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

A Discussion of selected references
389
Table A-54: Composition of tin(II) hydroxide oxide [1984ICH/TAK].
Composition Exp. 3SnO·2H 2 O 5SnO·2H 2 O
[1961DON/MOS]
3SnO·H 2 O
[1968HOW/MOS]
w(SnO) 92.72% 91.81% 94.92% 95.73%
w(H 2 O) 7.86% 8.19% 5.08% 4.27%
[1984KOC/TOP]
Based on the paper [1983TOP/KOC], additional experimental data and standard data of
several books and reviews (listed in a table) a standard Gibbs energy of formation of
SnS 2 was derived:
− 43.20 kcal·mol –1 (− 180.75 kJ·mol –1 ) for good crystallised solids
− 41.30 kcal·mol –1 (− 172.80 kJ·mol –1 ) for nearly amorphous SnS 2 .
ο
2
6
Also Δ fGm(
SnCl − , 298.15 K) = − 204.08 kcal·mol –1 (= − 856.88 kJ·mol –1 )
was derived from the model.
Table A-55: Experimental data on the solubility of SnS 2 at 25 °C and 1 bar H 2 S.
m (HCl) /mol·kg –1 m (Sn) × 100/mol·kg –1 m (HCl) /mol·kg –1 m (Sn) × 100/mol·kg –1
1.20 4.30 × 10 –3 4.29 5.16
1.84 1.75 × 10 –2 4.64 8.35
3.78 1.30 4.88 11.01
4.05 3.13 5.12 13.05
The standard Gibbs energy of formation of the sulfide ion used for the
calculations is too small (91.88 kJ·mol –1 ). Data for the complete series of tin(IV)
complexes are given without detailed information how the values have been obtained
(Table A-56).
All formation data of complexes are 50 to 100 kJ·mol –1 more negative than
those selected by this review. In their previous paper [1983TOP/KOC] the authors
mention formation of elemental sulfur during precipitation of SnS 2 . This reaction
Sn 4+ + 2 H 2 S SnS(s) + S + 4 H +
is accompanied by formation of the much more soluble SnS. Thus the more negative
formation Gibbs energies of chlorido complexes are required to adapt the data in the
model. Simulations using the selected data confirm that this reaction will proceed.
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012