(n.) A supposed metal, said by Phipson to be contained in commercial zinc; -- so called because certain of its compounds are darkened by exposure to light.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). actinium. Retrieved September 24, 2026, from http://smartdefine.org/actinium/definitions/1970668 |
| Chicago | Webster's. 2011. "actinium" http://smartdefine.org/actinium/definitions/1970668 (accessed September 24, 2026). |
| Harvard | Webster's 2011, actinium, Smart Define, viewed 24 September, 2026, <http://smartdefine.org/actinium/definitions/1970668>. |
| MLA | Webster's. "actinium" 27 May 2011. Web. 24 September 2026. <http://smartdefine.org/actinium/definitions/1970668> |