THE PROBLEMS OF SOLUTION 107 



Faraday made a series of experiments on the 

 passage of electricity through liquids, in this way 

 laying the foundations of our quantitative know- 

 ledge of that subject. He showed that the 

 transfer of a given quantity of electricity was 

 always accompanied by the liberation of a definite 

 quantity of one of the constituents of the solution, 

 a quantity proportional to the total electric 

 transfer, and to the chemical equivalent weight 

 of the substance liberated. The quantity of 

 electricity which passed, then, depended on the 

 number of chemical equivalents of substance 

 liberated, and not on their nature. These results 

 led to a definite view as to the nature of the 

 process of electrolysis. We must regard the 

 passage of an electric current through a solution 

 as due to the carriage by moving parts of the salt 

 of opposite electric charges in opposite directions 

 through the liquid. Under the influence of 

 applied electric forces, these carriers drift through 

 the solution, and finally give up their charges to 

 the electrodes, as the terminals by which the 

 current enters and leaves the solution are called. 

 With common salt, for example, a stream of 

 positively electrified sodium drifts with the electric 

 current, while negatively electrified chlorine passes 

 in the opposite direction. The moving parts of 

 the salt, with their accompanying electric charges, 

 were named Ions by Faraday ; the positive ion 

 which moves down the electric current is termed 

 the cation, and the negative ion which travels up 

 the electric stream is called the anion. The 

 electrodes to which they travel are known as the 

 cathode and anode respectively. The electric 

 charge on a single ion of a substance like sodium 



