Columbia Encyclopedia

(Encyclopedia) tellurium tĕlo͝orˈēəm [key] [Lat.,=earth], semimetallic chemical element; symbol Te; at. no. 52; at. wt. 127.60; m.p. 450℃; b.p. 990℃; sp. gr. 6.24 at 20℃; valence −2, +4, or +6. Telluriu...

(Encyclopedia) pollution allowance or emission rights, government-issued permit to emit a certain amount of a pollutant. The holder of the permit may use it to pollute legally, may trade permits, or may sell the per...

(Encyclopedia) Frasch process fräsh [key] [for Herman Frasch, the German-American chemist who devised it], process for the extraction of sulfur from subsurface deposits. Three pipes, one inside another, are sunk to...

(Encyclopedia) smog smŏg [key] [smoke+fog], dense, visible air pollution. Smog is commonly of two types. The gray smog of older industrial cities like London and New York derives from the massive combustion of coal...

(Encyclopedia) brimstone: see sulfur.

(Encyclopedia) sulphur: see sulfur.

(Encyclopedia)  CE5 Carbon cycle carbon cycle, in biology, the exchange of carbon between living organisms and the nonliving environment. Inorganic carbon dioxide in the atmosphere is converted by plants into sim...

(Encyclopedia) Keeling, Charles David, 1928–2005, U.S. geochemist, b. Scranton, Pa., Ph.D. Northwestern Univ., 1954. As a postdoctoral fellow at the California Institute of Technology (1953–56), he developed a s...

(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...

(Encyclopedia) ultramarine, blue pigment used chiefly as a coloring material and as a bluing agent. A double silicate of sodium and aluminum with some sulfur, it is prepared commercially from kaolin, sulfur, soda as...