MAXIMUM FLASH YIELD 1453 



law of monomolecular decomposition (identical with the law of radioactive 

 disintegration) determines that, after time t, the residue of unchanged 

 I'Eb complexes will be: 



(34.3) [I-Eb1 = [I-EB]oe-^A< 



where k^A i« the monomolecular velocity constant of the Emerson-Arnold 

 reaction. The yield per flash, which we assume to be equal to the amount 

 of I-Eb transformed during the dark interval, is: 



(34.4) P = [I-Eb]o - [I-Eb] = [I-Eb]o (1 - e-k^Atd) 

 One half the maximum yield is obtained when e~''^'' = 3^, or: 



(34.5) <i/, = In2/A"EA 



(this being the well-known relation between "half-time" and velocity con- 

 stant of a monomolecular process) . 



From what was said before about the influence of dark intervals on the 

 yield of nonsaturating flashes, it is obvious that the above equations can be 

 applied to saturating flashes only. Figure 34.11 is an illustration of this 

 fact. The plot of P against ta gives an exponential curve for saturating 

 flashes (90 klux for 0.0045 second) ; but the lower curve, which corresponds 

 to nonsaturating flashes, has no such simple shape. 



Table 34.11 contains the values of U/, and /tea calculated from the 

 measurements of different authors. The column headed ^b shows the 

 intervals required for the completion of the Emerson- Arnold reaction; 

 since the law of decay is exponential, the figures in this column can be only 

 approximate. 



Table 34.11 



Rate of the Emerson-Arnold Reaction in Chlorella 

 (Values in Parentheses are Rough Estimates) 



-1 



Author" Temp. ° C. h/j, sec. ts, sec. ^ea. sec. 



' EA 1.1 0^04 0^4 20 



WF 4.7 0.038 — 22 



EA 5.9 — (0.12) — 



EA 6.9 — (0.08) — 



EA 13 0.02 0.2 40 



WF . ..19.6 0.013 0.06 63 



PT .23.9 (0.005) 0.029 (165) 



PT 23.9 0.025'' 0.062* 33 



" EA = Emerson and Arnold (1932). WF = Weller and Frank (1941). PT = 

 Pratt and Trelease (1938). See also Gilmour et al. (1953). 

 '' In heavy water. 



Since the Emerson-Arnold reaction is a dark catalytic process, it can 

 be expected to possess a high temperature coefficient. The values of /cea in 



