tM'LENKAN & KENNEDY] RADIOACTIVITY OF POTASSIUM 21 



two samples of this salt exhibited activities which were approximately 

 only 5 per cent and 20 per cent respectively of that shewn by a 

 number of other specimens of the same composition. 



In addition to the results recorded in Table V it may be stated 

 that on one occasion a sample of potassium cyanide obtained from 

 Kahlbaum was compared with one of potassium sulphate and one of 

 potassium chloride obtained from Merck, and all three salts were 

 found to possess to within one per cent the same activity. On another 

 occasion a sample of potassium cyanide obtained from Kahlbaum 

 was compared with a specimen of the same salt manufactured by 

 Merck and was found to display an activity more than four times as 

 intense as that of the latter. 



In this connection the extremely low value found for the activity 

 of the sample of potassium sulphite tested merits special emphasis. 

 Potassium metal itself it will be seen exhibited a marked activity, 

 but the value assigned to it, however, is not to be taken as comparable 

 with the values recorded for the different salts of this metal, in as 

 much as it was not possible to prepare layers of the metal for examina- 

 tion as regular and uniform as those of the salts. 



Considering the results obtained with potassium salts as a whole 



it would appear that: the values found for ^ X 10^ shew such ex- 

 tremely wide variations, even after due allowance is made for the 

 density and the state of division of the compounds, as to practically 

 preclude the view that the activity of these salts is a normal atomic 

 property of the potassium. 



Second. That while one sample of sodium chloride in the form 

 of rock salt shewed an activity comparable with that exhibited by a 

 number of potassium salts, several other samples of rock salt were 

 found to be quite inactive. Metallic sodium, too, and also a specimen 

 of sodium carbonate, when examined, did not exhibit the slightest 

 trace of radioactivity, and consequently it would appear that the 

 activity observed in the single instance of sodium chloride men- 

 tioned was due to the presence in this salt of a trace of an active 

 impurity. The low values obtained by Elster and Geitel in their 

 measurements on the conductivity of air in a salt mine would also 

 support this view. 



Third. That with the exception of ammonium chloride which 

 emitted a feeble activity, none of the lithium and ammonium salts 

 shewed the slightest trace of radioactivity, and that a sample of 

 rubidium alum exhibited an activity which was extremely small, and 

 a specimen of caesium chloride one which was onl}^ just measurable. 



