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Precipitation of Thorium As Thorium Hydride from Thorium-Magnesium Solutions Paul F

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Precipitation of Thorium As Thorium Hydride from Thorium-Magnesium Solutions Paul F Ames Laboratory ISC Technical Reports Ames Laboratory 8-1957 Precipitation of thorium as thorium hydride from thorium-magnesium solutions Paul F. Woerner Iowa State College P. Chiotti Iowa State College Follow this and additional works at: http://lib.dr.iastate.edu/ameslab_iscreports Part of the Chemistry Commons Recommended Citation Woerner, Paul F. and Chiotti, P., "Precipitation of thorium as thorium hydride from thorium-magnesium solutions" (1957). Ames Laboratory ISC Technical Reports. 169. http://lib.dr.iastate.edu/ameslab_iscreports/169 This Report is brought to you for free and open access by the Ames Laboratory at Iowa State University Digital Repository. It has been accepted for inclusion in Ames Laboratory ISC Technical Reports by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Precipitation of thorium as thorium hydride from thorium-magnesium solutions Abstract The precipitation of thorium as thorium dihydride from thorium-magnesium solutions has been investigated over the temperature range of 665° to 810°0. It has been shown that thorium can be precipitated as thorium dihydride by equilibrating the thorium-magnesium solutions (containing 35 to 42 wt. % Th) with hydrogen gas at one atmosphere pressure. Disciplines Chemistry This report is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/ameslab_iscreports/169 / ISC-928 'f.., UNITED STATES ATOMIC ENERGY COMMISSION ·~ PRECIPITATION OF THORIUM AS THORIUM HYDRIDE FROM THORIUM-MAGNESIUM SOLUTIONS By Paul F. Woerner P. Chiotti August 1957 Ames Laboratory Iowa State College Ames, Iowa Technical Information Service Extension, Oak Ridge, Tenn. 'J F. H. Spedding, Director, Ames Laboratory. Work performed under Contract No. W-7405-Eng-82. LE GAL N OTIC E This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, express or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this r eport may not infringe privately owned r ights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. As used in the above, "person acting on behalf of the Commission" includes any em­ ployee or contractor of the Commission to the extent that such employee or contractor prepares, handles or distributes, or provides access to, any information pursuant to his employment or contract with the Commission. This report has been reproduced directly from the best available copy. Printed in USA. Price $1.25. Available from the Office of Technical Services, Department of Commerce, Washington 25, D. C. AEC Technical Information Service Extension oak Ridge, Tennenee iii ISC-928 TABLE OF CONTENTS Page ABSTRACT 1 I. INTRODUCTION 3 II. APPARATUS 11 III. EXPERIMENTAL 18 A. Materials 18 B. Experimental Procedure 19 c. Chemical Analysis 23 IV. EXPERIMENTAL RESULTS 25 v. THERMODYNAMIC CALCULATIONS AND DISCUSSION 34 VI. SUGGESTIOijS FOR FUTURE WORK 40 VII. LITERATURE CITED 41 1 ISC-928 PRECIPITATION OF THORIUM AS THORIUM HYDRIDE FROM THORIUM-MAGNESIUM SOLUTIONS* Paul F. Woerner and P. Chiotti ABSTRACT The precipitation of thorium as thorium dihydride from thorium-magnesium solutions has been investigated over the temperature range of 665° to 810°0. It has been shown that thorium can be precipitated as thorium dihydride by equili­ ~rating the thorium-magnesium solutions (containing 35 to 42 wt. %Th) with hydrogen gas at one atmosphere pressure. The concentration of thorium in the liquid phase for the reactions carried out at one atmosphere hydrogen pressure over the specified temperature range is given by the fol- lowing relation log10 NTh = -4609T± 209 + 2.824 ± 0.208, where ~Th represents the mole fraction of thorium in the liquid phase. The above equation was determined by a least squares treatment of the experimental data, and the limits in the equation represent the probable error for the con­ stants. It can be seen that the concentration of thorium * This report is based on an M. S. Thesis by Paul F. Woerner submitted August, 1957, to Iowa State College, Ames, Iowa. This work was done under contract with the Atomic' Energy Commission. 2 ISC-928 remaining in the liquid phase at equilibrium decreases as the reaction temperature is lowered. ,The concentration of thorium in the liquid, calculated from the above expression, is 25.03 wt. %at 800°C and 8 .11 wt. % at 675°C . The following analytical expressions have been determined for the activity coefficient of thorium in liquid magnesium at the equilibrium concentrations. v s -3091 + 3.835 l oglO 0 Th = T (A ) L - -4~91 + 4.336 (B) Th EquationA represents the activity coefficient of thorium relative to solid thorium and equation B represents the ac- tivity coefficient of thorium relative to liquid thorium. The activity coefficient of thorium in the solution relative to solid thorium as calculated from equation A is 3 . 