New Structure Type among Octahydrated Rare‐Earth Sulfates, β‐Ce2(SO4)3·8H2O,and a new Ce2(SO4)3·4H2O Polymorph

Syntheses, crystal structures and thermal behavior of two new hydrated cerium(III) sulfates are reported, Ce₂(SO₄)₃·4H₂O ( I ) and β‐Ce₂(SO₄)₃·8H₂O ( II ), both forming three‐dimensional networks. Compound I crystallizes in the space group P2₁/n. There are two non‐equivalent cerium atoms in the structure of I , one nine‐ and one ten‐fold coordinated to oxygen atoms. The cerium polyhedra are edge sharing, forming helically propagating chains, held together by sulfate groups. The structure is compact, all the sulfate groups are edge‐sharing with cerium polyhedra and one third of the oxygen atoms, belonging to sulfate groups, are in the S–Oμ₃–Ce₂ bonding mode. Compound II constitutes a new structure type among the octahydrated rare‐earth sulfates which belongs to the space group Pn. Each cerium atom is in contact with nine oxygen atoms, these belong to four water molecules, three corner sharing and one edge sharing sulfate groups. The crystal structure is built up by layers of [Ce(H₂O)₄(SO₄)]_nⁿ⁺ held together by doubly edge sharing sulfate groups. The dehydration of II is a three step process, forming Ce₂(SO₄)₃·5H₂O, Ce₂(SO₄)₃·4H₂O and Ce₂(SO₄)₃, respectively. During the oxidative decomposition of the anhydrous form, Ce₂(SO₄)₃, into the final product CeO₂, small amount of CeO(SO₄) as an intermediate species was detected.     

Infrarotspektroskopische und thermoanalytische Untersuchung von Trikobalt(II)-dihydroxidsulfat-dihydrat,Co3(OH)2(SO4)2 · 2H2O

The infrared spectra between 600 and 4000 cm^?1 of Co₃(OH)₂(SO₄)₂ · 2H₂O, Co₃(OH)₂(SO₄)₂, and Co₃(OD)₂(SO₄)₂ · 2D₂O are reported and discussed. The spectra are mainly examined in relation to the binding state of the water molecules. The results are in good agreement with the previously described crystal structure studies. Thermogravimetry, differential thermal analysis and X-ray diffraction methods were used to investigate the unusual thermal decomposition behaviour of Co₃(OH)₂(SO₄)₂ · 2H₂O. The kinetics of the dehydration reaction 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.     

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.     

Synthese,Kristallstrukturen und thermisches Verhalten von Er2(SO4)3 · 8 H2O und Er2(SO4)3 · 4 H2O

Syntheses, Crystal Structures, and Thermal Behavior of Er₂(SO₄)₃ · 8 H₂O and Er₂(SO₄)₃ · 4 H₂O Evaporation of aqueous solutions of Er₂(SO₄)₃ yields light pink single crystals of Er₂(SO₄)₃ · 8 H₂O. X-ray single crystal investigations show that the compound crystallizes monoclinically (C2/c, Z = 8, a = 1346.1(3), b = 667.21(1), c = 1816.2(6) pm, β = 101.90(3)°, R_all = 0.0169) with eightfold coordination of Er³⁺, according to Er(SO₄)₄(H₂O)₄. DSC- and temperature dependent X-ray powder investigations show that the decomposition of the hydrate follows a two step mechanism, firstly yielding Er₂(SO₄)₃ · 3 H₂O and finally Er₂(SO₄)₃. Attempts to synthesize Er₂(SO₄)₃ · 3 H₂O led to another hydrate, Er₂(SO₄)₃ · 4 H₂O. There are two crystallographically different Er³⁺ ions in the triclinic structure (P 1, Z = 2, a = 663.5(2), b = 905.5(2), c = 1046.5(2) pm, α = 93.59(3)°, β = 107.18(2)°, γ = 99.12(3)°, R_all = 0.0248). Er(1)³⁺ is coordinated by five SO₄^2– groups and three H₂O molecules, Er(2)³⁺ is surrounded by six SO₄^2– groups and one H₂O molecule. The thermal decomposition of the tetrahydrate yields Er₂(SO₄)₃ in a one step process. In both cases the dehydration produces the anhydrous sulfate in a modification different from the one known so far.     

