414 



Mr. S. Russ on the Diffusion of 



Actinium in Different Gases. 



For determining the coefficient of diffusion o£ the emanation 

 in different gases the following experimental arrangement 

 was used. A cylindrical vessel 12*5 cms. long and 7*5 cms. 

 diameter was fitted with a base on which was placed a tray 

 containing a preparation of actinium ; about 1 cm. above the 

 surface of the tray which was covered with tissue paper, 

 were suspended vertically two glass plates 10 cms. long, 

 2*2 cms. broad, and '2 cm. thick, which were kept separated 

 *2 cm. from one another. The plates were silvered and 



metallic connexions supplied, so that an electric field might 

 be applied between the two plates if necessary. It may be 

 stated here that the gradients obtained on the plates with, 

 and without, an electric field were identical, the only difference 

 being that nearly all of the activity was concentrated on the 

 negative plate when the field was applied, while it was shared 

 equally between the two plates with no field. 



The gases before entering the diffusion vessel were passed 

 through calcium chloride and cotton-wool tubes to render 

 them dry and dust free. The vessel was placed inside a 

 large tank of water, which prevented any appreciable change 

 of temperature occurring during an experiment. During 

 the whole course of the work the temperature varied between 

 10° and 18° C. 



The glass plates were usually exposed for about twenty- 

 four hours, and then they were removed in order to measure 



Table I. — Diffusion of Actinium Emanation. 



Distance in cms. 



Air. 



Log. of 

 Activity. 



Hydrogen. 



Log. of 

 Activity. 



Carbon 

 Dioxide. 



Log. of 

 Activity. 



Sulphur 

 Dioxide. 



Log. of 

 Activity. 



•5 



2-341 

 2-182 

 2-036 

 1-901 

 1-768 

 1-648 

 1-494 



1-224 



•964 



2194 

 2115 

 1-997 

 1-919 

 1-837 

 1-761 

 1-668 



1 : 496 



1-351 



2-581 

 2416 

 2233 

 2-026 

 1-846 

 1-710 

 1-531 

 1-391 

 1-212 

 1-112 



2-709 

 2-526 

 2-358 

 2-173 

 1-992 

 1-798 

 1-616 

 1-439 

 1-281 

 1-068 

 '912 



•75 



1-0 



1-25 



1-5 



1-75 



20 



225 



25 



275 



30 





Diffusion coefficient. 



K Experimental . . . 

 K Calculated 



Mean of 

 three 

 •096 

 ... 



Mean of 

 two 

 •330 

 •363 



Mean of 

 two 

 •073 

 •078 



Mean of 

 two 

 062 

 •064 



