Abstract
IT has been pointed out to us by Prof. C. O. Bannister and Mr. P. G. McCarthy, University of Liverpool, that the current/voltage relationships shown by the curve given in our previous communication1 do not apply to conditions in which the electrical energy is obtained directjy from a suitable low-tension supply, as distinct from the ‘potentiometer typeâ of circuit used in our work. We have confirmed that, with electrolyte and electrodes as previously described, the use of a 12-volt storage battery (with adjustable series resistance) gives a curve precisely similar to that obtained by Hedges2 for the anodic polarization of zinc in 8 per cent solution of sodium hydroxide. Up to a critical value in the neighbourhood of 1 volt, the potential difference across the bath terminals may be progressively increased, with an accompanying rapid increase in current density, as in our original experiments. The fall in current density beyond this point, however, is now accompanied by a sudden rise in potential to about 4 volts, no intermediate values being obtainable. Polishing of the zinc anode may still be effected, but only at the higher potentials, with simultaneous evolution of oxygen. Polishing at lower (controllable) potentials, without gas evolution, occurs only under conditions which give rise to the characteristic curve previously recorded, and this, we now find, is dependent on the use of the potentiometer arrangement, the advantages of which, in this type of work, are confirmed.
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References
NATURE, 142, 477 (1938).
J. Chem. Soc., 2581 (1926).
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VERNON, W., STROUD, E. Electrolytic Polishing of Zinc. Nature 142, 1161 (1938). https://doi.org/10.1038/1421161a0
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DOI: https://doi.org/10.1038/1421161a0
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