Ion flotation of dichromate and of complexed cyanide: Surfactants for qualitative analysis

Ion flotation studies have shown that a surface-active agent is useful for qualitative analysis of complex ions in dilute aqueous solution, with the surfactant forming a particulate complex with the complex ion of concern. Experiments with a monovalent, cationic surfactant have established the prevalence of Cr₂O₇^2- (HCrO₄^-) and not CrO₄^2-; of [Fe(CN)₆]^4- and [Fe(CN)₅H₂O]^3-; and of [FeFe(CN)₆]^2- and not [FeFe(CN)₆]^- or [Fe(CN)₆]^3-. The results can be contrasted to those with ions that do not form particulate complexes with the surfactant, such as HPO₄^2- and phenolate; with the latter, no qualitative analytical information can be gained. Ion flotation appears to be a promising technique in general for the determination of ionic species present in aqueous solution; the surfactant must react with the ion of significance to form a particulate complex and the initial surfactant concentration must be controlled carefully.