ACTIVATION OF ELECTRICAL CONTACTS BY ORGANIC VAPORS 803 



106 



> 



< 



O 



Q 



UJ 



D 



a 



UJ 



cr 



10 

 z 

 o 



^' 



UJ 



a 

 o 



a. 



UJ 



CD 



2 



D 

 Z 



:10= 



10* 





10 



20 30 40 



ATOMIC PER CENT OF NICKEL 



50 



60 



Fig. 11 — Resistance to activation of various alloys of nickel and palladium. 



that a heated molecule will evaporate rather than decompose, or whether 

 there are just fewer sites on the surface which can take molecules. 



C. ACTIVATION IN AIR 



Electrical contacts are not so readily activated by organic vapors in 

 the presence of air as they are when air is absent. Air inhibits the acti- 

 vating process in at least three different ways, and sometimes in a fourth 

 way. These are: 



1. Covering up the metal surface so that activating molecules cannot 

 be adsorbed upon it until some of it has been cleaned temporarily by 

 arcing. 



2. Offering obstruction in the path of organic molecules on their way 

 to an adsorption site on the metal, so that the molecules diffuse slowly 

 through air up to the surface, whereas in the absence of air, an adsorbed 

 film is formed much more quickly at the same pressure of the organic 

 vapor. 



