﻿in the Emission of Positive Thermions from Salts. 147 



It is known from the experiments of Garrett and of Horton 

 that the highest pressures in the present experiments cause 

 marked increases in the thermionic emission. In no case, 

 however, does the value o£ ejm suggest that gas molecules are 

 participating in the transfer of charge. If secondary maxima 

 due to oxygen, nitrogen, carbon monoxide, or carbon dioxide 

 existed they would have appeared in these curves. To settle 

 this point for the case of hydrogen curves were taken in this 

 gas at a pressure of about one millimetre and with a reduced 

 magnetic field. The arrows (fig. 3) indicate the positions at 



Fiff. 8. 



i 













xf 



y 





V 



\1 



c 



~s 









'--" — 



l_ 



wmich maxima due to atomic and molecular hydrogen would 

 appear on these curves if any appreciable part of the current 

 were carried by such atoms or molecules. 



Conclusions. 



1. The carbon monoxide or carbon dioxide which is some- 

 times emitted by samples of salts when heated is uncharged. 



2. The increase of thermionic emission from a salt which is 

 caused by the presence of a gas in contact with its surface is 

 not due to an emission of gas atoms or molecules which have 

 been absorbed by the salt and are emitted in a charged 

 condition. 



My sincere thanks are due to Prof. 0. W. Richardson for 

 much valuable advice throughout these investigations. 



L2 



