Quantitative goldbestimmung in filmmaterialien mittels flammenloser atomabsorption

A graphite rod electrothermal atomizer has been used for the AAS determination of traces of gold in hydrochloric and in hydrobromic acid solutions, and also after extraction into HBr-saturated methyl isobutyl ketone. Photographic film samples were decomposed first by enzyme action then by nitric acid/peroxide oxidation, and the gold was extracted into MIBK. For 10-μl aliquots of solution the 3s limits of detection were 3 × 10^?10g for aqueous solutions, 7 × 10^?10g for MIBK, and 7 × 10^?9 g/cm² for film.     

Zur Erklärung einiger Viskositätsanomalien von Solen im Couette-Apparat

Zusammenfassung Es werden zwei Viskositätsanomalien an Gelatine- und Stärkesolen zu erklären versucht, die bei Messungen mit dem Couette gefunden, aber nicht mit Kapülarviskosimetern bisher reproduziert worden sind. Die Erklärung läuft in einem Fall (Gelatinesol) auf die Anahme einer Adsorption des Kolloids am Innenzylinder heraus, die eine Erhöhung der Wandrauhigkeit im hydrodynamischen Sinne und damit eine scheinbare Steigerung der Viskosität zur Folge hat. Die Erklärung des zweiten Falles (Stärkesol) schließt an eine von E. Hatschek für einen Teil der Anomalie bereits gegebene Deutung an, vervollständigt sie aber in einem wesentlichen Punkt. Sie erklärt die Anomalie durch die im Couette während der Messungen selbst erfolgende Zerstörung der Solstruktur bis zum praktischen Verlust der sogen. Strukturviskosität und durch die dann eintretende Strukturturbulenz. Das Stärkesol verhält sich damit ganz analog dem von E. Hatschek und R. S. Jane neuerdings untersuchten Ammoniumoleatsol.Die beiden Anomalien erscheinen bewirkt durch die spezielle Konstruktion des Couette-Apparates. Ihre Nichtreproduzierbarkeit mit Kapillarviskosimetern steht nicht im Widerspruch zu der These des Verfassers, derzufolge alle wesentlichen viskosimetrischen Erscheinungen an kolloiden Systemen mit beiden Apparaturen in gleicher Form gefunden werden.Es wird auf die von der Prandtl'schen Schule studierten Erscheinungen der Wirbelbildung in Grenzschichten und auf die Möglichkeit hingewiesen, daß solche Vorgänge auch im Couette, speziell bei Solen, auftreten und zu Anomalien führen können.     

Darstellung und Reaktionen des 3-Ethinyl-2,4-diformyl-pentandials

Preparation and physical and chemical properties of 3-ethinyl-2,4-diformyl-pentandial (3 a) and its salts are described.3 a contains 2 malonaldehyde groups. Starting from3 a, 4H-pyranes, 4H-dihydropyridines, dipyrazoles, diisoxazoles, bisdiazepines and vinamidine derivates are obtained.

---

---

Mit 1 Abbildung     

Zur Umsetzung des 3,4,5,6-Tetrahydro-6-hydroxy-4,4,6-trimethyl-1,3-thiazin-2-thions mit sekundären Aminen

Tetrahydro-6-hydroxy-trimethyl-1,3-thiazine-2-thione (1) reacts with secondary amines via the dialkylammonium-3-oxoalkyldithiocarbamate3, either via isothiocyanates6 to 4-dialkylaminodihydro-2(1H)-pyridinethiones7 or to dialkylammonium dithiocarbamates (13), depending on the amine used and the reaction conditions. Subsequently, 6-dialkylaminotetrahydro-1,3-thiazine-2-thiones11 or tetrahydro-6-mercapto-1,3-thiazine-2-thione10 are formed. On being heated to reflux,11 reacts to pyridinethione7 and 4-dialkylaminodihydrothiopyranthione19. With secondary amines only13 is formed from tetrahydro-6-hydroxytetramethyl-1,3-thiazine-2-thione20. The reaction of dihydrotrimethyl-1,3-thiazine-2-thione21 with secondary amines leads to N,N-dialkylthioureas16 or dialkylammonium thiocyanates17 and with dialkylformamides 4-dialkylaminodihydropyridinethiones7 are formed. Dihydrotetramethyl-1,3-thiazine-2-thione24 reacts neither with secondary amines nor with dialkylformamides.     

