2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/28632A microscopic model which has proven useful in describing amphiphilic aggregates as inhomogeneities of a fluid is extended here to study the case of a two component surfactant mixture. We have chosen an effective interaction between the amphiphiles that mimics the mixture of cationic--anionic surfactants. In agreement with experiments, and other theoretical approaches, we find regions where spherical vesicles are stable, with a well defined radius. The experimental dependence of the radius on the chemical environment is also qualitatively reflected in our model.14 pages, 8 figures, to appear in LangmuirSoft Condensed MatterStatistical Mechanicstext