Oberflächenzusammensetzung,Löslichkeit und Ionenaktivitätsprodukt von Calcit in fremdionenhaltigen Lösungen

Surface Composition, Solubility, and the Ion Activity Product of Calcite in Solutions with Auxiliary Ions Using the method of simultaneous ion and isotope exchange the chemical composition of the surface layer of calcite powder in equilibrium with solutions of varying Me/Ca molar ratios is determined (Me = Mg²⁺, Co²⁺, Ni²⁺, and Fe²⁺ ions). The ion exchange isotherms show a marked bend in the surface reactivity when a surface molar ration of ～1 and ～3 is reached. The solubility of calcite initially decreases on the addition of Co²⁺ or Ni²⁺ ions to the solution whereas it increases in the presence of Mg²⁺ or Fe²⁺ ions. The activity product of the pseudo compound, Ca_xMe_(1–x)CO₃, decreases in the Ni²⁺, Co²⁺ or Fe²⁺ exchange experiments, however, it increases considerably in those with Mg²⁺ ions.     

Löslichkeitsprodukte von Metalloxiden und -hydroxiden. 11. Mitteilung [1]. Die Löslichkeit von α-GaO(OH) bei 60°C in perchlorsauren Lösungen konstanter Ionenstärke

The solubility equilibrium of α-GaO(OH) has been investigated at 60°C in solutions of perchloric acid having a constant ionic strength I = 3 m (Na, H)ClO₄. The hydrogen ion concentration of the equilibrated solutions was measured with a glass electrode and the concentration of the dissolved Ga^III was determined by chelometric titration. The experimental data can be explained by assuming the equilibrium .     

Zur Löslichkeit von Cobalt(IV) in Li8SiO6

On the Solubility of Cobalt(IV) in Li₈SiO₆ Li₈SiO₆ dissolves up to 2 at.‐%, cobalt(IV). Crystals of such solid solutions are transparent and of deep ruby red colour. Cobalt concentrations as determined by ICP‐OES, EDX and magnetic susceptibility measurements are in good accordance. The X‐ray powder diffraction and the magnetic properties confirm integration of Co⁴⁺ into the lithiumoxosilicate. These new results are indicating that the ruby red phase, previously addressed as “Li₈CoO₆”, is in fact cobalt doped Li₈SiO₆.     

Die Einwirkung ionisierender Strahlen auf das System Schwefeldioxid — Sauerstoff. VII. Untersuchungen über die Strahlenchemische Oxydation von Schwefeldioxid in schwefelsaurer Lösung

The Effect of Ionizing Radiation on the System SO₂? O₂. VII. Radiation-induced Oxidation of Sulfur Dioxide Dissolved in Sulfuric Acid The radiation-induced oxidation of oxygen-containing millimolar solutions of sulfur dioxide in 2 to 16 M sulfuric acid was investigated under influence of X-rays (65, 140 and 190kV) with dose rates ranging from 0.14 to 6.6 · 10¹⁵ eV · ml^?1 · s^?1. On the basis of previous publications a mechanism is derived from the dependence of radiation-chemical yield upon concentration of sulfuric acid and dose rate which proceeds with the HOOSO₂ · radical as an instable intermediate.     

Löslichkeiten und Aktivitätskoeffizienten von H2S in Elektrolytmischungen

From solubility measurements on hydrogen sulfide in aqueous solutions of the composition [H⁺] = HM, [Na⁺] = (I — H) M = A M, [Cl^?] = I M at 25°C, the molar and molal activity coefficients of H₂S have been calculated. The activity coefficients of H₂S in the electrolyte mixtures have been found to be additive functions of the activity coefficients in the individual electrolyte solutions at the same ionic strength. This result is predicted by the internal pressure theory of salt effects on non-electrolyte activity coefficients, provided that the volume change upon mixing two electrolyte solutions of the same ionic strength is zero.     

Über basische Aluminiumsalze und ihre Lösungen. VII. Zum Einfluß der Herstellungsbedingungen,der Konzentration und der Alterungszeit auf die Zusammensetzung von Lösungen basischer Aluminiumsalze

Basic Aluminium Salts and their Solutions. VII. Influence of Preparation, Concentration, and Aging on the Constitution of Solutions of Basic Aluminium Salts 0.1 to 4 molar basic aluminium chloride solutions – prepared by dissolving aluminium metal in substoichiometric quantities of hydrochloric acid and 10^?4 to 0.2 molar basic solutions of aluminium chloride and perchlorate – prepared by adding alkali to the solutions of the neutral salts were investigated for the kinetics of their reactions with ferrone and by ²⁷Al NMR spectroscopy. In all solutions the contents of polymeric species decreases at equal basicity with increasing aluminium concentration. On the other hand the Al₁₃O₄₀ complex is only formed in solutions prepared by addition of alkali. The differences of composition are confirmed by the aging behaviour of the solutions.     

