Volatility of Radium C. 135 



the three, radium 0, is not completely removed even by pro- 

 longed heating to 1320°. On the other hand, the author has 

 shown * that in tubes containing impure radium emanation 

 which has simply been pumped off from a radium solution, 

 and sparked down, and which therefore contains an excess 

 of hydrogen, radium A, radium B, and radium C are com- 

 pletely volatilized at a temperature of G50°. The apparent 

 inconsistency between the two sets of observations is now 

 very simply explained by JSchrader's results. Makower 

 determined the volatilization points of radium A, radium B, 

 and radium C, under conditions such that part at least of 

 each of the three products was oxidized. The author, on the 

 other hand, determined the volatilization points of the bodies 

 under conditions such that they were present, either as the 

 elements themselves, or as compounds other than oxides. This 

 is the chief reason for the differences in the two sets of results. 



A few experiments confirming the truth of this conclusion 

 will now be described. 



Experiments in Oxygen. — A tube of clear quartz, 10 cm. 

 long and diameter of .section 0*5 cm., was filled with oxygen 

 and about 30 millicuries of emanation. After the active 

 deposit had been formed in equilibrium amount, the tube 

 was placed in an electric furnace and heated, one end of the 

 tube being at 650°, the other at 300°. After 15 minutes it 

 was removed. Neither by electroscopic measurements of 

 the 7-ray effect, nor by a fluorescent test with a screen 

 of barium platinocyanide, could any change in the distribu- 

 tion of radium C be detected. The experiment was repeated 

 with the hotter end of the tube at a temperature of 1200°. 

 Again, after 15 minutes there was no appreciable change in 

 the distribution of radium (J. The volatilization point of 

 radium C in an atmosphere of oxygen from a quartz surface 

 is therefore greater than 1200°. This is consistent with 

 Makower's results. 



If the tube be heated at 900° or higher temperatures for 

 an hour, a marked change in the distribution of radium is 

 effected. Now, if radium C were volatile at 1200° or at 

 lower temperatures it is to be expected that some of it would 

 be volatilized in 15 minutes. This result must therefore 

 be explained by the growth of radium C from either radium 

 B or radium A volatilized at 900°. 



If the tube be heated at 700° for two hours, no change in 

 the distribution of radium C is effected. Hence it follows 

 that radium A, radium B, and radium C are all non-volatile 

 in an atmosphere of oxygen below 700°. 



* A. S. Russell, Proc. Roy. Soc. A. Jxxxvi; p. 244 (1912). 



