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Dieses Heft “Moderne Mobil” (Redaktion: Karin Berkemann) war für uns ein kleines Experiment. Die einzige Vorgabe an unsere fünf Autoren: “Wir bringen Dich, einen religiösen Raum des Neuen Frankfurt und ein Fortbewegungsmittel eben jener Epoche zusammen auf ein Foto. Beim Text dazu hast Du (bis auf die Zeichenzahl) völlig freie Hand.” Den Spaß haben mitgemacht die Frankfurter Kulturdezernentin Ina Hartwig, der Architekturhistoriker Wolfgang Voigt, der Politikwissenschaftler Philipp Sturm, der Journalist Daniel Bartetzko, die Theologin Karin Berkemann – und der Fotograf Andreas Beyer. Wie alle Ergebnisse dann am Ende ineinandergriffen, hat uns selbst überrascht. Aber lesen Sie doch selbst! Die Rechte für die einzelnen Textbeiträge liegen bei den Autor:innen, die Bildrechte sind jeweils am Bild selbst angegeben. Die einzelnen Heftbeiträge sind (in der jeweils aktuellen Form) online zugänglich., ISSN (online): 2365-0370, HBZ-ID: HT018260134, ZDB-ID: 1050988183

We became aware of the above paper by Kang et al., published online in the Journal of Chemical and Engineering Data.(1)

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.

Rose Hajdu, Marc Hirschfell, Wolfgang Voigt: Paul Bonatz. Bauten an Rhein und Neckar. Ernst Wasmuth Verlag Tübingen/Berlin 2014. 184 Seiten mit mehr als 200 überwiegend farbigen Abbildungen. Hardcover €35,–. ISBN 978-3-8030-0754-4

Wolfgang Voigt und Roland May: Paul Bonatz 1877 – 1956. Ernst Wasmuth Verlag Tübingen / Berlin 2010. 320 Seiten mit zahlreichen Abbildungen. Gebunden € 49,80. ISBN 978-3-8030-0729-2 (Buchhandelsausgabe)

Part of the process to ensure the safety of radioactive waste disposal is the predictive modeling of the solubility of all relevant toxic components in a complex aqueous solution. To ensure the reliability of thermodynamic equilibrium modeling as well as to facilitate the comparison of such calculations done by different institutions it is necessary to create a mutually accepted thermodynamic reference database. To meet this demand several institutions in Germany joined efforts and created THEREDA 15 (Moog et al., 2015). THEREDA is a suite of programs at the base of which resides a relational databank. Special emphasis is put on thermodynamic data along with suitable Pitzer coefficients which allow for the calculation of solubilities in high-saline solutions. Registered users may either download single thermodynamic data or ready-to-use parameter files for the geochemical speciation codes 20 PHREEQC, Geochemist’s Workbench, CHEMAPP, or TOUGHREACT. Data can also be downloaded in a generic JSON-format to allow for the import into other codes. The database can be accessed via the world wide web: www.thereda.de Prior to release, the released part of the database is subjected to many tests. Results are compared to results from earlier releases and among the different codes. This is to ensure that by additions of new and modification of existing data no adverse side 25 effects on calculations are caused. Furthermore, our website offers an increasing number of examples for applications, including graphical representation, which can be filtered by components of the calculated system. References Moog, H. C., Bok, F., Marquardt, C. M., and Brendler, V.: Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem., 55, 72-84, doi: 30 10.1016/j.apgeochem.2014.12.016, 2015.

Within the last two decades, a large number of articles were published that report, as the authors claim, ‘metastable phase equilibria’, or ‘metastable solubilities’. The main objective of these studies was to carry out experiments under conditions closely meeting those in solar evaporation ponds or industrial evaporation–crystallization processes. Occasionally, such studies were subject to controversial discussion and criticism and the question was raised whether metastable equilibrium data are worth being published at all. This paper provides a critical discussion of such evaporation experiments. The thermodynamic background of stable and metastable solubility and typical experimental difficulties in solubility determinations are discussed in detail. We also demonstrate that the knowledge of metastable equilibria is very useful in different research areas such as geochemistry or industrial application of solubility equilibria. Finally, it is shown that so-called ‘isothermal evaporation method’ used in the above-mentioned studies does not yield stable or metastable solubilities.

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.

