Other radio-active substances have each several derivatives: actinium has nine, uranium has four.
actinium, an element or elementary substance obtained in minute quantities in connection with the study of radioactivity.
For if actinium was an independent element we would be sure to find actinium haloes.
In 1902 Giesel discovered another substance which he called emanium, and which was considered to be identical with actinium.
Emanium was the name originally proposed by Giesel for the body now known as actinium.
M. Debierne has obtained a third radioactive substance from pitchblende, which he has called “actinium.”
The element has since been found in nature as a small constituent of the natural decay of actinium.
In this class are now placed also the three radio-active gases, emanating respectively from radium, thorium, and actinium.
On Rutherford's theory then, actinium should always accompany uranium and radium, but in very subordinate amount.
These are generally known as radium emanation, thorium emanation, and actinium emanation.
actinium ac·tin·i·um (āk-tĭn'ē-əm)
A radioactive element found in uranium ores. Its longest lived isotope is Ac 227 with a half-life of 21.6years. Atomic number 89; melting point 1,050°C; boiling point (estimated) 3,200°C; specific gravity (calculated) 10.07; valence 3.
A silvery-white, highly radioactive metallic element of the actinide series that is found in uranium ores. It is about 150 times more radioactive than radium and is used as a source of alpha rays and neutrons. Its most stable isotope has a half-life of about 22 years. Atomic number 89; melting point 1,050°C (1,922°F); boiling point (estimated) 3,200°C (5,792°F); specific gravity (calculated) 10.07; valence 3. See Periodic Table.