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ring, piece of jewelry

(Encyclopedia)ring, small ornamental hoop usually worn on finger or thumb, but it may be attached to the ear or the nose. Finger rings made of bronze, gold, and silver from the period c.2600–1500 b.c. have been f...

saturation, of an organic compound

(Encyclopedia)saturation, of an organic compound, condition occurring when its molecules contain no double or triple bonds and thus cannot undergo addition reactions. For example, ethane (H3C–CH3) is a saturated ...

Sabatier, Paul, French organic chemist

(Encyclopedia)Sabatier, Paul, 1854–1941, French organic chemist, D.Sc. Collège de France, 1880. He joined the faculty at the Univ. of Toulouse in 1882 and taught there until he retired in 1930. Sabatier was a co...

ytterbium

(Encyclopedia)ytterbium ĭtûrˈbēəm [key] [for Ytterby, a town in Sweden], metallic chemical element; symbol Yb; at. no. 70; at. wt. 173.054; m.p. 819℃; b.p. about 1,194℃; sp. gr. about 7.0; valence +2 or +3...

ammonium group

(Encyclopedia)ammonium group, in chemistry, a positively charged nitrogen atom joined by single bonds to four other atoms or groups. The simplest ammonium group, NH4+, is formed by protonation of ammonia, NH3, e.g....

connective tissue

(Encyclopedia)connective tissue, supportive tissue widely distributed in the body, characterized by large amounts of intercellular substance and relatively few cells. The intercellular material, or matrix, is produ...

tar and pitch

(Encyclopedia)tar and pitch, viscous, dark-brown to black substances obtained by the destructive distillation of coal, wood, petroleum, peat, and certain other organic materials. The heating or partial burning of w...

stones, precious

(Encyclopedia)stones, precious: see gem.

semiprecious stone

(Encyclopedia)semiprecious stone: see gem.

precious stone

(Encyclopedia)precious stone: see gem.