Conclusions1. Up to 1016/cm 2, the implantation fluence of a noble gas marker has no effect on the measurement of transport numbers.2. Noble gas markers do not, therefore, influence the transport mechanism during anodization, either by their presence or by any radiation damage accompanying their implantation.3. Implanted in trace amounts, 101~/cm ~ or less, noble gas markers have no effect on the kinetics of the anodization process and are therefore effectively inert.4. Neon behaves in the same way as the heavier noble gases and is thus also suitable as a marker. AcknowledgmentsThe author is indebted to D. Phillips for performing many of the experimental measurements, and to J. A. Davies for reviewing the manuscript. Especial thanks are due to one of the JOURNAL reviewers, for valuable suggestions on how to improve the presentation.ABSTRACT A recently developed, simple technique for determining cathode mass transfer coefficients in full scale electrowinning cells is discussed. The approach involves the determination of the limiting current for mass transfer controlled codeposition of silver in the cathode deposit. A rotating disk electrode was used to establish the validity of the method. Examples demonstrate the usefulness of the method for mapping local values of the mass transfer coefficient on the cathode under typical natural and forced convection flow regimes in electrowinning cells. Z Present address: Hooker Chemical Corporation, Niagara Falls, New York 14300.

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Horizontal and vertical mapping of the cathode mass transfer coefficient was used to compare the hydrodynamics of full height model electrowinning cells employing either natural convection or two methods of forced convection. The most sgnificant improvement in performance was achieved with uniform agitation resulting from sparging gas over the cathode surface.

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