Quecksilber(II)-titrationen mit Variaminblau als Redoxindicator

Zusammenfassung Es wird ein volumetrisches Verfahren zur Bestimmung von Rhodanid mit Quecksilber(II)-nitratmaßlösung gegen Variaminblau als Redoxindicator angegeben. Auch Quecksilber(II)-ionen können bestimmt werden, wenn man mit einem Überschuß an Rhodanid versetzt und mit der Maßlösung zurücktitriert. Die Methode liefert genaue und wenig streuende Resultate.

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Summary Thiocyanate can be determined by titration with mercuric nitrate standard solution using Variamine blue as redox indicator. The determination of mercuric ions is possible by adding an excess of thiocyanate and back titrating with the standard solution. Results are exact and deviations are small.

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I. Mitteilung: Gregorowicz, Z., u. F. Buhl: diese Z. 173, 115 (1960).     

Studies on mechanism and kinetics of reaction of CuSO4 with Cu2SO2

The reaction of CuSO₄ with Cu₂SO₂ to give Cu₂SO₄ was studied. The influence of the degree of reaction, the initial mixture composition and the temperature upon the reaction rate and the product composition was discussed. It was found that the reaction starts above 710 K and pure Cu₂SO₄ can be obtained under strictly defined conditions.     

The equilibria of phosphatidylcholine-fatty acid and phosphatidylcholine-amine in monolayers at the air/water interface

Monolayers of phosphatidylcholine, fatty acid and amine and binary mixtures phosphatidylcholine-fatty acid or phosphatidylcholine-amine were investigated at the air/water interface. Phosphatidylcholine (lecithin, PC), stearic acid (SA), palmitic acid (PA), decanoic acid (DA) and decylamine (DE) were used to the experiment. The surface tension values of pure and mixed monolayers were used to calculate π-A isotherms. The surface tension measurements were carried out at 22°C using an improved Teflon trough and a Nima 9000 tensiometer. The Teflon trough was filled with a subphase of triple-distilled water. Known amounts of lipid dissolved in 1-chloropropane were placed at the surface using a syringe. The interactions between lecithin and fatty acid as well as phosphatidylcholine and amine result in significant deviations from the additivity rule. An equilibrium theory to describe the behaviour of monolayer components at the air/water interface was developed in order to obtain the stability constants of PC-SA, PC-PA, PC-DA and PC-DE complexes. We considered the equilibrium between the individual components and the complex and established that lecithin and fatty acid as well as phosphatidylcholine and amine formed highly stable 1:1 complexes.     

Aldimines of 5-aminouracil as reagents in 1,3-dipolar cycloaddition reaction

Abstract  

The condensation of 5-aminouracil with aromatic aldehydes gave the appropriate C-arylimines, which were used in [2+3] cycloaddition with nitrile oxides derived from 4-substituted benzaldoximes. As a result of the dipolar cycloaddition reaction several hitherto unknown 5-(3,5-diphenyl-1,2,4-oxadiazol-4(5H)-yl)pyrimidine-2,4(1H,3H)-diones have been obtained in satisfactory yields.     

Anionic ring opening polymerization by alkali metal solutions

The alkali metal solutions were found to be active initiators in the ring-opening polymerization of β-lactones. The chemistry of those solutions and their activity as initiators were discussed.     

Ring-opening of 2,3-epoxy-1-propanol with R3Al: Unprecedented regiochemical switching simply achieved by changing alkyl substituents of aluminium reagent

Several control experiments were designed to optimize the reaction of 2,3-epoxy-1-propanol with R₃Al (R = Me, Et or ⁱBu) and to probe for the nature of aluminium-bound alkyl groups that influence the reactivity and selectivity. The reported studies revealed that the Et₃Al mediated reaction leads to the C-2 product in contrast to the well-known C-3 substitution promoted by Me₃Al.     

Thermal degradation kinetics of PET/SWCNTs nanocomposites prepared by the in situ polymerization

The decomposition and thermal behavior of poly(ethylene terephthalate) (PET)/carbon nanotubes (CNTs) nanocomposites were studied using thermogravimetric (TG) analysis in air atmosphere. A series of PET/single-walled CNTs (SWCNTs) materials of varying nanoparticles concentration were prepared using the in situ polymerization technique. Transmission electron microscopy and scanning electron microscopy micrographs verified that the dispersion of the SWCNTs in the PET matrix was homogeneous, while some relatively small aggregates co-existed at higher filler concentration. Two-stage decomposition was observed in the experiments. During first stage, strong chemical bonds are broken, i.e., aliphatic bonds and benzyl ring containing molecules decompose into small molecules in the gaseous phase. During second stage, when temperature is higher, the remaining nanotubes along with the residues of the first stage are burned. Kissinger and Coats–Redfern (5, 10, 20, 50 K min^?1) methods were applied to TG data to obtain kinetic parameters (activation energy, Arrhenius constant at 600 K and A factor) and Criado method to kinetics model analysis. In this kinetic model, energy activation is increasing with the increase of nanotubes concentration.     

Phase equilibria in the system FeVO4-WO3 in the solid state

The DTA and X-ray powder diffraction imply the following equilibria in the system FeVO₄-WO₃ up to the solidus line: from 550 to 650–670°C, the system components remain inert towards each other in the whole concentration range; above 670°C, at up to 66.67 mol% of WO₃. FeVO₄ and FeVW₂O₁₀ are in equilibrium, whereas from 66.67 mol% of WO₃ upwards FeVW₂O₁₀ and WO₃ are in equilibrium.

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Zusammenfassung DTA Untersuchungen und Debye-Scherrer-Aufnahmen lassen darauf schließen, daß im System FeVO₄-WO₃ bis zur Soliduslinie folgende Gleichgewichte festgestellt wurden: von 550 bis 650–670°C bleiben die Systemkomponenten im ganzen Konzentrationsbereich voneinander unberührt, oberhalb 670°C sind bis zu 66.67 Molprozent WO₃ die Verbindungen FeVO₄ und FeVW₂O₁₀ im Gleichgewicht vorhanden, oberhalb 66.67 Molprozent WO₃ hingegen die Verbindungen FeVW₂O₁₀ und WO₃.

     

Spin ground state and magnetic properties of cobalt(II): relativistic DFT calculations guided by EPR measurements of bis(2,4-acetylacetonate)cobalt(II)-based complexes

The spin ground state of the core ion and structure of the bis(2,4-acetylacetonate)cobalt(II) model complex and its synthetic aqua and ethanol derivatives, Co(acac)(2)L(n), (L = EtOH, H(2)O), were examined by means of density functional theory (DFT) calculations supported by electron paramagnetic resonance (EPR) measurements. Geometry optimizations were carried out for low-spin (doublet) and high-spin (quartet) states. For the Co(acac)(2) complex two possible conformations, a square-planar and a tetrahedral one, were taken into account. For all structures relative energies were calculated with both "pure" and hybrid functionals. The calculated data were complemented with the results of the EPR investigations carried out at liquid helium temperature, allowing for definite assignment of the high-spin state for the Co(acac)(2)(EtOH)(2) complex. However, because of the unresolved spectral features, only effective g-values could be assessed, whereas the zero-field splitting parameters (ZFS) were calculated by means of the spin-orbit mean field (SOMF) relativistic DFT method for which direct spin-spin (SS) and spin-orbit coupling (SOC) contributions were quantified.