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During investigations of the formation of hydrated magnesium carbonates, a sample of the previously unknown magnesium carbonate hexahydrate (MgCO3·6H2O) was synthesized in an aqueous solution at 273.15 K. The crystal structure consists of edge-linked isolated pairs of Mg(CO3)(H2O)4 octahedra and noncoordinating water molecules, and exhibits similarities to NiCO3·5.5H2O (hellyerite). The recorded X-ray diffraction pattern and the Raman spectra confirmed the formation of a new phase and its transformation to magnesium carbonate trihydrate (MgCO3·3H2O) at room temperature.

For lithium halides, LiX (X = Cl, Br and I), hydrates with a water content of 1, 2, 3 and 5 moles of water per formula unit are known as phases in aqueous solid–liquid equilibria. The crystal structures of the monohydrates of LiCl and LiBr are known, but no crystal structures have been reported so far for the higher hydrates, apart from LiI·3H2O. In this study, the crystal structures of the di- and trihydrates of lithium chloride, lithium bromide and lithium iodide, and the pentahydrates of lithium chloride and lithium bromide have been determined. In each hydrate, the lithium cation is coordinated octahedrally. The dihydrates crystallize in the NaCl·2H2O or NaI·2H2O type structure. Surprisingly, in the tri- and pentahydrates of LiCl and LiBr, one water molecule per Li+ ion remains uncoordinated. For LiI·3H2O, the LiClO4·3H2O structure type was confirmed and the H-atom positions have been fixed. The hydrogen-bond networks in the various structures are discussed in detail. Contrary to the monohydrates, the structures of the higher hydrates show no disorder.

Lithium can be found in its bound form in silicatic rocks and dissolved in salt lake brines. Both types of lithium resources, whose amounts exceed the expected demand for lithium by several times, are used for lithium recovery. The known lithium resources and their geochemical characteristics are reviewed together with the presently applied recovery processes which are still very similar to the historically early techniques. New processes for direct carbonization of zinnwaldite, hydrochloric and oxalic acid leaching as well as a new method for the recovery of lithium from magnesium-rich brines are presented.

Based on decomposition studies of zinnwaldite in Part I, a process for lithium carbonate production by supercritical carbon dioxide ( sc -CO 2 ) treatment was developed and optimised to high lithium yields. Sintered and ground zinnwaldite concentrate was subjected to CO 2 /water treatment at elevated pressure (100 bar) and moderate heating (230 °C). Mobilisation rates of over 70% were attained. The filtered lithium bicarbonate containing solution was concentrated by electrodialysis up to a lithium content of 8.5 g/L. Precipitation of lithium carbonate was achieved by CO 2 elimination at 90–95 °C. A high selectivity of CO 2 treatment for alkali metals, specifically for lithium, enables lithium carbonate product purities of ≥99.0% without additional rinsing.

Metal selenates crystallize in many instances in isomorphic structures of the corresponding sulfates. Sodium magnesium selenate decahydrate, Na2Mg(SeO4)2·10H2O, and sodium magnesium selenate dihydrate, Na2Mg(SeO4)2·2H2O, were synthesized by preparing solutions of Na2SeO4 and MgSeO4·6H2O with different molar ratios. The structures contain different Mg octahedra, i.e. [Mg(H2O)6] octahedra in the decahydrate and [MgO4(H2O)2] octahedra in the dihydrate. The sodium polyhedra are also different, i.e. [NaO2(H2O)4] in the decahydrate and [NaO6(H2O)] in the dihydrate. The selenate tetrahedra are connected with the chains of Na polyhedra in the two structures. O—H...O hydrogen bonding is observed in both structures between the coordinating water molecules and selenate O atoms.

The title carbonate hydrate, Cs2Mg4(CO3)5·10H2O, was crystallized at room temperature out of aqueous solutions containing caesium bicarbonate and magnesium nitrate. Its monoclinic crystal structure (P21/n) consists of double chains of composition 1 ∞[Mg(H2O)2/1(CO3)3/3], isolated [Mg(H2O)(CO3)2]2– units, two crystallographically distinct Cs+ ions and a free water molecule. The crystal under investigation was twinned by reticular pseudomerohedry.

