86 



Proceedings of the Royal Irish Academy. 



Examination of the Negative Ions. 



The curve given in fig. 3 shows that the slowest negative ion appears at 

 a voltage of about 200, and therefore has a mobility value of about 9. In 

 fig. 6, curve A gives the result of a close examination of the enrrent-voltage 

 curve in this region. It is clear that there are two bends quite close together. 

 The voltages are 191 and 202. On this occasion the product Vu had the 

 value 1832. This gives for the mobilities of the two ions the values 9'59 

 and 9'07. These values have been obtained repeatedly, and the curve A is 

 only one of many which are almost exactly identical. On another occasion 

 the curve B was obtained. Here it would seem that the slowest ion appeared 



















/ 





1 









/ 



i 



A 















/ 





/ 

















/ 

















/ 



^ 











y 



/ 



V 



y 











^ 



y 





y 











G- 



-— - 



-.r-^ 











Vo» 





Fig. 6." 



at a voltage of 190'5. The product Vic was now 1834, so that we find for the 

 mobility of the slowest ion the value 9"63. The current values are much 

 greater in this case for corresponding voltages, the difference being greater 

 than would appear from the figure, as the scale has been adjusted for 

 convenience of plotting. For example, the current values for 200 volts are 

 almost exactly in the ratio 4:1. 



Curve B was obtained soon after the vessel had been refilled with 

 hydrogen. It seems to correspond to some condition of dryness or purity 