Der Chemische Transport und die “Löslichkeit des Bodenkörpers in der Gasphase”

The Chemical Transport and the “Solubility of the Solid in the Gas Phase” The transport of a solid (or a liquid) via the gas phase by reversible chemical reactions may be described easily by means of the so called “solubility of the solid in the gas phase”. This applies also for chemically complicated systems, as well as for systems changing the number of gas moleculs with temperature. This investigation deals with: Definition of the (total) solubility γ. Examples. Variations of γ. Difference of total and reversible solubility. Application of γ for the calculation of transport rates in open and closed systems.     

Untersuchung der Löslichkeitsisothermen im System CuSeO4?H2SeO4?H2O bei 25 und 100°C,der Löslichkeitspolytherme im System CuSeO4?H2O und einiger Eigenschaften der erhaltenen Verbindungen

Investigation of the Isotherms of Solubility in the System CuSeO₄? H₂SeO₄? H₂O at 25 and 100°C, the Polytherm of Solubility in the System CuSeO₄? H₂O, and Some Properties of the Compounds Obtained Existence fields of different compounds from the three-component system CuSeO₄? H₂SeO₄? H₂O were determined. The polytherm of solubility in the system CuSeO₄? H₂O was studied. Data concerning dehydratation of CuSeO₄ · H₂O and thermal dissociation of CuSeO₄ · H₂O are given.     

Nanomolar Determination of Methyldopa in the Presence of Large Amounts of Hydrochlorothiazide Using a Carbon Paste Electrode Modified with Graphene Oxide Nanosheets and 3‐(4′‐Amino‐3′‐hydroxy‐biphenyl‐4‐yl)‐acrylic Acid

A novel electrochemical sensor for sensitive detection of methyldopa at physiological pH was developed by the bulk modification of carbon paste electrode (CPE) with graphene oxide nanosheets and 3‐(4′‐amino‐3′‐hydroxy‐biphenyl‐4‐yl)‐acrylic acid (3,′AA). Applying square wave voltammetry (SWV), in phosphate buffer solution (PBS) of pH 7.0, the oxidation current increased linearly with two concentration intervals of methyldopa, one is 1.0×10^?8–1.0×10^?6 M and the other is 1.0×10^?6–4.5×10^?5 M. The detection limit (3σ) obtained by SWV was 9.0 nM. The modified electrode was successfully applied for simultaneous determination of methyldopa and hydrochlorothiazide. Finally, the proposed method was applied to the determination of methyldopa and hydrochlorothiazide in some real samples.     

Electrochemical studies of determination of C.I. Direct Red 80 based on a gold nanoparticles-modified carbon paste electrode

In this paper, a simple, convenient and sensitive electrochemical method has been developed for the determination of C.I. Direct Red 80. A gold nanoparticle modified carbon paste electrode was fabricated and used for study and sensitive determination of Direct Red 80 by cyclic voltammetry and differential pulse voltammetry. The overall analysis involved a two-step procedure: an accumulation step under open-circuit conditions, followed by voltammetric measurements of Direct Red 80 in a 0.1?M phosphate buffer solution at pH?=?3.0. The experimental conditions, such as the medium, pH and accumulation time, were optimised. The oxidation peak current was proportional to the concentration of Direct Red 80 from 5.0?×?10^?8 to 5.0?×?10^?7?M and 5.0?×?10^?7 to 3.0?×?10^?6?M, and the detection limit was 1.15?×?10^?8?M (S/N?=?3). The proposed method was used to detect Direct Red 80 in natural water and sewage with good accuracy.     

