Hochdrucksynthese von Carbonaten. VI. Natrium-Lanthanoid-Carbonate

High Pressure Syntheses of Carbonates. VI. Sodium Lanthanoid Carbonates The ternary carbonates NaLn(CO₃)₂ with Ln = La to Lu and Y are synthesized by dehydration of NaLn(CO₃)₂ · xH₂O or by reaction of Na₂CO₃ with Ln₂(C₂O₄)₃ · xH₂O under 3000 bar CO₂ and 350–500°C. Two structures are found, characterized by IR and X-ray investigations and by thermal decomposition.     

热分析与气相色谱联用研究一水合草酸氢钾

用热分析与气相色谱联用技术(TA-GC)研究KHC₂O₄·H₂O的热分解表明,在空气和氦气当中,开始时缓慢分解,放出结晶水。接着KHC₂O₄快速分解成K₂C₂O₄,并释放出一些气体产物：O₂(分解初期)、CO、CO₂和H₂O。讨论了KHC₂O₄的分解机理。     

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.     

Thermal decomposition of synthetic hydrotalcites reevesite and pyroaurite

A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of synthetic hydrotalcites reevesite (Ni₆Fe₂(CO₃)(OH)₁₆·4H₂O) and pyroaurite (Mg₆Fe₂(SO₄,CO₃)(OH)₁₆·4H₂O) and the cationic mixtures of the two minerals. XRD patterns show the hydrotalcites are layered structures with interspacing distances of around 8.0. Å. A linear relationship is observed for the d(001) spacing as Ni is replaced by Mg in the progression from reevesite to pyroaurite. The significance of this result means the interlayer spacing in these hydrotalcites is cation dependent. High resolution thermal analysis shows the decomposition takes place in 3 steps. A mechanism for the thermal decomposition is proposed based upon the loss of water, hydroxyl units, oxygen and carbon dioxide.     

Graphit-hexachloroplatinat(IV) und Platin(IV)-chlorid-Graphit. Übergang eines Graphitsalzes in eine Metallchlorid-Graphitverbindung

Graphite hexachloro-platinate(IV) and platinum(IV) chloride graphite. Transition of a graphite salt into a metal chloride-graphite compound Whereas graphite does not react with PtCl₄ in Cl₂ atmosphere up to 350°C, with H₂PtCl₆ · xH₂O at 150°C graphite hexachloroplatinate (third intercalation stage) is obtained. The thermal decomposition of the graphite salt gives PtCl₄-graphite with the composition near [C₄₂]_Gr · PtCl_4,3.     

The study of thermal decomposition kinetics of zinc oxide formation from zinc oxalate dihydrate

This study is devoted to the thermal decomposition of ZnC₂O₄·2H₂O, which was synthesized by solid-state reaction using C₂H₂O₄·2H₂O and Zn(CH₃COO)₂·2H₂O as raw materials. The initial samples and the final solid thermal decomposition products were characterized by Fourier transform infrared and X-ray diffraction. The particle size of the products was observed by transmission electron microscopy. The thermal decomposition behavior was investigated by thermogravimetry, derivative thermogravimetric and differential thermal analysis. Experimental results show that the thermal decomposition reaction includes two stages: dehydration and decomposition, with nanostructured ZnO as the final solid product. The Ozawa integral method along with Coats–Redfern integral method was used to determine the kinetic model and kinetic parameters of the second thermal decomposition stage of ZnC₂O₄·2H₂O. After calculation and comparison, the decomposition conforms to the nucleation and growth model and the physical interpretation is summarized. The activation energy and the kinetic mechanism function are determined to be 119.7 kJ mol^?1 and G(α) = ?ln(1 – α)^1/2, respectively.     

