816 



Mr. A. B.Wood on the 



of these two substances. Such methods are rendered unsatis- 

 factory by impurities in the metal employed for the separation r 

 and it is only by taking special precautions that the Th C is 

 deposited free from Th D. It is interesting to note that 

 Hahn and Meitner * employed the method of volatilization 

 for the separation of Act C and ActD. V. Lerch and 

 v. Wartburg f also found that Th D was readily separated 

 from the active deposit by heat. 



Fiff. 3. 



100 X 



20 50 40 SO 60 70 



T/M£ /A/ M//VS. {AFTER ffEAtOML FF?OA1 FVtfK/lCfJ 



Fig. 3 A shows the result of an experiment in which the 

 whole of the Th D has been volatilized. It will be noticed 

 that there is a pronounced initial rise due to growth of Th D r 

 the curve then decaying with a period a little greater than 



* Hahn & Meitner, Phys. Zeit. ix. p. 649 (1908). 



t V. Lerch & v. Wartburg, Wien. Ber. cxviii. p. 1575 (1909). 



