Silent Discharge Involving Catalysis 181 



A TYPE OF SILENT DISCHARGE INVOLVING 

 CATALYSIS. 



F. O. Anderegg and E. H. Bowers, Purdue University. 



The complications occvirring at the solid surfaces in contact with 

 electrical discharges are not generally appreciated. As a result of con- 

 siderable study of chemical reactions in corona discharges the fact that 

 the solid-gas interface introduces variable factors has become more and 

 more evident. From a knowledge of the phenomena involved in con- 

 tact catalysis it has become increasingly clear that these two apparently 

 unrelated phenomena may be interdependent. The result of this dawn- 

 ing consciousness has led to a study of catalysis in chemical reactions 

 in corona discharges, the first report of which is given here. 



The theory of the action of a dielectric material in an electric field 

 was first given by Faraday^ who showed that the attraction between 

 charged bodies is inversely proportional to the dielectric constant of the 



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' , , I , , , , , , , I , ' , ' ' , ' ' I ' I 'i ' 1 1 ' ' ■ , / 1 ' 1 1 ' / , ' ' '\i ' II 1 1 1 / 'I ", "i. I /" "ii I' II 1 1 ', 



, I , , , , , 1 , 1 , 1 1 , 1 1 1 1 , 1 , , 1 1 1 1 1 , , I , I , , , , 



. I , ly '//// ///, /// "/ 

 , I I ^1 , , , II II , I ,,i / , , 



,l((ll(ll II II I II 



1 jKy 



/iir 2/<y I 



w)i)))iiiiiiiii)nii)ii)iiiii ii/ihiiinn!iiiiinnnitiin!!nninini inniiiihini)i)jiii)ir^ 



Fig-. 1. The interposition ol' a dielectric material of constant 2 has increased the 

 potential drop in the remaining' air space from 1.5 to 2 Kv. 



material separating them. Then, when equipotential lines are drawn 

 (normal, of course, to the lines of force), they will be spaced in pro- 

 portion to the dielectric constant of the material used. The term, spe- 

 cific inductive capacity, is more illustrative of the effect but its length 

 militates against its use. If sheets of dielectric material, such as glass, 

 are placed against one or both of parallel electrodes without filling the 

 whole space between them, there will be a distribution of equipotential 

 lines as given in figure 1. The equipotential lines are close together 

 in the gas filled space so that there is a large potential gradient in the 

 gas. It may be helpful to remember the analogy to contour lines on 

 a map. If the potential is sufficient the gas "breaks down", that is, 

 some of the molecules are ionized and a silent or corona discharge is 

 set up. The presence of solid dielectric tends to prevent sparking or 

 arcing over, so that with a suitably designed apparatus it is possible 

 to fill the whole of the space with a corona of high density. If a rod 

 of glass or other dielectric material is placed between parallel electrodes 

 the eflFect of the lines of force is as given in figure 2'. On placing two 



'Jeans. Electricity and Magnetism. 4th Ed. pp. 126-135 (1920). 

 " Jeans, loc. cit., p. 228. 



"Proc. 38th Meeting, 1922 (1923)." 