Influence of gas media on the thermal decomposition of second valence iron sulphates

FeSO₄·H₂O and FeSO₄ represent the second valence of iron sulphates. Number of studies has been done to understand formation of intermediate sulphates like FeOHSO₄ and Fe₂O(SO₄)₂, representing the oxidation of Fe²⁺ to Fe³⁺. At selected temperatures, both the thermo-dynamical equilibrium in the Fe–S–O system and the formation of the crystal structures in the solid phase are controlled by the partial pressure of water vapour and oxygen in the gas phase. The effects of the temperature and the partial pressure of gas components on the solid-phase content are demonstrated by phase diagrams. The study puts the accent on the influence of oxygen content in gas environment on processes of thermal decomposition of FeSO₄·H₂O and FeSO₄. At three quantities of oxygen content—0% (100% Ar), 21% (dry air) and 100% (pure O₂) the processes of oxidation and formatting metastable iron sulphates were examined by several experimental techniques. The thermal decomposition of samples was investigated by TG–DTG–DTA method in the temperature range 293–1400 K. Partial pressure of water vapour was determined by the quantity of water released from dehydration process of FeSO₄·H₂O. Infrared spectroscopy, Mössbauer spectroscopy and X-Ray powder diffraction method were used for identification of the new formed solid structures and for characterization of the content of the iron sulphates with different valencies of iron. The experimental data and their analyses give the possibility to determine the different stages of decomposition, related to the formation of intermediates. Depending on gas environment, the basic relationships for reaction kinetics is drawn. It is demonstrated on that correlation exists between the kinetic’s parameters and the content of oxygen in the gas phase.     

Heterogene Reactionen fester Nickel(II)-Komplexe. XXI. Thermische Zersetzung und Stereochemie der Thiocyanato-Nickel(II)-Komplexe mit Pyridin-N-Oxid und Methylsubstituierten Pyridin-N-Oxiden

Heterogeneous Reactions of Solid Nickel(II) Complexes. XXI. Thermal Decomposition and Sterochemistry of Thiocyanato-Nickel(II) Complexes with Pyridine N-Oxide and Methylsubstituted Pyridine N-Oxides The thermal decomposition was studied for the complexes: Ni(NCS)₂(pyNO)₃ · H₂O (I), (pyNO = pyridine N-oxide), Ni(NCS)₂(2-MepyNO)₃ (II) Me = Methyl, Ni(NCS)₂(3-MepyNO)₂ · C₂H₅OH (III) and Ni(NCS)₂(4-MepyNO)₂ · H₂O (IV). On heating the solvent molecules bonded escape and then the decomposition of heterocyclic ligands sets in. The spectral and magnetic data indicate a pseudooctahedral configuration of the starting complexes as also of Ni(NCS)₂(pyNO)₃ (V), Ni(NCS)₂(3-MepyNO)₂ (VI) and Ni(NCS)₂(4-MepyNO)₂ (VII), i. e. of the initial complexes without the solvent molecules. For complexes of the type of [Ni(NCS)₂L₃] · xH₂O (L = pyNO, x = 0, 1; L = 2-MepyNO and x = 0) a dimeric structure is assumed, while for those of the type of [Ni(NCS)₂L₂] · xH₂O (C₂H₅OH) (L = 3-MepyNO and 4-MepyNO, x = 0 or 1) a polymeric structure is supposed.     

Selective self-assembly synthesis of MnV2O6·4H2O with controlled morphologies and study on its thermal decomposition

The MnV₂O₆·4H₂O with rod-like morphologies was synthesized by solid-state reaction at low heat using MnSO₄·H₂O and NH₄VO₃ as raw materials. XRD analysis showed that MnV₂O₆·4H₂O was a compound with monoclinic structure. Magnetic characterization indicated that MnV₂O₆·4H₂O and its calcined products behaved weak magnetic properties. The thermal process of MnV₂O₆·4H₂O experienced three steps, which involves the dehydration of the two waters of crystallization at first, and then dehydration of other two waters of crystallization, and at last melting of MnV₂O₆. In the DSC curve, the three endothermic peaks were corresponding to the two steps thermal decomposition of MnV₂O₆·4H₂O and melting of MnV₂O₆, respectively. Based on the Kissinger equation, the average values of the activation energies associated with the thermal decomposition of MnV₂O₆·4H₂O were determined to be 55.27 and 98.30?kJ?mol^?1 for the first and second dehydration steps, respectively. Besides, the thermodynamic function of transition state complexes (??H ^??, ??G ^?? , and ??S ^?? ) of the decomposition reaction of MnV₂O₆·4H₂O were determined.     

