Transformation Products of Radium. 293 



that the ft ray activity arises from a product which is half 

 transformed in six days, and which is supplied at a constant 

 rate from a primary source, the latter being transformed at 

 a very slow rate. The results indicate that the primary source 

 itself does not emit ft rays, but that these arise from the 

 successive product. We have already seen that the a ray 

 activity, tested immediately after removal, is very small. We 

 may thus conclude that the primary matter is "rayless," 

 that is, it does not emit either a or ft rays, but that these arise 

 from the products of its transformation. 



In conformity with the nomenclature adopted in the pre- 

 vious paper (loc. cit.) this rayless product will be called radium 

 D. The ft ray product which arises from it will be called 

 radium E. The a. ray product (previously termed radium E) 

 will be called radium F, for we shall see later that the ft ray 

 product is the parent of the a ray product. 



We have seen that the increase of the « ray activity to a 

 maximum indicates the existence of a product which emits 

 ft rays, and which is half-transforined in about six days. 

 We shall now consider a method by which this product 

 radium E can be isolated, and its rate of transformation 

 directly measured. 



In my previous paper it was shown that if a platinum 

 plate, coated with the active deposit, were subjected to a 

 temperature of about 1000° C, the a ray activity was 

 nearly all lost, while the ft ray activity remained unaffected. 

 On examining the platinum plate about two months later, it 

 was found that the ft ray activity had in the meantime 

 decayed to a small fraction of its original value. This at 

 once suggested a possible means of separation of radium E. 

 A platinum plate, containing an active deposit two months 

 old, was heated in an electric furnace for four minutes at 

 about 1000° C. On testing it, the loss of the a ray activity 

 showed that the product radium F had been mostly volatilized. 

 The ft ray activity, as before, was not immediately altered by 

 the heating, but was found to lose its activity with the time. 



The activity decreased to about one quarter of the maximum 

 value and then remained constant. Subtracting this constant 

 value, the activity was found to decrease exponentially with 

 the time, falling to half value in about 4*5 days. This result 

 shows that not only most of the radium F, but also the greater 

 part of the parent substance radium D, had been volatilized 

 at or below 1000° C. Radium E was left behind, and, since 

 most of the parent matter had been removed, immediately 

 commenced to lose its activity. The constant activity which 

 remained behind was due to the fact that some of the radium 



