factors, e.g. kinetics and solubility, are sometimes involved, and linkage isomerism can occur, for example [Co(NH3)5(NCS)]Cl2 and [Co(NH3)5(SCN)]Cl2. It [SCN] is considered as a weak ligand. ([NCS] is a strong ligand) Test for iron(III) and cobalt(II) If [SCN]− is added to a solution with iron(III) ions, a blood-red solution forms mainly due to the formation of [Fe(SCN)(H2O)5]2+, i.e. pentaaqua(thiocyanato-N)iron(III). Lesser amounts of other hydrated compounds also form: e.g. Fe(SCN)3 and [Fe(SCN)4]−. Similarly, Co2+ gives a blue complex with thiocyanate. Both the iron and cobalt complexes can be extracted into organic solvents like diethyl ether or amyl alcohol. This allows the determination of these ions even in strongly coloured solutions. The determination of Co(II) in the presence of Fe(III) is possible by adding KF to the solution, which forms uncoloured, very stable complexes with Fe(III), which no longer react with SCN−. Phospholipids or some detergents aid the transfer of thiocyanatoiron into chlorinated solvents like chloroform and can be determined in this fashion. See also Sulphobes References Citations Anions Sulfur ions Concrete admixtures