Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 1, pp. 52−56.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
I.P. Sizeneva, Yu.A. Shchurov, V.A. Val’tsifer, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 1, pp. 53−57.
AND CORROSION PROTECTION OF METALS
Mercury Passivation Solutions of Potassium Chloride
and Sodium Hydroxide and Hypochlorite
I. P. Sizeneva, Yu. A. Shchurov, and V. A. Val’tsifer
Perm State University, Perm, Russia
Institute of Technical Chemistry, Ural Branch, Russian Academy of Sciences, Perm, Russia
Abstract—Formation of anodic films on the surface of mercury in solutions of potassium chloride and sodium
hydroxide and hypochlorite and the effect of these films on mercury passivation were studied by the potentiostatic
At present, oxidation of mercury with strong oxidiz-
ing agents, to which belongs sodium hypochlorite
(SHC), is a widely employed demercurization method.
Demercurization is mostly performed with neutral and
weakly acidic solutions, in which SHC shows a high
oxidizing power, but decomposes exceedingly rapidly.
Alkaline solutions of SHC are stable and belong to
reagents that react with mercury to give its insoluble and
low-volatile compounds. Such a treatment is necessary
for eliminating ﬁ ne mercury drops, which may remain
unnoticed in crevices and irregularities after mechanical
collection, and mercury adsorbed by various porous
surfaces. However, formation of difﬁ cultly soluble com-
pounds on the surface leads to passivation of mercury,
which adversely affects the kinetics and completeness of
It is known that there is no fundamental difference
between the anodic passivation of a metal and its
chemical passivation in solutions of oxidizing agents.
The dissolution rate of the metal and, consequently, the
degree of passivation of its surface are determined solely
by the electrode potential. In this case, it is unimportant
whether a given potential is maintained by polarization
of the metal by an external current or by introduction of
an oxidizing agent into a solution .
In this study, an electrochemical technique was used
to examine in the potentiostatic mode the capacity of
mercury for passivation in NaOCl, KCl, and NaOH
solutions. The last two solutions were chosen for
comparison, because formation of mercury oxide and
calomel on the mercury surface is the most probable in
alkaline solutions of SHC.
The measurements were made on a stationary mercury
electrode. Preliminarily degreased mercury for electrodes
was subjected to additional puriﬁ cation by multiple
passing of a dispersed metal through a 5% solution of
in 5% HNO3 and bidistillate.
A NaOCl solution was prepared by passing chlorine
at temperatures of –5 to 0°C through a sodium hydroxide
solution containing no carbonates. Chlorine was
obtained by reacting chemically pure hydrochloric acid
with potassium permanganate . The hypochlorite
concentration was determined iodometrically for the
Polarization curves were recorded with a Pi-50
potentiostat. A V7-34A digital voltmeter served for
additionally monitoring the potentials of the working
electrode. In the electrochemical cell 1 (Fig. 1), the
cathode and anode spaces are separated by a porous glass
partition 2. A saturated silver chloride reference electrode
3 was placed in the second lateral run-out whose nose is
situated near the working electrode. The potential of the
reference electrode was found experimentally to be
0.203 V (s.h.e.) at 20°C. A tube 4 mm in diameter was
sealed in the cell bottom. Mercury was poured into the
tube and acted as the working mercury electrode 4 with a
surface area of 0.126 cm
. An auxiliary platinum electrode
5 was introduced into the cathode space separated by the
diaphragm. After the measurements, the solution under
study and mercury were removed from the cell via a dis-
charge tube equipped with a cock 6.