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Guerrero

(Encyclopedia)Guerrero, state, 24,887 sq mi (64,457 sq km), S Mexico, on the Pacific Ocean. The capital is Chilpancingo. Dominated by the Sierra Madre del Sur, which ...

niobium

(Encyclopedia)niobium nīōˈbēəm [key], metallic chemical element; symbol Nb; at. no. 41; at. wt. 92.90638; m.p. about 2,468℃; b.p. 4,742℃; sp. gr. 8.57 at 20℃; valence +2, +3, +4, or +5. Niobium is a rare...

smog

(Encyclopedia)smog smŏg [key] [smoke+fog], dense, visible air pollution. Smog is commonly of two types. The gray smog of older industrial cities like London and New York derives from the massive combustion of coal...

bismuth

(Encyclopedia)bismuth bĭzˈməth [key] [Ger. Weisse Masse=white mass], metallic chemical element; symbol Bi; at. no. 83; at. wt. 208.98040; m.p. 271.3℃; b.p. about 1,560℃; sp. gr. 9.75 at 20℃; valence +3 or ...

Cyclades

(Encyclopedia)Cyclades sīˈklədēz [key], Gr. Kikládhes [Gr.,=circular], island group, c.1,000 sq mi (2,...

fungicide

(Encyclopedia)fungicide fŭnˈjəsīdˌ, fŭngˈgə– [key], any substance used to destroy fungi. Some fungi are extremely damaging to crops (see diseases of plants), and others cause diseases in humans and other ...

Kuril Islands

(Encyclopedia)Kuril Islands kyo͝orˈēlz, kyo͝orēlzˈ [key], Jap. Chishima-Retto, Rus. Kurilskiye Ostrova, island chain, c.6,020 sq mi (15,590 sq km), Sakhalin region, E Russia. They stretch c.775 mi (1,250 km) ...

ruthenium

(Encyclopedia)ruthenium ro͞othēˈnēəm [key], metallic chemical element; symbol Ru; at. no. 44; at. wt. 101.07; m.p. about 2,310℃; b.p. about 3,900℃; sp. gr. 12.41 at 20℃; valence commonly +2, +3, +4, +6, ...

tracer

(Encyclopedia)tracer, an identifiable substance used to follow the course of a physical, chemical, or biological process. In chemistry the ideal tracer has the same chemical properties as the molecule it replaces a...

actinium

(Encyclopedia)actinium ăktĭnˈēəm [key] [Gr.,=like a ray], radioactive chemical element; symbol Ac; at. no. 89; mass number of most stable isotope 227; m.p. about 1,050℃; b.p. 3,200℃±300℃; sp. gr. 10.07;...