Nolan — Ionic Mobilities in Air and Hydrogen. 



83 



sulphate, and finally bubbled through strong sulphuric acid before entering 

 the apparatus. The gas was allowed to flow through the apparatus for several 

 days. Most of the observations recorded subsequently were taken with a 

 stream of hydrogen passing slowly through. 



In tig. 3 the general form of the negative and positive current-voltage 

 curves are shown. The lower part of each curve is approximately linear, the 

 intersections with the voltage axis being at 20.3 in the case of the negative 



and 313 in the case of the positive. On this occasion the alternation 

 frequency was 51-9, hence the product Vu (critical voltage x mobility) = 

 n- X 51 9 X I6/J2 = 1840. Following the usual procedure then, we could 

 interpret these curves as indicating the existence of negative ions of mobility 



-^r^-r- = 9'06, and positive ions of mobility -— — = 5-88. But this ignores 

 2i\jo 313 



the fact that the curves do not approach the voltage axis in a linear fashion. 



This is not so noticeable in the case of the negative, but it is quite clear that 



the positive curve has a well-developed " tail." That the effect is not due to 



