Thorite

Thorium occurs in thorite and in thorianite. Large deposits of thorium minerals have been reported in New England and elsewhere, but these have not yet been exploited. Thorium is now thought to be about three times as abundant as uranium and about as abundant as lead or molybdenum. Thorium is recovered commercially from the mineral monazite, which contains from 3 to 9% Th02 along with rare-earth minerals. 

In 1789 M. H. Klaproth examined pitchblende, thought at the time to be a mixed oxide ore of zinc, iron and tungsten, and showed that it contained a new element which he named uranium after the recendy discovered planet, Uranus. Then in 1828 J. J. Berzelius obtained an oxide, from a Norwegian ore now known as thorite he named this thoria after the Scandinavian god of war and, by reduction of its tetrachloride with potassium, isolated the metal thorium. The same method was subsequendy used in 1841 by B. Peligot to effect the first preparation of metallic uranium. 

Other accessories that may play an important role in the fractionation of some U-series elements, include, monazite, apatite, allanite, titanite, thorite and chevkinite. Hermann (2002) has recently determined experimentally the partitioning of U, Th and lanthanides between allanite and granitic melt at 2.0 GPa and 900°C. He finds D ] = 20 and Z)tii = 60, confirming that allanite can play an important role in controlling U-Th budgets in silicic melts. The very high Z La in the same experiment (-200), indicates that allanite will also be an important host for Bi and Ac. 

Silicates Zircon, beryl, thorite, topaz, sillimanite... 

Thorium - the atomic number is 90 and the chemical symbol is Th. The name derives from Thor, the Scandanavian god of thunder . It was discovered in the mineral thorite (ThSi04) by the Swedish chemist Jons Jacob Berzelius in 1828. It was first isolated by the chemists D. Lely Jr. and L. Hamburger in 1914. 

Thorium is the 37th most abundant element found on Earth, and it makes up about 0.0007% of the Earths crust. It is mostly found in the ores of thorite, thorianite (the oxide of thorium), and monazite sand. It is about as abundant as lead in the Earths crust. As a potential fuel for nuclear reactors, thorium has more energy potential than the entire Earths supply of uranium, coal, and gas combined. 

About four years later in 1819, the Reverend Hans Morten Thrane Esmark (1801— 1882), an amateur mineralogist, found a black mineral in Norway and gave a sample of it to his father, a geology professor, for analysis. Unable to identify it, Professor Jens Esmark sent the sample for chemical analysis to Berzelius, who found that it contained 60% of a new type of earth oxide not recognized before. It was identified as the mineral thorite (ThSiO ). Berzelius reported his discovery in an 1829 publication and retained the name thorium, in honor of Thor, the Norse god of war. Berzelius is thus credited with thorium s discovery. 

Large thorium deposits have heen found in many parts of the world. It occurs in minerals thorite, ThSi04, and thorianite, Th02"U02. Thorium also is found in mineral monazite which contains between 3 to 9% Th02. Th02 is the principal source of commercial thorium. Abundance of thorium in earth s crust is estimated at about 9.6 mg/kg. Thorium and uranium are believed to have contributed much of the internal heat of the earth due to their radioactive emanations since earth s formation. 

Thorite and orangite (orange thorite) have a tetragonal structure and are isostructural with zircon. Steady-state spectra under X-ray and laser (337 nm) excitations are connected with REE " ", namely Sm " ", Tb ", Dy " " and Eu ". Reabsorption lines of Nd " have been also detected (Gorobets and Rogojine 2001). Laser-induced time-resolved luminescence enables us to detect Eu " and uranyl emission centers (Eig. 4.70). 

Fig. 4.70. Laser-induced steady-state luminescence spectra of thorite (a) and monazite (b-d) natural and heated demonstrating uranyl, Eu ", Sm and Nd " centers. Straight line-vertical polarization, dashed Zi e-horizontal polarization...

Th, thorium, was discovered in 1829 by Jons Jakob Berzelius, who isolated a new oxide from a recently discovered mineral which Jens Esmark had sent to him. He called the oxide thoria and the mineral thorite (ThSi04) after the Scandinavian god Thor. Berzelius subsequently made the metal by the reduction of ThF4 with Na. Th now is extracted from monazite, a phosphate of rare earths and Th. The mineral is heated in concentrated NaOH to give hydrous oxides, which are filtered out. HCl is then added to dissolve the solids and when the pH is adjusted to 3.5, Th02 precipitates and the rare earths remain in solution. The Th02 is solubilized and purified by solvent extraction. 

Although the mineral which H. M. T. Esmark discovered looked a great deal like gadolinite, his father believed it to be new, possibly a kind of tantalite. Berzelius analysis of it proved it to be a silicate of a new metal, which he named thorium (50, 60). Although Pastor Esmark wished to name the mineral berzelite, Berzelius preferred the shorter name thorite (45). 

Berzelius separates the earth thoria from thorite. 

In clay samples Zr-Th-rich coffinite was found around remnants of zircon. It is likely that it is the result of solid solution with zircon, ZrSi04 and thorite, ThSi04, which are isostruc-tural with coffinite (Finch Murakami 1999 Jensen Ewing 2001). The presence of phosphorus and sulphur in coffinite suggests that both elements substituted for Si in the coffinite structure. A previous study at the Bangombe site in Gabon has clearly shown that coffinites are most important secondary minerals for the retention of fissiogenic lanthanides and actinides (Stille et al. 2003). 

Wu and Farges (1999) have made use of eqn (9.17) relating bond valence to the coefficient of thermal expansion to confirm that it is possible to resolve the different thermal expansions of the long and short Th-O bonds in thorite (o -ThSi04) from XAFS spectra measured between room temperature and 1700K. They also use this relation to estimate the anharmonic corrections needed for the bond lengths determined from XAFS (Brown et al. 1995, pp. 358-9). 

Some miscellaneous AN expls havi ng no special names include the following a) A mixt of AN 93 6 and charcoal 6,4% similar to "thorite (< ) with the addition of a little A1 was used in bombs during the Spanish Civil War. This mixt had low brisance but comparatively high power (see also Ref 6s) b)Mixts of AN with trinitrophenoxyethanol,... 

Thorium occurs in monazite sand in Brazil, India, North and South Carolina this ore contains 3-9% thorium oxide, and is the chief source thorium is also found in thorite containing about 60% oxide and in thorianite. about 80% oxide. When heated with concentrated H2SO4 the minerals form thonum sulfate, from which, by a senes of reactions, thonum nitrate, the chief commercial compound, is obtained. 

The principal resource minerals for thorium are Monazite, a rare earth phosphate, Thorite, ThSi04, and Thorianite or Uranothorianite, (U, Th)02, of which Monazite is the most important. Thorium minerals are mainly concentrated in sedimentary ores derived from the heavy refractory... 

Figure 20 The thorium environments in (a) huttonite and (b) thorite. (Reproduced from M. Taylor and R. C. Ewing, Acta Crystallogr., 1978, B34, 1074, with the permission of the International Union of Crystallography)...

Thorite. An expl, patented in Fr by Bowden in 1895, which was prepd by blending powdered K chlorate with an aq sugar soln, followed by graining and drying. It was intended for both military and industrial use (Refs 4 6)... 

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