490 On the Mobilities of Ions in Air at Higli Pressures. 



Table II. 



Mobilities of ions at various pressures in air. 





Mobility in cm./sec. 

 per volt/cm. 



Mobility X Pressure. 



Eatio of 



Pressure in 

 Atmospheres. 









mobilities 



Positive = k- l . 



Negative —Jc 2 . 



Positive. 



Negative. 



Experimental 













Besults. 



19-70 xlO -3 



2830 XlO -3 









06-86 



1-32 



1-89 



1-43 



87-21 



16-13 



21-37 



1-41 



1-86 



1-33 



96-9 



14-92 



19 46 



1-40 



1-89 



1-30 



10853 



1365 



18-83 



1-48 



2-04 



1-38 



116-28 



12-87 



17-83 



1-50 



2-07 



1-39 



123-1 



12-31 



16-09 



1-52 



2-05 



1-36 



13275 



12-03 



15-36 



1-60 



2-04 



1-28 



145-35 



10-98 



15-20 



1-60 



2-21 



1-38 



15504 



10-82 



1424 



1-68 



2-21 



1-32 



164-73 



10-36 



14-08 



1-71 



2-32 



1-36 



175-4 



9-19 



12-46 



1-61 



2-19 



1-36 



181-5 



911 



11-97 



1-65 



2-17 



1-31 



Calculated on 













basis of pXk 













= constant. 



67-3 XlO -3 











20 



94-5 x 10" 3 



1 



34 



1-89 



1-41 



30 



449 



63 





, 



J% 





40 



33-5 



47-3 





} 



j5 





60 



224 



315 





\ 







80 



16-8 



23 6 





, 



rj 





100 



13-4 



18-9 







', 





120 



11-2 



15-8 







\ t 





140 



9-6 



135 





, 







160 



8-4 



11-8 





J 



?) 





180 



7*5 



10-5 







)} 





200 



6-7 



95 





' 



J! 





it will also be seen from the table and the diagram that the 

 mobility of the positive ion approached that of the negative 

 ion as the higher pressures were reached, the ratio of the 

 mobility of the negative ion to the positive ion dropping 

 from 1*43 at ti6'86 atmospheres to 1*31 at 181*5 atmospheres. 

 The departure from the inverse-pressure law, however, was 

 not very great. 



It will be recalled that Greinacher *, in his experiments 

 on the ionization of paraffin oil and of petrol ether by alpha 

 rays, found that the mobilities o£ the positive and negative 

 ions produced in these liquids were practically identical. 



* Greinacher, Phy?. Zt.'t. 10 Jahr. No. 25, p. 986. 



