IX, A, 1 



Wright and Smith: Radium Emanation 



61 



Table IV. — Effect of the distribution of a given weight of charcoal on the 

 amount of radium emanation absorbed. 



Date. 



Dura- 

 tion of 

 expo- 

 sure. 



Radium 



in 

 standard 

 solution 

 in errams 



X109. 



Electroscope read- 

 ing in divisions per 

 minute. 



Method used for putting 



standard solution in 



"steady state." 



Air was bubbled 

 through boiling so- 

 lution for 30 minutes 

 and then through so- 

 lution at atmospheric 

 temperature for 2. 5 

 hours. 



Remarks. 



Due to 

 emana- 

 tion from 

 solution 

 in time of 

 exposure. 



Deduced 

 on basis 

 of ema- 

 nation 

 from 

 solution 



in 

 20 hours. 



May 6. 1913 

 May 4, 191-3 



Mrs. 



10 



20 

 40 



0.628 

 0.628 

 0.628 



0.343 

 0.449 

 0.642 



0.686 



a 0.449 



0.321 



For collecting. 1 

 electr o s i 1 i c a 

 tube contain- 

 ing 140 grams 

 charcoal was 

 used. 



" Mean of 7 determinations. 



It is evident from a study of the results given in the last 

 three tables that a phenomenon analogous to saturation does 

 exist under certain conditions. The conditions under which the 

 experiments, the results of which are given in Tables III and 

 IV, were made were identical except for the distribution of 

 the charcoal. In both experiments the same weight of charcoal 

 was used, the charcoal being made at the same time and as 

 nearly as possible of the same-sized granules, the only difference 

 being that in the one case the emanation passed over 140 grams 

 of charcoal closely packed in a length of 96 centimeters while 

 in the other case it passed over the same amount of charcoal 

 packed in a column about 40 centimeters long. The apparent 

 conclusion is that the effect is not a case of saturation in the 

 ordinary sense of the word, but rather due to a continual 

 carrying forward of the emanation by the air current. The 

 shorter the column of charcoal through which the emanation 

 must pass, the greater the fraction of the total amount carried 

 out. This probably explains why Satterly obtained evidence 

 of saturation by lengthening the time of exposure, while at the 

 same time varying the strength of the solution within fairly 

 wide limits gave little evidence of the same effect. Assuming 

 complete absorption for exposures of three hours or less, Satterly 

 found that for a 21-hour exposure only about 62 per cent of the 

 total amount is absorbed. As an explanation of this, it is sug- 



