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sand

(Encyclopedia)sand, rock material occurring in the form of loose, rounded or angular grains, varying in size from .06 mm to 2 mm in diameter, the particles being smaller than those of gravel and larger than those o...

semiconductor

(Encyclopedia)CE5 N-type and P-type crystals: In a pure silicon crystal each silicon atom (Si) is surrounded by four valence electrons. In the N-doped semiconductor, illustrated in the left-hand figure, some sil...

Priestley, Joseph

(Encyclopedia)Priestley, Joseph, 1733–1804, English theologian and scientist. He prepared for the Presbyterian ministry and served several churches in England as pastor but gradually rejected orthodox Calvinism a...

dye

(Encyclopedia)dye, any substance, natural or synthetic, used to color various materials, especially textiles, leather, and food. Natural dyes are so called because they are obtained from plants (e.g., alizarin, cat...

concrete

(Encyclopedia)concrete, structural masonry material made by mixing broken stone or gravel with sand, cement, and water and allowing the mixture to harden into a solid mass. The cement is the chemically active eleme...

Curie

(Encyclopedia)Curie kürēˈ [key], family of French scientists. Pierre Curie, 1859–1906, scientist, and his wife, Marie Sklodowska Curie, 1867–1934, chemist and physicist, b. Warsaw, are known for their work o...

Humboldt, Alexander, Freiherr von

(Encyclopedia)Humboldt, Alexander, Freiherr von hŭmˈbōlt, Ger. älĕksänˈdər frīˈhĕr fən ho͝omˈbôlt [key], 1769–1859, German naturalist, inventor, explorer, and author, the most eminent scientist of ...

Antigua and Barbuda

(Encyclopedia)CE5 Antigua and Barbuda ăntēˈgə, –gwə, bärbo͞oˈdə, –byo͞oˈ– [key], independent Commonwealth nation (2020 est. pop. 97,928), 171 sq mi (442 sq km), We...

pepper

(Encyclopedia)pepper, name for the fruits of several unrelated Old and New World plants used as spices or vegetables or in medicine. True pepper is classified in the division Magnoliophyta, class Magnoliopsida,...

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...