56 THE ROYAL SOCIETY OF CANADA 
If there are n ions per c.c. close to the electrode, the number strik- 
ing it per sec. per sq. cm. isn V/4/67 where V is the velocity of agitation 
of the ions, according to the kinetic theory of gases. If we suppose 
that when an ion strikes the platinum, it gives up its charge, then we 
have 
where I denotes the saturation current per sq. cm. PF and 
k = 1-4en/mV so that 
E+————— 
1-4e\\/67 
mV?’ / i is independent of the temperature, and X for a molecule of nitro- 
gen at O°C and 760 mms. is 9-5 x 10—$ cm. Also mnV?/ne— 3 p/ne 
where p is the pressure of a gas containing n molecules per c.c. For 
a gas at atmospheric pressure, p — 1-01 x 10$ and ne — 2-6 x 10", so 
that mV? /1-4eX4/67 = 2 ES. units. 
Hence à —IF/(F + 2), and since 2 = p,kF, we get p= (I — i) / 2k. 
If S denotes the saturation current per cm., then S = 2zr, I also C= 
2rr, i and k — 1-3 x 10* in ES. units. Substituting these values in the 
expression found for V and the values of r, and r, we obtain 
0-275C 
V = —— + S&S —C) X 10— 
S — C 
which gives V in E.S. units. The saturation current per cm. for the 
curve in the figure is 5-6 X 10 E.S. units. Hence for this curve 
V = 0: mi — + = ( = x) 0-056 
The following table gives values of C/S calculated by this equation, 
and also the observed values of C/S taken off the curve :— 
