Manchester Memoirs, Vol. Ix. (igi 6), No. 11. 



XI. The Theory of Overvoltage. 



By Edgar Newbery, D.Sc. 



(Communicated by Professor Arthur Lapworth, D.Sc, F.R.S.). 

 (Received and read May gth, igi6.) 



When a metal such as copper is placed in a solution 

 of one of its salts, it immediately throws out ions of itself 

 into the solution, each carrying a positive charge and 

 leaving the metal itself with a negative charge. At the 

 same time ions from the solution carrying a positive 

 charge will deposit on the metal, and in a very short 

 interval of time a state of balance will be set up when the 

 number of ions leaving the metal will be equal to the 

 number arriving, i.e., the solution pressure of the metal 

 will be equal to the osmotic pressure of the ions. When 

 this state is reached there will be a definite difference of 

 potential between the metal and the solution (single 

 potential difference) which will depend on the nature of 

 the metal and the concentration of the solution. 



If a gas such as hydrogen or oxygen be bubbled round 

 a thin sheet of metal, preferably of platinum or palladium, 

 the metal will act as if it were composed oi a sheet of 

 conducting gas, its own properties being lost for the time, 

 and the gases on the metal will give out and receive ions 

 in the same way as a metal. If we take two such 

 electrodes, one surrounded with hydrogen and the other 

 with oxygen in an acid or alkaline electrolyte, we shall 



July iyth, igi6. 



