[en] We analyse here the thermodynamic behaviour of the thermal expansion coefficient for a number of liquids. The purpose of this work is to provide some general rules to develop equations of state models meeting the following criteria: thermodynamic consistency, generality, predictive power and accuracy to represent derived properties over wide ranges of pressure and temperature. The liquids included into our analysis have been selected to meet two criteria: (1) available experimental data over wide ranges of pressure and temperature (from the melting point up to the critical point), and (2) liquids composed of molecules with different geometries and interactions