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

A Discussion of selected references
391
done carefully. The hydrolysis of tin(II) was neglected during the evaluation of
experimental data, due to the low tin(II) concentration applied. Although this
assumption is not correct, in the concentration range used to determine log10 β 1
([F – ] tot = 0.3 to 0.7 mM, [F – ] tot /[Sn 2+ ] tot = 6 to 14) the effect of the hydrolysis is probably
not very large. The experimental data were evaluated graphically. This method works
reasonably well for the determination of log10 β 1 and log10 β 2 , but seems to fail for the
higher complexes. In aqueous solutions K 2 < K 3 for all ionic strengths applied. In
addition, K 2 < K 3 ~ K 4 ~ K 5 ~ K 6 was reported for 50 and 75% water-ethanol mixture.
Therefore an uncertainty of ± 0.3 was assigned to the log10 β 1 and log10 β 2 values, and
± 0.6 to log10 β 3 .
[1985MAT/EVA]
Abhurite is a new mineral species found in blister-like protuberances on the surface of
tin ingots submerged in a shipwreck about 100 years ago. X-ray-precession patterns
show that the crystals are rhombohedral, space group R3m, R3m or R32, and commonly
twinned on (0001). Results of the chemical analysis conform well to the formula
Sn 3 O(OH) 2 Cl 2 . Different formulae have been ascribed to tin(II) chloride-hydroxideoxide
phases which had been prepared previously but none of them appeared to be
identical with abhurite. Synthetic crystals prepared according to the procedure given in
[1963DON/MOS], however, produced an X-ray pattern nearly identical to that of
abhurite.
Matzko et al. report of a few other cases where basic tin(II) chlorides were
found on tin ingots exposed to marine waters or buried in soil.
A comparison of the experimentally determined composition with the required
ones in Table A-57 shows that the analytical data conform almost equally well to the
correct formula of abhurite and the one suggested by the authors.
Table A-57: Composition of tin(II) chloride hydroxide oxide [1985MAT/EVA].
†
‡
Composition
†
Sn 3 O(OH) 2 Cl 2 Sn 21 Cl 16 (OH) 14 O 6 (cr)
abhurite
w(Sn) 73.4 (74.65)% 73.45%
w(Cl) ‡ 15.7 (14.86)% 16.71%
w(O) 11.0 (10.06)% 9.43%
w(H) 0.4 (0.42)% 0.42%
The stoichiometrically required composition is given in parenthesis
On the basic tin(II) chloride, synthesised according to [1963DON/MOS], 16.9% Cl was
determined.
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012