130 Dr. Hans Sch ruder on the Existence of Chemical 



volatility of radium B. The figures also show the influence 

 of the surface on the volatility. 



Chlorine and hydriodic acid also increased considerably 

 the volatility both of actinium B and of actinium C. From 

 a quartz surface after treatment with hydriodic acid, 

 actinium C volatilizes at a lower temperature than actinium 

 B. At 560°, heating for two minutes caused about 40 per 

 cent, of actinium to volatilize, but only 13 per cent, of 

 actinium B. No more experiments were made, however, in 

 this direction, since it could hardly be hoped that they would 

 decide whether the change in volatility was due to a change 

 in the active material itself, or in the surface only. Jt is 

 possible that a very thin layer of water of thickness about 

 10~ 6 mm. which absorbs the gaseous acids may have a con- 

 siderable influence. 



In support of: this assumption it may be added that, after 

 treatment with gaseous hydrochloric acid, actinium B is 

 more easily dissolved off a platinum surface by water than 

 before such treatment. This is shown by the following 

 experiments : — A strip of platinum was cleaned by placing 

 it for a short time in boiling aqua regia. It was then heated 

 in the blowpipe flame, and on cooling was boiled in a solution 

 of ammonia. After it was heated again, it was exposed to 

 actinium emanation for one minute. It was then kept in a 

 slow current oE gaseous hydrochloric acid for twenty minutes. 

 Its activity was measured in an electroscope. The plate was 

 then immersed in water for one minute and moved uniEormly 

 in it. It was dried with filter-paper, and the variation of its 

 a-ray activity observed for the next twenty minutes. 



Two experiments were carried out exactly similar to these 

 two, except that the active material was not kept in an 

 atmosphere of hydrochloric acid after exposure to the 

 emanation, but kept in a desiccator for twenty minutes. 

 One series of results obtained is as follows : — 



Method of previous 

 treatment. 



Percentage loss of 

 actinium B due to 

 immersion in water 

 during one Tninute. 



! 1. ]Vot treated with acid 



'24 

 35 



82 



81 



! 2. Do. do 



; 1. Treated with HC1 which was 

 dried with H 2 S0 4 



2. Treated with HC1 which was 

 dried witli P 2 0- 





