136 



Mr. A. S. Kussell on th, 



If the volatilization be conducted inside a similar sealed tube 

 in an atmosphere of air, exactly similar results are obtained. 



Experiments in Hydrogen. — Very different, however, is the 

 character of the volatilization in an atmosphere of hydrogen. 

 The original observation that all the products are volatilized 

 at temperatures less than 650° was confirmed. Two more 

 tubes were filled with impure emanation in the ordinary way 

 and contain, therefore, in addition to hydrogen, carbon 

 dioxide and aqueous vapour. In a third tube no aqueous 

 vapour was present. A fourth contained only hydrogen and 

 emanation. The results, however, on the volatilization of the 

 active products were the same for all the tubes. 



The volatilization point of radium C in hydrogen has been 

 determined as follows : — The quartz tube was heated in such 

 a way that the radium C was entirely removed to one end. 

 This end was then inserted in the hottest part of an electric 

 furnace which was varied in temperature between 400° and 

 700°. Under the circumstances the radium C is volatilized 

 from the hotter end to a certain point at which it almost 

 entirely condensed. In four experiments the mean tempera- 

 ture of the part of the tube at which it deposited was 

 360°±20°. If this part were then raised to a higher tempera- 

 ture, say 50° higher, the radium C would move further along 

 the tube till it condensed on a part at a temperature of 360°. 



This result is quite consistent with the results of the Royal 

 Society paper, p. 245. There it is seen that radium C is 

 completely removed from one end of a long tube to the 

 other, provided the cooler end is at least at 400°. If it is at 

 320° it is not entirely removed. The temperature, therefore, 

 at which radium C is condensed on a quartz surface lies 

 between 400° and 320°. 



This volatilization temperature was confirmed by another 

 experiment. 



The hottest part of a furnace was uniformly heated at 

 360°. A small tube containing emanation and hydrogen 

 was placed inside the furnace so that one end was at a 

 temperature of 360° and the other at 350 D . The latter end 

 was the nearer of the two to a /3-ray electroscope. The 

 /3-ray activity (due, of course, to radium C) was measured 

 for half-an-hour after insertion of the tube. The following 

 is one set of results : — 



Time in minutes j j 2 



4 



6 



9 



10 



14 



15 i ]8 



| 



21 



36 



i 



1 



1 ! 



Activity iu div. per mm. . 33*6; 33*6 



34-3 



35-3 



360 



36-8 



362 



43-5J 435 



43-7 



1 

 45-0 



