermining the absorption constants of purified chlorophylls 

 in this laboratory, we had an excellent opportunity to repeat the 

 measurements of Zscheile and Harris on the fluorescence spectra of 

 freshly purified chlorophylls a and h in ether. The new curves are 

 compared in Fig. 6 with those of Zscheile and Harris which have been 

 recalculated to correct for the variation of the effective slit width with 

 wavelength due to their use of a prism. The need for such a correction 

 of their curves was pointed out to us by Dr. L. N. M. Duysens. The 

 agreement of the chlorophyll h curves is close, but the difference be- 

 tween the two chlorophyll a curves seems to be well outside the 



650 700 750 800 850 m^i 



VfAVElENGTH 



Fig. 7. Fluorescence spectrum in ether of "bacteriochlorophyll," measurements of 

 Vermeulen, Wassink, and Reman ( 1937 ) and of this laboratory. 



experimental error of either laboratory. Dr. Smith's absorption meas- 

 urements of his chlorophyll o also show a somewhat similar wave- 

 length shift. It appears that the chlorophyll a of the two laboratories 

 may actually have been composed of different isomeric fractions. 



Bacteriochlorophyll 



The dotted curve in Fig. 7 shows the fluorescence spectrum of 

 bacteriochlorophyll published by Vermeulen, Wassink, and Reman 

 (1937). The figure also shows the measurements of partially purified 

 bacteriochlorophyll prepared by Dr. Smith and Mr. Benitez. Pre- 

 sumably the differences between the curves are due to the use of 



