Röntgenographische Bestimmung der thermischen Störung in den Kristalliten partiell kristallisierter Polyäthylene

Summary The dielectricα _a - andβ _a -absorptions in the linear high polymers whose dipoles are short and rigidly attached to their main chains are investigated theoretically and compared with our observed data. Suffix “a” represents that dielectric absorption comes from amorphous part. Examples of this kind are polyvinyl chloride, polyvinyl bromide, polyethylene isophthalate, polyethylene terephthalate and polyoxymethylene. Theα _a -absorptions are attributed to the re-orientations of their dipoles due to the segmental micro-Brownian motions of the polymer chains in the amorphous part. Theβ _a -absorptions seem to be caused by local micro-Brownian motions of the polymer chains. Theβ _a -absorptions are described by a model of local viscoelastic relaxations of the “dipoles” in the vicinity of their equilibrium directions. Here, the term “dipole” represents the resultant dipole of the permanent dipoles in the motional unit which has about the same order of magnitude as the monomer unit. Thus the various properties ofα _a - andβ _a -absorptions are calculated and agree with our observed values at least semi-quantitatively. In the second section the equations ofα _a - andβ _a -absorptions are derived. The properties of theα _a -absorptions are calculated in the third section and compared with our observed data. The magnitudes ofα _a -absorptions of the semi-crystalline polymers are smaller than those of the amorphous polymers even in the amorphous samples of the semi-crystalline-polymers. The temperature dependence of the magnitude ofα _a -absorption is far gentler in the crystalline polymer compared with the amorphous at temperatures higher than glass transition temperature (T _g ). These observed tendencies are explained by our theory. The calculated values of the activation energies ofα _a -absorptions are 50 ≈ 150 kcal/mol, the same orders as the observed values. The shape of theα _a -absorption is given by the form [ε(iω) -ε∞]/[ε ₀-g3 _∞] = [(1+iω π ₁ (1 +iωπ ₂)^−1/2 at temperatures higher thanT _g . This is in good agreement with the observed shape in the amorphous polymer, not only for the order of breadth but also for the order of asymmetry. The shape of theα _a -absorption in the semi-crystalline polymer is given by a superposition of the above formula and leads to the same order of breadth as the observed shape, too. The properties ofβ _a absorptions are calculated in the fourth section with the aid of the above mentioned model. The calculated values of the magnitudeβ _a -absorptions show fairly good agreement with the observed values too. The temperature dependence of the magnitude ofβ _a -absorption is discussed. The calculated values of the activation energies of theβ _a -absorptions are of the order 10 ≈ 20 kcal/mol, in good agreement with the observed values. The shape ofβ _a -absorption is also given by a superposition of the above formula and leads to the same order of breadth as the observed shape. The order of asymmetry of our theoretical absorption curve agrees with that of the observed curve.

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Vorgetragen auf der Sitzung des Fachausschusses Physik der Hochpolymeren im Verband der Deutschen Physik. Gesellschaft auf der Physikertagung in Wien, 21. Okt. 1961.

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Mit 11 Abbildungen und 3 Tabellen     

LixNi0.5Co0.5O2的态密度计算及电化学性能研究

>为获得综合性能更好的锂离子二次电池正极材料, 分析了Co掺杂对Li_xNiO₂电化学性能的影响. 采用密度泛函DFT理论对Li_xNiO₂和Li_xNi_0.5Co_0.5O₂的平均放电电压和态密度进行了计算. 同时, 用共沉淀法制备了Li_xNiO₂和Li_xNi_0.5Co_0.5O₂锂离子二次电池正极材料, 并对其进行了XRD结构分析和恒流充放电测试. 实验和计算结果表明: 随锂离子嵌入正极(电池放电), 电池的电压逐渐降低, 材料的态密度峰向低能量方向移动; 与Li_xNiO₂相比, Li_xNi_0.5Co_0.5O₂的电压平台相对较高(当0.25≤x≤0.5), 而且在Li^＋嵌/脱时, Li_xNi_0.5Co_0.5O₂的结构变化相对较小; Co离子的掺入, 减小了NiO₆八面体的畸变度, 使材料的电化学稳定性得以提高. 在钴掺杂镍酸锂体系中, NiO₆和CoO₆具有相互的稳定作用.     