Ringschlüsse an Chinonylmethanfarbstoffen und analogen Merocyaninen. 2. Mitteilung. Dihydronaphthophenazinone; Beeinflussung der Löslichkeitseigenschaften durch Substitution,Isolierung und Charakterisierung einer Zwischenstufe des Ringschlusses

Cyclization Reactions of Quinonylmethane Dyes and Analogous Merocyanines. 2. Communication: Dihydro-oxo-naphto-phenazines. Correlation of Solubility and Substitution. Isolation and Characterization of an Intermediate Compound An intermediate compound of the cyclization reaction of 2-chloro-3-(1-cyclohexyl-3-methyl-1,2-dihydroquinoxalin-2-ylidenmethyl)-naphthoquinone was isolated and characterized by spectroscopic methods. 6-Chloro-8-cyclohexyl-5,8-dihydronaphtho[1,2-b]phenazinone was obtained as the final product of this reaction. Several more dihydronaphtho[1,2-b]phenazinone dyes were synthesized. The relationship of substitution and solubility of the dyes is discussed. The visible and ¹H-NMR. and some mass spectra of the dyes are given.     

6-Phenyl -2,3-Dihydro-asym-trirzine-3-thione as a Selectiue Reagent for the Spectrophotometric Determination of Copper

Abstract

A sensitive and highly selective spectrophotometric method is described for the determination of 12-120 μg of copper using 6-phenyl-2,3-dihydro-asym-triazine-3-thione (PDTT) as a complexing agent. The red 1:4 water soluble complex was measured at 540nm, ε=1.26×10⁴ 1. mol^?1cm^?1.

The method was applled for the determination of copper in standard steels (B.C.S.) and estimation of the solubility product of copper (I) iodide. Comperison was also made with the 2-2 biquinoline method.     

Das Löslichkeitsdiagramm des Systems ZnSeO4?H2SeO4?H2O und einige Eigenschaften der erhaltenen Verbindungen

Isotherms of Solubility in the System ZnSeO₄? H₂SeO₄? H₂O and Some Properties of the Compounds Obtained The isotherms of solubility in the system ZnSeO₄? H₂SeO₄? H₂O were studied at 25 and 100°C. Some properties of the compounds obtained were investigated.     

Development of an Amperometric Biosensor for β‐N‐Oxalyl‐L‐α,β‐Diaminopropionic Acid (β‐ODAP)

An amperometric method for the determination of the neurotoxic amino acid β‐N‐oxalyl‐L ‐α,β‐diaminopropionic acid (β‐ODAP) using a screen printed carbon electrode (SPCE) is reported. The electrode material was bulk‐modified with manganese dioxide and used as a detector in flow injection analysis (FIA). The enzyme glutamate oxidase (GlOx) was immobilized in a Nafion‐film on the electrode surface. The performance of the biosensor was optimized using glutamate as an analyte. Optimum parameters were found as: operational potential 440 mV (vs. Ag/AgCl), flow rate 0.2 mL min^?1, and carrier composition 0.1 mol L^?1 phosphate buffer (pH 7.75). The same conditions were used for the determination of β‐ODAP. The signal was linear within the concentration range 53–855 μmol L^?1 glutamate and 195–1950 μmol L^?1 β‐ODAP. Detection limits (as 3σ value) for both analytes were 9.12 and 111.0 μmol L^?1, respectively, with corresponding relative standard deviations of 3.3 and 4.5%. The biosensor retained more than 73% of its activity after 40 days of on‐line use.     

Fast detection of catechin in tea beverage using a poly-aspartic acid film based sensor

A fast and convenient analytical method is presented for the determination of catechin. The electrochemical response of catechin in pH 6.8 phosphate buffer solution is significantly enhanced by immobilization of a film of poly-aspartic acid on the surface of the glassy carbon electrode. The enhancement mechanism and effect factors such as pH value, accumulation time and scan rate, were explored. Under optimum conditions, the differential pulse voltammetry peak current of catechin is proportional to the concentration in the range from 2.5?×?10^?7 to 3.0?×?10^?5 molL^?1, with the detection limit of 7.2?×?10^?8 molL^?1. This method was also applied to the determination of catechin in tea beverage samples, and the recoveries were from 97.1% to 102.7%.     

Löslichkeitskonstanten und freie Bildungsenthalpien von Metallsulfiden, 4. Mitt.: Die Löslichkeit von H2S in HClO4−NaClO4−H2O-Mischungen

The solubility of H₂S at 25°C in solvents of the composition: [H⁺]=H M, [Na⁺]=(I?H)=A M, [ClO₄ ^?]=I M was investigated by iodometric determination of [H₂S]_tot in the saturated solutions. Kp₁₂=[H₂S]_tot·p _H2S ^?1 was calculated. The results are consistent with the equation:

$$\begin{gathered} \lg [H_2 S]_{tot} \cdot p_{H_2 S}^{ - 1} = --- 0,991_8 --- 0,059_0 [Na + ] + 0,008_1 [H + ]--- \hfill \\ ---0,000_1 [H + ]^4 . \hfill \\ \end{gathered} $$     

