1070-4272/05/7804-0546 C 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 4, 2005, pp. 546!548. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005,
Original Russian Text Copyright + 2005 by Sizeneva, Val’tsifer, Strel’nikov.
AND INDUSTRIAL INORGANIC CHEMISTRY
A Study of Mercury Dissolution in Aqueous Solutions
of Sodium Hypochlorite
I. P. Sizeneva, V. A. Val’tsifer, and V. N. Strel’nikov
Institute of Technical Chemistry, Ural Division, Russian Academy of Sciences, Perm, Russia
Received December 16, 2004
Abstract-Dissolution of mercury in aqueous solutions of sodium hypochlorite at pH 5.938.5, the cor-
responding reaction order, and the mechanism of this process were studied. The ratio of the rates of
mercury oxidation and sodium hypochlorite decomposition was analyzed.
Salts of hypochlorous acid, hypochlorites, find
wide application as strong oxidizing agents, their ox-
idizing power being largely determined by the acidity
of the medium.
The aim of this study was to assess the possibility
of using a sodium hypochlorite (NaClO) solution at
pH 5.938.5 for oxidation of mercury and to determine
the rate constants of mercury dissolution via its ox-
idation to Hg
ions in the above-mentioned acidity
Mercury was oxidized with an aqueous solution of
NaClO at pH 5.9, 6.5, 6.9, and 8.5 and temperatures
of 25 and 50oC; the concentration in terms of active
chlorine was 0.330.8 M. The required acidity was
created with a buffer phosphate solution obtained by
adding orthophosphoric acid, potassium dihydrophos-
phate, and sodium hydrophosphate to the NaClO so-
lution. The pH value was monitored with an EV-74
ionometer with glass and silver chloride electrodes.
The NaClO solution was produced by passing chlo-
rine through a carbonate-free solution of sodium hy-
droxide at a temperature of 35_0oC. The reaction
vessel was cooled with a mixture of sodium chloride
and ice. Chlorine was obtained by reacting chemically
pure hydrochloric acid with potassium permanganate.
The concentration of the hypochlorite was determined
A mercury drop of mass 0.0530.15 g was placed
in a hermetically sealable glass jars thermostated at
25 and 50oC, and 50 ml of a sodium hypochlorite so-
lution with certain acidity was added. The Hg
centration was determined at regular intervals of time
by a selective spectrophotometric technique with di-
thizone . The optical density of the solutions was
determined with a KFK-2 photoelectric colorimeter.
Mercury is a metal that is liquid at room temper-
ature. The high surface tension allows even com-
paratively large mercury drops to take the shape of
a sphere, the body with the smallest relative sur-
face area. Dissolution of mercury is a heterogeneous
process that occurs at the interface and depends on
the area and state of the surface. Kinetic character-
istics of the process of mercury dissolution in sodium
hypochlorite solutions were determined using the for-
mula established experimentally by A.N. Shchukarev
for the rate of dissolution of a solid body in a liquid
[2, 3]. This formula made it possible to calculate
the rate constant k of mercury dissolution:
w = kS(c
where w is the dissolution rate; S, area of contact be-
tween the solid and liquid; c, concentration of the sub-
stance being dissolved in the bulk of the liquid; c
concentration of a saturated solution; and k, constant
for the given experimental conditions.
As the concentration of a saturated solution was
taken the maximum possible concentration of Hg
ions. The latter was determined from the mass of
the mercury drop and the volume of the hypochlorite
solution in which it dissolved. The rate of mercury
dissolution was found from the concentration of mer-
cury(II) at certain instants of time. The contact area
was calculated from the mass of a spherical drop of
mercury and its density  at a given temperature.