Synthesis and thermal decomposition of some rare earth tetramethylammonium double sulphates

When reaction mixtures of rare earth(III) sulphates and tetramethylammonium sulphate in molar ratios of from 1∶4 to 1∶12 were evaporated at ambient temperature and the concentrated reaction mixture was treated with ethanol, double sulphates with general empirical formula (CH₃)₄NLn(SO₄)₂·2H₂O (Ln=Ho?Lu and Y) were obtained as reaction products. The crystalline products were identified by quantitative analysis, X-ray powder diffraction patterns and TG, DTG and DTA analysis. They were found to be isostructural. Their thermal decomposition took place in three stages. The temperature range of the dehydration mainly decreased from Ho to Lu. The thermal decomposition in the second and third stages occurred with many thermal events. As final product, Ln₂O(SO₄)₂ was obtained.     

Thermal and X-ray studies on double sulphates of uranium(IV) with magnesium,nickel, copper and zinc

Double sulphates of uranium(IV) with Mg, Ni, Cu and Zn with the general formula MU(SO₄)₃·8H₂O were prepared from their respective metal sulphates. All the four compounds are isostructural and belong to monoclinic system. The thermal decomposition at 850 °C results in a single phase of triuranates MU₃O₁₀ which on further heating above 980 °C decompose to give the metal oxide and U₃O₈ in case of Ni and Zn compounds and MUO₄ for Mg and Cu compounds. The activation energy for dehydration of these four compounds has been calculated using non-isothermal thermogravimetric data.

---

Zusammenfassung Aus den entsprechenden Metallsulfaten wurden sulfatische Doppelsalze von Uran(IV) und Mg, Ni, Cu und Zn mit der allgemeinen Formel MU(SO₄)₃·8H₂O dargestellt. Alle vier Verbindungen besitzen die gleiche Struktur und gehören dem monoklinen System an. Bei der thermischen Zersetzung bei 850 °C entsteht ein MU₃O₁₀ Einphasentriuranat, welches durch weiteres Erhitzen über 980 °C in das entsprechende Metalloxid sowie im Falle der Ni- und Zn-Verbindungen in U₃O₈, bei den Mg- und Cu-Verbindungen in MUO₄ zerfällt. Unter Anwendung nichtisothermer thermogravimetrischer Daten wurde die Aktivierungsenergie für die Dehydratation dieser vier Verbindungen berechnet.

---

, , , MU(SO₄)₃ · 8H₂O, . . 850° MU₃O₁₀, 980° U₃O₈ , MUO₄ . .

---

---

The authors thank Dr. D. D. Sood, Head, Fuel Chemistry Division, for constant encouragement.     

Nucleophilic addition to the double bond of 2,4,6-trinitrostyrene and transformations of adducts

Conditions were found under which 2,4,6-trinitrostyrene derived from 2,4,6-trinitrotoluene adds nucleophiles (thiophenol, aniline, and aliphatic amines) at the vinyl fragment to form the corresponding β-X-ethyl-2,4,6- trinitrobenzenes (X = PhS, PhNH, or R₂N). In the reactions with primary aromatic amines, the initially formed adducts undergo intramolecular replacement of the nitro group followed by aromatization of the indolines that formed to the corresponding N-substituted 4,6-dinitroindoles. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 1022–1025, April, 2005.     

Vibrational spectra of mono, di and trimethyl ammonium double sulphates of rare earths Pr, Nd, Ho and Eu

Infrared and Raman spectra of four rare earth (Ho, Eu, Nd and Pr) double sulphates have been recorded and analysed based on the vibrations of methyl ammonium cations, sulphate anions and water molecules. Formation of hydrogen bonds of the type N-H...O and O-H...O are identified in all the compounds. Bifurcated hydrogen bonds are present in the compounds with dimethyl ammonium cations. The sulphate anions are distorted and occupy a lower site symmetry in the compounds. The bands obtained for (CH(3))(2)NH(2) and SO(4)(2-) ions indicate that the structural bonding of (CH(3))(2)NH(2)Eu(SO(4))(2).H(2)O and (CH(3))(2)NH(2)Ho(SO(4))(2).4H(2)O is identical. Electronic transition bands of Eu(3+) and Nd(3+) observed in the Raman spectra of these two compounds have been identified and discussed.     

