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

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IX Group 16 compounds and complexes
to hydrolysis solubility measurements are rare and only tentative. According to
[1960DON/MOS] quite concentrated, transparent aqueous solutions are obtained by
adding water to the sulfate. Mass concentration varies from 352 g·dm –3 SnSO 4 at 20 °C
to 220 g·dm –3 at 100 °C [1960DON/MOS]. In 0.5 M sulfuric acid the corresponding
amounts of dissolved SnSO 4 are lower (23.2 g·dm –3 at 20 °C, 13.2 g·dm –3 at 100 °C).
The stability field of SnSO 4 and its hydrolysis products in the system SnO-SO 3 -H 2 O
have been determined by Denham and King at 25 °C and 50 °C [1935DEN/KIN].
Solubility of SnSO 4 drops sharply with increasing concentration of H 2 SO 4 , however, no
solubility constant can be derived from the data.
IX.1.2.4
Basic tin(II) sulfate
IX.1.2.4.1
Composition of basic tin(II) sulfate
From dilute aqueous solutions of tin(II) sulfate with a pH not higher than 2.4 a basic
compound Sn 3 (OH) 2 OSO 4 , tritin(II) dihydroxide oxide sulfate, crystallises
[1967DAV/DON], the crystal structure of which was determined [1975DAV/DON],
[1975GRI]. Several hydrated forms have been discussed on the basis of chemical
analyses [1882DIT2], [1926CAR], [1935DEN/KIN]. According to the study of
[1935DEN/KIN] at higher sulfate concentrations the compound SnSO 4·SnO represents
an equilibrium phase in aqueous solutions at 25 °C and 50 °C. Lundgren et al.
performed a crystal structure analysis of SnSO 4·SnO [1982LUN/WER].
Basic tin(II) sulfate is a rare corrosion product found on the surfaces of tin and
tin alloys. Tin(II) oxide sulfate, Sn 3 O 2 SO 4 , was identified on concretions of corroding
bronze objects recovered from seawater [1982MAC].
IX.1.2.4.2 Solubility of Sn 3 (OH) 2 OSO 4
Edwards et al. [1996EDW/GIL] precipitated Sn 3 (OH) 2 OSO 4 (cr) by hydrolysis of tin(II)
sulfate according to the following reaction
3 SnSO 4 (aq) + 3 H 2 O(l) Sn 3 (OH) 2 OSO 4 (cr) + 4 H + +
The dissolution reaction
Sn 3 (OH) 2 OSO 4 (cr) + 4 H + 3 Sn 2+ +
2
2SO − 4 .
2
SO − 4 + 3 H 2 O(l) (IX.12)
was studied by measuring the activities of hydrogen ion, tin(II) ion and sulfate ion with
glass, tin amalgam and sulfate ion selective electrodes, respectively. With
ο
log10
K s (IX.12) = − (5.01 ± 0.37), see Appendix A, thermodynamic auxiliary data for
2
SO − and H 2 O(l) taken from Table IV-1 and with (Sn 2+ 4
Δ
ο
fGm
, 298.15 K) selected by
this review
has been obtained.
Δ ο
f G m (Sn 3(OH) 2 OSO 4 , cr, 298.15 K) = − (1566.2 ± 2.3) kJ·mol –1
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012