The structure of the stable double salt MgCO3·MgCl2·7H2O, obtained from concentrated solutions of MgCl2, is characterized by double chains of MgO octahedra and carbonate ions parallel to (100), interconnected by chloride ions., MgCO3·MgCl2·7H2O is the only known neutral magnesium carbonate con­taining chloride ions at ambient conditions. According to the literature, only small and twinned crystals of this double salt could be synthesised in a concentrated solution of MgCl2. For the crystal structure solution, single-crystal diffraction was carried out at a synchrotron radiation source. The monoclinic crystal structure (space group Cc) exhibits double chains of MgO octa­hedra linked by corners, connected by carbonate units and water mol­ecules. The chloride ions are positioned between these double chains parallel to the (100) plane. Dry MgCO3·MgCl2·7H2O decom­poses in the air to chlorartinite, Mg2(OH)Cl(CO3)·nH2O (n = 2 or 3). This work includes an extensive char­acterization of the title com­pound by powder X-ray diffraction, thermal analysis, SEM and vibrational spectroscopy.

The previously unknown monoclinic form of potassium carnallite, KCl·MgCl2·6H2O, was found as a metastable phase occurring during crystallization studies of potash salt solutions., During evaporation of natural and synthetic K–Mg–Cl brines, the formation of almost square plate-like crystals of potassium carnallite (potassium chloride magnesium dichloride hexa­hydrate) was observed. A single-crystal structure analysis revealed a monoclinic cell [a = 9.251 (2), b = 9.516 (2), c = 13.217 (4) Å, β = 90.06 (2)° and space group C2/c]. The structure is isomorphous with other carnallite-type com­pounds, such as NH4Cl·MgCl2·6H2O. Until now, natural and synthetic carnallite, KCl·MgCl2·6H2O, was only known in its ortho­rhom­bic form [a = 16.0780 (3), b = 22.3850 (5), c = 9.5422 (2) Å and space group Pnna].

The synthesis routes of Gd(HCO3)3·5H2O and Ho(HCO3)3·6H2O, which are the only known bicarbonates of rare earth metals, were refuted and the published crystal structures were discussed. Because of the structural relationship of Ho(HCO3)3·6H2O to rare earth nitrate hexahydrates,[1] the synthesis of holmium nitrate hydrate was considered and the crystal structure of Ho(NO3)3·5H2O was solved by single crystal X-ray diffraction measurements. Ho(NO3)3·5H2O was determined to crystallize in the triclinic space group P1 (no. 2) with a = 6.5680(14) A, b = 9.503(2) A, c = 10.462(2) A, α = 63.739(14)°, β = 94.042(2)° and γ = 76.000(16)°. The crystal structure consists of isolated [Ho(H2O)4(NO3)3] polyhedra and non-coordinating water molecules. It is isotypic to other rare earth nitrate pentahydrates.

[MnIIxFeII1−x(H2O)6][LiFeIII(ox)3] (with 0 ≤ x ≤ 1) crystallizes in the space group P31c with a = 9.341(3) A, c = 10.226(3) A, c/a = 1.0947, and V = 772.8(5) A3 for Z = 2. The compound has a layered structure with two enantiomeric layers per unit cell. The layers are built up by an iron and lithium oxalate framework with intercalated M(II)-water octahedra of the formula [MnIIxFeII1−x(H2O)6][MIMIII(ox)3]. The value of x cannot be specified at present. The structure displays intermolecular hydrogen bonding between the layers.

A new basic nickel carbonate Ni12(CO3)8(OH)8·(x – 1)H2O or Ni12(CO3)8(OH)6O·xH2O (x = 6–8) was synthesized by two hydrothermal methods. The crystal structure was determined in the cubic space group P3m (215) with a = 8.3814(2) A by laboratory high-resolution X-ray powder diffraction with the application of global optimization methods and Rietveld refinement. The crystal structure consists of edge-linked [NiO6] octahedra and carbonate units that form cages. The interconnected cages form channels filled with disordered water molecules. This causes a zeolite-like behavior of the water molecules, as shown by thermogravimetric analysis coupled with infrared spectroscopy (TG–IR) and in situ X-ray powder diffraction experiments up to 300 °C. In addition, the title compound was characterized by elemental analysis, scanning electron microscopy, and Raman and UV/Vis spectroscopy. The title compound was proven to be a pure carbonate and not nickel hydrogen carbonate (PDF 15-0782), as was assumed before.

