Vibrational spectra of NH4-Ln(SO4)2·4H2O/D2O (LnLa and Ce)

Infrared and Raman spectra of NH₄Ce(SO₄)₂·4H₂O, NH₄La(SO₄)₂·4H₂O and the deuterated compounds NH₄Ce(SO₄)₂·4D₂O and NH₄La(SO₄)₂·4D₂O have been analysed. Splittings indicating the presence of two types of SO₄ ions are not observed. The SO bond strengths of the different SO₄ units are not significantly different. The SO₄ ion is distorted in these compounds. Deuteration causes changes in the SO₄ bond strength. Three crystallographically distinct water molecules exist in the unit cell.     

The kinetic parameters of thermal decomposition hydrated iron sulphate

The thermal decomposition of iron sulphate hexahydrate was studied by thermogravimetry at a heating rate of 5°C min^?1 in static air. The kinetic parameters were evaluated using the integral method by applying the Coats and Redfern approximation. The thermal stabilities of the hydrates were found to vary in the order. Fe₂(SO₄)₃·6H₂O → Fe₂(SO₄)₃·4.5H₂O → Fe₂(SO₄)₃·0.5H₂O The dehydration process of hydrated iron sulphate was found to conform to random nucleation mass loss kinetics, and the activation energies of the respective hydrates were 89.82, 105.04 and 172.62 kJ mol^?1, respectively. The decomposition process of anhydrous iron sulphate occurs in the temperature region between 810 and 960 K with activation energies 526.52 kJ mol^?1 for the D3 model or 256.05 kJ mol^?1 for the R3 model.     

Thermal decomposition study of selected isopolymolybdates

The thermal decomposition of ammonium trimolybdate (NH₄)₂Mo₃O₁₀·H₂O, anilinium trimolybdate (C₆NH₈)₂Mo₃O₁₀·4H₂O and anilinium pentamolybdate (C₆NH₈)₂Mo₅O₁₆ in air and nitrogen has been investigated. The decomposition of molybdates was studied in situ by powder X-ray diffraction. Moreover, results of TG, as well as scanning microscopy studies, are presented. It was found that during thermal treatment in air phases of MoO_x type are obtained, while thermal treatment in nitrogen leads to obtaining a mixture of Mo_yC_z and Mo_pN_q. It is worth noting that even though chemical decomposition and formation of new compounds took place, in some cases needle-like or plate-like shapes of crystallites were preserved during thermal treatment.     

IR spectra and thermal decomposition/dehydration of double complex salts of lanthanum(III) sulphate complex anions with several cobalt(III) ammine complex cations

Double complex salts of lanthanum(III) sulphate complex anions with several cobalt(III) ammine complex cations, [Co(NH₃)₆][La(SO₄)₃]·H₂O (1), (NH₄)₃[Co(NH₃)₅ H₂O]-[La(SO₄)₃]₂·2H₂O (2), and (NH₄)₃[Co(NH₃)₄(H₂O)₂][La(SO₄)₃]₂·2H₂O (3), were prepared by the addition of hexaamminecobalt(III), pentaammineaquacobalt(III), and cis- tetra-amminediaquacobalt(III) complexes to the solution containing lanthanum(III) ion and excess ammonium sulphate. The IR spectra of sulphate groups of these double complex salts were much more complicated than those of the almost free sulphate groups such as (NH₄)₂SO₄ and [Co(NH₃)₆]₂(SO₄)₃·5H₂O. Furthermore, values of activation energy in the dehydration process of 1, 2 and 3 were estimated using modified Doyle's and Wiedemann's method. They were 95.6 ± 4.3, 157.1 ± 15.5 and 163.2 ± 20.8 kJ mol^?1, respectively. Here, one molecule water is released per molecule of 1, 2 and 3.     

