﻿360 Mr. A. Fleck on the Condensation of 



Let the fraction of the condensed emanation entering the 

 gaseous phase per second be q, and of gaseous emanation 

 entering the condensed phase per second be p, so that \\q 

 and 1/p represent the average lives of the emanation molecule 

 in the condensed and gaseous phases respectively. Let the 

 fraction of the total emanation condensed be A. 



For the radium emanation 



or p/q = 



(1-A R ) 

 For the thorium emanation 



q A T + XA T = p( 1 — A T ) 



or 



X + q~ 1— A, 



T 



Consider now a case where the radium emanation would 

 be completely condensed and where the thorium emanation 

 once condensed does not volatilize again, i. e. let q = 0. The 

 thorium emanation is not completely condensed unless \ is 

 negligibly small compared with p. The ratio of the condensed 

 to uncondensed portion is that of p to \, or of 1/A, to 1/p, that 

 is the ratio of the period of average life of the thorium ema- 

 naion to its period of average life in the gaseous phase before 

 condensing. If 1/X, = 1/p, that is, if, on an average, the 

 emanation spends 78 seconds after formation before con- 

 densing, only one half will be condensed. The results 

 obtained may therefore be due to the rapid disintegration of 

 the emanation and the apparent separation effected by con- 

 densation may be a time separation of isotopes differing in 

 period, which is familiar enough, rather than due to a true 

 difference of volatility. 



General Remarks. 



It is observed in these experiments that the radium 

 emanation condensation curves have only the slightest 

 resemblance to each other, and the same remark applies to 

 the thorium emanation curves. Any quantity of emanation 

 in an exhausted sealed tube has at least one, and may have 

 two, condensation curves peculiar to itself. The natural 

 conclusion to be derived is that the residual gases play an 

 important part in determining the condensation curve of 

 emanation in any particular tube. This is perhaps not to be 



