An X-rya investigation of aggregate dimensions and local electron densities in micellar systems of sodium octanoate (NaC8) containing normal alcohols has been made, applying Luzzati's spherical micelle model. In aqueous solutions, the solubilizate being pentanol, octanol or decanol, the results indicate aggregates with thick polar layers, i.e., considerable hydration of the micelles. The thickness of the polar layer increases as the length of the hydrocarbon chain of the solubilizate increases. In the case of systems with "inverted" micelles, that is, where water is solubilized in decanol, the influence of the difference in electron density between the solvent (decanol) and the hydrocarbon part of the aggregates has been investigated. The X-ray data indicate relatively large regions with a high electron density in the interior of the "inverted" micelles. This electron density lies between the electron density of water and that of decanol. [ABSTRACT FROM AUTHOR]