The present volume is part of the Tungsten Supplement A series covering the production, use, physical properties, and chemical reactions of the metallic element. It treats the potentials and the cathodic and anodic behavior of tungsten electrodes in aqueous and nonaqueous solutions and in melts. This is supplemented by a description of the kinetics and the mechanism of the reactions found by polarographic and voltammetric experiments to proceed between mercury, amalgam, or inert electrodes and W ions in various media. In chapters "Electrodeposition" and "Electrolytic Etching, Polishing, and Machining" the present volume complements corresponding short sections in Supplement Volume A 1, treating technological aspects, by describing the processes occurring on a more scientific basis and by considering also the more recent literature. A great number of publications had to be evaluated, with the majority contributed by Russian authors.