Conference paper
Thermodynamic studies of the gold(III)/(I)/(0) redox system in ammonia-thiosulphate solutions at 25°C
Hydrometallurgy 2003: Proceedings of the 5th International Symposium (Vancouver, Canada, 24/08/2003–27/08/2003)
2003
Abstract
The reported values of the standard reduction potentials of the Au(NH 3)2+/Au(0) and Au(S2O 3)23-/Au(0) couples are reviewed to emphasise the experimental difficulties associated with the measurement of reliable values for these quantities. The standard reduction potential for Ag(I)/Ag(0) in ammonia and thiosulphate solutions measured at ionic strength 0.1 and 25&C is used to predict the following relevant stability constants (β) for gold complexes based on the linear free energy correlations: Au(NH 3)2+ β2 = 1013, Au(S2O3)23- β2 = 1024 and Au(NH3)43+ β 4 = 1033. The equilibrium constant (≈ 10 -11) for the reaction Au(S2O3)23- + 2NH3 = Au(NH3)2+ + 2S2O32- based on these stability constants is in reasonable agreement with the measured value (≈10-9) based on potentiometric and spectroscopic data when excess ammonia was added to a solution of Na3Au(S2O3)2. This also indicates that the stability constant of Au(NH3)2+ is 9 to 11 orders of magnitude less than that of Au(S 2O3)23-. Relevant species distribution and Eh-pH diagrams based on the revised data are presented.
Details
- Title
- Thermodynamic studies of the gold(III)/(I)/(0) redox system in ammonia-thiosulphate solutions at 25°C
- Authors/Creators
- G. Senanayake (Author/Creator)W.N. Perera (Author/Creator)M.J. Nicol (Author/Creator)
- Conference
- Hydrometallurgy 2003: Proceedings of the 5th International Symposium (Vancouver, Canada, 24/08/2003–27/08/2003)
- Identifiers
- 991005543717607891
- Murdoch Affiliation
- Parker Cooperative Research Centre for Integrated Hydrometallurgy Solutions
- Language
- English
- Resource Type
- Conference paper
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