THERMODYNAMIC STUDIES OF THE GOLD(III)/(I)/(0) REDOX SYSTEM IN AMMONIA-THIOSULPHATE SOLUTIONS AT 25°C

摘要

The reported values of the standard reduction potentials of the (Au(NH{sub}3){sub}2){sup}+/Au(0) and (Au(S{sub}2O{sub}3){sub}2){sup}(3-)/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{sub}3){sub}2){sup}+ β{sub}2 = 10{sup}13, (Au(S{sub}2O{sub}3){sub}2){sup}(3-) β