A novel solvent polymeric membrane electrode based on bis (1, 3, 4-thiadiazole) complexes of Hg (II) is described which has excellent selectivity and sensitivity toward iodide ion. The electrode, containing 1, 4-bis (5-methyl-1, 3, 4-thiadiazole-2-yl-thio) butanemercury (II) [Hg (II) BMTB (NO3) 4], has a Nernstian potentiometric response from 2.0*10) 8 to 2.0*10) 2mol L) 1 with a detection limit of 8.0*10) 9mol L)1 and a slope of) 59.0