Mössbauer study of iron reduction in hematite containing mineral originated from Aswan area in Egypt

Mössbauer spectroscopy was used to study iron reduction in mineral originated from Aswan area in Egypt. The Mössbauer spectra of samples heat treated at 1000 °C in hydrogen atmosphere show a gradually reduction process of hematite. The main phase of sample aged for 1 h is magnetite, while alpha-iron as well as some silicates and wustite type oxide can be detected in sample aged for 3 h. Further aging of sample results in dissolution of alloying elements /Si, Al/, being present in the samples. This process starts already in samples aged at 1000 °C for 4 h, but it is more expressive in minerals heat treated at 1200 °C or 1300 °C, when all paramagnetic phases disappeared.     

Spin Density Distribution in 2,4,6-Triphenylphenoxyl

The distribution of the unpaired electron over the oxygen and the 24 carbon atoms in the free 2,4,6-triphenylphenoxy radical was determined by electron spin resonance spectroscopy and quantum-mechanical approximation methods. The hyperfine splitting was evaluated with the aid of the spectra of triphenylphenoxyls deuterated in some or all of the substituent phenyl groups. The results of the quantum-mechanical approximations were checked by recording the ESR spectra of triphenylphenoxyls labeled with ¹³C in positions 1,2,3, or 4 of the central ring. The spin density distribution permits a first discussion of the ¹⁷O-coupling constants of correspondingly labeled triphenylphenoxyl and other organic free radicals.     

Calcul théorique des énergies de divers arrangements géométriques de la molécule (η5-C5H5)2TiCl2

The molecular energy of the complex (η⁵-C₅H₅)₂TiCl₂ has been calculated for experimental geometry and for several hypothetical forms by a semi-empirical CNDO/2 approach. The energy difference between experimental (quasi-tetrahedral) geometry and a planar geometry is ca. 20 kcal mol^?1. This difference is sufficiently high to explain the difficulty of the inversion process.     

Saturated heterocycles, 162 [1]. synthesis and steric structures of 3,4-disubstituted 1,6,7,11b-tetrahydropyrimido[6,1-a]isoquinolin-2-ones

The reaction of 1-(hydrazidomethyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline 3 with aromatic aldehydes yield hydrazones 4a,b or pyrimido[6,1-a]isoquinolines 5a-c depending upon the proportions of the reagents. With ketones, 3 gives only hydrazones 4a-d and 7 , which can be transformed to pyrimidoisoquinolines 10a-e and 11 with aldehydes. The ring closures are stereospecific; the relative configurations were determined by DNOE measurements.     

Ion-pair extraction of pentacaine from biological materials

Simple and rapid extraction method for quantitative and selective isolation of the new local anesthetic pentacaine from biological materials is proposed. The technique of ion-pair formation was found to be more effective than usual access using the extraction of the nonionized species. The extraction yield of the unchanged molecule³H-pentacaine after double extraction and single scrubbing was found to be more than 90%. The radiochemical purity was over 90%. The method appears suitable for pharmacokinetic studies in the animal body.     

Novel electroanalytical techniques for pollution analysis

Summary Two new analytical techniques are described. The so-called injection technique operates on evaluating a dynamic concentration signal as a result of following the concentration change in a certain part of a flow-through channel after injecting a sample or reagent at a small volume into the current of an appropriate solution flowing at a constant rate.The second technique, the programmed coulometric titration technique, also uses the flow-through channel principle; that means this novel technique allows the more precise titrimetric way of analysis in flowing solutions. In the case of both techniques potentiometric and voltammetric detectors were involved. Several examples proved the multifold advantages of these techniques for environmental analysis.

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Neue elektroanalytische Verfahren für die Umweltanalyse

Zusammenfassung Zwei neue Methoden werden beschrieben. Die sog. Injektionstechnik wertet ein dynamisches Konzentrationssignal aus, das sich aus der Änderung in einem Durchflußkanal ergibt, wenn Probe oder Reagens in kleinen Volumina in einen konstant fließenden Flüssigstrom injiziert werden. Das zweite Verfahren, die programmierte coulometrische Titration, erlaubt die Anwendung der genaueren titrimetrischen Technik auf fließende Lösungen. Bei beiden Methoden werden potentiometrische und voltammetrische Detektoren verwendet. Mehrere Beispiele zeigen die vielfachen Vorteile dieser Verfahren bei der Anwendung auf die Analyse von Umweltmaterial.

Presented at the 6th Annual Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria     

Assessment of drinking water radioactivity content by liquid scintillation counting: set up of high sensitivity and emergency procedures

In our institute, different procedures have been developed to measure the radioactivity content of drinking water both in normal and in emergency situations, such as those arising from accidental and terrorist events. A single radiometric technique, namely low level liquid scintillation counting (LSC), has been used. In emergency situations a gross activity screening is carried out without any sample treatment by a single and quick liquid scintillation counting. Alpha and beta activities can be measured in more than one hundred samples per day with sensitivities of a few Bq/L. Higher sensitivity gross alpha and beta, uranium and radium measurements can be performed on water samples after specific sample treatments. The sequential method proposed is designed in such a way that the same water sample can be used in all the stages, with slight modifications. This sequential procedure was applied in a survey of the Lombardia district. At first tap waters of the 13 largest towns were examined, then a more detailed monitoring was carried out in the surroundings of Milano and Lodi towns. The high sensitivity method for the determination of uranium isotopes was used to check the presence of depleted uranium in Lake Garda. Reduced equipment requirements and relative readiness of radiochemical procedures make LSC an attractive technique which can also be applied by laboratories lacking specific radiochemistry facilities and experience.     

