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  • 1
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Polarographic studies have been carried out on Zn−TLA and Ni−TLA systems at constant ionic strength (μ=0.5) at theD.M.E. The reduction of both Zn++ and Ni++ inTLA, was found to be irreversible. Hence, the kinetic parameters (transfer coefficient α and forward rate constantK f, h o ) have been calculated byKoutecky's theoretical treatment as extended byMeites andIsrael.
    Notes: Zusammenfassung An der Quecksilbertropfelektrode wurden bei konstanter Ionenstärke (μ=0,5) die Systeme Zink-Thiomilchsäure und Nickel-Thiomilchsäure polarographisch untersucht. Sowohl die Reduktion des Zn++ als auch die des Ni++ erwiesen sich in Thiomilchsäure als irreversibel. Daher wurden nach der vonMeites undIsrael weiterentwickelten theoretischen Methode vonKoutecky die kinetischen Parameter (Durchtrittsfaktor α und Geschwindigkeitskonstante der HinreaktionK f, h o berechnet.
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  • 2
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract The precise nature of the complex formation between Thallium(I) and β-mercaptopropionic acid in aqueous 0.1M-KNO3 has been investigated by potentiometric and conductometric titration techniques. It was found that Tl(I) forms only one, 1∶1, colourless complex predominating at pH 9.0–10.5. The stability constant of the complex has been determined by applyingCalvin andMelchior's extention ofBjerrum's method at three different temperatures. The logK values were found to be 2.775, 2.850 and 2.935 at 20, 30 and 40° C respectively. The thermodynamic functions of complexation, ΔG, ΔH and ΔS were also evaluated at 30° C and found to be −3.95 K-cal/mole, −3.34 K-cal/mole and +2.01 Cal/deg. respectively.
    Notes: Zusammenfassung Durch potentiometrische und konduktometrische Titrationen wird die genaue Zusammensetzung des Komplexes untersucht, der sich aus Thallium(I) und β-Mercaptopropionsäure in wäßriger 0,1m-KNO3-Lösung bildet. Es zeigt sich, daß Thallium nur einen einzigen Komplex bildet. Er ist farblos, hat die Molzusammensetzung 1∶1 und liegt besonders im pH-Bereich 9,0–10,5 vor. Durch Anwendung der vonCalvin undMelchior erweiterten Meßmethode vonBjerrum wird für drei verschiedene Temperaturen der Wert der Komplexbildungskonstante bestimmt. Als Werte für logK ergaben sich bei 20° 2,775, bei 30° 2,850 und bei 40° 2,935. Die Werte der thermodynamischen Zustandsfunktionen berechnen sich für die Komplexbildung zu ΔG=−3,95 kcal/Mol, ΔH=−3,34 kcal/Mol und ΔS=+2,01 cal/grad.
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  • 3
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Wir untersuchten polarographisch die Komplexierung von Zink mit Methoxyäthylthioglykolat (MET). Es zeigte sich, daß die Reduktion von Zn2+ reversibel und diffusionskontrolliert verläuft, und daß es sich dabei um einen Zwei-Elektronen-Übertragungsprozeß handelt. Wir legten der Interpretation der Daten, die sich beim Auftragen von Potential gegen Konzentration bei konstanter Ionenstärke ergaben, die Vorstellung zugrunde, daß sich drei komplexe Species (ZnA +, ZnA 2 und ZnA 3−) bilden. Die Auswertung erfolgte mit Hilfe der Methode vonDe Ford undHume. Die Bestimmung der Logarithmen der Stabilitätskonstanten bei 25°C führte zu Werten von 3.95, 6.95 bzw. 10.04.
    Notes: Abstract Complexation of zinc by methoxyethylthioglycolate (MET) has been studied polarographically. The reduction of Zn2+ inMET solution has been found to be reversible and diffusion controlled involving a two-electron transfer process. Potential vs. concentration data at constant ionic strength (μ-0.5M) have been interpreted on the basis of the formation of three complex species ZnA +, ZnA 2, and ZnA 3− employingDeFord andHume's method. The logarithms of their stability constants at 25°C were determined and found to be 3.95, 6.95, and 10.04, resp.
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  • 4
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Wir untersuchten auf polarographischem Wege die Kinetik der Entladung von Zn2+ und Ni2+ an der Quecksilbertropfelektrode in einem Thiomalatmedium konstanter Ionenstärke (μ=0,5). Wir stellten fest, daß die Reduktion von Zn2+ und Ni2+ irreversibel verläuft und berechneten daher die kinetischen Parameter (Übertragungskoeffizient α, Geschwindigkeitskonstante der HinreaktionK f,h o ) nach dem theoretischen Verfahren vonKoutecky in der vonMeites undIsrael erweiterten Form.
