32 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



H0O2 , a coiTesponding increase in ki' should have been found. However 

 no such rise occurred so we 'smoothed out' this initial rise in D to obtain 

 approximate values for the variation of D for H2O2 with rj"'^. The results 

 of this process for ki and k4 are shown in figure 7. The data support clearly 

 the concept that k4 is diffusion controlled at 25° for values of r/ from 0.9 

 to 65 cp. The scatter of the points could be due, at least in part, to the 



7.5 



7.0 



6.5 



k,,k^,ond -r- os functions of T"' 



iog,o K 



'°«ioi7 



mole 



log,, k 



dryi © 



^Hq = k col/mole 



-2 &. 



-&- 



AHa= 12.6 k col/mole 



2b' 



_1 L_ 



L 



2.5 



2.0 



1.5 



.30 .31 .32 .33 .34 .35 .36 



Fig. 5. Variation of ki and k4 with temperature. 



differences in D for H2O2 and O2 . The values of ki are diffusion inde- 

 pendent at the low r; values, but are diffusion limited at the high values. 

 The same conclusions were reached from the results of the rate of forma- 

 tion of p observed at 405 m^. 



Since k4 is diffusion controlled, any encounter with a sensitive area on 

 the surface of the molecule must lead to a reaction. In conformity with 

 other usage, we have called this area a reaction cross-section. Since ki and 

 k4 have approximately the same slope in the diffusion controlled region, 

 it is concluded that the sensitive area must have the same size. 