Bestimmung von Ascorbinsäure auf Grund ihrer in einem Landolt-System ausgeübten reduzierenden Wirkung

Zusammenfassung Im Bromat-Jodid-Ascorbinsäure-System hängt die Zeit, die bis zur Jodausscheidung vergeht, von der Konzentration der Ascorbinsäure ab. Unter entsprechenden Versuchsbedingungen ist die Reaktionszeit proportional der Ascorbinsäurekonzentration. Danach kann die Ascorbinsäure sowohl mit Hilfe der Simultankomparationsmethode, als auch chronometrisch bestimmt werden. Die Genauigkeit ist ± 3% im Bereich von 5 bis 300g/5 ml. Die Grenzen der Bestimmung sind 1g bzw. 1000g Ascorbinsäure in 5 ml.

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Determination of ascorbic acid on the basis of its reducing action in a landolt system

Summary In the bromate-iodide-ascorbic acid system, the time that elapses until the iodine appears is dependent on the concentration of the ascorbic acid. Under appropriate experimental conditions, the reaction time is proportional to the ascorbic acid concentration. Accordingly, the ascorbic acid may be determined with the aid not only of the simultaneous comparison method but also chronometrically. The precision is ± 3% in the 5–300g/5 ml range. The limits of the determination are 1g and 1000g ascorbic acid in 5 ml respectively.

     

Effect of the specific activity of the tracer on rat luteinizing hormone radioimmunoassay

Rat luteinizing hormone /LH/ was labelled with¹²⁵I by the Chloramine T method.¹²⁵I-LH, used as tracer in radioimmunoassay, was separated from the labelling reaction mixture by gel filtration. By using the proper protein/radioiodine ratio in the labelling reaction mixture the specific activity of¹²⁵I-LH was adjusted to 2.5–20.5 MBq g^–1. The influence of the specific activity on the assay parameters as well as on the tracer stability was investigated.     

Die katalytischen Reaktionen bei der Spurenanalyse und die Untersuchung ihrer Mechanismen. II Untersuchung der Tiron—H2O2-Reaktion

Zusammenfassung Die Oxydation von Tiron durch H₂O₂ in basischem Milieu wird durch Kobalt stark katalysiert. Die katalysierten Vorgänge sind p_H-abhängig. Im p_H-Bereich 9 bis 11 entsteht ein rotes Oxydationsprodukt unbekannter Struktur; wahrscheinlich handelt es sich um ein o-Chinonderivat. Mit Hilfe der katalytischen Reaktion können 10^–4 g Kobalt/5 ml nachgewiesen werden. In diesem p_H-Bereiche stabilisiert Tiron H₂O₂ bei 100° C, bei 40° C jedoch katalysiert es — in Abhängigkeit von der Konzentration des Tirons — den Zerfall des H₂O₂. Der Effekt spielt im Mechanismus der katalysierten Reaktion wahrscheinlich eine Rolle, doch können die Zusammenhänge an Hand der bisher veröffentlichten Angaben nicht klar gedeutet werden. Der die Reaktion begleitende bzw. ihr folgende Nebenvorgang kann auf den katalytischen Zerfall des H₂O₂ · OOH-Komplexes zurückgeführt werden. Zwischen p_H 7 und 9 entsteht bei der katalysierten Reaktion Semichinon, über p_H 11 oxydiert Tiron das Semichinon unter Ringspaltung und Abspaltung von 1 Mol Sulfat zu Verbindungen, die Säurecharakter tragen.

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Summary The oxidation of Tiron by H₂O₂ in basic milieu is strongly catalyzed by cobalt. The catalyzed reactions are p_H-dependent. A red oxidation product of unknown structure results in the p_H range 9 to 11; probably it is ano-quinone product. As little as 10^–4 g cobalt/5ml can be detected by this catalytic action. In this p_H region, Tiron stabilizes H₂O₂ at 100° C, but at 45° C it catalyzes the decomposition of H₂O₂, in relation to the concentration of the Tiron. The effect probably plays a rôle in the mechanism of the catalyzed reaction, but the up to now published informations are not sufficient to clarify the relationships. The auxiliary process, accompanying or following the reaction, can be attributed to the catalytic decomposition of the H₂O₂-OOH^– complex. Semiquinone is produced by the catalytic reaction between p_H 7 and 9, above p_H 11, the Tiron oxidizes the semiquinone with opening of the ring and splitting off of 1 mol of sulfate yielding compounds which have an acidic character.

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Résumé L'oxydation du Tiron par H₂O₂ en milieu basique est fortement catalysée par le cobalt. Les processus de catalyse dépendent du p_H. Dans le domaine de p_H de 9 à 11, il apparaît un produit d'oxydation rouge, de structure inconnue; il s'agit probablement d'un dérivé de l'o-quinone. La réaction catalytique permet de déceler 10^–4 g cobalt/5 ml. Dans ce domaine de p_H, à 100° C le Tiron stabilise l'eau oxygénée et à 45° C, suivant sa concentration, il catalyse la décomposition de l'eau oxygénée. L'effet joue probablement un rôle sur le mécanisme de la réaction catalysée; on ne peut pourtant pas interpréter clairement ces relations au moyen des indications publiées jusqu'ici. Le processus secondaire qui accompagne la réaction ou qui la suit, peut être ramené à la décomposition catalytique du complexe H₂O₂-OOH^–. Entre p_H 7 et 9, la réaction catalysée donne naissance à une semiquinone; au-dessus de p_H 11, le Tiron oxyde la semi-quinone avec ouverture du cycle et élimination d'une mole de sulfate ce qui donne ensuite des composés qui portent le caractère acide.