Study of the Graphite Electrode Surface with In and Pt Deposits

Electrolytic deposit of indium, platinum and platinum-indium alloy on the surface of graphite electrodes has been studied using the scanning electron microscopy and the stripping voltammetry. The scanning electron microscopy method has revealed that platinum-indium alloy on the surface of the graphite electrode contains indium, platinum and chlorine. But platinum is unable to be determined on the surface of the graphite electrode without a metal activator due to its precipitation in very small quantities. Under the anodic oxidation of indium-platinum precipitation, the anodic peaks caused by the selective electro-oxidation of indium from the intermetallic compounds with platinum are observed on the current-voltage curves. Wherein, platinum remains on the electrode surface, and can be oxidized from the electrode at the potentials of the electrode purification (more than 1 V).

Studies on explosive antimony. II―Its structure, electrical conductivity, and rate of crystallization

The first paper of this series dealt with the microscopically visible changes in structure that occur when the presumably amorphous electrolytic deposit of antimony "explodes." It was shown that a rapid (20-40 cm/sec) autogenous crystallization spreads spherically throughout the metal, leaving it with an onion-like structure visible on a polished and etched surface as a sequence of closely spaced (2000-3000 per/cm) concentric lines. The present paper is concerned with the nature of the amorphous deposit as revealed by a microscopic examination of etched surfaces, 3, and by a study of its electrical resistance, 4, The rate of crystallization at temperatures below that at which explosion occurs has also been determined, 5. It is found that the explosive deposits are characterized by a heterogeneous gel-like structure definitely oriented with respect to the cathode receiving surface. The electrical properties of the deposits are non-metallic in that conductivity is very small and has a positive exponential temperature coefficient. Ohm's law is obeyed, but Faraday's law does not seem to be involved, although a small polarization is built up at the higher temperatures. At temperatures too low to initiate explosion the deposits crystallize at a rate which is independent of the extent to which they have already crystallized. The rate of crystallization increases exponentially with the temperature.

IV. Some new phenomena of electrolysis

Whilst making a series of experiments on the “self-deposition of metals,” I observed, by trying a number of different metals, that several of them received an electrolytic deposit of cadmium by contact with cadmium in various solutions of that metal much more frequently than others; I therefore made various experiments to determine whether this was due to difference of density of current or to other causes. By means of these additional trials, I found, on passing an undivided current through a series of portions of the same metallic solution, that cathodes composed of different metals of equal amounts of immersed surface, required currents of different degrees of density to cause deposits of the same metal upon them, and that the differences in some cases were considerable. Another singular circumstance was also observed, viz., that the cathode which most readily received a deposit was frequently the one composed of the same kind of metal as that which was being deposited. I am now examining these new facts.