Crosslinking behavior and enhanced mechanical properties of acrylonitrile‐butadiene rubber composites by incorporating aluminum ammonium sulfate particles

The crosslinked structure formed by the metal coordination bonding provides excellent and new properties for rubber materials. Herein, the crosslinking of acrylonitrile‐butadiene rubber (NBR) is induced by introducing aluminum ammonium sulfate (NH₄Al(SO₄)₂·12H₂O) particles. The crosslinking behavior, morphology, mechanical properties, and the Akron abrasion resistance of NBR/NH₄Al(SO₄)₂·12H₂O composites were fully explored. The results show that the three‐dimensional crosslinking structure is held together by metal–ligand coordination bonds between the nitrile group and AI(III). The coordination crosslink density exhibits a considerable increase with the addition of NH₄Al(SO₄)₂·12H₂O. Thus, the mechanical properties and abrasion resistance of the obtained composites are better than that of NBR/sulfur system. Interestingly, the elongation at break for NBR/NH₄Al(SO₄)₂·12H₂O composites is over 2000% due to the nature of coordination bonds. The abrasion volume loss decreases to 0.4 cm³ for NBR/NH₄Al(SO₄)₂·12H₂O composites with 20 phr NH₄Al(SO₄)₂·12H₂O particles as compared to 0.75 cm³ for NBR/sulfur system. The obtained NBR composites with facile preparation and excellent mechanical properties make the composites based on metal coordination bonding attractive for practical use. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 879–886     

Organically‐Templated Zinc and Thorium Sulfates with Chain and Layered Structures

Amine‐templated zinc sulfates of the formulae, [Zn(SO₄)(H₂O)₂(C₁₀N₂H₈)] ( I ) and [C₃N₂H₁₂][Zn(SO₄)] ( II ) both with linear structures have been prepared under hydro/solvothermal conditions. Of these, I has the chain structure formed by ZnO₄N₂octahedra and SO₄ tetrahedra, while II comprises ladders formed by corner‐sharing four‐membered rings. Amine‐templated thorium sulfates of the formula [HN(CH₂)₆NH]₂[Th₂(SO₄)₆(H₂O)₂]·2H₂O, ( III ) and [H₂N(CH₂)₄NH₂][Th₃(SO₄)₇(H₂O)₄]·5H₂O ( IV ) are also obtained under hydrothermal conditions. III has a sheet structure consisting of cages whereas IV has a two‐dimensional structure derived from the connectivity of ladders.     

Variable temperature PXRD investigation of the phase changes during the dehydration of potassium Tutton salts

The thermal dehydration of the potassium Tutton salts K₂M(SO₄)₂·6H₂O (M = Mg, Co, Ni, Cu, Zn) was investigated using thermal gravimetric analysis (TG), differential scanning calorimetry (DSC), FTIR, and variable temperature powder X-ray diffraction. While each Tutton salts lost all six waters of hydration when heated to 500 K, the decomposition pathway depended on the divalent metal cation. K₂Ni(SO₄)₂·6H₂O lost all six waters in a single step, and K₂Cu(SO₄)₂·6H₂O consistently lost water in two steps in capped and uncapped cells. In contrast, multiple decomposition pathways were observed for the magnesium, cobalt, and zinc Tutton salts when capped and uncapped TG cells were used. K₂Zn(SO₄)₂·6H₂O lost the waters of hydration in a single step in an uncapped cell and in two steps in a capped cell. Both K₂Mg(SO₄)₂·6H₂O and K₂Co(SO₄)₂·6H₂O decomposed in a series of steps where the stability of the intermediates depended on the cell configuration. A greater number of phases were often observed in DSC and capped-cells TG experiments. A quasi-equilibrium model is presented that could explain this observation. These results highlight that experimental conditions play a critical role in the observed thermal decomposition pathway of Tutton salts.     

