Determination of NiS, NiSe and PdS formation orders during electroreduction of thiocyanate, selenocyanate and thiourea complexes of Ni(II) and PD(II) at mercury electrodes

Abstract The electroreduction of Ni(II) and PD(II) thiocyanate complexes, Ni(II) selenocyanate complexes and Ni(II) thiourea complexes has been studied at mercury electrodes. It has been confirmed in each case that the ligands undergo electroreduction, as do the metal ions, resulting in NiS, NiSe and PdS precipitate formation. A.c. chronoamperometry was used to determine the formation order of NiS and NiSe in the Ni(II)-thiourea and Ni(II)-selenocyanate systems. A new method of determining this reaction order was proposed on the basis of quantitative analysis of the electroreduction products obtained during potentiostatic electrolysis at a large mercury electrode. The formation orders of NiS and PdS in the Ni(II)-SCN − and Pd(II)-SCN − systems were determined by this method.