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.     

A procedure for silicate rock analysis based on ion exchange and complex-ion formation

A procedure for the analysis of silicate rocks based on ion exchange and complex-ion formation is described. Moisture (H₂O^-), SiO₂, TiO₂, Al₂O₃, P₂O₅, total iron, MgO, MnO, and CaO are determined in a 1-g sample. Other oxides, such as FeO, Na₂O and K₂O, and H₂O⁺ are determined in separate portions. The results for 6 silicates, including G-I and W-I, compare favorably with. those obtained by established procedures. Six complete analyses may be carried out in about 8 days.     

Zur Kenntnis der kristallinen Phasen in den Systemen MO?Al2O3?H2O (MI = K,Na)

On the Crystalline Phases of the Systems M O? Al₂O₃? H₂O (M^I = K, Na) In the system K₂O? Al₂O₃? H₂O the compounds K₂O · Al₂O₃ · 3 H₂O, K₂O · Al₂O₃ · 2 H₂O and K₂O · Al₂O₃ · 1 H₂O exist. The results of ²⁷Al and ¹H NMR and IR spectroscopic investigations as well as thermoanalytical measurements confirm the existence of dimeric anions with tetrahedrally coordinated Al for the 3-hydrate. In the case of the two other hydrates higher molecular anions occur, also formed by AlO₄ tetrahedra. In the system Na₂O? Al₂O₃? H₂O a compound with a composition Na₂O · Al₂O₃ · 2,5 H₂O and two alkali oxide rich phases (Na/Al > 3) are observed. In monosodium aluminate hydrate there are highly polymerized anions with tetrahedrally coordinated Al, whereas the alkali oxide rich phases are probably built up by monomeric [Al(OH)₆]^3? anions.     

Die Kristallstruktur des Natriumoxohydroxoaluminathydrates Na2[Al2O3(OH)2] · 1,5 H2O

The Crystal Structure of the Sodium Oxohydroxoaluminate Hydrate Na₂[Al₂O₃(OH)₂] · 1.5 H₂O The crystal structure of the sodium oxohydroxoaluminate hydrate Na₂[Al₂O₃(OH)₂] ·s 1.5 H₂O (up to now described as Na₂O · Al₂O₃ · 2.5 H₂O and Na₂O · Al₂O₃ · 3 H₂O, respectively) was solved. The X-ray single crystal diffraction analysis (tetragonal, space group P-42₁m, a = 10.522(1) Å, c = 5.330(1) Å, Z = 4) results in a polymeric layered structure, consisting of AlO_3/2(OH) tetrahedral groups. Between these layers the Na⁺ ions are situated, which form tetrameric groups of face-linked NaO₆ octahedra. The involved O^2? ions are due to Al? O? Al bridges, Al? OH groups and water of crystallization. ²⁷Al and ²³Na MAS NMR investigations confirm the crystal structure analysis. The relations between the crystallization behaviour of the compound and the constitution of the aluminate anions in the corresponding sodium aluminate solution and in the solid, respectively, are discussed.     

Ionic conductivity in Na+, K+, and Ag+ β″-alumina

This paper presents measurements of the ionic conductivity in single crystals of β″-alumina (0.84 M₂O · 0.67 MgO · 5.2 Al₂O₃, M = Na, K, Ag). Single crystals of sodium β″-alumina were grown from a melt of Na₂O, MgO, and Al₂O₃ at 1660 to 1730°C. Selected crystals were converted to the other isomorphs by ion exchange. The conductivity of sodium β″-alumina varies from 0.18 to 0.01 (ohm · cm)^?1 at 25°C depending upon crystal growth conditions. Potassium β″-alumina has the unusually high room temperature conductivity of 0.13 (ohm · cm)^?1. Silver β″-alumina has a slightly lower conductivity, 4 × 10^?3 (ohm · cm)^?1 at 25°C. The activation energies of sodium and potassium β″-alumina decrease with increasing temperature, while that of silver β″-alumina is constant from ?80 to 450°C.     