The crystal structures of the tri-, tetra- and nona­hydrate phases of Sr(ClO4)2 consist of Sr2+ ions coordinated by nine oxygen atoms from water mol­ecules and perchlorate tetra­hedra. O—H⋯O hydrogen bonds between water mol­ecules and ClO4 units lead to the formation of a three-dimensional network in each of the structures., The title compounds, strontium perchlorate trihydrate {di-μ-aqua-aquadi-μ-perchlorato-strontium, [Sr(ClO4)2(H2O)3]n}, strontium perchlorate tetra­hydrate {di-μ-aqua-bis­(tri­aqua­diperchloratostrontium), [Sr2(ClO4)4(H2O)8]} and strontium perchlorate nona­hydrate {hepta­aqua­diperchloratostrontium dihydrate, [Sr(ClO4)2(H2O)7]·2H2O}, were crystallized at low temperatures according to the solid–liquid phase diagram. The structures of the tri- and tetra­hydrate consist of Sr2+ cations coordinated by five water mol­ecules and four O atoms of four perchlorate tetra­hedra in a distorted tricapped trigonal–prismatic coordination mode. The asymmetric unit of the trihydrate contains two formula units. Two [SrO9] polyhedra in the trihydrate are connected by sharing water mol­ecules and thus forming chains parallel to [100]. In the tetra­hydrate, dimers of two [SrO9] polyhedra connected by two sharing water mol­ecules are formed. The structure of the nona­hydrate contains one Sr2+ cation coordinated by seven water mol­ecules and by two O atoms of two perchlorate tetra­hedra (point group symmetry ..m), forming a tricapped trigonal prism (point group symmetry m2m). The structure contains additional non-coordinating water mol­ecules, which are located on twofold rotation axes. O—H⋯O hydrogen bonds between the water mol­ecules as donor and ClO4 tetra­hedra and water mol­ecules as acceptor groups lead to the formation of a three-dimensional network in each of the three structures.

Water-rich aluminium halide hydrate structures are not known in the literature. The highest known water content per Al atom is nine for the perchlorate and fluoride. The nonahydrate of aluminium bromide, stable pentadecahydrates of aluminium chloride, bromide and iodide, and a metastable heptadecahydrate of the iodide have now been crystallized from low-temperature solutions. The structures of these hydrates were determined and are discussed in terms of the development of cation hydration spheres. The pentadecahydrate of the chloride and bromide are isostructural. In AlI3·15H2O, half of the Al3+cations are surrounded by two complete hydration spheres, with six H2O in the primary and 12 in the secondary. For the heptadecahydrate of aluminium iodide, this hydration was found for every Al3+.

The previously reported structures of the hydrates of simple inorganic salts that crystallize at room temperature are generally well determined. This is not true for water-rich hydrates, which crystallize at temperatures below 273 K. In this series, investigations of the crystal structures of water-rich hydrates crystallized from aqueous solutions at low temperatures are presented. Reported herein are the structures of a set of magnesium salts. Crystals of MgCl2·8H2O (magnesium dichloride octahydrate), MgCl2·12H2O (magnesium dichloride dodecahydrate), MgBr2·6H2O (magnesium dibromide hexahydrate), MgBr2·9H2O (magnesium dibromide nonahydrate), MgI2·8H2O (magnesium diiodide octahydrate) and MgI2·9H2O (magnesium diiodide nonahydrate) were grown from their aqueous solutions at temperatures below 298 K according to the solid–liquid phase diagrams. All structures are built up from Mg(H2O)6octahedra. Dimensions and angles in the hexaaqua cation complexes are very similar and variation is not systematic. The anions are incorporated into a specific network of O—H...Xhydrogen bonds.

The determination of the phase diagram of the binary system sodium perchlorate – water is reported. Beside the eutectic point, two polymorph crystal structures of sodium perchlorate dihydrate were determined. The two crystal structures are discussed, compared to each other and to other known sodiumhalide dihydrate crystal structures. The two polymorphs of the perchlorate dihydrate represent the two variants of connected octahedra in the layer structure found for sodium halide dihydrates.

