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Title: The chemistry of tin and lead archaeological artefacts.
Author: Edwards, Robert.
ISNI:       0000 0001 3441 2124
Awarding Body: University of Wales.Cardiff
Current Institution: Cardiff University
Date of Award: 1991
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The present work explores the long term corrosion phenomena of lead and tin in saline and other conditions. Thermodynamic results are presented for the minerals abhurite, blixite, mendipite, paralaurionite, stannite and the compounds Pb706Cl2.2H20 and Sn30(OH)2S04 at 298.2K and P = 105 Pa. At this temperature laurionite is stable, rather than its dimorph, paralaurionite, and mendipite is in fact metastable, being thermodynamically stable above 29 0 C. Kinetic influences are significant with respect to the sequence of formation of solid phases in the PbO - H20 - HCl system, and these have been elucidated for some important reactions. Penfieldite and fiedlerite appear to be metastable at all temperatures at 105 Pa. These results have been used to develop a model for the formation of lead(II) oxy- and hydroxy- chloride phases that are known as minerals and as corrosion products of lead-containing artefacts. The effect of C02 on the system is also discussed. A new synthesis of sn30(OH)2S04 is described, and its stability constant in aqueous solution has been determined by direct ~easurement of the activities of Sn2+ and s04 2- using ion selective electrodes. The true formula·of abhurite is Sn2l06(OH)14Cl16' which corresponds to a synthetic phase of known crystal structure. The results have been used to assess the relative stabilities of these compounds in the natural environment and their modes of occurrence in relation to other secondary Sn(II) and Sn(IV) species. Finally, some divalent metal hexahydroxystannates have been made, and their role in the corrosion of tin and its alloys assessed. The electrochemical oxidation of stannite has been studied and some correlation has been made between the supergene minerals formed and solution chemistry.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Inorganic chemistry