The publication demonstrates chelation studies of cobalt(III) with 1,2 bis(beta-aminoethoxy)ethane N,N,N',N' sodium sulfonate triacetic acid (ASTA). The results showed the effectiveness of ASTA as a chelating agent by molar ratio , continuous variation and slope ratio methods. Stable complex 1:1 was formed at pH from 6.0 to 10.5. Solutions of Co-ASTA chelate of different molar ratios at pH 6.5 and 8.0 were irraiated by different gamma radiation doses. The results showed a linear decrease of absorbance with dose which can be utilized as a dosimeter for weak dose rate measurement in the studied range. A proposed radiolytic mechanism is discussed. The degradation of ligand has been related to hydroxyl radical attack.