The synthesis, structural, and thermal characterization of lithium cyanate are reported in this work. LiOCN forms crystals in the trigonal crystal system. The structure was solved in the space group Rm. It is isomorphous to the structure of sodium cyanate. In the temperature range from –90 °C up to the melting point no phase transition was observed. Furthermore the vibrational Raman spectrum was measured. The system KOCN-LiOCN shows a dystecticum and the new phase was confirmed by powder X-ray diffraction.

Salts comprise a very large and important group of chemical compounds. Natural occurrence of salts and industrial processes of their recovery, conversion, purification, and use depend on solubility phenomena and their chemistry in aqueous solutions, mostly in multi-ion systems. Modeling of these processes as well as developing new ones requires knowledge of the properties of the aqueous salt solutions in extended T-p-x ranges including a growing number of components in solutions (CO2, SO2, lithium salts, salts of rare earth metals, actinides, etc.). At least for the thermodynamic properties, the general accepted methodology is to use thermodynamic databases of aqueous species and solids in combination with an appropriate ion-interaction model to perform equilibrium calculations for species distributions in solution and phase equilibria. The situation in respect to available thermodynamic models and data for their parameterization is discussed at selected examples. Thereby, the importance of accurate experimental determinations of phase equilibrium data for derivation of model parameters is emphasized. Furthermore, it is concluded that experimental investigations should follow a chemical systematic. Simple physical models or quantum chemical calculations cannot predict unknown quantities in the databases with sufficient accuracy. Finally, solubility changes in salt-water systems at enhanced temperatures are considered. Systems, which can be considered as molten hydrates, display interesting phase behavior and chemical reactivity as protic ionic liquids. The latter can be exploited in chemical syntheses to substitute mixtures of concentrated acids like HNO3/H2SO4 by simple salts like ferric nitrate. For an understanding of the chemical and phase behavior of water-salt systems in terms of structure–property relations, a renaissance of chemical guided basic investigations of such systems would be worthwhile.

The title compound was synthesized by the redox reaction of copper(II) perchlorate hexa­hydrate and metallic tin in perchloric acid. Both the pyramidal [Sn(H2O)3]2+ cations and tetra­hedral perchlorate anions lie on crystallographic threefold axes., The title compound, [Sn(H2O)3](ClO4)2, was synthesized by the redox reaction of copper(II) perchlorate hexa­hydrate and metallic tin in perchloric acid. Both the trigonal–pyramidal [Sn(H2O)3]2+ cations and tetra­hedral perchlorate anions lie on crystallographic threefold axes. In the crystal, the cations are linked to the anions by O—H⋯O hydrogen bonds, generating (001) sheets.

The search for literature data in the ternary systems M2+, Ca2+ + SO42− + H2O (M = Mg, Mn, Co, Ni, Cu, Zn) revealed a lack of data. A reason might be the difficulties of Ca analysis at high concentrated bivalent metal solutions. The solubility of gypsum was determined in MSO4 solutions (M = Mg, Mn, Co, Ni, Cu, Zn) over a broad concentration range at T = 298.15 K and T = 313.15 K. With increasing magnesium and heavy metal sulfate, respectively, the gypsum solubility decreases to a minimum and rises afterward to a maximum at about 1.2 mol MSO4/kg. Above that concentration, the solubility of gypsum decreases again until saturation with MSO4. At both temperatures and in the whole concentration range, no double salt formation was noticed. With increasing temperature, the solubility of gypsum increases also.

A new basic nickel carbonate Ni12(CO3)8(OH)8·(x – 1)H2O or Ni12(CO3)8(OH)6O·xH2O (x = 6–8) was synthesized by two hydrothermal methods. The crystal structure was determined in the cubic space group P3m (215) with a = 8.3814(2) A by laboratory high-resolution X-ray powder diffraction with the application of global optimization methods and Rietveld refinement. The crystal structure consists of edge-linked [NiO6] octahedra and carbonate units that form cages. The interconnected cages form channels filled with disordered water molecules. This causes a zeolite-like behavior of the water molecules, as shown by thermogravimetric analysis coupled with infrared spectroscopy (TG–IR) and in situ X-ray powder diffraction experiments up to 300 °C. In addition, the title compound was characterized by elemental analysis, scanning electron microscopy, and Raman and UV/Vis spectroscopy. The title compound was proven to be a pure carbonate and not nickel hydrogen carbonate (PDF 15-0782), as was assumed before.

