204 Faraday. 



Faraday's own view on this point* was that a plate of 

 amalgamated zinc, when placed in dilute sulphuric acid, " has 

 power so far to act, by its attraction for the oxygen of the 

 particles'in contact with it, as to place the similar forces already 

 active between these and the other particles of oxygen and 

 the particles of hydrogen in the water, in a peculiar state of 

 tension or polarity, and probably also at the same time to 

 throw those of its own particles which are in contact with the 

 water into a similar but opposed state. Whilst this state is 

 retained, no further change occurs: but when it is relieved 

 by completion of the circuit, in which case the forces determined 

 in opposite directions, with respect to the zinc and the electro- 

 lyte, are found exactly competent to neutralize each other, then 

 a series of decompositions and recompositions takes place 

 amongst the particles of oxygen and hydrogen which constitute 

 the water, between the place of contact with the platina and 

 the place where the zinc is active : these intervening particles 

 being evidently in close dependence upon and relation to each 

 other. The zinc forms a direct compound with those particles 

 of oxygen which were, previously, in divided relation to both 

 it and the hydrogen : the oxide is removed by the acid, and a 

 fresh surface of zinc is presented to the water, to renew and 

 repeat the action." 



These ideas were developed further by the later adherents 

 of the chemical theory, especially by Faraday's friend Christian 

 Friedrich Schonbein,f of Basle (6. 1799, d. 1868), the discoverer 

 of ozone. Schonbein made the hypothesis more definite by 

 assuming that when the circuit is open, the molecules of water 

 adjacent to the zinc plate are electrically polarized, the oxygen 

 side of each molecule being turned towards the zinc and being 

 negatively charged, while the hydrogen side is turned away 

 from the zinc and is positively charged. In the third quarter 



* Exp. &., 949. 



t Ann. d. Phys., Ixxviii (1849), p. 289, translated Archives des sc. phys., xiii 

 (1850), p. 192. Faraday and Schonbein for many years carried on a correspondence, 

 which has been edited by G. W. A. Kahlbaum and F. V. Darbishire : London, 

 Williams and Norgate. 



