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

306
A Discussion of selected references
[1961GOL/OGN]
The formation of the thiocyanato complexes of tin(II) was studied by a potentiometric
method using a tin amalgam electrode in aqueous solution as well as in methanol-water
and acetone-water mixed solvents at 20 °C. In aqueous solution 2.2 M NaClO 4 was
applied as inert electrolyte ([Sn 2+ ] tot = 0.0041 M) and the authors concluded the
2
formation of three complexes ( SnSCN
− q
q
, q = 1, 2, 3). The primary experimental data
reported in the paper indicate that the background electrolyte was almost entirely
replaced by NaSCN during the measurements. Due to the notable medium effect the
experimental data were re-evaluated. Since the lowest thiocyanate concentration was
0.228 M, only four data points are available up to 30% replacement of the background
electrolyte. The consideration of two species (SnSCN + and Sn(SCN) 2 (aq)) is sufficient
to describe the selected experimental data. The obtained formation constants are
log10 β
1
= (0.70 ± 0.01) and log10 β
2
= (1.65 ± 0.01). Considering the limited number
of data points, an uncertainty of ± 0.3 has been assigned to the above values.
[1961IVE/JAN]
This is an exhaustive account with full bibliographies of the experimental methods by
which the most reliable reference electrodes may be set up. The theoretical basis is
treated comprehensively. Temperature and composition information is given for
Calomel and Ag/AgCl electrodes, which is valuable throughout this review.
[1961RAB/MOO]
The authors re-evaluated the experimental data reported in [1950DUK/COU] and in
[1952VAN/RHO]. The first set of data was satisfactorily fitted by three constants for
the mono-, di- and trichlorido complexes (instead of the four constants given in
[1950DUK/COU]). The recalculation of the data reported in [1952VAN/RHO] did not
give consistent formation constants for the hydroxido complexes, therefore the presence
of Sn(OH) + and Sn(OH)Cl(aq) under the given conditions has been rejected. The above
conclusions are almost identical with those of the reviewers. Nevertheless, the
recalculated formation constants reported in [1961RAB/MOO] are not used in the
present assessment.
[1961TOB/HUG]
Potentiometric measurements using a tin amalgam electrode have been performed to
study the complex formation processes between tin(II) and chloride ion under nitrogen
atmosphere at 25 °C in 3 M (Na/H)ClO 4 medium. The formation constants of three
mononuclear complexes (SnCl + , SnCl 2 (aq), SnCl − 3
) have been reported. No evidence
was found for polynuclear complexes involving chloride bridges. The careful
measurements performed by the authors are similar to those reported in
[1952VAN/RHO], but somewhat more extended range of hydrogen ion concentrations
was used ([H + ] tot = 0.05, 0.1 and 0.5 M). The graphical presentation of the experimental
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012