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

302
A Discussion of selected references
The enthalpy increments of Table A-14 are represented to within the average
limits indicated by the equation below, see also Figure A-21.
SnS 2 (cr) (0.2%, 298-1000 K):
[H°(T) − H°(298.15 K)]/kJ·mol −1 = 64.89 T/K + 8.79 × 10 −3 (T/K) 2 − 20129.
Figure A-21: Enthalpy function of SnS 2 (cr).
60000
C p
/J·K –1·mol –1 = exp{a + b ln(T/K) + c [ln(T/K)] 2 + d [ln(T/K)] 3 }
[H°(T) -H°(298 K)]/J·mol –1
50000
40000
30000
20000
a = – 23.6488
b = 13.2230
c = – 2.10132
d = 0.112224
10000
calc. by integrating C p
[1980WIE/CSI2]
exp.data [1958ORR/CHR]
0
300 400 500 600 700 800 900 1000 1100
T / K
[1958TOB]
In this paper the hydrolysis of Sn(II) has been studied by a potentiometric method using
two sensors (glass and tin amalgam electrodes) at 25 °C and I = 3 M NaClO 4 ([Sn 2+ ] tot =
2.5, 5, 10, 20 and 40 mM). The evaluation of the experimental data indicated the
2
formation of Sn
3(OH) +
2
4
as the main product, while Sn
2(OH) +
2
and Sn(OH) + have
been suggested as minor products.
This is a well documented and careful work. Since the composition of the
minor hydrolysis products was later disputed [1964LIN/TU], [1976GOB],
[1997SAL/FER], the combined data sets of [1958TOB] and [1976GOB] were
re-evaluated for the purposes of this review. The combination of experimental data
provides an excellent opportunity to determine the composition and formation constant
of both mono- and oligonuclear complexes, since the total concentration of tin(II) varies
in a very wide range ([Sn 2+ ] tot = 0.02 to 40.0 mM). The assumption of the presence of
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012