Kritische studie über die quantitative bestimmung von sulfat

The gravimetric sulphate determination as barium sulphate works well with the usual precautions and Schleicher & Schuell blue ribbon filters without any agents for increasing crystal size or coagulation effects. Interference by foreign metal ions may be overcome by use of synthetic ion exchange resins.Treatment of filter papers with hydrochloric acid before filtration of barium sulphate precipitates is not necessary. Ignition temperatures should be kept below 600 °C.Smaller amounts of sulphate are preferably determined by volumetric or micro-volumetric methods, by colorimetric methods, or by turbidimetric methods. A turbidimetric titration to maximum of turbidity has been described above.Good results are claimed.     

Zur Chemie der Chlorthionitrenkomplexe des Rheniums Die Kristallstruktur von [N(SCl)2]⊕ [Re2Cl9]⊖

Chemistry of Chlorothionitrene Complexes of Rhenium. Crystal Structure of [N(SCl)₂]⊕ [Re₂Cl₉]? By reaction of S₃N₂Cl₂ with ReCl₅ the chlorothionitrene complex [ReCl₃(NSCl)₂]₂ is obtained in good yield; it has a dimer structure with chloro bridges. By the same reaction in POCl₃ solution the solvate [ReCl₃(NSCl)₂OPCl₃] is obtained. Instead, when a molar ratio of ReCl₅ and S₃N₂Cl₂ of 2:1 is taken, the product is [N(SCl)₂][Re₂Cl₉]. [ReCl₄(NSCl)OPCl₃] and excess PPh₃ react to give the nitrido complex [ReNCl₂(PPh₃)₂]. The crystal structure of [N(SCl)₂][Re₂Cl₉] was determined and refined with X-ray diffraction data (1021 independent reflexions, R = 0.031). It crystalizes in the space group C2/c with four formula units per unit cell (a = 1197, b = 1288, c = 1144 pm, ß = 107.83°). The [N(SCl)₂]⊕ cations have exactly C₂ and approximately C_2v symmetry; the NS bond lengths of 162 pm and the bond angles SNS (133.6°) and NSCl (117.6°) deviate considerably from the values of known [N(SCl)₂]⊕ structures. The [Re₂Cl₉]? anion consists of two face sharing octahedra and has a Re—Re distance of 270 pm. I. r. spectra of all compounds are reported and discussed.     

Die Reaktion von Trithiazylchlorid mit Titantetrachlorid Die Kristallstruktur von (S4N5)2[Ti2Cl10]

Reaction of Trithiazyl Chloride with Titanium Tetrachloride. Crystal Structure of (S₄N₅)₂[Ti₂Cl₁₀] In the reaction of trithiazyl chloride with titanium tetrachloride, chlorine is abstracted and the brown-yellow adduct TiCl₄(N₂S₂) is obtained. In this compound — according to its i.r. spectrum — a N₂S₂ ring is bonded to the titanium via the N atoms, thus forming a polymer. As a by-product, brown crystalline (S₄N₅)₂[Ti₂Cl₁₀] forms. Its crystal structure was determined and refined with X-ray diffraction data (R = 0.042 for 812 reflexions). It crystallizes in the monoclinic space group P2₁/c with two formula units per unit cell. The lattice constants are a = 670, b = 1 633, c = 1108 pm, β = 97.24°. The structure consists of S₄N₅^⊕ cations, which are nearly equal to those in [S₄N₅]Cl, and [Ti₂Cl₁₀]^2? anions, which are nearly identical with those in (PCl₄)₂[Ti₂Cl₁₀].     

