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 potassium bis -oxalatodiaqua-indate(III) monohydrate

Indium (III) is precipitated with oxalic acid in the presence of potassium nitrate maintaining an overall concentration of 0·125 M in HNO₃. Chemical analysis of the complex salt obtained indicates the formula, K[In(C₂O₄)₂]·3H₂O. Thermal decomposition studies show that the compound decomposes first to the anhydrous potassium indium oxalate and then to the final mixture of the oxides through formation of potassium carbonate and indium (III) oxide as intermediates. Isothermal study, X-ray diffraction pattern and IR spectral data support the proposed thermal decomposition mechanism.     

Synthesis,biological and physicochemical properties of Zinc(II) salicylate and 5-chlorosalicylate complexes with theophylline and urea

New zinc(II) salicylate complex compounds of general formula (X-C₆H₃-2-(OH)COO)₂Zn · L_n · xH₂O (where X = H, 5-Cl; L = theophylline, urea; n = 2, 4; x = 1, 2, 4) were prepared and their thermal, spectral and biological properties were studied. It was found that the thermal decomposition of hydrated compounds starts with the release of water. During the thermal decomposition of anhydrous compounds, the release of salicylic acid, theophylline, urea, CO₂, H₂O and C₆H₅Cl takes place. Zinc oxide was found as the final product of the thermal decomposition heated up to 900 °C. The complexes were tested against bacteria, yeasts and filamentous fungi. The highest biological activity show 5-chlorosalicylate compounds.     

Dehydration of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O studied by in situ Synchrotron X‐ray Powder Diffraction and Thermal Analyses

Dehydration is an important process which affects the chemical, physical and mechanical properties of materials. This article describes the thermal dehydration and decomposition of the Sorel cement phase 3Mg(OH)₂ · MgCl₂ · 8H₂O, studied by in situ synchrotron X‐ray powder diffraction and thermal analyses. Attention is paid on the determination of the chemical composition and crystal structure of the lower hydrates, identified as the phases 3Mg(OH)₂ · MgCl₂ · 5.4H₂O and 3Mg(OH)₂ · MgCl₂ · 4.6H₂O. The crystal structure of 3Mg(OH)₂ · MgCl₂ · 4.6H₂O is solved and refined by the Rietveld method and a structural model for the 3Mg(OH)₂ · MgCl₂ · 5.4H₂O phase is given. These phases show statistical distribution of water molecules, hydroxide and chloride anions positioned as ligands on the magnesium octahedra. A structural scheme of the temperature induced transformations in the thermal range from 25 to 500 °C is presented.     

Synthesis and Study of Rubidium Hexauranate Rb2[(UO2)6O3(OH)8]·6H2O and Products of Its Heat Decomposition

The interaction of hydrated uranium(VI) oxide UO₃·2.25H₂O (schoepite) with an aqueous solution of rubidium hydroxide in an autoclave at 100°C has yielded rubidium uranate Rb₂(UO₂)₆O₃(OH)₈·6H₂O. Composition and structure of the obtained compound have been determined by chemical analysis, IR spectroscopy, X-ray diffraction, and differential thermal analysis. The processes of its dehydration and thermal decomposition have been studied.

     

First Evidence for the Existence of Hexafluoroantimonic(V) Acid

By reacting IPr ? InBr₃ with AgSbF₆ in dichloroethane at room temperature, we could obtain single crystals comprising [{(IPr ? InBr₃)(Ag ? (CH₂Cl)₂)}₂][SbF₆]₂ ( 1 ) and two identical HSbF₆ units. It is presumed that the reaction gave rise to [IPr ? InBr_3?x][SbF₆]_x (x=1, 2, or 3) which reacted with adventitious water to give HSbF₆ and [IPr ? InBr_3?x(OH)][SbF₆]_x?1. The experiment was reproduced at 60 °C, eventually leading to the indium hydroxide [{IPr ? In(OH)_0.5(H₂O)_4.5}₂][SbF₆]₅ ( 2 ).     

