Chemical Thermodynamics of Tin - Volume 12 - OECD Nuclear ...

A Discussion of selected references
411
[1997SIP/CAP]
The hydrolysis of Tl(I) has been studied at 25 °C using 205Tl-NMR spectroscopy and
UV-Vis spectrophotometry in aqueous solutions with ionic strengths maintained by
NaClO 4 at 2, 4, 6, and 8 M. The formation constant and the spectral characteristics for
the hydroxido complex, TlOH (aq) have been determined. At high hydroxide ion
concentrations there is clear evidence from the UV-Vis data for the formation of a
Tl(OH) −
2
species. The spectrum and an estimated formation constant for this second
hydroxido complex are also reported.
[1997VAS]
Plyasunov and Grenthe’s [1996PLY/GRE] criticism provoked a scientific controversy.
Vasil’ev refutes Plyasunov and Grenthe’s arguments. This controversy is of scientific
interest for the TDB-Sn project.
[1998ODA/AMA]
This paper complements the solubility data reported in [1997AMA/CHI], using
identical experimental methods (see comments on [1997AMA/CHI]). The solubility of
amorphous SnO 2 in NaClO 4 , NaCl, Na 2 SO 4 , as well as in bentonite equilibrated systems
were measured to investigate the influence of additional ligands present in the solution.
No significant changes in solubility were observed in presence of Cl – or SO − , as
compared with the results obtained in NaClO 4 solution. On the other hand, in the
bentonite equilibrated solutions the solubility of tin(IV) increased by two orders of
magnitude. For the undersaturation experiments amorphous SnO 2 , formed during the
oversaturated measurements, was applied. The authors used a selected dataset, based on
the solubility data reported in [1997AMA/CHI] and those collected in this paper, to
determine the solubility of amorphous SnO 2 in ≈ 0.1 M NaClO 4 solution (in Table 1 and
2, the authors reported erroneous ionic strength data, in reality the ionic strength was
between 0.1 and 0.15 M; personal communication by Chie Oda).
The solubility data reported for I ≈ 0.1 M NaClO 4 were re-evaluated for the
purposes of this review. Using the dataset selected by the authors, including 30 points
from the oversaturation experiments (Figure VII-5, open squares), log10 K s,0
=
*
*
− (7.34 ± 0.09), log10 β 5,1 = − (7.76 ± 0.19) and log10 β 6,1 = − (18.14 ± 0.15) can be
calculated. However, this set does not include points between pH 8 and 10, where the
complex Sn(OH) −
5 dominates in the solution. Therefore, the re-evaluation included all
experimental points, both over- and undersaturation data reported for I ~ 0.1 M NaClO 4 .
As it can be seen from Figure VII-5, the experimental data show good consistency,
irrespective of the under- and oversaturated methods. The non-linear curve fitting
resulted in the following equilibrium constants: log10 K s,0
= − (7.22 ± 0.08),
*
*
log10 β 5,1 = − (8.38 ± 0.25) and log10 β 6,1 = − (18.01 ± 0.11). These values were used
to derive the selected thermodynamic constants. The uncertainties were increased by the
reviewers, due to the fact that the actual ionic strength varied between 0.1 and 0.15 M.
2
4
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012