“…A number of solution properties for mixed surfactant systems have already been published (1). In the last five years, several papers on mixtures of nonionic and ionic surfactants using capillary electrophoresis (2), molecular thermodynamic theory (3), potentiometry (4), regular solution theory (5,6), small-angle neutron scattering (7)(8)(9), surface tension (10,11), ultrafiltration (12,13), volumetry (14), and so on have been also published. 1 Fax: +81-93-693-3201.…”