A good quality crystals are grown by the addition of equimolar composition of the transition metal mercury (Hg) as mercurous chloride to potassium hydrogen phthalate [KHP: Hg (1:1)], by slow evaporation solution growth technique (SEST). The FTIR spectrum confirms that there is distortion in the structure of the crystals due to equimolar doping. The TGDTA gives the purity of the material and no decomposition is observed up to the melting point presence of mercury (Hg) is confirmed by energy dispersive X- ray spectroscopy (EDS). Scanning Electron Microscopy (SEM) reveals some modifications in surface morphology were observed due to doping. The transition metal mercury (Hg) doping results in multi-peaks in the (DC) diffraction curve with increased intensity and peak shift, due to its bigger size which is reported in powder X- ray diffraction (XRD). The presence of mercury (Hg) is quantified by inductively coupled plasma emission spectrometer (ICP) technique. The equimolar doping results in significant enhancement of second harmonic generation (SHG) resulting in morphological changes. In single crystal XRD, the cell parameter value of Hg is different from KHP with the change in system revealing some structural changes.