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

A Discussion of selected references
387
Table A-51: Solubility of SnS 2 in HCl.
[HCl]/M [Sn] × 100/M [HCl]/M [Sn] × 100/M
3.60 0.0042 4.66 8.76
4.00 0.13 4.73 11.88
4.28 5.32 4.74 21.49
Equilibrium data are listed in Table A-52.
Table A-52: Solubility of SnS 2 in CaCl 2 -HCl solutions.
[HCl]/M [CaCl 2 ]/M [Sn] × 100/M [HCl]/M [CaCl 2 ]/M [Sn] × 100/M
1.0 1.35 0.27 4.0 2.25 13.69
4.0 1.35 8.70 1.0 2.25 1.59
1.0 3.15 2.49 2.5 3.15 6.88
4.0 3.15 18.96 2.5 1.35 3.20
2.5 2.25 4.52
From the results of Table A-52 an equation for the equilibrium tin
concentration was derived (for the sake of brevity division by M was omitted):
[Sn] = 1/100 × (4.33 − 6.33 [HCl] − 0.85 [CaCl 2 ] + 1.78 [HCl] × [CaCl 2 ] + 1.45 [HCl] 2 ).
It is not clear to which extent the solubility data are influenced by the
formation of sulfur, because of the redox reaction
Sn 4+ + S 2– → Sn 2+ + S
a certain amount of Sn(II) is formed, precipitated as SnS or not. In any case the
solubility data of this paper should represent an upper limit. Chlorido-complex
formation plays an important role. No comment on hydrolysis of SnCl 4 is given.
[1984CHE/HSU]
2−x
Mössbauer spectroscopy was used to determine the formation constants of SnClx
(x = 1, 2, 3) complexes by adding aqueous NaCl (0 to 3 M) to a solution containing
0.05 M Sn(ClO 4 ) 2 and 0.5 M HClO 4 (I = 3.5 M (Na,H)(ClO 4 /Cl)). This is a more
accurate study than the authors’ previous reports ([1981CHE], [1981CHE2]),
nevertheless this paper also suffers some deficiency: (i) during the measurements the
3 M NaClO 4 background electrolyte was entirely replaced by NaCl, (ii) since fast frozen
solutions were used, the temperature at which the equilibrium ‘was frozen’ is unknown.
Although the formation constants determined by the authors based on the shift of
quadrupole splitting (see Table VIII-8) are relatively close to the other values in the
table, these constants were not used to derive selected data. The authors also studied the
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012