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

A Discussion of selected references
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Observation and identification of these phases will be useful in understanding
the stability of tin oxides/hydroxides in the weathering environment and the nature of
the metal’s corrosion products.
[2003LOR]
Basic quantities for the description of the solubility are reviewed and tabulated. It is
distinguished between quantities based on mass, on the amount of substance, on the
volume, and on combinations of these 3 terms. Furthermore, special quantities to
describe the solubility of gases are introduced. They are related to the amount fraction,
the molality, or to Henry's law constant of the dissolved gas. Approximate relations are
given connecting the Ostwald, Bunsen, and Kuenen (Künen) coefficients. Finally,
relations among the Sechenov parameters are presented describing salt effects on the
solubility of gases.
[2003YEN/GRO]
A thermodnamic assessment of the Hg-Sn system was carried out using the CALPHAD
method. The comprehensive assessment covers the extensive phase diagram data as
well as the enthalpy, activity, and vapour pressure data. Two cases of intermetallic
compounds. in the Hg + Sn system are considered. Case 1 considers the intermetallic
compounds β, γ, and HgSn 4 as having no solubility and can thus be treated as the
stoichiometric phases β-HgSn 38 , γ-HgSn 12 , and HgSn 4 . Case 2 uses a sublattice model to
more accurately describe a solubility of the γ phase; it also considers the stoichiometric
δ-HgSn 7 phase. The ε phase was considered to be metastable and neglected in the
thermodynamic assessment. Thermodynamic parameters were optimised using all the
assessed experimental thermodynamic and phase equilibrium data. Both calculated
phase diagrams of the Hg-Sn system (Cases 1 and 2) and the thermodynamic data are
reasonable and satisfactory when compared with literature data. Future crucial
experiments are suggested.
[2004DUN/CRA]
Corrosion products were examined from typical pewter artefacts originating from six
different submerged archaeological sites, dating to between ca. A.D. 1550 and 1733,
along the eastern seaboard of North America and in the Caribbean Sea. The artefacts
were viewed as 270 to 450 year long experiments revealing the phases and mechanisms
of tin corrosion in seawater. All of the samples analyzed exhibit abhurite
(Sn 21 Cl 16 (OH) 14 O 6 ), romarchite (SnO), and hydroromarchite (Sn 6 (OH) 4 O 4 ) forming at
the expense of the underlying artefact. Textural analysis suggests that abhurite is the
first alteration product to form at the expense of the pewter; romarchite subsequently
develops and then hydroromarchite. The outermost corrosion layers on several of the
most corroded artefacts also exhibit cassiterite (SnO 2 ) as a significant and apparently
final phase to form during alteration. The absence of this mineral on many samples
demonstrates that, while samples appeared to be stable under the conditions that were
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012