Über die Silicatanionenkonstitution in Tetraethylammoniumsilicaten und ihren wäßrigen Lösungen

On the Constitution of Silicate Anions in Tetraethylammonium Silicates and their Aqueous Solutions Investigations by paperchromatography, ²⁹Si-NMR spectroscopy and trimethylsilylation method show that concentrated solutions of tetraethylammonium (TEA) silicates with molar TEA:Si ratios from 2.8 to 1 contain mainly double three-ring silicate anions. Besides of these small amount of mono-, di-, tri-, tetra-, cyclotri-, cyclotetra-, double four-ring- and other polycyclic silicate anions are present. From these solutions a crystalline double three-ring silicate of the formula [N(C₂H₅)₄]₆[Si₆O₁₅] · 57 H₂O could be obtained by crystallization at low temperature. Concentrated solutions with TEA:Si ratios of 0.8 to 0.6 contain mainly double three-, double four-, double five- an probably double six-ring silicate anions. From such solutions always the solid TEA-double four-ring silicate is obtained by crystallization. The reasons for the prefered formation of double ring silicate anions in TEA-silicate solutions and their crystallization are discussed.     

IR-Untersuchungen an wäßrigen Lösungen von Metallchloriden

IR Spectra of Aqueous Solutions of Metal Chlorides Aqueous solutions of the chlorides of some monovalent and divalent metals have been investigated by IR-Spectroscopy. The spectra are registered as a function of the concentration of these solutions. The solutions of monovalent metal chlorides show no variations of the deformation band and the valence band to pure water. In solutions of divalent metal chlorides the positions of the bands are dependent on the concentration of solution.     

Zum Einfluß von Kaliumtricyanmethanid und -dicyanamid auf das anodische Verhalten von Kupfer in wäßrigen Lösungen

On the Influence of Potassium Tricyanmethanide and Dicyanamide on the Anodic Behaviour of Copper in Aqueous Solutions Electrochemical measurements on copper anodes in aqueous solutions of potassium tricyanmethanide and dicyanamide show a strong tendency of passivation of copper. Comparative galvanostatic investigations of copper in aqueous solutions of the potassium halides and pseudo-halides KX (X: Cl, Br, J, SCN, N(CN)₂, N(CN)₂, C(CN)₃) are indicating a clear increase in the efficiency of the formation of a passivating layer in the series Cl^? ? Br^?<J^?<SCN^?<N(CN)₂^?<C(CN)₃^?. In solutions of halides the first anodic process is followed by the second one at few increased potential, whereas a broad passive areal appears in solutions of pseudohalides, for instance in the cases of tricyanmethanide and dicyanamide.     

Dichten und scheinbare Molvolumina wäßriger Lösungen von Calciumnitrat und Calciumchlorid

Densities and Apparent Molal Volumes of Ca(NO₃)₂? CaCl₂ Aqueous Solutions Densities and apparent molal volumes of Ca(NO₃)₂? CaCl₂ aqueous solutions were determined as a function of temperature and concentration. The dependence of apparent molal volumes on the anion composition is discussed.     

Über den Anionenaufbau wäßriger Tetra-n-propyl- und Tetraethylammoniumsilicatlösungen

On the Anion Constitutions of Aqueous Tetra-n-propylammonium and Tetraethylammonnium Silicate Solutions The constitution of the silicate anions present in 0.1 M to 3 M tetrapropylammonium-(TPA-) and tetraethylammonium-(TEA-)silicate solutions with molar TPA/Si ratios of 3, 1 and 0.6 and TEA/Si ratios of 3 and 1 is investigated by means of trimethylsilylation. Up to 16 different oligomeric silicate anions are detected and estimated quantitively. Type and quantitative dis-tribution of the silicate anions are very similar in diluted 0.1 M TEA- and TPA-silicate solutions. Concentrated TEA-silicate solutions contain preferably Si₆O₁₅^6? anions whereas concentrated TPA-silicate solutions are characterized by a broad distribution of different oligomeric silicate anions. The anion distribution of TPA- and TEA -silicate solutions is compared with the results of tetramethyl- and tetrabutylammonium silicate solutions studied previously.     

Untersuchung der strahlenchmischen Oxydation von Ammoniak in 0,1 bis 16 molaren wäßrigen Lösungen

Radiation-Induced Oxidation of Ammonia in 0.1 to 16 Molar Aqueous Solution By γ-irradiation of oxygen-containing aqueous ammonia peroxonitrite, nitrite, nitrate, and nitric oxides are formed. From the dependence of reaction yield upon ammonia concentration, oxygen concentration, and dose rate a system of consequent reactions is derived for the kinetics of the reaction for which the reaction rate constants are calculated. On the basis of the results a tentative mechanism is proposed which includes reactions of amine radicals, peroxoamine radicals, and peroxonitrite ions.     

