Contribution a l'etude des effets catalytiques exerces par les composes soufres a l'electrode a gouttes de mercure. Cas de la thiouree

The influence of thiourea and some of its N-alkyl-derivatives on the reduction of various metallic cations (Ni²⁺, Co²⁺, Co²⁺) has been studied in neutral medium at the dropping mercury electrode. The polarographic curves exhibit kinetic prewaves reaching a 2^?_e amplitude at high concentration. In addition fairly large extra-currents can be detected at verynegative potentials. By resorting to classical and pulse polarography and to macro-electrolysis, it has been demonstrated that these currents are related to both the electroreduction of thiourea with production of sulphide and cyanide ions and catalytic discharge of water itself. The reaction mechanism is discussed in terms of the structure of the organic compound and the properties of the electrode metal surface, in connection with similar phenomena observed in the presence of thiocyanate ion (reduction of the thione group) and sulfur proteins (catalytic hydrogen evolution).