On the Photolysis of Barium Thiosulfate

Full text of DOI:10.1134/S0018143918020078

ISSN 0018-1439, High Energy Chemistry, 2018, Vol. 52, No. 2, pp. 194–195. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © N.B. Egorov, E.A. Popova, O.Kh. Poleshchuk, 2018, published in Khimiya Vysokikh Energii, 2018, Vol. 52, No. 2, pp. 177–178.
SHORT COMMUNICATIONS
PHOTOCHEMISTRY
On the Photolysis of Barium Thiosulfate
a,
a
a, b
N. B. Egorov *, E. A. Popova , and O. Kh. Poleshchuk
a
Tomsk Polytechnic University, Tomsk, 634050 Russia
Tomsk State Pedagogical University, Tomsk, 634061 Russia
b
*
e-mail: egorov@tpu.ru
Received July 13, 2017
DOI: 10.1134/S0018143918020078
The photolysis of thiosulfates of alkali and nonfer- tion, triply washed with water and then with ethanol,
rous metals is well-documented [1–5]. This cannot be and dried in a vacuum desiccator. The precipitate
said on the photolysis of alkaline earth metal thiosul- preparation procedure was multiply repeated to accu-
fates; therefore, in this work, we studied the photolysis mulate an amount sufficient for analysis. The concen-
of barium thiosulfate (BaS O ) in order to reveal the trations of barium ions before and after photolysis
2
3
conditions of photolysis and to determine the final were determined on an ICAP 6300 Duo atomic emis-
products.
sion spectrometer.
The diffractograms were recorded on a Rigaku Mini-
flex 600 diffractometer. The IR spectra were measured
on a Nicolet 6700 Fourier transform IR spectrometer in
We found experimentally that solid BaS O ⋅ H O
2
3
2
and its deaerated aqueous solutions are insensitive to
UV radiation. The irradiation of air-saturated aqueous
solutions of BaS O leads to a decrease in the concen-
–1
a range from 400 to 4000 cm . The samples were pre-
2
3
pared as pellets with KBr. The values of pH were mea-
sured on an inoLab pH/Ion 740 WTW ion meter with the
use of a Sentix 81 combined electrode.
tration of barium ions in solution (Fig. 1) and to the
formation of a colloidal solution, which decomposes
with time to form a white precipitate.
The diffractogram of the precipitate obtained by pho-
The synthesis of BaS O ⋅ H O was carried out in tolyzing aqueous BaS O solutions contained only lines
2
3
2
2 3
accordance with a published procedure [6]. A solution due to the BaSO
phase (PDF 01-072-1390). An IR-
4
–3
of BaS O with a concentration of 7.5 × 10 mol/L spectroscopic study of the precipitate showed that the IR
2
3
spectrum contained absorption bands at 1170, 1117, 1074,
and a volume of 40 mL was irradiated with the full
−
1
light of a DRT-240 high-pressure mercury-vapor lamp 997, and 611 cm , which are characteristic of BaSO .
4
for 40 min at room temperature. The resulting precip- Furthermore, the sediment exhibited absorption bands at
itate was separated from the solution by centrifuga- 925, 635, and 497 cm− characteristic of BaSO and
1
3
−1
absorption bands at 686, 556, and 540 cm characteris-
tic of BaS O . The intensity of the absorption bands of
2
3
8
6
4
2
BaSO was considerably higher than that of absorption
4
bands due to BaSO and BaS O .
3
2
3
The treatment of the photolysis product of BaS O
2
3
solutions, which was separated by centrifugation, with
n-hexane showed that the electron spectrum of the
extract did not contain absorption bands characteristic
of dissolved elemental sulfur. Its absence from the
solid-phase products of photolysis is a distinctive fea-
ture, as opposed to the products of photolysis of the
aqueous solutions of lead thiosulfate [7].
It was organoleptically revealed that the UV irradi-
ation of the air-saturated solutions of BaS O was
0
10
20
30
t, min
40
50
60
2
3
accompanied by the release of sulfur-containing gas.
The gas released during the photolysis of a BaS O
2
3
solution was transferred into a receiver by passing air
through the solution and analyzed with the aid of a
TRACE DSQ gas chromatography–mass spectrome-
Fig. 1. Changes in the concentration of barium ions in an
–3
aqueous solution of BaS O (7.5 × 10 mol/L) depending
2
3
on the time of UV irradiation.
194

ON THE PHOTOLYSIS OF BARIUM THIOSULFATE
195
try instrument. The analysis showed that in addition to This reaction is feasible because of a difference
the peaks of ions due to the components of air (N , O , between the solubility products of BaS O and BaSO ,
2
2
2
3
3
–
5
–7
Ar, CO , and H O), the gas phase exhibited the peaks which are 1.6 × 10 and 8.0 × 10 , respectively [10].
2
2
of ions with mass numbers (m/z) of 48 and 64, which
The presence of solid BaS O in the products of
photolysis can be due to the occlusion of the initial
2
3
+
belong to the fragment radical ion SO and the molec-
+
2
ular ion SO . This fact is indicative of the formation of solution, which is possible at a high rate of formation
sulfur dioxide (SO ) in the course of the photolysis of of the crystal lattice of the resulting particles.
2
the BaS O solution.
In summary, we experimentally found that only
2
3
air-saturated aqueous solutions of BaS O lead to its
The initial solutions of BaS O had nearly neutral val-
2
3
2
3
photolysis by UV light, identified the final products,
and proposed a reaction scheme for the UV photolysis
ues of pH. The irradiation of 20 mL of a solution for 10
min was accompanied by a change in the pH from 6.11 to
5
.05. Thus, the photolysis of the aqueous solutions of of aqueous solutions of BaS O with the participation
2 3
BaS O led to the accumulation of hydrogen ions.
of water and oxygen.
2
3
The experiments showed that BaSO , BaSO , SO ,
This work was carried out under a program ori-
ented to an increase in the competitive ability of the
Tomsk Polytechnic University.
4
3
2
+
and H are the final products of the photolysis of air-
saturated aqueous solutions of BaS O .
2
3
Taking into account the fact that the S–S bond is
the weakest bond in the thiosulfate ion [8] and the
thiosulfate group in BaS O ⋅ H O is mainly coordi-
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2
3
2
1
nated to the barium atom through oxygen [9], we
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tion of the photolysis products is the direct decompo-
sition of dissolved BaS O by UV radiation in the pres-
2
3
4
5
6
7
8
9
2
3
ence of oxygen:
BaS O + hν → BaSO + S.
(1)
2
3
3
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3
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4
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2
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2
3
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(2)
(3)
3
2
4
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S + H O + O → H SO .
2
2
2
3
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Thus, the photolysis of air-saturated aqueous solu-
tions of BaS O can be represented by the overall reac-
. Kharitonov, Yu.Ya., Knyazeva, N.A., and Goeva, L.V.,
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979.
2
3
tion scheme
BaS O + H O + 1.5O + hν→ BaSO + H SO . (4)
2
3
2
2
4
2
3
(
1
The dissolved BaS O and H SO can interact to
2
3
2
3
give BaSO3:
BaS O + H SO → BaSO + H S O .
(5)
Translated by V. Makhlyarchuk
2
3
2
3
3
2
2
3
HIGH ENERGY CHEMISTRY Vol. 52 No. 2 2018