Columbia Encyclopedia

Search results

500 results found

corundum

(Encyclopedia)corundum kərŭnˈdəm [key], mineral, aluminum oxide, Al2O3. The clear varieties are used as gems and the opaque as abrasive materials. Corundum occurs in crystals of the hexagonal system and in mass...

compost

(Encyclopedia)compost, substance composed mainly of partly decayed organic material that is applied to fertilize the soil and to increase its humus content; it is often used in vegetable farming, home gardens, flow...

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...

fungicide

(Encyclopedia)fungicide fŭnˈjəsīdˌ, fŭngˈgə– [key], any substance used to destroy fungi. Some fungi are extremely damaging to crops (see diseases of plants), and others cause diseases in humans and other ...

phosphorescence

(Encyclopedia)phosphorescence fŏsˌfərĕsˈəns [key], luminescence produced by certain substances after absorbing radiant energy or other types of energy. Phosphorescence is distinguished from fluorescence in th...

chlorate

(Encyclopedia)chlorate pərklōrˈāt, –klôrˈ– [key], salts of chloric acid, HClO3, and perchloric acid, HClO4, respectively. Perchlorates are safer to handle than chlorates; they are more stable when expos...

Fifty-four forty or fight

(Encyclopedia)Fifty-four forty or fight, in U.S. history, phrase commonly used by extremists in the controversy with Great Britain over the Oregon country. The rights of the United States, they maintained, extended...

phosphorus

(Encyclopedia)phosphorus fŏsˈfərəs [key] [Gr.,=light-bearing], nonmetallic chemical element; symbol P; at. no. 15; at. wt. 30.97376; m.p. 44.1℃; b.p. about 280℃; sp. gr. 1.82 at 20℃; valence −3, +3, or ...

histamine

(Encyclopedia)histamine hĭsˈtəmēnˌ [key], organic compound derived in the body from the amino acid histidine by the removal of a carboxyl group (COOH). Although found in many plant and animal tissues, histamin...

phosphate

(Encyclopedia)phosphate, salt or ester of phosphoric acid, H3PO4. Because phosphoric acid is tribasic (having three replaceable hydrogen atoms), it forms monophosphate, diphosphate, and triphosphate salts in which ...