Abstract: DETERMINATION OF STABILITY CONSTANTS OF URANYL WITH FULVIC ACID BY ION EXCHANGE METHODDU JINZHOU；TAO ZUYI（Department of Modern Physics，Lanzhou University，730000）LU CHANGOING（Biochemistry Division，Institute of Nanjing Soil Science，Academia Scinica，210008）ABSTRACT The stability constants of uranyl with the fulvic acid from weathered coal are determinedusing Ardakani-Stevenson＇s ion exchange method at ionic strength 0．1mol／kg and pH＝4．0and 7．2．The complexation constants are found to be 1gβ＝4．8 and 7．5 while complexationratio being 1：1 and 1:2，1gβ＝10．6and 16．5 while complexation ratio being 2：1 and 3：1．Inthe paper，the Ardakani-Stevenson＇s method has been modified. Key words Fulvic acid Uranyl Complexes Stability constant Ion exchange