the Cation in Voltaic Combinations. 451 



(oxygen) and not by any actual continuous combination of 

 these substances*. 



4. The above quotation from Lodge calls to mind a passage 

 in Sprague's 'Electricity/ p. 334 ; where he speaks of "the 

 struggle between the two metals for the possession of the 

 sulphuric radical." 



Sprague evidently pictures the molecules of H 2 S0 4 as 

 arranged in polarized molecular chains by the superior 

 attraction of the zinc for the S0 4 radical, 

 Zinc S0 4 H 2 S0 4 H 2 , &c. 



In much the same way Faraday pictured the molecular 

 arrangement " along the axis of power superinduced by the 

 current" in a decomposing electrolyte f= In thinking of the 

 action in the cell I provisionally picture the process in a 

 similar way, and regard the degree or intensity of this mole- 

 cular polarization as having in some way a relationship to 

 the electromotive force. The transformation of chemical 

 potential energy into current seems always a concomitant of 

 a two-endedness in one of the acting bodies — the electrolyte. 

 There is of course the familiar hypothesis which explains 

 everything, simply by saying that the anion has a negative 

 and the cation a positive charge ; but I am inclined to think 

 this says too much, and, to use an expression of Professor 

 G. F. Fitzgerald's, makes €t what is known to be complicated 

 appear unreally simple" J. 



5. On either view, however, any chemical attraction of the 

 negative plate for the cation would increase the electromotive 

 force of the cell. It appears to do so where the negative 

 plate consists of a high oxide like Mn0 2 or Pb0 2 . In what 

 follows an attempt is made to throw some light in the first 

 place on the question — 



Under ivhat conditions does a chemical attraction between the 

 negative plate and cation influence the electromotive force of the 

 cell? 



6. It follows also from the hypothesis, § 4, that any possible 

 attraction of the positive plate for the cation might also have 

 an effect on the electromotive force ; but this point has not, so 

 far as I know, been as yet considered, doubtless because in the 



* After this paper had been sent in, Dr. Lodge kindly referred me to 

 memoirs by Bosscha (Pogg. Ann. ciii. p. 517) and others, and notably a 

 paper by Sir William Thomson (Math, and Phys. Papers, i. p. 503), from 

 which it would appear that in certain cells the affinity of the negative 

 plate for the anion of the electrolyte is connected with a local conversion 

 of available chemical energy into heat, thus reducing the E.M.F. 



This is in agreement with what has been said regarding the dependence 

 of E.M.F. on the relative attractions of the two plates for the anion. 



t Exp. Res. i. p. 149, and plate iv. figs. 53, 54. 



X B. A. Keport 1890, Discussion on Theory of Solution, p. 19. 



2K2 



