Combustion curves of some Turkish lignites

In this study, combustion curves of twenty-five Turkish lignites were obtained through use of a differential thermal analyser. 20 mg lignite samples were heated at a constant rate of 10 deg·min^?1 in a 40 cc/min flow of air up to 1073 K and held for 10 minutes at this constant temperature. The combustion curves of the samples are compared and discussed.     

Synthesis and applications of poly(acryl<Emphasis Type="Italic">p</Emphasis>-aminobenzenesulfonamideamidine-<Emphasis Type="Italic">p</Emphasis>-aminobenzenesulfonylamide) chelating fiber for pre-concentrating and separating trace Bi(III), Hg(III), Au(III) and Pd(IV) from solution samples

Poly(acrylp-aminobenzenesulfonamideamidine-p-aminobenzenesulfonylamide) chelating fiber containing "S", "N", and "O" elements was synthesized from polyacrylonitrile fiber and p-aminobenzene sulfonamide and used to enrich and separate trace Bi(III), Hg(III), Au(III), and Pd(IV) ions from wastewater and ore sample solution. The enrichment acidity, flow rate, elution conditions, reuse, interference ions, saturated adsorption capacity, constant of adsorption rate, analytical accuracy, and actual samples on chelating fiber were investigated by means of inductively coupled plasma optical emission spectrometry (ICP-OES) with satisfactory results. Solutions of 100 ng mL^–1 of Bi(III), Hg(III), Au(III), and Pd(IV) ions can be enriched quantitatively by this chelating fiber at a rate of 1.0 mL min^–1 at pH 4 and desorbed quantitatively with 20 mL of 0.25 M HCl and 2% CS(NH₂)₂ solution at 50 °C (with recovery 97%). When the chelating fiber was reused for 20 times, the recoveries of the analyzed ions enriched by the fiber were still over 95% (except for Hg(III)). One thousand-fold excesses of Mn²⁺, Ca²⁺, Zn²⁺, Mg²⁺, Fe³⁺, Cu²⁺, Ni²⁺, Al³⁺, and Ba²⁺ ions and thousands-fold excesses of Na⁺ and K⁺ cause little interference in the pre-concentration and determination of the analyzed ions. The saturated adsorption capacity of Bi(III), Hg(III), Au(III), and Pd(IV) was 4.850×10^–4, 3.235×10^–4, 2.807×10^–4, and 3.386×10^–4 mol g^–1, respectively. The constants of adsorption rate were 0.409 min^–1 for Bi, 0.122 min^–1 for Hg, 0.039 min^–1 for Au, and 0.080 min^–1 for Pd. The relative standard deviations (RSDs) for the enrichment and determination of 10 ng mL^–1 Bi(III), Hg(III), Au(III), and Pd(IV) were lower than 2.3%. The results obtained for these ions in actual samples by this method were basically in agreement with the given values with average errors of less than 1.0%. FT-IR spectra shows that the existence of –SO₂–Ar, –H₂N–Ar, O=C–NH–, HN=C–NH–, and –HN–SO₂ functional groups are verified in the chelating fiber. From the FT-IR spectroscopy, we can see that Hg(III), Au(III), and Pd(IV) are mainly combined with nitrogen and sulfur (or oxygen), and Bi(III) is mainly combined with nitrogen (or oxygen) of the groups to form a chelating complex.     

Modulated Differential Scanning Calorimetry

The reproducibility and reliability of the TA Instruments Modulated Differential Scanning Calorimeter (MDSC) was tested over a range of conditions. The equipment base line was found to be fairly constant with a very small fluctuation (10 W), which means a 0.1 % fluctuation on the scale of a normal polymer MDSC curve. The excellent stability of the base line and the reasonable reproducibility of the curves (5%) suggest that frequent calibration is not required.The heat capacities calculated from the modulated response to the variable temperature depend on the frequency for a given cell constant. The heat capacity cell constant is a unique function of the modulation frequency:k _c =K _c ^o p/(p–6.3) wherep is the time of the periodicity expressed in seconds and K _c ^o is the heat capacity cell constant measured on a standard material and reduced to zero frequency. The cell constants depend on the flow rate of the helium according to:K(He)=K ^o(1.298–0.004424He+1.438·10^–5 He ²) whereHe is the flow rate of helium in ml min^–1 andK ^o represents a constant at 100 cm³ min^–1. There is a strong dependence of cell constant on the flow rate ranges from 10 to 80 cm³ min^–1, while above this rate (up to 135 ml min^–1) the cell constant approaches a plateau.     

