Phase equilibria in the system Na,K,Mg,Ca∥SO4,Cl-H2O at 25°C in the crystallization regions of MgCl2·6H2O, CaCl2·6H2O, and 2MgCl2·CaCl2·12H2O

The translation method is used to study equilibria in the system Na, K, Mg, Ca∥SO₄, Cl-H₂O at 25°C in the crystallization regions of MgCl₂·6H₂O, CaCl₂·6H₂O, and 2MgCl₂·CaCl₂·12H₂O. The participation of these salts in the formation of the geometrical images of the title system is determined. The relevant fragments of the equilibrium phase diagram are designed. Original Russian Text ? L. Soliev, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 5, pp. 841–845.     

Zum Aufbau Schlecht geordneter Calciumhydrogensilicate. II. Über eine aus Poly- und Disilicat bestehende Phase

On the Structure of Ill-crystallized Calcium Hydrogen Silicates. II. A Phase Consisting of Poly and Disilicate Both by condensation reactions of a calcium hydrogen disilicate phase [1] under the mother liquid at 80°C and by hydrothermal reactions of lime and silica at 150°C an ill-crystallized calcium hydrogen silicate phase is formed, being built up by nearly equal parts (referred to Si) of poly-and disilicate anions. The CaO content of the phase synthesized at 80°C varies between 1.1 and 2CaO/SiO₂, depending on the Ca(OH)₂ concentration in the mother liquid. In the phase formed at 150°C is CaO/SiO₂ = l.l–l.5. A proposal for the constitution of this phase is given.     

Calcium Hydroxide Chlorides: The Ternary System Ca(OH)2‐CaCl2‐H2O at 25, 40, and 60 °C,Phase Stoichiometry and Crystal Structure

The formation of calcium hydroxide chlorides is an important issue in processes of the chemical raw materials industry, in terms of purification of flue gases, and concrete/cement corrosion. Current information on phase compositions given in the literature are contradictory. In this work systematic solubility studies were carried out at 25, 40, and 60 °C in the system Ca(OH)₂‐CaCl₂‐H₂O and the compositions of the ternary solid phases were precisely determined using the Schreinemakers' method. Two ternary phases were identified, the hydrate 3Ca(OH)₂ · CaCl₂ · 12H₂O and the anhydrous calcium hydroxide chloride Ca(OH)₂ · CaCl₂. The crystal structure of 3Ca(OH)₂ · CaCl₂ · 12H₂O was solved by means of single‐crystal X‐ray diffraction at –123 °C (150 K).     

白硼钙石的合成新方法及其热化学研究(英)

0IntroductionTherearemanykindsofhydratedcalciumbo-rates,bothnaturalandsynthetic.Someofthemarematerialsusedinglass,potteryandporcelainenamelindustry,especiallyinunalkaliglassindustry.4CaO·5B2O3·7H2O,calledpriceite,isacalciumboratemin-eral,notfoundinCaO-B…     

Bestimmung der Art der Wasserbindung im Xonotlit 6 CaO-6 SiO2-H2O

The ¹H-NMR spectra of powdered synthetic xonotlite (5.64 CaO · 6SiO₂ · 1.56 H₂O) at +22 and ?150°C have been recorded. From the line shape the various bonding states of the protons are determined. Per 6 SiO₂ units, 1.46 H₂O are bound in form of OH groups and 0.20 H₂O exist at room temperature as mobile water molecules. By quantitative evaluation it is shown, that the constitution of the examined sample has to be represented by the formula (CaOH)_2.0Ca_3.6(H_0.8Si₆O₁₇). 0.2 H₂O. Line shape analysis provides the possibility to distinguish between CaOH and SiOH protons. The proton-proton distances are calculated, and by comparison with the known X-ray data the positions of the CaOH protons are proposed.     

