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paper

(Encyclopedia)paper, thin, flat sheet or tissue made usually from plant fiber but also from rags and other fibrous materials. It is used principally for printing and writing on but has many other applications. The ...

zinc oxide

(Encyclopedia)zinc oxide, chemical compound, ZnO, that is nearly insoluble in water but soluble in acids or alkalies. It occurs as white hexagonal crystals or a white powder commonly known as zinc white. Zinc white...

rosewood

(Encyclopedia)rosewood, popular name for the ornamental wood of several species of tropical trees, especially for the heartwood of certain leguminous trees of the genus Dalbergia of the family Leguminosae (pulse fa...

quince

(Encyclopedia)quince, shrub or small tree of the Asian genera Chaenomeles and Cydonia of the family Rosaceae (rose family). The common quince (Cydonia oblonga) is a spineless tree with edible fruits cultivated from...

abrasive

(Encyclopedia)abrasive, material used to grind, smooth, cut, or polish another substance. Natural abrasives include sand, pumice, corundum, and ground quartz. Carborundum (silicon carbide) and alumina (aluminum oxi...

ipecac

(Encyclopedia)ipecac ĭpˈĭkăk [key], drug obtained from the dried roots of a creeping shrub, Cephaelis (or Psychotria) ipecacuanha, native to Brazil but cultivated in other tropical climates. There are three var...

Empedocles

(Encyclopedia)Empedocles ĕmpĕdˈəklēz [key], c.495–c.435 b.c., Greek philosopher, b. Acragas (present Agrigento), Sicily. Leader of the democratic faction in his native city, he was offered the crown, which h...

sunstone

(Encyclopedia)sunstone. 1 Crystal mineral thought by some to have been used by the Vikings as an aid to navigation, especially in conditions of low visibility due to clouds or fog when the position of the sun was u...

mole, in chemistry

(Encyclopedia)mole, in chemistry, a quantity of particles of any type equal to Avogadro's number, or 6.02×1023 particles. One gram-molecular weight of any molecular substance contains exactly one mole of molecules...

mother-of-pearl

(Encyclopedia)mother-of-pearl or nacre nāˈkər [key], the iridescent substance that forms the lining of the shells of some fresh-water and some salt-water mollusks. Like the pearl it is a secretion of the mantle,...