The application of the new morphological index chi(T), which is an extension of Wiener’s index for the evaluation of the retention data of apolar and polar solutes used in inverse gas chromatography, is described. Indeed, chi(T) performs satisfactorily, surpassing the other molecular descriptors employed so far. Examples of applications on silica and graphite samples are presented. It appears that the new index allows a unique evaluation of the Lewis acid-base surface characteristics of solid surfaces.