the original activity, while thorium, after removal of Th X, always shows a residual activity of about 25 per cent. of the maximum value. This very small residual activity indicates that actinium, if completely freed from all its products, would not give out rays at all, in other words, the first change in actinium is a rayless one.
The radio-active products of actinium are shown graphically in Fig. 84. Some of their chemical and physical properties are tabulated below.
| Products | Time to be half transformed | Rays | Some Physical and Chemical properties |
|---|---|---|---|
| Actinium | ? | No rays | Insoluble in ammonia |
| Actinium X | 10·2 days | α, (β and γ) | Soluble in ammonia |
| Emanation | 3·9 secs. | α rays | Behaves as a gas |
| Actinium A | 35·7 mins. | No rays | Soluble in ammonia and strong acids. |
| Actinium B | 2·15 mins. | α, β and γ | Volatilized at 100°C. B can be separated from A by electrolysis |