Studies on lanthanoid sulphites: V. thermal decomposition of cerium and neodymium sulphites

The preparation and thermal behaviour of Ce₂(SO₃)₃· 3H₂O, Nd₂(SO₃)₃·6H₂O and Nd₂(SO₃)₃ have been studied. Cerium sulphite undergoes first dehydration which is followed by decomposition to CeO₂ in the temperature range 500 – 850 °C. The decomposition involves two intermediate phases both in air and nitrogen. According to the TG curves the phases in air are Ce₂(SO₃)₂SO₄ and Ce₂SO₃(SO₄)₂. In nitrogen, Ce₂O₂SO₄ was identified and this provides a synthetic route to cerium oxysulphate.Neodymium sulphite decomposes to Nd₂O₂SO₄ when heated in air or in nitrogen up to 950°C. The intermediate levels observed do not correspond to single phases, and the reaction mechanism depends strongly on the experimental conditions.     

TG/DTA/MS Study of the thermal decomposition of FeSO4·6H2O

The thermal decomposition of FeSO₄·6H₂O was studied by mass spectroscopy coupled with DTA/TG thermal analysis under inert atmosphere. On the ground of TG measurements, the mechanism of decomposition of FeSO₄·6H₂O is: i) three dehydration steps FeSO₄·6H₂O FeSO₄·4H₂O+2H₂O FeSO₄·4H₂O FeSO₄·H₂O+3H₂O FeSO₄·H₂O FeSO4+H₂O ii) two decomposition steps 6FeSO₄ Fe₂(SO₄)₃+2Fe₂O₃+2SO₂ Fe₂(SO₄)3 Fe₂O₃+3SO₂+3/2O₂ The intermediate compound was identified as Fe₂(SO₄)₃ and the final product as the hematite Fe₂O₃.     

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.     

Research of thermal decomposition of hydrated methanesulfonates

Hydrated methanesulfonates Ln(CH₃SO₃)₃·nH₂O (Ln=La, Ce, Pr, Nd and Yb) and Zn(CH₃SO₃)₂·nH₂O were synthesized. The effect of atmosphere on thermal decomposition products of these methanesulfonates was investigated. Thermal decomposition products in air atmosphere of these compounds were characterized by infrared spectrometry, the content of metallic ion in thermal decomposition products were determined by complexometric titration. The results show that the thermal decomposition atmosphere has evident effect on decomposition products of hydrated La(III), Pr(III) and Nd(III) methanesulfonates, and no effect on that of hydrated Ce(III), Yb(III) and Zn(II) methanesulfonates. This revised version was published online in August 2006 with corrections to the Cover Date.     

On the reduction of Cr3+ during the thermal decomposition of fluorochromates(III) with nitrogen containing cations

The thermal decomposition of [CO(NH₂)₂H]CrF₆·H₂O, (C₃N₆H₈)CrF₅·H₂O and the solid state reaction of CrF₃ and melamine are investigated under non-reciprocal quasi-static conditions and compared with the thermal behaviour of other fluorochromates(III) ([Cr(NH₃)₆]CrF₆, (NH₄)₃CrF and [C(NH₂)₃]₃CrF₆). The comparison of the results shows that the amount of chromium(II) in the final product is determined by the thermal stability and consequently by the decomposition temperature of the intermediates. Neither bonding properties in the starting materials nor the absolute amount of generated NH₃ influence the composition of the final product.     

A theoretical investigation on the structures of (NH3)·(H2SO4)·(H2O)0-14 clusters

