M'Clkj.land and Nolan — Ions produced by Bubbling Air. 55 



ion. Variations in the numbers, which will not seriously affect the bending 

 point, often change slightly the slopes of the lines. Thus curves which give 

 the same mobility will sometimes give a different fraction of the ionisation as 

 due to the particular ion, although the total quantity of ionisation is the same. 

 This error is all the more serious if the straight lines are short. These straight 

 lines are short, comparatively speaking, in the present work because there 

 are so many classes of ions, and the saturation voltages are not very widely 

 spaced. 



Effect of Time. 

 In the case of the ions derived from air bubbled through mercury, it was 

 found that the mobilities observed depended on the time-interval between the 

 bubbling and the measurement of the mobility. We have examined this effect 

 fully in the present paper in the case of the ions in air that has bubbled 

 through alcohol. The time-interval can be varied in two ways : by interposing 

 lengths of tubing between the alcohol and the measuring tube, or by varying 

 the rate of now of the air into the gasometer from the alcohol vessel. 

 Both methods were used, and measurements were made with a number of 

 widely different time-intervals. The tables numbered Table III (a),(b),(c), 

 (d), (e), give all the numbers observed in the series of experiments performed 

 with the object of investigating the time-effect. The pressure of air was 

 generally between 7"4 and 9'6 cms. of mercury. On a few occasions it was 

 as high as 11 cms. 



Table III. 



(«) Time — 43 sees. 





— 



_ 



— 



_ 



■0013 









■016? 



■0066? 



•0041 



■0024 



•0015 









■016 



•0080 



•0040 



■0023 



•0014 



•0006? 







- 





— 



— 



•0016? 







Means, 



•016 



■ooso 



•0041 



■0024 



•0014 



• iMMii; : 





(b) Time — 85 sees. 



Means, 



•00SS 



■0071 : 



•miss 



■0044 

 ■0044 



■0044 



•0024 r 

 ■0025 



■0025 



■0015 



■0015 



•0015 



1111111,1; 



00070 

 ■00074 

 •00073 



•00071 



■ .mi ;; 



•00035 



00031 