Hydrothermal Alteration of Andesite in Acid Solutions: Experimental Study in 0.05 M H2SO4 Solution at 110 °C

Hydrothermal experiments on an andesite have been carried out under the condition of 110 °C, autogeneous pressure, 0.05 M H₂SO₄ solution and renewal of acid solution every 6 hours. The experimental results indicate that the plagioclase and pyroxenes in the treated samples show micropits and microfractures. Small crystals readily suffered from alteration, as compared with large ones, and the susceptibility of the minerals to the acid solution is decreased in the order of plagioclase, augite, hypersthene and opaque minerals. Plagioclase, which is the most reactive mineral in the experiments, shows an increase of SiO₂, but a decrease of Al₂O₃, CaO and Na₂O as the experiments proceeded. The chemical change of the treated andesite, it indicates that the relative amounts of SiO₂, TiO₂, MgO, ΣFeO, MnO and K₂O increase, while those of Al₂O₃, CaO, Na₂O and P₂O₅ decrease with an increase of the experimental duration. The relative mobility of chemical elements listed in decreasing order is P, Ca, Al, Na, Si, K, Mg, Fe, Mn and Ti in terms of the K value. It is no wonder that Ca, Al and Na are more mobile than others because these elements are readily released into solution from the more reactive plagioclase, while Mg, Fe etc. still stay in the less reactive pyroxenes and opaque minerals.     

Solid Solutions of Calcium Aluminates C3A,C12A7 and CA with Sodium Oxide

The research concerns the influence of a substantial range of sodium ion concentrations on the structure of the calcium aluminates C₃A*, C₁₂A₇ and CA until CaO is emitted. The research also shows the influence of sodium ions of the cell parameters of each calcium aluminate and what reaction occur in mixtures of Na₂O and calcium aluminates at elevated temperatures. This revised version was published online in August 2006 with corrections to the Cover Date.     

Analysis of silicates

Conclusions Using a new rapid method, K₂O, Na₂O, CaO, MgO, Al₂O₃, and Fe₂O₃ were determined in silicates according to a single procedure, from a single sample.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1648–1655, August, 1967.     

Effect of the Composition of Raw Materials and Nucleating Agents. Crystallization behavior of nepheline-pyroxenic glass

Different combination of raw materials and nucleating agents were incorporated in the batch of nepheline-pyroxene glass to demonstrate their effect on the crystallization process. The effect of TiO₂, Cr₂O₃ and LiF with respect to crystallization of base glass was studied by differential thermal analysis (DTA).These materials improved the crystallization of glass between 50 to 150°C of heat treatment. When LiF+TiO₂ and TiO₂+Cr₂O₃ were put together in the glass batches, the rate of crystallization of glass was increased in the same manner. The presence of TiO₂+LiF+Cr₂O₃ improved the crystallization of the glass by decreasing the heat temperature by about 60°C. CaO/MgO and CaO/Na₂O ratios played an important role in the rate of crystal growth. The increase in the CaO/MgO ratio lowers the crystallization temperature by values ranging between 37 and 46°C. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nature of influence exerted by Na<Subscript>2</Subscript>SiF<Subscript>6</Subscript> on REE recovery from orthophosphoric acid solution in the course of CaSO<Subscript>4</Subscript>·0.5H<Subscript>2</Subscript>O crystallization

Chemical and X-ray phase analyses were used to study the influence exerted by Na₂SiF₆ on the isomorphic inclusion of cerium into the structure of CaSO₄?0.5H₂O precipitates formed from solutions of phosphoric acid hemihydrate (38 wt % P₂O₅). The poorly soluble suspensions of CaSO₄?0.5H₂O precipitates can serve as adsorbents for cerium compounds, with CaSO₄?0.5H₂O–NaCe(SO₄)₂?H₂O and CaSO₄?0.5H₂O–CePO₄?0.5H₂O solid solutions formed. The introduction of Na₂SiF₆ makes the sorption properties CaSO4?0.5H2O several times better because the Na₂SiF₆ phase is a source of sodium cations and creates the necessary Na: Ce ratio of 1: 1 for extracting cerium from the liquid phase into a precipitate in the form of a CaSO₄?0.5H₂O–[NaCe(SO₄)₂?H₂O + CePO₄?0.5H₂O] solid solution. Under the industrial conditions in which extraction phosphoric acid is manufactured, a similar isomorphous capture of rare-earth elements of the cerium group (La–Sm) may occur in joint precipitation of CaSO₄?0.5H₂O and Na₂SiF₆.     

