The ammine, thiosulfato, and mixed ammine/thiosulfato complexes of silver(I) and gold(I)
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The M(I)-NH3, M(I)-S2O32-, and M(I)-S2O32--NH3 systems (M = Ag, Au) were studied at 25 °C and at I = 0.1 M (NaClO4) using a variety of analytical techniques. For the Ag(I)-NH3-S2O 32- system, AgS2O3NH3- was detected with formation constant log β111 (for the reaction Ag+ + S2O32- + NH3 ↔ AgS2O3NH3-), of 11.2, 10.4, and 10.8 on the basis of silver potentiometry, UV-vis spectrophotometry, and hydrodynamic voltammetry, respectively. Also, the values of log β 101(AgNH3+), log β 102(Ag(NH3)2+), log β 120(AgS2O3-), and log β 120(Ag(S2O3)23-), obtained from silver potentiometry, were 3.59, 7.0, 8.97, 13.1, respectively. In the case of the ammine complexes, the log β101(AgNH 3+) and log β102(Ag(NH3) 2+) values were found to be 3.5 and 7.1, respectively, from the UV-vis spectrophotometric experiments. The mixed species AuS 2O3NH3- was detected in UV-vis spectrophotometric, hydrodynamic voltammetric, and potentiometric experiments with the stepwise formation constants (log K111) of -4.0, -3.5, -3.8, respectively, for the reaction Au(S2O3)23- + NH3 ↔ AuS2O3NH 3- + S2O32-. At higher [NH3]/S2O32-] ratios (>10 5), the formation of Au(NH3)2+ was also detected in spectrophotometric and potentiometric experiments with stepwise formation constants (log K102) of -5.4 and -5.3, respectively, according to the reaction AuS2O3NH 3- + NH3 ↔ Au(NH3) 2+ + S2O32-.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||Parker Cooperative Research Centre for Integrated Hydrometallurgy Solutions|
|Publisher:||American Chemical Society|
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