Mechanism and kinetics of inorganic sulphates decomposition

Thermal decomposition of different inorganic sulphates are presented. A number of techniques, but mainly TG and DTA, are used to prove the mechanism and kinetics of CaSO₄, BaSO₄, FeSO₄·xH₂O, Al₂(SO₄)₃·xH₂O under various gas atmospheres. It is shown how the partial pressure of gas components and heating rate may effect the mechanism and kinetic parameters. There are also examples on the effects of some additives and initial treatment on the thermal processes. On the base of the results obtained some recommendations are given concerning the precautions to be taken into account in the thermal decomposition studies and the sulphur recovering.     

Thermal decomposition of some metal sulphates

The thermal decomposition temperatures of some metal sulphates (iron, copper, cobalt, nickel, zinc and lead sulphates) have been investigated by TG and DTA. The mechanism of decomposition of these sulphates is discussed, making use of additional information obtained from isothermal studies and X-ray diffraction measurements. The activation energies of these reactions were calculated and found to increase, with almost the same increments, in the order Zn<Fe<Co<Ni<Cu.     

Identification of nitrates and sulphates with dynamic SIMS

Summary Sputter conditions are outlined for the identification of chemically sensitive salt compounds, such as nitrates or sulphates, in multicomponent samples of environmental origin using dynamic SIMS for depth-profiling with nanoscale resolution. Sputtering with 1 keV Xe⁺ has been found to be appropriate to enable both the emission of decisive molecular ions with enough intensity as well as substantial erosion for depth-profiling. The use of heavy projectiles reduces the destruction of chemical compounds in the surface of the solid and enhances sensitivity and identification power of SIMS. The method was applied to the analysis of urban outdoor aerosol particles to investigate the conversion of NaCl into Na₂SO₄ or NaNO₃ by the interaction of sea salt aerosol with the atmospheric pollutants NO_x and SO_x. Only NaNO₃ was found in the sea salt fraction.     

Thin-layer chromatography of organic sulphates, phosphates and nitrates

Inorganic oxyanions and their corresponding organic esters, such as sulphates, phosphates and nitrates, have been separated by thin-layer chromatography on cellulose and silica gel plates.     

Thermal analysis of hydrazinium metal sulphates and their hydrazinates

Thermal analysis of hydrazinium metal sulphates, (N₂H₅)₂ M(SO₄)-I, and their hydrazinates, (N₂H₅)₂−M(SO₄)₂3N₂H₄−II, whereM=Fe, Co and Ni have been investigated using thermogravimetry and differential thermal analysis. Type II compounds on heating decompose through an intermediate I and metal suphlate to the respective metal oxides.     

Bilayer characteristics and cholesterol effects of sodium dialkylmethyl sulphates

The gel-liquid crystal phase transitions (PT) in bilayers formed from a series of synthetic sodium dialkylmethyl sulphates have been studied by both fluorescence and differential scanning calorimetry (DSC) methods, which are between the transitions of the corresponding phospholipids and the quarternary ammonium salt bilayers possessing the same hydrocarbon chains. The fluorescence I₃/I₂ ratio (R) of probe pyrene in the bilayers decreases below and increases above the transitions respectively with increasing the chain length of the surfactants in the series SUDS, SPHS, and SHOS. In addition, the difference between the R above and below the transition (ΔR) is larger in the suspension prepared at the temperature above that of the transition than in that formed at room temperature. Intermembrane transfer and transbilayer migration (flip-flop) evaluated by means of DSC of a mixture of equimolar aqueous dispersions of SHOS and SPHS as well as by ESR of bilayer embedding the stable free radical 4-HD-TEMPO in the presence and absence of excess ascorbic acid take place noticeably only at the temperature above that of the transitions. Cholesterol has shown the same effect on ΔR as to decrease the length of the alkyl chain of the surfactants. It also causes a decrease of the fluorescence Intensity ratio of excimer to monomer of pyrene, I_e/I_m(S), in both phase. The results are discussed in terms of bilayer structure, chain fluidity, and permeability of water.     

Ring transformations of heterocyclic compounds. XIII. Bis(2,4,6-triarylphenyl) substituted bispyridinium salts from methyl derivatives by double pyrylium and thiopyrylium ring transformations

The synthesis of hitherto unknown 4,4′-bis(2,4,6-triarylphenyl) substituted bispyridinium diperchlorates 3 , in which the N-atoms are linked by a carbon chain, a heteroatom containing a carbon chain or a bis(methylene) substituted aromatic/heteroaromatic ring, from 4,4′-dimethylbispyridinium derivatives 2 by a double 2,6-[C₅+C] ring transformation of 2,4,6-triarylpyrylium and 2,4,6-triarylthiopyrylium salts 1/4 is reported. Spectroscopic data of the bispyridinium diperchlorates 3 and their mode of formation are discussed.     