Chemistry of borate in salt lake brine (XXXIV)

The crystallization processes of hydrated Mg-borates, boric, magnesium hydroxide and Mg-oxychloride from MgO-B₂O₃-18%MgCl₂-H₂O supersaturated solution at 20°C have been studied by kinetic method. The crystallization solid phases were characterized by X-ray powder diffraction, IR spectra, thermal analysis and chemical analysis. The liquid-solid phase diagram of thermodynamic nonequilibrium state has been given. In this phase diagram, there exist eight crystallization fields, boric acid(H₃BO₃), trigomagneborite(MgO · 3B₂O₃ · 7.5H₂O, MgO · 3B₂O₃ · 7H₂O), hungchaoite(MgO · 2B₂O₃ · 9H₂O), inderite(2MgO · 3B₂O₃ · 15H₂O), chloropinnoite(2MgO · 2B₂O₃ · MgCl₂ · 14H₂O), magnesium hydroxide(Mg(OH)₂) and magnesium oxychloride (5Mg(OH)₂ · MgCl₂ · 8H₂O).     

Pb(II) and Mn(II) Coordination Compounds Involving 5,5′‐(1,4‐Phenylene)bis(1H‐tetrazole):Synthesis,Characterization, and Effect on Thermal Decomposition of Ammonium Perchlorate

Two coordination compounds [Pb₄(BDT)₃(OH)₂(H₂O)₄]·H₂O ( 1 ) and [Mn(H₂O)₆]·(HBDT)₂·2H₂O ( 2 ) [H₂BDT?5,5′‐(1,4‐phenylene)bis(1H‐tetrazole)] had been hydrothermally synthesized. 1 and 2 had been characterized by single‐crystal X‐ray diffraction, IR, elemental and thermal analyses. Structural analysis reveals that 1 exhibits 2D layer structure extended through BDT with two different coordination modes rings in transverse and vertical. 2 consists of [Mn(H₂O)₆]²⁺, free HBDT and water. In addition, 1 and 2 were explored as luminescent materials and additives to promote the thermal decomposition of ammonium perchlorate by differential scanning calorimetry.     

Synthesis of magnesium oxychloride nanorods with controllable morphology and their transformation to magnesium hydroxide nanorods via treatment with sodium hydroxide

In this paper, the formation of magnesium oxychloride (Mg_x(OH)_yCl_z·nH₂O) nanorods from the system MgO-MgCl₂-H₂O is investigated thoroughly. By systematically changing the adding amounts of the three starting materials, short nanorods (<1 μ) or long nanorods (up to 20 μ) were obtained readily with the aspect ratio in the range of 10–70. The mechanism of the crystal growth and the change of the crystal phase from 5Mg(OH)₂·MgCl₂·8H₂O (phase 5) to 3Mg(OH)₂·MgCl₂·8H₂O (phase 3) is also discussed. The products were characterized by transmission electron microscopy X-ray diffraction, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis. The resulting magnesium oxychloride nanorods were further transformed to magnesium hydroxide (Mg(OH)₂) nanorods with the shape remained by treating with NaOH at room temperature. The results shown in this paper indicate a facile pathway to produce magnesium oxychloride or magnesium hydroxide nanorods with controllable morphology on large scale.     

Isothermal and rising temperature kinetic studies of doped nonstoichiometric basic nickel carbonate

The techniques of thermal analysis are used to determine the mode of decomposition of nickel carbonates doped by the method of coprecipitation. Nickel carbonate prepared by this method is basic in nature with the stoichiometryxNiCO₃·yNi(OH)₂·zH₂O. Isothermal Thermogravimetry was applied to determine the mechanism of decomposition. Rising temperature Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) were used to study the effects of doping on the kinetics of the decomposition. Doping was found to strongly influence the kinetics of the decomposition. The kinetics of thermal decomposition of the doped carbonates were compared with conductivity studies. A compensation effect has been observed and is discussed, in the thermal decomposition of the doped nickel carbonates. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Mass spectrometric and thermal analyses of the salt system Zn<Subscript>2</Subscript>(OH)<Subscript>2</Subscript>CO<Subscript>3</Subscript> · <Emphasis Type="Italic">x</Emphasis>H<Subscript>2</Subscript>O-NaCl

