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The stability constants of complex anion In(tiron)~-in mixed solvents of ethanol-water withweight percentages of ethanol being 0,5,15,25,35 and 50 have been measured spectrophotometricallyat 293 K,using NaClO_4 as supporting electrolyte with ionic strength ranging from 0.1 to 3.3mol·dm~(-3).The thermodynamic stability constants of In(tiron)~-in various mixed solvents have been obtained bya polynomial approximation equation based on Pitzer’s theory.As a comparison,the traditionalDebye-Hückel equation has also been used to treat the same data.The results show that this polynomialapproximate method is obviously superior to the old one.It was discovered that there is a linear rela-tion between the thermodynamic stability constants of In(tiron)~-and the mole fraction of organiccomponent in mixed solvents or the reciprocal of dielectric constants of mixed solvents.The mediumeffect and the standard free energy of transfer,ΔG_(tr)~0,for the coordination reaction:In~(3+)+tiron~(4-)=In(tiron)~-,have also been discussed.
The stability constants of complex anion In (tiron) ~ -in mixed solvents of ethanol-water with weight percentages of ethanol being 0,5,15,25,35 and 50 have been measured spectrophotometricallyat 293 K, using NaClO_4 as supporting electrolyte with ionic strength ranging from 0.1 to 3.3 mol · dm ~ (-3). The thermodynamic stability constants of In (tiron) ~ -in various mixed solvents have been obtained by a polynomial approximation equation based on Pitzer’s theory. As a comparison, the traditional Debye-Hückel equation has also been used to treat the same data. The results show that this polynomialapproximate method is obviously superior to the old one. It was discovered that there is a linear rela-tion between the thermodynamic stability constants of In (tiron) ~ -and the mole fraction of organiccomponent in mixed solvents or the reciprocal of dielectric constants of mixed solvents. The mediation effect and the standard free energy of transfer, ΔG_ (tr) ~ 0, for the coordination reaction: In ~ (3 +) + tiron ~ (4 -) = In (tiron) ~ -, have also been discussed.