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Badania kulometryczne na Wydziale Chemii Uniwersytetu Warszawskiego

Galus Z.

Wiadomości Chemiczne

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2015

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[Z] 69, 9-10

631--651

EN

The coulometric studies carried out in the Department of Chemistry of the University of Warsaw have been described. In the first part of this brief review there were discussed papers in which coulometric titration was used as a main method of the study. In this section the achievements of Stanisław Głąb and his coworkers in that field were shortly described and discussed. Both the use of the coulometric titration in elaboration of a new analytical titration methods and its application to the determination of equilibrium constants of several reactions have been presented. In the second part, the results obtained with the use of two variants of constant potential coulometry were presented. In the first classical variant, the thickness of the solution layer (d), from which occurs the diffusion to the electrode was much larger than the diffusion layer thickness (δ), d » δ. In the second variant inequality d « δ is obeyed. The later case relates to the so-called thin-layer chronocoulometry, when the reactive layer (solution or film on the electrode) is very thin. Some papers published by the researchers from the Chemistry Department of the University of Warsaw were presented, especially those where thin layers of heavy metal (as iron, nickel, cobalt and others) hexacyanoferrates such as for instance Prussian Blue, were deposited either on platinum, gold, glassy carbon electrodes or on carbon nanotubes. The transport of charge in such layers was briefly discussed. In the last part, the application of so-called voltochronocoulometry by researchers of the Chemistry Department of the University of Warsaw to the study of different electrode reactions and double layer phenomena is presented.

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Electrochemical and Electrogravimetric Investigations of Prussian Blue on the Gold Electrode in the Presence of Tallium(I) Ions

Rutkowska I., Stroka J., Wrona P., Galus Z.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 5

711-721

EN

Electrode processes of Prussian Blue (PB), deposited on the gold electrode, have been investigated in potassium and thallium salts solutions, using electrogravimetric and cyclic voltammetric methods. It is shown, that both electrode processes of PB (reduction of PB to Everitt's salt and its oxidation to Berlin Yellow) undergo changes, when potassium ions are replaced by thallium(I) ones. In the presence of thallium, the formation of new redox system is observed, and Tl(I) acts as a counter-ion. The equilibrium constant of the reaction: K(I)PB + Tl(I) = Tl(I)PB + K(I) was estimated to be equal to K = (1.7_0.6)×104. At the same time almost 50% of the PB layer looses its electrochemical activity, whereas the remaining PB phase is electrochemically active. After transfer of the electrode to KNO3 solution, majority of inactivated layer recovers its previous activity. These findings are tentatively interpreted as a result of formation of two phases of PB with Tl(I): electrochemically active and inactive. Both phases are in equilibrium, and thallium ions could be replaced by potassium one. In the case of the Fe(CN) /63 4 electrode process (at more positive potentials), in the presence of Tl(I) irreversible deactivation occurs, since in KNO3 solution, no reactivation of the electrode process is observed.

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Profesor Wiktor Kemula i jego rola w chemii analitycznej i elektroanalizie

Hulanicki A., Galus Z.

Kwartalnik Historii Nauki i Techniki

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2002

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R. 47, nr 1

33--46

EN

The period activity of Professor Wiktor Kemula in science coincided with the rapid development of chemistry, and particularly of electrochemistry and analytical chemistry. His early stay in the Herkovsky’s laboratory in Prague was specially fruitful in further research fields of Kemula. He contributed to several fundamental electrochemical concepts and later, in Lwow and in Warsaw, this was the main trend in his work. Among the main achievements are usually mentioned the creation of the new analytical techniques: chromato-polarography and the cyclic voltammetry with the stationary mercury drop electrode. The former, which combines the elements of separation and determination techniques into one coherent system, can be treated as a prototype of contemporary common coupled (or hyphenated) techniques, which became nearly a standard in complex analytical investigations. The latter developed continuously since the initial Kemula works, and is now termed stripping (or inverse) voltammetry. It is one of the most sensitive electroanalytical techniques, one of the cornerstones in inorganic trace analysis. In analytical chemistry Professor Kemula has foreseen that the quality problem is the basic one and has indicated the necessity of controlling the analytical results by parallel determinations using basically different methods. He also paid much attention to the study of analytical procedures, which, beside of sound theoretical basis, should found an immediate application in practice. Professor Wiktor Kemula was also much interested in teaching at the University, being involved in lecturing, inspecting the students laboratories, and improving the teaching programmes. He laid foundation of the Committee on Analytical Chemistry of the Polish Academy of Sciences, being its Chairman, and was a co-organiser of the Polish journal on analytical chemistry „Chemia Analityczna” and for many years its Editor-in-Chief.

