194 



Mr. J. S. Townsend. 



The solution of the problem requires a somewhat lengthy analysis, 

 so that we give here only the final result. 



The ratio of the number of ions (or molecules of the gas A) 

 coming out of the tube with B to the number which enter is 



7-313ks 44-5kz 



R = 4 [0-1952 € 2 " 2 v + 0-0243 e + &c], 



where z is the length of the tube. 



The other terms of the series are too small to be taken into con 

 sideration. 



Having determined the reduction in conductivity, due to tubes of 

 different lengths, the following values of the coefficients of diffusion 

 of ions into air, oxygen, carbonic acid, and hydrogen, were obtained. 



Table of Coefficients of Diffusion of Ions in dry Gases. 



Gas. 



k for + ions. 



k for — ions. 



Mean value 

 of K. 



Eatio of the 

 values of k. 



Oxygen. .. . 



-0274 

 0-025 

 0-023 

 0-123 



0-042 

 -0396 

 0-026 

 0-190 



'0347 

 -0323 

 -0245 

 0-156 



1-54 

 1-58 

 1-13 

 1-54 



Table of Coefficients of Diffusion of Ions in moist Gases. 



Gas. 



k for + ions. 



k for — ions. 



Mean value 



Of K. 



Ratio of the 

 values of k. 





0-032 



0-035 



-0335 



1-09 





0-0288 



0-0358 



'0323 



1-24 





0*0245* 



-0255 



0-025 



1-04 





0-128 " 



0-142 



-1350 



1 11 



We should expect from the experiments, that the above numbers 

 were correct to 5 per cent. 



Considering one of the equations of motion 



1 dp „ 



we see that when clpjdx — 0, the velocity u due to the electric force 

 X is nKeK/p. If the potential gradient is one volt per centimetre X = 

 1/300 in electrostatic units, and the corresponding value of u is 



Ke 

 300 



