770 Dr. A. N. Lucian on the Distribution of the 



where 



V = applied potential, 



cm 



& = 1*54 f-, mobility o£ the positive ion, assumed to 



sec. volt J r 



represent approximately the mobility o£ the deposit 

 particle also, 



a = '075 cm., the radius of the central electrode, 

 6 = 2*45 cm., the inner radius of the vessel, 

 X = 350 sec -1 , transformation const, of Act. A, 



that with 600 volts about 25 per cent, of the deposit reaches 

 the wire as actinium A, with 1000 volts less than 40 per 

 cent., and with the highest potential used (1700 volts) less 

 than 55 per cent. Since, as will be shown later, no increase 

 of potential difference above 1000 volts appreciably alters 

 the percentage of the cathode deposit, it may be assumed 

 that with increasing potentials the increased amount of 

 actinium A on the central electrode has no effect on the 

 distribution of the deposit ; at least, in so far as the final 

 result is concerned. It seems probable, therefore, that 

 actinium A and actinium B are born with the same physical 

 characteristics, and exhibit the same peculiarities in an 

 electric field. 



The following experimental results were obtained in con- 

 nexion with the three special objects of investigation men- 

 tioned in the introduction. 



First of all, the dependence of the distribution of activity 

 on the amount of emanation employed claimed attention and 

 was made the subject of investigation. It was found that 

 the cathode percentage, which we shall call Ay (activity at 

 potential V, referring to the cathode), depended to a great 

 extent on the amount of emanation used, for values of V up 

 to 600 volts or thereabouts. Above Y = 600, Ay was inde- 

 pendent of the amount of emanation used, when the amount 

 was not excessively large. The curves in fig. 2 represent 

 the results of these experiments and give an idea of the ratio 

 of amounts used in these experiments. Very excessive 

 amounts have not been tried, but there are strong indica- 

 tions that the above independence would no longer hold good. 



The points on the curves represent the percentage of the 

 total activity which is deposited on the cathode, for a given 

 amount of emanation. As has already been mentioned, the 

 activities on the case (anode) and the central electrode 

 (cathode) were measured separately and from these measure- 