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.     

Thermodynamic Investigation of Crystallization Behaviour of Pyroxenic Basalt-Based Glasses

For a series of pyroxenic basalt-based glasses, DTA was used to elucidate the changes occurring on including specified oxidizing agents and rectifying oxides Na₂O and/or CaO, or CaO+MgO to modify one or more of the ratios FeO:Fe₂O₃, CaO:Na₂O and CaO:MgO that affect the monominerality and crystallization behaviour. From comparisons of the positions, characters and intensities of the DTA peaks, the effects of the rectifying component on the crystallization processes were readily demonstrated. The higher crystallizabilities exhibited when MnO₂ was used as oxidizing agent and Na₂O and/or MgO as rectifying oxides were related to their effects in reducing the viscosity of the glass and in enhancing the nucleation rate of the glass.     

熔融制样X射线荧光光谱法测定碳酸盐岩样品中的主次成分

采用复合熔剂玻璃熔片法制备样片，X射线荧光光谱法测定碳酸盐岩样品中SiO₂、Fe₂O₃、Al₂O₃、TiO₂、CaO、MgO、K₂O、Na₂O、MnO和P₂O₅等主次成分.使用理论α系数校正基体效应，国家一级标准物质验证，方法简单快速.测量结果各元素相对标准偏差（RSD，n=12）低于10%（除含量在检出限附近的元素外），检出限低，能够符合地矿行业的要求.     

Porous Al2O3/Al Metal Ceramics Prepared by the Oxidation of Aluminum Powder under Hydrothermal Conditions Followed by Thermal Dehydration: IV. Effect of Oxide Additives on the Composition and Texture Characteristics of MO x /Al2O3/Al Composites

The synthesis, structure, and texture of metal ceramics based on Al₂O₃/Al with powdered oxide additives (CaO, MgO, Al₂O₃, La₂O₃, and TiO₂) were studied. Analytic expressions were derived to relate the main macroscopic characteristics of the composites.     

Farbeffekte in oxidischen and anderen Mn2+-Verbindungen – die Ligandenfeldspektren von MgO/MnO- und CaO/MnO-Mischkristallen sowie von MnAl2O4

Colour Effects in Oxidic and Other Mn²⁺ Compounds – the Ligand Field Spectra of Mixed Crystals MgO/MnO, CaO/MnO, and of MnAl₂O₄ The colour intensity and the shift of the hue is examined for mixed crystals Mg_1?xMn_x^IIO and Mn_1?y^IICa_yO in dependence of the Mn²⁺-concentration and interpreted in terms of Mn²⁺? Mn²⁺ pair interactions and variations of the Mn? O bond length, respectively. The experimental band positions (sextet-quartet transitions) could be fitted quantitatively – also in case of Mn²⁺ in tetrahedral (MnAl₂O₄) and dodecahedral oxygen coordination (Mn₃Al₂Ge₃O₁₂, MnY₂Mg₂Ge₃O₁₂) – by means of crystal field calculations. The obtained ligand field parameters are discussed in comparison with data for octahedral Mn²⁺ ions with H₂O, F^? and Cl^? as ligands.     

Zur Kenntnis von Natriumarseniten im Dreistoffsystem Na2O?As2O3?H2O bei 6°C

Concerning Sodium Arsenites in the Three Component System Na₂O? As₂O₃? H₂O at 6°C Four phases Na₂(H₂As₄O₈) 1c , NaAsO₂ · 4 H₂O 2c , Na₂(HAsO₃) · 5 H₂O 3c , and Na₅(HAsO₃)(AsO₃) · 12 H₂O 4c have been identified in the system Na₂O? As₂O₃? H₂O at 6°C and characterized by X-ray structural analysis. Polymetaarsenite anions, adopt in 1c and 2c , respectively, octet or doublet single chains.     

