Page:Radio-activity.djvu/281

 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}/N_{0} = ·0131.

Assuming that there is no decay during the interval,

N_{t} = 105 × 60 × q_{0}.

Thus     N_{0}/q_{0} = 480,000.

Making the small correction for the decay of activity during the interval,

N_{0}/q_{0} = 477,000.

We have previously shown that from the theory

N_{0}/q_{0} = 1/λ = 463,000.

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 1/2% 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.