Compounds of Skort-lioed Radioactive Elements 



129 



the temperature of the wire could not be kept uniform 

 owing to convection currents. The time during which the 

 wire was heated naturally affected the amount of actinium B 

 volatilized. If the wire were heated for 1 minute instead of 

 4 minutes at 900° only from 60 to 70 per cent, was removed. 



Chemical Treatment of the Active Material. — In the 

 following experiments, the active platinum wire was exposed 

 for 10 to 15 minutes to gases and vapours which were thought 

 cipable of acting chemically on the active material. 

 Hydrochloric, hydrobromic, hydriodic acids, bromine, and 

 chlorine were used for this purpose. The gases were dried 

 by sulphuric acid. Bromine, pure, from Kahlbaum, was used 

 directly. The action of hydrochloric acid gas on the active 

 material did not affect its volatility. Bromine, however, 

 produced an increase in the amount volatilized at a 

 given temperature. For instance, after treatment with 

 bromine, the wire was heated for 4 minutes to 675° at a 

 pressure of "004 mm., 77 per cent, of actinium B was 

 volatilized. From a wire not treated with bromine, on the 

 other hand, only 18 per cent, volatilized under the same 

 conditions of temperature and pressure. 



It might appear possible that this increase in volatility is 

 due to the action of the bromine on the platinum. Similar 

 experiments in which quartz surfaces were used instead of 

 platinum decided against this view. The experiments with 

 quartz surfaces were conducted at atmospheric pressure in 

 an ordinary electric furnace. 



The following table shows some of the results : — 



Not treated. 



Treated with bromine. 



Surface. 



1 



Temp. 



Per cent, 

 volatilized. 



Temp. 



Per cent, 

 volatilized. 



Quartz. 



650° 

 655° 

 670° 

 890° 



24 

 14 

 55 



75 



660° 



735° 



78 

 82 



Platinum. 



660° 



680° 





 2 



670° 



69 



It is seen that bromine has the effect of increasing the 

 Phil Mag. S. 6. Vol. 24. No. 139. July 1912. K 



