47 



a net oxidation, and I think this is due to the fact that the water under irradia- 

 tion decomposes not only to give radicals but also to give a certain, but smaller, 

 yield of peroxide molecules and hydrogen molecules. As the peroxide accumu- 

 lates in the solution, it can either act directly on the substrates or it can react 

 to some extent with H and OH to form oxidizing radicals that can produce this 

 net oxidation. The hydrogen molecules are, relatively speaking, inert. Is that 

 point clear? 



BARRON: Yes, that is what I thought; the reason there was no reduc- 

 tion was because the hydrogen atoms combined. 



ALLEN: No, I don't think this is so because the yield of molecular 

 hydrogen that one sees in many systems is much smaller than the yield of radi- 

 cals that one has to assume is present. But I think that what usually happens is 

 that the effects of the H and the OH in oxidation and reduction cancel out and any 

 net oxidation that you get (this is all in the absence of oxygen) is due to the pres- 

 ence of molecular peroxide that is formed directly from the water, to some de- 

 gree simultaneously with these radicals. 



BARRON: But there is no hydrogen peroxide formed by X radiation in 

 the absence of oxygen. 



ALLEN: That is true only if the water is very pure. In that case, the 

 radicals can act on the molecular hydrogen peroxide and the whole thing goes 

 back to water. If you add anything to the water, it will generally protect the 

 molecular hydrogen, which is less active than the peroxide, so that you do get 

 a net formation of hydrogen peroxide, and the peroxide can go ahead and subse- 

 quently produce oxidation. 



BARRON: In all our experiments, we have saturated the water with 

 nitrogen, purified by passage over copper wire heated at 800°C. We have never 

 found hydrogen peroxide in water saturated with pure nitrogen. 



ALLEN: If the water is purified, there is a radiation-induced reaction 

 between any molecular hydrogen and hydrogen peroxide that may be accumulat- 

 ing. The steady-state concentration of peroxide may be too low to detect, 



BARRON: However, we have one experiment with steroid hormones 

 where we can demonstrate reduction that is very similar to the reduction with 

 atomic hydrogen. The steroid has an absorption peak at 240 m|jL. This is due to 

 the carbonil groups. Irradiation in nitrogen gives a greater diminution of the 

 absorption spectrum than irradiation in the presence of oxygen. I thought this 

 was a reduction. So what we did was to pass hydrogen over colloidal palladium 

 and we found exactly the same diminution. 



ALLEN: Dr. L.H, Gray told me about some experiments that have 

 been done on irradiation of suspensions of T- 1 phage. Inactivation of this phage 

 proceeded with a much higher yield if the solution was saturated with nitrogen, 

 and a still higher amount of inactivation was found if both oxygen and hydrogen 

 were present. It was concluded from this that the main agent for inactivation of 

 the phage was the hydrogen atom. 



PATT: Along the same lines, Bachofer reported recently that oxygen 

 apparently protected phage against X radiation in contrast to the usual protective 

 effect of oxygen removal. It appears, however, that this effect may be due, or 

 at least related, to the presence of certain salts in the medium. I think the 

 work to which you refer was done by Alper; it has been reported in the British 



