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

388
A Discussion of selected references
possible complex formation between tin(II) and perchlorate ion, and concluded that no
complex formation occurs in the studied concentration range (0.05 M Sn(ClO 4 ) 2 , 0.5 M
HClO 4 and 0 to 4.0 M NaClO 4 ).
[1984HSU/CHE]
2−x
Mössbauer spectroscopy was used to determine the formation constants of SnBrx
(x = 1, 2, 3) complexes by adding aqueous NaBr (0 to 1 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 /Br)). Due to the relatively
low excess of bromide used, at the end of the titration the complexation reached only
n = 1.7 ( n = averaged ligand number), log 10 K 3 cannot be determined with acceptable
accuracy. As fast frozen solutions have to be used in Mössbauer spectroscopy, the
temperature at which the equilibrium ‘was frozen’ is also unknown. Therefore, though
the formation constants determined by the authors based on the shift of quadrupole
splitting (see Table VIII-11) are relatively close to the other values in the table, these
constants were not used to derive selected data.
[1984ICH/TAK]
The precipitates obtained by addition of a solution of NaHCO 3 to a solution of SnCl 2 at
various pH were studied by thermal analysis, Mössbauer spectroscopy, and X-ray
powder diffraction. The empirical formula of the tin(II) hydroxide chloride precipitate
in the range of pH 1.9 to 2.5 was determined to be 2SnO·SnCl 2·H 2 O, and the empirical
formula of the hydroxide obtained in the range of pH 7.0 to 7.7 was 3SnO·2H 2 O.
The composition of the tin(II) hydroxide chloride as well as the tin(II)
hydroxide was determined by thermal analysis. The mean values of the respective
results are listed in column 2 of Table A-53. Reliable analyses of tin(II) hydroxide
chloride are obviously rather difficult to carry out, thus the question arises whether
thermal analysis qualifies for this purpose.
Table A-53: Composition of tin(II) hydroxide chloride [1984ICH/TAK].
Composition Exp. 2SnO·SnCl 2·H 2 O 3SnO·SnCl 2·3H 2 O
[1963DON/MOS]
Sn 21 Cl 16 (OH) 14 O 6 (cr)
abhurite
w (SnCl 2 ) 37.24% 39.75% 29.27% 44.69%
w (SnO) 58.72% 56.48% 62.39% 51.59%
w (H 2 O) 4.04% 3.78% 8.34% 3.72%
The same argument applies when Ichiba and Takeshita’s thermo-analytical
results on tin(II) hydroxide oxide are compared with the predicted formulae, see
Table A-54.
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012