Valency of the Radio elements. 405 



The following results were obtained : — 



(1) D ^= 0-7%x2-17 = 0,329 • D ^ = 0-332 



0*57 



Di7°-6= (j.7^q x 9.|q —^ 332 . D 1S o = 0-335 



(- 7 ) T>i _ 0*? 



0-179 xH-64=°- 327 • D 16 ==0-33O 



D5 ^= 0-469 x 3-66 =°- 332 ' D - = 0-335. 

 Mean value Di S o = 0*333 sq. cm. per day. 

 The valency of radiothorium is therefore 4. 



It is apparent from this result, and the results given above, 

 that ThX diffuses twice as quickly as radiothorium, and 

 ThB four times as quickly. The upper layers after diffusion 

 have therefore proportionately more ThB than ThX, and 

 more ThX than radiothorium. In one experiment, for 

 example, after diffusion had taken place for two days the 

 ratios of the equilibrium amounts of radiothorium, ThX, and 

 ThB in the topmost layer were 1 : 18 : 81. 



(f) The diffusion constant of Ionium. 



A preparation of ionium containing thorium dissolved in 

 normal HC1 was allowed to diffuse in the usual manner. 

 The activities of the different layers were , measured in an 

 a-ray electroscope. The following results were obtained: — 



0-5 7 

 0-475x3-61 



Di 6 °=n «--.,,.., =0-308 . D 18 o = 0-331 



,11 0-57 



)l6 ° = 0^462x3-66^ 



DSo = „„^ ' ,»„ =0-315 . D 18 = = 0-327. 



Mean value Di 8 ° = 0*327 sq. cm. per day. 

 The valency of ionium is therefore 4. 



(g) The diffusion constant of Thorium. 



The solution used contained 24 mg. per c.c. ThCl 4 in normal 

 HC1. The amounts of thorium in the different layers were 

 obtained by igniting the thorium, and weighing it as oxide. 

 The following results were obtained : — 



DiW ,- ?'°\.^ =0-318 . D 15 , = 0-33: 



Dg°= ^ ,„,(., ^ =0-310 . D 1S o=0-325. 



0-460 x3' ( J0 

 0-57 



0-47 7 0>To-92 

 Mean value Di 3 o = 0'329 sq. cm. per day. 

 The valency of thorium is therefore 4. 



