302 Wellisch — Experiments on Active Deposit of Radium. 



that they are charged and is undoubtedly correct in his assump- 

 tion that they owe their charge to the ions present in the gas. 

 He shows also that the anomalous results obtained by Debierne* 

 in a series of experiments with regard to the diffusion of 

 radium active deposit can be explained by taking into con- 

 sideration the formation of aggregates. The present experi- 

 ments bring out several new points of interest but on the whole 

 serve merely to confirm the results of Eckmann in this con- 

 nection. 



With regard to the determination of D, Eckmann collected 

 the total amount of gas deposit on a piece of gauze; he found 

 for the particular vessel which he employed that this deposit 

 was equivalent to a formation for six minutes ; in other words, 



Q 



p = If (with the notation of Section 6). He then employed 



the formula G = ^ (Section 3) in order to estimate D, 



which came out as *06 ; this formula however neglects the dif- 

 fusion to top and bottom which was important for the cylinder 

 which he used. It is of interest to apply formula (8) in order 

 to evaluate D ; we find b given as 4 cni and I equal to 8 cm . 

 Equation (10) of Section 5 becomes now 



D = -0266 | ; 



using Eckmann's experimental value for p given above, we 



have D == -0443. 



Such an excellent agreement with the most probable value 

 obtained in the present investigation must be to some extent 

 fortuitous, but there can be little doubt as to the order of 

 magnitude of I). 



Summary. 



8. It is advisable to give here a brief synopsis of the results 

 obtained in the series of experiments dealing with the active 

 deposit of radium, including for the sake of convenience several 

 results previously published. 



Suppose a quantity of radium emanation is mixed with a 

 dry dust-free gas ; of the active deposit particles which are 

 produced a certain fraction are positively charged, the remain- 

 der being neutral. This fraction depends upon the nature of 

 the gas but not upon its pressure provided the pressure be 

 high enough to prevent any appreciable recoil on to the walls 

 *Debierne, Le Radium, vi, p. 27, 1909. 



