The states of water in the W/O microemulsions formed in H₂O/C₁₂-EO_x-C₁₂•2Br/n-hexanol/ n-heptane systems have been investigated by Fourier transform infrared spectroscopy (FT-IR). The results showed that there existed four states of water in the microemulsions, which were head-group-bound water, Br^--bound water, bulklike water and trapped water in the interface of the microemulsion water, respectively. The n_N＋, n_Br-, n_b and n_f, which represented respectively the numbers of the water corresponding to the above four states per surfactant molecule, were obtained by a deconvolution technique. With increasing water content W₀, n_b was increased rapidly but n_N＋ increased a little, whereas n_Br- and n_f were kept almost constant. These indicated that the water pool of the microemulsion grew gradually and the degree of the counter-ion dissociation was kept unchanged over the range of the ex-amined W₀.

Key words: H₂O/C₁₂-EO_x-C₁₂•, 2Br/n-hexanol/n-heptane, W/O microemulsion, FT-IR, water state