Beiträge zur Chemie des Bauxitaufschlusses. Untersuchungen im System Na2O?CaO?Al2O3?TiO2?H2O im Temperaturbereich 100–275°C

On the Chemistry of Bauxite Extraction. II. Studies in the System Na₂O? CaO? Al₂O₃? TiO₂? H₂O between 100 and 275°C The formation of crystalline compounds in the system Na₂O? CaO? Al₂O₃? TiO₂? H₂O was studied between 100 and 275°C. With caustic alkali concentrations up to 300 g Na₂O/l the calcium aluminate 3 CaO · Al₂O₃ · 6 H₂O is formed. With rising temperatures two different calcium titanates, among them perovskite, CaTiO₃, are identified. Above 200°C perovskite is formed at all concentrations investigated.     

Untersuchungen im System SrO?SiO2?H2O

Investigation on the System SrO? SiO₂? H₂O On addition sodium silicate solutions to solutions of Sr(OH)₂, at room temperature strontium hydrogensilicates are precipitated which are always amorphous and contain silicate anions of various condensation degrees. At about 100°C at first also amorphous products are formed containing lower- and higher-molecular silicate anions. On standing of these precipitates at about 80°C under the mother liquor, however, cristallization occurs under complete degradation of the higher-molecular anions to monomeric resp. dimeric silicate anions. In dependence on the Na₂O: SiO₂ ratio of the sodium silicate solutions and on the Sr(OH)₂ concentrations the following crystalline compounds are formed: 1.25 SrO · 1 SiO₂ · 2 H₂O, 3 SrO · 2 SiO₂ · 3 H₂O and 3 SrO · 2 SiO₂ · 4 H₂O, with monomeric silicate anions; 2 SrO · 2 SiO₂ · 1.5 H₂O; 2 SrO · 2 SiO₂ · 2 H₂O, and 2 SrO · 2 SiO₂ · 3 H₂O, with dimeric anions.     

Experimental Determination of the Isotherm at 15°C of the System Mg2+/Cl?, SO42–H2O

 The diagram of the ternary system Mg²⁺/Cl⁻, SO₄ ²⁻–H₂O was established at 15°C by means of analytical and conductimetric measurements. Three compounds were found in this diagram, which are MgSO₄·6H₂O, MgSO₄·7H₂O, and MgCl₂·6H₂O. The solubility field of MgSO₄·7H₂O is important whereas those of MgSO₄·6H₂O and MgCl₂·6H₂O are small. The compositions (mass-%) of the two invariant points determined by the two methods are: MgSO₄:MgCl₂=2.73:33.80 and MgSO₄: MgCl₂=3.38:28.91. Both the measured and the calculated isotherm at 15°C have been used for modelling of the diagram Mg²⁺/Cl⁻, SO₄ ²⁻–H₂O between 0 and 35°C. The polythermal invariant point was approximately located between 15 and 10°C.     

Zur Koordination des Aluminiums in den Calciumaluminathydraten 2 CaO · Al2O3 · 8 H2O und CaO · Al2O3 · 10 H2O

On the Coordination of Al in the Calcium Aluminate Hydrates 2 CaO · Al₂O₃ · 8 H₂O and CaO · Al₂O₃ · 10 H₂O By investigations with high-resolution ²⁷Al-NMR in solids it is shown that in the compound 2 CaO · Al₂O₃ · 8 H₂O the Al merely exist in octahedral coordination. According to this and considering its structural relationship with 4 CaO · Al₂O₃ · 19 H₂O the dicalcium aluminate hydrate is proposed to be formulated as [Ca₂Al(OH)₆][Al(OH)₃ (H₂O)₃]OH. Likewise for the compound CaO · Al₂O₃ · 10 H₂O the octahedral coordination of the Al is proved by ²⁷Al-NMR. This result corresponds with literature according to which a constitution as cyclohexaaluminate Ca₃[Al₆(OH)₂₄] · 18 H₂O is proposed.     

