Abstract: Hydration of sulfonate in water/AOT/n-heptane (AOT = sodium bis (2-ethylhexyl) sulfosuccinate) microemulsion system has been investigated by means of FT-IR.The results show that the hydration of sulfonate in the system leads to a shift of symmetricsulfonate stretching mode from 1051.39 cm^-1 to 1046.15 cm^-1 in the infrared spectra withthe increase of the molar ratio of water to AOT, W₀ The formation of microemulsionsweakens the interaction between counterion Na⁺ and —SO₃^-, groups, compared with that inthe solid state AOT.The splitting of the antisymmetric sulfonate stretching mode in the in-frared spectra reduces from ca.42 cm^-1 to 29 cm^-1 upon the addition of water into the sys-tem.The intensity of ~1215 cm^-1 increases, while the peak of ~1245 cm^-1 decreases corre-spondingly with the increase of W₀.

Key words: sodium bis (ethylhexyl) sulfosuccinate, microemulsion system, hydration, infrared spectrometry