﻿Thermions jrom the Salts of the Alkaline Earths. 

 Calcium. 



135 



The salts of calcium which have been tested are the 

 sulphate, the chloride, and the phosphate. The difficulty 

 with calcium is that half the electrolytic value of ejm lies so 

 near the value of ejm for potassium that it is not possible by 

 the method of this experiment to distinguish between them. 

 It is of interest, however, that out of thirteen determinations 

 all but one may be explained on either hypothesis. This 

 fact is also of importance as it shows what could not be 

 shown in the case of strontium, that none of the ions are 

 atoms of the metal carrying double charges as in electrolysis. 

 The one exception corresponds very nearly to sodium and 

 may very likely be due to that element as an impurity. 



Calcium Sulphate. 



Calcium sulphate was prepared from Baker's analysed 

 calcium chloride and Kahlbaum's ammonium sulphate. 



Momentary currents were noted for temperatures between 

 500° C. and 1000° C, but no steady emission was obtained 

 below the latter. Very good curves were obtained, however, 

 at and above this temperature. The corresponding data 

 appear in the first three lines below. 



Calcium Sulphate. 



V. 



H. 



d. 



2x. 



ejm. 



409 



2915 



1-29 



•343 



230 



407 



2915 



1-29 



•349 



236 



432 



2915 



1-29 



•327 



220 



150 



4600 



0-50 



•105 



258 



150 



4600 



0-50 



•0<J5 



215 



150 



4600 



0-50 



•105 



258 



( e M) Ca + + 



(e/™) K+ 



487 



249 



The data and results occurring in the remainder of the 

 Table are from previous experiments with the apparatus 

 used by Richardson. In these experiments the same high 

 temperature was required to obtain a measurable emission as 

 in those already mentioned. The observed values of ejm 

 point to either potassium or calcium carrying single charges, 

 while the temperature of emission argues more strongly in 

 favour of the latter. 



Calcium Chloride. 

 Although a great number of experiments have been made 

 to obtain results from this salt, satisfactory curves have been 

 obtained in but two cases. The samples under investigation 



