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iodine

(Encyclopedia)iodine īˈədīn, –dĭn [key] [Gr.,=violet], nonmetallic chemical element; symbol I; at. no. 53; at. wt. 126.90447; m.p. 113.5℃; b.p. 184.35℃; sp. gr. 4.93 at 20℃; valence −1, +1, +3, +5, o...

Hartford Convention

(Encyclopedia)Hartford Convention, Dec. 15, 1814–Jan. 4, 1815, meeting to consider the problems of New England in the War of 1812; held at Hartford, Conn. Prior to the war, New England Federalists (see Federalist...

superconductivity

(Encyclopedia)superconductivity, abnormally high electrical conductivity of certain substances. The phenomenon was discovered in 1911 by Heike Kamerlingh Onnes, who found that the resistance of mercury dropped sudd...

plutonium

(Encyclopedia)plutonium plo͞otōˈnēəm [key], radioactive chemical element; symbol Pu; at. no. 94; mass no. of most stable isotope 244; m.p. 641℃; b.p. 3,232℃; sp. gr. 19.84 at 20℃; valence +3, +4, +5, or ...

Whistler, James Abbott McNeill

(Encyclopedia)Whistler, James Abbott McNeill, 1834–1903, American painter, etcher, wit, and eccentric, b. Lowell, Mass. Whistler was dismissed from West Point for insufficient knowledge of chemistry and from the ...

progressive education

(Encyclopedia)progressive education, movement in American education. Confined to a period between the late 19th and mid-20th cent., the term “progressive education” is generally used to refer only to those educ...

manganese

(Encyclopedia)manganese măngˈgənēs, mănˈ– [key] [Lat.,=magnet], metallic chemical element; symbol Mn; at. no. 25; at. wt. 54.93805; m.p. about 1,244℃; b.p. about 1,962℃; sp. gr. 7.2 to 7.45, depending o...

marsupial

(Encyclopedia)marsupial märso͞oˈpēəl [key], member of the order Marsupialia, or pouched mammals. With the exception of the New World opossums and an obscure S American family (Caenolestidae), marsupials are no...

rat

(Encyclopedia)rat, name applied to various stout-bodied rodents, usually having a pointed muzzle, long slender tail, and dexterous forepaws. It refers particularly to the two species of house rat, Rattus norvegicus...

sirenian

(Encyclopedia)sirenian sīrēˈnēən [key] or sea cow, name for a large aquatic mammal of the order Sirenia. Living sirenians are the dugong and the manatee, both found in warm, shallow waters in sheltered regions...