Ac*tin"i*um (#), n. [Gr. , , ray.] Chem.

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 1913.

Editor's note: 'Phipson' appears to be Thomas Lamb Phipson, a London scientist of the late 1800's. His surmise appears to have been mistaken, and today's actinium 89 is not related to zinc.