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The electrode reactions of cryptate Cd(2,2,2)2+ at mercury electrodes

Łobacz M., Stroka J., Galus Z.

Chemia Analityczna

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2002

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Vol. 47, No. 3

347-359

EN

Voltocoulometric, chronocoulometric and cyclic voltammetric studies of the reduction of cadmium(II) complex with important in analysis cryptand (2,2,2) were described, with consideration of adsorption of (2,2,2) and Cd(2,2,2)(2+) on mercury electrodes. Aqueous solutions free and saturated with n-pentanol and n-octanol were investigated. It was found that the Cd(II) cryptate is not adsorbed on the Hg electrode contrary to similar lead(II) complex. Different behaviour of cadmium complex was explained by lower stability of the complex formed by Cd(2+) with ligand (2,2,2). The rate constant of the studied Cd(2,2,2)(2+)Cd(Hg) system is about three orders of magnitude lower than that reported for noncomplexed Cd(2+) jon in aqueous solution. The rate constant practically does not changed in the presence of n-pentanol or n-octanol, while the electroreduction of hydrated cadmium(II) cations is strongly inhibited by higher aliphatic alcohol adsorbed on the mercury electrodes. The nature of these differences was discussed.

PL

Stosując woltokulometrię, chronokulometrię i woltamperometrię cykliczną, jako techniki pomiarowe, zbadano redukcję kompleksu kadmu(II), z ważnym w analizie kryptandem (2,2,2). Szczególną uwagę zwrócono na adsorpcję tego kryptandu i badanego kompleksu Cd(2,2,2)(+2) na elektrodach rtęciowych. Prace prowadzono w roztworach wodnych i w roztworach nasyconych n-pentanolem i n-oktanolem. Stwierdzono, że Cd(2,2,2)(2+) nie adsorbuje się na elektrodzie Hg w przeciwieństwie do podobnego kompleksu ołowiu(II). Odmienne zachowanie kompleksu kadmu(Il) tłumaczymy niższą trwałością tworzonego przez Cd(2+) kompleksu z ligandem (2,2,2). Z badań kinetycznych wynika, że stała szybkości układu Cd(2,2,2)(2+)/Cd(Hg) jest trzy rzędy wielkości niższa niż stała hydratowanegojonu Cd(2+). Nie zaobserwowano wpływu n-pentanolu i n-oktanolu na szybkość badanego procesu, podczas gdy elektroredukcja hydratowanegojonu kadmu(Il) jest silnie inhibitowana przez adsorpcję na elektrodzie tych alifatycznych alkoholi. Dyskutowano przyczyny tych różnic.

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Non-Typical Influence of Adsorbed 1-Octanol on Electroreduction of 1-Nitropentane on Mercury Electrodes

Bogucka A., Gromulska A., Stroka J., Jitaru M., Galus Z.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 1

93-104

EN

The electroreduction of 1-nitropentane in the absence and in the presence of 1-octanol was studied. In the absence of inhibitor, 1-nitropentane at concentrations near to saturation is adsorbed weakly on mercury electrodes. In the presence of smaller concentrations of inhibitors, such as 1-octanol, 1-nitropentane electroreduction is inhibited less than that of nitromethane under comparable conditions. This difference was explained by the larger affinity of 1-nitropentane to the alcohol-rich surface phase and nitromethane to the aqueous solution phase. The increased affinity of the reactant to the electrode surface phase at the 1-octanol relative concentration, c/cs, exceeding 0.7, may explain the independence of the electroreduction rate constant of 1-nitropentane and, even, its increase when the bulk concentration of inhibitor approached the saturation.

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Electrochemical Charging of Indium Hexacyanoferrate Films in DMSO and AcetonitrileWater Mixtures Containing Alkali Metal Cations

Dzieniszewski R., Stroka J., Kulesza P. J., Galus Z.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 11

1753-1765

EN

Indium hexacyanoferrate films were investigated in water-acetonitrile and water- dimethylsulfoxide mixtures containing various alkali metal cations. The films, which were electrodeposited from the supporting electrolytes containing lithium cations, occurred to have fairly open structure permitting the transport of alkali metal cations in the solutions (mixtures) rich in nonaqueous solvents. The slopes of dependencies of formal potentials on the logarithms of concentrations of alkali metal cations were consistent with the predominant involvement of countercations in the redox reactions. But in the cases when the content of nonaqueous solvent was relatively high, the slopes were definitely lower than Nernstian (60mVper cation activity decade), thus implying a more complex mechanism of the reaction.