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THE RECOVERY OF TRANSMISSIVITY IN PASSIVE IRON 



WIRES AS A MODEL OF RECOVERY PROCESSES 



IN IRRITABLE LIVING SYSTEMS. 



Part IL 



By RALPH S. LILLIE. 



{From the Physiological Laboratory, Clark University, Worcester.) 



(Received for publication, June 20, 1920.) 

 Theoretical Considerations. 



The consideration of why transmission is only partial during the 

 early period after repassivation must take account of a number of 

 factors whose precise mode of action is not clear in all cases. It is 

 evident that the return to the passive state implies redeposition of a 

 continuous surface layer of oxidation product ; it is also evident from 

 the behavior of the newly passivated wire that when first deposited 

 this layer is in a different chemical and physical condition from that 

 which it afterwards attains when complete transmissivity is reestab- 

 lished. The question is what kind of change occurs in the surface 

 layer during the period of progressive recovery; e.g., in 70 per cent 

 HNO3 during the first 7 or 8 minutes after the spontaneous return of 

 passivity. 



Several peculiarities are to be noted in the character of the activa- 

 tion wave at the successive intervals. There is an evident correlation 

 between its speed and the distance which it travels. At first the local 

 reaction spreads slowly and for only a short distance; at each succes- 

 sive trial the wave travels faster and advances farther; eventually it 

 travels for an indefinite distance at a high speed (several hundred 

 centimeters per second) . It is also noticeable that an activation wave 

 which comes spontaneously to rest after traveling some distance is 

 visibly retarded through the last 2 or 3 cm. of its path (though not 



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