M'Ci-iELland and Nolan — Ions produced by Bubbling Air. 53 



Table I. 

 Mobilities in crns. per sec. under 1 volt per em. 





•017 



■0083 



•0042 



•0024 





•014 



•0075 



•0044 



•0027 





■012? 



■0078 



•0045 



•0019 





•017? 



•0078 



•0033 



■0024 ? 





■023? 



■0077 

 ■0080 

 0069 

 •0087 

 ■0085 ? 

 •0081 ? 

 •0087 ? 

 •0069 ? 

 •0071 ? 



•0036 

 •0043 

 •0035 

 0042 ? 

 ■0042 ? 

 ■0053 ? 

 •0039 ? 

 •0035 ? 



•0025 f 



Means, 



■015 



•0078 



•0040 



•0023 



All the values obtained are given. Those obtained from curves in which 

 there was some doubt about the exact point of bending have been marked 

 doubtful, and are not included in taking the mean. The ions can be divided 

 into four definite classes. The justification for placing numbers like '0033 

 (lowest in column 3) and - 0027 (highest in column 4) in different classes is 

 that we get "0033 and "0019 on the game curve, and - 0042 and -0027 on the 

 same curve. This division is supported by much better numbers given further 

 on. Most of these observations were taken before the importance of the 

 pressure at which the bubbling takes place was fully recognized. The pressure 

 is variable for these observations, and is not known with certainty. It is 

 probably between 17 cms. and 21 cms. of mercury for most of them. It was 

 found that the ion of mobility '015 cm./sec. was present only when the pressure 

 was reduced to about 17 cms. When the pressure was increased, the fastest 

 ion that could be detected was that of mobility "0078 cm./sec. A further 

 increase in the pressure of bubbling caused the disappearance of this ion. 

 Experiments were, accordingly, conducted on the effect of pressure. 



Variation with Pressure. 



A mercury manometer was placed between the cotton- wool plug by which 

 the air was filtered and the bubbling nozzle so as to give the excess pressure 

 inside the nozzle over the atmospheric pressure. The values given in 



[9*] 



