A New Approach to the Equilibrium Study of Iron(III) Thiocyanates Which Accounts for the Kinetic Instability of the Complexes Particularly Observable Under High Thiocyanate Concentrations

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de Berg, K., Maeder, M., & Clifford S. (2016). A new approach to the equilibrium study of iron(III) thiocyanates which accounts for the kinetic instability of the complexes particularly observable under high thiocyanate concentrations. Inorganica Chimica Acta, 445, 155-159. doi:10.1016/j.ica.2016.02.052

ISSN: 0020-1693


030207 Transition Metal Chemistry

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The kinetic instability of iron(III) thiocyanate complexes in aqueous solution, evidenced by the loss of solution colour with time, has made it difficult to determine reliable equilibrium data. A technique, which measures the absorbance of these solutions as a function of time within milliseconds of mixing Fe3+ with SCN- and which extrapolates to an initial spectrum at time zero, has been designed to overcome these difficulties and is described in this paper. Two complexes, Fe(SCN)2+ and Fe(SCN)2+, have been identified upon analysing the absorbance data for thiocyanate concentrations up to 0.25 M at 25oC and an ionic strength of 0.5 M. Equilibrium constants, K1 = and K2 = have been determined and comparisons made with the literature.


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