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  • Organic Chemistry  (13)
  • R/V Vereshchagin  (10)
  • pollen analytical standard techniques  (7)
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  • Polymer and Materials Science  (6)
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  • 1
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: The Rest Potentials and the Cathodic Polarizations of Active Chrome and a Chrome Iron Alloy in Sulfuric AcidThe cathodic polarization curves and the rest potentials of active chrome and a chrome iron alloy (25,6 pct chrome) were measured in dependance of the pH-value of the electrolyte. The behavior of the rest potential deviates from that of the hydrogen electrode. By means of the factors α and β they can be explained for the deposition of hydrogen as well as for the dissolution of metal. The equation of the rest potential is \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm V}_{\rm o} = {\rm B} - \frac{{0,058}}{{2\,\alpha + \beta }} \cdot {\rm p}_{\rm H} $$\end{document} where B is a constant factor. The sum 2 α - β is usually greater than 1.In the range of the pH-values investigated the cathodic polarization curves of the deposition of hydrogen are parallel. The exchange currents calculated from the logarithmic representation of the polarization curves rise with increasing concentration of the acid and increasing content of chrome in the alloy. The evaluation of the experimental results was carried out according to theroretical principles which had been applied successfully before.
    Notes: An aktivem Chrom und einer Eisen Chrom-Legierung mit 25,6%; Cr wurden in Abhängigkeit vom pH-Wert die Ruhepotentiale gemessen und kathodische Polarisationskurven aufgenommen. Die Ruhepotentiale zeigen ein gegenüber der reversiblen Wasserstoffelektrode abweichendes Verhalten, das mit Hilfe der Durchtrittsfaktoren α und ß für die H2-Entwicklung und für die Metallauflösung gedeutet werden kann. Es gilt für das Ruhepotential \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm V}_{\rm o} = {\rm B} - \frac{{0,058}}{{2\,\alpha + \beta }} \cdot {\rm p}_{\rm H} $$\end{document} mit B =const. Die Summe 2α+β ist in der Regel 〉 1.Die kathodischen Polarisationskurven der H2-Entwicklung verlaufen im untersuchten pH-Bereich parallel. Die aus der logarithmischen Darstellung ermittelten Ausgleichsströme, die der Korrosion entsprechen, steigen mit wachsender Säure-konzentration und mit wachsendem Cr-Gehalt der Eisen-Chrom-Legierung stark an. Die Auswertung der Versuchsergebnisse erfolgte nach den in letzter Zeit mit gutem Erfolg verwendeten kinetischen Ansätze.
    Additional Material: 11 Ill.
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  • 2
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Observations concerning primary and secondary passivationPotentiostatic and galvanostatic measurements in sulphuric acid electrolytes have been carried out on high-purity ironchrome alloys with chromium contents ranging from 5 to 70 per cent., as well as on high-purity chromium. These measurements were supplemented by the examination of passivation curves, using the galvanostatic insertion method.The passivation currents thus measured were found to differ considerably from the values known so far. The newly found values can be calculated with the aid of an approximation formula as a function of the chromium content. Apart from the “primary” passivation, it was possible, in the concentration range from about 10 to about 40 per cent. Cr, also to observe the „secondary“ passivation which is likewise governed by the current (i) / time (t) law characteristic for passivation generally: (i - i0) t = const. As this phenomenon is greatly dependent on the pH value of the electrolyte and on the presence of complex-forming substances, it is suggested that the phenomenon might be explained by the formation, due to hydrolysis of a second passivation layer.It is assumed that, in the state of “primary passivation” the alloys are covered by a very thin film comparable to that of passive chromium, and that this film is then covered by a “secondary” passivation layer of greater thickness, similar to the iron passivation layer.In the zone of primary passivation, the alloys are anodically dissolved over the whole area whilst, the zone of secondary passivation, strong pit corrosion can be observed.
    Notes: Es wurden an sehr reinen Eisen-Chrom-Legierungen mit Cr-Gehalten von 5 bis 70% sowie an reinstem Chrom potentionstatische und galvanostatische Messungen in Schwefelsäureelektrolyten durch geführt, die durch die Untersuchung von Passivierungskurven nach der galvanostatischen Einschaltmethode ergänzt wurden.Für die Passivierungsstrommengen wurden Werte gefunden, die von den bisher bekannten erheblich abweichen. Die neu ermittelten Werte lassen sich in Abhängigkeit von Cr-Gehalt der Legierungen durch eine Näherungsformel berechnen. Neben der „primären“ konnte im Konzentrationsbereich von etwa 10 bis 40% Cr auch die „sekundäre“ Passivierung beobachtet werden, für die ebenfalls das die Passivierung kennzeichnende Strom(i)-Zeit(t)-Gesetz (i-i0) = const. gilt. Wegen der starken Abhängigkeit dieses Vorganges von pH-Wert des Elektrolyten und der Anwesenheit von Komplexbildnern wird zu dessen Erklärung die hyrolysebedingte Bildung einer zweiten Passivschicht vor geschlagen.Es wird angenommen, daß die Legierungen im „primärpassiven“ Zustand mit einer sehr dünnen Schicht belegt sind, die mit derjenigen des passiven Chroms vergleichbar ist und auf der sich bei der „sekundären“ Passivierung eine dickere zweite Schicht aufbaut die einer Eisenpassivschicht ähnelt.Im primärpassiven Gebiet werden die Legierungen auf der ganzen Fläche anodisch aufgelöst, während im sekundärpassiven Bereich starke Lochfraßbildung beobachtet wird.
    Additional Material: 21 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 181 (1876), S. 129-153 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 184 (1877), S. 206-254 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 183 (1876), S. 102-141 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 201 (1880), S. 262-291 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 7
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 41 (1842), S. 303-306 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 173 (1874), S. 21-39 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 203 (1880), S. 174-235 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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