Thermochemische,kristallographische und infrarotuntersuchungen an calciumkupferhydroxychlorid-hydraten

Copper immersed in 1 N CaCl₂ solution containing NH₃ corrodes in the presence of oxygen with the formation of blue crystals of the compound 4 Cu(OH)₂ · CaCl₂ · 3.5 H₂O. The unit cell is tetragonal with a = 9.392 Å, c = 15.077 Å, c/a = 1.605; Z = 4. The calculated density is 2.818 g cm^?3 and the observed density 2.80 g cm^?3 at 22°C. The crystallographic aspect is P4₂**. Heating up to 400°C results in stepwise decomposition without sharp separation of the steps. The first step (165°C) gives 4 Cu(OH)₂ · CaCl₂ · 0.5 H₂O, tetragonal body centered, a = 9.34₂ Å, c = 7.53₃ Å, c/a = 0.806₄. The second step (215°C) gives CuO + 2 Cu(OH)₂ · CuO · CaCl₂ · H₂O, cubic primitive (pseudocubic?) a = 5.74 ± 0.017 Å and the third step (260°C): 4 CuO + CaCl₂.The first and the third step rehydrate in air at ambient temperature, the first step to the original material and the 3rd step to CuO + 3 Cu(OH)₂ · CaCl₂ · H₂O. This compound is hexagonal a = 6.66₃ Å, c = 5.81₅ Å, c/a = 0.872₇.The decomposition process is characterized by pseudomorphosis. At least for the first decomposition step, a topotaxial relationship is assumed.Diffraction and infrared data of the different compounds are given.     

Über den Einfluß von Kristallkeimen auf die Bildung von Silicaten der Zusammensetzung 3 CaO · 2 SiO2

On the Influence of Seed Crystals on the Formation of Calcium Silicates with the Composition 3 CaO · 2 SiO₂ The formation of the calcium silicates kilchoanite and rankinite of the composition 3 CaO · 2 SiO₂ is facilitated and enabled, respectively, in the presence of appropriate seed crystals. Kilchoanite (Ca₆[(SiO₄)(Si₃O₁₀)]) is formed from mixtures of CaO and SiO₂ in the autoclave at 200°C and from C? S? H (di, poly) under normal atmosphere at 700°C by seeding for example with kilchoanite, aluminium compounds, γ-Ca₂SiO₄. Rankinite (Ca₃Si₂O₇) can be synthesized under the same conditions, when rankinite itself is applied as seed crystal.     

Preparation and thermophysical properties of a novel form-stable CaCl<Subscript>2</Subscript>·6H<Subscript>2</Subscript>O/sepiolite composite phase change material for latent heat storage

In this work, CaCl₂·6H₂O/sepiolite was successfully designed and synthesized as a novel form-stable composite phase change material by vacuum impregnation method, using sepiolite as a sustainer and CaCl₂·6H₂O as phase change material. Scanning electron microscope and Fourier transform infrared spectroscopy measurements display that CaCl₂·6H₂O is filled into the porous structure of sepiolite by physical interactions. Phase transformation behavior and thermal stability were revealed from differential scanning calorimetry and thermogravimetric analysis, respectively. Results show that the melting enthalpy of the composite phase change material containing 70% CaCl₂·6H₂O can achieve 87.9 J g^?1, and the composite PCM has a good thermal stability in the temperature range from 25 to 100 °C. Meanwhile, the crystal structure of CaCl₂·6H₂O is maintained in the porous structure of sepiolite observed by X-ray diffraction. It means that sepiolite reduces the super-cooling of CaCl₂·6H₂O which ensures the good phase change behavior of the composites. These results exhibit that the CaCl₂·6H₂O/sepiolite composite phase change material possesses high latent heat. Moreover, low cost of the sepiolite enables the composites to be a good candidate for latent heat storage.     

