The modified groove tracking method (MGTM) along with the smoothed groove tracking method (SGTM) are applied to X-ray reflectivity data of liquid mercury at room temperature. It is demonstrated that it is possible to obtain non-unique profiles, which are physically reasonable, by SGTM. The SGTM yields independently an electron density profile which does contain the essential features of the electron density profile of liquid mercury proposed by D'Evelyn and Rice.