Activity coefficient data for 20 binary and seven ternary systems composed of nC6H14, nC7H16, nC8H18, C6H6, cy-C6H12, CCl4, CHCl3, (C4H9)3PO4 and UO2(NO3)2 · 2((C4H9)3PO4) have been measured at 25 °C by head-space gas chromatography. The results of correlation of the experimental data with three thermodynamic models, the Scatchard-Hildebrand, NRTL and UNIQUAC models, are compared. All three models can be used to predict activity coefficient data for ternary systems by means of binary parameters. © 1990.