Positive Ionization from Hot Salts. 



08o 



When the pressure was increased in the tube apparatus 

 the immediate response was in the direction of reduced 

 emission. A slow increase subsequently occurred which 

 carried the current to a higher steady value than that which it 



50 



40 



30 



eo 



10 



Fier. 1. 





-— 





^--^^v- 



^ == ^~~ = ~—~- 



2/ 



3^> 









1 s 

















/ 





1 



A/a, SO, 



/WSSSOXS (MMS.) 



had at the lower pressure. This effect was always observed 

 except at the very lowest pressures, and it occurred with all 

 the salts investigated. The converse effect occurred on re- 

 ducing the pressure ; the emission first increased and then 

 fell to a steady value. The effect with increasing pressure 

 might conceivably be due to a reduction in the temperature 

 of: the surface of the salt produced by letting in the cooler 

 air ; but this seems unlikely when one considers the small 

 amount of air let in at any one stage, and the fact that the 

 heating apparatus was getting rid of one kilowatt of power, 

 most of which, in all probability, went into the water-cooler. 

 It is also difficult to see how an explanation along similar 

 lines could account for the converse effect which occurs on 

 reducing the pressure. Another explanation of these effects 

 will be considered below. 



Tribasic Sodium Phosphate. — The current-E.M.F. curves 

 given bv this substance were quite similar to those obtained 

 in the two cases already described, the main difference being 

 that there was still less variation from one pressure to another. 

 The curves showing the variation with pressure, however, were 



Phil. Mag. IS. 6. Vol 22. No. 131. Nov. 191.1. 2 Z 



