BEHAVIOR OF ORGANIC COMPOUNDS 121 



In summation, irradiation of water results ultimately in formation of 

 hydrogen, oxygen, and hydrogen peroxide. With slow-particle irradia- 

 tion, the yields are determined by the dosage. With fast-particle irradi- 

 ation, yields are barely detectable without special provision for study. 

 With such irradiation, yields of the order of those obtained under slow- 

 particle irradiation may be obtained when oxygen or anions of suitably 

 low electron affinity are present. The results are understood in the 

 framework of a mechanism involving primary formation of free hydrogen 

 atoms and hydroxyl radicals and, when oxygen is present, secondary 

 formation of free hydroperoxyl radicals. According to Allen, the 

 number of moles of hydrogen gas formed per 100 ev in water is very 

 much the same with various dissolved anions [Br~, I~, N02~, SeOs^, 

 AsOs", Fe(CN)6~] present but is affected by the velocity of the impin- 

 gent particle. 



Obviously, any dissolved substance substantially affected by free 

 atomic hydrogen or by free radicals will change the nature of the gaseous 

 product and may, at the same time, be itself permanently affected.* 

 Fricke, Hart, and Smith (5) studied the products formed by irradiation 

 of aqueous solutions of organic compounds, and a number of workers 

 (6-11) have been investigating the mechanisms of these processes in a 

 detailed way. In the early work of Fricke and his -coworkers the results 

 were ascribed to the action of "activated water." Presently, the 

 "activated water" is believed to be free hydrogen atoms and hydroxyl 

 radicals. When oxygen is present, the free hydroperoxyl radical may be 

 added to this list. 



Behavior of Organic Compounds 



Elementary processes of radiation chemistry in organic compounds 

 may be understood in the light of the Eyring, Hirschfelder, and Taylor 

 (12) (EHT) mechanism as it has been interpreted by this writer (13-16) 

 and by ]\Iagee and Burton (17, 18). We may write for the processes 

 involving ionization f 



A ^ A+ + e (I) 



A+ + e -^ A* (IIg) 



* Such an effect has been known for many years. For example, A. Kailan (4) 

 noted that during the fumaric-maleic acid isomerization reaction in water there oc- 

 curred a simultaneous reaction which he at that time ascribed to intermediary of 

 hydrogen peroxide. 



t Processes involving excitation have already been discussed in this symposium 

 by Livingston. Here, we dismiss them temporarily with the statement that they 

 are akin to the phenomena of photochemistry. 



