448 



Mr. S. Ratner on the 



applied electric force X, which is in agreement with the 

 well-known experimental facts. But in the case of negative 

 ionization, wnen X is gradually increased the experiments 

 show that at a certain value of X = X X depending upon the 

 pressure of the gas a lack of proportionality between c and P 



c 

 suddenly comes in in such a way that p begins to increase. 



Equation (1) shows that in this case the velocity of an ion 

 increases more rapidly than the electric force, i. e., that its 

 mobility becomes abnormally great. The value of this 

 critical electric force, X^ decreases rapidly with diminution 

 of the pressure, so that at pressures below 200 mm. the same 

 effect is reached with comparatively small forces when the 

 ionic velocities are small enough to be measured by 

 Langevin's or Rutherford's method. 



In the curves L, II., III., IV., Y., and VI. (fig. 4), the 



Fig. 4. 



Electric Force in -~~ 



W 



600, 



mobilities ^ of the negative ion at pressures of 748. 



500, 400, 300, and 200 mm. respectively, are plotted against 

 the electric force X, and the curve VI (+) , which is a straight 

 line parallel to the axis of X, shows the mobility of the 



