A quantitative study of orthokinetic flocculation in suspensions

Summary The process of orthokinetic flocculation has been investigated in suspensions with low solid phase concentration of 10^–4 cm³/cm³, that are used for the determination of powder size distributions with sedimentation balances. Such diluted suspensions provide settling conditions which are very close to ideal ones, and do not require any corrections of the change of viscosity or density caused by the presence of the solid phase. They are used to derivate, with certain approximations, a theoretical expression for the dependence of the weight of one particle fraction upon the powder concentration. The theoretical investigations favour the expressionW _i=W _oi+K_iP², whereW _i is the weight of thei-fraction in powder, which is experimentally obtained by the sedimentation analysis;W _oi is the weight which should be obtained in the absence of flocculation;K _i is a constant, if the powder concentration is the only variable in a suspension, and includes many factors which do not depend on concentration. FinallyP is the total weight of the sediment.

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Zusammenfassung Der Prozeß der orthokinetischen Fällung wurde in Suspensionen mit niedrigen Konzentrationen von 10^–4 cm₃/cm³ der festen Phase untersucht, die für die Bestimmung der Pulvergrößenverteilung in Sedimentationsgleichgewicht Verwendung finden. Derart verdünnte Suspensionen ergeben nahezu ideale Absetzbedingungen und erfordern keine Korrekturen für Viskositäts- und Dichteänderungen durch die feste Phase. Sie erlauben mit gewissen Näherungen die Ableitung theoretischer Ausdrücke für das Gewicht einer Partikelfraktion von der Pulverkonzentraticn. Die theoretische Untersuchung läßt den AusdruckW _i=W _oi+K_iP², gewinnen, bei demW _i das Gewicht deri-ten Pulverfraktion darstellt, die experimentell bei der Sedimentationsanalyse erhalten wird.W _oi ist das Gewicht, das sich ohne Fällung ergeben sollte, K_i ist eine Konstante, wenn die Pulverkonzentration die einzige Veränderliche in der Suspension ist, und die vielen Faktoren, die aber nicht von der Konzentration abhängen, enthält.P ist schließlich das Gesamtgewicht des Sediments.

     

Kinetics of thermal decomposition of pyrite in an inert atmosphere

The thermal decomposition of pyrite in an inert atmosphere was studied in order to obtain a detailed knowledge of the kinetics and mechanism of the reaction 2 FeS₂=2FeS+S₂, which is one of the methods of producing elementary sulphur. The process was studied under isothermal conditions at temperatures of 600, 660, 700, 750, 800 and 850 °C in a nitrogen atmosphere, by means of a thermobalance. The rate-controlling processes were determined and their kinetic parameters were calculated. The optimum temperature for the process was found to be 800 °C.

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Zusammenfassung Es wurde die thermische Zersetzung von Pyrit in inerter Atmosphäre bestimmt, um detaillierte Informationen über Kinetik und Mechanismus der Reaktion 2 FeS₂=2FeS+S₂, einer der Darstellungsreaktionen von elementarem Schwefel zu erlangen. Der Vorgang wurde mittels einer Thermowaage unter isothermen Bedingungen bei Temperaturen von 600, 660, 700, 750, 800 und 850 °C untersucht. Es wurden die geschwindigkeitsbestimmenden Schritte bestimmt und deren kinetische Parameter errechnet. Als Optimumtemperatur für diesen Prozeß erwies sich 800 °C.

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- 2FeS₂=2FeS + S₂, . 600, 660, 700, 750, 800 850 ° . , 800°.

     

Voltammetric and titrimetric study of acid-base properties of some μ-oxo dimeric iron(III) complexes inDMF

Summary The acid-base properties of the -oxo bridged dimeric iron complexes [FeL]₂O with the ligands based on S-alkyl-1,4-bis(substituted salicylidene)isothiosemicarbazide and a tetramer with S-methyl-1,4-bis(salicylidene)isothiosemicarbazide, {[FeL]₂O}₂I₃·I₂, were investigated by cyclic voltammetry at glassy carbon electrode inDMF. Studies were carried out in the presence of either a weak (phenol) or a strong (HClO₄ aq.) acid. The stoichimoetry of the reaction, changes in the general voltammetric pattern and the electrode reaction mechanism were discussed. These studies served as the basis for three-electrode amperometric titrations to determine the content of several of these complexes.

