420 



Mr. S. Russ on the Diffusion of 



Diffusion of Thorium Emanation in Air and Argon. 



Since the time-periods of thorium and actinium emanations 

 are o£ the same order of magnitude, and previous work 

 (loc. cit.} has shown their diffusion coefficients to be similar, 

 the opportunity presented itself of comparing these two 

 emanations under precisely the same conditions of diffusion. 



The small diffusion vessels which had been used for actinium 

 were emptied of their preparations and thoria substituted. 

 The measurements were conducted in a similar way, except 

 that the a ray electroscope could not now be used, as the 

 thoria being considerably weaker in emanating power than 

 the actinium, the amount of active deposit collected was 

 smaller. The gradient along the metal rod was consequently 

 measured by means of a rather sensitive electrometer in the 

 manner already described for glass plates. 



Observations were made in air between 76 cms. and 

 S '25 cms. pressure, and in argon at 76 cms. 



The results are placed together in Table IV. and may be 

 seen in fig. 4, where the abscissa? represent the distances 



Table IV. 

 Diffusion of Thorium Emanation. 



Pressure ... 



Distance 

 in cms. 



Air. 



Argon. 



8 - 25cms. 



Log. of 



Activity. 



17*5 cms. 



Log. of 

 Activity. 



37-52 cms. 



Log. of 



Activity. 



76-12 cms. 



Log. of 

 Activity. 



76 cms. 



Distance i Log. of 

 in cms. Activity. 







2-401 

 2-375 

 2 327 

 2-289 

 2-255 

 2-206 

 2-169 

 2-131 

 2-094 

 2053 

 2-014 

 1-969 



2-472 

 2-406 

 2-354 

 2-285 

 2-239 

 2176 

 2116 

 2-058 

 1-989 

 1-937 

 1-874 



2-373 

 2-282 

 2-192 

 2-134 

 2-028 

 1-947 

 1-853 

 1-775 

 1-685 

 1-602 

 1-517 



2-568 

 2-453 

 2-329 

 2-203 

 2-082 

 1-962 

 1-833 

 1-713 



1-875 



•38 1 1-813 



•76 i -"Mi 



•8 



■ 1-6 



2-4 



114 



1-52 



1-90 



2-28 



266 



1-672 

 1-608 

 1-563 

 1-490 

 1-434 

 1-369 

 1-327 

 1-254 



3-2 



40 



4-8 ......... 



56 



6-4 



7-2 



! 5-42 ::.::: 



3-80 



80 



8-8 





Diff. coeff. K 



Pressure X } 



diff. coeff. L 



(PXK).. J 



•966 

 7-97 



•436 

 7-63 



•211 

 7-94 



•103 



7-88 



K experimental "084 

 K calculated . . . -087 



Mean value PxK = 7*85 



