Polarographic Behavior of Manganese(II) in the Presence of Oxalate Ions in Perchlorate and Sulfate Solutions

Journal of Solution Chemistry (Impact Factor: 1.18). 02/2011; 40(2):247-260. DOI: 10.1007/s10953-011-9649-7


The dc polarographic method has been applied to study coordination equilibria between Mn(II) and oxalate ions in perchlorate
and sulfate solutions. The stoichiometries of complexes formed in solution and those reduced at a dropping mercury electrode
were established. The stability constants of the Mn(II) oxalate and sulfate complexes, as well as their diffusion coefficients,
were determined at a constant ionic strength 0.5mol⋅L−1 and25 °C. The stabilities of these Mn(II) complexes were compared with the corresponding complexes of other divalent metal
ions. The polarographic method was able to identify complexes that have not been established by other methods and to determine
their stability constants with high accuracy.

KeywordsPolarography–Manganese(II) complexes–Oxalate complexes–Stability constants–Electrode reduction mechanism

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Available from: Jadwiga Urbańska, May 03, 2014
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    ABSTRACT: The complexation behavior of four systems involving cadmium(II) or zinc(II) in aqueous solutions with the biological buffers 3-[N,N-bis(2-hydroxyethyl)amino]-2- hydroxypropanesulfonic acid (DIPSO), and [(2-hydroxy-1,1-bis(hydroxymethyl)ethyl) amino]-1-propanesulfonic acid (TAPS) was studied by direct current polarography (DCP) and glass electrode potentiometry (GEP), at 25.0 ± 0.1 �C and ionic strength 0.1 mol�dm-3 KNO3. Except for the Cd–TAPS system, for which full characterization of the system was possible either by DCP or GEP, full characterization of the other metalbuffer systems (Zn–DIPSO, Zn–TAPS and Cd–DIPSO) was only possible using DCP. For Zn-buffers systems, ZnL? and ZnL(OH)� 2 (where L stands for buffer) were identified. For the Zn–DIPSO system, the overall stability constant values (as log10 b) are 2.1 ± 0.2 and 13.4 ± 0.2, respectively. For the Zn–TAPS system, the overall stability constants values (as log10 b) are 2.4 ± 0.1 and 12.9 ± 0.3, respectively. For the Cd–DIPSO system, the overall stability constants values (as log10 b) of CdL? and CdL(OH) are 2.9 ± 0.1 and 6.9 ± 0.3, respectively. For the Cd–TAPS system, only the species CdL? was identified with log10 b = 2.5 ± 0.1.
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