Study of the dual mode mechanism of dyeing, nylon with acid dyes, consisting of Langmuir-type sorption on charged terminal amino groups, accompanied by Nernst-type uptake, known as "overdyeing," is subject to complications primarily (but not exclusively) because of structural nonhomogeneity of the polymeric substrate. We present here a system that combines structural simplicity with ease of manipulation of amine content; wherein the nylon substrate is replaced by a liquid phase consisting of a specially selected amine dissolved in a suitable organic solvent. This system displays the characteristic features of the aforementioned dual mode dyeing mechanism, as shown by experimental data of the uptake of C.I. Orange 7 as a function of aqueous dye concentration and amine concentration in the organic phase. (c) 2006 Wiley Periodicals, Inc.