as one hundred. In column 3 is given the percentage proportion of the activity recovered.
| Time in days | Activity | Percentage Activity recovered |
|---|---|---|
| 0 | 25·0 | 0 |
| 0·70 | 33·7 | 11·7 |
| 1·77 | 42·7 | 23·7 |
| 4·75 | 68·5 | 58·0 |
| 7·83 | 83·5 | 78·0 |
| 16·0 | 96·0 | 95·0 |
| 21·0 | 100·0 | 100·0 |
The results are shown graphically in Fig. 85.
The decay curve of the radium emanation is shown in the same figure. The curve of recovery of the lost activity of radium is thus analogous to the curves of recovery of uranium and thorium which have been freed from the active products Ur X and Th X respectively. The intensity It of the recovered activity at any time is given by
where I₀ is the final value, and λ is the radio-active constant of the emanation. The decay and recovery curves