Tribochemistry and kinetics of Al2(SO4)3·xH2O decomposition

The thermal decomposition of tribochemically activated Al₂(SO₄)₃·xH₂O was studied by TG, DTA and EMF methods. For some of the intermediate solids, X-ray diffraction and IR-spectroscopy were applied to learn more about the reaction mechanism. Thermal and EMF studies confirmed that, even after mechanical activation of Al₂(SO₄)₃·xH₂O, Al₂O(SO₄)₂ is formed as an intermediate. Isothermal kinetic experiments demonstrated that the thermochemical sulphurization of inactivated Al₂(SO₄)₃·xH₂O has an activation energy of 102.2 kJ·mol^?1 in the temperature range 850–890 K. The activation energy for activated Al₂(SO₄)₃·xH₂O in the range 850–890 K is 55.0 kJ·mol^?1. The time of thermal decomposition is almost halved when Al₂(SO₄)₃·xH₂O is activated mechanically. The results permit conclusions concerning the efficiency of the tribochemical activation of Al₂(SO₄)₃·xH₂O and the chemical and kinetic mechanisms of the desulphurization process.     

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.     

Glass formation in the Al(IO3)3-Al2(SO4)3-H2O system

Glass-formation boundaries in the Al(IO₃)₃-Al₂(SO₄)₃-H₂O system are determined. The IR spectra of glassy and crystalline Al(IO₃)₃ · 8H₂O samples are measured. The structure and properties of glassy Al(IO₃)₃ · 10H₂O are compared to those of glassy Al₂(SO₄)₃ · 10H₂O.     

Glass formation in the systems Al2(SO4)3-MSO4-H2O (M = Cd2+, Zn2+, Mg2+) and Al2(SO4)3-Fe2(SO4)3-H2O

The glass formation region boundaries were found in the systems Al₂(SO₄)₃-MSO₄-H₂O, where M = Cd²⁺, Zn²⁺, and Mg²⁺, and Al₂(SO₄)₃-Fe₂(SO₄)₃-H₂O. The causes of the differences in glass-forming ability between the studied systems were analyzed. The structures and properties of glassy Al₂(SO₄)₃ · 11H₂O and Fe₂(SO₄)₃ · 11H₂O were compared.     

Synthesis of CeO2 by thermal decomposition of oxalate and kinetics of thermal decomposition of precursor

CeO₂ was synthesized by calcining Ce₂(C₂O₄)₃·8H₂O above 673 K in air. The precursor and its calcined products were characterized using thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectra, X-ray powder diffraction, scanning electron microscopy, and UV–Vis absorption spectroscopy. The result showed that cubic CeO₂ was obtained when the precursor was calcined above 673 K in air for 2 h. The UV–Vis absorption spectroscopy studies showed that superfine CeO₂ behaved as an excellent UV-shielding material. The thermal decomposition of the precursor in air experienced two steps, which are: first, the dehydration of eight crystal water molecules, then the decomposition of Ce₂(C₂O₄)₃ into cubic CeO₂. The values of the activation energies associated with the thermal decomposition of Ce₂(C₂O₄)₃·8H₂O were determined based on the Starink equation.     

Kinetics of the dehydration of CsNd(SO4)2 4 H2O

The kinetics of the dehydration of CsNd(SO₄)₂ · 4 H₂O to CsNd(SO₄)₂ · H₂O and then to CsNd(SO₄)₂ are studied by isothermal weight change. The reactions are phase-boundary-controlled. Reaction mechanism and activation energy depend on sample weight.     

