Valency of the Radio-elements. 591 



the diffusion of a radium E and radium D solution from a 

 1/1000 normal hydrochloric acid solution into one of the 

 same strength, which was also 1 N with respect to alcohol, 

 are given below. The experiment was carried out by 

 measuring the activity of the layers immediately after inter- 

 rupting a diffusion. This, with a very small correction for 

 the disintegration of radium E during the time of the ex- 

 periment, gave the diffusion constant of radium E. The 

 ratios of the activities were then measured about a month 

 later, after the radium D and radium E had attained equi- 

 librium, and thus the diffusion constant of radium D was 

 obtained. 



Diffusion constant of radium E. 



Di5o-2. 1^18 ' 



L iTOTb °- 36 °-39 



IL 1TOS5 °*± °- 37 



IV - 17OT5 0>36 °- 39 



Average value for D l8 ° is 0*38 sq. cm. per day* 



Diffusion constant of radium D. 



D150.2. Di8°. 



L m&m °- 53 °' 57 



IL » °- 52 0>56 



IV - tosb 0>51 °' 55 



Mean value for D 18 o is 0*56 sq. cm. per day. 



The addition of 5 per cent, of alcohol, therefore, lowered 

 the diffusion velocity of radium D about 16 per cent. If the 

 decrease is the same in the case of radium E, then the result 

 is the value 0*45 for the diffusion constant of radium in 

 water. This value is characteristic of an ion carrying three 

 charges. 



The Diffusion of Actinium. 



An almost invisible quantity of an actinium-lanthanum 

 preparation was dissolved in 1/100 N hydrochloric acid and 

 allowed to diffuse into 1/1000 N hydrochloric acid. After 

 the experiment had been going three days it was interrupted, 

 the layers evaporated, and their a-activities measured. This 

 activity comes from the radio-actinium, actinium X, actinium 

 emanation, actinium A, and actinium C which are present, 



2R2 