Effect of the Heating Rate on Crystallization Kinetics of Mg84Ni12.5Y3.5 Amorphous Ribbons

Crystallization kinetics of Mg₈₄Ni_12.5Y_3.5 amorphous ribbons produced by the melt-spinning method, was studied by DSC analysis and X-ray diffraction. The effect of heating rate (from 2 to 240 K min^–1) was investigated in the temperature range from 298 to 673 K. The results showed that the crystallization process took place in two stages: a) crystallization of part of the amorphous matrix to an intermediate phase and hcp-Mg, and b) transformation of the intermediate phase and the remaining amorphous material to Mg₂Ni+Mg (solid solution of Y in Mg). Increasing the heating rate from 2 to 240 K min^–1 results in increases of the temperature difference between the two-step crystallization of the first stage transformation processes from 33 to 56 K and in increases of the temperature difference between the two-stage transformation from 62 to 97 K.This revised version was published online in November 2005 with corrections to the Cover Date.     

Protein Binding Study of Isoflavones by High-Performance Frontal Analysis

High-performance frontal analysis was used for protein binding study of isoflavones (daidzein, genistin, and genistein) to human serum albumin. The analysis was performed on a Develosil 100-Diol-5 column (10 cm × 4.6 mm). Sodium phosphate solution (pH 7.4, ionic strength 0.17) was used as the mobile phase at a flow rate of 1 mL min^–1. UV wavelength was set at 260 nm. To ensure the drug to be eluted as a trapezoidal peak with a plateau, injection volumes of 700 L for daidzein and genistin, 900 L for genistein were chosen, respectively. Experimental data were fitted by Scatchard equation. The binding constants (K) and binding affinities (nK) of isoflavones to HSA were: K=1.581 × 10⁵ (L mol^–1), nK=0.77 × 10⁴ (L mol^–1) for daidzein, K=1.082 × 10⁵ (L mol^–1), nK=0.32 × 10⁴ (L mol^–1) for genistein, and K=3.533 × 10⁵ (L mol^–1), nK=0.70 × 10⁴ (L mol^–1) for genistin, respectively.     

Ion-chromatographic determination of fluorine in texas lignite

Summary Samples of approximately 1.0 g were taken from three Texas lignite cores and mineralized in oxygen bombs. The residue was dissolved in distilled water to a total volume of 50 ml. The resulting solutions were analyzed for fluoride by ion chromatography and with a fluoride-sensitive electrode. The results obtained with these two methods were in good agreement. The pH of solutions prepared from mineralized lignite samples must be adjusted to fall into the range 4 to 12 before fluoride is determined by ion chromatography. The calibration curve is linear to 10 mg/l F^– (in solution). Twenty g/l of F^– (in solution) corresponding to 1 mg/kg of dry lignite can still be determined. Ion chromatography has higher sensitivity for fluoride than fluoride-sensitive electrodes and provides at the same time information about other anionic species. The fluorine concentrations in the three cores varied from 10 to 140 mg/kg (dry lignite). Layers of clay interspersed between the lignite seams had higher fluorine concentrations than the lignite.

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Ionen-chromatographische Bestimmung von Fluor in Braunkohle aus Texas

Zusammenfassung Braunkohlenproben von etwa 1 g wurden in der Sauerstoffbombe mineralisiert, der Rückstand in Wasser gelöst und die Lösung mit Hilfe der Ionen-Chromatographie und mit einer fluoridsensitiven Elektrode auf Fluorid untersucht. Die mit beiden Methoden erhaltenen Ergebnisse stimmten gut überein. Vor der Ionen-Chromatographie müssen die Lösungen der mineralisierten Proben auf pH 4–12 eingestellt werden. Die Eichkurve verläuft bis 10 mg/l F^– linear. Noch 20 g/l F^– (in Lösung), entsprechend 1 mg/kg trockener Braunkohle, können bestimmt werden. Die Ionen-Chromatographie weist eine höhere Empfindlichkeit auf als fluorid-sensitive Elektroden und bietet darüber hinaus Information über andere Anionen. Die untersuchten Fluoridkonzentrationen lagen zwischen 10 und 140 mg/kg (trockene Braunkohle). Zwischengelagerte Lehmschichten wiesen höhere Fluorgehalte auf.

