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 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 ionization 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 obtained from the same equation used to determine the diffusion of the thorium emanation into air, p = p_{0}e^{-[sqrt](λ/K)x},  where λ is the constant of decay of activity of the radium emanation and x the depth of the layer of water from the surface. Putting α = [sqrt](λ/K), it was found that for water  α = 1·6, for toluol α = ·75. The value of λ 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 into water = ·066 cm.^2 / day. The value of K found by Stefan for the diffusion of carbon dioxide into water was 1·36 cm.^2/day. These results are thus in harmony 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. Condensation of the Emanations.

165. Condensation of the emanations. During an investigation of the effect of physical and chemical agencies on the thorium emanation, Rutherford and Soddy found that the