548 



Prof. Richardson and Mr. Hulbirt on the 



The average value o£ elm for the negative ions thus comes 

 out considerably lower than the standard value 1*88 x 10 7 . 

 The ratio of the two is 1*59. Assuming that the measure- 

 ments for the positive ions are subject to the same propor- 

 tional error, we get for the corrected values for the positive 

 thermions from platinum: e/w = 387 and ?n/H = 25'0. 



In what follows we shall apply the correction factor 1*59 

 which has been obtained for platinum to the other metals 

 investigated. This is legitimate, since the dimensions of the 

 apparatus were the same in every case, and with most of the 

 materials used it was not possible to push the temperatures 

 high enough to obtain the negative ionization without melting 

 them. 



In the experiments on platinum the average temperature 

 during the experiments on the positive ions was about 900° C. 

 (and with the negative ions about 1100° C). On account 

 of the falling off of the positive emission with time, it was 

 necessary to raise the temperature from time to time when 

 the measurements on the positive ions were being made. 

 This effect was not so noticeable with the other metals used, 

 and in fact in the case of silver the ionization appeared to 

 increase with lapse of time. This may be due to the strip 

 used becoming thinner owing to sputtering, and so requiring 

 a smaller current to heat it. 



The platinum strips used were always boiled in nitric acid 

 before testing. The method could not be used with most of 

 the other materials as they were soluble in nitric acid. They 

 were, however, cleaned with alcohol and distilled water 

 instead. 



Palladium, Copper, Silver, and Nickel. 



The numbers given by the above metals are exhibited in 

 the following tables, and do not appear to call for special 

 discussion. 





Pa Had 



ium. Positive Ions 









z. 



H. 



V. 



X. 



e/m. 



•433 



4850 



83 



1-05 





201 



•443 



4850 



165 



•71 



1 ; 



182 



•443 



4850 



329 



•57 







235 



•443 1 



4850 



41 



1-60 







230 



Average 



values ... e/m = 212, Corrected .. 

 m/R= 45-6, 



e/m= 

 m[EL = 



=337. 



= 28-7. 



