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



activity, however, may be easily explained in the light of 

 the above results. Uncharged recoil atoms are carried to the 

 screen by the electric wind, which is not stopped by the small 

 surface of the wires and passes by inertia to the plate 

 carrying to it a certain amount of active matter. If by 

 means of an additional source of ionization an electric wind 

 in the direction of the screen is produced in the vessel, a 

 greater part of the active deposit may be concentrated on 

 the plate. 



The same results have been obtained by exposing screened 

 plates into the vessel containing uncharged recoil atoms of 

 radium B (see sec. 3). 



On a Method of concentrating Active Deposit of Radium 

 on Plates in the absence of an Electric Field. 



9. It was shown in sec. 2 that when a stream of air con- 

 taining radioactive atoms strikes a plate normally, the greater 

 part of the activity is found to be deposited on the surface 

 of the plate. In later experiments it was found possible 

 to apply this principle for concentrating active deposit of 

 radium on plates exposed to the emanation in the absence 

 of an electric field. The current of air, which was produced 

 in a vessel K containing emanation by pressing the rubber 

 bulb R (fig. 6), passes through the tube t and strikes a plate 

 P"introduced into the vessel by means of the rod L and the 

 rubber stopper S. The walls of the vessel as well as the 

 plate P are earthed, so that when no current of air is produced 

 the activity of the plate is due to diffusion of the recoil atoms. 

 Now, if the bulb R is pressed, the radioactive atoms are carried 

 to the plate P by the current of air, and the experiments 

 show in this case a considerable increase in the activity of 

 the plate. The amount of active matter carried to the plate 

 by the current of air increases largely with the quantity of 

 emanation used, which is probably due to the accumulation 

 of the gas activity in the vessel (see sec. 10), but it always 

 remains less than the activity concentrated on an anode. It 

 seems that the electric wind is more efficient in carrying the 

 activity to the plate than an ordinary current of air, such as 

 that produced by pressing the rubber bulb. This is what 

 would be expected, since the electric wind directed by the 

 ions reaches the surface of the electrode, while a current of 

 air produced in a mechanical way diffuses in all directions 

 before reaching the plate. 



This method of concentrating active deposit of radium on 

 plates may, however, be useful in cases when no electric field 



