The diffusion coefficient of naphthalene in supercritical ethanol was measured at 519—534 K and 6.5—16.2 MPa by using the Taylor dispersion technique.The association factor of ethanol molecules was estimated according to the measured experimental data and the infinite diffusion coefficients of naphthalene in high-pressure ethanol published previously.It was shown that the association factor was only a function of temperature varying between 1.8 and 2.8 for liquid and supercritical ethanol.However

the association factor remarkably changed with pressure at the near-critical region of ethanol

reaching a maximum up to 14.