06 at 650°C and 9 . 00 at 800°C, whereas the activity coefficient of thorium in solution relative to liquid thorium as calculated from equation B is 0.80 at 650 °C and 3.33 at 8oo q~. It is apparent from these values that these solutions are not ideal. Although complete precipitation of the thorium from the liquid solution was not realized, it is felt that a reaction of thi s nature might be employed as a method for purifying crude thorium. 3 I. INTRODUCTION Gas-liquid metal reactions as a method of refining liq­ uid metals have been employed by the metal industry for some years. In these purification processes the more reactive impurities are preferentially oxidized by the gas employed to form either volatile or insoluble compounds which can be removed from the molten metal. A good example of such a process is the purification of pig iron in a Bessemer con­ verter wherein air is blown through the molten iron and the excess carbon is removed as carbon monoXide or dioxide, 'iihile other nonvolatile oxides such as Si02 collect as a slag on top of the molten iron. Other refining methods involving oxygen-liquid metal reactions have also been investigated and have been used extensively for refining metals. In all of these reactions the oxygen gas, which is bubbled through the melt, preferentially reacts with the more active impurities in the melt. These usually form insoluble stable oxides which can be removed from the melt by dressing or slagging. Reactions involving the formation of metallic chlorides by the action of gaseous chlorine with liquid metals have also received considerable attentione Since many chlorides are low-melting, volatile, and can be readily formed from the oxide, they are well suited for such processes. A typical re­ action involving chlorine gas is used in the Betterton proc­ ess (1). In this process gaseous chlorine is bubbled into 4 a molten lead-zinc solution. The gas preferentially reacts with the zinc to form zinc chloride whi.ch floats to the sur- face where it is drossed off. This procedure is very ef­ fective in removing zinc from lead. Little work has been done in the metal refining industry with gas-liquid metal reactions involving hydrogen gas. Al­ though considerable investigation has been carried out per­ taining to the formation of hydrides and their properties, they have not been widely employed in the refining of metals. In general,the binary compounds of hydrogen may be clas­ sified or divided into three Pfincipal categories according to differences in their struct~res, physical properties and I chemical behavior (2). These divisions include the ionic hydrides, covalent hydrides, arid trans i tiona! metal hydrides. I A fourth class in addition to the three major divisions may I be designated as the borderline: hydrides, which exhibit inter- mediate properties between the major divisions. The ionic hydrides are salt-like compound's in which hydrogen is con­ sidered to be present as the negatively charged hydride ion. The alkali and alkaline-earth metals, which are strongly positive element~ belong, to this group. The metals in this group, with the exception of beryllium and magnesium, combine directly with hydrogen to form their hydrides. The hydrides in this group possess high melting points, high heats of formation and a high degree of thermal stability. The co- 5 valent hydrides are formed by the elements found in Groups IIIB, IVB, VB, VIB, and VIIS of the Periodic Table. Com­ pounds j_n this group can be distinguished physically from the other types of hydrides in that they are volatile sub­ stances, and generally are gases or liquids under normal conditions. These exhibi-t nonpolar bonding of the electron­ sharing type and in general have low melting and low boiling points, and small heats of formation. The transition hy­ drides include the transition metals and the remaining metals. The majority of the hydrides formed in this class are prepared by direct union with hydrogen gas. In this class both endothermic and exothermic heats of formation are found; however, in general the reactions of the elements in Groups IIIA and IVA are very exothermic. There is no clear division of the compounds formed in this class. Metals in this class can absorb large amounts of hydrogen without suffering a change in their physical appearance. They are also capable of forming interstitial compounds with hydrogen. The formu­ las for these compounds are, for most cases, indefinite and do not correspond to even stoichiometric formulas. The purpose of the present investigation was to study the precipitation or thorium as the hydride from Th-Mg solu­ tions, arid to establish some of the thermodynamic properties of these solutions.
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