The solubility isotherm in the system LiNO3–KNO3–H2O was determined with an analytical method at 373 K. The data were compared with calculations from a six-parameter model of Pitzer and Simonson (J Phys Chem 90:3009, 1986) with parameters derived solely from water activities in a comparable temperature–composition range. A two-parameter BET model could predict the solubility data equally good if a regular solution term from data of the anhydrous molten system was added.

Lithium has become an energy critical element and thus the security of supply is of great importance. As a local German resource, attention was directed towards the mica-type mineral zinnwaldite. It represents a lithium-rich siderophyllite and corresponds to an intermediate polylithionite–siderophyllite solid solution with high contents of fluoride. Mineral samples from the deposit Zinnwald/Cinovec at the German/Czech border were analyzed and characterized by a variety of methods, particularly concerning its thermal behavior. Understanding the thermal behavior of the mica gives the opportunity to develop new and cost-efficient methods for lithium extraction. Investigations with different spectroscopic methods revealed the decomposition mechanisms. Starting at 300 °C, oxidation of Fe2+ catalyzed the dehydroxylation of the mica by dehydrogenation. This is followed by a dehydroxylation similar to the mechanism of dioctahedral micas. At higher temperatures, the release of HF was detected. At about 800 °C the precipitation of hematite was observed. The complete decomposition of Zinnwaldite takes place at 900 °C, it is accompanied by the liberation of SiF4 and leads to the formation of several solid decomposition products. By means of single-crystal diffraction using X-rays and neutrons the structural changes could be identified after annealing at 700 °C. The results point to a transformation into a polylithionite-like structure, the end member of the solid solution series.

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 title carbonate hydrate, Cs

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 formation of a previously unknown higher hydrated magnesium carbonate, MgCO3·6H2O, was confirmed. Its crystal structure differs from the other known magnesium carbonates significantly, but it exhibits similarities to NiCO3·5.5H2O., 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.

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.

The water activities of the systems MSO4 + H2O (M = Mn, Co, Ni, Cu, Zn) are essential data needed for simulating the hydrometallurgical process of these metals. In our previous work (J. Chem. Eng. Data, 2014, 59, 97–102), the experimental data of water activity for these binary systems have been reported at 323.15 K. As one part of this series of work, the experimental data of water activity for these systems are reported at 373.15 K. The reliability of the apparatus at 373.15 K was verified by measuring and comparing the water activities of the two reference systems, CaCl2 + H2O and LiCl + H2O. The results showed that the maximal relative deviation of the water activities between the reference systems was 0.054%. The water activities for the concerned five systems were found to be approximately the same at a certain salt molality below 1 M. The water activities of these systems decrease at a certain salt molality more than 1 M in the following sequence: aMnSO4 > aCuSO4(∼aZnSO4) > aCoSO4(∼aNiSO4). Further...

The water activities for the binary Li2SO4–H2O and MgSO4–H2O, as well as the ternary Li2SO4–MgSO4–H2O systems at 323.15 and 373.15 K were elaborately determined by isopiestic measurements. The relative deviation of the isopiestic molality of parallel samples in each experimental run is better than 0.2%. The experimental water activities in the binary systems were compared with literature data and good agreement was found. The results obtained show that at salt concentration below 3 m the isopiestic composition lines of the Li2SO4–MgSO4–H2O system obey the Zdanovskii rule, whereas above 3 m the composition lines positively deviate from the Zdanovskii rule.

A sample of pure, artificial hellyerite was synthesized in aqueous solution at 0 °C. The recorded X-ray diffraction pattern completely agrees with the reference data given for natural hellyerite. Laboratory high resolution X-ray powder diffraction, applying global optimization methods and Rietveld refinement, was employed to solve the crystal structure. Synthetic hellyerite was determined to crystallize in the primitive monoclinic space group P2/m (no. 10) with a = 10.769(2) A, b = 7.295(2) A, c = 9.343(2) A, and β = 94.042(2)°. The crystal structure consists of edge-linked, isolated pairs of Ni2(CO3)2(H2O)8 octahedra and non-coordinating water molecules. According to structure solution and thermal analysis the molecular formula of hellyerite was corrected from NiCO3·6H2O to NiCO3·5.5H2O. The title compound was characterized by scanning electron microscopy, IR-, Raman-, and UV/Vis spectroscopy.