Beiträge zur chemie der halogensilan-addukte XV. 2,2′-bipyridin- und 1,10-phenanthrolin-komplexe von halogendisilanen und Si3Cl8

A series of mono-bipy and -phen complexes (bipy = bipyridine, phen = phenanthroline) of the perhalodisilanes, Si₂F₆, Si₂Cl₆ and Si₂Br₆, mixed methylhalodisilanes (Si₂Me_nX_6?n, X = Cl, I; n = 2,3) and Si₃Cl₈ · bipy have been prepared by reaction of the components, and have been characterized. $\text{1}\text{1}$ complexes are obtained exclusively.The structures of all complexes involve coordination of the base to the more acidic silicon and perpendicular alignment of the SiSi axis on the plane of the ligand. This may be rationalised in terms of steric requirements of the different groups, the more demanding groups occupying the sterically more favorable positions vertical to the plane of the ligand. For Si₃Cl₈ · bipy, spectroscopic and chemical evidence suggests bipy-coordination to the center silicon. PMR investigations of the dissociation equilibria of the complexes in solution led to determination of the heats of formation of four of the complexes and to a qualitative estimation of the relative acceptor strengths of several disilanes. Contrary to expectation, silyl groups increase the acceptor strength of silicon considerably and in the order SiMe₃ < SiMe₂Cl < SiMeCl₂ < SiCl₃. The effect of a SiMe₃, substituent group may be compared to that of Cl. Methylchlorosilyl groups may exceed the effect of Cl as indicated by the increase in acceptor strength in the sequence (R =) Me < Ci < SiMe₂Cl < SiMeCl₂ for the acceptor RSiCl₂Me. Si₃Cl₈ is the strongest acceptor in the series. Assuming the structural suggestion for Si₃Cl₈ · bipy (center coordination) to be correct an increase in acceptor strength is indicated in the sequence SiCl₃(Si₂Cl₅) < SiCl₂(SiCl₃)₂ (Si = coordinating center). This may be interpreted mainly in terms of charge accepting capacity of the polarisable silyl groups. Another interesting sequence of acceptor strengths measured in this work is 1,1,2-Si₂Me₃F₃, 1,2-Si₂Me₂F₄ < Si₂Me₃Cl₃ < 1,2-Si₂Me₂Cl₄, showing fluorodisilanes to be weaker acceptors than chlorodisilanes. This result is compared to the heats of formation of SiX₄ · 2py complexes.     

Fluorimetric determination of phytic acid in urine based on replacement reaction

A sensitive fluorimetric method for determination of phytic acid in human urine samples was described. The method was based on a fluorimetric replacement reaction, in which the added phytic acid replaced the Cu²⁺ ion from Cu²⁺-gelatin complex, liberating the fluorescent gelatin molecule. The fluorescence of the solution was accordingly recovered proportionally to the amount of the foreign phytic acid. The excitation wavelength was 273.5 nm and the characteristic emission wavelength was 305.0 nm, respectively. The calibration graph was obtained by plotting the recovered fluorescent intensity at maximum 305.0 nm against the added standard phytic acid, and was divided into two sections. One section was linear over the range of 0.40-2.40 mg L⁻¹ with a linear regression equation of I_f = −0.895 + 15.146c (R² > 0.9993), and the other over the range of 2.40-9.20 mg L⁻¹ with a linear regression equation of I_f = −29.526 + 26.113c (R² > 0.9996), respectively. The relative standard deviation (R.S.D.) at 95% confidence degree for a 2.0 mg L⁻¹ of standard phytic acid within 1 month was less than 1.26% (n = 5), indicating the procedure is reproducible. The detection and the quantification limits of phytic acid were estimated to be 0.23 and 0.40 mg L⁻¹, respectively. The proposed method was applied to the determination of phytic acid in urine samples and the found concentrations of phytic acid in urine were in the range of 0.49-0.75 mg L⁻¹ with recoveries of 96.2-108.8%. Comparison of the obtained results with the reported HPLC was performed, indicating the proposed method was reliable.     

