SOME FERRIC HALIDE COMPLEXES, AND TERNARY COMPLEXES WITH THIOCYANATE IONS

Abstract
A spectrophotometric study of solutions containing ferric and bromide ions; ferric, bromide, and thiocyanate ions; and ferric, chloride, and thiocyanate ions is reported. The measurements were made at constant temperature and ionic strength. The data were interpreted with the help of the results from the first paper of this series. The data show that FeBr++ and FeBr2+ are formed, and values are obtained for the equilibrium constants for their formation from simple ions, and for the extinction coefficients of FeBr++. When thiocyanate is also present, the data can best be interpreted by assuming that FeSCNBr+ or FeSCNCl+ is formed. At high chloride concentrations it seems necessary to postulate also FeCl2+ and FeSCNCl2. Estimates are made for the equilibrium constants for the formation of all these species from simple ions. As with the corresponding sulphate complexes, there seems to be no particular reluctance to form mixed complexes such as FeSCNCl+, as compared with the 'simple' complexes such as FeCl2+.