Transmission ultraviolet-visible spectroscopy was employed to image concentration profiles of ferricyanide, generated in a channel-type cell by the oxidation of ferrocyanide on a gold electrode, by monitoring the absorbance as functions of distances either parallel to the flow or transverse to the flow. Steady state measurements performed under diffusion-limited conditions yielded excellent agreement with an earlier model of convection and diffusion, in the absence of any adjustable parameters. Transient measurements following the application of a current pulse showed that it was possible to detect substantially all of the produced ferricyanide, in agreement with Faraday’s law. With further development, spectroscopic methods should be useful for on-line chemical analysis under forced convection.