61 



ONSAGER: It is very difficult to develop a full-fledged kinetic theory for 

 diffusion in liquid and particularly perhaps in water. On the other hand, I don't 

 believe it is really necessary because all coefficients of diffusion are reasonably 

 small. 



MAGEE: You can do it if you like, but I -- 



ONSAGER: I don't want to. I rely on experience with more orthodox mole- 

 cules. 



MAGEE: As a matter of fact, it is certainly true that nothing about the dif- 

 fusion coefficients or reaction rates are known for radicals I don't know any ex- 

 perimental evidence at all. But I want to estimate this quantity y. 



ONSAGER: Let's see what you have done. 



MAGEE: So far I just have k. Now we can substitute and get 



n 2 



y= 



r \ 



The reason I am doing this in such detail is to give everyone a chance to 

 object. I think that lambda and sigma have to be about the same magnitude, and 

 so we can write 



r o 



POLLARD: What do you take for sigma and lambda? 



O 



MAGEE: I have taken 2 A for sigma and the same for lambda. For y = 5/6 

 this gives r Q = 22 A. If a Gaussian distribution for radicals is used instead of 

 this model I have described, the b value for the spur containing six radicals turns 

 out to be about 10 j^. This calculation is described in the paper by Samuel and 

 myself (7). 



BURTON: In this model your assumptions are substantially equivalent to 

 saying, in terms of chemistry, that the rate constant of the reaction giving H^ is 

 equal to the rate constant of the reaction giving H^O. 



MAGEE: That is right. 



BURTON: We all feel instinctively that is not so. 



MAGEE: We have started to look into a number of such questions. Of 

 course, it is very discouraging to try to make a priori calculations as to what 

 these rate constants are, but in this particular case there are factors which tend 

 to balance out. That is, I don't feel too bad about putting the k's for H^ and HOH 

 the same. However, I would think that the HOH might be a little faster. 



BURTON: If you put them the same, that is equivalent to saying quite apart 

 from the cr value, that the \ value is the same, and that I know is not true. If 

 you consider the H? and the H2O2, that is equivalent to saying that the X. value 

 for H and OH are the same. 



MAGEE: It is the parameter y that comes in. 



