Determination of227Ac in geological materials through neutron activation and alpha-spectrometric assay of induced228Th

A new route has been developed for the micro-determination of²²⁷Ac in geological materials by neutron activation. The method is based on intense neutron irradiation of the analysed samples followed by separation and α-spectrometric determination of²²⁸Th, the β-decay product of the 6.1 hrs²²⁸Ac isotope formed. Two alternatives are considered for analysis related to the origin of the analysed matrix. The high sensitivity of the method is documented by the determination of 10^?17 g²²⁷Ac/g sample. The method is successfully applied for age determination of five uranium containing materials and old uranium glass from Bohemia, CSSR.     

Eine neue Verbindung der Zusammensetzung 9 BaNiO2·2 BaCO3

Zusammenfassung Bei der Reaktion von BaCO₃ mit NiO bildet sich unter bestimmten Bedingungen ein kristallines Pulver der Zusammensetzung 9 BaNiO₂ · 2 BaCO₃. Die Verbindung zeigt scharfe Röntgeninterferenzen, die sich kubisch indizieren lassen. Es wurden elektronenmikroskopische Aufnahmen gemacht sowie Elektronenstrahlfeinbereichsbeugungen durchgeführt. Das IR-Spektrum wurde aufgenommen und die magnetische Suszeptibilität bestimmt.

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A new compound 9 BaNiO₂·2 BaCO₃

During the reaction of BaCO₃ with NiO under special conditions a crystalline powder with the composition 9 BaNiO₂ · 2 BaCO₃ is formed. This compound shows clear X-ray patterns which can be indexed using a cubic cell. Electron microscopic investigations have been carried out and selected area diffraction patterns have been taken. The IR-spectrum and the magnetic susceptibility have been proved.

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Mit 3 Abbildungen     

Datenverarbeitung in der analytischen Chemie

Zusammenfassung Die beiden Hauptaufgaben der analytischen Chemie sind nach wie vor die quantitative und die qualitative Analyse, die immer weiter in Richtung Ultraspurenbestimmung voranschreitet und so mit der quantitativen Analyse eng verknüpft ist.Ein Sonderfall der qualitativen Analyse ist die Strukturanalyse, die in der organischen Chemie größte Bedeutung hat. Die heute geübte Arbeitsweise umfaßt dabei die Gewinnung von Meßdaten in reiner Handarbeit, die teilmechanisierte Gewinnung von Meßdaten mit Hilfe der instrumentellen Analytik, wobei individuelle Hand- und Kopfarbeit nach wie vor überwiegt und schließlich die vollmechanisierte Gewinnung von Meß-daten, welche nur dann wirtschaftlich eingesetzt werden kann, wenn auch die Verarbeitung der Zwischendaten maschinell erfolgt. Am Beispiel der klassischen und der modernen Titration, der Gas-Chromatographie, der Massenspektrometrie und der Kopplungstechnik von stofftrennenden und strukturerkennenden Methoden werden die Arten der Datenerzeugung, die Vielfalt des Datenanfalles und die Anforderung an eine Datenverarbeitung unter dem Gesichtspunkt der industriellen Analytik diskutiert.Bei der instrumentellen Analyse entstehen meistens Daten mit viel höherer Geschwindigkeit und erheblich höherer Dichte als bei der klassischen Analyse. Es muß nun entschieden werden, ob eine Zwischenspeicherung (Schreiber, Magnetbandschreiber mit allen ihren Vorteilen) noch ausreicht, oder ob eine on-line-Verbindung mit einer Datenverarbeitungsanlage notwendig ist. Dies ist dann der Fall, wenn eine zeitraubende Zwischenspeicherung nicht mehr akzeptiert werden kann oder der Datenanfall pro Zeiteinheit durch Handarbeit nicht mehr ökonomisch bewältigt werden kann.Entscheidend ist es, die wirklich vertretbare Forderung nach der Geschwindigkeit, mit der die Enddaten ermittelt werden müssen, mit dem Zeitbedarf der Probengewinnung, Probennahme, Probenaufbereitung abzustimmen. Ferner ist es wichtig, den Umfang der wirklich nötigen Daten auf das Mindestmaß zu reduzieren. Die anschließende Berechnung über Aufwand und Ergebnis der Datenverarbeitung in der analytischen Chemie kann dann die richtige Antwort auf das zu wählende System — Rechenschieber, Tischrechner, programmierter Tischrechner, Kleinstcomputer, Computer — geben. Beispiele dazu werden diskutiert.

