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hydrogen

(Encyclopedia)hydrogen hīˈdrəjən [key] [Gr.,=water forming], gaseous chemical element; symbol H; at. no. 1; interval in which at. wt. ranges 1.00784–1.00811; m.p. −259.14℃; b.p. −252.87℃; density 0.08...

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...

nickel

(Encyclopedia)nickel, metallic chemical element; symbol Ni; at. no. 28; at. wt. 58.6934; m.p. about 1,453℃; b.p. about 2,732℃; sp. gr. 8.902 at 25℃; valence 0, +1, +2, +3, or +4. Nickel is a hard, malleable, ...

rubber

(Encyclopedia)CE5 Basic molecules in rubber rubber, any solid substance that upon vulcanization becomes elastic; the term includes natural rubber (caoutchouc) and synthetic rubber. The term elastomer is sometim...

Eakins, Thomas

(Encyclopedia)Eakins, Thomas āˈkĭnz [key], 1844–1916, American painter, photographer, and sculptor, b. Philadelphia, where he worked most of his life. Eakins is considered the foremost American portrait painte...

Eyck, van

(Encyclopedia)Eyck, van văn īk [key], family of Flemish painters, the brothers Hubert van Eyck, c.1370–1426, and Jan van Eyck, c.1390–1441. Of the van Eycks' works that have survived, the largest is an alta...

catalyst

(Encyclopedia)catalyst, substance that can cause a change in the rate of a chemical reaction without itself being consumed in the reaction; the changing of the reaction rate by use of a catalyst is called catalysis...

oxygen

(Encyclopedia)oxygen, gaseous chemical element; symbol O; at. no. 8; interval in which at. wt. ranges 15.99903–15.99977; m.p. −218.4℃; b.p. −182.962℃; density 1.429 grams per liter at STP; valence −2. T...

coffee

(Encyclopedia)coffee, a tree, its seeds, and the beverage made from them. The coffee tree, a small evergreen of the genus Coffea, has smooth, ovate leaves and clusters of fragrant white flowers that mature into dee...

ammonia

(Encyclopedia)ammonia, chemical compound, NH3, colorless gas that is about one half as dense as air at ordinary temperatures and pressures. It has a characteristic pungent, penetrating odor. Ammonia forms a minute ...