Concentration Cells in Ionized Gases. 689 



A considerable correction must be applied to Voo , to obtain 

 the true E.M.F. of the cell, E, because the insulation of 

 the electrometer quadrants cannot be considered perfect 

 when dealing with a cell of such feeble internal conductance 

 as is the case here. E may be obtained from the curves in 

 the following way. 



Let « be the conductance of the ionized air between the 

 electrodes, /3 the leakage conductance of the electrometer and 

 connexions, K the capacity of the quadrants, C the current 

 and V the P.D. between the quadrants at any time. Then \vg 

 have the two equations : — 



C=« (E-V) and C=/3Y+K^, 



dV 

 whence K^ = «E - (« + /3) V (2) 



The solution of (2) subject to V=— Voo when £ = and 

 V= + Voo when £ = oo is 



v = a V {1 - 2<r " r ' f (3) 



When the steady stage has been reached, 



Voo = -^_E (4) 



Absolute values of a and $ are not required for the 

 correction, as we may write (4) in the form 



E=(f±W?V„ (5) 



a/K 

 and - T ^ may be determined by equation (3) from obser- 



tions on the time curve from which Voo is determined. 

 Thus if Vi, V 2 are the values of V at times t x and t 2 , then 



« + £_ 1 Voo-Y, 



Also v may be obtained by a similar formula from the 



rate of leak of the charged insulated quadrants when the 

 ionizing agent is removed, in which case a is practically zero. 

 Consequently both numerator and denominator of (5) are 



determinate. ^ is a constant throughout all the experiments 



