Methodische Hinweise und Fehlerm?glichkeiten bei der Untersuchung membranfiltrierter w?\riger L?sungen

Zusammenfassung Es wird auf eine bisher nicht beachtete Fehlermöglichkeit bei der analytischen Untersuchung und Weiterverwendung von membranfiltrierten Lösungen hingewiesen. Die üblichen Membranfilter enthalten zur Hydrophilisierung bestimmte Mengen anionaktiver Tenside, die sich nur in wechselndem Ausma\e vor dem Gebrauch eluieren lassen. Bei der Untersuchung von membranfiltrierten Flu\-, Grund- und Trinkwasserproben findet man dadurch zu hohe Tensidkonzentrationen und bei der Austestung und Verwendung sterilfiltrierter Wirkstofflösungen u. a. können betrÄchtliche Störungen eintreten. Von Fall zu Fall ist darum eine sorgfÄltige Versuchskontrolle hinsichtlich einer spezifischen Tensidwirkung nötig.

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Summary Reference is made to a source of error so far unknown in analytical examinations of aqueous membrane-filtered solutions. Membrane filters usually contain a certain amount of anionic surface-active substances for hydrophilizing purposes. These substances are only partly eliminated before the use of the filter. Therefore, in samples of membrane-filtered river, underground and tap water concentrations are found higher than the actual detergent content. There may also be interferences with the testing of bio-active substances, for instance of antibiotics. Advice is given to control carefully the possible specific effect of surface-active substances during these experiments.

     

Spectroscopic study of 1-cyanoacetyl-2-alkylhydrazines and their ring isomers — 1-alkyl-5-amino-3-pyrazolones

The structures of 1-cyanoacetyl-2-alkylhydrazines and their ring isomers, viz., 1-alkyl-5-amino-3-pyrazolones, to which they are readily cyclized, were investigated by IR, UV, and PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 516–519, April, 1981.     

Complete thermodynamic analysis of the ionization of ortho-methoxybenzoic acid. Influence of the medium on the ortho effects

The ionization and solution enthalpies of o-methoxybenzoic acid have been measured in H₂O-DMSO mixtures. In the same solutions, the ΔG⁰ values for the ionization process have been determined by potentiometric measurements. A study of the ortho effects by means of a linear combination of the ordinary polar, proximity polar, and steric effects was also performed. The CH₃O group seems to undergo a partial steric inhibition of resonance. Finally, the proton transfer process from the ortho derivative to benzoic acid, compared with the same process in the gaseous phase, is presented.     

Triterpene glycosides of Acanthophyllum gypsophiloides IV. The structure of acanthophyllosides B and C

Summary Alternative structures for the acyloside chain of acanthophylloside B and C have been established.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 728–734, November–December, 1975.     

Frictional properties of dilute block-copolymer solutions and homopolymer solutions. Application to molecular weight determination.

An equation for the translational diffusion coefficient of block copolymers in dilute solution has been obtained by modifying Zimm's equation for homopolymers to take into account the existence of dissimilar segments in block copolymers. Illustrative calculations for homopolymers and block copolymers have been made and the results for homopolymers have been compared with experiments and with the calculations of Yamakawa and Fujii. A procedure has been proposed to determine the molecular weight of a block copolymer from measurements of its limiting viscosity number and its sedimentation coefficient or translational diffusion coefficient.     

Fluorescence of Xe2 molecules in the vacuum-ultraviolet

Fluorescence of the Xe₂ continuum between 1460 and 1800 Å has been observed during excitation of Xe₂ molecules with CO fourth positive bands from a microwave discharge lamp. Fluorescence spectra at different Xe and added gas pressures show that in collisions with Xe or Kr atoms, the excited Xe₂ diatoms are efficiently relaxed to low vibrational levels of the ¹Σ_u⁺ and ³Σ_u⁺ potentials without being quenched noticeably. With Kr the rate constant for relaxation out of the primarily excited high vibrational levels is found to be about 3×10^?11 cm³ molecule^?1 s^?1.     

Metallkomplexe mit anionischen Liganden von Elementen der 4. Hauptgruppe. VIII. Pentacarbonyl-trihalogenstannido-metallat(O)-Komplexe von chrom,molybdän und wolfram mit fluor- und jodhaltigen stannidliganden

Metal Complexes with Anionic Ligands of Elements of the Main Group IV. VIII Pentacarbonyltrihalogenostannidometalate(O) Complexes of Chromium, Molybdenum, and Tungsten with Fluorine and Iodine Containing Trihalogenostannido Ligands In methylenechloride [As(C₆H₅)₄][SnF₃] readily reacts with the metalhexacarbonyls forming the arsoniumsalts of the pentacarbonyltrifluorostannidometalate(O) complexes, [M(CO)₅SnF₃]^? (M ? Cr, Mo, W). Exclusively by the reaction of the intermediately formed complex Cr(CO)₅THF only one pure triiodostannidometalate(O) Complex, [N(C₂H₅)₄][Cr(CO)₅SnJ₃], could be isolated. The trihalogenostannidometalate(O) complexes [M(CO)₅SnClX₂]^? (X ? F: M ? Cr, Mo, W; X ? J: M ? Cr) could be prepared by SnX₂-insertion reactions of the [M(CO)₅Cl]^? complexes. The bonding properties of the halogenostannide ions are discussed on the bases of the IR spectra of their metalate(O) complexes.     

Die Analytik wasserl?slicher Cellulose?ther

Zusammenfassung Es werden allgemeine und qualitative Merkmale von Natrium-Carboxymethylcellulose, Methylcellulose und Hydroxyäthylcellulose sowie gravimetrische und titrimetrische Bestimmungsmöglichkeiten der wasserlöslichen Celluloseäther insbesondere im Zusammenhang mit dem Substitutionsgrad beschrieben.Verfahren zur Ermittlung der Viscosität von Lösungen, des Polymerisationsgrades und des Gelteilchengehaltes werden besprochen. Abschließend werden charakteristische Beispiele für das analytische Vorgehen bei Substanzgemischen gegeben, die nur einen geringen Anteil Celluloseäther enthalten.

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Analysis of water-soluble cellulose ethers

General and qualitative characteristics of sodium carboxymethylcellulose, methylcellulose and hydroxyethylcellulose are presented and gravimetric and titrimetric methods for the determination of water-soluble cellulose ethers are described, especially with regard to the degree of substitution. Procedures for the measurement of the viscosity of solutions, of the degree of polymerisation and of the content of gel particles are discussed. Characteristic examples are presented for the treatment of mixtures containing only a small percentage of cellulose ethers.

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Erweiterte und umgearbeitete Fassung eines Vortrages, gehalten am 28. 6. 1971 in Baden-Baden.

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Frau Dr. G. Bartelmus, Analyt. Laboratorium der Fa. Kalle AG, sprechen wir an dieser Stelle unseren herzlichen Dank für wertvolle Beratung aus.     

Synthesis and reactions of heterocyclic compounds

5-Azido-2-methylbenzthiazole, 6-azido-1, 2-dimethyl-, and 5-azido-2-methyl-1-phenylbenzimidazoles were prepared. By the reactions of these azides with alkyl halides the quaternary slats based on the cyanine dyes were obtained.