     

A study of the chemiluminescence behavior of myoglobin with luminol and its analytical applications

A chemiluminescence signal at 425 nm was observed when ferric state myoglobin was mixed with luminol in alkaline medium. Because the signal was remarkably enhanced in the presence of Fe(CN)₆ ^4–, analytical applications were investigated in a flow-injection system. The increase in chemiluminescence was linearly dependent on myoglobin concentration in the range 0.1 to 100 nmol L^–1, and the limit of detection was 0.04 nmol L^–1 with relative standard deviation 3.2% (3). It was also found that binding of Mb with the ligands CN^–, SCN^–, and F^– significantly inhibited the chemiluminescence reaction. The linear dynamic ranges for the ligands were 1.0–300.0, 0.1–3.0, and 0.5–100.0 nmol L^–1, and the limits of detection (S/N=3) 0.4, 0.04, and 0.2 nmol L^–1, for F^–, CN^–, and SCN^–, respectively. The relative standard deviations were 5.32%, 6.13%, and 3.38% for 0.1 nmol L^–1 CN^–, 0.5 nmol L^–1 SCN^–, and 1.0 nmol L^–1 F^–, respectively. At a flow rate of 2.0 mL min^–1 the assay could be accomplished in 1 min, including sampling and washing. The method has been successfully applied to the determination of myoglobin in human urine and F^– in water samples. A possible mechanism of chemiluminescence production by myoglobin and luminol is presented.     

Thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere

The conditions of thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere at heating rates of 10 and 5 deg·min^–1 were studied. At 10 deg · min^–1, the hemimellitate and trimesinate of copper(II) lose crystallization water and then decompose directly to CuO, whereas at 5 deg·min^–1 they decompose to CuO through Cu₂O. The trimellitate of copper(II) heated at various rates decomposes in the same way: it loses 1 water molecule and then decomposes directly to CuO.     

Sorption kinetics of tributyltin on Elbe river biofilms

For the first time detailed sorption kinetics of tributyltin on native Elbe river biofilms are presented. For this purpose a modified annular rotating continuous flow reactor has been used to develop a reproducible biofilm. Important parameters, such as flow rates, sheer forces, and nutrient concentrations could be varied independently and adjusted to natural conditions. Time-resolved sorption kinetics have been carried out with tributyltin, the most toxic compound in many antifouling paints. The highest sorption rates of tributyltin were observed during the first 0–10 min (0.60±0.05 g Sn m^–2min^–1) than they decreased to a value of 0.10±0.10 g Sn m^–2min^–1 (10–90 min) and increased to a value of 0.20±0.05 g Sn m^–2min^–1 (90–120 min).     

Isotope exchange between U/III/ and U/IV/ in the HCl-TBP extraction system

The measurement of the isotope-exchange reaction between U/IV/ in the organic phase and U/III/ in the aqueous phase in the extraction systems: 7-8M HCl—5–40% TBP /aromatic diluent or CCL₄/ were made. The high rate of exchange with the rate constant >10²M^–1min^–1 was observed.     

Application of thermogravimetry in the quality control of mebendazole

A study was made of the thermal behavior of the starting materials, their mixtures and the resulting mebendazole tablets. The thermal curves were obtained with a Shimadzu thermobalance, model TGA-50, using an air flow of 50 mL min^–1 and a heating rate of 10°C min^–1 in the temperature interval 30–900°C. The reaction constant velocities for the mebendazole salt and tablets were determined isothermally, using the Arrhenius expression. The thermal stability of mebendazole tablets is lower than that of the mebendazole salt, due to the presence of starch and lactose in the composition. Analysis of the data reveals that thermogravimetry is a powerful tool in pharmaceutical technology and quality control.The authors thank CNPq/PADCT for financial support.     

