ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 12, pp. 2166–2168. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © S.S. Ermakov, A.N. Mel’nichenko, A.A. Sheremet, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 12, pp. 2056–2058.
Evaluation of the Efficiency of Electrolysis in Cells
of Various Designs in Inversion-Voltammetric
Determination of Lead
S. S. Ermakov, A. N. Mel’nichenko, and A. A. Sheremet
St. Petersburg State University, St. Petersburg, Russia
Received April 9, 2008
Abstract—Efficiency of the stage of pre-electrolysis in inversion-voltammetric measurements was examined
in relation to the hydrodynamic modes used.
The pre-electrolysis stage is a constituent of sev-
eral electrochemical methods of analysis: inversion
voltammetry (IVA), controlled-potential coulometry
(CPC), and zero-reference combined electrochemical
technique [1–3]. It is known that the electrolyte agita-
tion efficiency strongly affects the sensitivity of the meth-
ods mentioned above, because in all of them, the depo-
sition current is inversely proportional to the diffusion
layer thickness δ, the parameter that characterizes
the intensity of mass transfer.
Traditionally, IVA measurements are carried out
with a rotating disk electrode (RDE), whose theory has
been developed by Levich . The same hydrody-
namic system was employed in [1, 5, 6] in a zero-
reference electrochemical method in which the pre-
electrolysis efficiency is determined by the coulomet-
possible, which allows use of large electrodes at small
solution volumes .
The limiting diffusion current to the RDE is given
by the equation 
K = DS/(δV ),
where D is the diffusion coefficient; S, electrode area;
δ, diffusion layer thickness; and V, volume of the so-
lution under study in the cell.
It follows from Eq. (1) that the constant K de-
pends not only on δ, but also on the working electrode
area S. The dependence of K on the volume has been
studied previously [1, 6]. In the RDE method, it is not
always possible to make larger the working electrode
area at a fixed solution volume, which is necessary for
using the zero-reference method. Another hydrody-
namic model, a rotating cylindrical electrode (RCE), is
where n is the number of electrons involved in the elec-
trode reaction; F, Faraday number; c
, solution concen-
tration in the cell; ν, kinematic viscosity; ω, angular
rotation rate; and D, diffusion coefficient.
The limiting diffusion current to the RCE can be
found using the equation [6, 7]
is the electrode diameter.
Equation (2) is satisfied for the RDE in a wide
range of rotation rates . For the RCE (the general
scheme of the electrode is shown in Fig. 1a), there ex-
ist three fluid flow modes resulting from different elec-
trode rotation rates.
(1) Simple laminar flow with concentric current
lines, observed at low cylinder rotation rates. This flow
merely sets the substance in a circular motion, without
any increase in the mass-transfer rate.
(2) Flow with Taylor vortices, a cellular flow with
a velocity component directed from one cylinder to-
ward the other. This flow is also regular, laminar, and
stable; it requires a higher electrode rotation rate and
contributes to the mass-transfer rate.