Grażyna Dalmata

The influence of thiourea on the electroreduction of Zn2+ ions in various supporting electrolytes in respect to the cap-pair effect

Abstract The mechanism of the cap-pair effect was examined with respect to its acceleration of the electro-reduction of Zn 2+ ions in NaCIO 4 , NaCl and NaBr. It was found that the presence of thiourea in the solution increased the rate of the electrode process; a role is played in the acceleration by the composition of zinc complexes formed in the bulk of the solution.

The Influence of Thiourea on the Two-Step Electroreduction of Zn(II) Ions

Summary. The two-step reduction of Zn(II) ions at a dropping mercury electrode in 1 M NaClO4/0.001 M HClO4 in the presence of thiourea was examined in wide potential and frequency ranges using the impedance method. The catalytic activity of thiourea concerns both electron transfer steps. It was found that the acceleration of the electroreduction process depends on the surface concentration of thiourea.Zusammenfassung. Die zweistufige Reduktion von Zn(II)-Ionen an einer Quecksilbertropfelektrode in 1 M NaClO4/0.001 M HClO4 in Gegenwart von Thioharnstoff wurde in einem breiten Potential- und Frequenzbereich mittels der Impedanzmethode untersucht. Die katalytische Aktivität von Thioharnstoff betrifft beide Elektronenübertragungsschritte. Es wurde beobachtet, daß die Beschleunigung der Elektroreduktion von der Oberflächenkonzentration des Thioharnstoffs abhängt.

Studies of the Effect of Thiourea on the Electroreduction of In(III) Ions in Perchloric Acid

The influence of thiourea on the electroreduction of In(III) ions on mercury electrode in perchloric acid solution was examined. It was observed, that thiourea can catalyze the electroreduction of In(III) ions. The presence of thiourea leads to multistage reaction where transfer of the first electron is principally catalyzed. Catalytic activity of thiourea is connected with its ability to remove molecules of coordinated water as well as with forming of active complexes of indium ions on the surface of electrode, facilitating transfer of electrons.

Application of the cap-pair effect in reducing the inhibition of electrode processes. The determination of zinc in the presence of tween-80

Abstract The “cap-pair” effect, which accelerates electrode processes, is shown to be useful in decreasing the effects of inhibitors on reduction processes. The determination of zinc in the presence of Tween-80 is used as an example. In the square-wave polarography of zinc at the 10 -5 M level, addition of thiourea (10 g l -1 ) eliminates or greatly reduces the inhibitory action of Tween-80, thus allowing precise determinations.