Production and Origin of Radium. 



745 



obtained using ammonium sulphide. This small precipitate con- 

 tained more than three quarters of the actinium in the original 

 preparation, showing that, under the experimental conditions, 

 a considerable concentration of the actinium had been effected. 

 This small precipitate (called actinium III.) was dissolved in 

 hydrochloric acid and its activity examined. The variation 

 of its activity is shown in fig. 2 (curve actinium III.). The 

 ammonia removed most of the actinium X, while most of the 

 radioactinium had been separated with actinium II. The 

 activity consequently rapidly increased, due to the fresh pro- 

 duction of radioactinium, and was still rising after an interval 

 of 120 days. This curve is very similar in shape to that given 

 by Hahn (Phil. Mag. June 1907) for the rise of a ray activity 

 of actinium freed from all its products. 



The solution actinium J II. was then tested to see if there 

 were any growth of radium in it. The observations are shown 

 in the following table : — 



Actinium III. 



I. 



II. 



III. 



Time in 

 da\ s. 



Divisions per minute 

 of electroscope. 



j Divisions per minute 

 in equilibrium. 



4 



•071 



•HO 



8 



•074 



•148 



12 



•077 



154 



10 



107 



■161 



4<> 



T30 



•130 



G4 



1-30 



•135 







Mean... '141 



Column II. gives the observed rate of leak of the electroscope 

 due to the emanation ; column III. the calculated rate of leak 

 of the equilibrium amount of emanation, supposing there was no 

 growth of radium in the solution. Considering the very small 

 rate of leak to be measured, the differences between the numbers 

 in column III. are not greater than the experimental errors. 

 The results thus clearly show that there is no certain growth 

 of radium in the solution. If there is any growth of radium 

 at all, it is certainly less than *02 of a division per minute 

 over a period of 64 days. The growth of the radium per 

 week, in the solution actinium II., which contains only about 

 half of the actinium in the solution III., corresponds to *26 

 division or to 2*38 divisions in 64 days. For equal quantities 

 of actinium, the growth of radium in solution III. is certainly 

 less than 1/200 of that observed in solution II. 



