IX, A, 1 Wright and Smith: Radium Emanation 57 



Although Satterly's results seemed fairly conclusive, we 

 thought it desirable, since we were working under different 

 climatic conditions, to repeat some of the experiments before 

 starting a long series of observations on the variation of the 

 emanation content with meteorological conditions. Several other 

 points also demanded consideration. These preliminary experi- 

 ments occupied a period of about eight months. 



In the preliminary experiments the points of especial investi- 

 gation were the following : 



(1) Is the standard solution put into the so-called "steady 

 state" by bubbling air through the cold solution for a period of 

 from two to three hours or is it necessary to boil the solution? 

 If the bubbling of air through the cold solution does not take out 

 the emanation as fast as it is formed, what per cent is taken out 

 by the process? 



(2) Does the charcoal become saturated with emanation for 

 the small amounts dealt with in the experiment? 



(3) Does the charcoal itself contain radium; that is, is there 

 an accumulation of emanation in the charcoal itself with time? 



TESTS ON THE FIRST POINT 



Since a solution of radium bromide which had been allowed 

 to stand for some time would have accumulated radium emana- 

 tion, it is necessary before starting a test to put the solution into 

 what has generally been called the "steady state;" that is, extract 

 from the solution all accumulated emanation. Boltwood has 

 shown experimentally that the radium emanation is completely 

 removed from a solution of radium bromide by rapid boiling 

 for several minutes. But since a test on the emanation in the 

 air occupies a period of several hours, it is inconvenient to boil 

 the solution for that length of time, even if by the use of con- 

 densers the possibility of bodily carrying over some of the radium 

 bromide could be entirely eliminated. Both Satterly and Eve 

 were content with bubbling air through the cold solution, assum- 

 ing that not only was the solution first put into the steady state, 

 but that during a test the emanation would be removed as rapidly 

 as it was formed. However, no account is given of any effort 

 to prove the correctness of their assumption. 



For an accurate determination of the emanation content of the 

 atmosphere, it is not suflScient to show that bubbling air through 

 the cold solution does not extract all the emanation, but it is 

 also necessary to determine accurately what fraction of the 

 whole amount is removed from the solution under the conditions 



