On the retrograde condensation of one or two liquids

This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out.     

Photometrische Bestimmung von Titan in molybd?nhaltigen St?hlen mit Tetrahydroxyphenazin

Zusammenfassung Tetrahydroxyphenazin (THP) bildet mit Titan im sauren Medium Komplexe mit sehr hohen Werten des Extinktionskoeffizienten. Es wird ein Bestimmungsverfahren für Titan in molybdänhaltigen Stählen beschrieben, bei dem die störenden Elemente mit einem Gemisch aus Tri-n-butylphosphat und Chloroform extrahiert werden. Das in der wäßrigen Phase verbleibende Titan wird mit THP photometrisch bestimmt. Die hochempfindliche Methode erlaubt Titanbestimmungen im Nanomol-Bereich. Bei Stahlproben mit 0,2–0,7% Ti (in Gegenwart von 0–2% Mo) ergab sich ein Variationskoeffizient von 0,4 bis 2,4%.

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Photometric determination of titanium in molybdenum steels with tetrahydroxyphenazine

Complexes with very high molar extinction coefficients are produced in the reaction of tetrahydroxyphenazine (THP) with titanium in acid solution. In the method described titanium is determined photometrically by complexing with THP in the aqueous phase after extracting the interfering elements with a mixture of tri-n-butyl-phosphate and chloroform. This highly sensitive method is applicable for determination of titanium in the nanomolar region. With steel samples containing 0.2–0.7% of Ti (in presence of 0–2% of Mo) variation coefficients of 0.4 to 2.4% have been obtained.

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Für die Durchführung dieser Arbeit wurden dankenswerterweise Forschungsmittel aus dem ERP-Sondervermögen bereitgestellt.Dem Verbande der Chemischen Industrie und der Deutschen Forschungsgemeinschaft, die diese Arbeit unterstützt haben, danken wir bestens.     

Spectral investigation of cw rf-pumped atomic Xe laser with a slab geometry

A radiofrequency excited atomic Xe slab laser with an active volume of 2 × 10 × 300 mm³ using a quartz envelope containing the laser-gas mixture shows a stable cw performance with an output power of almost 1 W. The free-running system oscillates, depending on gas composition and density, on several lines between 1.73 and 3.51 m. Line competition phenomena are observed. Single-line oscillation yields more than 500 mW.     

Fundamentals of lead acid cells: Part IV. The reduction of porous PbO2 electrodes in sulphuric acid

The reduction behaviour of porous lead dioxide electrodes is shown to be independent of rotation speed in a large excess of 5 M H₂SO₄. The reduction peak is broadened by the porosity. This porosity broadening is interpreted in terms of the reaction being driven more deeply into the pore structure as the front of the electrode becomes progressively more ressstive. The effect of different potential sweep rates on the current response and the effects of progressive redox cycles can be fully explained on this model.     

A new intramolecular cyclisation reaction—I : Novel synthesis of benzo(k,1)thioxanthene-3,4-dicarboxylic anhydride and derived dyestuffs

A new direct synthesis of benzo(k,1)thioxanthene-3,4-dicarboxylic anhydride from 4-nitro-naphthalene-1,8-dicarboxylic anhydride and 2-aminobenzenethiol is reported; 4-(2-aminophenylthio) naphthalene-1,8-dicarboxylic anhydride and 4-phenylthionaphthalene-1,8-dicarboxylic anhydride are also formed. Similar reaction in presence of amyl nitrite or sodium nitrite results in formation of larger amounts of 4-phenylthionaphthalene-1,8-dicarboxylic anhydride, together with other products arising from the oxidation of 2-aminobenzenethiol; one such product is the new heterocycle 9,10-dithiaphenanthrene. 4-(2-Aminophenylthio)-naphthalene-1,8-dicarboxylic anhydride is rapidly converted by amyl nitrite or sodium nitrite in dimethylformamide into benzo(k,1)thioxanthene-3,4-dicarboxylic anhydride, constituting a novel one-stage intramolecular cyclisation reaction of greater convenience than the conventional two stage Pschorr cyclisation.     

Nanoscale borromeates

[Structure: See text] In addition to a parent zinc(II) Borromean ring (BR) complex, the preparation and characterization of two hexasubstituted BR complexes with either 4-acetoxymethylphenyl or 4-methylthiophenyl substituents associated in turn with all six pyridyl rings has been achieved convergently in good yields by appealing to the dynamic features of the reactions between primary amino groups in a preformed acyclic ligand and 2,6-diformylpyridine. Two molecules of the acyclic ligands react with two molecules of 2,6-diformylpyridine to form a cyclic [2 + 2] tetraimine in the presence of Zn(II) ions as templates in 2-propanol at 70 degrees C. The successful preparation of the two derivatives by convergent template-directed syntheses opens up opportunities to self-assemble, under equilibrium control, numerous nanoscale metallo-organic particles with potentially useful properties.