1070-4272/02/7501-0029$27.00C2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 1, 2002, pp. 29!33. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 1,
2002, pp. 30!33.
Original Russian Text Copyright + 2002 by Tikhomirov, Lavrenyuk, Orlov, Vidyaev.
OF SYSTEMS AND PROCESSES
Decomposition Kinetics of Alkali Metal Gallams
in Hydroxide Aqueous Solutions
I. A. Tikhomirov, P. I. Lavrenyuk, A. A. Orlov, and D. G. Vidyaev
Tomsk Polytechnic University, Tomsk, Russia
Received May 18, 2001
Abstract-The decomposition kinetics of alkali metal gallams in LiGa3LiOH, NaGa3NaOH, KGa3KOH,
LiGa3NaOH, LiGa3KOH, and KGa3NaOH systems in the 40380oC range was studied. The rate constant and
current density of decomposition were determined. The rate equation of gallam decomposition under the
given experimental conditions was obtained.
Thanks to the high environmental safety and valu-
able properties of gallium and its compounds, the
areas of their practical use are steadily expanding.
In particular, in the exchange separation and purifica-
tion of alkali metals to prepare alkali metal hydrox-
ides  the substitution of highly toxic amalgams by
gallium compounds (gallams) [2, 3] is of particular
importance. The efficiency of the exchange reaction
depends on the decomposition kinetics of the inter-
metallic compound (gallam) at contact with aqueous
solution of alkali metal hydroxide, because at its de-
composition alkali metal partially passes into solution.
If the rate of gallam decomposition is higher than or
equal to the rate of element exchange in the system
studied, the separation of alkali metals is impossible.
Thus, analysis of the kinetics and mechanism of the
above processes is urgent. In this work we studied the
kinetic parameters of decomposition of gallams upon
their contact with aqueous alkali solutions in the
LiGa3LiOH, NaGa3NaOH, KGa3KOH, LiGa3NaOH,
LiGa3KOH, and KGa3NaOH systems.
Lithium, sodium, and potassium gallams were
prepared by direct dissolution of the corresponding
alkali metal in gallium. In our work we used LE-1
brand lithium, chemically pure grade (99.9%) gallium,
and pure grade sodium and potassium. The aqueous
solutions of lithium, sodium, and potassium hydrox-
ides were prepared by dissolving the corresponding
chemically pure grade hydroxide in distilled water.
The experiments were performed at 40380oC, because
gallam solidified at the concentration more than 1.5 M
and temperature lower than 40oC , whereas at tem-
peratures higher than 80oC the aqueous solution of
alkali metal hydroxide strongly evaporates, which is
unacceptable for the separation processes.
The scheme of the experimental unit is shown in
Fig. 1. The experiments were carried out in a cylin-
drical cell 1 (30 mm in diameter) equipped with a
water jacket, which was heated to a required tempera-
ture with a thermostat 2. In the course of experiments
the cell was first charged with hydroxide solution 3,
Fig. 1. Scheme of experimental laboratory unit: (1) cylin-
drical cell with a water jacket, (2) thermostat, (3) aqueous
hydroxide solution, (4) gallam, (5) propeller stirrer,
(6) electrical motor, and (7) valve.