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ammonium nitrate

(Encyclopedia)ammonium nitrate, chemical compound, NH4NO3, that exists as colorless, rhombohedral crystals at room temperature but changes to monoclinic crystals when heated above 32℃. It is extremely soluble in ...

Crutzen, Paul Jozef

(Encyclopedia)Crutzen, Paul Jozef, 1933–2021, Dutch atmospheric chemist, grad. Univ. of Stockholm (Ph.D. 1968, D.Sc. 1973). After working (1977–80) for the Nation...

anesthesia

(Encyclopedia)anesthesia ănĭsthēˈzhə [key] [Gr.,=insensibility], loss of sensation, especially that of pain, induced by drugs, especially as a means of facilitating safe surgical procedures. Early modern medic...

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...

smog

(Encyclopedia)smog smŏg [key] [smoke+fog], dense, visible air pollution. Smog is commonly of two types. The gray smog of older industrial cities like London and New York derives from the massive combustion of coal...

ocher

(Encyclopedia)ocher ōˈkər [key], mixture of varying proportions of iron oxide and clay, used as a pigment. It occurs naturally as yellow ocher (yellow or yellow-brown in color), the iron oxide being limonite, or...

microelectronics

(Encyclopedia)microelectronics, branch of electronic technology devoted to the design and development of extremely small electronic devices that consume very little electric power. Although the term is sometimes us...

erbium

(Encyclopedia)erbium ûrˈbēəm [key] [from Ytterby, a town in Sweden], metallic chemical element; symbol Er; at. no. 68; at. wt. 167.259; m.p. 1,529℃; b.p. 2,863℃; sp. gr. 9.05 at 25℃; valence +3. Erbium is...

hemoglobin

(Encyclopedia)hemoglobin hēˈməglōˌbĭn [key], respiratory protein found in the red blood cells (erythrocytes) of all vertebrates and some invertebrates. A hemoglobin molecule is composed of a protein group, kn...

thermite

(Encyclopedia)thermite [from Thermit, a trade name], mixture of powdered or granular aluminum metal and powdered iron oxide. When ignited it gives off large amounts of heat. In wartime it has been used in incendiar...