A NONLINEAR CORRELATION OF HIGH-PRESSURE VAPOR-LIQUID-EQUILIBRIUM DATA FOR ETHYLENE PLUS N-BUTANE SHOWING INCONSISTENCIES IN EXPERIMENTAL COMPOSITIONS

The modified Leung-Griffiths model is applied to the previously unpubl ished data, tabulated here, of Williams for high-pressure vapor-liquid equilibria of ethylene + n-butane. It is not possible to obtain a hig hly accurate correlation with the experimentally stated compositions, but evidence is given that those composition measurements may be suspe ct, although pressure, temperature, and density data are accurate. A s implex optimization method was used for the parameters of the model, a nd the compositions were also treated as adjustable parameters. With t his method a much more accurate correlation is obtained, but the optim ized compositions differ in two of four cases by more than 3% from the stated compositions.