The diffusion coefficients of five carboxylic acids-formic acid, acetic acid, propionic acid, succinic acid, citric acid-in the phases of water saturated by 1-butanol (water-rich phase) and 1-butanol saturated by water (1-butanol-rich phase) at 25 degreesC were measured. The semi-empirical model suggested by Perkins-Geankoplis was applied to predict the value of the diffusion coefficients, while the equations of Wilke-Chang and Hayduk-Laudie were selected to calculate the diffusion coefficients in water and the models of Scheibel and Lusis-Ratcliff were for the diffusion coefficients in 1-butanol. By comparing the calculated and experimental data, it was found that the diffusion coefficients in the water-rich and 1-butanol-rich phases could be predicted very well with the combination of the equations of Hayduk-Laudie and Scheibel. (C) 2002 Elsevier Science B.V. All rights reserved.