[Sn(H2O)3](ClO4)2 is prepared by the redox reaction of Cu(ClO4)2 and Sn in HClO4 followed by crystallization in a freezer (253 K).

A series of symmetrical dialkyl ammonium salts, DC n X, has been prepared and characterized with respect to temperature and enthalpy of solid–solid phase transitions, temperature of melting, thermal stability as well as the reversibility of the phase transitions. The number of carbon atoms, C n , was varied between 8 and 18 and as anions X halides, nitrate, chlorate, perchlorate and hydrogen sulphate had been chosen. In dependence on chain length and anion type transition temperatures from 20 to 100 °C were observed. Mass specific solid–solid transition enthalpies reach values of 185 J g −1 , which makes this class of substances attractive for heat storage applications. The influence of anion type on the transition enthalpies is explained in terms of packing requirements, hydrogen bond network formation and contributions from hindered anion rotation.

The title compound, MgCl2·4H2O, was crystallized at 403 K and its structure determined at 200 K. The structure is built up from MgCl2(H2O)4octahedra with atransconfiguration. Each complex is situated on a crystallographic twofold axis, with the rotation axis aligned along one H2O—Mg—OH2axis. They are connected by a complex network of O—H...Cl hydrogen bonds. The structure contains two-dimensional sections that are essentially identical to those in the reported tetrahydrates of CrCl2, FeCl2, FeBr2and CoBr2, but they are stacked in a different manner in MgCl2·4H2O compared with the transition metal structures.

The crystal structures of the title compounds, crystallized from low-temperature solutions, are determined by single crystal XRD.

The system MgCl2–MgSO4–H2O has been investigated experimentally and modeled thermodynamically according to the Pitzer method at 50 and 75°C. It was found that, even when seemingly all requirements for reaching the stable thermodynamic equilibrium are fulfilled, the crystallization of higher hydrates as metastable phases is possible, and cannot be avoided in each crystallization field of a stable lower hydrate of magnesium sulfate. Crystallization of MgSO4 · x H2O (x = 1, 4, 6) and MgCl2 · 6 H2O at 50°C and of MgSO4 · H2O and MgCl2 · 6 H2O at 75°C as stable phases has been observed. Three metastable crystallization fields of MgSO4 · x H2O (x = 4, 6, 7) have been detected at 50°C and two of MgSO4 · x H2O (x = 4, 6) at 75°C. The results obtained and the contradictions existing in the literature with respect to the solubility and the crystallizing solid phases are discussed in terms of the crystal structures.

The title compound, lithium magnesium chloride heptahydrate, LiCl.MgCl(2).7H(2)O, was analyzed in 1988 by powder X-ray diffraction [Emons, Brand, Pohl & Kohnke (1988). Z. Anorg. Allg. Chem. 563, 180-184] and a monoclinic crystal lattice was determined. In the present work, the structure was solved from single-crystal diffraction data. A trigonal structure was found, exhibiting a network structure of Mg(H(2)O)(6) octahedra and Li(H(2)O)Cl(3) tetrahedra connected by H...Cl hydrogen bonds. The [Li(H(2)O)](+) unit is coordinated by distorted edge-connected Cl(-) octahedra.

A metastable sodium-containing hemihydrate ((6-x)CaSO4ċxNa2SO4ċ3H2O, 0 ≤ x ≤ 1) limited by the pentasalt composition Na2SO4ċ5CaSO4ċ3H2O occurs as an intermediate solid phase in the systems Na2SO4-CaSO4-H2O, NaCl-Na2SO4-CaSO4-H2O, and NaCl-CaSO4-H2O. X-Ray structure determination of a crystal with pentasalt composition results in a super-structure of the pure hemihydrate (CaSO4ċ0.5H2O), in which one Ca2+ion is statistically replaced by two Na+ ions. One Na+ cation is situated in a Ca2+ position in only one of the three chains of CaSO4 forming an axis of nearly three fold symmetry along the c-axis. The second Na+ is located in the water channel neighbouring to the first Na+. The hydrate crystallized in a monoclinic space group C121 (No. 5) with a=24.1781(11), b=13.805(2), c=12.7074(12) A, β=90.089(12)°. The dehydration temperature of the hydrates depends on their Na+ ion content. A high Na+ content (in water channels) blocks the water escape strongly, and the dehydration temperature increases. Thermal behaviour is also effected by the crystal sizes. The thermograms of small crystals as opposed to large ones show a exothermic effect adjoining the endothermic dehydration. This may be indicative for a change in the dehydration mechanism upon crystal size.

