ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 1, pp. 1! 6. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + N.A. Potolokov, A.V. Serov, V.N. Potolokov, A.V. Zhuravlev, V.P. Kolganov, E.G. Zhukov, V.A. Fedorov, V.I. Kholstov, 2007,
published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 1, pp. 3!8.
AND INDUSTRIAL INORGANIC CHEMISTRY
Reduction of Arsenic Trichloride with Hydrogen
N. A. Potolokov, A. V. Serov, V. N. Potolokov, A. V. Zhuravlev, V. P. Kolganov,
E. G. Zhukov, V. A. Fedorov, and V. I. Kholstov
Research Institute of Electronics Materials, Open Joint-Stock Company, Kaluga, Russia
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
Kaluga Branch, Timiryazev Moscow Agricultural Academy, Kaluga, Russia
Federal Industry Agency, Moscow, Russia
Received March 3, 2006
Abstract-The composition of an equilibrium vapor!gas mixture in the range 700!1100 K was estimated
for the reaction of arsenic trichloride with hydrogen taken in excess of a = 1.0!2.5 as compared to the
stoichiometry. The temperatures of the onset of arsenic condensation (dew point) were found. Kinetic param-
eters of the chemical reaction were determined. Optimal conditions for the reduction of arsenic trichloride
with hydrogen were refined and conditions for the condensation of arsenic with the minimum fraction of
the amorphous modification were found.
The reaction of gaseous arsenic trichloride with
hydrogen is one of the most important stages of the
preparation of high-purity elemental arsenic .
Systematic study of AsCl
reduction with hydrogen is
required for the development of physical and chemical
principles for producing high-purity arsenic from an
unconventional raw material, products of the detoxica-
tion (utilization) of chemical weapons (lewisite).
The feasibility of organizing industrial production of
high-purity arsenic-containing compounds on the
basis of lewisite has been substantiated in .
It was found by studying thermodynamic and ki-
netic features of the AsCl
reduction with hydrogen
 that the degree of conversion of arsenic tri-
chloride is sufficiently high even at temperatures
above 600 K and small hydrogen excesses against
a stoichiometry. The chemical equilibria for real reac-
tion conditions were simulated in .
This paper deals with an experimental study of the
reduction of AsCl
with hydrogen. Appreciable atten-
tion is given to the process kinetics, and also to the
optimization of conditions for the production of high-
purity arsenic from unconventional raw materials,
products of lewisite detoxication and wastes from
First we made a thermodynamic estimation of the
arsenic trichloride reduction with hydrogen:
= exp (!,G
Such representation of the AsCl
arsenic is admissible, as it was shown previously
[5, 7] that As
is the main arsenic species in the vapor
phase at temperatures below 1100 K in the presence
of a hydrogen excess a < 5 against the stoichiometry.
Equilibrium constants (2) of reaction (1) were calcu-
lated for the range 70031100 K and an excess (a =
132.5) of hydrogen against the stoichiometry by two
** is the reduced thermodynamic potential.
Both methods give similar K
values varying from
3.4 0 10
to 6.0 0 10
varied from 60
to 100 kJ mol
. From the resulting K
estimated the composition of the equilibrium vapor3
gas mixture for a total pressure of 1 atm in the reac-
tion zone. The calculated data are given in Fig. 1,
which shows that the calculated partial pressures P
of arsenic vapor are practically independent of the
process temperature and decrease by a factor of 1.7
with increasing a from 1 to 2.5. The partial pressure