Some studies on thallium oxalates

Two methods (the Horowitz-Metzger and the Dharwadkar-Karkhanavala) for calculating the apparent activation energies of different thallium(I) oxalates were compared. The Dharwadkar-Karkhanavala method gave consistent values.     

Some studies on thallium oxalates — IV

Thallium(III) was precipitated with oxalic acid in the presence of 0.025M RbNO₃ (or 0.0125M Rb₂SO₄) in 0.1M HNO₃ (or 0.05M H₂SO₄). Chemical analysis of the solid obtained corresponds to the formula Rb[Tl^III(C₂O₄)₂]·4 H₂O. Thermal studies (TG, DTG and DTA) indicated the dehydration and redox decomposition of the thallic salt to the thallous salt, and finally to a mixture of rubidium carbonate and oxides of thallium(I) and thallium(III). Infrared absorption spectra, microscopic observations and X-ray diffraction data were used to characterize the original salt, as well as the intermediates formed during the thermal decomposition of the salt. On the basis of these results, the salt may be represented as: Rb[Tl^III(C₂O₄)₂(H₂O)₂]·2 H₂O.

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Zusammenfassung Thallium (III) wurde mit Oxalsäure in Gegenwart von 0.025M RbNO₃ (oder 0.0125M Rb₂SO₄) in 0.1M HNO₃ (oder 0.05M H₂SO₄) gefällt. Die chemische Analyse der erhaltenen Festsubstanz entspricht der Formel Rb[Tl^III(C₂O₄)₂]·4H₂O. Thermische Untersuchungen (TG, DTG und DTA) zeigen die Dehydratisierung und Redoxzersetzung vom Thallitsalz zum Thallitsalz und schließlich zu einem Gemisch von Rubidiumcarbonat und Oxiden der Thallium(I) und Thallium(III). Infrarot-Absorptionsspektren, mikroskopische Beobachtungen und Röntgendiffraktionsdaten werden zur Charakterisierung des ursprünglichen Salzes sowie der während der thermischen Zersetzung des Salzes entstandenen Zwischenprodukte angewandt. Durch diese Ergebnisse kann das Salz wie folgt beschrieben werden: Rb[Tl^III(C₂O₄)₂(H₂O)₂]·2H₂O.

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() 0.025M RbNO₃ ( 0.0125M Rb₂SO₄) 0.1M HNO₃ ( 0.05M H₂SO₄) , Rb[Tl¹¹¹(C₂O₄)₂]. 4₂. (, ) - (). , , , . , Rb[Tl¹¹¹(C₂O₄)₂(H₂O)₂·2₂O.

     

Some studies on thallium oxalates. XIII. Sodium bis-oxalatodiaquothallate(III) monohydrate

Sodium bis-oxalatodiaquothallate(III) monohydrate has been prepared and characterised by chemical, thermal, X-ray diffraction and infrared spectroscopic methods. Thermoanalytical studies indicated that the complex decomposes through the formation of a mixture of thallium(I) oxalate and sodium oxalate, the final product at 650° being a mixture of thallium(I) oxide, thallium(III) oxide and sodium carbonate.

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Zusammenfassung Natrium-bis-oxalatodiaquothallat(III)-Monohydrat wurde hergestellt und chemisch, thermoanalytisch, röntgendiffraktometrisch und infrarotspektroskopisch charakterisiert. Thermoanalytische Untersuchungen haben ergeben, daß sich der Komplex unter Bildung eines Gemisches von Thallium(I)- und Natriumoxalat als Zwischenprodukt zersetzt. Endprodukt der Zersetzung bei 650° ist ein Gemisch von Thallium(I)-oxid, Thallium(III)-oxid und Natriumcarbonat.

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, --- () . , . 650° - .