Die Reaktionen von Eisen(III)-chlorid mit Trithiazylchlorid. Die Kristallstruktur von [S4N4Cl]+[FeCl4]⊖

Reactions of Iron Trichloride with Trithyazyl Chloride. Crystal Structure of [S₄N₄Cl]⁺[FeCl₄]^? Iron trichloride reacts with (NSCl)₃ yielding S₄N₄[FeCl₄]₂, S₃N₃Cl₂[FeCl₄] or S₄N₄Cl[FeCl₄], depending on the reaction conditions. The i.r. spectra prove the presence of [FeCl₄]^? ions for all three compounds. The ⁵⁷Fe-Mössbauer spectra show a slight quadrupole splitting at 80 K for S₃N₃Cl₂[FeCl₄] (ΔE^Q = 0.42 mm · s^?1) and S₄N₄Cl[FeCl₄] (ΔE^Q = 0.23 mm · s^?1), which indicates a slight deformation of the FeCl₄^? tetrahedra. The crystal structure of S₄N₄Cl[FeCl₄] was determined and refined with X-ray diffraction data (2549 independent reflexions, R = 0.026). S₄N₄Cl[FeCl₄] crystallizes in the triclinic space group P1 with two formula units per unit cell. The lattice constants are a = 712, b = 911, c = 1006 pm, α = 76.5°, β = 83.8° and γ = 80.5°. The structure consists of the so far unknown [S₄N₄Cl]^⊕ cations and slightly deformed FeCl₄^? ions. The [S₄N₄Cl]^⊕ ion consists of a S₄N₄ ring built up of two nearly planar S₃N₂ fragments having a dihedral angle of 136°. The average SN bond length is 157 pm, the SCI bond length 214 pm.     

Ion chromatographic determination of platinum in biotic materials

A method for the determination of platinum is presented. The procedure consists of a high-pressure digestion of the sample followed by an ion Chromatographic separation. Then the platinum chloro complex is detected by UV-absorption.     

Enhancement of the solubilities of polycyclic aromatic hydrocarbons by weak hydrogen bonds with water

Summary The thermodynamics of mobile order is applied to predict the aqueous solubility of liquid and solid aliphatic and polycyclic aromatic hydrocarbons. The solubility values are mainly determined by the magnitude of the hydrophobic effect. However, contrary to the solubilities of the alkanes, the solubilities of polycyclic aromatic hydrocarbons in water predicted in absence of solute-solvent hydrogen (H) bonds are systematically too low. This shows the contribution of weak specific interactions between the OH groups and the electrons of the aromatic substances. According to the theory, these interactions are characterized by a stability bility constant K_o which can be derived from solubility data. At 25°C, this constant amounts to 80 cm³/mol, the order of magnitude of which can be explained by the competition of these intermolecular bonds with the rather weak self-association bonds in the secondary chains of water.     

High-pressure transformations of NdI2

A p,T-diagram for NdI₂ is reported. The transformation from an SrBr₂-type arrangement to a Ti₂Cu-type structure takes place between 10 and 20 Kb, with a negative slope for the phase boundary. Due to kinetic hindrance at lower temperatures, an intermediate phase with a CaF₂-type arrangement can be detected by in situ X-ray investigations. A mechanism for the transformation is proposed. Structural parameters are refined by Rietveld analysis, and the compressibilities of the phases are given.     

2D-NMR: Part VI. 2D-INADEQUATE spectral analysis and crystal structure of tricyclo[7.3.1.02,7]tridecane

2-Hydroxy-13-oxo-tricyclo[7.3.1.0^2,7]tridecane derivatives can be obtained by reaction of cyclohexanone with alcohols under alkaline conditions. The unambiguous assignment of all signals of the¹H-NMR- and¹³C-NMR-spectrum is possible by 2D-¹H-¹³C-shift correlation and 2D-INADEQUATE. Compound1 crystallizes in space group P2₁/n witha=8.518 (1),b=14.789 (2),c=19.321 (2) Å, =94.91 (1)°,Z=8,D _c =1.22 Mg cm^–3. The structure refined toR=0.100 andR _w =0.097 for 1719 observed reflections. Two independent molecules form centrosymmetric hydrogen-bonded dimers.Part V:Haslinger E.,Kalchhau-ser H.,Robien W.,Steindl H., Monatsh. Chem.115, 597 (1984).