THORIUM IN AN ELECTRIC FIELD. — HENDERSON. 11 



The distribution of the thorium active deposit was also 

 measured in cylindrical vessels. The vessels were of the 

 usual type. Air dried by passing over phosphorus pentoxide 

 was passed over thoriuiji hydroxide, and then through the 

 testing vessel at a slow enough rate so that practically all 

 the emanation would decay in the vessel. The activities of 

 the rod and casC; the rod being used as cathode, were measured 

 by means of a Dolezalek electrometer. The activity of the 

 rod was measured in a cylindrical vessel, free from active 

 deposit, of the same dimensions as the anode case; while 

 the latter was tested with a clean rod similar in dimensions 

 to that used as cathode. The same general results were ob- 

 tained as with the parallel plate vessels although the voltage 

 necessary to bring over a given fraction of the rest atoms on 

 to the cathode was higher owing to the difference in shape of 

 the vessels. A similar rise of percentage cathode activity 

 with voltage was found. With 280 volts (the highest used), 

 the percentage cathode activity was 95.3. 



From these experiments it will be seen that parallel plates 

 and cylindrical vessels give concordant results. 



To test if the variations between thorium and radium 

 might be due to a surface effect of the electrodes, experi- 

 ments were made to see if the surface conditions of the elec- 

 trodes had any effect on the distribution of the rest atoms. 



Experiments with copper and lead electrodes gave results 

 similar to those obtained with zinc plates. The state of polish 

 of the electrodes also had no effect on the distribution. These 

 results are in accordance with those found for radium by 

 Wellisch^ and by Walmsley-. 



An interesting result found by Godlewski^ might be re- 

 ferred to here. He found that on electrolyzing a solution of 

 actinium, the active deposit was transported to the cathode, 

 only when the cathode plate had previously been used as 



1. Wellisch, Am. Joum. Sci. Oct. 13. 



:'.. Walmsley Phil. Mag. Oct. 14. 



3. Godlewski, Bull. Acad. Sci. de Cracovie, June 1913. 



