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Wu, Chien-Shiung

(Encyclopedia)Wu, Chien-Shiung chyĕnˈ-shyo͝ongˈ wo͞o [key], 1912–97, Chinese-American physicist. She emigrated to the United States from China in 1936 and received a Ph.D. from the Univ. of California, Berke...

thorium

(Encyclopedia)thorium thôrˈēəm [key] [from Thor], radioactive chemical element; symbol Th; at. no. 90; mass number of most stable isotope 232; m.p. about 1,750℃; b.p. about 4,790℃; sp. gr. 11.7 at 20℃; va...

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...

rheostat

(Encyclopedia)rheostat rēˈəstătˌ [key], device whose resistance to electric current depends on the position of some mechanical element or control in the device. Typically a rheostat consists of a resistance el...

Organization for the Prohibition of Chemical Weapons

(Encyclopedia)Organization for the Prohibition of Chemical Weapons (OPCW), international body (est. 1997) responsible for the implementation of the Chemical Weapons Convention (CWC), which aims at the destruction o...

strontium

(Encyclopedia)strontium strŏnˈshēəm [key] [from Strontian, a Scottish town], a metallic chemical element; symbol Sr; at. no. 38; at. wt. 87.62; m.p. 769℃; b.p. 1,384℃; sp. gr. 2.6 at 20℃; valence +2. Stro...

Fischer-Tropsch process

(Encyclopedia)Fischer-Tropsch process fĭshˈər-trōpsh [key], method for the synthesis of hydrocarbons and other aliphatic compounds. Synthesis gas, a mixture of hydrogen and carbon monoxide, is reacted in the pr...

krypton

(Encyclopedia)krypton krĭpˈtŏn [key] [Gr.,=hidden], gaseous chemical element; symbol Kr; at. no. 36; at. wt. 83.798; m.p. −156.6℃; b.p. −152.3℃; density 3.73 grams per liter at STP; valence usually 0. Kr...

tin

(Encyclopedia)tin, metallic chemical element; symbol Sn [Lat. stannum]; at. no. 50; at. wt. 118.710; m.p. 231.9681℃; b.p. 2,270℃; sp. gr. 5.75 (gray), 7.3 (white); valence +2 or +4. Tin exhibits allotropy; abov...

hydrogen bomb

(Encyclopedia)hydrogen bomb or H-bomb, weapon deriving a large portion of its energy from the nuclear fusion of hydrogen isotopes. In an atomic bomb, uranium or plutonium is split into lighter elements that togethe...