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The diffusion coefficient of cobalt(II) and bisulphate in moderately acidic sulphate solutions
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The diffusion coefficient of cobalt(II) and bisulphate in moderately acidic sulphate solutions

J. Xiong, P.M. May and I.M. Ritchie
Electrochimica Acta, Vol.32(7), pp.1035-1038
1987
DOI: https://doi.org/10.1016/0013-4686(87)90029-6
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Abstract

A value for the diffusion coefficient of cobalt(II) in 0.5 M sodium sulphate solutions (pH 2–6) equal to (6.4 ± 0.3) × 10−10 m2 s−1 has been determined by the rotating disc method. The precision of the diffusion coefficient measurements was found to decrease significantly with decreasing pH. This effect has been attributed to increases in both the background current and hydrogen evolution, which causes noise in the limiting currents. The background current is due to the discharge of protons and bisulphate ions. Since proton and bisulphate diffusion in a sulphate solution are thought to be coupled by a rapid equilibrium, it is only possible to determine a joint diffusion coefficient for the two species. From a series of such measurements, a value of (18 ± 2) × 10−10 m2 s−1 was determined by extrapolation for the (hypothetical) isolated HSO−4 species.

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