THE KINETICS OF THE COMPLEXING OF FERRIC ION BY THIOCYANATE AND CHLORIDE IONS (thesis)

An apparatus for rapidly mixing two solutions and recording the light absorption, which was developed by Connick and Below, has been modified. The mixing characteristics were studied and models were developed in an attempt to umder stand the observed mixing phenomena. The apparatus was applied to a study of the kinetics of the reactions Fe/sup +++/ + SCN/sup -/ = FeSCN/sup ++/ and Fe/ sup +++/ Cl/sup -/ = FeCl/sup ++/ in aqueous solution, with both reactions having the forward rate law STAd(FeX/sup ++/)/dt = k/sub 1/ (Fe/sup +++/) (X/sup -/) + k/ sub 2/ (Fe/sup +++/)(X/sup -/)/(H/sup +)!, where X/sup -/ represents either SC N/ sup -/ or Cl/sup -/. The rate constants k/sub 1/ and k/sub 2/ have been measured as a function of temperature, and the heats and entropies of activation have been calculated. Mechanisms for the observed rate law have been discussed and the entropies of activation were compared with those for analogous reaction rates and with some equilibrium entropies of complexing. A rate for chloride complexing of ferric ion was obtained from nuclear magnetic resonance studies and compared with the results of the spectrophotometric kinetic study. (auth)