Abstract
The fast reduction of copper(II) by the thiosulfate ion in aqueous solution is preceded by the extremely rapid formation of a Cu(S203)22~complex with stability constant ß (3.6±0.5)X104M"2at25.0°C and ionic strength0.2M(NaC104). The tetrathionate ion and a (thiosulfato) copper(I) complex are formed in the redox reaction,the rate of which is secondorderin [Cu(II)] and independent of [S2O32"] in high excess of thiosulfate.The limiting value of the observed second-order rate constant is fc4=(1.05±0.08)X1056M"1s~*.The mechanism involves an intermolecularrate-determining step between two molecules of the bis(thiosulfato) copper(II) complex.