The gas phase over nanocomposites consisting of zinc carbonate hydroxide (ZCH) Zn₂(OH)₂CO₃ · xH₂O(x = 1, 3) dispersed in a NaCl matrix has been characterized by high-temperature mass spectrometry and on-line FTIR spectroscopy coupled with thermal analysis. Volatile zinc-sodium chloro complexes are in equilibrium with ZCH-rich nanocomposites at 20–700°C under mass spectrometric conditions. This is evidence that sodium chloride reacts readily with zinc oxide nanoparticles. The thermal events in the ZCH-NaCl (Li₂CO₃) system have been investigated by differential scanning calorimetry.     

Synthesis and Thermal Study of Magnesium Complexes with 8-hydroxyquinolinate Derivatives

Magnesium ion was reacted with 5,7-dibromo-, 5,7-dichloro-, 7-iodo-and 5-chloro-7-iodo-8-hydroxyquinoline, in acetone/ammonium hydroxide medium under constant stirring to obtain (I) Mg[(C₉H₄ONBr₂)₂]·2H₂O; (II) Mg[(C₉H₄ONCl₂)₂]·3H₂O; (III) Mg[(C₉H₅ONI)₂]·2H₂O and (IV)Mg[(C₉H₄ONICl)₂]·2.5H₂O complexes. The compounds were characterized by elemental analysis, IR spectra, ICP, TG-DTA and DSC. Through thermal decomposition residues were obtained and characterized, by X-ray diffractometry, as a mixture of hexagonal MgBr₂ and cubic MgO to the (I) compound at 850°C; cubic MgO to the (II), (III) and (IV) compounds at750, 800 and 700°C, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nonanatrium-bis(hexahydroxoaluminat)-trihydroxid-hexahydrat (Na9[Al(OH)6]2(OH)3 · 6H2O) – Kristallstruktur,NMR-Spektroskopie und thermisches Verhalten

Nonasodium Bis(hexahydroxoaluminate) Trihydroxide Hexahydrate (Na₉[Al(OH)₆]₂(OH)₃ · 6H₂O) – Crystal Structure, NMR Spectroscopy and Thermal Behaviour The crystal structure of the nonasodium bis(hexahydroxoaluminate) trihydroxide hexahydrate Na₉[Al(OH)₆]₂(OH)₃ · 6H₂O (4.5 Na₂O Al₂O₃ · 13.5 H₂O) (up to now described as 3 Na₂O · Al₂O₃ · 6H₂O, 4Na₂O · Al₂O₃ · 13 H₂O and [3 Na₂O · Al₂O₃ · 6H₂O] [xNaOH · yH₂O], respectively) was solved. The X-ray single crystal diffraction analysis (triclinic, space group P1 , a = 8.694(1) Å, b = 11.344(2) Å, c = 11.636(3) Å, α = 74.29(2)°, β = 87.43(2)°, γ = 70.66(2)°, Z = 2) results in a structure, consisting of monomeric [Al(OH)₆]^3? aluminate anions, which are connected by NaO₆ octahedra groups. Furthermore the structure contains both, two hydroxide anions only surrounded by water of crystallization and OH groups of [Al(OH)₆]^3? aluminate anions and a hydroxide anion involved in three NaO₆ coordination octahedra directly and moreover connected with a water molecule by hydrogen bonding. The results of ²⁷Al and ²³Na-MAS-NMR investigations, the thermal behaviour of the compound and possible relations between the crystal structure and the conditions of coordination in the corresponding sodium aluminate solution are discussed as well.     