Kinetik der Entstehung des Zinktartrats

Zusammenfassung Aus potentiometrischen Daten wurde die Konstante der Entstehungsgeschwindigkeit des Zinktartrates bei 18° berechnet. Ihr durchschnittlicher Wert beträgt 1,3·10² mol·min^–1 und der Wert der Zerfallsgeschwindigkeitskonstante beläuft sich im Durchschnitt auf 7,5·10^–2 mol·min^–1.     

Thermal behaviour of amorphous Li2ZrO3 prepared by sol-gel technique

The results of the investigations of thermal behaviour of Li₂ZrO₃, prepared in the amorphous state by means of sol-gel technique are demonstrated. The thermal treatment was carried out in air under constant heating rate of 5 deg·min^–1 and cooling rate of 2.5 deg·min^–1. The methods of DTA, TG, Emanation Thermal Analysis (ETA) and dilatometry were used, for characterization of the thermal behaviour in dynamic conditions. The X-ray diffraction patterns were used for characterization of the phase changes observed by TA Methods.

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Zusammenfassung Ergebnisse aus Untersuchungen des thermischen Verhaltens von Li₂ZrO₃, hergestellt mittels einer Sol-Gel-Technik im amorphen Zustand werden dargelegt. Die thermische Behandlung wurde in Luft bei einer konstanten Aufheizgeschwindigkeit von 5 Grad·min^–1 und einer Abkühlgeschwindigkeit von 2,5Grad·min^–1 durchgeführt. Zur Beschreibung des thermischen Verhaltens unter dynamischen Verhältnissen wurden DTA, TG, Emanationsthermoanalyse und Dilatometrie angewendet. Zur näheren Charakterisierung der bei TG beobachteten Phasenumwandlungen wurde Röntgendiffraktion verwendet.

     

Glass Forming Properties of Benzodiazepines and Co-evaporate Systems with Poly(hydroxyethyl Methacrylate)

In the present study, we report on the thermal properties of a series of benzodiazepines. The heat of fusion varied between approximately 25 and 40 kJ mol^–1, except for oxazepam and lorazepam where dimerization in the solid state increased the heat of fusion to 78.54(±0.37) and 77.03 (±0.84)kJ mol^–1, respectively. Heating alprazolam at a low rate (0.5 K min^–1) showed that polymorphs I and II are an enantiotropic pair with a solid-solid transition at 481.4 K It was shown that all benzodiazepines could be transformed to the glassy state by cooling fused samples, irrespective of the cooling rate. The size of the relaxation endotherm accompanying the glass transition increased by heating the glassy drugs at a higher rate through T_g or by cooling the fused samples at a slower rate. The time dependence of the glass to liquid transition can be described to a good approximation as a first order transformation. The Gordon-Taylor equation was used to predict T_g of a binary mixture of temazepam, diazepam or prazepam with polyHEMA. It was shown that the predictability was acceptable as long as the drug concentration was below 10%w/w; at higher concentration, specific drug-polymer interactions causing changes in free volume of the system could not be ignored.This revised version was published online in November 2005 with corrections to the Cover Date.     

Evaluation of combustion characteristics of different size elbistan lignite by using TG/DTG and DTA

In this research, the relationship between particle size and combustion kinetics and combustion properties of lignite samples was examined by utilizing the thermogravimetric (TG/DTG) and differential thermal analysis (DTA) techniques. The lignite samples separated into different size fractions were subjected to non-isothermal thermogravimetric analysis between ambient and 900°C in the presence of 50 mL min⁻¹ air flow rate. Activation energy (E) and Arrhenius constant (A _r) of combustion reaction of each size was evaluated by applying Arrhenius kinetic model to the resulting data. Combustion properties of the samples were interpreted by careful examination of the curves. The apparent activation energies in major combustion region were calculated as 41.03 and 53.11 kJ mol⁻¹ for the largest size (−2360+2000 μm) and the finest size (−38 μm), respectively.     