Crystal Structures of [Cu2(bpy)2(H2O)(OH)2(SO4)]·4H2O and [Cu(bpy)(H2O)2]SO4 with bpy = 2, 2′‐Bipyridine

Two sulfato Cu^II complexes [Cu₂(bpy)₂(H₂O)(OH)₂(SO₄)]· 4H₂O ( 1 ) and [Cu(bpy)(H₂O)₂]SO₄ ( 2 ) were synthesized and structurally characterized by single crystal X—ray diffraction. Complex 1 consists of the asymmetric dinuclear [Cu₂(bpy)₂(H₂O)(OH)₂(SO₄)] complex molecules and hydrogen bonded H₂O molecules. Within the dinuclear molecules, the Cu atoms are in square pyramidal geometries, where the equatorial sites are occupied by two N atoms of one bpy ligand and two O atoms of different μ₂—OH groups and the apical position by one aqua ligand or one sulfato group. Through intermolecular O—H···O and C—H···O hydrogen bonds and intermolecular π—π stacking interactions, the dinuclear complex molecules are assembled into layers, between which the hydrogen bonded H₂O molecules are located. The Cu atoms in 2 are octahedrally coordinated by two N atoms of one bpy ligand and four O atoms of two H₂O molecules and two sulfato groups with the sulfato O atoms at the trans positions and are bridged by sulfato groups into ¹[Cu(bpy)(H₂O)₂(SO₄)_2/2] chains. Through the interchain π—π stacking interactions and interchain C—H···O hydrogen bonds, the resulting chains are assembled into bi—chains, which are further interlinked into layers by O—H···O hydrogen bonds between adjacent bichains.     

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.     

Synthesis,Crystal Structure and Magnetic Behaviour of {[Co(dimb)2(H2O)2]·(NO3)2·(H2O)2}n

The title complex {[Co(dimb)₂(H₂O)₂]·(NO₃)₂·(H₂O)₂}_n ( 1 ) (dimb = 1,3‐di(imidazol‐1‐ylmethyl)‐5‐methylbenzene) has been hydrothermally synthesized by the reaction of dimb with Co(NO₃)₂·6H₂O in aqueous solution. The cobalt(II) atoms are linked by bridging dimb ligands to form 2D corrugated and wavy networks containing Co₄(dimb)₄ macrocyclic motifs. Two neighboring independent layers interlinked each other in a parallel fashion to construct three‐dimensional structure by O–H···O, N–H···O and C–H···O hydrogen bonds. Magnetic measurement shows the weak antiferromagnetic interaction with a one‐dimensional chain model in the range of 5–300 K, with J of –0.68 cm⁻¹.     

Darstellung und Eigenschaften von Na2CuII (SO4)2 · 6 H2O

Preparation and Properties of Na₂Cu^II (SO₄)₂ · 6 H₂O The preparation of the complex compound of Na₂Cu(SO₄)₂ · 6 H₂O is described. Its structure and properties were investigated using spectral methods (u.v.-vis., i.r., n.m.r.), by means of X-ray powder diffraction, and by thermal methods. On the basis of experimental results it is suggested that another member of the Tutton salts series has been prepared, appearring isostructural with them and showing the less distorted coordination polyhedron of [Cu(H₂O)₆]²⁺ from them. On its dehydration oxygen atoms from the sulphate groups enter the coordination sphere of Cu^II and the symmetry of SO₄^2? becomes lower. The experimental results indicate that Na₂Cu(SO₄)₂ · 6 H₂O as also Na₂Cu(SO₄)₂ as likewise Na₂Cu(SO₄)₂ · 2 H₂O are monoclinic.     

Dynamic and controlled rate thermal analysis of halotrichite

Three halotrichites namely halotrichite Fe²⁺SO₄·Al₂(SO₄)₃·22H₂O, apjohnite Mn²⁺SO₄·Al₂(SO₄)₃·22H₂O and dietrichite ZnSO₄·Al₂(SO₄)₃·22H₂O, were analysed by both dynamic, controlled rate thermogravimetric and differential thermogravimetric analysis. Because of the time limitation in the controlled rate experiment of 900 min, two experiments were undertaken (a) from ambient to 430 °C and (b) from 430 to 980 °C. For halotrichite in the dynamic experiment mass losses due to dehydration were observed at 80, 102, 319 and 343 °C. Three higher temperature mass losses occurred at 621, 750 and 805 °C. In the controlled rate thermal analysis experiment two isothermal dehydration steps are observed at 82 and 97 °C followed by a non-isothermal dehydration step at 328 °C. For apjohnite in the dynamic experiment mass losses due to dehydration were observed at 99, 116, 256, 271 and 304 °C. Two higher temperature mass losses occurred at 781 and 922 °C. In the controlled rate thermal analysis experiment three isothermal dehydration steps are observed at 57, 77 and 183 °C followed by a non-isothermal dehydration step at 294 °C. For dietrichite in the dynamic experiment mass losses due to dehydration were observed at 115, 173, 251, 276 and 342 °C. One higher temperature mass loss occurred at 746 °C. In the controlled rate thermal analysis experiment two isothermal dehydration steps are observed at 78 and 102 °C followed by three non-isothermal dehydration steps at 228, 243 and 323 °C. In the CRTA experiment a long isothermal step at 636 °C attributed to de-sulphation is observed.     