Humidity controlled thermal analysis

The low temperature formation of crystalline zinc oxide via thermal decomposition of zinc acetylacetonate monohydrate C₁₀H₁₄O₄Zn·H₂O was studied by humidity controlled thermal analysis. The thermal decomposition was investigated by sample-controlled thermogravimetry (SCTG), thermogravimety combined with evolved gas analysis by mass spectrometry (TG-MS) and simultaneous differential scanning calorimetry and X-ray diffractometry (XRD-DSC). Decomposition of C₁₀H₁₄O₄Zn·H₂O in dry gas by linear heating began with dehydration around 60°C, followed by sublimation and decomposition above 100°C. SCTG was useful because the high-temperature parallel decompositions were inhibited. The decomposition changed with water vapor in the atmosphere. Formation of ZnO was promoted by increasing water vapor and could be synthesized at temperatures below 100°C. XRD-DSC equipped with a humidity generator revealed that C₁₀H₁₄O₄Zn·H₂O decomposed directly to the crystalline ZnO by reacting with water vapor.     

Complexes of dicamba with cadmium(II), copper(II), mercury(II), lead(II) and zinc(II)

New solid complexes of a herbicide known as dicamba (3,6-dichloro-2-methoxybenzoic acid) with Pb(II), Cd(II), Cu(II) and Hg(II) of the general formula M(dicamba)₂·xH₂O (M=metal, x=0-2) and Zn₂(OH)(dicamba)₃·2H₂O have been prepared and studied. The complexes have different crystal structures. The carboxylate groups in the lead, cadmium and copper complexes are bidentate, chelating, symmetrical, in Hg(dicamba)₂·2H₂O - unidentate, and in the zinc salt - bidentate, bridging, symmetrical. The anhydrous compounds decompose in three stages, except for the lead salt whose decomposition proceeds in four stages. The main gaseous decomposition products are CO₂, CH₃OH, HCl and H₂O. Trace amounts of compounds containing an aromatic ring were also detected. The final solid decomposition products are oxychlorides of metals and CuO. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of barium(II) tetraphenylborate

Barium(II) tetraphenylborate, Ba(Bph₄))₂·4H₂O was prepared, and its decomposition mechanism was studied by means of TG and DTA. The products of thermal decomposition were examined by means of gas chromatography and chemical methods. A kinetic analysis of the first stage of thermal decomposition was made on the basis of TG and DTG curves and kinetic parameters were obtained from an analysis of the TG and DTG curves using integral and differential methods. The most probable kinetic function was suggested by comparison of kinetic parameters. A mathematical expression was derived for the kinetic compensation effect.     

The thermal decomposition of ammonium heptamolybdate

The thermal decomposition of ammonium heptamolybdate has been investigated by TG. The decomposition is discussed, making use of additional information obtained from isothermal studies, X-ray and IR measurements. The formation of two new compounds, namely (NH₄)₂O · 14 MoO₃ and (NH₄)₂O · 22 MoO₃, prior to the formation of MoO₃ is detected, as well as the main intermediate compounds (NH₄)₂O · 2.5 MoO₃ or (NH₄)₂O · 3 MoO₃ (according to the water content of the starting material) and (NH₄)₂O · 4 MoO₃.     

Thermal Behaviour of Some Polyhydrocarboxylic Coordination Compounds with Neodium

New Nd-Co based polynuclear coordination compounds containing as ligand polyhydrocarboxylic acid as tartaric, malic and gluconic acids were prepared, namely: [NdCo(tart)₃]·4H₂O, (NH₄)[NdCo_0.5Cu_0.5(tart)₃]·4H₂O, (NH₄)[NdCo(malic)₃]·4H₂O, (NH₄)[NdCo_0.5Cu_0.5(malic)₃]·4H₂O, [NdCo(gluc)₄]·4H₂O and [Nd₂CoCu(gluc)₇]·5H₂O. A comparison between the thermal behaviour of the studied polynuclear coordination compounds concerning thermal stability and thermal decomposition stoichiometry was inferred. Oxalic and malonic intermediates were identified at about 300°C in the thermal decomposition of tartaric and malic compounds. In all the decomposition processes at about 400°C the presence of oxocarbonate is shown. The residual products are mixed oxides of perovskite type. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

