200 Faraday. 



established the accuracy of this law,* he found by a comparison 

 of different electrolytes that the mass of any ion liberated by 

 a given quantity of electricity is proportional to its chemical 

 equivalent, i.e. to the amount of it required to combine with 

 some standard mass of some standard element. If an element 

 is %-valent, so that one of its atoms can hold in combination 

 n atoms of hydrogen, the chemical equivalent of this element 

 may be taken to be 1/n of its atomic weight ; and therefore 

 Faraday's result may be expressed by saying that an electric 

 current will liberate exactly one atom of the element in 

 question in the time which it would take to liberate n atoms 

 of hydrogen.-)- 



The quantitative law seemed to Faraday:}: to indicate that 

 " the atoms of matter are in some way endowed or associated 

 with electrical powers, to which they owe their most striking 

 qualities, and amongst them their mutual chemical affinity." 

 Looking at the facts of electrolytic decomposition from this 

 point of view, he showed how natural it is to suppose that 

 the electricity which passes through the electrolyte is the exact 

 equivalent of that which is possessed by the atoms separated at 

 the electrodes ; which implies that there is a certain absolute 

 quantity of the electric power associated with each atom of 

 matter. 



The claims of this splendid speculation he advocated with 

 conviction. " The harmony," he wrote, " which it introduces 

 into the associated theories of definite proportions and electro- 

 chemical affinity is very great. According to it, the equivalent 

 weights of bodies are simply those quantities of them which 

 contain equal quantities of electricity, or have naturally equal 

 electric powers ; it being the ELECTRICITY which determines the 

 equivalent number, because it determines the combining force. 

 Or, if we adopt the atomic theory or phraseology, then the 



*Exp. Res., 713-821. 



t In the modern units, 96580 coulombs of electricity must pass round the 

 circuit in order to liberate of each ion a number of grams equal to the quotient of 

 the atomic weight by the valency. 



J Exp. Res., 852. Ibid., 869. 