FeCl2-Na2SO3-H2O system as a basis for recovery of iron(II) sulfite from solution

The FeCl₂-Na₂SO₃-H₂O system was studied along seven sections with the molar ratios Na₂SO₃: FeCl₂ = 5: 1, 5: 2, 5: 3, 5: 4, 5: 5, 5: 10, and 5: 15, including six points on each section where pH ranges from 1.5 to 4.0 in 0.5 steps. Equal-undersedimentation lines for cations and anions were plotted. The iron(II) system forms sodium ferrisulfites NaFe₅O_0.5(SO₃)₅ · 5H₂O, NaHFe₅(SO₃)₆ · 5H₂O, Na₂Fe₅(SO₃)₆ · 4H₂O, and NaHFe₂(SO₃)₃; the iron(III) system forms Na₂Fe₆(SO₃)₇ · 10H₂O. The regions where these compounds sediment were demarcated, and their characterizations were carried out.     

Syntheses and Structures of Na2Mg3(OH)2(SO4)3·4H2O and K2Mg3(OH)2(SO4)3·2H2O

The crystal structures of Na₂Mg₃(OH)₂(SO₄)₃ · 4H₂O and K₂Mg₃(OH)₂(SO₄)₃ · 2H₂O, were determined from conventional laboratory X‐ray powder diffraction data. Synthesis and crystal growth were made by mixing alkali metal sulfate, magnesium sulfate hydrate, and magnesium oxide with small amounts of water followed by heating at 150 °C. The compounds crystallize in space group Cmc2₁ (No. 36) with lattice parameters of a = 19.7351(3), b = 7.2228(2), c = 10.0285(2) Å for the sodium and a = 17.9427(2), b = 7.5184(1), c = 9.7945(1) Å for the potassium sample. The crystal structure consists of a linked MgO₆–SO₄ layered network, where the space between the layers is filled with either potassium (K⁺) or Na⁺‐2H₂O units. The potassium‐bearing structure is isostructural to K₂Co₃(OH)₂(SO₄)₃ · 2(H₂O). The sodium compound has a similar crystal structure, where the bigger potassium ion is replaced by sodium ions and twice as many water molecules. Geometry optimization of the hydrogen positions were made with an empirical energy code.     

Solubility of Double Alkali Metal (Na, K) Rare-Earth (La, Ce) Sulfates in Sulfuric-Phosphoric Acid Solutions at 20°C

The dependence of the solubility of NaLa(SO₄)₂·H₂O, NaCe(SO₄)₂·H₂O, KLa(SO₄)₂·H₂O, and KCe(SO₄)₂·H₂O on the concentration of acids in sulfuric, phosphoric, and sulfuric-phosphoric acid solutions containing up to 36 wt % H₂SO₄ and 33.12 g l_-1 H₃PO₄ was studied at 20°C.     

Synthetic ferric sulfate trihydrate,Fe2(SO4)3·3H2O,a new ferric sulfate salt

Ferric sulfate trihydrate has been synthesized at 403 K under hydrothermal conditions. The structure consists of quadruple chains of [Fe₂(SO₄)₃(H₂O)₃] parallel to [010]. Each quadruple chain is composed of equal proportions of FeO₄(H₂O)₂ octahedra and FeO₅(H₂O) octahedra sharing corners with SO₄ tetrahedra. The chains are joined to each other by hydrogen bonds. This compound is a new hydration state of Fe₂(SO₄)₃·nH₂O; minerals with n = 0, 5, 7.25–7.75, 9 and 11 are found in nature.