The states of water in water/Triton X-100/n-butanol/cyclohexane reverse microemulsion, trapped water, bound water and free water, have been studied at various molar ratio of water to Triton X-100, mass ratio of water to oil (f) and the content of n-butanol by means of Fourier transform infrared spectroscopy (FT-IR). It was found that the water pools formed after R_w being larger than 8 as f was 2.8 and m_n-butanol/m_{Triton X-100} was 0.5|and the number of free water, the trapped water of per Triton X-100 molecule increased with R_w, while the number of the bounded water was almost constant at 2|the mass ratio of water to oil (1～6.7) had little effect on the FT-IR spectroscopy of the reverse microemulsion at R_w of 20 and m_n-butanol/m_{Triton X-100} of 0.5. In addition, the n-butanol molecules interacted with both molecules of Triton X-100 and water, and it retarded the formation of free water.

Key words: reverse microemulsion, FT-IR, water state, Triton X-100, n-butanol