37 



ONSAGER: If the concentration of H30 + is what it happens to be in pure 

 water, it is 10"?. 



ALLEN: Two ions and they are each 10"? molar. Then the combination 

 time is about 10"4 second or something like that. 



ONSAGER: Yes. 



ALLEN: This is just from electric attraction alone. This does not take into 

 account thermal motion. 



ONSAGER: Thermal motion did not make any difference. That is a pretty 

 result of Langevin's theory (13). 



PLATZMAN: What I have suggested, then, is that after the electrons are 

 thermalized by the processes mentioned, there occur two possibly rather time- 

 consuming steps, in succession. First, the hydration, or "trapping" of the 

 electron, and second, the attachment of the hydrated electron to the OH radical. 

 Each of them probably consumes a minimum of 10" 11 second, the latter probably 

 a good deal longer. "Trapping" of the electron might suggest that the distances 

 from the positive ions reached by the ejected electrons are not, after all, very 

 great. This is not true, however, because of the great mobility of the trapped 

 electrons. 



A further and final point concerns the observability of these trapped elec- 

 trons. If I am correct, the trapped electrons will play a decisive role in con- 

 structing the chemical kinetics. It becomes very interesting to see whether 

 these speculations can be substantiated or contradicted by experiments. However, 

 unless there is something that we don't understand to prevent the attachment 

 from proceeding once the electron is trapped, I doubt whether the color will ever 

 be directly observable. There is still the possibility of measuring the conductiv- 

 ity of pure water during irradiation. I do not know about the feasibility of such 

 an experiment. I found in the literature some alleged discoveries of augmenta- 

 tion of conductivity, but they are highly suspect. 



ALLEN: The blue color would be a more sensitive test than the change of 

 conductivity. 



PLATZMAN: No. I don't think so. 



ALLEN: Remember that the water has much conductivity to begin with. 



PLATZMAN: Yes, that is correct. One would probably have to measure 

 the frequency-dependent conductivity. 



This is all that I wanted to say. I greatly regret the incomplete and tentative 

 nature of some of these considerations. But, having to open the discussion at 

 hand, I could not do otherwise than tell you of this new work. Let me return to 

 my original remarks, which were that it is far from unlikely that the over-all 

 picture I have given you will be found to be incorrect, at least in part. But still 

 I feel reasonably confident that some of the scenery which we have been contem- 

 plating is authentic. 



BURTON: Dr. Platzman, you say the hydrogen atom is formed substantial- 

 ly away from the region where the positive water ions appear? 



PLATZMAN: Yes. 