Linear expansion of the eigenvalues of a Hermitian matrix and its application to the analysis of the electronic spectra of 3d ions in crystals

It is shown that the eigenvalues E_i of a Hermitian matrix H with matrix elements H_ij = Σ_kA^k_ija_k, where A^k_ij are known numbers and a_k a set of parameters, can be exactly expanded as $\text{E}{}_{\mathrm{i}}\text{= Σ}{}_{\mathrm{k}}\text{(}\text{?E}{}_{\mathrm{i}}\text{?a}{}_{\mathrm{k}}\text{)a}{}_{\mathrm{k}}$. This property is applied to the analysis of the optical spectra of transition metal ions in crystals proposed by L. Pueyo, M. Bermejo, and J. W. Richardson (J. Solid State Chem.31, 217, 1980), and it is shown that this method represents the best fit of the Hamiltonian eigenvalues to the observed (or calculated) spectrum. Further advantages of using this property, in connection with the spectral analysis, are the minimization of the errors associated with the numerical approximations and a reduction in computer time. In the molecular orbital calculation of the optical or uv spectra of these systems, this linear expansion of the eigenvalues give a detailed interpretation of the improvements produced by refined calculations, such as those including configuration interaction. In particular, the changes in one-electron energy and in open-shell repulsion interactions associated with the refinement can be clearly and easily formulated. As examples, the computed spectra of CrF^4?₆ and CrF^3?₆ are discussed.     

A thermometric study of the dissolution of copper in acid solutions

The dissolution of Cu in solutions of HNO₃ of different concentrations has been studied by the thermometric method. Starting from the initial temperature, T_i, the temperature—time curves exhibit an induction period followed by a rapid rise in temperature to a maximum value, T_m, attained t min after the start of the reaction. T_m increases and t decreases with increase of the acid concentration, M. ΔT (i.e.T_m ? T_i) and the reaction number (R.N. = (T_m ? T_i)/t) vary with M according to: ΔT = k(M ? M₀) and R.N. = A₁Mⁿ, where k, M₀, A₁ and n are constants.The effect of varying concentrations of HCl, H₂SO₄ and H₃PO₄ on the R.N. of Cu in 3.5 M HNO₃ was examined. Small amounts of these acids lower the R.N. (inhibition) due to the displacement of an active species on the surface of the metal by the anion of the acid. Larger additions of the acids accelerate dissolution. The concentration at which the added acid changes from corrosion-inhibitor to accelerator varies as HCl < H₂SO₄ < H₃PO₄. This sequence is considered to parallel the strength of adsorption of the respective anions. The results of experiments with salt additions confirm this view; all salts act only as dissolution-retardants. Calculations pertaining to the effect of the various ions on the R.N. support the conclusion that the dissolution of Cu in HNO₃ is autocatalytic in nature, and depends on the [H⁺]/[NO₃^?] ratio.Cu does not dissolve in air-free, cold HCl. Attack takes place, however, in the presence of KNO₃. Under these conditions attack is of the pitting- rather than the general type. The temperature rises suddenly after an incubation period, which decreases in length with increase of the amount of the added salt.Proof of the involvement of HNO₂ in the autocatalytic cycle of Cu dissolution in HNO₃ is obtained from the results of urea additions to the solution.     