Ternary clusters (NH₃)·(H₂SO₄)·(H₂O)_n have been widely studied. However, the structures and binding energies of relatively larger cluster (n > 6) remain unclear, which hinders the study of other interesting properties. Ternary clusters of (NH₃)·(H₂SO₄)·(H₂O)_n, n = 0-14, were investigated using MD simulations and quantum chemical calculations. For n = 1, a proton was transferred from H₂SO₄ to NH₃. For n = 10, both protons of H₂SO₄ were transferred to NH₃ and H₂O, respectively. The NH₄⁺ and HSO₄⁻ formed a contact ion-pair [NH₄⁺-HSO₄⁻] for n = 1-6 and a solvent separated ion-pair [NH₄⁺-H₂O-HSO₄⁻] for n = 7-9. Therefore, we observed two obvious transitions from neutral to single protonation (from H₂SO₄ to NH₃) to double protonation (from H₂SO₄ to NH₃ and H₂O) with increasing n. In general, the structures with single protonation and solvated ion-pair were higher in entropy than those with double protonation and contact ion-pair of single protonation and were thus preferred at higher temperature. As a result, the inversion between single and double protonated clusters was postponed until n = 12 according to the average binding Gibbs free energy at the normal condition. These results can serve as a good start point for studies of the other properties of these clusters and as a model for the solvation of the [H₂SO₄-NH₃] complex in bulk water.     

Thermoanalytical investigations of tris(ethylenediamine)nickel(II) oxalate and sulphate complexes

Investigations on the thermal behaviour of [Ni(en)₃]C₂O₄·2H₂O and [Ni(en)₃]SO₄ have been carried out in air and helium atmosphere. Simultaneous TG/DTA coupled online with mass spectroscopy (MS) in helium atmosphere detected the presence of H₂, O, CO, N₂/CH₂=CH₂ and CO₂ fragments during the decomposition of tris(ethylenediamine)nickel(II) oxalate and H₂, O, NH, NH₂, NH₃ and N₂/CH₂=CH₂ fragments for tris(ethylenediamine)nickel(II) sulphate complex. The thermal events during the decomposition were monitored by temperature-resolved X-ray diffraction. In air, both the complexes give nickel oxide as the final product of the decomposition. In helium atmosphere, tris(ethylenediamine)nickel(II) oxalate gives nickel as the residue, whereas tris(ethylenediamine)nickel(II) sulphate gives a mixture of nickel and nickel sulphide phases as the final residue. Kinetic analyses of these complexes by isoconversional methods are discussed and compared.     

Vibrational and optical reflectance spectra of silver and copper sulfamides

Infrared (300 K, 77 K), Raman and diffuse reflectance spectra (300 K, 100 K and 20 K) of the diamagnetics Ag₃ (HN₂SO₂)·NH₃·H₂O, Ag₃(DN₂SO₂)·ND₃·D₂O and Cu₃(HN₂SO₂)·NH₃·H₂O have been recorded. Vibrational assignments are proposed, based on a comparison with the assignments for the parent sulfamide. The possibility of metal-metal interactions in these compounds is discussed.     

Evidence of quasi-intramolecular redox reactions during thermal decomposition of ammonium hydroxodisulfitoferriate(III), (NH4)2[Fe(OH)(SO3)2]·H2O

Synthesis of ammonium hydroxodisulfitoferriate(III), (diammonium catena-{bis(μ ²-sulfito-κO,κO)-μ ²-hydroxo-κ²O}ferrate(III) monohydrate) (NH₄)₂[Fe(OH)(SO₃)₂]·H₂O (compound 1) and its thermal behavior is reported. The compound is stable in air. Its thermal decomposition proceeds without the expected quasi-intramolecular oxidation of sulfite ion with ferric ions. The disproportionation reaction of the ammonium sulfite, formed from the evolved NH₃, SO₂ and H₂O in the main decomposition stage of 1, results in the formation of ammonium sulfate and ammonium sulfide. The ammonium sulfide is unstable at the decomposition temperature of 1 (150 °C) and transforms into NH₃ and H₂S which immediately forms elementary sulfur by reaction with SO₂. The formation and decomposition of other intermediate compounds like (NH₄)₂S_nO_x (n = 2, x = 3 and n = 3, x = 6) results in the same decomposition products (S, SO₂ and NH₃). Two basic iron sulfates, formed in different ratios during synthesizing experiments performed under N₂ or in the presence of air, have been detected as solid intermediates which contain ammonium ions. The final decomposition product was proved to be α-Fe₂O₃ (mineral name hematite).