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Voltammetrische und titrimetrische Untersuchung der Säure-Base-Eigenschaften einiger -oxo dimerer Eisen(III)-Komplexe inDMF-Lösungen

Zusammenfassung Die Säure-Base-Eigenschaften einiger dimerer -oxo-Eisen(III)-Komplexe [FeL]₂O mit Liganden auf Basis von 1,4-bis(substituierten Salicyliden)S-(alkyl)isothiosemicarbaziden sowie eines tetrameren Komplexes mit 1,4-Bis(salicyliden)S-methylisothiosemicarbazid, {[FeL]₂O}₂I₃·I₂, wurden mittels zyklischer Voltammetrie an der Glaskohlenstoffelektrode inDMF-Lösungen untersucht. Die Messungen wurden in Gegenwart entweder einer schwachen (Phenol) oder einer starken (HClO₄ aq.) Säure ausgeführt. Die Stöchiometrie der Reaktion, die Änderungen der voltammetrischen Kurven und der Elektroden-Reaktionsmechanismus wurden diskutiert. Diese Untersuchungen stellten eine Basis für Drei-Elektroden amperometrische Titrationen dar, die für die Bestimmung des Gehalts einiger dieser Komplexe angewendet wurden.

     

“EXTSANGLE” — An extension of the efficiency conversion program “SOLANG” to sources with a diameter larger than that of the Ge-detector

The computer program SOLANG, originally developed by MOENS et al. for the efficiency conversion via effective solid angles (), is extended in this work to cylindrical sources with a diameter larger than that of the Ge-detector. New program, named EXTSANGLE, is experimentally checked in our three laboratories. For the most unfavourable case from the standpoint of the accuracy of (bulky source counted at the top of detector), discrepancies were below 7% in the whole range of gamma-energies considered (88–1115 keV), with an average of 3–4%. EXTSANGLE is extensive and flexible with respect to the data input, storage and output, thus contributing to the automation of a gamma-spectrometry laboratory dealing, for instance, with the k₀-NAA and/or environmental radioactivity monitoring.     

Synthesis,crystal, and molecular structures of HIDA and its monomethyl ester

A simple procedure for synthesis of HIDA (2,6-dimethylphenylcarbamoylmethyl iminodiacetic acid) is described. It was obtained in better yield by reaction of 2,6-dimethylphenylcarbamoylmethyl chloride with iminodiacetic acid in carbon tetrachloride. The HIDA (A) was identified by IR and¹H NMR spectroscopy. Two types of crystals were detected in the crystal final product. Since they could be separated, the crystals:A andB were investigated by X-ray analysis. Crystal and molecular structures were solved by direct methods and refined by full-matrix least-squares technique toR=0.047 andR=0.056, respectively. In the structure ofA, the N2 atom is protonated and the molecule exists as a zwitterion. The crystal structure of compoundA is stabilized by strong hydrogen bonds, which are reflected in higher close-packing coefficient, density, and melting point, compared to compoundB. CompoundB is a monomethyl ester of HIDA, which is present as an impurity in the final recrystallized product.     

Application of an indicating system of bismuth electrodes for the determination of organic bases and acids in nonaqueous solutions

Summary Tertiary amines and salts of organic acids have been titrated by means of perchloric acid applying a biamperometric indicating system consisting of a polarised or unpolarised pair of bismuth electrodes. Also, mono- and polycarboxylic acids, alone and in mixtures, have been determined with a strong base using the same end-point detection technique. The results obtained are in good agreement with those of potentiometry or catalytic thermometry.

