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silica

(Encyclopedia)silica or silicon dioxide, chemical compound, SiO2. It is insoluble in water, slightly soluble in alkalies, and soluble in dilute hydrofluoric acid. Pure silica is colorless to white. It occurs in sev...

sprue

(Encyclopedia)sprue, chronic disorder of the small intestine caused by impaired absorption of fat and other nutrients. Two forms of the disease exist. Tropical sprue occurs in central and northern South America, As...

caffeine

(Encyclopedia)caffeine kăfēnˈ [key], odorless, slightly bitter alkaloid found in coffee, tea, kola nuts (see cola), ilex plants (the source of the Latin American drink maté), and, in small amounts, in cocoa (se...

pepsin

(Encyclopedia)pepsin, enzyme produced in the mucosal lining of the stomach that acts to degrade protein. Pepsin is one of three principal protein-degrading, or proteolytic, enzymes in the digestive system, the othe...

Wolfe, Tom

(Encyclopedia)Wolfe, Tom (Thomas Kennerly Wolfe, Jr.), 1931–2018, American journalist and novelist, b. Richmond, Va., B.A. Washington and Lee Univ., 1951, Ph.D. Yale, 1957. He began his writing career as a newspa...

Adirondack Mountains

(Encyclopedia)Adirondack Mountains ădˌərŏnˈdăk [key], mountain mass, NE N.Y., between the St. Lawrence valley in the north and the Mohawk valley in the south; rising to 5,344 ft (1,629 m) at Mt. Marcy, the hi...

adsorption

(Encyclopedia)adsorption, adhesion of the molecules of liquids, gases, and dissolved substances to the surfaces of solids, as opposed to absorption, in which the molecules actually enter the absorbing medium (see a...

lithography

(Encyclopedia)lithography lĭthŏgˈrəfē [key], type of planographic or surface printing. It is distinguished from letterpress (relief) printing and from intaglio printing (in which the design is cut or etched in...

paper

(Encyclopedia)paper, thin, flat sheet or tissue made usually from plant fiber but also from rags and other fibrous materials. It is used principally for printing and writing on but has many other applications. The ...

fluorine

(Encyclopedia)fluorine flo͞oˈərēn, –rĭn [key], gaseous chemical element; symbol F; at. no. 9; at. wt. 18.9984; m.p. −219.6℃; b.p. −188.14℃; density 1.696 grams per liter at STP; valence −1. Fluorin...