﻿132 



Mr. Clinton J. Davisson on the Positive 



Strontium. 



The salts of strontium that have been tested are the same 

 as were tested in the case of barium, and, as in the case of 

 those salts, the values of e/m are found to approximate to 

 one-half the value of elm for the metallic ions, as computed 

 from chemical data. Values of e/m corresponding to 

 potassium are more common among the results for strontium 

 than among those for barium. 



Strontium Sulphate. 



This salt was prepared from H. TrommsdorfFs strontium 

 chloride and Kahlbaum's ammonium sulphate. All usual 

 precautions were taken in the preparation of this and other 

 salts to avoid alkaline impurities. The experiment was 

 carried out as in the case of barium sulphate. A steady 

 emission was obtained at a temperature as low as 550° C. 

 The data for observations made at this temperature are given 

 on the top line below : — 



Strontium Sulphate. 



v - 



H. 



d. 



2x. 



e/m. 



\^ m K + + 



(«/*)*+ 



280 



2915 



T305 



0-425 



230 



1 



222 



249 



277 



2915 



1-305 



0-286 



104 







275 



2915 



1-305 



0-289 



105 



1 





This value of e/m is taken to indicate an emission of 

 potassium. It may be argued, of course, that 230 agrees 

 more nearly with fhe electrolytic value of e/m for strontium 

 than that for potassium, and that the ions are atoms of 

 strontium carrying a double charge. That such is the true 

 explanation is rendered improbable by the fact that this would 

 make strontium an exception to an otherwise general rule. 

 The view that the emission was potassium is also strengthened 

 by the fact that the temperature of emission was but 550° C. 

 or thereabouts. 



The data given on lines two and three were obtained after 

 this same supply of strontium had been subjected to twenty- 

 one hours of continuous heating, during which the temper- 

 ature had been gradually increased from about 550° C. to 

 3 000° C. These values of e/m agree well with the relation 

 suggested by the results on the salts of barium. 



