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allotropy

(Encyclopedia)allotropy əlŏˈtrəpē [key] [Gr.,=other form]. A chemical element is said to exhibit allotropy when it occurs in two or more forms in the same physical state; the forms are called allotropes. Allot...

oxidation and reduction

(Encyclopedia)oxidation and reduction, complementary chemical reactions characterized by the loss or gain, respectively, of one or more electrons by an atom or molecule. Originally the term oxidation was used to re...

Pettenkofer, Max von

(Encyclopedia)Pettenkofer, Max von mäks fən pĕtˈənkōˌfər [key], 1818–1901, German chemist and hygienist. He studied medicine at Munich. Pettenkofer is considered a founder of epidemiology and is known for...

stereochemistry

(Encyclopedia)stereochemistry, study of the three-dimensional configuration of the atoms that make up a molecule and the ways in which this arrangement affects the physical and chemical properties of the molecule. ...

chloride

(Encyclopedia)chloride klōrˈīd, klôrˈ– [key], chemical compound containing chlorine. Most chlorides are salts that are formed either by direct union of chlorine with a metal or by reaction of hydrochloric ac...

Bessemer process

(Encyclopedia)CE5 Bessemer converter Bessemer process bĕsˈəmər [key] [for Sir Henry Bessemer], industrial process for the manufacture of steel from molten pig iron. The principle involved is that of oxidati...

cyclic compound

(Encyclopedia)cyclic compound, any one of a class of compounds whose molecules contain a number of atoms bonded together to form a closed chain or ring. If all of the atoms that form the ring are carbon, the compou...

Helmont, Jan Baptista van

(Encyclopedia)Helmont, Jan Baptista van yän bäptĭsˈtä vän hĕlˈmônt [key], 1577–1644, Flemish physician, chemist, and physicist. He attributed physiological changes to chemical causes, but his conclusions...

Odessa, city, United States

(Encyclopedia)Odessa ōdĕsˈə [key], city (1990 pop. 89,699), seat of Ector co., W Tex.; founded 1881, inc. 1927. Great oil deposits just to the south changed Odessa from a small ranch town into a large and growi...

Ponca City

(Encyclopedia)Ponca City, city (1990 pop. 26,359), Kay co., N Okla., on the Arkansas River; founded 1893 with the opening of the Cherokee Strip, inc. 1899. It is a trade, processing, and shipping hub in a grain, li...