An experimental investigation is presented of the foam separation of cyanide, complexed with ferrous iron, using a cationic surfactant, ethylhexa-decyldimethylammonium bromide (EHDA-Br). The effects of pH over the range 5.8–11.4, of iron concentration, and of surfactant and cyanide concentrations on the separation of noncomplexed and complexed cyanide are established. Prior to surfactant addition and foaming, variation of the iron-to-cyanide ratio in the initial solutions produced different species of complexed cyanide, ranging from [Fe(CN)6]4-to polynucleated [FeFe(CN)6]2-, which, in turn, brought about markedly different solution characteristics. Initial solutions containing 0.206 and 0.351 moles of iron per mole of cyanide exhibited contrasting foam separation behavior, at pH 7 and below, but not at pH 8 and above.