Ionization from Certain Hot Salts. 24:7 



have been found to be present for which the value of e/m 

 corresponds to singly charged atoms, either of potassium or 

 sodium, or of both these elements; so that the results 

 confirm the conclusion previously reached by Richardson*. 



It is possible that the characteristic emission from these 

 salts occurs, but is too small for measurement with the 

 apparatus used. It will be remembered that in many of the 

 experiments a barely noticeable emission was detected at 

 temperatures slightly below the melting point. If the 

 apparatus could be made more delicate, it would be inter- 

 esting to see whether or not this is the case. 



Molybdenite has been found to possess a number of inter- 

 esting electrical properties which include the following : — 



(1) In the range of temperature between that of the room 

 and a brilliant red heat this mineral exists in two distinct 

 states. 



(2) The resistance in the low voltage or low temperature 

 state is very nearly an inverse exponential function of the- 

 absolute temperature. 



(3) At ordinary room temperatures the resistance is a 

 function of the applied potential difference and appears to 

 approach the value infinity as the potential approaches the 

 value zero. 



(4) The conduction of electricity is evidently carried on 

 mainly by electrons. 



Two conclusions maybe stated in regard to the thermionic 

 emission from molybdenite. 



I. A large emission from impurities, — principally the 

 ordinary K + -emission. 



II. A characteristic emission of Mo + ions, apparently 

 having no exclusive relation to the break or to either state. 



In conclusion, I wish to express my thanks to Prof. 0. W. 

 Richardson, who suggested the problem and under whose 

 instruction the experiments were started, and to Prof. E. P. 

 Adams for many helpful suggestions during the carrying on 

 of the work. I am also indebted to Prof. Augustus Trow- 

 bridge for suggesting the test of molybdenite and for 

 valuable advice during the trial of that substance. 



Palmer Laboratory, Princeton, N.J. 

 April 26, 1916. 



* Phil. Mag. vol. xxii. p. 669 (1911) ; Roy. Soc. Proc. A. vol. lxxxix.. 

 p. 507 (1914)'. 



