Page:Radio-activity.djvu/312

 Fig. 61.

The emanation from 60 milligrams of radium bromide in solution was allowed to collect for 8 days and then drawn off through the inverted siphon E (Fig. 61) into the explosion burette F. This gas consisted for the most part of hydrogen and oxygen, produced by the action of the radiations on the water of the solution. After explosion, the excess of hydrogen mixed with emanation was left some time in contact with caustic soda, placed in the upper part of the burette, in order to remove all trace of carbon dioxide. In the meantime the upper part of the apparatus had been completely evacuated. The connection C to the pump was closed, and the hydrogen and emanation were allowed to enter the apparatus, passing over a phosphorous pentoxide tube D. The emanation was condensed in the lower part of the capillary tube A, by surrounding it with the tube B filled with liquid air. The process of condensation was rendered manifest by the brilliant luminosity of the lower part of the tube. The mercury from the burette was then allowed to run to G, and the apparatus again completely evacuated. The connection of the pump was again closed, the liquid air was removed and the volatilized emanation forced into the fine capillary tube A. Observations were then made, from day to day, of the volume of the emanation. The results are given in the table below.

Time       Volume         Time          Volume Start    0·124 cub. mm. 7 days    0·0050 cub. mm. 1 day    0·027   "         9  "       0·0041   " 3  "      0·011   "        11  "       0·0020   " 4  "      0·0095  "        12  "       0·0011   " 6  "      0·0063  "        28  "       0·0004   "

The volume contracted with the time, and was very small after a month's interval, but the minute bubble of the emanation still retained its luminosity to the last. The tube became deep purple in colour, which rendered readings difficult except with a strong light. There was a sudden decrease in the first day,