Fluorescence enhancement effect for the determination of DNA with calcein-cetyl trimethyl ammonium bromide system

A new spectrofluorimetric method was developed for the determination of trace amounts of DNA using the calcein as a fluorescent probe. In the presence of appropriate amounts of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB), the anionic dye calcein dimerizes. The weak fluorescence intensity of the dimer was enhanced by adding DNA at pH 6–7. The interaction between calcein–CTAB and DNA was studied on the basis of this behavior and a new method was developed for determining DNA. Under the optimal conditions, the enhanced fluorescence intensity was in proportion to the concentration of DNA in the range of 4.0 × 10⁻⁶ to 8.0 × 10⁻⁵ g L⁻¹ for fsDNA and thermally denatured ctDNA (4.5 × 10⁻⁶ to 9.0 × 10⁻⁵ g L⁻¹). The detection limits (S/N = 3) were 2.0 × 10⁻⁶ and 2.2 × 10⁻⁶ g L⁻¹, respectively. This method was used for determining the concentration of DNA in synthetic samples with satisfactory results.     

Determination of enthalpies of formation of organic free radicals from bond dissociation energies 2. Halosubstituted radicals

The enthalpies of formation (ΔH _f ^o) for 23 halosubstituted radicals were determined from the published data on bond dissociation energies. The ΔH _f ^o values of the corresponding molecules necessary for the calculation of ΔH _f ^o of the radicals were taken from handbooks or calculated by the additive-group method. The conjugation energies of the radicals are calculated, and the effect of substituents at the π-system on these values was shown. Errors of determination of the ΔH _f ^o values of the radicals were estimated. For Part 1, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 643–646, April, 1998.     

1D + 1D model of a DMFC: localized solutions and mixedpotential

Our 1D + 1D model of DMFC reveals a new effect. At infinitely small total current in the cell, near the channel inlet forms a “bridge”, a narrow region with finite local current density. The bridge short-circuits the electrodes, thus reducing cell open-circuit voltage. In our previous work the effect is described for the case of equal methanol λ^a and oxygen λ^c stoichiometries. In this Letter, we analyze the general case of arbitrary λ^a and λ^c. In the case of λ^a > λ^c current may occupy finite domain of the cell surface. Asymptotic solution for the case of λ^a  λ^c shows, that the size of this domain is proportional to oxygen stoichiometry. In the opposite limit of λ^a  λ^c local current exponentially decreases with the distance along the channel. Asymptotic solutions suggest that the bridge forms regardless of the relationship between λ^a and λ^c. In all cases local current density in the bridge increases with the rate of methanol crossover and decreases with the growth of the “rate-determining” stoichiometry. The expression for voltage loss at open-circuit is derived.     

Nanostructuring in the process of the formation of mixed-anion compounds: Rare-earth borogermanates, germanophosphates, and borotungstates

Specific features of the textures (the preferred orientation of the nanometer building blocks) in the structures of mixed-anion compounds—rare-earth borogermanates, germanophosphates, and borotungstates that arise from the acid-base interaction in the Ln₂O₃-B₂O₃-GeO₂, Ln₂O₃-GeO₂-P₂O₅, and Ln₂O₃-B₂O₃-WO₃ systems (Ln = La-Gd)—have been studied. Based on characteristic texture traits, the mixed-anion compounds of early rare-earth elements can be divided into three groups: (i) Ln₂O₃: E_xO_y > 1, (ii) Ln₂O₃: E_xO_y = 1, and (iii) Ln₂O₃: E_xO_y < 1. Because of the dominant structural effect of the basic oxide Ln₂O₃ in the compounds of the first group, the structures of Nd₁₄O₈(BO₃)₆(GeO₄)₂ and Pr₁₁O₁₀(GeO₄)(PO₄)₃ are composed of infinite [LnO_n] bands and layers and discrete groups [EO_m] located in the interband and interlayer spaces. The dominant structural effect of the acid oxides [E_xO_y] in the compounds of the third group leads to the appearance of ring textures composed of [LnO_n], as well as to the appearance of chains and networks composed of [EO_m], in the structures of Ln(BGeO₅) and Ln(BO₂)(WO₄). Original Russian Text ￠ G.A. Bandurkin, N.N. Chudinova, G.V. Lysanova, K.K. Palkina, E.V. Murashcva, V.A. Krut’ko, G.M. Balagina, 2006, published in Zhurnal Neorganicheskoi Khimii, 2006, Vol. 51, No. 2, pp. 334–347.     

