tailieunhanh - Encyclopedia of Global Resources part 17

Encyclopedia of Global Resources part 17 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 130 Borax Global Resources the group. There is only one naturally occurring isotope so the atomic weight of bismuth is known very precisely. The element is brittle and white in appearance with a pink tinge. It occurs in a variety of crystalline structures. The metal has a high resistivity and melts at Celsius with a boiling point of 1 564 Celsius. Bismuth is unusual in that its volume expands by about 3 percent when it solidifies from the liquid. The solid has a density of grams per cubic centimeter. Description Distribution and Forms With a rarity akin to that of silver bismuth is a relatively minor component of the Earth s crust. It possesses some unique credentials For example all elements with an atomic number higher than bismuth are radioactive. It is one of three elements that is less dense in the solid phase than in the liquid. It is also one of only a handful of metals that can be found in nature in their elemental or native form. Elemental bismuth is not particularly toxic an unusual property in heavy metals. However inorganic bismuth compounds are often extremely poisonous. The relative rarity of bismuth has minimized its environmental impact. History The earliest recorded use of bismuth was in the mid-1400 s as an alloying material in casting type. German scientist Georgius Agricola stated that bismuth was a metal in the same family of metals as tin and lead. In 1753 French chemist Claude François Geoffroy identified bismuth as a chemical element confirming Agricola s postulation. Obtaining Bismuth In addition to the native state bismuth occurs in ores as an oxide sulfide and carbonate. Because of the scarcity of bismuth ores in the Earth s crust it is not mined directly but is typically produced commercially by extracting and refining it from the anode sludge generated during the electrochemical production of other metals. Annual world production of bismuth is on the order of 6 000 metric tons. Uses of Bismuth Functioning as a .