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iridium

(Encyclopedia)iridium ĭrĭdˈēəm [key], metallic chemical element; symbol Ir; at. no. 77; at. wt. 192.217; m.p. about 2,410℃; b.p. about 4,130℃; sp. gr. 22.55 at 20℃; valence +3 or +4. Iridium is a very ha...

fatty acid

(Encyclopedia)fatty acid, any of the organic carboxylic acids present in fats and oils as esters of glycerol. Molecular weights of fatty acids vary over a wide range. The carbon skeleton of any fatty acid is unbran...

Wieland, Heinrich

(Encyclopedia)Wieland, Heinrich, 1877–1957, German chemist, Ph.D. Univ. of Munich, 1901. Wieland was a professor at the Technical Univ. of Munich from 1913 to 1921, the Univ. of Freiburg from 1921 to 1925, and th...

oxide

(Encyclopedia)oxide, chemical compound containing oxygen and one other chemical element. Oxides are widely and abundantly distributed in nature. Water is the oxide of hydrogen. Silicon dioxide is the major componen...

South Shetland Islands

(Encyclopedia)South Shetland Islands, barren, snow-covered archipelago off N Antarctic Peninsula, W Antarctica; Livingston and King George islands are the largest. The South Shetlands were bases for sealers in the ...

W and Z particles

(Encyclopedia)W and Z particles, elementary particles that mediate, or carry, the fundamental force associated with weak interactions. The discovery of the W and Z particles at CERN near Geneva, Switzerland, in the...

ink

(Encyclopedia)ink, pigmented fluid used for writing and drawing, or a viscous compound used for printing, both of various colors but most frequently black. The oldest known variety, India ink or China ink, is still...

tartaric acid

(Encyclopedia)tartaric acid, HO2CCHOHCHOHCO2H, white crystalline dicarboxylic acid. It occurs as three distinct isomers, the dextro-, levo-, and meso- forms. The dextro- and levo- forms are optically active; the me...

astringent

(Encyclopedia)astringent əstrĭnˈjənt [key], substance that shrinks body tissues. Astringent medicines cause shrinkage of mucous membranes or exposed tissues and are often used internally to check discharge of s...

amino acid

(Encyclopedia)CE5 General formula of an amino acid CE5 Peptide bond between two molecules of the amino acid alanine amino acid əmēˈnō [key], any one of a class of simple organic compounds containin...