     

Thermal decomposition of compounds containing the hydrazinium cation as a ligand

A thermal investigation of M(N₂H₅)₂(SO₄)₂, where M = Mn(II) or Co(II), has been carried out. On heating, the complexes become MSO₄ via an intermediate compound, M(N₂H₄)_0·5(HSO₄)(SO₄)_0·5. The intermediate compound has been isolated and characterised by elemental analyses, IR spectra, diffuse reflectance spectra, magnetic and conductance data. The intermediate compound seems to possess pseudo-tetrahedral coordination where one SO₄ group is tetradentate and bonded with four different metal ions which are surrounded by HSO₄ groups and hydrazines bridging two metal ions. The X-ray powder diffraction pattern of the intermediate derived from the cobalt(II) complex has been obtained and the d-values are reported. Activation energies (E^*) and enthalpy changes (ΔH) for each decomposition step have also been calculated. The probable mechanisms of decompositions are discussed.     

Identification of Saturating Solid Phases in the System Ce2(SO4)3-H2O from the Solubility Data

Saturating solid phases, Ce₂(SO₄)₃·hH₂O, with hydrate numbers h equal to 12, 9, 8, 5, 4 and 2, have been identified by critical evaluation of the solubility data in the system Ce₂(SO₄)₃—H₂O over the temperature range 273–373 K. The results are compared with the respective TG—DTA—DSC and X-ray data. The solubility smoothing equations, transition points and solution enthalpy estimators of the identified hydrates are given. The stable equilibrium solid phases are concluded to be only Ce₂(SO₄)₃·9H₂O at 273–310 K, Ce₂(SO₄)₃·4H₂O at 310–367 K and Ce₂(SO₄)₃·2H₂O at 367–373 K. Divergencies of up to 185% in the reported solubility data are mainly due to a variety of metastable equilibria involved in the close crystallization fields, and incorrect assignments of the saturating solid phases. Since a similar variety of the hydrate numbers exists for the analogous La(III) system, it most probably also occurs for the corresponding Pu(III), Np(III) and U(III) systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

TG,DTA, FTIR and Raman spectral analysis of Zna/Mgb ammonium sulfate mixed crystals

To understand the structural and thermal properties of the mixed crystals, thermogravimetric (TG) and differential thermal analysis (DTA), and FTIR and Raman spectral studies were carried out for the mixed crystals of Zn_a/Mg_b ammonium sulfate of composition namely 'a' (fraction by mass of salt Zn[NH₄]₂[SO₄]₂·6H₂O to the total salt (both Zn[NH₄]₂[SO₄]₂·6H₂O, Mg[NH₄]₂[SO₄]₂·6H₂O or it can be explained as Zn_aMg_b[NH₄]₂[SO₄]₂·6H₂O, a + b =1), and a = 0.1, 0.25, 0.333, 0.5, 0.666, 0.75 and 0.9 grown by a solution technique. From the correlation and analysis of the results obtained for the various crystals, the desolvation, decomposition, crystalline transition phenomena were identified. By close comparison of the endotherms, obtained for the various crystals, it was found that isomorphous substitution takes place in the crystals. Up to 0.5, Zn²⁺ ion replaces isomorphous Mg²⁺ ions in the lattice sites of Mg[NH₄]₂[SO₄]₂·6H₂O and above 0.5, Mg²⁺ ions occupies the Zn²⁺ ion in the lattice sites of Zn[NH₄]₂[SO₄]₂·6H₂O. Both crystals belong to monoclinic system with P 2(1)/a symmetry. The vibrations of NH₄ ⁺ ion, SO₄ ^2- ion, the complex [Mg(OH₂)₆]²⁺ the complex [Zn(OH₂)₆]²⁺ and the three different water molecules are identified. The linear distortion of SO₄ ^2- ion is found to be greater than its angular distortion, while the NH₄ ⁺ ion has suffered more angular distortion. The possibility of free rotation of the NH₄ ⁺ ion is ruled out.