Synthesis and Crystal Structure of the First Thallium Hydrous Nesosilicate Tl4SiO4·0.5H2O

Orange prismatic crystals of the first thallium hydrous nesosilicate Tl₄SiO₄·0.5H₂O have been obtained by evaporation from aqueous solution. There are three symmetrically independent Tl⁺ cations and five symmetrically independent oxygen atoms in the structure of Tl₄SiO₄·0.5H₂O. The O(4) and O(5) atoms belong to water molecules. Coordination polyhedra of the Tl⁺ cations are strongly distorted because of the stereoactive behavior of lone electron pairs. The structure of Tl₄SiO₄·0.5H₂O contains sheets of SiO₄ tetrahedra and Tl coordination polyhedra. The sheets have the composition [Tl₃SiO₄]^– and are parallel to [100]. Within the sheets, SiO₄ tetrahedra link to thallium polyhedra though common corners. The sheets are linked by dimers of face‐sharing Tl(3)O₅ polyhedra, thus providing interconnection of the sheets into a framework. The framework has large elliptical channels occupied by water molecules (OW2) and electron pairs of Tl⁺ cations.The comparison with some other M⁺ (M = K, Ag, Tl) silicates is given.     

Experimental Densities, Speeds of Sound, Isentropic Compressibilties and Shear Relaxation Times of CaSO4·2H2O + CaCl2 + H2O and CaSO4·2H2O + NaCl + H2O Systems at Temperatures 30 and 35 °C

Speeds of sound, u, have been measured as a function of concentration for the systems, CaSO₄·2H₂O +CaCl₂ + H₂O and CaSO₄·2H₂O + NaCl + H₂O, at temperatures of 30 and 35 °C. Derived parameters such as the isentropic compressibility, κ _S , and the shear relaxation time,τ,were calculated using the experimental speed of sound data in combination with viscosity values from our earlier work. Results have been compared with those of the CaCl₂+ H₂Oand NaCl + H₂O systems reported in literature,to examine the effect of adding CaSO₄·2H₂O(s).Values of κ _S for the system,CaSO₄·2H₂O + CaCl₂+H₂O,are smaller compared with those for the CaCl₂+ H₂O system.Values of τ are lower at lower concentrations and then cross over in a narrow concentration region.Values of κ _S for the system,CaSO₄·2H₂O+NaCl+H₂O, are also smaller when compared with those forthe NaCl +H₂O system.For this system the τ values are higher. These τ values reach a minimum at a certain concentration of NaCl in the solution and then increase with further increases in concentration.The influenceof solvent-separated and/or solvent-shared ion pairs plays a dominant role at higher concentrations for both systems.Results have been interpreted and discussed in terms of the expansion and contraction of the primary hydration shell of the ionic species present in the studied systems.     

2‐Amino­pyridinium–fumarate–fumaric acid (2/1/1)

The title complex, 2C₅H₇N₂⁺·C₄H₂O₄²⁻·C₄H₄O₄, contains cyclic eight‐membered hydrogen‐bonded rings involving 2‐­aminopyridinium and fumarate ions. The fumaric acid mol­ecules and fumarate ions lie on inversion centers and are linked into zigzag chains by O—H⋯O hydrogen bonds. The dihedral angle between the pyridinium ring and the hydrogen‐bonded fumarate ion is 7.60 (4)°. The fumarate anion is linked to the pyridinium cations by intermolecular N—H⋯O hydrogen bonds. The heterocycle is fully protonated, thus enabling amine–imine tautomerization.     

New Fluoromanganate(III) Hydrates: Mn3F8 · 12H2O and AgMnF4 · 4H2O

Single crystals of fluoride hydrates Mn₃F₈ · 12 H₂O and AgMnF₄ · 4 H₂O have been prepared and characterized by X-ray methods. Mn₃F₈ · 12 H₂O crystallizes in the space group P1 (a = 623.0(3), b = 896.7(4), c = 931.8(4) pm, α = 110.07(2)°, β = 103.18(2)°, γ = 107.54(2)°, Z = 1); AgMnF₄ · 4 H₂O crystallizes in the space group P2₁/m (a = 700.9(2), b = 726.1(1), c = 749.4(3) pm, β = 107.17(3)°, Z = 2). Both structures contain Jahn-Teller-distorted [Mn(H₂O)₂F₄]^? anions as well as crystal water molecules and exhibit a complex hydrogen bond network between anions and cations, i. e. [Mn(H₂O)₆]²⁺ for the first and a polymeric [Ag(H₂O)₂]^? cation for the second compound.     