     

Some studies on thallium oxalates. I. Thermal decomposition of ammonium bisoxalatothallate(III)

Trivalent thallium is precipitated in the presence of 0.1 M HNO₃ (or 0.05 M H₂SO₄) and O.1 M NH₄NO₃ (or 0.05 M (NH₄)₂SO₄) with oxalic acid. The chemical analysis of the salt obtained correspondens to the formula, NH₄[Tl(C₂O₄)₂]·3H₂O. The thermal decomposition studies of the complex indicate the formation of the intermediates ammonium thallous oxalate (stable from 150° to 160°C) and thallous oxalate (stable up to 290°C) and the final product to be a mixture of 25% of thallous oxide and 75% of thallic oxide (stable from 450° to 650°C). The infrared absorption spectra, X-ray diffraction patterns, microscopic observations and the electrical resistance measurements are used to characterise the complex and the intermediates of its thermal decomposition.     

Some studies on thallium oxalates. II. Thermal decomposition of potassium bisoxalato diaquothallate(III) dihydrate

Potassium bisoxalato diaquothallate(III) dihydrate is obtained by precipitating thallium(III) with oxalic acid from slightly acidic (HNO₃ or H₂SO₄) solutions in the presence of potassium ions. The thermal decomposition behaviour of the complex is studied using the techniques of TG, DTA and DTG. The solid complex salt and the intermediate products of its thermal decomposition are characterised using IR absorption spectra, microscopic observations, electrical conductivity measurements and X-ray diffraction data.     

Thermal studies on beryllium titanyl/zirconyl oxalates

Beryllium titanyl oxalate tetrahydrate and beryllium zirconyl oxalate tetrahydrate were prepared in aqueous medium and characterized by elemental analyses, magnetic susceptibility measurements and IR spectral studies. The thermal behaviour of these compounds under non-isothermal conditions was investigated by thermogravimetric, derivative thermogravimetric and differential scanning calorimetric (DSC) techniques. The intermediates obtained at the end of the various thermal decomposition steps were identified on the basis of elemental analyses and IR spectral studies. The decomposition proceeds through three major steps, viz, dehydration of the hydrate, decomposition of the oxalate to carbonate and decomposition of the carbonate to oxide. The graphical method of Coats and Redfern was employed to calculate kinetic parameters such as apparent activation energy and order of reaction. Heats of reaction for the different decomposition steps were calculated from the DSC curves.     

Thermal studies on yttrium,neodymium and holmium oxalates

The thermal decomposition patterns of Y₂(C₂O₄)₃ · 9 H₂O, Nd₂(C₂O₄)₃ · 10 H₂O and Ho₂(C₂O₄)₃ · 5.5 H₂O have been studied using TG and DTG. The hydrated neodymium oxalate loses all the water of hydration in one step to give the anhydrous oxalate while Y₂(C₂O₄)₃ · 9 H₂O and Ho₂(C₂O₄)₃ · 5.5 H₂O involve four or more dehydration steps to yield the anhydrous oxalates. Further heating of the anhydrous oxalates results in the loss of CO₂ and CO to give the stable metal oxides.     

Preparation and thermal decomposition of some oxomolybdenum(VI) oxalates

Anionic oxomolybdenum(VI) oxalates having the general formula A₂[Mo₂O₆(C₂O₄)], where A = K⁺ and NH⁺₄, are prepared and characterized by chemical analysis and IR spectra, and their thermal decomposition studied using TG and DTA techniques. Both the compounds are anhydrous and the decomposition of oxalate takes place in a single step. The ammonium compound decomposes between 255 and 320°C to give MoO₃ as the end product, while the potassium compound decomposes between 300 and 380°C to give K₂Mo₂O₇ as the end product. Both the products were characterized by chemical analysis, IR and X-ray studies. The X-ray diffraction patterns of the two oxalato complexes confirm that they are crystalline compounds.     

Thermal studies on beryllium,magnesium and calcium hafnyl oxalates

Beryllium hafnyl oxalate tetrahydrate, magnesium hafnyl oxalate tetrahydrate and calcium hafnyl oxalate tetrahydrate abbreviated as BHO, MHO and CHO, respectively, have been prepared in an aqueous medium and characterized by elemental analysis, magnetic susceptibility measurements and infrared spectral data. The thermal behaviour of these compounds in non-isothermal conditions have been investigated by employing TG, DTG and DSC techniques. The intermediates obtained at the end of various thermal decomposition steps were identified on the basis of elemental analysis and infrared spectral studies. The graphical method of Coats and Redfern has been employed to evaluate the kinetic parameters such as apparent activation energy and order of reaction. Heat of reaction for different decomposition steps have been calculated from the DSC curves.     

