When the space containing the radium communicates with a second by a tube, solids contained in the second become equally active after a sufficient time. The transmission of the activating property can even take place from one to the other through a capillary tube.
When the gas which has been made active by remaining in one space containing radium is passed into another, it retains for a considerable time the property of rendering radioactive solids that are brought in contact with it. The gas thus removed from the action of the radium gradually loses, nevertheless, its power of causing radioactivity. It disappears as a function of the time, according to an exponential law. It loses one-half of its value every four days.
To interpret this phenomenon it must be assumed that radium continuously gives off a constant radioactive emanation. This emanation spreads into the air in a closed space, and acting on solids, makes them radioactive. When the air is transferred to another space, the emanation is carried along with it. Finally, it is destroyed spontaneously with such velocity that the quantity of emanation in the gas diminishes by one-half every four days.
In a space containing radium there is established a state of equilibrium when the quantity of emanation in the space is such that the loss of emanation resulting from its spontaneous destruction is exactly compensated by the continued supply coming from the radium.
Figure II
The following experiment can be performed: The glass receiver,
(Fig. II.), filled with air, communicates through the constricted part,
