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half-life

(Encyclopedia)half-life, measure of the average lifetime of a radioactive substance (see radioactivity) or an unstable subatomic particle. One half-life is the time required for one half of any given quantity of th...

chelating agents

(Encyclopedia)chelating agents kēˈlātĭng [key]. Certain organic compounds are capable of forming coordinate bonds (see chemical bond) with metals through two or more atoms of the organic compound; such organic ...

speech defect

(Encyclopedia)speech defect, any condition that interferes with the mental formation of words or their physical production. Speech defects in children generally become apparent in the early school years. Speech pro...

coal

(Encyclopedia)coal, fuel substance of plant origin, largely or almost entirely composed of carbon with varying amounts of mineral matter. Coal is found in beds or seams interstratified with shales, clays, sands...

expansion

(Encyclopedia)expansion, in physics, increase in volume resulting from an increase in temperature. Contraction is the reverse process. When heat is applied to a body, the rate of vibration and the distances between...

ferrous sulfate

(Encyclopedia)ferrous sulfate or iron (II) sulfate, chemical compound, FeSO4. It is known as the monohydrate, FeSO4·H2O; the tetrahydrate, FeSO4·4H2O; the pentahydrate, FeSO4·5H2O; and the heptahydrate, FeSO4·7...

jasper, type of quartz

(Encyclopedia)jasper, opaque, impure cryptocrystalline quartz, usually red, but also yellow, green, and grayish blue. It is used as a gem. Ribbon jasper has the colors in stripes. ...

monism

(Encyclopedia)monism mōˈnĭzəm [key] [Gr.,=belief in one], in metaphysics, term introduced in the 18th cent. by Christian von Wolff for any theory that explains all phenomena by one unifying principle or as mani...

musk

(Encyclopedia)musk, odorous substance secreted by an abdominal gland of the musk deer, used in perfume as a scent and fixative. The gland, found only in males, grows to the size of a hen's egg; the secretion is red...

uric acid

(Encyclopedia)uric acid yo͝orˈĭk [key], white, odorless, tasteless crystalline substance formed as a result of purine degradation in man, other primates, dalmatians, birds, snakes, and lizards. The last three gr...