Thermal decomposition of titanyl oxalates IV. Strontium and calcium titanyl oxalates

Thermal decomposition of strontium titanyl oxalate tetrahydrate and calcium titanyl oxalate hexahydrate have been studied employing TG, DTA, gas and chemical analysis. The decompositions proceed through three major steps: dehydration, decomposition of the oxalate to a carbonate and the decomposition of the carbonate to yield the final products, the metatitanates. The intermediates of the oxalate decomposition are found to be Sr₂Ti₂O_4+x(CO₃)₂-x(CO₂)_x and Ca₂Ti₂O₄(CO₃)₂, respectively. The entrapment of carbon dioxide in the former and the presence of non-equivalent carbonate groups in the latter are substantiated by their i.r. spectra. The penultimate solid residues are poorly crystalline Sr₂Ti₂O₅CO₃ and amorphous Ca₂Ti₂O₅CO₃. Decompositions of these carbonates are accompanied by growth in particle size of the products, SrTiO₃ and CaTiO₃, respectively.     

FT-Raman spectroscopic studies of metal oxalates and their mixtures

The Raman spectra of a number of Group I and II metal oxalates are presented. From quantitative spectroscopic studies of the pure compounds and of mixtures of calcium, potassium and magnesium oxalates, it has been demonstrated that each component can be determined in the prepared mixtures to better than 2%. Comparisons made with the Raman spectra of lithium and sodium oxalates indicate that there are characteristic differences in the observed spectra of the Group I metal oxalates and that several vibrational bands of C₂O²⁻₄ are sensitive to the cation, being shifted to lower wavenumbers as the cation mass increases from Li to K.     

Some studies on synergic extraction of mixed ligand species of uranium(VI)

The extraction of U(VI) by mixtures of HTTA and TBP from aqueous thiocyanate medium has been studied. From the data obtained it was observed that the predominant uranium species extracted, causing synergic enhancement in the extraction of U(VI), is UO₂(SCN)TTA · 2TBP when benzene and cyclohexane are used as diluents, and that at a very low concentration of TBP the contribution of additional species, viz. UO₂(TTA)₂ · TBP becomes significant. With chloroform as diluent, however, both of these species are contributing to the synergic enhancement. The extraction of a quaternary uranium species, UO₂(SCN)TTA · 2TBP, involving the participation of the aqueous anion is thus established. Equilibrium constants for the various extraction equilibria involved are calculated.     

Electron-impact studies of organometallic molecules—VI. Some transition metal derivatives of alicyclic fluorocarbons

The mass spectra of a series of alicyclic fluorocarbon complexes of manganese, rhenium, iron and ruthenium are described and discussed. It is shown that the breakdown of these complexes after ionization depends on the nature of the metal, and of the other groups attached to the metal. Effects due to elimination of metal halides, formation of metal fluoride ions, and ligand transfer reactions are found, and result in significant differences in the fragmentation patterns of the complexes from those of the parent fluorocarbons.     

Vibrational studies of anhydrous lithium,sodium and potassium oxalates

The IR and Raman spectra of sodium oxalate and the IR spectrum of lithium oxalate are re-examined. The Raman spectrum of lithium oxalate is presented for the first time. A recent structural study is used as the basis for the first detailed vibrational study of anhydrous potassium oxalate, phase II.     

Theoretical studies of thermal decomposition of anhydrous cadmium and silver oxalates

Detailed analysis of the results of full potential linearized augmented plane wave (FP LAPW) ab initio calculations for anhydrous silver and cadmium oxalates, reported in first part of this paper [1] has been presented. Additional calculations of Bader’s AIM (Atoms in Molecules) topological properties of the electron density, bond orders (Pauling, Bader, Cioslowski and Mixon) and bond valences according to bond valence model have been done. The obtained results show the similarities in electronic structure of both compounds and support the conclusion, that during the thermal decomposition process, these compounds should most probably decompose to metal and carbon dioxide, in agreement with the experiment.