442 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



the electrolites at their anodes, and act just as chlorine, iodine, or any other anion 

 would act which might have been previously chosen as that which should be used to 

 throw the voltaic circle into activity. 



944. The following experiments complete the series of proofs of the origin of the 

 electricity in the voltaic pile. A fluid amalgam of potassium, containing not more 

 than a hundredth of that metal, was put into pure water, and connected through 

 the galvanometer with a plate of platina in the same water. There was immediately 

 an electric current from the amalgam through the electrolyte to the platina. This 

 must have been due to the oxidation only of the metal, for there was neither acid nor 

 alkali to combine with, or in any way act on, the body produced. 



945. Again, a plate of clean lead and a plate of j)latina were put into pure water. 

 There was immediately a powerful current produced from the lead through the fluid 

 to the platina : it was even intense enough to decompose solution of the iodide of 

 potassium when introduced into the circuit in the form of apparatus already described 

 (880.), fig. 1. Here no action of acid or alkali on the oxide formed from the lead 

 could supply the electricity : it was due solely to the oxidation of the metal. 



946. There is no point in electrical science which seems to me of more importance 

 than the state of the metals and the electrolytic conductor in a simple voltaic circuit 

 before and at the moment when metallic contact is first completed. If clearly under- 

 stood, I feel no doubt it would supply us with a direct key to the laws under which 

 the great variety of voltaic excitements, direct and incidental, occur, and open out 

 various new fields of research for our investigation. 



947. We seem to have the power of deciding to a certain extent in numerous cases 

 of chemical afl&nity, (as of zinc with the oxygen of water, &c. &c.) which of two modes 

 of action of the attractive power shall be exerted (996.). In the one mode we can 

 transfer the power onwards, and make it produce elsewhere its equivalent of action 

 (867. 917.) ■» ill the other, it is not transferred, but exerted wholly at the spot. The 

 first is the case of volta-electric excitation, the other ordinary chemical affinity : but 

 both are chemical actions and due to one force or principle. 



948. The general circumstances of the former mode occur in all instances of voltaic 

 currents, but may be considered as in their perfect condition, and then free from those 

 of the second mode, in some only of the cases ; as in those of plates of zinc and platina 

 in solution of potassa, or of amalgamated zinc and platina in dilute sulphuric acid. 



949. Assuming it sufficiently proved, by the preceding experiments and considera- 

 tions, that the electro-motive action depends, when zinc, platina, and dilute sulphuric 

 acid are used, upon the mutual affinity of the metal zinc and the oxygen of the 

 water (921. 924.), it would appear that the metal, when alone, has not power enough, 

 under the circumstances, to take the oxygen and expel the hydrogen from the com- 

 bination ; for, in fact, no such action takes place. But it would also appear that it 

 has power so far to act, by its attraction for the oxygen of the particles in contact 



