Abstract: In a dilute sulfuric acid medium,trace amounts of NO_2~- ion show strong catalytic effect on the oxidation reaction between methyl orange and potassium bromate.Furthermore,methyl orange exhibits a sensitve polarographic wave at -0.59 V(VS.SCE).The kinetic polarographic determination method of trace amount of NO_2~- was established based on the change of methyl orange concentration in the catolytic reaction.The detection limit and the linear range of NO_2~- are 0.002 72 mg/L and 0.005 2～0.533 6 mg/ L,repecti...