[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 term oceanic salts concerns the salts, which can be formed from solutions containing the major ions of seawater, that is the hexary system Na+, K+, Mg++, Ca++, Cl–, SO4 ––H2O. Besides in geochemistry of evaporites and the potash extraction the solubility equilibria and properties of aqueous solutions containing these ions are of importance in many fields of science and technology in a wide range of temperature and composition. After a short introduction into the types of subsystems and the main features of their solubility diagrams the known salt phases, their properties and stability are listed and discussed with a focus on recent work and discoveries. The status of solubility data evaluation of the multi-component system is discussed from the view point of the data itself and the possibilities and limitations of applying thermodynamic modelling. This is demonstrated with the data compilation of Usdowski and Dietzel, the Pitzer models of Harvie, Möller and Weare as well as the model developed in the THEREDA project. Future work should be directed to improve accuracy of solubility data in multi-component solutions combined with modelling and to consider kinetics and mechanistic aspects in crystallization of phases like anhydrite or polyhalite.

Land-based aquaculture is an increasingly important method of fish production, and fish grown in such systems may be exposed to substantially higher carbon dioxide concentrations than fish in the wild. Chronic exposure to elevated CO2 levels in recirculated aquaculture systems can correlate with lower growth and condition indices for many fish species, however, the physiological basis behind this loss of performance is largely unknown. The aim of this study was to investigate the growth, condition and protein catabolism rates of juvenile turbot (55-176 g) reared for 8 weeks at three different dissolved carbon dioxide concentrations: 5, 26, and 42 mg l(-1) (-3000, 15000, 25000 mu atm; pH 7.37, 6.66, 6.44). A commercial diet was administered once per day until satiation, and uneaten food was collected from a solids collector. Oxygen consumption and ammonia excretion were measured weekly using high precision automated methods in a recirculating aquaculture respirometer system. Increased CO2 levels were associated with reduced condition factor, feed intake and weight gain. Compared to the low CO2 treatment, the specific growth rates under the medium and high treatments were reduced by 21% and 58%, respectively. Feed conversion ratios were similar between treatments. The oxygen consumption rates broadly followed a dose-response pattern, where fish in the low CO2 treatment exhibited the highest respiration rates. Comparison of ammonia quotients over time and at comparable feed intake showed the rates of protein catabolism correlated with CO2 exposure levels. By the end of the 8 week trial fish from the high CO2 treatment exhibited up to 3 times the protein catabolism rates observed in the low treatment, and the medium treatment was approximately intermediate between the two. The conclusion from the study was that the loss of growth and condition of turbot reared at elevated CO2 concentrations (relevant to land-based aquaculture systems) can be traced to decreased feed intake and an increased reliance on protein as a fuel source. (C) 2015 Elsevier B.V. All rights reserved.

Metal selenates crystallize in many instances in isomorphic structures of the corresponding sulfates. Sodium magnesium selenate decahydrate, Na

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 crystal structures of the two hydrates Na2SeO4·10H2O and Na2SeO4·7.5H2O are studied for the first time. The structures of Na2SO4·10H2O and Na2SO4·7H2O are reinvestigated as a function of temperature with respect to the degree of disorder of the O atoms of {\rm SO}_{4}^{2-} in the decahydrate and the O atom of water in the heptahydrate. For Na2SO4·10H2O, the unit site occupancy factor (SOF) of O atoms of {\rm SO}_{4}^{2-} was determined at 120 K. After the temperature dependence of the lattice parameters was studied from 120 to 260 K, it was shown that SOF decreased from 1.0 at 120 K to 0.247 at room temperature. The interesting fact that two salts with different chemical compositions and different crystal structures (Na2SO4·7H2O, tetragonal, space groupP41212 and Na2SeO4·7.5H2O, monoclinic, space groupC2/c) can act mutually as a crystal nucleus is accounted for by similarities in certain fragments of their crystal structures. This phenomenon is attributed to similarities between particular elements of their structures.

Solubility phase diagrams of mixtures of salts and water are of interest in various application fields and can be calculated using the modified BET model. In comparison with other thermodynamic models, the modified BET model requires only two salt-specific model parameters and has shown to possess a predictive capability. In this work, the modified BET equations are extended in order to calculate solubility phase diagrams of concentrated salt solutions with relatively high water activities within the range of undersaturation. As an example, BET parameters of NaCl are determined and applied to calculate solubility phase diagrams of NaCl + H 2 O, NaCl + LiCl + H 2 O, and NaCl + CaCl 2 + H 2 O within the temperature range of around 250–500 K. In the ternary systems, the best agreement with solubility data from literature is obtained using constant BET parameters of NaCl and an additional temperature-dependent regular solution parameter to account for salt-salt interaction.