American Heritage® Dictionary of the English Language, Fourth Edition
- 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.
Century Dictionary and Cyclopedia
- n. A supposed chemical element found associated with zinc. Its chemical and physical properties have not been fully investigated.
- 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. It has not been obtained in a state of sufficient purity to give any characteristic spectrum and is identified and recognized entirely by its radioactive properties. Actinium itself has not been found to emit a radiation but undergoes disintegration with the formation of a series of radioactive products known as radioactinium, axtinium-X, actinium emanation, actinium A, actinium B, and actinium C. Of these, the first, second, third, and fifth emit alpha-rays, the fourth beta-rays, and the sixth beta- and gamma-rays (see
obscure rays). These products are present in all ordinary actinium preparations. The occurrence of actinium indicates that it is a disintegration product of uranium, although its genetic relationship to ionium and radium has not yet been established. Actinium is identical with the emanium of Giesel. See emanation.
- n. a radioactive, metallic chemical element (symbol: Ac) with an atomic number of 89; found in uranium ores
GNU Webster's 1913
- n. (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.
- n. a radioactive element of the actinide series; found in uranium ores
- actin- + -ium (Wiktionary)
- From Greek aktīs, aktīn-, ray (from its radioactivity). (American Heritage® Dictionary of the English Language, Fourth Edition)
“In collaboration with Rona, she applied her method to the study of the ranges of alpha particles emitted from actinium and polonium. 6 7”
“Hahn's radiothorium and actinium salts also followed him to Emil Fischer's laboratory in Berlin. 30”
“In France, Debierne had discovered actinium and Giesel claimed to have found a different element, emanium.”
“With Ramsay's consent, Hahn had taken with him the radiothorium he separated from samples of barium chloride and the actinium that he and a collaborator had earlier proved to be identical to the new element that the German chemist Friedrich Giesel had named emanium.”
“M. and Mme. Curie, radium was also discovered by them in collaboration with Bémont, and actinium by Debierne.”
“It is likely that the actinium series is related to that of radium.”
“And it is not inconceivable that the still more unstable emanation from the matter named actinium by Debierne and emanium by Giesel may be found to possess an even higher atomic weight than uranium; judging by the phenomenon of brilliant illumination when a preparation of emanium is held above a screen of zinc sulphide, the impression is formed that a very dense matter is falling down on the screen.”
“Considerable work, guided by the theory of radioactive transformations, has led to approximately 30 new radioactive elements being envisaged, classified in 4 series according to the primary substance: these series are uranium, radium, thorium and actinium.”
“Other radioactive elements have been discovered since: actinium (Debierne), radiothorium and mesothorium (Hahn), ionium (Boltwood), etc.”
“This at once offered an explanation of the fact observed by Debierne that actinium as well as radium produced helium.”
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