Volatility of Th 



I). 



811 



for exactly 4 minutes, then quickly removed and three or four 

 more observations of its activity taken. 



Fig. 1 shows the results o£ a typical experiment, and the 

 method of calculating the percentage of Th D volatilize 1 in 

 the furnace. The portion A of the curve represents the decay 

 of activity before heating, the interval a b is the time during 

 which the Th D is heated, and the portion JB represents the 

 decay of the activity after heating. It was found in all 

 experiments that the decay before and after heating was 

 identical; and from a large number of very consistent ex- 

 periments the value of 3*1 minutes was obtained from the 

 period of Th D. A simple calculation gives at once the 

 percentage which has been removed by heating. 



Fig. 2. 



300 400 500 600 700 



Temperature , Cea/t/gradl — ■* 



Experiments of the above nature were carried out at 

 temperatures varying from 200° C. to 1000° ft, and the 

 results of a few of these are embodied in curve (A), fig. 2. 



3G2 