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Anwendung eines Indikationssystems aus Wismutelektroden zur Bestimmung von organischen Basen und Säuren in nichtwäßrigen Lösungen

Zusammenfassung Tertiäre Amine und Salze organischer Säuren werden durch Titration mit einer Lösung von Perchlorsäure quantitativ bestimmt. Das verwendete Indicatorsystem besteht aus einem Paar polarisierter oder nichtpolarisierter Wismutelektroden. Das gleiche System wurde auch angewandt auf die titrimetrische Bestimmung von Mono- und Polycarbonsäuren mit einer starken Base. Die Ergebnisse stimmen gut mit denen der potentiometrischen bzw. katalytisch-thermometrischen Methode überein.

     

New99mTc-diiodine substituted IDA derivative (DIIODIDA) for hepatobiliary imaging

A new diiodine substituted IDA derivative, 2,4-diiodine-6-methyl IDA (DIIODIDA) was synthesized and labeled with^99mTc. It was established that^99mTc-DIIODIDA had high radiochemical purity. Biodistribution and influence of bilirubin on^99mTc-DIIODIDA biokinetics has been studied in rats and compared to the corresponding results for^99mTc-SOLCOIODIDA. Related to^99mTc-SOLCOIODIDA,^99mTc-DIIODIDA has much better biliary exretion (55.18 versus 43.63%). No change of^99mTc-DIIODIDA biokinetics, under influence of bilirubin was noticed. Biliary excretion of^99mTc-SOLCOIODIDA has been reduced for about 60%. The protein binding of^99mTc-DIIODIDA and^99mTc-SOLCOIODIDA were also determined, using in vitro method of precipitation. These results showed that^99mTc-DIIODIDA hepatobiliary imaging agent is superior to the presently used^99mTc-monoiodine IDA derivatives.     

Transition metal complexes with thiosemicarbazide-based ligand – Part LV: Synthesis and X-ray structural study of novel Ni(II) complexes with pyridoxal semicarbazone and pyridoxal thiosemicarbazone

Reaction of aqueous solutions of Ni(NO₃)₂ and pyridoxal semicarbazone (PLSC) in the presence of NaN₃ afforded two complexes, viz. green, paramagnetic binuclear octahedral [Ni₂(PLSC)₂(μ_1,1-N₃)₂(N₃)₂] · 2H₂O (1) and, as admixture, red, octahedral [Ni(PLSC–H)₂] · 2H₂O (2) complex. Under the same reaction conditions, pyridoxal thiosemicarbazone (PLTSC) gave only one diamagnetic square-planar, red complex [Ni(PLTSC–H)N₃] · H₂O (3). In the absence of NaN₃, the reaction of PLTSC and Ni(NO₃)₂ yielded brown paramagnetic octahedral complex [Ni(PLTSC)₂](NO₃)₂ · H₂O (4).     

Application of Blanc’s law at arbitrary electric field to gas density ratios

Application of Blancs law for drift velocities of electrons and ions in gas mixtures at arbitrary reduced electric field strengths E/n₀ was studied theoretically and by numerical examples. Corrections for Blancs law that include effects of inelastic collisions were derived. In addition we have derived the common mean energy procedure that was proposed by Chiflikyan in a general case both for ions and electrons. Both corrected common E/n₀ and common mean energy procedures provide excellent results even for electrons at moderate E/n₀ where application of Blancs law was regarded as impossible. In mixtures of two gases that have negative differential conductivity (NDC) even when neither of the two pure gases show NDC the Blancs law procedure was able to give excellent predictions.     

Guiding center theory for ion holes in magnetized plasmas

A drift-kinetic theory for ion phase-space vortices in magnetized plasmas is developed, taking into account the effects of the ion polarization and anisotropic heating by ion beams. It provides a theoretical explanation for the bipolar electrostatic structures in the auroral zone of the Earth's magnetosphere and their spatial and temporal scales, as observed by S3-3, Viking, FREJA, Polar, and FAST spacecrafts. Several types of quasi-three-dimensional ion holes are obtained analytically, in the form of either cylinders or ellipsoids. Although topologically different, they produce similar signals on the spacecraft and cannot be distinguished on the basis of the existing satellite data.