[m'lennan & KENNEDY] RADIOACTIVITY OF POTASSIUM 27 



of radium. With the object of testing this surmise a sample of potas- 

 sium sulphate which had been found to exhibit a comparatively- 

 high activity, was heated to a little over lOOO^'C, and maintained at 

 that temperature for a considerable time. 



After the salt had been subjected to this treatment it was again 

 examined, but was found to possess exactly the same activity as 

 before being heated. 



Similar attempts were made to reduce the activities of samples 

 of potassium chloride and potassium cyanide, but in none of these 

 tests was any reduction of activity obtained as a result of the heating. 



To test still further the possibility of driving off by volatilisa- 

 tion any active impurities which might be present, a quantity of 

 active potassium sulphate, contained in a graphite crucible, which, 

 on examination, shewed no sign of activity, was placed in a coke 

 furnace, first melted and then heated as highly as possible for a time. 

 During this heating the sulphate became partially converted into the 

 sulphides of potassium. After cooling the mixture, which was ground 

 to a fine powder and tested for radioactivity in the manner indicated 

 above, was found to possess the same activity as before the treatment. 



As the melting point of potassium sulphate is approximately 

 1060°C and in as much as the temperature of the salt during this 

 experiment was raised very much beyond this point, it is clear that 

 a temperature was reached considerably above the points of 

 volatilisation of the radium products of slow decay, and it follows 

 therefore from the absence of any loss of activity from the heating 

 that none of these active products were present in the salt and that 

 the source of its activity must be sought for elsewhere. 



The only remaining known active product, whose presence in 

 the salt could account for its activity appeared to be uranium X., and 

 although it was not clear how such a product could become mixed 

 with the salts of potassium, attempts were made to separate it out by 

 recrystallisation, by precipitation with ammonium carbonate, and also 

 by treating solutions of the salts with ether after the manner of Meyer 

 and Schweidler.^ By none of these processes, however, was it found 

 possible to effect to a measurable degree the separation of any active 

 product. 



Attempts were also made with some of the salts to separate out 

 by electrolysis active impurities which might be present but it was 

 again found impossible to bring about any separation of the active 

 constituents in this way. 



1 Meyer and Schweidler, Wein, Ber 113, July 1904. 



