A new model for the excess Gibbs energy has been developed. The model has three binary parameters. The presence of the third parameter, kij, the power of the composition, gives to the model an extraordinary flexibility. The model has been widely tested for different types of equilibria, such as binary liquid‐vapour equilibria, both isothermal and isobarid; as well as on liquid‐liquid equilibria, binary, ternary and quaternary, for both correlation and prediction. Results obtained for the average errors were always lower than those obtained by the Van Laar, Wilson and UNIQUAC models, and even by a three parameter model such as NRTL.