CaCl2·6H2O/Expanded graphite composite as form-stable phase change materials for thermal energy storage

In this study, CaCl₂·6H₂O/expanded graphite (EG) composite was prepared as a novel form-stable composite phase change material (PCM) through vacuum impregnation method. CaCl₂·6H₂O used as the PCM was dispersed by surfactant and then, was absorbed into the porous structure of the EG. The surfactant was used to enhance the bonding energy between CaCl₂·6H₂O and EG, which fulfilled the composites with good sealing performance and limited the leakage of the inside CaCl₂·6H₂O. Differential scanning calorimetry and thermal gravimetric analysis show that all the composite PCMs possess good thermal energy storage behavior and thermal stability. Thermal conductivity measurement displays that the conductivities of the samples have been significantly improved due to the highly thermal conductive EG. The thermal conductivity of the sample including 50 mass% CaCl₂·6H₂O (8.796 W m^?1 K^?1) is 14 times as that of pure CaCl₂·6H₂O (0.596 W m^?1 K^?1). Therefore, the obtained composite PCMs are promising for thermal energy storage applications.     

Effects of heating rate (1–300° h−1) on the non-isothermal thermogravimetry of CuSO4 · 5 H2O

The course of the reaction CuSO₄ · 5 H₂O ? CuSO₄ · H₂O + 4 H₂O was studied by non-isothermal thermogravimetry with various heating rates ranging from 1 to 300° h^?. The measurements were made either in static air, in a dry nitrogen stream, or in water vapor at a reduced pressure (9 mm Hg). In static air, the shape of the TG curve changed drastically at a heating rate of 13 to 15° h^?, and this change was explained by considering the nature of the plateaus and inflections present. In a dry nitrogen stream, the dehydration is made much easier at slow heating rates and occurs almost in one step at 2° h^?; in water vapor at 9 mm Hg, on the other hand, a very distinct two-step curve is obtained at 1° h^?. This can reasonably be compared with the phase diagram of copper sulfate.     

Zum Aufbau schlecht geordneter Calciumhydrogensilicate. I. Bildung und Eigenschaften einer schlecht geordneten Calciumhydrogendisilicatphase

On the Structure of Ill-crystallized Calcium Hydrogen Silicates. I. Formation and Properties of an Ill-crystallized Calcium Hydrogen Disilicate Phase Investigations on ill-crystallized calcium hydrogen silicates (C? S? H phases) prepared by precipitation from sodium silicate solutions with calcium chloride have shown that at temperatures 0°C primarily hydrogen silicates with such an anion composition will be formed, which had been present before in the sodium silicate solution. They are not stable. On storing the precipitate in the mother liquid at 0°C they are converted into disilicate with a composition of 1.1–1.5 CaO/SiO₂, if the concentration of Ca(OH)₂ is more than 0.8 g/l. After drying the thermally very instable solid at ?10°C the calcium hydrogen disilicate phase can be isolated. A structure proposal for this phase is given.     

Phase equilibria in the Na,K,Mg,Ca‖SO4,Cl-H2O system at 25°C in the MgSO4 · 5H2O and MgSO4 · 4H2O crystallization region

Phase equilibria in the Na,K,Mg,Ca‖SO₄,Cl-H₂O system at 25°C in the MgSO₄ · 5H₂O and MgSO₄ · 4H₂O crystallization region are studied using the translation method. MgSO₄ · 5H₂O and MgSO₄ · 4H₂O, which are equilibrium phases of the system at 25°C, are each involved in two invariant points, seven monovariant curves, and nine divariant fields. Fragments of the phase equilibria diagram for the title system in the MgSO₄ · 5H₂O and MgSO₄ · 4H₂O crystallization region are constructed.