Effect of Chloride on the Photometric Determination of Thiocyanates in Solutions Using Iron(III)

In determining thiocyanates by photometry as complexes with iron in chloride-containing solutions, it is necessary to take into account the complex dependence of the absorbance of solutions on their composition because of the formation of iron chloride complexes, as well as ternary colored iron thiocyanate and chloride complexes. A mathematical model relating the equilibrium concentrations of components in solutions with the total concentrations of all forms of these components is developed, and the molar absorption coefficients of the [Fe(SCN)]2+ and [Fe(SCN)Cl]+ complexes are determined on its basis. An example of a technological process for the purification of a thiocyanate-containing solution by a two-temperature sorption method is considered, the analytical support of which by the known methods leads to incorrect results, but becomes possible using the developed model.