vl] RADIO-ACTIVE EMANATIONS 235 
Diffusion of the Emanation into Liquids. 
155. Experiments have been made by Wallstabe’ on the 
coefficient of diffusion of the radium emanation into various liquids. 
The radium emanation was allowed to diffuse into a closed reservoir, 
containing a cylinder of the liquid under observation. The cylinder 
was provided with a tube and a stop-cock extending beyond the 
closed vessel, so that different layers of the liquid could be removed. 
The liquid was then placed in a closed testing vessel, where the 
lonization current due to the escape of the emanation from the 
liquid was observed to rise to a maximum after several hours, and 
then to decay. This maximum value of the current was taken as 
a measure of the amount of emanation absorbed in the liquid. 
The coefficient of diffusion K of the emanation into the liquid 
can be obtaimed from the same equation used to determine the 
diffusion of the thorium emanation into air, 
x 
Fs Leslie e 
where X is the constant of decay of activity of the radium emana- 
tion and «x the depth of the layer of water from the surface. 
Putting a= oh = it was found that 
for water a=1°6, 
for toluol a =°75. 
The value of \ expressed in terms of a day as the unit of time 
is about ‘17. 
Thus the value of K for the diffusion of the radium emanation 
cm.” 
nd 
The value of K found by Stefan? for the diffusion of carbon 
into water = ‘(066 
cm.” 
day 
mony with the conclusion drawn from the diffusion of the radium 
emanation into air, and show that the radium emanation behaves 
as a gas of high molecular weight. 
dioxide into water was 1°36 These results are thus in har- 
1 Phys. Zeit. 4, p. 721, 1903. 
2 Wien. Sitzungsber. 2, p. 371, 1878. 