Untersuchungen zur adsorptiven Anreicherung von Elementspuren an Adsorberharzen

Summary The use of a short column filled with 0.5 g Amberlite XAD resin is characterized for the trace preconcentration from aqueous solutions. For this a suitable algorithm describing the breakthrough curves of columns with a low number of theoretical plates is applied. The influence of the flow rate on the maximal sampling volume is examined. For the sorption of 1,10-phenanthroline the number of theoretical plates of the column with flow rates between 6–80 ml · min^–1 was determined to be 1–20. The results indicate that flow rates of 10–40 ml · min^–1 are generally suitable for quantitative trace preconcentration.

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Teil III: Fresenius Z Anal Chem (1989) 334:514–520     

Sorption of hafnium on hydrous titanium oxide using radiotracer technique

The sorption of hafnium on hydrous titanium oxide (TiO₂·1.94 H₂O) has been studied in detail. Maximum sorption of hafnium can be achieved from a pH 7 buffer solution containing boric acid and sodium hydroxide using 50 mg of the oxide after 30 minutes shaking. The value ofk _d, the rate constant of intraparticle transport for hafnium sorption, from 0.01M hydrochloric and perchloric acid and pH 7 buffer solutions has been found to be 17 mmole·g^–1·min^–2. The kinetics of hafnium sorption follows Lagergren equation in 0.01M HCl solution only. The values of the overall rate constantK=6.33·10^–2 min^–1 and of the rate constant for sorptionk ₁=6.32·10^–2 min^–1 and desorptionk ₂=2.28·10^–5 min^–1 have been evaluated using linear regression analysis. The value of correlation factor() is 0.9824. The influence of hafnium concentration on its sorption has been examined from 4.55·10^–5 to 9.01·10^–4 M from pH 7 buffer solution. The sorption data followed only the Langmuir sorption isotherm. The saturation capacity of 9.52 mmole·g^–1 and of a constant related to sorption energy have been estimated to be 2917 dm³·mole^–1. Among all the additional anions and cations tested only citrate ions reduce the sorption significantly. Under optimal experimental conditions selected for hafnium sorption, As(III), Sn(V), Co(II), Se(IV) and Eu(III) have shown higher sorption whereas Mn(II), Ag(I) and Sc(III) are sorbed to a lesser extent. It can be concluded that a titanium oxide bed can be used for the preconcentration and removal of hafnium and other metal ions showing higher sorption from their very dilute solutions. The oxide can also be employed for the decontamination of radioactive liquid waste and for pollution abatement studies.     

Solubility of Solid 1-Hexyne in Liquid Argon and Nitrogen at the Standard Boiling Points of the Solvents

The solubilities of solid 1-hexyne in liquid argon at 87.3 and in liquid nitrogen at 77.4 K have been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in 1-hexyne. The experimental value of the mole fraction solubility of solid 1-hexyne in liquid argon at 87.3 K is (0.85 ± 0.19) × 10^–7 and (1.25 ± 0.08) × 10^–8 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbon in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l ₁₂ were also calculated. At 90.0 K liquid argon is a better solvent for solid 1-hexyne than is liquid nitrogen.     

Heat Capacities and Thermodynamic Properties of Fenpropathrin (C22H23O3N)

The heat capacities of fenpropathrin in the temperature range from 80 to 400 K were measured with a precise automatic adiabatic calorimeter. The fenpropathrin sample was prepared with the purity of 0.9916 mole fraction. A solid—liquid fusion phase transition was observed in the experimental temperature range. The melting point, T_m, enthalpy and entropy of fusion, _fusH_m, _fusS_m, were determined to be 322.48±0.01 K, 18.57±0.29 kJ mol^–1 and 57.59±1.01 J mol^–1 K^–1, respectively. The thermodynamic functions of fenpropathrin, H_(T)—H_(298.15), S_(T)—S_(298.15) and G_(T)—G_(298.15), were reported with a temperature interval of 5 K. The TG analysis under the heating rate of 10 K min^–1 confirmed that the thermal decomposition of the sample starts at ca. 450 K and terminates at ca. 575 K. The maximum decomposition rate was obtained at 558 K. The purity of the sample was determined by a fractional melting method.This revised version was published online in November 2005 with corrections to the Cover Date.