Negative Ions at Low Pressures. 



325 



intervals T T and T 2 . When k lf k 2 , and /jl are known we can 

 determine the value of n\. 



d/h,X 



djh 2 x 



Variation of Q with X. — Considered as a function of X, 



\id 



Q varies as e "G-- ^ ne smallest value of X which can send 

 any charge fco the plate is d/kiY, and when X = (///c 2 T, Q 

 reaches the maximum value Ne. The Q and X graph has a 

 point of inflexion when 



X=/idl2k a =Ydl2n\{h-lc a ). 



The shape of the graph is shown in fig. 2. From the 



I'V- 2. 



djkj 



djk 2 T 



points 1* and Q the values of k x and /\> can be determined, 

 and /a, and therefore rik by means of the equation 



"*«*U -£(£-£> 



where Q, and Q 2 are the values corresponding to Xj and X 2 

 respectively. 



