Diffusion of 



Thorium 



and Actinium Emanations 



P. 





PXD (corrected). 



42-75 cm. 





7-50 



42-0 „ 





8-30 



36-95 „ 





6-80 



33-25 „ 





7-40 



32-5 „ 





6-77 



20-7 „ 





7-23 



19-9 „ 





7-50 



18-2 „ 





6-82 



17-45 „ 





7-87 



15-9 „ 





7-25 



15-7 „ 





7-44 





Mean . 



. 7-44 



641 



The value of D in air at 76 cm. pressure and 15° C.=*098. 



Experiments with Glass Plates. — The values of the product 

 PxD for actinium show even larger variations than those 

 for thorium emanation. It was thought that perhaps the 

 brass plates, about "5 mm. thick, were not sufficiently rigid 

 and that they did not always occupy the same relative 

 positions. The measurements for actinium were therefore 

 repeated, using glass plates 2 mm. thick, covered with tinfoil 

 on the sides facing one another, except at the edges, which 

 were left uncovered for insulating purposes. 



P. 



PXD (corrected) 



43-75 cm. 



8-57 



39-8 „ 



8-17 



34-35 „ 



8-04 



32-55 „ 



8-23 



27-25 „ 



7-70 



25-0 „ 



8-07 



22-2 „ 



7-94 



17-6 „ 



7-95 



14-35 „ 



8-41 



11-85 „ 



7-87 





Mean . . 8-12 



The value of D in air at 76 cm. pressure and 15° C.=-107. 



Evidently the form of the apparatus has a considerable 

 effect on the results. 



If the value of PxD for thorium emanation is altered 

 in the same degree, it should now be about 7*13. To test 

 this point the determinations with thorium emanation were 



