Chemical Affinity in terms of Electromotive Force. 195 



polarization then existent being governed by the proportions 

 of " nascent " hydrogen and oxygen that were being evolved 

 the instant previously and the mean densities of the aura?, 

 i. e. by the values of n^ and n 2 and h x and h 2 in the expression 



e = E l + \(l-n l )B: i -nJi l + (l-n 2 )H 2 -n 2 Ji 2 -t(M)} X J 



(§ 61). After the lapse of a given time, however, more or less 

 of the " nascent" hydrogen and oxygen have rearranged 

 themselves, and more or less of the original aura round each 

 electrode has become reconverted into water by the effects of 

 diffusion (bringing oxygen-containing fluid to the hydrogen- 

 electrode and vice versa) ; so that from these causes n Y and n 2 

 have increased, each of these changes diminishing the value 

 of e, the polarization. Simultaneously, however, each aura 

 has been more or less reinforced by the passage outwards of 

 occluded gas from within, each of these changes tending to 

 increase e. Presumably the greater the extent to which the 

 aura was wasted, so to speak, by diffusion, the more rapidly 

 would this outward passage of occluded gases take place ; so 

 that finally the rate of fall of polarization is gradually re- 

 tarded, first because as the " nascent" hydrogen and oxygen 

 become expended by spontaneous rearrangement this source 

 of fall of polarization regularly diminishes, and secondly 

 because the greater the fall the more energetic is the restoring 

 influence of the outward passage of the occluded gases, at 

 least until the amount occluded becomes materially reduced in 

 quantity. When the amount of fall is such that the rate of 

 outward passage of occluded gases almost balances the rate of 

 wasting of aura through diffusion, the rate of fall of polarization 

 becomes almost insensible, at any rate for periods of time not 

 too prolonged. This point was reached in many of the ex- 

 periments, in particular those with the "largest " voltameter 

 and polarizations of values not exceeding a few tenths of a 

 volt (§ 71). Ultimately, however, the occluded gases become 

 ■exhausted and the aurse diminish to inappreciable quantities, 

 the value of e diminishing to a quantity too small to measure. 

 This result requires an enormous length of time to bring 

 it about by the action of diffusion on]y ; if, however, the 

 voltameter-plates are united by an external connecting-wire, 

 a current flows through that wire, and work is done at the 

 expense of the energy stored up, so to speak, in the aura? and 

 occluded gases of the electrodes. The capacity of the con- 

 denser virtually formed by the voltameter-plates simply means 

 the quantity of electricity that can be made to flow in this 

 way, and will approach the more nearly to the quantity of 

 electricity that passed in forming the aura? and charging the 



