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Guericke, Otto von

(Encyclopedia)Guericke, Otto von ôˈtō fən gāˈrĭkə [key], 1602–86, German physicist, noted for his study of pneumatics. He carried out his most important researches while burgomaster (1646–81) of Magdebu...

Huaynaputina

(Encyclopedia)Huaynaputina, volcano, 15,912 ft (4,850 m) high, Moquegua region, S Peru, in the central Andes. A stratovolcano, it lies on the W rim of the Río Tambo canyon and has several ash cones within its crat...

Popocatépetl

(Encyclopedia)Popocatépetl pōpəkătˈəpĕtəl, pōpōˌkätāˈpətəl [key] [Nahuatl,=smoking mountain], volcano, 17,887 ft (5,452 m) high, in the Cordillera de Anáhuac, central Mexico, on the Puebla-Mexico s...

niello

(Encyclopedia)niello nēĕlˈō [key] [Ital. from Latin nigellus=blackish], black metallic alloy of sulfur, copper, silver, and usually lead, used as an inlay on engraved metal. The metal surface is brushed with a ...

mercaptan

(Encyclopedia)mercaptan thīˈōl [key], any of a class of organic compounds containing the group –SH bonded to a carbon atom. The volatile low-molecular-weight mercaptans have disagreeable odors. Mercaptans are ...

anhydride

(Encyclopedia)anhydride ănhīˈdrīd, –drĭd [key] [Gr.,=without water], chemical compound formed by removing water, H2O, from another compound; the anhydride can also react with water to form the original compo...

Urey, Harold Clayton

(Encyclopedia)Urey, Harold Clayton yo͝orˈē [key], 1893–1981, American chemist, b. Walkerton, Ind., grad. Univ. of Montana (B.S., 1917), Ph.D. Univ. of California, 1923. He taught at Johns Hopkins (1924–29), ...

gypsum

(Encyclopedia)gypsum jĭpˈsəm [key], mineral composed of calcium sulfate (calcium, sulfur, and oxygen) with two molecules of water, CaSO4·2H2O. It is the most common sulfate mineral, occurring in many places in ...

Goslar

(Encyclopedia)Goslar gôsˈlär [key], city, Lower Saxony, central Germany, at the northern foot of the Har...

Pesaro

(Encyclopedia)Pesaro pāˈzärō [key], city (1991 pop. 88,713), capital of Pesaro e Urbino prov., in the Marche region, central Italy, on the Adriatic Sea at the mouth of the Foglia River. It is an agricultural an...