Zweifach phosphonylierte Triphenylphosphane – neue Liganden mit ausgezeichneter Wasserlöslichkeit

Triphenylphosphine Diphosphonates – New Ligands with Excellent Water‐Solubility A highly selective method for the functionalization of triarylphosphines with phosphonate moieties has been developed. New ligands with excellent solubility in water, such as the previously unknown triphenylphosphine‐diphosphonates PhP[3‐C₆H₄–PO₃Na₂]₂ and PhP[4‐C₆H₄–PO₃Na₂]₂, are accessible by this efficient synthesis route.     

Ionic liquids with an anion of N-lauroyl sarcosinate in membranes of ion-selective electrode

The study considers solubility in water, extractivity, and electrode properties of ionic liquids (IL), lauroyl tetrahexylammonium (THALS) and tetraoctylammonium lauroyl sarcosinate (TOALS). The values of solubility, found by potentiometry using ion-selective membranes of PVC-electrodes (ISE) have appeared to be 3.0 ± 0.4 mM and 0.011 ± 0.005 mM, for THALS and TOALS, respectively. Both IL quantitatively recover nitrophenol (99.9%) into chloroform from aqueous solutions in the pH range from 2 to 12. The application of IL as the active components of PVC-ISE enables the determination of lauroyl sarcosinate anion in the concentration range 1 × 10^?2?C1 × 10^?4 M for THALS and 1 × 10^?2?C1 × 10^?5 M for TOALS and the determination of mononitrophenols, 2,4-dinitrophenols and picrates (1 × 10^?2 M?C1 × 10^?5 M). A solid-state sensor based on screen-printed electrode modified by TOALS IL has been proposed. The electrode has been used for the determination of 4-nitrophenol in the concentration range 1 × 10^?2?C1 × 10^?5 M, the operational stability of the electrode is 10 days.     

Ultrasensitive Determination of Vitamin B12 Using Disposable Graphite Screen‐Printed Electrodes and Anodic Adsorptive Voltammetry

A facile, rapid and ultra‐sensitive method for the determination of vitamin B₁₂ (cyanocobalamin) at the sub‐nanomolar concentration range by using low‐cost, disposable graphite screen‐printed electrodes is described. The method is based on the cathodic preconcentration of square planar vitamin B_12s, as occurred due to the electro reduction of Co(III) center in vitamin B_12a to Co(I), at ?1.3 V versus Ag/AgCl/3 M KCl for 40 s. Then, an anodic square wave scan was applied and the height of the peak appeared at ca. ?0.73 V versus Ag/AgCl/3 M KCl, due to the oxidation of Co(I) to Co(II) in the adsorbed molecule, was related to the concentration of the vitamin B₁₂ in the sample. EDTA was found to serve as a key‐component of the electrolyte by eliminating the background signal caused by metal cations impurities contained in the electrolyte (0.1 M phosphate buffer in 0.1 M KCl, pH 3). It also blocks trace metals contained in real samples, thus eliminating their interference effect. The method was optimized to various working parameters and under the selected conditions the calibration curve was linear over the range 1×10^?10–8×10^?9 mol L^?1 vitamin B₁₂ (R²=0.994), while the limit of detection for a signal‐to‐noise ratio of 3 (7×10^?11 mol L^?1 vitamin B₁₂) is the lowest value of any reported in the literature for the electrochemical determination of vitamin B₁₂. The sensors were successfully applied to the determination of vitamin B₁₂ in pharmaceutical products.     

Darstellung von Alkalichlorowolframaten(V) aus WCl6 in chloridhaltigen Lösungsmitteln

Preparation of Compounds AWCl₆ from WCl₆ in Cl^?-containing Solvents In Glyme, ACN or CH₂Cl₂ WCl₆ is reduced by Cl^? to WCl₆^?. From those solutions compounds AWCl₆ can be isolated with A = Cs (Glyme, ACN), A = Rb, K, NH₄(ACN) and A = N(C₂H₅)₄ (CH₂Cl₂). By concentrating of glyme-solutions a precipitate of A₂WCl₆ is formed by disproportionation. In methanol/HCl also solvolysis to oxo-compounds of W⁶⁺ takes place as function of the H⁺-concentration. With N(C₂H₅)₄Cl not only chlorotungstates but also methoxy- and oxo-spezies of W⁵⁺ can be isolated.