    Notes: Abstract Kinetics of discharge of Zn2+ and Ni2+ have been studied polarographically in thiomalate media of constant ionic strength (μ=0.5) at the dropping mercury electrode. The reduction of both Zn2+ and Ni2+ was found to be irreversible. Hence, the kinetic parameters (transfer coefficient α, and forward rate constantK j,h o ) have been calculated byKoutecky's theoretical treatment as extended byMeites andIsrael.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 107 (1976), S. 1423-1427 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The polarographic behaviour of n-butyl thioglycolate, [HSCH2OOC(C4H9)] has been studied in 25% ethanol, 0.1M-KNO3 and 0.002% Triton X-100 in the pH range 1.96–11.84 at the d.m.e. The polarograms consist of two waves, a pre-wave of constant height followed by a normal anodic wave. The electrode reaction is reversible and diffusion controlled involving one electron transfer process. The maximum number of moles adsorbed per unit area is 1.30×10−9 mole/cm2, i.e. 7.82×1014 molecules/cm2, which corresponds to an area 12.84 Å per adsorbed molecule. The adsorption coefficient and molar adsorption energy have been calculated to be 43.4×104 and 142.8 kcal/mole respectively. The dissociation constant (pK) of the sulphydryl group is found to be 9.4.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 108 (1977), S. 829-833 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract dl Aspartic acid is reduced at the d.m.e. in 0.1M tetramethylammonium bromide, tetraethylammonium bromide, sodium chloride, potassium chloride, potassium nitrate, sodium perchlorate and lithium sulphate; in aqueous media. The waves are irreversible, diffusion controlled involving one electron transfer process determined by millicoulometry. The values of the kinetic parameters, transfer coefficient (α) and formal rate constant (k° f, h) have been calculated byKoutecky's method and are 0.479 and 15.9×10−16 respectively.
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  • 7
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The complexation of UO2 +2 and Th+4 ions with 2-mercaptoethanol has been studied by potentiometric and conductometric titration techniques. Uranyl ion forms 1∶1 and 1∶2 complexes in the pH-range 3.3–6.5 and thorium ion forms 1∶2, 1∶3, and 1∶4 complexes in the pH-range 3.2–4.8 with considerable overlapping. Their logk stab. values are determined at 10, 20, and 30°C at ionic strength μ=0.1M (NaClO4) by applyingCalvin-Melchior's extension of theBjerrum method. The overall changes in thermodynamic functions ΔG, ΔH, and ΔS accompanying complexation determined at 20°C are −19.48 kcal/mole, −22.77 kcal/mole, −11.23 cal/deg·mole for uranyl complexes and −33.94 kcal/mole, −4.93 kcal/mole, 99.00 kcal/deg·mole for thorium complexes, resp.
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  • 8
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract The formation and composition of cadmium vanadates obtained by the interaction of cadmium sulphate and different alkali vanadates (ortho-, pyro-, meta- and poly-) have been investigated by means of amperometric titrations of the reactants at several concentrations. The well defined breaks in the titration curves provide cogent evidence for the formation of cadmium orthovanadate (3 CdO·V2O5) and cadmium pyrovanadate (2 CdO·V2O5) in the pH ranges 7.5–8.5 and 6.5–7.5 respectively. The precipitation of cadmium orthovanadate has been found to be almost quantitative and the amperometric titration offer a simple and rapid method for the determination of vanadium(V) in solution at suitable concentrations. The solubilities of cadmium orthovanadate and cadmium pyrovanadate have been determined polarographically at 37°C and are found to be 1.90·10−2 g/l and 4.10·10−2 g/l resp.
    Notes: Zusammenfassung Die Bildung und Zusammensetzung von Cadmiumvanadaten, die man durch Wechselwirkung von Cadmiumsulfat mit verschiedenen Alkalivanadaten (ortho-, pyro-, meta- und poly-) erhält, wurde durch amperometrische Titration der Reaktanten bei verschiedenen Konzentrationen untersucht. Die gut definierten Knicke der Titrationskurven liefern eindeutige Beweise für die Bildung von Cadmiumorthovanadat (3 CdO·V2O5) und Cadmiumpyrovanadat (2 CdO·V2O5) in den pH-Bereichen 7,5–8,5 bzw. 6,5–7,5. Es zeigte sich, daß die Fällung von Cadmium-orthovanadat fast quantitativ, und die amperometrische Titration eine einfache und rasche Methode zur Bestimmung von Vanadium(V) in Lösungen geeigneter Konzentration ist. Die Löslichkeiten von Cadmium-orthovanadat und-pyrovanadat wurden polarographisch bei 37°C zu 1,90·10−2 g/l bzw. 4,10·10−2 g/l bestimmt.
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  • 9
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The complexes of uranyl ion with diisopropylaminoethanethiol hydrochloride have been investigated by potentiometric and conductometric titration techniques in aqueous 0.1 M KNO3. It was observed that below pH 4.5, two complexes 1∶1 and 1∶2 are formed with considerable overlapping and the latter complex is more stable. Their log Kstab values have been computed by alternative methods and are found to be 8.33 and 7.42 at 30°C and 8.40 and 7.72 at 40°C. The values of ΔG, ΔH and ΔS for complexation at 40°C are −23.25 kcal/mole, 16.46 kcal/mole and 128.0 cal/degree/mole respectively.
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  • 10
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reduction of thorium at the dropping mercury electrode in presence of ethylene bis(3-mercaptopropionate) has been found to be irreversible and kinetically controlled. The kinetics of the electrode reaction has been investigated adopting the treatment followed byKoutecky.
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