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

A Discussion of selected references
303
2
two species ( Sn
3(OH) +
4
and Sn(OH) + ) provides an excellent fit to the whole set of
*
*
experimental data ( log10 β
43
= − (6.75 ± 0.01) (3σ) and log10 β
11
= − (3.71 ± 0.01).
2
Including Sn
2(OH) +
2
into the equilibrium model, a slight (0.5%) decrease of the fitting
parameter was obtained, but as its concentration never exceeds one percent of [Sn 2+ ] tot ,
the formation of this species cannot be justified. The presence of Sn
2(OH) +
3
(suggested
by [1964LIN/TU]) was rejected by the computer program PSEQUAD
[1991ZEK/NAG].
Apart from the importance for the hydrolysis of Sn 2+ , this paper contains also
potentiometric data for a Sn(Hg) sat | Sn 2+ salt bridge H + | H 2 (g) | Pt cell. Thus, once the
activity of Sn in the Sn(Hg) sat phase is known, the standard potential of Sn 2+ /Sn can be
calculated. An attempt to extract from these data information on the standard electrode
potential of reaction
Sn 2+ + H 2 (g) β-Sn + 2 H +
failed, see Appendix A entry for [1967KRA].
[1959ROB/STO]
In this classical textbook on electrolyte solutions the relationship between molality
based γ i and amount concentration based y i activity coefficients has been derived most
elegantly. In the light of this relationship the so far neglected Eq. (VI.5), connecting
concentration and molality based standard electrode potentials, has been developed.
In addition activity coefficient data listed in this book enable in many cases to
apply the SIT approach.
[1960DON/MOS]
Anhydrous tin(II) sulfate was prepared by reaction of tin with CuSO 4 in boiling water,
evaporating most of the water, filtration of the crystals, washing with alcohol and ether
and drying at 100 °C. Chemical analysis confirmed the formula.
“Clear solutions can be obtained at 20 °C provided that the concentration is
greater than 18.9 g/100 mL”.
No details of the procedure and time of equilibration are given.
Table A-15: Solubility of tin sulfate at different temperatures.
t / °C 20 30 50 60 100
Water 35.2 33.4 30.0 28.2 22.0
(a)
N-H 2 SO 4 23.2 22.6 20.6 19.0 13.2
N-NaOH (b) 2.27 2.29 2.52 2.62 -
(a) Propably 1.0 N H 2 SO 4 .
(b) Stannite expressed as g SnSO 4 .
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012