McCLia.r.ANi) and Nolan — Ions Produced by Phosphorus. 7 



fii'sl llie only additional ion we could dcte(;t was tlial of nioliility '028, hut 

 when the drying was improved the other two appeared. The other ions wo 

 observed are ions we have found before. Saturation was not obtained with 

 the ion of mobility •0041. We failed to discover tlie ioii of moliility 'OOTi. 

 Later results show that its non-appearance is not due to drying. 



In Table III [b) some numbers obtained with a time-interval of "6 sec. 

 are given. More reliable observations for the fastest ion were taken as it 

 was present as a bigger fraction of the ionisation with the shorter interval. 

 No attempt was made to find more mobile ions. Perhaps with shorter 

 intervals smaller ions would appear. It would be difficult, with the present 

 method of working, to measure mobilities much sooner after the production 

 of the ions than '6 see. 



Dried Air. Large Ions. 



In order to examine the larger ions with dried air, the apparatus was 



arranged so that there was a time-interval of 1'3 sees. The long mobility 



tube, suitable for measuring low mobilities, was again used. The following 

 mobilities were observed : — 



•016 -0080 -0042 -0012 •00066 



These five classes can all be identified with types given above. We now 

 observe the ion of mobility ^0074 (the present reading being -0080), which we 

 failed to get a few days previously. No essential change has been made in 

 the conditions. The change in the time-interval, or the fact that there is a 

 different mobility tube, should not affect the formation of this ion. The 

 same inexplicable variation has manifested itself with dried, just as with 

 undried, air. The ion of mobility ^0024, which we observed with uudried 

 air, is missing now. It represented only a small fraction of the ionisation 

 before. It is probable that its non-appearance on tliis occasion does not 

 mean a definite change brought about by drying, but is similar to the non- 

 appearance of the ion of mobility -0074 at different times. 



The most prominent ion with dried air is the ion of mobility ^0012. It 

 gives about 50 per cent, of the ionisation. Witii undried air the ion of 

 mobility •00063 was the most prominent. Drying favours the observation 

 of rhe faster ions. Complete saturation was not obtained with the observa- 

 tion '00060, but the last straight line was so slightly inclined to the voltage 

 axis that we were unable to measure any further mobilities. With undried 

 air, and the same time-interval, we were able to measure the ion of mobility 

 •00031. This, again, indicates the action of drying in bringing smaller ions 

 into prominence. If we take the grouping theory as right, we may say that 

 the grouping of the mobile ions to form the slow ions is retarded by drying. 



