Mercury (II) forms a yellow Coloured water soluble complex with Diacetyl Monoxime Isonicotinoyl hydrazone(DMIH) reagent in acidic buffer PH 5.5 with ? max at 351 nm. The molar absorptivity and sandell’s sensitivity are 2.23 X 104 L.mol-1 cm-1 and 0.00225 µg/cm2 respectively. The Beer’s law validity range is1.003 – 12.03 µg/mL. Mercury (II) forms (M:L) 1:1 complex with DMIH and stability constant of the complex is 6.692 X 106. The derivative spectrophotometric determination of Hg (II) was carried out by measuring peak height method. The developed derivative spectrophotometric method was employed for the determination of Mercury (II) in synthetic samples of alloy. The effect of various diverse ions was also studied.