Study on the non-isothermal kinetics of decomposition of 4Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>·2H<Subscript>2</Subscript>O<Subscript>2</Subscript>·NaCl

The non-isothermal decomposition kinetics of 4Na₂SO₄·2H₂O₂·NaCl have been investigated by simultaneous TG-DSC in nitrogen atmosphere and in air. The decomposition processes undergo a single step reaction. The multivariate nonlinear regression technique is used to distinguish kinetic model of 4Na₂SO₄·2H₂O₂·NaCl. Results indicate that the reaction type Cn can well describe the decomposition process, the decomposition mechanism is n-dimensional autocatalysis. The kinetic parameters, n, A and E are obtained via multivariate nonlinear regression. The n ^th-order with autocatalysis model is used to simulate the thermal decomposition of 4Na₂SO₄·2H₂O₂·NaCl under isothermal conditions at various temperatures. The flow rate of gas has little effect on the decomposition of 4Na₂SO₄·2H₂O₂·NaCl.     

Specific features of absorption of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, and Pb<Superscript>2+</Superscript> cations from aqueous solutions by calcium phosphates

Kinetic characteristics of the interaction of trisubstituted calcium phosphate Ca₃(PO₄)₂ · xH₂O with Cu²⁺, Zn²⁺, Co²⁺, and Pb²⁺ ions in aqueous solutions were studied.     

Eine Kristalline Kieselsäure mit hoher Einlagerungsfähigkeit

Crystalline Silicic Acid with Distinct Intracrystalline Reactivity The crystalline silicic acid H₂Si₂₀O₄₁ · xH₂O is obtained from its alkali and alkaline-earth salts by cation exchange. The crystalline silicic acid and its salts form layered host lattiees which interealate many organic compounds. The increased intracrystalline reactivity and the reversible swelling in water distinguish H₂Si₂₀O₄₁ · xH₂O from the other silicic acids. Differences between samples of H₂Si₂₀O₄₁ · xH₂O are detected by intracrystalline reactions more clearly than by X-ray diffraction studies. Thermal dehydration at about 150°C gives Siliea-X, a partially dehydrated form (about SiO₂ · 0,09 H₂O). The aggregation of the plate-like crystals to spherical aggregates provides an interesting material for interface reactions.     

Research on thermal decomposition of trinitrophloroglucinol salts by DSC, TG and DVST

The thermal decomposition of the four nitrogen-rich salts of ammonia (NH₄), aminoguanidine (AG), carbohydrazide (CHZ) and 5-aminotetrazo (ATZ) based on trinitrophloroglucinol (H₃TNPG) was investigated using the differential scanning calorimetry (DSC), thermogravity (TG), and dynamic vacuum stability test (DVST). DSC and TG methods research the complete decomposition, while DVST method researches the very early reaction stage. The peak temperatures of DSC curves are consistent with the temperatures of maximum mass loss rates of TG curves. The apparent activation energies of these H₃TNPG-based salts obtained by DSC and DVST have the same regularity, i.e., (ATZ)(H₂TNPG)·2H₂O < (CHZ)(HTNPG)·0.5H₂O < NH₄(H₂TNPG) < (AG)(H₂TNPG). The thermal stability order is (ATZ)(H₂TNPG)·2H₂O < (CHZ)(HTNPG)·0.5H₂O < (AG)(H₂TNPG) < NH₄(H₂TNPG), which was evaluated by DVST according to the evolved gas amount of thermal decomposition. DVST can monitor the real-time temperature and pressure changes caused by thermal decomposition, dehydration, phase transition and secondary reaction, and also evaluate the thermal stability and kinetics.      

Products and kinetics of non-isothermal decomposition of vanadium(IV) oxide compounds

The kinetics of dehydration and decomposition of VOSO₄·2H₂O, VOSO₄ and VOSeO₃·H₂O was studied under non-isothermal heating on a derivatograph. The stages and products of the thermal decomposition were determined. It was proved that VOSO₄·2H₂O decomposes to V₂O₅ while VOSeO₃·H₂O − to V₂O₄. A number of kinetic models and calculation procedures were used to determine the values of the kinetic parameters characterizing the process. The parameters calculated were compared and analyzed. IR-spectra of the initial substances and the solid residue after decomposition are presented.