| actinium | <chemistry> 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. Origin: Gr, ray. Source: Websters Dictionary (01 Mar 1998) |
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| emanation | 1. Any substance that flows out or is emitted from a source or origin. 2. The radiation from a radioactive element. Origin: L. E-mano, pp. -atus, to flow out Actinium emanation, radon-219. Radium emanation, radon-222. Thorium emanation, radon-220. See: emanon. (05 Mar 2000) |