BLEACHING OF CHLOROPHYLL IN METHANOL 



1497 



obtained in air-free solution. Significant results were obtained mainly 

 with chlorophyll b; figures 35.2A and 35. 2B show the decay curves of its 

 phototrope as determined at X 468 and 524.5 m^u, respectively. The first 

 curve is consistent with the assumption of a single phototrope (the same 

 holds for 470.5 and 427.5 m^i) ; but the 524.5 m/x curve indicates the succes- 

 sive formation of two photoproducts — one with decreased, and one with 



t X 10^ sec. 



Fig. 35. 2B. Decay of chlorophjdl b absorption at 524.5 m^ after a flash 

 (Livingston and Ryan 1953). Dashed hne, uncorrected observations; soUd line, 

 correction for scattered flash light; dotted Hne, corrected decay curve. 



increased absorption. The second, longer lived phototrope must be iden- 

 tical with that known from steady light experiments (table 35. lA). Pre- 

 viously described kinetic experiments indicated that this phototrope is a 

 free radical, disappearing by a bimolecular reaction. Analysis of the decay 

 curves in figure 35. 2B makes it likely that the short-lived intermediary 

 product, not observed in steady light — at least, not in the (relatively) 

 weak light which had been used for this purpose — disappears by a first-order 

 reaction (simple monomolecular decay, or — more likely — "self-quenching" 

 by encounters with normal chlorophyll molecules). Livingston and Ryan 



