i 



Michael Faraday, his Life and Works. 421 



ordinary electricity, rendered as continuous as possible by leaving 

 a stratum of air interposed between the metallic points which 

 convey and carry off the electricity from a machine, and a strip 

 of moistened paper which this electricity traverses ; he observes 

 that the deposition of the elements separated from the decom- 

 posed liquid takes place against the surface of the air which is 

 in contact with the paper. Then, investigating the decomposi- 

 tions effected by the pile, he examines the various explanations 

 which have been given of this phenomenon, and concludes that 

 it is much rather a chemical phenomenon than a truly electrical 

 one. In other words, it is a peculiar form of affinity which, 

 under the influence of electricity, is exerted between the neigh- 

 bouring molecules, so that the decomposition is the easier in 

 proportion as the affinity is stronger. He shows that the transfer 

 of the elements can only take place between bodies the consti- 

 tuent parts of which have an affinity for each other; and if these 

 elements separate in a free state against the surface of the me- 

 tallic poles of the pile, this is because they cannot combine with 

 the substance of these poles; for whenever this combination is 

 possible, they are no longer set free. Water in some cases, air 

 in others, as we have already seen, may serve as poles just as well 

 as solid bodies. Faraday justly rejects the old idea of certain 

 physicists who attributed electrochemical decompositions to the 

 ordinary electrical attractions and repulsions exerted upon the 

 elements of a conductive liquid by the voltaic poles immersed 

 in it. .j The metallic wires, or other conductors, which trans- 

 mit electricity into a liquid, are merely, according to him, the 

 roads by which the electric current passes into the liquid ; there- 

 fore, to exclude any idea of electrical tension which is more or 

 less implied in the name pole, Faraday proposed to substitute 

 for the denomination poles that of electrodes. He likewise ap- 

 plied the term electrolysis to the chemical decomposition effected 

 by electricity, reserving that of analysis for the ordinary chemical 

 decompositions in which electricity does not assist. Lastly, he 

 gives the name of electrolytes to those compound bodies which 

 are capable of being decomposed by the electric current. 



After this preliminary and general study of the subject, 

 Faraday enumerates the results which he obtained by submit- 

 ting to electrochemical decomposition a very great number of 

 compounds, some of them simple acids or simple bases, others 

 saline combinations. He dwells particularly on the secondary 

 effects often manifested in these decompositions, especially in 

 the case of aqueous solutions, in which decomposition of the 

 water and of the substance dissolved takes place at the same 

 time. But the essential point of his researches is the law at 

 which he arrived as to the definite nature of electrochemical de- 



