ELECTROLYSIS 185 



Current. If the solution is moderately strong hydrogen gas is 

 evolved from one pole, and chlorine gas from the other. 1 These 

 two substances Faraday called the " ions " of hydrochloric acid, 

 According to the older hypothesis introduced by Grotthus in 

 1805 it was supposed that throughout the liquid, between the 

 poles or electrodes while in action, the molecules were ranged in a 

 series of polar chains, the positive constituent, in this case the 

 hydrogen, facing in one direction toward the negative plate or 

 cathode, while the negative constituent, in this case chlorine, 

 was drawn toward the positive plate or anode. In the process 

 of electrolysis the positive hydrogen atoms moved from molecule 

 to molecule along the chain until at the end, at the surface of the 

 cathode, they were attracted away and then appeared in the 

 free state in the form of hydrogen gas. The negative atoms of 

 chlorine were supposed to move in a similar manner along the 

 chain in the opposite direction. This may be represented in the 

 following diagram : 



Immediately before Decomposition 

 HC1 HC1 HC1 HC1 HC1 HC1 



During electrolysis. First phase 

 H C1H C1H C1H C1H C1H Cl 



In order to explain the continuance of the process it is then 

 necessary to assume that the new molecules turn round so that 

 their ions face the electrodes to which they then move. 



During electrolysis. Second phase 

 H HC1 HC1 HC1 HC1 HC1 Cl 



According to this idea the effect of the current is first to cause 

 all the molecules between the electrodes to arrange themselves 

 in lines having the ionic constituents facing in opposite directions. 

 This would appear to involve the setting up of a peculiar structure 

 or at least a tactical arrangement of the particles in the liquid 

 which should have some effect on its optical or other properties. 

 Nothing of the kind can, however, be detected in the space 

 occupied by the liquid between the electrodes. Secondly, the 



1 If weak the liquid gires hydrogen at the cathode and hydrochloric acid 

 with oxygen at the anod*. 



