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n. A radioactive element found in uranium ores, used in equilibrium with its decay products as a source of alpha rays. Its longest lived isotope is Ac 227 with a half-life of 21.6 years. Atomic number 89; melting point 1,050°C; boiling point (estimated) 3,200°C; specific gravity (calculated) 10.07; valence 3. See Table at element.

n. a radioactive, metallic chemical element (symbol: Ac) with an atomic number of 89; found in uranium ores

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.

n. A supposed chemical element found associated with zinc. Its chemical and physical properties have not been fully investigated.

n.

n. A radioactive substance found by Debierne to exist in the residues remaining from pitchblende after the extraction of the uranium: a new radio-element closely related in its chemical behavior to lanthanum, from which it has not as yet been found possible to separate it completely.

n. a radioactive element of the actinide series; found in uranium ores

"M. and Mme. Curie, radium was also discovered by them in collaboration with Bémont, and actinium by Debierne."

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