24 NEWBERV, The Theory of Overvoltage. 



Tafel also considers that the gas penetrates the 

 electrode but further assumes that the formation of 

 gaseous H 2 from H" ions is a process requiring time. 

 H" ions (or atoms) will therefore accumulate at the surface 

 of the electrode under pressure and tend to re-enter the 

 solution thus giving rise to an excess back E. M. F. 

 Some metals he considers exert a catalytic influence on 

 the reaction 2 H" = 2 + H 2 and thus lower the over- 

 voltage. 



This ascribing of a ' catalytic ' influence to the metals 

 is not an explanation, but merely a substitution of one 

 term for another, neither of which is understood. Hence 

 this part of the theory has been passed over by most 

 scientists, though an attempt has lately been made to 

 revive it in America. 



Bose assumes that the gas dissolves in the metal and 

 is there dissociated into atoms which take on electrical 

 charges. Particles of electricity are present in the form 

 of ' neutrons,' ©, and the metal behaves as a solvent 

 dissociating these and also the H r The free H then 

 combines with a + ve charge forming ions which tend to 

 pass into the electrolyte giving rise to an excess back 

 E. M. F., i.e., to overvoltage. 



This theory is open to so many objections that it has 

 received little or no support recently and is now practically 

 abandoned. 



Reichenstein considers that overvoltage is a measure 

 of the difference between the rate of formation of ions 

 and their disappearance by combination to form com- 

 plexes or by other means. The ion, after giving up its 

 charge, passes into a metastable form of gas or metal, 

 which further changes to the stable form, each process 



