Abstract: DETERMINATION OF NEPTUNIUM BY AMPEROMETRIC TITRATIONCAO XISHOU；XU SHENGCHANG；WU PEILI；WEN ZHENJUN（China Institute of Atomic Energy，P.O. Box 275，Beijing，102413）ABSTRACT Neptunium is oxidized to Np（Ⅵ）in 0．5mol／l acid medium by AgO. Excess AgO is de-stroyed by aminesulfonic acid．Then Np（Ⅵ）is titratcd to Np（Ⅳ）in 3mol／l acid medium byFe（Ⅱ）．Excess Fe（Ⅱ）is re-titrated by standard potassium dichromate solution. In order toobtain precise and accurate results for such a small sample， weight burets are frequently usedtaking aliquots and the titrants.A platinum indication electrod and a calomel reference elec-trod are used to measure the cell amperage. The relative standard deviation for the determi-nation of 2mg neptunium is less than 0．3％.The relative deviation of the present methodcompared with the constant current coulometry is less than 0．22％. Key words Neptunium Accurate determination Amperometric titration