Active Deposit of Radium in Electric Fields. 5-JL7 



the cathode deposit would increase with the applied poten- 

 tial to a maximum of 100 per cent, of the total deposit 

 produced by the emanation, whereas if the field were reversed 

 this maximum would be very much diminished, as is borne 

 out by the previous results. The experiments do not bear 

 out the assumption that has been sometimes made, that the 

 uncharged active matter collected by a surface is propor- 

 tional to its area. 



A second series of experiments was carried out using the 

 same set of electrodes, in which both the outer case and the 

 rods were earth-connected. Under these circumstances the 

 surfaces exposed to the emanation became active by the 

 diffusion of the deposit to the electrodes, so that a comparison 

 of the activities of wires of various diameters gives the 

 variation of activity due to diffusion alone, from an initially 

 uniform atmosphere of active deposit. The results are 

 embodied in the following table, the wire of diameter 2 mm. 

 has been used as a standard and the two curves made to 

 coincide at this value. 



Electrode. 



Anode activity. 

 P.D. 960 volts. 



Activity. 

 P.D. zero. 



1. 

 2. 



3. 

 4. 

 5. 



1-00 

 1-37 

 1-67 

 1-89 

 1-98 



1-03 

 1-34 



1-67 

 1-92 

 205 



It is seen that within the limits of experimental error the 

 two curves are identical, showing that the anode activity 

 using high potentials is apparently collected on wires of 

 different sizes in exactly the same way as when there is no 

 field between the electrodes. Thus the anode deposit appears 

 due to the diffusion of uncharged active matter from a 

 uniform distribution of uncharged deposit in the emanation- 

 bearing gas. The coincidence of the two curves also supports 

 the view that the emanation absorbed by the metal surfaces 

 has little bearino; on the origin of the anode activity. 



Experiments wit It Radium A (short exposures). 



A simple calculation of the mean time taken for the atom 

 of active deposit to reach the electrode after it- format ion 

 from the emanation, shows that with the electric fields 



2N2 