Effect of ODS-Modified Shirasu Porous Glasses on Retention and Selectivity in Liquid Chromatography

Shirasu porous glass (SPG, S0) prepared from Japanese volcanic ashes has been studied for the purpose of obtaining low cost and easy availability materials for chromatography, especially for separation and collection of large amounts of sample. After treatment of S0 with 6M HCl and refluxing in an oil bath for 16h, the glass produced was determined to be: 0.94 wt% Al₂O₃, 0.10 wt% Na₂O, 0.04 wt% CaO and 0.01 wt% Fe₂O₃ in treated Shirasu porous glass. On the other hand, the original S0 was determined to be 11.0 wt% Al₂O₃, 8.7 wt% Na₂O, 2.30 wt% CaO and 0.34 wt% Fe₂O₃, respectively. Experimental results showed that ODS-modified Shirasu porous glass gave a significant improvement in the separation of the model compounds.     

Kinetic studies of the crystallization process of glass-ceramics based on basalt

The crystallization kinetic of the basalt glass ceramic of the oxide composition, (%): SiO₂ − 50.82; Al₂O₃ − 12.05; Fe₂O₃ − 9.28; CaO − 15.48; MgO − 11.08; Na₂O+K₂O − 1.14; TiO₂ − 0.15, with addition of 10% TiO₂ as nucleating agent has been studied using thermal analysis under non-isothermal conditions. In this order, the non-isothermal DTA curves were obtained at different heating rates between 4 and 20°C min⁻¹ in the temperature range of 25–1000°C using a Derivatograph-C (MOM, Hungary). The kinetic parameters of the crystallization process were calculated on the basis of Ozawa-Flynn-Wall, Friedman, Budrugeac-Segal and non-parametric kinetic methods.     

Nonanatrium-bis(hexahydroxoaluminat)-trihydroxid-hexahydrat (Na9[Al(OH)6]2(OH)3 · 6H2O) – Kristallstruktur,NMR-Spektroskopie und thermisches Verhalten

Nonasodium Bis(hexahydroxoaluminate) Trihydroxide Hexahydrate (Na₉[Al(OH)₆]₂(OH)₃ · 6H₂O) – Crystal Structure, NMR Spectroscopy and Thermal Behaviour The crystal structure of the nonasodium bis(hexahydroxoaluminate) trihydroxide hexahydrate Na₉[Al(OH)₆]₂(OH)₃ · 6H₂O (4.5 Na₂O Al₂O₃ · 13.5 H₂O) (up to now described as 3 Na₂O · Al₂O₃ · 6H₂O, 4Na₂O · Al₂O₃ · 13 H₂O and [3 Na₂O · Al₂O₃ · 6H₂O] [xNaOH · yH₂O], respectively) was solved. The X-ray single crystal diffraction analysis (triclinic, space group P1 , a = 8.694(1) Å, b = 11.344(2) Å, c = 11.636(3) Å, α = 74.29(2)°, β = 87.43(2)°, γ = 70.66(2)°, Z = 2) results in a structure, consisting of monomeric [Al(OH)₆]^3? aluminate anions, which are connected by NaO₆ octahedra groups. Furthermore the structure contains both, two hydroxide anions only surrounded by water of crystallization and OH groups of [Al(OH)₆]^3? aluminate anions and a hydroxide anion involved in three NaO₆ coordination octahedra directly and moreover connected with a water molecule by hydrogen bonding. The results of ²⁷Al and ²³Na-MAS-NMR investigations, the thermal behaviour of the compound and possible relations between the crystal structure and the conditions of coordination in the corresponding sodium aluminate solution are discussed as well.     

Subsolidus equilibria in the system BaO.TiO2.Al2O3

The subsolidus phase equilibrium relations in the system BaO.TiO₂.Al₂O₃ have been investigated using conventional solid state reaction techniques and X-ray powder diffraction. The existence of three known ternary compounds, BaTi₅Al₂O₁₄, BaTiAl₆O₁₂, and Ba₃TiAl₁₀O₂₀, was confirmed and their stability relations were studied. Various tie-lines existing between the ternary compounds and the binary titanates and aluminates of barium were established and a subsolidus phase diagram showing the phase assemblages compatible at 1200°C is presented.