Thorium pressure

Kohl and Steams [1974KOH/STE] have also measured the pressures of ThC4(g) in the vapour over ThC2 (cr) + C(cr). At 2700 K, the ThC4(g) pressure is 15% of the thorium pressure, so this species cannot be neglected. Jackson et al. [1964JAC/BAR] do not report observing it in their measurements at lower temperatures and this is consistent with the data derived below. 

Spinels. There are limited experimental data on uranium and thorium partitioning between magnetite and melt (Nielsen et al. 1994 Blundy and Brooker 2003). Both studies find U and Th to be moderately incompatible. Blundy and Brooker s results for a hydrous dacitic melt at 1 GPa and 1025°C give Du and D h. of approximately 0.004. The accuracy of these values is compromised by the very low concentrations in the crystals and the lack of suitable SIMS secondary standards for these elements in oxide minerals. Nonetheless, these values are within the range of Djh of magnetites at atmospheric pressure 0.003-0.025 (Nielsen et al. 1994). It is difficult to place these values within the context of the lattice strain model, firstly because there are so few systematic experimental studies of trace element partitioning into oxides and secondly because of the compositional diversity of the spinels and their complex intersite cation ordering. 

Allegre CJ, Dupre B, Lewin E (1986) Thorium/uranium ratio of the Earth. Chem Geol 56 217-227 Allegre CJ, Turcotte D (1986) Implications of a two-component marble-cake mantle. Nature 323 123-127 Asimow PD, Hirschmann MM, Ghiorso MS, O Hara MJ Stolper EM (1995) The effect of pressure-induced solid-solid phase transitions on decompression melting of the mantle. Geochim Cosmochim Acta 59 4489-4506... 

Iseler, G. W. et al., Int. Conf. Indium Phosphide Relat. Mater., 1992, 266 Reaction of beryllium, copper, manganese, thorium or zirconium is incandescent when heated with phosphorus [1] and that of cerium, lanthanum, neodymium and praseodymium is violent above 400°C [2], Osmium incandesces in phosphorus vapour, and platinum bums vividly below red-heat [3], Red phosphorus shows very variable vapour pressure between batches (not surprising, it is an indeterminate material). This leads to explosions when preparing indium phosphide by reactions involving fusion with phosphorus in a sealed tube [4],... 

If hydrogen gas is added to the reaction mixture of J, and 11 the hydrogenolysis reaction of thorium-to-carbon sigma bonds (J-1 22) allows interception of species 13 and thus, catalytic hydrogenation of the inserted carbon monoxide functionality. At 35 C under 0.75 atm initial H2 pressure with [JJ =9.0 x 10" M and [ 1JJ = 6.5 x 10" M, hydrogenation and isomerization are competitive and both the enolate and the alkoxide reduction product 14 are produced (eq.(13)). Under these conditions, turnover fre-... 

The Van Arkel process can also be used to prepare actinide metals if the starting compound reacts easily with the transporting agent (I2). The thorium and protactinium carbides react with I2 to give volatile iodides above 350°C these are unstable above 1200°C and decompose into the actinide metals and iodine. Attempts to prepare other actinides, such as U and Pu, through the process were not successful, because from Th to Pu along the actinide series, the vapour pressure of the iodide decreases and the thermal stability increases. 

The light actinide metals (Th, Pa, and U) have extremely low vapor pressures. Their preparation via the vapor phase of the metal requires temperatures as high as 2375 K for U and 2775 K for Th and Pa. Therefore, uranium is more commonly prepared by calciothermic reduction of the tetrafluoride or dioxide (Section II,A). Thorium and protactinium metals on the gram scale can be prepared and refined by the van Arkel-De Boer process, which is described next. 

Proceeding from thorium to plutonium along the actinide series, the vapor pressure of the corresponding iodides decreases and the thermal stability of the iodides increases. The melting point of U metal is below 1475 K and for Np and Pu metals it is below 975 K. The thermal stabilities of the iodides of U, Np, and Pu below the melting points of the respective metals are too great to permit the preparation of these metals by the van Arkel-De Boer process. 

Hatcher, S.R., Banerjee, S, Lane, A.D, Tamm, H., Veeder,J.I. "Thorium Cycle in Heavy Water Moderated Pressure Tube (CANDU) Reactors" American Nuclear Society Meeting, San Francisco AECL-5398, 1975... 

Eleven months after intratracheal and intraperitoneal injection of thorium dioxide in rats, a sharp and persistent fall in blood pressure was found (Syao-Shan 1970). The fall in blood pressure could not be directly attributed to the chemical or radiological effects of thorium. 

Syao-Shan, Y. 1970. The effect of thorium dioxide on arterial pressure and threshold of stimulation of the nerve muscle apparatus in rats. In Lefavet, Kurlyandskaya, eds. The toxicology of radioactive substances, Vol. 4. New York, Pergamon Press, 58-65. 

Once a star has expended its supply of energy, it will contract to a glowing white ember called a white dwarf. The elements produced in the interior of a star depend on the size of the star. Small stars do not have sufficient mass to produce the temperatures required to create the heaviest elements. The most massive stars, though, may go through a series of rapid contractions in their final stages. These massive stars have the ability to generate the temperatures and pressures necessary to produce the heaviest elements such as thorium and uranium. The final fate of these massive stars is a cataclysmic explosion called a supernova. It is in this manner that scientists believe all the naturally occurring elements in the universe... 

R. Ferreira Paradoxial Violations of Koop-man s Theorem with Special Reference to the 3 d Transition Elements and the Lanthanides. Cfionne/fe.-Band and Localized States in Metallic Thorium, Uranium, and Plutonium, and in some Compounds, Studied by X-Ray Spectroscopy V. Gutmann, H Mayer The Application of the Functional Approach to Bond Variations under Pressure... 

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