﻿644 Prof. J. A. Pollock on a 



Instability of the Jon. 

 The curve in fig. 4 show? that at a pressure of about 

 fifteen millimetres the mobility of the ion increases very 

 rapidly with increase in the value of the vapour-pressure. 



Fisr. 4. 





1 







1 





Q 



i 







IS 



o 



9d 







c 







c 



_0_ 



o 



— 



ex 



g 



C i 



o 



















o 



o-o 

 oo' 5j0 







1,00 







l|SO 



- 



MOBILITY-RECIPROCAL 



On many occasions, as already mentioned, successful simul- 

 taneous observations of the intermediate and large ions were 

 obtained^ but with vapour-pressures exceeding seventeen 

 millimetres, while the observations of the large ions were 

 equally good, all trace of the intermediate ion disappeared. 

 To be quite definite, above this pressure no evidence was 

 ever found of any class of ions with a mobility between 1/50 

 and 1/3000. Disintegration of the ion at a critical vapour- 

 pressure is unlikely, and it is much more probable, assuming 

 a rigid nucleus, that the adsorbed fluid is in the condition of 

 a dense vapour, and that at the critical pressure it changes 

 its state to that of a liquid, like the moisture adsorbed by 

 glass and shellac in Trouton's experience. 



Such a change means a decrease in the energy of the 

 aggregation, and is to be expected when the molecules of 



