| The dates of discovery of these elements as 1789 for uranium, 1829 for thorium, 1899 for actinium and 1913 for protactinium. |
| A proposal was patented for a ceramic block pessary using radioactive elements such as thorium, actinium and even radium. |
| For if actinium was an independent element we would be sure to find actinium haloes. |
| Element 121 should be similar in its chemical properties to lanthanum and actinium, but detailed properties have not been predicted. |
| These are generally known as radium emanation, thorium emanation, and actinium emanation. |
| On Rutherford's theory then, actinium should always accompany uranium and radium, but in very subordinate amount. |