Crystals of MgCl2·8H2O (I), MgCl2·12H2O (II), MgBr2·6H2O (III), MgBr2·9H2O (IV), MgI2·8H2O (V), and MgI2·9H2O (VI) are grown from their aqueous solutions at below 298 K according to their solid-liquid phase diagrams.

Single crystals of the title compound are prepared by thermal decomposition of the corresponding hexahydrate at 403 K.

The title compound, lithium magnesium chloride heptahydrate, LiCl.MgCl(2).7H(2)O, was analyzed in 1988 by powder X-ray diffraction [Emons, Brand, Pohl & Kohnke (1988). Z. Anorg. Allg. Chem. 563, 180-184] and a monoclinic crystal lattice was determined. In the present work, the structure was solved from single-crystal diffraction data. A trigonal structure was found, exhibiting a network structure of Mg(H(2)O)(6) octahedra and Li(H(2)O)Cl(3) tetrahedra connected by H...Cl hydrogen bonds. The [Li(H(2)O)](+) unit is coordinated by distorted edge-connected Cl(-) octahedra.

Etude de la variation de l'energie standard de Gibbs pour les reactions reciproques haute temperature: AX+BY=AY+BX

The enthalpies of mixing measured for the systems x(ZnCl2+RH2O)-(1−x)(LiCl+RH2O) are reported. In contrast to the exothermic effects for R=4, the mixing processes at R=6 are considerably endothermic. For R=5, the sign of ΔH M depends on the composition. The mixing enthalpies of these hydrated melts are controlled by an endothermic step in the chlorocomplex formation of zinc and the exothermic hydration of lithium cations.

Aus EMK-Messungen von Konzentrationsketten mit Uberfuhrung an den Systemen NaBr–(CaBr2, SrBr2, BaBr2) und KBr– (CaBr2, SrBr2, BaBr2) wurden in Verbindung mit thermodynamischen Aktivitatsdaten und Aquivalentleitfahigkeiten die inneren Uberfuhrungszahlen, Exzesuberfuhrungszahlen und die relativen Kationenbeweglichkeiten berechnet. In allen Mischungen sind die Exzesuberfuhrungszahlen der Alkalimetallionen Groser als Null mit Maximalwerten im Bereich von 30–40 Mol-% Erdalkalimetallbromid. Die Beweglichkeiten der Alkalimetallionen nehmen in allen Systemen mit steigendem Erdalkalimetallbromidgehalt ab. Das Verhalten der Erdalkalimetallionen hangt von ihrem Ionenradius ab. Mit steigendem Molenbruch der Alkalimetallbromide nimmt die Beweglichkeit der Calciumionen ab, der Bariumionen bei hohen Alkalimetallbromidgehalten zu, wahrend sie bei den Strontiumionen im NaBr-System nahezu konstant bleibt und im KBr-System sinkt. Electrical Transport Properties of Molten Alkali Bromide – Alkaline Earth Bromide Binary Mixtures From e.m.f. measurements of concentration cells with transference of the systems NaBr– (CaBr2, SrBr2, BaBr2) and KBr– (CaBr2, SrBr2, BaBr2) in connection with thermodynamic activity data and equivalent conductivities, the internal transference numbers, excess transference numbers and the relative cation-anion mobilities were calculated by using the well-known relations. For all mixtures the excess transport numbers are greater than zero, show maxima values in the range of 30…40 mole percent alkaline earth bromide. The mobilities of the alkali ions decrease in all systems with increasing alkaline earth content. The mobility behaviour of the alkaline earth ions varies with their ionic radius. With increasing mole fraction of alkali bromide the mobility of the calcium ions decreases, that of the barium ions increases in the region of high alkali bromide concentrations and that of the strontium ions remains approximately constant in the system containing NaBr and decreases in the system with KBr.