Thorium oxalate

The simplest dicarboxylate ligand is oxalate, 020 . Thorium oxalate complexes have been used to produce high density fuel pellets, which improve nuclear fuel processes (73). The stabiUty of oxalate complexes and the relevance to waste disposal have also been studied (74). Many thorium oxalate complexes are known, ranging from the simple Th(C20 2 >5rl2 complex salts such as where n = 4, 5, or 6 and where the counterions... 

Thorium metal, 24 759-761 in alloys, 24 760-761 preparation of, 24 759-760 properties of, 24 760-761 reactions of, 24 761 Thorium nitrate, 24 757, 766 Thorium oxalates, 24 768-769 Thorium oxide, 21 491 Thorium oxides, 24 757, 761-762 Thorium oxyhalides, 24 762 Thorium perchlorate, 24 764 Thorium phosphates, 24 765-766 Thorium pnictides, 24 761 Thorium sulfate, 24 764 Thorium-uranium fuel cycle, 24 758-759 Thorocene, 24 772 Thorotrast, 24 775-776 3A zeolite. See Zeolite 3A Three-boiling beet sugar crystallization scheme, 23 463-465 Three-color photography, 19 233-234 3D models, advantages of, 19 520-521 3D physical design software, 19 519-521 3D QSAR models, 10 333. See also QSAR analysis... 

Thorium oxide, has the highest melting point of the usual ceramic materials (3390°C). It is used to form ceramics, Th02, as the so-called meta-Th02, freshly prepared by low temperature decomposition of thorium oxalate it is fairly soluble in acids and tends (especially in the presence of nitrate ions) to form colloidal solutions which can be dried to form stable gels that can be sintered to give high-density ceramic bodies. 

The compound also can be prepared by many other methods including thermal decomposition of thorium oxalate, hydroxide, carbonate, or nitrate. Heating thorium metal in oxygen or air, and hydrolysis of thorium halides also yield thorium dioxide. 

Oxalic acid solution white, crystalline precipitate of thorium oxalate, Th(C204)2 (distinction from aluminium and beryllium), insoluble in excess of the reagent and in 0-5m hydrochloric acid. 

Ammonium oxalate solution white precipitate of thorium oxalate, which dissolves on boiling with a large excess of the reagent forming trioxalato-thorate(IV) anion, [Th (COO)2 3]2, but is reprecipitated upon the addition of hydrochloric acid (difference from zirconium). 

Separation. Cerium and thorium salts are precipitated in Group IIIA. They may be separated from the other metals of the group by dissolving the precipitate in dilute HC1 and adding oxalic acid solution, when the oxalates of both metals are precipitated. The thorium and cerium may be separated (a) by dissolving the thorium oxalate in a mixture of ammonium acetate solution and... 

In contrast, dehydration of 2-alcohols over alumina yields mixtures rich in the 2-olefins. The most active catalysts were prepared by calcining thorium oxalate at 350-450° for a few hours. 

Thorium oxalate yielded [94] the carbonate below 593 K, but reactions at higher temperature yielded Th02 directly. The rate controlling process changed across the temperature interval studied (573 to 623 K). The decomposition of cadmium oxalate at 620 K may be represented [95] as ... 

The precipitation of thorium oxalate with calcium as collector is a much favoured separation method [3]. In a weakly acid medium (pH 1-4) it can be precipitated with oxalic acid. Rare-earth metals and U(IV) are also precipitated, but many metals (e.g., Fe, Al, Ti, Zr, Nb, and Mo) remain in solution as soluble oxalate complexes. 

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. 

Thorium oxalate, ThfCjOdi 611 0, Is precipitated as a while amorphous powder when oxalic acid is adtled to a solution of n thorium salt. It dissolves readily in solutions of ammonium ourhunate uud ammonium oxalate, but is less Roluble in sulfuric, acid than tho ran earth oxalates and is insoluble in nitric acid. Double alkali oxalates, acid oxalates, and mixed salts have been prepared. 

Thorium oxalate is precipitated when a solution of oxalic acid is added to a solution of a thorium salt. This is a commonly used intermediate step in producing thorium dioxide from thorium nitrate solution (Sec. 10.1). Quantitative precipitation of thorium from solutions up to... 

Precipitation of thorium oxalate with oxalic acid. 

The chloride must be purified by distillation to free it from unreacted solids and from impurities in the carbon. This is difflcult because of the hygroscopicity of ThCU and its high boiling point, 942°C. An alternative process [C6] reacts thorium oxalate with an excess of carbon tetrachloride and a small amount of chlorine as catalyst,... 

A2. Ayers, A. S. Precipitation of Thorium Oxalate from Nitric Acid Solutions, Paper 7.9 of Report TID-5223,1952. 

Dash, S., Krishnan, R., Katnruddin, M., Tyagi, A. K., Baldev Raj., Temperature programmed deeomposition of thorium oxalate hexahy-drate, J. Nucl. Mater., 295, (2001), 281-289. Cited on page 347. 

The preparation of potassium tetraoxalatothorate 4-hydrate is based on the observation of Cleve that insoluble thorium oxalate dissolves in boiling potassium oxalate solution under unspecified concentration conditions. 

Kali HL, Gordon L (1953) Quantitative insolubility of thorium oxalate. Anal Chem 25 1256 Khlebnikov N, WhicheUo J, Parise D (2006a) In 47th INMM annual meeting, Nashville Khlebnikov N, Parise D, WhicheUo J (2006b) In IAEA symposium on international safeguards, lAEA-CN-148/32, Vienna... 

---