Chimie douce preparation of CuxZn3−xV2O7(OH)2·yH2O isostructural to trigonal zinc pyrovanadate

New Cu_xZn_3−xV₂O₇(OH)₂·yH₂O (0 < x ≤ 1.5) isostructural to zinc pyrovanadate Zn₃V₂O₇(OH)₂·2H₂O, were successfully prepared by using a chimie douce technique. The method consists in mixing zinc nitrate and copper nitrate with a boiling solution of vanadium oxide (obtained by reacting V₂O₅ with few millilitres of 30 vol.% H₂O₂ followed by addition of distilled water). When ammonium hydroxide NH₄OH 10% was added (pH ≈ 6), a precipitate was obtained. Using powder X-ray diffraction data, the crystal structures of as-prepared samples were determined by Rietveld refinement. Copper substitutes zinc in the zinc pyrovanadate lattice and is found to introduce distortion in the structure, which is mainly due to the Jahn–Teller effect. Distortion becomes more pronounced when the amount of copper is increased. This restricts the amount of copper which can be incorporated in the hexagonal zinc pyrovanadate lattice.     

CaNa[Cr(OH)6] – A Layered Hydroxochromate(III) with Ordered Brucite Structure and its Thermal Decomposition

Green single-crystals of the hydroxochromate(III) CaNa[Cr(OH)₆] were grown under highly alkaline hydrothermal conditions at about 200 °C. The starting materials Ca(NO₃)₂ · 6H₂O and Cr(NO₃)₃ · 9H₂O were reacted in a mixture of water and sodium hydroxide with the molar ratio of 2.8:1. CaNa[Cr(OH)₆] crystallizes in the non-centrosymmetric trigonal space group R3 with the lattice parameters a = 583.86(2) pm and c = 1428.73(6) pm [T = 100(1) K]. Characteristically, the crystals are reverse-obverse as well as inversion twins. The crystal structure is a stack of uncharged metal hydroxide layers, which can be regarded as a cation-ordered rhombohedral variant of the Mg(OH)₂ (brucite) structure type. The oxidation state of chromium(III) and its coordination by hydroxide groups was confirmed by UV/Vis and IR spectroscopy, respectively. Temperature-dependent magnetic measurements revealed paramagnetic behavior with an effective moment of 3.82 μ_B per chromium atom. The thermal decomposition of CaNa[Cr(OH)₆] takes place at about 225 °C, where the fast elimination of 1.5 equivalents of water is followed by the oxidation of chromium(III) to chromium(VI). Upon further heating to 1000 °C and 1200 °C, the intermediate decomposition products CaCrO₄ and Na₂CrO₄ transform into the oxochromates(V) Ca₅(CrO₄)₃O_0.5 and Ca₃(CrO₄)₂, respectively.     

The Non‐Isothermal Decomposition Kinetics of NaNTO·H2O and the Relationship between its Structure and Properties

NaNTO·H₂O was prepared by mixing 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) aqueous solution and sodium hydroxide aqueous solution. Its thermal decomposition and kinetics were studied under non‐isothermal conditions by DSC and TG/DTG methods. The kinetic parameters were obtained from analysis of the DSC and TG/DTG curves by the Kissinger method, the Ozawa method, the differential method and the integral method. The most probable mechanism function for the thermal decomposition of the first stage was suggested by comparing the kinetic parameters. The critical temperature of thermal explosion (T_b) was 240.93 °C. The theoretical investigation on the structure unit of the title compound was carried out by DFT‐B3LYP/CEP‐31G methods; atomic net charges and the population analysis were discussed.     

Reaction of bismuth nitrate with sodium citrate in water-glycerol solutions

The reaction in a Bi(NO₃)₃-Na₃Hcit-(H₂O + glycerol) system was studied in a wide range of component ratios by the solubility method and pH-metry in combination with chemical analysis of solid phases. Poorly soluble phases of Bi(Hcit) _x (OH)_{3(1 − x)} · mH₂O (x < 1) and sodium bismuth citrate NaBiCit · 3H₂O were obtained. The compounds synthesized were characterized, and their compositions were refined by X-ray diffraction, DTG, and IR spectroscopy.     

