Abstract
The conductance behavior of mixtures was investigated with the following systems in aqueous solutions of various ionic strengths at 25°C; NaCl - KCl, NaCl - NaClO4, NaCl - Na2SO4, [CO-(NH3)6] Cl3 - Na2SO4 and [CO(en)3]Cl3 - Na2SO4. Appreciable deviations of the measured conductivities from additivity were observed in the last two systems involving the cobalt(III) complexes. The deviation was attributed to the ion-pair formation of the complex cations with sulfate ions; the ion-pair formation constants at various ionic strengths were determined by means of computer analysis of the deviation without relying on the Onsager conductance equation. The thermodynamic ion-pair formation constants at 25°C were as follows: logK=3.53 for [CO(NH3)3+·SO42− and logK=3.60 for [CO(NH3]3+·SO42−. The analysis of conductance behavior of mixtures was proved to be a useful method of studying ion-pair formation particularly at relatively high ionic strengths.

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