Profile of the Refractive Index in the Cathodic Diffusion Layer of an Electrolyte Containing CuS04 and H2SO

The profile of the refractive index in the cathodic diffusion layer of a solu-tion containing 1.85M H2SO4 and 0.05M CuSO4 was measured by holographic interferometry. Measurement was carried out at various heights from the lower edge of the cathode and also at various cathodic current densities up to the l imiting value. The theoretical expression for the difference of the re-fractive index between the cathode surface and the bulk electrolyte was de-rived assuming a uniform distribution of the local cathodic current density. Experimental results obtained at the current densities below one-half of the l imiting value were in good agreement with the theoretical value. Measure-ment was also conducted with the solutions containing 1.85M H2SO4 and 0.01, 0.02, 0.03, 0.04, and 0.05M CuSO4, respectively, at their cathodic l imiting current densities. H2SO4 concentration at the cathode surface was estimated from the interferogram and CuSO4 concentration at the cathode surface was presumed to be virtually zero at the l imiting current. The estimated H2804 concentratio