| Time in minutes | Theoretical value of activity | Observed value of activity |
|---|---|---|
| 36 | 100 | 100 |
| 40 | 99·8 | 99·5 |
| 50 | 93·4 | 92 |
| 60 | 83·4 | 82 |
| 80 | 63·7 | 61·5 |
| 100 | 44·8 | 42·5 |
| 120 | 30·8 | 29 |
There is thus a good agreement between the calculated and observed values of the activity measured by the β rays.
The results are satisfactorily explained if it is supposed:—
(1) That the change B into C (half transformed in 21 minutes) does not give rise to β rays;
(2) That the change C into D (half transformed in 28 minutes) gives rise to β rays.
222. These conclusions are very strongly supported by observations of the decay measured by the β rays for a long exposure. The curve of decay is shown in Fig. 88 and Fig. 89, curve I.
P. Curie and Danne made the