stances, but materialized with a firm basis of the stable isola-In the system of a homologous series of sodium alkyl sulfates, tion of such complexes as a new chemical species (2, 3).
including SLS (sodium lauryl sulfate) and other anionic surfac-
The surfactant molecular complexes were produced from tants with various phenols and other materials as additives, the aqueously solubilized solution systems which were treated surfactant molecular complex formation was obviously proved by the conventional method. After an attainment of homogefrom results of X-ray diffraction experiment on their powdery neous solubilization of several aromatic solubilizates by a specimens and from the elementary analysis such as UV spectroscationic surfactant such as CTAB, the crystalline surfactant copy. Especially, well-grown single crystals occurring in a SOS molecular complexes were precipitated from the transparent (sodium octyl sulfate)/2-naphthol system provided detailed strucsolubilized solution system, when allowed to cool for a petural knowledge of the anionic surfactant molecular complex to establish the unambiguous existence of those complex species. In riod of time. When the solutions were warmed up, the precipcomparison with previous results of the cationic surfactant molecitated surfactant molecular complex crystals were again disular complexes, significant variation observed in the X-ray diffracsolved into a homogeneous solution instantaneously, retograms of the anionic complex species deduced almost no change sulting in the original solubilized solution system restoring or only slight contraction of the unit cell of the anionic mother all the solution characteristics. Thus, the crystallization and surfactant crystals along their longest lattice direction, while in dissolution were perfectly reversible like any other common all cationic complexes a clear expansion was involved associated water-soluble crystalline material (2, 3). These observations with the additive intrusion into the surfactant crystal lattices. The strongly suggest that apparent implicacies of a phenomenon, remarkable features on the diffractograms of the anionic complex ''solubilization,'' can easily be understood; i.e., the solubilispecies also corresponded well to observations in which many sorts zation is simply the dissolution of crystalline surfactant comof anionic complex species were hydrated and the additive stability plex species which are provided in the systems in the course occluded in their mother surfactant crystal structure was very poor compared with the cationic complex species.