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calcium carbonate

(Encyclopedia)calcium carbonate, CaCO3, white chemical compound that is the most common nonsiliceous mineral. It occurs in two crystal forms: calcite, which is hexagonal, and aragonite, which is rhombohedral. Calci...

Prelog, Vladimir

(Encyclopedia)Prelog, Vladimir vlädyēˈmĭr prāˈlôg [key], 1906–98, Swiss chemist, b. Sarejevo, Austria-Hungary (now in Bosnia and Herzegovina). Educated in Prague, he worked in Yugoslavia until the German i...

castor bean

(Encyclopedia)castor bean, bean produced by Ricinus communis, a plant of the spurge family, widely cultivated as an ornamental. Moles die when they eat the roots. It has long been used as an ordeal poison in parts ...

Pune

(Encyclopedia)Pune or Poona both: po͞oˈnə [key], city (1991 pop. 2,493,987), Maharashtra state, W central India. It is a district administrative and commercial center with automotive vehicle works, appliance fac...

pyroxene

(Encyclopedia)pyroxene pīˈrŏksēn [key], name given to members of a group of widely distributed rock minerals called metasilicates in which magnesium, iron, and calcium, often with aluminum, sodium, lithium, man...

Ramsay, Sir William

(Encyclopedia)Ramsay, Sir William, 1852–1916, Scottish chemist. He was professor of chemistry at University College, Bristol (1880–87), and at University College, London (1887–1912). In his early experiments ...

polychlorinated biphenyl

(Encyclopedia)polychlorinated biphenyl or PCB, any of a group of organic compounds originally widely used in industrial processes but later found to be dangerous environmental pollutants. Polychlorinated biphenyl i...

metallurgy

(Encyclopedia)metallurgy mĕtˈəlûrˌjē [key], science and technology of metals and their alloys. Modern metallurgical research is concerned with the preparation of radioactive metals, with obtaining metals econ...

uranium

(Encyclopedia)uranium yo͞orāˈnēəm [key], radioactive metallic chemical element; symbol U; at. no. 92; mass number of most stable isotope 238; m.p. 1,132℃; b.p. 3,818℃; sp. gr. 19.1 at 25℃; valence +3, +4...

zirconium

(Encyclopedia)zirconium zərkōˈnēəm [key], metallic chemical element; symbol Zr; at. no. 40; at. wt. 91.224; m.p. about 1,852℃; b.p. 4,377℃; sp. gr. 6.5 at 20℃; valence +2, +3, or +4. Zirconium is a very ...

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