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functional group

(Encyclopedia)CE5 functional group, in organic chemistry, group of atoms within a molecule that is responsible for certain properties of the molecule and reactions in which it takes part. Organic compounds are f...

magic square

(Encyclopedia)magic square, a square divided into parts with letters or numbers inscribed therein that, whether combined vertically, horizontally, or diagonally, form the same sum or the same word. In ancient times...

Berthollet, Claude Louis, Comte

(Encyclopedia)Berthollet, Claude Louis, Comte klōd lwē, kôNt bĕrtōlāˈ [key], 1748–1822, French chemist. His contributions to chemistry include the analysis of ammonia and prussic acid and the discovery of ...

Plücker, Julius

(Encyclopedia)Plücker, Julius yo͞oˈlyo͝os plüˈkər [key], 1801–68, German mathematician and physicist. He became professor of mathematics (1836) and of physics (1847) at the Univ. of Bonn. He is known for h...

Richards, Theodore William

(Encyclopedia)Richards, Theodore William, 1868–1928, American chemist, b. Germantown, Pa., Ph.D. Harvard, 1888. Richards was a professor at Harvard from 1891 until his death in 1928. In 1914 he received the Nobel...

hafnium

(Encyclopedia)hafnium hăfˈnēəm [key], metallic chemical element; symbol Hf; at. no. 72; at. wt. 178.49; m.p. about 2,227℃; b.p. 4,602℃; sp. gr. 13.31 at 20℃; valence +4. Hafnium is a lustrous, ductile, si...

aromatic compound

(Encyclopedia)aromatic compound, any of a large class of compounds that includes benzene and compounds that resemble benzene in certain of their chemical properties. Originally applied to a small class of pleasant-...

mendelevium

(Encyclopedia)mendelevium mĕndəlāvˈēəm [key], artificially produced radioactive chemical element; symbol Md; at. no. 101; mass no. of most stable isotope 258; m.p. 827℃; b.p. and sp. gr. unknown; valence +1...

vortex

(Encyclopedia)vortex vôrˈtĕks [key], mass of fluid in whirling or rotary motion. To simplify the analysis, vortex motion usually describes motions in a frictionless fluid. In such cases the absence of friction w...

geometry

(Encyclopedia)geometry [Gr.,=earth measuring], branch of mathematics concerned with the properties of and relationships between points, lines, planes, and figures and with generalizations of these concepts. Eucli...