Koordinationschemie von Dinitroresorcin mit Kupfer-, Kobalt-, Nickel-, Eisen- und Zinksalzen

The reactions of the bidentate dinitrosoresorcinol (DNR) with copper, cobalt, nickel, iron and zinc salts were investigated. This ligand was found to react with these metal salts in aqueous media where hydrogen ion was confirmed to be liberated except in case of iron. The solid complexes were prepared in alcoholic media. Chemical analyses, magnetic and spectral data were compatible to determine the structure of these complexes and their mode of chelation.

---

---

Mit 2 Abbildungen     

Beiträge zur Chemie der Pyrrolpigmente, 19. Mitt.: Die elektrochemische Oxidation von Pyrromethenonen und Pyrromethenen (Gallenpigment-Partialstrukturen)

The electrochemical oxidation of arylmethylene-pyrrolinones, pyrromethenones and pyrromethenes as representative bile pigment partial structure models was investigated by means of a rotating disc platinum electrode using acetonitrile as the solvent. Two different oxidation reactions were found. The first reaction being a reversible one-electron oxidation with compounds of the arylmethylene-pyrrolinone series and pyrromethenones which are unsubstituted in position 5 of the pyrrole ring. A two step reaction (the first one reversible, the second irreversible) on the other hand was found to be typical for pyrromethenones bearing a methyl group in this position.Through protonation the first step is at a higher potential, whereas the second one is lowered and becomes reversible. The resulting oxidation pattern can be interpreted analogous to the oxidation of hydroquinones in aprotic solvents.The geometrical isomers of a pyrromethenone were oxidized at appr. the same potential, but there is a strong dependence of the potential of the first oxidation step on the substitution: a higher degree of alkylation favours oxidation by lowering the oxidation potential.

---

---

Mit 1 Abbildung     

N-Monobromamide: Darstellung durch Bromierung mit „Dibromisocyanursäure”, Eigenschaften

By reaction of primary carboxamides with “dibromoisocyanuric acid” (DBI) N-monobromoamides can be readily obtained as well as the N,N-dibromoamides described in an earlier paper¹. Reactions, some of them new, and properties of these compounds are described and compared with those of the N,N-dibromoamides. Like other compounds bearing the NHBr group^{2, 3} the N-monobromocarboxamides disproportionate at room temperature according to: 2 RCONHBr ? ? RCONH₂+RCONBr₂. For CH₃CONHBr the equilibrium constant was found to beK=0.02. In aqueous solution they behave as weak acids. The dissociation constants of eight compounds [R=?CH₃, ?C₂H₅, ?CH₂Cl, ?CHCl₂, ?CCl₃, ?CF₃, ?C(CH₃)₃ and ?C₆H₅] were measured: they differ from those of the corresponding carboxylic acids by about three powers of ten.     

Zum Mechanismus der Hydrogenolyse aromatisch gebundenen Halogens

The selective chlorination of a m/p-xylene mixture, followed by distillation of the unreacted p-xylene, leaves a residue containing up to 90% of monochlorinated m-xylenes. m-Xylene is recovered from the latter by heterogeneous catalytic hydrogenolysis in the gas-phase. It was found that the hydrogenolysis on certain noble metal catalysts proceeds according to an ionic reaction mechanism at temperatures below a definite temperature range. At temperatures above this range hydrogenolysis follows a radical reaction mechanism.     

Metallchelate mit Acetophenon-Benzoylhydrazon und Acetophenon-Salicoylhydrazon

The stoichiometry and structure of acetophenone benzoylhydrazone and acetophenone salicoylhydrazone chelates with some divalent metal ions are studied by conductometric titration and visible and infra-red absorption spectrophotometry. The results are supported by analysis of the solid complexes. The infra-red study revealed that coordination occurs through C=O and C=N groups. The shift in the C=O and C=N bands is utilised for the determination of bond lengths.     

Zur Kenntnis der thermischen Zersetzung von Ammoniumhexafluoroscandat,-titanat,-vanadat und-chromat

Thermal analysis supported by kinetic calculations was applied exhaustively to these compounds. Under dynamic conditions, tetrafluorometallates(III), which as intermediates, could not be isolated, for the first three compounds. In each case, the final step was the pure metal(III) fluoride. Ammonium hexafluorochromate(III) decomposed directly to the pure chromium(III) fluoride. The decomposition rate of all compounds slowed down towards the end, probably for kinetic reasons. Polymorphic transitions of ammonium hexafluorotitanate(III) were observed at 35 and 100°C. Ammoniumhexafluoroscandate(III) underwent polymorphic transition at 47°C. The decomposition patterns for all these compounds were similar. Conditions for the preparation of pure ammonium tetrafluorometallates(III) of Sc, Ti and V are described.