Solubility product of galena at 298°K: A possible explanation for apparent supersaturation in nature |
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Authors: | AD Uhler GR Helz |
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Institution: | Department of Chemistry, University of Maryland, College Park, MD 20742 USA |
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Abstract: | The synthetic chelating agent ethylenediaminetetraacetic acid (EDTA) has been used to evaluate the stoichiometric solubility product of galena (PbS) at 298°K: This method circumvents the possible uncertainties in the stoichiometry and stability of lead sulfide complexes. At infinite dilution, , and at an ionic strength corresponding to seawater (), . Using the value of at infinite dilution, and the free energies of formation of HS? and Pb2+ at 298°K (literature values), the free energy of formation of PbS at 298°K is computed to be . Galena is shown to be more than two orders of magnitude more soluble than indicated by calculations based on previous thermodynamic data. |
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