Actinium and Thorium Emanation. 



417 



"with an ebonite plug 3 cms. long resting on the base of the 

 vessel. A uniform layer of actinium was spread over the 

 plug, a hole through the centre of which served to keep a 

 metal rod along the axis of the cylinder, which was made of 

 brass. The metal rod consisted of small segments of brass 

 sliding on a central steel rod. On applying an electric field 

 between the rod and containing vessel, the active deposit was 

 directed to the rod and the gradient determined by placing 

 each of the small brass segments successively into an a ray 

 electroscope and measuring the ionization thereby produced. 

 The gradient on the plates was determined in the manner 

 already described. The results of the two methods of measure- 

 ment are given in Table II. and seen in fig. 2 (p. 418), 

 where the gradients obtained with the segmented rod are 

 drawn above those measured from the glass plates. 



Table II. 

 Diffusion of Actinium Emanation in : — 



Distance 

 in cms. 



Air. 



Parallel 



Log. of 

 Activity. 



Argon. 



' Plates. 



Log. of 

 Activity. 



Distance 

 in cms. 



. / /'/-. | Argon. 



Segmented Bod. 



Log. of ' Log. of 

 Activity. Activity. 



'5 



2-550 



2-454 

 2301 

 2-178 

 2033 

 1885 

 1-781 

 1-623 

 1-489 

 1-382 

 1231 

 1-020 

 •896 



2-574 

 2-438 

 2-297 

 2-143 

 L-983 

 1-841 

 1-713 

 1 -582 

 1-455 

 L-305 

 1175 

 956 

 •612 



1 -37 . . . 





•75 



10 



2-009 

 2 380 

 2153 

 1-885 

 1 -682 

 1-438 

 1163 

 1-014 



2-472 

 2-2C0 

 1-897 

 1-686 

 1-470 

 1 -239 

 •990 



1-25 



1 -82 . 



1-5 



2-27 



1-75 



2-73 . 



2-0 



318 



225 



3-62... 



2-5 



407 ... 



275 



4-53 . . . 



30 





3-5 



4-0 





Diff. coeff. K 

 Experimental 

 Calculated ... 



Mean 

 -118 



f three 

 .106 



•100 





Mean of two 

 •122 -109 

 104 



The coefficients obtained by the two different methods 

 agree well with one another, also with the numbers calcu- 

 lated from Graham's law, making use of the numerical values 

 obtained for air. 