Influence of MgO (CaO) on the structure of silicate-phosphate glasses

Thermal and structural properties of model silicate-phosphate glasses containing the different amounts of the glass network modifiers, i.e. Mg²⁺ and Ca²⁺ were studied. To explain the changes of the parameters characterizing the glass transition effect (T_g, Δc_p) and the crystallization process (T_c, ΔH) depending on the cations modifiers additions, analysis of the bonds and chemical interactions of atoms in the structure of glasses was used. ³¹P MAS-NMR spectra of SiO₂–P₂O₅–MgO(CaO)–K₂O glasses show that the phosphate complexes are mono- and diphosphate. It has been found that increasing amounts of Mg²⁺ or Ca²⁺ cations in the structure of glasses causes the reduction of the degree of polymerization of the phosphate framework (Q¹→Q⁰). The influence of increasing of modifiers in the structure of silicate- phosphate glasses on the number of non-bridging oxygens per SiO₄ tetrahedron and density of glasses was presented.     

Characterization of Ascentis RP-Amide column: Lipophilicity measurement and linear solvation energy relationships

This study investigates lipophilicity determination by chromatographic measurements using the polar embedded Ascentis RP-Amide stationary phase. As a new generation of amide-functionalized silica stationary phase, the Ascentis RP-Amide column is evaluated as a possible substitution to the n  -octanol/water partitioning system for lipophilicity measurements. For this evaluation, extrapolated retention factors, log k^′_w$\text{log}{k^{\prime }}_w$, of a set of diverse compounds were determined using different methanol contents in the mobile phase. The use of n-octanol enriched mobile phase enhances the relationship between the slope (S  ) of the extrapolation lines and the extrapolated log k^′_w$\text{log}{k^{\prime }}_w$ (the intercept of the extrapolation), as well as the correlation between log P   values and the extrapolated log k^′_w$\text{log}{k^{\prime }}_w$ (1:1 correlation, r² = 0.966). In addition, the use of isocratic retention factors, at 40% methanol in the mobile phase, provides a rapid tool for lipophilicity determination. The intermolecular interactions that contribute to the retention process in the Ascentis RP-Amide phase are characterized using the solvation parameter model of Abraham. The LSER system constants for the column are very similar to the LSER constants of the n-octanol/water extraction system. Tanaka radar plots are used for quick visual comparison of the system constants of the Ascentis RP-Amide column and the n-octanol/water extraction system. The results all indicate that the Ascentis RP-Amide stationary phase can provide reliable lipophilic data.     

Influence of Anions on Electrochemical Properties of Polypyrrole-Modified Electrodes

The influence of anions ClO₄ ^–, NO₃ ^–, Cl^–, SO₄ ^2–, and DDS^– (dodecyl sulfate) on the cyclic voltammetric response of polypyrrole-modified electrodes is studied. The change in the film composition is examined by electron probe microanalysis. It is established that essential changes in the shape of voltammograms take place during cycling if the anions are not sufficiently freely mobile in the polymer film and insertion of cations from the solution is necessary to guarantee electroneutrality of the system. Some differences between the mobility of Cl^– ions and ClO₄ ^– or NO₃ ^– ions are in good agreement with the results of semi-empirical quantum chemical calculations showing that the interaction of Cl^– and Br^– ions with pyrrole oligomers is stronger than that of NO₃ ^– or ClO₄ ^– ions. Nevertheless, it is established that the peak current determined from voltammograms increases linearly with the increase of the scan rate with very high correlation coefficient. It means that it is possible to describe the behavior of ClO₄ ^–, NO₃ ^– and Cl^– ions in the framework of the model of free ions. The redox behavior of the PPy films doped with anions of low mobility such as SO₄ ^2– and DDS^– depends essentially on the nature of cations in the test solution. It is found that the mobility of cations increases in the row Li⁺ < Na⁺ < K⁺ < Cs⁺. The mobility of DDS^– ions in the PPy in ethanolic solution is significantly higher and their electrochemical properties are quite similar to PPy|Cl or NO₃ ^– film in aqueous solution.     

