The precipitation of sodium alkyl sulfate with cetylpyridinium chloride was obtained under optimized conditions. The conditions for the most efficient formation of precipitates were obtained as longer alkyl chain length of alkyl Sulfate (C (14)), higher pH (pH 12), 1.5 M NaCl, and equimolar ratio between anionic and cationic surfactants. The structures and physical properties of surfactant precipitates were investigated with SEM, UV-vis, and FT-IR spectroscopy and light scattering. The precipitate of sodium alkyl sulfate with cetylpyridinium chloride was studied with the pressure-area isotherm at the air/water interface. In addition, the surface morphology of the Langmuir-Blodgett film of surfactant precipitate was observed with atomic force microscopy. (c) 2007 Elsevier Inc. All rights reserved.