History
(Planet Uranus, named after the Greek Ouranos, the son and husband of Gaia) Yellow-colored glass, containing more than 1% uranium oxide and dating back to 79 A.D., has been found near Naples, Italy. Klaproth recognized an unknown element in pitchblende and attempted to isolate the metal in 1789.
The metal apparently was first isolated in 1841 by Peligot, who reduced the anhydrous chloride with potassium.
Sources
Uranium, not as rare as once thought, is now considered to be more plentiful than mercury, antimony, silver, or cadmium, and is about as abundant as molybdenum or arsenic. It occurs in numerous minerals such as pitchblende, uraninite, carnotite, autunite, uranophane, and tobernite. It is also found in phosphate rock, lignite, monazite sands, and can be recovered commercially from these sources.
The United States Department of Energy purchases uranium in the form of acceptable U3O8 concentrates. This incentive program has greatly increased the known uranium reserves.
Uranium can be prepared by reducing uranium halides with alkali or alkaline earth metals or by reducing uranium oxides by calcium, aluminum, or carbon at high temperatures. The metal can also be produced by electrolysis of KUF5 or UF4, dissolved in a molten mixture of CaCl2 and NaCl. High-purity uranium can be prepared by the thermal decomposition of uranium halides on a hot filament.
Properties
Uranium exhibits three crystallographic modifications as follows: alpha --(688єC)--> beta --(776єC)--> gamma. Uranium is a heavy, silvery-white metal which is pyrophoric when finely divided.
It is a little softer than steel, and is attacked by cold water in a finely divided state. It is malleable, ductile, and slightly paramagnetic.
In air, the metal becomes coated with a layer of oxide. Acids dissolve the metal, but it is unaffected by alkalis.
A Periodic Table of the Elements at Los Alamos National Laboratory |
