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

A Discussion of selected references
329
Figure A-28: Third-law analysis of reaction β-Sn(cr) + PbCl 2 (cr) SnCl 2 (cr) + Pb(cr).
27
26
recalculated data using [1970BUG/SHE]
Δ r
H° m
(298.15 K) / kJ·mol –1
25
24
23
22
21
300 350 400 450 500
T / K
[1970CHI]
The formation of Mg(II)-, Ca(II)-, Zn(II)- and Cu(II)-phosphato complexes have been
studied by potentiometric titrations at 37 °C. The formation of complexes with similar
composition was suggested by the author, then reported for Sn(II) in [1968CIL] and
[2000CIA/IUL2].
[1970KUR/BAR]
The solubility of Sn(IV) hydroxide in KOH and NaOH solutions depending on the pH
at 100, 200 and 300 °C has been studied. The solubility decrease with rising
temperature (up to 2 × 10 –5 mol·dm –3 Sn) is accompanied by a change of the
composition of the solid phase which at 100 °C corresponds to varlamoffite, SnO 2·xH 2 O
and at 300 °C to cassiterite, SnO 2 . By the method of solubility the complexing in the
systems Sn(OH) 4 -KOH-H 2 O and Sn(OH) 4 -NaOH-H 2 O at 100 °C has been investigated.
In neutral and alkaline solutions (pH 7-11) complexes Sn(OH) i
4− i
(where i is a posive
or negative integer) are formed. Stability constants β i0 of these complexes: β 30 =
5.0 × 10 46 , β 40 = 2.6 × 10 51 , β 50 = 4.0 × 10 54 , β 60 = 4.1 × 10 57 , have been calculated as well
as their hydrolysis constants: K 30 = 2.9 × 10 –8 , K 40 = 8.7 × 10 –10 , K 50 = 5.7 × 10 –10 .
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012