Flow-injection chemiluminescence determination of aminomethylbenzoic acid and aminophylline based on N-bromosuccinimide-luminol reaction

A novel and sensitive chemiluminescence (CL) method for the determination of aminomethylbenzoic acid and aminophylline coupled with flow-injection analysis (FIA) technique is developed in this paper. It is based on the inhibition effect of the studied drugs on the chemiluminescence emission of N-bromosuccinimide-luminol (NBS-luminol) system. Under the optimum conditions, the decreased CL intensity is linear with the concentration of aminomethylbenzoic acid in the range of 2×10⁻⁸ to 1.0×10⁻⁶ g ml⁻¹ and with the concentration of aminophylline in the range of 1×10⁻⁷ to 7.0×10⁻⁶ g ml⁻¹, respectively. The detection limit is 7.0×10⁻⁹ g ml⁻¹ for aminomethylbenzoic acid (3σ) and 3.4×10⁻⁸ g ml⁻¹ for aminophylline (3σ). The relative standard deviations (R.S.D.) for 11 parallel measurements of 2.0×10⁻⁷ g ml⁻¹ aminomethylbenzoic acid and 1.0×10⁻⁶ g ml⁻¹ aminophylline are 2.6 and 3.0%, respectively. The proposed methods have been applied for the determination of the studied drugs in their pharmaceutical formulations with satisfactory results. The possible use of the proposed system for the determination of aminomethylbenzoic acid in plasma sample was also tested. The possible inhibition mechanism of aminomethylbenzoic acid and aminophylline on luminol-NBS system was discussed briefly.     

Determination of cyanide in blood by electrospray ionization tandem mass spectrometry after direct injection of dicyanogold

An electrospray ionization tandem mass spectrometric (ESI-MS-MS) method has been developed for the determination of cyanide (CN^–) in blood. Five microliters of blood was hemolyzed with 50 μL of water, then 5 μL of 1 M tetramethylammonium hydroxide solution was added to raise the pH of the hemolysate and to liberate CN^– from methemoglobin. CN^– was then reacted with NaAuCl₄ to produce dicyanogold, Au(CN)₂^–, that was extracted with 75 μL of methyl isobutyl ketone. Ten microliters of the extract was injected directly into an ESI-MS-MS instrument and quantification of CN^– was performed by selected reaction monitoring of the product ion CN^– at m/z 26, derived from the precursor ion Au(CN)₂^– at m/z 249. CN^– could be measured in the quantification range of 2.60 to 260 μg/L with the limit of detection at 0.56 μg/L in blood. This method was applied to the analysis of clinical samples and the concentrations of CN^– in the blood were as follows: 7.13 ± 2.41 μg/L for six healthy non-smokers, 3.08 ± 1.12 μg/L for six CO gas victims, 730 ± 867 μg for 21 house fire victims, and 3,030 ± 97 μg/L for a victim who ingested NaCN. The increase of CN^– in the blood of a victim who ingested NaN₃ was confirmed using MS-MS for the first time, and the concentrations of CN^– in the blood, gastric content and urine were 78.5 ± 5.5, 11.8 ± 0.5, and 11.4 ± 0.8 μg/L, respectively.     

The hard-sphere model for linear and regular star polybutadienes

The dilute solution properties of linear, 18-arm, and 270-arm star polybutadienes have been studied in a theta solvent and in a good solvent. Values of the radius of gyration R_G, the second virial coefficient A₂, the intrinsic viscosity [η], and the diffusion coefficient D₀ have been measured for each polymer. The ratios R_T/R_G, R_V/R_G, and R_H/R_G for each type of polymer are used to compare the four dilute solution properties. R_T is termed the “thermodynamic radius.” It is the radius of the hard sphere with the same excluded volume as the polymer coil. R_T is calculated from A₂ by R_T = (3A₂M₂/16ηN_A)^1/3. R_V and R_H are equivalent hard spheres defined for the intrinsic viscosity and translational diffusion coefficient, respectively. R_T/R_G, R_V/R_G, and R_H/R_G increase from about 0.7 for linear polymer coils as the number of arms in the star increases. Values of the ratios for the 18-arm stars are less than the value for the hard-sphere, but the values of the ratios of the 270-arm stars are equal to the hard-sphere limit within experimental error.     