Some factors influencing the solubilities of amine sulphates

The relationship between the molecular structures of amines and the solubilities of their sulphates has been examined with the object of finding a better reagent than benzidine for the determination of sulphate. It has been established that the two aromatic rings must have a tendency to be coplanar and collinear, if the sulphate solubility is to be low. With the help of this theory, 4 : 4'-diaminotolane sulphate has been found to be less soluble than bcnzidine sulphate.     

Physicochemical transformations during synthesis of double K−Zr phosphates in a melt of potassium nitrate

Double phosphates of K and Zr with three-dimensional and layered structure were synthesized in a melt of potassium nitrate in the temperature range of 300–550°C. The double phosphates were formed with participation of three components of a reaction mixture: ZrOCl₂·8H₂O−(NH₄)₂HPO₄−KNO₃, in which potassium nitrate was both an active component of the reaction mixture and the reaction medium. The influence of the nature of the starting reagents on the composition of the reaction products and on the sequence and stoichiometry of the reactions proceeding, in the reaction mixture were studied by thermogravimetry and mass-spectrometry. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 666–670, April, 1997.     

Thermophysical Investigations of the Polymorphous Phases of Calcium Carbonate

1. Results of thermodynamic and kinetic investigations for the different crystalline calcium carbonate phases and their phase transition data are reported and summarized (vaterite: V; aragonite: A; calcite: C). A→C: T _tr=455±10°C, Δ_tr H=403±8 J mol^–1 at T _tr, V→C: T _tr=320–460°C, depending on the way of preparation,Δ_tr H=–3.2±0.1 kJ mol^–1 at T _tr,Δ_tr H=–3.4±0.9 kJ mol^–1 at 40°C, S _V ^Θ= 93.6±0.5 J (K mol)^–1, A→C: E _A=370±10 kJ mol^–1; XRD only, V→C: E _A=250±10 kJ mol^–1; thermally activated, iso- and non-isothermal, XRD 2. Preliminary results on the preparation and investigation of inhibitor-free non-crystalline calcium carbonate (NCC) are presented. NCC→C: T _tr=276±10°C,Δ_tr H=–15.0±3 kJ mol^–1 at T _tr, T _tr – transition temperature, Δ_tr H – transition enthalpy, S ^Θ – standard entropy, E _A – activation energy. 3. Biologically formed internal shell of Sepia officinalis seems to be composed of ca 96% aragonite and 4% non-crystalline calcium carbonate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermally induced polytype transformations among the layered double hydroxides (LDHs) of Mg and Zn with Al

The hydrotalcite-like layered double hydroxide (LDH) of Mg with Al shows dramatic changes in the peaks arising from the (h0l)/(0kl) family of reflections in its powder X-ray diffraction pattern during thermal treatment. DIFFaX simulations show that these changes arise due to the transformation of the disordered 3R1 polytype into the 1H polytype on dehydration. The 1H polytype is an essential precursor to the decomposition reaction, which results in the formation of an oxide residue with the rock salt structure. In contrast, the LDH of Zn with Al does not undergo any such transformation, retaining the structure of the 3R1 polytype until decomposition into the oxide residue. Given the poor octahedral site preference of the Zn2+ ion, the 1H polytype is neither structurally stable nor is it topochemically necessary for the thermal decomposition of the Zn-Al LDH, the end product of the decomposition reaction being an oxide with the wurtzite structure.     

Double sulphates of plutonium(III) and lanthanides with sodium

Sodium plutonium double sulphate monohydrate, NaPu(SO₄)₂ · H₂O and its lanthanide isomorphs NaLn(SO₄)₂ · H₂O (Ln ≡ Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) were synthesized and characterised by chemical and X-ray diffraction methods. All these compounds belonged to the same structural family where the Pu³⁺ or Ln³⁺ ion is coordinated to nine oxygen atoms. The structure of NaPu(SO₄)₂ · H₂O was found in the present work to be isomorphous with NaCe(SO₄)₂ · H₂O reported in the literature. The unit cells of all the lanthanide compounds showed regular contraction with atomic number.