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Summary Quantitative und qualitative analysis continue to be the two main fields of analytical chemistry, and analytical chemistry keeps moving forward in the direction of minimum-concentration analysis, thus being closely related to quantitative analysis.Structural analysis, which is of outstanding importance in organic chemistry, is a special form of qualitative analysis. Modern procedures include methods in which the data are gathered exclusively by hand, semi-mechanized methods using instrumental techniques (in which the hand and the head still play a predominant role) and, last but not least, fully mechanised techniques which are uneconomical unless the intermediate data are also processed by machine. The types of data processing, the complexity of the data obtained and the requirements to be met by the processing system are discussed from the point of view of industrial analysis with reference to classical and modern titration, gas chromatography, mass spectrometry and systems combining separation and structure-finding methods.Instrumental methods usually yield the information at much higher speed and in rather more concentrated form than classical procedures. It is now necessary to decide wether intermediate storage ([magnetic tape] recording equipment with all its advantages) is still adequate or wether some on-line connection to a computer is required. The latter is a must when time-consuming intermediate storage is not acceptable or the amount of data obtained per unit time cannot be economically dealt with by hand.The important thing is to correlate the (really justifiable) demand for the speed of determining the final data to the time required for preparing, taking and processing the samples. Calculation of the expenditure incurred and the results of data processing can provide the right answer as to the equipment to be used, i. e. slide rule, calculating machine, programmed calculating machine, mini-computer or computer. Examples are discussed.

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Herrn Professor Dr. Steinhofer zum 60. Geburtstag gewidmet.     

Study of occupational health impact of atmospheric pollution on exposed workers at an iron and steel complex by using neutron activation analysis of scalp hair

The occupational health impact of atmospheric pollution on exposed workers at one iron and steel complex was studied by instrumental neutron activation analysis of workers' hair samples and medical examination. The experimental results indicate that there is a positive correlation between the high inhalation amounts of iron and other trace elements by the exposed workers and the symptom of their high blood pressure and hypoglycemia, which implies that the atmospheric environment polluted by iron and steel industry has an adverse health impact on the exposed workers. The measures to relieve and abate the occupational diseases caused by air-borne particulate matter should be taken     

Thio-sugars. IV. Synthesis of carbohydrate 1,3-glycol (six-membered) thionocarbonates and their attempted O-S rearrangement

Four six-membered cyclic thionocarbonates (two sec-sec and two prim-sec) were prepared and their radical-promoted O-S rearrangement reaction was examined. The results revealed that the reaction in six-membered rings is difficult compared with the simple rearrangement in five-membered rings. In the course of syntheses of the substrates, interesting acyl migration during the stannylation process occurred.     

Enumeration of wurtzite derivatives and related dipolar tetrahedral structures

Pólya's theorem and related results are used to count and classify by space group all possible wurtzite derivatives with small unit cells having composition ABX₂, AB₂X₃, AB₃X₄, or ABC₂X₄. The same arguments are applied to the dipolar tetrahedral structures, which resemble wurtzite but have a different pattern of occupancy of the tetrahedral voids in the hcp anion framework. Covalent molecular orbital and electrostatic calculations are used to study the two real and eight hypothetical structures for Li₃PO₄. Both predict shared edges to be destabilizing, in keeping with Pauling's rules.     

Weak transverse magnetic field effect on the viscosity of Ni(NO3)2H2O solution

Experiments performed at 25°C show that transversally applied magnetic field H of strength of 12 kG; at high concentrations decreases the viscosity of Ni(NO₃)₂H₂O solution. At low concentrations, however, the applied magnetic field increases the viscosity of Ni(NO₃)₂H₂O solution in such a way as the observed effect value approaches the already measured viscosity increase of the pure water at the same magnetic field and temperature conditions.     

Normal coordinate ab initio force relaxation

A procedure for optimization of molecular geometries is presented, combining ab initio calculations with vibrational molecular data from spectroscopy or empirical force fields. Theoretical cartesian forces are transformed to vibrational normal coordinate forces from which geometry increments are calculated. Test results indicate that the method saves considerable effort compared to other optimization schemes.     

An automated procedure for the simultaneous determination of specific conductance and pH in natural water samples

An automated, continuous-flow system is utilized to determine specific conductance and pH simultaneously in natural waters. A direct electrometric procedure is used to determine values in the range pH 4–9. The specific conductance measurements are made with an electronically modified, commercially available conductivity meter interfaced to a separate module containing the readout control devices and printer. The system is designed to switch ranges automatically to accommodate optimum analysis of widely varying conductances ranging from a few μmhos cm^-1 to 15,000 μmho cm^-1. Thirty samples per hour can be analyzed. Comparison of manual and automated procedures for 40 samples showed that the average differences were 1.3% for specific conductance and 0.07 units for pH. The relative standard deviation for 25 replicate values for each of five samples was significantly less than 1% for the specific conductance determination; the standard deviation for the pH determination was ? 0.06 pH units.     

Photoassociative spectroscopy of pure long-range molecules

We have experimentally studied the “pure long-range” state, 0 _g ^? , of³⁹K₂ for the first time by high resolution photoassociative spectroscopy of ultracold potassium atoms. Well-resolved vibrational levels have yielded molecular constants for this state. Analytical expressions for the potential energy curves of the two pure long-range states, 0 _g ^? and 1 _u , are obtained. All the available theoretical and experimental molecular constants of the three special long-range potentials with extrema for all the alkali metals are summarized.