Thorium carbonate

Thorium carbides, 24 761, 4 689—690 Thorium carbonate, 24 765 Thorium carboxylates, 24 768-769 Thorium chlorides, 24 762-763 Thorium complexes allyl, 24 773... 

The physical and chemical properties of elemental thorium and a few representative water soluble and insoluble thorium compounds are presented in Table 3-2. Water soluble thorium compounds include the chloride, fluoride, nitrate, and sulfate salts (Weast 1983). These compounds dissolve fairly readily in water. Soluble thorium compounds, as a class, have greater bioavailability than the insoluble thorium compounds. Water insoluble thorium compounds include the dioxide, carbonate, hydroxide, oxalate, and phosphate salts. Thorium carbonate is soluble in concentrated sodium carbonate (Weast 1983). Thorium metal and several of its compounds are commercially available. No general specifications for commercially prepared thorium metal or compounds have been established. Manufacturers prepare thorium products according to contractual specifications (Hedrick 1985). 

Characteristic Thorium dioxide (tetrahydrate) (tetrahydrate) Thorium carbonate... 

Benzyl methyl ketone. Fill the Pyrex combustion tube with catalyst and proceed as in Expt 5.92 but use a temperature of 400-450 °C for the conversion of thorium carbonate into the corresponding oxide 6-12 hours are usually... 

Tetrakis(indenyl)thorium(rV), Th(C9H7)4, is known and well characterized. As depicted in (11), the thorium is bonded to carbons of the five-membered ring of the indenyl ligand, albeit not in an fashion. The shortest thorium-carbon... 

The Cp3ThR complexes have been used to measure metal alkyl bond disruption enthalpies for a series of thorium alkyl complexes for both solution and gas phases. The thorium carbon bonds appear to be relatively strong when compared to other metal-carbon linkages, and solution bond disruption enthalpies range from ca. 75 to 90kcalmol . ... 

Thorium. Experimental and theoretical studies of thorium speciation, solubility, and sorption in low-ionic-strength waters are described by Langmuir and Herman (1980), Laflamme and Murray (1987), Osthols et ai (1994), Osthols (1995), and Quigley et al. (1996). Langmuir and Herman (1980) provide a critically evaluated thermodynamic database for natural waters at low temperature that is widely used. However, it does not contain information about important thorium carbonate complexes, and the stability of phosphate complexes may be overestimated (US EPA, 1999b). 

An alternative separation of thoria, based on the low solubility of lanthanides in a mixture of phosplioric and sulphuric acids, is to treat monazite at 225° with concentrated sulphuric acid and to leave most of the lanthanide sulphates behind by extracting the semi-solid mass with water. Tlie crude thorium sulphate is crystallised by concentrating the liquor, washed with cold concentrated sulphuric acid to remove phosphoric acid and redissolved in 25% sulphuric acid. The solution of the sulphate is boiled with ammonium carbonate to precipitate basic thorium carbonate. This is washed with a very little dilute nitric acid and calcined to thoria. 

Thorium nitrate reacts with sodium carbonate to make thorium carbonate and sodium nitrate. Thorium carbonate does not dissolve in water, so it forms a white precipitate. Sodium nitrate stays dissolved in water. The stirring is continued for a couple of minutes after all the sodium carbonate has been added, then it is allowed to settle. The thorium carbonate settles into a gooey gunk at the bottom of the beaker. As much of the water as possible is poured off. Then 600 ml of distilled water is added to the thorium carbonate and stirred around with a clean glass rod. The chemist makes sure that all the thorium carbonate gets into contact with the clean water, and that any lumps are broken up. This dissolves any remaining sodium nitrate. 

The thorium carbonate is allowed to settle again, then as much of the water as possible is poured off. Small amounts of distilled water are added and stirred in until a fairly thick paste is formed. Now the purified pumice pebbles are added and stirred around until they are all evenly coated with thorium carbonate. 

Now the tube furnace is heated to 425-45O0C, while the slow stream of nitrogen continues through the tube. The heat turns the thorium carbonate into thorium oxide. The heating continues for 12 hours, after which the... 

Separation. — The separation of thorium from the rare earth metals with which it is still mixed may be accomplished by three methods (1) the carbonate separation depends on the fact that thorium carbonate is much more soluble in sodium carbonate than the carbonates of the rare earth metals (2) by the fractional crystallization of the mixed sulfates at 15°-20°, crystals of Th(S04)2 8 H20 are obtained at the insoluble end of the series (3) thorium oxalate forms a soluble double salt with ammonium oxalate, while the rare earth oxalates are almost insoluble in this reagent. Some other methods which have been suggested are fractionation of the chromates,4 of the hydrogen alkyl sulfates,5 of the acetates, by the use of sebacic add 6 and hydrogen peroxide. 

Reference [II] summarizes the somewhat conflicting data on the system thorium-carbon. From maxima in the melting point curve, it is concluded that two compounds exist ... 

Addition of an alkali carbonate to an aqueous solution of a thorium salt first precipitates a basic thorium carbonate of variable composition. Like uranyl carbonate, thorium carbonate dissolves in an excess of alkali carbonate, in this case forming the complex ion [Th(COs)4(OH)2] -. 

C3. Chiotti, P. Thorium-Carbon System, Report AECD-3072, June 5, 1950. 

The following thorium carbonate solid phases have been synthesised in corresponding bicarbonate or carbonate solutions and characterised by chemical analysis, thermogravimetry and X-ray diffraction ... 

The analysis of experimental data is facilitated if the temaiy system is rednced to a formaf three-component system by keeping the concentration of one component, A, constant and varying the other two, B and C. These data provide information on the stoichiometry of the complexes with respect to the two components that are varied and their conditional equilibrinm constants. By repeating the investigation in new series of experiments where the concentration of A is still constant bnt with the valnes (Ai, A2, A3 etc.) in the different series, one can determine the stoichiometiy with respect to A and the equilibrium constants for the temaiy complexes. The choice of components in the thorium carbonate system depends on the pH region investigated at low pH where the partial pressure of CO2 can be measured it is practical to use C02(g) as one of the components, the other two being the concentrations of Th" and H. The chemical equilibria are then formulated as ... 

The equilibrium constants selected in this review for solid and aqueous thorium carbonate compounds and the corresponding molar standard Gibbs energies of formation are summarised in Table XI-6. 

Benz, R., Stone, P. L., Thorium-carbon phase eqnilibria. High Temp. ScL, 1, (1969), 114-127. Cited on page 340. 

Benz, R., Balog, G., X-ray diffraction of elevated-temperature thorium-carbon-nitrogen alloys. High Temp. Sci., 3, (1971), 511-522. Cited on page 340. 

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