Zum Mechanismus der Photochemie von 2-Alkylindazolen in wässerigen Lösungen

Mechanistic studies on the photochemistry of 2-alkylindazoles in aqueous solutions. The photochemistry of 2-alkylindazoles 1 in aqueous solutions is rather complex, the relative yields of different products being dependent on the pH-value of the irradiated solution: In neutral or basic solutions (pH > 7) as well as in most of the organic solvents isomerization to 1-alkyl-benzimidazoles 2 takes place. In dilute sulfuric acid (pH 2–4) this reaction is suppressed and the dihydro-azepinones 3 and 4 are formed. Irradiation in strongly acid solutions (pH < 1) yields the o-amino-acetophenones 5 (Scheme 1). The relative quantum yields of the photoproducts 2–5 have been measured as a function of the pH-value of the irradiated solution (Fig. 1). A comparison of these yields with the protonation equilibrium of the indazole in its first excited singlet state (pK = 2.8) suggests that 2 and 3 are both photoproducts of the neutral indazole molecule, whereas 4 as well as 5 are formed from the protonated indazole. The rearrangement of the indazole 1 to the benzimidazole 2 proceeds via an intermediate 6 , which can be produced in high concentrations by monochromatic irradiation of 1 at low temperatures. The thermal reactivity of this intermediate in dilute sulfuric acid could be investigated: At pH 8 the only product is the benzimidazole 2 . With decreasing pH-value increasing amounts of 3 are formed and at pH < 4 the formation of 2 is completely suppressed, the only product being the azepinone 3 . Thus, 3 is a solvolysis product of the intermediate 6 (Scheme 2). The most probable primary product of singlet indazolium is the nitrenium ion 7 . From this intermediate the formation of 5 can proceed in well-known thermal reactions. The formation of 4 is possibly due to a further protonation equilibrium nitrenium-nitrene. The nitrene 7 can be converted into the azepinone 4 via the azirine 8 (Scheme 3). The pK-values of different indazoles and intermediates are listed in the Table.     

Über den Abbau von Kieselsol,Kieselgel und Aerosil in wäßrigen Tetramethylammoniumhydroxidlösungen

On the Degradation of Silicic Acid Sols, Silicic Acid Gel, and Aerosil in Aqueous Tetramethylammonium Hydroxide Solutions Investigations by trimethylsilylation and molybdate methods show that the degradation rate of silicic acid sols in tetramethylammonium (TMA) hydroxide solution depends on their average particle size. Under equivalent conditions (TMA/Si = 1, C = ～1,4 M, T: 25°C) the degradation of a silicic acid sol, silicic acid gel, and Aerosil takes place with different rates, which correlate with the specific surface of the investigated SiO₂ products. Regardless of the SiO₂ source the silicate anions of the three solutions are built up from the same types. During degradation the solutions with the same chemical composition show a similar anion distribution, which differs from analogous TMA-silicate solutions, the anions of which are in an equilibrium state.     

Metallchlorid-Graphitverbindungen aus nichtwäßrigen Lösungsmitteln Einlagerung aus Thionylchloridlösungen

Metal Chloride-Graphite Compounds from Nonaqueous Solvents. Intercalation from Thionylchloride Solutions The intercalation of UCl₅, AlCl₃, NbCl₅, TaCl₅, and MoOCl₄ from SOCl₂ solutions is investigated. From concentrated UCl₅ solutions, dependent on the temperature, two compounds are obtained: UCl₅-graphite and UCl₅–SOCl₂-graphite, both with the structure of a first intercalation stage. The other metal chlorides are intercalated without SOCl₂: AlCl₃ to a second stage; NbCl₅, TaCl₅ and MoOCl₄ to a third stage. Chlorine additionally bound in the AlCl₃, NbCl₅ and TaCl₅ compounds results from a decomposition reaction of the SOCl₂.     

Über die Gleichgewichte in wäßrigen Polyvanadatlösungen Neuauswertung der potentiometrischen Meßdaten von Ingri und Brito

Equilibrium Studies on Aqueous Polyvanadate Solutions. A New Interpretation of the Potentiometric Data of Ingri and Brito A reaction scheme for the hydrolysis of the vanadate ion VO₄^3? in aqueous media derived from theoretical investigations on the formation mechanisms and structures of polymetalate ions has been tested by means of the potentiometric data (z,log c, C_V(V)) for the polyvanadate system given by Ingri and Brito. Whereas the set of species proposed by these authors only produced an agreement factor σ_Z = 0.0091, our model realizes σ_Z = 0.0071 at a level of the random errors of σ_Z = 0.0064 and leads to a rather more well-balanced deviation diagram ΔZ(Z). We thus see for the first time a self-contained and detailed picture of the polyvanadate system free of contradictions: The monomeric, tetrahedral vanadate ions polymerize on protonation at first forming an unbroken sequence of chains of VO₄ tetrahedra sharing corners as far as ring closure of the chains, mainly formation of the tetrameric ring, is possible. The drivingforces for polymerization are the condensation of water molecules (an entropy effect) and the formation of π-bonds in the V? O? V bridges (strengthening of the bondings), both of them reaching a maximum in rings. The smallest possible, the trimeric ring does not occur because of unfavourable (too small) angles in the V? O? V bridges; the pentameric ring is handicaped for statistical reasons (meeting of the ends of the chain, law of mass action and others). All the species occur according to their basicity as determined mainly by the charge number and by the number of the terminal oxygen atoms in unprotonated, mono- and diprotonated form (chains) or only in unprotonated form (rings). On stronger protonation, as is well known, the V₁₀O₂₈^6? ion and its protonated forms as well as the VO₂⁺ ion composed of VO₆ octahedrct appear.