Cathodic processes of platinum electrodes during Na2MoO3-MoO3 melt electrolysis

It has been shown previously that during polarization of a platinum cathode in the Na2MoO4-MoO3 system the evolution of molybdenum dioxide is preceded by a wave which, in the authors' opinion, can be attributed to changes in ionic composition of the melt layer next to the cathode, and in particular to the appearance of lower, reduced forms of the ions. In tungstate melts, the evolution of bronze or other products is preceded by alloy electrolysis of molybdate melts. The present work was undertaken in order to elucidate the conditions under which a platinum electrode can be used as an indicator electrode for electrochemical investigations in molybdate melts. The experiments used ''chemically pure'' MoO3 and ''analytically pure'' Na2MoO4.2H2O. On the basis of the investigation it is concluded that alloys of platinum with molybdenum are formed at the cathode when the melt contains relatively small amounts of MoO3