176 



LIGHT AND LI IE 



E 

 E 



c 

 



■p 



3 



CO 



c 

 d 



0) 



u 

 o 

 +J 

 o 



Q. 



800 _ 



700 



600 



500 



- 400 _ 



300 _ 



zoo_ 



100 - 



100 700 iOO 400 



Time (minutes) 



500 



lig. 2. l)eca\ ol chfiiiiliiminescence ol /iiu ictraphenylpoiphiiie in same run illus- 

 I rated in Fig. I. 



show an initial somewhat rapid phase as well. Further, the ratio of 

 initial rate to steady rate for both peroxide decomposition and 

 luminescence intensity is the same, within experimental error. At 

 lower initial concentration ratios of porphyrin to peroxide the ap- 

 parent ki's and k,'s both increase. The rate law for the irreversible 

 porphyrin decomposition is somewhat more complex. Within a given 

 run, the rate appears to be second order in peroxide and first order 

 in porphyrin (Table 1) . However, variation of the initial peroxide 

 concentration [THP],„ indicates that a better fit is obtained by a 

 rate proportional to the product [THP]2 [THP],,-^ [ZnTPP]. 



2. Ratio of peroxide to porphyrin decomposed. Over about the 

 first (peroxide) hall-lile, about thirty molecules of peroxide are de- 

 composed for every mole of dye which disappears. Despite the kinetic 

 complications, this ratio is remarkably constant over the temperature 