Kinetic and thermodynamic studies of MgHPO<Subscript>4</Subscript> · 3H<Subscript>2</Subscript>O by non-isothermal decomposition data

The thermal decomposition of magnesium hydrogen phosphate trihydrate MgHPO₄ · 3H₂O was investigated in air atmosphere using TG-DTG-DTA. MgHPO₄ · 3H₂O decomposes in a single step and its final decomposition product (Mg₂P₂O₇) was obtained. The activation energies of the decomposition step of MgHPO₄ · 3H₂O were calculated through the isoconversional methods of the Ozawa, Kissinger–Akahira–Sunose (KAS) and Iterative equation, and the possible conversion function has been estimated through the Coats and Redfern integral equation. The activation energies calculated for the decomposition reaction by different techniques and methods were found to be consistent. The better kinetic model of the decomposition reaction for MgHPO₄ · 3H₂O is the F _1/3 model as a simple n-order reaction of “chemical process or mechanism no-invoking equation”. The thermodynamic functions (ΔH*, ΔG* and ΔS*) of the decomposition reaction are calculated by the activated complex theory and indicate that the process is non-spontaneous without connecting with the introduction of heat.     

Über die komplexen Hydroxide des Chroms: Na9[Cr(OH)6]2(OH)3 · 6 H2O und Na4[Cr(OH)6]X · H2O (X = Cl, (S2)1/2) – Synthese,Kristallstruktur und thermisches Verhalten

Complex Hydroxides of Chromium: Na₉[Cr(OH)₆]₂(OH)₃ · 6 H₂O and Na₄[Cr(OH)₆]X · H₂O (X = Cl, (S₂)_1/2) – Synthesis, Crystal Structure, and Thermal Behaviour Green plate‐like crystals of Na₉[Cr(OH)₆]₂(OH)₃ · 6 H₂O (triclinic, P1, a = 872.9(1) pm, b = 1142.0(1) pm, c = 1166.0(1) pm, α = 74.27(1)°, β = 87.54(1)°, γ = 70.69(1)°) are obtained upon slow cooling of a hot saturated solution of Cr^III in conc. NaOH (50 wt%) at room temperature. In the presence of chloride or disulfide the reaction yields green prismatic crystals of Na₄[Cr(OH)₆]Cl · H₂O (monoclinic, C2/c, a = 1138.8(2) pm, b = 1360.4(1) pm, c = 583.20(7) pm, β = 105.9(1)°) or green elongated plates of Na₄[Cr(OH)₆](S₂)_1/2 · H₂O (monoclinic, P2₁/c, a = 580.8(1) pm, b = 1366.5(3) pm, c = 1115.0(2) pm, β = 103.71(2)°), respectively. The latter compounds crystallize in related structures. All compounds can be described as distorted cubic closest packings of the anions and the crystal water molecules with the cations occupying octahedral sites in an ordered way. The thermal decomposition of the compounds was investigated by DSC/TG or DTA/TG and high temperature X‐ray powder diffraction measurements. In all cases the final decomposition product is NaCrO₂.     

三水合希土氯化物(镨、钆)与18－冠－6配合物的热化学研究

制备了ＲＥＣｌ３．３Ｈ２Ｏ（ＲＥ＝Ｐｒ，Ｇｄ）与１８Ｃ６的固态配合物，其化学组成为：ＲＥＣｌ３，１８Ｃ６．３Ｈ２Ｏ。对其进行了ＩＲ，溶解度、ＤＴＧ和ＴＧ分析，推测了热分解机理，测量了２９８．１５Ｋ时１８Ｃ６及两种配合物在无水乙醇中的积分，及ＲＥＣｌ３，３Ｈ２Ｏ在１８Ｃ６－Ｃ２Ｈ２ＯＨ溶液中的溶解配位热效应，依据本文所设计的热化学循环，求得了ＲＥＣｌ３，３Ｈ２Ｏ（ｓ）与１８Ｃ６（ｓ）生成ＲＥＣｌ３，