Columbia Encyclopedia

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fossil

(Encyclopedia)fossil, remains or imprints of plants or animals preserved from prehistoric times by the operation of natural conditions. Fossils are found in sedimentary rock, asphalt deposits, and coal and sometime...

photometry

(Encyclopedia)photometry fōtŏmˈətrē [key], branch of physics dealing with the measurement of the intensity of a source of light, such as an electric lamp, and with the intensity of light such a source may cast...

compound

(Encyclopedia)compound, in chemistry, a substance composed of atoms of two or more elements in chemical combination, occurring in a fixed, definite proportion and arranged in a fixed, definite structure. A compound...

chlorine

(Encyclopedia)chlorine klōrˈēn, klôrˈ– [key] [Gr.,=green], gaseous chemical element; symbol Cl; at. no. 17; interval in which at. wt. ranges 35.446–35.457; m.p. −100.98℃; b.p. −34.6℃; density 3.2 g...

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...

potassium

(Encyclopedia)potassium pətăsˈēəm [key], a metallic chemical element; symbol K [Lat. kalium=alkali]; at. no. 19; at. wt. 39.0983; m.p. 63.25℃; b.p. 760℃; sp. gr. .862 at 20℃; valence +1. Potassium is a s...

tobacco

(Encyclopedia)tobacco, name for any plant of the genus Nicotiana of the Solanaceae family (nightshade family) and for the product manufactured from the leaf and used in cigars and cigarettes, snuff, and pipe and ch...

symbol

(Encyclopedia)symbol, sign representing something that has an independent existence. The most important use of symbols is in language. To say so, however, does not solve the perennial philosophical questions as to ...

heart, in anatomy

(Encyclopedia)CE5 Cross section of heart, with arrows indicating direction of blood flow heart, muscular organ that pumps blood to all parts of the body. The rhythmic beating of the heart is a ceaseless activit...

calcium

(Encyclopedia)calcium kălˈsēəm [key] [Lat.,=lime], metallic chemical element; symbol Ca; at. no. 20; at. wt. 40.078; m.p. about 839℃; b.p. 1,484℃; sp. gr. 1.55 at 20℃; valence +2. Calcium is a malleable, ...