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scintillation counter

(Encyclopedia)scintillation counter, device for detecting and measuring radiation by means of tiny visible flashes produced by the radiation when it strikes a sensitive substance known as a phosphor (see phosphores...

Concordat of 1801

(Encyclopedia)Concordat of 1801, agreement between Napoleon Bonaparte and Pope Pius VII that reestablished the Roman Catholic Church in France. Napoleon took the initiative in negotiating this agreement; he recogni...

sediment

(Encyclopedia)sediment, mineral or organic particles that are deposited by the action of wind, water, or glacial ice. These sediments can eventually form sedimentary rocks (see rock). Sediments form sedimentary ...

phospholipid

(Encyclopedia)phospholipid fŏsˌfōlĭpˈĭd [key], lipid that in its simplest form is composed of glycerol bonded to two fatty acids and a phosphate group. The resulting compound called phosphatidic acid contains...

ammonium chloride

(Encyclopedia)ammonium chloride əmōˈnēəm klôrˈīd [key], chemical compound, NH4Cl, a white or colorless, odorless, water-soluble, cubic crystalline salt with a biting taste, commonly known as sal ammoniac. I...

silica gel

(Encyclopedia)silica gel, chemical compound. It is a colloidal form of silica, and usually resembles coarse white sand. It may be prepared by partial dehydration of metasilicic acid, H2SiO3. Because it has many tin...

septic tank

(Encyclopedia)septic tank, underground sedimentation tank in which sewage is retained for a short period while it is decomposed and purified by bacterial action. The organic matter in the sewage settles to the bott...

pearl, gem

(Encyclopedia)pearl, hard, rounded secretion formed inside the shell of certain mollusks, used as a gem. It is secreted by the epithelial cells of the mantle, a curtain of tissue between the shell and body mass, an...

anise

(Encyclopedia)anise ănˈĭs [key], annual plant (Pimpinella anisum) of the family Umbelliferae (parsley family), native to the Mediterranean region but long cultivated elsewhere for its aromatic and medicinal qual...

ginger

(Encyclopedia)ginger, common name for members of the Zingiberaceae, a family of tropical and subtropical perennial herbs, chiefly of Indomalaysia. The aromatic oils of many are used in making condiments, perfumes, ...