446 Mr. S. Ratner on the Distribution of the Active 



of the active deposit does not diffuse to the walls of the 

 vessel but remains suspended in the gas. The particles 

 forming this gas activity are generally supposed to be charged 

 partly positively, and partly negatively, in order to account 

 for the fact that they may be concentrated on the anode as 

 well as on the cathode. 



Various experiments have been undertaken in order to 

 study the nature of the gas activity in the light of the results 

 given above. In the first place the question of the charge of 

 the active particles was investigated. For this purpose a 

 needle electrode raised to a high potential, as described 

 in sec. 7, was exposed to a large quantity of emanation in 

 Wertenstein's exposing vessel which contained a large 

 amount of gas activity. The activity acquired by the 

 needle was found to be very small and of the same order as 

 in the absence of an electric field. Now, simple calculations 

 show that if these particles were charged they would reach 

 the needle even when their mass was as large as the large 

 particles of tobacco-smoke, whose mobility is of the order of 

 •0001 j^.* In this case the velocity of the active particles 

 in the neighbourhood of the needle charged to a potential of 

 50,000 volts would be more than enough to enable them to 

 travel against the electric wind. If seems therefore necessary 

 to suppose either that the aggregates forming the gas activity 

 are large compared with the visible particles of tobacco- 

 smoke, which is very improbable, or that they are uncharged 

 particles. 



Experiments were also carried out in order to investigate 

 the amount of activity suspended in the gas. For this 

 purpose the gas activity was allowed to accumulate in the 

 vessel for several hours, and then an electrode was intro- 

 duced into the vessel and exposed to the emanation for 

 1 minute, an interval of time which was found sufficient to 

 concentrate the whole gas activity on the electrode. This 

 activity was then analysed and compared with the activity of 

 another electrode exposed for the same interval of time to 

 the emanation now free from gas activity. It was found 

 in this way that the active matter accumulated in the gas 

 during a long time consists of radium (A + B + C) in equi- 

 librium, and that the amount of the gas activity largely 

 increases with the quantity of emanation present in the 

 vessel. When large quantities of emanation (of the order 

 of 100 millicuries) were used, the amount of the active 

 deposit acquired by the electrode did not depend appreciably 



* De Broglie, Le Radium, 1909. 



