A weight of ·03 gr. of radium chloride of activity 1000 times that of uranium was placed in a Drechsel bottle and a sufficient amount of water drawn in to dissolve it. The released emanation was swept out by a current of air into a small gas holder and then into a testing cylinder. The initial saturation current was proportional to _N₀_. A rapid current of air was then passed through the radium solution for some time in order to remove any slight amount of emanation which had not been removed initially. The Drechsel bottle was closed air-tight, and allowed to stand undisturbed for a definite time _t_. The accumulated emanation was then swept out as before into the testing vessel. The new ionization current represents the value of _N_{t}_ the amount of emanation formed in the compound during the interval _t_. In the experiment _t_ = 105 minutes, and the observed value _N__{t} ----- = ·0131. _N₀_ Assuming that there is no decay during the interval, _N_{t}_ = 105 × 60 × _q₀_. _N₀_ Thus --- = 480,000. _q₀_ Making the small correction for the decay of activity during the interval, _N₀_ ----- = 477,000. _q₀_ We have previously shown that from the theory _N₀_ 1 ----- = ---- = 463,000. _q₀_ λ The agreement between theory and experiment is thus as close as could be expected from the nature of the experiments. This experiment proves conclusively that the rate of production of emanation in the solid compound is the same as in the solution. In the former case it is occluded, in the latter it escapes as fast as it is produced. It is remarkable how little emanation, compared with the amount stored up in the compound, escapes from solid radium chloride in a dry atmosphere. One experiment showed that the emanating power in the dry solid state was less than ½% of the emanating power of the solution. Since nearly 500,000 times as much emanation is stored up in the solid compound as is produced per second, this result showed that the amount of emanation which escaped per second was less than 10⁻⁸ of that occluded in the compound. If a solid radium chloride compound is kept in a moist atmosphere, the emanating power becomes comparable with the amount produced per second in the solution. In such a case, since the rate of escape is continuous, the amount occluded will be much less than the amount for the non-emanating material.