A semi-automatic system for activation analysis using the WWR nuclear reactor

A semi-automatic pneumatic transport system for nuclear reactors is described. The sealed polyethylene capsules containing the sample are placed into transport containers. Ten such containers are placed manually into a feeding device. All subsequent operations (irradiation, removal of the capsule from the container, and transport of the capsule to the laboratory for activity measurement) are automated. Total time from the completion of irradiation to the beginning of measurement is 10–20 sec.     

A semi-automatic system for operation of electrical detection for a spark-source mass-spectrometer

A semi-automatic control system has been developed for a spark-source mass-spectrometer, which permits close interaction between the operator, the instrument via electrical ion-detection and a computer via time-sharing (remote terminal) facilities.     

A membrane method for degassing nonaqueous liquids

Degassing of nonaqueous solvents is useful for their applications in chemical synthesis and in maintaining purity (against oxidative degradation) during long term storage. In addition, degassed solvents have been found to be of value in the production of oil and water emulsions. Currently, there are three main methods for degassing solvents. These are the freeze-pump-thaw process, partial degassing using sonication under slight vacuum and purging, where one active gas (usually oxygen) is replaced with an inert gas (e.g., nitrogen). In this work we have demonstrated the potential application of hollow-fibre membranes to efficiently degas water-immiscible, hydrophobic liquids. Mixtures of dodecane and water, separately degassed using membranes, show an enhanced dispersion of dodecane, similar to that previously reported for freeze-thaw degassed mixtures.     

New solvents for cellulose: Hydrazine/thiocyanate salt system

The hydrazine/thiocyanate system was found to be an excellent solvent for cellulose. The solubility and solution properties were investigated. Even at room temperature, the combinations of hydrazine and lithium, sodium, and potassium thiocyanate had high dissolution power for cellulose, up to an 18% (w/w) maximum, unrelated to the polymorph, whereas a combination with ammonium thiocyanate exhibited a solubility difference among celluloses I, II, and III. The effect of the temperature cycling of the system for the rapid dissolution of cellulose was investigated thermodynamically. In these systems, a high concentration of salts was necessary to effect the cellulose dissolution; this suggested that an undissociated salt–solvent complex played an important role in the cellulose dissolution as implied by electroconductivity measurements of the hydrazine/salt system. Gel and liquid‐crystal formation was observed in all systems above 4 and 6% (w/w) cellulose concentrations, respectively. The values of both critical concentrations were quite similar to those observed in the ammonia/ammonium thiocyanate system studied earlier in our laboratories. The gelation temperature was between approximately 10 and 50 °C, depending on the salt and cellulose concentration. The dependence of the cellulose solubility on the degree of polymerization was also examined. It is suggested that these solvent systems have great potential for the fiber and film formation of cellulose. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 601–611, 2002; DOI 10.1002/pola.10135     

Solvent system selection in counter-current chromatography using conductor-like screening model for real solvents

The aim of this investigation was to minimize the experimental effort for solvent system selection in counter-current chromatography. The separation mechanism in counter-current chromatography is based exclusively on the partitioning of the solute between the two liquid phases. Therefore, a quantum chemical method combined with statistical thermodynamics (conductor-like screening model for real solvents, COSMO-RS) was used for the prediction of the partition coefficient. A comparison of the experimental and predicted data for five model solutes systems demonstrated the potential of the use of COSMO-RS as a screening tool for the solvent system selection.     

The degassing behaviour of natural glasses and implications for their origin

Degassing experiments showed that a remarkable difference exists between glasses from a range of geological environments. The released gases were thermally analysed by a simultaneous thermogravimetric, mass spectrometric (partial pressure), and total pressure measurements of evolved gases by heating from room temperature to 1450°C. Detailed degassing studies on natural glasses from various terrestrial environments show that the degassing behaviour of glasses differs strongly, also in respect of the manmade glasses. The gas release profiles of natural glasses can be divided into three groups: 1) volcanic glasses, 2) impact glasses and 3) silica glasses and tectites.The degassing behaviour of manmade glasses is determined by the melting technique, the raw materials, and the fining agents. Gas release curves are suitable tools for the identification of vitreous samples of unknown origin but it is impossible to gain data of physico-chemical conditions of the glass formation process or for the polymerization state of the melt.

---

Zusammenfassung Entgasungsexperimente zeigen, daß zwischen Gläsern von einer Reihe von geologischen Umfeldern bemerkenswerte Unterschiede bestehen. Die beim Erhitzen von Raumtemperatur auf 1450°C freigesetzten Gase wurden thermisch mittels simultanen thermogravimetrischen, massenspektrometrischen (Partialdruck) und Gesamtdruckmessungen analysiert. Ausführliche Entgasungsstudien an natürlichen Gläsern aus verschiedenen Landschaftsgebieten zeigen, daß sich das Entgasungsverhalten der Gläser stark unterscheidet, auch im Vergleich zu künstlich erzeugten Gläsern. Die Gasfreisetzungsprofile natürlicher Gläser können in drei Gruppen unterteilt werden: 1.) vulkanische Gläser, 2.) Aufschlaggläser und 3. Silikatgläser und Tektite.Das Entgasungsverhalten künstlich hergestellter Gläser wird durch die Schmelztechnik, die Rohstoffe und die Läutermittel bestimmt. Entgasungskurven sind ein geeignetes Mittel zur Identifizierung glasähnlicher Proben unbekannten Ursprunges. Es ist jedoch nicht möglich, Daten über physikalisch-chemische Bedingungen der Glasbildungsprozesse oder über den Polymerisationsgrad der Schmelze zu erhalten.

---

---

Dedicated to Prof. Dr. H. J. Seifert on the occasion of his 60^th birthday     

Vacuum for Balances

This paper deals with the design of gravimetric apparatus with regard to the requirements of vacuum. Items discussed include the calculation of suction speed and ultimate vacuum, the choice of the pump and of the method of pressure control, and the design of the balance and the balance stand. This revised version was published online in July 2006 with corrections to the Cover Date.     

Experimental justification of the effectivity of the separating power of solvents for extractive distillation of the propylene oxide-methanol binary system

Highly selective protic and aprotic solvents were compared in terms of their effectivity as extractive distillation agents for the propylene oxide-methanol system. Separating agents were chosen on the basis of their solubility data. A relationship between the capacity of the separating agent and the degree of extraction of propylene oxide was established.     

A twinned mercury-filled glass electrode system for acid-base titrations in a number of non-aqueous solvents

A pair of mercury-filled glass electrodes is proposed for acid-base titrations in non-aqueous solvents or their mixtures with each other or with water.