Volumetric properties of aqueous solutions of quinic acid and its sodium salt

Abstract  

The apparent molar volume of quinic acid and its sodium salt were determined from the density data of aqueous solutions up to molality of 0.4 mol kg⁻¹ and in the temperature range from 293.15 to 328.15 K. The apparent molar volume of sodium quinate comprises the ionic and the associated ion-pair contributions. From the apparent molar volumes of quinic acid and the quinate ion, the molecular contributions to that of quinic acid are derived. At 298.15 K, the limiting apparent molar volume of quinic acid is 119.8 ± 0.5 cm³ mol⁻¹, and that of the quinic ion is 111.6 ± 0.3 cm³ mol⁻¹. Similarly, at 298.15 K, the limiting apparent molar expansibility of sodium quinate is 0.198 ± 0.003 cm³ mol⁻¹ K⁻¹, and that of quinic acid is 0.142 ± 0.003 cm³ mol⁻¹ K⁻¹. From these limiting ionic and molecular apparent molar volumes, the limiting volume change caused by ionization of quinic acid was calculated as −8.2 cm³ mol⁻¹ at 298.15 K. The coefficients of thermal expansion of these solutions were calculated from the density data, and from these the apparent molar expansibilities of quinic acid and its sodium salt were derived.     

Entwässerung von Kristallhydraten als Verfahren zur Reinigung von Salzen, 7. Mitt.: Über die Änderung der isomorphen Verunreinigung bei der Entwässerung von Na2SO4·10 H2O in dessen gesättigter Lösung bei der Übergangstemperatur sowie durch organische Flüssigkeiten

Zusammenfassung Es wurde die Gehaltsänderung der isomorphen Verunreinigung zweier Systeme: Na₂SO₄·10 H₂O/Na₂SeO₄·10 H₂O und Na₂SO₄·10 H₂O/Na₂CrO₄·10 H₂O während der Entwässerung sowohl in deren gesätt. Lösung bei der Übergangstemp. als auch durch Lösungsmittel (CH₃OH und C₂H₅OH) untersucht.Der nach beiden genannten Methoden durchgeführte Entwässerungsprozeß ist von einer Verminderung der isomorphen Verunreinigung begleitet. Der Reinigungskoeffizient (W) hängt mit der Beschaffenheit der isomorphen Verunreinigung und deren Konzentration im ursprünglichen Kristallhydrat zusammen. Wenn die Entwässerung unter Einwirkung organischer Lösungsmittel verläuft, istW auch noch von der Natur des Entwässerungsmittels selbst sowie von der Löslichkeit der isomorphen Verunreinigung im verwendeten Lösungsmittel abhängig.

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Dehydration of crystal hydrates as a method of purifying salts, VII: Investigation of the alteration of isomorphous contaminant content during the dehydration ofNa ₂ SO ₄·10 H₂ O in its saturated solution at the transition temperatur and by employing organic solvents

The change in the content of isomorphous contaminant of the two systems Na₂SO₄·10 H₂O/Na₂SeO₄·10 H₂O and Na₂SO₄·10 H₂O/Na₂CrO₄·10 H₂O during dehydratation has been investigated both in their saturated solution at the temperature of transition and by the solvents CH₃OH and C₂H₅OH.The dehydratation process, carried out by either method mentioned, is accompanied with a decrease of the isomorphous contaminant content in the crystalline mass. The coefficient of purification (W) depends on the nature of the isomorphous contaminant and its concentration in the initial crystallohydrate. In the case, when dehydratation takes place under the action of organic solvents,W depends also on the nature of the dehydratation agent itself, as well as on the solubility of the isomorphous contaminant in the employed solvent.

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Mit 2 Abbildungen